Dopamine Molecules on Au_core−Ag_shell Bimetallic Nanocolloids: Fourier Transform Infrared, Raman, and Surface-Enhanced Raman Spectroscopy Study Aided by Density Functional Theory

Abstract

Adsorption of dopamine (DA) on a Au core -Ag shell bimetallic nanocolloidal surface has been investigated using surface-enhanced Raman spectroscopy (SERS). The normal Raman spectra (NRS) of DA molecules in bulk and in aqueous solution have been investigated in depth. The vibrational signatures, as observed from the Raman and FTIR spectra of the molecule, have been assigned from the potential energy distributions. The pH-dependent NRS of the DA molecule in aqueous solution has been recorded to elucidate the protonation effect and preferential existence of different forms of the molecule. The pH-dependent SERS spectra of the molecule adsorbed on the bimetallic Au core -Ag shell nanocolloidal surface are also reported. The enhancement of bands in the pH-dependent SERS spectra suggests that the molecules are adsorbed onto the bimetallic Au core -Ag shell surface with the molecular plane tilted with respect to the silver surface of Au core -Ag shell bimetallic nanoparticles. The model study authenticates the spectral disposition and orientation of the molecule. Thus, experiment and theory keep abreast of the variety of DA structures envisaged from SERS studies on a new substrate.

Infrared spectra of protonated neurotransmitters: dopamine

“…For example, Pande et al measured surface-enhanced Raman spectra of dopamine on bimetallic nanocolloids and report calculations of the bare molecule in different charge states. 4 Interestingly, their calculated structure for dopamineH + (t3 in Fig. 1) differs from the lowest-energy isomer identified in the present work (gÀ1 in Fig.…”

“…4 For example, parkinsonism is associated with a reduced dopamine level, whereas schizophrenia can be related to an increased dopamine activity. 5 At physiological pH values, i.e.…”

Electrochemical fabrication of Rh–Pd particles and electrocatalytic applications

“…In recent years, bimetallic nanoparticles have an attractive area of research within nanobiotechnology and nanoelectrochemistry for their unusual optical, catalytic, and magnetic properties. Thus, bimetallic nanoparticles composed of two different metal elements are of greater interest than monometallic nanoparticles [8,9]. Palladium (Pd) and rhodium (Rh) are the noble metals which can be crystallized with a face centered cubic (FCC) packing [10].…”

Fabrication of Chitosan-gold Nanocomposites Combined with Optical Fiber as SERS Substrates to Detect Dopamine Molecules

“…The Raman peak at 1565 cm 1 was assigned to cathechol ring moiety of dopamine molecules and the peak at 1348 cm 1 was assigned to the stretching of the catechol C-O band. 36 According to Figure 5(b), the intensity of Raman peak was increased in proportion to dopamine concentrations. …”