Preparation of multifunctional magnetic-fluorescent nanocomposites for analysis of tetracycline hydrochloride

A multifunctional nanocomposite for highly sensitive and rapid detection of tetracycline hydrochloride (TC) has been developed using magnetic quantum dots (MQDs). The thiolated quantum dots (QDs) were conjugated with amino-coated Fe3O4 and subjected to crosslinking modification with EDC/NHS through covalent binding. The obtained MQDs were shown to possess superparamagnetic characteristics and fluorescence properties and exhibit a strong orange metal-to-ligand charge transfer emission. The MQDs were characterized by fluorescence spectrophotometry, X-ray powder diffraction, Fourier transform infrared spectroscopy, physical property measurement and transmission electron microscopy. The multifunctional nanomaterial shows excellent fluorescence properties that allow for highly sensitive and short response time for TC detection. Under optimum conditions, a linear calibration plot of the quenched fluorescence intensity at 593 nm against the concentration of TC was observed in the range from 10 to 700 nmol L-1 with a detection limit of 1.2 nmol L-1. The recovery detected with this method was from 95.7% to 99.3% with a relative standard deviation (R. S. D.) below 3%. This method manifested several advantages such as high sensitivity, non-toxicity, short analysis time, low cost and ease of operation.