Influence of Dopamine Concentration and Surface Coverage of Au Shell on the Optical Properties of Au, Ag, and Ag_coreAu_shell Nanoparticles

Abstract

Gold (Au), silver (Ag), and Ag core Au shell nanoparticles (NPs) were explored as optical sensing agents for the sensitive detection of dopamine (DA) neurotransmitters in surface-enhanced Raman scattering (SERS) measurements. In these colloidal systems, dopamine (DA) molecules played as a cross-linker between M NPs (Au or Ag NPs), allowing them to reside in the confined junctions (i.e., hot spots) between aggregated NPs. The progressive addition of DA molecules (from 1 × 10 −6 to 1 × 10 −3 M) consequently decreased a primary absorption peak attributed to the characteristic M NPs and generated a secondary absorption peak at longer wavelengths attributed to heavily aggregated M NPs formed by molecular bridging effects of DA molecules at high concentrations. The aggregation degree of M NPs was also dependent on the surface states of Au and Ag NPs, i.e., DA molecules with positive amine groups induced more aggregations of Au NPs in comparison to Ag NPs with less negative charges. As the final outcome, Au NPs demonstrated higher sensitivity in SERS detection of DA at low concentrations (1 × 10 −7 to 1 × 10 −5 M), whereas Ag NPs exhibited the stronger Raman signals of DA molecules at high concentrations (1 × 10 −4 to 1 × 10 −3 M). Besides, Ag core Au shell NPs with the lowest surface coverage of Au shell exhibited more sensitive and stronger SERS activity for DA molecules than that of singular Au NPs, probably due to the combined contribution by Ag core with strong SERS intensity and Au shell with high SERS sensitivity.

Noble Metal Nanoparticles in Cancer Therapy: Properties Challenges and Clinical Applications.

“…Silver nanoparticles (SNPs) are of special interest of remarkable antimicrobial and localized surface plasmon resona nce properties, due to which they have got properties such as broad-spectrum antimicrobial, surface-enhanced Rama n spectroscopy (SERS), chemical /biological sensors and biomedicine materials, biomarker (10) and soon.…”

Flower-like gold nanostructures electrodeposited on indium tin oxide (ITO) glass as a SERS-active substrate for sensing dopamine

“…Thus, the sensitive and selective detection of abnormal dopamine level in biological fluid is very important in the early detection of several diseases such as schizophrenia, Huntington's and Parkinson's disease [1][2][3]. Common detection methods for neurotransmitters are based on electrochemistry [4][5][6][7][8], chromatography coupled to spectrometry [9][10][11][12][13], fluorescence [14][15][16] or surfaceenhanced Raman scattering [17][18][19][20][21]. The well-known electrochemical oxidation has some limitations due to its low selectivity to dopamine in the presence of many interfering components such as excessive ascorbic acid (AA), uric acid (UP) and epinephrine (EP) [5].…”

The characteristic AgcoreAushell nanoparticles as SERS substrates in detecting dopamine molecules at various pH ranges

“…[1][2][3] The core-shell NPs often exhibit enhanced physico-chemical properties (such as optical, electronic, and catalytic properties) over their monometallic counterparts, as a result of the localized electric field enhancement in the core-shell nanostructure. [4][5][6] The plasmonic core-shell NPs can also have a strong absorption in the near-infrared region, which can lead to a photothermal effect, consequently interplaying as a theranostic particle system with diagnostic and therapeutic capability. [7][8][9] Surface-enhanced Raman scattering (SERS) is a promising and highly sensitive and selective optical analysis technique.…”

“…In practice, DA is N-protonated (H 3 DA + ) (pH ,9.05), but negatively charged under basic pH conditions. 4 The zeta potential of the freshly prepared Ag core Au shell NPs is -15.43±7.32 mV at pH 5. When the pH of the solution changes to pH 10, the zeta potential increases to -45.68±7.32 mV.…”

“…40,41 In other words, one terminal amine group attaches to the individual core-shell NPs and the remaining hydroxyl groups interact with each other via a hydrogen bonding network, consequently leading to the aggregation of core-shell NPs. 4 In contrast, there is no distinct change in the peak position when the solution pH deviates from the intermediate pH range, indicating the negligible cross-linking effects by the DA molecules. Figure 4D demonstrates the change of the particle size as a function of solution pH.…”