Invited paperDetermination of superoxide anion radical by modified CdTe quantum dots

- A novel fluorescence probe was designed for determination of superoxide anion radical.
- The fluorescence probe was based on l-cysteine Schiff base and CdTe quantum dots.
- The fluorescence probe has a high selectivity towards O2−.
- The Schiff base was served as spacer molecule for fluorescence assay.

A novel fluorescence probe for determination of superoxide anion radical (O2−) was developed with CdTe quantum dots(QDs) modified by thiophene-2-formaldehyde shrinked l-cysteine Schiff base, which was characterized by Fourier transform infrared (FT-IR), thermal gravimetric analysis (TGA), ultraviolet-visible (UV-vis) and fluorescent spectrum. The particle size of CdTe QDs was 3.1 nm as confirmed by X-ray powder diffraction pattern (XRD) and Transmission Electron Microscope (TEM) in presence of β-cysteamine (CA). The fluorescent results showed that the fluorescence intensity of CdTe QDs was decreased with modified Schiff base at 305 nm, but enhanced at 610 nm with O2− and showed an apparent linear dependence in the concentration scope of 2.0 × 10−5-1.0 × 10−4 mol L−1 (r = 0.9934) with a detection limit of 1.8 × 10−6 mol L−1, which exhibited high selectivity and stability towards O2−.

Fig. 6 shows the fluorescence spectra of the Schiff base (1.0 × 10−5 mol L−1) and the CdTe QDs (1.678 × 10−5 mol L−1). It can be seen from Fig. 6 that the strongest emission (Fig. 6b) wavelength is at 337 nm (λex = 305 nm, Fig. 6a), due to the closed-loop in the formation of Schiff base and the closed-ring structure which showed excellent fluorescence intensity. And CdTe QDs have significant fluorescence properties, the strongest emission located at 610 nm (Fig. 6d) (λex = 305 nm, Fig. 6c), the emission spectrum is narrow and symmetrical, and the excitation spectrum is broad.105