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Book Review An Introduction to Ultrathin Organic Films from LangmuirЦBlodgett to Self-Assembly. By A. Ulman

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example, the information that two atoms cannot lie one
above the other) one can obtain an improvement over the
“random atom model” used in the direct method.
The lack of uniformity, and the inevitable repetitions resulting from the lack of coordination between the individual
contributions, cannot detract significantly from the generally very positive impression given by this book, which includes research results extending up to 1991. This fascinating
universal concept opens up many new possibilities for the
analysis of spectra, images, and X-ray scattering data. Several of the authors extol the virtues of the method too enthusiastically for this reviewer’s taste; an extreme example of this
tendency was an article in The Times (London, 1984), in
which it was claimed that MEM analysis would make it
possible to record 13C NMR spectra at natural abundance
on living animals. However, this is rectified by other chapters
that present an objective appraisal. The figures, text, and
mathematical formulas are all of an exemplary standard.
Because of the wide range of aspects covered in this book, it
can be thoroughly recommended, not only for spectroscopists, “imagers”, and X-ray crystallographers, but also
for all readers with interests in physical chemistry or information science.
Christian Griesinger
Institut fur Organische Chemie
der Universitat Frankfurt/Main (FRG)
An Introduction to Ultrathin Organic Films from LangmuirBlodgett to Self-Assembly. By A . Ulman. Academic Press,
New York, 1991. XIII, 442 pp., hardcover $65.00.ISBN 0-12-708230-1
In an article in the journal Science in 1936, Irving Langmuir addressed the following words to the international scientific community: “Today. . . I propose to tell you of a real
two-dimensional world in which phenomena occur that are
analogous to those described in ‘Flatland’. I plan to tell you
about the behavior of molecules and atoms that are held at
the surface of solids and liquids.” One could hardly have a
more comprehensive, and at the same time precise, statement
of what research in the area of ultrathin organic films is
about. No doubt that is why Abraham Ulman has chosen to
preface his book with this quotation from Langmuir who, in
collaboration with Kathleen Blodgett, developed the Langmuir-Blodgett (LB) technique.
Most of those engaged in research on ultrathin organic
films are either chemists or physicists, and it is to these that
Ulman’s book is directed. In 440 pages the author introduces
readers to a field that has developed at a remarkable rate
during the last 15 years. This development stems to a large
extent from the elegant experiments carried out by Hans
Kuhn in the mid-sixties. Those experiments established the
basic principles of a supramolecular architecture, and made
it possible to position molecules and monomolecular films
with separations of the order of 50 8, with a precision better
than 5 8,. At that time the experiments confirmed Foerster’s
prediction of a transfer of energy from a donor dye molecule
to a nearby acceptor dye molecule; nowadays they form part
of the practical laboratory training of advanced students.
Ulman’s book consists of five parts as follows:
1) Techniques for characterizing the intrinsic properties of
films and the properties of their surfaces. Here the author
describes most of the analytical methods used, starting with
the measurement of thickness by ellipsometry, and continuing through scattering techniques for determining the structures of films, to surface characterization techniques such as
Angew. Chem.
Int. Ed. Engl. 1992, 31, No. 7
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contact angle measurements, and the most recently developed imaging techniques such as scanning tunneling microscopy and atomic force microscopy. Only a few methods
are not mentioned; one of these is the vibrating quartz crystal technique for measuring the mass of material deposited
on a surface.
2) Preparing monomolecular films and transfering them
onto solid supports (Langmuir-Blodgett films). Here “film
balance” techniques are described, whereby molecules are
spread on the surface of a liquid to form a monomolecular
layer, which is subsequently compressed into a close-packed
state, and this film is then transfered onto a solid support.
This section also describes the preparation of substrate surfaces, the transfer process, and the types of materials that
have so far been used to make Langmuir-Blodgett films.
Ulman attempts to relate the molecular structures, transfer
conditions, and substrate properties to the properties of the
resulting films, so far as this is possible from the details given
in the original papers. The types of amphiphiles discussed
include both substances of low molecular mass and polymers.
3) Preparing monomolecular and multimolecular films by
self-assembly (SA) techniques (chemi- and physisorption). In
this section Ulman draws a rather arbitrary (but, nevertheless, commonly accepted) distinction between LB films and
those described here. The term “self-assembly” is meant to
imply that the molecules spontaneously form an ordered
structure on the surface of the substrate. In contrast to the
LB technique, no film balance is needed; instead, the adsorption takes place directly from the solution. The focus of
interest is therefore the kinetic aspects, which are here discussed in detail. The cost of the apparatus needed to lay
down a monomolecular film by this method is considerably
less than with the LB technique. However, if one wishes to
build up multimolecular films the choice of compounds that
can be used is severely limited, since the bonding between
successive layers is usually covalent.
4) Model calculations for monomolecular film systems. In
this short section the author outlines the current position
regarding the theoretical description of two-dimensional
molecular aggregates. It becomes apparent that methods for
calculating or predicting the properties of these complex systems are still at an early stage of development. The dilemma
is that the results obtained using simplified models are of
doubtful value, whereas the established methods cannot be
applied to systems with such a large number of degrees of
freedom.
5 ) Potential applications of ultrathin films. This section
reviews the importance of ultrathin films for materials science. Although at present (October 1991) there are only two
commercial products on the market that are based on LB or
SA films, there is an enormous amount of scientific and
industrial interest in these systems. The most promising
forms of supramolecular architecture are the polar film systems, which have applications in nonlinear optics and as
pyroelectric detectors for infrared radiation. Other potential
fields of application are in photoresists or electronresists, in
sensors, in optical data storage, in gas separation, in friction
reduction, and in conducting films.
The book is essentially what its title promises: an introduction. It includes about 1900 references to original papers
and reviews. The literature coverage extends to the end of
1989, and is quite comprehensive. However, contrary to
what one might expect from the title, Ulman restricts the
discussion to Langmuir-Blodgett and self-assembly systems.
Other important types of layered films, such as self-supporting (e.g., liquid crystalline) films, films consisting of lipid
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double layers, or films prepared by spin-coating or vapor
deposition techniques, are not mentioned. Also the subject
index is definitely a weak point, as it is neither sufficiently
comprehensive nor suitably constructed to do justice to the
contents. Often it is easier to locate a topic by searching for
the relevant chapter in the contents list. Despite these criticisms, the book can be recommended to everyone who seeks
an up-to-date survey of the area of LB and SA films, but
does not expect to find here a work of reference providing a
detailed solution to every problem-the field of ultrathin
films is still too new for that.
Gero Dtcher
Institut fur Physikalische Chemie
der Universitat Mainz (FRG)
Inorganic Biochemistry of Iron Metabolism. (Ellis Horwood
Series in Inorganic Chemistry). By R . R. Crichton. Ellis
Horwood, New York, 1991. 263 pp.. hardcover $85.95.ISBN 0-13-728742-9
Although it is well known that iron is essential for virtually
all forms of life, there are still many unanswered questions
concerning the metabolism of the metal. In this book, Professor Crichton provides a useful survey of current understanding, with the first nine chapters dealing with the topics
of general iron biochemistry, iron uptake, transport, storage
and homeostasis, and then iron imbalance and its effects in
relation to human health treated in the last three chapters.
The area the book covers is so vast that it is impossible to
provide precise details of all the known and postulated biochemical pathways involved in iron metabolism within the
book’s 263 pages. Instead the author has furnished us with
an excellent bibliography which reflects his wide reading in
the field, and upon which he draws frequently within the
text, making this an invaluable source-book. There are one
or two places where this system falls down, such as in the
discussion of hemoprotein structures in Chapter 2, where it
is not made clear which references relate to the protein structures discussed, but in general the references are helpful and
up-to-date, which will be appreciated by the intended readership of researchers and advanced students.
A much more serious problem occurs in the first chapter,
where the relevant inorganic chemistry of iron is considered.
Unfortunately the very first page contains much which is
simply wrong. It is well-known that iron(III), for example,
can have coordination numbers greater than the maximum
of six suggested. It is also inadvisable to describe a five-coordinate stereochemistry as octahedral! For any worker not
familiar with Iigand field therory, the account of “weak- and
strong-field ligands”, and the unwise attempt to describe
them simultaneously in terms of the “soft/hard principle”,
will probably leave him bewildered. Those who are used to
such approaches are probably best advised to treat this first
page as an unfortunate misinterpretation of the theory and
ignore it completely.
The chapters that deal more with the microbiology and
biochemistry involved in metabolic processes may seem hard
to digest for chemists, at least on a first reading. However,
for those interested in understanding iron metabolism such
topics are an essential part. Professor Crichton is obviously
quite at home with many of these areas, and his straightforward style helps in leading us through some of the more
involved chapters, such as those on “Microbial iron and
intracellular release” (Ch. 3) and ‘‘Iron assimilation in plants
and fungi“ (Ch. 4).
The chapter on “Intracellular iron storage” (Ch. 8) is perhaps somewhat shorter than would be expected in view of the
author’s involvement in this field, but it is here more than
anywhere else that Professor Crichton’s often anecdotal style
comes to the fore. I doubt that any British scientist could
suppress a smile when reading the implied comparison between the contemporaneous Oxford chemists who have been
dubbed “Iron Lady” in recognition of their rather different
achievements.
The book ends with a consideration of the clinical aspects
of iron imbalance. The problems of anemia and iron overload are described with their medical consequences. Then the
roles iron plays in mechanisms of oxidative damage, which
may lead to a variety of medical conditions, such as inflammatory arthritis, induced by the presence of unwanted free
radicals, are discussed. Finally, the possible relationship between iron imbalance and infection is considered.
In summary, this book provides a useful addition to the
existing literature. It is a readable account of a large and
complicated subject and will provide researchers with many
useful literature sources. The author’s statement in his preface that his long association with iron has not bred contempt “but rather an increasing wonder at what iron, associated with low molecular weight and protein ligands, and
often with metal and other nonmetal cofactors, can do in
biological systems”, is evident from the text. Although the
book may raise more questions than it can answer, we are
left with a clear idea about where our problems in understanding iron metabolism lie, and also how these problems
have been approached to date.
A . K. Powell
School of Chemical Sciences
University of East Anglia, Norwich (UK)
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