Table of contents

Porous anodic aluminium oxide (AAO) membranes have various practical applications in separation and purification technologies. Numerous approaches have been utilized to tailor the transport properties of porous AAO films, but all of them assume an isotropic nature of anodized aluminium. Here, the impact of aluminium crystallography on the permeability of AAO membranes is disclosed. A comparative study of AAO membranes formed on low-index aluminium surfaces by anodizing in a sulphuric acid electrolyte is presented. Small-angle x-ray scattering is used to quantify the out-of-plane pore arrangement. AAO grown on an Al(100) substrate possesses a porous structure with minimal point defects and pore tortuosity, providing the highest permeability of individual gases in a series of AAO membranes. These findings can also be applied for the fabrication of highly permeable AAO membranes on polycrystalline Al foils.

Nanostructured n-type metal oxides/p-type boron-doped diamond heterojunctions have demonstrated a typical rectification feature and/or negative differential resistance (NDR) potentially applied in wide fields. Recently, the fabrication and electronic transport behavior of n-WO₃ nanorods/p-diamond heterojunction at high temperatures were studied by Wang et al (2017 Appl. Phys. Lett.110 052106), which opened the door for optoelectronic applications that can operate at high-temperatures, high-power, and in various harsh environments. In this perspective, an overview was presented on the future directions, challenges and opportunities for the optoelectronic applications based on the n-WO₃ nanostructures/p-diamond heterojunction. We focus, in particular, on the prospects for its high temperature NDR, UV photodetector, field emission emitters, photocatalyst and optical information storage for a wide range of new optoelectronic applications.

The emergence of multi-drug resistant bacterial infections has resulted in increased interest in the development of alternative systems which can sensitize bacteria to overcome resistance. In an attempt to contribute to the existing literature of potential antibacterial agents, we present here, a first report of the antibacterial potential of FeCo nanoparticles, both as stand-alone devices and in presence of magnetic field, against the bacterial strains of S. aureus and E. coli. A relatively simple polyol process was employed for nanoparticle synthesis. Formation of FeCo alloy in the desired BCC phase was confirmed by x-ray diffraction with a high saturation magnetization (M_s ∼ 180 Am²kg⁻¹). Uniformly sized spherical structures with sharp edges were obtained. Solution stability was confirmed by the zeta potential value of −27.8 mV. Dose dependent bacterial growth inhibition was observed, the corresponding linear correlation coefficients being, R² = 0.74 for S. aureus and R² = 0.76 for E. coli. Minimum inhibitory concentration was accordingly ascertained to be >1024 μg ml⁻¹ for both. Bacterial growth curves have been examined upon concomitant application of external magnetic field of varying intensities and revealed considerable enhancement in the antibacterial response upto 64% in a field of 100 mT. An effort has been made to understand the bacterial inhibitory mechanism by relating with the chemical and physical properties of the nanoparticles. The ease of field assisted targeting and retrieval of these highly magnetic, antibacterial nano-devices, with considerably improved response with magnetic fields, make them promising for several medical and environment remediation technologies.

The development of nanophotonic devices has presented a revolutionary means to manipulate light at nanoscale. How to efficiently design these devices is an active area of research. Recently, artificial neural networks (ANNs) have displayed powerful ability in the inverse design of nanophotonic devices. However, there is limited research on the inverse design for modeling and learning the sequence characteristics of a spectrum. In this work, we propose a deep learning method based on an improved recurrent neural network to extract the sequence characteristics of a spectrum and achieve inverse design and spectrum prediction. A key feature of the network is that the memory or feedback loops it comprises allow it to effectively recognize time series data. In the context of nanorods hyperbolic metamaterials, we demonstrated the high consistency between the target spectrum and the predicted spectrum, and the network learned the deep physical relationship concerning the structural parameter changes reflected on the spectrum. The effectiveness of our approach is also tested by user-drawn spectra. Moreover, the proposed model is capable of predicting an unknown spectrum based on a known spectrum with only 0.32% mean relative error. The prediction model may be helpful to predict data beyond the detection limit. We propose this versatile method as an effective and accurate alternative to the application of ANNs in nanophotonics, paving way for fast and accurate design of desired devices.

We demonstrate band to band tunneling (BTBT) in a carbon nanotube (CNT) field effect transistor. We employ local electrostatic doping assisted by charged traps within the oxide to produce an intramolecular PN junction along the CNT. These characteristics apply for both metallic (m-CNTs) and semiconducting (SC-CNTs) CNTs. For m-CNTs we present a hysteretic transfer characteristic which originates from local electrostatic doping in the middle segment of the CNT. This controlled doping is reversible and results in formation and destruction of a PN junction along the CNT channel. For SC-CNTs we observe BTBT, and analysis based on the WKB approximation reveals a very narrow depletion region and high transmission probability at the optimal energy bands overlap. These results may assist in developing a non-volatile one-dimensional PN junction memory cell and designing a tunneling based field effect transistor.

The unbalanced charge transport is always a key influencing factor on the device performance of quantum dot light-emitting diodes (QLEDs), particularly for the blue QLEDs due to their large optical band gap. Here, a method of electron transport layer (ETL) doping was developed to regulate the energy levels and the carrier mobility of the ETL, which resulted in more balanced charge injection, transport and recombination in the blue emitting CdZnS/ZnS core/shell QLEDs. Consequently, an enhanced performance of blue QLEDs was achieved by modulating the charge balance through ETL doping. The maximum external quantum efficiency and luminance was dramatically increased from 2.2% to 7.3% and from 3786 cd m⁻² to 9108 cd m⁻², respectively. The results illustrate that charge transport layer doping is a simple and effective strategy to regulate the charge injection barrier and carrier mobility of QLEDs.

Highly efficient, all-solution processed inverted quantum dot light-emitting diodes (QLEDs) are demonstrated by employing 1,3,5-tri(m-pyrid-3-yl-phenyl)benzene (TmPyPB) layer as electron blocking layer. Electron injection from ZnO electron transport layer to quantum dots (QDs) emission layer (EML) can be adjusted by thickness of TmPyPB layer, enabling the balanced charge carriers in QDs EML. With optimal thickness of this TmPyPB adjuster, 59.7% increment in the device current efficiency (from 8.2 to 13.1 cd A⁻¹) and 46.2% improvement in the maximum luminance (from 31916 to 46674 cd m⁻²) are achieved, compared with those of the control QLED which has double hole transport layer structure. On the other hand, we find luminescence quenching process, which often happens at the interface of ZnO nanoparticles and QDs, is not obvious in our QLEDs, in which the ZnO layer is fabricated in precursor method, and this conclusion is verified through Time Resolution Photoluminescence test. In a word, this strategy provides a direction for optimizing charge carrier balance in all-solution processed inverted QLED.

It is very urgent to build memristive synapses and even wearable devices to simulate the basic functions of biological synapses. The linear conductance modulation is the basis of analog memristor for neuromorphic computing. By optimizing the interface engineering wherein Ta/TiO_x/TaO_x/Ru was fabricated, all the memristor devices with different TiO_x thickness showed electroforming-free property. The short-term and long-term plasticity in both potentiation and depression behaviors can be mimicked when TiO_x was fixed at 25 nm. The presented memristive synapses simulated the stable paired-pulse facilitation and spike-timing dependent plasticity performance. The potentiation and depression in linearity and symmetry improved with the TiO_x thickness increasing, which provides the feasibility for the application of artificial neural network. In addition, the device deposited on polyimide (PI) still exhibits the synaptic performance until the bending radii reaches 6 mm. By carefully tuning the interface engineering, this study can provide general revelation for continuous improvement of the memristive performance in neuromorphic applications.

Junctionless tunneling field-effect transistor (JL-TFET) is an excellent potential alternative to conventional MOSFET and TFET due to the lack of a steep doping profile, which makes it easier to fabricate. JL-TFET not only offers a lower subthreshold swing (SS) compared to MOSFET, but mitigates the low on-current problem associated with conventional TFET. The DC and analog characteristics of JL-TFET can be further improved by design modifications. In this research, we have presented two novel structures of JL-TFET: stimulated n-pocket JL-TFET (SNPJL-TFET) and SNPJL-TFET with heterogeneous gate dielectric. The performance of these devices has been gauged against conventional JL-TFET. Both novel structures exhibit excellent performance including point SS around 20 mV/dec, high I_ON/I_OFF in the order of 10¹⁴ and lower threshold voltage (V_T). By analyzing RF and linearity parameters such as the transconductance generation factor, F_T, transit time, total factor productivity, second-order voltage intercept point, third-order voltage intercept point, third-order input intercept point and third-order intermodulation distortion, it is observed that the proposed devices are more suitable for RF applications since they show superiority in most of the analyzed parameters.

Two different dewetting methods, namely pulsed laser-induced dewetting (PLiD)—a liquid-state dewetting process and thermal dewetting (TD)—a solid-state dewetting process, have been systematically explored for Ag thin films (1.9–19.8 nm) on Si substrates for the fabrication of Ag nanoparticles (NPs) and the understanding of dewetting mechanisms. The effect of laser fluence and irradiation time in PLiD and temperature and duration in TD were investigated. A comparison of the produced Ag NP size distributions using the two methods of PLiD and TD has shown that both produce Ag NPs of similar size with better size uniformity for thinner films (<6 nm), whereas TD produced bigger Ag NPs for thicker films (≥8–10 nm) as compared to PLiD. As the film thickness increases, the Ag NP size distributions from both PLiD and TD show a deviation from the unimodal distributions, leading to a bimodal distribution. The PLiD process is governed by the mechanism of nucleation and growth of holes due to the formation of many nano-islands from the Volmer−Weber growth of thin films during the sputtering process. The investigation of thickness-dependent NP size in TD leads to the understanding of void initiation due to pore nucleation at the film-substrate interface. Furthermore, the linear dependence of NP size on thickness in TD provides direct evidence of fingering instability, which leads to the branched growth of voids.

The thermal stability of antireflective moth-eye topographical features fabricated by nanoimprint lithography on poly (methyl methacrylate) (PMMA) incorporating TiO₂ nanoparticles is explored. The effect of nanoparticle load on the relaxation dynamics of the moth-eye nanostructure is evaluated via grazing incidence small angle x-ray scattering measurements by in situ monitoring the structural decay of the nanopatterns upon thermal annealing. It is demonstrated that the incorporation of TiO₂ nanoparticles to the imprinted surface nanocomposite films delays greatly the pattern relaxation which, in turn, enhances the stability of the patterned topography even at temperatures well above the polymer glass transition (T_g). The improved thermal behavior of the antireflective films will significantly enhance their functionality and performance in light-trapping applications where temperatures typically rise, such as solar devices or solar glass panels.

Monoclinic scheelite bismuth vanadate is an efficient photocatalyst for water splitting. In this paper, we perform DFT + U calculations to investigate the structural, electronic, and optical properties, water adsorption and the oxygen evolution reaction processes on BiVO₄ (001) and BiVO₄ (110) surfaces in acidic medium both in the gas and solution (water) phases. The structural, electronic, optical, and water adsorption properties reveal that BiVO₄ (001) surface is energetically more stable than BiVO₄ (110) surface in vacuum. On other hand, the water oxidation mechanisms reveal that BiVO₄ (110) surface in water and in strained form in vacuum is energetically more stable than BiVO₄ (001) surface in water and in strained form in vacuum both U = 0 and 2.1 V. The free energy of adsorption for all systems at U = 2.1 V reduce about 2 times than that at U = 0 V. Such analyzes provide important insights into the role of different facets on BiVO₄ surface for photocatalytic reactions.

The operating principle of Pirani pressure sensors is based on the pressure dependence of a suspended strip's electrical conductivity, caused by the thermal conductance of the surrounding gas which changes the Joule heating of the strip. To realize such sensors, not only materials with high temperature dependent electrical conductivity are required, but also minimization of the suspended strip dimensions is essential to maximize the responsivity and minimize the power consumption. Due to this, nanomaterials are especially attractive for this application. Here, we demonstrate the use of a multi-layer suspended graphene strip as a Pirani pressure sensor and compare its behavior with existing models. A clear pressure dependence of the strip's electrical resistance is observed, with a maximum relative change of 2.75% between 1 and 1000 mbar and a power consumption of 8.5 mW. The use of graphene enables miniaturization of the device footprint by 100 times compared to state-of-the-art. Moreover, miniaturization allows for lower power consumption and/or higher responsivity and the sensor's nanogap enables operation near atmospheric pressure that can be used in applications such as barometers for altitude measurement. Furthermore, we demonstrate that the sensor response depends on the type of gas molecules, which opens up the way to selective gas sensing applications. Finally, the graphene synthesis technology is compatible with wafer-scale fabrication, potentially enabling future chip-level integration with readout electronics.

Recent advances in the nanofabrication and modeling of metasurfaces have shown the potential of these systems in providing unprecedented control over light–matter interactions at the nanoscale, enabling immediate and tangible improvement of features and specifications of photonic devices that are becoming always more crucial in enhancing everyday life quality. In this work, we theoretically demonstrate that metasurfaces made of periodic and non-periodic deterministic assemblies of vertically aligned semiconductor nanowires can be engineered to display a tailored effective optical response and provide a suitable route to realize advanced systems with controlled photonic properties particularly interesting for sensing applications. The metasurfaces investigated in this paper correspond to nanowire arrays that can be experimentally realized exploiting nanolithography and bottom-up nanowire growth methods: the combination of these techniques allow to finely control the position and the physical properties of each individual nanowire in complex arrays. By resorting to numerical simulations, we address the near- and far-field behavior of a nanowire ensemble and we show that the controlled design and arrangement of the nanowires on the substrate may introduce unprecedented oscillations of light reflectance, yielding a metasurface which displays an electromagnetic behavior with great potential for sensing. Finite-difference time-domain numerical simulations are carried out to tailor the nanostructure parameters and systematically engineer the optical response in the VIS-NIR spectral range. By exploiting our computational-methods we set-up a complete procedure to design and test metasurfaces able to behave as functional sensors. These results are especially encouraging in the perspective of developing arrays of epitaxially grown semiconductor nanowires, where the suggested design can be easily implemented during the nanostructure growth, opening the way to fully engineered nanowire-based optical metamaterials.

Recent advances in the nanofabrication and modeling of metasurfaces have shown the potential of these systems in providing unprecedented control over light–matter interactions at the nanoscale, enabling immediate and tangible improvement of features and specifications of photonic devices that are becoming always more crucial in enhancing everyday life quality. In this work, we theoretically demonstrate that metasurfaces made of periodic and non-periodic deterministic assemblies of vertically aligned semiconductor nanowires can be engineered to display a tailored effective optical response and provide a suitable route to realize advanced systems with controlled photonic properties particularly interesting for sensing applications. The metasurfaces investigated in this paper correspond to nanowire arrays that can be experimentally realized exploiting nanolithography and bottom-up nanowire growth methods: the combination of these techniques allow to finely control the position and the physical properties of each individual nanowire in complex arrays. By resorting to numerical simulations, we address the near- and far-field behavior of a nanowire ensemble and we show that the controlled design and arrangement of the nanowires on the substrate may introduce unprecedented oscillations of light reflectance, yielding a metasurface which displays an electromagnetic behavior with great potential for sensing. Finite-difference time-domain numerical simulations are carried out to tailor the nanostructure parameters and systematically engineer the optical response in the VIS-NIR spectral range. By exploiting our computational-methods we set-up a complete procedure to design and test metasurfaces able to behave as functional sensors. These results are especially encouraging in the perspective of developing arrays of epitaxially grown semiconductor nanowires, where the suggested design can be easily implemented during the nanostructure growth, opening the way to fully engineered nanowire-based optical metamaterials.

We report here the successful operation of WS₂-QD/RGO hybrid temperature sensor, which performs instant measurement like thermometer in a wide temperature range: 77–398 K, in both static- and instant mode. All this was possible by embedding WS₂-QDs on electrically conducting RGO layer, synthesized on cotton textile fabric. The device is simple, scalable, flexible and cost-effective. Successful trial to monitor human body temperature is conducted with fast response- and recovery time ∼0.60 and 11.3 s with an exceptional resolution ∼0.06 K. Crucial parameters such as temperature coefficient of resistance (TCR) and thermal hysteresis (H_th) were theoretically analyzed to understand the intricate mechanism behind the working of a temperature sensor; temperature sensing data at both high- and low temperatures are outstanding as well as competitive. To mention, a few of these parameters are found comparable and even superior to some of the devices as reported. This sensor device proved its flexibility and stability under various in situ mechanical deformation tests, showing its promising potential for future generation wearable health monitoring devices. To the best of our knowledge, this is the first report on WS₂ in general, and WS₂-QDs, in specific, based temperature sensing device and its operational demonstration as of now.

To develop excellent photoelectronic and photovoltaic devices, a semiconductor with high photoelectron production efficiency and broad band absorption is urgently required. In this article, novel II-type PbSe/ZnSe hetero-nanobelts with enhanced near-infrared absorption have been synthesized via a facile strategy of a partial cation-exchange reaction and thermal treatment. Derived from ZnSe·0.5N₂H₄ nanobelts as templates, the belt-like morphology was preserved. Due to the mismatch of the crystal type and parameters between PbSe and ZnSe, the formed PbSe in the form of nanoparticles were separated out and decorated on the nanobelts. Furthermore, the composition ratio of Pb/Zn can be tuned through manipulating the adding amount of Pb²⁺ cations, the reaction temperature and time. The ultraviolet−visible−infrared diffuse spectra measurements suggest that the as-prepared PbSe/ZnSe hetero-nanobelts exhibited a broad band absorption from 300 to 1000 nm. In addition, they demonstrated excellent photoresponsivity in the same wavelength region and displayed a peak at approximately 840 nm. Finally, the enhanced photoelectronic sensing mechanism was discussed.

Measuring solution concentration plays an important role in chemical, biochemical, clinical diagnosis, environmental monitoring, and biological analyses. In this work, we develop a transmission-mode localized surface plasmon resonance sensor chip system and convenient method which is highly efficient, highly sensitive for detection sensing using multimode fiber. The plasmonically active sensor's surface AuNPs with high-density NPs were decorated onto 1 cm sensing length of various clad-free fiber in the form of homogeneous monolayer utilizing a self-assembly process for immobilization of the target molecule. The carboxyl bond is formed through a functional reaction on the sensor head. Using the significance in the refractive index difference and numerical aperture, which is caused by a variation in the concentration of measuring bovine serum albumin (BSA) protein which can be accurately measured by the output signal. The refractive index variation of the medium analyte layer can be converted to signal output power change at the He–Ne wavelength of 632.8 nm. The sensor detection limit was estimated to be 0.075 ng ml⁻¹ for BSA protein which shows high sensitivity compared to other types of label-free optical biosensors. This also leads to a possibility of finding the improvement in the sensitivity label-free biosensors. The conventional method should allow multimode fiber biosensors to become a possible replacement for conventional biosensing techniques based on fluorescence.

All inorganic perovskite nanocrystals CsPbX₃(X = Cl, Br, I) are the great potential candidates for the application of high-performance light emitting diodes (LED) due to their high Photoluminescence Quantum Yield (PLQY), high defect tolerance, narrow full-width half-maximum and tunable wavelength of 410–700 nm. However, the application of red-emitting (630–650 nm) CsPbBr_xI_3-x nanocrystals are perplexed by phase segregation due to the composition of mixed halides and the difference in halide ion mobility. Herein, we provide an effective strategy to suppressing the migration of Br/I ions through Ni²⁺ doping via a facile Hot-Injection method and the PLQY was improved as well. DFT calculations show that the introduction of Ni²⁺ causes a slight contraction of the host crystal structure, which improves the bond energy between Pb and halides and reduces the level of surface defects. Therefore, the phase stability is improved by Ni²⁺ doping because the phase segregation caused by ion migration in the mixed phase is effectively inhibited. Meanwhile, the non-radiative recombination in the exciton transition process is reduced and the PLQY is improved. What's more, benefiting from the suppressed ion migration and enhanced PLQY, we combine the Ni²⁺-doped CsPbBr_xI_3-x nanocrystals with different Br/I ratios and YAG: Ce³⁺ phosphors as color conversion layers to fabricate high efficiency WLED. When the ratio of Br/I is 9:11, WLED has a color coordinate of (0.3621, 0.3458), the color temperature of 4336 K and presents a high luminous efficiency of 113.20 lm W⁻¹, color rendering index of 94.9 under the driving current of 20 mA and exhibits excellent stability, which shows great potential in the application of LED.

All inorganic perovskite nanocrystals CsPbX₃(X = Cl, Br, I) are the great potential candidates for the application of high-performance light emitting diodes (LED) due to their high Photoluminescence Quantum Yield (PLQY), high defect tolerance, narrow full-width half-maximum and tunable wavelength of 410–700 nm. However, the application of red-emitting (630–650 nm) CsPbBr_xI_3-x nanocrystals are perplexed by phase segregation due to the composition of mixed halides and the difference in halide ion mobility. Herein, we provide an effective strategy to suppressing the migration of Br/I ions through Ni²⁺ doping via a facile Hot-Injection method and the PLQY was improved as well. DFT calculations show that the introduction of Ni²⁺ causes a slight contraction of the host crystal structure, which improves the bond energy between Pb and halides and reduces the level of surface defects. Therefore, the phase stability is improved by Ni²⁺ doping because the phase segregation caused by ion migration in the mixed phase is effectively inhibited. Meanwhile, the non-radiative recombination in the exciton transition process is reduced and the PLQY is improved. What's more, benefiting from the suppressed ion migration and enhanced PLQY, we combine the Ni²⁺-doped CsPbBr_xI_3-x nanocrystals with different Br/I ratios and YAG: Ce³⁺ phosphors as color conversion layers to fabricate high efficiency WLED. When the ratio of Br/I is 9:11, WLED has a color coordinate of (0.3621, 0.3458), the color temperature of 4336 K and presents a high luminous efficiency of 113.20 lm W⁻¹, color rendering index of 94.9 under the driving current of 20 mA and exhibits excellent stability, which shows great potential in the application of LED.

Polyhedral carbon nano-onions (CNOs) compared with traditional quasi-spherical CNOs are more stable and have less defects, which will greatly broaden their potential applications. However, there still lacks of a suitable synthetic method. Here, we developed a simple molecular fusion route and templet growth method by which polyhedral CNOs can be successfully synthesized. Characterization of the polyhedral CNOs by transmission electron microscopy, x-ray diffraction and Raman spectroscopy indicates that they have an ultra-high degree of graphitization and a large cavity diameter of about 10 nm, which results in their low density of 1.42 g cm⁻³. In addition, the deeper reaction mechanism of polyhedral CNOs growth was also elucidated. It was found that the channel structure and the absorption of the templet play the crucial role during the formation of polyhedral CNOs.

Hollow-structured NiO + Ni nanofibers wrapped by graphene were designed and successfully fabricated via a simple method. First, solid NiO + Ni nanofibers were prepared by electrospinning followed by calcination. Here, a portion of the metallic Ni was retained to improve the electrochemical performance of NiO by adjusting the calcination temperature. Next, the nanofibers were thoroughly mixed with different amounts of graphene and calcinated once more to form hollow-structured NiO + Ni nanofibers with an extremely high specific surface via the reaction between graphene and NiO on the nanofiber surface and subsequent migration of NiO into the nanofibers. Results showed that the obtained hollow-structured NiO + Ni electrode demonstrates optimal electrochemical performance when the graphene content is controlled to 3 wt%. The first cycle discharge/charge specific capacity of the electrode peaked (1596/1181 mAh · g⁻¹ ) at 100 mA · g⁻¹, with a coulombic efficiency of approximately 74% (60% for 0 wt% graphene, 65% for 1 wt% graphene, and 51% for 4 wt% graphene). It also presented excellent cycling stability after 100 cycles at 100 mA · g⁻¹ on account of its high retained discharge specific capacity (251 mAh · g⁻¹ for 0 wt% graphene, 385 mAh · g⁻¹ for 1 wt% graphene, 741 mAh · g⁻¹ for 3 wt% graphene, and 367 mAh · g⁻¹ for 4 wt% graphene). Moreover, the synthesized electrode possessed outstanding rate capability owing to its large average discharge specific capacity of approximately 546 mAh · g⁻¹ (45 mAh · g⁻¹ for 0 wt% graphene, 256 mAh · g⁻¹ for 1 wt% graphene, and 174 mAh · g⁻¹ for 4 wt% graphene) from 100 mA · g⁻¹ to 2000 mA · g⁻¹. The observed improvement in electrochemical performance could be attributed to the increase in active sites and decrease in charge transport distance in the hollow-structured NiO + Ni nanofibers. Excessive introduction of graphene caused a sharp loss in electrochemical performance due to the agglomeration of graphene sheets on the nanofiber surfaces.

InGaN nanostructures are among the most promising candidates for visible solid-state lighting and renewable energy sources. To date, there is still a lack of information about the influence of the growth conditions on the physical properties of these nanostructures. Here, we extend the study of InGaN nanowires growth directly on Si substrates by plasma-assisted molecular beam epitaxy. The results of the study showed that under appropriate growth conditions a change in the growth temperature of just 10 °C leads to a significant change in the structural and optical properties of the nanowires. InGaN nanowires with the areas containing 4%–10% of In with increasing tendency towards the top are formed at the growth temperature of 665 °C, while at the growth temperatures range of 655 °C–660 °C the spontaneously core–shell NWs are typically presented. In the latter case, the In contents in the core and the shell are about an order of magnitude different (e.g. 35% and 4% for 655 °C, respectively). The photoluminescence study of the NWs demonstrates a shift in the spectra from blue to orange in accordance with an increase of In content. Based on these results, a novel approach to the monolithic growth of In_xGa_1−xN NWs with multi-colour light emission on Si substrates by setting a temperature gradient over the substrate surface is proposed.

In this work, heterostructures of coupled TiO₂@MoS₂ with different phases of MoS₂ were synthesized via hydrothermal technique. The prepared materials were thoroughly characterized using various techniques, including XRD, SEM, transmission electron microscopy, Brunauer–Emmet–Teller, XPS, Zeta potential and UV–vis spectroscopy. The optimized nanocomposites were tested for the photocatalytic degradation of methyl Orange (MO) under visible light as well as the adsorption of Rhodamine b (RhB) and methelene blue (MB) dyes. The TiO₂@1T/2H-MoS₂ heterostructures exhibited a narrow bandgap compared to the other studied nanomaterials. A remarkable photodegradation efficiency of TiO₂@1T/2H-MoS₂ was observed, which completely degraded 20 ppm of MO after 60 min with high stability over four successive cycles. This can be assigned to the formation of unique heterostructures with aligned energy bands between MoS₂ nanosheets and TiO₂ nanobelts. The formation of these novel interfaces promoted the electron transfer and increased the separation efficiency of carriers, resulting in high photocatalytic degradation. Furthermore, the adsorption efficiency of TiO₂@1T/2H-MoS₂ was unique, 20 ppm solutions of RhB and MB were removed after 1 and 2 min, respectively. The superior adsorption performance of the TiO₂@1T/2H-MoS₂ can be attributed to its high surface area (279.9 m² g⁻¹) and the rich concentration of active sites. The kinetics and the isothermal analysis revealed that the TiO₂@1T/2H MoS₂ heterstructures have maximum adsorption capacity of 1200 and 970 mg g⁻¹ for RhB and MB, respectively. This study provides a powerful way for designing an effective photocatalyst and adsorbent TiO₂-based nanocomposites for water remediation.

Two-dimensional (2D) molybdenum ditelluride (MoTe₂) is a member of the transition-metal dichalcogenides family, which is an especially promising platform for surface-enhanced Raman scattering (SERS) applications, due to its excellent electronic properties. However, the synthesis of large-area highly crystalline 2D MoTe₂ with controllable polymorphism is a huge challenge due to the small free energy difference (∼40 meV per unit cell) between semiconducting 2H-MoTe₂ and semi-metallic 1 T'-MoTe₂. Herein, we report an optimized route for the synthesis of 2H- and 1 T'-MoTe₂ films by atmospheric-pressure chemical vapor deposition. The SERS study of the as-grown MoTe₂ films was carried out using methylene blue (MB) as a probe molecule. The Raman enhancement factor on 1 T'-MoTe₂ was found to be three times higher than that on 2H-MoTe₂ and the 1 T'-MoTe₂ film is an efficient Raman-enhancing substrate that can be used to detect MB at nanomolar concentrations. Our study also imparts knowledge on the significance of a suitable combination of laser excitation wavelength and molecule-material platform for achieving ultrasensitive SERS-based chemical detection.

Amorphous alloys (AAs) are promising materials due to their unique properties and have been applied in various biomaterial coatings and micro-electro-mechanical systems. However, they have seldom been applied in the optical nano-device. Here, we systematically investigate morphology, microstructure, mechanical and optical properties of an Au–Cu–Si AA and successfully design and fabricate a broadband optical absorber using the Au–Cu–Si AA. Such device achieves an average absorption up to about 95% from 500 to 1500 nm with a thickness less than 300 nm. This is of significance for exploration the feasibility of AAs application in the field of optical nano-devices.

Atomic layer deposition method was used to grow thin films consisting of ZrO₂ and MnO_x layers. Magnetic and electric properties were studied of films deposited at 300 °C. Some deposition characteristics of the manganese(III)acetylacetonate and ozone process were investigated, such as the dependence of growth rate on the deposition temperature and film crystallinity. All films were partly crystalline in their as-deposited state. Zirconium oxide contained cubic and tetragonal phases of ZrO₂, while the manganese oxide was shown to consist of cubic Mn₂O₃ and tetragonal Mn₃O₄ phases. All the films exhibited nonlinear saturative magnetization with hysteresis, as well as resistive switching characteristics.

By adoption of a high permittivity ZrO₂ capping layer (ZOCL), enhanced ferroelectric properties were achieved in the Hf_0.5Zr_0.5O₂ (HZO) thin films. For HZO thin film with 10 Å ZOCL, the 2P_r value can reach as high as ∼43.1 μC cm⁻² under a sweep electric field of 3 MV cm⁻¹. In addition, a reduced coercive field of 1.5 MV cm⁻¹ was observed, which is comparable to that of HZO with metallic CL. Furthermore, the homogeneity of ferroelectric orthorhombic phase in HZO films was observed to be clearly increased, as evidenced by nanoscale piezoelectric force microscopy measurements. These results demonstrate that ZOCL is very favorable for high performance ferroelectric HZO films and their future device applications.

Bismuth sulfide (Bi₂S₃) is a promising material for thermoelectric applications owing to its non-toxicity and high abundance of bismuth (Bi) and sulfur (S) elements on earth. However, its low electrical conductivity drastically reduces the value of the figure of merit (ZT). In this work, we have synthesized three-dimensional (3D) hierarchical Bi₂S₃ nanoflowers (NFs) by the hydrothermal route and further incorporated them with conducting polymer polyaniline (PANI) by simple chemisorption method. We have investigated the thermoelectric properties of the as-prepared Bi₂S₃ NFs and PANI/Bi₂S₃ nanocomposite samples and it is demonstrated that the incorporation of the PANI matrix with the 3D hierarchical Bi₂S₃ NFs provides a conducting substrate for the easy transport of the electrons and reduces the barrier height at the interface, resulting in ∼62% increment in the electrical conductivity as compared to Bi₂S₃ NFs. Moreover, a decrement in the thermal conductivity of the PANI/Bi₂S₃ nanocomposite is observed as compared to pristine Bi₂S₃ NFs due to the increased phonon scattering at the interfaces facilitated by the hierarchical morphology of the NFs. Furthermore, an increment in the electrical conductivity and simultaneous decrement in the thermal conductivity results in an overall ∼20% increment in the figure of merit (ZT) for PANI/Bi₂S₃ nanocomposite as compared to pristine Bi₂S₃ NFs. The work highlights an effective strategy of coupling 3D hierarchical metal chalcogenide with conducting polymer for optimizing their thermoelectric properties.

Since the successfully synthesis of monolayer graphene, carbon-based materials have attracted wide and extensive attentions from researches. Due to the excellent transport capacity and conductivity, they are promising to be applied in electronic devices, even substituting the silicon-based electronic devices, optoelectronics and spintronics. Nevertheless, due to the non magnetic feature, many efforts have been devoted to endow carbon materials magnetism to apply them in the spintronic devices fabrication. Herein, a strategy of Cr cation solely anchored on two-dimensional carbon nanosheets by Cr–N bonds is developed, which introduces magnetism in carbon nanosheets. By extended x-ray absorption fine structure characterization, Cr cations are demonstrated to be atomically dispersed with Cr–N₃ coordination. And after Cr–N₃ anchored, carbon nanosheets exhibit ferromagnetic features with paramagnetic background. The magnetization varies with Cr content and reaches the maximum (Cr: 2.0%, 0.86 emu g⁻¹) under 3 T at 50 K. The x-ray magnetic circular dichroism and first-principle calculations indicate that the magnetism is caused by the Cr³⁺ component of the anchored Cr cations. This study sets a single cation anchoring carbon as a suitable candidate for future spintronics.