Sensitive fluorescence and chemiluminescence procedures for methamphetamine detection based on CdS quantum dots

Abstract

Two novel, simple and sensitive fluorescence (FL) and chemiluminescence (CL) procedures were established for methamphetamine (MA) determination. l-Cysteine capped CdS quantum dots (QDs) were synthesized by a simple one-step hydrothermal procedure and characterized by their specific absorption and emission spectra. The structure and morphology of QDs were investigated using X-ray diffraction (XRD) pattern, transmission electron microscopy (TEM) and scanning electron microscope (SEM). It is found that the prepared CdS QDs have a remarkable promoting effect on rhodamine B (RhoB)-cetyltrimethylammonium bromide (CTAB)-KMnO4 CL reaction. Based on this influence, a new efficient CL system was introduced. On the other hand, the FL and CL emission intensities of QDs undergo a remarkable alteration in the presence of low quantities of MA. The optimization of the effective parameters was performed and the high sensitivity was obtained in 0.013molL−1 Tris buffer at pH=6.5 with 0.2mmolL−1 CdS QDs. In this condition, MA had a notable linear quenching effect on the FL emission of QDs which formed the basis of simple FL probe for sensitive determination of MA in the range of 6.7–400ngmL−1. Also, MA can remarkably enhance the intensity of developed CL system. Under the optimized conditions (0.15molL−1 H2SO4, 0.15mmolL−1 RhoB, 0.13mmolL−1 QDs, 0.3mmolL−1 CTAB and 0.4mmolL−1 KMnO4), the improved CL intensity was proportional to the concentration of MA in the range of 0.25–125ngmL−1 with limit of detection (3s) of 0.086ngmL−1, which is over 20 times better than the introduced FL method. The developed FL and CL methods were exploited for accurate determination of MA in human urine samples.