Inhibiting effect of molybdenum disulfide nanosheets on cathodic Ru(bpy)32+ electrochemiluminescence in ionic liquids and its sensing application

Abstract

Strong cathodic electrochemiluminescence (ECL) behavior of needle-like structure Ru(bpy) 3 2+ was obtained in 1-(2-hydroxyethyl)-3-methimidazole tetrafluoroborate without the need of additional coreactant. Molybdenum disulfide nanosheets (MoS 2 NSs) exhibited apparent inhibiting effect on the cathodic ECL signal through energy transfer and charge transfer process. As a result, a label-free ECL aptasensor was fabricated for the detection of lysozyme in HomimBF 4 . • Strong cathodic Ru(bpy) 3 2+ ECL was obtained in ionic liquid without coreactant. • MoS 2 nanosheets exhibited greatly inhibiting effect of ECL. • A “off-on” mode aptasensor for lysozyme was fabricated. Electrochemiluminescence (ECL) behaviors of needle-like structure Ru(bpy) 3 2+ was investigated in three room temperature ionic liquids with different cations such as 1-(2-hydroxyethyl)-3-methylimidazolium tetrafluoroborate (HomimBF 4 ), 1-ethyl-3-methylimidazolium tetrafluoroborate (EmimBF 4 ), and 1-hexyl-3-methylimidazolium tetrafluoroborate (HmimBF 4 ). The results revealed that both cathodic ECL and anodic ECL could be obtained in ionic liquids without the need of additional coreactant, which could simplify the fabricating process of biosensor. Strongest cathodic ECL signal can be obtained in HomimBF 4 which was selected as medium in biosensing investigation. Several experimental parameters, such as potential window, potential scan rate and direction, different atmosphere, and ECL spectrum were studied and the possible ECL mechanisms were proposed. Apparent inhibiting effect of molybdenum disulfide nanosheets (MoS 2 NSs) on the cathodic ECL signal was observed and used to fabricate “off-on” mode ECL sensor for lysozyme in HomimBF 4 . In the range of 1.0 × 10 -12 to 5.0 × 10 -9 mol L -1 , the ECL intensity varied linearly with the logarithmic of lysozyme concentration with a detection limit of 0.163 pM. The fabricated ECL sensor showed high sensitivity and good selectivity in the detection of lysozyme, revealing that ionic liquid is the potential promising medium for ECL sensor.