Gold nanoparticles-based SERS nanosensor for thiram and chloramphenicol monitoring in food samples: Insight into effects of analyte molecular structure on their sensing performance and signal enhancement

• Published in: Applied surface science Vol. 584; p. 152555
• Main Authors: Ha Anh, Nguyen, Quan Doan, Mai, Xuan Dinh, Ngo, Quang Huy, Tran, Quang Tri, Doan, Le, Anh-Tuan
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.05.2022
• Subjects: Analyte molecular structure; Chemical enhancement; Electromagnetic enhancement; SERS sensor; Analyte molecular structure; SERS sensor; Chemical enhancement; Electromagnetic enhancement
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2022.152555

[Display omitted] •Electrochemically-synthesized gold nanoparticles (e-AuNPs) were employed effective surface enhancement Raman spectroscopy (SERS)-based sensors for thiram and chloramphenicol (CAP), between which the thiram sensor exhibited better performance in terms of sensibility and reliability.•Thiram adsorbed on e-AuNPs obeying Langmuir model as monolayer adsorption at one binding site while CAP adsorption better obeyed Freundlich one as multilayer at two potential adsorbing sites.•Sulfur-containing structure, small and simple molecules, S-S bond cleavage, low steric hindrance and monolayer adsorption allowed thiram to adsorb better on e-AuNP surface and in the hotspots created in the nano-gap between e-AuNPs.•Analyte molecular structure showed significant effects on SERS signal enhancement in both chemical and electromagnetic mechanism.•Thiram and CAP was detectable in real samples of tap water and orange juice (for thiram), as well as shrimp and beef (for CAP) at the concentration as low as 10-8 M and 10-7 M, respectively. Electrochemically synthesized gold nanoparticles (e-AuNPs) were deposited on aluminum substrates to fabricate effective surface enhanced Raman spectroscopy (SERS) sensors for thiram and CAP monitoring in food samples, between which the thiram sensor showed better performance in terms of sensibility, reliability and practicability. Regarding that the differences in SERS performance of the two sensors were closely associated to the distinction in molecular structure of the two analytes, we investigated the effects of analyte molecular structure on the sensing performance, especially the enhancement factors (EFs), of the sensors. As the enhancement of SERS signal is explained by both chemical and electromagnetic mechanisms (CM and EM), the investigation was also carried out in two directions. On one hand (CM), the adsorption of the analytes on the surface of e-AuNPs was studied by using both Langmuir and Freundlich isotherm models to qualitatively evaluate their adsorption capacity on e-AuNPs. On the other hand (EM), SERS measurements of thiram and CAP were performed on a set of substrates, on which the interpaticle distance between e-AuNPs were controlled by pH adjustment before deposition, to study their adsorption ability in the hotspots. The obtained results showed that thiram adsorption obeyed Langmuir model, thus, thiram residues adsorbed as a monolayer on the e-AuNPs surface at the same adsorbing site. In contrast, CAP adsorption obeyed Freundlich one with multilayer adsorption and two potential adsorbing sites. In addition, with sulfur-containing structure, small and simple molecule, capability of S-S bond cleavage and smaller steric hindrance, thiram exhibited better adsorption ability not only on the surface of e-AuNPs but also in the nano-gaps between them. Therefore, on SERS substrates that e-AuNPs were deposited before the addition of analyte, analyte molecular structure still shows great effects on sensing performance of the sensors, especially on the enhancement factors, in both CM and EM.