Stiffness of the interface between a colloidal body-centered cubic crystal and its liquid

Equilibrium interfaces were established between body-centered cubic (BCC) crystals and their liquid using charged colloidal particles in an electric bottle. By measuring a time series of interfacial positions and computing the average power spectrum, their interfacial stiffness was determined according to the capillary fluctuation method. For the (100) and the (114) interfaces, the stiffnesses were 0.15 and 0.18kBT/σ2(σ: particle diameter), respectively, and were isotropic in the plane of the interface. For comparison, similar charged colloids were used to create an interface between a face-centered cubic (FCC) crystal and its liquid. Its stiffness was significantly larger: 0.26kBT/σ2. This result gives experimental support to the explanations offered for the preferential nucleation of BCC over FCC in metallic alloys.

Effects of Various Inhibitors on the Nucleation of Calcium Oxalate in Synthetic Urine

A new synthetic urine was adopted in this work to study the nucleation kinetics of calcium oxalate using a batch crystallizer for various supersaturations at 37 °C. In the studied new synthetic urine, three additional components (urea, uric acid and creatinine) within the normal physiological ranges were added to the commonly-used synthetic urine to simulate human urine more closely. The interfacial energy for the nucleation of calcium oxalate was determined based on classical nucleation theory using the turbidity induction time measurements. The effects of various inhibitors, including magnesium, citrate, hydroxycitrate, chondroitin sulfate, and phytate, on the nucleation of calcium oxalate were investigated in detail. Scanning electron microscopy was used to examine the influences of these inhibitors on the preferential nucleation of the different hydrates of calcium oxalate crystals.

Golgi SM protein Sly1 promotes productive trans-SNARE complex assembly through multiple mechanisms

SUMMARYSNARE chaperones of the Sec1/mammalian Unc-18 (SM) family have critical roles in SNARE-mediated membrane fusion. Using SNARE and Sly1 mutants, and a new in vitro assay of fusion, we separate and assess proposed mechanisms through which Sly1 augments fusion: (i) opening the closed conformation of the Qa-SNARE Sed5; (ii) close-range tethering of vesicles to target organelles, mediated by the Sly1-specific regulatory loop; and (iii) preferential nucleation of productive trans-SNARE complexes. We show that all three mechanisms are important and operate in parallel, and we present evidence that close-range tethering is particularly important for trans-complex assembly when cis-SNARE assembly is a competing process. In addition, the autoinhibitory N-terminal Habc domain of Sed5 has at least two positive activities: the Habc domain is needed for correct Sed5 localization, and it directly promotes Sly1-dependent fusion. Remarkably, “split Sed5,” with the Habc domain present only as a soluble fragment, is functional both in vitro and in vivo.

Self-organized twist-heterostructures via aligned van der Waals epitaxy and solid-state transformations

Vertical van der Waals (vdW) heterostructures of 2D crystals with defined interlayer twist are of interest for band-structure engineering via twist moiré superlattice potentials. To date, twist-heterostructures have been realized by micromechanical stacking. Direct synthesis is hindered by the tendency toward equilibrium stacking without interlayer twist. Here, we demonstrate that growing a 2D crystal with fixed azimuthal alignment to the substrate followed by transformation of this intermediate enables a potentially scalable synthesis of twisted heterostructures. Microscopy during growth of ultrathin orthorhombic SnS on trigonal SnS2 shows that vdW epitaxy yields azimuthal order even for non-isotypic 2D crystals. Excess sulfur drives a spontaneous transformation of the few-layer SnS to SnS2, whose orientation – rotated 30° against the underlying SnS2 crystal – is defined by the SnS intermediate rather than the substrate. Preferential nucleation of additional SnS on such twisted domains repeats the process, promising the realization of complex twisted stacks by bottom-up synthesis.

Epitaxial stabilization versus interdiffusion: synthetic routes to metastable cubic HfO2 and HfV2O7 from the core–shell arrangement of precursors

Metastable cubic HfO2 is prepared by preferential nucleation using a lattice crystallographic relationship.

Tin nanoparticles embedded in a carbon buffer layer as preferential nucleation sites for stable sodium metal anodes

High-capacity sodium anodes with long-term reversibility and stability are presented by synthesizing tin nanoparticles homogeneously embedded within a conductive carbon network.

Active sites in heterogeneous ice nucleation—the example of K-rich feldspars

Ice formation on aerosol particles is a process of crucial importance to Earth’s climate and the environmental sciences, but it is not understood at the molecular level. This is partly because the nature of active sites, local surface features where ice growth commences, is still unclear. Here we report direct electron-microscopic observations of deposition growth of aligned ice crystals on feldspar, an atmospherically important component of mineral dust. Our molecular-scale computer simulations indicate that this alignment arises from the preferential nucleation of prismatic crystal planes of ice on high-energy (100) surface planes of feldspar. The microscopic patches of (100) surface, exposed at surface defects such as steps, cracks, and cavities, are thought to be responsible for the high ice nucleation efficacy of potassium (K)–feldspar particles.