Yao Suwei

Preparation and characterization of silver colloids with different morphologies under ultrasonic field

In the ultrasonic field, stable silver colloids were produced by the reduction of AgNO3 with the protection of PVP using KBH4 or N2H4·H2O as reductant. The main factors affecting the morphology of silver nanoparticles, such as distribution of the ultrasonic field, ultrasonic time, ultrasonic power, and the species of reductant, were studied. The silver colloids were identified by TEM and spectrophotometry. The results indicate that the factors such as distribution of the ultrasonic field, ultrasonic time, ultrasonic power, and the species of reductant have a great impact on the morphology of the silver nanoparticles. The size of the silver nanoparticles decreases with the ultrasonic power and ultrasonic time increasing. Ag nanoparticles prepared in standing wave field preferentially grow in a certain direction, which is propitious for forming hexagonal-and spherical-like silver nanoparticles. Monodispersed spherical silver nanoparticles are easily synthesized in the diffusion field. The stability of silver colloid becomes improved by ultrasonic treatment. For example, precipitate is not found after several weeks for the silver colloid prepared with an ultrasonic treatment time of 180 min. The silver nanoparticles prepared without ultrasonic treatment are large spherical-like and hexagonal. Well-dispersed spherical silver particles with a mean size of about 20 nm have been prepared under ultrasonic treatment. Spherical, spherical-like, and hexagonal silver nanoparticles can be obtained by changing the reductants.

热处理工艺对TiO 2 纳米管阵列结构及其光电性能的影响

通过阳极氧化法在钛箔上制备了TiO 2 纳米管阵列, 在不同热处理工艺下使其晶化. 利用扫描电子显微镜(SEM)和X射线衍射(XRD)对TiO 2 纳米管阵列的形貌和结构进行了表征. 结果表明, 阳极氧化法制备的TiO 2 纳米管经450~750℃热处理后为纳米晶结构, 平均晶粒尺寸随退火温度升高而增大, 相同温度下氮气气氛中热处理的TiO 2 平均晶粒尺寸小于空气气氛中热处理的TiO 2 . 氮气气氛下退火可拓宽TiO 2 由锐钛矿型(Anatase)向金红石型(Rutile)结构转变的热处理温度范围, 650℃以上退火处理后, TiO 2 纳米管中掺杂有少量的氮. 光照开路电位测试和稳态极化曲线测试结果表明, 在氮气气氛中、经650℃退火处理2 h制备的TiO 2 纳米管阵列电极光电响应性能最佳, 此时TiO 2 为锐钛矿型和金红石型的混晶结构.

One-pot Hydrothermal Synthesis of Novel NiCoO 2 /Reduced Graphene Oxide Composites for Supercapacitors

Novel NiCoO2/rGO composites with a structure of NiCoO2 nanoparticles anchored on layers of reduced graphene oxide(rGO) were synthesized via a simple one-pot hydrothermal method and were used as faradaic electrodes for supercapacitors. The microstructures of NiCoO2/rGO composites were characterized by means of field emission scanning electron microscopy(FESEM), transmission electron microscopy(TEM), X-ray diffraction(XRD) and thermogravimetric analysis(TGA). When acting as faradaic electrodes for supercapacitors, NiCoO2/rGO composites exhibited a specific capacity of 288 C/g at the current density of 2 A/g and maintained 139.98 C/g at 20 A/g. High capacity retention ratios up to 88% could be achieved after 1000 cycles at a current density of 2 A/g. The outstanding cycling stability was primarily attributed to the combination of mixed transition metal oxides and rGO, which not only maintains a high electrical conductivity for the overall electrode but also prevents the aggregation and volume expansion of electrochemical materials during the cycling processes.

Measurement of Surface Potential at Metal/Organic-Material Interfaces by Electro-Absorption Method

The surface potential built-in vacuum deposited phthalocyanine (Pc) film on aluminium electrode is investigated by the electro-modulation method. To avoid the influence of charge injection, a sandwiched cell (Al–Pc–air–ITO) is fabricated. The modulation signal, which depends on the external electric field intensity, is detected. The properties of electro-absorption (EA) and electro-reflectance (ER) signals are analysed. The existence of the surface potential at the metal/organic-material interface induces 1f referenced ER signals. As a result, the surface potential built across the vacuum-deposited Pc film on the aluminium electrode is estimated to be 1.23 V.

Analysis of Second-Harmonic Generation from CuttbPc LB Film/Metal Interface

Second-harmonic generation signals from a CuttbPc LB film deposited on metal (Al or Au)–glass substrates were investigated. It was observed that there were two second-harmonic peaks at the wavelength of 1060 and 1250 nm in the CuttbPc/Al film, but only one peak at 1050 nm in the CuttbPc/Au film. Meanwhile the surface electric potentials (SEP) at the interfaces of LB film/metals were also measured using a Kelvin probe. The SEP in the CuttbPc/Al decreases and eventually approaches a saturated value of -1.0 V as the film thickness increases, while the SEP in the CuttbPc/Au is nearly zero. Based on the experimental results and theoretical analysis, it was considered that the space-charge-induced electric field makes a main contribution to the second-harmonic generation at 1250 nm in the CuttbPc/Al film.