Perumal Rameshkumar

An electrochemical sensing platform based on a reduced graphene oxide–cobalt oxide nanocube@platinum nanocomposite for nitric oxide detection

We report a facile one-pot hydrothermal synthesis of a reduced graphene oxide–cobalt oxide nanocube@platinum (rGO–Co3O4@Pt) nanocomposite and its application toward the electrochemical detection of nitric oxide (NO). The rGO–Co3O4@Pt nanocomposite was characterized by field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX) mapping, X-ray diffraction (XRD) and Raman analyses. The nanocomposite modified glassy carbon (GC) electrode was used for the electrochemical oxidation of nitric oxide (NO) and it showed better catalytic performance in terms of catalytic peak current and shift in overpotential when compared to those of rGO, Co3O4 nanocubes and rGO–Co3O4 nanocomposite modified electrodes. The rGO–Co3O4@Pt nanocomposite modified electrode showed a better sensing ability toward the in situ generated NO in NO2− containing phosphate buffer solution (PBS) than the other controlled modified electrodes. The Pt nanoparticles present in the nanocomposite could enhance the sensing performance and the limit of detection (LOD) was found to be 1.73 μM with a signal-to-noise (S/N) ratio of ∼3 using the amperometric i–t curve technique. Furthermore, the nanocomposite modified electrode showed selectivity toward the detection of NO in the presence of a 100-fold higher concentration of other physiologically important analytes. The proposed sensor was stable, reproducible and selective toward the detection of NO.

Facile synthesis of graphene oxide–silver nanocomposite and its modified electrode for enhanced electrochemical detection of nitrite ions

In this report, silver nanoparticles (Ag NPs) were successfully deposited on graphene oxide (GO) sheets to form GO-Ag nanocomposite using garlic extract and sunlight and the nanocomposite modified glassy carbon (GC) electrode was applied as an electrochemical sensor for the detection of nitrite ions. The formation of GO-Ag nanocomposite was confirmed by using UV-visible absorption spectroscopy, TEM, XRD and FTIR spectroscopy analyses. Further, TEM pictures showed a uniform distribution Ag on GO sheets with an average size of 19 nm. The nanocomposite modified electrode produced synergistic catalytic current in nitrite oxidation with a negative shift in overpotential. The limit of detection (LOD) values were found as 2.1 µM and 37 nM, respectively using linear sweep voltammetry (LSV) and amperometric i-t curve techniques. The proposed sensor was stable, reproducible, sensitive and selective toward the detection nitrite and could be applied for the detection of nitrite in real water sample.

Ternary nanohybrid of reduced graphene oxide-nafion@silver nanoparticles for boosting the sensor performance in non-enzymatic amperometric detection of hydrogen peroxide

A sensitive and novel electrochemical sensor was developed for the detection of hydrogen peroxide (H2O2) using a reduced graphene oxide-nafion@silver6 (rGO-Nf@Ag6) nanohybrid modified glassy carbon electrode (GC/rGO-Nf@Ag6). The GC/rGO-Nf@Ag6 electrode exhibited an excellent electrochemical sensing ability for determining H2O2 with high sensitivity and selectivity. The detection limit of the electrochemical sensor using the GC/rGO-Nf@Ag6 electrode for H2O2 determination was calculated to be 5.35×10-7M with sensitivity of 0.4508µAµM-1. The coupling between rGO-Nf with silver nanoparticles (AgNPs) significantly boosted the electroanalytical performance by providing more active area for analyte interaction, thereby allowing more rapid interfacial electron transfer process. The interfering effect on the current response of H2O2 was studied and the results revealed that the sensor electrode exhibited an excellent immunity from most common interferents. The proposed non-enzymatic electrochemical sensor was used for determining H2O2 in apple juice, and the sensor electrode provided satisfactory results with reliable recovery values. These studies revealed that the novel GC/rGO-Nf@Ag6 sensor electrode could be a potential candidate for the detection of H2O2.

The biogenic synthesis of a reduced graphene oxide–silver (RGO–Ag) nanocomposite and its dual applications as an antibacterial agent and cancer biomarker sensor

Cancer nanotechnology encourages cutting edge research utilizing nanomaterials for the diagnosis, therapy and prevention of cancer. Recognition of cancer-related biomarkers in the body has made early detection possible and thus, paves the way towards devising methods to control it from progressing to advanced stages. Hydrogen peroxide (H2O2) is a critical biomolecule, which plays an important dual role in cancer progression. Herein, we have developed a sensitive method for the detection of H2O2 utilizing a reduced graphene oxide–silver (RGO–Ag) nanocomposite. This RGO–Ag nanocomposite was prepared using a green and facile one-step synthesis approach utilizing the extract of a medicinal mushroom, Ganoderma lucidum. The higher content of polysaccharides in this extract makes it a potent reducing agent for the combined reduction of GO and AgNO3 to produce the RGO–Ag nanocomposite. The properties of the RGO–Ag obtained were characterized by UV-Vis spectroscopy, SEM, TEM, XRD, FT-IR and XPS techniques. The RGO–Ag modified electrode showed good electrocatalytic activity towards H2O2 when compared to other modified electrodes. Furthermore, it showed an LOD of 136 nM, which was determined using the LSV technique. The amperometric i–t curve displayed two different linear ranges of 1–100 μM and 100–1100 μM with an LOD of 3 and 56 nM, respectively. This excellent electrochemical performance towards H2O2 detection could contribute to advances in current cancer diagnosis. The RGO–Ag nanocomposite was also explored as a potential antibacterial agent. Owing to its synergistic effects, RGO–Ag showed a comparable antibacterial activity to the standard antibiotic, chloramphenicol. The combined antibacterial effects and sensing potential make this RGO–Ag nanocomposite a promising candidate for future health care.

Nitrite ion sensing properties of ZnTiO3–TiO2 composite thin films deposited from a zinc–titanium molecular complex

A titanium based heterobimetallic molecular precursor, [Zn2Ti4(μ-O)6(TFA)8(THF)6]·THF (1) (where TFA = trifluoroacetato; THF = tetrahydrofuran), has been designed and scrutinised for its various physicochemical properties by melting point analysis, microanalysis, Fourier transform infra-red spectroscopy, proton nuclear magnetic resonance spectroscopy, thermogravimetry and single crystal X-ray structural analysis. ZnTiO3–TiO2 composite thin films were grown on a fluorine doped tin oxide (FTO) coated conducting glass substrate at 550 °C from three different solutions of (1) viz. methanol, THF and acetonitrile, by the aerosol-assisted chemical vapour deposition technique. The phase identification, chemical composition and microstructure of the fabricated thin films that were probed by powder X-ray diffraction, Raman spectroscopy, energy dispersive X-ray analysis and scanning electron microscopy revealed the formation of a 1 : 1 ratio of ZnTiO3 : TiO2 composite microspheres of diverse designs and textures depending on the type of deposition solvent used. The direct band gap energy of 3.1 eV was estimated by UV-visible spectrophotometry of the ZnTiO3–TiO2 film fabricated from methanol solution and the film electrode was further tested as an electrochemical sensor for the detection of nitrite ions.

Electrochemical properties of silver nanoparticle-supported reduced graphene oxide in nitric oxide oxidation and detection

This article reports the effect of ascorbic acid in the formation of a reduced graphene oxide–silver (rGO–Ag) nanocomposite and its influence on the electrochemical oxidation of nitric oxide (NO). The formation of the rGO–Ag nanocomposite was confirmed using UV-visible absorption spectroscopy, X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) analyses. Crystalline and spherical Ag nanoparticles (NPs) with an average particle size of 2 nm were found in the rGO–Ag nanocomposite with the assistance of 5.0 M ascorbic acid. The electrochemical properties of the rGO–Ag nanocomposite-modified glassy carbon (GC) electrode were investigated for the oxidation of NO. The rGO–Ag (5.0 M) nanocomposite-modified electrode displayed a higher catalytic current response compared to other controlled modified electrodes in cyclic voltammetry toward the oxidation of NO in 0.1 M phosphate buffer (pH 2.5). The electroanalytical application of the nanocomposite was performed using an amperometry technique, and the limit of detection (LOD) was found to be 2.84 μM for the in situ detection of NO. The present nanocomposite was stable, sensitive, and selective in the presence of the common physiological interferents such as ascorbic acid, uric acid, dopamine, glucose, urea, and NaCl.