Determination of 2,4-dichlorophenol in water samples using a chemiluminescence system consisting of graphene quantum dots, rhodamine B and cerium(IV) ion

Fast and effective assessment of 4-chlorophenol as a persistent organic pollutant (POP) using a multi-walled carbon nanotube-modified screen-printed carbon electrode (C/MWCNT-COOH/SPCE)

In this study, a rapid, precise, and targeted electroanalytical method was developed for the trace determination of 4-chlorophenol (4-CP). The study reports the use of cyclic voltammetry (CV) to characterize the electrochemical response of 4-CP and the optimization of differential pulse voltammetry (DPV) settings for its sensitive quantification. Screen-printed carbon electrodes (SPCEs) were selected for the sensitive detection of 4-CP using DPV. The incorporation of multi-walled carbon nanotubes functionalized with carboxyl groups (MWCNT-COOH) as a modifier on the working SPCE significantly enhances the electrode's performance, resulting in a 5-fold increase in sensitivity compared to that of the unmodified SPCE. Under optimal conditions, oxidation peak current exhibited a detection limit of 9.2 nM and was proportional to 4-CP concentration in the range of 0.01-1.3 μM. Additionally, the constructed sensor demonstrated high stability, high selectivity, good reproducibility, and excellent feasibility. These findings suggest that the C/MWCNT-COOH/SPE offers a simple, rapid, and cost-effective method for the prospective online assessment of 4-CP in various samples with different matrices.

Cu doped ceria nanoparticles- rhodamine B as a novel chemiluminescence system and its application for nitrite detection in water and food samples

Fe, Ni, and Cu doped ceria nanoparticles (CeNPs) were prepared with a simple and one-pot hydrothermal synthesis method. We investigated the chemiluminescence (CL) interaction between these NPs and rhodamine B (Rh B) and found that the highest CL intensity was related to the Rh B- Cu doped CeNPs. We assigned that to the higher catalytic property of Cu doped NPs compared to the others. Cu doped CeNPs have been applied for the first time as a catalyst in chemiluminescence reactions. Rh B- Cu doped CeNPs reaction was introduced as a novel CL system, and its mechanism was studied. Considering the sensitivity, simplicity, portability, and rapidness of the CL methods, we applied the introduced reaction to the development of a CL sensor for nitrite monitoring. In the presence of nitrite, the CL intensity of the system decreased, and there was a linear relationship between the CL intensity and nitrite concentration in the range 0.5-100 µM. Based on this fact, a sensitive and selective CL sensor with the detection limit of 0.2 µM was established for nitrite detection in various food and water samples.

Unveiling carcinogenic pollutant levels in environmental water samples through facile fabrication of gold nanoparticles on sulfur-doped graphitic carbon nitride

Extensive utilization of pesticides and herbicides to boost agricultural production increased the environmental health risks, which can be mitigate with the aid of highly sensitive detection systems. In this study, an electrochemical sensor for monitoring the carcinogenic pesticides in the environmental samples has been developed based on sulfur-doped graphitic-carbon nitride-gold nanoparticles (SCN-AuNPs) nanohybrid. Thermal polycondensation of melamine with thiourea followed by solvent exfoliation via ultrasonication leads to SCN formation and electroless deposition of AuNPs on SCN leads to SCN-AuNPs nanohybrid synthesis. The chemical composition, S-doping, and the morphology of the nanohybrid were confirmed by various microscopic and spectroscopic tools. The as-synthesized nanohybrid was fabricated with glassy carbon (GC) electrode for determining the carcinogenic hydrazine (HZ) and atrazine (ATZ) in field water samples. The present sensor exhibited superior electrocatalytic activity than GC/SCN and GC/AuNPs electrodes due to the synergism between SCN and AuNPs and the amperometric studies showed the good linear range of detection of 20 nM-0.5 mM and 500 nM-0.5 mM with the limit of detection of 0.22 and 69 nM (S/N = 3) and excellent sensitivity of 1173.5 and 13.96 μA mM-1 cm-2 towards HZ and ATZ, respectively. Ultimately, the present sensor is exploited in environmental samples for monitoring HZ and ATZ and the obtained results are validated with high-performance liquid chromatography (HPLC) technique. The excellent recovery percentage and close agreement with the results of HPLC analysis proved the practicability of the present sensor. In addition, the as-prepared materials were utilized for the photocatalytic degradation of ATZ and the SCN-AuNPs nanohybrid exhibited higher photocatalytic activity with the removal efficiency of 93.6% at 90 min. Finally, the degradation mechanism was investigated and discussed.

Fast, selective, and sensitive detection of 2,4-dichlorophenol by an imprinted polymer functionalized core-offset U-shaped fiber sensor

Pollution monitoring in waterways and oceans is often performed in a laboratory on samples previously taken from the environment. The integration of molecular imprinting polymer nanoparticles (MIP-NPs) with a novel, to the best of our knowledge, fiber optic interferometer allowed a fast and selective detection of water pollutant 2,4-Dichlorophenol (2,4-DCP). The proposed sensor with an increased surface-to-volume ratio of MIP-NPs provided an enhanced sensitivity of 17.1 nm/µM and a wide operating range of 0.1-100 µM. It showed a highly repeatable performance and potential to measure up to nM concentrations. This integrated technique is suitable for the development of compact, stable, precise, and sensitive biosensors for online monitoring and remote chemical sensing applications.

CuO nanoleaf and β-cyclodextrin functionalized reduced graphene oxide: a highly selective and sensitive electrochemical sensor for the simultaneous detection of 2-chlorophenol and 2, 4-dichlorophenol

Chlorophenols are considered priority pollutants and are harmful to humans and the environment; consequently, sensitive, and selective detection of chlorophenols is very significant. In the present article, a glassy carbon electrode was modified by copper oxide nanoleaves, β-cyclodextrin, and reduced graphene oxide through an electrostatic self-assembly method (CuO NLs-β-CD-rGO-GCE) and successfully utilized for the selective and sensitive detection of 2-chlorophenol (2-CP) and 2,4-dichlorophenol (2,4-DCP). The modified electrodes were characterized by using SEM, EDX, ATR-FTIR, CV, and EIS. The electrochemical behaviour of 2-CP and 2,4 DCP on different modified electrodes was investigated by cyclic voltammetry whereas differential pulse voltammetry was used for the quantitative determination of chlorophenols. Under the optimized conditions, the anodic peak current displayed a good linear relationship to concentration in the range of 5 to 50 μM for 2-CP and 5 to 30 μM for 2,4-DCP, with detection limits of 0.22 nM and 0.52 nM, respectively. Moreover the proposed sensor exhibited good reproducibility, high sensitivity, and long term stability. To further study the practical applicability of the newly developed sensor, the modified electrode was successfully used to determine 2-CP and 2,4-DCP in a water sample with good recovery.

Rapid and sensitive online determination of ozone via gas-liquid chemiluminescence synergistically enhanced by graphene quantum dots and Triton X-100

The determination of the ozone concentration in the atmosphere is an urgent need but most current methods are limited by large-scale equipment or complex procedures. Herein, a gas-liquid chemiluminescence (GL-CL) assay based on a portable GL-CL detector platform was reported for the fast and sensitive online determination of ozone. Graphene quantum dots (GQDs) and Triton X-100 were employed to synergistically enhance the CL intensity of chromotropic acid (CA)-ozone. The increase was about seven-fold upon the addition of GQDs and Triton X-100. The potential enhancement mechanism was also investigated. The speculated CL enhancement mechanism was that GQDs could catalyze dissolved oxygen in the CA solution to produce more free radicals in the presence of UV-light, and these radicals converted CA into more active compounds that could react with ozone and emit photons. The free radicals, active compounds and luminophores were protected from water quenching by micelles produced by dissolving Triton X-100 in water and as a result, CL was markedly enhanced. Most importantly, the response time of the GL-CL detector platform towards ozone was less than 0.5 s. Based on this outcome, a GL-CL assay for detecting atmospheric ozone was successfully developed with a linear range from 0.1 to 150 ppbv and a detection limit of 0.02 ppbv. This work provides a rapid and sensitive method for the online measurement of ozone, and has great potential in environmental applications; the potential applications of GQDs and Triton X-100 in the field of GL-CL have also been highlighted.

Recent Advances in Nanomaterials Based Molecularly Imprinted Electrochemical Sensors

Nanotechnology and molecular imprinting both are omnipresent in the modern scientific world. Molecular recognition in the biological systems was mimicked to an extreme extent with its difficulties through molecular imprinting. Solving the problems related to this mimicking was the goal of science and technology. Some challenges like difficulties with the imprinting of protein, poor compatibility with aqueous environments, template leakage, and heterogeneous populations of binding sites in the polymers that contribute to a high level of nonspecific binding sites were addressed with recent advancement in the modern era. These issues were solved later with nano level instrumentations and inventions. Different types of nanomaterials were employed for this research on molecular recognition through MIPs to enhance selectivity, sensitivity and stability to specific systems such as sensors. This review paper attempts to give all the recent advances in molecular imprinting and the potential of nanomaterials in electrochemical sensors.

Single-Piece All-Solid-State Potential Ion-Selective Electrodes Integrated with Molecularly Imprinted Polymers (MIPs) for Neutral 2,4-Dichlorophenol Assessment

A novel single-piece all-solid-state ion-selective electrode (SC/ISE) based on carbon-screen printed is introduced. Polyaniline (PANI) is dissolved in a membrane cocktail that contains the same components used for making a conventional ion-selective polyvinyl chloride (PVC) matrix membrane. The membrane, having the PANI, is directly drop-casted on a carbon substrate (screen-printed-carbon electrode). PANI was added to act as an intermediary between the substrate and the membrane for the charge transfer process. Under non-equilibrium sensing mechanism, the sensors revealed high sensitivity towards 2,4-dichlorophenol (DCP) over the linearity range 0.47 to 13 µM and a detection limit 0.13 µm. The selectivity was measured by the modified separate solution method (MSSM) and showed good selectivity towards 2,4-DCP over the most commonly studied ions. All measurements were done in 30 mm Tris buffer solution at a pH 5.0. Using constant-current chronopotentiometry, the potential drift for the proposed electrodes was checked. Improvement in the potential stability of the SPE was observed after the addition of PANI in the sensing membrane as compared to the corresponding coated-wire electrode (membrane without PANI). The applicability of the sensor has been checked by measuring 2,4-DCP in different water samples and the results were compared with the standard HPLC method.

A highly selective chemiluminescent probe for the detection of chromium(VI)

In present work, rhodamine B hydrazide and rhodamine 6G hydrazide were synthesized and the chemiluminescence performance has been investigated. Based on the chemiluminescence of rhodamine 6G hydrazide‑chromium(VI), a selective and sensitive method for the direct detection of chromium(VI) was developed. The chemiluminescence intensity was linearly related to the concentration of chromium(VI) in the range of 2.60×10^-8-8.00×10^-6mol/L with a correlation coefficient of r=0.998 and a detection limit of 1.4×10^-8mol/L (S/N=3). The results indicated rhodamine 6G hydrazide was an excellent chemiluminescent probe for chromium(VI) without reduction of chromium(VI) to chromium(III). A possible mechanism of CL emission was also suggested.

Recent progress in two-dimensional inorganic quantum dots

This review critically summarizes recent progress in the categories, synthetic routes, properties, functionalization and applications of 2D materials-based quantum dots (QDs).

Recent advances in chemiluminescence based on carbonaceous dots

Herein, a broad overview concerning the most recent progress of carbon dots (CDs) in chemiluminescence (CL) as well as the mechanisms and applications are presented. CDs have excellent optical and electronic properties and are very important advancement in the fast growing domain of nanotechnology. CDs enhance the ultraweak CL of different systems. The mechanisms and applications of these enhanced CL reactions are discussed. It is worthy to note that CDs participate in CL reactions as catalysts, energy acceptors or are directly involved in redox reactions with radicals in CL systems. Sometimes, these processes taking place simultaneously to enhance CL intensity. In this report, recent advances in CD based CL are comprehensively summarized and their applications in detection of various reagents and biological molecules are reviewed. The challenges and future prospects of this field are also discussed.

Recent advances in nanomaterials for water protection and monitoring

Nanomaterials (NMs) for adsorption, catalysis, separation, and disinfection are scrutinized. NMs-based sensor technologies and environmental transformations of NMs are highlighted.