Synthesis of a New Bimetallic Re(I)–NCS–Pt(II) Complex as Chemodosimetric Ensemble for the Selective Detection of Mercapto-Containing Pesticides

Electrochromic behavior of fac-tricarbonyl rhenium complexes

Tricarbonyl rhenium complex shows good electrochromic performance with a colored stage of green, rapid response and good switching stability.

Recent Advances on Detection of Insecticides Using Optical Sensors

Insecticides are enormously important to industry requirements and market demands in agriculture. Despite their usefulness, these insecticides can pose a dangerous risk to the safety of food, environment and all living things through various mechanisms of action. Concern about the environmental impact of repeated use of insecticides has prompted many researchers to develop rapid, economical, uncomplicated and user-friendly analytical method for the detection of insecticides. In this regards, optical sensors are considered as favorable methods for insecticides analysis because of their special features including rapid detection time, low cost, easy to use and high selectivity and sensitivity. In this review, current progresses of incorporation between recognition elements and optical sensors for insecticide detection are discussed and evaluated well, by categorizing it based on insecticide chemical classes, including the range of detection and limit of detection. Additionally, this review aims to provide powerful insights to researchers for the future development of optical sensors in the detection of insecticides.

Selective Detection of Methomyl Pesticide by a Catalytic Chemosensing Assay

The catalytic chemosensing assay (CCA), a new indicator displacement assay, was developed for selective detection of methomyl, a highly toxic pesticide. Trimetallic complex {[Fe^II (dmbpy)(CN)₄ ]-[Pt^II (DMSO)Cl]₂ -[Ru^II (bpy)₂ (CN)₂ ]} (1; dmbpy=4,4'-dimethyl-2,2'-bipyridine, bpy=2,2'-bipyridine) was synthesized as a task-specific catalyst to initially reduce and degrade methomyl to CH₃ SH/CH₃ NH₂ /CH₃ CN/CO₂ . The thus-produced CH₃ SH interacts with the trimetallic complex to displace the cis-[Ru^II (bpy)₂ (CN)₂ ] luminophore for monitoring. Other pesticides, including organophosphates and similar carbamate pesticides, remained intact under the same catalytic conditions; a selective sensing signal is only activated when 1 recognizes methomyl. Furthermore, 1 can be applied to detect methomyl in real water samples. In the luminescent mode of the assay, the method detection limit (MDL) of 1 for methomyl (LD₅₀ =17 mg kg^-1 ) was 1.12 mg L^-1 .

Fluorescence tuning behavior of carbon quantum dots with gold nanoparticles via novel intercalation effect of aldicarb

A simple, sensitive and rapid fluorometric system has been developed for the detection of aldicarb (ALD) based on inner filter effect (IFE) of gold nanoparticles (AuNPs) on fluorescence (FL) intensity of carbon quantum dots (CQDs). Addition of CQDs into AuNPs, gets them aggregated due to electrostatic interaction resulting in quenching the FL intensity of CQDs. With addition of ALD into AuNPs, an intercalated layer was formed between them through Au-N and Au-S bond which reduced IFE of AuNPs. Hence, CQDs FL intensity recovered along with ALD concentration varying between 3.8 and 76 µg L^-1 with lower detection limit of 3.02 µg L^-1. The spiked real samples study in fruits, vegetables and soft drinks revealed that this sensing platform was repeatable and effective for real samples. The validation of proposed method indicates that the ALD sensor is promising and adaptable for everyday on spot environment and food safety monitoring.

One-Step Synthesized ZnO np-Based Optical Sensors for Detection of Aldicarb via a Photoinduced Electron Transfer Route

Pesticides are used in agriculture for crop production enhancement by controlling pests, but they have acute toxicological effects on other life forms. Thus, it becomes imperative to detect their concentration in food products in a fast and accurate manner. In this study, ZnO nanoparticles (ZnO nps) have been used as optical sensors for the detection of pesticide Aldicarb via a photoinduced electron transfer (PET) route. ZnO nps were synthesized directly by calcining zinc acetate at 450, 500, and 550 °C for 2 h. ZnO nps were characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and UV-vis absorption and photoluminescence (PL) spectroscopies to study the phase, crystallinity, shape, morphology, absorbance, and fluorescence of the prepared ZnO nps. XRD and Raman studies confirmed the crystalline nature of ZnO nps. The average crystallite size obtained was 13-20 nm from the XRD study. The SEM study confirmed spherical-shaped ZnO nps with average sizes in the range of 70-150 nm. The maximum absorbance was obtained in the 200-500 nm regions with a prominent peak absorbance at 372 nm from UV-vis spectra. The corresponding band gap for ZnO nps was calculated using Tauc's plots and was found to be 3.8, 3.67, and 3.45 eV for the 450, 500, and 550 °C calcined samples, respectively. The fluorescence spectra showed an increase in the intensity along with the increase in the size of ZnO nps. The ZnO nps (samples calcined at 500 and 550 °C) exhibited a response toward Aldicarb, owing to their pure phase and higher PL intensity. Both the samples showed systematic detection of Aldicarb in the range of 250 pM to 2 nM (500 °C) and 250 pM to 5 nM (550 °C). Among the various quenching mechanisms, PET was found to be the dominant process for the detection of Aldicarb. This method can be used for the detection of Aldicarb in real (food) samples using a portable fluorimeter.

Bimetallic-based food sensors for meat spoilage: Effects of the accepting metallic unit in Fe(II)CNMA (MA = Pt(II) or Au(I)) on device selectivity and sensitivity

Technologies for monitoring meat spoilage are important to ensuring consumer safety. As dimethyl sulfide (DMS) is a reliable marker for meat freshness, sensitive and selective DMS sensors are of great interest. Herein, two trinuclear cyano-bridged bimetallic donor-acceptor ensembles, Fe^II(bpy)₂(CN)₂-[Pt^II(DMSO)Cl₂]₂ (1) and Fe^II(bpy)₂(CN)₂-[Au^ICl]₂, were synthesized, and corresponding solid-supported sensors were fabricated to determine the effect of the acceptor metal (M_A) on DMS detection. Changing M_A from Au^I to Pt^II improved the sensitivity and selectivity owing to changes in the relative thermodynamic stabilities of the complex and M_A-DMS adduct. When applied to real meat samples, 1 exhibited a linear spectroscopic response to DMS, even in the presence of interfering compounds, with a method detection limit of 1.0 ppm. The total bacteria count and gas chromatography-mass spectrometry results revealed that the spectroscopic signal generated by 1 correlated with the microbial growth level and DMS concentration during meat spoilage.

A poly(thymine)-templated fluorescent copper nanoparticle hydrogel-based visual and portable strategy for an organophosphorus pesticide assay

Since fluorescence assays with high sensitivity for organophosphorus pesticides (OPs) are urgently required to protect the ecosystem and prevent disease, an environmentally friendly and label-free fluorescent probe is desirable. Herein, a poly-thymine30 DNA-templated copper nanoparticle (poly T30-Cu NPs) hydrogel fluorescent probe was explored for the construction of an OPs sensing platform via tyrosinase (TYR) enzyme-controlled quenching. Initially, TYR can efficiently quench the fluorescence of poly T30-Cu NPs; however, when OPs are mixed with a certain amount of TYR, the fluorescence of poly T30-Cu NPs can be recovered. Based on this phenomenon, we designed a functionalized hydrogel based on poly T30-Cu NPs for portable and visible detection of OPs with high sensitivity and selectivity. This proposed fluorescent platform was demonstrated to enable rapid detection of OPs (paraoxon as the model analyte) and provide excellent sensitivity with a detection limit of 3.33 × 10-5 ng μL-1 and a linear range of 1.0 × 10-4-1.0 ng μL-1. The fluorescent probe does not require a sophisticated synthesis and labeling process; in addition, it is environmentally friendly because of the presence of a biotemplate of DNA and biocompatible copper. Moreover, the functional hydrogel combines the features of portability, visualization, fast signal response and environmental anti-interference that make the proposed strategy more feasible in complex practical detection.

Template protection of gold nanoclusters for the detection of organophosphorus pesticides

A simple and economic fluorescence sensing method has been developed. This method based on trypsin digestion of the template of BSA-AuNCs for the sensitive detection of OPs.

Catalyst displacement assay: a supramolecular approach for the design of smart latent catalysts for pollutant monitoring and removal

Latent catalysts can be tuned to function smartly by assigning a sensing threshold using the displacement approach for targeted analytes. Three cyano-bridged bimetallic complexes were synthesized as "smart" latent catalysts through the supramolecular assembly of different metallic donors [FeII(CN)6]4-, [FeII(tBubpy)(CN)4]2-, and FeII(tBubpy)2(CN)2 with a metallic acceptor [CuII(dien)]2+. The investigation of both their thermodynamic and kinetic properties on binding with toxic pollutants provided insight into their smart off-on catalytic capabilities, enabling us to establish a threshold-controlled catalytic system for the degradation of pollutants such as cyanide and oxalate. With these smart latent catalysts, a new catalyst displacement assay (CDA) was demonstrated and applied in a real wastewater treatment process to degrade cyanide pollutants in both domestic (level I, untreated) and industrial wastewater samples collected in Hong Kong, China. The smart system was adjusted to be able to initiate the catalytic oxidation of cyanide at a threshold concentration of 20 μM (the World Health Organization's suggested maximum allowable level for cyanide in wastewater) to the less harmful cyanate under ambient conditions.

An on–off–on gold nanocluster-based fluorescent probe for sensitive detection of organophosphorus pesticides

In this study, a highly sensitive fluorescent probe based on bovine serum protein-protected gold nanoclusters (BSA-AuNCs) was developed for the determination of organophosphorus pesticides (OPs).

Fluorescent Chemosensors for Selective and Sensitive Detection of Phosmet/Chlorpyrifos with Octahedral Ni(2+) Complexes

The hexadentate ligands H2L1-L3 with mixed S, N, O donor sites and possessing substituents having either "no" or electron-releasing/withdrawing nature at terminal ends are synthesized. The ligands H2L1-L3 were tested for binding with library of metal ions, wherein maximum efficiency was observed with Ni(2+), and it motivated us to prepare the Ni(2+) complexes. The ligand H2L1 underwent deprotonation and formed binuclear complex when interacted with Ni(2+) as evident from its crystal structure. The H2L2 and H2L3 having electron-withdrawing/electron releasing groups, respectively, were also deprotonated; however, they afforded mononuclear complexes with Ni(2+) ion. This signifies the importance of steric parameters instead of electronic factors in these particular cases. Impressed by differential behavior of complexes of H2L1 and H2L2/H2L3 with Ni(2+) and their photophysical and electrochemical properties, all the metal complexes were studied for their chemosensing ability. Nowadays with increased use of organophosphate, there is alarming increase of these agents in the environment, and thus we require efficient technique to estimate the level of these agents with high sensitivity and selectivity in aqueous medium. The Ni(2+) complexes with hydrophobic nature were suspended into aqueous medium for testing them as sensor for organophosphate. The (L1)2.(Ni(2+))2 could sense phosmet with detection limit of 44 nM, whereas L2.Ni(2+) and L3.Ni(2+) exhibited the detection limits of 62 and 71 nM, respectively, for chlorpyrifos.

A highly selective on–off–on responsive lanthanide(iii) based probe for recognition of copper and hydrogen sulfide

Highly selective EuL1 was developed for the detection of Cu(ii) ions with binding constant of 74 026 ± 2899 M⁻¹ and a sensitive detection limit. The stable EuL1Cu showed a specific binding response to H₂S with detection limit of 2.7 ± 0.1 μM. Its on–off–on luminescent response was observed by alternate addition of Cu(ii) and H₂S ions.