Preparation And Application Of Au,Cu Nanoparticles And Their Composite Materials

The rapid development of nanoscience and nanotechnology has greatly promoted the wide application of nanomaterials in the various fields.In particular,metal nanoparticles have been widely concerned in these fields including optics,catalysis and biology because of their good biocompatibility,surface plasmon resonance absorption effect,surface-enhanced Raman effect and catalytic properties.Therefore,designing and constructing metal nanoparticles and their composite materials with special properties have become a hot spot in nanomaterial field in recent years.In this paper,gold nanoparticles as a saturated absorber for modulating 2 ?m laser,gold-copper bimetal nanoparticles supported on titanium dioxide nanobelts for selective oxidation of benzyl alcohol and copper-loaded titanium dioxide nanobelts for the preparation of nanoporous ceramics were studied in detail.The main research contents are summarized as follows:(1)The spherical-like Au nanoparticles with uniform particle size and average diameter of 15 nm were prepared by chemical reduction method,and then they were made into two saturable absorbers with different Au NPs density(S1 and S2)for Tm:YAP solid-state lasers.Their practical modulation properties at 2 ?m were investigated in the solid-state laser by initiating and stabilizing the Q-switching operation.Under the modulation of S1,laser pulses with shortest pulse duration of 1 ?s and repetition rate of 99 kHz were delivered from the structured Q-switched laser,corresponding to a pulse power of 6.1 ?J and a peak power of 6 W.Compared to S1,S2 had a narrower laser pulse duration,higher repetition rate and peak power,and lower pulse energy.These data illustrated the increase in the density of Au NPs played an important role in narrowing the delivered pulse.And Au NPs with the small size and spherical-like shape were helpful to improve the stability of the subsequently established Q-switched lasers.Besides,due to the large third-order nonlinear coefficient of Au NPs,the realized Q-switched lasers showed very low threshold in this work.These results well indicated the promising potential of Au NPs as saturable absorber for modulating 2 ?m laser.(2)Cu nanoparticles were loaded H2Ti3O7 nanobelts by deposition-precipitation method to obtain Cu/TiO2-NB with one-dimensional structure.Then,Cu nanoparticleson Cu/TiO2-NB were replaced by HAuCl4 in situ to prepare Au-Cu/TiO2-NB bimetallic catalyst.The composition and structure of Au-Cu/TiO2 NB bimetallic catalyst were analyzed by ICP-AES,SEM,HR-TEM,and XPS.We found that the Au-Cu bimetals were uniformly dispersed on the TiO2 nanobelts and the particle size was no larger than 2 nm.And the catalytic performance of Au-Cu/TiO2-NB was also evaluated by catalytic oxidation of benzyl alcohol.Based on the analysis of experimental data,the catalytic efficiency and stability of Au-Cu/TiO2-NB bimetallic catalyst was higher than that of the corresponding single metal catalyst(Au/TiO2-NB or Cu/TiO2-NB),and its catalytic activity could be regulated by changing the ratio of Au/Cu and the reaction temperature.When the ratio of Au/Cu was 1:3.85 and the reaction temperature was 280 ?,the conversion rate of benzyl alcohol was more than 90%and the selectivity of the product benzaldehyde was also as high as 98%in this catalytic system.It was also found that the high activity and selectivity of the Au-Cu/TiO2 NB bimetallic catalyst hardly decreased after the catalytic reaction was run for up to 30 hours.Even Au-Cu/TiO2-NB was reused,its catalytic activity rarely changed.(3)Cu/TiO2-NB porous ceramic membrane was prepared by tabletting and calcining one-dimensional Cu/TiO2-NB nanostructure,and the effects of calcination temperature and atmosphere on the structure and mechanical strength of the ceramic membranes were investigated in detail.It was found that the porous ceramic membrane obtained by calcination at 800 ? and N2 atmosphere had higher porosity,smaller pore size and better mechanical strength.Moreover,Cu nanoparticles in the ceramic membrane existed in the form of Cu(0),indicating that the ceramic membrane had high oxidation resistance and stability.These data provided prerequisite that Cu/TiO2-NB porous ceramic membrane was expected to be applied to membrane reactors.It was also found that Cu nanoparticles acted as binders to weld TiO2 nanobelts together,which could effectively reduce the sintering temperature in preparing ceramic membrane.This work would open up a new path for the preparation of new inorganic ceramic membrane at lower temperatures.