Antimonene Quantum Dots:Large-scale Synthesis Via Liquid-phase Exfoliation And Intriguing Nonlinear Optical Properties

Antimonene,in succession to black phosphorus,is another two-dimensional group-VA material.Since 2015,besides intensive research efforts on the atomic structure,electronic properties and synthesis of antimonene,scientists also have conducted applied researches on semiconductor and nonlinear optical devices,molecular adsorption and thermoelectric applicaitons based on antimonene.In addition,the antimonene quantum dots(SbQDs)as derivatives of antimonene,have also received the attention of researchers recently and the potential applications in photothermal therapy have been reported.Here,we report on the experimental results of large-quantity,high-quality synthesis of SbQDs via liquid exfoliation.Firstly,the dispersion concentration and stability of SbQDs in NMP solvent have been studied in this work.Furthermore,Transmission electron microscopy(TEM)and atomic force microscopy(AFM)reveal that the obtained SbQDs have a lateral size of approximately 2.6 nm and a thickness of about 2.8nm.Besides,Raman spectroscopy and HRTEM indicate that the obtained SbQDs have layered atomic structure consisting of buckled hexagonal rings as in the β-phase bulk antimony.X-ray photoelectron spectroscopy(XPS)confirm the obtained SbQDs covered by antimonic oxide.More importantly,saturable absorption of SbQDs have been explored by Z-scan technique.the modulation depth and the saturable intensity of it are found to be about 1.1%and 6.303GW/cm2,respectively.The saturable absorber mirror(SAM)have been fabricated by spin-coating the SbQDs on the reflective mirror.By using the SbQDs SAM in the 639nm Pr:YLF laser,stable Q-switching is realized.The average output power is 83mW and the corresponding pulse width is 255ns,repetition rate being 227kHz.In addition,the optical-optical conversion and slope efficiencies are 10.4%and 10.1%,which is the first report of SbQDs in Q-switching.Lastly,the spatial self-phase modulation effect(SSPM)has been investigated.Nonlinear refractive index(n2,8.1292×10-15m2/W)of SbQDs at 633nm also have been measured.The principle of two-color all-optical switching in SbQDs and the test equipment have been described in this work.It has successfully realized the modulation of the light from the visiable to near infrared under the control of the light of 1064nm.