Temperature-tunable plasmonic property and SERS activity of the monodisperse thermo-responsive composite microgels with core–shell structure based on gold nanorod as core

The monodisperse thermo-responsive composite microgels with well-defined core–shell structure based on gold nanorod as core and crosslinked poly(N-isopropylacrylamide) as shell were fabricated by seed-precipitation polymerization method using butenoic acid modified AuNRs as seeds. Their core–shell structure and thermo-responsive property were verified by electron transmission microscopy, atomic force microscopy and dynamic light scattering technique, respectively. The ultraviolet–visible-near infrared absorption spectra measured at various temperatures show that the longitudinal localized surface plasmon resonance (LSPR) wavelength of the AuNR embodied inside the microgel can be reversibly tuned from 750 to 800 nm as temperature is changed within the range from 30 to 40 °C, indicating that the plasmonic property of the composite microgel is temperature-tunable. When the composite microgels are used as surface enhanced Raman scattering (SERS) substrates for detection of the analyte having low affinity toward metal surface, their SERS activity can be modulated by temperature due to existence of the entrapment effect during their temperature triggered volume phase transition.