Single-molecule detection of dihydroazulene photo-thermal reaction using break junction technique

Abstract

Charge transport by tunnelling is one of the most ubiquitous elementary processes in nature. Small structural changes in a molecular junction can lead to significant difference in the single-molecule electronic properties, offering a tremendous opportunity to examine a reaction on the single-molecule scale by monitoring the conductance changes. Here, we explore the potential of the single-molecule break junction technique in the detection of photo-thermal reaction processes of a photochromic dihydroazulene/vinylheptafulvene system. Statistical analysis of the break junction experiments provides a quantitative approach for probing the reaction kinetics and reversibility, including the occurrence of isomerization during the reaction. The product ratios observed when switching the system in the junction does not follow those observed in solution studies (both experiment and theory), suggesting that the junction environment was perturbing the process significantly. This study opens the possibility of using nano-structured environments like molecular junctions to tailor product ratios in chemical reactions.

Transition from Tunneling Leakage Current to Molecular Tunneling in Single-Molecule Junctions

“…18,29 Recently, quantum interference effects in single-molecule junctions were reported to significantly change the charge-transport properties through minor chemical structural and environmental variations within almost the same molecular length. 8,29,54,55 The conductance enhancement through constructive quantum interference inside the nanogap offers the potential to significantly surpass the tunneling leakage current and push the limit to an even smaller length scale. 56…”

Metal–Single-Molecule–Semiconductor Junctions Formed by a Radical Reaction Bridging Gold and Silicon Electrodes

“…[6][7][8][9][10][11] Such contacts are spontaneously formed from dilute solutions of thiols. [12][13][14] Although widely used, molecular electronics on gold platforms suffer from major drawbacks, such as the lability of the S-Au bonds, electric field-induced structural changes and the lack of tunability of the electric properties of the gold substrate which limits the scope of these junctions. [15][16] In the last few years there has been an increasing interest in expanding the field of molecular electronics from gold towards semiconducting platforms, particularly GaAs [17][18] and Si.…”

Low Tunneling Decay of Iodine-Terminated Alkane Single-Molecule Junctions

“…Understanding the electron transport of single-molecule junctions is crucial for the development of molecular electronic devices [ 1 – 16 ]. The non-resonant tunneling model has often been used to describe the electron transport process through small molecule, where contact conductance, molecular length, and the tunneling decay constant are the main parameters [ 17 , 18 ].…”