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

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 0.013 mol L^− 1 Tris buffer at pH = 6.5 with 0.2 mmol L^− 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 6.7–400 ng mL^− 1. Also, MA can remarkably enhance the intensity of developed CL system. Under the optimized conditions (0.15 mol L^− 1 H₂SO₄, 0.15 mmol L^− 1 RhoB, 0.13 mmol L^− 1 QDs, 0.3 mmol L^− 1 CTAB and 0.4 mmol L^− 1 KMnO₄), the improved CL intensity was proportional to the concentration of MA in the range of 0.25–125 ng mL^− 1 with limit of detection (3 s) of 0.086 ng mL^− 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.