Junlei Wang,Xueqin Wang,Qihui Chen,Helong Xu,Man Dai,Mei Zhang,Wenyi Wang,Hua Song
The microstructure of photocatalysts plays a key role in enhancing their photocatalytic performance. Herein, resorcinol/formaldehyde (RF) polymer resin was prepared using the extended Stöber process and used for hard templates. Hollow TiO 2 spheres (HTS) were synthesized via hydrolysis of a versatile kinetics-controlled coating and carbonization method. The physicochemical properties of as-prepared catalysts were characterized. The pure RF template had a uniform diameter of ~450 nm. By adjusting the ammonia dosage from 0.1 to 0.35 mL, monodisperse RF@TiO 2 spheres were obtained with a porous TiO 2 shell of ~25–160 nm in thickness. The concentration of ammonia had a significant effect on the micromorphology, and hence, the photocatalytic properties of the HTS. The Brunauer-Emmett-Teller surface area and pore volume were ~30 m 2 /g and 0.082 cm 3 /g, respectively. The intrinsically high conductivity of the HTS microspheres and their high surface area resulting from this robust hollow structure was beneficial for photocatalytic performance toward phenol decomposition.
Xiaosong Guo,Xiaoguang Yu,Yulu Chen,Zijia Feng,Qinglin Li,Zhenheng Sun,Guicun Li,Chuncheng Hao,Qingquan Lei
Hollow TiO2 nanospheres were fabricated and adopted as dispersing materials in ER fluids with different viscosities in order to investigate variation of polarized particles before and after the formation of chainlike structure in electrorheological (ER) fluids. Results showed that the ER fluid with low viscosity had better ER efficiency than that with high viscosity, which was ascribed to the better ability of low viscosity ER fluid in maintaining chainlike structures. From an analysis of dielectric properties, it was found that increase of permittivity of ER fluids at low frequency should result from the distribution change of polarized particles in ER fluids. Distribution variation of polarized particles would induce the increase of electric field strength in the region of chainlike structure, which was called “secondary polarization”. This secondary polarization led to an increase of the number of charges on the surface of polarized particles, causing further enhancement of electrostatic interactions between polarized particles. Moreover, the magnitude of polarized charge caused by secondary polarization was much larger than that caused by interface polarization, which suggested that the secondary polarization played an important role in the ER phenomenon. A novel model with detailed explanation about the ER effect is proposed. Furthermore, relationships among the polarizability of dispersed particles, characteristic of dielectric spectrum at low frequency, and ER properties are discussed in detail.
Xin He,Caiyun Jiang,Jie Yang,Shuangchao Sheng,Yuping Wang
5-Hydroxymethylfurfural (5-HMF) is a heterocyclic compound with six carbons commonly found in heat-treated carbohydrate-rich foods. 5-HMF exceeding the specified limit is cytotoxic to the human body, and will be converted into carcinogenic substances (5-sulfoxide methyl furfural) after long-term accumulation in the body. Therefore, it is highly necessary to develop a sensitive and accurate detection method for 5-HMF in the field of food safety. In this study, a photoelectric sensing method was developed for the highly sensitive detection of 5-HMF using hollow TiO2 nanospheres successfully synthesized by template, sol–gel and lye etching methods. The structure and composition of the materials were studied by XRD, XPS, SEM and TEM. The electrochemical and photoelectrochemical properties of an h-TiO2 electrode probe based on indium tin oxide (ITO) slides were investigated. The results indicated that the linear relationship of 5-HMF is good in the concentration range of 10−11–10−7 M, and the detection limit of 5-HMF is 0.001 nM. Moreover, the PEC sensor shows high accuracy in the detection of actual samples.
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