Advanced algorithms for PALS analysis of self-assembled amphiphiles

Carlos Pascual-Izzara, Aurelia Dong, Steven J Pas, Benjamin James Boyd, Calum John Drummond, Anita Hill

Research output: Chapter in Book/Report/Conference proceedingConference PaperResearchpeer-review

2 Citations (Scopus)


Self-assembled amphiphile systems are utilized in a wide variety of applications including drug delivery and energy storage. Nano-scale physical and chemical interactions govern the packing of self-assembled amphiphilic molecules, resulting in thermodynamically stable phases of defined geometries. Possible phases include micellar, hexagonal, cubic, lamellar and sponge phases. The internal nano-structure of the amphiphile self-assembly materials plays an important role in the properties of these systems and their application. To date small angle x-ray scattering (SAXS) has been the most common technique used to characterize their structure. We explore positron annihilation lifetime spectroscopy (PALS) as an alternative and/or complementary technique for this purpose, using the phytantriol/water system. While PALS is a well established technique for characterizing many materials, the coexistence of aqueous and hydrophobic regions in a soft self-assembled amphiphile material poses a challenge to the analysis and interpretation of the results. In order to alleviate these difficulties we developed a computer program for general-purpose PALS data analysis called PAScual. Amongst the most salient features of this new code are the possibility to perform bounded fits and the option of using advanced algorithms to provide a more robust and unbiased fit: on the one hand, it incorporates a global nonlinear optimization routine based on the Simulated Annealing algorithm and, on the other hand it gives information on the reliability of the results by means of a Markov Chain Monte-Carlo Bayesian Inference method. In this work we present the newly developed PALS data analysis techniques as well as the results for the phitantriol/water system, comparing them with additional data obtained from complementary techniques.
Original languageEnglish
Title of host publicationPositron and Positronium Chemistry
EditorsS.J. Wang, Z.Q. Chen, B. Wang, Y.C. Jean
Place of PublicationPfaffikon Switzerland
PublisherTrans Tech Publications
Number of pages3
ISBN (Electronic)9783038132585
ISBN (Print)9780878493487
Publication statusPublished - 2009
EventInternational Workshop on Positron and Positronium Chemistry 2008 - Wuhan University, Wuhan, China
Duration: 11 May 200815 May 2008
Conference number: 9th

Publication series

NameMaterials Science Forum
PublisherTrans Tech Publications
ISSN (Print)0255-5476
ISSN (Electronic)1662-9752


WorkshopInternational Workshop on Positron and Positronium Chemistry 2008
Abbreviated titlePPC-9

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