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Self-Assembled Soft Matter Nanostructures at Interfaces

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A special issue of International Journal of Molecular Sciences (ISSN 1422-0067). This special issue belongs to the section "Materials Science".

Deadline for manuscript submissions: closed (25 February 2013) | Viewed by 176072

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Special Issue Editor

Prof. Dr. Martin Schoen

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Guest Editor

Stranski Lab for Physical and Theoretical Chemistry, Berlin Institute of Technology, 17. Juni 135, 10623 Berlin, Germany
Interests: statistical physics; computer simulation; classical density functional theory; soft matter; phase behavior and transport; self-assembly; fluids at interfaces
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Self-assembly of small chemical units into larger structures is one of the most promising routes for the fabrication of nanostructured functional systems. Depending on size, shape, and functionality of the molecular building blocks and the prevailing external conditions, a broad variety of supramolecular structures can result. Potential applications of this “bottom-up” strategy range from molecular electronics and photonics, nano-optics and nano-lithography, to drug delivery systems and medical devices. To design such nanostructured systems with well-defined and reproducible functionalities, the principles underlying the self-assembly process need to be better understood. Specifically, it is crucial to understand and eventually control the mechanisms driving self-assembly at given external conditions. However, to date most of the research in the field of self-assembly has been done on bulk systems. On the contrary, this special issue of the International Journal of Molecular Science will be devoted exclusively to self-assembly at interfaces. If an interface is present different length scales will be important in the self-assembly process. A typical example is self-assembly at chemically patterned solid substrates. Here size and shape of these patterns can have a significant impact on the structures of self-assembled, supramolecular entities and their stability. Therefore, the present special issue of the International Journal of Molecular Science aims at combining papers reporting forefront theoretical and experimental research on self-assembled nanostructures at interfaces.

Prof. Dr. Martin Schoen
Guest Editor

Manuscript Submission Information

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Keywords

self-assembly
interface
soft matter
nanostructures
nanoparticles
pattern formation
membranes
vesicles

Published Papers (12 papers)

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Research

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2329 KiB

Open AccessArticle

Bending of Layer-by-Layer Films Driven by an External Magnetic Field

by Celina M. Miyazaki, Antonio Riul, Jr., David S. Dos Santos, Jr., Mariselma Ferreira, Carlos J. L. Constantino, Marcelo A. Pereira-da-Silva, Ricardo Paupitz, Douglas S. Galvão and Osvaldo N. Oliveira Jr.

Int. J. Mol. Sci. 2013, 14(7), 12953-12969; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms140712953 - 24 Jun 2013

Cited by 9 | Viewed by 9124

Abstract

We report on optimized architectures containing layer-by-layer (LbL) films of natural rubber latex (NRL), carboxymethyl-chitosan (CMC) and magnetite (Fe₃O₄) nanoparticles (MNPs) deposited on flexible substrates, which could be easily bent by an external magnetic field. The mechanical response depended on the number of deposited layers and was explained semi-quantitatively with a fully atomistic model, where the LbL film was represented as superposing layers of hexagonal graphene-like atomic arrangements deposited on a stiffer substrate. The bending with no direct current or voltage being applied to a supramolecular structure containing biocompatible and antimicrobial materials represents a proof-of-principle experiment that is promising for tissue engineering applications in biomedicine. Full article

(This article belongs to the Special Issue Self-Assembled Soft Matter Nanostructures at Interfaces)

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22880 KiB

Open AccessArticle

Ordering of Polystyrene Nanoparticles on Substrates Pre-Coated with Different Polyelectrolyte Architectures

by Zuleyha Yenice, Matthias Karg and Regine Von Klitzing

Int. J. Mol. Sci. 2013, 14(6), 12893-12913; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms140612893 - 20 Jun 2013

Cited by 3 | Viewed by 10922

Abstract

Adjusting the inter-particle distances in ordered nanoparticle arrays can create new nano-devices and is of increasing importance to a number of applications such as nanoelectronics and optical devices. The assembly of negatively charged polystyrene (PS) nanoparticles (NPs) on Poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) brushes, quaternized PDMAEMA brushes and Si/PEI/(PSS/PAH)2, was studied using dip- and spin-coating techniques. By dip-coating, two dimensional (2-D), randomly distributed non-close packed particle arrays were assembled on Si/PEI/(PSS/PAH)2 and PDMAEMA brushes. The inter-particle repulsion leads to lateral mobility of the particles on these surfaces. The 200 nm diameter PS NPs tended to an inter-particle distance of 350 to 400 nm (center to center). On quaternized PDMAEMA brushes, the strong attractive interaction between the NPs and the brush dominated, leading to clustering of the particles on the brush surface. Particle deposition using spin-coating at low spin rates resulted in hexagonal close-packed multilayer structures on Si/PEI/(PSS/PAH)2. Close-packed assemblies with more pronounced defects are also observed on PDMAEMA brushes and QPDMAEMA brushes. In contrast, randomly distributed monolayer NP arrays were achieved at higher spin rates on all polyelectrolyte architectures. The area fraction of the particles decreased with increasing spin rate. Full article

(This article belongs to the Special Issue Self-Assembled Soft Matter Nanostructures at Interfaces)

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Graphical abstract

1210 KiB

Open AccessArticle

Structure Formation of Ultrathin PEO Films at Solid Interfaces—Complex Pattern Formation by Dewetting and Crystallization

by Hans-Georg Braun and Evelyn Meyer

Int. J. Mol. Sci. 2013, 14(2), 3254-3264; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms14023254 - 05 Feb 2013

Cited by 11 | Viewed by 9201

Abstract

The direct contact of ultrathin polymer films with a solid substrate may result in thin film rupture caused by dewetting. With crystallisable polymers such as polyethyleneoxide (PEO), molecular self-assembly into partial ordered lamella structures is studied as an additional source of pattern formation. Morphological features in ultrathin PEO films (thickness < 10 nm) result from an interplay between dewetting patterns and diffusion limited growth pattern of ordered lamella growing within the dewetting areas. Besides structure formation of hydrophilic PEO molecules, n-alkylterminated (hydrophobic) PEO oligomers are investigated with respect to self-organization in ultrathin films. Morphological features characteristic for pure PEO are not changed by the presence of the n-alkylgroups. Full article

(This article belongs to the Special Issue Self-Assembled Soft Matter Nanostructures at Interfaces)

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389 KiB

Open AccessArticle

Monovalent Ions and Water Dipoles in Contact with Dipolar Zwitterionic Lipid Headgroups-Theory and MD Simulations

by Aljaž Velikonja, Šarka Perutkova, Ekaterina Gongadze, Peter Kramar, Andraž Polak, Alenka Maček-Lebar and Aleš Iglič

Int. J. Mol. Sci. 2013, 14(2), 2846-2861; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms14022846 - 29 Jan 2013

Cited by 27 | Viewed by 7637

Abstract

The lipid bilayer is a basic building block of biological membranes and can be pictured as a barrier separating two compartments filled with electrolyte solution. Artificial planar lipid bilayers are therefore commonly used as model systems to study the physical and electrical properties of the cell membranes in contact with electrolyte solution. Among them the glycerol-based polar phospholipids which have dipolar, but electrically neutral head groups, are most frequently used in formation of artificial lipid bilayers. In this work the electrical properties of the lipid layer composed of zwitterionic lipids with non-zero dipole moments are studied theoretically. In the model, the zwitterionic lipid bilayer is assumed to be in contact with aqueous solution of monovalent salt ions. The orientational ordering of water, resulting in spatial variation of permittivity, is explicitly taken into account. It is shown that due to saturation effect in orientational ordering of water dipoles the relative permittivity in the zwitterionic headgroup region is decreased, while the corresponding electric potential becomes strongly negative. Some of the predictions of the presented mean-field theoretical consideration are critically evaluated using the results of molecular dynamics (MD) simulation. Full article

(This article belongs to the Special Issue Self-Assembled Soft Matter Nanostructures at Interfaces)

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931 KiB

Open AccessArticle

Adhesion-Induced Phase Behavior of Two-Component Membranes and Vesicles

by Tahereh Rouhiparkouhi, Thomas R. Weikl, Dennis E. Discher and Reinhard Lipowsky

Int. J. Mol. Sci. 2013, 14(1), 2203-2229; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms14012203 - 22 Jan 2013

Cited by 8 | Viewed by 5937

Abstract

The interplay of adhesion and phase separation is studied theoretically for two-component membranes that can phase separate into two fluid phases such as liquid-ordered and liquid-disordered phases. Many adhesion geometries provide two different environments for these membranes and then partition the membranes into two segments that differ in their composition. Examples are provided by adhering vesicles, by hole- or pore-spanning membranes, and by membranes supported by chemically patterned surfaces. Generalizing a lattice model for binary mixtures to these adhesion geometries, we show that the phase behavior of the adhering membranes depends, apart from composition and temperature, on two additional parameters, the area fraction of one membrane segment and the affinity contrast between the two segments. For the generic case of non-vanishing affinity contrast, the adhering membranes undergo two distinct phase transitions and the phase diagrams in the composition/temperature plane have a generic topology that consists of two two-phase coexistence regions separated by an intermediate one-phase region. As a consequence, phase separation and domain formation is predicted to occur separately in each of the two membrane segments but not in both segments simultaneously. Furthermore, adhesion is also predicted to suppress the phase separation process for certain regions of the phase diagrams. These generic features of the adhesion-induced phase behavior are accessible to experiment. Full article

(This article belongs to the Special Issue Self-Assembled Soft Matter Nanostructures at Interfaces)

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2203 KiB

Open AccessArticle

Micelle and Bilayer Formation of Amphiphilic Janus Particles in a Slit-Pore

by Gerald Rosenthal and Sabine H. L. Klapp

Int. J. Mol. Sci. 2012, 13(8), 9431-9446; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms13089431 - 26 Jul 2012

Cited by 17 | Viewed by 6650

Abstract

We employ molecular dynamics simulations to investigate the self-assembly of amphiphilic Janus particles in a slit-pore consisting of two plane-parallel, soft walls. The Janus particles are modeled as soft spheres with an embedded unit vector pointing from the hydrophobic to the hydrophilic hemisphere. The structure formation is analyzed via cluster size distributions, density and polarization profiles, and in-plane correlation functions. At low temperatures and densities, the dominating structures are spherical micelles, whereas at higher densities we also observe wall-induced bilayer formation. Finally, we compare the MD results with those from a previous density functional study. Full article

(This article belongs to the Special Issue Self-Assembled Soft Matter Nanostructures at Interfaces)

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734 KiB

Open AccessArticle

Diffusivity Maximum in a Reentrant Nematic Phase

by Tillmann Stieger, Marco G. Mazza and Martin Schoen

Int. J. Mol. Sci. 2012, 13(6), 7854-7871; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms13067854 - 21 Jun 2012

Cited by 4 | Viewed by 6568

Abstract

We report molecular dynamics simulations of confined liquid crystals using the Gay–Berne–Kihara model. Upon isobaric cooling, the standard sequence of isotropic–nematic–smectic A phase transitions is found. Upon further cooling a reentrant nematic phase occurs. We investigate the temperature dependence of the self-diffusion coefficient of the fluid in the nematic, smectic and reentrant nematic phases. We find a maximum in diffusivity upon isobaric cooling. Diffusion increases dramatically in the reentrant phase due to the high orientational molecular order. As the temperature is lowered, the diffusion coefficient follows an Arrhenius behavior. The activation energy of the reentrant phase is found in reasonable agreement with the reported experimental data. We discuss how repulsive interactions may be the underlying mechanism that could explain the occurrence of reentrant nematic behavior for polar and non-polar molecules. Full article

(This article belongs to the Special Issue Self-Assembled Soft Matter Nanostructures at Interfaces)

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580 KiB

Open AccessArticle

Vibrational Stark Effect of the Electric-Field Reporter 4-Mercaptobenzonitrile as a Tool for Investigating Electrostatics at Electrode/SAM/Solution Interfaces

by Gal Schkolnik, Johannes Salewski, Diego Millo, Ingo Zebger, Stefan Franzen and Peter Hildebrandt

Int. J. Mol. Sci. 2012, 13(6), 7466-7482; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms13067466 - 18 Jun 2012

Cited by 57 | Viewed by 10110

Abstract

4-mercaptobenzonitrile (MBN) in self-assembled monolayers (SAMs) on Au and Ag electrodes was studied by surface enhanced infrared absorption and Raman spectroscopy, to correlate the nitrile stretching frequency with the local electric field exploiting the vibrational Stark effect (VSE). Using MBN SAMs in different metal/SAM interfaces, we sorted out the main factors controlling the nitrile stretching frequency, which comprise, in addition to external electric fields, the metal-MBN bond, the surface potential, and hydrogen bond interactions. On the basis of the linear relationships between the nitrile stretching and the electrode potential, an electrostatic description of the interfacial potential distribution is presented that allows for determining the electric field strengths on the SAM surface, as well as the effective potential of zero-charge of the SAM-coated metal. Comparing this latter quantity with calculated values derived from literature data, we note a very good agreement for Au/MBN but distinct deviations for Ag/MBN which may reflect either the approximations and simplifications of the model or the uncertainty in reported structural parameters for Ag/MBN. The present electrostatic model consistently explains the electric field strengths for MBN SAMs on Ag and Au as well as for thiophenol and mercaptohexanoic acid SAMs with MBN incorporated as a VSE reporter. Full article

(This article belongs to the Special Issue Self-Assembled Soft Matter Nanostructures at Interfaces)

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Graphical abstract

563 KiB

Open AccessArticle

Polymorphism in Self-Assembled Structures of 9-Anthracene Carboxylic Acid on Ag(111)

by Chao Lu, Yinying Wei, Erkuang Zhu, Janice E. Reutt-Robey and Bo Xu

Int. J. Mol. Sci. 2012, 13(6), 6836-6848; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms13066836 - 05 Jun 2012

Cited by 8 | Viewed by 7356

Abstract

Surface self-assembly process of 9-anthracene carboxylic acid (AnCA) on Ag(111) was investigated using STM. Depending on the molecular surface density, four spontaneously formed and one annealed AnCA ordered phases were observed, namely a straight belt phase, a zigzag double-belt phase, two simpler dimer phases, and a kagome phase. The two high-density belt phases possess large unit cells on the scale length of 10 nm, which are seldom observed in molecular self-assembled structures. This structural diversity stems from a complicated competition of different interactions of AnCA molecules on metal surface, including intermolecular and molecular-substrate interactions, as well as the steric demand from high molecular surface density. Full article

(This article belongs to the Special Issue Self-Assembled Soft Matter Nanostructures at Interfaces)

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Review

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2268 KiB

Open AccessReview

Adsorption and Self-Assembly of Large Polycyclic Molecules on the Surfaces of TiO₂ Single Crystals

by Szymon Godlewski and Marek Szymonski

Int. J. Mol. Sci. 2013, 14(2), 2946-2966; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms14022946 - 30 Jan 2013

Cited by 45 | Viewed by 9265

Abstract

Titanium dioxide is one of the most frequently studied metal oxides, and its (110) rutile surface serves as a prototypical model for the surface science of such materials. Recent studies have also shown that the (011) surface is relatively easy for preparation in ultra-high vacuum (UHV) and that both the (110) and (011) surfaces could be precisely characterized using scanning tunneling microscopy (STM). The supramolecular self-assembly of organic molecules on the surfaces of titanium dioxide plays an important role in nanofabrication, and it can control the formation and properties of nanostructures, leading to wide range of applications covering the fields of catalysis, coatings and fabrication of sensors and extends to the optoelectronic industry and medical usage. Although the majority of experiments and theoretical calculations are focused on the adsorption of relatively small organic species, in recent years, there has been increasing interest in the properties of larger molecules that have several aromatic rings in which functional units could also be observed. The purpose of this review is to summarize the achievements in the study of single polycyclic molecules and thin layers adsorbed onto the surfaces of single crystalline titanium dioxide over the past decade. Full article

(This article belongs to the Special Issue Self-Assembled Soft Matter Nanostructures at Interfaces)

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1592 KiB

Open AccessReview

Experimental Aspects of Colloidal Interactions in Mixed Systems of Liposome and Inorganic Nanoparticle and Their Applications

by Raphael Michel and Michael Gradzielski

Int. J. Mol. Sci. 2012, 13(9), 11610-11642; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms130911610 - 17 Sep 2012

Cited by 88 | Viewed by 11483

Abstract

In the past few years, growing attention has been devoted to the study of the interactions taking place in mixed systems of phospholipid membranes (for instance in the form of vesicles) and hard nanoparticles (NPs). In this context liposomes (vesicles) may serve as versatile carriers or as a model system for biological membranes. Research on these systems has led to the observation of novel hybrid structures whose morphology strongly depends on the charge, composition and size of the interacting colloidal species as well as on the nature (pH, ionic strength) of their dispersing medium. A central role is played by the phase behaviour of phospholipid bilayers which have a tremendous influence on the liposome properties. Another central aspect is the incorporation of nanoparticles into vesicles, which is intimately linked to the conditions required for transporting a nanoparticle through a membrane. Herein, we review recent progress made on the investigations of the interactions in liposome/nanoparticle systems focusing on the particularly interesting structures that are formed in these hybrid systems as well as their potential applications. Full article

(This article belongs to the Special Issue Self-Assembled Soft Matter Nanostructures at Interfaces)

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757 KiB

Open AccessReview

Structural DNA Nanotechnology: From Design to Applications

by Reza M. Zadegan and Michael L. Norton

Int. J. Mol. Sci. 2012, 13(6), 7149-7162; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms13067149 - 11 Jun 2012

Cited by 63 | Viewed by 81014

Abstract

The exploitation of DNA for the production of nanoscale architectures presents a young yet paradigm breaking approach, which addresses many of the barriers to the self-assembly of small molecules into highly-ordered nanostructures via construct addressability. There are two major methods to construct DNA nanostructures, and in the current review we will discuss the principles and some examples of applications of both the tile-based and DNA origami methods. The tile-based approach is an older method that provides a good tool to construct small and simple structures, usually with multiply repeated domains. In contrast, the origami method, at this time, would appear to be more appropriate for the construction of bigger, more sophisticated and exactly defined structures. Full article

(This article belongs to the Special Issue Self-Assembled Soft Matter Nanostructures at Interfaces)

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