Tunable localized surface plasmon resonance in copper sulfide nanocrystals (Cu2-xS) for surface-enhanced near-infrared absorption spectroscopy

Cu2-xS nanoparticles have the ability to absorb radiation in the near infrared (NIR) range. This is due to localized surface plasmon resonance (LSPR) of free holes in the valence band. This fact makes it possible to use copper sulfide nanoparticles for sensing application in the NIR range. Our study showed that Cu2-xS nanoparticles have a significant localized surface plasmon resonance. The LSPR of nanoparticles was tuned by adjusting the concentrations of Cu and S. In this case, the plasmon peak reaches a maximum at values of about 1210 nm. Thus, highly localized electromagnetic field of Cu2-xS NPs can be successfully applied for to detection of vibrational bands (overtones) of various molecules in the NIR region. We showed the splitting of longitudinal and transverse dipolar resonance modes of Cu1.4S was changed in the presence of N-Methylamine molecules.