Hierarchies of networked phases induced by multiple liquid–liquid critical points

Abstract

Nanoparticles and colloids functionalized by four single strands of DNA can be thought of as designed analogs to tetrahedral network-forming atoms and molecules, with a difference that the attached DNA strands allow for control of the length scale of bonding relative to the core size. We explore the behavior of an experimentally realized model for nanoparticles functionalized by four single strands of DNA (a tetramer), and show that this single-component model exhibits a rich phase diagram with at least three critical points and four thermodynamically distinct amorphous phases. We demonstrate that the additional critical points are part of the Ising universality class, like the ordinary liquid-gas critical point. The dense phases consist of a hierarchy of interpenetrating networks, reminiscent of a woven cloth. Thus, bonding specificity of DNA provides an effective route to generate new nano-networked materials with polyamorphic behavior. The concept of network interpenetration helps to explain the generation of multiple liquid phases in single-component systems, suggested to occur in some atomic and molecular network-forming fluids, including water and silica. DNA functionalization ͉ nanoparticles ͉ self-assembly ͉ polyamorphism ͉ nanotechnology T echnological developments are creating a wide variety of building blocks that play the role of ''functionalized atoms'' for designed materials (1, 2). Borrowing ideas from biological specificity (3-6), it is now possible to control bonding between engineered building blocks in a selective way, moving in the direction of an effective synthetic bottom-up strategy for selfassembly. The complementary binding of base pairs, combined with the ability to directly control the base sequence, makes DNA an ideal candidate for the development of network-based, nanostructured materials (5-8). A variety of experiments (7)(8)(9)(10)(11)(12)(13)(14)(15) have demonstrated the possibility to realize nanostructured, DNAbased materials, including ordered crystal structures (9, 10).By grafting short single strands of DNA to core particles, the core can act as a ''node'' of a complex network formed when single strands combine into dsDNA. Longer linking ''arms'' may be achieved by using a double-stranded spacer near the core nanoparticle (9, 10). With an intelligent choice of the core, it is possible to control the number of attached strands and thus the nearest-neighbor coordination of the functionalized nanoparticle, providing a direct route to study materials where the bonding coordination is much less than that of spherically symmetric molecules (16). In such limited coordination systems, the general features of network formation are expected to be observed.By functionalizing the central core with four DNA strands, we expect to generate an engineered analog of tetrahedral networkforming atoms or molecules, in which the bonding contribution to the interparticle interaction energy can be tuned by modulating the length L of the DNA strand, as well as the chemical properties of the solvent....

Understanding water’s anomalies with locally favoured structures

“…In fact, the order parameter z includes the local configurations responsible for water's two-length scales average interaction 3 . It shows also strong analogies with the concept that network interpenetration can sustain one or multiple LLCPs 57 . On the other hand, we note that, within the two-state model, the presence of a critical point associated with demixing is not a necessary condition for the existence of thermodynamic anomalies, and the anomalies survive even if the mixture lacks a critical point, (J ¼ 0 in equation (1)) 23 .…”

Accurate phase diagram of tetravalent DNA nanostars

“…The phase behavior of a very primitive model for DNA tetramers, composed by four DNA strands attached to a central core, has been previously numerically investigated in a series of studies [17,19,33]. This simple model predicted the existence of a gas-liquid unstable region at low densities, followed at larger densities by a gel phase in which tetramers form an extended network of fully bonded particles.…”

Pressure-induced transformations in computer simulations of glassy water

“…[32][33][34][35][36] In addition, the possibility of a LLPT has been seen in computer simulations of many other pure fluids. [37][38][39][40][41][42][43][44] More importantly, technical questions regarding equilibration raised in Refs. 30 and 31, have no bearing on the qualitative transformations of the glassy states we examine, which are inherently nonequilibrium.…”