Preparation Of Carbon Nano Dots Assemblies And Their Photoelectric Properties

Carbon nano dots have brought about a lot of attention as a kind of latest fluorescent carbon nanomaterials.Because of their unique fluorescent properties and low toxicity,they have been hold great promise in many aspects,such as environmental monitoring,photocatalysis,biological imaging and photoelectric field.However,due to the dimensional limits and surface defects,their application in solid devices and commercial fields are nearly impossible.In order to overcome the dimensional limits and realize their wide use,we assemble the monodispersed carbon nano dots to form ordered structures in the size of μm through self-assembly method.The main contents of this paper are listed as following:Carbon nano dots with green fluorescence(g-CNDS)under UV light in the size of 1-5nm had been synthesized via microwave assisted pyrolysis of glycerol,then g-CNDS were chemically reduced to transform carboxyl and carbonyl groups into hydroxyl groups.Carbon nano dots with blue fluorescence(b-CNDS)under UV light were obtained.The as-prepared two kinds of carbon nano dots were structurally compared to study their difference in chemical,physical and optical properties.The results showed that b-CNDS possessed more sp2 hybridized carbon contents,more hydroxyl bonding contents and less oxygen-containing groups when compared with g-CNDS.The structural difference resulted in different luminescent machanisms: g-CNDS had a dominant defect state emission and a lower quantum yield while b-CNDS had a dominant intrinsic state emission and a higher quantum yield.Small molecular weight compound Upy containing quadruple hydrogen bonding system was grafted onto the surface of b-CNDS.In this way carbon nano dots assemblies were obtained.The assemblies were in the form of monodispersed carbon nano dots when dissolved in polar solvents like DMF,while the assemblies remained its oval-shaped form in μm size when dissolved in nonpolar solvents like CHCl3.The as-prepared assemblies were integrated into a hybrid film photoswitch as the electron-acceptor with P3 HT,which was used as the electron-donator.The performance of the device was studied in contrast to b-CNDS/P3 HT and PCBM/P3 HT hybrid film photoswitches.The results showed that the mixture of the assemblies with P3 HT could enhance the effective separation of electron-holes and guarantee high mobility of the carrier.The as-prepared device showed similar performance when compared with PCBM/P3 HT.As a result,the assemblies were considered as potential electron-acceptors candidate for PCBM.