Study On Preparation Of Carbon Dots And Their Application In Nitrile Butadiene Rubber

In this paper,two types of carbon sources?citric acid and glucose?were selected,and two types of carbon dots with different functional groups were prepared by microwave method,which were named as CDs-CA and CDs-Glu respectively.By characterizing the two types of carbon dots,we can understand their structural differences and lay a foundation for subsequent understanding of fluorescence properties.Testing the optical properties of these two types of carbon dots and changing their external environment?pH,metal ions?,we can observe the changes in their fluorescence properties,and understand their fluorescence mechanisms.On the basis of these two types of carbon dots,each type of carbon dots was refined into 5 carbon dots by changing the ratio of synthetic raw materials,and the differences in fluorescence properties were further studied in depth to understand the fluorescence mechanism.Besides,the prepared carbon dots were applied to nitrile butadiene rubber?NBR?,and the influence of carbon dots on the properties of NBR was explored.By systematically comparing the two types of carbon dots,it can be seen that the type of carbon source directly affects the type of functional groups on the surface of CDs.The surface functional groups of CDs-CA are mainly carboxyl,amino and amide groups,while the mainly surface functional groups of CDs-Glu are hydroxyl.Both dilute aqueous solutions of CDs-CA and CDs-Glu exhibit photoluminescence?PL?characteristics related to the excitation wavelength,but their PL characteristics are different at different pH values.In addition,they both show selectivity and sensitivity to Fe³⁺and Cu²⁺.When Fe³⁺and Cu²⁺are added to the CDs aqueous solution,the PL strength decreases,which is called quenching effect.The higher the concentration of Fe³⁺and Cu²⁺,the more obvious the quenching effect.Based on the above results,the changes of structure and properties in the CDs-CA system were studied.The results showed that with the increase of the amount of urea,the FTIR spectra showed that the amino groups on the surface of CDs-CA increased,the I_D/I_G trend in the Raman spectra decreased,and the peak position of the X-ray diffraction spectra shifted.The absorption peak of the ultraviolet-visible absorption spectra also changes.It was found in its fluorescence emission spectra that with the increase of urea,the emission peak wavelength of CDs-CA would shift to the right to a certain extent;the emission intensity of CDs-CA would be complicated to change.This might be due to the increase of the amount of-NH₂ on the surface of CDs-CA,which would form complex emission traps and different surface states.At the same time,the changes of structure and properties in the CDs-Glu system were studied.Increasing in the amount of KDP,the type of the functional group and the structure of the carbon core would not change.It was found from their fluorescence emission spectra that the amount of KDP added would not change the rate of change of?_em with?_ex,but would change the emission intensity of CDs-Glu.It showed that under the stimulation of different excitation wavelengths,the change of the peak position was consistent with the change of the conjugate structure.The change of the fluorescence intensity is related to the number of functional groups.In addition,applying the prepared carbon dots to NBR in this paper,we explored their influence on the properties of NBR.Compared with pure NBR,both NBR-CDs-CA and NBR-CDs-Glu with higher strength and elongation at break.By adding CDs-Glu,the glass transition temperature T_g and the storage modulus value were increased.As the hot air aging time increased,the tensile strength of the rubber material generally decreased,the elongation at break decreased,the infrared peak strength decreased,the hardness increased,and the crosslinking density increased.However,after CDs-CA was added,these trends were significantly suppressed.Besides,the effect was more significant as the amount of CDs-CA was increased.Therefore,CDs-CA could effectively enhance the aging resistance of NBR.