Straightening of chemically deposited CdS nanowires through annealing towards improved PV device performance

Cadmium sulfide (CdS) thin film consisting of nanowires over a flat CdS thin film were synthesized by depositing cadmium hydroxide [Cd(OH)₂] nanowires (NW) bundles, followed by conversion to sulfide phase by using ion exchange route at room temperature (300 K) based on negative free energy of formation. The influence of post annealing treatment on as-deposited CdS NW films has been studied in the temperature range 423–523 K through the observation of nanowires alignments. The annealing effect on the intrinsic properties have been studied in relation with the crystallites sizes, micro strain, dislocation density and optical band gap of the deposited films. Furthermore, the behavior of inter- and intramolecular hydroxide ion (OH⁻) has been investigated from FTIR analysis. Additionally, the effects of post annealing on photovoltaic device performance has been scrutinized and the obtained results were correlated with structural and optical properties.     

Oxa-perfluoroalkyl end-capped PEG-based amphiphilic fluorocarbon polymer: synthesis and self-assembly behavior in water

Oxy-perfluoroalkylated end-capped polyethylene glycol (PEG) was synthesized by the reaction of PEG and polyethylene glycol monomethylether (PEG(MeO)) with trimer of hexafluoropropylene oxide (HFPO). The structures of the fluorinated polymers were characterized by ¹H NMR, ¹⁹F NMR and FTIR. Their surface activities study shows that the fluorinated polymers have high surface activity. Core-shell micellization of the fluorinated polymers was inferred from the ¹⁹F NMR spectra derived in two different solvent environments (CDCl₃ and D₂O). Their self-assembly behaviors in water were studied in detail by pyrene fluorescence techniques, dynamic light scattering and scan electron microscopy. The results demonstrated that due to different fluorine content PEGF with two end-capped fluorocarbon groups can form large aggregates with the diameter size of about 132 nm, whereas PEG(MeO)F with only one-end-capped fluorocarbon groups forms small micelles with the size of round 12 nm.     

Considerable Enhancement of Field Emission of SnO2 Nanowires by Post-Annealing Process in Oxygen at High Temperature

The field emission properties of SnO₂ nanowires fabricated by chemical vapor deposition with metallic catalyst-assistance were investigated. For the as-fabricated SnO₂ nanowires, the turn-on and threshold field were 4.03 and 5.4 V/μm, respectively. Considerable enhancement of field emission of SnO₂ nanowires was obtained by a post-annealing process in oxygen at high temperature. When the SnO₂ nanowires were post-annealed at 1,000 °C in oxygen, the turn-on and threshold field were decreased to 3.77 and 4.4 V/μm, respectively, and the current density was increased to 6.58 from 0.3 mA/cm² at the same applied electric field of 5.0 V/μm.     

Heterostructure-based 3D-CdS/TiO2 nanotubes/Ti: Photoelectrochemical performances and interface simulation investigation

Heterojunction can effectively improve the charge separation efficiency and facilitate electron transfer, producing a strong photoelectric signal. By using 3D-TiO₂ nanotubes/Ti foil as support, CdS–TiO₂ heterojunction electrodes with different CdS proportions were fabricated as photoelectrochemical (PEC) biosensor to respond the visible irradiation and improve the PEC performance of TiO₂ nanotubes. Density functional theory (DFT) simulation was conducted to clarify the PEC process of CdS–TiO₂NTs and revealed the important role of CdS in enhancing electron–hole separation on TiO₂ nanotubes. Owing to the 3D tubular structure of the support, 2 mM CdS–TiO₂ nanotubes/Ti PEC electrode exhibited low detection limit of 0.27 μM and good sensitivity of 328.87 μA mM^?1 cm^?2 for glucose in the range of 2–9 μM under visible illumination. The fabricated CdS–TiO₂ nanotubes/Ti biosensor also showed high selectivity and good stability, which indicated a new candidate for biosensors.     

Greenish-yellow emitting CdS: Sm3+ nanoparticles: Structural and optical analysis

Different concentrations of trivalent samarium (Sm³⁺) ions doped cadmium sulphide (CdS) nanoparticles were fabricated by one-step solid-state method at low temperature using C₁₀H₆(SO₃Na)₂ as surfactant for optoelectronic and solar cell applications. They were characterized through powder X-ray diffraction, Fourier transform infrared, Raman, scanning electron microscopy, transmission electron microscopy, UV–Vis absorption and photoluminescence studies. These nanoparticles establish cubic structure without any foreign phase and it was confirmed by Raman studies. The Raman spectrum of CdS nanoparticles shows first three longitudinal optical phonon orders. The adjacent lattice fringes were spaced about 0.30 nm. The direct band gap energy was found slightly higher than the bulk crystallites. The photoluminescence spectra of CdS: Sm³⁺ exhibits a broad peak at 563 nm with a shoulder at around 607 nm corresponding to Sm³⁺: ⁴G_5/2 → ⁶H_7/2 transition at 402 nm excitation. A luminescence quenching was noticed at higher Sm³⁺ ions concentration due to transfer of energy among the excited Sm³⁺ ions. The CdS: Sm³⁺ particles were fabricated with a size of the order of nanoscale and they can be used for efficient energy conversion. The studied CdS: Sm³⁺ nanoparticles are suitable for optoelectronic and solar cell applications.     

Large-scale AlN nanowires synthesized by direct sublimation method

Hexagonal aluminum nitride (AlN) nanowires were fabricated by direct sublimation method without a catalyst layer. The obtained nanowires have diameters of about 30–100 nm and length up to tens of micrometers. TEM observation indicates that these nanowires are single-crystalline and grow along [0 0 0 1] direction. It is thought that vapor–solid (VS) mechanism should be responsible for the growth of AlN nanowires. In addition, room temperature Raman scattering and photoluminescence spectra from AlN nanowires were studied. Photoluminence spectrum of the AlN nanowires shows a wide emission band centered of 517 and 590 nm, which is related to N vacancies and the transition from the level of V_N⁺ to ground state of the deep level of [V_Al^3? + 3O_N⁺] defects, respectively.     

Fabrication and properties of a dense SiC NWs-toughened α-Si3N4 composite coating on porous Si3N4 ceramics

A dense SiC nanowires-toughened α-Si₃N₄ coating was prepared using a two-step technique for protecting porous Si₃N₄ ceramic against mechanical damage, and effect of SiC nanowires content on microstructures and properties of the coating were investigated. XRD, SEM and TEM analysis results revealed that as-prepared coatings consisted of α-Si₃N₄, O'-Sialon, SiC nanowires and Y–Al–Si–O–N glass phase. Furthermore, Vickers hardness of the coated porous Si₃N₄ ceramics increased gradually with the increasing SiC nanowires content from 0 to 10 wt%, which is attributed to the gradual improvement in intrinsic elastic modulus (E), hardness (H) and H³/E² of the coatings. But, when the SiC nanowires content was 15 wt%, the thickness of the coating became relatively thinner, so that its protective ability was weakened and Vickers hardness started to decrease accordingly. Meanwhile, the assistance of SiC nanowires enhanced fracture toughness of the coatings obviously because SiC nanowires in the coatings can produce various toughening mechanisms during mechanical damage. When the SiC nanowires content was 10 wt%, its fracture toughness reached the maximum value, which was 6.27 ± 0.05 MPa·m^1/2.     

In-situ generation Cu2O/CuO core-shell heterostructure based on copper oxide nanowires with enhanced visible-light photocatalytic antibacterial activity

As visible light-driven photocatalysts in wastewater treatment, Cu₂O/CuO composites have garnered considerable attention. Herein, Cu₂O/CuO core–shell nanowires were fabricated directly on a Cu mesh using a simple two-step synthesis process involving a wet chemical method and rapid annealing. Unlike conventional composite nanowires, controllable core–shell nanowires exhibit high photoelectrochemical properties and overcome the problems associated with the recovery of powder-based photocatalysts. The presence and structural distribution of the Cu₂O/CuO core–shell nanowires were confirmed using X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy. Among the samples subjected to different rapid annealing temperatures for 180 s, the sample exposed to rapid annealing at 350 °C achieved the highest photocurrent density of ?6.96 mA cm^?2. In the core–shell nanowires fabricated on the samples, the ratio of Cu₂O/CuO was 1:1. The photocatalytic activity of the Cu₂O/CuO nanowire samples was also determined by measuring methyl blue degradation to determine their applicability in wastewater treatment. A remarkable photocatalytic degradation rate of 91.6% was achieved at a loading bias voltage of ?0.5 V. The Cu₂O/CuO heterojunction enhanced the photodegradation of the samples because the different bandgaps improved the dissociation of the photogenerated electron–hole pairs. Furthermore, the antibacterial activity of the Cu₂O/CuO nanowires exhibited considerable resistance against Escherichia coli and photocatalytic antibacterial treatment for only 20 min under visible light killed 10⁶ CFU/mL of E. coli. Therefore, the Cu₂O/CuO controllable core–shell nanowires with a high photodegradation performance and excellent antibacterial activity under general illumination show diverse applications in water treatment.     

Investigation of thermodynamic properties of the binary system polyethylene glycol/CO2 using new methods

The solubility and diffusivity of CO₂ in polyethylene glycols (PEGs) of different molecular weight measured by two different methods are discussed in the present work. Before solubility measurements, the melting temperatures of PEG with different molecular weights were determined by means of differential scanning calorimetry. For the purpose of the present study a temperature of 343 K was chosen as the working temperature for both employed methods since all studied polymers are in liquid state at this temperature. All samples were analyzed at isothermal conditions and in the pressure range from 0 MPa up to 30.0 MPa. A set of absorption experiments on the PEG/CO₂ systems was performed using an external balance method. In order to validate results obtained by the new method they were compared to the data obtained at the same process conditions by a method using magnetic suspension balance (MSB).     

Electrochemical synthesis of CdS nanowires by underpotential deposition in anodic alumina membrane templates

Cadmium sulfide (CdS) nanowires were electrosynthesized within the pores of the anodic alumina membranes (AAM) using underpotential deposition (UPD) through an electrochemical co-deposition at room temperature (25 °C). The nanowire arrays were grown from an aqueous solution of CdSO₄, ethylenediaminetetraacetic acid (EDTA), and Na₂S at pH 4.0. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-vis absorption spectroscopy, and energy dispersive spectroscopy (EDS) were employed to characterize the nanowires. These nanowires have uniform diameters of approximately 90 nm, and their lengths are up to 7 μm. XRD analysis reveals that the electrosynthesized nanowires deposited at −500 mV (vs. Ag/AgCl) have a preferential orientation along (1 1 0) direction for hexagonal crystal. Electrochemical and EDS results of the deposits confirm that the atomic ratio of Cd to S is very close to 1:1 stoichiometry. UV-vis absorption measurement shows a blue-shifted absorption at 488 nm because of the quantum confinement at low dimensions.     

Facile three-step strategy to design CdS@Bi2Se3 core-shell nanostructure: An efficient electrode for supercapacitor application

In this study, we utilized a successive ionic layer adsorption and reaction (SILAR) route to attach bismuth selenide (Bi₂Se₃) nanoparticles on one dimensional (1D) cadmium sulfide nanowires (CdS NWs) at ambient temperature (27 °C) to design CdS@Bi₂Se₃ core-shell nanostructure towards active electrode for supercapacitor application. To verify and explore the retrieved surface configuration, structural, elemental, compositional, and surface morphological investigations were performed. The designed CdS@Bi₂Se₃ core-shell nanostructure not only offers the tremendous number of active areas, but also a continuous and quick one directional electron transport channels, demonstrating noticeable electrochemical performance with specific capacitance of 198 F g⁻¹ (aerial capacitance 59.5 mF/cm²) with 80% cyclic retention @ 2000 cycles. Superior electrochemical activity was enhanced through the mutualistic involvement of Na⁺ ion insertion/extraction via non-stoichiometric bismuth selenide, which was well supported through electrochemical impedance (EIS) studies.     

Elaboration of PEG/PA66 blends in a twin-screw batch-type mini-extruder: Process study and modelling

This paper deals with the development of the morphology in polyethylene glycol (PEG) and polyamide 66 (PA66) immiscible blends exhibiting an extremely low viscosity ratio (η_PEG/η_PA66=3-4×10^-5). These materials were obtained by melt mixing, under different operating conditions, using a twin-screw batch-type DSM mini-extruder.Scanning electron microscopy, followed by quantitative image analysis was used to determine PEG particles size distribution (PSD) as a function of blends composition and screw rotation speed. Experiments carried out with two mixing time (5 and 10 min) showed no significant difference of PSD. So, to avoid thermal degradation of the products, the mixing time was set up at 5 min for all experiments. The influence of PEG concentration and screw rotation speed on PSD appeared to be similar to that obtained in a previous study for the same blends elaborated in a Haake internal mixer. The results clearly showed that the average particle diameters decreased as screw rotation speed increased and as PEG concentration decreased. However, this decrease is less important using the twin-screw batch-type mini-extruder with which the particle sizes are smaller. The particles sizes were then correlated to blend composition, shear rate and viscosity ratio owing to an extension of Serpe's model. The unknown parameters of the corresponding model were estimated on the basis of experimental data. This enabled then to predict with a good precision the influence of the process operating conditions on the morphology of the dispersed phase.     

Electrospinning-derived YVO4:Er/Yb nanowires and nanotubes with temperature sensitivity of their up-converted emission

YVO₄:Er/Yb nanowires and nanotubes phosphors were prepared by electrospinning technique following calcination at different heating rates. The obtained nanowires are of 80–200 nm in diameter and are single crystals or polycrystalline in phase. The outer diameter of the obtained nanotubes is 50–200 nm with a wall thickness of 20–30 nm. The up-conversion properties of YVO₄:Er³⁺/Yb³⁺ nanowires and nanotubes were investigated. All samples were found to produce a green up-converted emission. The temperature-sensing features of YVO₄:Er³⁺/Yb³⁺ nanowires and nanotubes were investigated through the fluorescence intensity ratio approach, and the sensitivity of temperature was determined over the temperature range of 30–390 °C. The temperature sensing sensitivities of the mixed YVO₄:Er³⁺/Yb³⁺ nanowire samples and nanotubes exceeded the single YVO₄:Er³⁺/Yb³⁺ nanowire samples because of higher Yb³⁺-doped concentrations. The morphology influence on optical properties was studied at a fixed doping rare earth concentration and size. The temperature sensitivities of YVO₄:Er/Yb samples depended on the Yb ion concentrations rather than the morphology. The significant temperature sensitivity indicates its potential for use as an optical temperature sensing probe.     

Enhanced blue-light photocatalytic H2 production using CdS nanofiber

The photocatalytic activity of CdS nanosphere, nanorod or nanofiber was investigated for the hydrogen production from either methanol–water or sulfide/sulfite solution irradiated with blue light. The nanostructured CdS were obtained by the precipitation method at high ethylenediamine content solutions and at moderate temperature conditions. The synthesized CdS nanofiber using CS₂ as sulfur source presented the highest photocatalytic activity for the H₂ production (954 μmol h^− 1 g^− 1) in the reaction system with four blue LED lamps. This high photoactivity was attributed to the quantum confinement effect generated by the small particle size of the nanofibers (D = ~ 5 nm and L = 25 nm).     

Z-scheme g-C3N4 nanosheet photocatalyst decorated with mesoporous CdS for the photoreduction of carbon dioxide

Herein, novel mesoporous CdS nanoparticle (NP)-incorporated porous g-C₃N₄ nanosheets with large surface areas and varying CdS NP percentages were constructed for the first time. The synergistic effect of mesoporous CdS NPs and porous g-C₃N₄ nanosheets indicated effective charge carrier separation and promoted CO₂ photoreduction to form CH₃OH upon illumination. The highest yield of CH₃OH over 3% CdS-g-C₃N₄ heterostructures was determined to be approximately 1735 μmol g^?1, which was 3.8- and 5.50 times greater than those of mesoporous CdS NPs and pristine g-C₃N₄ nanosheets, respectively. In addition, the mesoporous 3%CdS-g-C₃N₄ heterostructure showed an outstandingly enhanced CO₂ photoreduction rate of 192.7 μmol g^?1 h^?1, which was estimated to be ~4.1 and 5.9- times better than CdS (47.1 μmol g^?1 h^?1) and pristine g-C₃N₄ (32.6 μmol g^?1 h^?1), respectively. The photoreduction performance was retained at approximately 94.7% after five cycles of illumination for 45 h. The remarkable synthesized mesoporous CdS-g-C₃N₄ heterostructure played an essential role, with its narrow bandgap and high surface area enabling improved photoinduced carrier separation and a widened range of light absorption. A plausible mechanism for CO₂ photoreduction by the mesoporous CdS-g-C₃N₄ heterostructure was proposed and verified by photoelectrochemical and photoluminescence measurements.     

Synthesis of Indium Nanowires by Galvanic Displacement and Their Optical Properties

Single crystalline indium nanowires were prepared on Zn substrate which had been treated in concentrated sulphuric acid by galvanic displacement in the 0.002 mol L⁻¹ In₂(SO₄)₃-0.002 mol L⁻¹ SeO₂-0.02 mol L⁻¹ SDS-0.01 mol L⁻¹ citric acid aqueous solution. The typical diameter of indium nanowires is 30 nm and most of the nanowires are over 30 μm in length. XRD, HRTEM, SAED and structural simulation clearly demonstrate that indium nanowires are single-crystalline with the tetragonal structure, the growth direction of the nanowires is along [100] facet. The UV-Vis absorption spectra showed that indium nanowires display typical transverse resonance of SPR properties. The surfactant (SDS) and the pretreatment of Zn substrate play an important role in the growth process. The mechanism of indium nanowires growth is the synergic effect of treated Zn substrate (hard template) and SDS (soft template).     

Large amplitude oscillatory shear rheology for nonlinear viscoelasticity in hectorite suspensions containing poly(ethylene glycol)

The effect of poly(ethylene glycol) (PEG) on the nonlinear viscoelasticity of Laponite suspensions containing NaCl was investigated with large amplitude oscillatory shear rheology. The molecular weight (M_w) of PEG was 4k, 10k and 35k, and the concentration of PEG was varied from 0.063 wt% to 2.4 wt%. The dynamic strain sweep showed that the nonlinearity appeared at γ₀ > 30% with a stress overshoot at γ₀ = 50-70%. The intensity ratio I_3/1 from Fourier-transform increased with γ₀ when entering the nonlinear regime and leveled off at γ₀ ≥ 100% with higher slope and constant value for the PEG of higher M_w or lower concentration. I_3/1 revealed the structure difference in the suspensions induced by adsorbing PEG in the nonlinear regime. The minimum- and large-strain rate viscosities η_M and η_L from the Lissajous curve were found to be sensitive to the nonlinear viscoelasticity and the peak of η_M and η_L appeared at lower γ₀ with higher maximum following the same dependency as I_3/1 on PEG M_w and concentration. The overall nonlinearity parameters N_E and N_V were proposed in this paper and demonstrated to reflect the difference in the Laponite suspensions with PEG more clearly and more effectively.     

From hydrated layered-spinel lithium manganate composite to high-performance spinel LiMn2O4: A novel synthesis tuned by the concentration of LiOH

To obtain high-performance spinel LiMn₂O₄, various types of hydrated layered-spinel lithium manganate composites have been controllably synthesized through the hydrothermal process. It is found that the composition and morphology of these intermediate products can be tuned by the concentration of LiOH: Li⁺ act as the template and OH^- provide the required alkaline environment. In particular, the nanostructure varies from nanowires to nanosheets at different levels, depending on the phase ratio of the spinel phase ranging from 0% to 100%. Phase purity and the corresponding electrochemical properties of the as-prepared LiMn₂O₄ products are further tailored through the subsequent heat treatment. With the optimized LiOH concentration of 0.08 M, the resulting LiMn₂O₄ cathode material exhibits the best electrochemical performance with the initial discharge capacity of 121.7 mA h g⁻¹ at 1 C and 117.8 mA h g⁻¹ at 30 C, while a retention over 90% can be achieved after 1500 cycles. This study will help deepen understanding of the function mechanisms and further direct the novel synthesis from hydrated layered-spinel lithium manganate composites to high-performance spinel LiMn₂O₄ cathode materials.     

Electron field emission properties on UNCD coated Si-nanowires

The electron field emission (EFE) properties of Si-nanowires (SiNW) were improved by coating a UNCD films on the SiNWs. The SiNWs were synthesized by an electroless metal deposition (EMD) process, whereas the UNCD films were deposited directly on bare SiNW templates using Ar-plasma based microwave plasma enhanced chemical vapor deposition (MPE–CVD) process. The electron field emission properties of thus made nano-emitters increase with MPE–CVD time interval for coating the UNCD films, attaining small turn-on field (E₀ = 6.4 V/μm) and large emission current density (J_e = 6.0 mA/cm² at 12.6 V/μm). This is presumably owing to the higher UNCD granulation density and better UNCD-to-Si electrical contact on SiNWs. The electron field emission behavior of these UNCD nanowires emitters is significantly better than the bare SiNW ((E₀)_SiNWs = 8.6 V/μm and (J_e)_SiNWs < 0.01 mA/cm² at the same applied field) and is comparable to those for carbon nanotubes.     

β-MnO2 nanowires: A novel ozonation catalyst for water treatment

Using Mn(NO₃)₂ and ozone as raw materials, β-MnO₂ nanowires with diameters of about 6–12 nm, lengths of 2–5 μm and surface area of 73.54 m² g⁻¹ were synthesized by a simple hydrothermal process. The influences of synthesis conditions such as hydrothermal temperature, reaction time and ozone were investigated, and the growth process of β-MnO₂ nanowires was discussed. The catalytic properties of β-MnO₂ nanowires for the degradation of phenol were evaluated. β-MnO₂ nanowires revealed good separability and remarkable catalysis for the degradation of phenol.