Synthesis And Luminescent Properties Study Of Carbon Quantum Dots And Perovskite Quantum Dots Materials

Carbon quantum dots and perovskite quantum dots act as a new type of low-dimensional nanomaterials,due to their excellent physical and chemical properties,causing great interest in researchers and having potential value in many fields.From the point of view of synthesis,the synthetic raw materials of these two types of quantum dots are cheap and easy to obtain,the synthesis method is simple and the synthesis time is short.In terms of structure,carbon quantum dots are composed of graphitized carbon nuclei and amorphous carbon,and there are many functional groups on the surface,usually spherical,while perovskite quantum dots are in the shape of cube or octahedron,and the chemical general formula is ABX₃,where X is usually a non-metallic element with a small radius,and their particle size is small.From the perspective of properties,they have excellent photoluminescence characteristics,which make the carbon quantum dots and perovs and titanium mine points have modifiable,and the carbon quantum dots have low toxicity and good biocompatibility,and the luminescence efficiency of perovskite quantum dots is very high.From the application,carbon quantum dots and perovskite quantum dots have a wide range of applications in biomara,sensors,catalysis,light emitting lighting,single photon light source,etc.Although carbon quantum dots and perovskite quantum dots have made great progress,there are still many key problems to be solved,mainly in the following aspects:(1)Their luminescence mechanism is very complex,and there is no clear and accurate explanation at present.(2)In biological applications,the long-wavelength emission of carbon quantum dots has attracted much attention,but there are few reports on the synthesis of water-soluble high-fluorescence quantum yields.(3)Based on the excellent physical and chemical properties of perovskite quantum dots and carbon quantum dots,their applications are becoming more and more extensive.In addition to the existing photoluminescence properties of carbon quantum dots and perovskite quantum dots,the development of other properties will enable these two kinds of quantum dots to shine in more fields.In this paper,the research of carbon quantum dots and perovskite quantum dots focuses on the following aspects:(1)The optical properties of carbon quantum dots can be controlled by adjusting the mole ratio of reactants and reaction temperature to change the graphitization degree,surface states and surface functional group content of the synthesized carbon quantum dots.(2)The perovskite quantum dots were synthesized by thermal injection method,and the emission wavelength was adjusted in the whole visible light region.Based on the concept of semiconductor nanocrystalline doping,other elements were mixed into the perovskite quantum dots to cause the change of fluorescence properties of the perovskite quantum dots,and the perovskite quantum dots with different emission were successfully synthesized.(3)The applications of carbon quantum dots and perovskite quantum dots with different optical properties in White Light-Emitting Diode(WLED),biological imaging and photothermal fields are explored.The specific content of this paper is as follows:Firstly,using triammonium citrate and urea as raw materials and N,N-dimethylamide as solvent,a series of full-color emission fluorescent carbon quantum dots were synthesized at different molar ratios at different temperatures.The photoluminescence spectra of carbon quantum dots cover the whole visible region,ranging from 440 nm to 625 nm.Through the characterization of optical properties,microstructure and structure of carbon quantum dots,we found that with the increase of graphitization degree and graphitized carbon,the fluorescence emission peak of carbon quantum dots appears red-shift.At the same time,with the increase of reaction temperature,N accelerate into carbon nuclei,makes carbon quantum dots surface state change,the change of the surface state and at the same time also makes the carbon quantum dots optical band gap also change,this is the red beam emitted from the carbon quantum dots moving an important factor,Fourier transform infrared spectroscopy and the results of electron diffraction spectroscopy,also proved that the surface state change is affecting the carbon quantum dots launch red-shift.Secondly,in order to further explore the control perovskite optical properties of quantum dots,we tried to perovskite quantum dots doped with other elements,expect to change on the optical properties and electric properties,synthesis method of perovskite in thermal injection of quantum dots at the same time,and to which mixed with manganese,sodium and elements such as copper,got different ions doped perovskite quantum dots.The introduction of these elements changes the surface defects and energy levels of perovskite quantum dots and improves the optical properties of the perovskite quantum dots.We carried out a series of studies on the undoped and doped perovskite quantum dots,and verified whether the doping was successful by means of micro-morphology and structural element analysis.Furthermore,their optical and electrical properties are studied deeply.Finally,in order to further expand the carbon quantum dots and the application of perovskite quantum dots,we will in the synthesis of different optical properties of quantum dots and carbon perovskite quantum dots applied in different areas:(1)We will be full color of synthetic carbon quantum dots is applied in biological imaging,through Hela(Human cervical cancer cells)and carbon quantum dots ultra high biocompatibility,and by using laser confocal microscope observed carbon quantum dots on Hela perfect imaging and high biocompatibility.(2)We applied full-color carbon quantum dots and CsPbCl₃ perovskite quantum dots doped with manganese ions to light-conversion LEDs.By adjusting the type and content of carbon quantum dots and the ratio of CsPbCl₃ perovskite quantum dots to commercial green phosphors,we successfully encapsulated white LEDs,and obtained white LEDs with excellent performance and high display index.(3)We applied perovskite quantum dots(CsPbCl₃)doped with manganese ions in the field of temperature measurement by means of fluorescence intensity ratio technique,using the dual emission centers of perovskite quantum dots.CsPbBr₃ perovskite quantum dots doped with sodium and copper ions are encapsulated into electroluminescent diodes(LEDs),which can change from green light to blue light.Perovskite quantum dots doped with other elements expand their applications in different fields.