| The quantum dots(QD)composite film are widely used in the display device instead of phosphor.Cadmium selenide(CdSe)quantum dots are widely used in quantum dots composite film by virtue of their stable chemical properties,wave-length adjustable in visible range and solution processing.However,there are many serious problems for quantum dots composite films such as low fluorescence efficiency,high fabrication cost and poor luminous efficiency of composite films.In this paper,not only the high-efficient CdxZn1-xSeyS1-y nuclear shell quantum dot but also polydiallyl dimethyl ammonium chloride/quantum dot([PDDA/QD]n)quantum dot composite film were prepared by using the low cost assembly technology.The synthesis mechanism,morphology and fluorescence enhancement characteristics of the Au/PDDA/QD and/Au/SiO2/QD quantum dot composite films were investigated in detail.The main research contents were as follows:Firstly,we use cadmium oxide(CdO)as the source of cadmium,selenium powder as a source of selenium(Se),two hydrated zinc acetate as the source of zinc,sulfur powder as the source of sulfur source,respectively,to prepare oil phase CdSe,CdxZn1-xSeyS1-y quantum dots with a method of high temperature thermal injection.And the phase transfer method was used to prepare water phase quantum dots with mercaptopropionic acid as ligand.The effects of the chemical reaction time and the precursors' ratios in the precursor solutions on the performance of quantum dots were investigated in detail.The results showed that when the precursors' ratio Se/Cd=0.25,the as synthesized CdSe quantum dots with the quantum dots yield of 43%.When the precursors' ratio Se/Cd=0.25,the as synthesized core/shell quantum dots exhibited excellent performances such as the quantum yield(QY)of 90%,narrow half peak width(FWHM)of 20nm,uniform particle distribution with grain size of 13nm,fluorescent lifetime of 13ns with near-single exponential decay characteristics(Single-decay,the goodness of fit=1.29).When 5ml mercaptopropionic acid(MPA)was added,water-soluble quantum dots with quantum yield(QY)of 80%,and fluorescent lifetime= 15.6ns were synthesized.Secondly,gold nanoparticles were synthesized by using trisodium citrate as reducing agent and tetrachloric acid as the gold source,respectively.And polymer electrolyte polydiallyl dimethylammonium chloride(PDDA)was used as surfactant to assembly the quantum dots films with[PDDA/QD]n architecture and surface plasmon fluorescence-enhanced quantum dot films with Au/PDDA/QD architecture via layer-by-layer assembly technology.The results showed that the fluorescence intensity and absorbance of the quantum dot luminescent film gradually increased with the increase of assembly layers from one layer to fifteen layers.When 0.7ml,1ml,5ml,10ml of trisodium citrate solution were added,gold nanoparticles with grain-size of 54nm,42nm,23nm,13nm were obtained and their corresponding the quantum dots luminescent films with fluorescence enhancement factors of 2.5,6.8,11.8,4.3 under 5 min assembly time were fabricated,respectively.The quantum dot luminescent film with fluorescence enhancement factor of 15 were obtained by using gold nanoparticles with grain size of 42 um under 1 min assembly time.In order to further improve the fluorescence performance of the quantum dot composite film,surface plasmon fluorescence-enhanced quantum dot films with Au/SiO2/QD architecture were formed by using the silicon dioxide as insulation layer,which was obtained from trimethylaminane(TDMAS)and ozone precursors by ALD technology.The results showed that high quality SiO2 film with Si:O=1:2.105 was obtained.The quantum dot luminescent films with fluorescence enhancement factors of 2.3-24 were obtained when the thickness of SiO2 films were controlled between 2nm to 8nm.Especially,when the thickness of SiO2 film was 4nm,the quantum dots composite film obtained 24 times fluorescence enhancement and its fluorescent lifetime decreased to 0.448ns. |
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