Preparation Of CQDs And CQDs/TiO₂ And Their Photocatalytic Performance In Microwave Field

Carbon quantum dots（CQDs）have the advantages of low toxicity,good luminescent stability,and more critical lowcost.Therefore,CQDs have been widely concerned in catalysis,biological imaging,fluorescence sensing and other fields.In this paper,glucose was used as the carbon source material,and a microwave drainage method was used tosynthesize ultrafine CQDs by changing the drainage time.On this basis,the CQDs/Ti O₂composite with high photocatalytic activity was prepared by hydrothermal method.The ultra-fine CQDs were successfully prepared by microwave drainage method.The structures and properties of the samples were characterized by UV,FT-IR,XRD,XPS,TEM and PL spectroscopy.The influence of drainage time on the structure and properties of CQDs was investigated by photocatalytic degradation of Rh B.The optimal preparation conditions of microwave drainage method were determined:microwave power 150 W,reaction temperature 150℃,reaction time 9 min（drainage time 2 min）.Under these conditions,the degradation rate of the CQDs to Rh B was 85.79%under the irradiation of microwave electrodeless lamp（MEDL）for 10 min.In addition,CQDs and activated sludge were cultured together to investigate the effect of CQDs on biological activity.It has been found that the CQDs can be absorbed and utilized by microorganisms as carbon source,which proves that the prepared CQDs catalyst has excellent biocompatibility.In order to further improve the photocatalytic efficiency of CQDs and expand the utilization of Ti O₂to different wavelengths of light,the CQDs prepared above were compounded on the surface of Ti O₂by hydrothermal method,and a CQDs/Ti O₂composites photocatalyst was developed.The structure of the CQDs/Ti O₂composite was characterized,and the photocatalytic degradation of Rh B by the CQDs/Ti O₂composite was tested in the MEDL photocatalytic system.The effects of the composite ratio of CQDs and Ti O₂,hydrothermal temperature and hydrothermal time on the structure and properties of CQDs/Ti O₂composite were investigated.The experimental results show that when the CQDs:Ti O₂=1:4,the hydrothermal temperature is 180℃,and the hydrothermal time is 7 h,the prepared CQDs/Ti O₂composite has the highest photocatalytic activity,and the degradation rate of Rh B in 5 min is as high as 90.1%.In addition,the photocatalytic mechanism of the degradation of Rh B by CQDs/Ti O₂composite was discussed by using the method of active species capture experiment.