Preparation And Characterization Of Quantum Dots/Polymer Ultrafine Composite Fibers

One-dimensional(1D)nanomaterials,such as nanowires,nanorods,nanobelts, and nanotubes(length in several micormeter)have been fabricated through self-assembly technique.Electrospinning have been proven to be a versatile and effective method for manufacturing a sheet of microscale to nanoscale continous composite ultrafine fibers with the combination of the semiconductor with the polymer. As an important embranchment of nanocomposites,these nanocomposites that adulterated semiconductor nanoparticle with polymer nanofibers have the potential applications in various fields.The organometallic approach has been exploited to controllable synthesis highly monodisperse CdS quantum dots in non-coordinating solvents octadecene.A good optical properity and obvious quantum confinement effect for CdS nanoparticle was observed by UV-Vis absorption and fluorescence spectrum.Characterization on the morphology,structure and size distribution of core-shell nanocrystals has been performed with X-ray diffraction(XRD),transmission electronic microscopy(TEM), dynamic light scattering size analyzer and select area electron diffraction.The results show that the CdS nanoparticles of cubic blende have good homogeneity and uniform size distribution.The effects of growth/nuclei temperature,reaction time and oleic acid concentration on the growth kinetics,size and size dispersion were investigated.Zinc ethylxanthate was used as precursors to obtain highly luminescent CdS/ZnS core/shell nanocrystals.The results demonstrated that ZnS grew on the surface of the CdS.The resulting highly luminescent CdS/ZnS core/shell nanocrystals have good size dispersion homogeneity exhibiting narrow emission linewidths of 18-20 nm(FWHM) in the blue spectral region with quantum yield approach to 40%. Blending electrospinning of CdS nanoparticles with poly(ethylene oxide) solution was employed to fabricate ultrafine composite fibers.The results demonstrated QDs have homogeneous distribution and good optical performance in the PEO/CdS composite fibers due to the interactions between CdS and PEO.Besides,In comparion with the CdS/PEO composie solution and solvent casting PEO/CdS film, CdS nanoaprtucle embedding in polymer ultrafine fibers have uniform size distribution and high monodisperity.Fluorescence spectra of PEO ultrafine fibers incorporated with CdS mixtures of different sizes indicating the distribution of CdS QDs within the electrospun fibrous mat as good and uniform as that in solution.The photoluminescence(PL)intensity can be easily controlled on broad range by changing content of the CdS particles in the composite fibers.The electrospinning voltage was also found to play an important role on enhancing the passivation effect of PEO so as to enhance the band edge emission as well as weaken the trap state emission of CdS nanoparticles.The combination of PANI and CdS nanoparticles in PEO matrix was also electrospun into 1D ultrafine fiber.The introduction of conducting polymer PANI did not alter the dispersion nature of CdS in PEO matrix.However,the PL intensity of PEO/CdS composite fibers was enhanced by the addition of PANI.The energy levels of CdS and PANI matched properly and enable the transfer of the photo-generated electrons of PANI to the conduction band of CdS and the transfer of the photo-generated holes of PANI to the valence band of CdS.The photo-generated charge transfer mechanism was introduced to explain this enhancement effect.In summary,electrospinning has been proved to be a relatively simple and versatile method for generating 1D nanostructures from semiconductor nanoparticles and matrix polymers.The resulting PL nanocomposites will have a variety of applications in photoluminescent,electroluminescent,non-linear optical devices and photocathodes for solar cells.