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利用光致发光谱(Photoluminescence,PL)、X射线吸收精细结构(X-ray Absorption Fine Structure,XAFS)和MALDI-TOF质谱等技术研究了化学还原法合成的Cu金属纳米团簇的发光性能及其结构。PL谱表明随着反应溶液中十二硫醇(C12SH)和2-巯基-5-正丙烷基嘧啶(C7H10N2S,2-mercapto-5-n-propylpyrimidine,MPP)配体比例的增加,Cu纳米团簇主发光峰的波长从618 nm逐渐蓝移到571 nm。质谱的结果说明以MPP作为单一配体时的主要产物为Cu5[MPP]3;而当为MPP与C12SH两种混合配体时,Cu纳米团簇中Cu原子数变小,组成变为Cu4[MPP][C12SH];并且随着C12SH比例增加,Cu4[MPP][C12SH]产物的组成保持不变。XAFS结果则进一步表明随着C12SH比例的增加,Cu纳米团簇的Cu-S键长从0.228 nm缩短到0.224 nm,原子构型从双三角锥结构转变为四面体。综合以上结果,认为Cu纳米团簇的原子数的减少导致团簇的光致发光从618nm蓝移至597 nm;而Cu-S键长的缩短引起Cu(I)-S杂化的HOMO-LUMO带隙增大,从而导致团簇的发光波长进一步从597 nm蓝移至571 nm。
The luminescent properties of Cu metal nanoclusters synthesized by chemical reduction method were studied by photoluminescence (PL), X-ray absorptive fine structure (XAFS) and MALDI-TOF mass spectrometry structure. PL spectra showed that with the increase of the proportion of dodecyl mercaptan (C12SH) and 2-mercapto-5-n-propylpyrimidine (MPP) ligand in the reaction solution, The luminescence peak wavelength of the cluster is blue shifted from 618 nm to 571 nm. The results of mass spectrometry showed that the main product of MPP as a single ligand was Cu5 [MPP] 3. When the two ligands were MPP and C12SH, the number of Cu atoms in Cu nanoclusters became smaller and the composition became Cu4 [ MPP] [C12SH]; and as the C12SH ratio increases, the composition of the Cu4 [MPP] [C12SH] product remains unchanged. XAFS results further show that with the increase of C12SH ratio, the Cu-S bond length of Cu nanoclusters is shortened from 0.228 nm to 0.224 nm, and the atomic configuration changes from bipyramidal structure to tetrahedron. Based on the above results, it is considered that the reduction of the number of Cu nanoclusters leads to the blue-shift of the photoluminescence of the clusters from 618 nm to 597 nm. The shortening of the Cu-S bond length leads to the Cu (I) -S hybrid HOMO-LUMO The bandgap increases, resulting in a further shift of the luminescence wavelength of the cluster from 597 nm to 571 nm.