Nanoscale local hydrogen-bonding sensing using single-molecule spectroscopic imaging

Abstract

Hydrogen bonds play significant roles in many chemical and biological processes. However, it remains challenging to probe the local hydrogen-bonding characters at the nanoscale. Herein, we developed a new single-molecule sensing approach to examine the nature of the local hydrogen bonding characters with surrounding molecules at the single-molecule level by employing a single-molecule spectroscopic imaging technique and a Nile blue (NB) dye as a single-molecule sensor. This method is based on the recent developments in single-molecule spectroscopic imaging that enabled local chemical property sensing at the single-molecule level, which is generally masked in the ensemble averages of bulk measurements. By observing the single-molecule fluorescence spectrum of hydrogen-bonding sensor, NB dye, under different chemical conditions, we could differentiate their hydrogen-bonding characteristics at the single-molecule level, even in the solvent mixtures. We believe that the results will be effective in probing different chemical properties of unknown solvent molecules at the single-molecule level, which could not be achieved using any previously reported method.