Three-dimensional self-assembled monolayer (3D SAM) of n-alkanethiols on copper nanoclusters
Three-dimensional self-assembled monolayer (3D SAM) of n-alkanethiols on copper nanoclusters
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DOI：
10.1021/jp049006r
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发表时间：
2004-07-29
影响因子：
3.3
通讯作者：
Chin, WS
中科院分区：
文献类型：
--
作者：
Ang, TP;Wee, TSA;Chin, WS
在铜纳米团簇上形成了异辛硫醇、1-正十二硫醇和1-十二硫醇的三维自组装单分子膜(3D SAM)。对纳米颗粒的形貌和光谱进行了表征，并通过热分析和变温分析研究了三维自组装膜的构象。透射电子显微镜结果表明，铜团簇由类似于3-5 nm的球状结构组成。IR、XPS和C-13 CPMAS核磁共振结果证实了烷基硫醇是通过-SH基团化学吸附的，烷基硫醇在铜纳米团簇上的堆积密度随烷基链长度的增加而增加。通过红外光谱和~(13)C CPMAS核磁共振谱的分析，推测硫醇链为全反式之字形构象。在X射线衍射仪上观察到的小角度峰进一步表明，这些链之间存在强烈的交错作用，形成了超晶格结构。随着温度的升高，VT-FTIR和VT-C-13 CPMAS核磁共振表征了链间侧向相互作用的破坏。结晶填料的这种熔融是吸热的，但在DSC中重新加热时观察到一个放热峰。我们将这种放热“结晶”归因于紧凑链的构象记忆效应。我们发现，与以前报道的金和银团簇相比，铜纳米团簇的熔点和热焓要高得多。
Three-dimensional self-assembled monolayer (3D SAM) of I-octanethiol, 1-decanethiol, and 1-dodecanethiol has been formed on copper nanoclusters. The morphology and spectroscopy of the nanoparticles were characterized while the conformation of the 3D SAMs was investigated with thermal and variable-temperature analyses. TEM results suggest the copper clusters consist of a spherical shape of similar to3-5 nm. IR, XPS, and C-13 CPMAS NMR results confirm that alkanethiols are chemisorbed via the -SH group and the packing density of the alkanethiols on copper nanoclusters increases with the alkyl chain lengths. The thiol chain is deduced to adopt the all-trans zigzag conformation through the analysis by IR and 13C CPMAS NMR. Low-angle peaks observed in XRD further suggest strong interdigitation among these chains to form superlattice structures. On increasing temperature, VT-FTIR and VT-C-13 CPMAS NMR depict the disruption of lateral interaction between the chains. This melting of crystalline packing is endothermic but an exothermic peak was observed upon reheating in DSC. We attribute this exothermic "crystallization" to the conformational memory effect of the compact chains. We have found that much higher melting points and enthalpies are obtained on copper nanoclusters as compared to earlier reports on gold and silver clusters.