| In recent years,a great progress has been made in the preparation of carbon dots as well as the optical performance investigation.However,there still have many theoretical and experimental problems need to be explored.For example,in terms of the preparation of carbon dots,various approaches were used to synthesize fluorescent carbon dots,including laser ablation method,microwave-assisted method,and electrochemical method.However,the relationship between the functional group on the surface of carbon dots and the light emission mechanism of carbon dots are still not very clear.Therefore,exploration of an environmental friendly preparation method and find an effective optical preporty adjustment approach,as well as searching a higher quantum yield of fluorescent carbon dots are very important.In this work,amino acids and organic acids as raw materials were employed to prepare fluorescent carbon dots by thermal decomposition polymerization approach.Meanwhile,the morphology of the carbon dots and the organic fluorescent molecules are characterized respectively.Moreover,the structure,optics,and electrical properties are studied to explain the light emission mechanism.The main contents of this article are as follows:(1)Firstly,L-cystrine was employed to prepare fluorescent carbon dots by thermal decomposition polymerization.We found that N and S hetroatom dopping could largely enhance the fluorescent intensity and evidently increase the charge transport efficiency of carbon dots.Moreover,a novel low-dimensional carbon nanocomposite on the basis of zero-dimensional carbon dots and two-dimensional graphene oxide sheets was prepared and its photoelectronic conversion performance was investigated.In this work,electrophoretic deposition approach was used to build nanocomposite photoelectrode of p-type graphene oxide(GO)and n-type nitrogen and sulfur atoms co-doped carbon dot(NS-CD).The photoelectrochemical performance measurement results indicated that the NS-CD’s charge carriers recombination was greatly suppressed and its photocurrent response activity was evidently enhanced by adding GO.It is anticipated that this work may provide a valuable step for the further development of all carbon-based optoelectronic devices with excellent performance.(2)Highly fluorescent and biocompatible gel analogs are desirable for many potential applications,but their synthetic processes are somehow complicated.Herein,we have explored the easibility of synthesis of unconventional fluorescence gel analogs from small organic molecules under mild conditions.A new blue-fluorescent gel analogs with high quantum yield(89.6%)and eutectic feature prepared by simple heat treatment of citric acid(CA)and L-cysteine(Cys)aqueous mixtures below 100℃ in air was reported.The as-prepared fluorescent material possess the features of facile preparation,low cost,scalable production and easy to process,making it suitable for applications on fluorescent labeling and light-emitting devices.This new finding opens a new venue for the preparation of fluorescent gel analogs.(3)The majority of conventional organic fluorescent scaffolds are generally based on conjugated structures,in which carbon-carbon double/triple bonds or aromatic ring-based πelectrons are usually regarded as the main building unit for the photoluminescent centre.Presented herein is a new type of emissive architecture with a simple non-aromatic functional group of 2,5-dioxo-1-pyrrolidine,achieved based on a typical hyperconjugated system in the ring-fused unit supported by the lone pair electrons on the N occupied p-orbital and the neighboring π-orbitals on the C=O.This fluorescent compound demonstrates high photostability,good solubility,low cytotoxicity and excellent cellular imaging capability.This architecture is a significant departure from conventional fluorescent scaffold and the development of this simple fluorescent architecture represents a new direction in developing fluorescent materials. |
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