Continuous and Rapid Synthesis of UiO-67 by Electrochemical Methods for the Electrochemical Detection of Hydroquinone

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.

Electrochemical Synthesis and Electrocatalytic Oxygen-Evolution Performance of Two-Dimensional NiCo-BPDC Materials

Metal-organic frameworks (MOFs) have been widely studied as electrocatalysts, and the research strategy to improve their electrocatalytic oxygen evolution reaction (OER) performance is to modify their structure. In this paper, two-dimensional bimetallic MOFs were constructed to improve electrocatalytic OER performance. Using a mild electrochemical method with Ni and Co as metal sources and 4, 4 '-biphenyl dicarboxylic acid (H2BPDC) as ligand, two-dimensional NiCo-BPDC was synthesized and then deposited on a carbon cloth electrode. The results show that NiCo-BPDC/CC possessed a low overpotential of 356 mV at a current density of 20 mA cm-2 with a small Tafel slope of 86 mV dec-1 in 1.0 M KOH solution. The two-dimensional NiCo-BPDC exhibits excellent electrocatalytic OER performance because the coordination of Ni and Co in the material and the interaction of the two-dimensional materials provide a large electrochemically active surface area and expose more metal active sites for OER, thus improving the reaction efficiency and indicating NiCo-BPDC as potential OER electrocatalyst.

A porous Ti-based metal-organic framework for CO2 photoreduction and imidazole-dependent anhydrous proton conduction

The anhydrous proton conductivity of Im@IEF-11 resulting from the integration of imidazole and porous IEF-11 has been investigated, and the highest proton conductive value can reach up to 7.64 × 10^-2 S cm^-1. Furthermore, IEF-11 is also developed to reduce CO₂ due to its reasonable structure and suitable energy band, and its CO formation rate is 31.86 μmol g^-1 h^-1.

N, S dual doped mesoporous carbon assisted simultaneous electrochemical assay of emerging water contaminant hydroquinone and catechol

Heteroatom doped mesoporous carbon materials are promising catalysts for the electrochemical sensing application. Herein, we report highly efficient dual heteroatom-doped hexagonal mesoporous carbon (MC) derived from Santa Barbara Amorphous-15 (SBA-15) hard template for the detection of phenolic isomers. The synthesis involves dopamine hydrochloride (DA)/thiophene complex, which helps to attain perfectly retained N and S dual doped mesoporous carbon (NS-MC) framework. NS-MC exhibits higher surface area (951 m² g^-1) as well as higher pore volume (0.12 cm³ g^-1) with huge graphitic, pyridinic and thiophenic defective sites which facilitates the well-resolved simultaneous electrochemical detection of phenolic isomers hydroquinone (HQ) and catechol (CC). Our results demonstrate that as-synthesized NS-MC material had a LOD of 0.63 μM and 0.29 μM for HQ and CC, respectively. From the calibration curve, sensitivities of proposed sensor were found to be 9.44, 2.71 μA μM^-1 cm^-2 and 20.80, 10.02 μA μM^-1 cm^-2 for HQ and CC, respectively with good linear ranges of 10-45 μM and 45-115 μM for HQ; 2-16 μM and 16-40 μM for CC. The NS-MC modified electrode exhibited good selectivity over various possible interferences. The present investigation reveals that the proposed NS-MC material is a promising metal-free catalyst which boosted to electrochemically detect both HQ and CC, present in the municipal tap as well as natural river stream water samples.

Bifunctional Sensors Based on Phosphomolybdates for Detection of Inorganic Hexavalent Chromium and Organic Tetracycline

Exploring effective sensors for detecting possible hazards in a water system are greatly significant. This work proposed a strategy for stable and effective bifunctional sensors via incorporating hourglass-type phosphomolybdates into metal-organic fragments to construct a high-dimensional framework. Two hourglass-type phosphomolybdate-based electrochemical sensors toward heavy metal ion Cr(VI) and tetracycline (TC) detection were designed with the formula [Co^II₂(H₂O)₄Na^I₂][Co^II(Hbpe)][Na^I(bpe)_1.5]{Co^II[P^V₄Mo^V₆O₃₁H₆]₂}·9H₂O (1) and [Co^II(H₂O)₄Na^I₃][Co^II(Hbpe)][Co^II(bpe)]{Co^II[P^V₄Mo^V₆O₃₁H₆]₂}·9H₂O (2) [bpe = 1,2-di(4-pyridyl)ethylene]. Structural analysis showed that hybrids 1 and 2 possess three-dimensional POM-supported network features with favorable stability and exhibit reversible redox properties. Experiments found that this kind of hybrids as efficient sensors have excellent electrochemical performance toward Cr(VI) detection with high sensitivities of 0.111 μA·μM^-1 for 1 and 0.141 μA·μM^-1 for 2, fast response time of 1 s, and low detection limits of 30 nM for 1 and 27 nM for 2, which far meet the standard of WHO for drinking water. Moreover, hybrids 1-2 also exhibit fast responses to TC detection with sensitivities of 0.0073 and 0.022 μA·mM^-1 and detection limits of 0.426 and 0.084 mM. This work offers a novel strategy for the purposeful design of efficient POM-based electrochemical sensors for accurate determination of contaminants in a practical water system.

Facile Green Approach for Developing Electrochemically Reduced Graphene Oxide-Embedded Platinum Nanoparticles for Ultrasensitive Detection of Nitric Oxide

Nitric oxide (NO) plays a crucial and important role in cellular physiology and also acts as a signaling molecule for cancer in humans. However, conventional detection methods have their own limitations in the detection of NO at low concentrations because of its high reactivity and low lifetime. Herein, we report a strategy to fabricate Pt nanoparticle-decorated electrochemically reduced graphene oxide (erGO)-modified glassy carbon electrode (GCE) with efficiency to detect NO at a low concentration. For this study, Pt@erGO/GCE was fabricated by employing two different sequential methods [first GO reduction followed by Pt electrodeposition (SQ-I) and Pt electrodeposition followed by GO reduction (SQ-II)]. It was interesting to note that the electrocatalytic current response for SQ-I (184 μA) was ∼15 and ∼3 folds higher than those of the bare GCE (11.7 μA) and SQ-II (61.5 μA). The higher current response was mainly attributed to a higher diffusion coefficient and electrochemically active surface area. The proposed SQ-I electrode exhibited a considerably low LOD of 52 nM (S/N = 3) in a linear range of 0.25-40 μM with a short response time (0.7 s). In addition, the practical analytical applicability of the proposed sensor was also verified.