Preparation And Application Of Excitation-dependent Multicolor Carbon Dots

Carbon dots(CDs)are of great interest because their photophysical properties are similar to semiconductor quantum dots in many respects.Due to the unique properties of carbon dots,such as good photostability and no strict and complex preparation steps,they have great potential in the fields of biological imaging,sensing and photocatalysis.However,most of the carbon dots prepared are blue,and the fluorescence emission peak is concentrated at 410-440 nm,which greatly limits the application of carbon dots.Therefore,it is necessary to develop effective methods to prepare carbon dots that emit light at long emission wavelengths and have high fluorescence quantum yield.Doping is the most widely used method to adjust the photoluminescence performance at present.Inspired by this,we realized the luminescence in the long wavelength region by doping N and S elements.The specific work contents are as follows:(1)Using dithiothreitol and p-phenylenediamine as raw materials,a multicolor fluorescent carbon dot with excitation dependence was synthesized by simple hydrothermal method.From the excitation wavelength of 330 nm to 590 nm,the emission peak of carbon dots changes continuously,and the corresponding emission covers the whole visible spectrum,realizing panchromatic fluorescence emission from blue to red.The carbon dots have three main emission peaks,which are 400,500 and620 nm respectively,and reach their maximum values at 340,380 and 590 nm respectively,and the three maximum fluorescence intensities are almost the same.We propose a new strategy for long wavelength emission by doping S element to generate defect sites at carbon dots.In addition,when the multicolor carbon dots are used to prepare fluorescent films,the fluorescence properties can be retained,which provides a new direction and idea for the development of solid-state luminescence.(2)Using the characteristics of multicolor carbon dots,it is applied to OH^-colorimetric detection and the construction of multi-dimensional sensing platform for metal ions.The multicolor carbon dots solution showed different colors at different concentrations of sodium hydroxide,which changed from light blue to purple under visible light.The color span was obvious.It could be used for OH^-colorimetric detection and quantitative analysis in the concentration range of Sodium hydroxide from 1 to 11?M.In the presence of metal ions,the fluorescence of the multicolor carbon point can cause fluorescence quenching,and the quenching degree of the three main emission peaks is different.Using this characteristic,a three-channel sensing platform was constructed with multicolor carbon dots and twelve metal ions to distinguish and detect different metal ions.And it can distinguish and detect different concentrations of Cu²⁺,and can be quantitatively analyzed in a certain range,the detection range is 0.2-1.2 mM.