Study On Photoelectric Properties Of Magnetically Controlled Graphene Quantum Dots

In recent years,with the application and development of graphene technology,its stable physical and chemical properties,high conductivity and other excellent characteristics make graphene become the focus of domestic and foreign scholars.Graphene fragments are the key to the investigation of physical and chemical properties.The zero-dimension quantum dots have the unique quantum confinement effect and edge effect,which make graphene quantum dots widely concerned by many scholars in the field of optoelectronics.Faraday optical rotation effect and conductivity are the two important parameters in the study of photoelectric properties of graphene quantum dots,which makes it have important research value.The most popular research on Faraday effect of graphene quantum dots is mainly about the cyclotron frequency and conductivity,but the rotation angle and Verdet constant also play a key role in Faraday effect.Therefore,in this paper,the relationship between the optical rotation angle and the Verdet constant of graphene quantum dots under electrostatic field,the magnetic field strength,the wavelength of incident light,temperature and concentration,is respectively studied using the extinction method of photodetectors.The experimental results show that:(1)the optical rotation angle and Verdet constant of graphene quantum dots decrease with the increase of wavelength and increase with the increase of temperature.(2)the optical rotation angle of graphene quantum dots will increase with the increase of magnetic field intensity and decrease with the increase of concentration.(3)the Verdet constant of graphene quantum dots does not change significantly with the magnetic field strength and concentration,and remains basically stable.(4)it is calculated that the Verdet constant of graphene quantum dots is always greater than zero under different conditions,and we can concluded that graphene quantum dots belong to right-handed materials.The effective conductivity of graphene quantum dots has a wide range of applications in real life.However,there are few studies on the effective conductivity of graphene quantum dots composite materials,and the mechanism of conductivity is often involved in exploring its physical and chemical properties.In addition,there is a lack of theoretical model and experimental data in the study of the conductivity of graphene quantum dots solution.In this paper,based on the conductivity theory of composite materials with ellipsoidal particles,an effective conductivity model of graphene quantum dot solution is established.Combined with the experimental results and compared with the H-S model,the percolation model,the effective media theoretical(EMT)model and the general effective model(GEM),the GEM model is finally determined as the best model to predict the effective conductivity of graphene quantum dot solutions with different volume fractions,and the corresponding percolation threshold and critical index are obtained.Meanwhile,the influence of temperature,frequency and magnetic field strength on the effective conductivity of graphene quantum dots solution is studied,and the variation trend under different factors is also analyzed.The conclusions are as follows:(1)when the frequency increases to 1MHz,the effective conductivity of graphene quantum dots will increase sharply,but the change of magnetic field strength has little effect on the effective conductivity of graphene quantum dots.(2)when the concentration of graphene quantum dots solution is low,the effective conductivity does not change significantly with temperature(3)when the concentration is high,the conductivity will increase with the increase of temperature.This study further improves the optimization and design of the effective conductivity model of graphene quantum dots.