Flocculation and SERS Activation of Au Nanoparticles Using Cationic and Neutral Cresyl Violet Molecules

Abstract

The flocculates of gold nanoparticles (AuNPs), which are a few closely adjacent AuNPs in solution providing enormous surface enhanced Raman scattering (SERS) intensity, were successfully formed using oxazine dye molecules. We found that neutral cresyl violet (CV 0 ) molecules with two dihydro amino groups (-NH2) chemisorb on Au surfaces via lone pair electrons at amino groups, whereas cationic CV + molecules physisorb using electrostatic interaction between their positively charged amino groups and negatively charged AuNPs. Neutralization of CV + gave appreciable peak shifts of their SERS bands, which also showed considerable spectral changes upon the deuteration of the amino groups, and thus assigned to vibrational modes of the amino groups. We found that diethyl substituent in amino groups in nile blue (NB), which has an oxazine structure similar to CV, sterically hinders chemisorption on AuNPs. Accordingly, NB + physisorbed on as-prepared AuNP exclusively with electrostatic forces, whereas NB 0 did not chemisorb on Au surfaces. Thus, the AuNP flocculates were readily formed using electrostatic and chemical interaction between target molecules and metal nanoparticles, albeit chemisorption was quite sensitive to bulky structure of substituent.

Plasmon resonance tuning in metal nanostars for surface enhanced Raman scattering

“…Figure 4 shows SERS spectra recorded from arrays with different nanostar sizes and for two different excitation wavelengths, namely 633 nm and 830 nm. In agreement with the transmittance measurements reported in figure 2, the small nanostars S1 yield the highest enhancement for 633 nm excitation, while the S3 nanostars are most efficient for the The Raman bands in the spectrum evidence that the chemisorption of the CV molecules to the Au film was formed via their -N-H 2 group [45]. Figure 4(b) shows a SERS spectrum recorded with an excitation source in the NIR (wavelength = 830 nm) from CV molecules chemisorbed on S3 nanostars.…”

Elucidation of photophysical changes and orientation of acridine orange dye on the surface of borate capped gold nanoparticles using multi-spectroscopic techniques

“…21 Single molecule detection using Raman scattering has been realized using this effect when the nano-gap separation and the adsorption of target molecules are precisely adjusted. [22][23][24][25][26][27][28][29] In addition to the surface enhanced resonance Raman spectroscopic (SERRS) technique, many promising applications of dye-nanoparticle combinations have continued to emerge in recent years. The interparticle interactions and reactivities, especially in cases involving a chemisorbed chromophore on the NP surface, can lead to efficient fluorescence quenching.…”