Macroscopic Alignment of Silver Nanoparticles in Reverse Hexagonal
Liquid Crystalline Templates
Martin Andersson1*, Viveka Alfredsson3, Per Kjellin1 and Anders E.C. Palmqvist1,2*
1
Department of Applied Surface Chemistry, and 2Competence Centre for Catalysis
Chalmers University of Technology, SE-412 96 Göteborg, Sweden
3
Physical Chemistry, Lund University, SE-221 00 Lund, Sweden
*Corresponding authors: martina@surfchem.chalmers.se;
anders.palmqvist@surfchem.chalmers.se
Abstract
Nanostructured noble metals are of interest, since their physiochemical properties have a flora
of applications in fields as diverse as photovoltaics, catalysis, electronic and magnetic devices
etc. A range of physical and chemical methods has been utilized to prepare nanosized noble
metals, and several of these are based on the use of a structure-directing template. Among the
wet-chemical methods the ones based on the use of self-assembled amphiphilic templates
have proven to be particularly successful in the preparation of nanostructured noble metals.
Hexagonal and cubic liquid crystalline templates have proven useful for the synthesis of
mesoporous materials of both oxides and noble metals1-3. Qi et al4 have showed that a
lamellar liquid crystalline phase consisting of C12E4 surfactants and water can be used to
produce silver nanoparticles with a narrow size distribution.
In this work a flexible method of preparing and macroscopically aligning nanoparticles of
crystalline silver into millimeter long fibers is presented. The approach utilizes the dual
functionality of a reverse hexagonal liquid crystalline template containing a built-in reducing
agent facing the aqueous domain. The method is advantageous in that its slow kinetics allows
for a thorough introduction of a silver salt into the liquid crystal before the reduction takes
place, allowing for an efficient loading of the template and a retained mesoscopic ordering as
evidenced by SAXS. It was confirmed by 1H-NMR that the oxyethylene groups of the
amphiphilic polymer reduce the silver ions while being oxidized to aldehydes. The silver
nanoparticles are monodisperse and in the same size range as the diameter of the aqueous
domain of the liquid crystal (4 nm) further supporting that the silver particles form inside the
liquid crystal. TEM images confirm the macroscopic alignment of silver nanoparticles into
fibrils and the packing of fibrils into millimeter long fibers. The diameter of the fibrils and
fibers ranges from 30 nm to several hundreds of micrometers. Electron diffraction analysis of
a collection of silver nanoparticles confirms their crystallinity as three diffraction rings could
be indexed to the face centered cubic structure of silver.
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