Synthesis And Applications Of Efficient Chemiluminescent Carbon Dots

Chemiluminescence(CL)is a kind of phenomenon induced by chemical reaction which transfer chemical energy to light energy.With the development of technology,CL has gradually developed from the traditional cold light source,immunochemiluminescence detection,CL analysis to the life sciences fields such as in vivo immunobioimaging and in situ bioimaging.Compared with the traditional photoluminescence(PL)imaging,CL can effectively reduce the background light interference caused by different substances in the organism,thus significantly improve the signal-to-noise ratio of immunoimaging/bioimaging and the sensitivity of in-situ detection.In recent years,it has attacted more and more attention.Carbon dots(CDs)is a new class of carbon nanomaterials since the discovery of fullerene,carbon nanotubes and graphene.With high PL efficiency,good biocompatibility and simple preparation routes,it is very promising to explore the CL emission of CDs in different CL systems,and then develop their applications in different fields.However,until now,there were only a few reports about CDs-related CL,and these CDs-related CL illustrate low efficiency,weak brightness and the short duration.In this work,the study is focused on the problems of low brightness and efficiency,short duration and single color of CDs-related CL.Due to the easily adjusted energy band structure,the high brightness,multicolor,deep-red and near-infrared(NIR)chemiluminescent CDs in the chemical reaction of peroxalate-hydrogen peroxide(H2O2)are realized by tuning the solvent and nitrogen doping.On this basis,the CL performance of CDs is further improved by surface chemical engineering.With these efficient chemiluminescent CDs,the application of high quality of information and pattern encryption,the quantitative detection of H2O2 and glucose,and the in vivo CL imaging of reactive oxygen species(ROS)in mice were realized.The results include the following aspects:1.Synthesis of multicolor and long lifetime chemiluminescent CDs and their application in information encryption.By adjusting the graphitization degree and the size of conjugated sp2 region,the CDs with blue,green and red fluorescence were synthesized.The mutlticolor CL system was constructed by energy transfer between the CDs and the energrtic intermediate generated in the CL reation of peroxalate-H2O2.The maximum CL quantum yield(CL QY)is 9.32 × 10-3 einsteins mol-1,brightness is 3.28 cd m-1,and the lifetime is 186.4 s.It is the best value ever reported in the previous CDs-related CL.Based on the bright and multicolor CL of these CDs,the potential application of CDs’ CL in information storage and encryption was demonstrated.2.The improvement of CL performance of CDs by nitrogen doping and surface chemical engineering.With the merit of the energy level alignment between the CDs and the energy-rich intermediate generated in the peroxalate system,controllable nitrogen doping route was design to establish high-brightness chemiluminescent CDs.Actually,these controllable nitrogen-doped chemiluminesent CDs were synthesized by microwave-assisted pyrolysis of different ratio of citric acid and urea.With experiment and calculation,the increased graphitic nitrogen doping can enhance the chemically initiated electron exchange(CIEE)and change the chemical doping in C=C sp2 domains,resulting in tunable CL wavelength.Moreover,the research illustrate that the CL of CDs was affected by solvent environment,especially quenched by water.On the basis,surface chemical engineering was first attempted to reduce the energy transfer between CDs triggered by water,and then improve the CDs’ CL performance.The modified CDs with maximum CL Q Y of 1.15 × 10-2 einsteins mol-1 and maximum brightness of 5.11 cd m-2 which was comparable with Rhodamine B were achieved.These works revealed the importance of CDs’ structure in the CL process,and paves the way to design efficient chemiluminescent CDs for practical applications.3.Synthesis of the deep-red and NIR chemiluminescent CDs and their applications in glucose detection and in vivo CL imaging for ROS.The deep-red chemiluminescent CDs was achieved with citric acid and urea for the first time.The instantaneous CL efficiency of the system could be(8.22±0.30)X 10-3 einsteins mol-1.The sensitive detection of H2O2 was realized in the CL analysis with CDs as CL probe with a detection limit(LOD)of 11.7 μm,and then the detection of glucose was further realized with a LOD of 12.6 μM.Due to the deep-red CL,the chemiluminescent sensor was potential to be applied for blood glucose analysis and endogenous bioimaging.Moreover,the deep-red/NIR chemiluminescent CDs was further synthesized and the chemiluminescent polymer nanoparticles(P-CDs)were assembled with these CDs to achieve the CL bioimaging.The advantages of deepred/NIR CL of P-CDs in organism was verified by the subcutaneous injection in mice and the in vivo imaging system.The linear response between the integrated CL intensity of P-CDs and the concentration of H2O2 was verified.Moreover,imaging of inflammatory H2O2 in a mouse model of peritonitis was achieved by employing the PCD as a sensor.The present work exhibits considerable potential for CDs as new class of CL probes for in vivo imaging applications in the diagnosis and treatment of inflammation or cancers.