Preparation And Assembly Behavior Of ZnO Nanocrystals

Zinc oxide(Zn O)nanocrystals are a kind of important semiconductor nanomaterials.Up to now,they are widely used in the fields of light-emitting diodes,fluorescent labeling,solar cells,antibacterial and photocatalysis owing to their unique properties such as surface effect,small size effect,quantum size effect and dielectric limit effect.Zn O nanocrystals with smaller particle size and controllable size could play a greater extent in application.In this paper,Zn O nanocrystals with controllable sizes were obtained by selecting different alcohol as solvent,changing the reaction time,reaction temperature and concentration of precursor without adding bases and surfactants.Zn O nanocrystals with narrow size distribution were synthesized by solution chemical method by using n-hexanol as solvent.The synthesized Zn O nanocrystals were characterized by Ultraviolet–visible spectroscopy(UV-Vis),transmission electron microscopy(TEM)and X-ray diffraction(XRD).The effects of the amount of water,reaction temperature,the concentration of precursor and reaction time on the growth rate and size of Zn O nanocrystals were systematically studied.The particle size of Zn O nanocrystals was obtained by effective mass model,and the relationship between radius and time were obtained by Lifshitz,Slyozov and Wagner(LSW)equation.The growth kinetics of Zn O nanocrystals was further discussed.The results indicate that using n-hexanol as solvent,the growth rate of Zn O nanocrystals is fast,the size of nanoparticles is small and evenly distributed.Changing the kind of alcohol solvent and prolonging the reaction time in the experiment,using anhydrous ethanol as solvent,reaction temperature and the concentration of precursor,and further explore the time of the absorption peak of Zn O nanocrystal.After the reaction,γ-aminopropyl triethoxysilane(KH550)or the PVP surfactant was added to coat the Zn O nanocrystals inhibiting further aggregation between nanocrystals.The properties of Zn O nanocrystals are not only related to crystal size,but also closely related to their morphology.Redispersing the obtained Zn O nanocrystals in ethanol solvent into water,changing the temperature and time,and assembling by adjusting the interaction force of Zn O nanocrystals.The results show that the nanocrystals could self-assemble into nanosheets through hydrogen bond,Van der Waals force and other forces.