Preparation Of Coal-Carbom Quantum Dots From Coal And Their Fluorescence

So far,the most widely used is metal semiconductor quantum dots(QDs).But one of the biggest shortcoming of these QDs is toxicity.So scientists are trying to find a new kind of QDs-carbon quantum dot(CQDs)with diameter no more than 20 nm or(10 nm).Without toxicity,CQDs have good biocompatibility,higher luminance,and light stability.CQDs are widely used in imaging of biology or medical and sensors et al.In order to prepare CQDs,adequate raw materials is essential.Coal is main source of energy in China.Coal with low degree of coalification is called low-ranked coal.CQDs are prepared from low-ranked coal in our research.CQDs were prepared by nitric acid oxidation and microwave digestion respectively.Low-rank coal from different producing regions was studied.Experimental conditions such as temperature,time,acid concentration and purification were optimized.Longkou deashing coal is best.Reaction temperature is 130?,reaction time of 12 h.Structure(particle size,functional group etc.)and properties of CQDs were characterized by Fourier Transform infrared spectroscopy(FTIR)?Carbon Nuclear magnetic resonance(13CNMR)?X-ray diffraction(XRD)?Photoelectron spectroscopy(XPS)?Transmission electron microscope(TEM)?Atomic force microscope(AFM)? Raman spectroscopy(Raman)? and Fluorescence spectroscopy(PL).Fluorescence of CQDs are investigated under laser resource.The mechanism of coal reacting with nitric acid to produce CQDs was proposed:In addition to nitrification of the coal molecules,aromatic clumps polycyclic aromatic induced by Scholl reaction are also accompanied.Quantum yield(QY)was increased after CQDs were modified by polyethylene glycol(PEG)and superacid(difluoromethane TFSI)respectively.Fluorescent electrospinning PVA membrane and fluorescent ink are prepared respectively with CQDs.The results is good.