Large-Scale Fabrication of Ultrasensitive and Uniform Surface-Enhanced Raman Scattering Substrates for the Trace Detection of Pesticides

Abstract

Technology transfer from laboratory into practical application needs to meet the demands of economic viability and operational simplicity. This paper reports a simple and convenient strategy to fabricate large-scale and ultrasensitive surface-enhanced Raman scattering (SERS) substrates. In this strategy, no toxic chemicals or sophisticated instruments are required to fabricate the SERS substrates. On one hand, Ag nanoparticles (NPs) with relatively uniform size were synthesized using the modified Tollens method, which employs an ultra-low concentration of Ag+ and excessive amounts of glucose as a reducing agent. On the other hand, when a drop of the colloidal Ag NPs dries on a horizontal solid surface, the droplet becomes ropy, turns into a layered structure under gravity, and hardens. During evaporation, capillary flow was burdened by viscidity resistance from the ropy glucose solution. Thus, the coffee-ring effect is eliminated, leading to a uniform deposition of Ag NPs. With this method, flat Ag NPs-based SERS active films were formed in array-well plates defined by hole-shaped polydimethylsiloxane (PDMS) structures bonded on glass substrates, which were made for convenient detection. The strong SERS activity of these substrates allowed us to reach detection limits down to 10−14 M of Rhodamine 6 G and 10−10 M of thiram (pesticide).

Mussel-Inspired Fabrication of SERS Swabs for Highly Sensitive and Conformal Rapid Detection of Thiram Bactericides

“…As the solutions were dried, the thiram residues were collected by the CS@PDA@AgNPs swabs via a surface swabbing method, and detected with the Renishaw inVia9 Raman Microscope. As shown in Figure 6a–c, the characteristic peaks of the thiram molecules, such as at 561 cm −1 attributed to υ(S-S), 1147 cm −1 corresponding to ρ(-CH3) and υ(C-N), and 1380 cm −1 ascribed to υ(C-N), were clearly detected, which was consistent with the previous reports for the thiram SERS analysis [41,44]. At the same time, even if the thiram concentration decreased to 1 × 10 −7 M, the above characteristic SERS peaks could still be clearly discerned, demonstrating a high SERS sensitivity for the CS@PDA@AgNPs swabs to detect thiram residues from various surfaces.…”

Immobilization and 3D Hot-Junction Formation of Gold Nanoparticles on Two-Dimensional Silicate Nanoplatelets as Substrates for High-Efficiency Surface-Enhanced Raman Scattering Detection

“…The technique has since been widely used in biological [2], medical [3,4], environmental engineering [5], materials science [6,7], and quality analysis applications [8] because it offers increased Raman intensity by several orders of magnitude. Further, it offers sufficient sensitivity for single-molecule detection [9] and trace chemical analysis [10]. In this context, it is also known that rough metal nanoparticles (NPs) exhibit a large increase in surface plasmon excitation with electric field application, thus enhancing the Raman signal strength [11].…”

Trace analysis of organic compounds in foods with surface‐enhanced Raman spectroscopy: Methodology, progress, and challenges

“…This “dried colloid” method is simple and widely applied in analyzing food or other samples, but the distribution of the target compound and nanoparticles on the surface of a sample holder could be very complicated, depending on the surface properties (for example, charge) of both nanoparticles and the target molecules (Culha, ). Typically, the coffee ring effect results in the majority of dispersed or dissolved nanoparticles and chemicals being dragged to the edge of the droplet mainly due to the capillary flow, leading to the difficulty to obtain reproducible SERS spectrum for the analyte (Culha, ; Zhu et al., ). Quite some efforts have been made to suppress the coffee ring effect through control the capillary flow so that more even distribution of nanoparticles and analyte molecules onto a sample holder could be obtained (Culha, ; Lu et al., ; Zhu et al., ).…”

“…Typically, the coffee ring effect results in the majority of dispersed or dissolved nanoparticles and chemicals being dragged to the edge of the droplet mainly due to the capillary flow, leading to the difficulty to obtain reproducible SERS spectrum for the analyte (Culha, ; Zhu et al., ). Quite some efforts have been made to suppress the coffee ring effect through control the capillary flow so that more even distribution of nanoparticles and analyte molecules onto a sample holder could be obtained (Culha, ; Lu et al., ; Zhu et al., ). However, most recently, there are reports on applying coffee ring effect to separate and concentrate analyte molecules and nanoparticles from the bulk solution to improve the performance of SERS analysis (Mampallil & Eral, ; Pan et al., ; Xu, Du, Jing, Zhang, & Cui, ).…”