https://iopscience.iop.org/article/10.1149/2.0161808jes/pdf

Review—Surface-Enhanced Raman Scattering Sensors for Food Safety and Environmental Monitoring

Plasmonics has drawn significant attention in the area of biosensors for decades due to the unique optical properties of plasmonic resonant nanostructures. While the sensitivity and specificity of molecular detection relies significantly on the resonance conditions, significant attention has been dedicated to the design, fabrication, and optimization of plasmonic substrates. The adequate choice of materials, structures, and functionality goes hand in hand with a fundamental understanding of plasmonics to enable the development of practical biosensors that can be deployed in real life situations. Here we provide a brief review of plasmonic biosensors detailing most recent developments and applications. Besides metals, novel plasmonic materials such as graphene are highlighted. Sensors based on Surface Plasmon Resonance (SPR), Localized Surface Plasmon Resonance (LSPR), and Surface Enhanced Raman Spectroscopy (SERS) are presented and classified based on their materials and structure. In addition, most recent applications to environment monitoring, health diagnosis, and food safety are presented. Potential problems related to the implementation in such applications are discussed and an outlook is presented.

/pdf/are-plasmonic-optical-biosensors-ready-for-use-in-point-of-3ouhch18eh.pdf

Are plasmonic optical biosensors ready for use in point-of-need applications?

Terrestrial life may be carbon-based, but most of its mass is made up of water. Access to clean water is essential to all aspects of maintaining life. Mainly due to human activity, the strain on the water resources of our planet has increased substantially, requiring action in water management and purification. Water quality sensors are needed in order to quantify the problem and verify the success of remedial actions. This review summarizes the most common chemical water quality parameters, and current developments in sensor technology available to monitor them. Particular emphasis is on technologies that lend themselves to reagent-free, lowmaintenance, autonomous and continuous monitoring. Chemiresistors and other electrical sensors are discussed in particular detail, while mechanical, optical and electrochemical sensors also find mentioning. The focus here is on the physics of chemical signal transduction in sensor elements that are in direct contact with the analyte. All other sensing methods, and all other elements of sampling, sample pre-treatment as well as the collection, transmission and analysis of the data are not discussed here. Instead, the goal is to highlight the progress and remaining challenges in the development of sensor materials and designs for an audience of physicists and materials scientists.

https://iopscience.iop.org/article/10.1088/1361-6463/aabb93/pdf

Review on water quality sensors

Surface-enhanced Raman spectroscopy (SERS) combined with chemometric models were employed to develop a rapid, low-cost, and sensitive method for qualitative and quantitative analysis of chlorpyrifos residues in tea. Au@Ag nanoparticles (NPs) with high enhancement factor were synthesized and coupled with chemometric algorithms for SERS measurements. K-nearest neighbors (KNN) classification models gave the best performance model with high classification rates (90.84–100.00%) achieved. For the quantification models for predicting chlorpyrifos contents, the genetic algorithm-partial least squares (GA-PLS) models and synergy interval partial least squares-genetic algorithm (siPLS-GA) models applied to standard normal variate transformation (SNV) preprocessed training and validation data set showed better prediction performances with excellent regression quality (slope = 0.98–1.00), higher correlation coefficient of determination (r2 = 0.96–0.98), and lower root-mean-square error of prediction (RMSEP = 0.29, 0.31) than other quantification models. Paired sample t-test exhibited no statistically significant difference between the reference values determined by GC-MS and the predicted values in most quantification models. The proposed method would be a more effective and powerful tool for classification and determination of chlorpyrifos (CPS) residues in tea samples.

Qualitative and quantitative analysis of chlorpyrifos residues in tea by surface-enhanced Raman spectroscopy (SERS) combined with chemometric models

Metal-organic framework (MOF-5) coated SERS active gold gratings: A platform for the selective detection of organic contaminants in soil

Here we report a surface plasmon-polariton based functionalized SERS platform for the detection of heavy metal ions. Homogenous distribution of the plasmon intensity on the ordered plasmon structure and high affinity of diethylenetriaminepentaacetic acid (DTPA) to heavy metal ions allows the efficient entrapping of heavy metal ions as well as their selective and sensitive detection (LOD was found 10−14 M). Periodical gold structure was created using the excimer laser beam treatment of polymer surface and further coating by gold. DTPA molecules were covalently attached to the gold surface through the two step procedure: (i) grafting of 4-aminophenylene groups via diazonium chemistry and (ii) their acylation by DTPA-anhydride. Grafted DTPA molecules showed high SERS response, due to the SPP excitation and propagation on the gold grafting. Efficient chelating of heavy metal ions by DTPA molecules from solution results in pronounced changes of their SERS response. The shift of carbonyl Raman peak position was found to be dependent on the atomic number of heavy metal ions, enabling the selective detection even in the mixture of few metals. Applied SERS platform can be realized using the portable SERS spectrophotometer and requires the minimal equipment cost as well as the experimental time.

M. Erzina

Papers

Pretreatment-free selective and reproducible SERS-based detection of heavy metal ions on DTPA functionalized plasmonic platform