Construction Of NIR-Response ZGGO：Cr³⁺/Y³⁺@SiO₂@MS（M=Pb，Cu₂）Nanocomposites And Their Potential Applications

In recent years,the construction of multifunctional nanocomposites based on autofluorescence-free afterglow imaging of near-infrared（NIR）long afterglow luminescent nanoparticles for precision medical treatment of organisms has become a research hotspot.In particular,the multifunctional nanocomposites constructed based on Cr³⁺ions-doped gallium zinc germanate long afterglow nanoparticles have gained certain breakthroughs in biomedical fields such as bioimaging,temperature sensing,and photothermal therapy.However,there are still some deficiencies,such as the particle size distribution is not uniform enough;the afterglow luminescence performance needs to be further improved.Meanwhile,the process of photothermal treatment has the following drawbacks:the optimal treatment time window can not be accurately grasped;the laser power is too large and thus easy to cause photodamage to normal biological tissues;and the photothermal diagnosis and treatment of the integration of multi-functional nano-platforms are mostly used in the excitation of a single wavelength,which is not conducive to the reduction of the laser power and the expansion of the depth of the tissue application and so on.Therefore,it becomes urgent to develop small-size visual diagnostic nanocomposites with deep tissue application depth and biocompatibility under multi-wavelength NIR light excitation by combining uniform small-size ultra-long NIR afterglow luminescent nanoparticles and photothermal agents with excellent photothermal conversion performance in the NIR region.Therefore,our main research results are as follows:Firstly,Zn₂Ga_2.98-xY_xCr_0.02Ge_0.75O₈(ZGGO:Cr_0.02,Y_x)persistent luminescent nanoparticles（PLNPs）with different concentrations were synthesized by a hydrothermal method combined with vacuum heat treatment.As the Y³⁺ions concentration increased from0 to 0.05,the average size of the grains decreased from 53 nm to 28 nm and the shape of the nanoparticles from irregular to near-spherical due to the surface charge modification that inhibited the growth rate of the nanocrystals.Based on spectral analysis and first principles calculations,the NIR emission peaks at 703 nm and 743 nm under 590 nm photoexcitation are attributed to the ⁴T₂→⁴A₂transition of Cr³⁺ions occupying octahedral Ga³⁺ions sites and the⁴A₂→⁴T₁ transition of Cr³⁺ions occupying octahedral Ga³⁺ions sites,respectively.It is also found that Y³⁺ions are more likely to occupy the tetrahedral Ga³⁺ions sites,which not only led to the generation of more anti-site defect pairs and thus enhanced the afterglow luminescence performance(λ_mon=697 nm),but also increased the rigidity of the PLNPs and the improved dispersibility of PLNPs in different simulated body fluids induced by complete surface modification（i.e.SiO₂coating）.Meanwhile,NIR afterglow luminescence signals of PLNPs in deep tissues could be detected under 635 nm laser irradiation.The results suggest that ZGGO:Cr_0.02,Y_0.03@SiO₂nanoparticles have potential applications in biomedical fields based on NIR-response.Secondly,by means of electrostatic adsorption,a uniform small-size Pb S@PVP nano-photothermal agent（34.9±3.38 nm）with good light absorption and biocompatibility at the first biological window（650-950 nm）are combined with amino-modified ZGGO:Cr_0.02,Y_0.03@SiO₂nanoparticlestoconstructthevisualized ZGGO:Cr_0.02,Y_0.03/Pb S@PVP multifunctional nano photothermal diagnosis and treatment system with deep tissue application depth.Through a series of studies and analyses,the multifunctional nanocomposites show good heating performance and good photothermal stability and physicochemical stability.Moreover,the photothermal conversion efficiency of the multifunctional nanocomposites under 635 nm and 808 nm laser irradiation are 50.5%and41.1%,respectively.Under the safe laser exposure power of human skin,the nanocomposites not only can use a single 635 nm beam to realize afterglow imaging and photothermal sterilization process in vivo and in vitro simultaneously,but also can be assisted by a 808 nm beam to realize the visualization and precise photothermal sterilization for deeper tissues,which extends the application depth of multifunctional nanocomposites in biological tissues and improves the effect of photothermal diagnosis and treatment.Meanwhile,an ratiometric nanoprobe was constructed by afterglow the Cr³⁺ions of the ZGGO:Cr_0.02,Y_0.03/Pb S@PVP nanocomposites.Therefore,the nanocomposites show potential application in the field of photothermal diagnosis and treatment of deep tissue tumors.Finally,near-spherical Cu₂S quantum dots（QDs）（7.62 nm）were synthesized by a simple aqueous phase synthesis method.The absorption intensity of the biocompatible Cu₂S QDs are stronger at 808 nm than at 635 nm,which is beneficial to the photothermal sterilization of deeper tissues.Then,the initial ZGGO:Cr_0.02,Y_0.03/Cu₂S nanocomposites are synthesized by electrostatic adsorption.And then,the surface of the initial nanocomposites are modified by PSS to improve the dispersion stability and further reduce the biotoxicity.At this point,the biocompatible PLNPs-Cu₂S multifunctional nanocomposites are synthesized.After a series of performance characterization and analysis,it is found that the PLNPs-Cu₂S multifunctional nanocomposites have a higher photothermal conversion efficiency at 808 nm（56%）than the ZGGO:Cr_0.02,Y_0.03/Pb S@PVP nanocomposites,and the afterglow luminescence performance are not affected too much.The one-to-many coupling of long afterglow nanoparticles and photothermal agents was successfully achieved,which improved the accuracy of monitoring the photothermal therapy process.Moreover,the nanocomposites had good structural stability,photothermal stability,and physicochemical stability.Meanwhile,PLNPs-Cu₂S nanocomposites with acid-aggregation characteristics can effectively fulfill targeted photothermal therapy for broad-spectrum bacterial infections in vivo and in vitro.Therefore,PLNPs-Cu₂S nanocomposites integrating real-time afterglow imaging,temperature monitoring,and photothermal sterilization functions demonstrate the potential for the application of precise photothermal treatment of deep-tissue pathogenic bacterial infections under dual-wavelength near-infrared light excitation（635 nm laser:afterglow imaging,temperature detection;808 nm laser:photothermal sterilization）.The laser efficiency is improved and the light damage is reduced.