Page 198 - Organic Electronics in Sensors and Biotechnology

Progress and Challenges in OLED-Based Chemical and Biological Sensors 175

0.05
0.012
1 PtOEP
0.04 4 2 3 PtOEP + mirror 0.010 4 1 2 3 PdOEP
Intensity (arb. units) 0.03 3 4 PtOEP + mirror + dopant Intensity (arb. units) 0.008 3 4 PdOEP + dopant + mirror
PdOEP + mirror
PtOEP + dopant
PdOEP + dopant
0.006
0.02
0.01 2 0.004
0.002
2
1
0.00 0.000 1
0 100 200 300 400 0 1 2 3 4
Time (μs) Time (ms)
(a) (b)
FIGURE 5.8 Effect of the titania dopant embedded in the PS fi lm and Al mirrors on
the PL decay of (a) PtOEP:PS and (b) PdOEP:PS fi lms in water in equilibrium with Ar
(~0 ppm DO). The fi lms were prepared by drop-casting 60 μL of toluene solution
containing 1 mg/mL TiO , 1 mg/mL dye, and 50 mg/mL PS. (See also color insert.)
2

8 PS:PDMS 2:1

PL intensity (arb. units) 6 PS

4

2

0

0 100 200 300 400
Time (μs)

FIGURE 5.9 Enhancement of the PL intensity of a PtOEP-based gas-phase
O sensor in an Ar atmosphere at 23°C by using a 2:1 (by weight) PS:PDMS
2
polymer blend.

with linear 1/τ vs. [O ] calibrations. Thus, OLED/sensing film arrays,
2
which are simple to fabricate and are of small size, are particularly
promising for real-world applications. The use of such arrays will
additionally improve the accuracy in analyte monitoring via redun-
dant measurements. For example, one such simple array could com-
prise two sensing films: a 1:10 PtOEP:PS film that exhibits near linear
SV plot over the whole 0 to 100% range (data not shown), which would
be excited by Alq OLED pixels, and a PdOEP:PS film, that is very sen-
3
sitive to low levels of O and exhibits a linear behavior up to ~40% O
2 2