Silver Nanoparticle-Based Surface-Enhanced Raman Spectroscopy for the Rapid and Selective Detection of Trace Tropane Alkaloids in Food

Abstract

Recently, surface-enhanced Raman Spectroscopy (SERS) has been widely applied for rapid detection of trace targets in various fields. However, two key issues are still being explored: (1) how to form effective “SERS hotspots” for the trace qualitation with high sensitivity; (2) how to quantitatively identify trace target in complicated matrix in a highly selective and fast manner. Here, aiming at these two key points, we developed an effective and simple protocol for the rapid detection of three tropane alkaloids (TAs), typical toxicants in public security. Taking the advantage of the coadsorption with the specific adsorbed I− during the formation of hotspots by the highly concentrated halide salts, the detection sensitivity of TAs was improved up to 4 orders over the case of Cl−. Under the optimized condition, the lowest detectable concentration of these three TAs was down to the 1 μg/L level. Through the use of drink and food samples, the strong nonspecific competitive adsorption from the complicated matrix was significantly weakened by the simple dilution. The recovery was increased almost 2 orders over that of direct detection, irrespectively of the distinctly changed interferences in different samples. The proposed strategy, improving qualitative sensitivity by forming effective hotspots and quantitative analysis by dilution, not only provides a rapid detection for trace TAs in various foods in case of emergency first response but also could be easily extended to other SERS-based analysis.

Surface-enhanced Raman spectroscopy: benefits, trade-offs and future developments

“…Therefore, it is important to understand the factors governing the behaviour of the colloidal nanoparticle to ensure the effective formation and control of nanoparticle aggregates. 69 Techniques like dynamic light scattering (DLS), 70 in situ transmission electron microscopy (TEM), 71 high-sensitivity ow cytometry (HSFCM) 72 and zeta potential measurements 73 are useful for measuring the state of colloids during the dynamic aggregating process. Meanwhile, the theoretical approach known as the extended Derjaguin, Landau, Verwey, and Overbeek (x-DLVO) model can be used to determine and predict the state of nanoparticle colloids and buffer compatibility.…”

Key Role of Direct Adsorption on SERS Sensitivity: Synergistic Effect among Target, Aggregating Agent, and Surface with Au or Ag Colloid as Surface-Enhanced Raman Spectroscopy Substrate

“…(2) Considering the coadsorption between the positively charged TAs and the negatively charged iodide ions (specifically adsorbed on Ag surface), the so-formed SERS hot spots exhibited high selectivity and sensitivity toward trace TAs detection. 17 Here, a direct adsorption scenario of trace target on SERS active substrate was proposed for acquiring high SERS sensitivity, with the systematical investigation of the SERS performance of three trace positively charged molecules containing basic amino group, namely koumine (KM), gelsemine (GM), and scopolamine hydrobromide (SH) (related chemical structures and description are shown in Figure S1). The universality of the scenario was further demonstrated by trace detections of 4-mercaptobenzoic acid, one typical SERS probe molecule, and quinolones, widely used antibiotics.…”

Solution-Based SERS Detection of Weak Surficial Affinity Molecules Using Cysteamine-Modified Au Bipyramids

“…As shown in Figure 3a, after ligand exchange, the UV−vis spectra of Au BPs show a significant blue shift from 721 to 705 nm, indicating that the ligand exchange from CTAB to cysteamine induces the transformation of the LSPR band of Au BPs. 26,36 During the pretreatment for the ligand exchange, a slight blue shift (about 10 nm) in LSPR can be observed after centrifugation and washing the CTAB Au BPs with water two times; this indicates the partial removal of CTAB from the Au BP surface. After the washing process, the UV−vis spectra (Figure 3a) show that Au BPs are still well dispersed and stable in the solution.…”