Preparation And Photocatalytic Properties Of Carbon Quantum Dots And Their Metal Compounds Composites

As a new type of null-dimension nanomaterials,the grain size of Carbon quantum dots?CQDs?are generally less than 10nm.It has been widely concerned in many fields because of its simple preparation,low cost,abundant source elements and so on.In recent years,in addition to the application of fluorescence imaging,biological detection and drug loading.The carbon quantum dots have shown excellent performance in the capture,transfer and storage of light energy.Due to the strong absorption of carbon dots in ultraviolet region and the large number of electron hole recombination centers are shown in the the carbon quantum dots,it is necessary to enhance the absorption of carbon quantum dots in the visible region and the speed of the charge.In this paper,the carbon quantum dots and several other photosensitive metal compounds were combined to improve these shortcomings which can not only to enhance the absorption in the visible light region,promote the transfer speed of electron and hole,but also the redox conversion efficiency of organic compounds is significantly improved under visible light irradiation.The main contents and achievements of this paper are as follows:?1?First,the composite Cu_1.8S/CQDs was prepared by stepwise hydrothermal method,and the morphology,structure and properties of the composite was characterized by TEM,XRD,XPS,fluorescence spectrophotometer and UV VIS spectrophotometer.The light can catalysis and restore the tert butyl para quinone?TBBQ?,the conversion of Cu_1.8S/CQD to TBBQ was about 90%after lighting for 15 minutes while the single CQDs conversion rate is about 55%.It was found that the amount of active hydroxyl?·OH?of Cu_1.8S/CQD synthesized by the step method was about five times that of one step synthesis by Using terephthalic acid?TA?to detect the production of active hydroxyl in the photocatalytic process.The Cu_1.8S/CQD which prepared by step by step method can not only promote the separation and transfer of charge,but also reduce the recombination of electron hole and has higher photocatalytic activity.?2?Second the prepared CQDs was coupled by ultrasonic electrostatics and nickel foam?NF?,then the hydrothermal method was used to form Ni₃S₂ which was on the nickel foam to enhance their connection and finally the CQDs/Ni₃S₂ which was supported by nickel foam was formed.The pore volume,specific surface area and pore size distribution of the foam nickel supported CQDs/Ni₃S₂ and single foam nickel were compared by BET test and The morphology,structure and photocatalytic properties were tested at the same time.The results of photocatalytic experiment showed that the rate of activated hydroxy·OH and the oxidation of tert butyl hydroquinone?TBHQ?which were producted by the foam nickel supported CQDs/Ni₃S₂ were significantly improved.Finally,the effect of CQDs loading on the photocatalytic performance of CQDs/Ni₃S₂ supported by nickel foam was studied.The photocatalyst made by this method is more easy to recover and separate from the powder catalyst.?3?Third,the mesoporous and amorphous nanoscale composite material CQDs@NiB was prepared by mixing and hydrothermal method.The transmission electron microscopy?TEM?showed that the spherical structure containes a large number of hollow nanoscale channels which are beneficial to the catalytic reaction.The structure and properties of CQDs@NiB were also analyzed and the results of photocatalytic experiment showed that the conversion of nitrobenzene derivatives by CQDs@NiB photocatalytic reduction was significantly improved.The BET test results showed that the diameter of the NiB hollow nanoscale with CQDs composite decreases.The electrochemical test showed that the in situ composite CQDs@NiB can not only reduce the interface impedance,but also increase the charge transfer and change the position structure of the NiB band.