Zaiyin Huang

Room-temperature synthesis, growth mechanism and properties of uniform CdMoO4 nano-octahedra

Large-scale, uniform and single-crystalline CdMoO4 nano-octahedra have been successfully synthesized via a reverse-microemulsion route at room temperature. The structures and morphologies of the as-prepared products were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and selected area electron diffraction (SAED). The effect of various reaction conditions on the morphology and size of CdMoO4 products was investigated. The results show that the water content (ω), initial concentration of reagents and reaction temperature play important roles in governing the final product. A possible four-step growth mechanism was proposed for the formation of CdMoO4 nano-octahedra. Room-temperature photoluminescence (PL) spectra of CdMoO4 crystallites were measured, indicating that their optical properties obviously depend on the particle sizes and morphologies. Moreover, temperature-dependent photoluminescence and electrochemical behavior of CdMoO4 nano-octahedra were tested for the first time. The results suggest their prospective applications for optoelectronic devices and sensor construction.

Reaction Kinetic Parameters and Surface Thermodynamic Properties of Cu2O Nanocubes

Cuprous oxide (Cu2O) nanocubes were synthesized by reducing Cu(OH)2 in the presence of sodium citrate at room temperature. The samples were characterized in detail by field-emission scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, X-ray powder diffraction, and N2 absorption (BET specific surface area). The equations for acquiring reaction kinetic parameters and surface thermodynamic properties of Cu2O nanocubes were deduced by establishment of the relations between thermodynamic functions of Cu2O nanocubes and these of the bulk Cu2O. Combined with thermochemical cycle, transition state theory, basic theory of chemical thermodynamics, and in situ microcalorimetry, reaction kinetic parameters, specific surface enthalpy, specific surface Gibbs free energy, and specific surface entropy of Cu2O nanocubes were successfully determined. We also introduced a universal route for gaining reaction kinetic parameters and surface thermodynamic properties of nanomaterials.

Synthesis and Surface Thermodynamic Functions of CaMoO4 Nanocakes

CaMoO4 nanocakes with uniform size and morphology were prepared on a large scale via a room temperature reverse-microemulsion method. The products were characterized in detail by X-ray powder diffraction, field-emission scanning electron microscopy, transmission electron microscopy, and high-resolution transmission electron microscopy. By establishing the relations between the thermodynamic functions of nano-CaMoO4 and bulk-CaMoO4 reaction systems, the equations for calculating the surface thermodynamic functions of nano-CaMoO4 were derived. Then, combined with in-situ microcalorimetry, the molar surface enthalpy, molar surface Gibbs free energy, and molar surface entropy of the prepared CaMoO4 nanocakes at 298.15 K were successfully obtained as (19.674 ± 0.017) kJ·mol−1, (619.704 ± 0.016) J·mol−1, and (63.908 ± 0.057) J·mol−1·K−1, respectively.

Morphology Effect on the Kinetic Parameters and Surface Thermodynamic Properties of Ag3PO4 Micro-/Nanocrystals

Considerable effort has been exerted using theoretical calculations to determine solid surface energies. Nanomaterials with high surface energy depending on morphology and size exhibit enhanced reactivity. Thus, investigating the effects of morphology, size, and nanostructure on the surface energies and kinetics of nanomaterials is important. This study determined the surface energies of silver phosphate (Ag3PO4) micro-/nanocrystals and their kinetic parameters when reacting with HNO3 by using microcalorimetry. This study also discussed rationally combined thermochemical cycle, transition state theory, basic theory of chemical thermodynamics with thermokinetic principle, morphology dependence of reaction kinetics, and surface thermodynamic properties. Results show that the molar surface enthalpy, molar surface entropy, molar surface Gibbs free energy, and molar surface energy of cubic Ag3PO4 micro-/nanocrystals are larger than those of rhombic dodecahedral Ag3PO4 micro-/nanocrystals. Compared with rhombic dodecahedral Ag3PO4, cubic Ag3PO4 with high surface energy exhibits higher reaction rate and lower activation energy, activation Gibbs free energy, activation enthalpy, and activation entropy. These results indicate that cubic Ag3PO4 micro-/nanocrystals can overcome small energy barrier faster than rhombic dodecahedral Ag3PO4 micro-/nanocrystals and thus require lower activation energy.

Electrochemical Sensor for the Determination of Theophylline Based on Molecularly Imprinted Polymer with Ethylene Glycol Maleic Rosi- nate Acrylate as Cross-linker

A novel electrochemical sensor for the determination of theophylline based on ethylene glycol maleic rosinate acrylate as the cross linking agent and acrylic acid as functional monomer was fabricated by molecularly imprinted technology. A molecularly imprinted polymers (MIPs) membrane was synthesized on the surface of a glassy carbon electrode in vacuum drying oven by free radical polymerization method. The electrochemical behavior of the membrane was characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and chronoamperometry. Under optimum conditions, it was found that the response of peak currents was linear to the concentration of theophylline in range of 2.00×10

In situ growth mechanism and the thermodynamic functions of zinc oxide nano-arrays and hierarchical structure

We report the one-step synthesis of zinc oxide nanomaterials with arrays and hierarchical structure at room temperature. The zinc oxide nanomaterials can be synthesized via a simple method without catalyst. Furthermore, we explained the growth mechanisms of the two systems. In situ growth experiment provided the information of thermodynamics and kinetics, and based on that, growth mechanism was given a further explanation via the curve of in situ growth. Moreover, the relations between thermodynamic functions and the potential difference can be established by the electrochemical method. Take bulk zinc oxide reference. The thermodynamic functions of nano zinc oxide such as standard molar entropy, standard molar Gibbs free energy of formation, and standard molar enthalpy of formation can be calculated. The change rules of thermodynamic functions at different reaction times evidenced the growth mechanism more deeply. This work may contribute to the analysis of growth mechanism for nanostructures and obtain the thermodynamic functions of nanomaterials.

Size effect on thermodynamic parameters for the peanut-like CaMoO4 micro/nano reaction systems

Peanut-like CaMoO4 micro/nano structures with three different sizes were harvested by a simple reverse-microemulsion method at room temperature. Employing synthesized micro/nano CaMoO4 and HCl as reaction systems, thermodynamic parameters such as standard molar enthalpy of reaction ΔrHmθ, standard molar Gibbs free energy of activation Δr≠Gmθ, standard molar enthalpy of activation Δr≠Hmθ, and standard molar entropy of activation Δr≠Smθ were successfully acquired for the first time by in situ microcalorimetry. Furthermore, change regularities of the thermodynamic parameters for the micro/nano reaction systems were obtained and discussed. It demonstrated that size effect has significant influence on thermodynamic parameters of micro/nano material reaction systems.

Room-temperature synthesis of MnMoO4·H2O nanorods by the microemulsion-based method and its photocatalytic performance

Manganese molybdate hydrates (MnMoO4·H2O) nanorods have been synthesized at room temperature by a facile water-in-oil reverse microemulsion method. This technique was carried out in the reverse microemulsion of OP-10 (Polyoxyethylene octylphenol ether)-n-octanol-water-cyclohexane with a water/surfactant molar ratio ω = 10. Field-emission scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images showed that the diameters of these formed nanorods about 70 nm and lengthe up to 4 μm, respectively. High-resolution transmission electron microscopy (HRTEM) results showed that each nanorod was formed by serveral nanobelts which are stacked by a layer-by-layer process. These unique nanorods demonstrate good photocatalytic properties.

Preparation of Sb2O3 Submicron Rod Arrays by the Carbothermal Reduction Method

Sb2O3 submicron rod arrays were fabricated by carbothermal reduction method using antimony doped tin oxide (ATO) nanoparticles and graphite powder as source materials. The obtained products were characterized by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM). The results demonstrated that the samples were single-crystal Sb2O3 submicron rod arrays. The room-temperature photoluminescence (PL) measurement exhibited two violet emission peaks which could be indexed to oxygen vacancies related defect emission. Also, blue shift and intensity decrease were observed when the excitation wavelength changed from 365 nm into 325 nm.