Positron probing of the micellar template interior in MCM-41

What can positronium tell us about adsorption?

“…Recently, one of the most promising techniques for these purposes seems to be the method based on measurements of the positronium (i.e., bound state of positron and electron) annihilation lifetime. Positron annihilation lifetime spectroscopy (PALS) makes it possible to characterize of many types of free volumes within a wide range of pore sizes, regardless of whether they are present in solid or in liquid (Goworek et al 1997(Goworek et al , 1998He et al 2007;Koshimizu et al 2008;Kullmann et al 2010;Thraenert et al 2007;Zaleski et al 2003Zgardzińska and Goworek 2010.…”

Synthesis and characterization of nanostructural polymer–silica composite: Positron annihilation lifetime spectroscopy study

“…In order to characterize the form of dispersed silica particles (various structural kinds of silicon atoms) the composite sample was investigated using 29 Si CP-MAS NMR spectroscopy. The spectrum shown in Fig.…”

“…For the calculation of DFT pore size distribution the following assumptions were taken into account: the nitrogen adsorption on carbon/silica, cylindrical pore shape, NL DFT equilibrium model. 29 Si magic-angle spinning (MAS) NMR spectra of the solid samples were obtained at the resonance frequency of 59.6 MHz on a Bruker Avance -300 spectrometer. For 29 Si NMR 4 mm circonia rotors spun at 8 kHz were used.…”

“…Positronium annihilation lifetime spectroscopy is a promising technique which allows investigation of any free volumes in the range of diameters from angstroms to tens of nanometers [27][28][29][30]. The PALS technique is particularly suitable for determination of size of pores in solids, including closed pores and space between fine particles themselves.…”

Positronium as a probe of small free volumes in crystals, polymers and porous media

“…The PALS method allows to observe the structural chan-ges of the raw material during the process of template removal. The formation of a porous structure in MCM-41 with octa-decyltrimethylammonium tem-plate can be observed in PALS spectra measured as a function of annealing tempe-rature [215].…”