Copper nanocluster-enhanced luminol chemiluminescence for high-selectivity sensing of tryptophan and phenylalanine.

A remarkable method for the highly sensitive detection of phenylalanine and tryptophan based on a chemiluminescence (CL) assay was reported. It was found that fluorescent copper nanoclusters capped with cysteine (Cys-CuNCs) strongly enhance the weak CL signal resulting from the reaction between luminol and H2 O2 . Of the amino acids tested, phenylalanine and tryptophan could enhance the above CL system sensitively. Under optimum conditions, this method was satisfactorily described by a linear calibration curve over a range of 1.0 × 10-6 to 2.7 × 10-5  M for phenylalanine and 1.0 × 10-7 to 3.0 × 10-5  M for tryptophan, respectively. The effect of various parameters such as Cys-CuNC concentration, H2 O2 concentration and pH on the intensity of the CL system were also studied. The main experimental advantage of the proposed method was its selectivity for two amino acids compared with others. To evaluate the applicability of the method to the analysis of a real biological sample it was used to determine tryptophan and phenylalanine in human serum and remarkable results were obtained.