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Professor
Stephen Mann FRS |
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Centre for Organized Matter Chemistry Tel: +44 (0) 117 9289935 Fax: +44 (0) 117 9251295 |
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Titles and Abstracts of Recent Talks -
Biomineral-inspired Synthesis and Self-assembly of Nanoparticle Arrays
and Nanostructured Materials.
Organized-matter chemistry is concerned with the synthesis, characterization
and application of complex materials that exhibit order on length scales from
the molecular to macroscopic. Recently, new strategies have been developed for
the synthesis of organized inorganic nanostructures based on biomolecular
templates, facilitated self-assembly of nanoparticle building blocks, and
mesoscale transformations in complex fluids. A key aspect of this approach is
the integration of organic self-organization and inorganic assembly such that
hybrid materials are constructed by direct or synergistic templating. This
principle will be illustrated using several examples of our most recent work
including the synthesis and assembly of mesostructured silica in lipid
helicoids and tobacco mosaic virus liquid crystals, DNA-driven self assembly of
gold nanorods, and the synthesis of linear chains of nanoparticles and nanofilament
arrays in water-in-oil microemulsions.
Supramolecular templating of organized inorganic matter
Organized-matter chemistry is concerned with the synthesis, characterization
and application of complex materials that exhibit order on length scales from
the molecular to macroscopic. This talk will present an overview of several
recent strategies in which the synthesis of organized inorganic nanostructures
is controlled by organic supramolecular structures. A key aspect of this
approach is the integration of organic self-organization and inorganic assembly
such that hybrid materials are constructed by direct or synergistic templating.
This principle will be illustrated using several examples of our most recent
work including the synthesis and assembly of mesostructured silica in lipid
helicoids and tobacco mosaic virus liquid crystals, DNA-driven self assembly of
gold nanorods, and the surfactant-mediated synthesis of linear chains of
nanoparticles and nanofilament arrays in water-in-oil microemulsions.
Synthesis and Design of Biomimetic Inorganic Materials and
Nanostructures.
The study of biominerals, such as bones, shells and teeth, is providing
new ideas and inspirations for materials chemistry. This lecture describes
recent approaches to the "morphosynthesis" of inorganic materials,
colloids and nanostructures with complex form and functionalized architecture.
A key aspect of this approach is the integration of organic self-organization
and inorganic assembly such that hybrid materials are constructed by
template-directed processes. This principle will be illustrated using several
examples of our recent work, including the synthesis and assembly of
mesostructured silica in lipid helicoids, metallic nanowires in tobacco mosaic
virus particles, formation of microporous calcium carbonate colloids in foams
and emulsion droplets, and the synthesis of linear chains of nanoparticles and
complex nanofilament arrays in water-in-oil microemulsions.
Nanotechnology in the test-tube
The assembly and organization of small-scale structures is a key challenge in
nanotechnology. Current approaches tend to be based on sophisticated physical
methods, such as the high resolution patterning of surfaces for controlled
deposition of metallic nanoparticles and thin films. In contrast, chemical
methods for the spontaneous formation of nanostructures with higher-order
architectures have only recently been investigated. This short talk presents
some new ideas and experiments concerned with the direct coupling of chemical
synthesis and self-assembly to produce organized arrays of inorganic
nano-crystals and nano-wires. The reactions take place in nano-sized water
droplets that are surrounded by a shell of surfactant molecules and dispersed
in oil as a stable emulsion. Aqueous salts, such as barium chloride and sodium
sulfate, are encapsulated separately within the droplets, which are then mixed
together to induce barium sulfate nucleation within the confined reaction
space. By changing the chemical conditions, the system can be directed along
various reaction pathways due to modifications in the strength of interactions
between the surfactant molecules and the growing crystal surface. Weak
interactions result in discrete nanoparticles, whereas intermediate binding
gives rise to the spontaneous assembly of linear chains of regularly stacked
nano-crystals interspaced with surfactant molecules. In contrast, very strong
interactions inhibit crystallization such that amorphous barium sulfate
nanoparticles are nucleated within the water droplets. These particles are
unstable and slowly transform into crystalline barium sulfate within a few
hours. Remarkably, this process produces unusual life-like microstructures,
such as coiled nanofilament bundles, twisted helicoids and hierarchically
stacked cones, due to competing forces arising from the reorganization of
surface-bound surfactant molecules in association with inorganic
crystallization. Our results indicate that the emergence of complexity and
long-range organization in nanostructures can be achieved by time- and
scale-dependent coupling of interactive components, and suggests that chemical
routes will play an important role in the development of new materials and
devices in nanotechnology.
Sol-gel Synthesis of Organized Matter.
The study of biological silicification in unicellular organisms such as diatoms
and radiolaria, is providing new ideas and inspirations for the synthesis of
organized inorganic matter. This lecture describes recent approaches to the "synthesis-with-construction"
of silica-based materials with structural and morphological organization across
a range of length scales. Several themes are addressed. These include the
template-directed synthesis of covalently linked organosilicate hybrid clays
with lamellar structure, and of ordered mesoporous MCM-41-type hybrid
materials. The former are produced by reaction of organosiloxanes in the
presence of inorganic templates (mono-octahedral Mg/OH/O brucite layers),
whereas the latter are synthesized by co-condensation of siloxanes and
organo-siloxanes in the presence of cylindrical micellar templates consisting
of long chain surfactant molecules. In addition, the use of larger templates,
such as ordered arrays of bacterial cellular filaments, in the formation of
ordered macrostructures of amorphous silica or mesoporous silica, is described.
Finally, a new method for synthesizing silica with microskeletal architecture
is discussed. The approach employs condensation reactions in compartmentalized
liquids as a means of generating organized patterns of inorganic matter.
Biomimetic Synthesis of Complex Inorganic Materials.
The study of biominerals, such as bones, shells and teeth, is providing new
ideas and inspirations for materials chemistry. This lecture describes recent
approaches to the "synthesis-with-construction" of inorganic
materials with complex form and organized architecture. The key concepts to be
discussed include, self-assembly and preorganization, molecular and spatial
templating, length scale patterning, and morphosynthesis using organized
reaction media. These will be illustrated by reference to recent work on;
(a) the use of the iron storage protein, ferritin, to prepare dispersed
nanocolloids with magnetic and semiconducting properties,
(b) the self- and coassembly of surfactant micelles with cylindrical
microstructures for the template-directed synthesis and patterning of iron
oxides, gold nanoparticles and mesoporous silica, (c) the fabrication of
bacterial superstructures to pattern CdS nanocrystalline superlattices and
ordered macroporous silicas, and (d) the exploitation of compartmentalized
liquids, such as reverse micelles and microemulsions for the synthesis of
complex micro-skeletal forms of materials such as calcium carbonate, calcium
phosphate and transition metal oxides.
The Chemistry of Form
The emergence of complex form in living and non-living systems remains a deep
question for scientists attempting to understand the origins and development of
shape and structure. In recent years, biologists and physicists, respectively,
have made significant advances in explaining fundamental problems in fields
such as morphogenesis and pattern formation. Chemists, on the other hand, are
only just beginning to contemplate the possibility of preparing man-made
materials with life-like form. This review traces a route to the direct
synthesis of inorganic structures with biomimetic form, beginning from an
understanding of crystal morphology and biomineralization. The equilibrium form
of crystals can be modified by surface-active additives but only within limits
dictated by the symmetry of the unit cell. In contrast, biological minerals,
such as shells, bones and teeth, are distinguished by a complexity of form that
bears little resemblance to the underlying order of their inorganic crystals.
By understanding the constructional processes that give rise to the inorganic
structures of life it should be possible to develop a chemistry of form in the
laboratory. For example, complex small-scale inorganic architectures are
produced at room temperature by undertaking precipitation reactions in
self-assembled organic media, such as surfactant micelles, block copolymer
aggregates and microemulsion droplets. Unusual inorganic forms emerge when
these reaction fields are subjected to instability thresholds and synthesis and
self-assembly can be coupled to produce materials with higher-order
organization. Like their biological counterparts, these hard inorganic
structures represent new forms of organized matter which originate from soft
chemistry.
Biomimetic Materials Chemistry: From Magnetic Proteins to Skeletons in
the Beaker.
The study of biominerals, such as bones, shells and teeth, is providing new
ideas and inspirations for materials and colloidal chemistry. This lecture
describes recent approaches to the "synthesis-with-construction" of
inorganic materials with organized architectures. Several themes are addressed.
Firstly, the use of the iron storage protein, ferritin, to prepare dispersed
nanocolloids with magnetic and semiconducting properties is described.
Secondly, surfactant micelles with cylindrical microstructures have been
utilised in the template-directed synthesis and patterning of iron oxides, gold
nanoparticles and mesoporous silica. Ordered macroporous silicas can be
prepared by using bacterial superstructures to template longer length scales in
inorganic deposition. Finally, bicontinuous microemulsions have been exploited
in the "inorganic morphosynthesis" of complex micro-skeletal forms of
either calcium carbonate or calcium phosphate. These materials, which resemble
biomineral architectures, originate from self-organized transitory reaction
environments that are replicated in the inorganic materials by rapid
crystallization processes.
Learning about Surface Design from Biomimetics.
A central idea in biomineralization is that the nucleation, growth and
patterning of inorganic structures are controlled by interfacial interactions
between mineral and protein/lipid surfaces. The study of inorganic-organic
interfaces is therefore an important aspect of biomimetic materials chemistry
which seeks to develop new synthetic routes to functional materials that are
organized on various length scales from the nano- to macroscopic. This lecture
illustrates the potential importance of electrostatic, stereochemical and
geometric complementarity in oriented crystal nucleation under compressed
Langmuir monolayers, and how some of these interactions can be used in the
direct or synergistic templating of complex three-dimensional structures such
as helical silica-lipid composites and silica-surfactant mesophases. New
approaches, involving (i) biomolecular (antigen) coupling of gold nanoparticles
via surface-adsorbed antibodies, (ii) synthesis and self-assembly of
nanoparticle superstructures via hydrophobic-driven surface interactions in
complex fluids, and (iii) emergent self-organization of calcium phosphate-block
co-polymer nested colloids, are also described.
Inorganic Morphosynthesis in Self-organized Reaction Environments.
Organized-matter chemistry is concerned with the synthesis, characterization
and application of complex materials that exhibit order on length scales from
the molecular to macroscopic. Recently, biomimetic strategies have been developed
for the synthesis of organized inorganic-based structures. A key aspect of this
approach is the integration of organic self-assembly and inorganic reaction
chemistry such that hybrid materials are constructed either by direct or
synergistic templating. This lecture illustrates how organic mesophases and
complex fluids - for example, lyotropic liquid crystals, lipid helices, viroid
tubes, polymer micelles, microemulsions, foams - can be used for the one-step
synthesis of inorganic (silica, iron oxide, BaSO4, Ca phosphate, CaCO3 etc.)
architectures with unusual morphological form (morphosynthesis). In particular,
the lecture focuses on the emergence of organized colloidal superstructures,
such as nested calcium phosphate-block copolymer micelles (collaborative work
with Prof. M. Antonietti,
Nanotectonics: Coupled Synthesis and Self-assembly of Nanoparticle-based
Higher-order Structures.
Recently, new strategies have been developed for the synthesis of organized
inorganic nanostructures using nanoparticle-based building blocks
(nanotectonics). A key aspect of this approach is the integration of organic
self-organization and nanoparticle assembly such that hybrid materials are
constructed by direct or synergistic templating. This principle will be
illustrated using several examples of our recent work including the control of
nanoparticle assembly by biological superstructures, such as supercellular
bacterial threads and 2-D porous protein crystals, and via interparticle
conjugation using biomolecular-based surface recognition. The lecture will also
focus on the coupled synthesis and self-assembly of higher-order
nanoparticle-based structures, such as linear chains and nanofilament arrays of
BaSO4 and BaCrO4 crystallites, in complex fluids (microemulsions).
Holey Silica! - from Interior Design to Nanotectonics.
Organized-matter chemistry is concerned with the synthesis, characterization
and application of complex materials that exhibit structural and compositional
order on length scales from the molecular to macroscopic. Porous materials such
as mesoscopically ordered silicas, represent an important class of organized
matter that originates from synthetic strategies involving template-directed
self-assembly. In general, this strategy is based on structural and
morphological replication of organic architectures and although usually limited
to the mesoscopic scale, in principle there is no reason why the method should
not be extended to longer length scales and to systems involving multiplex
templating. To illustrate this, examples of porous silicas prepared using
liquid crystals of tobacco mosaic virus (TMV), sponge-like organic matrices of
biomineralized cuttlebone, organic crystal fibres, and threads of bacterial
superstructures fibres will be briefly presented in the lecture. A
complementary approach to porous architectures involves the use of
nanoparticle-based building blocks (nanotectonics), which are positioned and
assembled within the void spaces of ordered organic templates. Clearly, if the
nanoparticles have structured porous interiors then these can be incorporated
into the walls of the higher-order assembly to produce hierarchical materials.
For this reason, we have recently synthesized nanoparticles with various types
of porous interiors zeolite (silicalite), MCM-41, and a new structure
consisting of radially arranged linear channels and used these building blocks
in association with various templates, such as bacterial superstructures, latex
beads, and sponge-like polymer gels. Aspects of this work will be reviewed in
the lecture.