Absorption spectra were recorded on a Shimadzu-2550 UV–vis
spectrophotometer using a 1.0 cm quartz cell. All fluorescence
measurements were carried out on a F-4500 spectrofluorimeter
(Hitachi, Japan) equipped with a xenon lamp source and a1.0 cm
quartz cell. The scan speed was 240 nm min–1 and band pass was
2.5nm for excitation and 5.0 nm for emission.Curcumin was the
product of Shanghai Chemical Corp.,which was dissolved in
acetonitrile.The tetrabutylammonium salts of the tested anions
and perchlorate salts of the tested metal ions were the products of
Sigma Corp. Acetonitrile was of chromatographic grade from
Merck Corp.in China.