Spontaneously formed Si–S bonds enable monolayer and single-molecule Si–molecule–Si circuits.

Here we show that within a single polyhedral metal oxide nanoparticle a nanometer-scale lateral or vertical sliding of a small metal top contact ( e. g., <50 nm) leads to a 10-fold change in current rectification ratios. Electron tunneling imaging and constant-force current-potential analysis in atomic force microscopy demonstrate that within an individual p-n rectifier (a CuO nanocrystal on silicon) the degree of current asymmetry can be modulated predictably by a set of geometric considerations. We demonstrate the concept of a single nanoscale entity displaying an in-built range of discrete electrical signatures and address fundamental questions in the direction of "landing" contacts in single-particle diodes. This concept is scalable to large 2D arrays, up to millimeters in size, with implications in the design and understanding of nanoparticle circuitry.

The phenomenon of surface electrification upon contact is a long-standing scientific puzzle, with for instance written accounts of charged samples of amber attracting feathers dating back to the 600 B.C. Electrostatic hazards associated with electrical insulators subject to mechanical friction are well documented, and the design of commercial products, such as copiers and laser printers, is based on the static charging of electrical insulators. Nonetheless, the physical-chemical origin of this phenomenon remains debated. This Perspective outlines recent advances in our understanding of the mechanism behind contact electrification, as well as the emerging research area of electrochemistry on insulators. Research is beginning to demonstrate how to exploit static charges present on insulating surfaces, with the goal of driving redox reactivity. These studies have helped to clarify the triboelectrification mechanism and have defined new platforms for electrochemiluminescence, metal nucleation, and mask-free lithography. This Perspective will help researchers working within electrochemistry, physics, green energy, sensing, and materials to gain an understanding of the implications of contact electrification to their respective fields. Special attention is given to the chemical, electronic, and mechanical factors influencing triboelectrochemical reactions, concluding with the perceived challenges facing further development of this field.