Preparation Of CdS-based Composite Nano-fluorescence Probes And Their Applications

Fluoremetry possesses some characteristics including good selectivity, high sensitivity, various analytical parameters, and simple operation, which make it more favorable for constructing fluorescent chem/biosensing. However, not many fluorescent reagents are available and traditional fluorescent reagents, e.g. fluorescent dyes, have some drawbacks such as strong background fluorescence, unstable optical properties, photobleaching. This restricts the wider application of fluoremetry. So, it is very interesting to develop fluorescent reagents with stable fluorescence signal.Quantum dot CdS, as a new semiconductive nanomaterial, exhibit lots of amazing propreties such as high luminescence efficient, tunable size, narrow emission spectrum and wide emission range. However, CdS still has some drawbacks including many defects on the surface, unstable luminescence signal and scavceness of functional groups.Considering two points mentioned above, we prepared two kinds of CdS-based composite nanoparticles with stable luminescence signal, and also investigated their applications in chem/biosensing. The details are summarized as follows:(1) CdS-based composite nanoparticles with poly (N-(Hydroxymethyl) -acrylamide) (N-MAM) in aqueous solution under ultrasonic irradiation, which characterized by TEM, UV spectrometry and spectrofluorometry. Taking advantage of synchronous fluorescence technique, a simple method with high sensitivity was developed for the determination of trace DNA using CdS/PN-MAM as fluorescence probe. The possible mechanisms were also proposed. Under the optimum experimential conditions, the linear ranges of the calibration curves are 0.08-30.0 ug mL^-1 for ctDNA and 0.05-35.0 ug ml^-1 for hsDNA, respectively. The detection limits are 1.5ng mL^-1 for ctDNA and 2.2ng mL^-1 for hsDNA, respectively. The regression coefficients are 0.9974 for ctDNA and 0.9966 for hsDNA, respectively. The proposed method was applied to the determination of DNA in the synthetical samples with satisfactory results. (2) Eu3+- doped CdS nanoparticles were prepared in aqueous solution at room temperature. Using Eu3+-doped CdS composite nanoparticles as fluorescence probe, a new method for Hg detection was developed and the mechanisms was also discussed, under the optimum experimential conditions, the quenched fluorescence intensity increased linearly with the concentration of Hg(II) ranging from 10 nmol L^-1 to 1500 nmol L^-1. The limit of detection for Hg(II) was 0.25 nmol L^-1. The regression coefficient is 0.9975. The proposed method was used to test Hg +in water sample with satisfactory results. The recovery and relative standard deriation are very satisfactory.