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.
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Nanotechnology encompasses the understanding of the fundamental physics, chemistry, biology and technology of nanometre-scale objects.
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Yi-Teng Huang et al 2021 Nanotechnology 32 132004
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.
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.
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.
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 MoS2 transferred using PDMS. We show that a UV-ozone pre-cleaning of the PDMS surface before exfoliation significantly reduces organic residues on transferred MoS2 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.
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.
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.
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.
Eleonora Bonaventura et al 2024 Nanotechnology 35 23LT01
Heterostacks formed by combining two-dimensional materials show novel properties which are of great interest for new applications in electronics, photonics and even twistronics, the new emerging field born after the outstanding discoveries on twisted graphene. Here, we report the direct growth of tin nanosheets at the two-dimensional limit via molecular beam epitaxy on chemical vapor deposited graphene on Al2O3(0001). The mutual interaction between the tin nanosheets and graphene is evidenced by structural and chemical investigations. On the one hand, Raman spectroscopy indicates that graphene undergoes compressive strain after the tin growth, while no charge transfer is observed. On the other hand, chemical analysis shows that tin nanosheets interaction with sapphire is mediated by graphene avoiding the tin oxidation occurring in the direct growth on this substrate. Remarkably, optical measurements show that the absorption of tin nanosheets exhibits a graphene-like behavior with a strong absorption in the ultraviolet photon energy range, therein resulting in a different optical response compared to tin nanosheets on bare sapphire. The optical properties of ultra-thin tin films therefore represent an open and flexible playground for the absorption of light in a broad range of the electromagnetic spectrum and technologically relevant applications for photon harvesting and sensors.
Xiuyun Zhao and Vesa-Pekka Lehto 2021 Nanotechnology 32 042002
Batteries are commonly considered one of the key technologies to reduce carbon dioxide emissions caused by the transport, power, and industry sectors. We need to remember that not only the production of energy needs to be realized sustainably, but also the technologies for energy storage need to follow the green guidelines to reduce the emission of greenhouse gases effectively. To reach the sustainability goals, we have to make batteries with the performances beyond their present capabilities concerning their lifetime, reliability, and safety. To be commercially viable, the technologies, materials, and chemicals utilized in batteries must support scalability that enables cost-effective large-scale production.
As lithium-ion battery (LIB) is still the prevailing technology of the rechargeable batteries for the next ten years, the most practical approach to obtain batteries with better performance is to develop the chemistry and materials utilized in LIBs—especially in terms of safety and commercialization. To this end, silicon is the most promising candidate to obtain ultra-high performance on the anode side of the cell as silicon gives the highest theoretical capacity of the anode exceeding ten times the one of graphite. By balancing the other components in the cell, it is realistic to increase the overall capacity of the battery by 100%–200%. However, the exploitation of silicon in LIBs is anything else than a simple task due to the severe material-related challenges caused by lithiation/delithiation during battery cycling. The present review makes a comprehensive overview of the latest studies focusing on the utilization of nanosized silicon as the anode material in LIBs.
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Thinh-Vuong Duc et al 2024 Nanotechnology 35 285705
Transparent heaters (THs) find widespread application in various indoor and outdoor settings, such as LCD panels and motorcycle helmet visors. Among the materials used for efficient TH performance, the AgNW network stands out due to its high conductivity, substantial transmittance, and minimal solution requirement. Extensive research has been directed towards enhancing AgNW characteristics, focusing on smaller diameters and longer wires. In TH applications, the primary considerations include a rapid response and elevated temperature. Consequently, this research delves into investigating the impact of parameters like diameter, length, and density on random AgNW networks under varying applied voltages. The finite element method is employed for analyzing temperature changes in response to voltage application, particularly in scenarios involving small-scale setups with high-density and high-percolation AgNW networks. The results reveal a significant increase in the thermal transition rate, ranging from 28% to 36%, with varying densities in the random network. Within the same density, the AgNW network with larger diameters and lengths demonstrates the highest temperatures, aligning with previous calculations. Furthermore, a trade-off exists between optical properties in smaller diameters and electrical properties in larger diameters within a relatively narrow temperature range.
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 AgNO3 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 106. 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).
Yang Li et al 2024 Nanotechnology 35 285703
Nitrogen dioxide (NO2) is a major pollutant that poses significant risks to sustainable human life. As a result, a growing focus has been placed on the development of highly selective and sensitive gas sensors for NO2. Traditional cutting-edge non-organic NO2 gas detectors often necessitate stringent production conditions and potentially harmful materials, which are not environmentally friendly, and these shortcomings have limited their widespread practical use. To overcome these challenges, we synthesized self-assembled peptide nanotubes (SPNTs) through a molecular self-assembly process. The SPNTs were then combined with SnO2 in varying proportions to construct NO2 gas sensors. The design of this sensor ensured efficient electron transfer and leverage the extensive surface area of the SPNTs for enhanced gas adsorption and the effective dispersion of SnO2 nanoparticles. Notably, the performance of the sensor, including its sensitivity, response time, and recovery rate, along with a lower detection threshold, could be finely tuned by varying the SPNTs content. This approach illustrated the potential of bioinspired methodologies, using peptide self-assemblies, to develop integrated sensors for pollutant detection, providing a significant development in environmentally conscious sensor technology.
Sheraz Ahmad et al 2024 Nanotechnology 35 285401
The discovery of novel electrode materials based on two-dimensional (2D) structures is critical for alkali metal-ion batteries. Herein, we performed first-principles computations to investigate functionalized MXenes, Mo2BT2 (T = O, S), which are also regarded as B-based MXenes, or named as MBenes, as potential anode materials for Li-ion batteries and beyond. The pristine and T-terminated Mo2BT2 (T = O, S) monolayers reveal metallic character with higher electronic conductivity and are thermodynamically stable with an intrinsic dipole moment. Both Mo2BO2 and Mo2BS2 monolayers exhibit high theoretical Li/Na/K storage capacity and low ion diffusion barriers. These findings suggest that functionalized Mo2BT2 (T = O, S) monolayers are promising for designing viable anode materials for high-performance alkali-ion batteries.
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 (μXRF) 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 μXRF 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 μXRF are explained and a validation of ref.-free μXRF 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 μXRF for quantitative analysis.
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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.
Ya Shen et al 2024 Nanotechnology 35 242002
With the increasing integration density of silicon-based circuits, traditional electrical interconnections have shown their technological limitations. In recent years, GeSn materials have attracted great interest due to their potential direct bandgap transition and compatibility with silicon-based technologies. GeSn materials, including GeSn films, GeSn alloys, and GeSn nanowires, are adjustable, scalable, and compatible with silicon. GeSn nanowires, as one-dimensional (1D) nanomaterials, including out-of-plane GeSn nanowires and in-plane GeSn nanowires, have different properties from those of bulk materials due to their distinctive structures. However, the synthesis and potential applications of out of plane GeSn nanowires are rarely compared to highlighting their current development status and research trends in relevant review papers. In this article, we present the preparation of out-of-plane GeSn nanowires using top-down (etching and lithography) and bottom-up (vapor–liquid–solid) growth mechanism in the vapor-phase method and supercritical fluid–liquid–solid, solution-liquid–solid, and solvent vapor growth mechanisms in the liquid-phase method) methods. Specifically, the research progress on typical out of plane GeSn nanowires are discussed, while some current development bottlenecks are also been identified. Finally, it is also provided a brief description of the applications of out-of-plane GeSn nanowires with various Sn contents and morphologies.
Yan Cheng et al 2024 Nanotechnology 35 242001
Flexible photodetectors (PDs) have garnered increasing attention for their potential applications in diverse fields, including weather monitoring, smart robotics, smart textiles, electronic eyes, wearable biomedical monitoring devices, and so on. Notably, perovskite nanostructures have emerged as a promising material for flexible PDs due to their distinctive features, such as a large optical absorption coefficient, tunable band gap, extended photoluminescence decay time, high carrier mobility, low defect density, long exciton diffusion lengths, strong self-trapped effect, good mechanical flexibility, and facile synthesis methods. In this review, we first introduce various synthesis methods for perovskite nanostructures and elucidate their corresponding optical and electrical properties, encompassing quantum dots, nanocrystals, nanowires, nanobelts, nanosheets, single-crystal thin films, polycrystalline thin films, and nanostructured arrays. Furthermore, the working mechanism and key performance parameters of optoelectronic devices are summarized. The review also systematically compiles recent advancements in flexible PDs based on various nanostructured perovskites. Finally, we present the current challenges and prospects for the development of perovskite nanostructures-based flexible PDs.
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He et al
In this paper, a new Janus-structured nano drug delivery carrier Fe3O4@TiO2&mSiO2 was designed and synthesized, which consisted of a spherical head and a closely connected rod. The head was a nanocomposite of core/shell structure with magnetic spinel ferric tetraoxide core and anatase titanium dioxide shell (Fe3O4@TiO2), and the rod was ordered mesoporous silica (mSiO2). The nanocarriers showed excellent magnetic targeting capability (saturation magnetization, 25.18 emu g-1). The core/shell heads endowed the carriers with fine microwave responsiveness. The pore volume of mesoporous nanocarriers was 0.101 cm3 g-1, and the specific surface area was 489.0 m2 g-1. Anticancer drug doxorubicin could be loaded in the mesoporous of the carriers to form Fe3O4@TiO2&mSiO2-DOX. The drug loading capacity was 10.4%. Fe3O4@TiO2&mSiO2-DOX exhibited acid-sensitive and microwavesensitive release properties along with good bio-compatibility. Fe3O4@TiO2&mSiO2 Janus nanoparticles are expected to be ideal drug carriers.
Xie et al
Selective and sensitive detection of volatile organic compounds (VOCs) holds paramount importance in real-world applications. This study proposes an innovative approach utilizing a single ReS2 field-effect transistor (FET) characterized by distinct in-plane anisotropy, specifically tailored for VOC recognition. The unique responses of ReS2, endowed with robust in-plane anisotropic properties, demonstrate significant difference along the a-axis and b-axis directions when exposed to four kinds of VOCs: acetone, methanol, ethanol, and IPA. Remarkably, the responses of ReS2 were significantly magnified under ultraviolet (UV) illumination, particularly in the case of acetone, where the response amplified by 10-15 times and the detection limit decreasing from 70 ppm to 4 ppm compared to the dark conditions. Exploiting the discernible variances in responses along the a-axis and b-axis under both UV and dark conditions, the data points of acetone, ethanol, methanol and IPA gases were clearly separated in the principal component space without any overlap through principal component analysis (PCA), indicating that the single ReS2 FET has a high ability to distinguish various gas species. The exploration of anisotropic sensing materials and light excitation strategies can be applied to a broad range of sensing platforms based on 2D materials for practical applications.
Almarzooqi et al
Graphene oxide (GO)-based membranes hold significant promise for applications ranging from energy storage to protective coatings, to saline water and produced water treatment, owing to their chemical stability and unique barrier properties achieving a high selectivity for water permeation. However, unmodified GO membranes are not stable when submerged in liquid water, creating challenges with their commercial utilization in aqueous filtration and pervaporation applications. To mitigate this, we develop an approach to modify GO membranes through a combination of low temperature thermal reduction and metal cation crosslinking. We demonstrate that Zn2+–rGO and Fe3+–rGO membranes had the highest permeation flux of 8.3 ±1.5 L m-2 h-1 and 
7.0 ± 0.4 L m-2 h-1, for saline water separation, respectively, when thermally reduced after metal cross-linking; These membranes maintained a high flux of 7.5 ± 0.7 L m-2 h-1, and 5.5 ± 0.3 L m-2 h-1 for produced water separation, respectively. All the membranes had a salt rejection higher than 99%. Fe3+ crosslinked membranes presented the highest organic solute rejections for produced water of 69%. Moreover, long term pervaporation testing was done for the Zn2+–rGO membrane for 12 hours, and only a minor drop of 6% in permeation flux in permeation flux was observed, while Zn2+–GO had a drop of 24%. Both modifiers significantly enhanced the stability with Fe3+–rGO membranes display the highest mechanical abrasion resistance of 95% compared to non-reduced and non-crosslinked GO. Improved stability for all samples also led to higher selectivity to water over organic contaminants and only slightly reduced water flux across the membrane.
Jarrar et al
Carbon-based electrode materials have widely been used in supercapacitors. Unfortunately, the fabrication of the supercapacitors includes a polymeric binding material that leads to an undesirable addition of weight along with an increased charge transfer resistance. Herein, binder-free and lightweight electrodes were fabricated using a powder processing of carbon nanofibers (CNFs) and graphene nanoplatelets (GNPs) resulting in hybrid all-carbon composite material. The structural, morphological, and electrochemical properties of the composite electrodes were studied at different concentrations of GNPs. The specific capacitance (Cs) of the CNFs was improved by increasing the concentration of GNPs in the composite. A maximum Cs of around 120 F g−1 was achieved at 90 wt.% GNPs which is around 5-fold higher in value than the pristine CNFs in 1 M KOH, which then further increased to 189 F g−1 in 6 M KOH electrolyte. The energy density of around 20 Wh kg−1 with the corresponding power density of 340 W kg−1 was achieved in the supercapacitor containing 90 wt.% GNPs. The enhanced electrochemical performance of the composite is related to the presence of a synergistic effect and the CNFs establishing conductive/percolating networks. Such binder-free all-carbon electrodes can be a potential candidate for next-generation energy applications.
Wang et al
The revelation of MoS2 as an efficient electromagnetic wave (EMW) absorbing material has ratcheted up people's attention to other transition metal dichalcogenides (TMDs). To date, extensive studies have been conducted on the semiconducting VIB-Group TMDs while research into metallic VB-Group TMDs has been relatively rare. In this work, we successfully fabricated VB-Group VSe2 microspheres through a facile one-step hydrothermal method and used them as EMW absorbers. The flowerlike VSe2 microspheres based on VSe2 nanosheets exhibited a minimum reflection loss of 46.58 dB with an effective absorption bandwidth of 4.86 GHz. The influence of material morphology, microstructure, and dielectric properties on the EMW absorption performance was systematically investigated. The hierarchically layered structure promoted dielectric loss and EMW absorption by means of multiple reflection, interfacial polarization and related relaxation, and enhanced attenuation ability. This work not only demonstrates that VSe2 is potentially a high-efficiency single component EMW absorber, but also provides fresh insights into exploration on the EMW loss mechanisms of the metallic TMD-based absorbing materials.
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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 AgNO3 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 106. 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 (μXRF) 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 μXRF 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 μXRF are explained and a validation of ref.-free μXRF 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 μXRF for quantitative analysis.
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.
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.
Khalfan Almarzooqi et al 2024 Nanotechnology
Graphene oxide (GO)-based membranes hold significant promise for applications ranging from energy storage to protective coatings, to saline water and produced water treatment, owing to their chemical stability and unique barrier properties achieving a high selectivity for water permeation. However, unmodified GO membranes are not stable when submerged in liquid water, creating challenges with their commercial utilization in aqueous filtration and pervaporation applications. To mitigate this, we develop an approach to modify GO membranes through a combination of low temperature thermal reduction and metal cation crosslinking. We demonstrate that Zn2+–rGO and Fe3+–rGO membranes had the highest permeation flux of 8.3 ±1.5 L m-2 h-1 and 
7.0 ± 0.4 L m-2 h-1, for saline water separation, respectively, when thermally reduced after metal cross-linking; These membranes maintained a high flux of 7.5 ± 0.7 L m-2 h-1, and 5.5 ± 0.3 L m-2 h-1 for produced water separation, respectively. All the membranes had a salt rejection higher than 99%. Fe3+ crosslinked membranes presented the highest organic solute rejections for produced water of 69%. Moreover, long term pervaporation testing was done for the Zn2+–rGO membrane for 12 hours, and only a minor drop of 6% in permeation flux in permeation flux was observed, while Zn2+–GO had a drop of 24%. Both modifiers significantly enhanced the stability with Fe3+–rGO membranes display the highest mechanical abrasion resistance of 95% compared to non-reduced and non-crosslinked GO. Improved stability for all samples also led to higher selectivity to water over organic contaminants and only slightly reduced water flux across the membrane.
Sabreen Jarrar et al 2024 Nanotechnology
Carbon-based electrode materials have widely been used in supercapacitors. Unfortunately, the fabrication of the supercapacitors includes a polymeric binding material that leads to an undesirable addition of weight along with an increased charge transfer resistance. Herein, binder-free and lightweight electrodes were fabricated using a powder processing of carbon nanofibers (CNFs) and graphene nanoplatelets (GNPs) resulting in hybrid all-carbon composite material. The structural, morphological, and electrochemical properties of the composite electrodes were studied at different concentrations of GNPs. The specific capacitance (Cs) of the CNFs was improved by increasing the concentration of GNPs in the composite. A maximum Cs of around 120 F g−1 was achieved at 90 wt.% GNPs which is around 5-fold higher in value than the pristine CNFs in 1 M KOH, which then further increased to 189 F g−1 in 6 M KOH electrolyte. The energy density of around 20 Wh kg−1 with the corresponding power density of 340 W kg−1 was achieved in the supercapacitor containing 90 wt.% GNPs. The enhanced electrochemical performance of the composite is related to the presence of a synergistic effect and the CNFs establishing conductive/percolating networks. Such binder-free all-carbon electrodes can be a potential candidate for next-generation energy applications.
Justinas Jorudas et al 2024 Nanotechnology
Fifty percents absorption by thin film, with thickness is much smaller than the skin depth and optical thickness much smaller than the wavelength, is a well-known concept of classical electrodynamics. This is a valuable feature that has been numerously widely explored for metal films, while chemically inert nanomembranes are a real fabrication challenge. Here we report the 20 nm-thin pyrolyzed carbon film (PyC) placed on 300 nm-thick silicon nitride (Si3N4) membrane demonstrating an efficient broadband absorption in the terahertz and near infrared ranges. While the bare Si3N4 membrane is completely transparent in the THz range, the 20 nm thick PyC layer increases the absorption of the PyC coated Si3N4 membrane to 40%. The reflection and transmission spectra in the near infrared region reveal that the PyC film absorption persists to a level of at least 10% of the incident power. Such a broadband absorption of the PyC film opens new pathways toward broadband bolometric radiation detectors.
Min Fu and Kevin Critchley 2024 Nanotechnology
Inkjet printing (IJP) has become a versatile, cost-effective technology for fabricating organic and hybrid electronic devices. Heavy-metal-based quantum dots (HM QDs) play a significant role in these inkjet-printed devices due to their excellent optoelectrical properties. Despite their utility, the intrinsic toxicity of HM QDs limits their applications in commercial products. To address this limitation, developing alternative HM-free quantum dots (HMF QDs) that have equivalent optoelectronic properties to HM QD is a promising approach to reduce toxicity and environmental impact. This article comprehensively reviews HMF QD-based devices fabricated using IJP methods. The discussion includes the basics of IJP technology, the formulation of printable HMF QD inks, and solutions to the coffee ring effect (CRE). 

Additionally, this review briefly explores the performance of typical state-of-the-art HMF QDs and cutting-edge characterization techniques for QD inks and printed QD films. The performance of printed devices based on HMF QDs is discussed and compared with those fabricated by other techniques. In the conclusion, the persisting challenges are identified, and perspectives on potential avenues for further progress in this rapidly developing research field are provided.
Sunaan Malik et al 2024 Nanotechnology
Paper is an ideal substrate for the development of flexible and environmentally sustainable ubiquitous electronic systems. When combined with nanomaterial-based devices, it can be harnessed for various Internet-of-Things applications, ranging from wearable electronics to smart packaging. However, paper remains a challenging substrate for electronics due to its rough and porous nature. In addition, the absence of established fabrication methods is impeding its utilization in wearable applications. Unlike other paper-based electronics with added layers, in this study, we present a scalable spray-lithography on a commercial paper substrate. We present a non-vacuum spray-lithography of chemical vapor deposition (CVD) single-layer graphene (SLG), carbon nanotubes (CNTs), and perovskite quantum dots (QDs) on a paper substrate. This approach combines the advantages of two large-area techniques: CVD and spray-coating. The first technique allows for the growth of SLG, while the second enables the spray coating of a mask to pattern CVD SLG, electrodes (CNTs), and photoactive (QDs) layers. We harnessed the advantages of perovskite QDs in photodetection, leveraging their strong absorption coefficients. Integrating them with the graphene enhanced the photoconductive gain mechanism, leading to high external responsivity. The presented device shows high external responsivity of ~520A/W at 405nm at <1V bias due to photoconductive gain mechanism. The prepared paper-based photodetectors (PDs) achieved an external responsivity of 520 A/W under 405 nm illumination at <1V operating voltage. To the best of our knowledge, our devices have the highest external responsivity amongst paper-based PDs. By fabricating arrays of PDs on a paper substrate in the air, this work highlights the potential of this scalable approach for enabling ubiquitous electronics on paper.
Hon Nhien Le et al 2024 Nanotechnology
Graphene oxide nanosheet (GO) is a multifunctional platform for binding with nanoparticles and stacking with two dimensional substrates. In this study, GO nanosheets were sonochemically decorated with zinc oxide nanoparticles (ZnO) and self-assembled into a hydrogel of GO-ZnO nanocomposite. The GO-ZnO hydrogel structure is a bioinspired approach for preserving graphene-based nanosheets from van der Waals stacking. X-ray diffraction analysis (XRD) showed that the sonochemical synthesis led to the formation of ZnO crystals on GO platforms. High water content (97.2 %) of GO-ZnO hydrogel provided good property of ultrasonic dispersibility in water. Ultraviolet-visible spectroscopic analysis (UV-Vis) revealed that optical band gap energy of ZnO nanoparticles (~ 3.2 eV) GO-ZnO nanosheets (~ 2.83 eV). Agar well diffusion tests presented effective antibacterial activities of GO-ZnO hydrogel against gram-negative bacteria (E. coli) and gram-positive bacteria (S. aureus). Especially, GO-ZnO hydrogel was directly used for brush painting on biodegradable polylactide (PLA) thin films. Graphene-based nanosheets with large surface area are key to van der Waals stacking and adhesion of GO-ZnO coating to the PLA substrate. The GO-ZnO/PLA films were characterized using photography, light transmittance spectroscopy, coating stability, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopic mapping (EDS), antibacterial test and mechanical tensile measurement. Specifically, GO-ZnO coating on PLA substrate exhibited stability in aqueous food simulants for packaging application. GO-ZnO coating inhibited the infectious growth of E. coli biofilm. GO-ZnO/PLA films had strong tensile strength and elastic modulus. As a result, the investigation of antibacterial GO-ZnO hydrogel and GO-ZnO coating on PLA film is fundamental for sustainable development of packaging and biomedical applications.