Effective Production of OH Radicals in Ar Plasma Jet

Transcription

1 The 75th JSAP Autumn Meeting September 17, 214, Sapporo Campus, Hokkaido University 17p-S1-6 Effective Production of OH Radicals in Plasma Jet Kazuhiro Takahashi *, Kohki Satoh and Hidenori Itoh Centre of Environmental science & Disaster mitigation for Advanced Research, Muroran Institute of Technology, Muroran , Japan Contents 1. Background & Objective 2. Experimental Apparatus & Conditions 3. Results 4. Conclusions

2 Background Plasma jet Plasma is generated between electrodes by a dielectric barrier discharge in a tube. The plasma is pushed out of the tube by feed gas, allowing the plasma to reach a solid and liquid surface easily. copper tube aluminium sheet Plasma jet can be used in the fields of plasma medicine [1] and disinfection [2]. ROS/RNS (Reactive Oxygen Species/Reactive Nitrogen Species) such as O, OH and NO x are regarded as important species. For the effective use of plasma-jet property and expanding its applications, to investigate and control the kinds and quantities of these species is essential. [1] S. Hamaguchi: J. Plasma Fusion Res., 87, 1 (211) 696 [2] D. Shibahara et al.: J. Inst. Electrostat. Jpn., 34, 1 (21) 2

3 Background & Objectives Takeuchi et al. (Proc. of the 74th JSAP Autumn Meeting, 8-133, 213) calculated the density of OH radical in plasma on gas-liquid interface, and reported that OH radicals produced in the plasma react with themselves to form H 2 O 2. The concentration of OH radicals may be deduced from that of H 2 O 2. Objectives To investigate the kinds and quantities of ROS/RNS in plasma jet and deionised-water exposed to the plasma jet. To control the kinds and quantities of the species. We generated an plasma jet, and carried out the optical emission spectroscopy of the plasma jet. We exposed deionised-water to the plasma jet, and analysed ROS/RNS dissolved in the deionised-water using liquid chromatograph. We investigated the effect of H 2 O addition to gas from the measurements of H 2 O 2 in the water.

4 Experimental apparatus & conditions (1 L/min) copper tube (f 3 x 2 mm) aluminium sheet 1 mm Air ( or.1 L/min) glass tube (f 6 x 3 mm)

5 Experimental apparatus & conditions Power supply Applied voltage: AC 13 kv p-p Frequency: 17 khz Input power : 4 W 1 voltage [kv] Photograph before time [ s] 1 /Air aluminium sheet (1 L/min) copper tube (f 3 x 2 mm) 1 mm Air ( or.1 L/min) glass tube (f 6 x 3 mm) 15 mm

6 Experimental apparatus & conditions Power supply Applied voltage: AC 13 kv p-p Frequency: 17 khz Input power : 4 W 1 voltage [kv] Photograph before time [ s] 1 /Air aluminium sheet (1 L/min) copper tube (f 3 x 2 mm) 1 mm Air ( or.1 L/min) glass tube (f 6 x 3 mm) Spectrometre VIS/IR region resolution:.31 nm range: 66 ~ 17 nm UV/VIS region resolution:.33 nm range: 23 ~ 67 nm 15 mm

7 Experimental apparatus & conditions Power supply Applied voltage: AC 13 kv p-p Frequency: 17 khz Input power : 4 W 1 voltage [kv] Photograph before time [ s] 1 /Air aluminium sheet (1 L/min) copper tube (f 3 x 2 mm) 1 mm Air ( or.1 L/min) glass tube (f 6 x 3 mm) column eluent detector sampling time HPLC condition IC NI-424 CH 3 COOH (3. mmol/l) + KOH (2.25 mmol/l) (ph = 5.5) UV (at 22nm) 3, 6, 9, 12, 15 min 65 mm deionised water (2mL) Autosampler 15 mm

8 Experimental apparatus & conditions Power supply Applied voltage: AC 13 kv p-p Frequency: 17 khz Input power : 4 W 1 voltage [kv] Photograph before time [ s] 1 RH % RH 14% or /H 2 O (1 L/min) aluminium sheet copper tube (f 3 x 2 mm) 1 mm glass tube (f 6 x 3 mm) column eluent detector sampling time HPLC condition IC NI-424 CH 3 COOH (3. mmol/l) + KOH (2.25 mmol/l) (ph = 5.5) UV (at 22nm) 3, 6, 9, 12, 15 min 65 mm deionised water (2mL) Autosampler 15 mm

9 1. ROS/RNS measurement in plasma jet and deionised-water after plasma jet exposure

10 Emission spectra in VIS/IR region intensity [a.u.] I (4p 4s) O (3p 3s) /Air wavelength [nm] in I(4p), O(3p) in /Air (= 1/1) I(4p), O(3p)

11 Emission spectra in UV/VIS region intensity [a.u.] OH (A 2 S + X 2 P) NO (A 2 S + X 2 P) (,2) (,1) 25 (,3) (1,) N 2 (2nd pos., C 3 P u B 3 P g ) (,) (,1) wavelength [nm] in I(4p, 5p), O(3p), N 2 (C 3 P u ), OH(A 2 S + ) (,2) 38 (,3) 4 I (5p 4s) 42 /Air in /Air (= 1/1) I(4p, 5p), O(3p), N 2 (C 3 P u ), OH(A 2 S + ), NO(A 2 S + )

12 Measurement of ROS/RNS in deionised-water after plasma jet exposure min exposure () 4 intensity [a.u.] injection shock retention time [min] intensity [a.u.] retention time [min]

13 intensity [a.u.] Measurement of ROS/RNS in deionised-water after plasma jet exposure min exposure () reference H 2 O 2 (88 ppb) injection shock intensity [a.u.] NO 2 - (5 ppb) NO 3 - (62 ppb) H 2 O ppb retention time [min] needle wash solution retention time [min] dissolved oxygen 2.2 NO NO 3-58 ppb 119 ppb

14 Production in plasma and ROS/RNS production /Air Production in plasma jet concentration [ppb] H 2 O 2 ROS N 2 + * (meta) N + N + (e = 9.8 ev) O 2 + * (meta) O + O + (e = 5.2 ev) H 2 O + * (meta) OH + H + ROS/RNS Production in gas-phase (e = 5.1 ev) OH + OH H 2 O 2 (k = 2.6x1-11 cm 3 /s) N + O + M NO + M (k = 3.8x1-33 cm 6 /s) concentration [ppb] NO exposure time [min] NO 3 - RNS 15 NO + O + M NO 2 + M RNS Production in deionised-water 2NO 2 + H 2 O HNO 2 + HNO 3 (k = 6.8x1-32 cm 6 /s) NO + OH HNO 2 (k = 3.3x1-11 cm 3 /s) NO 2 + O + M NO 3 + M (k = 1.3x1-31 cm 6 /s) NO 2 + OH HNO 3 (k = 2.8x1-11 cm 3 /s) NO 2 + NO 3 N 2 O 5 (k = 1.9x1-12 cm 3 /s) N 2 O 5 + H 2 O 2HNO exposure time [min] 15

15 Production in plasma and ROS/RNS production /Air Production in plasma jet concentration [ppb] H 2 O 2 /Air ROS N 2 + * (meta) N + N + (e = 9.8 ev) O 2 + * (meta) O + O + (e = 5.2 ev) H 2 O + * (meta) OH + H + ROS/RNS Production in gas-phase (e = 5.1 ev) OH + OH H 2 O 2 (k = 2.6x1-11 cm 3 /s) N + O + M NO + M (k = 3.8x1-33 cm 6 /s) concentration [ppb] NO exposure time [min] - NO 3 /Air /Air RNS 15 NO + O + M NO 2 + M RNS Production in deionised-water 2NO 2 + H 2 O HNO 2 + HNO 3 (k = 6.8x1-32 cm 6 /s) NO + OH HNO 2 (k = 3.3x1-11 cm 3 /s) NO 2 + O + M NO 3 + M (k = 1.3x1-31 cm 6 /s) NO 2 + OH HNO 3 (k = 2.8x1-11 cm 3 /s) NO 2 + NO 3 N 2 O 5 (k = 1.9x1-12 cm 3 /s) N 2 O 5 + H 2 O 2HNO exposure time [min] 15

16 Production in plasma and ROS/RNS production /Air Production in plasma jet concentration [ppb] H 2 O 2 /Air ROS N 2 + * (meta) N + N + (e = 9.8 ev) O 2 + * (meta) O + O + (e = 5.2 ev) H 2 O + * (meta) OH + H + ROS/RNS Production in gas-phase (e = 5.1 ev) OH + OH H 2 O 2 (k = 2.6x1-11 cm 3 /s) N + O + M NO + M (k = 3.8x1-33 cm 6 /s) concentration [ppb] NO exposure time [min] - NO 3 /Air /Air RNS 15 NO + O + M NO 2 + M RNS Production in deionised-water 2NO 2 + H 2 O HNO 2 + HNO 3 (k = 6.8x1-32 cm 6 /s) NO + OH HNO 2 (k = 3.3x1-11 cm 3 /s) NO 2 + O + M NO 3 + M (k = 1.3x1-31 cm 6 /s) NO 2 + OH HNO 3 (k = 2.8x1-11 cm 3 /s) NO 2 + NO 3 N 2 O 5 (k = 1.9x1-12 cm 3 /s) N 2 O 5 + H 2 O 2HNO exposure time [min] 15

17 2. Effective production of OH radical

18 Effect of H 2 O addition into gas H 2 O 2 concentration [ppm] RH % 5 1 exposure time [min] 15 Between electrodes + e fast * (meta) or * + e slow Outside of tube H 2 O + * (meta) OH + H + H 2 O 2 production OH + OH H 2 O 2

19 Effect of H 2 O addition into gas H 2 O 2 concentration [ppm] RH % RH 8% RH 14% 5 1 exposure time [min] 15 Between electrodes + e fast * (meta) or * + e slow H 2 O + e fast OH + H + e slow Outside of tube H 2 O + * (meta) OH + H + H 2 O 2 production OH + OH H 2 O 2 /H 2 O H 2 O addition to gas leads to the increase of the concentration of OH radicals produced by the plasma jet.

20 Effect of H 2 O addition into gas H 2 O 2 concentration [ppm] RH % RH 8% RH 14% 5 1 exposure time [min] 15 Between electrodes + e fast * (meta) or * + e slow H 2 O + e fast OH + H + e slow Outside of tube H 2 O + * (meta) OH + H + H 2 O 2 production OH + OH H 2 O 2 /H 2 O H 2 O addition to gas leads to the increase of the concentration of OH radicals produced by the plasma jet. The concentration of OH radical may not be proportional to the increase of the relative humidity of gas.

21 Conclusions We generated an plasma jet, and carried out optical emission spectroscopy of the plasma jet. The emissions of, OH, N 2 and O are observed, and that of NO is observed only when air is mixed into the plasma jet. We exposed deionised-water to the plasma jet, and analysed ROS/RNS dissolved in the deionised-water. H 2 O 2, NO 2- and NO 3- are dissolved in the deionised-water after the plasma jet exposure. Air mixture into the plasma jet leads to RNS production. OH radical concentration increase by H 2 O addition to gas, but that may not be proportional to the H 2 O concentration in gas.

22 Thank you for your attention!