Electrochemical biosensors based on in situ grown carbon nanotubes on gold microelectrode array fabricated on glass substrate for glucose determination.

A highly sensitive electrochemical sensor is reported for glucose detection using carbon nanotubes grown in situ at low temperatures on photolithographically defined gold microelectrode arrays printed on a glass substrate (CNTs/Au MEA). One of the main advantages of the present design is its potential to monitor 64 samples individually for the detection of glucose. The selectivity of the fabricated MEA towards glucose detection is achieved via modification of CNTs/Au MEA by immobilizing glucose oxidase (GOx) enzyme in the matrix of poly (paraphenylenediamine) (GOx/poly (p-PDA)/CNTs/Au MEA). The electrocatalytic and electrochemical responses of the proposed sensing platform towards glucose determination were examined via cyclic voltammetry and electrochemical impedance spectroscopy. The developed impedimetric biosensor exhibits a good linear response towards glucose detection, i.e., 0.2-27.5 µM concentration range with sensitivity and detection limits of 168.03 kΩ-1 M-1 and 0.2 ± 0.0014 µM, respectively. The proposed glucose biosensor shows excellent reproducibility, good anti-interference property, and was successfully tested in blood serum samples. Further, the applicability of the proposed sensor was successfully validated through HPLC. These results supported the viability of using such devices for the simultaneous detection of multiple electroactive biomolecules of physiological relevance.

Ultrasound-enhanced remediation of toxic dyes from wastewater by activated carbon-doped magnetic nanocomposites: analysis of real wastewater samples and surfactant effect.

Water pollution has become a worldwide threat as the natural water resources are shrinking day by day. Emergent actions are needed to conserve water stocks to fulfill the sustainable development goals. Herein, we have prepared activated carbon-doped magnetic nanocomposites (AC@CoFe2O4) with environment friendly approach and characterized for FTIR, XRD, SEM, EDS, BET surface area, and pHzpc. AC@CoFe2O4 nanocomposite was applied for the decolorization of toxic food dyes (rhodamine B and tartrazine) from wastewater. Effect of ultrasonic waves, pH, contact time, surfactants, temperature, and analysis of real wastewater systems were studied. Adsorption isotherm, kinetics, and thermodynamics of the experiment were calculated for the present removal process. The effect of ultrasonication shows that the maximum removal percentage for RhB was found to be 92% and for tartrazine, it was found to be 86% at 60 min. Ultrasound-assisted adsorption and degradation revealed good results because of the formation of highly active ·H and ·OH radicals in the liquid through the decomposition of water molecules by the formation of hot spots under ultrasonic waves. Highest decolorization of 69% was obtained for RhB with anionic surfactant SDS and climax decolorization of tartrazine was acquired in case of CTAB as 60.5%. Analysis of real wastewater samples shows that the decolorization of RhB was found to be ~ 91% from well-water and ~ 95% removal of tartrazine was observed from submersible water on AC@CoFe2O4 nanocomposites. The decolorization best fitted (R2 < 0.988) with Langmuir model and value of Langmuir climax decolorization efficiency (Q0) was found to be 142.68 and 435.72 mg/g for RhB and tartrazine, respectively. Kinetic analysis revealed that adsorption follows pseudo-second-order equation. The dye-loaded AC@CoFe2O4 nanocomposites were recycled by 0.1 M HCl or NaOH and regenerated AC@CoFe2O4 nanocomposites were used up to five rounds with better adsorption efficiency.

An impedimetric biosensor based on electrophoretically assembled ZnO nanorods and carboxylated graphene nanoflakes on an indium tin oxide electrode for detection of the DNA of Escherichia coli O157:H7.

Aminopropyltrimethoxysilane (APTMS)-functionalized zinc oxide (ZnO) nanorods and carboxylated graphene nanoflakes (c-GNF) were used in a composite that was electrophoretically deposited on an indium tin oxide (ITO) coated glass substrate. The modified ITO electrodes were characterized using various microscopic and spectroscopic techniques which confirm the deposition of the APTMS-ZnO/c-GNF composite. The electrodes have been used for the covalent immobilization of an Escherichia coli O157:H7 (E. coli)-specific DNA prob. Impedimetric studies revealed that the gene sensor displays linear response in a wide range of target DNA concentration (10-16 M to 10-6 M) with a detection limit of 0.1 fM. The studies on the cross-reactivity to other water-borne pathogens show that the bioelectrode is highly specific. Graphical abstractSchematic illustration for fabrication of nucleic acid biosensor for E. coli DNA detection using an ITO electrode modified with siloxane-functionalized zinc oxide (ZnO) nanorods and carboxylated graphene nanoflakes (c-GNFs).