Grazing-Incidence Neutron-Induced Fluorescence Probes
Density Profiles of Labeled Molecules at Solid/Liquid Interfaces
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Abstract
We
report on the use of characteristic prompt γ-fluorescence
after neutron capture induced by an evanescent neutron wave to probe
densities and depth profiles of labeled molecules at solid/liquid
interfaces. In contrast to classical scattering techniques and X-ray
fluorescence, this method of “grazing-incidence neutron-induced
fluorescence” combines direct chemical specificity, provided
by the label, with sensitivity to the interface, inherent to the evanescent
wave. We demonstrate that the formation of a supported lipid membrane
can be quantitatively monitored from the characteristic fluorescence
of <sup>157</sup>Gd<sup>3+</sup> ions bound to the headgroup of chelator
lipids. Moreover, we were able to localize the <sup>157</sup>Gd<sup>3+</sup> ions along the surface normal with nanometer precision.
This first proof of principle with a well-defined model system suggests
that the method has a great potential for biology and soft matter
studies where spatial resolution and chemical sensitivity are required