Selective Detection of Dialkyl Phthalate by Molecular-sieving Sensor

1. Selective Detection of Dialkyl Phthalate by Molecular-sieving Sensor Naonobu Katada, Ken-ichi Fukuchi, Hideyuki Iwata, and Miki Niwa Tottori Univ., Fuji Electric Systems Co. Ltd.

2. Selective Detection of Dialkyl Phthalate by Molecular-sieving Sensor Naonobu Katada, Ken-ichi Fukuchi, Hideyuki Iwata, and Miki Niwa Tottori Univ., Fuji Electric Systems Co. Ltd. DAP (dialkyl phthalate) = plasticizer Several mg m-3 of DAP gives damage for device on semiconductor surface Practical method for analysis of DAP in mg m-3 scale DOP (Dioctyl phthalate) DEHP (Bis-2-ethylhexylphthalate) DBP (Dibutyl phthalate)

3. SnO2 semiconductor gas sensor H2O CO2 CH4 [ ] O2- O2- O2- O2- O2- O2- Sn4+ O2- Sn4+ O2- Sn2+ O2- Sn4+ O2- Sn4+ O2- Sn4+ O2- O2- O2- O2- O2- O2- O2- e- → Sn4+ Sn4+ Sn4+ O2- Sn4+ O2- Sn4+ Sn4+ O2- O2- O2- O2- O2- O2- O2- O2- O2- O2- Sn4+ O2- Sn4+ O2- Sn4+ O2- Sn4+ O2- Sn4+ O2- Sn4+ O2- O2- O2- O2- O2- O2- O2- Electrical response to flammable compound Reactive for any of organic compound

4. There are other gases [toluene, isopropanol (IPA) and methylethyl ketone (MEK)] even in clean rooms. Selective detection is needed.

5. CVD of SiO2 in the presence of molecular template on SnO2 surface CO2, H2O CHO - O O J. Chem. Soc., Chem. Commun.,1995, 623. Si(OCH3)4 Molecular sieving property + SnO2’s Sensing Function O2 SiO2 layer SnO2

6. Shape-selective adsorption Bull. Chem. Soc. Jpn.,78, 1425 (2005). Application to molecular-sieving sensor Sens. Actuators, B: Chem.,124, 398 (2007)

7. Aim of this study Application of molecular-sieving sensor to detection of DAP in the co-presence of toluene, IPA and MEK 1. Selective detection 2. Detection in mg m-3 scale 3. Prototype analyzer

8. Experimental O O O O O O SnO2 Pd/SnO2 powder, 20 m2 g-1 100 nm 5 mm Pt wire

9. Preparation He Sample Electric furnace ・1-Naphthaldehyde (template) was injected at 343 K ・Si(OCH3)4 vapor was fed at 473 K ・O2 was fed at 673 K [Sens. Actuators, B: Chem.,124, 398 (2007)]

10. Sensor measurements Air (100 cm3 min-1) DOP / Toluene / Air 0.5 mm3 liquid 673 K Electric resistance Very low concentration of DOP / Air 1. Purification of DOP vapor was carried out; DOP liquid was heated at 383 K for 10 h in He flow. He was further flowed at room temperature for 24 h. DOP vapor was trapped to confirm the purity. 2. Thus prepared 4.8 mg m-3 DOP / air was diluted with pure air. 3. Equipment was heated and completely purged before the measurements.

11. Results and Discussion Pd/SnO2 (unmodified) sensor 0.5 mm3 (as liquid) of DBP Toluene MEK DEHP IPA DOP All compounds detected

12. SiO2/Pd/SnO2 prepared using 1-NA template (molecular-sieving) sensor DBP DEHP DOP IPA MEK Toluene DOP, DEHP, DBP --- selectively detected Toluene, MEK, IPA --- not detected

13. Why? Detected by molecular-sieving sensor DOP, DEHP, DBP, linear alkane, ethanol Undetected Toluene, IPA, MEK, benzene, branched alkane, dimethyl phthalate (DMP)

14. Detection of mg m-3 of DOP Response of Pd/SnO2 to steady flow of DOP/air 1600 mg m-3 Detection limit = 500 Target = mg m-3 But the target is not far! Concentration of DOP using an adsorbent column is attempted. 1 -1 /R a R 0.5 800 640 480 16 160 0 80 0 320 -600 0 600 1200 1800 t / s

15. sample 300 cm3 min-1×100 min N2 6-way valve O2 furnace adsorbent trap (porous polymer beads) sensor flush by heating vent

16. Response by Pd/SnO2 Air + DOP Air + Toluene (110 mg m-3) 5 5 4 4 3 3 -1 -1 /R /R a R a R 2 2 (toluene only) 8.0 mg m-3 C = 0 ppb DOP 1 1 4.8 mg m-3 0 0 0 500 1000 0 500 1000 t / s t / s 5 - 8 mg m-3 DOP was detected.

17. Selective response by SiO2/Pd/SnO2 Air + Tol. (110 mg m-3) 0.4 0.3 0.2 - 1 /R a R 0.1 C = 0 DOP 0 -0.1 0 500 1000 t / s Air + DOP + DOP 0.4 8.0 mg m-3 0.3 8.0 mg m-3 0.2 -1 /R 4.8 mg m-3 a R 4.8 mg m-3 0.1 0 C = 0 DOP -0.1 0 500 1000 t / s DOP (5 - 8 mg m-3), detected Toluene (110,000 mg m-3), not affecting Selective detection of pollutant at a low concentration

18. sample 300 cm3 min-1×100 min N2 6-way valve O2 furnace adsorbent trap (porous polymer beads) sensor flush by heating vent Complex valves N2 and O2 supply

19. sample (250 cm3 min-1×40 min) adsorbent trap (MCM-41, mesoporous silica) furnace 313 ～ 423 K ←→ 673 K sensor vent Simple system

20. 40 cm Prototype analyzer 14 cm 35 cm

21. Temperature controllers Sample air Adsorbent column Electric furnace Sensors Pump Electric tester

22. Response by Pd/SnO2 Air + DOP 120 mg m-3 Collected for 40 min-1 1.5 -1 24 mg m-3 1 /R a R 4.8 mg m-3 0.5 2.4 mg m-3 A signal (noise) was observed by heating adsorbent. C = 0 DOP 0 -200 0 200 400 600 t / s 5 - 8 mg m-3 is safely detected in any case.

23. Response by Pd/SnO2 Air + Toluene (110 mg m-3) + DOP Air + DOP 120 mg m-3 Collected for 40 min-1 1.5 -1 24 mg m-3 1 /R a R 4.8 mg m-3 0.5 2.4 mg m-3 C = 0 DOP 0 -200 0 200 400 600 Unmodified sensor Continuous flow of toluene --> Complex change Signal by DOP hidden t / s

24. Air + Toluene (110 mg m-3) + DOP Collected for 40 min-1 Unmodified sensor Continuous flow of toluene --> Complex change Signal by DOP hidden Molecular-sieving sensor Response to toluene --> Suppressed 3 - 5 mg m-3 of DOP detected These are tentative results; final tests are now proceeding.

25. Conclusions 1. The molecular-sieving sensor (SiO2/Pd/SnO2) detected ○ DOP, DEHP, DBP (ethanol, linear alkane) × Toluene, IPA, MEK (DMP, branched alkane) 2. About 5 mg m-3 of DOP could be detected when a suitable adsorption - desorption system was combined. 3. 5 mg m-3 of DOP was detected within 50 min in the co-presence of 110 mg m-3 of toluene by a prototype analyzer. Thank you for your kind attention!