We studied the directed assembly of soft nanoparticles through rapid micromixing of polymers in solution with a nonsolvent. Both experiments and computer simulations were performed to elucidate the underlying physics and to investigate the role of various process parameters. In particular, we discovered that no external stabilizing agents or charged end groups are required to keep the colloids separated from each other when water is used as the nonsolvent. Furthermore, the size of the nanoparticles can be reliably tuned through the mixing rate and the ratio between polymer solution and nonsolvent. Our results demonstrate that this mechanism is highly promising for the mass fabrication of uniformly sized colloidal particles, using a wide variety of polymeric feed materials.

1 2Obtaining quantitative information about the timescales associated with sediment transport, 3 storage, and deposition in continental settings is important but challenging. The uranium-series 4 comminution age method potentially provides a universal approach for direct dating of 5 Quaternary detrital sediments, and can also provide estimates of the sediment transport and 6 storage timescales. (The word "comminution" means "to reduce to powder," reflecting the start 7 of the comminution age clock as reduction of lithic parent material below a critical grain size 8 threshold of ~50 m.) To test the comminution age method as a means to date continental 9 sediments, we applied the method to drill-core samples of the glacially-derived Kings River Fan 10 alluvial deposits in central California. Sediments from the 45 m core have independently-11 estimated depositional ages of up to ~800 ka, based on paleomagnetism and correlations to 12 nearby dated sediments. We characterized sequentially-leached core samples (both bulk 13 sediment and grain size separates) for U, Nd, and Sr isotopes, grain size, surface texture, and 14 mineralogy. In accordance with the comminution age model, where 234 U is partially lost from 15 small (<50 µm) sediment grains due to alpha recoil, we found that ( 234 U/ 238 U) activity ratios 16 *Manuscript Click here to view linked References 2 generally decrease with age, depth, and specific surface area, with depletions of up to 9% relative 17 to radioactive equilibrium. The resulting calculated comminution ages are reasonable, although 18 they do not exactly match age estimates from previous studies and also depend on assumptions 19 about 234 U loss rates. The results indicate that the method may be a significant addition to the 20 sparse set of available tools for dating detrital continental sediments, following further 21 refinement. Improving the accuracy of the method requires more advanced models or 22 measurements for both the recoil loss factor f  and weathering effects. We discuss several 23 independent methods for obtaining f  on individual samples that may be useful for future studies. 24

Geometrically structured polymer nanocolloids, including Janus nanocolloids, have been widely investigated for their unique properties, which are derived from their anisotropy. Controlled surface decoration with inorganic nanoparticles could induce another level of functionality into structured nanocolloids that could enable applications in fields ranging from rewriteable electronics to biphasic catalysis. Here, we demonstrate flash nanoprecipitation (FNP) as a one-step, scalable process platform for manufacturing hybrid polymer-inorganic nanocolloids in which one phase is selectively decorated with a metal nanocatalyst by tuning the molecular interactions between the feed ingredients during the process. For instance, by modifying the polymer end-group functionality, we document the ability to tune the location of the metal nanocatalyst, including placement at the nanocolloid circumference. Moreover, the addition of molecular additives is shown to transform the Janus nanocolloid structure from spherical to dumbbell or snowman while maintaining the ability to control the nanocatalyst location. In considering the flexibility and continuous nature of the FNP process, it offers an industrial-scale platform for the manufacturing of nanomaterials that are anticipated to impact many technologies.

Colloids with internally structured geometries have shown great promise in applications ranging from biosensors to optics to drug delivery, where the internal particle structure is paramount to performance. The growing demand for such nanomaterials necessitates the development of a scalable processing platform for their production. Flash nanoprecipitation (FNP), a rapid and inherently scalable colloid precipitation technology, is used to prepare internally structured colloids from blends of block copolymers and homopolymers. As revealed by a combination of experiments and simulations, colloids prepared from different molecular weight diblock copolymers adopt either an ordered lamellar morphology consisting of concentric shells or a disordered lamellar morphology when chain dynamics are sufficiently slow to prevent defect annealing during solvent exchange. Blends of homopolymer and block copolymer in the feed stream generate more complex internally structured colloids, such as those with hierarchically structured Janus and patchy morphologies, due to additional phase separation and kinetic trapping effects. The ability of the FNP process to generate such a wide range of morphologies using a simple and scalable setup provides a pathway to manufacturing internally structured colloids on an industrial scale.