Complexation of proteins with polyelectrolytes or block copolymers can lead to phase separation to generate a coacervate phase or self-assembly of coacervate core micelles. However, many proteins do not coacervate at conditions near neutral pH and physiological ionic strength. Here, protein supercharging is used to systematically explore the effect of protein charge on the complex coacervation with polycations. Four model proteins were anionically supercharged to varying degrees as quantified by mass spectrometry. Proteins phase separated with strong polycations when the ratio of negatively charged residues to positively charged residues on the protein (α) was greater than 1.1-1.2. Efficient partitioning of the protein into the coacervate phase required larger α (1.5-2.0). The preferred charge ratio for coacervation was shifted away from charge symmetry for three of the four model proteins and indicated an excess of positive charge in the coacervate phase. The composition of protein and polymer in the coacervate phase was determined using fluorescently labeled components, revealing that several of the coacervates likely have both induced charging and a macromolecular charge imbalance. The model proteins were also encapsulated in complex coacervate core micelles and micelles formed when the protein charge ratio α was greater than 1.3-1.4. Small angle neutron scattering and transmission electron microscopy showed that the micelles were spherical. The stability of the coacervate phase in both the bulk and micelles improved to increased ionic strength as the net charge on the protein increased. The micelles were also stable to dehydration and elevated temperatures.

Self-assembling peptides represent a growing class of inexpensive, environmentally benign, nanostructured materials. In particular, diphenylalanine (FF) self-assembles into nanotubes with remarkable strength and thermal stability that have found use in a wide variety of applications, including as sacrificial templates and scaffolds for structuring inorganic materials and as interfacial "nanoforests" for superhydrophobic surfaces and high-performance supercapacitors and biosensors. However, little is known about the assembly mechanisms of FF nanotubes or the forces underlying their stability. Here, we perform a variety of molecular dynamics simulations on both zwitterionic and capped (uncharged) versions of the FF peptide to understand the early stages of self-assembly. We compare these results to simulations of the proposed nanotube X-ray crystal structure. When comparing the zwitterionic and uncharged FF peptides, we find that, while electrostatic interactions steer the former into more ordered dimers and trimers, the hydrophobic side chain interactions play a strong role in determining the structures of larger oligomers. Simulations of the crystal structure fragment also suggest that the strongest interactions occur between side chains, not between the charged termini that form salt bridges. We conclude that the amphiphilic nature of FF is key to understanding its self-assembly, and that the early precursors to nanotube structures are likely to involve substantial hydrophobic clustering, rather than hexamer ring motifs as has been previously suggested.

The 18-electron ternary intermetallic systems TiNiSn and TiCoSb are promising for applications as high-temperature thermoelectrics and comprise earth-abundant, and relatively nontoxic elements. Heusler and half-Heusler compounds are usually prepared by conventional solid state methods involving arc-melting and annealing at high temperatures for an extended period of time. Here, we report an energy-saving preparation route using a domestic microwave oven, reducing the reaction time significantly from more than a week to one minute. A microwave susceptor material rapidly heats the elemental starting materials inside an evacuated quartz tube resulting in near single phase compounds. The initial preparation is followed by a densification step involving hot-pressing, which reduces the amount of secondary phases, as verified by synchrotron X-ray diffraction, leading to the desired half-Heusler compounds, demonstrating that hot-pressing should be treated as part of the preparative process. For TiNiSn, high thermoelectric power factors of 2 mW/mK2 at temperatures in the 700 to 800 K range, and zT values of around 0.4 are found, with the microwave-prepared sample displaying somewhat superior properties to conventionally prepared half-Heuslers due to lower thermal conductivity. The TiCoSb sample shows a lower thermoelectric figure of merit when prepared using microwave methods because of a metallic second phase.

Luminescence thermometry has substantially progressed in the last decade, rapidly approaching the performance of concurrent technologies. Performance is usually assessed through the relative thermal sensitivity, Sr, and temperature uncertainty, δT. Until now, the state‐of‐the‐art values at ambient conditions do not exceed maximum Sr of 12.5% K−1 and minimum δT of 0.1 K. Although these numbers are satisfactory for most applications, they are insufficient for fields that require lower thermal uncertainties, such as biomedicine. This has motivated the development of materials with an improved thermal response, many of them responding to the temperature through distinct photophysical properties. This paper demonstrates how the performance of multiparametric luminescent thermometers can be further improved by simply applying new analysis routes. The synergy between multiparametric readouts and multiple linear regression makes possible a tenfold improvement in Sr and δT, reaching a world record of 50% K−1 and 0.05 K, respectively. This is achieved without requiring the development of new materials or upgrading the detection system as illustrated by using the green fluorescent protein and Ag2S nanoparticles. These results open a new era in biomedicine thanks to the development of new diagnosis tools based on the detection of super‐small temperature fluctuations in living specimens.

Elastin-like polypeptides (ELPs) are one of the most widely-studied classes of protein material because of their lower critical solution temperature (LCST)-like thermoresponsive behavior in aqueous solutions. Here, it is shown that ELPs also exhibit cononsolvency effects, similar to many other water-soluble polymers. The effect of solvent composition on the dilute solution phase behavior of an elastin-like polypeptide is studied here in water/alcohol blends that contain 0−40 vol % methanol, ethanol, isopropanol, or 1-propanol. In all systems studied, the ELP exhibits cononsolvency behavior at low alcohol content, as indicated by a decrease in the transition temperature of the ELP. When the alcohol added is ethanol, isopropanol, or 1-propanol, the decrease in transition temperature is followed by a region of complete ELP insolubility, and, finally, the emergence of upper-critical solution transition (UCST)-like behavior. The ELP is completely soluble at all temperatures measured at alcohol contents above 40 vol %. The effect of sodium chloride on this ELP cononsolvency in water/ethanol blends was also studied. Unlike the previously studied polymer poly(N-isoropylacrylamide) (PNIPAM), ELP exhibits nonmonotonic changes in transition temperature with the addition of sodium chloride at ethanol contents that produce UCST-like transitions of the ELP. This discovery of ELP cononsolvency in water/alcohol systems introduces a new handle with which the solubility of ELPs can be tuned.