Nanobelts of semiconducting oxides

Exploring the antibiofilm and toxicity of tin oxide nanoparticles: Insights from in vitro and in vivo investigations

BACKGROUND INFORMATION

The advancement of biological-mediated nanoscience towards higher levels and novel benchmarks is readily apparent, owing to the use of non-toxic synthesis processes and the incorporation of various additional benefits. This study aimed to synthesize stable tin oxide nanoparticles (SnO2-NPs) using S. rhizophila as a mediator.

METHODS

The nanoparticles that were created by biosynthesis was examined using several analytical techniques, including Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM), X-ray diffraction (XRD), UV-visible (UV-vis) spectroscopy, and energy dispersive X-ray spectroscopy (EDS).

RESULTS

The results obtained from the characterization techniques suggest that S. rhizophila effectively catalyzed the reduction of SnCl2 to SnO2-NPs duration of 90 min at ambient temperature with the ƛmax of 328 nm. The size of the nano crystallite formations was measured to be 23 nm. The present study investigates nanoscale applications' antibacterial efficacy against four bacterial strains, including Klebsiella Sp, Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli. The observed zone of inhibition for the nanoparticles (NPs) varied from 10 to 25 mm. The research findings demonstrate that the nanoparticles (NPs) are effective as antibacterial, phytotoxic, and cytotoxic agents.

Associations of maternal exposure to multiple plasma trace elements with the prevalence of fetal congenital heart defects: A nested case-control study

BACKGROUND

Scanty knowledge prevails regarding the combined impact of multiple plasma trace elements and main contributors on the prevalence of congenital heart defects (CHDs) in offspring. Thus, we performed a nested case-control analysis in a neonates cohort to investigate this important public health issue.

METHODS

We selected 164 pairs of cases and non-malformed controls from live births registered in the parent cohort (n = 11,578) at the same hospital. Plasma levels of 14 trace elements were determined by inductively coupled plasma-mass spectrometry. The odds ratios (ORs) of exposure were compared between cases and controls. Bayesian Kernel Machine Regression (BKMR) and Quantile g-Computation (QgC) models were employed to assess the cumulative effect of exposure to trace elements.

RESULTS

We found positive associations and linear dose-response relationships between plasma Pb and Sn and CHD. BKMR models indicated that the overall effect of the trace element mixture was associated with CHDs below the 45th percentile or above the 50th percentile, and the combined effect was primarily attributed to Sn and Pb. The QgC model indicated significantly increased odds of CHD with simultaneous exposure to all studied trace elements (OR: 2.19, 95%CI: 1.44-3.33).

CONCLUSIONS

This study is the first to report an association between elevated levels of mixed trace elements in maternal plasma with an increased prevalence of fetal CHDs, particularly in the case of Pb and Sn. Findings from this study provide further evidence of the important of heavy metal pollution to human health, and can help stakeholders prioritize policies and develop interventions to target the leading contributors to human exposure.

Low-dimensional nanostructures for monolithic 3D-integrated flexible and stretchable electronics

Flexible/stretchable electronics, which are characterized by their ultrathin design, lightweight structure, and excellent mechanical robustness and conformability, have garnered significant attention due to their unprecedented potential in healthcare, advanced robotics, and human-machine interface technologies. An increasing number of low-dimensional nanostructures with exceptional mechanical, electronic, and/or optical properties are being developed for flexible/stretchable electronics to fulfill the functional and application requirements of information sensing, processing, and interactive loops. Compared to the traditional single-layer format, which has a restricted design space, a monolithic three-dimensional (M3D) integrated device architecture offers greater flexibility and stretchability for electronic devices, achieving a high-level of integration to accommodate the state-of-the-art design targets, such as skin-comfort, miniaturization, and multi-functionality. Low-dimensional nanostructures possess small size, unique characteristics, flexible/elastic adaptability, and effective vertical stacking capability, boosting the advancement of M3D-integrated flexible/stretchable systems. In this review, we provide a summary of the typical low-dimensional nanostructures found in semiconductor, interconnect, and substrate materials, and discuss the design rules of flexible/stretchable devices for intelligent sensing and data processing. Furthermore, artificial sensory systems in 3D integration have been reviewed, highlighting the advancements in flexible/stretchable electronics that are deployed with high-density, energy-efficiency, and multi-functionalities. Finally, we discuss the technical challenges and advanced methodologies involved in the design and optimization of low-dimensional nanostructures, to achieve monolithic 3D-integrated flexible/stretchable multi-sensory systems.

Low-Vacuum Catalyst-Free Physical Vapor Deposition and Magnetotransport Properties of Ultrathin Bi2Se3 Nanoribbons

In this work, a simple catalyst-free physical vapor deposition method is optimized by adjusting source material pressure and evaporation time for the reliable obtaining of freestanding nanoribbons with thicknesses below 15 nm. The optimum synthesis temperature, time and pressure were determined for an increased yield of ultrathin Bi2Se3 nanoribbons with thicknesses of 8-15 nm. Physical and electrical characterization of the synthesized Bi2Se3 nanoribbons with thicknesses below 15 nm revealed no degradation of properties of the nanoribbons, as well as the absence of the contribution of trivial bulk charge carriers to the total conductance of the nanoribbons.

Organic and inorganic nanomaterials: fabrication, properties and applications

Nanomaterials and nanoparticles are a burgeoning field of research and a rapidly expanding technology sector in a wide variety of application domains. Nanomaterials have made exponential progress due to their numerous uses in a variety of fields, particularly the advancement of engineering technology. Nanoparticles are divided into various groups based on the size, shape, and structural morphology of their bodies. The 21st century's defining feature of nanoparticles is their application in the design and production of semiconductor devices made of metals, metal oxides, carbon allotropes, and chalcogenides. For the researchers, these materials then opened a new door to a variety of applications, including energy storage, catalysis, and biosensors, as well as devices for conversion and medicinal uses. For chemical and thermal applications, ZnO is one of the most stable n-type semiconducting materials available. It is utilised in a wide range of products, from luminous materials to batteries, supercapacitors, solar cells to biomedical photocatalysis sensors, and it may be found in a number of forms, including pellets, nanoparticles, bulk crystals, and thin films. The distinctive physiochemical characteristics of semiconducting metal oxides are particularly responsible for this. ZnO nanostructures differ depending on the synthesis conditions, growth method, growth process, and substrate type. A number of distinct growth strategies for ZnO nanostructures, including chemical, physical, and biological methods, have been recorded. These nanostructures may be synthesized very simply at very low temperatures. This review focuses on and summarizes recent achievements in fabricating semiconductor devices based on nanostructured materials as 2D materials as well as rapidly developing hybrid structures. Apart from this, challenges and promising prospects in this research field are also discussed.

Luminescence properties of Ln3+ doped BaMoO4 (Ln3+ = Sm3+ and Dy3+) phosphors under UV excitation

Ln³⁺ doped BaMoO₄ (Ln ³⁺ = Sm³⁺ and Dy³⁺) nanoparticles have been synthesized successfully using ethylene glycol as a solvent. All the prepared samples are well indexed into the pure scheelite-type tetragonal structure of BaMoO₄, the doping of trivalent ions (Ln³⁺) in to the bivalent host ions (Ba²⁺) sites of the BaMoO₄ do not change the pure tetragonal structure of BaMoO₄ although there is a charge difference between Ba²⁺ and Ln³⁺. The SEM image of the prepared BaMoO₄ samples shows a number of uniform shuttle-like nanocrystalline with protrusion in the middle. The doping of Ln³⁺ ions do not change the morphology of the BaMoO₄. The photoluminescence study has been carried in detail by measuring the excitation and emission spectra of the prepared samples. The excitation spectrum consists of a broad band with a maximum at about 268 nm thereby demonstrating the transfer of energy from MoO^2-₄ groups to the doped Ln³⁺ ions. Yellow emission is dominated over blue in case of Dy³⁺ doped BaMoO₄ and in Sm³⁺ doped BaMoO₄ red emission dominated over other lights under UV excitation. The luminescence intensity is highest at 10 at.% Ln³⁺ under the UV excitation. Under this UV excitation BaMoO₄:Sm³⁺ exhibits strong orange-red and BaMoO₄:Dy³⁺ greenish-yellow emissions. Excitation of Dy³⁺ in thin film of BaMoO₄ emits an intense yellow color which could be applicable in the field of biological assays and biological fluorescence labeling.

Anisotropic Heavy-Metal-Free Semiconductor Nanocrystals: Synthesis, Properties, and Applications

Heavy-metal (Cd, Hg, and Pb)-containing semiconductor nanocrystals (NCs) have been explored widely due to their unique optical and electrical properties. However, the toxicity risks of heavy metals can be a drawback of heavy-metal-containing NCs in some applications. Anisotropic heavy-metal-free semiconductor NCs are desirable replacements and can be realized following the establishment of anisotropic growth mechanisms. These anisotropic heavy-metal-free semiconductor NCs can possess lower toxicity risks, while still exhibiting unique optical and electrical properties originating from both the morphological and compositional anisotropy. As a result, they are promising light-emitting materials in use various applications. In this review, we provide an overview on the syntheses, properties, and applications of anisotropic heavy-metal-free semiconductor NCs. In the first section, we discuss hazards of heavy metals and introduce the typical heavy-metal-containing and heavy-metal-free NCs. In the next section, we discuss anisotropic growth mechanisms, including solution-liquid-solid (SLS), oriented attachment, ripening, templated-assisted growth, and others. We discuss mechanisms leading both to morphological anisotropy and to compositional anisotropy. Examples of morphological anisotropy include growth of nanorods (NRs)/nanowires (NWs), nanotubes, nanoplatelets (NPLs)/nanosheets, nanocubes, and branched structures. Examples of compositional anisotropy, including heterostructures and core/shell structures, are summarized. Third, we provide insights into the properties of anisotropic heavy-metal-free NCs including optical polarization, fast electron transfer, localized surface plasmon resonances (LSPR), and so on, which originate from the NCs' anisotropic morphologies and compositions. Finally, we summarize some applications of anisotropic heavy-metal-free NCs including catalysis, solar cells, photodetectors, lighting-emitting diodes (LEDs), and biological applications. Despite the huge progress on the syntheses and applications of anisotropic heavy-metal-free NCs, some issues still exist in the novel anisotropic heavy-metal-free NCs and the corresponding energy conversion applications. Therefore, we also discuss the challenges of this field and provide possible solutions to tackle these challenges in the future.

Resilient and Antipuncturing Si3N4 Nanofiber Sponge

Ceramic nanofibrous nanostructure-based sponges have attracted significant attention due to ultrahigh porosity, low thermal conductivity, large specific area, and chemical stability. From the regulation of the fiber itself to the construction method of 3D networks, efforts are being made to improve the mechanical properties of ceramic sponges for practical applications. So far resilient compressibility has been realized in ceramic nanofibrous-based sponges via structural design, but they still show brittle fracture under a more complex stress state. Herein, we introduced a highly aligned and interwoven Si₃N₄ nanofiber sponge, which exhibits superflexibility, large break elongation (>80%), large-strain reversible stretch (20%), and good resistance to tensile fatigue. The ceramic sponge also displays reversible compressibility up to 60% strain, puncture resistance, high air filtration efficiency (>99.8%), and low pressure drop (38% of cotton fiber), making the ceramic sponge a high-performance wearable respirator to protect us from harm due to PM_2.5 pollution and possible microorganisms.

Germanium Diselenide Ribbons with Orthorhombic Crystal Structure

Many materials are known to exist in several stable polymorphs, but synthesis only provides access to a subset. This situation is exemplified by the dichalcogenide semiconductor GeSe₂. Besides the amorphous form, which attracted intense interest, crystalline GeSe₂ in the bulk and in nanostructures such as flakes and nanobelts invariably adopts the 2D/layered monoclinic β-phase. Hence, the properties of other polymorphs such as the orthorhombic 3D GeSe₂ phase remain unknown. Here, we report the high-yield synthesis of orthorhombic GeSe₂ nanoribbons by GeSe/Se vapor transport over Au catalysts. Access to air-stable monocrystalline, single-phase ribbons enabled investigating the properties of orthorhombic GeSe₂ including its characteristic Raman spectrum. Optical absorption on ensembles and cathodoluminescence spectroscopy on individual ribbons show a wide bandgap and intense band-to-band emission in the visible, with a broad sub-bandgap emission tail. Our results establish orthorhombic GeSe₂ ribbons as a promising wide-bandgap semiconductor nanostructure for applications in optoelectronics and energy conversion.

Charge transport mechanisms in free-standing devices with electrospun electrodes

Embedding electronic and optoelectronic devices in common, daily use objects is a fast developing field of research. New architectures are needed for migrating from the classic wafer- based substrates. Novel types of flexible PMMA/Au/Alq₃/LiF/Al structures were obtained starting from electrospun polymer fibers. Thus, using an electrospinning process poly (methyl metacrylate) (PMMA) nanofibers were fabricated. A thin Au layer deposition rendered the fiber array conductive, this being further employed as the anode. The next steps consisted of the thermal evaporation of tris(8-hydroxyquinolinato) aluminum (Alq₃) and aluminum deposition as the cathode. The Au covered PMMA nanofiber layer had a similar behavior with an indium tin oxide film i.e. low sheet resistance 10.6 Ω/sq and high transparency. The low electrode resistivities allow an electron drift mobility of about 10^-6cm²V^-1s^-1at a low applied field, similar to the counterpart structures based on thin films. Concerning the relaxation processes in these structures, the Cole-Cole plots exhibit a slightly deformed semicircle, indicating a more complex equivalent circuit for the processes between metal electrodes and the active layer. This equivalent circuit includes reactance equivalent processes at the anode, cathode, in the active layer and most probably originates from the roughness of the metallic electrodes.

Al2O3/ZnO Heterostructure-Based Sensors for Volatile Organic Compounds in Safety Applications

Monitoring volatile organic compounds (VOCs) in harsh environments, especially for safety applications, is a growing field that requires specialized sensor structures. In this work, we demonstrate the sensing properties toward the most common VOCs of columnar Al₂O₃/ZnO heterolayer-based sensors. We have also developed an approach to tune the sensor selectivity by changing the thickness of the exposed amorphous Al₂O₃ layer from 5 to 18 nm. Columnar ZnO films are prepared by a chemical solution method, where the exposed surface is decorated with an Al₂O₃ nanolayer via thermal atomic layer deposition at 75 °C. We have investigated the structure and morphology as well as the vibrational, chemical, electronic, and sensor properties of the Al₂O₃/ZnO heterostructures. Transmission electron microscopy (TEM) studies show that the upper layers consist of amorphous Al₂O₃ films. The heterostructures showed selectivity to 2-propanol vapors only within the range of 12-15 nm thicknesses of Al₂O₃, with the highest response value of ∼2000% reported for a thickness of 15 nm at the optimal working temperature of 350 °C. Density functional theory (DFT) calculations of the Al₂O₃/ZnO(1010) interface and its interaction with 2-propanol (2-C₃H₇OH), n-butanol (n-C₄H₉OH), ethanol (C₂H₅OH), acetone (CH₃COCH₃), hydrogen (H₂), and ammonia (NH₃) show that the molecular affinity for the Al₂O₃/ZnO(1010) interface decreases from 2-propanol (2-C₃H₇OH) ≈ n-butanol (n-C₄H₉OH) > ethanol (C₂H₅OH) > acetone (CH₃COCH₃) > hydrogen (H₂), which is consistent with our gas response experiments for the VOCs. Charge transfers between the surface and the adsorbates, and local densities of states of the interacting atoms, support the calculated strength of the molecular preferences. Our findings are highly important for the development of 2-propanol sensors and to our understanding of the effect of the heterojunction and the thickness of the top nanolayer on the gas response, which thus far have not been reported in the literature.

Abrupt change from moderate positive to colossal negative thermal expansion caused by imidazolate composite formation

This work describes temperature-induced crystallization processes and reaction mechanisms occurring in the borohydride-imidazolate system. In the course of thermal evolution, crystal structures of two novel bimetallic imidazolates AMnIm₃ (A = Na, K) were solved using synchrotron radiation powder diffraction data. Both the alkali metal cation and the Mn cations exhibit distorted octahedral coordination while each imidazolate is surrounded by two alkali metal and two manganese atoms. Extensive study of the thermal expansion behaviour revealed that the expansion of the bimetallic imidazolates does not proceed uniformly over the entire temperature range but rather abruptly changes from a colossal negative to a moderate positive volume expansion. Such behaviour is caused by the coherent intergrowth of the coexisting phases which form a composite, a positive lattice mismatch and a tensile strain during the coexistence of NaMIm₃ (M = Mg and Mn) and NaIm or HT-NaIm. Such coherent coalescence of two materials opens the possibility for targeted design of zero thermal expansion materials.

GRAPHICAL ABSTRACT

Crystal structures of AMnIm₃ (A = Na, K) were determined. Coherently intergrown NaMIm₃/NaIm (M = Mg, Mn) present colossal negative thermal expansion.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s10853-022-07360-z.

Inhibition of Staphylococcus aureus α-Hemolysin Production Using Nanocurcumin Capped Au@ZnO Nanocomposite

Nanoparticles of gold with zinc oxide (Au@ZnO NPs) were prepared by laser ablation and then capped with curcumin nanoparticles (Cur-Au@ZnO NPs). The synthesized NPs were characterized using different techniques, including transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), UV-visible spectroscopy, and X-ray diffraction. In addition, the ability of NPs as a promising antibacterial agent was tested against Staphylococcus aureus through the agar well diffusion method and AO/EtBr staining assay. The results showed that the prepared nanoparticles (Cur-Au@ZnO) served as an antibacterial agent and can destroy the bacterial cells by losing the cell wall integrity and penetrating the cytoplasmic membrane. Moreover, the findings confirmed the role of the formed NPs in attenuation of the adherence and invasion of S. aureus to rat embryonic fibroblast (REF) cells. Furthermore, the activity of Cur-Au@ZnO NPs against the S. aureus α-hemolysin toxin was evaluated using the western blot technique, using human alveolar epithelial cells (A549), and through histopathology examination in a mouse model. In conclusion, the built Cur-Au@ZnO NPs can be used as a potential antibacterial agent and an inhibitor of α-hemolysin toxin secreted by S. aureus. These NPs may offer a new strategy in combating pathogen infections and in the future for biomedical and pharmaceutical applications.

Metal Oxide Chemiresistors: A Structural and Functional Comparison between Nanowires and Nanoparticles

Metal oxide nanowires have become popular materials in gas sensing, and more generally in the field of electronic and optoelectronic devices. This is thanks to their unique structural and morphological features, namely their single-crystalline structure, their nano-sized diameter and their highly anisotropic shape, i.e., a large length-to-diameter aspect ratio. About twenty years have passed since the first publication proposing their suitability for gas sensors, and a rapidly increasing number of papers addressing the understanding and the exploitation of these materials in chemosensing have been published. Considering the remarkable progress achieved so far, the present paper aims at reviewing these results, emphasizing the comparison with state-of-the-art nanoparticle-based materials. The goal is to highlight, wherever possible, how results may be related to the particular features of one or the other morphology, what is effectively unique to nanowires and what can be obtained by both. Transduction, receptor and utility-factor functions, doping, and the addition of inorganic and organic coatings will be discussed on the basis of the structural and morphological features that have stimulated this field of research since its early stage.

ZnO nanostructured materials and their potential applications: progress, challenges and perspectives

Extensive research in nanotechnology has been conducted to investigate new behaviours and properties of materials with nanoscale dimensions. ZnO NPs owing to their distinct physical and chemical properties have gained considerable importance and are hence investigated to a detailed degree for exploitation of these properties. This communication, at the outset, elaborates the various chemical methods of preparation of ZnO NPs, viz., the mechanochemical process, controlled precipitation, sol-gel method, vapour transport method, solvothermal and hydrothermal methods, and methods using emulsion and micro-emulsion environments. The paper further describes the green methods employing the use of plant extracts, in particular, for the synthesis of ZnO NPs. The modifications of ZnO with organic (carboxylic acid, silanes) and inorganic (metal oxides) compounds and polymer matrices have then been described. The multitudinous applications of ZnO NPs across a variety of fields such as the rubber industry, pharmaceutical industry, cosmetics, textile industry, opto-electronics and agriculture have been presented. Elaborative narratives on the photocatalytic and a variety of biomedical applications of ZnO have also been included. The ecotoxic impacts of ZnO NPs have additionally been briefly highlighted. Finally, efforts have been made to examine the current challenges and future scope of the synthetic modes and applications of ZnO NPs.

A review: zinc oxide nanoparticles - friends or enemies?

Modern nanotechnology allows obtaining zinc oxide nanomaterials with unique properties that let its use in a wide range of commercial applications. Direct contact with these particles as well as their release into the environment is almost inevitable. This review aims to consider whether the toxicity of zinc oxide nanoparticles found in numerous test models is a real threat to humans and plants. Emerging reports indicated both the risks and benefits associated with the use of zinc oxide nanoparticles in a manner dependent on the concentration and a method of synthesis, as well as the tested object. The amounts needed to achieve the antibacterial activity of ZnO-NPs, and the reported amounts of these nanoparticles in consumer products are sufficient to have a negative impact on living organisms. The most sensitive to their action are human cells, and the mechanism of cytotoxicity is mainly associated with the formation of oxidative stress caused by the action of zinc ions. ZnO-NPs in small concentration can have positive affect to plants, but it poses a threat to more sensitive ones.

CircuitBot: Learning to survive with robotic circuit drawing

Robots with the ability to actively acquire power from surroundings will be greatly beneficial for long-term autonomy and to survive in uncertain environments. In this work, a scenario is presented where a robot has limited energy, and the only way to survive is to access the energy from an unregulated power source. With no wires or resistors available, the robot heuristically learns to maximize the input voltage on its system while avoiding potential obstacles during the connection. CircuitBot is a 6 DOF manipulator capable of drawing circuit patterns with graphene-based conductive ink, and it uses a state-of-the-art continuous/categorical Bayesian Optimization to optimize the placement of conductive shapes and maximize the energy it receives. Our comparative results with traditional Bayesian Optimization and Genetic algorithms show that the robot learns to maximize the voltage within the smallest number of trials, even when we introduce obstacles to ground the circuit and steal energy from the robot. As autonomous robots become more present, in our houses and other planets, our proposed method brings a novel way for machines to keep themselves functional by optimizing their own electric circuits.

Strategies to Enhance ZnO Photocatalyst's Performance for Water Treatment: A Comprehensive Review

Despite the photocatalytic organic pollutant degradation using ZnO started in 1910-1911, many challenges are still ahead, and several critical issues have to be addressed. Large band gap, and short life-time of photogenerated electrons and holes are critical issues negatively affect the photocatalytic activity of ZnO. Various approaches have been introduced to overcome these issues including intrinsic doping, extrinsic doping, and heterostructure. This review introduces unique and deep insights into tuning of the photocatalytic activity of ZnO. It starts by description of how to tune the photocatalytic activity of pristine ZnO through tuning its morphology, surface area, exposed face, and intrinsic defects. Afterward, the review explains how the Z-scheme approach succeed to address the redox weakened issue of heterojunction approach. In general, this review provides a clear image that helps the researcher to tune the photocatalytic activity of pristine ZnO and its heterostructure.

Facile and scaleable transformation of Cu nanoparticles into high aspect ratio Cu oxide nanowires in methanol

In this work, a facile synthetic route for the preparation of high aspect ratio Cu oxide nanowires is reported. The preparation of the Cu oxide nanowires begins with the generation of pure Cu nanoparticles by inert gas condensation (IGC) method, follows by dispersing the obtained nanoparticles in methanol with the aid of ultrasonication. The mixture is stored at different temperature for the transformation from Cu nanoparticle to Cu oxide nanowires. The influences of the kind of solution, the ratio of methanol to Cu nanoparticle, dispersion time and temperature towards the generation of Cu oxide nanowires are studied in detail. Scanning electron microscopy studies indicate that high aspect ratio Cu oxide nanowires with diameter of a few tens of nanometers and length up to several tens of micrometers could be obtained under proper conditions. The mechanism for the transformation of Cu nanoparticles to Cu oxide nanowires is also investigated.

We proposed a facile synthetic route to Cu oxide nanowires with a high aspect ratio. The approach shown in this work is suitable for scale-up synthesis.

Highly sensitive, scalable, and rapid SARS-CoV-2 biosensor based on In2O3 nanoribbon transistors and phosphatase

Developing convenient and accurate SARS-CoV-2 antigen test and serology test is crucial in curbing the global COVID-19 pandemic. In this work, we report an improved indium oxide (In₂O₃) nanoribbon field-effect transistor (FET) biosensor platform detecting both SARS-CoV-2 antigen and antibody. Our FET biosensors, which were fabricated using a scalable and cost-efficient lithography-free process utilizing shadow masks, consist of an In₂O₃ channel and a newly developed stable enzyme reporter. During the biosensing process, the phosphatase enzymatic reaction generated pH change of the solution, which was then detected and converted to electrical signal by our In₂O₃ FETs. The biosensors applied phosphatase as enzyme reporter, which has a much better stability than the widely used urease in FET based biosensors. As proof-of-principle studies, we demonstrate the detection of SARS-CoV-2 spike protein in both phosphate-buffered saline (PBS) buffer and universal transport medium (UTM) (limit of detection [LoD]: 100 fg/mL). Following the SARS-CoV-2 antigen tests, we developed and characterized additional sensors aimed at SARS-CoV-2 IgG antibodies, which is important to trace past infection and vaccination. Our spike protein IgG antibody tests exhibit excellent detection limits in both PBS and human whole blood ((LoD): 1 pg/mL). Our biosensors display similar detection performance in different mediums, demonstrating that our biosensor approach is not limited by Debye screening from salts and can selectively detect biomarkers in physiological fluids. The newly selected enzyme for our platform performs much better performance and longer shelf life which will lead our biosensor platform to be capable for real clinical diagnosis usage.

ELECTRONIC SUPPLEMENTARY MATERIAL

Supplementary material (materials and methods for device fabrication, functionalization of In₂O₃ devices, photographs of the liquid gate measurement setup, mobilities of the nine devices labeled in Fig. 1(b), family curves of I _DS-V _DS with the liquid gate setup and current change after bubbling the substrate solution (current vs. time curve for S1 antigen detection)) is available in the online version of this article at 10.1007/s12274-022-4190-0.

Facile green synthesis of ZnO–CuO nanocomposites using areca catechu leaves and their in vitro antidiabetic and cytotoxicity studies

The fabrication and diverse applications of mixed oxides have received immense interest due to numerous prospects for better functional performance in tuning their properties compared to the basic metal oxides. Herein, we report synthesis of ZnO-CuO nanocomposites (NCs) using a simple and green route solution combustion method. The as-prepared ZnO-CuO NCs have been characterised through x-ray diffraction (XRD), energy dispersive x-ray (EDX) with scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. The results revealed that as-prepared ZnO-CuO NCs have spherical and rod-shaped structures with an average size between 10 and 30 nm. Further, ZnO-CuO NCs were tested for antidiabetic and anticancer properties. Amylase inhibition and MTT assays were carried out with different concentrations of NCs. The biological results depicted that the as-prepared nanocomposites exhibited significant cytotoxic effects with IC50 value of 13.29 μg mg−1. These observations further showed that the newly synthesised ZnO–CuO NCs are interesting and promising nanomaterials in pharmaceutical and healthcare sector.

Experimental investigation of performance tailoring of the multifunctional sensor using transition metal (Fe) doped ZnO nanorods synthesized via a facile solution-based method

A systematic interpretation of the undoped and Fe doped ZnO based multifunctional sensor developed employing economic and facile low-temperature hydrothermal method is reported. The tailoring of the performance improvement of the sensor was deliberately carried out using varied concentration (1, 3 and 5 Wt%) of Fe dopant in ZnO nanorods. The structural and morphological analysis reveal the undisturbed ZnO hexagonal wurtzite structure formation and 1D morphology grown even when the dopant is added. The optical property study evidences a decreased bandgap (3.10 eV) and decreased defects of 5 Wt% of Fe dopant in ZnO nanorods based sensor compared to the undoped one. The electrical process transpiring in the tailored multifunctional sensor is investigated using photoconductivity and impedance analysis elucidates proper construction of p-n junction between the piezoelectric n-type active layer (undoped and Fe doped ZnO nanorods) and p-type PEDOT:PSS ((poly(3,4-ethylene dioxythiophene) polystyrene sulfonate)) and reduced internal resistance of 5 Wt% of Fe dopant in ZnO nanorods based sensor (131.97 Ω) respectively. The investigation on the experimental piezoelectric acceleration and gas sensing validation and the performance measurement were interpreted using test systems. A revamped output voltage of 3.71 V for 1 g input acceleration and a comprehensive sensitivity of 7.17 V g^-1was achieved for the 5 Wt% of Fe dopant in ZnO nanorods based sensor sensor. Similarly, an upgraded sensitivity of 2.04 and 6.75 for 5 Wt% of Fe dopant in ZnO nanorods based sensor was obtained when exposed to 10 ppm of target gases namely CO and CH₄respectively at room temperature. Appending to this, acceptable stability of the sensor for both the sensing (acceleration and gas) was also attained manifesting its prospective application in multifunctional based systems like sewage systems.

Multiple Regulation Effects of Ammonium Acetate on ZnO Growth Process in Chemical Bath Deposition

Chemical bath deposition method has been used to synthesize a variety of ZnO morphology structures. However, the specificity and interaction of acetate and ammonium ions with ZnO crystal during the growth process remain elusive. This study contributes to understand the roles of ammonium acetate on the growth mechanism of ZnO in Zn(NO₃ )₂ -HMTA system. The growth process indicates that the nucleation experienced Zn²⁺ -layered basic zinc salts (LBZs)-ZnO process, while the self-assembled unit changed from urchin-shaped, rod-shaped to a fully coupled twin-shaped structure with increasing ammonium acetate concentration. Ammonium acetate dominates the growth process by combing the ligand-ligand interaction of acetate ions binding to the same Zn-rich (0001) polar surface and ammonium ions regulating hexamethylenetetramine (HMTA) hydrolysis. Relatively regular hexagonal wurtzite structure and a dissolve-renucleation-regrowth process which retains the twin-shaped template and renucleates at the same position are observed at ∼10 mM ammonium acetate. Photoelectrochemistry (PEC) measurements show that the uniform hexagonal ZnO rods (Y-10, the sample named as Y-x (x represents x mM ammonium acetate, herein, x is 10 mM)) have a maximum photocurrent density of 1.54 mA cm^-2 at 1.23 V (vs. RHE), much higher than that of the dumbbell-shaped ZnO rods (Y-50, 0.20 mA cm^-2 ) at the same voltage. These results provide a further explanation of morphology regulation mechanisms on ZnO synthesis processes and pave the road for more practical applications.

Coating of ZnO Nanoparticle on Cotton Fabric to Create a Functional Textile with Enhanced Mechanical Properties

The goal of this research is to develop a functional textile with better mechanical properties. Therefore, nano ZnO is synthesized, characterized, and applied to cotton fabric by mechanical thermo-fixation techniques. The synthesized nanoparticles are characterized by SEM and XRD analysis. The ZnO nanoparticle alone, ZnO nanoparticle with a binder, and ZnO with a binder and wax emulsion are then applied on cotton woven fabrics using three different recipes. The surface morphology of the treated fabric is studied using SEM and EDS. Antimicrobial activity, UV protection property, and crease resistance are all tested for their functional characteristics. In addition, all vital mechanical characteristics are assessed. The results suggest that using only nano ZnO or nano ZnO with a binder enhances functional features while deteriorating mechanical capabilities. Nano ZnO treatment with the third recipe, which includes the addition of an emulsion, on the other hand, significantly enhances mechanical and functional characteristics. Consequently, this study provides information to optimize the confidence of textile researchers and producers in using nano ZnO and understanding its features in key functional fabrics.

Moringa oleifera Leaf Extract-Mediated Green Synthesis of Nanostructured Alkaline Earth Oxide (MgO) and Its Physicochemical Properties

The magnesium oxide nanoparticles (MgO NPs) were prepared from Moringa oleifera leaf extract. Phytochemicals are derived from plant extract which are served as stabilizing and capping agents. This green route has been attracted owing to speed, reliable, and eco-friendly and cost-effective one. The synthesized magnesium oxide nanoparticles were taken into three different calcination temperatures (500, 600, and 700°C). The powder X-ray diffraction (PXRD) study shows a pure phase of face-centered cubic structure. Periclase MgO nanoparticles were prepared. The optical band gap of MgO nanoparticles is 4.5 eV, and its absorption in the UV region was observed by UV-visible spectroscopy (UV-Vis). Photoluminescence spectra have exhibited multicolor emissions were being at UV and visible region due to defect centers (F centers) of MgO nanoparticles. EDX (energy dispersive X-ray spectrum) has given the stoichiometric ratio of Mg and O. The functional groups have been studied by Fourier transformed infrared spectroscopy (FTIR), surface morphology transformation has been identified by scanning electron microscopy (SEM) studies, and VSM measurements have given the information of diamagnetic nature of MgO nanoparticles. H-R TEM micrographs have confirmed that particles were in nanorange matched with XRD report. Polycrystalline nature has been observed pattern information. TG-DSC characterization revealed phase transition and weight loss information. D-band and G-band of MgO nanoparticles are studied by micro-Raman analysis. Dielectric analysis has proven that MgO nanoparticles will be a promising candidate for linear dielectric ceramics, thermistor. The present resent studies have revealed that MgO powder will be an economical and promising candidate in superconductor, optoelectronic device, and energy storage applications.

From Chain- to Graphene-like Hydroxyl-terminated (ZnO)n Clusters with n≤6 Obtained via Zinc Dimethoxide Hydrolysis and Condensation: Ab initio Structural, Electronic, Vibrational and Optical Properties Calculations

Recent reports are focusing on the structural evolution from the atomic-scale and also at the expenses of alkyl zinc alkoxide precursors towards (ZnO)_n clusters and nanostructures with different interesting motifs, but still not much is known about their electronic properties. In this manuscript, we present a theoretical study using DFT and TD-DFT methodologies on the hydrolysis and condensation of zinc dimethoxide precursor in its monomeric, dimeric and trimeric forms towards thermodynamically stable hydroxyl-terminated (ZnO)_n clusters with novel chain- and graphene-like fashions. For all cases, distinct vibrational and optical spectra features were assigned evidencing a global monotonic decrease in the opto-electronic gap with increasing oligomerization and cyclization stages. In addition, the electron-affinity of all clusters was also observed to be enhanced with increasing oligomerization and cyclization stages and the electronic charge localization in -e charged clusters was observed to be strongly related to the presence of zinc-oxo subunits and other particular structural features. Our calculations also indicate that the stabilization through hydroxyl termination of both chain- and graphene-like ZnO clusters not only could be a promising driving force to obtain larger atomic-scale 1D and 2D nanostructures but also envisage interesting properties, particularly as electronic acceptor materials for energy applications.

Effect of Asymmetry Mechanical Loads on the Potential Barrier Region of a Piezoelectric pn Junction

The nonlinear governing equations on the coupling between electromechanical fields and charge carrier in a thermal equilibrium piezoelectric pn junction subjected to asymmetric mechanical loads are established in this article. Effect of mechanical loads on the basic physical parameters of a piezoelectric pn junction, such as potential barrier region width, contact potential difference, electric potential, and carrier concentrations are analyzed numerically. Results show that asymmetry compressive stresses exert more influence on the movement of the potential barrier region's boundary and the migration of carrier compare to asymmetry tensile stresses. It is also found that asymmetry compressive stresses lead to a pn junction with a thin potential barrier region which enhances the chance of carrier's passing through of potential barrier region. The obtained results are useful in reducing the disadvantage of capacitance on rectification characteristic and can be used to tune the I - V characteristic of the pn junction working with bias voltage.

Electronic and optical properties of tapered tetrahedral semiconductor nanocrystals

The quantum confinement effect resulting from size reduction drastically alters the electronic structure and optical properties of optoelectronic materials. Quantum confinement in nanomaterials can be efficiently controlled by morphology variation combined characteristics of nanomaterials, such as their size, shape, and spatial organization. In this study, considering indium arsenide (InAs) in tetrahedral semiconductors as an example, we demonstrated the controllable morphology evolution of InAs nanostructures by tuning the growth conditions. We used the atomistic pseudopotential method to investigate the morphology-dependent electronic and optical properties of InAs nanostructures: tapered and uniform nanostructures, including the absorption spectra, single-particle energy levels, distribution and overlap integral of band-edge states, and exciton binding energies. Compared with uniform nanomaterials, a weaker quantum confinement effect was observed in the tapered nanomaterials, because of which tapered InAs nanostructures have a smaller bandgap, larger separation of photoinduced carriers, and smaller exciton binding energy. The absorption spectra of InAs nanostructures also exhibit strong morphology dependence. Our results indicate that morphology engineering can be exploited as a potential approach for modulating the electronic and optoelectronic properties of nanomaterials.

Metal-Oxide Based Nanomaterials: Synthesis, Characterization and Their Applications in Electrical and Electrochemical Sensors

Pure, mixed and doped metal oxides (MOX) have attracted great interest for the development of electrical and electrochemical sensors since they are cheaper, faster, easier to operate and capable of online analysis and real-time identification. This review focuses on highly sensitive chemoresistive type sensors based on doped-SnO₂, RhO, ZnO-Ca, Sm_x-CoFe_2−xO₄ semiconductors used to detect toxic gases (H₂, CO, NO₂) and volatile organic compounds (VOCs) (e.g., acetone, ethanol) in monitoring of gaseous markers in the breath of patients with specific pathologies and for environmental pollution control. Interesting results about the monitoring of biochemical substances as dopamine, epinephrine, serotonin and glucose have been also reported using electrochemical sensors based on hybrid MOX nanocomposite modified glassy carbon and screen-printed carbon electrodes. The fundamental sensing mechanisms and commercial limitations of the MOX-based electrical and electrochemical sensors are discussed providing research directions to bridge the existing gap between new sensing concepts and real-world analytical applications.

Recent advances in ZnO nanostructure-based electrochemical sensors and biosensors

Nanostructured metal oxides, such as zinc oxide (ZnO), are considered as excellent materials for the fabrication of highly sensitive and selective electrochemical sensors and biosensors due to their good properties, including a high specific surface area, high catalytic efficiency, strong adsorption ability, high isoelectric point (IEP, 9.5), wide band gap (3.2 eV), biocompatibility and high electron communication features. Thus, ZnO nanostructures are widely used to fabricate efficient electrochemical sensors and biosensors for the detection of various analytes. In this review, we have discussed the synthesis of ZnO nanostructures and the advances in various ZnO nanostructure-based electrochemical sensors and biosensors for medical diagnosis, pharmaceutical analysis, food safety, and environmental pollution monitoring.

Triboelectric nanogenerators for human-health care

Since the world's first triboelectric nanogenerator (TENG) was proposed in 2012, numerous TENG-based devices and equipment have sprung up in various fields. In particular, TENG has great potential in the field of human-health care due to its small size, self-powered and low cost. With the continuous deepening of TENG research, its structure, function and technical concept are becoming more and more abundant. In order to summarize the progress and development status of TENG in health care, based on the different types of applications subdirection, this paper reviews the TENG-based research work of this field in recent eight years. The characteristics of various types of TENG-based applications and their corresponding technologies are introduced and analyzed, under the comparison of their structure and performance. This review is dedicated to provide reference and inspiration for the future development and innovation of TENG for health care.

Interfacial Charge Transport in 1D TiO2 Based Photoelectrodes for Photoelectrochemical Water Splitting

1D nanostructured photoelectrodes are promising for application as photoelectrochemical (PEC) devices for solar energy conversion into hydrogen (H₂ ) owing to the optical, structural, and electronic advantages. Titanium dioxide (TiO₂ ) is the most investigated candidate as a photoelectrode due to its good photostability, low production cost, and eco-friendliness. The obstacle for TiO₂ 's practical application is the inherent wide bandgap (UV-lights response), poor conductivity, and limited hole diffusion length. Here, a comprehensive review of the current research efforts toward the development of 1D TiO₂ based photoelectrodes for heterogeneous PEC water splitting is provided along with a discussion of nanoarchitectures and energy band engineering influences on interfacial charge transfer and separation of 1D TiO₂ composited with different dimensional photoactive materials. The key focus of this review is to understand the charge transfer processes at interfaces and the relationship between photogenerated charge separation and photoelectrochemical performance. It is anticipated that this review will afford enriched information on the rational designs of nanoarchitectures, doping, and heterojunction interfaces for 1D TiO₂ based photoelectrodes to achieve highly efficient solar energy conversion.

Construction of Zn/Ni Bimetallic Organic Framework Derived ZnO/NiO Heterostructure with Superior N-Propanol Sensing Performance

Bimetallic organic frameworks (Bi-MOFs) have been recognized as one of the most ideal precursors to construct metal oxide semiconductor (MOS) composites, owing to their high surface area, various chemical structures, and easy removal of the sacrificial MOF scaffolds through calcination. Herein, we synthesized Zn/Ni Bi-MOF for the first time via a facile ion exchange postsynthetic strategy, formed a three-dimensional framework consisting of infinite one-dimensional chains that is unattainable through the direct solvothermal approach, and then transformed the Zn/Ni Bi-MOF into a unique ZnO/NiO heterostructure through calcination. Notably, the obtained sensor based on a ZnO/NiO heterostructure exhibits an ultrahigh response of 280.2 toward 500 ppm n-propanol at 275 °C (17.2-fold enhancement compared with that of ZnO), remarkable selectivity, and a limit of detection of 200 ppb with a notable response (2.51), which outperforms state-of-the-art n-propanol sensors. The enhanced n-propanol sensing properties may be attributed to the synergistic effects of several points including the heterojunction at the interface between the NiO and ZnO nanoparticles, especially a one-dimensional chain MOF template structure as well as the chemical sensitization effect of NiO. This work provides a promising strategy for the development of a novel Bi-MOF-derived MOS heterostructure or homostructure with well-defined morphology and composition that can be applied to the fields of gas sensing, energy storage, and catalysis.

Applications of Low-Melting-Point Metals in Rechargeable Metal Batteries

Low-melting-point (LMP) metals represent an interesting family of electrode materials owing to their high ionic conductivity, good ductility or fluidity, low hardness and/or superior alloying capability, all of which are crucial characteristics to address battery challenges such as interfacial incompatibility, electrode pulverization, and dendrite growth. This minireview summarizes recent research progress of typical LMP metals including In, Ga, Hg, and their alloys in rechargeable metal batteries. Emphasis is placed on mainstream electrochemical storage devices of Li, Na, and K batteries as well as the representative multi-valent metal batteries. The fundamental correlations between unique physiochemical properties of LMP metals and the battery performance are highlighted. In addition, this article also provides insights into future development and potential directions of LMP metals/alloys for practical applications.

Electron energy loss spectroscopy and first-principles study of GaN via Zn doping

The electronic structure of GaN and GaN:Zn was investigated by electron energy loss spectroscopy and first-principles calculations. In the low-loss spectrum, the interband transitions are assigned to the observed energy loss peaks. After Zn doping, impurity levels are introduced to the density of states and hybrid orbitals of N 2p and Zn 3d are formed around the Fermi level. In the nitrogen K-edge, an additional peak was observed due to the formation of donor defect states. A core-hole effect is believed to be significant for simulation of the N K-edge for both GaN and GaN:Zn.

Textiles Functionalized with ZnO Nanoparticles Obtained by Chemical and Green Synthesis Protocols: Evaluation of the Type of Textile and Resistance to UV Radiation

The study evaluates five types of commercial textiles with different cotton and polyester contents widely used in the garment industry. These textile samples have been subjected to treatment by the exhaustion method using zinc oxide nanoparticles (NP ZnO) (textile functionalization) with the aim of improving their efficiency in blocking UV radiation. The ZnO nanoparticles have been obtained by two methods: The green or also called biosynthesis (using the extract of Coriandrum sativum as an organic reducing agent), and the chemical method (using NaOH as an inorganic reducing agent). The results related to the green method show having achieved a defined geometric configuration with an average size of 97.77 nm (SD: 9.53). On the contrary, the nanostructures obtained by the chemical method show pentagonal configurations with average sizes of 113 nm (SD: 6.72). The textiles functionalized with NP ZnO obtained by biosynthesis showed a better efficiency in blocking ultraviolet radiation (UV).

Self-inhibition effect of metal incorporation in nanoscaled semiconductors

There has been a persistent effort to understand and control the incorporation of metal impurities in semiconductors at nanoscale, as it is important for semiconductor processing from growth, doping to making contact. Previously, the injection of metal atoms into nanoscaled semiconductor, with concentrations orders of magnitude higher than the equilibrium solid solubility, has been reported, which is often deemed to be detrimental. Here our theoretical exploration reveals that this colossal injection is because gold or aluminum atoms tend to substitute Si atoms and thus are not mobile in the lattice of Si. In contrast, the interstitial atoms in the Si lattice such as manganese (Mn) are expected to quickly diffuse out conveniently. Experimentally, we confirm the self-inhibition effect of Mn incorporation in nanoscaled silicon, as no metal atoms can be found in the body of silicon (below 10¹⁷ atoms per cm^-3) by careful three-dimensional atomic mappings using highly focused ultraviolet-laser-assisted atom-probe tomography. As a result of self-inhibition effect of metal incorporation, the corresponding field-effect devices demonstrate superior transport properties. This finding of self-inhibition effect provides a missing piece for understanding the metal incorporation in semiconductor at nanoscale, which is critical not only for growing nanoscale building blocks, but also for designing and processing metal-semiconductor structures and fine-tuning their properties at nanoscale.

Emergence and Control of Stacking Fault Formation during Nanoparticle Cation Exchange Reactions

Cation exchange reactions modify the composition of a nanocrystal while retaining other features, including the crystal structure and morphology. In many cases, the anion sublattice is considered to be locked in place as cations rapidly shuttle in and out. Here we provide evidence that the anion sublattice can shift significantly during nanocrystal cation exchange reactions. When the Cu⁺ cations of roxbyite Cu_1.8S nanorods exchange with Zn²⁺ to form ZnS nanorods, a high density of stacking faults emerges. During cation exchange, the stacking sequence of the close-packed anion sublattice shifts at many locations to generate a nanorod product containing a mixture of wurtzite, zincblende, and a wurtzite/zincblende polytype that contains an ordered arrangement of stacking faults. The reagent concentration and reaction temperature, which control the cation exchange rate, serve as synthetic levers that can tune the stacking fault density from high to low, which is important because once introduced, the stacking faults could not be modified through thermal annealing. This level of synthetic control through nanocrystal cation exchange is important for controlling properties that depend on the presence and density of stacking faults.