Green emission to probe photoinduced charging events in ZnO-Au nanoparticles. Charge distribution and fermi-level equilibration
Green emission to probe photoinduced charging events in ZnO-Au nanoparticles. Charge distribution and fermi-level equilibration
复制标题
DOI：
10.1021/jp0275037
复制
发表时间：
2003-07-31
影响因子：
3.3
通讯作者：
Kamat, PV
中科院分区：
文献类型：
--
作者：
Subramanian, V;Wolf, EE;Kamat, PV
ZnO纳米粒子中的光致电子积累导致激子带的漂白以及绿色发射的猝灭。在不存在电子清除剂的情况下，光生电子存储在导带边缘附近，并通过非辐射过程促进电荷复合。通过将UV照射的ZnO悬浮液暴露于电子受体（O-2或噻托溴铵染料），存储的电子被释放，并且原始激子带和可见发射被恢复。用电子受体噻托溴铵染料滴定存储在ZnO纳米颗粒中的电子，显示出存储的电子和发射猝灭之间的线性关系。当金纳米粒子被添加到预紫外线照射的ZnO胶体，只有部分恢复的发射被视为。另一方面，Pt纳米颗粒引起猝灭发射的几乎完全恢复，因为电子被释放到溶液中。在紫外光照射的ZnO和金纳米粒子之间的电荷分布的费米能级的平衡的结果。此外，电子转移到金属纳米核，然后平衡继续，直到费米能级达到接近ZnO的导带边缘。半导体和金属层之间的相互作用，导致费米能级平衡的基本理解是重要的评估贵金属在光催化反应中的作用。
Photoinduced electron accumulation in ZnO nanoparticles results in the bleaching of the exciton band as well as quenching of green emission. In the absence of an electron scavenger, photogenerated electrons are stored near the conduction band edge and promote charge recombination via a nonradiative process. By exposing the UV-irradiated ZnO suspension to an electron acceptor (O-2 or thionine dye) the stored electrons are discharged and the original excitonic band and the visible emission are restored. Titration of electrons stored in ZnO nanoparticles with an electron acceptor, thionine dye, shows a linear relationship between stored electrons and the emission quenching. When gold nanoparticles are added to pre-UV-irradiated ZnO colloids, only partial recovery of the emission is seen. Pt nanoparticles on the other hand caused almost complete recovery of the quenched emission as the electrons are discharged into the solution. The charge distribution between UV-irradiated ZnO and gold nanoparticles results in equilibration of the Fermi level. Furthermore, the transfer of electrons to the metal nanocore followed by equilibration continues until the Fermi level reaches close to the conduction band edge of ZnO. Basic understanding of the interaction between the semiconductor and metal layers leading to Fermi-level equilibration is important for evaluating the role of noble metals in photocatalytic reactions.