Low Temperature Wet Chemical Process Research Articles

Effects of precursors and caustic bases on structural and vibrational properties of ZnO nanostructures elaborated by hydrothermal method

The effects of zinc ions source (zinc acetate and zinc sulfate) and caustic bases (sodium and potassium hydroxides) on structural, morphological and vibrational properties of ZnO nanostructures elaborated by simple low temperature wet chemical process are studied. The samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared (FTIR) and Raman spectroscopies. XRD results show that ZnO structures are polycrystalline hexagonal wurtzite with high crystal quality. SEM images reveal that the morphologies of the nanostructures are nanopencils except in those synthesized with zinc sulfate precursor and sodium hydroxide caustic base, where pencils agglomerate to form sand rose-like morphologies. EDAX measurements confirm the purity of the elaborated specimens by the presence of only Zn and O atoms in the samples. Raman spectroscopy studies show that the peaks, related to E2 high mode, are more intense in ZnO structures elaborated with zinc acetate when NaOH is used, and in ZnO structures elaborated with zinc sulfate when KOH is employed.

Mesoporous Mn3O4 coated reduced graphene oxide for high-performance supercapacitor applications

We report the facile synthesis of mesoporous Mn3O4 coated reduced graphene oxide (rGO) nanocomposite using a simple low temperature wet chemical process and demonstrated the nanocomposite material as high-performance electrodes for electrochemical supercapacitor. The nanocomposite structure is unique as it consists of an ultra-thin, mesoporous (pore size ∼1.9–2.6 nm) with oriented pore size of Mn3O4 layer deposited on the surface of rGO. The structure and the orientation of nanopores in the Mn3O4 layer were further confirmed using HRTEM, while structural and morphological analysis were carried out using XRD, Raman spectroscopy, SEM, TEM, and SAED. The pore size and the pore distributions were verified using BET surface area technique, which demonstrated the nanocomposite exhibits uniform distribution of pores of dimension ∼1.9–2.6 nm throughout. The electrocatalytic behavior of the nanocomposite was found to be ideal for their use as supercapacitor electrodes as high-performance charge storage devices. Finally, we demonstrate the supercapacitor electrode using Mn3O4-rGO nanocomposite followed by their electrochemical characterizations for electrocatalytic activity for charge storage. The hybrid material shows best capacitance value of 221 F g−1 at current density 0.15 A g−1 with good cycling stability. We believe that our investigations will pave a pathway towards various new applications, including, electrochemical catalysis, sensing, energy harvesting and storage and many more.

Influence of dipping cycle on SILAR synthesized NiO thin film for improved electrochemical performance

NiO thin films have been successfully synthesized using by successive ionic layer absorption and reaction (SILAR) technique which is simple, cost-effective and low-temperature wet chemical process. Influences of deposition cycle on structural and morphological property were investigated using XRD and FESEM. Surface morphological study shows formation of highly porous network which provides more active sites and deposition path for electrolyte ions. NiO thin film based electrode provides highest specific capacitance of 1341 Fg−1 at the voltage scan rate of 2 mVs−1 for the film deposited at 40 deposition cycle. From charging -discharging curve of NiO electrode, specific capacitance value of 877 Fg−1 at current 1 Ag−1for the film deposited at 40 deposition cycle was observed. It shows highest specific energy of 64.8 Wh Kg−1. The NiO electrode exhibited long-term cycle stability with 90% capacitance retention after 1000 cycle. Such attractive electrochemical performance of the formed electrode is suitable for the manufacturing of the good quality supercapacitors for commercial application.

44Ti self-diffusion in nanocrystalline thin TiO2 films produced by a low temperature wet chemical process

Grain boundary self-diffusion of titanium in nanocrystalline TiO2 films is investigated in an extended temperature interval by the radiotracer technique applying the 44Ti isotope. The diffusion annealing treatments are performed at low and high oxygen partial pressures. At low oxygen partial pressure Ti grain boundary self-diffusion follows an Arrhenius type temperature dependence with the pre-exponential factor of 7.25×10−12m2/s and the activation enthalpy of 74.7kJmol−1. At high oxygen partial pressure Ti diffusion follows an Arrhenius type temperature dependence below 773K and changes drastically the behavior above 773K indicating a possible grain boundary structure transition.

Well Oriented ZnO Nanorods Array: Negative Resistance and Optical Switching

Well‐oriented ZnO nanorods (NRs) arrays were grown on Si, alumina, quartz, and FTO substrates through a ZnO seed layer followed by low temperature wet chemical process. The influence of sputtered ZnO seed layer thickness (100, 50, 32, and 16 nm), annealing temperature and CuOx coverage on the characteristics of ZnO NRs were investigated in this study. The crystalline structural, chemical, morphological, optical, and electrical properties of ZnO NRs arrays were studied by X‐ray diffraction (XRD), field emission‐ scanning electron microscopy equipped by energy dispersive X‐ray spectroscopy (FE‐SEM/EDX), Raman scattering, UV/Vis ‐ near IR absorption spectroscopy and current‐voltage characteristic. XRD and Raman spectra measurement revealed that the synthesize ZnO displayed hexagonal wurtzite structure. The individual rod diameter, density, and orientation can be controlled by varying the seed layer thickness. The mean diameter and maximum length of ZnO NRs are around 55–66 nm and 282 nm, respectively. ZnO NRs/ ZnO thin film structure shows optical switching and negative differential resistance behavior as applicable to ON/OFF gate and memory devices.

Microwave Assisted Synthesis and Characterization of Nanostructure Zinc Oxide-Graphene Oxide and Photo Degradation of Brilliant Blue

Zinc Oxide-Graphene Oxide (ZnO-GO) nanocomposite have been fabricated by facile, low-temperature wet chemical process assisted with microwave irradiation and used for the photo degradation of Brilliant Blue under UV-Vis light radiation. The in-situ formed ZnO nano wires were randomly decorated on the surfaces and the edges of graphene oxide sheets, simultaneously reduced directly capable of forming the graphene sheets. The lattice constants and band gap energy of ZnO has been altered compared with pure nano-sized ZnO particles, which are confirmed by XRD. The graphene oxide sheets were anchored/tailored with ZnO particles and the photo degradation of Brilliant Blue were performed under UV-Vis light radiations. The results shows that graphene oxide hybridized with ZnO could produce an efficient photo-catalytic activity and the degree of photocatalytic activity enhancement strongly depends on bonding of ZnO nanowires and GO. The enhancements of photocurrent and photo catalytic activity attributed to the suppression of charge carrier's recombination resulting from the interaction between ZnO and GO. The optical, structural and morphology of the pure ZnO and ZnO-GO nanostructures were systematically studied by X-ray diffraction (XRD), Fourier Transformation Infrared spectroscopy (FTIR), UV-Vis spectroscopy, Raman spectroscopy, Photoluminescence spectroscopy, Energy dispersive spectroscopy (EDS), field emission scanning electron microscopy (FESEM).

Field electron emission from structure-controlled one-dimensional CuO arrays synthesized by wet chemical process

One-dimensional CuO nanostructure arrays have been synthesized on Cu foil by a low-temperature wet chemical process. Different CuO nanostructures including nanorods with facet heads, nanorods with needle-like tips and nanotubes are shaped simply by varying the concentration of oxidant. Field emission measurements show that CuO nanorods with needle-like tips are of superior performance than other shapes, having a turn-on field of 3.5V/μm and a field enhancement fact or of 2107. The good field emission performance is assigned to the sharp tips contributing to the high field enhancement effect and to the moderate density reducing the field screening effect.

Development of efficient chemi-sensor and photo-catalyst based on wet-chemically prepared ZnO nanorods for environmental remediation

Highly sensitive ammonia chemical sensor has been fabricated by using efficient ZnO nanorods (NRs) synthesized by low temperature wet-chemical process. The fabricated ammonia sensor showed excellent sensitivity ∼5.538μA/cm2/mM, lower-detection limit (∼0.11μM), and large-linear dynamic range (LDR, 0.5μM to 0.5mM) with good linearity (R=0.7102) in short response time (10.0s). Additionally, ZnO NRs displayed excellent performance in degrading acridine orange (AO), methylene blue (MB), and amido black (AB). The structural and morphological characterizations of the synthesized ZnO was carried out by field emission scanning electron microscopy (FESEM), powder X-ray diffraction (XRD), Fourier transform infrared spectrophotometer (FT-IR), and UV–vis spectrophotometer, which confirmed that the synthesized product is wurtzite type well-crystalline rod-shape structure with an average diameter of 58.61±5.0nm.

Molybdenum Sulfide/N-Doped CNT Forest Hybrid Catalysts for High-Performance Hydrogen Evolution Reaction

Cost effective hydrogen evolution reaction (HER) catalyst without using precious metallic elements is a crucial demand for environment-benign energy production. Molybdenum sulfide is one of the promising candidates for such purpose, particularly in acidic condition, but its catalytic performance is inherently limited by the sparse catalytic edge sites and poor electrical conductivity. We report synthesis and HER catalysis of hybrid catalysts composed of amorphous molybdenum sulfide (MoSx) layer directly bound at vertical N-doped carbon nanotube (NCNT) forest surface. Owing to the high wettability of N-doped graphitic surface and electrostatic attraction between thiomolybdate precursor anion and N-doped sites, ∼2 nm scale thick amorphous MoSx layers are specifically deposited at NCNT surface under low-temperature wet chemical process. The synergistic effect from the dense catalytic sites at amorphous MoSx surface and fluent charge transport along NCNT forest attains the excellent HER catalysis with onset overpotential as low as ∼75 mV and small potential of 110 mV for 10 mA/cm(2) current density, which is the highest HER activity of molybdenum sulfide-based catalyst ever reported thus far.

Highly efficient and stable DSSCs of wet-chemically synthesized MoS2 counter electrode

A competitive power conversion efficiency of 7.01% is achieved for TiO2-based dye-sensitized solar cells (DSSCs) using a chemically stable and mechanically robust molybdenum di-sulfide (MoS2) counter electrode, synthesized using a simple, scalable and low-temperature wet-chemical process, owing to its good redox reaction stability.

Assembled Monolayer Nanorod Heterojunctions

Compositional and interfacial control in heterojunction thin films is critical to the performance of complex devices that separate or combine charges. For high performance, these applications require epitaxially matched interfaces, which are difficult to produce. Here, we present a new architecture for producing low-strain, single-crystalline heterojunctions using self-assembly and in-film cation exchange of colloidal nanorods. A systematic set of experiments demonstrates a cation exchange procedure that lends precise control over compositional depths in a monolayer film of vertically aligned nanorods. Compositional changes are reflected by electrical performance as rectification is induced, quenched, and reversed during cation exchange from CdS to Cu(2)S to PbS. As an additional benefit, we achieve this single-crystal architecture via an inherently simple and low-temperature wet chemical process, which is general to a variety of chemistries. This permits ensemble measurement of transport through a colloidal nanoparticle film with no interparticle charge hopping.

Photobleaching Properties of YVO4:Eu3+ Nanophosphors Synthesized by Hydrothermal Treatment

When YVO4:Eu3+ nanophosphors synthesized by a low-temperature wet chemical process in the presence of citrate ions are continuously excited by UV light, the photoluminescence (PL) intensity gradually decreases. This photobleaching is accompanied with the reduction of V5+ to V4+, as confirmed by electron paramagnetic resonance spectroscopy. Hydrothermal treatment of YVO4:Eu3+ nanophosphors in the presence of PO4 3- ions produces Y(V,P)O4:Eu3+ through the partial replacement between VO4 3- and PO4 3-, and hence results in the increase in the PL intensity and the suppression of photobleaching.

Low temperature wet chemical synthesis of good optical quality vertically alignedcrystalline ZnO nanorods

The growth of ZnO nanorods on Au-coated ITO substrates using a low temperature wetchemical process is presented. Electron microscopy and x-ray diffraction observationsreveal that the crystalline ZnO nanorods are preferentially oriented along thec axis. Room temperature photoluminescence (PL) measurements reveal a strong band edgeemission at 382 nm, a signature of good crystallinity, with a weak and broad orange–redemission, which is typically attributed to the oxygen interstitials, in the range between 520and 720 nm. Other than the second order feature of the band edge emission at 760 nm, nored or near-infrared bands are observed. The effect of precursor concentration on themorphological, structural and PL properties are studied, and the results are discussed.