Preparation And Multifunctional Applications Of Fluorescent Carbon Dots And Its Hybrid Phosphor

Fluorescent carbon dots have emerged as a class of newly-developing carbonaceous fluorescent nanomaterial,because of their superior properties such as good biocompatibility,stable fluorescent properties,easy surface-functionalization and so on,which render them the great potential prospect in the fields of optoelectronic devices,fluorescent labeling,biosensing,photocatalysis and so on.Given that the unique optical and biological characteristics of carbon dots,their multifunctional groups and multicolor fluorescence can meet the needs of construction of different carbon dot-based composite and study of its multifunctional applications.In this work,we have carried out the construction and multifunctional study of fluorescent carbon dot and its hybrid phosphor,conducted an in-depth study of fluorescent properties of carbon dots that dispersed as liquid form and dispersed in the solid-state matrix,and realized the multifunctional applications of carbon dots in plant growth,bioimaging,temperature sensing,organic molecule detection,and LEDs.The relevant summaries are listed as follows:（1）Fluorescent carbon dots（CDs）have been intensely studied in the fields of bioscience and bioimaging,but the reports about the effects of CDs upon plants are rare.Herein,mung bean plant was employed as a model plant to study the phytotoxicity,uptake,and translocation of red-emissive CDs in mung bean plant.The cultivation with CDs at a concentration range from 0.1 to 1.0 mg/m L gave rise to physiological response of mung bean plant and it turned out that CDs imposed no phytotoxicity on mung bean growth.The lengths of the root and stem appeared as an increasing trend up with the treatment of 0.4mg/m L.Confocal imaging displayed that CDs were transferred from the root to the stem and leaf through the apoplastic pathway by the vascular system.The uptake kinetics showed that the CDs were plenty absorbed by mung beans when they germinated and grew.Based on the unique optical properties of CDs,it is feasible to realize the fluorescent imaging in the plant.（2）Through a facile sol-gel method,a series of carbon dots（CDs）grafted CaAl₁₂O₁₉:Mn⁴⁺（CAO）color-tunable phosphors were obtained.Through the hydrolysis and condensation reactions of silica precursor,CDs can be incorporated into the highly flexible silica network by combined with CAO to achieve flexible color tunable luminescent materials.By adjusting the mass ratio of CDs and CAO and tuning the excitation wavelength,the color of luminescence can be systematically regulated from purplish-red（0.504,0.250）to greenish-blue（0.238,0.192）.Moreover,the temperature-dependent optical characteristics of the hybrid phosphors make them suitable as thermometers in the range of 80 to 300 K.（3）By using carbon dots（CDs）as the sensitive fluorophore and YVO₄:Eu³⁺nanoparticles as the reference fluorophore,the ratiometric fluorescent molecularly imprinted sensor has been constructed for effectively sensitive and selective determination of 4-nitrophenol（4-NP）.Through the hydrolysis and condensation reactions of silica precursor,CDs and YVO₄:Eu³⁺nanoparticles can be assembled into the silica networks by silylation reaction through one pot synthesis procedure.The as-prepared sensor can emit characteristic luminescence of CDs（blue）and YVO₄:Eu³⁺（red）under an excitation.Upon the addition of 4-NP,the fluorescence of CDs is selectively quenched,giving rise to the ratiometric fluorescence response.Under the optimal conditions,the sensor is highly sensitive in the range from 0 to 12.0μM and shows the limit of detection as low as 0.15μM in the detection of 4-NP,which possibly benefits from the tailor-made imprinted cavities for binding 4-NP.Moreover,the constructed method has been successfully applied in the detection of 4-NP in the real water and human urea sample,which provides great potential for monitor 4-NP in the environment.