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Silver nanoparticles (AgNPs) are widely being incorporated into products such as socks [1, 2], sports wears and wound dressings [3, 4] to serve as antibacterials and to inhibit unwanted odours. As these products are washed, the silver nanoparticles leach out, dispersing in water where they may release silver ions. Although the only contraindication of high levels of silver in humans is argyria [5], it is said to be very toxic to aquatic organisms that make up the base of a series of food chains. In this study, silver nanoparticles were synthesised by the citrate reduction method following the procedure of Lee and Meisel [6]. The nanoparticles were prepared in the presence of various anions and in pure water in order to examine the effect of the medium on the release of Ag(I). AgNPs were characterised by UV-Vis spectrometry, dynamic light scattering (DLS) and atomic force microscopy (AFM). The decrease in surface plasmon resonance (SPR) peak of the nanoparticles after dialysis indicates that quite a number of conduction electrons have gone into reaction, hence lowering of resonant frequency. The diameters of the nanoparticles as measured by DLS ranged from 102 nm in the 10 mM chloride AgNPs before dialysis to 892 nm in the 50 mM sample after dialysis, indicating aggregation over the dialysis period. On the other hand, particle sizes in terms of both height and diameter as measured by AFM decreased after dialysis. This could be explained that in spite of aggregation in solution, the AgNPs deposit as islands about 1 particle in height on the AFM substrate (Si wafer). Release of Ag(I) from the NPs was monitored by anodic stripping voltammetry at glassy carbon electrodes. Two interesting observations were made: (i) there is substantial (90 mM) Ag(I) present in the initial NP preparation and (ii) the concentration of Ag(I) after 73 h of dialysis remained easily detectable at about 4 µM irrespective of the concentration of chloride present. References 1 T.M. Benn, P.Westerhoff. Environ. Sci. Technol. 2008, 42, 4133-4139. 2 D.E Meyer, M.A. Curran, M.A. Gonzalez. J Nanopart Res. 2011, 13, 147-156. 3 A. Hebeish, M.H. El-Rafie, M.A. El-Sheikh, A.A. Saleem, M.E. El-Naggar. Intnal. Journ. of Macromolecules. 2014, 65, 509-515. 4 T. Maneerung, S. Tokura, R. Rujiavanit. Carbohydrate Polymers. 2008, 72, 43-51. 5 WHO Guidelines for Drinking-water quality. 2003. World Health Organisation, Geneva. 6 P.C. Lee, D. Meisel. J. Phys. Chem. 1982, 86, 3391-3395. Figure 1

The reduction of Ru(NH3)63+ at Bi electrodes in aqueous KCl is much slower than at Pt electrodes. Differential capacitance and ex situ photoemission spectra indicate the presence of a thin oxide layer about 1.5 nm thick on the Bi surface near the formal potential of −0.217 V vs Ag/AgCl/1 M KCl(aq). Despite the presence of this oxide, reproducible impedance spectra near the formal potential were obtained for Ru(NH3)63+ that could be analyzed by using a Randles circuit modified to incorporate a constant phase element. The value of the standard rate constant was 1.47±0.44×10−3 cm s−1. Under the same conditions, impedance spectra for Pt/Ru(NH3)63+ were reversible up to the highest frequencies (105 Hz) employed. The charge‐transfer resistance−dc potential curves obtained from the impedance spectra were fitted by a regression model, which contained no a priori assumption about the potential dependence of the transfer coefficient except piecewise linearity. The measured transfer coefficients show clear evidence of diffuse layer effects, but, in addition, an increase in transfer coefficient at the most negative potentials studied was observed and interpreted in terms of the reduction and thinning of the anodic oxide.