Fig. 1: Characterization of a single molecule/gold nanorod detection system for acoustic vibrations.

a Schematic of the nano-acoustic detector based on the distance variation between the molecule and the nanorod. The molecule-nanorod detection system was first embedded in the PMMA film, which was attached on the two prongs of the tuning fork. Then, the tuning fork was driven at the resonant frequency by a signal generator and vibrated periodically. b The fluorescence intensity traces of crystal violet (CV) molecules film. Inset: the chemical structure of CV. c Statistics of total on-state duration time of individual CV molecules. d Characteristic distribution of the geometric size of gold nanorods. Their aspect ratio (length/diameter) is 2.2 ± 0.4. Inset: SEM image of a drop of gold nanorod suspension dried on a silicon chip; Scale bar: 100 nm. e Absorption spectrum of a suspension of gold nanorods (yellow shaded area), absorption (blue solid line), and fluorescence (red solid line) spectra of CV in the PMMA film. There is a significant spectral overlap between CV molecules and gold nanorods. The vertical black dashed-dotted line is the excitation light source guided by the black solid arrow, and the vertical red dashed line is the peak of the fluorescence spectrum of CV guided by the black solid arrow.