Visual Detection Of Heavy Metal Ions Based On Multicolor Fluorescent Carbon Dots Paper Sensor

Carbon dots(CDs)are a new type of fluorescent carbon nanoparticles.In comparison with conventional semiconductor quantum dots and organic dyes,CDs not only have the advantages of nontoxicity and high biocompatibility,but also have excellent water solubility,an adjustable luminous range,high photostability,rich sources of cheap raw materials,easy large-scale syntheses and other excellent characteristics.These excellent properties endow CDs with great potential in many fields,such as chemical sensing,biological sensing,biological imaging,optronics,nanomedicine and catalysis.With these excellent properties,as well as important applications,CDs have attracted widespread attention in the past decade.In this dissertation,based on the preparation of multicolor carbon dots by hydrothermal method,dual-emission CDs fluorescent test paper was constructed to semi-quantitative and visual assay of mer ury ions(Hg2+)and copper ions(Cu2+)in the envirolment.The main results are as follows:(1)Visual assay of mercury ions by fluorescent test paper constructed with dual-emission CDs.Gelatin and 3-aminophenylboronic acid were used as raw materials and heated to 200? for 3 h by hydrothermal method to prepare CDs with an average particle diameter of 9 nm.At the excitation wavelength of 290 nm,the emission peak of the CDs is located at 380 nm,and the CDs emitting blue fluorescence under the irradiation of 254 nm UV lamp.Phenylenediamine and ethanol were used as raw materials and heated to 180 °C for 12 h by hydrothermal method to prepare CDs with an average particle diameter of 3 nm.At the excitation wavelength of 290 nm,the emission peak of the CDs is located at 620 nm,and the CDs emitting red fluorescence under the irradiation of 254 nm UV lamp.The constructed ratio fluorescent probe which consists of a mixture of blue CDs and red CDs with the fluorescence intensity of 6:1 can visually detect Hgig2+ with high selectivity and sensitivity.The blue fluorescence can be sensitively and selectively quenched by Hg2+,while the red fluorescence serves as the internal reference.This highly sensitive ratio probe responds to Hg2+ with a series of naked eye visible changes in fluorescence color under UV light with a detection limit as low as 0.14 nM.In addition,the ratio fluorescent probe solution was printed on the filter paper to preparaed fluorescent test paper,which reallized sensitive,rapid,on-site,and visual detection of Hg2+.(2)Visual assay of copper ions by fluorescent test paper constructed with dual-emission CDs.Citric acid and polyethyleneimine were used as raw materials and heated to 200 ?for 6 h by hydrothermal method to prepare CDs with an average particle diameter of 5 nm.At the excitation wavelength of 360 nm,the emission peak of the CDs is located at 440 nn,and the CDs emitting blue fluorescence under the irradiation of 365 nm UV lamp.Phenylenediamine and ethanol were used as raw materials and heated to 180 ?for 12 h by hydrothermal method to prepare CDs with an average particle diameter of 3 nm.At the excitation wavelength of 360 nm,the emission peak of the CDs is located at 610 nm,and the CDs emitting red fluorescence under the irradiation of 365 nm UV lamp.The constructed ratio fluorescent probe which consists of a mixture of blue CDs and orange CDs with the fluorescence intensity of 4:1 can visually detect Cu2+ with high selectivity and sensitivity.The blue fluorescence can be sensitively and selectively quenched by Cu2+,while the orange fluorescence serves as the intellal reference.This highly sensitive ratio probe responds to Cu2+ with a series of naked eye visible changes in fluorescence color under UV light with a detection limit as low as 7.31 nM.In addition,the ratio fluorescent probe solution was printed on the filter paper to preparaed fluorescent test paper,which reallized sensitive,rapid,on-site,and visual detection of Cu2+.