Table of contents

In this letter we report the effect of vertical scaling on the optical and electrical performance of mid-wavelength infrared heterojunction phototransistors based on type-II InAs/GaSb/AlSb superlattices. The performance of devices with different base thickness was compared as the base was scaled from 60 down to 40 nm. The overall optical performance shows enhancement in responsively, optical gain, and specific detectivity upon scaling the base width. The saturated responsivity for devices with 40 nm bases reaches 8845 and 9528 A W⁻¹ at 77 and 150 K, respectively, which is almost five times greater than devices with 60 nm bases. The saturated optical gain for devices with 40 nm bases is measured as 2760 at 77 K and 3081 at 150 K. The devices with 40 nm bases also exhibit remarkable enhancement in saturated current gain, with 17690 at 77 K, and 19050 at 150 K.

A non-raster scanning technique for atomic force microscopy (AFM) imaging which combines rotational and translational motion is presented. The use of rotational motion for the fast scan axis allows us to significantly increase the scanning speed while imaging a large area (diameter > 30 μm). An image reconstruction algorithm and the factors influencing the resolution of the technique are discussed. The experimental results show the potential of the rotational scanning technique for high-throughput large area AFM investigation.

One of the most fascinating possibilities enabled by metamaterials is the strong reduction of the electromagnetic scattering from nanostructures. In dielectric nanoparticles, the formation of a minimal scattering state at specific wavelengths is associated with the excitation of photonic anapoles, which represent a peculiar type of radiationless state and whose existence has been demonstrated experimentally. In this work, we investigate the formation of anapole states in generic dielectric structures by applying a Fano–Feshbach projection scheme, a general technique widely used in the study of quantum mechanical open systems. By expressing the total scattering from the structure in terms of an orthogonal set of internal and external modes, defined in the interior and in the exterior of the dielectric structure, respectively, we show how anapole states are the result of a complex interaction among the resonances of the system and the surrounding environment. We apply our approach to a circular resonator, where we observe the formation of higher-order anapole states, which are originated by the superposition of several internal resonances of the system.

A methodology is developed to reconstruct the force applied to an atomic force microscopy (AFM) cantilever given the shape in which it vibrates. This is accomplished by rewriting Bernoulli–Euler beam theory such that the force on the cantilever is approximated as a linear superposition of the theoretical cantilever eigenmodes. The weighting factors in this summation are calculated from the amplitude and phase measured along the length of the cantilever. The accuracy of the force reconstruction is shown to depend on the frequency at which the measurement is performed, the number of discrete points measured along the length of the cantilever, and the signal-to-noise ratio of the measured signal. In contrast to other AFM force reconstruction techniques, this method can reconstruct the distribution of force applied over the length of the AFM cantilever. However, this method performs poorly for localized forces applied to the cantilever, such as is typical of most tip–sample interaction forces. Proof of concept experiments are performed on an electrostatically excited cantilever and the expected force distribution is recovered. This force reconstruction technique offers previously unavailable insight into the distributed forces experienced by an AFM cantilever.

In two earlier communications (Chatterjee et al 2012 Nanotechnology23 085103, Chatterjee et al 2014 Nanotechnology25 135101), we reported the development of a simple and unique method of synthesizing highly stable metallic copper nanoparticles (Cu NPs) with high antibacterial activity. Here we report on the cytotoxic potency of the NPs against cancer cells. The value of the IC50 dose of the Cu NPs against human skin cancer cell A-375 was found to be 1.71 μg ml⁻¹ only, which was much less than values reported so far, and this concentration had no cytotoxic effect on normal white blood cells. The NPs caused (i) lowering of cell membrane rigidity, (ii) DNA degradation, (iii) chromosomal condensation, (iv) cell cycle arrest in the G2/M phase, (v) depolarization of the mitochondrial membrane and (vi) apoptosis of cells. Cellular apoptosis occurred in the caspase-9-mediated intrinsic pathway. This study revealed that our Cu NPs had high anticancer properties by killing tumor cells through the apoptotic pathway. Since this particle has high antibacterial activity, our Cu NPs might be developed in future as a dual action drug—anticancer as well as antibacterial.

Silicon nanoparticles (SiNPs) prepared by mechanical grinding of luminescent porous silicon were coated with a biopolymer (dextran) and investigated as a potential theranostic agent for bioimaging and sonodynamic therapy. Transmission electron microscopy, photoluminescence and Raman scattering measurements of dextran-coated SiNPs gave evidence of their enhanced stability in water. In vitro experiments confirmed the lower cytotoxicity of the dextran-coated NPs in comparison with uncoated ones, especially for high concentrations of about 2 mg ml⁻¹. Efficient uptake of the NPs by cancer cells was found using bioimaging in the optical transmittance and photoluminescence modes. Treatment of the cells with uptaken SiNPs by therapeutic ultrasound for 5–20 min resulted in a strong decrease in the number of living cells, while the total number of cells remained nearly unchanged. The obtained data indicate a 'mild' effect of the combined action of ultrasonic irradiation and SiNPs on cancer cells. The observed results reveal new opportunities for controlling the photoluminescent and sonosensitizing properties of silicon-based NPs for applications in the diagnostics and mild therapy of cancer.

Graphene is a favorable candidate for electrodes of organic light emitting diodes (OLEDs). Graphene has quite a high work function of ∼4.5 eV, and has been extensively studied when used as anodes of OLEDs. In order to use graphene as a cathode, the electron injection barrier between the graphene cathode and the electron transport layer has to be low enough. Using 4,7-diphenyl-1,10-phenanthroline (Bphen):Cs₂CO₃ to n-dope graphene is a very good method, but the electron injection barrier between the n-doped graphene and Bphen:Cs₂CO₃ is still too high to be ∼1.0 eV. In this work, in order to further reduce the electron injection barrier, a novel method is suggested. On the graphene cathode, a Sm layer with a lot of nano-hollows, and subsequently a layer of Bphen:Cs₂CO₃, are deposited. The Bphen:Cs₂CO₃ can n-dope graphene in the nano-hollows, and the Fermi level of the graphene rises. The nano Sm layer is very easily oxidized. Oxygen adsorbed on the surface of graphene may react with Sm to form an O⁻–Sm⁺ dipole layer. On the areas of the Sm oxide dipole layer without nano-hollows, the electron injection barrier can be further lowered by the dipole layer. Electrons tend to mainly inject through the lower electron barrier where the dipole layer exists. Based on this idea, an effective inverted small molecular OLED with the structure of graphene/1 nm Sm layer with a lot of nano-hollows/Bphen:Cs₂CO₃/Alq₃:C545T/NPB/MoO₃/Al is presented. The maximum current efficiency and maximum power efficiency of the OLED with a 1 nm Sm layer are about two and three times of those of the reference OLED without any Sm layer, respectively.

For their spintronic applications the magnetic and optical properties of diluted magnetic semiconductors (DMS) have been studied widely. However, the exact relationships between the magnetic interactions and optical emission behaviors in DMS are not well understood yet due to their complicated microstructural and compositional characters from different growth and preparation techniques. Manganese (Mn) doped ZnSe nanoribbons with high quality were obtained by using the chemical vapor deposition (CVD) method. Successful Mn ion doping in a single ZnSe nanoribbon was identified by elemental energy-dispersive x-ray spectroscopy mapping and micro-photoluminescence (PL) mapping of intrinsic d–d optical transition at 580 nm, i.e. the transition of ⁴T₁(⁴G) → ⁶A₁(⁶s),. Besides the d–d transition PL peak at 580 nm, two other PL peaks related to Mn ion aggregates in the ZnSe lattice were detected at 664 nm and 530 nm, which were assigned to the d–d transitions from the Mn²⁺–Mn²⁺ pairs with ferromagnetic (FM) coupling and antiferromagnetic (AFM) coupling, respectively. Moreover, AFM pair formation goes along with strong coupling with acoustic phonon or structural defects. These arguments were supported by temperature-dependent PL spectra, power-dependent PL lifetimes, and first-principle calculations. Due to the ferromagnetic pair existence, an exciton magnetic polaron (EMP) is formed and emits at 460 nm. Defect existence favors the AFM pair, which also can account for its giant enhancement of spin–orbital coupling and the spin Hall effect observed in PRL 97, 126603(2006) and PRL 96, 196404(2006). These emission results of DMS reflect their relation to local sp-d hybridization, spin–spin magnetic coupling, exciton–spin or phonon interactions covering structural relaxations. This kind of material can be used to study the exciton–spin interaction and may find applications in spin-related photonic devices besides spintronics.

We present a careful numerical study of nanoparticle (NP) faceting, highlighting the great influence of small morphological changes of NP-mirror cavities on near-field enhancement in the nanoparticle-on-mirror (NPOM) system. Using a 3D finite element method (FEM) plasmon mapping method, the active transverse cavity modes can be confirmed. For the dominant mode, we have found that, by increasing the facet width, the resonance can be tuned linearly to the red with little decrease of the peak near-field intensity. It is further demonstrated that by increasing the NP size, the near-field intensity can be strongly enhanced. Understanding of such extreme optics benefits significantly both the optimized design of potential plasmonic devices and the fundamental understanding of nano-optics. Collaborative experimental considerations are expected with the rapid development of nanotechnology.

Sulfur vacancies (S-vacancies) are common in monolayer MoS₂ (mMoS₂). Finding an effective way to control rather than abolish the effect of S-vacancies on contact properties is vital for the application of mMoS₂. Here, we propose the adsorption of gases to passivate the S-vacancies in Pt–mMoS₂ interfaces. Results demonstrate that gases are stably and preferentially adsorbed at S-vacancies. The n-type Schottky barriers of Pt–mMoS₂ interfaces are reduced significantly upon the adsorption electron-donor gases, especially Cl₂. The n-type transport character of the Pt–mMoS₂ interface can be changed to p-type by the adsorption of electron-acceptor gases. As the adsorption concentration increases, both n- and p-type Schottky barriers are further reduced, and the lowest n- and p-type Schottky barriers are 0.36 and 0 eV, respectively. Note that the variations in Schottky barriers are independent of the oxidizing ability of gases but relative to the average number of valence electrons per gas atom. Analysis demonstrates that although gases at S-vacancies cannot cause gap states to vanish, and can even enhance Fermi level pinning, they modulate charge redistribution and the potential step at the interface region. Moreover, with increasing adsorption concentration, the valence band maximum of mMoS₂ shows the opposite variation tendency to that of the potential step. Our results suggest that adsorption of gases is an effective way to passivate S-vacancies to modulate the transport properties of Pt–mMoS₂ interfaces.

Ultra-thin anodic aluminum oxide (AAO) membranes are efficient templates for the fabrication of patterned nanostructures. Herein, a three-step etching method to control the morphology of AAO is described. The morphological evolution of the AAO during phosphoric acid etching is systematically investigated and a nonlinear growth mechanism during unsteady-state anodization is revealed. The thickness of the AAO can be quantitatively controlled from ∼100 nm to several micrometers while maintaining the tunablity of the pore diameter. The AAO membranes are robust and readily transferable to different types of substrates to prepare patterned plasmonic nanoarrays such as nanoislands, nanoclusters, ultra-small nanodots, and core–satellite superstructures. The localized surface plasmon resonance from these nanostructures can be easily tuned by adjusting the morphology of the AAO template. The custom AAO template provides a platform for the fabrication of low-cost and large-scale functional nanoarrays suitable for fundamental studies as well as applications including biochemical sensing, imaging, photocatalysis, and photovoltaics.

Anodic aluminum oxide (AAO) substrates with a self-ordered triangular array of nanopores provide the means to fabricate multiple forms of nano materials, such as nanowires and nanoparticles. This study focuses on nanostructures that emerge in thin films of metals thermally evaporated onto the surface of AAO. Previous work showed that films of different evaporated metals assume dramatically different structures, e.g. an ordered triangular array of nearly monodisperse nanoparticles forms for lead (Pb) while a polycrystalline nanohoneycomb structure forms for silver (Ag). Here, we present investigations of the effects of substrate temperature and deposition angle that reveal the processes controlling the nano particle array formation. Our findings indicate that arrays form provided the grain nucleation density exceeds the pore density and the atomic mobility is high enough to promote grain coalescence. They introduce a method for producing films with anisotropic grain array structure. The results provide insight into the influence of substrate nano-morphology on thin film growth energetics and kinetics that can be harnessed for creating films with other novel nano-structures.

The thermal conductivity of superlattice films is generally anisotropic and should be studied separately in the in-plane and cross-plane directions of the films. However, previous works have mostly focused on the cross-plane thermal conductivity because the electrons and phonons in the cross-plane direction of superlattice films may result in much stronger interface scattering than that in the in-plane direction. Nevertheless, it is highly desirable to perform systematic studies on the effect of interface formation in semiconducting superlattice films on both in-plane and cross-plane thermal conductivities. In this study, we determine both the in-plane and cross-plane thermal conductivities of Al₂O₃ (AO)/ZnO superlattice films grown by atomic layer deposition (ALD) on SiO₂/Si substrates in the temperature range of 50–300 K by the four-point-probe 3-ω method. Our experimental results indicate that the formation of an atomic AO layer (0.82 nm) significantly contributes to the decrease of the cross-plane thermal conductivity of the AO/ZnO superlattice films compared with that of AO/ZnO thin films. The cross-plane thermal conductivity (0.26–0.63 W m⁻¹ K⁻¹ of the AO/ZnO superlattice films (with an AO layer of ∼0.82 nm thickness) is approximately ∼150%–370% less than the in-plane thermal conductivity (0.96–1.19 W m⁻¹ K⁻¹) of the corresponding film, implying significant anisotropy. This indicates that the suppression of the cross-plane thermal conductivity is mainly attributed to the superlattice, rather than the nanograin columnar structure in the films. In addition, we theoretically analyzed strong anisotropic behavior of the in-plane and cross-plane thermal conductivities of the AO/ZnO superlattice films in terms of temperature dependence.

The potential of MoO₂ crystal as an electrode material is reported, and nanostructural MoO₂ systems, including nanoparticles, nanospheres, nanobelts and nanowires, were synthesized and proved to be advanced electrode materials. A two-dimensional (2D) geometric structure represents an extreme of surface-to-volume ratio, and thus is more suitable as an electrode material in general. Stimulated by the recent fabrication of 2D MoO₂, we adopted an ab initio molecular dynamics simulation and density functional theory calculation to study the stability and electrochemical properties of a MoO₂ sheet. Identified by a phonon dispersion curve and potential energy curve calculations, the MoO₂ sheet proved to be dynamically and thermally stable. After lithiation, similar to most promising 2D structures, we found that a Li atom can strongly adsorb on a MoO₂ sheet, and the lithiated MoO₂ sheet presented excellent metallic properties. Note that, compared with most promising 2D structures, we unexpectedly revealed that the diffusion barrier of the Li atom on the MoO₂ sheet was much lower and the storage capacity of the MoO₂ sheet was much larger. The calculated energy barrier for the diffusion of Li on the MoO₂ sheet was only 75 meV, and, due to multilayer adsorption, the theoretical capacity of the MoO₂ sheet can reach up to 2513 mA h g⁻¹. Benefiting from general properties, such as strong Li-binding and excellent conductivity, and unique phenomena, such as ultrafast diffusion capacity and astonishing storage capacity, we highlight a new promising electrode material for the Li-ion battery.

Porous ZnMn₂O₄ microspheres were prepared via a facile co-precipitation method followed by calcination at various temperatures and evaluated as anode materials for lithium ion batteries. The sample prepared at 600 °C outperformed the other samples in terms of electrochemical performance with high reversible capacity, high-rate capability, and excellent cycling performance. The capacity of the sample remained as high as 999 mAh g⁻¹ at a current rate of 100 mA g⁻¹ after 50 cycles—one of the best ever reported for ZnMn₂O₄-based materials. A high reversible capacity of 400 mAh g⁻¹ was retainable at a current density of 2000 mA g⁻¹ after 2500 cycles. A novel electrochemical reaction mechanism of ZnMn₂O₄ anodes was established and investigated at length. The Mn₃O₄ observed during the charge process was largely responsible for the enhanced performance, as confirmed by x-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. The relatively large surface area, abundant porosity, large ion exchange space, and strong mechanical stability of the porous connected 3D framework were responsible for the unique oxidation/reduction Mn²⁺ ↔ Mn³⁺ process we observed.

We present a novel microfluidic chip based method for the detection of micro RNA (miRNA) via the combination of fluorescence and surface enhanced Raman scattering (SERS) spectroscopies. First, silver nanoparticles (Ag NPs) are immobilized onto a glass slide, forming a SERS enhancing substrate. Then a specificially designed molecular beacon (MB) is attached to the SERS substrate. The 3' end of the MB is decorated with a thiol group to facilitate the attachment of the MB, while the 5' end of the MB is labeled with an organic dye 6-FAM, which is used both as the fluorophore and SERS reporter. In the absence of target miRNA, the MB will form a hairpin structure, making 6-FAM close to the Ag NPs. Hence, the fluorescence of 6-FAM will be quenched and the Raman signal of 6-FAM will be enhanced. On the contrary, with target miRNA present, hybridization between the miRNA and MB will unfold the MB and increase the distance between 6-FAM and the Ag NPs. Thus the fluorescence of 6-FAM will recover and the SERS signal of 6-FAM will decrease. So the target miRNA will simultaneously introduce opposite changing trends in the intensities of the fluorescence and SERS signals. By combining the opposite changes in the two optical spectra, an improved sensitivity and linearity toward the target miRNA is achieved as compared with using solely fluorescence or SERS. Moreover, introducing the microfluidic chip can reduce the reaction time, reagent dosage and complexity of detection. With the improved sensitivity and simplicity, we anticipate that the presented method can have great potential in the investigation of miRNA related diseases.

ZnS nanotubes (NTs) were successfully prepared via a one-step thermal evaporation process without using any templates. The resulting NTs were single crystalline and structurally uniform. Based on experimental analysis, a tube-growth vapor–liquid–solid process was proposed as the growth mechanism of ZnS NTs. A metal–semiconductor–metal full-nanostructured ultraviolet (UV) photodetector with ZnS NTs as the active layer, and Ag nanowires of low resistivity and high transmissivity as electrodes, was fabricated and characterized. The ZnS NT-based device displayed a high I_on/I_off ratio of up to ∼1.56 × 10⁵ with a high response to UV incident light at low operation voltage. This work is a meaningful exploration for preparing other one-dimensional semiconductor NTs, and developing a high-performance and power-saving UV sensor.

The nucleation density and average size of graphene crystallites grown using cold wall chemical vapor deposition (CVD) on 4 μm thick Cu films electrodeposited on W substrates can be tuned by varying growth parameters. Growth at a fixed substrate temperature of 1000 °C and total pressure of 700 Torr using Ar, H₂ and CH₄ mixtures enabled the contribution of total flow rate, CH₄:H₂ ratio and dilution of the CH₄/H₂ mixture by Ar to be identified. The largest variation in nucleation density was obtained by varying the CH₄:H₂ ratio. The observed morphological changes are analogous to those that would be expected if the deposition rate were varied at fixed substrate temperature for physical deposition using thermal evaporation. The graphene crystallite boundary morphology progresses from irregular/jagged through convex hexagonal to regular hexagonal as the effective C deposition rate decreases. This observation suggests that edge diffusion of C atoms along the crystallite boundaries, in addition to H₂ etching, may contribute to shape evolution of the graphene crystallites. These results demonstrate that graphene grown using cold wall CVD follows a nucleation and growth mechanism similar to hot wall CVD. As a consequence, the vast knowledge base relevant to hot wall CVD may be exploited for graphene synthesis by the industrially preferable cold wall method.

Herein we report on the synthesis and characterization of novel crystalline hexagonal boron nitride (h-BN) quantum- and nanodots embedded in large-area boron carbon nitride (BCN) films. The films were grown on a Cu substrate by an atmospheric pressure chemical vapour deposition technique. Methane, ammonia, and boric acid were used as precursors for C, N and B to grow these few atomic layer thick uniform films. We observed that both the size of the h-BN quantum/nanodots and thickness of the BCN films were influenced by the vaporization temperature of boric acid as well as the H₃BO_{3 (g)} flux over the Cu substrate. These growth conditions were easily achieved by changing the position of the solid boric acid in the reactor with respect to the Cu substrate. Atomic force microscope (AFM) and TEM analyses show a variation in the h-BN dot size distribution, ranging from nanodots (∼224 nm) to quantum dots (∼11 nm) as the B-source is placed further away from the Cu foil. The distance between the B-source and the Cu foil gave an increase in the C atomic composition (42 at% C–65 at% C) and a decrease in both B and N contents (18 at% B and 14 at% N to 8 at% B and 7 at% N). UV–vis absorption spectra showed a higher band gap energy for the quantum dots (5.90 eV) in comparison with the nanodots (5.68 eV) due to a quantum confinement effect. The results indicated that the position of the B-source and its reaction with ammonia plays a significant role in controlling the nucleation of the h-BN quantum- and nanodots. The films are proposed to be used in solar cells. A mechanism to explain the growth of h-BN quantum/nanodots in BCN films is reported.

This paper reports on a simple and environmentally friendly photochemical process capable of generating nano-layers (8–22 nm) of silver nanostructures directly onto glass surfaces. This approach opens the way to large-scale functionalized surfaces with plasmonic properties through a single light-induced processing. Thus, Ag nanostructures top-coated were obtained through photo-reduction, at room temperature, of a photosensitive formulation containing a metal precursor, free from extra toxic stabilizers or reducing agents. The reactive formulation was confined between two glass slides and exposed to a continuous near-UV source. In this way, stable silver nano-layers can be generated directly on the substrate with a very good control of the morphology of as-synthesized nanostructures that allows tailoring the optical properties of the coated layers. The position and width of the corresponding surface plasmon resonance bands can be adjusted over a broad spectral window. By extension, this low-cost and easy-to-apply process can also be used to coat ultra thin layers of metal nanostructures on a variety of substrates. The possibility of controlling of nanostructures shape should achieve valuable developments in many fields, as diverse as plasmonics, surface enhanced Raman scattering, nano-electronic circuitry, or medical devices.

High-performance supercapacitors are very desirable for many portable electronic devices, electric vehicles and high-power electronic devices. Herein, a facile and binder-free synthesis method, galvanic displacement of the precursor followed by heat treatment, is used to fabricate ultrathin Co₃O₄ nanosheet arrays on nickel foam substrate. When used as a supercapacitor electrode the prepared Co₃O₄ on nickel foam exhibits a maximum specific capacitance of 1095 F g⁻¹ at a current density of 1 A g⁻¹ and good cycling stability of 71% retention after 2000 cycling tests. This excellent electrochemical performance can be ascribed to the high specific surface area of each Co₃O₄ nanosheet that comprises numerous nanoparticles.

Perpendicularly attached MoS₂ nanosheets on MoO₂ conductive nanofibers were synthesized by combining electrospinning, calcination, and sulfurization processes. Compared to randomly stacked MoS₂ nanosheets on MoO₂ nanofiber, they show greater hydrogen evolution reaction (HER) performance (i.e., onset potential of −180 mV versus normal hydrogen electrode with the Tafel slope of 59 mV dec⁻¹). HER performance decreases with increasing MoS₂ nanocrystal size.

The controllable self-assembly of nanosized building blocks into larger specific structures can provide an efficient method of synthesizing novel materials with excellent properties. The self-assembly of nanocrystals by assisted means is becoming an extremely active area of research, because it provides a method of producing large-scale advanced functional materials with potential applications in the areas of energy, electronics, optics, and biologics. In this study, we applied an efficient strategy, namely, the use of 'pressure control' to the assembly of silver sulfide (Ag₂S) nanospheres  with a diameter of approximately 33 nm into large-scale, uniform Ag₂S sub-microspheres with a size of about 0.33 μm. More importantly, this strategy realizes the online control of the overall reaction system, including the pressure, reaction time, and temperature, and could also be used to easily fabricate other functional materials on an industrial scale. Moreover, the thermodynamics and kinetics parameters for the thermal decomposition of silver diethyldithiocarbamate (Ag(DDTC)) are also investigated to explore the formation mechanism of the Ag₂S nanosized building blocks which can be assembled into uniform sub-micron scale architecture. As a method of producing sub-micron Ag₂S particles by means of the pressure-controlled self-assembly of nanoparticles, we foresee this strategy being an efficient and universally applicable option for constructing other new building blocks and assembling novel and large functional micromaterials on an industrial scale.

In this paper, a new method for the synthesis of silver carbon nanotube (Ag/CNT) composite films as conductive connection units for flexible electronic devices is presented. This method is about a two-component solution process by spin coating with an after-treatment annealing process. In this method, multi-walled carbon nanotubes (MWCNTs) act as the core of silver heterogeneous nucleation, which can be observed and analyzed by a field-emission scanning electron microscope. With the effects of mechanical interlocking, chemical grafting, and annealing, the interfacial adhesive strength between films and PET sheets was enhanced to 12 N cm⁻¹. The tensile strength of the Ag/CNT composite films was observed to increase by 38% by adding 5 g l⁻¹ MWCNTs. In the four-probe method, the resistivity of Ag/CNT-5 declined by 78.2% compared with pristine Ag films. The anti-fatigue performance of the Ag/CNT composite films was monitored by cyclic bending deformation and the results revealed that the growth rate of electrical resistance during the deformation was obviously retarded. As for industrial application, this method provides an efficient low-cost way to prepare Ag/CNT composite films and can be further applied to other coating systems.

This study focused on the synthesis of α-MoO₃/rGO (rGO, reduced graphene oxide). One-dimensional nanohybrids under mild conditions and a low temperature wet chemical route produced highly pure single-crystalline orthorhombic α-MoO₃ on GO sheets. Four nanohybrids, labeled as GMO-0, GMO-1, GMO-2 and GMO-3, were synthesized with different mass chargings of GO (0 mg, 40 mg, 60 mg and 100 mg, respectively). The photocatalytic performance for reduction of organic pollutants was analyzed. The presence of different amounts of GO in the prepared metal oxide hybrids altered the performance of the material as elaborated by the Brunauer–Emmett–Teller surface area, UV–visible diffuse reflectance spectra and the resulting reduction of organic dyes depicted by photocatalytic experiments. GO as a support material and active co-catalyst decreased the band gap of α-MoO₃ (2.82 eV) to lower values (2.51 eV), rendering the prepared hybrids usable for visible-light-induced photocatalysis. The large specific surface area (72 m² g⁻¹) of the mesoporous α-MoO₃/rGO nanohybrid made it an efficient photocatalyst for the elimination of azo dyes. Very fast reduction (100%) of Rhodamine B was observed in a few minutes, while Congo Red was degraded by 76% in 10 min, leading to the formation of stable intermediates that were completely neutralized in 12–14 h under light irradiation. The amount of GO loaded in the samples was limited to a point to achieve better results. After that, increasing the amount of GO decreased the extent of degradation due to the presence of a higher electron acceptor. Photocatalytic experiments revealed the synergistic effect, high selectivity of the prepared nanohybrids and degradation of azo dyes. The kinetics of the degradation reaction were studied and found to follow a pseudo first-order reaction.

We report a GaAs_0.96Bi_0.04/GaAs multiple quantum well (MQW) light emitting diode (LED) grown by molecular beam epitaxy using a two-substrate-temperature (TST) technique. In particular, the QWs and the barriers in the intrinsic region were grown at the different temperatures of ${T}_{{\rm{GaAsBi}}}$ = 350 °C and ${T}_{{\rm{GaAs}}}\,=\,550\,^\circ {\rm{C}},$ respectively. Investigations of the microstructure using transmission electron microscopy (TEM) reveal homogeneous MQWs free of extended defects. Furthermore, the local determination of the Bi distribution profile across the MQWs region using TEM techniques confirm the uniform Bi distribution, while revealing a slightly chemically graded GaAs-on-GaAsBi interface due to Bi surface segregation. Despite this small broadening, we found that Bi segregation is significantly reduced (up to 18% reduction) compared to previous reports on Bi segregation in GaAsBi/GaAs MQWs. Hence, the TST procedure proves as a very efficient method to reduce Bi segregation and thus increase the quality of the layers and interfaces. These improvements positively reflect in the optical properties. Room temperature photoluminescence and electroluminescence (EL) at 1.23 μm emission wavelength are successfully demonstrated using TST MQWs containing less Bi content than in previous reports. Finally, LED fabricated using the present TST technique show current–voltage (I–V) curves with a forward voltage of 3.3 V at an injection current of 130 mA under 1.0 kA cm⁻² current excitation. These results not only demonstrate that TST technique provides optical device quality GaAsBi/GaAs MQWs but highlight the relevance of TST-based growth techniques on the fabrication of future heterostructure devices based on dilute bismides.

Using monochromated electron energy loss spectroscopy in a probe-corrected scanning transmission electron microscope we demonstrate band gap mapping in ZnO/ZnCdO thin films with a spatial resolution below 10 nm and spectral precision of 20 meV.

We propose a new multi-image method for obtaining the frequency shift, tunneling current and local contact potential difference (LCPD) on a TiO₂(110) surface with atomic resolution. The tunneling current image reveals rarely observed surface oxygen atoms contrary to the conventional results. We analyze how the surface and subsurface defects affect the distribution of the LCPD. In addition, the subsurface defects are observed clearly in the tunneling current image, in contrast to a topographic image. To clarify the origin of the atomic contrast, we perform site-dependent spectroscopy as a function of the tip–sample distance. The multi-image method is expected to be widely used to investigate the charge transfer phenomena between the nanoparticles and surface sites, and it is useful for elucidating the mechanisms of catalytic reactions.

A porous and interconnected nanorod-like FeP structure on titanium plate has been fabricated by a simple hydrothermal method and followed by a calcination process. The nanorod is assembled by many paralleled FeP nanowires with a porous structure. With the porous surface structure of FeP nanorods and the synergetic effect from the electronic conductive Ti support, this binder-free FeP electrode brings about a desirable electrocatalytic activity for the hydrogen evolution reaction (HER), showing a low onset overpotential of 23 mV and a small Tafel slope of 39 mV dec⁻¹. Meanwhile, its catalytic activity could be maintained almost unchanged for at least 12 h in an acidic solution. This work provides us an effective HER electrocatalyst which can be easily produced on a large scale and at low cost.

Nanofluids—engineered colloidal suspensions in base liquids—have captivated the interest of researchers over the last two decades for various existing as well as emerging technological applications. The main impetus for the synthesis of such novel nanocomposite liquids is the potential to alter properties of the base liquid, such as its viscosity, thermal conductivity, and surface tension, and to introduce specific optical and magnetic properties. Numerous studies suggest trends and explanations for the effects associated with the addition of nanoparticles, and that deviation from the base liquid properties are dependent on nanoparticle concentration. However, there remains a certain ambiguity in the available literature. The wetting behavior and surface tension of nanofluids are particular examples where highly conflicting results exist. In this study, we used multi-walled carbon nanotubes (MWCNTs) functionalized by plasma treatment and dispersed in reverse osmosis water and 99% anhydrous ethanol. Our observations reveal that the surface tension and wetting behavior of the stable aqueous and ethanol-based nanofluids containing plasma functionalized MWCNTs are unaffected by the MWCNT loading up to 120 (0.012) and ∼210 (0.021) ppm (vol%), respectively. The ethanol-based MWCNT nanofluids allowed us to extend the study to higher loadings, and a linear increase of the surface tension past ∼200 ppm was observed. Conversely, nanofluids containing non-functionalized or surfactant-stabilized MWCNTs show drastically different contact angle values when compared to the base liquids even at very low concentrations (less than 100 ppm). We demonstrate that the stability of nanofluid and method of stabilization are crucial parameters in determining the wetting behavior of nanofluids.

We have developed a simultaneous electronic and structural characterization method for studying the formation process for Au nanowires. The method is based on two-probe electronic transport measurement of free-standing Au nanowires and simultaneous structural characterization using scanning electron microscopy (SEM). We measured the electronic currents during the electromigration (EM)-induced narrowing process for the free-standing Au nanowires. A free-standing Au nanowire with a desired conductance value was fabricated by EM. Simultaneous SEM and conductance measurements revealed the EM-induced narrowing process for the Au wires, in which material transfer in the nanowires caused growth towards the positively biased electrode and contact failure at the negatively biased electrode. The narrowed free-standing Au nanowires were stable and could be maintained for more than 10 h without their conductance changing. These results indicate the high stability of the EM-processed Au nanowires compared to Au nanowires fabricated by mechanical elongation or the breaking of Au nanocontacts.

P-type SnSe compositing with 2D MoSe₂ materials have been prepared by the solid solution method followed by the spark plasma sintering technique. The total thermal conductivities of SnSe/MoSe₂ composites were found to be higher than for pristineSnSe at room temperature; and the disparity between them becomes smaller at higher temperatures, where the low thermal conductivities remained. Both the carrier concentration and the carrier mobility were significantly improved after MoSe₂ was introduced into the SnSe matrix along the direction perpendicular to the pressing direction, leading to an extraordinary enhancement in electrical transport performance. The maximum ZT of 0.5 was obtained at 773 K for SnSe + 1.5%MoSe₂ along the direction perpendicular to the pressing direction; this value is 1.5 times as large as that of the pristine SnSe.

We investigate nanoscale local anodic oxidation (LAO) on hydrogen-intercalated graphene grown by controlled sublimation of silicon carbide (SiC). Scanning probe microscopy was used as a lithographic and characterization tool in order to investigate the local properties of the nanofabricated structures. The anomalous thickness observed after the graphene oxidation process is linked to the impact of LAO on the substrate. Micro-Raman (μ-Raman) spectroscopy was employed to demonstrate the presence of two oxidation regimes depending on the applied bias. We show that partial and total etching of monolayer graphene can be achieved by tuning the bias voltage during LAO. Finally, a complete compositional characterization was achieved by scanning electron microscopy and energy dispersive spectroscopy.

InAsSb nanowires (NWs) with a high Sb content have potential in the fabrication of advanced silicon-based optoelectronics such as infrared photondetectors/emitters and highly sensitive phototransistors, as well as in the generation of renewable electricity. However, producing optically efficient InAsSb NWs with a high Sb content remains a challenge, and optical emission is limited to 4.0 μm due to the quality of the nanowires. Here, we report, for the first time, the success of high-quality and optically efficient InAsSb NWs enabling silicon-based optoelectronics operating in entirely mid-wavelength infrared. Pure zinc-blende InAsSb NWs were realized with efficient photoluminescence emission. We obtained room-temperature photoluminescence emission in InAs NWs and successfully extended the emission wavelength in InAsSb NWs to 5.1 μm. The realization of this optically efficient InAsSb NW material paves the way to realizing next-generation devices, combining advances in III-V semiconductors and silicon.

A compact proximal retarding field analyzer for scanning probe energy loss spectroscopy measurements is described. Using the scanning tunneling microscope (STM) tip as a field emission (FE) electron source in conjunction with this analyzer, which is placed at a glancing angle to the surface plane, FE sample current and electron reflectivity imaging may be performed simultaneously. This is demonstrated in measurements of Ag nanostructures prepared on graphite by electron-beam lithography, where a material contrast of 13% is observed, with a lateral resolution of 25 nm, between the silver and graphite in electron reflectivity images. Topological contrast mechanisms such as edge enhancement and shadowing are also observed, giving rise to additional features in the electron reflectivity images. The same instrument configuration has been used to measure electron energy loss spectra on bare graphite, where the zero loss peak, π band plasmon loss peak and secondary electron peaks are observed. Using this simple and compact analyzer an STM, with sufficient open access to the tip-sample junction, may easily be augmented to provide simultaneous elemental and topographic mapping, supplementing STM image measurements with FE sample current and electron reflectivity images, as well as electron energy loss spectroscopy measurements, in the same instrument.