| Full text | |
| Author(s): |
Marques, Flavia C.
;
Alves, Raisa Siqueira
;
dos Santos, Diego Pereira
;
Andrade, Gustavo F. S.
Total Authors: 4
|
| Document type: | Journal article |
| Source: | Physical Chemistry Chemical Physics; v. 24, n. 44, p. 10-pg., 2022-10-28. |
| Abstract | |
The present study reports a direct approach to generate efficient hot spots using a nonresonant molecule bound to the inner part or hot spots that can increase the SERS sensitivity to obtain spectra of one and a few molecules. The 4-Mercaptobenzoic acid (4-MBA) adsorbate, connected to the Ag surface by a thiolate-Ag bonding, was able to trigger a self-assembly process of AgNP, which occurred by cooperative hydrogen bonds between the carboxylic groups of 4-MBA located in different nanoparticles when the pH was adjusted to 4. The self-assembly structure was characterized by UV-Vis spectroscopy and SERS (Surface Enhancement Raman Scattering), and DFT-based calculation of the model complex [AgNP-(4-MBA)(2)-AgNP] was employed to improve the understanding of the self-assembled complex formation through the comparison of calculated and experimental SERS spectra. The SERS signal of 4MBA on AgNP above the pK(a) of the carboxyl group was not observed below 1 x 10(-6) mol L-1 in any condition. Additionally, the SERS spectra of 4-bromobezenothiol (4-BrBT) at 5.0 x 10(-7 )mol L-1 had no bands assignable to 4-BrBT, reinforcing the hypothesis that the SERS intensification for 4-MBA in low concentrations (below 1 x 10(-6) mol L-1) is due to the hydrogen bonding triggered self-assembly of AgNP below 4-MBA pK(a). The average SERS of the 4-MBA in low surface coverage shows a mixture of structures, such as protonated and deprotonated 4-MBA, as well as a small amount of benzenethiol coming from decarboxylation of part of 4-MBA molecules. The few molecules SERS detection of 4-MBA was demonstrated experimentally and the experimental results were associated with a greater number of hot spots formed, being befitting with the generalized Mie theory simulations. (AU) | |
| FAPESP's process: | 16/21070-5 - Vibrational spectroscopy with spatial resolution |
| Grantee: | Mauro Carlos Costa Ribeiro |
| Support Opportunities: | Research Projects - Thematic Grants |