optical chemical sensor systems based on photosensitive hybrid sol-gel glass b.d. maccraith, s....
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Optical Chemical Sensor Systems based on Photosensitive Hybrid Sol-Gel Glass
B.D. MacCraith, S. Aubonnet, H. Barry, C. von Bültzingslöwen, J.-M. Sabattié, C.S. Burke
Optical Sensors Laboratory - National Centre for Sensor ResearchDublin City University - Ireland
Sol-gel solution Concentration of
the catalyst (mol/l)
pH
Sample A 0.1 (HCl) 0.58
Coudray preparation 0.01 (HCl) 0.92
Sample B 0.01 (HCl) 1.64
Sample C 0.01 (NaOH) 6.14
Sample D 0.1 (NaOH) 7.12
Sample E 1 (NaOH) 10.74
Tailoring the microstructure
Basic RecipeMAPTMS / Zirconium propoxide
TEOS / methacrylic acidRu tris diphenyl phenanthroline
water acid / base catalyst (cf. table)
0 20 40 60 80 100
1.0
1.2
1.4
1.6
1.8
2.0
2.2
2.4
2.6
2.8
pH=10.74 KSV
=0.0169 pH=7.12 K
SV =0.0137
pH=6.14 KSV
=0.0115 pH=1.64 K
SV =0.0105
pH=0.58 KSV
=0.0097 Coudray K
SV =0.000833
% O2
I0 / I
Stern-Volmer plots
4 Doped Materials: Oxygen SensingThe luminescence of ruthenium poly-pyridyl complexes is
quenched reversibly by oxygen (Dynamic Quenching)
Such complexes (e.g. Ru tris diphenyl phenanthroline) can be excited by blue LEDs and emit in red
Quenching process described by Stern-Volmer equation
I0 / I = 1 + KSV [ O2]
where I0 is the unquenched luminescence intensity
The Stern-Volmer constant Ksv is a direct measure of sensitivity
KSV D, the diffusion coefficient of O2 in the matrix
2 ObjectivesTo demonstrate the capability of doped photo-patternable sol-gel
glass for sensor applications.To investigate the tunability of such sensor systemsTo exploit the photolithographic properties of these materials to
prepare a range of sensor configurations.To demonstrate the usefulness of this system for micro-total-analysis
(Lab-on-a-chip) devices.
1 IntroductionMuch interest in hybrid organic-inorganic sol-gel glasses that can be
photo-patterned by UV irradiation.Principal application is the fabrication of integrated optic devices for
telecommunication applications, e.g. splitters, DWDM’s.These materials have considerable potential for chemical sensing
systems, including optodes (doped materials) and micro-total-analysis (Lab-on-a-chip) devices.
5 Sensor Configurations Photosensitive sol-gel glass can be used to
produce a range of useful sensing configurations, e.g. integrated optic structures and arrays of sensor spots
The fluorescence is captured in each waveguide and can be observed at the channel output.Average ridge thickness of 14.5m
200 m
Photopatterned array of doped sensor spots
DetectorArray
SensorSpot
Waveguide
Blue LED
6 Microsystems (Lab-on-a-chip)Major developments in miniaturised
sensor systems with high levels of integration and functionality, e.g. -TAS (micro-total-analysis systems)
Key -TAS elements include microfluidic channels and patterned surfaces
UV-photolithographic sol-gel materials can be used for rapid prototyping, templating of PDMS (poly-dimethyl siloxane), and patterning of surfaces.
UV-cured sol-gel ridges (50 m width)
Silicon substrate
PDMS micro channels
PDMS drop
7 Conclusions
UV-curable sol-gel materials combine the versatility of the sol-gel process with the capabilities of photolithography.
Tunable doped sensor materials, waveguide sensor structures and sensor arrays can be fabricated with this process.
Future work: micro-optical sensor chips and multi- analyte sensor systems
3 Photosensitive Sol-Gel PreparationPrinciples: Presence of UV curable moiety (MAPTMS -
methacryloxypropyl-trimethoxysilane) enables spatially selective curing of sol-gel matrix.
The Photoinitiator splits into radicals upon UV illumination (Step 1).
The photoinitiator radicals react with the unsaturated groups of MAPTMS (Step 2).
The reaction propagates by radical addition to unsaturated groups of MAPTMS (Step 3).
The non-polymerised MAPTMS is washed away using Isopropanol
CH2
CH3
O
O
Si(OCH3)3O
.
O
OH
O
.OH .UV
.CH3
O
O
Si(OCH3)3
H
CH3
O
O
Si(OCH3)3
CH2
Step 1
Step 2
Step 3
Photoinitiator
MAPTMS
Mask
IPA wash
Substrate
Photosensitive layer
Substrate
UV light
Photopatterning