Preparation Of Rice Husk Quantum Dots And Their Detection Of Heavy Metal Ions

As an agriculture country for China,which is rich in the biomass resources such as straw bran,rice husk,brans and waster during the processing.Biomass resources have the characteristics of renewable and environment protection,convenient transportation and storage and low-cost so that they could be used as a substitute for the petroleum fuels.Nowadays,with the deterioration of ecological environment and shortage of resources,biomass resources have become the research topic.In China,with the developing of urbanization and industry,human's activities have been resulted in the serious environment pollution,specially,the water resources had been polluted obviously.The carbon quantum dots?CQDs?have the low toxicity,the stability photo-luminescent,hydrophilic properties and friendly-environment and low cost merits that has been extensively applied in biological,medical and chemical areas and so on.If the biomass could be used to prepare the biomass carbon dots to diagnose the content of heavy-metal ions in the waste water.It will play the dominant role in the application of carbon dots.The CQDs were prepared via a hydrothermal method with the different kinds of modifier.The blue-green photo-luminescent of CQD are DMA-CQDs,DMF-CQDs,ACA-CQDs,and the blue photo-luminescent are BMA-CQDs?HMT-CQDs.The product rate of luminescent are 12.54%,10.28%,13.43%,10.69%and 8.72%,respectively.The physical and chemical properties of CQDs were investigated by the FTIR,UV-Vis,Zeta potential meter and luminescent spectroscopy.The effects of modifiers,the waves of excitation wavelength,p H and temperature on the strength of luminescent of CQDs.Results indicated that the optimum excitation wave of HMT-CQDs was 300 nm,and the others were also at 300 nm.The emission peak of CQDs was changed from 430 to 520 nm at excitation wave condition when the ACA was as a modifier.It is known that the optimal excitation wavelength of HMT-CQDs is 300 nm and that of other quantum dots is 300 nm.When the modifier was ACA,the emission peak of the carbon quantum dot at 320nm changed from 450nm to 520nm,and the optimal p H environment of each quantum dot was selected for detection.It is also found that the change trend of different modified carbon quantum dot aqueous solutions with temperature is more obvious,all of them show obvious decrease with the increase of temperature and have the best fluorescence intensity in low temperature environment.Five kinds of different modified carbon quantum dots were synthesized as fluorescent probes to detect several common heavy metal ions in water,and it was found that ACA-CQDs,DMA-CQDs and HMT-CQDs could successfully detect heavy metal ions Pb²⁺,Cu²⁺and Cr⁶⁺respectively.Using the fluorescence quenching principle of QDs,a simple,rapid and efficient method for detecting Pb²⁺,Cu²⁺and Cr⁶⁺heavy metal ions in water was established.