Covalent Modification Of Phosphorene By Free Radicals For Durable Air And Water Stability

Black phosphorus?BP?,as a new two-dimensional material,exhibits good charge carrier mobility(about 10000 cm²V^-1s^-1 at room temperature)and adjustable bandgap?0.3-2.0 eV?.Compared with other two-dimensional materials,especially graphene and transition metal dichalcogenides?TMDs?,it has great potential for diverse application.However,the chemical degradation of BP when exfoliated to nanoscale dimensions results in its rapid loss of semiconductor performance in the presence of external oxygen and water.Covalent modification is a very promising method.On the one hand,the covalent interaction between organic molecules and phosphorus atoms on the surface of phosphorene can improve the stability of phosphorene in the external environment;On the other hand,the desired chemical activity can be obtained by modification without affecting its electrical transport properties.In addition,it is a relatively cheap,easy and controllable approach.Till now,chemical modification scheme shows a promising prospect to protect phosphorene from degradation,however,it remains only a few.This work mainly focuses on improving the stability of phosphorene in the air and water by covalent modification of free radicals,including the following two parts:1.The covalent modification of BP nanoflakes?BPNFs?by the carbon free radicals from azobisisobutyronitrile?AIBN?molecules.The computational and experimental results show that AIBN carbon free radicals have been successfully covalently attached to the surface of BPNFs.The covalent modification by forming the P-C bonds significantly improved the stability of BPNFs in the air and aqueous solution.In addition,the obtained BPNFs-AIBN still maintained good optical properties of BPNFs.2.The covalent modification of BP quantum dots?BPQDs?by the oxygen free radicals from2,2,6,6-tetramethylpiperidine-1-oxy?TEMPO?molecules in the process of BPQDs preparation.The computational and experimental results indicate that the obtained product of BPQDs-TEMPO by covalent modification forming the P-O bonds between TEMPO oxygen free radicals has obvious stability in air.In addition,we also use 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl?TEMPOL?molecules for covalent modification by the same method and obtain similar effects of stabilizing BPQDs.Due to the remarkable stability and optical properties of phosphorene?BPNFs and BPQDs?modified by carbon free radicals?AIBN?and oxygen free radicals?TEMPO and TEMPOL?in the external environment,we believe that modified phosphorene will be of great value in the electrical and photoelectric applications.In addition,this work proves again that it is possible to protect phosphorene from degradation by the method of free radicals covalent modification,which provides a useful strategy for the protection of phosphorene.