| Black Phosphorus(BP),as a new two-dimensional layered inorganic semiconductor material,has attracted wide attention of researchers.Phosphorus is a highly efficient flame retardant element and also exists in large quantities in human body.As a stable allotrope of P element,BP has the characteristics of thermodynamic stability,adjustable band gap,degradability,good photothermal conversion efficiency,biosafety,etc.,and has been widely used in the field of flame retardant and photothermal therapy.The stripping of bulk crystal BP into nanoscale materials,mainly including black phosphorus nanosheets(BPNS)and black phosphorus quantum dots(BPQD),is the basis of application in flame retardant and photothermal fields.However,the yield of BP nanomaterials prepared by liquid phase stripping method commonly used in laboratory is low,so the efficient preparation of BPNS and BPQD is still urgently needed.Few studies focused on the effect of BP nanomaterials of different sizes on the flame retardant and pyrolysis behavior of polymers.In addition,in the field of photothermal antitumor application,due to the complexity of tumor tissue,the effect of single photothermal treatment is often difficult to be satisfactory,so it is of great significance to prepare multi-mode combined treatment nanocomposites.In this paper,starting from the preparation of BP nanomaterials,the thermal stability and photothermal properties of BP of different sizes were studied.Finally,the composite material containing BP was designed and prepared.On the one hand,the size correlation of the flame retardant properties of BP nanomaterials was discussed in depth combined with pyrolysis kinetics;on the other hand,combined with the photothermal conversion properties of BP,its application in the field of anti-tumor was explored through multi-mode collaboration.The main research work is as follows:(1)Aiming at the low efficiency of pure liquid phase stripping method,the combination of high energy ball milling and ultrasonic liquid phase stripping was adopted to destroy large layer structure of BP by using the pressure of ball milling,which significantly increased the efficiency of ultrasonic liquid phase stripping of BP,and the yield of small size BPNS was increased to 3.58 times of that of pure ultrasonic stripping.In order to solve the problem of poor stability caused by nanoscale BP aggregation,BP nanomaterial modified with polyethylene glycol was further used to improve the stability of BPNS and BPQD in aqueous solution.(2)The performance difference between BPNS and BPQD was tested and compared from two aspects of flame retardant and photothermal conversion performance,so as to provide reference for subsequent application.On the one hand,the thermal stability of BPNS and BPQD was analyzed and compared by thermogravimetric infrared spectroscopy.The results show that both BPNS and BPQD have excellent thermal stability,that is,the size has little influence on the thermal stability of BP nanomaterials.On the other hand,the photothermal performance of BPNS and BPQD was compared by using 808 nm laser test,and the results showed that BPNS showed better photothermal performance under the same conditions.(3)Based on the similar thermal stability of BPNS and BPQD,the flame retardant polyvinyl alcohol/black phosphorus(PVA/BP)composite film was prepared by using BPNS and BPQD as nano-flame retardants,and the effects of different addition amounts of BPNS and BPQD on the pyrolysis and flame retardant properties of PVA were further studied.The results showed that the T50wt%and carbon residue rate of PVA/BPQD films were higher than those of PVA/BPNS films under the same dosage.The Kissinger method,F-W-O method and DAEM method were used to calculate the activation energy of the pyrolysis.The addition of BPNS and BPQD significantly increased the activation energy of the two pyrolysis stages of PVA,and BPQD showed a greater increase in the activation energy of the S1 stage.C-R method predicted that the mechanism function of PVA at two pyrolysis stages was F3 chemical reaction model,and the reaction mechanism model did not change after the addition of BPNS and BPQD.The MCC test results showed that the addition of BPQD greatly reduced the peak heat release rate and the total heat release.The TG-IR results showed that the absorption strength of volatile products in PVA/BPQD composite film was the lowest among all samples.Overall,BPQD was superior to BPNS in improving the flame retardant property of PVA nanocomposites.(4)Based on the good photothermal performance of BPNS and the limited effect of single hyperthermia,BPNS was selected as the carrier to combine oxygen-deficient titanium dioxide(B-TiO2)nanoparticles on its surface,and polymer modification was used to improve the biocompatibility and solution stability to prepare BP-B-TiO2 nanocomposites.The combined effect of photothermal/sonodynamic therapy on tumor was studied.Under ultrasonic stimulation,PPBP-B-TiO2 produced a large number of ROS.Meanwhile,thanks to the excellent photothermal conversion ability of BPNS,the photothermal conversion efficiency of PPBP-B-TiO2 nanocomposites was as high as 44.1%.The results of both in vitro and in vivo experiments showed excellent therapeutic effect under synergistic stimulation.In addition,the biosafety analysis combined with major organs and blood biochemistry showed that the side effects on the above indexes were negligible,which provides a new case for the design of a novel BP based nanocomposite for multi-mode collaborative tumor therapy. |
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