Temperature dependence of phase diagrams and dynamics in nanocrystal assembly by solvent evaporation.

We provide a systematic study of the phase diagram and dynamics for single component nanocrystals (NCs) by a combination of a self-consistent mean-field molecular theory (MOLT-CF) and molecular dynamics (MD) simulations. We first compute several thermodynamic functions (free energy, entropy, coefficient of thermal expansion and bulk modulus) as a function of temperature by both MOLT-CF and MD. While MOLT-CF correctly captures the trends with temperature, the predicted coefficients of thermal expansion and bulk moduli display quantitative deviations from MD and experiments, which we trace back to the mean-field treatment of attractions in MOLT-CF.

Solvent Isotherms and Structural Transitions in Nanoparticle Superlattice Assembly.

We introduce a Molecular Theory for Compressible Fluids (MOLT-CF) that enables us to compute free energies and other thermodynamic functions for nanoparticle superlattices with any solvent content, including the dry limit. Quantitative agreement is observed between MOLT-CF and united-atom molecular dynamics simulations performed to assess the reliability and precision of the theory. Among other predictions, MOLT-CF shows that the amount of solvent within the superlattice decreases approximately linearly with its vapor pressure and that in the late stages of drying, solvent-filled voids form at lattice interstitials.

Theoretical treatment of complex coacervate core micelles: structure and pH-induced disassembly.

Complex coacervate core micelles (C3Ms) are supramolecular soft nanostructures formed by the assembly of a block copolymer and an oppositely charged homopolymer. The coacervation of the charged segments in both macromolecules drives the formation of the core of the C3M, while the neutral block of the copolymer forms the corona. This work introduces a molecular theory (MOLT) that predicts the internal structure and stimuli-responsive properties of C3Ms and explicitly considers the chemical architecture of the polyelectrolytes, their acid-based equilibria and electrostatic and non-electrostatic interactions.

Molecular Theory: A Tool for Predicting the Outcome of Self-Assembly of Polymers, Nanoparticles, Amphiphiles, and Other Soft Materials.

The supramolecular organization of soft materials, such as colloids, polymers, and amphiphiles, results from a subtle balance of weak intermolecular interactions and entropic forces. This competition can drive the self-organization of soft materials at the nano-/mesoscale. Modeling soft-matter self-assembly requires, therefore, considering a complex interplay of forces at the relevant length scales without sacrificing the molecular details that define the chemical identity of the system.

Body centered tetragonal nanoparticle superlattices: why and when they form?

Body centered tetragonal (BCT) phases are structural intermediates between body centered cubic (BCC) and face centered cubic (FCC) structures. However, BCC ↔ FCC transitions may or may not involve a stable BCT intermediate. Interestingly, nanoparticle superlattices usually crystallize in BCT structures, but this phase is much less frequent for colloidal crystals of micrometer-sized particles.

Simulation and optimization of a lamella settler for cattle feedlot wastewater treatment and nutrients recovery. Experimental validation in the field.

Cattle concentrated animal feeding operations (feedlots), whose number has grown considerably in the last years, generate large volumes of wastewaters with a high organic load. The wastewaters are formed by rainfall-runoff of the accumulated manure and may contain hormones and antibiotics, which hampers the use of biological treatments. In this work, the feasibility of continuous separation of the suspended colloidal organic matter and nutrients to clarify the liquid and recover the solid is studied.

Liquid-polymer triboelectricity: chemical mechanisms in the contact electrification process.

Liquid-polymer contact electrification between sliding water drops and the surface of polytetrafluoroethylene (PTFE) was studied as a function of the pH and ionic strength of the drop as well as ambient relative humidity (RH). The PTFE surface was characterized by using SEM, water-contact-angle measurements, FTIR spectroscopy, XPS, and Raman spectroscopy. The charge acquired by the drops was calculated by detecting the transient voltage induced on a specifically designed capacitive sensor.

The Phase Behavior of Nanoparticle Superlattices in the Presence of a Solvent.

Superlattices of nanoparticles coated by alkyl-chain ligands are usually prepared from a stable solution by evaporation, therefore the pathway of superlattice self-assembly critically depends on the amount of solvent present within it. This work addresses the role of the solvent on the structure and the relative stability of the different supercrystalline phases of single-component superlattices (simple cubic, body-centered cubic (BCC), face-centered cubic (FCC), and hexagonal close-packed). The study is performed with a molecular theory for nanoparticle superlattices introduced in this work, which predicts the structure and thermodynamics of the supercrystals explicitly treating the presence and molecular details of the solvent and the ligands.