Crosslinked FAPbBr₃ Nanocrystals/Polymethacrylate Nanocomposites With High Stability And High Fluorescence Are Constructed In Situ

In recent years,perovskite nanocrystals（PNCs）have received wide attentions in the field of materials science owing to their high color purity,high absorption coefficient,high photoluminescence quantum yield（PLQY）,high defect tolerance,and tunable PL across the whole visible spectrum.However,PNCs are prone to degrade induced by the external factors,such as light,heat,water,oxygen,electrical field and polar reagents,mainly due to their inherent ionic nature,low formation energy,highly dynamic ligands and massive surface defects.The poor stability has severely hindered the commercial applications.Therefore,it is urgent to explore an effective approach to improve the stability of PNCs.To improve the stability of PNCs,many kinds of strategies have been developed,mainly including ion doping,surface ligand engineering and encapsulation engineering,etc.Of them,the fabrication of PNCs/polymer nanocomposites via polymer encapsulation has become a promising strategy owing to the combination of both advantageous characteristics,namely the intriguing optoelectronic features of PNCs,as well as the easy processability and high robustness of polymers.At present,the polymer encapsulation strategies mainly include physical blending,grafting approach,in-situ polymerization of monomers in the presence of PNCs and in-situ growth of PNCs in the polymer matrices.Specially,the in-situ PNCs growth approach has attracted tremendous research interest.In-situ growth of PNCs in the polymer matrices can effectively regulate the crystal growth of PNCs by taking full advantages of the polymer,and simultaneously prevent the external environment from corroding PNCs.However,the state-of-the-art processes of in-situ growth of PNCs are complicated and involved the use of a large amount of toxic and strong polar solvents or high temperature,resulting in the poor quality and distribution of PNCs in polymers.Meanwhile,most polymers in the in-situ PNC growth approach are linear polymers,which are still susceptible to solvents and temperature,limiting the further development.In this scenario,herein,the purpose of this thesis is to design and develop a novel,facile,efficient and green method for the fabrication of highly luminescent and extremely stable cross-linked PNCs/polymer composites through the in-situ growth of PNCs in the cross-linked polymers.The main contents are as follows.Firstly,the cross-linked FAPbBr₃PNCs/polymethyl methacrylate（PMMA）nanocomposite films are in-situ fabricated using the two-step method.In this method,the lead methacrylate（Pb（MAA）₂）is selected as the lead source,which contains C=C and Pb²⁺.The main process of the two-step preparation method is as follows:（1）the pre-crosslinked film（Pre（MMA-MAA））containing Pb²⁺is prepared by pre-crosslinking Pb（MAA）₂and methyl methacrylate（MMA）under the initiation of initiator.（2）the cross-linked FAPbBr₃PNCs/P（MMA-MAA）nanocomposite films are fabricated by adding the FABr/isopropyl alcohol（IPA）solution to the Pre（MMA-MAA）films,followed by thermal annealing.The results show that Pb（MAA）₂can not only cross-link with polymer monomers to form stable cross-linked polymer network,but also realize the uniform dispersion of Pb²⁺in the cross-linked polymer network at the atomic scale,thereby promoting the uniform dispersion of the in-situ-grown FAPbBr₃PNCs with narrow grain size distribution and high crystallinity.In the meanwhile,benefited from the intimate encapsulation of the cross-linked polymer network,the nanocomposite films exhibit high PL,high PLQY（>90%）and excellent moisture,thermal and water stability.Moreover,the cross-linked FAPbBr₃PNCs/PMMA nanocomposite films also display good stability in various extreme environments,such as strong acid or alkali aqueous solutions and strong polar alcohol solvents.Secondly,the cross-linked FAPbBr₃PNCs/polymethacrylate composites are in-situ fabricated using the one-pot polymerization method.By directly adding the isopropyl alcohol solution of FABr into the mixed solution of Pb（MAA）₂,oleic acid,oleamine,methacrylate monomer,the cross-linked FAPbBr₃PNCs/polymethacrylate composites are prepared via heating cross-linking.In the one-pot polymerization method,the in-situ growth of FAPbBr₃PNCs and in-situ crosslinking polymerization of methacrylate monomers can occur at the same space and time,realizing the polymer encapsulation of PNCs.The results show that the in-situ-grown PNCs performing the high crystallinity,high PL and narrow halfwidth of PL spectra.Meantime,the composites display good stability in various extreme environments,such as water,oxygen,light,heat,strong acid or alkali aqueous solutions and strong polar alcohol solvents.Moreover,the impacts of four methacrylate monomers,i.e.methyl methacrylate（MMA）,ethyl methacrylate（EMA）,butyl methacrylate（BMA）and isobutyl methacrylate（IBMA）,on the optical properties of composites have been researched in this paper.The results show that the carbon chain length and configuration of monomers can influence the optical properties and stability of PNCs.Our work provides a new approach and route for preparation of highly stable and highly luminescent PNCs/polymer nanocomposites.