室温下基于微等离子体放电发射光谱法检测甲烷

Emission Spectrometry for the Detection of Methane Based on Gas Ionization Discharge Microplasma at Room Temperature

建立了一套针板电极交流放电微等离子发生装置,以氮气作为载气,甲烷为分析气体,放电电压为1.32 kV,放电距离为3 mm,Pt丝和Pt/MWNT复合纳米粒子修饰FTO电极为放电电极,放电频率为30kHz,功率消耗为13 W,利用发射光谱法检测放电过程中产生的微等离子体发射光谱,用于在室温下检测甲烷气体。在交流电压下,检测到甲烷的谱线有CH,C_2和H_α,以C_2谱线作为甲烷分析线,发现C_2谱线强度与甲烷浓度在0.5%~4.0%(φ)的范围内呈线性,检出限(S/N=3)为0.19%。以H_α谱线为分析线,H_α谱线强度与甲烷浓度在0.1%~3.0%(φ)范围内呈线性,检测限(S/N=3)为0.03%(φ)。对于3.2%的甲烷气体,平行测定11次,在Pt/MWNT/FTO电极上以C_2谱线为分析线和以H_α谱线为分析线的相对标准偏差分别为1.3%和1.9%。说明Pt/MWNT纳米复合材料修饰电极提高了分析方法的重现性和精密度。以空气混合气体为稀释气体,甲烷气体放电行为与纯氮气中放电行为有较大差异,C_2峰消失,只有H_α峰存在。H_α峰强度与甲烷浓度在0.5%~4%范围内有线性相关性。与其他的光发射光谱检测系统相比,该系统装置尺寸小,制备简单且在室温下操作。

A microplasma-generating device was developed by using needle-plate electrode discharge with the incorporation a Pt/carbon nanotube（CNT） nanocomposite-decorated FTO electrode.When an alternating current voltage of 1.32 kV and a low power consumption of 13 W in nitrogen（N_2） carrier gas are applied,the system can be applied to detect methane at room temperature.The main characteristic lines were assigned to CH,C_2 and H_α during the discharge process of CH_4 at room temperature.The emission intensity of C_2 at 516 nm is linear with the concentration of CH_4 from 0.5%to 4.0%（φ）,and the detection limit（S/N=3） is 0.19%（φ）.The emission intensity of H_α at 656 nm is linear with the concentration of CH_4 from 0.1%to3.0%（φ）with the detection limit（S/N=3） is 0.03%（φ）.The relative standard deviation（RSD） is less than 2%from 11 repetitive analyses using 3.2%CH_4.The Pt/CNT nanocomposite-modified FTO electrode exhibited enhanced sensing performance with precise,repeatability and linear correlation compared with that of the pure MWNT/FTO electrode and bare FTO electrode.When CH_4 were discharged in air,the emission spectra of CH_4 was different from that in N_2.It was found that C_2 peak was disappeared and the H_α intensity was also liner to the concentration of CH_4 in the range of 0.5%~4%.The established system exhibited advantages with small size,simple fabrication and operation at room temperature compared to other detection system.