纳米TiO_2及ZnO悬浮液中·OH的生成

GENERATION OF HYDROXYL RADICALS IN NANOSCALE TiO_2 AND ZnO SUSPENSIONS

采用气相色谱法间接测定了光照下纳米及常规TiO2、ZnO悬浮液中.OH的产生情况.结果表明,光照下常规TiO2及ZnO悬浮液中没有检测到.OH,而纳米TiO2及ZnO悬浮液在日光灯及紫外灯照射下的.OH生成量与时间之间具有较好的线性关系,120h内溶液中.OH含量随纳米颗粒浓度(<200mg.l-1)的升高而逐渐升高;但当纳米颗粒浓度高于200mg.l-1时,.OH含量不再随纳米颗粒浓度升高而增加.本实验中不同光照条件下纳米颗粒悬浮液中.OH产生速率各不相同,其中普通日光灯照射下.OH产生速率最慢、紫外光(254nm)其次、太阳光最快,而避光条件下没有检测到.OH.同时,.OH的产生与纳米颗粒化学组成十分相关,在日光灯照射下纳米TiO2的.OH产生速率为纳米ZnO的2—4倍(200mg.l-1的纳米TiO2、ZnO在日光灯照射下的.OH生成速率分别为0.0239mmol.l-.1h-1、0.010mmo.ll-1.h-1).由于.OH是活性氧簇(ROS)中毒性最强的自由基之一,所以金属纳米氧化物颗粒在不同条件下产生的ROS应作为纳米材料水生态毒理学研究的主要因素之一.

Using 2-propanol as a scavenger to produce acetone,the hydroxyl radicals（·OH） produced in nanoparticle suspensions was determined by GC/FID.The results show that no ·OH was found in bulky TiO2 and ZnO suspension,while both the nano-sized TiO2 and ZnO suspensions generated ·OH with light illumination,and the ·OH generation kinetics follows pseudo-zero-order reaction model under UV-light and white-light.Under light illumination,the amount of ·OH in suspension increased with nanoparticle concentration（〈200mg·l^-1）,and reached the maximum when the concentration was higher than 200mg·l^-1.The rate of generation reaction was different for each illumination condition,which was highest for sunlight,followed by UV-light,then fluorescent lamp respectively.However,no ·OH was found in nanoparticle suspension in the dark.The chemical composition also affected the ·OH generate rates,and the activity of nanosized TiO2 is about 2-4 times higher than nanosized ZnO（the rates for generation of ·OH in 200mg·l^-1 nano-sized TiO2 and ZnO are 0.0239mmol·l^-1·h^-1,0.010mmol·l^-1·h^-1 respectively.Since ·OH is one kinds of most toxic ROS,the results implicated that aquatic biological and toxicological studies using nanomaterials should take into consideration ROS produced by nanoparticle suspension under light illumination.