The adsorption of benzene on Si(111)-7×7 has been studied using high-resolution electron energy loss spectroscopy (HREELS) and thermal desorption spectroscopy (TDS). Both chemisorbed and physisorbed benzene were observed at an adsorption temperature of 110 K. Chemisorbed benzene desorbs molecularly at 350 and 364 K while physisorbed molecules desorb at 180 K. In the HREELS studies, two separate energy losses at 2920 and 3025 cm -1 were observed for chemisorbed benzene, attributable to the C-H stretching vibrations of sp 3 and sp 2 carbon atoms, respectively. In addition, the formation of Si-C bond is also evidenced at a vibrational frequency of 540 cm -1 . Our results clearly demonstrate that benzene is di-σ bonded to the adjacent adatom and rest atom on Si(111)-7×7, forming a 1,4-cyclohexadiene-like structure.

A general and facile approach has been developed to prepare various metal oxide nanocrystals from commercially available metal acetate precursors using an amine-mediated reaction. The influence of temperature and capping agents on the yield and final morphology of the metal oxides nanocrystals was investigated. The approach was applied in the synthesis of shape-controlled ZnO nanocrystals. ZnO nanowires, nanorods, bullets and triangular nanocrystals were successfully prepared by tuning the molar ratio between amine to zinc acetate precursor. On the basis of FTIR and NMR spectroscopic studies, we propose that the amine could mediate the breakdown of the metal acetates through a nucleophilic attack mechanism. The results suggest that amine can play dual role as both the attacking agent and capping agent in this new methodology.

The first aqueous preparation of luminescent CdS QDs from a single precursor is reported. These water-soluble CdS quantum dots with tunable sizes between 25 and 40 Å were produced from a readily prepared [(2,2‘-bipyridine)Cd(SC{O}Ph)2] complex by simply refluxing in an aqueous solution. The as-prepared nanoparticles are fairly uniform in size without the need of size sorting, and exhibit a quantum confinement effect. The size of the nanoparticles is tunable by varying the capping agent-to-precursor molar ratio. The green- and yellow-emitting quantum dots obtained via this simple route are water soluble and have OH functionality that is suitable for further applications. The particle aging kinetics was investigated by monitoring the optical band edge absorption and was found to follow the Ostwald ripening mechanism. When the amount of capping agent used is 10 mmol, unprecedented dimerization of some QDs upon prolong reflux to form nanocrystals double the size is detected. Thus, a common red shift of the absorption band edge is not detected and the growth of larger QDs seems to arise from the coalescence of two QDs.

Dodecanethiol-protected copper/silver bimetallic nanoclusters were prepared by a liquid-phase method using different copper to silver feed ratios. The morphology and size of the prepared nanoclusters were analyzed with X-ray diffraction (XRD) and transmission electron microscopy (TEM), while their spectroscopic and surface properties were characterized by infrared (IR) and X-ray photoelectron spectroscopy (XPS), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), and 13C cross-polarization magic angle spinning NMR (13C CPMAS NMR). TEM analysis indicated that all the bimetallic clusters prepared are approximately 4-6 nm in size. On the other hand, the results of XRD, XPS, and Fourier transform infrared (FTIR) spectroscopy suggested that the surfaces of the alloy nanoclusters are mostly enriched with the less noble metal copper atoms. This surface enrichment of copper may be attributed to a galvanic exchange process during preparation, and the extent of enrichment is directly related to the copper feed ratio used. Interestingly, DSC studies showed two melting transitions in some of these alloy samples, suggesting different packing behavior of the dodecanethiol chains onto the heterogeneously intercalated silver- and copper-rich surfaces.