Preparation Of Carbon Quantum Dots And Detection Of Cu²⁺ And Fe³⁺

Carbon nanomaterials mainly include carbon nanoparticles,carbon nanotubes,graphene and fullerenes.These carbon materials have many excellent properties,such as excellent magnetic,electrical,optical properties and so on.In particular,carbon quantum dots have attracted widespread attention since the first discovery in 2004.Carbon quantum dots are a kind of carbon nanometer material with good dispersion,which has quantum confinement effect and edge effect.As a new type of fluorescent carbon nanomaterials,carbon quantum dots have many excellent properties,including lower toxicity,excellent light stability,good biocompatibility,chemical inertness and low cost.These excellent properties make it widely used in environmental monitoring,biosensing,biological imaging,solar cells,light-emitting diodes,photoelectric conversion and photocatalysis.The properties of carbon quantum dots are closely related to the structures.The structures of carbon quantum dots include molecular structure and crystal structure.The molecular structure of the carbon quantum dots determines the electronic structure.The emission spectrum of the photoluminescence will gradually move in the long wavelength direction with the increase of the oxygen functional groups on the surface.The electronic structures of carbon quantum dots can also be modulated by incorporating nitrogen,phosphorus,boron,sulfur and other elements,which helps to modify the optical properties.The crystal structure determined the surface structure and the surface structure of carbon quantum dots is closely related to their properties.Therefore,the study of the molecular structure and crystal structure of carbon quantum dots are very important.But the carbon quantum dots prepared by various materials and methods are all complex mixtures.Not only the composition is intricate,but also the crystal structure is diverse,which brings definite challenges for studying the relationship between the structure and properties of carbon quantum dots.The following is the brief introduction.（1）The blue fluorescent carbon quantum dots were prepared by using the organic compound 9-Hydroxyphenalenone（HPHN）as raw material.The size distribution of HPHN quantum dots is in 3-6 nm by transmission electron microscopy and dynamic light scattering.The difference of absorption spectra between the HPHN solution and HPHN quantum dots was also studied.The results showed that the surface structure and the crystal structure of the HPHN quantum dots have important effects on the optical properties.The prepared HPHN quantum dots can be used for the detection of copper ions.The fluorescence quenching mechanism of of HPHN quantum dots by copper ions has been studied experimentally and theoretically.（2）Carbon quantum dots（CQDs）can be prepared by hydrogen peroxide oxidation and ozone oxidation using coking coal as raw material.The size of the carbon quantum dots obtained by the two methods is about 3 nm.The two carbon quantum dots emit yellow fluorescence under the irradiation of 365 nm ultraviolet lamp.Fluorescent carbon quantum dots prepared by hydrogen peroxide oxidation have strong fluorescence intensity in acidic and alkaline environments,but carbon quantum dots prepared by ozone oxidation emit weaker fluorescence in alkaline environment.Both of the two carbon quantum dots can be functionalized to explore applications in the field of photocatalysis.（3）BF2（HPHN）was furthermore synthesized by using HPHN as raw material,which has good selectivity for Fe³⁺.The detection limit is 0.09 μM.