Variable temperature UV/Vis spectrophotometer for study of NHC-stabilized gold nanoclusters

金属纳米颗粒和纳米团簇通常是高度着色的，这使得紫外可见光谱学成为分析它们的有力技术。最初开发金属纳米粒子是因为它们的颜色。在一项可以追溯到15世纪的技术中，工匠们在熔融玻璃中加入氯化金，从而产生了明亮的红色玻璃，这实际上是被困在玻璃中的金纳米颗粒。同样，黄色的玻璃是由银纳米颗粒产生的。这些红色和黄色的玻璃被用于制作彩色玻璃窗。金属纳米团簇也是有色的，但在几个重要方面与纳米粒子有本质上的不同。首先，它们通常更小，大小在3到300个金原子之间。其次，它们作为单分子实体制备和分离，其中纳米颗粒仍然作为具有不同程度多分散性的混合物分离。最后，由于这两种性质，纳米团簇的光谱中没有等离子体信号，它们具有离散的分子跃迁。因此，紫外可见光谱是分析金属纳米团簇的一种非常有价值的方法。分解成纳米粒子的特点是等离子体峰的出现和单个跃迁的损失。从小簇到大簇的变化也很容易被紫外可见观察到，并且与计算研究相结合，在结构识别方面非常有效。***虽然它们是令人着迷的分子，但金属纳米团簇的制备仍然使用黑箱方法，使得结构的控制和预测主要是热力学问题：即，通过控制合成或通过选择性蚀刻/结晶或纯化方法分离出最稳定的结构。值得注意的是，尽管这些材料已经被发现了几十年，但我们无法为它们的制备写出一个平衡的方程。该提案中要求的基础设施对于纠正这一错误至关重要。使用n -杂环碳烯作为配体是简化这一过程的关键部分，因为纳米簇合成的起始材料是简单的有机金属NHC-Au-X，而不是未知的[RS-Au-]聚合物。然而，如果没有能力通过紫外可见光谱分析反应的进展并了解过程，我们几乎不可能获得理解和优化这些有趣材料合成所需的洞察力。同样，如果没有温度控制的UV/vis分析，理解我们正在制备的新型nhc功能化纳米团簇的稳定性将非常困难。如果没有这台仪器，这些独特的分子材料在太阳能电池、生物成像和催化方面的应用将是不可能的。Crudden和Stamplecoskie小组的HQP每天都要亲自使用这个仪器。**

Metal nanoparticles and nanoclusters are often highly coloured, making UV-vis spectroscopy a powerful technique for their analysis. Metallic nanoparticles were initially developed for their colour. In a technique dating back to the 15th century, artisans added gold chloride to molten glass, which resulted in bright red glasses, which were actually gold nanoparticles trapped in glass. Similarly yellow glasses resulted from the generation of silver nanoparticles. These red and yellow glasses were used in the preparation of stained-glass windows. Metal nanoclusters are also coloured but are substantially different from nanoparticles in several important ways. Firstly, they are typically smaller, with sizes ranging from 3 to 300 gold atoms. Secondly, they are prepared and isolated as single molecular entities, where nanoparticles are still isolated as mixtures with varying levels of polydispersity. Finally, because of these two properties, nanoclusters do not have plasmonic signals in their optical spectra, they have discrete molecular transitions. Because of this, UV-visible spectroscopy is a highly valuable method for the analysis of metal nanoclusters. Decomposition to nanoparticles is characterized by the appearance of plasmonic peaks and loss of individual transitions. The change from small clusters to larger clusters is also easily observed by UV-visible, and, in combination with computational studies, is highly effective at structural identification. *** Although they are fascinating molecules, metallic nanoclusters are still prepared using a black box approach that makes control of and prediction of structure largely a thermodynamic issue: namely, the most stable structures are isolated either by control of synthesis or by selective etching/crystallization or purification methods. Remarkably, despite the fact that these materials have been known for decades, a balanced equation cannot be written for their preparation. The infrastructure requested in this proposal is critical in righting this wrong. The use of N-heterocyclic carbenes as ligands is a key part in simplifying this process, since the starting material for the nanocluster synthesis is a simple organometallic NHC-Au-X species, rather than an unknown [RS-Au-] polymer. However, without the ability to analyze reactions as they progress by UV-visible spectroscopy and understand the process, it will be virtually impossible to gain the insight we need to understand and optimize the synthesis of these interesting materials. Similarly, understanding the stability of the novel NHC-functionalized nanoclusters we are preparing will be exceptionally difficult without temperature-controlled UV/vis analysis. Developing applications of these unique molecular materials, namely in solar cells, bio-imaging and catalysis, will be impossible without this instrument. HQP in the Crudden and Stamplecoskie groups will have hands on use of this instrument on a daily basis. **