Self-assembly of inverse patchy colloids with tunable patch coverage

Abstract

We report a simple and scalable technique for the preparation of patchy particles with tunable patch coverage. These particles are categorized as inverse patchy colloidal particles (IPCs) as the patches repel each other while patch and non-patch surfaces attract. We demonstrate the effect of patch coverage, concentration of electrolyte and concentration of particles on the self-assembly of IPC particles. The study identifies various clustering zones such as (1) finite-sized clusters, (2) chain-like assemblies and (3) irregular amorphous aggregates. The linear assemblies are observed over a wide range of particle concentrations and salt concentrations. The anisotropic electrostatic interaction controls the formation of chain-like assemblies. In an extended study, we use negatively charged isotropic colloidal (NCIC) particles to tune the self-assembly of IPC particles. Interestingly, we observe significant improvement in the clustering efficiency of IPC particles leading to the formation of co-polymeric, flexible branched chains. Depending on the number ratio of NCIC particles with respect to IPC particles, the clustering process is classified into three different phases such as (1) finite-sized, (2) linear and (3) dispersed state. Using a quantitative analysis we show that such evolution of structures is attributed to seeding and crowding effects caused by the addition of NCIC particles. The use of NCIC particles thus control the self-assembly of inverse patchy colloids and tune the number and shape of the self-assembled structures.

Study of the aggregation behavior of Janus particles by coupling experiments and Brownian dynamics simulations

“…However, for the smaller S, < P 2 > is negative, the unmodified parts are rather orthogonally oriented. All these observations are in agreement with previous observations from the literature [36,49,50].…”

Limiting the valence: advancements and new perspectives on patchy colloids, soft functionalized nanoparticles and biomolecules

“…Colloids characterized by well-defined surface regions carrying different surface charges can be generally described as charged patchy particles; in order to emphasize that these units are a different class of patchy colloids with respect to conventional patchy particles, they are often referred to as inverse patchy colloids (IPCs): 90 the term inverse refers to the fact that, while conventional patchy systems are typically characterized by the presence of attractive regions on the surface of otherwise repulsive particles, IPCs carry extended patches that repel each other and attract those parts of the colloid that are free of patches. This class of systems was originally introduced to describe complex units emerging from the adsorption of charged polyelectrolyte stars onto the surface of oppositely charged colloids, 91 but it now includes micro-scale particles manufactured with a binary 92 or ternary 41 distribution of the surface charge. Clearly, also Janus particles with differently charged hemispheres 39,43,93 can be considered as (the simplest case of) IPC units.…”

Mono-patchy zwitterionic microcolloids as building blocks for pH-controlled self-assembly

“…Sabapathy and co-workers have used a pair potential for the interaction between two mono-patchy IPCs derived on the basis of potential equation proposed by Hoffmann, Bianchi and Likos. 14,25,34 Further simplification of this equation is possible taking into account the analysis made in the ref. 25.…”

“…14,25,34 Further simplification of this equation is possible taking into account the analysis made in the ref. 25. These authors calculated the electrostatic interaction energy of a pair of IPC particles at a fixed separation distance and at different orientations and showed that this energy is only weakly dependent on the kink angle between interacting IPCs in aggregates: the value of this function grows only by 50% in the physically reasonable range of kink angles from 50 to 120 degrees.…”

“…[19][20][21] As mentioned above, a localized well-defined patch-to-patch interaction, e.g., attractive or repulsive electrostatic interactions serve as driving force for the formation of superstructures. [22][23][24][25][26] Despite a variety of theoretical investigations on quantification of the interactions between charged patchy or non-patchy particles, so far there have not been many experimental studies in this regard. [27][28][29][30][31][32][33][34] For example, inverse patchy colloids (IPC) were considered as a new type of heterogeneously charged particles in theoretical and experimental investigations.…”