Preparation And Application Of Bagasse Based Carbon Quantum Dots And Their Composites

Carbon quantum dots are generally defined as spherical or quasi spherical carbon nanoparticles or polymers with a size of less than 10 nm.They have the characteristics of light stability,wide absorption spectrum,high quantum yield,chemical inertia,low toxicity and high biocompatibility.They are widely used in the fields of environmental ion detection,biological sensing and imaging,drug delivery,fluorescent probes,photocatalysis and so on.Bagasse is the waste of sugar cane to produce sucrose.It is a biomass resource with high carbon content.It can be used as the initial carbon source for the synthesis of carbon quantum dots.In this study,carbon quantum dots were prepared from bagasse by hydrothermal method.The fluorescence properties of carbon quantum dots were improved by doping atoms in situ.The synthesized carbon dots and hydrogels were combined to improve their functionality.A series of carbon quantum dots obtained are applied to ion detection.The main research is as follows:（1）.Carbon quantum dots doped with N/S elements were synthesized by hydrothermal method with bagasse as carbon source and N/S elements introduced by urea and ammonium sulfate.The synthesized carbon quantum dots have different fluorescence spectra and different sizes.After optimizing the synthesis conditions,the absolute quantum yield of N-doped carbon quantum dots（N-CQDs）is about 177%higher than that of undoped carbon quantum dots（CQDs）.And the absolute quantum yield of N/S double doped carbon quantum dots（N/S-CQDs）is about 44%higher than that of N-doped carbon quantum dots（N-CQDs）.The optimized carbon quantum dots are in a p H environment of 1-13 and after standing for a long time,it still maintains high stability and high fluorescence effect.（2）.Carbon quantum dots（N-CQDs）synthesized from bagasse and urea have good fluorescence performance and high stability.They are used as probes to detect different metal ions.The results show that the prepared N-CQDs have strong selectivity for Fe³⁺.Through fitting and mechanism analysis,it is concluded that the quenching of N-CQDs by Fe³⁺ions belongs to dynamic quenching,and the concentration range of Fe³⁺ions is（0-200μM）N-CQDs can be used to detect Fe³⁺ions.（3）Carbon quantum dots（N/S-CQDs）synthesized from bagasse and ammonium sulfate have nitrogen and sulfur double doping.Compared with N-CQDs,they have stronger fluorescence intensity and higher quantum yield.They are used as probes to detect different metal ions.The results show that the prepared N/S-CQDs have strong selectivity for Hg²⁺ions.Through fitting and mechanism analysis,it is concluded that the quenching of N/S-CQDs by Hg²⁺ions also belongs to dynamic quenching,and the concentration range of Hg²⁺ions is（0-200μM）The linear correlation is good,so N/S-CQDs can also be used to detect Hg²⁺ions.（4）The fluorescence intensity carbon quantum dots synthesized by hydrothermal method are synthesized from ammonium sulfate and bagasse（N/S-CQDs）.And they are combined with chitin hydrogel to form a carbon quantum dot chitin gel system called fluorescent intelligent hydrogel.The absolute quantum yield increased by 272%compared with N/S-CQDs,and the ability of fluorescent intelligent hydrogel to detect Hg²⁺ions has also been improved.