Detection of low molecular weight toxins using an optical phase method of ellipsometry

Microcystin-LR produced by bacterial algae: Optical detection and purification of contaminated substances

“…TIRE measurements were carried out using the experimental set-up described earlier [17][18][19] which was based on M2000 J.A. Woollam spectroscopic ellipsometer with the addition of 68 • glass prism in optical contact with a gold coated glass slide and the reaction cell attached underneath (see the scheme in Fig.…”

“…Dynamic spectral measurements were used for the study of kinetics of adsorption and binding and allowed the evaluation of the association constant of the immune reaction; while the spectra of « and obtained from single spectroscopic scans were used for data fitting and subsequent evaluation of the thickness of adsorbed molecular layers. TIRE measurements and fitting procedure were described in detail previously [17][18][19].…”

“…As has been described earlier [8,[17][18][19], the spectra of two ellipsometric parameters « and are recorded, where « is related to the amplitude ratio (tan « = A p /A s ) of p-and s-components of polarized light while is the phase shift between them. Because is about 10 times more sensitive than « to small changes in the thickness and/or refractive index of the coating on top of Au layer [18], further data analysis is mostly based on ( ) spectra.…”

“…5 calibrated vs the concentration of MC-LR could be used for sensing purposes straightaway, we evaluated the molecular layer thickness increment by doing data TIRE fitting to the reflective system model consisting of glass (BK7) as an ambient, Cr/Au metal layer, deposited molecular layer, and aqueous solution. The procedure of data fitting has been described in detail previously [10,[17][18][19]. It is based on solving Fresnel equations and minimizing the error function between calculated and experimentally obtained « and parameters at each spectral point using least-square technique.…”

“…The adsorbed molecular layers were modelled by Cauchy dispersion n = A + B/ 2 + C/ 4 typical for transparent (k = 0) dielectric materials. Since all molecular layers used have similar refractive index (n = 1.42 at 633 nm) [10,[17][18][19] it was fixed during the fitting and all changes in the adsorbed layers were associated with changes in the effective layer thickness (d).…”