Preparation And Regulation Of LDHs-based Composite Luminescent Materials And Their Exploration Of Research

Layered double hydroxides(LDHs)is one type of important two-dimensional inorganic layered materials,which can be intercalated and assembled with one or more kinds of luminescent guest molecules to build LDHs-based composite luminescent materials,due to its unique structure.The LDHs provides confinement environment for the luminescent molecules in the interlayer,which is beneficial for their radiative transitions,and improving their luminescent performance.In this paper,with the aim of improving luminescent properties of guest molecules,CdTe quantum dots(CdTe QD),cyanine dye(Cy3)and arachidic acid(AA)were assembled with LDHs to form(CdTeQD@LDHs/AA)n and(Cy3@LDHs/AA)n ultrathin films(UTFs)via L angmuir-B lodgett(LB)technology based on the electrostatic interactions,respectively.In the basis of intercalation properties of LDHs,2,2',4,4'-Tetrahydroxybenzophenone(BP2),2-Hydroxy-4-Methoxy benzophenone-5-Sulfonic acid(BP4),Di sodium 2,2'-dihydroxy-4,4'-dimethoxy-5,5'-disulfobenzophenone(BP9)and decanesulfonic acid sodium salt(DES)were co-intercalated into LDHs to form DES-BP(x%)/LDHs(BP:BP2?BP4?BP9),respectively,which can be regarded as 2D interlayer supramolecular infinite solid solution(2D ISISSs)based on structure analysis.The regulation and optimization of optical properties of(CdTe QD@LDHs/AA)n,(Cy3@LDHs/AA)n LB UTFs and DES-BP(x%)/LDHs 2D ISISSs were realized and their applications were explored according to their structures and properties.This work provides simple and effective designs to improve the optical performance of guest molecules and extend their applications.The main research contents are as follows:Preparation of amphiphilic(CdTe QD@LDHs/AA)n LB UTFs and their detection for organic volatile gases(VOCs):Inspired by biomembranes,(CdTe QD@LDHs/AA)n LB UTFs were prepared by LB method based on electrostic interactions between LDHs and CdTe.QD,AA.The amphiphilic(CdTe QD@LDHs/AA)n LB UTFs have periodic,ordered structure and uniform surface confirmed from the results of SAXRD,SEM,UV-vis absorption and photoemission spectra.Compared with(CdTe QDs@LDHs)n films prepared by layer by layer method(LbL),the photoluminescence intensity,lifetime and quantum yield of the amphiphilic(CdTe QD@LDHs/AA)n LB UTFs were increased by about 10,2 and 3 times,respectively,which are attributed to the spacing effect of AA,which is conducive to the uniform dispersion of CdTe QDs and the reduction of the non-radiative transition caused by the intermolecular interaction.Compared with CdTe QD/AA)n LB UTFs,the luminescence intensity of(CdTe QD@LDHs/AA)n LB UTFs were increased to 5 times,which indicated that LDHs rigid layer provide better interlayer confinement environment for CdTe QDs that inhibit the quenching phenomenon caused by the aggregation between molecules.(CdTe QD@LDHs/AA)n LB UTFs exhibited selective detection for VOCs with different polarity:irreversible fluorescence quenching for amines with strong polarity and reversible fluorescence enhancement for non-amines.Based on the analysis of SAXRD and ATR-FTIR,it is speculated that the fluorescence enhanced/quenched dual-mode response of the film to VOCs is attributed to the different adsorption ability of the amphiphilic structure for VOCs with different polarity.Preparation of amphiphilic(Cy3@LDHs/AA)n LB UTFs and its fluorescence response to temperature:to expand the range of assembled guest molecules in LDHs-based films,zwitterions Cy3 were assembled with LDHs to prepare(Cy3@LDHs/AA)n LB UTFs based on supramolecular electrostatic interaction between Cy3 and LDHs.The results of SAXRD,SEM and AFM show that the film has highly ordered structure and uniform morphology,and its deposition process is uniform monitored by UV-vis absorption and photoemission spectra.Compared with Cy3 solution,the lifetime,quantum yield and radiative transition rate constant(kr)of(Cy3@LDHs/AA)n LB UTFs were increased about 6,12 and 2 times,respectively,which are attributed to the separation and dispersion effect of AA and the rigid confinement environment of LDHs which is beneficial for the uniform dispersion of Cy3 in the film state,and effectively inhibit the intermolecular ?-? stacking or dipole dipole interaction,and thus improve the luminescence performance of Cy3.Importantly,(Cy3@LDHs/AA)n LB UTFs has a reversible response to temperature stimulation,and ts luminescence intensity decreases with the increase of temperature,which can be attributed to the non radiative transition.In this work,the immobilization and enhanced luminescent properties of zwitterions Cy3 have been realized which extend the range of guest molecules in LDHs-based films and inspire others to deeply understand the electrostatic assembly.Preparation,regulation of DES-BP(x%)/LDHs 2D ISISSs and their applications in bio-imaging:Based on the intercalation properties of LDHs,three kinds of UV absorbers(BP:BP2,BP4,BP9)were selected to form DES-BP(x%)/LDHs 2D ISISSs by coprecipitation method.Compared with pure BP solid,the luminescence performance of DES-BP(x%)/LDHs 2D ISISSs is greatly improved,and their emission wavelength is adjustable between 480-520 nm,via changing x%.Among them,DES-BP2(4%)/LDHs,DES-BP4(8%)/LDHs and DES-BP9(16%)/LDHs have optimal luminescent intensity.Compared with pure BP2 solid,the quantum yield,lifetime,fluorescence intensity and kr of DES-BP2(4%)/LDHs were increased nearly 13,4,75 and 4 times respectively;compared with pure BP4 solid,the quantum yield,lifetime,fluorescence intensity and kr of DES-BP4(8%)/LDHs was increased nearly 14,4,45 and 3 times respectively;compared with pure BP9 solid,the quantum yield,lifetime,fluorescence intensity and kr of DES-BP9(16%)/LDHs was increased nearly 30,10,100 and 4 times,respectively.Meanwhile,the nonradiative transition rate constants(knr)of DES-BP2(4%)/LDHs,DES-BP4(8%)/LDHs and DES-BP9(16%)/LDHs were decreased by 2,5 and 5 times,respectively.More importantly,compared with BP2,BP4 and BP9,DES-BP(x%)/LDHs exhibited a new phenomenon of upconversion luminescence.Based on the excellent luminescent properties,biocompatibility and cell penetrability of DES-BP(x%)/LDHs,they were applied into up/down conversion laser confocal fluorescence imaging and fluorescence lifetime imaging.Compared with original BP molecules,DES-BP(x%)/LDHs has outstanding lysosomal imaging ability,therefore,DES-BP(x%)/LDHs can be used as fluorescent probes in the field of bio-imaging.