The Preparation And Characterization Of Full Color Emissive Carbon Dots

Carbon dots(CDs),as a rising star in carbon-based materials family,have drawn considerable attention in recent years due to their exceptional physicochemical properties.For their superiority in tunable photoluminescence properties,low toxicity,low cost,biocompatibility,simple synthetic routes,chemical inertness,and ease of modification,CDs have found many applications in the fields of nanomedicine,optronics,photocatalysis and fluorescence sensors,etc.However,the major disadvantages of these reported CDs stem from complex procedures for their separation and purification,the difficulty in preparing long-wavelength,low product yield and multicolor(capable of single wavelength excitation)emissive products.Therefore,this paper will be carried out as the following three parts work,focusing on the facile methods for the preparation of high product yield,multicolor PL CDs,and novel applications of the multicolor fluorescent CDs.In section 2,we report the preparation of blue luminescence CDs via a facile solvothermal route using citric acid as a carbon precursor and urea for surface passivation.Then the surface of resultant CDs is modified by glutathione(GSH).Through the comparison for FTIR spectrum of CDs and GSH-CDs,demonstrate that GSH has been successfully modified on the surface of CDs.GSH has many functional groups(thiols,carboxyl and amino groups),which make fluorescent CDs exhibit good dispersion,high fluorescence and AIEE phenomenon in aqueous solution.On the basis of AIEE phenomenon induced by temperature and Fe3+ ions,the PL intensity of GSH-CDs increases progressively with increasing temperature over a wide temperature range(25–80 °C)with small temperature resolution(～0.5 °C),resultant CDs has great potential as optical thermometry device,as well as a promising candidate in detecting Fe3+ ions sensitively and selectively.Moreover,the utilization of GSH-CDs for monitoring temperature and Fe3+ ions in cells has been successfully demonstrated.Thus,resultant GSH-CDs hold great promise as an alternative to conventional fluorescent probes for biolabeling,sensing and other applications.In section 3,the green fluorescence CDs is prepared by a solvothermal carbonization method using sucrose as carbon precursor,H3PO4 as dopant and oxidizing agent,and ethanol as reaction medium.What’s more,the problems of purification and separation are solved by a silica column chromatography.Resultant CDs show bright green fluorescence with high quantum yield(~6%),which are stable with different ionic strengths and exposing photo time.Importantly,the fluorescence of resultant CDs exhibits a reversible linear response to temperature in a wide range of 20–85 °C.Moreover,the temperature resolution better than 0.5 °C and high sensitive variation of ~1.3% °C-1 are observed in a broad physiological temperature range of 20–40 °C.Therefore,the as-prepared CDs possess high water solubility,stable fluorescence,small size,and good biocompatibility,which make them promising candidate for thermometry device in biological media.In section 4,we design a green,microwave-assisted treatment of p-phenylenediamine(p-PD)for preparing red emissive CDs.The as-prepared CDs are characterized by PL,TEM,AFM,FTIR,and XPS,etc,from which their structural information and property are interpreted.Importantly,the as-prepared CDs can be used as an on–off fluorescent chemosensors for the specifically detection of glutathione(GSH)based on aggregation-induced fluorescence quenching.Interestingly,the quenched fluorescence can be recovered by increasing temperature,the CDs-GSH mixture can behave as an off–on fluorescent probe for temperature,which show fast response and good reversibility.Owing to their superiority in long-wavelength emission,well water-soluble,and biocompatible,the red-emitting CDs can be used as fluorescent probes for biological imaging in living cell.Furthermore,we design homology rings on filter paper written with CDs for visual on-site sensing of p H value.We also show that the resultant Y,G,B-CDs can be conveniently utilized to fabricate multicolor light-emitting polymer composite film with high optical performance.In view of the facile fabrication process and pH-deduced emission intensity change for the R-CDs,this work may bring us a bright outlook in practical applications such as bioimaging,Fluorescent ink and optical devices.