包覆硬脂酸膜α－Fe_(2)O_(3) 超微粒子的光谱及光电化学研究

UV-Vis Spectral and Photoelectrochemical Studies on the α-Fe_(2)O_(3) Ultrafine Particles with a Layer of Stearic Acid

采用相转移法制备了以硬脂酸（ＳＴ）修饰的α－Ｆｅ_２Ｏ_３超微粒子，测量了其紫外－可见吸收光谱。随着粒子尺寸的减小，光谱吸收阈值发生红移，表现出介电限域效应。用循环伏安法和光电流～电势曲线研究了介电限域效应对α－Ｆｅ_２Ｏ_３超微粒子电化学及光电化学性质的影响。循环伏安结果表明，表面修饰ＳＴ的α－Ｆｅ_２Ｏ_３超微粒子电化学可逆性较裸露粒子好。光电流－电位的关系表明，超微粒子周围的介质性质也影响了微粉的光电化学性质。

The α-Fe_2O_3 ultrafine particles coated with a layer of stearic acid(ST) were prepared by phase transfer method.There is a significant red shift of optical absorption band edge with the decrease of size particles which exhibits the dielectric confinement effect. The effect of dielectric confinement on the electrochemical and photoelectrochemical properties of α-Fe_2O_3 ultrafine particles was investigated by using cyclic voltammetry and photocurrent measurement.The coating layer with smaller dielectric constant decreases the shielding to the electric lines,so that the platinum electrode deposed by the coated particles is more electrochemically reversible than by the naked particles.A cathodic photocurrent is observed with both kinds of particles in the region of-600～267 mV,but there is a fine distinction in the cathodic photocurrent of two kinds of electrodes,which comes from the dielectric confinement effect.A weak anodic photocurrent is observed in the potential region of>260 mV.