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Nanoscience and nanotechnology

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Exploring frontiers of mechanical engineering

MIT Department of Mechanical Engineering grad students are undertaking a broad range of innovative research projects.

May 3, 2024

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Physicists arrange atoms in extremely close proximity

The technique opens possibilities for exploring exotic states of matter and building new quantum materials.

May 2, 2024

How light can vaporize water without the need for heat

Surprising “photomolecular effect” discovered by MIT researchers could affect calculations of climate change and may lead to improved desalination and drying processes.

April 23, 2024

“Nanostitches” enable lighter and tougher composite materials

In research that may lead to next-generation airplanes and spacecraft, MIT engineers used carbon nanotubes to prevent cracking in multilayered composites.

April 16, 2024

Tackling cancer at the nanoscale

In MIT’s 2024 Killian Lecture, chemical engineer Paula Hammond described her groundbreaking work on nanoparticles designed to attack tumor cells.

April 10, 2024

Propelling atomically layered magnets toward green computers

MIT scientists have tackled key obstacles to bringing 2D magnetic materials into practical use, setting the stage for the next generation of energy-efficient computers.

April 4, 2024

Unlocking new science with devices that control electric power

Seron Electronics, founded by Mo Mirvakili PhD ’17, makes research equipment with applications including microelectronics, clean energy, optics, biomedicine, and beyond.

MIT researchers discover “neutronic molecules”

Study shows neutrons can bind to nanoscale atomic clusters known as quantum dots. The finding may provide insights into material properties and quantum effects.

April 3, 2024

A first-ever complete map for elastic strain engineering

New research by a team of MIT engineers offers a guide for fine-tuning specific material properties.

March 29, 2024

VIAVI Solutions joins MIT.nano Consortium

International technology company becomes sustaining member of industry group.

March 28, 2024

Students explore career opportunities in semiconductors

Global Semiconductor Alliance’s Women’s Leadership Initiative provides inspiration and guidance to MIT students.

March 22, 2024

Creative collisions: Crossing the art-science divide

A collaboration between ACT and MIT.nano, the class 4.373/4.374 (Creating Art, Thinking Science) asks what it really takes to cultivate dialogue between disciplines.

March 19, 2024

Pushing material boundaries for better electronics

Associate Professor Jeehwan Kim is exploring systems that could take over where silicon leaves off.

MIT scientists use a new type of nanoparticle to make vaccines more powerful

Study shows metal-organic particles can both deliver vaccines and act as an adjuvant to generate a strong immune response at a lower dose.

March 6, 2024

Study unlocks nanoscale secrets for designing next-generation solar cells

The work will help researchers tune surface properties of perovskites, a promising alternative and supplement to silicon, for more efficient photovoltaics.

February 28, 2024

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Nanotechnology News

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Nanotechnology

Purpose-led Publishing is a coalition of three not-for-profit publishers in the field of physical sciences: AIP Publishing, the American Physical Society and IOP Publishing.

Together, as publishers that will always put purpose above profit, we have defined a set of industry standards that underpin high-quality, ethical scholarly communications.

We are proudly declaring that science is our only shareholder.

Nanotechnology encompasses the understanding of the fundamental physics, chemistry, biology and technology of nanometre-scale objects.

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Andrew Maicke et al 2024 Nanotechnology 35 275204

Perpendicular magnetic tunnel junction (pMTJ)-based true-random number generators (RNGs) can consume orders of magnitude less energy per bit than CMOS pseudo-RNGs. Here, we numerically investigate with a macrospin Landau–Lifshitz-Gilbert equation solver the use of pMTJs driven by spin–orbit torque to directly sample numbers from arbitrary probability distributions with the help of a tunable probability tree. The tree operates by dynamically biasing sequences of pMTJ relaxation events, called 'coinflips', via an additional applied spin-transfer-torque current. Specifically, using a single, ideal pMTJ device we successfully draw integer samples on the interval [0, 255] from an exponential distribution based on p -value distribution analysis. In order to investigate device-to-device variations, the thermal stability of the pMTJs are varied based on manufactured device data. It is found that while repeatedly using a varied device inhibits ability to recover the probability distribution, the device variations average out when considering the entire set of devices as a 'bucket' to agnostically draw random numbers from. Further, it is noted that the device variations most significantly impact the highest level of the probability tree, with diminishing errors at lower levels. The devices are then used to draw both uniformly and exponentially distributed numbers for the Monte Carlo computation of a problem from particle transport, showing excellent data fit with the analytical solution. Finally, the devices are benchmarked against CMOS and memristor RNGs, showing faster bit generation and significantly lower energy use.

Syed Nabeel Ahmed and Waseem Haider 2018 Nanotechnology 29 342001

There has been a considerable amount of research in the development of sustainable water treatment techniques capable of improving the quality of water. Unavailability of drinkable water is a crucial issue especially in regions where conventional drinking water treatment systems fail to eradicate aquatic pathogens, toxic metal ions and industrial waste. The research and development in this area have given rise to a new class of processes called advanced oxidation processes, particularly in the form of heterogeneous photocatalysis, which converts photon energy into chemical energy. Advances in nanotechnology have improved the ability to develop and specifically tailor the properties of photocatalytic materials used in this area. This paper discusses many of those photocatalytic nanomaterials, both metal-based and metal-free, which have been studied for water and waste water purification and treatment in recent years. It also discusses the design and performance of the recently studied photocatalytic reactors, along with the recent advancements in the visible-light photocatalysis. Additionally, the effects of the fundamental parameters such as temperature, pH, catalyst-loading and reaction time have also been reviewed. Moreover, different techniques that can increase the photocatalytic efficiency as well as recyclability have been systematically presented, followed by a discussion on the photocatalytic treatment of actual wastewater samples and the future challenges associated with it.

Daniele Ielmini and Stefano Ambrogio 2020 Nanotechnology 31 092001

Artificial intelligence (AI) has the ability of revolutionizing our lives and society in a radical way, by enabling machine learning in the industry, business, health, transportation, and many other fields. The ability to recognize objects, faces, and speech, requires, however, exceptional computational power and time, which is conflicting with the current difficulties in transistor scaling due to physical and architectural limitations. As a result, to accelerate the progress of AI, it is necessary to develop materials, devices, and systems that closely mimic the human brain. In this work, we review the current status and challenges on the emerging neuromorphic devices for brain-inspired computing. First, we provide an overview of the memory device technologies which have been proposed for synapse and neuron circuits in neuromorphic systems. Then, we describe the implementation of synaptic learning in the two main types of neural networks, namely the deep neural network and the spiking neural network (SNN). Bio-inspired learning, such as the spike-timing dependent plasticity scheme, is shown to enable unsupervised learning processes which are typical of the human brain. Hardware implementations of SNNs for the recognition of spatial and spatio-temporal patterns are also shown to support the cognitive computation in silico . Finally, we explore the recent advances in reproducing bio-neural processes via device physics, such as insulating-metal transitions, nanoionics drift/diffusion, and magnetization flipping in spintronic devices. By harnessing the device physics in emerging materials, neuromorphic engineering with advanced functionality, higher density and better energy efficiency can be developed.

R Jalal et al 2024 Nanotechnology 35 265705

W-doped ZnO thin films deposited on Si substrates with (100) orientation by sol–gel spin coating method at temperature 500 °C. W/Zn atomic ratio varies from 0% to 4%. Then, the UV detection performance analysis of p–n heterojunction UV photodetectors based on W-doped ZnO/Si is analyzed. The current–voltage curves of W-doped ZnO/Si are investigated in dark and exhibit diode-like rectifying behavior. Among doped ZnO/Si, sample with atomic ratio of W/Zn = 2% is the best candidate to study photodetector characteristics in UV range. The resulting device exhibits a rectification ratio RR of 5587 at ±5 V, a higher responsivity of 3.84 A W −1 and a photosensitivity value of 34 at 365 nm under 0.5 mW cm −2 . The experimental findings reveal that the UV detection performance of the heterojunction-based photodetectors strongly dependent on the properties of metal oxide layer. The main goal of this work is to investigate the effect of W doping on the performance of ZnO/Si based photodetectors. Based on our results, it is observed that 2 at% of W dopant is the optimum amount of doping for high performance photodetector of ZnO:W/Si heterojunction thanks to the suppressed recombination ratio and enhanced carrier separation properties in the depletion zone.

Achint Jain et al 2018 Nanotechnology 29 265203

Integrating layered two-dimensional (2D) materials into 3D heterostructures offers opportunities for novel material functionalities and applications in electronics and photonics. In order to build the highest quality heterostructures, it is crucial to preserve the cleanliness and morphology of 2D material surfaces that come in contact with polymers such as PDMS during transfer. Here we report that substantial residues and up to ∼0.22% compressive strain can be present in monolayer MoS 2 transferred using PDMS. We show that a UV-ozone pre-cleaning of the PDMS surface before exfoliation significantly reduces organic residues on transferred MoS 2 flakes. An additional 200 ◦ C vacuum anneal after transfer efficiently removes interfacial bubbles and wrinkles as well as accumulated strain, thereby restoring the surface morphology of transferred flakes to their native state. Our recipe is important for building clean heterostructures of 2D materials and increasing the reproducibility and reliability of devices based on them.

Lior Shani et al 2024 Nanotechnology 35 255302

Semiconductor nanowire (NW) quantum devices offer a promising path for the pursuit and investigation of topologically-protected quantum states, and superconducting and spin-based qubits that can be controlled using electric fields. Theoretical investigations into the impact of disorder on the attainment of dependable topological states in semiconducting nanowires with large spin–orbit coupling and g -factor highlight the critical need for improvements in both growth processes and nanofabrication techniques. In this work, we used a hybrid lithography tool for both the high-resolution thermal scanning probe lithography and high-throughput direct laser writing of quantum devices based on thin InSb nanowires with contact spacing of 200 nm. Electrical characterization demonstrates quasi-ballistic transport. The methodology outlined in this study has the potential to reduce the impact of disorder caused by fabrication processes in quantum devices based on 1D semiconductors.

Yi-Teng Huang et al 2021 Nanotechnology 32 132004

Lead-halide perovskites have demonstrated astonishing increases in power conversion efficiency in photovoltaics over the last decade. The most efficient perovskite devices now outperform industry-standard multi-crystalline silicon solar cells, despite the fact that perovskites are typically grown at low temperature using simple solution-based methods. However, the toxicity of lead and its ready solubility in water are concerns for widespread implementation. These challenges, alongside the many successes of the perovskites, have motivated significant efforts across multiple disciplines to find lead-free and stable alternatives which could mimic the ability of the perovskites to achieve high performance with low temperature, facile fabrication methods. This Review discusses the computational and experimental approaches that have been taken to discover lead-free perovskite-inspired materials, and the recent successes and challenges in synthesizing these compounds. The atomistic origins of the extraordinary performance exhibited by lead-halide perovskites in photovoltaic devices is discussed, alongside the key challenges in engineering such high-performance in alternative, next-generation materials. Beyond photovoltaics, this Review discusses the impact perovskite-inspired materials have had in spurring efforts to apply new materials in other optoelectronic applications, namely light-emitting diodes, photocatalysts, radiation detectors, thin film transistors and memristors. Finally, the prospects and key challenges faced by the field in advancing the development of perovskite-inspired materials towards realization in commercial devices is discussed.

Arne Laucht et al 2021 Nanotechnology 32 162003

Quantum phenomena are typically observable at length and time scales smaller than those of our everyday experience, often involving individual particles or excitations. The past few decades have seen a revolution in the ability to structure matter at the nanoscale, and experiments at the single particle level have become commonplace. This has opened wide new avenues for exploring and harnessing quantum mechanical effects in condensed matter. These quantum phenomena, in turn, have the potential to revolutionize the way we communicate, compute and probe the nanoscale world. Here, we review developments in key areas of quantum research in light of the nanotechnologies that enable them, with a view to what the future holds. Materials and devices with nanoscale features are used for quantum metrology and sensing, as building blocks for quantum computing, and as sources and detectors for quantum communication. They enable explorations of quantum behaviour and unconventional states in nano- and opto-mechanical systems, low-dimensional systems, molecular devices, nano-plasmonics, quantum electrodynamics, scanning tunnelling microscopy, and more. This rapidly expanding intersection of nanotechnology and quantum science/technology is mutually beneficial to both fields, laying claim to some of the most exciting scientific leaps of the last decade, with more on the horizon.

Karl Berggren et al 2021 Nanotechnology 32 012002

Recent progress in artificial intelligence is largely attributed to the rapid development of machine learning, especially in the algorithm and neural network models. However, it is the performance of the hardware, in particular the energy efficiency of a computing system that sets the fundamental limit of the capability of machine learning. Data-centric computing requires a revolution in hardware systems, since traditional digital computers based on transistors and the von Neumann architecture were not purposely designed for neuromorphic computing. A hardware platform based on emerging devices and new architecture is the hope for future computing with dramatically improved throughput and energy efficiency. Building such a system, nevertheless, faces a number of challenges, ranging from materials selection, device optimization, circuit fabrication and system integration, to name a few. The aim of this Roadmap is to present a snapshot of emerging hardware technologies that are potentially beneficial for machine learning, providing the Nanotechnology readers with a perspective of challenges and opportunities in this burgeoning field.

U Banin et al 2021 Nanotechnology 32 042003

This roadmap on Nanotechnology for Catalysis and Solar Energy Conversion focuses on the application of nanotechnology in addressing the current challenges of energy conversion: 'high efficiency, stability, safety, and the potential for low-cost/scalable manufacturing' to quote from the contributed article by Nathan Lewis. This roadmap focuses on solar-to-fuel conversion, solar water splitting, solar photovoltaics and bio-catalysis. It includes dye-sensitized solar cells (DSSCs), perovskite solar cells, and organic photovoltaics. Smart engineering of colloidal quantum materials and nanostructured electrodes will improve solar-to-fuel conversion efficiency, as described in the articles by Waiskopf and Banin and Meyer. Semiconductor nanoparticles will also improve solar energy conversion efficiency, as discussed by Boschloo et al in their article on DSSCs. Perovskite solar cells have advanced rapidly in recent years, including new ideas on 2D and 3D hybrid halide perovskites, as described by Spanopoulos et al 'Next generation' solar cells using multiple exciton generation (MEG) from hot carriers, described in the article by Nozik and Beard, could lead to remarkable improvement in photovoltaic efficiency by using quantization effects in semiconductor nanostructures (quantum dots, wires or wells). These challenges will not be met without simultaneous improvement in nanoscale characterization methods. Terahertz spectroscopy, discussed in the article by Milot et al is one example of a method that is overcoming the difficulties associated with nanoscale materials characterization by avoiding electrical contacts to nanoparticles, allowing characterization during device operation, and enabling characterization of a single nanoparticle. Besides experimental advances, computational science is also meeting the challenges of nanomaterials synthesis. The article by Kohlstedt and Schatz discusses the computational frameworks being used to predict structure–property relationships in materials and devices, including machine learning methods, with an emphasis on organic photovoltaics. The contribution by Megarity and Armstrong presents the 'electrochemical leaf' for improvements in electrochemistry and beyond. In addition, biohybrid approaches can take advantage of efficient and specific enzyme catalysts. These articles present the nanoscience and technology at the forefront of renewable energy development that will have significant benefits to society.

Latest articles

Haonan Zhao et al 2024 Nanotechnology 35 292002

Recent advances in materials science, device designs and advanced fabrication technologies have enabled the rapid development of transient electronics, which represents a class of devices or systems that their functionalities and constitutions can be partially/completely degraded via chemical reaction or physical disintegration over a stable operation. Therefore, numerous potentials, including zero/reduced waste electronics, bioresorbable electronic implants, hardware security, and others, are expected. In particular, transient electronics with biocompatible and bioresorbable properties could completely eliminate the secondary retrieval surgical procedure after their in-body operation, thus offering significant potentials for biomedical applications. In terms of material strategies for the manufacturing of transient electronics, silicon nanomembranes (SiNMs) are of great interest because of their good physical/chemical properties, modest mechanical flexibility (depending on their dimensions), robust and outstanding device performances, and state-of-the-art manufacturing technologies. As a result, continuous efforts have been made to develop silicon-based transient electronics, mainly focusing on designing manufacturing strategies, fabricating various devices with different functionalities, investigating degradation or failure mechanisms, and exploring their applications. In this review, we will summarize the recent progresses of silicon-based transient electronics, with an emphasis on the manufacturing of SiNMs, devices, as well as their applications. After a brief introduction, strategies and basics for utilizing SiNMs for transient electronics will be discussed. Then, various silicon-based transient electronic devices with different functionalities are described. After that, several examples regarding on the applications, with an emphasis on the biomedical engineering, of silicon-based transient electronics are presented. Finally, summary and perspectives on transient electronics are exhibited.

P Mukherjee et al 2024 Nanotechnology 35 295502

Numerous efforts have been undertaken to mitigate the Debye screening effect of FET biosensors for achieving higher sensitivity. There are few reports that show sub-femtomolar detection of biomolecules by FET mechanisms but they either suffer from significant background noise or lack robust control. In this aspect, deformed/crumpled graphene has been recently deployed by other researchers for various biomolecule detection like DNA, COVID-19 spike proteins and immunity markers like IL-6 at sub-femtomolar levels. However, the chemical vapor deposition (CVD) approach for graphene fabrication suffers from various surface contamination while the transfer process induces structural defects. In this paper, an alternative fabrication methodology has been proposed where glass substrate has been initially texturized by wet chemical etching through the sacrificial layer of synthesized silver nanoparticles, obtained by annealing of thin silver films leading to solid state dewetting. Graphene has been subsequently deposited by thermal reduction technique from graphene oxide solution. The resulting deformed graphene structure exhibits higher sensor response towards glial fibrillary acidic protein (GFAP) detection with respect to flat graphene owing to the combined effect of reduced Debye screening and higher surface area for receptor immobilization. Additionally, another interesting aspect of the reported work lies in the biomolecule capture by dielectrophoretic (DEP) transport on the crests of the convex surfaces of graphene in a coplanar gated topology structure which has resulted in 10 aM and 28 aM detection limits of GFAP in buffer and undiluted plasma respectively, within 15 min of application of analyte. The detection limit in buffer is almost four decades lower than that documented for GFAP using biosensors which is is expected to pave way for advancing graphene FET based sensors towards ultrasensitive point-of-care diagnosis of GFAP, a biomarker for traumatic brain injury.

Dongseong Yang et al 2024 Nanotechnology 35 295202

Achieving energy-efficient and high-performance field-effect transistors (FETs) is one of the most important goals for future electronic devices. This paper reports semiconducting single-walled carbon nanotube FETs (s-SWNT-FETs) with an optimized high- k relaxor ferroelectric insulator P(VDF-TrFE-CFE) thickness for low-voltage operation. The s-SWNT-FETs with an optimized thickness (∼800 nm) of the high- k insulator exhibited the highest average mobility of 14.4 cm 2 V −1 s −1 at the drain voltage ( I D ) of 1 V, with a high current on/off ratio ( I on/off >10 5 ). The optimized device performance resulted from the suppressed gate leakage current ( I G ) and a sufficiently large capacitance (>50 nF cm −2 ) of the insulating layer. Despite the extremely high capacitance (>100 nF cm −2 ) of the insulating layer, an insufficient thickness (<450 nm) induces a high I G , leading to reduced I D and mobility of s-SWNT-FETs. Conversely, an overly thick insulator (>1200 nm) cannot introduce sufficient capacitance, resulting in limited device performance. The large capacitance and sufficient breakdown voltage of the insulating layer with an appropriate thickness significantly improved p-type performance. However, a reduced n-type performance was observed owing to the increased electron trap density caused by fluorine proportional to the insulator thickness. Hence, precise control of the insulator thickness is crucial for achieving low-voltage operation with enhanced s-SWNT-FET performance.

Ali Al Hassan et al 2024 Nanotechnology 35 295705

We report on the fabrication of a novel design of GaAs/(In,Ga)As/GaAs radial nanowire heterostructures on a Si 111 substrate, where, for the first time, the growth of inhomogeneous shells on a lattice mismatched core results in straight nanowires instead of bent. Nanowire bending caused by axial tensile strain induced by the (In,Ga)As shell on the GaAs core is reversed by axial compressive strain caused by the GaAs outer shell on the (In,Ga)As shell. Progressive nanowire bending and reverse bending in addition to the axial strain evolution during the two processes are accessed by in situ by x-ray diffraction. The diameter of the core, thicknesses of the shells, as well as the indium concentration and distribution within the (In,Ga)As quantum well are revealed by 2D energy dispersive x-ray spectroscopy using a transmission electron microscope. Shell(s) growth on one side of the core without substrate rotation results in planar-like radial heterostructures in the form of free standing straight nanowires.

Shahzad Hussain et al 2024 Nanotechnology 35 295704

Most of the applied research on BiFeO 3 (BFO) focuses on magnetoelectric and spintronic applications. This calls for a detailed grasp of multiferroic and conduction properties. BFO thin films with (100) epitaxial growth has been deposited on a LaNiO 3 (LNO) buffered Pt/Ti/SiO 2 /Si(100) substrate using RF magnetron sputtering. The film formed at 15 mTorr, 570 °C, and with Ar/O 2 4:1 had a reasonably high degree of (100)-preferential orientation, the least surface roughness, and a densely packed structure. We obtained ferroelectric loops with strong polarization (150 μ C cm −2 ). The leakage current density is as low as 10 –2 A cm −2 at 100 kV cm −1 , implying that space-charge-limited bulk conduction (SCLC) was the primary conduction channel for carriers within BFO films. Local electrical conduction behavior demonstrates that at lower voltages, the grain boundary dominates electrical conduction and is linked to the displacement of oxygen vacancies in the grain boundary under external electric fields. We hope that a deeper understanding of the conduction mechanism will help integrate BFO into viable technologies.

Review articles

Zhongliang Xiao et al 2024 Nanotechnology 35 292001

In the context of 'energy shortage', developing a novel energy-based power system is essential for advancing the current power system towards low-carbon solutions. As the usage duration of lithium-ion batteries for energy storage increases, the nonlinear changes in their aging process pose challenges to accurately assess their performance. This paper focuses on the study LiFeO 4 (LFP), used for energy storage, and explores their performance degradation mechanisms. Furthermore, it introduces common battery models and data structures and algorithms, which used for predicting the correlation between electrode materials and physical parameters, applying to state of health assessment and thermal warning. This paper also discusses the establishment of digital management system. Compared to conventional battery networks, dynamically reconfigurable battery networks can realize real-time monitoring of lithium-ion batteries, and reduce the probability of fault occurrence to an acceptably low level.

Luca Piantanida et al 2024 Nanotechnology 35 273001

DNA Nanotechnology is being applied to multiple research fields. The functionality of DNA nanostructures is significantly enhanced by decorating them with nanoscale moieties including: proteins, metallic nanoparticles, quantum dots, and chromophores. Decoration is a complex process and developing protocols for reliable attachment routinely requires extensive trial and error. Additionally, the granular nature of scientific communication makes it difficult to discern general principles in DNA nanostructure decoration. This tutorial is a guidebook designed to minimize experimental bottlenecks and avoid dead-ends for those wishing to decorate DNA nanostructures. We supplement the reference material on available technical tools and procedures with a conceptual framework required to make efficient and effective decisions in the lab. Together these resources should aid both the novice and the expert to develop and execute a rapid, reliable decoration protocols.

Aini Ayunni Mohd Raub et al 2024 Nanotechnology 35 242004

Nanostructured metal oxide semiconductors have emerged as promising nanoscale photocatalysts due to their excellent photosensitivity, chemical stability, non-toxicity, and biocompatibility. Enhancing the photocatalytic activity of metal oxide is critical in improving their efficiency in radical ion production upon optical exposure for various applications. Therefore, this review paper provides an in-depth analysis of the photocatalytic activity of nanostructured metal oxides, including the photocatalytic mechanism, factors affecting the photocatalytic efficiency, and approaches taken to boost the photocatalytic performance through structure or material modifications. This paper also highlights an overview of the recent applications and discusses the recent advancement of ZnO-based nanocomposite as a promising photocatalytic material for environmental remediation, energy conversion, and biomedical applications.

Hao Liu et al 2024 Nanotechnology 35 242003

Over the past few decades, single-element semiconductors have received a great deal of attention due to their unique light-sensitive and heat-sensitive properties, which are of great application and research significance. As one promising material, selenium, being a typical semiconductor, has attracted significant attention from researchers due to its unique properties including high optical conductivity, anisotropic, thermal conductivity, and so on. To promote the application of selenium nanomaterials in various fields, numerous studies over the past few decades have successfully synthesized selenium nanomaterials in various morphologies using a wide range of physical and chemical methods. In this paper, we review and summarise the different methods of synthesis of various morphologies of selenium nanomaterials and discuss the applications of different nanostructures of selenium nanomaterials in optoelectronic devices, chemical sensors, and biomedical applications. Finally, we discuss possible challenges for selenium nanodevices and provide an outlook on the future applications of selenium nanomaterials.

Accepted manuscripts

Mientjes et al 

Topological crystalline insulators (TCIs) are interesting for their topological surface states, which hold great promise for scattering-free transport channels and fault-tolerant quantum computing. A promising TCI is SnTe. However, Sn-vacancies form in SnTe, causing a high hole density, hindering topological transport from the surface being measured. This issue could be relieved by using nanowires with a high surface-to-volume ratio. Furthermore, SnTe can be alloyed with Pb reducing the Sn-vacancies while maintaining its topological phase. Here we present the catalyst-free growth of monocrystalline PbSnTe in molecular beam epitaxy (MBE). By the addition of a pre-deposition stage before the growth, we have control over the nucleation phase and thereby increase the nanowire yield. This facilitates tuning the nanowire aspect ratio by a factor of four by varying the growth parameters. These results allow us to grow specific morphologies for future transport experiments to probe the topological surface states in a Pb1-xSnxTe-based platform.

Bassi et al 

For deep ultraviolet (UV-C) photodetectors, Gallium oxide (Ga2O3) is a suitable candidate owing to its intrinsic ultra-wide band gap and high stability. However, its detection is limited within the UV-C region, which restricts it to cover a broad range, especially in visible and near-infrared (NIR) region. Therefore, constructing a heterostructure of Ga2O3 with an appropriate material having a narrow band gap is a worthwhile approach to compensate for it. In this category, PtS2 group-10 transitional metal dichalcogenide (TMDC) stands at the top owing to its narrow band gap (0.25-1.65 eV), high mobility, and stability for heterostructure synthesis. Moreover, heterostructure with Ga2O3 sensing in UV and PtS2 broad response in visible and IR range can broaden the spectrum from UV to NIR and to build broadband photodetector. In this work, we fabricated a 2D-3D PtS2-x/Ga2O3 heterostructure based broadband photodetector with detection from UV-C to NIR region. In addition, the PtS2-x/Ga2O3 device shows a high responsivity of 38.7 AW 1 and detectivity of 4.8 × 1013 Jones under 1100 nm light illumination at 5V bias. A fast response of 90 ms /86 ms illustrates the device's fast speed. An interface study between the PtS2-x and Ga2O3 was conducted using X-ray photoelectron spectroscopy and Ultraviolet photoelectron spectroscopy (UPS) which confirmed type-I band alignment. Finally, based on their band alignment study, a carrier transport mechanism was proposed at the interface. This work offers a new opportunity to fabricate large-area high-performance 2D-3D heterostructures based photodetectors for future optoelectronics devices.

Chiang 

A novel ballistic model for the subthreshold current of nanosheet transistors is successfully developed based on the Landauer approach with the three-dimensional number of channels. The ballistic threshold voltage can also be achieved through the calculated free charge density induced by the three-dimensional density-of-states equal to the substrate doping concentration. It indicates that under the low drain voltage corresponding to the fermi distribution function, the subthreshold current is mainly governed by the low contact potential. However, under the high drain voltage corresponding to the fermi distribution function, the thermal voltage, instead of the contact potential between the source and drain, initiates the subthreshold current. Besides subthreshold current and threshold voltage, the ballistic conductance and subthreshold swing are also revealed in the subthreshold conduction. It indicates that the thin silicon, thin gate oxide, heavy substrate doping density, and high work function will alleviate the ballistic effects, decrease the subthreshold current/swing, and increase the threshold voltage/ballistic resistance.

Bhattacharya et al 

We have investigated the PECVD growth of the phosphorus-doped hydrogenated nanocrystalline silicon (n-nc-Si:H) film as an electron-selective layer in silicon heterojunction (SHJ) solar cells. The effect of power densities on the precursor gas dissociation are investigated using optical emission spectra and the crystalline fraction in n-nc-Si:H films are correlated with the dark conductivity. With the Pd of 122 mW/cm2 and ~2% phosphorus doping, we observed Raman crystallinity of 53%, high dark conductivity of 43 S/cm, and activation energy of ~23 meV from the ~30 nm n-nc-Si:H film. The n-nc-Si:H layer improves the textured c-Si surface passivation by two-fold to ~2 ms compared to the phosphorus-doped hydrogenated amorphous silicon (n-a-Si:H) layers. An enhancement in the open-circuit voltage and external quantum efficiency (from >650 nm) due to the better passivation at the rear side of the cell after integrating the n-nc-Si:H layer compared to its n-a-Si:H counterpart. An improvement in the charge carrier transport is also observed with an increase in fill factor from ~71 % to ~75 %, mainly due to a reduction in electron-selective contact resistivity from ~271 mΩ-cm2 to ~61 mΩ-cm2. Finally, with the relatively better c-Si surface passivation and carrier selectivity, a power conversion efficiency of ~19.90% and pseudo-efficiency of ~21.90% have been realized from the SHJ cells.&#xD;

Aparicio-Huacarpuma et al 

In this study, copper thin films were deposited through thermal evaporation, with film thickness controlled by modulating the Z-position. The grain size (< D >) exhibited a power law relationship (< D >∝ ω n ) with n approximately 0.41 for as-fabricated copper films. Resistivity ranged from 3.3 to 4.6 µΩ·cm, aligning with expectations for crystallites sized between 20 and 26 nm. Cuprite (Cu 2 O) thin films were produced via thermal annealing, revealing crystallite sizes from ∼9 nm to ∼24 nm as film thickness increased. Optical bandgap varied monotonically from 2.31 to 2.17 eV with increasing film thickness, attributed to the quantum confinement effect. Refractive index and extinction coefficient also showed film-thickness dependence, with a linear relationship observed between the refractive index and charge carrier density. Electrical measurements indicated p-type semiconductors with carrier concentrations of ∼ 10 14 cm −3 , slightly decreasing with film thickness. Thinner cuprite films exhibited enhanced sensitivity to ethanol gas at room temperature, holding promise for he development of highly responsive gas sensors&#xD;for portable devices, especially for ethanol breath testing.

More Accepted manuscripts

Open access

Mathijs Mientjes et al 2024 Nanotechnology

Marlen Alexis Gonzalez-Reyna et al 2024 Nanotechnology

For the first time, this study shows the nanoarchitectonic process to obtain an acetogenin-enriched nanosystem (AuNPs-Ac) using an aqueous extract from Annona cherimola Mill (ACM) composed of gold nanoparticles embedded in an organic matrix that acts as stabilizing agent and presents anti-inflammatory activity and cytotoxical effect against HepG2 cell line, promoting apoptosis. The synthesis of AuNPs-Ac was confirmed by X-ray diffraction analysis, showing metallic gold as the only phase, and the scanning transmission microscope showed an organic cap covering the AuNPs-Ac. Fourier-transformed infrared suggests that the organic cap comprises a combination of different annonaceous acetogenins, alkaloids, and phenols by the presence of bands corresponding to aromatic rings and hydroxyl groups. High-Performance Liquid Chromatography has demonstrated the presence of annonacin, a potent acetogenin, in the extract of ACM. An in vitro anti-inflammatory activity of the extract of ACM and the AuNPs-Ac was performed using the albumin denaturation method, showing a nonlinear response, which is better than sodium diclofenac salt in a wide range of concentrations that goes from 200 to 400 µg/mL with both samples. The viability assay was studied using trypan blue, treating IMR90 and HepG2 at different concentrations of AuNPs-Ac. The results defined a median lethal dose of 800 µg/mL against HepG2 through apoptosis according to the ratio of caspase-cleaved 9/alpha-tubulin evaluated. It was also demonstrated that the nanosystem presents a higher cytotoxic effect on the HepG2 cell line than in IMR90, suggesting a targeted mechanism. In addition, the nanosystem performs better than using only the extract of ACM in the anti-inflammatory or antiproliferative test, attributed to their higher surface area.

Ibukun Israel Olaniyan et al 2024 Nanotechnology

The realization of perovskite oxide nanostructures with controlled shape and dimensions remains a challenge. Here, we investigate the use of helium and neon focused ion beam (FIB) milling in an ion microscope to fabricate BaTiO3 nanopillars of sub-500 nm diameter from BaTiO3 (001) single crystals. Irradiation of BaTiO3 with He ions induces the formation of nanobubbles inside the material eventually leading to surface swelling and blistering. Ne FIB is shown to be suitable for milling without inducing surface swelling. The resulting defect-free single crystal nanostructures are enveloped by a neon-rich amorphous and a point defect-rich crystalline layers both on top and lateral sides. The amorphous shell can be selectively removed by dipping the nanostructures in diluted HF. The geometry and beam-induced damage of the milled nanostructures depend strongly on the patterning parameters and can be well controlled. Ne ion milling is shown to be an effective method to rapidly prototype BaTiO3 crystalline nanostructures.

Yucheng Hu et al 2024 Nanotechnology 35 295702

Cathodoluminescence and electron backscatter diffraction have been applied to exactly the same grain boundaries (GBs) in a Cu(In,Ga)S 2 solar absorber in order to investigate the influence of microstructure on the radiative recombination behaviour at the GBs. Two different types of GB with different microstructure were analysed in detail: random high angle grain boundaries (RHAGBs) and Σ3 GBs. We found that the radiative recombination at all RHAGBs was inhibited to some extent, whereas at Σ3 GBs three different observations were made: unchanged, hindered, or promoted radiative recombination. These distinct behaviours may be linked to atomic-scale grain boundary structural differences. The majority of GBs also exhibited a small spectral shift of about ±10 meV relative to the local grain interior (GI) and a few of them showed spectral shifts of up to ±40 meV. Red and blue shifts were observed with roughly equal frequency.

Wei Cheat Lee et al 2024 Nanotechnology 35 295301

A hierarchical sea urchin-like hybrid metal oxide nanostructure of ZnO nanorods deposited on TiO 2 porous hollow hemispheres with a thin zinc titanate interface layer is specifically designed and synthesized to form a combined type I straddling and type II staggered junctions. The HHSs, synthesized by electrospinning, facilitate light trapping and scattering. The ZnO nanorods offer a large surface area for improved surface oxidation kinetics. The interface layer of zinc titanate (ZnTiO 3 ) between the TiO 2 HHSs and ZnO nanorods regulates the charge separation in a closely coupled hierarchy structure of ZnO/ZnTiO 3 /TiO 2 . The synergistic effects of the improved light trapping, charge separation, and fast surface reaction kinetics result in a superior photoconversion efficiency of 1.07% for the photoelectrochemical water splitting with an outstanding photocurrent density of 2.8 mA cm −2 at 1.23 V versus RHE.

Rahnuma Rahman et al 2024 Nanotechnology

Stochastic neurons are efficient hardware accelerators for solving a large variety of combinatorial optimization problems. "Binary" stochastic neurons (BSN) are those whose states fluctuate randomly between two levels +1 and -1, with the probability of being in either level determined by an external bias. "Analog" stochastic neurons (ASNs), in contrast, can assume any state between the two levels randomly (hence "analog") and can perform analog signal processing. They may be leveraged for such tasks as temporal sequence learning, processing and prediction. Both BSNs and ASNs can be used to build efficient and scalable neural networks. Both can be implemented with low (potential energy) barrier nanomagnets (LBMs) whose random magnetization orientations encode the binary or analog state variables. The difference between them is that the potential energy barrier in a BSN LBM, albeit low, is much higher than that in an ASN LBM. As a result, a BSN LBM has a clear double well potential profile, which makes its magnetization orientation assume one of two orientations at any time, resulting in the binary behavior. ASN nanomagnets, on the other hand, hardly have any energy barrier at all and hence lack the double well feature. That makes their magnetizations fluctuate in an analog fashion. Hence, one can reconfigure an ASN to a BSN, and vice-versa, by simply raising and lowering the energy barrier. If the LBM is magnetostrictive, then this can be done with local (electrically generated) strain. Such a reconfiguration capability heralds a powerful field programmable architecture for a p-computer whereby hardware for very different functionalities such as combinatorial optimization and temporal sequence learning can be integrated in the same substrate in the same processing run. This is somewhat reminiscent of heterogeneous integration, except this is integration of functionalities or computational fabrics rather than components. The energy cost of reconfiguration is miniscule. There are also other applications of strain mediated barrier control that do not involve reconfiguring a BSN to an ASN or vice versa, e.g., adaptive annealing in energy minimization computing (Boltzmann or Ising machines), emulating memory hierarchy in a dynamically reconfigurable fashion, and control over belief uncertainty in analog stochastic neurons. Here, we present a study of strain engineered barrier control in unconventional computing.

Irene Ayuso-Perez et al 2024 Nanotechnology

Semiconductor nanowires (NWs) are promising candidates for use in electronic and optoelectronic applications, offering numerous advantages over their thin film counterparts. Their performance relies heavily on the quality of the contacts to the NW, which should exhibit ohmic behavior with low resistance and should be formed in a reproducible manner. In the case of heterostructure NWs for high-mobility applications that host a two-dimensional electron gas (2DEG), ohmic contacts are particularly challenging to implement since the NW core constituting the conduction channel is away from the NW surface. We investigated contact formation to modulation-doped GaAs/(Al,Ga)As core/shell NWs using scanning transmission electron microscopy (STEM), energy dispersive X-ray spectroscopy (EDX) and electron tomography (ET) to correlate microstructure, diffusion profile and chemical composition of the NW contact region with the current-voltage (I-V) characteristics of the contacted NWs. Our results illustrate how diffusion, alloying and phase formation processes essential to the effective formation of ohmic contacts are more intricate than in planar layers, leading to reproducibility challenges even when the processing conditions are the same. We demonstrate that the NW geometry plays a crucial role in the creation of good contacts. Both ohmic and rectifying contacts were obtained under nominally identical processing conditions. Furthermore, the presence of Ge in the NW core, in the absence of Au and Ni, was found as the key factor leading to ohmic contacts. The analysis contributes to the current understanding of ohmic contact formation to heterostructure core/shell NWs offering pathways to enhance the reproducibility and further optimization of such NW contacts.&#xD;

Robert Daly et al 2024 Nanotechnology 35 285704

Surface enhanced Raman spectroscopy (SERS) is a powerful analytical technique that has found application in the trace detection of a wide range of contaminants. In this paper, we report on the fabrication of 2D silver nanodendrites, on silicon chips, synthesized by electrochemical reduction of AgNO 3 at microelectrodes. The formation of nanodendrites is tentatively explained in terms of electromigration and diffusion of silver ions. Electrochemical characterization suggests that the nanodendrites do not stay electrically connected to the microelectrode. The substrates show SERS activity with an enhancement factor on the order of 10 6 . Density functional theory simulations were carried out to investigate the suitability of the fabricated substrate for pesticide monitoring. These substrates can be functionalized with cyclodextrin macro molecules to help with the detection of molecules with low affinity with silver surfaces. A proof of concept is demonstrated with the detection of the herbicide 2-methyl-4-chlorophenoxyacetic acid (MCPA).

Philipp Hönicke et al 2024 Nanotechnology 35 285702

Spatially resolved x-ray fluorescence (XRF) based analysis employing incident beam sizes in the low micrometer range ( μ XRF) is widely used to study lateral composition changes of various types of microstructured samples. However, up to now the quantitative analysis of such experimental datasets could only be realized employing adequate calibration or reference specimen. In this work, we extent the applicability of the so-called reference-free XRF approach to enable reference-free μ XRF analysis. Here, no calibration specimen are needed in order to derive a quantitative and position sensitive composition of the sample of interest. The necessary instrumental steps to realize reference-free μ XRF are explained and a validation of ref.-free μ XRF against ref.-free standard XRF is performed employing laterally homogeneous samples. Finally, an application example from semiconductor research is shown, where the lateral sample features require the usage of ref.-free μ XRF for quantitative analysis.

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• 1990-present Nanotechnology doi: 10.1088/issn.0957-4484 Online ISSN: 1361-6528 Print ISSN: 0957-4484

EDITORIAL article

This article is part of the research topic.

Opportunities and Challenges for Nanotechnology in Sustainable Agri-Food Production

Editorial: Opportunities and Challenges for Nanotechnology in Sustainable Agri-Food Production Provisionally Accepted

• 1 Amity University, India
• 2 Natural and Medical Sciences Research Center, University of Nizwa, Oman
• 3 Chungnam National University, Republic of Korea

The final, formatted version of the article will be published soon.

The United Nations has given 17 Sustainable Development Goals (SDG), and Goal 2 is about creating a world free of hunger by 2030. The rising population and climate changes may aggravate the problems of malnutrition, and burden the existing food production and distribution (Fróna et al. 2019). So, agricultural resources must be used wisely to increase crop production and provide sustainable, quality food to the global population. There is an immediate need to develop novel tools to assist current agriculture and food industry practices in achieving sustainability. The recent development in science and technologies based on nanomaterials has created a lot of interest and expectation in solving the existing problems in various fields. Nanotechnology deals with manipulating and using materials fabricated in nanometre regimes for their novel properties due to their small size. The application of engineered nanomaterials (ENM) has been researched for their role in futuristic agriculture and food production. The recent development of precision farming/site-specific crop management can benefit from nano-based technologies (Otari et al. 2024, Pudake et al. 2019). With the help of recent emerging tools such as artificial intelligence, efficient and sensitive nano biosensors can bring a new uprising in crop production by providing highresolution and real-time tools to monitor spatial and temporal deviations in their health.Another aspect of precision farming is the targeted release or slow release of agri-inputs in the current cropping system to achieve its high-use efficiency. The emerging field of plant nanobionics is developing plants with novel supplemented functions for their better performance under adverse conditions or to play a new role in agriculture (Lew et al. 2020).Nanotechnology has shown great potential for changing the food packaging industry for sustainability. The characteristics like barrier properties, antimicrobial packaging, and food quality sensing are some of the aspects being explored with the help of nanoscience. Active and intelligent packaging is the future of the food industry, and nano-enabled packaging materials have the potential to increase the shelf life of food (de Sousa et al. 2023). Another approach of ENM application in food improvement is as an ingredient or extended-release or preservation of nutraceuticals. As an ingredient, the nanomaterials can be used as food anticaking agents, nano-additives in the form nutraceuticals, and other similar applications in processed food (Wasilewska et al. 2023).So, nanomaterials' potential application in the agri-food industry makes them a resourceful tool for the future. However, its successful application for sustainable agriculture will require intensive research to overcome the unaddressed challenges. This 'Research Topic' highlights the latest advances in nanotechnology for increasing plant production and sustainable use of agri-inputs. It also aims to cover research on various aspects of nanomaterials in the food industry.Developing eco-friendly methodologies in nanomaterial synthesis is important in deciding its suitability in biological applications. Recently, several inorganic nanoparticles with definite chemical composition, size, and morphology have been synthesized by different bioorganisms or their extract/by-products. These bioinspired nanomaterials have shown promising results in many cutting-edge biological areas (Karunakaran et al. 2023). Deepa et al. demonstrated the biogenic synthesis of silver nanoparticles from potato peels as a promising strategy for producing antimicrobial agents. The authors found that an extract of potato peels can be used as a cheap, productive, and readily available source of biomolecules that are required for Ag precursor reduction and biosynthesis of NP. The disc diffusion technique was utilized to check the antimicrobial activity of AgNPs against both -Grampositive bacteria, Staphylococcus aureus (ATCC 25923), and Gram-negative bacteria, Escherichia coli (ATCC 25922). The results have indicated that the antibacterial properties of AgNPs could be used in the food industry to avoid microbial contamination. It was evaluated for potential in the purification of industrial wastewater, and the results confirmed the excellent antibacterial ability of AgNPs. The results have the potential to add value to the farm waste and, therefore, can be an essential finding for sustainability in the agriculture and food industry. In continuation of this study, Flores-Contreras et al. have summarized the opportunities for the biosynthesis of nanomaterials by agricultural waste and its application as antimicrobials for food preservation. They have emphasized that this method of synthesis of ENMs is a sustainable and innovative alternative in the circular economy of recycling biowaste. This review provides evidence that summarises the usage of various agri-waste as a source for organic NPs as the top-down approach or assisting the synthesis of inorganic NPs by a bottom-up approach. These NPs have shown remarkable antimicrobial and antioxidant activities and can be used for manufacturing nanocomposites that are suitable for food preservation. This paper has also discussed the molecular mechanism of nanoparticles' antimicrobial action; like the production of reactive oxygen species (ROS), hindrance in metabolic pathways, inhibition of DNA replication, or cell wall/membrane damage are the mechanisms for NP toxicity. This is also true in the case of dose-dependent toxicity in humans, which is a main cause of concern for the safety of nanoparticles in the food industry.Authors suggest that extensive studies are needed to unravel the effects of NPs on human health.Nanobiosensor deployment for pathogen detection in agriculture has become one of the fastest-growing nanotechnology applications in recent days (Ray et al. 2023). Nanobiosensors have physical transducer probes modified with NPs for a biological molecule or complete cell detection. An ideal biosensor should be economical, sensitive, easily portable, minimal or non-invasive, and rapid with real-time monitoring. Virk et al. have presented a perspective review emphasizing the role of nano biosensors in controlling plant diseases. The review discusses the types of nano biosensors, their application in disease management, and pesticide/toxin detection. Along with the summary of recent advancements in the field of nano biosensors in the agricultural and food industry, the challenges and the prospects are also highlighted to achieve the large-scale application. The major limitations of nano-based sensing devices are high cost and product sensitivity. Other limitations of biosensors are the energy requirement and their durability in harsh environmental conditions. So, developing energy-efficient and stable sensors is the future direction of research.As mentioned earlier, modern-day agriculture relies on various agrochemicals to enhance crop production by providing nutrients and controlling crop pests. However, their indiscriminate use has currently caused several threats to human and environmental health.Dangerous consequences of this overexploitation on ecological balance and conservation of soil biodiversity are major focus areas for sustainable crop production in many countries (Andrade et al. 2021). The solution to this problem is using nanoscale agrochemicals such as nanofertilizers and nanopesticides that are more sustainable and efficient.

Keywords: nanomaterial, Agriculture, susatinability, nanosensors, biosynthesis, MOF

Received: 19 Apr 2024; Accepted: 01 May 2024.

Copyright: © 2024 Pudake, Mohanta and Mahato. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY) . The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Ramesh N. Pudake, Amity University, Noida, India

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A Peek Inside the Brains of ‘Super-Agers’

New research explores why some octogenarians have exceptional memories.

By Dana G. Smith

When it comes to aging, we tend to assume that cognition gets worse as we get older. Our thoughts may slow down or become confused, or we may start to forget things, like the name of our high school English teacher or what we meant to buy at the grocery store.

But that’s not the case for everyone.

For a little over a decade, scientists have been studying a subset of people they call “super-agers.” These individuals are age 80 and up, but they have the memory ability of a person 20 to 30 years younger.

Most research on aging and memory focuses on the other side of the equation — people who develop dementia in their later years. But, “if we’re constantly talking about what’s going wrong in aging, it’s not capturing the full spectrum of what’s happening in the older adult population,” said Emily Rogalski, a professor of neurology at the University of Chicago, who published one of the first studies on super-agers in 2012.

A paper published Monday in the Journal of Neuroscience helps shed light on what’s so special about the brains of super-agers. The biggest takeaway, in combination with a companion study that came out last year on the same group of individuals, is that their brains have less atrophy than their peers’ do.

The research was conducted on 119 octogenarians from Spain: 64 super-agers and 55 older adults with normal memory abilities for their age. The participants completed multiple tests assessing their memory, motor and verbal skills; underwent brain scans and blood draws; and answered questions about their lifestyle and behaviors.

The scientists found that the super-agers had more volume in areas of the brain important for memory, most notably the hippocampus and entorhinal cortex. They also had better preserved connectivity between regions in the front of the brain that are involved in cognition. Both the super-agers and the control group showed minimal signs of Alzheimer’s disease in their brains.

“By having two groups that have low levels of Alzheimer’s markers, but striking cognitive differences and striking differences in their brain, then we’re really speaking to a resistance to age-related decline,” said Dr. Bryan Strange, a professor of clinical neuroscience at the Polytechnic University of Madrid, who led the studies.

These findings are backed up by Dr. Rogalski’s research , initially conducted when she was at Northwestern University, which showed that super-agers’ brains looked more like 50- or 60-year-olds’ brains than their 80-year-old peers. When followed over several years, the super-agers’ brains atrophied at a slower rate than average.

No precise numbers exist on how many super-agers there are among us, but Dr. Rogalski said they’re “relatively rare,” noting that “far less than 10 percent” of the people she sees end up meeting the criteria.

But when you meet a super-ager, you know it, Dr. Strange said. “They are really quite energetic people, you can see. Motivated, on the ball, elderly individuals.”

Experts don’t know how someone becomes a super-ager, though there were a few differences in health and lifestyle behaviors between the two groups in the Spanish study. Most notably, the super-agers had slightly better physical health, both in terms of blood pressure and glucose metabolism, and they performed better on a test of mobility . The super-agers didn’t report doing more exercise at their current age than the typical older adults, but they were more active in middle age. They also reported better mental health .

But overall, Dr. Strange said, there were a lot of similarities between the super-agers and the regular agers. “There are a lot of things that are not particularly striking about them,” he said. And, he added, “we see some surprising omissions, things that you would expect to be associated with super-agers that weren’t really there.” For example, there were no differences between the groups in terms of their diets, the amount of sleep they got, their professional backgrounds or their alcohol and tobacco use.

The behaviors of some of the Chicago super-agers were similarly a surprise. Some exercised regularly, but some never had; some stuck to a Mediterranean diet, others subsisted off TV dinners; and a few of them still smoked cigarettes. However, one consistency among the group was that they tended to have strong social relationships , Dr. Rogalski said.

“In an ideal world, you’d find out that, like, all the super-agers, you know, ate six tomatoes every day and that was the key,” said Tessa Harrison, an assistant project scientist at the University of California, Berkeley, who collaborated with Dr. Rogalski on the first Chicago super-ager study.

Instead, Dr. Harrison continued, super-agers probably have “some sort of lucky predisposition or some resistance mechanism in the brain that’s on the molecular level that we don’t understand yet,” possibly related to their genes.

While there isn’t a recipe for becoming a super-ager, scientists do know that, in general , eating healthily, staying physically active, getting enough sleep and maintaining social connections are important for healthy brain aging.

Dana G. Smith is a Times reporter covering personal health, particularly aging and brain health. More about Dana G. Smith

A Guide to Aging Well

Looking to grow old gracefully we can help..

The “car key conversation,” when it’s time for an aging driver to hit the brakes, can be painful for families to navigate . Experts say there are ways to have it with empathy and care.

Calorie restriction and intermittent fasting both increase longevity in animals, aging experts say. Here’s what that means for you .

Researchers are investigating how our biology changes as we grow older — and whether there are ways to stop it .

You need more than strength to age well — you also need power. Here’s how to measure how much power you have  and here’s how to increase yours .

Ignore the hyperbaric chambers and infrared light: These are the evidence-backed secrets to aging well .

Your body’s need for fuel shifts as you get older. Your eating habits should shift , too.

People who think positively about getting older often live longer, healthier lives. These tips can help you reconsider your perspective .

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Voters’ views of Trump and Biden differ sharply by religion

The U.S. electorate continues to be sharply divided along religious lines.

The latest Pew Research Center survey finds that most registered voters who are White Christians would vote for Republican Donald Trump over Democrat Joe Biden if the 2024 presidential election were held today. More than half of White Christians think Trump was a “great” or “good” president and don’t think he broke the law in an effort to change the outcome of the 2020 election.

In stark contrast, most registered voters who are Black Protestants or religious “nones” – those who self-identify as atheists, agnostics or “nothing in particular” – would vote for Biden over Trump. Large numbers in these groups also say Trump was a “terrible” president and that he broke the law trying to overturn the 2020 election results.

Pew Research Center conducted this analysis to highlight religious differences in U.S. voters’ views about the 2024 presidential election. For this analysis, we surveyed 8,709 adults – including 7,166 registered voters – from April 8 to 14, 2024. Everyone who took part in this survey is a member of the Center’s American Trends Panel (ATP), an online survey panel that is recruited through national, random sampling of residential addresses. This way nearly all U.S. adults have a chance of selection. The survey is weighted to be representative of the U.S. adult population by gender, race, ethnicity, partisan affiliation, education and other categories.  Read more about the ATP’s methodology .

Here are the  questions used for this report , along with responses, and the  survey methodology . Here are details about sample sizes and margins of error for groups analyzed in this report.

Religion and the 2024 presidential election

While most White Christian voters say they would vote for Trump over Biden if the election were held today, there are some differences by religious tradition. Trump draws support from:  

• 81% of White evangelical Protestant voters
• 61% of White Catholics
• 57% of White Protestants who are not evangelical

By contrast, 77% of Black Protestant voters say they would vote for Biden over Trump. Most religious “nones” also say this, including:

• 87% of atheist voters
• 82% of agnostics
• 57% of those whose religion is “nothing in particular” 

These presidential preferences reflect the partisan leanings of U.S. religious groups . White Christians have been trending in a Republican direction for quite some time, while Black Protestants and religious “nones” have long been strongly Democratic.

The Center’s new survey includes responses from Jews, Muslims, Buddhists, Hindus and people from many other religious backgrounds, as well as adherents of smaller Christian groups like Hispanic Protestants and members of the Church of Jesus Christ of Latter-day Saints (widely known as Mormons). However, the survey does not include enough respondents from these smaller religious categories to be able to report on them separately.

Church attendance and voting preferences in 2024

Among Christians, support for Trump is somewhat higher among regular church attenders than non-churchgoers. Overall, 62% of Christian voters who say they go to church at least once or twice a month support Trump over Biden. Among Christians who go to church less often, 55% would vote for Trump if the election were today.

Among White evangelical Protestant voters, 84% of regular churchgoers say they would vote for Trump, compared with 77% of White evangelicals who don’t go to church regularly.

White nonevangelical Protestants are the only Christian group in which support for Trump is significantly stronger among nonattenders than among regular churchgoers.

Voters’ views of Biden and Trump as presidents

About three-quarters of White evangelical Protestant voters say Trump was a “great” (37%) or “good” (37%) president. Roughly half of White Catholics and White nonevangelical Protestants share this view.

When it comes to Biden, atheists and Black Protestants rate the current president’s performance most favorably. Roughly half of voters in each of these groups say Biden is a great or good president.

Overall, Trump gets higher marks on these questions than Biden. This is because Trump supporters are more inclined to say he was a great or good president than Biden supporters are to say the same about him.

Views of whether Trump broke the law in effort to change 2020 election outcome

People in the religious groups that are most supportive of Biden tend to think Trump broke the law in an effort to change the outcome of the 2020 election. Most atheists (83%) say this, as do 70% of Black Protestants and 63% of agnostics.

By contrast, just 16% of White evangelical Protestants say Trump broke the law trying to change the 2020 election outcome. Another 15% of White evangelicals say they think Trump did something wrong but did not break the law, while the largest share by far (47%) say Trump did nothing wrong.

Note: Here are the  questions used for this report , along with responses, and the  survey methodology .

• Donald Trump
• Election 2024
• Religion & Politics

Gregory A. Smith is an associate director of research at Pew Research Center .

In Tight Presidential Race, Voters Are Broadly Critical of Both Biden and Trump

Changing partisan coalitions in a politically divided nation, about 1 in 4 americans have unfavorable views of both biden and trump, 2024 presidential primary season was one of the shortest in the modern political era, americans more upbeat on the economy; biden’s job rating remains very low, most popular.

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Virginia Tech graduate, May Mobility research and policy leader to speak at D.C. area commencement

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Nicole DePuis, a 2018 graduate of Virginia Tech's School of Public and International Affairs, will deliver this spring’s greater Washington, D.C., metro area commencement address to more than 130 graduates and their friends and family on Sunday, May 12.

DePuis currently serves as the policy and advocacy lead for May Mobility, an autonomous vehicle company that focuses on accessible and shared rides. Over the course of her career, her work and research has focused on the role technology plays in various facets of life, including mobility and travel behavior, professional and industrial shifts, and policy-making and governance tendencies.

Her areas of expertise and interest include automation and autonomous vehicles, connected infrastructure, transportation, telecommunications, smart city applications, artificial intelligence, and machine learning. She has published articles in both peer-reviewed and policy-oriented outlets and authored numerous research reports on these and other topics.

“We are delighted that DePuis will join us to share her educational and professional journey with our graduating students as a testament to there being no one 'right' path and remind them that staying open to a wide variety of possibilities will result in a rich and fulfilling career,” said Barbara Hoopes, interim associate dean of the Graduate School in the Washington, D.C., area.

This year’s graduating class will include 58 students in the D.C. area affiliated with the Virginia Tech Innovation Campus who will earn master's degrees in computer science and computer engineering. 

Student speakers will include Patricia Grace '22, who will receive a master’s degree in urban and regional planning with certificates in natural resources and economic development, and Cameron Simmons '21, who will receive his dual MBA-Master of Information Technology.

The D.C. area ceremony will begin at 1 p.m. at George Mason University’s Center for the Arts in Fairfax and will be livestreamed and available to watch on demand. More information and details on the D.C. area commencement ceremony can be found at nvc.vt.edu/commencement .

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What marijuana reclassification means for the United States

The U.S. Drug Enforcement Administration will move to reclassify marijuana as a less dangerous drug, a historic shift to generations of American drug policy that could have wide ripple effects across the country.

FILE - Marijuana plants are seen at a secured growing facility in Washington County, N.Y., May 12, 2023. The U.S. Drug Enforcement Administration will move to reclassify marijuana as a less dangerous drug, a historic shift to generations of American drug policy that could have wide ripple effects across the country. (AP Photo/Hans Pennink, File)

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Budtender Rey Cruz weighs cannabis for a customer at the Marijuana Paradise on Friday, April 19, 2024, in Portland, Ore. (AP Photo/Jenny Kane)

Cloud 9 Cannabis employee Beau McQueen, right, helps a customer, Saturday, April 13, 2024, in Arlington, Wash. The shop is one of the first dispensaries to open under the Washington Liquor and Cannabis Board’s social equity program, established in efforts to remedy some of the disproportionate effects marijuana prohibition had on communities of color. (AP Photo/Lindsey Wasson)

WASHINGTON (AP) — The U.S. Drug Enforcement Administration is moving toward reclassifying marijuana as a less dangerous drug. The Justice Department proposal would recognize the medical uses of cannabis , but wouldn’t legalize it for recreational use.

The proposal would move marijuana from the “Schedule I” group to the less tightly regulated “Schedule III.”

So what does that mean, and what are the implications?

WHAT HAS ACTUALLY CHANGED? WHAT HAPPENS NEXT?

Technically, nothing yet. The proposal must be reviewed by the White House Office of Management and Budget, and then undergo a public-comment period and review from an administrative judge, a potentially lengthy process.

Still, the switch is considered “paradigm-shifting, and it’s very exciting,” Vince Sliwoski, a Portland, Oregon-based cannabis and psychedelics attorney who runs well-known legal blogs on those topics, told The Associated Press when the federal Health and Human Services Department recommended the change.

“I can’t emphasize enough how big of news it is,” he said.

It came after President Joe Biden asked both HHS and the attorney general, who oversees the DEA, last year to review how marijuana was classified. Schedule I put it on par, legally, with heroin, LSD, quaaludes and ecstasy, among others.

Biden, a Democrat, supports legalizing medical marijuana for use “where appropriate, consistent with medical and scientific evidence,” White House press secretary Karine Jean-Pierre said Thursday. “That is why it is important for this independent review to go through.”

Cloud 9 Cannabis employee Beau McQueen, right, helps a customer, Saturday, April 13, 2024, in Arlington, Wash. (AP Photo/Lindsey Wasson)

IF MARIJUANA GETS RECLASSIFIED, WOULD IT LEGALIZE RECREATIONAL CANNABIS NATIONWIDE?

Ap audio: what marijuana reclassification means for the united states.

AP correspondent Haya Panjwani reports on a proposal for the federal government to reclassify marijuana in what would be a historic shift that could have wide ripple effects across the country.

No. Schedule III drugs — which include ketamine, anabolic steroids and some acetaminophen-codeine combinations — are still controlled substances.

They’re subject to various rules that allow for some medical uses, and for federal criminal prosecution of anyone who traffics in the drugs without permission.

No changes are expected to the medical marijuana programs now licensed in 38 states or the legal recreational cannabis markets in 23 states, but it’s unlikely they would meet the federal production, record-keeping, prescribing and other requirements for Schedule III drugs.

There haven’t been many federal prosecutions for simply possessing marijuana in recent years, even under marijuana’s current Schedule I status, but the reclassification wouldn’t have an immediate impact on people already in the criminal justice system.

“Put simple, this move from Schedule I to Schedule III is not getting people out of jail,” said David Culver, senior vice president of public affairs at the U.S. Cannabis Council.

But rescheduling in itself would have some impact, particularly on research and marijuana business taxes.

WHAT WOULD THIS MEAN FOR RESEARCH?

Because marijuana is on Schedule I, it’s been very difficult to conduct authorized clinical studies that involve administering the drug. That has created something of a Catch-22: calls for more research, but barriers to doing it. (Scientists sometimes rely instead on people’s own reports of their marijuana use.)

Marijuana plants are seen at a secured growing facility in Washington County, N.Y., May 12, 2023. (AP Photo/Hans Pennink, File)

Schedule III drugs are easier to study, though the reclassification wouldn’t immediately reverse all barriers to study.

“It’s going to be really confusing for a long time,” said Ziva Cooper, director of the University of California, Los Angeles Center for Cannabis and Cannabinoids. “When the dust has settled, I don’t know how many years from now, research will be easier.”

Among the unknowns: whether researchers will be able to study marijuana from state-licensed dispensaries and how the federal Food and Drug Administration might oversee that.

Some researchers are optimistic.

“Reducing the schedule to schedule 3 will open up the door for us to be able to conduct research with human subjects with cannabis,” said Susan Ferguson, director of University of Washington’s Addictions, Drug & Alcohol Institute in Seattle.

WHAT ABOUT TAXES (AND BANKING)?

Under the federal tax code, businesses involved in “trafficking” in marijuana or any other Schedule I or II drug can’t deduct rent, payroll or various other expenses that other businesses can write off. (Yes, at least some cannabis businesses, particularly state-licensed ones, do pay taxes to the federal government, despite its prohibition on marijuana.) Industry groups say the tax rate often ends up at 70% or more.

The deduction rule doesn’t apply to Schedule III drugs, so the proposed change would cut cannabis companies’ taxes substantially.

They say it would treat them like other industries and help them compete against illegal competitors that are frustrating licensees and officials in places such as New York .

“You’re going to make these state-legal programs stronger,” says Adam Goers, of The Cannabist Company, formerly Columbia Care. He co-chairs a coalition of corporate and other players that’s pushing for rescheduling.

It could also mean more cannabis promotion and advertising if those costs could be deducted, according to Beau Kilmer, co-director of the RAND Drug Policy Center.

Rescheduling wouldn’t directly affect another marijuana business problem: difficulty accessing banks, particularly for loans, because the federally regulated institutions are wary of the drug’s legal status. The industry has been looking instead to a measure called the SAFE Banking Act . It has repeatedly passed the House but stalled in the Senate.

ARE THERE CRITICS? WHAT DO THEY SAY?

Indeed, there are, including the national anti-legalization group Smart Approaches to Marijuana. President Kevin Sabet, a former Obama administration drug policy official, said the HHS recommendation “flies in the face of science, reeks of politics” and gives a regrettable nod to an industry “desperately looking for legitimacy.”

Some legalization advocates say rescheduling weed is too incremental. They want to keep the focus on removing it completely from the controlled substances list, which doesn’t include such items as alcohol or tobacco (they’re regulated, but that’s not the same).

Paul Armentano, the deputy director of the National Organization for the Reform of Marijuana Laws, said that simply reclassifying marijuana would be “perpetuating the existing divide between state and federal marijuana policies.” Kaliko Castille, a past president of the Minority Cannabis Business Association, said rescheduling just “re-brands prohibition,” rather than giving an all-clear to state licensees and putting a definitive close to decades of arrests that disproportionately pulled in people of color.

“Schedule III is going to leave it in this kind of amorphous, mucky middle where people are not going to understand the danger of it still being federally illegal,” he said.

This story has been corrected to show that Kaliko Castille is a past president, not president, of the Minority Cannabis Business Association and that Columbia Care is now The Cannabist Company.

___ Peltz reported from New York. Associated Press writers Colleen Long in Washington and Carla K. Johnson in Seattle contributed to this report.