The Preparation,Assembly And Aplication Of Multicolor Carbon Dots

As a new kind of carbon nanomaterials,carbon dots?CDs?have overcome some shortcomings,commom in traditional fluorescent materials,and possess excellent luminescence properties,good biocompatibility and spectrally tunable performance.Therefore they have made an important impact on biosensors,environmental monitoring,and optoelectronic devices.In this paper,we mainly introduce the preparation of multicolor CDs and its application in the field of optoelectronic devices and biosensors.First,we propose a simple and easy way to realize gram-scale synthesis of citric acid-derived multicolor CDs.Citric acid?carbon sources?and urea?nitrogen sources?are solvothermally treated to synthesize CDs.By regulating the pyrolysis temperature from 120°C to 180°C,two,four,and six light-emitting CDs can be obtained,of which emission wavelength shift from 440 to 585 nm.The result reveals that temperature has a huge impact on the evolution of surface states.Increasing temperature brings enhanced surface functionalization and passivation,resulting in red shift of emission wavelength and enhancement of quantum yield.On this basis,the clear luminescent mechanism for citric acid-based multicolor CDs are proposed.Second,multicolor fluorescent CDs/polymer composites with anti-quenching solid-state fluorescence are fabricted by simple physical blending.And then them are used as emissive layer to fabricate a series of CDs-based multicolor light-emitting diodes?LEDs?.Subsequently,by regulating the proportion of various CDs/polymer phosphors,white LEDs is realized with Commission Internationale de L'Eclairage1931?CIE?of?0.32,0.33?and color rendering index?CRI?of 82.7.The as-prepared CDs-based multicolor/white color LEDs show promising applications in displays and novel lighting sources.Third,we report the design and implementation of solid white-light-emitting phosphors?WCDs@PS?,which are combined blue and orange emissive CDs?BCDs and OCDs,the mass ratio of OCDs:BCDs=1.2:1?assisted by polystyrene?PS?through self-assembly technique.Based on these phosphors,the obtained WLEDs display a warm white light with a CIE coordinate of?0.35,0.36?,high CRI of 93.2,low correlated color temperature?CCT?of 4075 K,and a luminous efficiency?LE?up to 14.8 lm?W^-1.Importabtly,this WLEDs exhibit temperature-dependent emission performance,of which the light-emission spectrum can be in situ adjusted from white??⁴00-730 nm?to blue??⁴40 nm?in the range of 20-80?C.Temperature-driven tunable CDs-based LEDs as a thermochromism device may develop application of lighting systems in special displays.At last,a CDs based dual-emission temperature sensor is fabricated through electrostatic self-assembly of two kinds of fluorescent CDs with opposite charges.This dual-emission platform consists of several nearly-spherical CDs with two emission centers at blue?440 nm?and orange?590 nm?regions.The orange fluorescence exhibits discernible response to external temperatures in the range of¹5 to 85°C;on the other hand,the blue fluorescence remains nearly constant.Due to temperature impacts the surface states of orange emissive CDs,leaving the blue emissive CDs unaffected,the continuous fluorescence color change in response to increasing temperature from orange to blue.By taking advantage of the high reproducibility and sensitivity?0.93%/°C?of CDs based dual-emission thermometry,it is successfully used for the accurate measurement of intracellular temperature variations.