| Semiconductor photocatalytic materials have broad application prospects in solving environmental pollution and energy shortage.However,traditional semiconductor materials can only use ultraviolet light or part of visible light due to the limitation of their band gap.NaYF4 doped Yb,Tm is an up-conversion fluorescent material,capable of converting long-wavelength near-infrared to short-wavelength ultraviolet or visible light.Aiming at the disadvantage that semiconductor materials cannot absorb near infrared,traditional semiconductor photocatalytic materials are combined with up-conversion materials such as NaYF4:Yb,Tm,so that semiconductor materials can utilize near infrared light through up-conversion process,thus achieving the effect of improving photocatalytic activity.The main study of this paper are reported as follows:(1)NaYF4:Yb,Tm@SiO2 composite with hydrophilic surface was prepared by solvent thermal method and anti-microemulsion method.Then CdS shells with a thickness of about 5 nm were grown on the surface of SiO2 by in-situ growth method,so hydrophilic NaYF4:Yb,Tm@SiO2@CdS composite was synthesized.XRD,TEM,PL and XPS were used to analyze the phase,morphology,fluorescence characteristics and element composition of the composite.Under the irradiation of near-infrared light,the photocatalytic experiment was carried out on the organic dye rhodamine B(RhB).The results showed that the photocatalytic degradation rate could reach 78%within 35min under the visible-near infrared light(Vis/NIR)irradiation,which was higher than the catalytic efficiency of pure CdS(55%).(2)NaYF4:Yb,Tm was synthesized by hydrothermal method using oleic acid as template.Subsequently,the hydrophobic NaYF4:Yb,Tm was improved through acid treatment.Finally,cubic phase CdS shell with a thickness of 22-25 nm was deposited on the surface by in-situ growth method.So NaYF4:Yb,Tm@CdS photocatalytic composite was prepared.Phase,element composition,morphology and fluorescence properties of the composites were characterized by XRD,XPS,TEM and PL.Under the irradiation of NIR,RhB was used as the organic pollutant molecule to explore its photocatalytic activity.The results showed that the degradation rate was up to 82%under the irradiation of Vis/NIR light,which was 17%higher than that of the pure CdS.In addition,photocatalytic cycle experiment of NaYF4:Yb,Tm@CdS showed good stability under the irradiation of NIR light.(3)NaYF4:Yb,Tm@TiO2 photocatalytic composite was prepared by coating an anatase TiO2 shell on the surface of NaYF4:Yb,Tm with polyvinylpyrrolidone(PVP)as template and TBOT as titanium source.XRD,XPS,SEM,TEM,FL and UV/Vis spectra were used to test the phase,element composition,morphology,fluorescence and absorption properties of NaYF4:Yb,Tm@TiO2 samples.The analysis results show that TiO2 precipitates successfully on the surface of NaYF4:Yb,Tm and can absorb NIR light.Under the irradiation of Vis/NIR light,its photocatalytic activity was explored.The experimental results showed that NaYF4:Yb,Tm@TiO2 could degrade RhB by 53%,and its catalytic activity was higher than that of pure TiO2(35%),and its catalytic rate was 2.12 times higher than that of pure TiO2.In addition,NaYF4:Yb,Tm@TiO2 composite exhibited good stability in photocatalytic cycle experiments under NIR irradiation.(4)NaYF4:Yb,Tm/ln2S3 photocatalyst was synthesized by one-step hydrothermal method with n-methylpyrrolidone(NMP)as coupling agent.The phase,morphology,fluorescence properties,element composition and specific surface area of the samples were analyzed by XRD,SEM,HRTEM,PL,EDS,BET and other instruments.The analysis results show that the surface of ?-NaYF4:Yb,Tm is covered with cubic phase ln2S3 shells with thickness of 3 nm,which enables ln2S3 to absorb NIR light through upconversion process.In addition,NaYF4:Yb,Tm@ln2S3 complex has a specific surface area of 20.02 m2/g,which is much larger than that of pure ln2S3(1.07 m2/g),which is conducive to improving photocatalytic activity.RhB was photocatalyzed under irradiation of Vis/NIR light,and the results showed that the adsorption and degradation rate of RhB was 90%within 16 min,which was higher than that of pure ln2S3(50%),and its apparent rate constant was 3.22 times higher than that of pure ln2S3.The study of photocatalytic mechanism reveals that the active groups of NaYF4:Yb,Tm/ln2S3 photocatalytic composites participating in the photocatalytic reaction are mainly superoxide radicals(·O2-).Figure:88,table:3,reference:120... |
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