Nanowires of metal (Cd, Cu) halide complexes with 8-hydroxyquinoline for photoelectrochemical and electrochemiluminescence sensing

Metal-hydroxyquinoline-halogen (MqX, M = Cd, Cu; q = 8-hydroxyquinoline; X = Cl, Br, I) nanowires are synthesized via a sonochemical-assisted method. The elemental analysis (EA), inductively coupled plasma-optical emission spectroscopy (ICPAES), and X-ray photoelectron spectroscopy (XPS) support an M/q/X ratio of 1:1:1. The electron microscope images reveal a typical CdqX and CuqX nanowire diameter of 30-50 nm and a nanowire length of 400-600 nm. In addition, the synthesis of the MqX nanowires is only observed when there is an excess of halide ions (X/q molar ratio of 3 or greater). This halide deficiency results in the formation of micrometer-sized Mq(2) sheets. We demonstrated the conversion of the MqX nanowires to Mq(2) micro-sheets in an ultrasonic bath of 1 M 8-Hq ethanol solutions (50%, w/w) at 50 degrees C for 2 h, but not vice versa. The MqX nanowires exhibited excellent properties for photoluminescence, electro chemilumine scence (ECL), and photoelectrochemistry (PEC). The CdqBr and CdqI nano-wires were coated onto a glass carbon and a fluorine-doped tin oxide glass electrode to develop the above ECL and PEC methods for the detection of H2O2 and Cu2+, respectively. In the range of 2 to 14 mu M, the ECL intensity of the CdqBr nanowires was inversely proportional to the concentration of H2O2 with a detection limit of 0.26 mu M. For Cu2+ sensing, the photocurrent of the CdqI nanowires exhibited a linear response to Cu2+ over the range of 2 to 16 mu M of which a detection limit of 0.2 mu M was observed.