Light-emitting Regulation On S And N Co-doped CDs And Its Applications

Carbon dots?CDs?was first discovered by scientists in 2004 as a superior photoluminescent material.Although carbon dots are attracting more and more attention,the problems they face are also obvious:?1?most carbon dots are confined to the short-wavelength range,and the fluorescence quantum yield is mostly low.Moreover,the low fluorescence quantum yield of long wavelength luminescent carbon dots hinder the applications.?2?The phosphorescence of carbon dots have become a hotspot in recent years,but there are some problems existed such as the FL QY is still low,and the afterglow time cannot be regulated etc.In this thesis,it was by means of the sulfur and nitrogen elements,synthesized blue and multicolor carbon dots by hydrothermal and solvothermal methods and carried out the application in ion detection and light-emitting devices utilizing these materials and the search of phosphor.The specific contents are as follows:1.Blue carbon dots were synthesized from citric acid?CA?and guanidine thiocyanate?GITC?via an N and S co-doped hydrothermal procedure.In the present structure characterization,N and S elements could be sufficiently doped by means of the heteroatom or the functional groups bonded on the surface of CDs.In view of the triexponential feature of fluorescence lifetimes of CDs,one possibility was proposed to be co-existence of two types of CDs with different surface states.Additionally,the as-prepared CDs were used as a sensing probe for the detection of Ag⁺taking into consideration.The changes of fluorescence intensities were linearly proportional to the different concentration ranges of Ag⁺.And for the first time,the-S-C?N group was found to accelerate the quenching of CDs towards Ag⁺,promising a new approach for efficient detection of Ag⁺for the application in industrial pollutants.2.Using aforementioned compounds again,we developed a facile route to synthesize multi-color-emissive CDs governed by a solvothermal method.The absolute fluorescence quantum yields of blue?432nm?,green?510nm?and yellow?584nm?carbon dots were 21.1%,11.0%and 55.4%,respectively.By means of the analysis,the different graphitic degrees and surface states formed under the participation of S and N elements in as-prepared CDs determine the fluorescent color,and large sp²-conjugated domains within the YR-CDs is closely related to high QY.In the application of these carbon points,we found that YR-CDs have high sensitivity and selectivity to Ag⁺and Fe³⁺ion detection.The three phosphors were mixed in a certain proportion to make a white light emitting film,and the CIE coordinate was?0.34,0.34?.3.By adjusting the molar ratio of thiourea and o-phenylenediamine,the phosphor-tunable S,N co-doped carbon dots were synthesized by the solid state method.By optical characterization of the prepared carbon dots,it was found that the longest phosphorescence lifetime was 309.95ms.It was also found that with the increase in the rate of thiourea to o-phenylenediamine,S,N co-doped carbon dots could be adjusted from orange phosphorescence?580nm?to green phosphorescence?520nm?.It provides a new field of vision for the development and application of phosphorescent carbon dots.