Chemical Solution Method Research Articles

Preparation of CuSbS2 thin films by a facile and low-cost chemical solution method

In this paper, CuSbS2 thin films were prepared by a facile and environmental-friendly chemical solution method at low temperature. The effect of sulfurization temperature was studied. The properties of CuSbS2 thin films were investigated by X-ray diffraction, scanning electron microscopy, UV–Vis and photocurrent response measurement. The results indicated CuSbS2 thin films sulfurized at 350 °C showed better crystallinity and no impurity phase. The as-prepared CuSbS2 film had a band gap of 1.5 eV and an obvious photoconductivity.

Optical Properties of Tin Monoxide Nanoshells Prepared via Self-Assembly

Recently, layered IV–VI metal monochalcogenides have attracted a lot of attention because of their unique properties. Among them, tin monoxide (SnO) has been widely studied as thin films for the application in high-mobility p-channel transistor and photoelectricity device fabrication. In this work, we successfully synthesized SnO nanoshells through a facile solution chemical method. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images confirmed the morphology of these nanoshells. The surface chemical composition was investigated by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Raman and photoluminescence spectra were used to study the optical properties of nanoshells with different sizes, which were formed in different concentrations. We found that the special nanostructure may result in abundant Sn or O vacancies on the surface of nanoshells, and these defects resulted in a broad photoluminescent signal. This work provided a solution synthesis method to prepare SnO and other IV–VI metal monochalcogenides as well as their promising applications in optical device.

Facile synthesis of Pd-decorated ZnO nanoparticles for acetone sensors with enhanced performance

ZnO and Pd nanoparticles (NPs) with average diameter of 38 and 10 nm were prepared in advance through a chemical solution method. Pd-functionalized ZnO nanoparticles (Pd@ZnO) were simply synthesized by adding ethanol solution of Pd NPs into ZnO powder, and annealing in argon atmosphere at 500 °C for 1 h after grinding for 30 min. The morphology and structure of the materials were systemically analyzed using Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM) techniques. A weak peak in the XRD pattern of Pd@ZnO belonging to the (111) plane of elemental Pd indicated successfully loading of Pd. EDS and TEM results further confirmed successfully coating of Pd NPs onto the surface of ZnO. Sensors using ZnO NPs decorated with Pd (1 wt%) on the surface of exhibited highly elevated sensitivity of 76 in comparing with the response of 36 when based on pure ZnO NPs. In addition, such modification also resulted in a decrease in the operating temperature from 370 to 340 °C for 100 ppm acetone vapor. The sensing mechanism of the sensor based on Pd@ZnO NPs is discussed. Addition of Pd NPs can play an important role in improving the performance of gas sensors, including high sensitivity, good selectivity, and short response/recovery times.

Deposition of Highly Crystalline Covellite Copper Sulphide Thin Films by SILAR

Thin films of the covellite phase of CuS are of special importance due to their properties for optoelectronic device applications. Their preparation by chemical solution methods could enable their deposition on flexible substrates at low temperature for large area applications. Successive Ionic Layer Adsorption and Reaction (SILAR) is a promising option because it is simple, inexpensive, and allows the control of thickness and composition. However, low crystalline CuS thin films have been reported so far. In this work, highly polycrystalline CuS thin films were successfully grown at room temperature by SILAR using CuSO4 and Na2S as the ionic solutions without post‐deposition annealing. The films obtained at different SILAR cycles resulted in good appearance, uniformity, well adhered to the substrate, and presented the covellite structure as the predominant crystalline phase. X‐ray diffraction analysis showed important details about the films growth evolution, which were in agreement with results from atomic force microscopy and ellipsometry. All the films exhibited low electrical resistivity in agreement with the metallic behavior observed in the infrared region of their transmittance spectra. These results demonstrate a direct method of obtaining highly polycrystalline CuS thin films at low temperature, which could open a new range of applications.

Synthesis of α-Mns Hierarchical Architectures By Chemical Vapor Deposition and Its Application As Anode Electrode for Li-Ion Batteries

MnS is a wide band gap (3.1 - 3.7 eV) p-type direct semiconductor that exists in three crystallographic polymorphs; the green α-MnS is the most stable with a rock-salt crystal structure, and the two metastables zincblende (β-MnS) and wurzite (γ-MnS) crystal structures. In particular, α-MnS have been reported to provide very good electrochemical performance for alternative anode electrodes to fabricate flexible all-solid state supercapacitors and electrodes for Li-ion batteries. α, γ, or β-MnS materials are usually synthesized by the chemical solution methods, such as solvothermal and hydrothermal techniques. However, our method in this work consists in the synthesis of free standing α-MnS hierarchical architectures by Chemical Vapor Deposition technique, which is suitable to prepare electrodes for Li-ion batteries. In this presentation, we discuss: a) the growth mechanism of α-MnS by Chemical Vapor Deposition technique; b) its structural, morphological, and compositional characterization; and c) the cyclic voltammetry, charge-discharge behavior, and cycling capacity of coin cells using α-MnS as the anode electrode.

Effect of Surface Passivation on CdxNi1-xS Thin Films Embedded with Nickel Nanoparticles

Certain treatments done to binary CdS , such as incorporating Ni onto CdS produces ternary thin films may cause major optical parameters that have a number of applications including for solar cell device fabrication. In this paper, we report on the effect of surface passivation on the band gap and other related optical properties of CdNiS thin films. Thin films for Cd x Ni 1-x S were prepared on glass substrates by chemical solution method. Effects of surface passivation and variation of the volume of nickel ions on the optical properties CdS hence obtaining Cd x Ni 1-x S thin films was investigated. It was observed that the thin films hard an average Transmittance above 68 %, with reflectance below 25 % across UV-VIS-NIR region. A plot of ( αhν ) 2 versus hν gave energy band gap between 2.55–3.49 eV for as-grown samples and 2.82–3.50 eV for annealed samples. The passivated samples had band gap energy values within the range 2.85–3.12 eV. It was concluded that an increase in concentration of Cd 2+ and Ni 2+ ions in the reaction led to an increase the band gap while optical conductivity ranged between 3.78x10 11 –2.40x10 12 S -1 .

Electric and Mechanical Switching of Ferroelectric and Resistive States in Semiconducting BaTiO3-δ Films on Silicon.

Materials that can couple electrical and mechanical properties constitute a key element of smart actuators, energy harvesters, or many sensing devices. Within this class, functional oxides display specific mesoscale responses which often result in great sensitivity to small external stimuli. Here, a novel combination of molecular beam epitaxy and a water-based chemical-solution method is used for the design of mechanically controlled multilevel device integrated on silicon. In particular, the possibility of adding extra functionalities to a ferroelectric oxide heterostructure by n-doping and nanostructuring a BaTiO3 thin film on Si(001) is explored. It is found that the ferroelectric polarization can be reversed, and resistive switching can be measured, upon a mechanical load in epitaxial BaTiO3-δ /La0.7 Sr0.3 MnO3 /SrTiO3 /Si columnar nanostructures. A flexoelectric effect is found, stemming from substantial strain gradients that can be created with moderate loads. Simultaneously, mechanical effects on the local conductivity can be used to modulate a nonvolatile resistive state of the BaTiO3-δ heterostructure. As a result, three different configurations of the system become accessible on top of the usual voltage reversal of polarization and resistive states.

Effect of the morphology of solution‐grown ZnO nanostructures on gas‐sensing properties

AbstractDespite the great potential of zinc oxide (ZnO) nanostructures as a sensing material for high‐performance gas sensors, the correlation between the morphology of ZnO nanostructure and its gas‐sensing performance has not been systematically investigated yet. In this work, ZnO nanostructures with controlled morphologies were synthesized by low‐temperature solution route and chemical bath deposition method. Thin film gas sensors were fabricated from the nanostructures and the sensor performance such as the response, recovery time, and stability was examined for several gases. It is demonstrated that the gas‐sensing performance of a ZnO nanostructure sensor is strongly influenced by its morphology. One dimensional ZnO nanocones are highly promising for practical application to gas sensors, due to their large surface area per unit mass and unique conical structure.

Polyethylene Terephthalate Thin Film Incorporating Green Emitting Up-Conversion Phosphor

Er3+-doped CaTiO3 up-conversion phosphor was prepared by chemical solution method. Host thin film to incorporate up-conversion phosphor was a nanostructured organo-silicon compound prepared from methyl tri-methoxysilane and 3-glycidoxy-propyl-trimethoxy-silane. Further, we prepared a phosphor paste by mixing the organo-silicon compound with 3 mol% Er3+-doped CaTiO3. Subsequently, this paste was coated on polyethylene terephthalate, followed by heat-treatment at 120°C. The visible emission was found to be at the region 525 ~ 530 nm, 540 ~ 560 nm, and 650 ~ 660 nm corresponding to the 2H11/2 ® 4I15/2, 4S3/2 ® 4I15/2, and 4F9/2 ® 4I15/2 transitions of Er3+ ions, respectively. The transmission of performance IR detection cards is to be above 90% in the range from 200 to 1600 nm because the weak infrared light should pump the CaTiO3 up-conversion phosphor. The prepared up-conversion phosphor films can potentially be used as low-power IR detectors in optical fiber communication and medical instrument.

La0.8Sr0.2MnO3-Based Perovskite Nanoparticles with the A-Site Deficiency as High Performance Bifunctional Oxygen Catalyst in Alkaline Solution.

Perovskite (La0.8Sr0.2)1-xMn1-xIrxO3 (x = 0 (LSM) and 0.05 (LSMI)) nanoparticles with particle size of 20-50 nm are prepared by the polymer-assisted chemical solution method and demonstrated as high performance bifunctional oxygen catalyst in alkaline solution. As compared with LSM, LSMI with the A-site deficiency and the B-site iridium (Ir)-doping has a larger lattice, lower valence state of transition metal, and weaker metal-OH bonding; therefore, it increases the concentration of oxygen vacancy and enhances both oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). LSMI exhibits superior ORR performance with only 30 mV onset potential difference from the commercial Pt/C catalyst and significant enhancement in electrocatalytic activity in the OER process, resulting in the best oxygen electrode material among all the reported perovskite oxides. LSMI also exhibits high durability for both ORR (only 18 mV negative shift for the half-wave potential compared with the initial ORR) and OER process with 10% decay. The electrochemical results indicate that the A-site deficiency and Ir-doping in perovskite oxides could be promising catalysts for the applications in fuel cells, metal-air batteries, and solar fuel synthesis.

Hexagonal plate-shaped CuSe nanocrystals by polylol solution chemical synthesis

ABSTRACT(0001)-oriented hexagonal klockmannite CuSe nanoplates were successfully synthesized by polylol solution chemical method, in which triethylene glycol (TEG), triethylenetetramine (TETA) and polyvinylpyrrolidone (PVP) were used as the reaction solvent, reducing agent and capping agent, respectively. The influence of synthesis temperature, TETA adding amounts and refluxing time was mainly investigated.

Mode‐matching analysis of a spit‐circular cavity resonator for measurement of the dielectric constant for film on a substrate

In this paper, we apply the mode‐matching technique (eigenmode expansion) to formulate an analytical model for a split cylindrical cavity resonator with a thick ceramic film layer sandwiched between two‐layer alumina substrates. We then compute the resonant frequencies with the TE011 mode with an eigenvalue problem approach using the model formula. The quality factor (Q‐factor) of the resonator is also calculated by applying the perturbation method to the analytical model. The validity of the proposed analytical technique is confirmed by applying this method to the estimation of permittivity of thick films as an inverse problem. Ceramic films (2 µm thickness) were synthesized using a chemical solution method onto 200‐µm‐thick, 50‐mm‐diameter alumina substrates. The complex permittivity of the films was then determined using the TE011 mode split cylindrical cavity resonator in the 10‐GHz band. The extent of the edge effect at a sample insertion space was evaluated by comparing the estimated results through TE wave analysis using the mode‐matching method when the transverse resonance technique and the perturbation method were applied to calculate the resonant frequency and the dielectric Q‐factor. The results obtained indicate that a difference of 0.153% in the permittivity of the alumina substrate causes differences of 6.10 and 3.75% in the measured permittivity and loss tangent, respectively, of 2‐µm‐thick ceramic film with a permittivity of ∼50. Differences in permittivity and loss tangent were more pronounced with thinner films. It was also confirmed that the estimated results for permittivity and the loss tangent values of these ceramic films were affected by the estimated permittivity value of the alumina substrate. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Chemical synthesis and granulometric composition of CaZr0.9Y0.1O3–δ powders

CaZr0.9Y0.1O3–δ powders were synthesized by chemical solution methods: modified Pechini method and from solutions of inorganic salts in water and ethanol. The structure crystallizes into the orthorhombic type upon annealing at 1000°C for powders prepared by the Pechini method and from solution of salts in water. It was shown that CaZr0.9Y0.1O3–δ powders synthesized by various methods have different dispersities. The results obtained in a study of the granulometric composition by the sedimentation method and microscopic analysis enable fabrication of dense and mechanically strong electrolyte films and ceramics.

Synthesis and enhanced gas sensing properties of flower-like ZnO/α-Fe2O3 core-shell nanorods

This paper reports a facile two-step synthesis route for the preparation of flower-like ZnO/α-Fe2O3 nanorods (NRs). Flower-like ZnO NRs with the average diameter about 810nm and length about 4.5µm were firstly synthesized via a chemical solution method, and then ZnO NRs was coated with a continuous α-Fe2O3 layer to form ZnO/α-Fe2O3 core-shell structure through an ionic-layer adsorption and reaction method. The gas-sensing results show that the ZnO/α-Fe2O3 NRs exhibit excellent sensitivity, selectivity, and response-recovery capacity to ethanol vapor at a low optimum temperature of 240°C. In particular, compared with pure ZnO NRs and α-Fe2O3 nanoparticles (NPs), the ZnO/α-Fe2O3 NRs show an obvious improvement in gas sensing properties. The substantial improvement of sensing properties may be attributed to the unique microstructure and heterojunction formed between ZnO and α-Fe2O3.

Effect of lead-free (CH3NH3)3Bi2I9 perovskite addition on spectrum absorption and enhanced photovoltaic performance of bismuth triiodide solar cells

Active composite layers of bismuth triiodide (BiI3) and lead-free (CH3NH3)3Bi2I9 (MBI) perovskite were prepared using a simple chemical solution method under ambient conditions for thin-film solar cells. Results of X-ray diffraction and scanning electron microscopy indicated that the crystallization and surface morphologies of the composite films varied with perovskite contents. Multi-absorption was observed in the composite films due to the bandgap difference between BiI3 and MBI perovskite. Moreover, band bending at the BiI3-perovskite interfaces resulted in the realignment of energy levels in the composite films, and this phenomenon was beneficial to the efficient injection of excited electrons from the active layers into the TiO2 layers. Accordingly, due to the optimized crystallization and realigned energy level, when 20% of MBI perovskite was introduced into the active layers, the open-circuit voltage obviously increased from 0.44 V to 0.57 V in the (BiI3)0.8(MBI)0.2 composites solar cells, enhancing their power conversion efficiency by 67% compared with that in pure BiI3 solar cell. This study developed a new route for designing more efficient lead-free solar cells.

Chemical Solution Deposition of Epitaxial YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7-x</sub> /CeO<sub>2</sub>/ La<sub>2</sub>Zr<sub>2</sub>O<sub>7</sub> Multilayer Films on Biaxially-Textured Ni-W Tapes

CeO2/La2Zr2O7 composite buffer layers were deposited on Ni-W tapes using chemical solution method. YBa2Cu3O7-x (YBCO) films were then deposited on the CeO2/La2Zr2O7 composite buffer layers using a low-fluorine solution route. Effect of the annealing temperature and annealing atmosphere on the texture of the CeO2 layers was investigated. It was found that CeO2 film annealed at 1000°C under the atmosphere of N2 containing of 5vol. %H2 shows a high degree of c-orientation on La2Zr2O7 (LZO) film. Effect of oxygen partial pressure on the properties of YBCO films deposited on the CeO2/LZO buffer layers was also investigated. The YBCO annealed under N2 containing of 500ppm O2 shows the optimal properties, with critical current density (Jc) of 1MA/cm2 at 77K, 0T.

Controlled synthesis of upconverting nanoparticles/CuS yolk-shell nanoparticles for in vitro synergistic photothermal and photodynamic therapy of cancer cells.

Synergistic photodynamic and photothermal therapy of cancer cells is of considerable scientific and technological interest. In this work, we demonstrate a sacrificial template strategy to fabricate yolk-shell nanoparticles combining upconversion nanoparticles (UCNPs) and CuS nanoparticles. Lanthanide-doped upconversion nanoparticles of NaYF4:30% Yb,1% Nd,0.5% Er@NaYF4:20% Nd (also denoted as UCNPs) have been prepared as 808 nm light excited remote-controlled nanotransducers for in vitro cancer cell treatment. The upconversion fluorescence of the as-prepared UCNPs@CuS yolk-shell nanoparticles is completely quenched under the excitation of an 808 nm laser, which demonstrates that the energy transfer between the UCNPs and CuS is very efficient. In addition, the as-prepared UCNPs@CuS nanoparticles show higher production ability for hydroxyl radicals (˙OH) and singlet oxygen (1O2) compared to CuS hollow nanospheres of similar size. In particular, the excited shell layer (CuS) showed an enhanced photothermal effect while producing reactive oxygen species (ROS) including singlet oxygen (1O2) and hydroxyl radicals (˙OH) after being exposed to near infrared (NIR) light. Thus, the as-prepared UCNPs@CuS yolk-shell nanoparticles exhibited the synergistic effect of photothermal and photodynamic therapy of cancer cells, which resulted in significant cell death after exposure to an 808 nm laser. The synthetic strategy will provide an alternative method to fabricate other UCNP based core-shell nanoparticles for potential and important applications in bionanotechnology including theranostics, multimodal treatment, magnetic resonance imaging-guided photodynamic therapy, etc.

Characterization of reduced graphene oxide produced through a modified Hoffman method

AbstractLarge-scale fabrication of graphene and reduced graphene oxide (rGO) is important for industrial and research applications of this material. Chemical solution methods offer a low-cost alternate to produce rGO with high yield. This research is to explore the effect of chemical and thermal reduction on the quality of chemically synthesized graphene and its derivatives. A top-down process involved the chemical oxidation of the precursor graphite powder (size ~10 μm) using a concentrated mixture of sulphuric acid and nitric acid. Oxidized graphite powder was thermally exfoliated at 1,050°C for 30 s to produce graphene oxide (GO). Chemical reduction in GO sheets with sodium borohydride led to the formation of rGO. Characterization by Raman spectroscopy revealed an intensity ratio of 2D/G bands of rGO as approximately 0.5 indicating a multi-layered structure. X-ray diffraction, field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) results indicated a multi-layered rGO wit...

A unique Cu2O/TiO2 nanocomposite with enhanced photocatalytic performance under visible light irradiation

A unique Cu2O/TiO2 nanocomposite with high photocatalytic activity was synthesized via a two-step chemical solution method and used for the photocatalytic degradation of organic dye. The structure, morphology, composition, optical and photocatalytic properties of the as-prepared samples were investigated in detail. The results suggested that the Cu2O/TiO2 nanocomposite is composed of hierarchical TiO2 hollow microstructure coated by a great many Cu2O nanoparticles. The photocatalytic performance of Cu2O/TiO2 nanocomposite was evaluated by the photodegradation of methylene blue (MB) under visible light, and compared with those of the pure TiO2 and Cu2O photocatalysts synthesized by the identical synthetic route. Within 120min of reaction time, nearly 100% decolorization efficiency of MB was achieved by Cu2O/TiO2 photocatalyst, which is much higher than that of pure TiO2 (26%) or Cu2O (32%). The outstanding photocatalytic efficiency was mainly ascribed to the unique architecture, the extended photoresponse range and efficient separation of the electron-hole pairs in the Cu2O/TiO2 heterojunction. In addition, the Cu2O/TiO2 nanocomposite also retains good cycling stability in the photodegradation of MB.

Superior La1 − xSrxCoO3 − δ ceramic electrode fabrication by MOCSD for low-temperature SOFC application

Metal-organic chemical-solution-deposited lanthanum strontium cobaltite (LSC, La1−xSrxCoO3−δ) nanoporous thin films were fabricated for use as cathodes for low-temperature solid oxide fuel cells (LT-SOFCs). Electrochemical performance and durability were evaluated under continuous operation by comparing with typical Pt-cathode SOFCs. In the initial stage of operation, SOFCs with Pt cathodes showed higher output power density for its superior catalytic activity. However, the overall performance of SOFCs with Pt cathodes gradually degraded due to thermal instability, while the performance with LSC cathodes remained stable for 10h of continuous operation. In addition, by taking advantage of wet chemical solution methods, the amount of dopant was systematically varied to investigate its effect on fuel cell performance (La1−xSrxCoO3−δ, x=0.4, 0.5, 0.6). The fuel cell sample with the dopant ratio x=0.5 showed the highest peak power density independent of the operating temperature. This result implies that LSC cathodes deposited by chemical solution deposition show better operational durability than Pt cathodes and provided potentiality of replacing precious metal cathode for low-temperature SOFCs.