Tuning the shell thickness of N-doped interconnected hollow carbon sphere for the electrochemical sensing of antibiotic drug chloramphenicol.

N-doped hollow carbon spheres (NHCSs) with different shell thicknesses are constructed using various amounts of SiO2 precursor. An interconnected framework with diminished wall thickness ensures an efficient and continuous electron transport which helps to enhance the performance of NHCS. Improvement of the electrocatalytic performance was shown in the determination of antibiotic drug chloramphenicol (CAP) due to the unique hollow thin shell morphology, ample defect sites, accessible surface area, higher surface-to-volume ratio and an synergistic effect. Boosted electrocatalytic activity of 1.5 N-doped HCS (1.5 NHCS) was applied to detect CAP with a linear range and detection limit of 1-1150 µM and 0.098 µM (n = 3), respectively, with superior storage stability and considerable sensitivity. These results suggest that the proposed work can be successfully applied to the determination of CAP in milk and water samples.

High Electrochemical Performance and Enhanced Electrocatalytic Behavior of a Hydrothermally Synthesized Highly Crystalline Heterostructure CeO2@NiO Nanocomposite.

A CeO2-based heterostructure nanocomposite has been attractive as an electrode material for energy storage and as an electrochemical sensor. In the present work, a CeO2@NiO nanocomposite was prepared by a simple hydrothermal method. The structural and morphological information on the heterostructure CeO2@NiO nanocomposite were obtained by using different characterization methods like X-ray diffraction, UV-visible, Fourier transform infrared, electron paramagnetic resonance, Raman, field-emission scanning electron microscopy, high-resolution transmission electron microscopy, energy-dispersive X-ray elemental color mapping, X-ray photoelectron spectroscopy, and thermogravimetric analysis. Compared with pristine CeO2, the heterostructure CeO2@NiO nanocomposite exhibits a higher electrochemical performance with a specific capacitance of 317 F g-1 at a current density of 1 A g-1 in a 1 M KOH electrolyte. This device demonstrates a high energy density and a power density of 11 Wh kg-1 and 750 W kg-1, respectively. Besides, it was found that CeO2@NiO/glassy carbon electrode (GCE) shows appreciable electrocatalytic activity toward NO2- oxidation. The CeO2@NiO-modified electrode displays a linear response for NO2- oxidation between 0.001 × 10-6 and 4 × 10-3 M. Apart from high sensitivity (2260 µA mM-1 cm-2), the CeO2@NiO-modified electrode also exhibits good selectivity and long-term stability for nitrite (NO2-) detection in a water real sample, and the obtained results showed excellent recovery. The encouraging electrochemical performance of the CeO2@NiO nanocomposite provides a promising approach for the development of multifunctional electrode materials for future energy storage devices and sensors.

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.

Structural and morphological tuning of Cu-based metal oxide nanoparticles by a facile chemical method and highly electrochemical sensing of sulphite.

A facile one-step chemical method is introduced for the successful synthesis of Cu2O, CuO and CuNa2(OH)4 crystal structures and their electrochemical properties were also investigated. X-ray diffraction studies revealed that these copper-based oxide nanoparticles display different crystal structures such as cubic (Cu2O), monoclinic (CuO) and orthorhombic [CuNa2(OH)4]. The microstructural information of nanoparticles was investigated by transmission electron microscopy. It shows attractive morphologies of different orientation such as rod like structure, nanobeads and well-aligned uniform nanorod for Cu2O, CuO and CuNa2(OH)4, respectively. Electrochemical sensing of sulphite (SO32-) on these three copper-based oxide modified electrodes was investigated. Among the three different crystal structures, CuO shows promising electrocatalytic activity towards oxidation of sulphite. A linear variation in peak current was obtained for SO32- oxidation from 0.2 to 15 mM under the optimum experimental condition. The sensitivity and detection limit were in the order of 48.5 µA cm-2 mM-1 and 1.8 µM, respectively. Finally, practical utility of CuO modified electrode was demonstrated for the estimation of sulphite in commercial wine samples.

Sunlight-driven enhanced photocatalytic activity of bandgap narrowing Sn-doped ZnO nanoparticles.

In this paper, we grab to utilize one of the trending techniques with efficient implications in wastewater treatment of organic pollutants, the photocatalytic degradation method shining out in the research field. Herein, tin (Sn)-doped zinc oxide (ZnO) nanoparticles (NPs) (Sn/ZnO) with different doping concentrations (1, 2, 3, 4, and 5 wt%) were synthesized via a simple co-precipitation assisted method and later subjected for their physico-chemical, morphological, and optical characterization. In addition, photocatalytic activity as the concerned study was investigated as to record the different doping levels of Sn/ZnO to examine the effect of doping concentration in relation with the degradation efficiency. We know that the optical bandgap of pure ZnO was 3.26 eV while it tends to increase slightly upon increasing the doping concentration. In the present investigation, methylene blue (MB) dye was used as a model pollutant to evaluate the photocatalytic activity of Sn/ZnO photocatalysts under natural sunlight. Varied doping concentrations of Sn/ZnO were compared with different characterization techniques while XRD analysis shows up 4-Sn/ZnO with sharp peak at (1 0 1) plane with smaller grain size in comparison to other Sn/ZnO samples. The morphological recognition depicts the hexagonal structure with smaller size for 4-Sn/ZnO which offers more active sites with improved photocatalytic activity, higher surface area for the transportation of pollutants. Fluorescence spectra results revealed that Sn dopant suppresses the charge carrier recombination. The lower intensity of PL indicated reduced recombination rate, which resulted in enhancing the photocatalytic activity. To investigate the possible mechanism, kinetics and reusability studies were performed. The 4% Sn-doped ZnO nanoparticle concentration showed highest photocatalytic activity when compared with other doping levels.

Visible light-driven photocatalytic dye degradation under natural sunlight using Sn-doped CdS nanoparticles.

Herein, cadmium sulfide (CdS) nanoparticles (NPs) and different concentrations (1-5 and 10 wt %) of Sn-doped CdS NPs were prepared by a chemical precipitation method using PVP as a capping agent. The synthesized NPs were characterized using various characteristic techniques such as XRD, SEM, TEM, Raman spectroscopy, UV-Vis, and photoluminescence to investigate structural, morphological, and optical properties. Optical band gap of CdS has been tuned by substitution of Sn with different concentrations. Pure CdS and Sn-doped CdS NPs were used for the photocatalytic degradation of methylene blue (MB) dye under direct sunlight irradiation. The photocatalytic activity of the Sn-doped CdS NPs is attributed to the interface actions between Sn and CdS, which significantly decreases the recombination of a photogenerated electron-hole pair. The degradation efficiencies were found to be 91.39% and 97.56% within 180 min for pure CdS and Sn-doped CdS NPs, respectively. Among the catalysts, 4% Sn-doped CdS NPs exhibit best photocatalytic degradation efficiency after 180 min of irradiation.

Hierarchical porous carbon derived from waste amla for the simultaneous electrochemical sensing of multiple biomolecules.

For the first time, highly porous and hierarchical carbon with high surface area (∼2430 m2 g-1) has been prepared from waste amla fruits at different carbonization temperatures viz., 700 °C, 800 °C and 900 °C by a simple and eco-friendly method for the simultaneous electrochemical sensing of biologically important compounds such as ascorbic acid (AA), dopamine (DA), uric acid (UA) and nitrite. The porous carbon materials synthesized at 700 °C, 800 °C and 900 °C are denoted as ABC-700, ABC-800 and ABC-900, respectively. The structural and morphological evaluations of as-synthesized hierarchical porous carbon are carried out with advanced tools and the existence of porous morphology is ascertained. The morphology, amorphous nature, disordered nature, surface area, pore volume, thermal stability and elemental composition of the as-prepared porous carbon are investigated by SEM, HRTEM, FT-IR, Raman, TGA, BET, XPS, EDAX and CHNS analysis. Compared with ABC-700 and ABC-900, the electrochemical sensing ability was higher in the case of ABC-800. Therefore, further electrochemical sensing studies are carried out by using ABC-800. The limit of detection for the simultaneous determination of AA, DA, UA and NO2- are 13.7 µM, 3.2 µM, 1.1 µM and 3.3 µM, respectively. The sensitivity are (0.55, 0.01), (4.73, 0.11), 0.11 and 0.57 µA cm-2 µM-1 and linear ranges are (33-166, 166-26470), (1.6-72, 82-2630), 1.6-4134 and 4.9-1184 µM, respectively for AA, DA, UA and NO2-. The porous carbon based sensor also proves reliable operational stability, long time stability, selectivity and good antifouling properties. The porous carbon based sensor was successfully applied to the practical application for the detection of these biomolecules in the real samples of urine.