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Optical sensors based on surface plasmon resonance (SPR) are utilized for detecting toxic heavy metals in solutions. To improve the sensitivity of SPR sensors, nanostructured thin films with active layers can be synthesized. In this study, the response to Pb (II) was measured and compared for SPR sensors incorporating gold-chitosan-graphene oxide (Au/CS/GO) nanostructured thin films and Au/CS films. The characterization of Au/CS/GO using FESEM analysis revealed a film composed of nanosheets with wrinkled, rough surfaces. The results from XRD analysis confirmed the successful incorporation of GO in the prepared films. Additionally, AFM analysis determined that the Au/CS/GO films had a root mean square (rms) roughness of 28.38 nm and were considerably rougher than the Au/CS films. Upon exposure to a 5 ppm Pb (II) ion solution, the Au/CS/GO films exhibited higher SPR sensitivity, as much as 1.11200 ppm−1, than Au/CS films, 0.77600 ppm−1. This enhancement of the SPR response was attributed to strong covalent bonding between CS and GO in these films. These results indicated that the Au/CS/GO films show potential for the detection of heavy metal pollution in environmental applications.

Background:Galls of Quercus infectoria have been traditionally used to treat common ailments, including yeast infections caused by Candida species.Objective:This study aimed to evaluate the in vitro anti-Candida activity of Q. infectoria gall extracts against selected Candida species.Materials and Methods:Methanol and aqueous extracts of Q. infectoria galls were tested for anti-Candida activity against Candida albicans, Candida krusei, Candida glabrata, Candida parapsilosis and Candida tropicalis. The minimum inhibitory concentrations were determined using the two-fold serial dilution technique of concentrations ranging from 16 mg/ml to 0.03 mg/ml. After 24 h, the minimum fungicidal concentrations were determined by subculturing the wells, which showed no turbidity on the agar plate. Potential phytochemical group in the crude extracts was screened by phytochemical qualitative tests and subsequently subjected to the gas chromatography-mass spectrometry analysis.Results:Both methanol and aqueous extracts displayed substantial anti-Candida activity and pyrogallol was the major component of both crude extracts.Conclusions:Data from current study suggested that Q. infectoria gall extracts are a potential source to be developed as anti-candidiasis.

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