Preparation And Luminescence Properties Of ZnS/CNTs Nano Composite Materials

Sulfides have drawn a lot of attentions owing to their exceptional physical andchemistry properties on optical, electrical, magnetic, and so on. In this thesis, a veryimportant sulfide semiconductor material ZnS was selected as research object, toprepare ZnS/CNTs nanocomposite materials. The composition materials werecharacterized by using TEM, PL and XRD, and the influences of the synthesis methods,the styles of reactants and carrier, the concentration of doped Cu²⁺and pH value of theprecursors were carefully analyzed.In the first part, precipitation method and reflux method ZnS/CNTs were investigatedto synthesized ZnS/CNTs nanocomposite materials. It was found that the differentinduced orders of reactants lead to different coating effects in precipitation method, andreflux method showed a better coating effect than precipitation method. Using252nm asexciated wavelength, the photoluminescence lines indicated that ZnS/CNTsnanocomposite materials exhibited a stronger emission at397nm and a lower emissionat282nm. The fabric of ZnS/CNTs nanocomposite materials synthesized byprecipitation method is hexagonal wurtzite, while the fabric synthesized by refluxmethod is the compound of hexagonal wurtzite and cubic sphalerite.In the second part, the effect of CNTs sizes and surface fuctional groups on thenanocomposite materials was studied in reflux method which exhibited better coatingeffect. The testing results showed that the CNTs with a size longer than30nm and withthe–COOH as the fuctional groups on the surface exhibited a better coating effect, andthe ZnS nanoparticles own a higher crystallinity. This result indicats that the size ofCNTs and the existed of surface fuctional groups play a key role in the recombinationprocess. The PL analysis indicated that the ZnS/CNTs nanocomposite materialsexhibited a stronger emission at393nm and a lower emission at282nm.Compared withZnS nanocrystals, ZnS/CNTs nanocomposite materials had a7nm blue shift. XRD analysis showed that the fabric of ZnS/CNTs nanocomposite materials is the compoundof hexagonal wurtzite and cubic sphalerit.In the third part, the effect doped of Cu²⁺on the ZnS/CNTs nanocomposite materialswas studied. The results showed that the doped of Cu²⁺not only affect the shape ofZnS/CNTs nanocomposite materials, but also affect their luminescent capability. The PLspectra showed that the emission peaks are at449nm and538nm. In a certain range,with the doping ratio increasing, the luminescence intensity of the composite increased.As the n(Cu²⁺)：n(Zn²⁺)=1%, the luminescence intensity is the strongest, then, as thethe doping concentration increased, the emission peak became weaker on the contrary.This phenomenon is caused by the concentration quenching. The testing results showedthat the ZnS/CNTs nanocomposite materials synthesizd in the acidic and alkalescentconditions exhibited different luminescence intensity: the latter exhibited a strongerluminescence than the former, and the emission peak of the latter showed a blue shiftphenomenon than the former.