Self-Assembled Monolayers of Alkylselenolates on Gold with Lifetime Over Two Hundred Days

Self-assembled monolayers (SAMs), based on thiol-metal chemistry, are widely investigated in multiple fields such as optics, biochemistry and organic electronics due to their simplicity, repeatability and controllability. The thiol-based SAMs, however, go no further than laboratory studies due to their weak property against oxidation. Therefore, it is necessary to pursuit an alternative anchoring group, which is expected to form similar supramolecular structure as thiol-SAMs and meanwhile, possesses air-stability with long lifetime. Here, we proposed diselenide as an advantageous candidate since selenium has similar properties as sulfur which enables it to be a promising precursor for well-ordered SAMs. By spectroscopy and tunnelling current, we demonstrated the chemisorbed and densely packed selenium-SAMs has, indeed, been fabricated. Notably, when we stored the selenium-SAMs in ambient condition, they own rigorously long-lifetime in ambient conditions over 200 days by the reason of the strong selenium-gold bond. We surveyed the stability of selenium-SAMs by the observations of a minor fluctuations of tunnelling current and the value of decay coefficient through SAMs as a function of days. Additionally, spectroscopy provides detailed structural characterization as the oxidation is much slow with selenium-gold bond and there was nearly no desorption of alkylselenolates during this process. Finally, we performed DFT calculations and the results illustrate the stronger binding energy and weaker affinity to oxygen of selenium-SAMs compared with thiol-SAMs, leading to the merely impossibility of peroxidation of selenium-gold bond.