水溶性金单层包覆团簇的制备与光学性能分析

Preparation and photics properties of water-soluble Au monolayer protected clusters

采用硼氢化钠在水溶液中还原氯金酸,并以水溶性硫醇巯基丁二酸在生成的金核表面包覆单分子层的方法,制备了单层包覆金团簇(MPC)。傅里叶变换红外光谱仪结果表明,巯基丁二酸与金形成了Au-S键,并得到了Aux(SR)y形式的MPC。TEM照片显示,当Au和S的物质的量的比为1∶3时,金MPC的核尺寸约为2 nm。探讨了制得的金MPC的紫外-可见吸收特性及荧光特性,发现金MPC水溶液在520 nm附近无紫外吸收现象,而在451及480 nm波长紫外光激发下,可在796 nm附近观察到明显的荧光现象。反映表面等离子基元共振的520 nm附近吸收峰的消失是量子尺寸效应作用的结果。荧光现象与金MPC表面全充满的5d10和6(sp)1导带间的带间跃迁有关。

The synthesis and characterization of mercaptosuccinic acid monolayer protected water-soluble gold clusters （Au MPC） are described. TEM photograph displays that when Au/S mole ratio is 1 ：3, size of Au core of MPC is about 2 nm. Results of the FTIR spectra indicate that the mercaptosuccinic acid chains are assembled on the gold cores via the Au-S bond. UV-vis absorbance and luminescence of Au MPC in aqueous media were studied. There is no UV-vis absorbance around 520 nm but visible luminescence around 796 nm at the 451 nm and 480 nm excitation. Absorption band in the visible region around 520 nm reflects the surface plasmon band（SPB） that is due to the collective oscillations of the electron gas at the surface of nanoparticles （6 s electrons of the conduction band for Au MPC）. The SPB is absent for Au MPC with core diameter less than 2 nm due to the quantum size effects. The mechanism for the luminescence is hypothesized to be associated with interband transitions between the filled 5d^10 band and 6（sp）^1 conduction band.