Detecting Of Methane Gas And Synthesis Carbon Dots Based On Micro-plasma Discharge Method

The micro-plasma has advantage of low gas consumption, low energy consumption, high electron density, high energy density and easy to react. Besides, small in size, light weight also have favorable to develop of portable instrument and be used for on-line testing.The Pt/MWNT nanocomposites were prepared by microwave, and characterized with TEM. A microplasma-generating device was developed using needle-plate electrode discharge with the incorporation a Pt/carbon nanotube nanocomposite-decorated FTO electrode. CH4 gas was used as a model analytical gas, and nitrogen gas was used as the carrier gas. The discharge voltage, discharge distance and modified layer on the electrodes were investigated to choose the optimum condition on the emission intensity of C2 and H? of methane. Under the optimization condition, the emission intensity of C2 is linear with the concentration of CH4 from 0.5% to 4.0%(V/V), with a linear regression equation was I=8714.7C-4266.9(R2=0.9899) and the detection limit(s/n=3) is 0.01%. The emission intensity of H? is linear with the concentration of CH4 from 0.1% to 3.0%(V/V), with a linear regression equation was I=1096.8C+2389.8(R2=0.9916) and the detection limit(s/n=3) is 0.19%. The modified layer of Pt/MWNT nanocomposites on FTO electrode notably improved the reproducibility and precision of analytical methods. The RSD of C2 improved from 11.9% to 1.3%, the RSD of H? improved from 10.8% to 1.9%. And the developed system can also be applied to the determination of the content of carbon dioxide in the mixed gas of methane and carbon dioxide(carbon dioxide mixed methane gas), and the content of methane in the mixed gas of air and methane(air mixed gas of methane). Besides, the developed system showed good stability after continuous discharge 12 h at room temperature.A low energy liquid discharge plasma approach has been developed for synthesis CDs by applying a high electric potential between Pt electrodes in ethanol solvent. Naphthalene as a model of small organic molecule provides carbon source. Synthesis of CDs showed the maximum emission wavelength at 385 nm, which the emission-independent excitation wavelength and quantum yield was 4.2%. Optical property and morphology of CDs was characterized with Ultraviolet-visible spectroscopy, Photoluminescence spectroscopy, Transmission electron microscopy, Fourier transforms infrared spectroscopy and X-ray diffraction measurements. Moreover, the obtained CDs can also generate chemiluminescence(CL) emission with directly oxidizated by potassium peroxydisulfate, which suggests its promising applications in chemical sensing. Meanwhile, six organic materials with different groups in benzene ring have effect on the fluorescent properties of CDs were investigated. The results showed that discharge products of indole and acetaminophen the maximum emission peak position shifted to longer and the fluorescence intensity enhanced.Compared to other micro-plasma discharge device, the device used in the experiment has advantages of small in size, portable, easy preparation, operation at room temperature and low power consumption. This system provided reference for the determination of the gas, and the liquid micro-plasma device for synthesis of CDs are simple and low energy consumption.