Preparation Of Fluorescent Carbon Dots By Acid Assisted One-step Solvothermal Methods And Applications

Compared with traditional inorganic semiconductor quantum dots and organic dyes,carbon dots have excellent properties such as low toxicity,good biocompatibility,adjustable fluorescence,and resistance to photobleaching,which make them have huge potential for applications in biological and optoelectronic fields.As for the regulation of the fluorescence properties of carbon dots,common methods include heteroatom doping,acid modulation,adjustment of reaction conditions,etc.The fluorescence of some carbon dots involves solvent-dependent and concentration-dependent properties.To further explain these properties,the study of their fluorescence origin is particularly important.In addition,when the concentration of CDs increases or they aggregate,the fluorescence quenching occurs due to resonance energy transfer between particles and direct π-π interactions.This characteristic of carbon dots has greatly hindered the application of their solid-state powder such as optoelectronic devices.To address this problem,researchers have provided many strategies.Among them,the hydrolytic condensation with a silane coupling agent to provide a solid dispersion matrix is a relatively simple method,and the obtained carbon dots have high fluorescence quantum yields and good compatibility with inorganic substrates such as glass and ceramics.However,this method faces a series of problems.The inability to obtain a solid powder directly and the need for subsequent processing steps such as hydrolytic condensation and drying to obtain the powder.Most of the carbon dots through this method are blue-green fluorescent,and there are few long-wavelength fluorescent carbon dots.To solve the above problems,the contents of this paper are as follows.(1)Using 3-formylphenylboronic acid as the boron source and pphenylenediamine as the nitrogen source,acid treatment with concentrated hydrochloric acid was used to obtain boron-nitrogen co-doped carbon dots by solvothermal.The morphological structure of the carbon dots was analyzed by FT-IR,XPS,TEM,Raman and other tests.At the same time,the fluorescence properties of carbon dots treated with different amounts of acid were compared,the concentration dependence and solvent dependence of fluorescence were discussed,and the potential application of carbon dots in p H sensing and detection of trace water was explored.(2)Based on citric acid and N-[3-(trimethoxysilyl)propyl]ethylenediamine,the hydrolytic condensation of the silane coupling agent was catalyzed by concentrated hydrochloric acid to directly produce blue fluorescent carbon dots-based powder in one step.The powder is water-soluble and can be hydrolytically condensed with 3-aminopropyltriethoxysilane,which can be applied to glass surface to build blue fluorescent LSCs.(3)Based on the epoxy-amino reaction between p-phenylenediamine and 3-glycidoxypropyltrimethoxysilane,the yellow fluorescent carbon dots-based particles were fabricated by one-step solvothermal method.The adjustment of the particle morphology and the regulation of its fluorescence quantum yield can be achieved by regulating the addition of the silane coupling agent.The yellow fluorescent particles were used with 450 nm chips to build white LEDs with a color rendering index of84.2 and good current and working time stability.