Investigating The Photoelectric And Photocatalytic Properties Of Carbon Quantum Dots Derived From Biomass

As a new type of carbon nanomaterials,carbon dots（CDs）have potential applications in many fields（especially in optics and photocatalysis）and have attracted extensive research interest because of their excellent optical properties,high solubility,high stability,rich sources of raw materials,wide range of light absorption and other unique properties.The preparation of CDs from waste biological resources has the advantages of low raw material cost,non-toxicity,good biocompatibility,high recovery efficiency and so on.However,due to the lack of understanding of the relationship between the functionalization of biological resource groups and luminescence properties,CDs with narrow red emission has been rarely prepared from non-toxic biological resources.In addition,the high solubility of pure CDs limits its application in photocatalytic degradation of organic pollutants in aqueous solution.High solubility results in low photosensitization efficiency and poor recyclability of CDs.This problem can be solved by hybridizing with other wide band gap semiconductor catalysts（such as g-C₃N₄）to construct a metal-free carbon-based photocatalytic system.Based on the research status,aiming at the main problems of biology-based CDs in the field of optics and photocatalysis,carbon spots with narrow band red light emission were synthesized by using biomass resources,and the luminescence and photocatalytic performance of the composite catalysts were studied.The main content consists of two interrelated parts,as follows:（1）CDs was synthesized from tea waste residue to realize ultra-narrow red emission.In this work,water-soluble carbon spots with narrow band red light emission were synthesized green by using biomass resources as precursors.The synthesized carbon points show deep red luminescence related to excitation and have a wide absorption range from ultraviolet to visible region.The emission center of CDs is 678 nm,and the FWHM is narrow30 nm.The red emitted CDs was used as a fluorescent probe for the detection of Fe³⁺and Cu²⁺ions.It showed good selectivity and sensitivity to the detected metal ions,and the detection limits were 7.2μmol·L^-1 and 0.47μmol·L^-1,respectively.The results of cell imaging show that the narrowband emitted CDs has good biocompatibility and is an excellent fluorescent probe material for medical and health care.This work is expected to provide a new research idea for the preparation of bio-based carbon points with high luminescent properties.（2）CDs-supported lamellar g-C₃N₄enhanced photocatalytic degradation.In this work,CDs modified lamellar g-C₃N₄ was successfully prepared by heat treatment of CDs modified dicyandiamide.The prepared photocatalyst was characterized and its photocatalytic activity for the degradation of tetracycline hydrochloride（TC）was systematically tested.Photocatalytic experiments showed that the degradation rate of TC by the prepared CDs-CN reached 80.7%within 1 hour,which was 59.8%higher than that of pure g-C₃N₄（50.5%）.The highest degradation rate constant of TC by the catalyst is 0.0457 min^-1,which is 4.66times higher than that of pure CN(0.0098 min^-1)and 76.2 times that of pure CDs(0.0006min^-1).The carrier dynamics of the composites was analyzed by photoelectrochemical method,which showed that the loading of CDs promoted the separation of photogenerated carriers.Finally,the mechanism of photocatalytic degradation of TC was deeply analyzed and discussed.This work provides a new method for the construction of metal-free carbon-based photocatalytic materials.In a word,facing the demand for high-performance carbon spots in the field of biomarkers and environmental photocatalysis,carbon spots with narrow band red light emission were synthesized by using biomass resources,and the luminescence and photocatalytic properties of the composite catalysts were studied.It has been proved that the synthesized bio-based CDs has excellent optical properties,and the performance of the photocatalyst supported on CDs has been greatly improved.This work provides a new idea for the study of high-performance bio-based carbon points.