Photoelectrochemical sensing of Cu2+ ions with SnO2/CdS heterostructural films

We report here on preparation of SnO2/CdS heterostructural films on fluorine-doped tin oxide (FTO) substrates and their application in selective sensing of Cu2+ ions by photoelectrochemistry. Films of SnO2 particles were first synthesized by thermal decomposition of SnSO4 that was spreaded on the FTO substrates by solution evaporation, and SnO2/CdS heterostructural films were then obtained by performing successive ionic layer adsorption and reaction (SILAR) on the SnO2 films. The anodic photocurrent density on the prepared FTO/SnO2/CdS films was as high as 1.4 mA cm−2 in 1 M Na2SO3 solution under visible illumination due to effective light absorption and charge separation of the heterostructure. Cu2+ sensing was based on the interaction between Cu2+ and CdS by immersing the heterostructural film electrode into a Cu2+-containing sample for 5 min. The binding of Cu2+ by S2− onto the heterostructural surface led to decrease in photocurrent on the FTO/SnO2/CdS/CuxS film electrode in the Na2SO3 solution, and the decrease extent of photocurrent depended on the Cu2+ concentration in the sample solution. The proposed photoelectrochemical device for the detection of Cu2+ ions can be easily fabricated with good selectivity, low detection limit (0.55 μM), and acceptable detection range (1.00–38.0 μM), which can be applied to detect Cu2+ ions in drinking water.