Synthesis and characterization of a novel nitric oxide fluorescent probe CdS-PMMA nanocomposite via in-situ bulk polymerization.

A novel nitric oxide (NO) fluorescent probe CdS-poly(methyl methacrylate) (PMMA) nanocomposites with different molar ratios of CdS quantum dots (QDs) to PMMA are developed successfully via in-situ bulk polymerization method. The optical properties of CdS/PMMA nanocomposites are studied by UV-Vis absorption spectra and fluorescence (FL) spectra in detail. It is demonstrated that the optical properties from such nanocomposite solution are tuned and stabilized by simply varying the concentration of CdS in the final product. X-ray diffraction (XRD) patterns of CdS-PMMA nanocomposite with higher loading of CdS show broad pattern for cubic CdS, which has narrow particle size distribution with less than 5 nm in PMMA observed by transmission electron microscopy (TEM). The surface morphological characterization of the CdS-PMMA nanocomposite has been done through atomic force microscopy (AFM). The thermo-gravimetric analyses (TGA) and differential scanning calorimetry (DSC) confirm the enhanced thermal stability of CdS-PMMA nanocomposites than PMMA. NO can coordinate with Cd(2+) as a ligand for transition metal complexes, which will cause a quenching effect on the fluorescence of CdS QDs. Therefore, a significant quenching effect on the fluorescence of the CdS-PMMA nanocomposite is observed in the presence of NO. The fluorescence responses are concentration-dependent and can be well described by the typical Stern-Volmer equation, and a linear calibration I0/I=1.0021+0.1944[NO] (R(2)=0.96052) is obtained in the range from 1.4×10(-5) to 9.3×10(-3) mol/L NO with a detection limit of 1.0×10(-6) mol/L (S/N=3).