基底电位对硫醇自组装膜形成的影响

应用电位阶跃法,在不同组装电位下制备金/正十二硫醇自组装单分子膜.交流阻抗谱表征该硫醇膜的电化学性质,发现金基底的电位对硫醇自组装膜的形成有重要影响.在-0.8~-0.4 V的电位区间内,随着组装电位的增加,该自组装膜的致密性、有序性增加,缺陷减少,并于0.4 V时达到最佳.组装电位高于0.4 V,膜的致密性、有序性降低,缺陷增多.本文为硫醇及其衍生物的电位调控组装提供了重要依据.     

Determination of self-exchange rate of alkanethiolates in self-assembled monolayers on gold using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

In this paper, we describe a new method for determining the exchange rates of alkanethiolates in self-assembled monolayers (SAMs) on gold using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) to analyze the compositions of the alkanethiolate in SAMs rapidly and directly. In particular, to investigate the self-exchange of alkanethiols, we prepared a deuterated alkanethiol that has the same molecular properties as the non-deuterated alkanethiol but a different molecular weight. SAMs consisting of deuterated alkanethiolates were immersed in a solution of the non-deuterated alkanethiol, and the influences of the immersion time, temperature, concentration, and solvent on the self-exchange rates were investigated. Furthermore, we assessed the exchange rates among alkanethiols with different carbon chain lengths and different size of ethylene glycol units. In addition, we performed molecular dynamics simulations using a model SAM system in order to understand the molecular mechanism of the exchange process.     

Collision-induced diffusion and vacancy migration in alkanethiol monolayers on Au(1 1 1)

Scanning tunneling microscopy is used to characterize the collision-induced migration of molecules within well-ordered octanethiol and nonanethiol self-assembled monolayers. A seeded molecular beam is used to create xenon atoms with a kinetic energy of 1.3 eV, and collisions with these atoms cause measurable changes in alkanethiol monolayer surface structure. Migration rates are calculated and compared for molecules in close-packed domains, at domain-boundary defects, and along the perimeter of vacancy-island defects. The number of nearest-neighbor molecules (within the 5 Å lattice distance) is strongly predictive of molecular stability with respect to xenon bombardment, and the overall dependence of stability on nearest neighbors is well fit by a simple exponential curve. The incident direction of the molecular beam is not observed to influence the direction of molecular motion; however, in some cases, migration correlates strongly to surface lattice directions. Finally, there is no evidence that substrate restructuring or gold-atom diffusion accompanies alkanethiol migration under these non-equilibrium conditions.