Template- and Additive-free Electrosynthesis and Characterization of Spherical Gold Nanoparticles on Hydrophobic Conducting Polydimethylsiloxane.

Carbon-doped poly(dimethylsiloxane) (C-PDMS) modified with gold nanoparticles (AuNPs) is a highly promising material for the development of flexible lab-on-chip biosensors. Here, we present an electrochemical method to prepare stabilizer-free AuNPs directly on hydrophobic conducting substrates like C-PDMS without physical or chemical pre-treatment of the C-PDMS substrate. Using a potentiostatic triple pulse strategy, spherical, non-stabilized AuNPs of diameter 76±5 nm could be deposited within 5 s with narrow size-dispersion on the hydrophobic C-PDMS substrate in the absence of any structure directing or stabilizing agent. The detailed investigation of the mechanism of electrochemical formation of gold seeds and their three-dimensional growth on the hydrophobic surface along with nanomechanical atomic force-scanning electrochemical microscopy (QNM-AFM-SECM) characterization as well as conductive AFM allowed developing this fast electrochemical strategy with control in the desired size and size-dispersion of AuNPs. A detailed electrochemical investigation using cyclic voltammetry, anodic differential pulse voltammetry, and electrochemical impedance spectroscopy was conducted to characterize the electrochemical behavior of uncapped AuNPs deposited on C-PDMS. The Fc+ (MeOH)2 /Fc(MeOH)2 redox reaction at AuNPs-C-PDMS showed an improved charge transfer coefficient and heterogeneous charge transfer rate constant compared to the bare C-PDMS substrate.

Scope of detection and determination of gallium(III) in industrial ground water by square wave anodic stripping voltammetry on bismuth film electrode.

Gallium(III) in ground water may cause human health hazards due to the antineoplastic and antimicrobial activities of gallium. However, the exposure limit of Ga(III) has not been set. This paper demonstrates the scope of employing the square wave anodic stripping voltammetry (SWASV) on bismuth film electrode (BiFE) for selective and sensitive detection of Ga(III) as well as its accurate and precise determination. The key parameters were optimized and the bismuth film morphology was characterized. The performance of BiFE was also compared with that of the mercury film electrode (MFE). The performance of BiFE was also studied for interferences of Zn(II), Cd(II), Tl(I) and Cu(II) ions. Gaussian peak fitting was performed to improve the calibration curve and the fitting process revealed almost similar stripping peak heights as obtained from the experimentally observed data though slight improvement in calibration was obtained from the peak area analysis. A good linear dynamic range (R(2)=0.996) was obtained in the concentration range of 20-100 µg/L with a limit of detection (LOD) of 6.6 µg/L (S/N=3) of Ga(III). A relative standard deviation of 2.9% (n=10) was obtained for 20 µg/L of Ga(III) solution. The practical analytical utility of the method was verified by the determination of Ga(III) in spiked water samples, where 100-105% recovery of Ga(III) was achieved.