Positron annihilation lifetime spectroscopy (PALS): a probe for molecular organisation in self-assembled biomimetic systems

Abstract

Positron annihilation lifetime spectroscopy (PALS) has been shown to be highly sensitive to conformational, structural and microenvironmental transformations arising from subtle geometric changes in molecular geometry in self-assembling biomimetic systems. The ortho-positronium (oPs) may be considered an active probe that can provide information on intrinsic packing and mobility within low molecular weight solids, viscous liquids, and soft matter systems. In this perspective we provide a critical overview of the literature in this field, including the evolution of analysis software and experimental protocols with commentary upon the practical utility of PALS. In particular, we discuss how PALS can provide unique insight into the macroscopic transport properties of several porous biomembrane-like nanostructures and suggest how this insight may provide information on the release of drugs from these matrices to aid in developing therapeutic interventions. We discuss the potentially exciting and fruitful application of this technique to membrane dynamics, diffusion and permeability. We propose that PALS can provide novel molecular level information that is complementary to conventional characterisation techniques.

Linking the structures, free volumes, and properties of ionic liquid mixtures

“…Similarly, there is also some evidence that the o -Ps preferentially locates in the hydrophobic domains of self-assembled amphiphiles, given the diffusion length of o -Ps in liquids is ∼10 nm. 66 Moreover, the timescale of 129 Xe NMR measurements (s) is approximately 9 orders of magnitude greater than those of PALS measurements (ns) meaning 129 Xe NMR measurements give insight into the dynamic free volume of the fluid over a relatively large timescale whereas PALS probes the free volume in very short snap shots, essentially capturing free volume as accessible and static as long as motions of the liquid molecules through that volume are slower than 0.3 GHz.…”

Luminescence rise time in self-activated PbWO4 and Ce-doped Gd3Al2Ga3O12 scintillation crystals

“…Faster detector response is seeked for in high-energy physics to prevent pile-up effect in high-luminosity experiments [1][2]. Faster readout improves the signal to noise ratio and, therefore, allows a decrease of the injected dose to the patient to accumulate sufficient information in positron emission tomography (PET) [3], positron annihilation lifetime spectroscopy (PALS) [4], and other scintillatorbased medical devices. Time resolution of ~200 ps is reported for detectors based on LYSO:Ce [5] and PWO with readout using avalanche photodiodes [6].…”

High-Barrier Polyimide Containing Carbazole Moiety: Synthesis, Gas Barrier Properties, and Molecular Simulations

“…The positron lifetime curves of Kapton, 2,7-CPPI and 2,7-CPI film are shown in Figure 7 . The slope of the decay curve for Kapton was lower than those of 2,7-CPPI and 2,7-CPI, indicating the larger size of the free volume in Kapton [ 45 ]. The raw data obtained were resolved into two finite lifetime components using the PATFIT program which assumes a Gaussian distribution for the logarithm of the lifetime for each component.…”