Chemical and Materials Sciences Division, Pacific Northwest National Laboratory, P.O. Box 999, MSIN K8-88, Richland, Washington 99352, USA.
ACS Nano. 2012 Jan 24;6(1):573-82. doi: 10.1021/nn2039565. Epub 2011 Dec 14.
Monodisperse gold clusters have been prepared on surfaces in different charge states through soft landing of mass-selected ions. Ligand-stabilized gold clusters were prepared in methanol solution by reduction of chloro(triphenylphosphine)gold(I) with borane tert-butylamine complex in the presence of 1,3-bis(diphenylphosphino)propane. Electrospray ionization was used to introduce the clusters into the gas phase, and mass selection was employed to isolate a single ionic cluster species (Au(11)L(5)(3+), L = 1,3-bis(diphenylphosphino)propane), which was delivered to surfaces at well-controlled kinetic energies. Using in situ time-of-flight secondary ion mass spectrometry (TOF-SIMS), it is demonstrated that the Au(11)L(5)(3+) cluster retains its 3+ charge state when soft landed onto the surface of a 1H,1H,2H,2H-perfluorodecanethiol self-assembled monolayer (FSAM) on gold. In contrast, when deposited onto 16-mercaptohexadecanoic acid (COOH-SAM) and 1-dodecanethiol (HSAM) surfaces on gold, the clusters exhibit larger relative abundances of the 2+ and 1+ charge states, respectively. The kinetics of charge reduction on the FSAM and HSAM surfaces are investigated using in situ Fourier transform ion cyclotron resonance (FT-ICR) SIMS. It is shown that an extremely slow interfacial charge reduction occurs on the FSAM surface while an almost instantaneous neutralization takes place on the surface of the HSAM. Our results demonstrate that the size and charge state of small gold clusters on surfaces, both of which exert a dramatic influence on their chemical and physical properties, may be tuned through soft landing of mass-selected ions onto carefully selected substrates.
已通过质量选择离子的软着陆在不同荷电状态的表面上制备了单分散金纳米簇。在 1,3-双（二苯基膦基）丙烷的存在下，用三（三苯基膦）金（I）氯与硼烷叔丁胺络合物还原，在甲醇溶液中制备了配体稳定的金纳米簇。采用电喷雾电离将纳米簇引入气相，并采用质量选择将单一离子纳米簇物种（Au(11)L(5)(3+)，L = 1,3-双（二苯基膦基）丙烷）分离出来，该物种以受控的动力学能量输送到表面。使用原位飞行时间二次离子质谱（TOF-SIMS），证明了当 Au(11)L(5)(3+)纳米簇软着陆到金的 1H,1H,2H,2H-全氟癸硫醇自组装单层（FSAM）表面上时，它保留其 3+荷电状态。相比之下，当沉积在金上的 16-巯基十六烷酸（COOH-SAM）和 1-十二硫醇（HSAM）表面上时，纳米簇分别表现出更大的 2+和 1+荷电状态的相对丰度。使用原位傅里叶变换离子回旋共振（FT-ICR）SIMS 研究了 FSAM 和 HSAM 表面上的电荷还原动力学。结果表明，在 FSAM 表面上发生极其缓慢的界面电荷还原，而在 HSAM 表面上则几乎瞬间发生中和。我们的结果表明，通过质量选择离子软着陆到精心选择的基底上，可以调节表面上小金纳米簇的尺寸和荷电状态，这两者都会对其化学和物理性质产生巨大影响。
