Emanuela Bianchi | Technische Universität Wien (original) (raw)
Papers by Emanuela Bianchi
Journal of Physics: Condensed Matter, 2015
Im Rahmen dieser Diplomarbeit wurden Kristalle aus sogenannten "patchy particles" unter... more Im Rahmen dieser Diplomarbeit wurden Kristalle aus sogenannten "patchy particles" untersucht. Diese Bezeichnung stellt einen Sammelbegriff für Teilchen mit einer heterogenen Oberflächenbeschaffenheit dar; hier wechselwirken bestimmte Regionen der Oberfläche anders als andere Regionen. Wir untersuchen zwei Arten von "patchy particles": einerseits Janus Teilchen, bei denen der Großteil der Oberfläche nicht wechselwirkend ist, während der Rest der Oberfläche, die "patches", aufeinander anziehend wirken. Andererseits sogenannte "inverse patchy colloids", die aus negativ geladenen Kolloiden und darauf adsorbierten positiv geladen Regionen bestehen. Durch diese stark anisotrope Wechselwirkung der Teilchen kann eine Vielzahl an interessanten Kristallen entstehen. Daher werden Partikel als mögliche Bausteine von neuartigen funktionalen Materialien gehandelt: durch die richtige Wahl der äußeren Bedingungen soll das Entstehen einer erwünschten Struktur ...
Nanoscale, Jan 2, 2017
Materials with well-defined architectures are heavily sought after in view of their diverse techn... more Materials with well-defined architectures are heavily sought after in view of their diverse technological applications. Among the desired target architectures, lamellar phases stand out for their exceptional mechanical and optical features. Here we show that charged colloids, decorated on their poles with two oppositely charged regions possess the unusual ability to spontaneously assemble in different morphologies of (semi-)ordered, layered particle arrangements which maintain their structural stability over a surprisingly large temperature range. This remarkable capacity is related to a characteristic bonding mechanism: stable intra-layer bonds guarantee the formation of planar aggregates, while strong inter-layer bonds favor the stacking of the emerging planar assemblies. These two types of bonds together are responsible for the self-healing processes occurring during the spontaneous assembly. The resulting phases are characterized by parallel, densely packed, particle layers conn...
Journal of Physics: Condensed Matter, 2015
Inverse Patchy Colloids (IPCs) differ from conventional patchy particles because their patches re... more Inverse Patchy Colloids (IPCs) differ from conventional patchy particles because their patches repel (rather than attract) each other and attract (rather than repel) the part of the colloidal surface that is free of patches. These particular features occur, .e.g., in heterogeneously charged colloidal systems. Here we consider overall neutral IPCs carrying two, relatively small, polar patches. Previous studies of the same model under planar confinement have evidenced the formation of branched, disordered aggregates composed of ring-like structures. We investigate here the bulk behavior of the system via molecular dynamics simulations, focusing on both the structure and the dynamics of the fluid phase in a wide region of the phase diagram. Additionally, the simulation results for the static observables are compared to the Associative Percus Yevick solution of an integral equation approach based on the multi-density Ornstein-Zernike theory. A good agreement between theoretical and numerical quantities is observed even in the region of the phase diagram where the slowing down of the dynamics occurs.
Faraday Discussions, 2015
We consider a novel class of patchy particles inspired by polymer-based complex units where the l... more We consider a novel class of patchy particles inspired by polymer-based complex units where the limited valence in bonding is accompanied by soft interactions and incessant fluctuations of the patch positions, possibly leading to reversible modifications of the patch number and size. We introduce a simple model that takes into account the aforementioned features and we focus on the role played by the patch flexibility on the self-organization of our patchy units in the bulk, with particular attention to the connectivity properties and the morphology of the aggregated networks.
We study the behavior of negatively charged colloids with two positively charged polar caps close... more We study the behavior of negatively charged colloids with two positively charged polar caps close to a planar patterned surface. The competition between the different anisotropic components of the particle-particle interaction patterns is able by itself to give rise to a rich assembly scenario: colloids with charged surface patterns form different crystalline domains when adsorbed to a homogeneously charged substrate. Here we consider substrates composed of alternating (negative/neutral, positive/neutral and positive/negative) parallel stripes and, by means of Monte Carlo simulations, we investigate the ordering of the colloids on changing the number of the stripes. We show that the additional competition between the two different lengths scales characterizing the system (i.e., the particle interaction range and the size of the stripes) gives rise to a plethora of distinct particle arrangements, where some well-defined trends can be observed. By accurately tuning the substrate charg...
arXiv: Soft Condensed Matter, 2020
Anisotropy at the level of the inter-particle interaction provides the particles with specific in... more Anisotropy at the level of the inter-particle interaction provides the particles with specific instructions for the self-assembly of target structures. The ability to synthesize non-spherical colloids, together with the possibility of controlling the particle bonding pattern via suitably placed interaction sites, is nowadays enlarging the playfield for materials design. We consider a model of anisotropic colloidal platelets with regular rhombic shape and two attractive sites placed along adjacent edges and we run Monte Carlo simulations in two-dimensions to investigate the two-stage assembly of these units into clusters with well-defined symmetries and, subsequently, into extended lattices. Our focus is on how the site positioning and site-site attraction strength can be tuned to obtain micellar aggregates that are robust enough to successively undergo to a second-stage assembly from sparse clusters into a stable hexagonal lattice.
Nanoscale
Snapshot of an equilibrium configuration of a self-assembled DCS brush in the bulk.
Soft Matter
The patch arrangement determines the prevalence of micelles over chains as well as the geometrica... more The patch arrangement determines the prevalence of micelles over chains as well as the geometrical shape of the forming micelles.
Journal of Physics: Condensed Matter
Patchy colloidal platelets with non-spherical shapes have been realized with different materials ... more Patchy colloidal platelets with non-spherical shapes have been realized with different materials at length scales ranging from nanometers to microns. While the assembly of these hard shapes tends to maximize edge-to-edge contacts, as soon as a directional attraction is added—by means of, e.g. specific ligands along the particle edges—a competition between shape and bonding anisotropy sets in, giving rise to a complex assembly scenario. Here we focus on a two-dimensional system of patchy rhombi, i.e. colloidal platelets with a regular rhombic shape decorated with bonding sites along their perimeter. Specifically, we consider rhombi with two patches, placed on either opposite or adjacent edges. While for the first particle class only chains can form, for the latter we observe the emergence of either chains or loops, depending on the system parameters. According to the patch positioning—classified in terms of different configurations, topologies and distances from the edge center—we ar...
Soft Matter
We study the behavior of negatively charged colloids with two positively charged polar caps close... more We study the behavior of negatively charged colloids with two positively charged polar caps close to a planar patterned surface.
The European physical journal. E, Soft matter, Jan 28, 2018
Inverse patchy colloids are patchy particles with differently charged surface regions. In this pa... more Inverse patchy colloids are patchy particles with differently charged surface regions. In this paper we focus on inverse patchy colloids with two different polar patches and an oppositely charged equatorial belt, and we describe a model and a reliable and efficient numerical algorithm that can be applied to investigate the properties of these particles in molecular dynamics simulations.
Current Opinion in Colloid & Interface Science
Inverse patchy colloids are nano-to micro-scale particles with a surface divided into differently... more Inverse patchy colloids are nano-to micro-scale particles with a surface divided into differently charged regions. This class of colloids combines directional, selective bonding with a relatively simple particle design: owing to the competitive interplay between the orientation-dependent attraction and repulsion-induced by the interactions between like/oppositely charged areas-experimentally accessible surface patterns are complex enough to favor the stabilization of specific structures of interest. Most important, the behavior of heterogeneously charged units can be ideally controlled by means of external parameters, such as the pH and the salt concentration. We present a concise review about this class of systems, spanning the range from the synthesis of model inverse patchy particles to their self-assembly, covering their coarse-grained modeling and the related numerical/analytical treatments.
Current Opinion in Colloid & Interface Science
We present a concise review of the large variety of self-assembly scenarios observed in solutions... more We present a concise review of the large variety of self-assembly scenarios observed in solutions of diblock copolymer stars with a solvophilic inner block and a solvophobic outer block. A variety of modeling approaches and simulation techniques at different levels of detail reveals that individual molecules assume configurations akin to patchy colloids, but with a patchiness that depends on physical parameters and can adjust to external stimuli such as temperature and pH. These soft, patchy building blocks inter-associate at finite concentrations into micellar or gel-like solutions, including spherical and wormlike micelles, or they display macroscopic phase separation. The connections between single-molecule conformation and the structure of the concentrated solution are discussed, and coarse-grained strategies for these novel molecular entities are critically compared to one another.
Physical chemistry chemical physics : PCCP, Jan 2, 2017
Limited bonding valence, usually accompanied by well-defined directional interactions and selecti... more Limited bonding valence, usually accompanied by well-defined directional interactions and selective bonding mechanisms, is nowadays considered among the key ingredients to create complex structures with tailored properties: even though isotropically interacting units already guarantee access to a vast range of functional materials, anisotropic interactions can provide extra instructions to steer the assembly of specific architectures. The anisotropy of effective interactions gives rise to a wealth of self-assembled structures both in the realm of suitably synthesized nano- and micro-sized building blocks and in nature, where the isotropy of interactions is often a zero-th order description of the complicated reality. In this review, we span a vast range of systems characterized by limited bonding valence, from patchy colloids of new generation to polymer-based functionalized nanoparticles, DNA-based systems and proteins, and describe how the interaction patterns of the single buildi...
We generalize the inverse patchy colloid model that was originally developed for heterogeneously ... more We generalize the inverse patchy colloid model that was originally developed for heterogeneously charged particles with two identical polar patches and an oppositely charged equator to a model that can have a considerably richer surface pattern. Based on a Debye-Hueckel framework, we propose a coarse-grained description of the effective pair interactions that is applicable to particles with an arbitrary patch decoration. We demonstrate the versatility of this approach by applying it to models with (i) two differently charged and/or sized patches, and (ii) three, possibly different patches.
Soft matter, Jan 25, 2015
We investigate the self-assembly of colloidal Janus particles under shear flow by employing hybri... more We investigate the self-assembly of colloidal Janus particles under shear flow by employing hybrid molecular dynamics simulations that explicitly take into account hydrodynamic interactions. Under quiescent conditions, the amphiphilic colloids form spherical micellar aggregates of different sizes, where the solvophobic hemispheres are directed towards the core and the solvophilic caps are exposed to the solvent. When sufficiently strong shear is applied, the micelles disaggregate with a consequent decay of the average cluster size. Nonetheless, we find an intermediate shear rate regime where the balance between rearrangement and dissociation favors the growth of the aggregates. Additionally, our simulations show that clusters composed of either 6 or 13 particles are the most stable towards the shear flow due to their high geometric symmetry. Our findings open up a new range of applications for Janus particles, ranging from biotechnology to sensor systems.
Journal of Physics: Condensed Matter, 2015
Im Rahmen dieser Diplomarbeit wurden Kristalle aus sogenannten "patchy particles" unter... more Im Rahmen dieser Diplomarbeit wurden Kristalle aus sogenannten "patchy particles" untersucht. Diese Bezeichnung stellt einen Sammelbegriff für Teilchen mit einer heterogenen Oberflächenbeschaffenheit dar; hier wechselwirken bestimmte Regionen der Oberfläche anders als andere Regionen. Wir untersuchen zwei Arten von "patchy particles": einerseits Janus Teilchen, bei denen der Großteil der Oberfläche nicht wechselwirkend ist, während der Rest der Oberfläche, die "patches", aufeinander anziehend wirken. Andererseits sogenannte "inverse patchy colloids", die aus negativ geladenen Kolloiden und darauf adsorbierten positiv geladen Regionen bestehen. Durch diese stark anisotrope Wechselwirkung der Teilchen kann eine Vielzahl an interessanten Kristallen entstehen. Daher werden Partikel als mögliche Bausteine von neuartigen funktionalen Materialien gehandelt: durch die richtige Wahl der äußeren Bedingungen soll das Entstehen einer erwünschten Struktur ...
Nanoscale, Jan 2, 2017
Materials with well-defined architectures are heavily sought after in view of their diverse techn... more Materials with well-defined architectures are heavily sought after in view of their diverse technological applications. Among the desired target architectures, lamellar phases stand out for their exceptional mechanical and optical features. Here we show that charged colloids, decorated on their poles with two oppositely charged regions possess the unusual ability to spontaneously assemble in different morphologies of (semi-)ordered, layered particle arrangements which maintain their structural stability over a surprisingly large temperature range. This remarkable capacity is related to a characteristic bonding mechanism: stable intra-layer bonds guarantee the formation of planar aggregates, while strong inter-layer bonds favor the stacking of the emerging planar assemblies. These two types of bonds together are responsible for the self-healing processes occurring during the spontaneous assembly. The resulting phases are characterized by parallel, densely packed, particle layers conn...
Journal of Physics: Condensed Matter, 2015
Inverse Patchy Colloids (IPCs) differ from conventional patchy particles because their patches re... more Inverse Patchy Colloids (IPCs) differ from conventional patchy particles because their patches repel (rather than attract) each other and attract (rather than repel) the part of the colloidal surface that is free of patches. These particular features occur, .e.g., in heterogeneously charged colloidal systems. Here we consider overall neutral IPCs carrying two, relatively small, polar patches. Previous studies of the same model under planar confinement have evidenced the formation of branched, disordered aggregates composed of ring-like structures. We investigate here the bulk behavior of the system via molecular dynamics simulations, focusing on both the structure and the dynamics of the fluid phase in a wide region of the phase diagram. Additionally, the simulation results for the static observables are compared to the Associative Percus Yevick solution of an integral equation approach based on the multi-density Ornstein-Zernike theory. A good agreement between theoretical and numerical quantities is observed even in the region of the phase diagram where the slowing down of the dynamics occurs.
Faraday Discussions, 2015
We consider a novel class of patchy particles inspired by polymer-based complex units where the l... more We consider a novel class of patchy particles inspired by polymer-based complex units where the limited valence in bonding is accompanied by soft interactions and incessant fluctuations of the patch positions, possibly leading to reversible modifications of the patch number and size. We introduce a simple model that takes into account the aforementioned features and we focus on the role played by the patch flexibility on the self-organization of our patchy units in the bulk, with particular attention to the connectivity properties and the morphology of the aggregated networks.
We study the behavior of negatively charged colloids with two positively charged polar caps close... more We study the behavior of negatively charged colloids with two positively charged polar caps close to a planar patterned surface. The competition between the different anisotropic components of the particle-particle interaction patterns is able by itself to give rise to a rich assembly scenario: colloids with charged surface patterns form different crystalline domains when adsorbed to a homogeneously charged substrate. Here we consider substrates composed of alternating (negative/neutral, positive/neutral and positive/negative) parallel stripes and, by means of Monte Carlo simulations, we investigate the ordering of the colloids on changing the number of the stripes. We show that the additional competition between the two different lengths scales characterizing the system (i.e., the particle interaction range and the size of the stripes) gives rise to a plethora of distinct particle arrangements, where some well-defined trends can be observed. By accurately tuning the substrate charg...
arXiv: Soft Condensed Matter, 2020
Anisotropy at the level of the inter-particle interaction provides the particles with specific in... more Anisotropy at the level of the inter-particle interaction provides the particles with specific instructions for the self-assembly of target structures. The ability to synthesize non-spherical colloids, together with the possibility of controlling the particle bonding pattern via suitably placed interaction sites, is nowadays enlarging the playfield for materials design. We consider a model of anisotropic colloidal platelets with regular rhombic shape and two attractive sites placed along adjacent edges and we run Monte Carlo simulations in two-dimensions to investigate the two-stage assembly of these units into clusters with well-defined symmetries and, subsequently, into extended lattices. Our focus is on how the site positioning and site-site attraction strength can be tuned to obtain micellar aggregates that are robust enough to successively undergo to a second-stage assembly from sparse clusters into a stable hexagonal lattice.
Nanoscale
Snapshot of an equilibrium configuration of a self-assembled DCS brush in the bulk.
Soft Matter
The patch arrangement determines the prevalence of micelles over chains as well as the geometrica... more The patch arrangement determines the prevalence of micelles over chains as well as the geometrical shape of the forming micelles.
Journal of Physics: Condensed Matter
Patchy colloidal platelets with non-spherical shapes have been realized with different materials ... more Patchy colloidal platelets with non-spherical shapes have been realized with different materials at length scales ranging from nanometers to microns. While the assembly of these hard shapes tends to maximize edge-to-edge contacts, as soon as a directional attraction is added—by means of, e.g. specific ligands along the particle edges—a competition between shape and bonding anisotropy sets in, giving rise to a complex assembly scenario. Here we focus on a two-dimensional system of patchy rhombi, i.e. colloidal platelets with a regular rhombic shape decorated with bonding sites along their perimeter. Specifically, we consider rhombi with two patches, placed on either opposite or adjacent edges. While for the first particle class only chains can form, for the latter we observe the emergence of either chains or loops, depending on the system parameters. According to the patch positioning—classified in terms of different configurations, topologies and distances from the edge center—we ar...
Soft Matter
We study the behavior of negatively charged colloids with two positively charged polar caps close... more We study the behavior of negatively charged colloids with two positively charged polar caps close to a planar patterned surface.
The European physical journal. E, Soft matter, Jan 28, 2018
Inverse patchy colloids are patchy particles with differently charged surface regions. In this pa... more Inverse patchy colloids are patchy particles with differently charged surface regions. In this paper we focus on inverse patchy colloids with two different polar patches and an oppositely charged equatorial belt, and we describe a model and a reliable and efficient numerical algorithm that can be applied to investigate the properties of these particles in molecular dynamics simulations.
Current Opinion in Colloid & Interface Science
Inverse patchy colloids are nano-to micro-scale particles with a surface divided into differently... more Inverse patchy colloids are nano-to micro-scale particles with a surface divided into differently charged regions. This class of colloids combines directional, selective bonding with a relatively simple particle design: owing to the competitive interplay between the orientation-dependent attraction and repulsion-induced by the interactions between like/oppositely charged areas-experimentally accessible surface patterns are complex enough to favor the stabilization of specific structures of interest. Most important, the behavior of heterogeneously charged units can be ideally controlled by means of external parameters, such as the pH and the salt concentration. We present a concise review about this class of systems, spanning the range from the synthesis of model inverse patchy particles to their self-assembly, covering their coarse-grained modeling and the related numerical/analytical treatments.
Current Opinion in Colloid & Interface Science
We present a concise review of the large variety of self-assembly scenarios observed in solutions... more We present a concise review of the large variety of self-assembly scenarios observed in solutions of diblock copolymer stars with a solvophilic inner block and a solvophobic outer block. A variety of modeling approaches and simulation techniques at different levels of detail reveals that individual molecules assume configurations akin to patchy colloids, but with a patchiness that depends on physical parameters and can adjust to external stimuli such as temperature and pH. These soft, patchy building blocks inter-associate at finite concentrations into micellar or gel-like solutions, including spherical and wormlike micelles, or they display macroscopic phase separation. The connections between single-molecule conformation and the structure of the concentrated solution are discussed, and coarse-grained strategies for these novel molecular entities are critically compared to one another.
Physical chemistry chemical physics : PCCP, Jan 2, 2017
Limited bonding valence, usually accompanied by well-defined directional interactions and selecti... more Limited bonding valence, usually accompanied by well-defined directional interactions and selective bonding mechanisms, is nowadays considered among the key ingredients to create complex structures with tailored properties: even though isotropically interacting units already guarantee access to a vast range of functional materials, anisotropic interactions can provide extra instructions to steer the assembly of specific architectures. The anisotropy of effective interactions gives rise to a wealth of self-assembled structures both in the realm of suitably synthesized nano- and micro-sized building blocks and in nature, where the isotropy of interactions is often a zero-th order description of the complicated reality. In this review, we span a vast range of systems characterized by limited bonding valence, from patchy colloids of new generation to polymer-based functionalized nanoparticles, DNA-based systems and proteins, and describe how the interaction patterns of the single buildi...
We generalize the inverse patchy colloid model that was originally developed for heterogeneously ... more We generalize the inverse patchy colloid model that was originally developed for heterogeneously charged particles with two identical polar patches and an oppositely charged equator to a model that can have a considerably richer surface pattern. Based on a Debye-Hueckel framework, we propose a coarse-grained description of the effective pair interactions that is applicable to particles with an arbitrary patch decoration. We demonstrate the versatility of this approach by applying it to models with (i) two differently charged and/or sized patches, and (ii) three, possibly different patches.
Soft matter, Jan 25, 2015
We investigate the self-assembly of colloidal Janus particles under shear flow by employing hybri... more We investigate the self-assembly of colloidal Janus particles under shear flow by employing hybrid molecular dynamics simulations that explicitly take into account hydrodynamic interactions. Under quiescent conditions, the amphiphilic colloids form spherical micellar aggregates of different sizes, where the solvophobic hemispheres are directed towards the core and the solvophilic caps are exposed to the solvent. When sufficiently strong shear is applied, the micelles disaggregate with a consequent decay of the average cluster size. Nonetheless, we find an intermediate shear rate regime where the balance between rearrangement and dissociation favors the growth of the aggregates. Additionally, our simulations show that clusters composed of either 6 or 13 particles are the most stable towards the shear flow due to their high geometric symmetry. Our findings open up a new range of applications for Janus particles, ranging from biotechnology to sensor systems.