In situ Activation of Thick-film Disposable Copper Electrodes for Sensitive Detection of Malachite Green Using Electrochemical Surface-enhanced Raman Scattering (EC-SERS)

A porous silicon composite with irregular silver nano-dendritic particles: a rapid optical sensor for trace detection of malachite green in freshwater fish

This study focused on creating a SERS composite particle specifically designed for detecting malachite green. We synthesized silver nano-dendritic structures on p-type porous silicon using an external electric field, separating them from the silicon wafer. Ultrasonic crushing yielded irregular silver nanodendrite-modified porous silicon composite particles. Upon being tested in an aqueous solution of malachite green, these composite particles demonstrated significant surface-enhanced Raman scattering effects. Our findings highlight the exceptional performance of the SERS substrate composed of porous silicon and irregular silver nano-dendritic particles. It exhibited high sensitivity, specificity, consistent signal strength, and reliability in detecting trace amounts of malachite green in water. Under ideal conditions, the substrate could detect malachite green at concentrations as low as 10-8 M. Moreover, its swift response to trace amounts of malachite green in fish underscores its potential as an effective Raman detector.

Review on combining surface-enhanced Raman spectroscopy and electrochemistry for analytical applications

The discovery of surface enhanced Raman scattering (SERS) from an electrochemical (EC)-SERS experiment is known as a historic breakthrough. Five decades have passed and Raman spectroelectrochemistry (SEC) has developed into a common characterization tool that provides information about the electrode-electrolyte interface. Recently, this technique has been successfully explored for analytical purposes. EC was found to highly improve the performances of SERS sensors, providing, among others, controlled adsorption of analytes and increased reproducibility. In this review, we highlight the potential of EC-SERS sensors to be implemented for point-of-need (PON) analyses as miniaturized devices, and their ability to revolutionize fields like quality control, diagnosis or environmental and food safety. Important developments have been achieved in Raman spectroelectrochemistry, which now represents a promising alternative to conventional analytical methods and interests more and more researchers. The studies included in this review open endless possibilities for real-life EC-SERS analytical applications.

Investigation of Sulfur Doping in Mn-Co Oxide Nanotubes on Surface-Enhanced Raman Scattering Properties

Doping engineering is an efficient strategy to manipulate the optoelectronic properties of metal oxides for sensing, catalysis, and energy applications. Herein, we have demonstrated the fabrication of sulfur (S)-doped Mn-Co oxides to regulate their band and surface electronic structures, which is beneficial to enhancing the charge transfer (CT) between the metal oxides and their adsorbed molecules. As expected, significantly enhanced SERS signals are achieved on S-doped Mn-Co oxide nanotubes, and the minimum detection concentration can reach as low as 10^-8 M. Furthermore, the change in the electronic structure caused by S-doping provides different microelectric fields to influence the orientation of the interaction between the probe molecules and the substrate. Additionally, the evaluation of the oxidase-like catalytic activity of the substrate proved that, with an increase in the ratio of Co²⁺/Co³⁺ content, the number of electrons on the substrate increases, which promotes the CT process and further increases the degree of CT. The nonmetallic doping route in semiconducting metal oxides can provide effective and stable SERS activity; moreover, it provides a new strategy for exploring the relationship between CT in catalysis and SERS performance of semiconductors.

Rapid Determination of the 'Legal Highs' 4-MMC and 4-MEC by Spectroelectrochemistry: Simultaneous Cyclic Voltammetry and In Situ Surface-Enhanced Raman Spectroscopy

The synthetic cathinones mephedrone (4-MMC) and 4-methylethcathinone (4-MEC) are two designer drugs that represent the rise and fall effect of this drug category within the stimulants market and are still available in several countries around the world. As a result, the qualitative and quantitative determination of 'legal highs', and their mixtures, are of great interest. This work explores for the first time the spectroelectrochemical response of these substances by coupling cyclic voltammetry (CV) with Raman spectroscopy in a portable instrument. It was found that the stimulants exhibit a voltammetric response on a gold screen-printed electrode while the surface is simultaneously electro-activated to achieve a periodic surface-enhanced Raman spectroscopy (SERS) substrate with high reproducibility. The proposed method enables a rapid and reliable determination in which both substances can be selectively analyzed through the oxidation waves of the molecules and the characteristic bands of the electrochemical SERS (EC-SERS) spectra. The feasibility and applicability of the method were assessed in simulated seized drug samples and spiked synthetic urine. This time-resolved spectroelectrochemical technique provides a cost-effective and user-friendly tool for onsite screening of synthetic stimulants in matrices with low concentration analytes for forensic applications.

Detection of dithiocarbamate, chloronicotinyl and organophosphate pesticides by electrochemical activation of SERS features of screen-printed electrodes

Enhancement of Raman intensity due to the electrochemical surface-enhanced Raman scattering (EC-SERS) effect is an interesting alternative to overcome the lack of sensitivity traditionally associated with Raman spectroscopy. Furthermore, activation of metallic screen-printed electrodes (SPEs) by electrochemical route leads to the reproducible generation of nanostructures with excellent SERS properties. EC-SERS procedure proposed in this work for the detection of several pesticides (thiram, imidacloprid and chlorpyrifos) with different nature, uses gold SPEs as SERS substrates, but also includes a preconcentration step as the initial and essential stage. Taking into account the small volume of solution employed, only 60 µL, the preconcentration cannot be performed for more than 15 min in order to ensure the proper contact of the solution with WE, RE and CE. Furthermore, selected temperature, 34 °C, is not very high to allow the exhaustive control of the drop volume. Optimization of preconcentration parameters (time and temperature) displays a crucial step, particularly in the detection of low concentrations of pesticides, because it will provide higher Raman intensity in EC-SERS experiments. After the initial step, gold SPEs were electrochemically activated by cyclic voltammetry, allowing the detection of very low concentration (µg·L^-1) of pesticides due to the generation of fresh nanostructures with SERS effect.

Spectroelectrochemistry, the future of visualizing electrode processes by hyphenating electrochemistry with spectroscopic techniques

Reviewing the future of electrochemistry combined with infrared, Raman, and nuclear magnetic resonance spectroscopy as well as mass spectrometry.

Spectroelectrochemical elucidation of B vitamins present in multivitamin complexes by EC-SERS

Raman spectroelectrochemistry based on electrochemical surface-enhanced Raman scattering (EC-SERS) effect is an interesting alternative to overcome the lack of sensitivity of normal Raman spectroscopy. Electrochemical activation of metallic screen-printed electrodes (SPEs) leads to the reproducible generation of nanostructures with excellent SERS properties. In that way, gold SPEs circumvent the traditional reproducibility limitation and produce the enhancement of the Raman intensity to favor the detection of low concentrations. Furthermore, fingerprint features of Raman spectroscopy make possible the dynamic spectroelectrochemical analysis of B vitamins. The accuracy assignments of Raman bands associated with B1, B2, B3, B6 and B12 vitamins present in multivitamin complexes provides valuable information, allowing us not only the detection of B vitamin present in mixtures, but also to understand the interaction between vitamins and metallic SERS surfaces.