Synthesis and characterization of a flexible fluorescent magnetic Fe3O4@SiO2/CdTe-NH2 nanoprobe

In this study, we designed and synthesized two novel fluorescent magnetic nanoparticles. Fe3O4@SiO2-NH-GSH-CdTe (FSGC) (GSH = glutathione) nanoparticles were synthesized using amino-functionalized Fe3O4@SiO2 nanoparticles and GSH-stabilized CdTe quantum dots (CdTe QDs), while flexible Fe3O4@SiO2-NH-GSH-CdTe-NH-NH2 (FSGCN) nanoparticles were synthesized using the FSGC precursor and 1,6-hexamethylenediamine. These two kinds of nanoprobes exhibited excellent magnetic and fluorescent properties. By comparing the fluorescence quenching effect of folic acid (FA) on FSGC and FSGCN, we found that the quenching effect of FA on FSGC was acute and the process was too fast to determine the FA content. However, the quenching effect of FA on flexible FSGCN was mild and hence it could be used as a nanoprobe to determine FA concentration. At physiological pH, the fluorescence quenching effect of FA on the FSGCN nanoprobes was fitted according to the Stern–Volmer equation with a linear response in the concentration range of 0.14 to 4.20 μg mL−1 with a detection limit of 15.1 × 10−9 g mL−1 (S/N = 3) under optimized experimental conditions. The proposed flexible nanoprobe was successfully used to determine the content of FA in folic acid tablets. Recovery was found to be in the range of 92.7%–105.6% with a relative standard deviation of 1.12%–3.84%. Owing to their good stability, environment-friendly characteristics, high selectivity, and good optical properties and biocompatibility, these nanoprobes have potential for usage in practical applications. The quenching reaction between folic acid (FA) and Fe3O4@SiO2/CdTe with short active groups is acute and could not to accurately detect. The quenching reaction between FA and Fe3O4@SiO2/CdTe-NH2 with suitable active groups synthesized by us is mild and could be using to accurately detect. [Display omitted] •A flexible fluorescent magnetic nanoprobe was designed and synthesized.•This nanoprobe contains free amino groups as flexible active groups.•The properties of the nanoprobe were characterized by different techniques.•Quenching effect of folic acid (FA) on the probe was mild and it could detect FA.•The method of FA detection is convenient, accurate, and selective.