Electrochemical and in situ spectroelectrochemical studies of gold nanoparticles immobilized Nafion matrix modified electrode

Electrochemical and in situ spectroelectrochemical behaviours of phenosafranine (PS+) were studied at the gold nanoparticles (AuNps) immobilized Nafion (Nf) film coated glassy carbon (GC) and indium tin oxide (ITO) electrodes. Cyclic voltammetric studies showed that the PS+ molecules strongly interact with the AuNps immobilized in the Nf matrix through the electrostatic interaction. The presence of AuNps in the Nf film improved the electrochemical characteristics of the incorporated dye molecules. The emission spectra of Nf-AuNps-PS+ films showed that the incorporated PS+ was quenched by AuNps and it could be explained based on the electronic interaction between the AuNps and PS+ molecules. The in situ spectroelectrochemical study showed an improved electrochemical characteristic of the incorporated PS+ molecules at the ITO/Nf-AuNps electrode when compared to the ITO/Nf electrode

Incidence and prevalence of dermatophytosis in and around Chennai, Tamilnadu, India

Background: Dermatophytes are group of fungi that infect keratinized tissues of human and animals. The group consist of three different genera namely, Trichophyton, Microsporum, Epidermophyton and several species within each genera. Among Trichophyton, Trichophyton rubrum is predominant, followed by various strains of Trichophyton mentagrophytes, which include both anthropophiles and zoophiles. Prevalence of dermatophytes varies with location and environmental condition. The infection is common worldwide with higher prevalence in tropical countries like India. Molecular diagnosis renders accurate identification of clinical dermatophyte isolates to species level. The main objective of this study was to determine the prevalence of dermatophytoses, isolate and identify the dermatophyte from samples of clinically suspected cases attending tertiary care centre using conventional and molecular methods.Methods: A total of 210 patients showing lesions typical of dermatophytes infection from outpatient Department of dermatology were sent to mycology unit, Department of Microbiology for the period of April 2011-March 2014 were studied. Diagnosis was confirmed by conventional and polymerase chain reaction - restriction fragment length polymorphism (PCR-RFLP) technique.Results: Out of 210 samples received, tinea corporis was the predominant clinical site which was followed by tinea cruris. A total of 143 dermatophytes were isolated from the clinical samples. T. rubrum was the predominant etiological agent with 70/143 isolates and T. mentagrophytes was the second most common with 64/143 isolates. Amplification of internal transcribed spacers (ITS) was successful in all the clinical isolates by PCR and produced species specific banding pattern in RFLP using restriction enzyme Mva I.Conclusions: Among dermatophytoses, T. rubrum was the predominant etiological agent present in the whole of Chennai District and T. mentagrophytes takes the second place

Proton coupled electron transfer reaction of phenols with excited state ruthenium(II) - polypyridyl complexes

The reaction of phenols with the excited state, *[Ru(bpy)3]2+ (E0 = 0.76V) and *[Ru(H2dcbpy)3]2+, (dcbpy = 4,4'-dicarboxy-2,2'-bipyridine) (E0 = 1.55 V vs. SCE) complexes in CH3CN has been studied by luminescence quenching technique and the quenching is dynamic. The formation of phenoxyl radical as a transient is confirmed by its characteristic absorption at 400 nm. The kq value is highly sensitive to the change of pH of the medium and ΔG0 of the reaction. Based on the treatment of kq data in terms of energetics of the reaction and pH of the medium, proton coupled electron transfer (PCET) mechanism has been proposed for the reaction

A novel and disposable amperometric hydrazine sensor based on polydimethyldiallylamine stabilized copper(II)hexacyanoferrate nanocubes modified screen-printed carbon electrode

© 2017 The Authors. A cubic shaped copper(II)hexacyanoferrate was prepared by wet chemical method by mixing an equimolar concentration of CuCl 2 with K 3 [Fe(CN) 6 ] 2 in the presence of poly(diallyldimethylammonium chloride) (PDDA). The X-ray diffraction, field emission scanning electron microscopy, elementa l analysis, Fourier transform infrared spectroscopy and thermal gravimetric analysis were used to confirm the formation of PDDA stabilized copper(II)hexacyanoferrate nanocubes (PDDA@copper(II)hexacyanoferrate nanocubes). The electrocatalytic behavior of the PDDA@copper(II)hexacyanoferrate nanocubes modified screenprinted carbon electrode (SPCE) towards electrochemical oxidation of hydrazine was studied by cyclic voltammetry (CV). The CV results revealed that PDDA@copper(II)hexacyanoferrate nanocubes modified SPCE exhibits an enhanced electrocatalytic activity and lower oxidation potential towards hydrazine than bare SPCE. Under optimized conditions, amperometric i-t method was used for the determination hydrazine, and PDDA@copper(II)hexacyanoferrate nanocubes modified SPCE can able to detect hydrazine in the linear concentration ranges from 0.03 to 533.6 μM with a detection limit of 10 nM. The PDDA@copper(II)hexacyanoferrate nanocubes modified SPCE is highly selective in the presence of potentially active interfering compounds including high concentration of ascorbic acid. In addition, the developed hydrazine sensor shows acceptable practicality with excellent long-term stability towards the detection of hydrazine

A robust nitrobenzene electrochemical sensor based on chitin hydrogel entrapped graphite composite

© 2017 An amperometric nitrobenzene (NB) sensor has been developed based on a glassy carbon electrode (GCE) modified with the composite of chitin hydrogel stabilized graphite (GR-CHI) composite. The physicochemical characterization confirmed the formation of GR-CHI composite and was formed by the strong interaction between GR and CHI. Furthermore, GR-CHI composite modified GCE was used to study the electrochemical reduction behavior of NB by cyclic voltammetry (CV) and compared with GR and CHI modified GCEs. The CV results confirmed that GR-CHI composite modified electrode has high catalytic ability and lower reduction potential toward NB than other modified electrodes due to the combined unique properties of exfoliated GR and CHI. The GR-CHI composite modified electrode can be able to detect the NB in the linear response range from 0.1 to 594.6 µM with the lower detection limit of 37 nM by amperometric i–t method. The selectivity of the sensor is evaluated in the presence of nitroaromatic, biologically active and dihydroxybenzene compounds. The sensor shows appropriate practicality and good repeatability toward detection of NB in lab water samples

An endophyte Paenibacillus dendritiformis strain APL3 promotes Amaranthus polygonoides L. sprout growth and their extract inhibits food-borne pathogens

Green leafy vegetables are rich sources of antioxidants and minerals, which prevent food-borne pathogen infections during our diet. This study was aimed to isolate and identify the plant growth-promoting endophytic bacterium from several plant species to enhance the growth of Amaranthus polygonoides L. and their antimicrobial potential against food-borne pathogens. Seven endophytic bacterial isolates were tested on two Amaranthus species to identify the suitable beneficial bacterium. The antioxidants capacity and antimicrobial activity of bacterial isolate (APL3) treated plants were analyzed. The bacterial isolate, APL3 showed a significantly higher growth of A. polygonoides L. than other isolates. It was identified as Paenibacillus dendritiformis strain APL3 by 16S rRNA gene sequencing and phylogenetic analysis. The endophyte (APL3) treated A. polygonoides L. sprouts had higher antioxidants potentials and significantly inhibited the growth of Escherichia coli, Salmonella sp., Staphylococcus sp. and Pseudomonas sp. The results of the present study suggest that utilization of P. dendritiformis strain APL3 triggers the growth of A. polygonoides L. and induces metabolic changes in plants to improve their antimicrobial properties to prevent foodborne pathogens

A novel amperometric gallic acid sensor based on polymelamine entrapped graphene composite

© 2017 The Authors. The present work describes an amperometric determination of gallic acid (GA) using a glassy carbon electrode (GCE) modified with graphene (GR) and polymelamine (PM) composite. The GR/PM composite modified electrode was prepared by electropolymerization of melamine on GR modified GCE. The as-prepared GR/PM composite was characterized by scanning electron microscopy, elemental mapping and Fourier transform infrared spectroscopy. The GR/PM composite modified GCE was used as electrocatalyst for oxidation of GA, and the composite modified electrode shows an enhanced catalytic activity than electrodes modified with GR and PM. Under optimum conditions, amperometric i-t was used to determine the GA, and the amperometric response of GA was linear over the concentration ranging from 0.1 to 728.9 μM. The limit of detection and sensitivity of the sensor was estimated as 0.027 μM and 0.697 μAμM -1 cm -2 , respectively. The GR/PM composite modified electrode exhibits high selectivity in the presence of range of potentially interfering polyphenol compounds, dopamine, uric acid and ascorbic acid. As a proof of concept, the practicality of the sensors was examined in green tea samples, and shows acceptable practicality for the determination of GA

Preparation and characterization of a novel hybrid hydrogel composite of chitin stabilized graphite: Application for selective and simultaneous electrochemical detection of dihydroxybenzene isomers in water

The development of new and robust sensors for real-time monitoring of environmental pollutants have received much attention. Therefore, in the present work, we have fabricated a simple and robust electrochemical sensor for the simultaneous electrochemical determination of dihydroxybenzene isomers using chitin (CHI) stabilized graphite (GR) hydrogel composite modified electrode. The GR-CHI hydrogel composite was prepared by a simple sonication of raw GR in CHI solution and the as-prepared materials were characterized by range of physicochemical methods. Compared with CHI and GR modified electrodes, the GR-CHI hydrogel composite modified electrode shows an excellent electron transfer ability and enhanced electrocatalytic activity towards hydroquinone (HQ), catechol (CC) and resorcinol (RC). Differential pulse voltammetry was used for the simultaneous determination of HQ, CC and RC. Under optimized conditions, the fabricated electrode detects the HQ, CC and RC in the linear response from 0.2 to 110.6 µM, 0.3 to 110.6 µM and 1.3 to 133.4 µM, respectively. The detection limit for HQ, CC and RC were 0.065 µM, 0.085 µM and 0.35 µM, respectively. The sensor shows its appropriate practicality towards the determination of HQ, CC and RC in different water samples

Graphene dispersed cellulose microfibers composite for efficient immobilization of hemoglobin and selective biosensor for detection of hydrogen peroxide

© 2017 Elsevier B.V. In the present work, we have investigated the electrochemical behavior and electrocatalysis of hemoglobin (Hb) immobilized on a glassy carbon electrode (GCE) modified with a graphene-cellulose microfiber (GR–CMF) composite. The GR–CMF composite was characterized by scanning electron microscopy, elemental analysis, and Raman and Fourier transform infrared spectroscopy. Well-defined electrochemical redox characteristics of Hb were observed for Hb immobilized on a GR–CMF composite modified GCE, with a formal potential of −0.306V and a peak to peak separation of approximately 67 mV. Due to the high biocompatibility of the GR–CMF composite, the electrochemical behavior of the Hb heme redox couple (FeII/FeIII) was enhanced for Hb immobilized on the GR–CMF composite when compared to Hb immobilized on pristine GR. The heterogeneous electron transfer constant (ks) was calculated as 6.17 s−1, and is higher than previously reported for Hb immobilized GR supports. The Hb immobilized GR–CMF composite modified electrode was used for the quantification of H2O2 under optimal conditions, and shows a wider linear amperometric response ranging from 0.05 to 926 M. The limit of detection of the biosensor was 0.01 M with the sensitivity of 0.49 A M−1 cm−2. The biosensor also showed high selectivity in the presence of the range of interfering compounds and exhibits good operational stability and practicality in the detection of H2O2

A novel non-enzymatic glucose sensor based on melamine supported CuO nanoflakes modified electrode

In the present work, we describe a simple electrochemical synthesis of CuO nanoflakes (CuO-NFs) using Cu-melamine complex. The as-prepared CuO nanoflakes was characterized by different physicochemical methods such as high-resolution scanning electron microscopy, elemental analysis and elemental mapping. The effect of different potential cycling towards the morphology of CuO-NFs was studied and discussed. Furthermore, CuO-NFs modified electrode was used as an electrocatalyst for oxidation of glucose in 0.1 M NaOH, and the observed electrochemical oxidation current of glucose was higher than CuNPs modified electrode. Amperometric i-t method was used for the determination of glucose using CuO-NFs modified electrode. Under optimal conditions, the amperometric i-t response of the sensor was linear over the glucose concentrations ranging from 1.0 µM to 1.445 mM with the detection limit of 0.35 µM. In addition, the selectivity of the sensor was tested in the presence of different potentially interfering compounds. The practicality of the sensor was also evaluated in human serum samples and shows acceptable recovery of glucos