Friday, June 15, 11:15 - 11:30 Biological and Medical Applications
Application of Total Internal Reﬂection Ellipsometry
for thin ﬁlm characterisation and sensing
A. Nabok, A. Tsargorodskaya, and Suryajaya
Sheﬃeld Hallam University, Materials and Engineering Research Institute, City Campus,
Howard Street. Sheﬃeld, S1 1WB, UK
Recently developed method of Total Internal Reﬂection Ellipsometry (TIRE) [1, 4] represents a suc-
cessful combination of a sensitive analytical tool of spectroscopic ellipsometry with Kretschmann
SPR geometry. The method of TIRE was experimentally realised on the basis of M2000V J.A. Wool-
lam spectroscopic ellipsometer with the addition of a prism, which allows coupling polarized light
at an angle close to total internal reﬂection into thin metal ﬁlm (see Fig. 1). A cell with the inlet
and outlet tubes is attached to the bottom of the slide enabling the measurements in diﬀerent
media and performance of diﬀerent bio-reactions.
Figure 1: Figure 2:
Typical TIRE spectra of Ψ(λ) and ∆(λ) measured on a gold coated slide are shown in Fig. 1.
The Ψ(λ) spectrum, representing a ratio of amplitudes of p- and s- components of E-vector (tan Ψ =
Ep /Es ) resembles SPR curves, while the spectrum of ∆(λ), which is a phase shift between p- and
s-components (∆ = ϕp − ϕs ), appears in Fig. 1 as an almost vertical drop in ∆ (from 270◦ down
to -90◦ ). The modeling showed much higher sensitivity of the parameter ∆ (as compared to Ψ) to
changes in the thickness and refractive index of thin transparent ﬁlms, so that the registration of
∆(λ) is highly recommended for sensing applications. Another experimental possibility of TIRE
kinetics measurements is particularly important for sensing. The method of TIRE was successfully
applied in the following research projects:
1. The registration of low molecular weight toxins, such as herbicides simazine and atrazine ,
T-2 mycotoxin , and an oestrogen like nonylphenol, in their low concentrations in water
down to ppb level. TIRE kinetics measurements proved high speciﬁcity of binding the above
toxins to respective antibodies.
2. The recognition of genomic DNA of diﬀerent species of ﬁsh (salmon and herring) via electro-
static adsorption of a single strand DNA (ss-DNA) on the surface and subsequent binding
of another ss-DNA from solution . This ﬁnding is very promising for the development of
sensors for crude DNA analysis.
Friday, June 15
3. Evaluation of optical parameters of electrostatically assembled ﬁlms containing CdS and ZnS
colloid nanoparticles , promising novel materials for tuneable LED and sensors.
1. M. Poksinski, H. Arwin, Thin Solid Films 455-456, 716 (2004).
2. H. Arwin, M. Poksinski, K. Iohansen, Appl. Optics 43, 3028 (2004).
3. A. Nabok, A. Tsargorodskaya, A. Hassan, N. Starodub, Appl. Surf. Sci. 246, 381 (2005).
4. A. Nabok, A. Tsargorodskaya, A. Holloway, N. Starodub, et al., Biosens. & Bioelectron 22, 885 (2006).
5. A. Nabok, A. Tsargorodskaya, F. Davis, S.P.J. Higson, Biosens. & Bioelectron, (2007) (in submission).
6. Suryajaya, A. Nabok, A. Tsargorodskaya, F. Davis, et al., Thin Solid Films, (2007) (in submission).