Functional Modification And Application Of Different Dimensional Carbon Materials

As a representative of emerging carbon nanomaterials in the 21st century,zero-dimensional carbon dots?CDs?and two-dimensional graphene are very attractive in the fields of optoelectronics,sensing,construction,catalysis and other fields due to their excellent characteristics.However,CDs usually face the adverse effects of aggregation-induced quenching effect.Due to their organic nature and surface activity,their stability needs to be improved.As for graphene materials,surface inertness limits their applications in cement-based materials and biomass catalysis.Therefore,exploring the functional modification methods of CDs and graphene and studying their application potential in related fields are important topics to promote the development of carbon nanomaterials.In this paper,from the composite modification of CDs and the surface modification of graphene,the performance and application of solid-state light-emitting CDs in the field of fluorescence,and functionalized graphene in the fields of cement-based materials and biomass catalysis were studied.The specific research contents are as follows:?1?Preparation and performance of CDs-doped aluminum-based luminescent materialsCDs-doped AlOOH luminescent materials?CDs@AlOOH?were directly prepared via the pyrolysis method by using organic aluminum salt.The effects of pyrolysis parameters on the products were explored.The formation mechanism of CDs@AlOOH was clarified,which provided a green and efficient synthesis strategy for solid-state light-emitting CDs.The luminescence properties of CDs@AlOOH were studied,and it was clarified that the luminescence mechanism was dominated by CDs emission and enhanced by the energy transfer from F/F⁺color center of AlOOH.In addition,the doping state of pyrrole N and pyridine N in CDs was conducive to enhancing fluorescence emission.By adjusting the pyrolysis temperature?T_D?,the concentration and state of CDs were adjusted,leading to a tunable luminescence performance of CDs@AlOOH.The thermal stability of CDs@AlOOH was studied.The results showed that the protective effect of AlOOH matrix on CDs enables CDs@AlOOH to obtain a long-time thermal stability.After heating treatment for 100 h,250 h,and 500 h,the luminescent properties could be maintained 98%,90%,80%of the initial one,respectively.Based on the broad emission feature and the adjustable light color of CDs@AlOOH,a high color rendering white light output was achieved,by matching with UV or blue LED chips.This study provided a novel solution for the application of CDs materials in the field of solid-state lighting.?2?Preparation and performance of CDs-doped scandium-based luminescent materialsBy using ScOOH or Sc₂O₃ as host,the realization method and related performance and applications of CDs-doped scandium-based luminescent materials were explored.First,ScOOH luminescent materials were synthesized,and the adjustment from?to?phases was explored.The structure,composition and luminescence properties of ScOOH were analysised,and the results showed that CDs was not be formed in the product.The fluorescence emission of ScOOH was derived from the transition of oxygen defect?V_O?related energy levels,and the first-principles calculation was used to investigate the effect of V_O on the electronic structure of ScOOH.Based on the temperature sensitivity of the V_O emission,coupled with rare earth ions(Eu³⁺or Tb³⁺)f-f transition emission,a dual emission mechanism was realized,which could be applied to self-reference temperature sensing.In addition,CDs-doped Sc₂O₃luminescent materials?CDs@Sc₂O₃?were synthesized by using one-step oleylamine-assisted pyrolysis process,which provided a direct synthesis scheme for nano-scale solid-state luminescent CDs.The luminescence properties of CDs@Sc₂O₃ were studied,and the compatibility of CDs emission with rare earth ions(Eu³⁺or Pr³⁺)f-f transition emission was also explored,and then a dual emission mechanism was realized.The thermal stability of CDs@Sc₂O₃ was studied.The results showed that the Sc₂O₃ matrix had a protective effect on CDs,allowed CDs@Sc₂O₃ a good thermal stability.After 1 h heating treatment,the luminescence performance of CDs@Sc₂O₃ could maintain 96%of the initial one,which was beneficial to broaden the application range and applicable conditions of solid-state light-emitting CDs.?3?Research on surface modification and application of grapheneBased on effect of surface functional groups,the performance and application of functionalized graphene in the fields of cement-based materials and biomass catalysis were studied.First,in view of the application potential of sulfonated graphene?SG?in cement-based materials,the influence of SG on the rheological properties of cement paste was investigated.The results showed that the introduction of SG reduced the fluidity of the cement paste,improved the rheological parameters,and increased the stability and thixotropy.The relavant mechanism was clarified,that is,the complexation,adsorption,and mechanical riveting occurred between SG and cement slurry components gave rise to a large number of flocculation structures,and then affected the slurry rheological properties.A synergistic method by using high-performance polycarboxylic acid water-reducing agent?PCE?and SG was proposed to improve the rheological properties of cement paste,which provided a new idea for the practical application of SG in cement-based materials.In addition,based on the development trend of functionalized graphene in the field of catalysis,graphene oxide?GO?with multi-functional group was synthesized.Through the adjustment of synthesis process parameters,the type and content of GO surface functional groups were adjusted,and the sulfate group from the intermediate state was retained.By using the reaction of catalytic conversion of furfuryl alcohol?FA?to ethyl levulinate?EL?,the catalytic activity of GO was evaluated.The correlation between the distribution of multifunctional groups and GO catalytic activity was established.The catalytic mechanism of GO was clarified,which was dominated by sulfate groups and synergistically enhanced by multi-functional groups.Through the design of synthetic process parameters,the catalytic performance of GO was improved,and a simple and effective strategy was provided for the optimization of the performance of functionalized graphene.