Electrocatalytic oxidation of l-Trp at poly(l-methionine)/graphene composite film modified glassy carbon electrode (PLME/GR/GCE) were investigated by differential pulse voltammetry.

In the present study, a new fluorescence probe based on dithizone-etched CdTe nanoparticles was designed for the sensitive and selective detection of cadmium ions in environmental samples via a reversible off-on fluorescence mode. At first, the initial bright fluorescence of L-cysteine-capped CdTe NPs could be effectively quenched in the presence of dithizone (DZ) due to the chemical etching effect, which results from the breaking of Cd-thiol layers by DZ, thus leading to a decrease in the NPs surface passivation. Then, upon the addition of Cd 2+ , the weak fluorescence of the CdTe NPs-DZ system gradually recovered, owing to the occurrence of Cd-thiol passivation layers on the surface of the NPs.Under optimal conditions, a good linear relationship was obtained in the range from 0.4 mM to 15.4 mM for Cd 2+ , with a detection limit of 0.13 mM. In addition, this CdTe NPs-based nanosensor presents remarkable selectivity for Cd 2+ over other metal ions and was successfully applied for the detection of Cd 2+ in real water samples with satisfactory results, demonstrating its potential application for the determination of Cd 2+ in the environment.

A novel imprinted sensor for ultra-trace cholesterol (CHO) detection based on electropolymerized aminothiophenol (ATP) molecularly imprinted polymer (MIP) on a glassy carbon electrode (GCE) modified with dopamine@graphene (DGr) and bioinspired Au microflowers has been developed in this work. As the specific recognition element, the bioinspired Au microflowers were formed by Au nanoparticles (AuNPs) and wrapped by bionic polydopamine film (PDA) through electropolymerization method. These excellent biocompatible materials could capture the target CHO effectively. The morphology of the MIP modified electrode was characterized by scanning electron microscopy (SEM) and atomic force microscope (AFM). The hydrogen-bonding interaction between templates and monomers was characterized by ultraviolet spectroscopy. Under the optimal experimental conditions, the sensor's linear response range was between 10 and 10 M, with a detection limit of 3.3×10 M, which was much more sensitive than most available CHO detection methods in previously reports. Moreover, the MIP sensor exhibited high sensitivity for CHO, low interference, and good stability. The human serum samples analysis confirmed the applicability of this MIP sensor to quantitative analysis of ultra-trace CHO.