The Preparation Of Core-shell Structure Polyacrylic Acid Modified Upconversion Nanoparticles Using Photocatalysis ATRP

The upconversion nanoparticles(UCNP)consist of matrix material doped with lanthanides that can emits visible or ultraviolet light when exposed to infrared light.UCNP have been applied in the fields of anti-counterfeiting materials,optical devices,biological and medical because of its low background autofluorescence intensity,large penetration depth,excellent chemical and physical stability.However,the currently prepared UCNP having uniform morphology and small size are usually hydrophobic with long carbon chain compounds(oleic acid,oleylamine,etc.)as surface ligands.So it is necessary to hydrophilic surface modification of UCNP,expanding the fields of application.Atom transfer radical polymerization(ATRP)is a kind of active/controlled radical polymerization,which is mainly used to prepare a series of specific compositions and structures such as block copolymers,star-like polymers,hyperbranched polymers,nanoreactors,etc.In recent years,metal-free photocatalysis ATRP has developed rapidly.Compared with the traditional ATRP,there is no metal residue in the product,and the reaction conditions are milder,which is an economical and environmentally friendly polymerization method.In this paper,the UCNP of different morphology were prepared by different methods,ligands ratio and reaction time,then these factors affecting the morphology of UCNP were studied.The UCNP were surface modified by metal-free photocatalysis ATRP to prepare core-shell structure polyacrylic acid modified UCNP.The details are as follows:1.Using 6-aminocaproic acid and oleic acid as double ligands,the UCNP-NH2/OA with-NH2 and-OA on the surface was prepared by solvothermal method,and the effect of ligands ratio on morphology was studied.Then UCNP-NH2/OA reacted with 2-bromoisobutyryl bromide to prepare UCNP-Br/OA with ATRP photoinitiate sites on the surface.And the surface of the UCNP was modified with polyacrylic acid to prepare UCNP@polyacrylic acid core-shell structure nanomaterial by metal-free photocatalysis ATRP.2.Amidation reaction of 6-aminocaproic acid with 2-bromoisobutyryl bromide was carried out to synthesize a bifunctional ligand BiBAHA.Then BiBAHA and oleic acid were used as double ligands to prepare UCNP-Br/OA with-Br and-OA on the surface by one-step solvothermal method,and the effect of reaction time on morphology was studied.Then,the surface of the UCNP was modified with polyacrylic acid to prepare UCNP@polyacrylic acid core-shell structure nanomaterial by metal-free photocatalysis ATRP.3.The UCNP-OA with oleic acid ligand was prepared by thermal decomposition method.In the presence of NOBF4,the oleic acid ligand was detached by ligand exchange reaction,then reacted with BiBAHA to prepare UCNP-Br with photoinitiate sites.Finally,the surface of the UCNP was modified with polyacrylic acid to prepare UCNP@polyacrylic acid core-shell structure nanomaterial by metal-free photocatalysis ATRP.