SERS Enhancement on the Basis of Temperature-Dependent Chemisorption: Microcalorimetric Evidence

• Published in: Chemphyschem 2016-12, Vol.17 (24), p.4144-4148
• Main Authors: Roy, Chandra Nath, Ghosh, Debasmita, Mondal, Somrita, Kundu, Somashree, Maiti, Susmita, Saha, Abhijit
• Format: Article
• Language: English
• Subjects: chemisorption; crystal violet; Dyes; Rhodamine 6G; SERS; silver nanoparticles; Spectrum analysis; Temperature
• ISSN: 1439-4235; 1439-7641
• DOI: 10.1002/cphc.201600941

The mechanism of surface‐enhanced Raman spectroscopy (SERS) is not very clear in view of the magnitude of the contribution of electromagnetic factor as well as the chemical mechanism. This report presents the extent of adsorption at different temperatures in terms of signal enhancements in SERS employing silver nanoparticles (AgNPs) of various shapes as substrate and dye molecules, crystal violet or Rhodamine 6G, as model Raman probes. Initially, the SERS signal increases with increasing temperature until a maximum intensity is reached, before it gradually decreases with increasing temperature. This trend is independent of the shape of the Raman substrates and probes. However, the temperature at which maximum intensity is obtained may depend upon the nature of the Raman probe. The energetics involved in the chemisorption process between dye molecules and AgNPs were determined through isothermal titration calorimetry and their implications for the observed SERS signals were assessed. The maximum heat change occurred at the temperature at which the maximum signal enhancement in SERS was obtained and the enhanced interaction at optimum temperature was confirmed by absorption spectroscopy. Feel‐good temperature: We demonstrate the extent of adsorption at different temperatures in terms of signal enhancements in SERS for silver nanoparticles of various shapes as substrate and dye molecule, crystal violet or Rhodamine 6G as model Raman probes. These results are correlated with energetics determined by ITC.