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  g m -3 of DAP gives damage for device on semiconductor surface Practical method for analysis of DAP  g m -3 Practical method for analysis of DAP in  g m -3 scale DOP (Dioctyl phthalate) DEHP (Bis-2-ethylhexylphthalate) 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. DBP (Dibutyl phthalate)

Sn 4+ SnO 2 semiconductor gas sensor O 2- Sn 4+ O 2- Sn 2+ O 2- Sn 4+ O 2- Sn 4+ O 2- Sn 4+ O 2- Sn 4+ O 2- Sn 4+ O 2- Sn 4+ O 2- Sn 4+ O 2- Sn 4+ O 2- Sn 4+ O 2- Sn 4+ O 2- Sn 4+ O 2- Sn 4+ O 2- Sn 4+ O 2- Sn 4+ O 2- Sn 4+ O 2- [ ] O 2- CH 4 CO 2 H2OH2OH2OH2O O 2- Electrical response to flammable compound Reactive for any of organic compound e- →e- →e- →e- →

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

SnO 2 OO - Si(OCH 3 ) 4 Molecular sieving property + SnO 2 ’s Sensing Function O2O2O2O2 CHO SiO 2 layer CO 2, H 2 O CVD of SiO 2 in the presence of molecular template on SnO 2 surface J. Chem. Soc., Chem. Commun., 1995, 623.

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

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  g m -3 scale 3. Prototype analyzer

Experimental Pd/SnO 2 powder, 20 m 2 g -1 Pt wire OOOO SnO 2 OO 100 nm 5 mm

He Sample Electric furnace ・ 1-Naphthaldehyde (template) was injected at 343 K ・ Si(OCH 3 ) 4 vapor was fed at 473 K ・ O 2 was fed at 673 K [Sens. Actuators, B: Chem., 124, 398 (2007)]Preparation

Air (100 cm 3 min -1 ) Electric resistance 0.5 mm 3 liquid 673 K Sensor measurements DOP / Toluene / Air 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.

DOP DBP DEHP Toluene IPA MEK All compounds detected Results and Discussion 0.5 mm 3 (as liquid) of Pd/SnO 2 (unmodified) sensor

DOP DBP DEHP Toluene IPA MEK DOP, DEHP, DBP --- selectively detected Toluene, MEK, IPA --- not detected SiO 2 /Pd/SnO 2 prepared using 1-NA template (molecular-sieving) sensor

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

Detection of  g m -3 of DOP Response of Pd/SnO 2 to steady flow of DOP/air t / s R a /R  g m Detection limit = 500 Target =  g m -3 But the target is not far! Concentration of DOP using an adsorbent column is attempted.

vent sample adsorbent trap (porous polymer beads) furnace sensor 6-way valve O2O2 N2N2 flush by heating 300 cm 3 min -1 ×100 min

t / s R a /R 8.0  g m  g m -3 Response by Pd/SnO 2 Air + DOP Air + Toluene (110 mg m -3 ) t / s C DOP = 0 ppb R a /R (toluene only)  g m -3 DOP was detected.

t / s R a /R C DOP =  g m mg m -3 Selective response by SiO 2 /Pd/SnO 2 Air + DOP 4.8  g m  g m t / s C DOP = 0 R a /R - 1 Air + Tol. (110 mg m -3 ) DOP (5 - 8  g m -3 ), detected Toluene (110,000  g m -3 ), not affecting Selective detection of pollutant at a low concentration + DOP

vent sample adsorbent trap (porous polymer beads) furnace sensor 6-way valve O2O2 N2N2 flush by heating 300 cm 3 min -1 ×100 min Complex valves N 2 and O 2 supply

vent sample (250 cm 3 min -1 ×40 min) adsorbent trap (MCM-41, mesoporous silica) furnace sensor Simple system 313 ～ 423 K ←→ 673 K

35 cm 14 cm 40 cm Prototype analyzer

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

A signal (noise) was observed by heating adsorbent  g m -3 is safely detected in any case R a /R t / s 120  g m -3 C DOP =  g m  g m  g m -3 Collected for 40 min -1 Response by Pd/SnO 2 Air + DOP

R a /R t / s 120  g m -3 C DOP =  g m  g m  g m -3 Collected for 40 min -1 Response by Pd/SnO 2 Air + DOP Air + Toluene (110 mg m -3 ) + DOP Unmodified sensor Continuous flow of toluene --> Complex change Signal by DOP hidden

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

Conclusions 1. The molecular-sieving sensor (SiO 2 /Pd/SnO 2 ) detected ○ DOP, DEHP, DBP (ethanol, linear alkane) × Toluene, IPA, MEK (DMP, branched alkane) 2. About 5  g m -3 of DOP could be detected when a suitable adsorption - desorption system was combined  g 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!