Spontaneous redox continuum reveals sequestered technetium clusters and retarded mineral transformation of iron.

The sequestration of metal ions into the crystal structure of minerals is common in nature. To date, the incorporation of technetium(IV) into iron minerals has been studied predominantly for systems under carefully controlled anaerobic conditions. Mechanisms of the transformation of iron phases leading to incorporation of technetium(IV) under aerobic conditions remain poorly understood.

Metal-Organic Framework-Based Microfluidic Impedance Sensor Platform for Ultrasensitive Detection of Perfluorooctanesulfonate.

The growing global concerns to public health from human exposure to perfluorooctanesulfonate (PFOS) require rapid, sensitive, detection where current, state-of-the-art techniques are yet to adequately meet sensitivity standards of the real world. This work presents, for the first time, a synergistic approach for the targeted affinity-based capture of PFOS using a porous sorbent probe that enhances detection sensitivity by embedding it on a microfluidic platform. This novel sorbent-containing platform functions as an electrochemical sensor to directly measure PFOS concentration through a proportional change in electrical current (increase in impedance).

Probing the Sorption of Perfluorooctanesulfonate Using Mesoporous Metal-Organic Frameworks from Aqueous Solutions.

One approach to reduce increasing concentrations of toxic per- and polyfluoroalkyl substances (PFAS) involves the capture of PFAS from aqueous media using porous materials. The use of highly porous, tunable metal organic framework (MOF) materials is appealing for targeted liquid phase sorption. In this work, we demonstrate the excellent capture of perfluorooctanesulfonate (PFOS) using both the chromium and iron analogs of the MIL-101 framework.

Carbon Nanotube Porins in Amphiphilic Block Copolymers as Fully Synthetic Mimics of Biological Membranes.

Biological membranes provide a fascinating example of a separation system that is multifunctional, tunable, precise, and efficient. Biomimetic membranes, which mimic the architecture of cellular membranes, have the potential to deliver significant improvements in specificity and permeability. Here, a fully synthetic biomimetic membrane is reported that incorporates ultra-efficient 1.

Impact of Solution Chemistry and Particle Anisotropy on the Collective Dynamics of Oriented Aggregation.

Although oriented aggregation of particles is a widely recognized mechanism of crystal growth, the impact of many fundamental parameters, such as crystallographically distinct interfacial structures, solution composition, and nanoparticle morphology, on the governing mechanisms and assembly kinetics are largely unexplored. Thus, the collective dynamics of systems exhibiting OA has not been predicted. In this context, we investigated the structure and dynamics of boehmite aggregation as a function of solution pH and ionic strength.

Near surface nucleation and particle mediated growth of colloidal Au nanocrystals.

During non-classical growth of nanostructures via assembly of primary nuclei, nucleation and assembly are assumed to be distinct processes: nanoparticles nucleate randomly and aggregate to form extended structures through Brownian motion in the presence of long-range attractive interactions. Here we investigate the relationship between these two processes by using in situ AFM, in situ, ex situ and cryo TEM and UV-Vis spectroscopy to observe growth of colloidal gold and simulations to develop a mechanistic model of the process. Our results reveal an inexorable link between nucleation and assembly with nuclei forming almost exclusively within a ∼1 nm interfacial region of existing particles.

Importance of interlayer H bonding structure to the stability of layered minerals.

Layered (oxy) hydroxide minerals often possess out-of-plane hydrogen atoms that form hydrogen bonding networks which stabilize the layered structure. However, less is known about how the ordering of these bonds affects the structural stability and solubility of these minerals. Here, we report a new strategy that uses the focused electron beam to probe the effect of differences in hydrogen bonding networks on mineral solubility.

Trace Uranium Partitioning in a Multiphase Nano-FeOOH System.

The characterization of trace elements in minerals using extended X-ray absorption fine structure (EXAFS) spectroscopy constitutes a first step toward understanding how impurities and contaminants interact with the host phase and the environment. However, limitations to EXAFS interpretation complicate the analysis of trace concentrations of impurities that are distributed across multiple phases in a heterogeneous system. Ab initio molecular dynamics (AIMD)-informed EXAFS analysis was employed to investigate the immobilization of trace uranium associated with nanophase iron (oxyhydr)oxides, a model system for the geochemical sequestration of radiotoxic actinides.

Cation-Dependent Hierarchical Assembly of U60 Nanoclusters into Macro-Ion Assemblies Imaged via Cryogenic Transmission Electron Microscopy.

Self-assembly of ([UO2(O2)OH]60)(60-) (U60), an actinide polyoxometalate with fullerene topology, can be induced by the addition of mono- and divalent cations to aqueous U60 solutions. Dynamic light scattering and small-angle X-ray scattering lend important insights into assembly in this system, but direct imaging of U60 and its assemblies via transmission electron microscopy (TEM) has remained an elusive goal. In this work, we used cryogenic TEM to image U60 and secondary and tertiary assemblies of U60 to characterize the size, morphology, and rate of formation of the secondary and tertiary structures.

Oriented aggregation: formation and transformation of mesocrystal intermediates revealed.

Oriented aggregation is a special case of aggregation in which nanocrystals self-assemble and form new secondary single crystals. This process has been suggested to proceed via an intermediate state known as the mesocrystal, in which the nanocrystals have parallel crystallographic alignment but are spatially separated. We present the first direct observations of mesocrystals with size and shape similar to product oriented aggregates by employing cryo-TEM to directly image the particles in aqueous suspension.