Nano-viscosity of supercooled liquid measured by fluorescence correlation spectroscopy: Pressure and temperature dependence and the density scaling

Abstract

Single particle experiments: fluorescence correlation spectroscopy (FCS) and particle tracking (PT) allow to obtain the nano-viscosity of the system from the measured self/tracer translational diffusion coefficients, using the Stokes-Einstein (SE) relation. In order to perform such measurements as function of pressure and temperature a new sample cell was designed and is described in this work. We show that this cell in combination with a long working distance objective of the confocal microscope can be used for successful FCS, PT and confocal imaging experiments in broad pressure (0.1-100 MPa) and temperature ranges. The temperature and pressure dependent nanoviscosity of a van der Waals liquid obtained from the translational diffusion coefficient measured in this cell by means of FCS obeys the same scaling as the rotational relaxation and macro-viscosity of the system.

Nanomolar Nitric Oxide Concentrations in Living Cells Measured by Means of Fluorescence Correlation Spectroscopy

“…We used only a fluorescent dye, 4,5-diaminofluorescein diacetate (DAF-2DA), a well-known reagent for detecting NO in an aqueous solution. FCS was frequently used in previous studies of fluorophores in solution and has become a routine method for determining properties such as diffusion coefficients and viscosity, chemical rate constants, molecular concentrations, aggregation processes, fluorescence brightness, triplet state lifetimes, and other molecular parameters [ 30 , 31 , 32 , 33 ]. Much less frequent was the application of FCS in studies of living cells, even though it is an excellent analytical tool for studying the concentrations, propagation, interactions, and internal dynamics of various molecules at nanomolar concentrations [ 34 , 35 , 36 ].…”