Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026, China.
Langmuir. 2012 May 1;28(17):6736-41. doi: 10.1021/la300786w. Epub 2012 Apr 18.
Pd nanocrystals were prepared by the reduction of a H(2)PdCl(4) aqueous solution with C(2)H(4) in the presence of different amounts of poly(N-vinyl-2-pyrrolidone) (PVP). Their average size decreases monotonically as the PVP monomer/Pd molar ratio increases up to 1.0 and then does not vary much at higher PVP monomer/Pd molar ratios. Infrared spectroscopy and X-ray photoelectron spectroscopy results reveal the interesting size-dependent interaction of PVP molecules with Pd nanocrystals. For fine Pd nanocrystals capped with a large number of PVP molecules, each PVP molecule chemisorbs with its oxygen atom in the ring; for large Pd nanocrystals capped by a small number of PVP molecules, each PVP molecule chemisorbs with both the oxygen atom and nitrogen atom in the ring, which obviously affects the structure of chemisorbed PVP molecules and even results in the breaking of involved C-N bonds of some chemisorbed PVP molecules. Charge transfer always occurs from a chemisorbed PVP ligand to Pd nanocrystals. These results provide novel insights into the PVP-metal nanocrystal interaction, which are of great importance in the fundamental understanding of surface-mediated properties of PVP-capped metal nanocrystals.
钯纳米晶是通过在不同量的聚（N-乙烯基-2-吡咯烷酮）（PVP）存在下，用 C（2）H（4）还原 H（2）PdCl（4）水溶液制备的。随着 PVP 单体/钯摩尔比的增加，它们的平均尺寸单调减小，达到 1.0 后，在更高的 PVP 单体/钯摩尔比下变化不大。红外光谱和 X 射线光电子能谱结果揭示了 PVP 分子与钯纳米晶之间有趣的尺寸依赖性相互作用。对于被大量 PVP 分子覆盖的细钯纳米晶，每个 PVP 分子通过其环上的氧原子化学吸附；对于被少量 PVP 分子覆盖的大钯纳米晶，每个 PVP 分子通过环上的氧原子和氮原子化学吸附，这明显影响了化学吸附 PVP 分子的结构，甚至导致一些化学吸附 PVP 分子中涉及的 C-N 键断裂。电荷总是从化学吸附的 PVP 配体转移到钯纳米晶上。这些结果为 PVP-金属纳米晶相互作用提供了新的见解，这对于理解 PVP 包覆金属纳米晶的表面介导性质具有重要意义。
