Critical stresses in mechanochemical reactions

Abstract

The rates of mechanochemical reactions are generally found to increase exponentially with applied stress.

Tribochemical nanolithography: selective mechanochemical removal of photocleavable nitrophenyl protecting groups with 23 nm resolution at speeds of up to 1 mm s−1

“…48 Atomic force microscopy has proved to be a powerful tool for the investigation of tribochemical modification, 49 and has also been used to modify surfaces at the nanometre scale via utilization of the energy dissipated in the tip-sample contact. 19,50–52…”

“…In recent years there has been an explosion of interest in mechanochemistry, [17][18][19] the mechanical activation of chemical reactivity. [19][20][21][22][23][24][25][26][27][28][29][30][31] In bulk phases, mechanical grinding enables solventless mechanochemical synthesis, 21,32 attracting growing interest as a means to mitigate the environmental impact of chemical processes. 33 At interfaces, tribochemical processes are known to play a role in determining the performance of lubrication systems.…”

“…48 Atomic force microscopy has proved to be a powerful tool for the investigation of tribochemical modication, 49 and has also been used to modify surfaces at the nanometre scale via utilization of the energy dissipated in the tip-sample contact. 19,[50][51][52] Here we examine the use of a mechanochemical process to drive a very specic chemical transformation: the selective removal of photocleavable protecting groups in nm regions of space. Inspired by the work of Fodor et al on light-directed chemical synthesis, 5 previous work in this laboratory has utilized aminosilanes with photocleavable nitrophenyl protecting groups for near-eld lithography.…”

Exploring mechanochemical reactions at the nanoscale: theory versus experiment

“…An additional challenge for testing mechanochemical theories, in particular, for stress-induced reactions as opposed to those carried out by pulling single molecules, is to exert precise stresses on well-defined systems and to accurately measure their reaction rates. We address this issue by using a nanomechanochemical reactor of about 60 nm 2 in size 47 formed by compressing a reactant-covered single-crystal substrate using an AFM tip. 41,48 This allows elastic contact mechanics to be used to calculate the stresses at the center of the contact 49 and to ensure that the reaction rate is measured on pristine regions of the surface.…”

“…41,48 This allows elastic contact mechanics to be used to calculate the stresses at the center of the contact 49 and to ensure that the reaction rate is measured on pristine regions of the surface. 1,47 We study the surface mechanochemical decomposition of methyl thiolate (CH 3 -S) on Cu(100), where the mechanical reaction pathway has been extensively investigated under ultrahigh-vacuum conditions, which we have previously demonstrated can decompose under the influence of normal stresses. 1,50,51 This model system is sufficiently simple that it is amenable to analysis using first-principles density-functional theory (DFT) calculations.…”