Synthesis And Photocatalytic Properties Of The Composites Between Carbon Dots And Noble Metal

Carbon dots (CDs) as a novel carbon nanomaterials, has broad application prospects inthe degradation of harmful substances in the environment and preparation of hydrogen energybecause it may be used as a powerful energy converter in the design of catalyst for itsexcellent light-induced electron transfer and two-photon absorption characteristics. But now,the research on CDs catalyst is still at an initial stage, and the catalytic efficiency of CDs is nothigh, which greatly restricted the use of CDs in the industry. Thus the development of newcomposite photocatalyst based on CDs is extremely important. Noble metal exhibiting strongabsorption in the visible region because of its plasma resonance effect, has been widelyconcerned. By combining the noble metal with CDs, a highly efficient compositephotocatalyst with the advantages of these two materials is expected to produce to be appliedin environment and energy field. Therefore, we mainly focused on preparing the compositesbetween CDs and noble metal by liquid-phase chemical reduction, and analyzed the effects ofsize, structure and morphology on properties of the obtained composites. In this dissertation,several works have been done as follows:(1) The composites between carbon dots and gold nanostructure (CDs/Au) were successfullyprepared via a ultrasonic treatment. And transverse electric and magnetic field (TEM),fluorescence spectrophotometer and ultraviolet spectrophotometer (UV) were employed toanalyze the size, structure, morphology and properties of the composites. The resultsdemonstrate that CDs/Au show enhanced photocatalytic performance compared with thesimple CDs and gold nanostructure. At the same time, when the CDs were combined withsmaller gold nanoparticles, the degradation rates of CDs/Au are relatively higher.(2) The composites between carbon dots and silver nanostructure (CDs/Ag) were successfullysynthesized by in-situ synthesis and simple mixing, respectively. The products obtained byin-situ synthesis exhibit stronger light absorption and higher abilities of methylene blue degradation than those of simple mixing. Therefore, we mainly focused on in-situ synthesis ofCDs/Ag and systematically analyzed the effects of H2O2addition and the fluorescenceintensity of CDs on photocatalytic activities of the obtained CDs/Ag. The experimental resultsindicate that the amount of H2O2addition can change the morphology and light absorption ofCDs/Ag, and then results in different photocatalytic performances. The possible mechanismof photocatalytic activities from the in-situ synthesized CDs/Ag could be strong combinationbetween CDs and Ag nanocrystals that induced much stronger surface plasma resonance, thusenhancing light absorption and the light energy conversion efficiency.(3) The composites between CDs with different fluorescence emission and silvernanostructure were successfully synthesized by in-situ synthesis. The CDs/Ag obtained fromCDs with stronger fluorescence emission shows stronger light absorption and higherphotocatalytic activities.The above results illuminated that the well-designed CDs nanostructure like Au and Agnanoparticles with surface plasmon resonance could enhance light absorption, and theseparation of photoinduced charge carriers could also be intensified for the interface bettweenCDs and the Au nanostructure. These studies provide a feasible approach to designphotocatalyst with high activity, which would promote the application of photocatalytictechnology in the fields of environment and energy.