A Cu-functionalized MOF and multi-walled carbon nanotube composite modified electrode for the simultaneous determination of hydroquinone and catechol

Spindle shaped Fe-Ni metal organic frameworks wrapped with f-MWCNTs for the efficacious sensing of tartrazine

A facile hydrothermal route was employed for the synthesis of iron-nickel bimetal organic frameworks (Fe-Ni bi-MOFs) and composite with an acid functionalized multi-walled carbon nanotubes (Fe-Ni MOF/f-MWCNTs) for electrochemical detection of tartrazine. The as-prepared Fe-Ni MOF/f-MWCNTs was confirmed by the several physicochemical studies. A micro spindle shaped, highly porous, and crystalline Fe-Ni MOF/f-MWCNTs was noticed. The high sensitivity and stability of Fe-Ni MOF/f-MWCNTs/GCE modified electrode was analyzed. Due to its high porosity nature, the analyte molecule effectively gets adsorbed on the modified electrode and undergo electrochemical oxidation effectively. The modified electrode exhibits low limit of detection (LOD) and limit of quantification (LOQ) as 0.04 × 10-6 mol/L and 0.13 × 10-6 mol/L towards tartrazine. These results reveal the potential applications of Fe-Ni MOF/f-MWCNTs/GCE as modified electrode material for sensitive detection of tartrazine along with its robust reproducibility, stability, and effective sensing properties.

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.

P3MOT-decorated metal-porphyrin-based zirconium-MOF for the efficient electrochemical detection of 4-nitrobenzaldehyde

A novel hybrid composite integrating conductive poly-3-methoxythiophene and PCN-222(Fe) (porphyrin-metal-organic frameworks) was synthesized using an in situ polymerization strategy. Leveraging the large specific area of MOFs and the low electrical resistance of conductive polymers, the modified electrode proved to be a promising candidate for the electrochemical detection of 4-nitrobenzaldehyde. The electrocatalytic response was measured using differential pulse voltammetry techniques and cyclic voltammetry, where the linear concentration range of analyte detection was estimated to be 0-900 μM and the detection limit was 0.233 μM with high selectivity toward the analyte. The sensor demonstrated repeatability and stability, allowing the direct electroanalytical measurement of 4-nitrobenzaldehyde in real samples with reliable recovery. This methodology expands the application of porphyrin MOFs for the electroanalytical sensing of environmental contaminants.

Fabrication of Poly (Trans-3-(3-Pyridyl)Acrylic Acid)/Multi-Walled Carbon Nanotubes Membrane for Electrochemically Simultaneously Detecting Catechol and Hydroquinone

Herein, conductive polymer membrane with excellent performance was successfully fabricated by integrating carboxylated multi-walled carbon nanotubes (MWCNTs) and poly (trans-3-(3-pyridyl) acrylic acid) (PPAA) film. The drop-casting method was employed to coated MWCNTs on the glassy carbon electrode (GCE) surface, and PPAA was then electropolymerized onto the surface of the MWCNTs/GCE in order to form PPAA-MWCNTs membrane. This enables the verification of the excellent performances of proposed membrane by electrochemically determining catechol (CC) and hydroquinone (HQ) as the model. Cyclic voltammetry experiments showed that the proposed membrane exhibited an obvious electrocatalytic effect on CC and HQ, owing to the synergistic effect of PPAA and MWCNTs. Differential pulse voltammetry was adopted for simultaneous detection purposes, and an increased electrochemical responded to CC and HQ. A concentration increase was found in the range of 1.0 × 10^-6 mol/L~1.0 × 10^-4 mol/L, and it exhibited a good linear relationship with satisfactory detection limits of 3.17 × 10^-7 mol/L for CC and 2.03 × 10^-7 mol/L for HQ (S/N = 3). Additionally, this constructed membrane showed good reproducibility and stability. The final electrode was successfully applied to analyze CC and HQ in actual water samples, and it obtained robust recovery for CC with 95.2% and 98.5%, and for HQ with 97.0% and 97.3%. Overall, the constructed membrane can potentially be a good candidate for constructing electrochemical sensors in environmental analysis.

Synchronized electrochemical detection of hydroquinone and catechol in real water samples using a Co@SnO2–polyaniline composite

The conductive composite Co@SnO₂–PANI was successfully synthesized using hydrothermal/oxidative synthesis. Using differential pulse voltammetry, a glassy carbon electrode modified with a CoSnO₂–PANI (polyaniline)-based electrochemical biosensor has been created for the quick detection of two phenolics, hydroquinone (Hq) and catechol (Cat). Differential pulse voltammetry (DPV) measurements revealed two well-resolved, strong peaks for GCE@Co–SnO₂–PANI, which corresponded to the oxidation of Hq and Cat at 275.87 mV and +373.76 mV, respectively. The oxidation peaks of Hq and Cat mixtures were defined and separated at a pH of 8.5. High conductivity and remarkable selectivity reproducibility was tested by electrochemical impedance spectroscopy, chronoamperometry, and cyclic voltammetry techniques in standard solution and real water samples. The proposed biosensor displayed a low detection limit of 4.94 nM (Hq) and 1.5786 nM (Cat), as well as a large linear range stretching from 2 × 10⁻² M to 2 × 10⁻¹ M. The real-sample testing showed a good recovery for the immediate detection of Hq (96.4% recovery) and Cat (98.8% recovery) using the investigated sensing apparatus. The synthesized biosensor was characterized by XRD, FTIR, energy dispersive spectroscopy and scanning electron microscopy.

The sensors are effectively used in the determination of Hq and Cat in a real water sample.

Dual fluorescent aptasensor for simultanous and quantitative detection of sulfadimethoxine and oxytetracycin residues in animal-derived foods tissues based on mesoporous silica

Herein, we developed a dual fluorescent aptasensor based on mesoporous silica to simultaneously detect sulfadimethoxine (SDM) and oxytetracycline (OTC) in animal-derived foods. We immobilized two types of aptamers modified with FAM and CY5 on the silica surface by base complementary pairing reaction with the cDNA modified with a carboxyl group and finally formed the aptasensor detection platform. Under optimal conditions, the detection range of the aptasensor for SDM and OTC was 3-150 ng/mL (R ² = 0.9831) and 5-220 ng/mL (R ² = 0.9884), respectively. The limits of detection for SDM and OTC were 2.2 and 1.23 ng/mL, respectively. The limits of quantification for SDM and OTC were 7.3 and 4.1 ng/mL, respectively. Additionally, the aptasensor was used to analyze spiked samples. The average recovery rates ranged from 91.75 to 114.65% for SDM and 89.66 to 108.94% for OTC, and all coefficients of variation were below 15%. Finally, the performance and practicability of our aptasensor were confirmed by HPLC, demonstrating good consistency. In summary, this study was the first to use the mesoporous silica-mediated fluorescence aptasensor for simultaneous detection of SDM and OTC, offering a new possibility to analyze other antibiotics, biotoxins, and biomolecules.