Determination of molecular structures of organic-inorganic hybrid perovskite(OIHP)nanocrystals at the single-nanocrystal and ensemble levels is essen-tial to understanding the mechanisms responsible for their size-dependent optoelectronic properties and the nanocrystal assembling process,but its detection is still a bit challenging.In this study,we demonstrate that femtosecond sum frequency generation(SFG)vi-brational spectroscopy can provide a highly sensitive tool for probing the molecular structures of nanocrys-tals with a size comparable to the Bohr diameter(～10 nm)at the single-nanocrystal level.The SFG signals are monitored using the spectral features of the phenyl group in(R-MBA)PbBr3 and(R-MBA)2PbI4 nanocrystals(MBA:methyl-benzyl-ammonium).It is found that the SFG spectra exhibit a strong resonant peak at 3067±3 cm-1(v2 mode)and a weak shoulder peak at 3045±4 cm-1(v7a mode)at the ensemble level,whereas a peak of the v2 mode and a peak at 3025±3 cm-1(v20b mode)at the single-nanocrystal level.The nanocrystals at the single-nanocrystal level tend to lie down on the surface,but stand up as the ensemble number and the averaged sizes increase.This finding may provide valuable information on the structural origins for size-dependent photo-physical properties and photoluminescence blinking dynamics in nanocrystals.

Renlong Zhu;Quanbing Pei;Junjun Tan;Xiaoxuan Zheng;Shuji Ye

Hefei National Research Center for Physical Sciences at the Microscale,and Department of Chemical Physics,University of Science and Technology of China,Hefei 230026,China

化学物理学报（英文版）

[1]Renlong Zhu;Quanbing Pei;Junjun Tan;Xiaoxuan Zheng;Shuji Ye-.Sum Frequency Generation Vibrational Spectra of Perovskite Nanocrystals at the Single-Nanocrystal and Ensemble Levels)[J].化学物理学报（英文版）,2022(05):738-746

Vibrational,brational,PbBr3,v7a,v20b,blinking

Sum,Frequency,Generation,Spectra,Perovskite,Nanocrystals,Single,Ensemble,Levels,Determination,molecular,structures,inorganic,hybrid,perovskite,OIHP,nanocrystals,single,ensemble,levels,essen,tial,understanding,mechanisms,responsible,their,dependent,optoelectronic,properties,assembling,process,but,its,detection,still,challenging,In,this,study,demonstrate,that,femtosecond,sum,frequency,generation,SFG,spectroscopy,can,provide,highly,sensitive,tool,probing,comparable,Bohr,diameter,signals,are,monitored,using,spectral,features,phenyl,group,MBA,2PbI4,methyl,benzyl,ammonium,It,found,exhibit,strong,resonant,peak,mode,weak,shoulder,whereas,tend,lie,down,surface,number,averaged,sizes,increase,This,finding,may,valuable,information,structural,origins,physical,photoluminescence,dynamics

0.509252