Surface Deposition Resulting from Collisions between Diglycine and Chemically Modified Alkylthiolate Self-Assembled Monolayer Surfaces

We
report results from quantum mechanics/molecular mechanics (QM/MM)
direct dynamics simulations of hyper-thermal collisions between N-protonated
diglycine (gly2-H+) and a chemically modified
(−COCl headgroup placed on the center chain) octanethiolate
self-assembled monolayer (SAM) surfaces. Both fragmentation and reactivity
are observed with the probability of each increasing with collision
energy. Fragmentation occurs with a probability of 0.98 (out of 1)
for a collision energy of 100 eV. Surface deposition, a subgroup of
reactivity, is examined and compared to the experimental work of Laskin
and co-workers (Phys. Chem. Chem. Phys. 2008, 10, 1079–90). We find that intact surface
deposition is a rare event, peaking in probability at a collision
energy of approximately 30–40 eV, which is in excellent agreement
with experiment.

我们报道了N质子化二甘氨酸（gly2-H+）与经化学修饰（主链带有−COCl头基）的辛硫醇自组装单分子层（SAM）表面之间发生超热碰撞的量子力学/分子力学（QM/MM）直接动力学模拟结果。研究中同时观测到碎裂与反应活性两类过程，二者的发生概率均随碰撞能量升高而提升。当碰撞能量为100 eV时，碎裂的发生概率可达0.98（总概率为1）。我们对属于反应活性子类别的表面沉积过程进行了分析，并与Laskin及其合作者的实验工作（Phys. Chem. Chem. Phys. 2008, 10, 1079–90）进行了对比。研究发现完整表面沉积属于罕见事件，其发生概率在碰撞能量约30~40 eV时达到峰值，该结果与实验数据高度吻合。