Plasmon-enhanced fluorimetric and colorimetric dual sensor based on fluorescein/Ag nanoprisms for sensitive determination of mancozeb

A portable europium complex-loaded fluorescent test paper combined with smartphone analysis for the on-site and visual detection of mancozeb in food samples

The on-site detection of mancozeb in food samples holds immense value for food safety. A red-fluorescent europium complex (Eu-PYDC-Phen) has been prepared and employed as a fluorescence probe for mancozeb detection. The optimized probe suspension exhibits excellent detection performances, including a wide linear range (0-0.24 mM), low detection limit (65 nM), rapid response (2 mins) and high selectivity. Moreover, a portable detection platform was carefully designed, integrating the Eu-PYDC-Phen-based fluorescent test strips with smartphone color recognition software. This innovative platform enables visual and on-site detection of mancozeb in tomato, apple, and lettuce, achieving satisfactory recovery rates (90.34 to 106.50%). Furthermore, the integration of machine learning techniques based on hierarchical clustering algorithm has the potential to further improve the prediction and decision-making efficiency in mancozeb detection. This work provides an economical, convenient, and reliable strategy for on-site detection of pesticide in agricultural products, thereby making a meaningful contribution to food safety.

Plasmonic nanoparticle etching-based optical sensors: current status and future prospects

Plasmonic nanoparticles are an emerging tool for developing label-free multicolorimetric sensors for biosensing and chemosensing applications. The color absorbed by nanoparticles from visible light is influenced by their size, shape, orientation, and interparticle distance. Differently sized and shaped gold and silver nanoparticles exhibit a wide range of colors, aiding in the development of label-free sensors. Etching is the process of oxidizing nanoparticles, which alters their aspect ratio, shape, plasmonic peak, and outward appearance. It is typically used to create sensitive sensing platforms. Through etching, analytes could be detected in a simple, sensitive, and selective manner. The multicolor readout of nanoparticle etching-based multicolorimetric sensors can overcome the limitations of conventional colorimetric assays and improve the accuracy of visual inspection. This review discusses different approaches for target sensing using nanoparticle etching strategies like direct etching, enzyme-mediated etching, chemical reaction-driven etching, and anti-etching-based sensors and their mechanisms. In the future, etching strategies could be modified into portable sensing devices to detect a variety of analytes, which will aid in the development of on-time, in situ, and point-of-care sensing systems.

A dual-optical sensor for mancozeb by UCNP@PVP@MnO2 nanozyme

In this work, a fluorescence/colorimetric dual-mode detection method based on MnO₂ nanoflower-decorated upconversion nanoparticles: NaYF₄:Yb/Er@polyvinylpyrrolidone@MnO₂ (UCNP@PVP@MnO₂) was proposed to detect the presence of mancozeb (MB). In this detection system, the MnO₂ nanoflowers in the nanocomplex of UCNP@PVP@MnO₂ would quench the fluorescence of the UCNP. With the addition of H₂O₂ and 3,3',5,5'-tetramethylbenzidine (TMB), the reaction between MnO₂ and H₂O₂ resulted in the dissolution of MnO₂ and the dissolution of the MnO₂ layer contributed to the fluorescence recovery of UCNP. Simultaneously, MnO₂ oxidized the colorless TMB to a blue product oxidized 3,3',5,5'-tetramethylbenzidine (oxTMB). The blue solution was able to quench the recovered fluorescence of UCNP due to the fluorescence inter filter effect (IFE) between the UCNP and blue oxTMB. Finally, with the addition of MB, the oxTMB was reduced to TMB by MB and the color of the solution became lighter while the fluorescence intensity of the solution increased. The detection method had a good linear range of 5-120 μM and 0.5-60 μM for fluorescence and colorimetric detection, respectively, and the limits of detection (LOD) were 2.34 and 0.245 μM, respectively.

Colorimetric Sensors for Chemical and Biological Sensing Applications

Colorimetric sensors have been widely used to detect numerous analytes due to their cost-effectiveness, high sensitivity and specificity, and clear visibility, even with the naked eye. In recent years, the emergence of advanced nanomaterials has greatly improved the development of colorimetric sensors. This review focuses on the recent (from the years 2015 to 2022) advances in the design, fabrication, and applications of colorimetric sensors. First, the classification and sensing mechanisms of colorimetric sensors are briefly described, and the design of colorimetric sensors based on several typical nanomaterials, including graphene and its derivatives, metal and metal oxide nanoparticles, DNA nanomaterials, quantum dots, and some other materials are discussed. Then the applications, especially for the detection of metallic and non-metallic ions, proteins, small molecules, gas, virus and bacteria, and DNA/RNA are summarized. Finally, the remaining challenges and future trends in the development of colorimetric sensors are also discussed.

Sample Preparation Methods for Metal Containing Pesticides in Food and Environmental Samples

Metal-containing pesticides are used in many areas for purposes such as harvest efficiency and keeping pests away from the vegetable environment. Metal-containing pesticides are in the form of dithiocarbamate complexes and are named differently according to the type of metal they contain and are used for different purposes. Since the presence of these pesticides even at residue level threatens human and environmental health, their determination at trace level is important. In this review, studies on the determination of metal-containing dithiocarbamate pesticides in different matrices are discussed. This review on the analysis of dithiocarbamate pesticides with different techniques will shed light on the studies to be carried out for the determination of these pesticides one by one in different matrices.