Electro-oxidative determination of aromatic amine (o-phenylenediamine) using organic-inorganic hybrid composite

Capsulation of red emission chromophore into the CoZn ZIF as nanozymes for on-site visual cascade detection of phosphate ions, o-phenylenediamine, and benzaldehyde

Accurate on-site profiling of the pollutants is of vital significance for estimating environmental pollution. Herein, we propose a paper-based fluorescence-sensing system to precisely report the level of multiple pollutants. A high-performance fluorescence-sensor for apparatus-free and visual on-site tandem precisely reporting phosphate ions (Pi), o-phenylenediamine (OPD), and benzaldehyde (BA) levels have been fabricated successfully by introducing synthesized red emission (>600 nm) fluorescent chromophore 10-(diethylamino)-3-hydroxy-5,6-dihydrobenzo [c]xanthen-12-ium (HTD) into the environment of CoZn zeolitic imidazolate framework (CoZn ZIF) by a simple stirring method. CoZn ZIF@HTD with the bimetallic nodes not merely provided main Zn²⁺ sites for specific recognition of Pi to generate an enhanced red fluorescent optical signal, Co³⁺/Co²⁺ exhibited excellent peroxidase-like activity for the catalytic oxidation of OPD substrate in the presence of H₂O₂ resulting in color changing from red to yellow. Subsequently, the obvious yellow fading of the OPDox species took place with the addition of BA. By virtue of the sensitively visual tandem detection of Pi, OPD, and BA, the sensor can be applied to real wastewater samples. Meanwhile, this fluorescent sensor was further adopted for practical application in confocal cell imaging and security inks. Overall, this work established a fluorescent sensing system with integrated multifunctional applications for environmental and biological samples, implying the great potential for simultaneous real-time cascade detection of various important pollutants with the merit of low-cost, time-saving, and easy-to-use.

N-substituted CQDs impregnated by Fe3O4 heterostructure: Bifunctional catalyst for electro-catalytic and photo-catalytic detection of an environmental hazardous organic pollutant

ortho-Nitroaniline (o-NA) compounds are deemed to be a strongly toxic pollutant in nature and potentially carcinogenic; however, they are frequently utilized to synthesize dyes, pesticides, medicines, fungicides, pigments, and other organic chemicals. Their detection in an aqueous medium is fundamentally required to avoid the potential hazardous being created by these compounds. In this study, a novel sensor based on an Iron oxide (Fe3O4) containing highly dispersed nitrogen-doped carbon quantum dots (N-CQDs@Fe3O4 NFs) was demonstrated for the electrochemical detection of o-NA using differential pulse voltammetry (DPV) and cyclic voltammetry (CV) techniques. N-CQDs@Fe3O4 NFs were synthesized by hydrothermal method and studied by various analytical and spectroscopy techniques, which collectively reveal that the as-prepared composite has superior physical and chemical properties. The DPV study indicated that the o-NA sensor had a good limit of detection, linear range, and sensitivity in the range of 1.2 nm, 0.03-386.84 μM, and 36.5575 μA μM-1 cm-2, respectively, along with the sensor showed superior sensitivity when compared to the previously reported modified electrodes. Further, N-CQD/Fe3O4 NFs worked as heterogeneous catalysts for the photocatalytic reduction of o-NA to o-phenylenediamine (o-PD) in an aqueous medium. The reaction was examined under UV-Visible spectroscopy, and the complete photocatalytic reduction was observed for the N-CQD/Fe3O4 NFs in about 6 min with 96% as compared to other control samples; thus, authenticating the superiority of the synthesized composite in rendering the real-time applications.

Rapid and sensitive detection of selective 1,2-diaminobenzene based on facile hydrothermally prepared doped Co3O4/Yb2O3 nanoparticles

In this approach, the performance of a newly developed sensor probe coated with low-dimensional Co₃O₄/Yb₂O₃ nanoparticles (NPs) in rapidly detecting 1,2-diaminobenzene was evaluated by an electrochemical technique. The sensor probe was fabricated by depositing a very thin layer consisting of synthesized Co₃O₄/Yb₂O₃ NPs using a 5% Nafion conducting binder onto a glassy carbon electrode (GCE). The facile hydrothermally prepared Co₃O₄/Yb₂O₃ NPs were totally characterized by conventional methods such as FTIR, UV-vis, TEM, XPS, EDS, and XRD analyses. The fabricated chemical sensor probe was found to exhibit long-term activity, stability in electrochemical response, good sensitivity (5.6962 μAμM^-1cm^-2), lowest detection limit (0.02±0.001 pM), and broad linear dynamic range (0.1 pM to 0.01 mM). The observed performances suggest that the newly introduced sensor could play an efficient role in detecting 1,2-diaminobenzene especially in healthcare and environmental applications on a broad scale.

The fabrication of a chemical sensor with PANI-TiO2 nanocomposites

In this study, conjugated conducting polyaniline was fabricated onto titania nanoparticles (PANI-TiO₂ NPs) using a microwave-accelerated reaction system. The synthesized nanoparticles were characterized using the techniques of electron microscopy (e.g., FE-SEM and TEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), and ultraviolet-visible (UV-Vis) spectrometry. An ultrasensitive sensor using the electrochemical (I–V) approach was fabricated using a thin film of PANI-TiO₂ NPs on a glassy carbon electrode (GCE), and it was found to be selective towards 1,2-diaminobenzene (1,2-DAB) in a buffer phase. From current versus concentration studies, the calibration curve was plotted to estimate the sensor's analytical parameters. The highest sensitivity (19.8165 μA μM⁻¹ cm⁻²) and lowest detection limit (0.93 ± 0.05 pM) were obtained from the electrochemical assessment by applying a signal-to-noise ratio of 3. A linear calibration plot was attained over a large range of concentration (LDR: 1.0 pM to 0.01 mM). The selective 1,2-DAB sensor was found to be efficient and reproducible in performance, yielding significant results with a fast response time (12.0 s). Therefore, the overall results of the 1,2-DAB chemical sensor suggest that this detection approach might be an easy way to develop an efficient electrochemical sensor for the protection of the environment as well as for use in the healthcare field on a broad scale.

The conjugated conducting polyaniline was fabricated onto PANI-TiO₂ nanoparticles prepared by microwave-accelerated reaction system for the development an efficient and sensitive electrochemical sensor to protect the environment and healthcare fields in a broad scale.