Integration of solid-phase microextraction and surface-enhanced Raman spectroscopy for in-vivo screening of polybrominated diphenyl ether

The monitoring of polybrominated diphenyl ethers (PBDEs) is of great significance owing to their high persistence, bioaccumulation, and toxicity to humans and animals. In this study, a sensitive and reproducible probe that integrates solid-phase microextraction and surface-enhanced Raman spectroscopy (SPME-SERS) was developed for screening PBDEs in multiphase specimens, including live fish, water, and electrical products. A roughed Cu fiber with an Ag layer was fabricated with dual functions. BDE-15 was readily extracted and detected on the SPME-SERS probe consisting of propanethiol-modified Ag nanoplates on a Cu wire. A clear linear relationship (R² = 0.988) was established between the SERS intensity at 782 cm^-1 and the logarithmic concentrations (from 100 ppb to 100 ppm), with a detection limit of 15 ppb. This proposed method enables continuous in vivo monitoring in fish without complicated pretreatments. The results obtained by this SPME-SERS approach were validated by high-performance liquid chromatography and showed good agreement. This "extracting and detecting" SPME-SERS method provides a potential tool to monitor the occurrence, formation, and migration of PBDEs.

Nanopillar-Assisted SERS Chromatography

Practical implementation of surfaced enhanced Raman spectroscopy (SERS) sensing is hindered by complexity of real-life samples, which often requires long and costly pretreatment and purification. Here, we present a novel nanopillar-assisted SERS chromatography (NPC-SERS) method for simultaneous quantitation of target molecules and analysis of complex, multicomponent fluids, e.g., human urine spiked with a model drug paracetamol (PAR). Gold-coated silicon nanopillar (AuNP) SERS substrates and a centrifugal microfluidic platform are tactfully combined, which allows (i) a precise and fully automated sample manipulation and (ii) spatial separation of different molecular species on the AuNP substrate. The NPC-SERS technique provides a novel approach for wetting the stationary phase (AuNP) using the "wicking effect", and thus minimizes dilution of analytes. Separation of PAR and the main human urine components (urea, uric acid, and creatinine) has been demonstrated. Quantitative detection of PAR with ultrawide linear dynamic range (0-500 ppm) is achieved by analyzing the spreading profiles of PAR on the AuNP surface. NPC-SERS transforms SERS into a sensing technique with general applicability, facilitating rapid and quantitative detection of analytes in complex biofluids, such as saliva, blood, and urine.

Galvanic displacement-induced codeposition of reduced-graphene-oxide/silver on alloy fibers for non-destructive SPME@SERS analysis of antibiotics

This work describes the integration of solid-phase microextraction (SPME) and surface-enhanced Raman spectroscopy (SERS) by codeposition of a hybrid consisting of reduced graphene oxide and silver on silver-copper alloy fibers. The morphology and structure of the coating were characterized by a variety of microscopic and spectroscopic techniques that confirmed the hybrid structure of the material. A galvanic-displacement-induced process is assumed to be involved during the codeposition of the hybrid coating on the alloy. In this process, Ag(I) is reduced to Ag(0) by Cu(0), and the presence of conjugated domains in GO facilitates the long-range transfer of electrons from Cu to Ag+. Simultaneously, GO accepts electrons and is converted into RGO. The hybrid coating exhibits a high SERS enhancement factor and good spatial uniformity. The needle-like coated alloy fibers are shown to be a viable tool for non-destructive sampling and SERS-based determination of trace levels of the antibiotics sulfadiazine and sulfamethoxazole in a spiked tissue mimic. The SERS peaks at 1149 cm^-1 for sulfadiazine and 1144 cm^-1 for sulfamethoxazole are selected as the reference peaks in the quantitative analysis. The linear range is from 0.01 to 100 μg·cm^-3. The detection limits are 1.9 ng·cm^-3 for sulfadiazine and 4.4 ng·cm^-3 for sulfamethoxazole. Graphical abstract Schematic presentation of I: Galvanic-displacement-induced reduction of graphene oxide (brown films) and Ag⁺ (purple dots) on silver-copper alloy; II: Codeposition of reduced-graphene-oxide (grey films)/Ag (blue stars) on alloy fiber; III: Non-destructive SPME of antibiotics from spiked tissue mimic; IV: SERS detection using Raman spectroscope.

Facing Challenges in Real-Life Application of Surface-Enhanced Raman Scattering: Design and Nanofabrication of Surface-Enhanced Raman Scattering Substrates for Rapid Field Test of Food Contaminants

Surface-enhanced Raman scattering (SERS) is capable of detecting a single molecule with high specificity and has become a promising technique for rapid chemical analysis of agricultural products and foods. With a deeper understanding of the SERS effect and advances in nanofabrication technology, SERS is now on the edge of going out of the laboratory and becoming a sophisticated analytical tool to fulfill various real-world tasks. This review focuses on the challenges that SERS has met in this progress, such as how to obtain a reliable SERS signal, improve the sensitivity and specificity in a complex sample matrix, develop simple and user-friendly practical sensing approach, reduce the running cost, etc. This review highlights the new thoughts on design and nanofabrication of SERS-active substrates for solving these challenges and introduces the recent advances of SERS applications in this area. We hope that our discussion will encourage more researches to address these challenges and eventually help to bring SERS technology out of the laboratory.

Combination of a graphene SERS substrate and magnetic solid phase micro-extraction used for the rapid detection of trace illegal additives

Surface enhanced Raman scattering (SERS) is an ultra-sensitive spectroscopy technique, which can provide rich structural information for a great number of molecules, while solid phase micro-extraction (SPME) is an efficient method for sample pretreatment in analytical chemistry, particularly in a micro-system.

Pollutant capturing SERS substrate: porous boron nitride microfibers with uniform silver nanoparticle decoration

How to concentrate target molecules on the surface of a SERS substrate is a key problem in the practical application of SERS. Herein, we designed for the first time a pollutant capturing surface enhanced Raman spectroscopy (SERS) substrate, namely porous BN microfibers uniformly decorated with Ag nanoparticles, in which the BN microfibers adsorb pollutants, while the Ag nanoparticles provide SERS activity. This SERS substrate captures pollutants from an aqueous solution completely and accumulates them all on its surface without introducing noise signals. The pores of BN protect the silver particles from aggregation which makes BN/Ag a stable and recyclable SERS substrate. What's more, while the dyes are thoroughly concentrated from a diluted solution, the SERS detection limit is easily enhanced, from 10(-6) M to 10(-9) M.

Hydrophobic gold nanostructures via electrochemical deposition for sensitive SERS detection of persistent toxic substances

The hydrophobic gold nanostructures were used for direct SERS detection of PTS with high sensitivity.

Silver nanoparticle aggregates on metal fibers for solid phase microextraction–surface enhanced Raman spectroscopy detection of polycyclic aromatic hydrocarbons

Silver–copper fibers loaded with silver nanoparticles are used for SPME–SERS detection of polycyclic aromatic hydrocarbons, which can be further confirmed by GC-MS.

Cysteamine-modified silver nanoparticle aggregates for quantitative SERS sensing of pentachlorophenol with a portable Raman spectrometer

Cysteamine-modified silver nanoparticle aggregates has been fabricated for pentachlorophenol (PCP) sensing by surface-enhanced Raman spectroscopy (SERS) using a portable Raman spectrometer. The cysteamine monolayers could preconcentrate PCP close to the substrate surface through the electrostatic interaction, which makes the SERS detection of PCP possible. Moreover, the Raman bands of cysteamine could be used as the internal spectral reference in the quantitative analysis. Qualitative detection of PCP was carried out by SERS without any sample pretreatment. Quantitative analysis of PCP was further realized based on the prepared substrate, as the log-log plot of normalized SERS intensity of PCP versus its concentrations exhibits a good linear relationship. The SERS signals collected on 20 randomly selected points show that the relative standard deviation of the normalized Raman intensity is 5.8%, which indicates the substrate had good uniformity. The PCP sensor also shows good long-term stability in the analyte solution. The substrate was cyclic immersed into PCP and methanol solution; after several cycles, the sensor still had good adsorption to PCP, which revealed the sensor has good reusability. Coupling with a portable Raman spectrometer, the cysteamine-modified silver nanoparticle aggregates have the potential to be used for in situ and routine SERS analysis of PCP in environmental samples.