Layer-by-Layer Assembly Of Film Materials And Their Application In Catalysis

Layer-by-Layer(LbL)method provides new horizons for surface molecular engineering.The method is a simple technique without complicated instruments.The main driving force for LbL assembly has been already expanded from electrostatic interaction to hydrogen bonds,molecular recognition,charge-transfer,and stepwise stereo-complex assembly.The direct application of films as the catalysts is an interesting topic that attracts much attention and opens up an avenue to reduce amount of the catalyst.This thesis focused on the preparation of film materials using LbL method and their application in catalysis.This thesis includes two parts.(1)On the basis of Pd-N interaction,the ligand isonicotinic acid(3-pyridylmethylene)hydrazide and K2PdCl4 was used for the preparation of metal-organic films by LbL method.UV-Vis spectra,atomic force microscopy(AFM),transmission electron microscopy(TEM),inductively coupled plasma optical emission spectrometer(ICP-OES)and X-ray photoelectron spectroscopy(XPS)were applied to study the growth process of the resulting LbL multilayers.Results showed that the growth process of the composite films is just LbL.The(Pd/ligand)10 LbL films were further applied as catalysts for the hydrogenation of nitroarenes.The results indicated that our films behave a good catalyst activity.What’s more,XPS and TEM detected that palladium nanoparticles have been in situ produced within films after hydrogenation reaction,it is the reason that the films can be well applied as catalyst reservoirs capable of progressively producing amounts of Pd NPs and used as catalyst for the hydrogenation of nitroarenes.It is worth mentioning that our catalytic film can be easily removed from the reaction system in any time during the reaction and possesses good recyclability even after been reused five times.(2)This section demonstrated a photoactivity and selectivity enhancement in alcohol photo oxidation using LbL film catalyst TiO2-(PW]2-TH)8(PW12 = PW]2O40,TH = thionine).Here,sensitized by the commercial dye thionine,the photo response of porous anatase TiO2 microspheres extends from the UV to the visible region.The results showed that in all cases,various benzylic alcohols can be effectively transformed to their corresponding aldehydes with almost absolute selectivity,which is much higher than that of commercial TiO2-(PW12-TH)8(Degussa P25).In particular,the presence of PW12 enables reaching the highest photocatalytic activity,which is nearly three times than that of Ti02@TH.Electron paramagnetic resonance(EPR)spectra explored main reactive species in the proposed system.The high photocatalytic activity of this system is due to the smooth electron transfer from photoactivated TH to anatase,and then electron scavenged by the surface adsorbed 02 to produce superoxide radical anions incessantly.Accordingly,a systematic understanding of the mechanism of ternary Ti02-(PW12-TH)8 with enhanced visible-light for selective transformation is also proposed.