Study On Modulation Of Optical And Electrical Properties Of Symmetric Graphene Quantum Dots

Graphene quantum dots have a series of advantages and are widely studied and applied in optoelectronic devices,photocatalysis,biological imaging,cell imaging,drug delivery and fluorescent probes,etc.,and the performance of graphene quantum dots includes many aspects.One of the important ways to change its performance is to dope graphene quantum dots or modify the surface of graphene quantum dots.Nitrogen-doped graphene quantum dots have been extensively studied.After the graphene quantum dots are doped with nitrogen,many of their properties have undergone important changes,especially the band gap has been greatly improved.Among them,there are many reports about boron and sulfur doped graphene quantum dots,but there are relatively few researches and applications about symmetrically doped graphene quantum dots.We use symmetrically doped graphene quantum dots to modulate the electronic and optical properties.The main content of this article includes the following aspects:(1)Explore the influence of the size of GQDs on its electronic and optical properties,and study the electronic properties of GQDs of different sizes,including electronic properties and optical properties.Studies have shown that the binding energy and specific binding energy increase with the expansion of the size of GQDs,and the HOMO-LUMO energy gap value decreases with the increase of the cluster size of GQDs;the change of the size is infrared spectrum,Raman spectrum and ultraviolet-visible The absorption spectrum has a modulating effect,and the ultraviolet-visible absorption spectrum has a red shift as the size increases.(2)Through B/N single atom doping,understand the influence of B/N doping at different positions on the electronic and optical properties of GQDs.First,consider the influence of different doping positions on the electronic properties and optical properties of GQDs under the same atom doping;secondly,when comparing the same doping positions,analyze the effects of different doping atoms on the electronic properties and optical properties of GQDs.The results show that as the position of B doping gets closer to the edge,the band gap first decreases and then increases;when the position of N doping gets closer to the edge,the band gap first increases and then decreases;B The closer the doping is to the edge of the cluster,the longer the wavelength of the absorption peak is,and the frequency decreases,resulting in a red shift;the closer the doping is to the cluster edge,the shorter the wavelength of the absorption peak is,and the frequency increases.Blue shift phenomenon.(3)Doping at the central carbon ring of regular hexagonal GQDs,using three kinds of doping of B/N diatoms,including B diatom doping,N diatom doping and BN heteroatom doping,taking into account The symmetry of doping atoms,each type of doping is carried out separately for ortho doping,meta doping and para doping.Using related quantum chemistry calculation software,the electronic and optical properties of these doped GQDs were studied.Studies have shown that no matter what kind of doping,the band gap of the meta position is lower than that of the ortho position and the para position,and the difference between the band gap of the ortho position and the para position is small;No matter what kind of doping,the absorption peak intensity of meta doping is lower than that of ortho doping and para doping,and the wavelength corresponding to the absorption peak of meta doping appears red-shifted.