Metal-free Sulfur-doped graphitic carbon nitride-modified GCE-based electrocatalyst for the enhanced electrochemical determination of Omeprazole in Drug formulations and Biological Samples.

This study presents a novel sulfur-doped graphitic carbon nitride (S@g-C3 N4 ) with a wider potential range as electrocatalyst for electrochemical sensor application. The S@g-C3 N4 nanosheets were successfully prepared with a ball milling method by mixing appropriate molar concentration required precursors. The as-synthesized heteroatom-doped graphitic carbon nitride is characterized by spectroscopic techniques including PL, DRS-UV, FT-IR, and Brunauer-Emmett-Teller equation. The morphological features were studied by FE-SEM and HR-TEM analysis. Chit-S@g-C3 N4 -modified glassy carbon electrode (GCE) was employed for the electrochemical detection of omeprazole (OMZ) use in drug formulations. We have noted an oxidation peak current response at a potential of +0.8 V versus Ag/AgCl in PBS medium (0.1 M, pH 7.0). Differential pulse voltammetry amperometry experimental method can be used to measure the concentration of OMZ for quantitative studies in known samples. Under the optimized experimental condition, the calibration plot was constructed by plotting the peak currents versus OMZ in the linear ranges from 6.0 × 10-7 to 26 × 10-5  M. The linear regression equation is estimated to be Ip (µA) = 0.9518 (C/µM) + 0.3340 with a good correlation coefficient of 0.9996. The lower determination limit was found to be 20 nM and the current sensitivity was calculated (31.722 µA µM-1  cm-2 ). The developed sensor was utilized successfully to determine the OMZ concentration in drug formulations and biological fluids. These results revealed that the Chit-S@g-C3 N4 -modified GCE showed excellent electroanalytical performance for the detection of OMZ at a low LOD, wider linear range, high sensitivity, good reproducibility, long-term storage stability, and selectivity with an acceptable relative standard deviation value.

Voltammetric determination of caffeic acid by using a glassy carbon electrode modified with a chitosan-protected nanohybrid composed of carbon black and reduced graphene oxide.

Differential pulse voltammetry (DPV) was employed for the determination of caffeic acid (CA) in acidic solutions by using a glassy carbon electrode (GCE) modified with a chitosan-protected nanohybrid composed of carbon black and reduced graphene oxide. Electrochemical impedance spectroscopy and cyclic voltammetry were utilized to study the interfacial electron transfer on the modified GCE. Cyclic voltammetry shows that CA exhibits a reversible redox reaction with an oxidation peak at + 0.30 V (vs. Ag/AgCl) and a reduction peak at + 0.24 V in pH 3.0 solution at a scan rate of 50 mV·s-1. Under the optimized experimental conditions, the response to CA is linear in 0.3× 10-9 to 57.3 × 10-5 M concentration range. The limit of detection is 0.03 × 10-9 M (at an S/N ratio of 3), and the electrochemical sensitivity is 5.96 µA∙ µM-1∙cm-2. This sensor for CA displays better sensitivity and a response over a wider concentration range. It was applied to the determination of CA at trace levels in various (spiked) wine samples. Graphical abstract Schematic presentation of a sensitive electrochemical method for the quantitative detection of caffeic acid using chitosan protected carbon black and reduced graphene oxide. It can be used for the quantitative detection of caffeic acid in wine samples.

Amperometric determination of nitrite using natural fibers as template for titanium dioxide nanotubes with immobilized hemin as electron transfer mediator.

A sensing device was constructed for the amperometric determination of nitrite. It is based on the use of titanium dioxide (TiO2) nanotubes template with natural fibers and carrying hemin acting as the electron mediator. A glassy carbon electrode (GCE) was modified with the hemin/TNT nanocomposite. The electrochemical response to nitrite was characterized by impedance spectroscopy and cyclic voltammetry. An amperometric study, performed at a working potential of + 0.75 V (vs. Ag/AgCl), showed the sensor to enable determination of nitrite with a linear response in the 0.6 to 130 µM concentration range and with a 59 nM limit of detection. Corresponding studies by differential study voltammetry (Ep = 0.75 V) exhibited a linear range from 0.6 × 10-6 to 7.3 × 10-5 M with a limit of detection of 84 nM. The sensing device was applied to the determination of nitrite in spiked tap and lake water samples. Graphical abstract Natural fibers templated synthesis of TNT immobilized hemin as electron transfer mediator for quantitative detection of nitrite with detection limit of 59 nM and good electrochemical sensitivity and the method can be used for quantitative determination of nitrite in water samples.

Piper nigrum leaf and stem assisted green synthesis of silver nanoparticles and evaluation of its antibacterial activity against agricultural plant pathogens.

Utilization of biological materials in synthesis of nanoparticles is one of the hottest topics in modern nanoscience and nanotechnology. In the present investigation, the silver nanoparticles were synthesized by using the leaf and stem extract of Piper nigrum. The synthesized nanoparticle was characterized by UV-vis spectroscopy, X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), energy dispersive X-ray analysis (EDAX), and Fourier Transform Infrared Spectroscopy (FTIR). The observation of the peak at 460 nm in the UV-vis spectra for leaf- and stem-synthesized silver nanoparticles reveals the reduction of silver metal ions into silver nanoparticles. Further, XRD analysis has been carried out to confirm the crystalline nature of the synthesized silver nanoparticles. The TEM images show that the leaf- and stem-synthesized silver nanoparticles were within the size of about 7-50 nm and 9-30 nm, respectively. The FTIR analysis was performed to identify the possible functional groups involved in the synthesis of silver nanoparticles. Further, the antibacterial activity of the green-synthesized silver nanoparticles was examined against agricultural plant pathogens. The antibacterial property of silver nanoparticles is a beneficial application in the field of agricultural nanotechnology.

A novel visible light active rare earth doped CdS nanoparticles decorated reduced graphene oxide sheets for the degradation of cationic dye from wastewater.

A variety of rare earth metals (La, Sm, Nd, Ce, Gd) doped cadmium sulfide (RE-CdS) grafted reduced graphene oxide (G) sheet nanocomposites estimated imperative attention due to their visible light-driven, tunable band gap and high surface to volume ratio were investigated for the photocatalytic degradation of cationic dye from aqueous solution. The formation of wurtzite (hexagonal) crystal structures of cadmium sulfide nanoparticles (NPs) was confirmed by Powder X-ray diffraction spectra and the average crystallite size was determined to be 10 ± 2 nm. HRTEM analysis confirmed the homogeneous distribution of RE-CdS NPs over the G sheets. The photocatalytic behaviour of the RE-CdS decorated G sheets was studied using a textile dye methylene blue (MB) under sunlight. The result indicates that among the various RE-CdS nanocomposites studied, Cerium-cadmium sulfide-reduced graphene oxide (Ce-CdS-G) shows highest MB degradation of 99.0 ± 0.4% within 90 min under sunlight. The result confirms that RE-CdS-G nanocatalyst efficiently accelerates the separation and slows down the recombination rate in photo excited charge carriers. The catalytic activity was retained over 80% of its original value even after four successive runs and the present method can be employed for the large-scale synthesis of RE-CdS-G nanocatalyst.

Targeting and sensing cancer cells with ZnO nanoprobes in vitro.

A new class of zinc oxide quantum dots (ZnO QDs) was investigated as nanoprobes for targeting cancer cells in vitro. ZnO nanoparticles were synthesized using conventional sol-gel method and encapsulated using trimethoxy aminopropyl silane. Transferrin, the ligand targeting the cancer cells, was conjugated to the ZnO QDs. In vitro imaging studies using MDA-MB-231 showed the biocompatible ZnO nanoprobe selectively binding to the cell surface receptor and internalizing through receptor-mediated endocytosis. Time-lapsed photobleaching studies indicate the ZnO QDs to be resistant to photobleaching, making them suitable for long term imaging purpose. Investigation of the ZnO nanoprobe as a platform for sensitive bioassays indicates that it can be used as an alternative fluoroprobe for cancer cell targeting and sensing applications.

Human papilloma virus DNA-biomarker analysis for cervical cancer: Signal enhancement by gold nanoparticle-coupled tetravalent streptavidin-biotin strategy.

Human papillomavirus (HPV) is a double-standard DNA virus, as well as the source of infection to the mucous membrane. It is a sexually transmitted disease that brings the changes in the cervix cells. Oncogenes, E6 and E7 play a pivotal role in the HPV infection. Identifying these genes to detect HPV strains, especially a prevalent HPV16 strain, will bring a great impact. Among different sensing strategies for pathogens, the dielectric electrochemical biosensor shows the potential due to its higher sensitivity. In this research, HPV16-E7 DNA sequence was detected on the carbodiimidazole-modified interdigitated electrode (IDE) surface with the detection limit of 1 fM. To enhance the sensitivity, the target sequence was conjugated on gold nanoparticle (GNP) and attained detection to the level of 10 aM. This produced ~100 folds improvement in detecting HPV16-E7 gene and 4 folds increment in the current flow. The stability of HPV16-E7 DNA sequences on GNP was verified by the salt-induced GNP aggregation. The current system has shown the higher specificity by comparing against non-complementary and triple-mismatched DNA sequences of HPV16-E7. This demonstration in detecting HPV16-E7 using dielectric IDE sensing system with a higher sensitivity can be recommended for detecting a wide range of disease-causing DNA-markers.

Gelatin stabilization of quantum dots for improved stability and biocompatibility.

We herein report an aqueous synthesis of gelatin stabilized CdTe/CdS/ZnS (CSSG) core/double shell quantum dots (QDs) with improved biocompatibility. The as-synthesized QDs were characterized by ultraviolet-visible (UV-vis) and photoluminescence (PL) spectroscopic techniques, x-ray diffraction technique (XRD), x-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The CSSG QDs revealed high photoluminescence quantum yield (PLQY) with excellent stability over a period of one year and retained 90% of its initial PLQY without any aggregation or precipitation under ambient condition. The cell viability study conducted on HeLa, cervical cancer cell lines indicated that the gelatin stabilization effectively decreased the QDs cytotoxicity by about 50%. The CSSG QDs were conjugated with transferrin (Tf) for the efficient delivery to the cancer cells followed by fluorescence imaging. The results showed that the CSSG QDs illuminates the entire cell which renders the QDs as cell labeling markers. The gelatin stabilized core/double shell QDs are potential candidates for long time fluorescent bio-imaging.

Shape- and Size-Controlled Synthesis of Silver Nanoparticles Using Aloe vera Plant Extract and Their Antimicrobial Activity.

Biogenic synthesis of silver nanoparticles (AgNP) was performed at room temperature using Aloe vera plant extract in the presence of ammoniacal silver nitrate as a metal salt precursor. The formation of AgNP was monitored by UV-visible spectroscopy at different time intervals. The shape and size of the synthesized particle were visualized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations. These results were confirmed by X-ray powder diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analyses and further supported by surface-enhanced Raman spectroscopy/Raman scattering (SERS) study. UV-visible spectrum has shown a sharp peak at 420 nm and further evidenced by FTIR peak profile (at 1587.6, 1386.4, and 1076 cm-1 with corresponding compounds). The main band position with SERS was noticed at 1594 cm-1 (C-C stretching vibration). When samples were heated under microwave radiation, AgNP with octahedron shapes with 5-50 nm were found and this method can be one of the easier ways to synthesis anisotropic AgNP, in which the plant extract plays a vital role to regulate the size and shape of the nanoparticles. Enhanced antibacterial effects (two- to fourfold) were observed in the case of Aloe vera plant protected AgNP than the routinely synthesized antibiotic drugs. Shape and size-controlled synthesis of silver nanoparticles using Aloe vera plant extract.

Biopolymers Regulate Silver Nanoparticle under Microwave Irradiation for Effective Antibacterial and Antibiofilm Activities.

In the current study, facile synthesis of carboxymethyl cellulose (CMC) and sodium alginate capped silver nanoparticles (AgNPs) was examined using microwave radiation and aniline as a reducing agent. The biopolymer matrix embedded nanoparticles were synthesized under various experimental conditions using different concentrations of biopolymer (0.5, 1, 1.5, 2%), volumes of reducing agent (50, 100, 150 µL), and duration of heat treatment (30 s to 240 s). The synthesized nanoparticles were analyzed by scanning electron microscopy, UV-Vis spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy for identification of AgNPs synthesis, crystal nature, shape, size, and type of capping action. In addition, the significant antibacterial efficacy and antibiofilm activity of biopolymer capped AgNPs were demonstrated against different bacterial strains, Staphylococcus aureus MTCC 740 and Escherichia coli MTCC 9492. These results confirmed the potential for production of biopolymer capped AgNPs grown under microwave irradiation, which can be used for industrial and biomedical applications.

Treatment of petroleum refinery wastewater by ultrasound-dispersed nanoscale zero-valent iron particles.

Petroleum refineries release wastewater, which is rich in organic pollutants and cannot be treated easily. This study presents the treatment of petroleum refinery wastewater using nanoscale zero valent iron (NZVI) in the presence of ultrasonication. NZVI characteristics were analyzed using SEM and XRD. The influence of NZVI dosage and initial pH on % chemical oxygen demand (COD) reduction was studied. From the results, it can be inferred that a dosage of 0.15 g/l and an initial pH are optimum for the effective degradation of effluents. The degradation data were found to follow first order kinetics. The results indicate that using NZVI in combination with ultrasonication is an efficient method for the treatment of petroleum refinery wastewater.