Simultaneous electrochemical sensing of dihydroxybenzene isomers at multi-walled carbon nanotubes aerogel/gold nanoparticles modified graphene screen-printed electrode

MoS2_CNTs_aerogel-based PEDOT nanocomposite electrochemical sensor for simultaneous detection of chloramphenicol and furazolidone in food samples

Toxic intermediates in food caused by chloramphenicol (CP) and furazolidone (FZ) have gained interest in research toward their detection. Hence, fast, reliable, and accurate detection of CP and FZ in food products is of utmost importance. Here, a novel molybdenum disulfide-connected carbon nanotube aerogel/poly (3,4-ethylenedioxythiophene) [MoS2/CNTs aerogel/PEDOT] nanocomposite materials are constructed and deposited on the pretreated carbon paste electrode (PCPE) by a facile eletropolymerization method. The characterization of MoS2/CNTs aerogel/PEDOT nanocomposite was analyzed by scanning electron microscopy (SEM), cyclic voltammetry, and differential pulse voltammetry. The modified MoS2/CNTs aerogel/PEDOT nanocomposite has improved sensing characteristics for detecting CP and FZ in PBS solution. For this work, we have studied various parameters like electrocatalytic activity, the effect of scan rates, pH variation studies, and concentration variation studies. Under optimum conditions, the modified electrode exhibited superior sensing ability compared to the bare and pretreated CPE. This improvement in electrocatalytic activity can be the higher conductivity, larger surface area, increased heterogeneous rate constant, and presence of more active sites in the MoS2/CNTs aerogel/PEDOT nanocomposite. The modified electrode demonstrated distinct electrochemical sensing toward the individual and simultaneous analysis of CP and FZ with a high sensitivity of 0.701 µA. µM-1 .cm-2 for CP and 0.787 µA. µM-1 .cm-2 for FZ and a low detection limit of 3.74 nM for CP and 3.83 nM for FZ with good reproducibility, repeatability, and interferences. Additionally, the prepared sensor effectively detects CP and FZ in food samples (honey and milk) with an acceptable recovery range and a relative standard deviation below 4%.

Electrochemical Sensing Systems for the Analysis of Catechol and Hydroquinone in the Aquatic Environments: A Critical Review

Because of their unique physical, chemical, and biological characteristics, conductive nanomaterials have a lot of potential for applications in materials science, energy storage, environmental science, biomedicine, sensors/biosensors, and other fields. Recent breakthroughs in the manufacture of carbon materials, conductive polymers, metals, and metal oxide nanoparticles based electrochemical sensors and biosensors for applications in environmental monitoring by detection of catechol (CC) and hydroquinone (HQ) are presented in this review. To achieve this goal, we first introduced recent works that discuss the effects of phenolic compounds and the need for accurate, inexpensive, and quick monitoring, and then we focused on the use of the most important applications of nanomaterials, such as carbon-based materials, metals, and metal oxides nanoparticles, and conductive polymers, to develop sensors to monitor catechol and hydroquinone. Finally, we identified challenges and limits in the field of sensors and biosensors, as well as possibilities and recommendations for developing the field for better future applications. Meanwhile, electrochemical sensors and biosensors for catechol and hydroquinone measurement and monitoring were highlighted and discussed particularly. This review, we feel, will aid in the promotion of nanomaterials for the development of innovative electrical sensors and nanodevices for environmental monitoring.

Microbial synthesis of antimony sulfide to prepare catechol and hydroquinone electrochemical sensor by pyrolysis and carbonization

The application of antimony sulfide sensors, characterized by their exceptional stability and selectivity, is of emerging interest in detection research, and the integration of graphitized carbon materials is expected to further enhance their electrochemical performance. This study represents a pioneering effort in the synthesis of carbon-doped antimony sulfide materials through the pyrolysis of the mixture of microorganisms and their synthetic antimony sulfide. The prepared materials are subsequently applied to electrochemical sensors for monitoring the highly toxic compounds catechol (CC) and hydroquinone (HQ) in the environment. Via cyclic voltammetry (CV) and impedance testing, we concluded that the pyrolytic product at 700 °C (Sb-700) demonstrated the best electrochemical properties. Differential pulse voltammetry (DPV) revealed impressive separation when utilizing Sb-700/GCE for simultaneous detection of CC and HQ, exhibiting good linearity within the concentration range of 0.1-140 μM. The achieved sensitivities of 24.62 μA μM-1 cm-2 and 22.10 μA μM-1 cm-2 surpassed those of most CC and HQ electrochemical sensors. Meanwhile, the detection limits for CC and HQ were as low as 0.18 μM and 0.16 μM (S/N = 3), respectively. Additional tests confirmed the good selectivity, reproducibility, and long-term stability of Sb-700/GCE, which was effective in detecting CC and HQ in tap water and river water, with recovery rates of 100.7%-104.5% and 96.5%-101.4%, respectively. It provides a method that combines green microbial synthesis and simple pyrolysis for the preparation of electrode materials in CC and HQ electrochemical sensors, and also offers a new perspective for the application of microbial synthesized materials.

Effect of Modification of a Laccase-Based Electrochemical Biosensor with Carbon Nanotubes on Signal Separation of Dihydroxybenzene Isomers

This work describes a new electrochemical biosensor for the simultaneous determination of catechol and hydroquinone. A laccase biorecognition layer was deposited using an innovative soft plasma polymerization technique onto a multiwalled carbon nanotube (MWCNT)-modified glassy carbon electrode (GCE) to sufficiently separate catechol (CT) and hydroquinone (HQ) oxidation peaks. The electrochemical analysis carried out for MWCNTs with various morphologies was supported by density functional theory (DFT) calculations showing differences in the electronic structures of both dihydroxybenzene isomers and the MWCNTs forming the biosensor interlayer. The best biosensor peak separation and biosensor analytical parameters were observed for the device containing 75 μg of MWCNTs with a higher internal diameter. For this laccase-based biosensor, a linearity range from 0.1 to 57 μM for catechol and 0.5 to 57 μM for hydroquinone as well as a sensitivity of 0.56 and 0.54 μA/μM for catechol and hydroquinone was observed, respectively. The limit of detection (LOD) values were 0.028 and 0.15 μM for CT and HQ, respectively. This biosensor was also characterized by good selectivity, stability, and reproducibility. It was successfully applied for the quantification of contaminants in the analysis of natural water samples.

Green synthesis of Au@g-C3N4 nanocomposite using Hyssopus officinalis extract and its sensing application for vortioxetine determination

Herein, we introduce a stable and green Au@g-C3N4 nanocomposite as a selective electrochemical sensor for vortioxetine (VOR) determination. The electrochemical behavior of VOR on the developed electrode was investigated through cyclic voltammetry (CV), differential pulse voltammetry (DPV), electrochemical impedance spectroscopy (EIS), and chronoamperometry. The Au@g-C3N4 nanocomposite was thoroughly observed by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), Raman spectroscopy, and scanning electron microscopy. The Au@g-C3N4 nanocomposite had a higher conductivity and a narrower band gap than pure g-C3N4, causing higher electrochemical activity for VOR detection. Moreover, Au@g-C3N4 on the glassy carbon electrode (Au@g-C3N4/GCE) monitored a low level of VOR with high efficiency and low interference as an environmentally friendly processing approach. Interestingly, the as-fabricated sensor exhibited an ultrahigh selectivity for recognizing VOR with a detection limit (LOD) of 3.2 nM. Furthermore, the developed sensor was applied to determine VOR in pharmaceutical and biological samples, which indicated a high selectivity in the presence of interferences. This study suggests new insights into the phytosynthesis synthesis of nanomaterials with excellent biosensing applications.

Bacterial enzymatic degradation of recalcitrant organic pollutants: catabolic pathways and genetic regulations

Contamination of soil and natural water bodies driven by increased organic pollutants remains a universal concern. Naturally, organic pollutants contain carcinogenic and toxic properties threatening all known life forms. The conventional physical and chemical methods employed to remove these organic pollutants ironically produce toxic and non-ecofriendly end-products. Whereas microbial-based degradation of organic pollutants provides an edge, they are usually cost-effective and take an eco-friendly approach towards remediation. Bacterial species, including Pseudomonas, Comamonas, Burkholderia, and Xanthomonas, have the unique genetic makeup to metabolically degrade toxic pollutants, conferring their survival in toxic environments. Several catabolic genes, such as alkB, xylE, catA, and nahAc, that encode enzymes and allow bacteria to degrade organic pollutants have been identified, characterized, and even engineered for better efficacy. Aerobic and anaerobic processes are followed by bacteria to metabolize aliphatic saturated and unsaturated hydrocarbons such as alkanes, cycloalkanes, aldehydes, and ethers. Bacteria use a variety of degrading pathways, including catechol, protocatechuate, gentisate, benzoate, and biphenyl, to remove aromatic organic contaminants such as polychlorinated biphenyls, polycyclic aromatic hydrocarbons, and pesticides from the environment. A better understanding of the principle, mechanisms, and genetics would be beneficial for improving the metabolic efficacy of bacteria to such ends. With a focus on comprehending the mechanisms involved in various catabolic pathways and the genetics of the biotransformation of these xenobiotic compounds, the present review offers insight into the various sources and types of known organic pollutants and their toxic effects on health and the environment.

A single-atom cobalt integrated flexible sensor for simultaneous detection of dihydroxybenzene isomers

Simultaneous detection of dihydroxybenzene isomers including hydroquinone (HQ), catechol (CC), and resorcinol (RS) is significant for water quality control as they are highly toxic and often coexist. However, it is a great challenge to realize their accurate and simultaneous detection due to their similarity in structure and properties. Herein, an electrochemical flexible strip with single-atom cobalt (SA-Co/NG) was constructed through high-resolution electrohydrodynamic (EHD) printing for dihydroxybenzene isomer's simultaneous detection. Results showed that the provided SA-Co/NG strip exhibited excellent sensing performance with reliable repeatability, reproducibility, long-term stability, and flexibility. Linear ranges of 0.50-31 745 μM, 0.50-5909 μM, and 0.50-153.5 μM were achieved for HQ, CC, and RS, respectively, with a detection limit of 0.164 μM. Based on the experimental data, the mechanism concerning SA-Co/NG catalytic activity towards HQ can be deduced, starting from the combination of Co* and OH^- in water, followed by the formation of Co-OH-dihydroxybenzene, and finally leading to O-H bond dissociation to generate benzoquinone. As for CC or RS, pyridinic N or CO synergistic with a single Co atom catalyzes their oxidation. Besides, the printed flexible SA-Co/NG strip further demonstrates the accurate and simultaneous detection of HQ, CC, and RS in textile wastewater, proposing a powerful practical application.

Highly Sensitive Detection of Carcinoembryonic Antigen via an Electrochemical Platform Fabricated by AuNPs/Streptavidin/Reduced Graphene Oxide

Tumor markers are one of the important indicators for early cancer diagnosis. As a new analytical method, electrochemical immunosensing analysis has the advantages of high sensitivity, good selectivity, and rapid detection, which is of great significance for the detection of tumor markers. In this work, an AuNP/reduced graphene oxide (AuNP/rGO) composite was synthesized. We used it for electrochemical sensor fabrication with the assistance of the biotin–streptavidin protein (SA) system to further amplify the signal to achieve sensitive detection of carcinoembryonic antigen (CEA). In addition, AuNPs have been incorporated due to their good electrical conductivity and biocompatibility, which can accelerate electron transfer at the electrode interface and improve the loading capacity to capture antibodies. The fabricated AuNPs/SA/rGO has a large working surface area and high material utilization ratio, which improves the catalytic capacity of H₂O₂ reduction and effectively amplifies the current signal. The linear range of the response current signal of the sensor toward the CEA concentration is 20 fg/ml to 200 ng/ml, and the limit of detection can achieve 6.2 fg/ml. In addition, the fabricated immunosensor has good reproducibility, selectivity, and stability.

Hybridized 1D-2D MnMoO4-MXene nanocomposites as high-performing electrochemical sensing platform for the sensitive detection of dihydroxybenzene isomers in wastewater samples

Hydroquinone (HQ) and catechol (CC) are the two major dihydroxybenzene isomers, are considered one of the toxic pollutants in wastewater, which often coexisted and impede each other during sample identification. For practical analysis and simultaneous detection of HQ and CC in wastewater, we fabricate a hybrid electrochemical sensor with electrospun one-dimensional (1D) MnMoO₄ nanofibers coupled with a few-layered exfoliated two-dimensional (2D) MXene. The facilitated abundant defective edges of 1D MnMoO₄ and 2D MXene nanoarchitecture accelerated the effect of synergistic signal amplification and exhibited high electrocatalytic activity towards the oxidation of hydroquinone and catechol. MnMoO₄-MXene-GCE showed oxidation potentials of 0.102 V and 0.203 V for hydroquinone and catechol, respectively. It revealed the distinguished and simultaneous detection range of 0.101 V with a strong anodic peak current. Noteworthily, the proposed 1D-2D hybridized MnMoO₄-MXene-GCE sensor exhibited a wide linear response from 5 nM to 65 nM for hydroquinone and catechol. Moreover, it showed a low detection limit of 0.26 nM and 0.30 nM for HQ and CC with high stability, respectively. The feasible 1D-2D MnMoO₄-MXene nanocomposite-based biosensor effectively detected hydroquinone and catechol in hazardous water pollutants using the differential pulse voltammetric technique with recovery values.

Simultaneous Detection of Dihydroxybenzene Isomers Using Electrochemically Reduced Graphene Oxide-Carboxylated Carbon Nanotubes/Gold Nanoparticles Nanocomposite

An electrochemical sensor based on electrochemically reduced graphene oxide (ErGO), carboxylated carbon nanotubes (cMWCNT), and gold nanoparticles (AuNPs) (GCE/ErGO-cMWCNT/AuNPs) was developed for the simultaneous detection of dihidroxybenzen isomers (DHB) hydroquinone (HQ), catechol (CC), and resorcinol (RS) using differential pulse voltammetry (DPV). The fabrication and optimization of the system were evaluated with Raman Spectroscopy, SEM, cyclic voltammetry, and DPV. Under optimized conditions, the GCE/ErGO-cMWCNT/AuNPs sensor exhibited a linear concentration range of 1.2–170 μM for HQ and CC, and 2.4–400 μM for RS with a detection limit of 0.39 μM, 0.54 μM, and 0.61 μM, respectively. When evaluated in tap water and skin-lightening cream, DHB multianalyte detection showed an average recovery rate of 107.11% and 102.56%, respectively. The performance was attributed to the synergistic effects of the 3D network formed by the strong π–π stacking interaction between ErGO and cMWCNT, combined with the active catalytic sites of AuNPs. Additionally, the cMWCNT provided improved electrocatalytic properties associated with the carboxyl groups that facilitate the adsorption of the DHB and the greater amount of active edge planes. The proposed GCE/ErGO-cMWCNT/AuNPs sensor showed a great potential for the simultaneous, precise, and easy-to-handle detection of DHB in complex samples with high sensitivity.