The Preparation And Application Of Carbon Nanodots With Tunable Photoluminescence Wavelength

Carbon Nanodots(CDs)refer to fluorescent carbon nanomaterials with particle size less than 10 nm.Compared with traditional metal and semiconductor quantum dots,Carbon Nanodots have incomparable advantages,such as simple preparation,low cost,good water solubility,high biocompatibility,low toxicity and excellent fluorescence properties,which lead to applications in bioimaging,biosensing,photocatalysis and luminescent devices.This paper aims at solving the problem of Aggregation-caused Quenching(ACQ)of conventional Carbon Nanodots,and develops a novel sulfur-nitrogen co-doped Carbon Nanodots(CD1),which completely overcome the ACQ phenomenon and exhibit the characteristics of Aggregation-induced Emission(AIE).With the increase of CD1 concentration,its blue fluorescence is inhibited due to the ACQ phenomenon,accompanied by the appearance and gradual enhancement of yellow fluorescence.The obtained CD1 pure solid powder has high brightness yellow emission,and its Photoluminescence Quantum Yield(PLQY)is as high as 65%.The photoluminescence(PL)spectra,absorption spectra,and time-resolved decay curves show that there is a Fo?rster resonance energy transfer between monodisperse CD1 nanoparticles and large CD1 agglomerated particles,which eventually leads to the enhancement of yellow fluorescence.To take advantage of its high PLQY and strong AIE phenomenon,CD1 was applied to the color conversion layer on the blue light-emitting diode chip to prepare White Light-Emitting Diode(WLED).White light coordinates of the resulting devices are(0.29,0.38)and(0.32,0.42),which is close to pure white light(0.33,0.33),and the luminous efficiency is as high as 97.8 and 93.9 lm/W,respectively.In this paper,a concentration-dependent fluorescence tunable Carbon Nanodots was developed and used for bacterial identification,especially for some pathogenic bacteria.Considering the differences in diversity among bacterial species,such as cell wall,thickness of cell membrane and p H of cytoplasm,as well as the difference in metal ion content,the concentration of carbon Nanodots entering different types of bacteria in the same time will vary.Therefore,the stained samples of different types of bacteria exhibited different photoluminescence spectra,thereby achieving rapid(10 minutes)identification of eight types of bacteria.