Semiconductor quantum dots (QDs) are widely used in many areas of biological analysis, due to their unique optical properties. They exhibit high photostability, narrow and sharp emission spectra, relatively high quantum efficiency and generally long photoluminescence decay times, which arise from quantum confinement combined with large biochemically accessible surface. Fluorescent "turn-off" sensors based on water-soluble quantum dots (QD) are increasingly attracting attention due to their aforementioned unique properties. In this study, a method based on the fluorescence “turn-off” model with water-soluble CdSe/ZnS QDs as fluorescent probes for differentiation of isoniazid, hydrazine and their mixtures as well as pharmaceutical tablets containing isoniazid has been established. The fluorescence of the QDs can be quenched in different degrees in light of positions and intensities of the fluorescent peaks in the presence of the analytes. we showed that the pattern-based sensing with one type of QDs employing non-specific interactions can be achieved by using titration fluorescence spectra. Response patterns are systematically differentiated through the implementation of three pattern recognition algorithms, such as linear discriminant analysis (LDA), principal component analysis (PCA) and hierarchical cluster analysis (HCA) with high classification accuracy. Therefore, the concept of pattern-based sensing (or ‘differential sensing’) helps to design receptors that differentially interact with various analyte components and expand their application prospects
