The Study On Carbon Quantum Dots Catalyzed By Visible Light And Near-infrared Light Induced Atom Transfer Radical Polymerization (ATRP)

Light-induced atom transfer radical polymerization is a simple and efficient method that can prepare complex and functional polymers.It has the advantages of a wide range of applicable monomers,mild reaction conditions,and the ability to control the polymerization process through"ON/OFF"light.At present,most of the photocatalysts used in light-induced ATRP are transition metals,organic dyes,organic catalysts and semiconductor nanoparticles.However,transition metals,organic dyes and organic catalysts are toxic,expensive and difficult to prepare.Semiconductor nanoparticles are also complicated to synthesize.And the light sources used are usually ultraviolet light or visible light,which would bring some side reactions and limit its application in biology.Therefore,researchers currently hope to find a photocatalyst with good biocompatibility and excellent photocatalytic performance.This thesis used carbon quantum dots as photocatalysts to conduct ATRP polymerization under visible light and near-infrared light.By preparing different types of N-doped carbon quantum dots,the effect of the doped N type on the photocatalytic ATRP of carbon quantum dots was studied;then the upconversion material was combined with carbon quantum dots to prepare UCNP@SiO₂@CDs nanoparticles.The polymerization kinetics of ATRP under the irradiation of visible light and near-infrared light were studied,and the penetration performance of near-infrared light was studied.The specific research content is as follows:(1)Different N types of carbon quantum dots were prepared by hydrothermal method.The carbon quantum dots were synthesized by different precursors.When the ratio of citric acid and ethylenediamine was changed,the ratio of pyridinic N and pyrrolic N in the prepared carbon quantum dots would change.The less citric acid,the less the content of pyridinic N.(2)Carbon quantum dots can be used as photocatalysts for ATRP polymerization.Carbon quantum dots(CD₁ and CD₂)containing pyridinic N had better catalytic effects.The polymerization process conformed to the characteristic of"living"/controlled,indicating that pyridinic N was important for ATRP.The higher the pyridinic N content,the faster the ATRP polymerization rate.The fluorescence quenching study found that CD₁ can be better quenched by CuBr₂/PMDETA complex,while the CD₄ was not quenched.The quenching results were consistent with the experimental results.(3)Due to the problems that carbon quantum dots cannot use long-wavelength light and recycling,we added upconversion nanomaterials into the polymerization system,and successfully carried out the ATRP reaction under visible light and near-infrared light irradiation,near-infrared light can pass through the pigskin barrier to initiate polymerization,and all polymerization results were in line with the characteristics of the free radical"living"/controlled.More importantly,the nanoparticles can be recovered by centrifugation,which proved that UCNP@SiO₂@CDs nanoparticles can be recycled.