Flexible Cascaded Wire-in-Cavity-in-Bowl Structure for High-Performance and Polydirectional Sensing of Contaminants in Microdroplets

Abstract

To improve the drawback of surface-enhanced Raman scattering (SERS) sensors that are sensitive to excitation angles and realize the monitoring of contaminants in complex environments, we have proposed and prepared a cascaded wire-in-cavity-in-bowl (WICIB) structure on flexible polydimethysiloxane, with feasibility for plasmonic coupling. We demonstrated that the WICIB structure can serve as a highly sensitive, homogeneous, and stable SERS substrate for conventional detection. The plasmonic coupling and distribution of the enhanced electromagnetic field were evidently proven by finite element simulations, and the strong electromagnetic field was regulated around the wire and inside the cavity, which is very beneficial for the polydirectional and in situ detection. By virtue of the triple synergistic enhancement effect and unique optical properties, we successfully achieved the in situ detection of the residual pollutant molecules, ziram and 2-naphthalenethiol, in microdroplets of apple juice and lake water. Accordingly, such a flexible SERS sensor exhibits great potential in on-site environmental monitoring.

Gold-Deposited Graphene Nanosheets for Self-Cleaning Graphene Surface-Enhanced Raman Spectroscopy with Superior Charge-Transfer Contribution

“…Since the discovery of the exceptionally strong Raman signal of pyridine adsorbed over electrochemically rough silver electrodes, surface-enhanced Raman spectroscopy (SERS) has been promisingly employed for trace-level identification of multiple hazardous molecules. − The precisely engineered structural designs and compositional peculiarities of nanostructures promote highly localized electromagnetic fields at the nanoarchitectures (also known as electromagnetic enhancement) along with a favorable metal–molecule interaction-induced charge transfer mechanism (also known as chemical enhancement). ,,, Together, these two factors significantly enhance the SERS signal intensity, enabling sensitive detection of a diverse category of targeted analytes down to the atto-molar (∼10 –18 M) detection limits. − Owing to its rapidness, cost-effectiveness, label-free, and minimally invasive detection capabilities, SERS has shown enormous potential in specific molecular identification as well as in studying the distinct surface interactions among the analyte and nanoplasmonic substrates. Along with the signal enhancement capabilities, the practical routine implementation of the nanoplasmonic SERS substrates is potentially affected by the nonuniformity and poor repeatability of the SERS signal, limiting the uniformly reproducible SERS identification of target analytes .…”

Reversible Thermoelectric Regulation of Electromagnetic and Chemical Enhancement for Rapid SERS Detection

“…Surface-enhanced Raman scattering (SERS) is a powerful analytical tool to achieve fast, on-site, and ultrasensitive detection. − It has been widely used in chemical analysis, biosensing, and environmental monitoring. − In principle, the SERS enhancement mechanism can be divided into an electromagnetic mechanism (EM) induced by local surface plasmon resonance (LSPR) and a chemical mechanism (CM) induced by charge transfer (CT). − These two mechanisms have been demonstrated to significantly influence the intensities of the Raman signals. To achieve dual EM- and CM-enhanced SERS substrates, pure metals are typically coupled with other functional materials to form, e.g., Ag nanowires-GaN nanoparticles, Au/Ag–TiO 2 , graphene/silver nanoparticles (Ag NPs), and Ag@ Ni–Fe layered double hydroxides etc. Although these SERS platforms have achieved ultrahigh performance enhancement, the optical property of the SERS substrate is fixed after fabrication, which is not conducive to further improving the detection sensitivity in an effective and facile way.…”

Photoactive Au@MoS2 Micromotors for Dynamic Surface-Enhanced Raman Spectroscopy Sensing

“…10−12 Different approaches have been proposed to combine the potential of SERS-based detection with other existing promising technologies. Among them, the use of microfluidic platforms 13 or the combination of wire-in-cavity-in-bowl structures 14 for SERS sensing has been recently explored in the literature. Yet, the incorporation of micromotors as platforms for reliable SERS detection has been scarcely exploited.…”