Effect of Lithium Ion on Electrochemiluminescent Response of Sensors Based on Langmuir-Blodgett Films with Polycyclic Organic Phosphors

This work reports the results of electrolysis of an aqueous solution containing lithium perchlorate as a supporting electrolyte and tripropylamine (TPrA) electrochemiluminescence (ECL) as a coreactant on ITO electrodes modified with a 9.,10-diphenylanthracene (DPA) phosphor in a polymethylmethacrylate (PMMA) matrix deposited by the Langmuir-Blodgett method. The results show that lithium perchlorate solution gives a background ECL signal in the absence of coreactant, and when TPrA is added, the shape and appearance of the ECL emission change., whereas TPrA/DPA system gives no ECL emission. Changing lithium perchlorate to sodium perchlorate leads to the disappearance of ECL, and purification with an organic solvent of lithium perchlorate does not affect the light emission, indicating the specific behavior of the lithium-ion during electrolysis. Special attention is also paid to the procedure of cleaning ITO substrates before film deposition and after its use with chloroform vapor in a distillation setup.