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
J. Chem. Soc., Chem. Commun., 1995, 623.
Si(OCH3)4
Molecular sieving property SnO2s 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
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 Tolu
ene, 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-1100 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 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-1100 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-140 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 --gt
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 --gt
Complex change Signal by DOP hidden
Molecular-sieving sensor Response to toluene --gt
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!