Calibration of an optical fluorescence method for film thickness measurement

Abstract

We describe the calibration of a technique allowing quantitative measurements of industrial coatings with thicknesses as small as 10-20 nm. Wax films doped with fluorescent rhodamine dye have been deposited by an electrospray method onto an optically flat surface of aluminium-coated glass. The films were of 220-450 nm peak thickness, which we measured with an optical profilometer using laser triangulation. Possession of a set of films allowing an absolute calibration of the fluorescence intensity versus thickness to be achieved for application in trials of the fluorescence method for measuring coating thicknesses of 10-20 nm under industrial process conditions.

A Novel Set-Up for In Situ Measurement and Mapping of Lubricant Film Thickness in a Model Rolling Bearing Using Interferometry and Ratiometric Fluorescence Imaging

“…By contrast, in fluorescence measurement mode, the triggering pulse is used to activate the excitation LED. This is because there is an upper limit to how long and how intensely the contact zone can be illuminated before fluorescence photobleaching and saturation [37,38] adversely affect the quality of the measurements.…”

“…Although the inner filter effect can occur for a single dye system, it is more pronounced in the case of a mixture of two dyes [38]. This fluorescence quenching effect may occur whenever there is a spectral overlap between the donor dye (D) emission and the acceptor dye (A) absorption spectra so that a radiative transfer process can take place between them whereby a photon emitted by D is absorbed by A.…”

How to Improve Quality Assurance in Fluorometry: Fluorescence-Inherent Sources of Error and Suited Fluorescence Standards

“…Other suggested standards include concentrated solutions of fluorophores like fluorescein and rhodamine dyes on a regular slide [103] for shading or flat field correction, fixed fluorescent cells [104] or fluorescent polymers, which can, however, suffer from spatial non-uniformity leading to inhomogeneous emission [105], immobilized particle arrays [106] or wax films doped with fluorescent dyes [107]. Recently, organic and inorganic systems containing uniformly dispersed luminescent nanocrystals at various concentrations have been suggested as potential fluorescence standards for microscopy [108].…”

Highly sensitive rapid fluorescence detection of protein residues on surgical instruments

“…a To whom correspondence should be addressed: J.S.Barton@hw.ac.uk The fluorescence signal power, P F , is usually estimated as [4] P F ≅ I 0 SlησD ( 1 ) where I 0 is the excitation radiation power density, S is the excitation spot area, l is the thickness of the fluorescently labelled protein layer, η is the quantum efficiency, σ is the absorption cross section, and D is uniform (bulk) concentration of the fluorophore. In our case equation (1) 2 ) and the absorption cross section of the fluorophore (≤ 10 -15 cm 2 ).…”