Silver nanoparticle was synthesized using D-glucosamine chitosan base as green reducing agent at elevated temperature in alkaline pH ranges. The excess of D-glucosamine chitosan base was used as it is both stabilizing and reducing agent at different pHs, regulates the shape and size of the silver nanoparticles. The progressive growth of silver nanoparticles was monitored by UV-Visible spectral studies. A sharp peak at 420 nm indicates the formation of spherical silver nanoparticles. The size and shape of silver nanoparticles were observed from Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) methods. The anisotropically grown nanoparticles were used as probe for Surface Enhanced Raman Studies (SERS) using ATP (4-aminothiophenol) as a model system. The catalytic behavior of silver nanoparticles was exploited for 4-nitrophenol reduction and observed that the reduction reaction follows pseudo first order kinetics with a rate constant 0.65 min. The antibacterial activity of silver nanoparticles was also tested for both gram-positive and -negative microorganisms, in which higher zone of inhibition was observed for gram negative microorganism.
Paracetamol (PAR) is an effective antipyretic and analgesic drug utilized worldwide, safer at therapeutic levels but over-dosing and the chronic usage of PAR results in accumulation of toxic metabolites, which leads to kidney and liver damages. Hence, a simple, rapid, cost-effective, and sensitive analytical technique is needed for the accurate determination of PAR in pharmaceutical and biological samples. Though numerous techniques have been reported for PAR detection, electrochemical methods are being receiving more interest due to their advantages. Moreover, in the past few decades, room temperature ionic liquids (RTILs) have been utilized in electrochemical sensors due to their attractive properties. In this present review, authors gathered research findings available for the determination of PAR using RTIL-based electrochemical sensors and discussed. The advantages and limitations in these systems as well as the future research directions are summarized.
This research presents a simple, fast and simultaneous electrochemical quantitative determination of nucleobases, for example guanine (G), adenine (A), and thymine (T) in a beef and chicken livers samples to measure the quality of food products based on hybrids of graphitic carbon nitride/Graphene nanoflakes (g-C3N4/GNF) modified electrode. Graphitic carbon nitride (g-C3N4) made of graphite-like covalent link connects nitrogen, nitride, and carbon atoms in the structural design with improved the electrical properties and low band gap semiconductor. The g-C3N4/GNF nanocomposite was synthesized by the hydrothermal treatment to form a porous g-C3N4 interconnected three dimensional (3D) network of g-C3N4 and GNF. The 3D g-C3N4/GNF/GCE was utilized for the detection of nucleic acid bases with a well resolved oxidation peak for the individual analyte. The electrocatalytic current was established to be a linear range from 0.3 × 10-7 to 6.6 × 10-6, 0.3 × 10-7 to 7.3 × 10-6, and 5.3 × 10-6 to 63.3 × 10-4 M for G, A, and T with a detection limit of 4.7, 3.5 and 55 nM, respectively. The diffusion co-efficient and the kinetic parameters were derived from the chronoamperometry technique. The proposed sensing strategy has been effectively used for the application in real sample analysis and observed that the electrode free from the surface fouling.
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.
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.
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.
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.
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.
Myocardial infarction (MI) is highly related to cardiac arrest leading to death and organ damage. Radiological techniques and electrocardiography have been used as preliminary tests to diagnose MI; however, these techniques are not sensitive enough for early-stage detection. A blood biomarker-based diagnosis is an immediate solution, and due to the high correlation of troponin with MI, it has been considered to be a gold-standard biomarker. In the present research, the cardiac biomarker troponin I (cTnI) was detected on an interdigitated electrode sensor with various surface interfaces. To detect cTnI, a capture aptamer-conjugated gold nanoparticle probe and detection antibody probe were utilized and compared through an alternating sandwich pattern. The surface metal oxide morphology of the developed sensor was proven by microscopic assessments. The limit of detection with the aptamer-gold-cTnI-antibody sandwich pattern was 100 aM, while it was 1 fM with antibody-gold-cTnI-aptamer, representing 10-fold differences. Further, the high performance of the sensor was confirmed by selective cTnI determination in serum, exhibiting superior nonfouling. These methods of determination provide options for generating novel assays for diagnosing MI.