Eur. Phys. J. E (2017) 40: 7
https://doi.org/10.1140/epje/i2017-11493-8

Regular Article

Phase behaviour in complementary DNA-coated gold nanoparticles and fd-viruses mixtures: a numerical study

¹ Physics Department, University of Rome “La Sapienza”, Rome, Italy
² Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, CB3 0HE, Cambridge, UK

^* e-mail: massimilianochiappini@gmail.com
^** e-mail: ee247@cam.ac.uk
^*** e-mail: francesco.sciortino@uniroma1.it

Received: 13 September 2016
Accepted: 19 December 2016
Published online: 24 January 2017

Abstract

A new gel-forming colloidal system based on a binary mixture of fd-viruses and gold nanoparticles functionalized with complementary DNA single strands has been recently introduced. Upon quenching below the DNA melt temperature, such a system results in a highly porous gel state, that may be developed in a new functional material of tunable porosity. In order to shed light on the gelation mechanism, we introduce a model closely mimicking the experimental one and we explore via Monte Carlo simulations its equilibrium phase diagram. Specifically, we model the system as a binary mixture of hard rods and hard spheres mutually interacting via a short-range square-well attractive potential. In the experimental conditions, we find evidence of a phase separation occurring either via nucleation-and-growth or via spinodal decomposition. The spinodal decomposition leads to the formation of small clusters of bonded rods and spheres whose further diffusion and aggregation leads to the formation of a percolating network in the system. Our results are consistent with the hypothesis that the mixture of DNA-coated fd-viruses and gold nanoparticles undergoes a non-equilibrium gelation via an arrested spinodal decomposition mechanism.