O pda

Glucose (Wako Pure Chemicals, > 98.0%), poly(ethylene glycol) (PEG-200, Aldrich), 1,4-phenylenediamine dihydrochloride (p-PDA, Tokyo Chemical Industry, > 98.0%), 1,2-phenylenediamine dihydrochloride (o-PDA, Tokyo Chemical Industry, > 98.0%), and p-toluidine hydrochloride (Wako Pure Chemicals, > 98.0%) were used as received. Other reagents were of guaranteed-grade, and were used without further purification. All aqueous solutions were prepared using water treated by a Milli-Q system (Millipore Corp., Bedford, MA). UV-vis absorption and photoluminescence spectra were measured by a UV-vis spectrophotometer (JASCO, V-570) and a fluorescence spectrophotometer (Hitachi, F-2500), respectively. The quantum yield of CND was determined using quinine sulfate 15 (Φ = 0.546 in 0.5 M H2SO4) as a standard. A pH meter (Horiba, Model F-52) equipped with a combination glass electrode (Horiba, 9611-10D) was calibrated by standard buffer solutions (pH 12.45, 9.18, 6.86, 4.01, and 1.68 at 25°C).

DAB, DMB, and o-PDA were purchased from Tokyo Chemical Industry. PdCl2, H2PtCl6•6H2O, RHCl3•3H2O, NaCl, and HCl (reagent grade, purchased from Wako Pure Chemical Industries) were used to prepare the initial solutions to be used in metal recovery experiments. An analytical-grade AgNO3 solution was purchased from Wako Pure Chemical Industries and used to determine the Cl -concentration in aqueous solution. All chemicals were used without further purification, and all experiments were performed at room temperature.