In-situ resonant band engineering of solution-processed semiconductors generates high performance n-type thermoelectric nano-inks.

Thermoelectric devices possess enormous potential to reshape the global energy landscape by converting waste heat into electricity, yet their commercial implementation has been limited by their high cost to output power ratio. No single "champion" thermoelectric material exists due to a broad range of material-dependent thermal and electrical property optimization challenges. While the advent of nanostructuring provided a general design paradigm for reducing material thermal conductivities, there exists no analogous strategy for homogeneous, precise doping of materials.

Atomically Thin Interfacial Suboxide Key to Hydrogen Storage Performance Enhancements of Magnesium Nanoparticles Encapsulated in Reduced Graphene Oxide.

As a model system for hydrogen storage, magnesium hydride exhibits high hydrogen storage density, yet its practical usage is hindered by necessarily high temperatures and slow kinetics for hydrogenation-dehydrogenation cycling. Decreasing particle size has been proposed to simultaneously improve the kinetics and decrease the sorption enthalpies. However, the associated increase in surface reactivity due to increased active surface area makes the material more susceptible to surface oxidation or other side reactions, which would hinder the overall hydrogenation-dehydrogenation process and diminish the capacity.

Long-Range Order in Nanocrystal Assemblies Determines Charge Transport of Films.

Self-assembly of semiconductor nanocrystals (NCs) into two-dimensional patterns or three-dimensional (2-3D) superstructures has emerged as a promising low-cost route to generate thin-film transistors and solar cells with superior charge transport because of enhanced electronic coupling between the NCs. Here, we show that lead sulfide (PbS) NCs solids featuring either short-range (disordered glassy solids, GSs) or long-range (superlattices, SLs) packing order are obtained solely by controlling deposition conditions of colloidal solution of NCs. In this study, we demonstrate the use of the evaporation-driven self-assembly method results in PbS NC SL structures that are observed over an area of 1 mm × 100 μm, with long-range translational order of up to 100 nm.

Solution-Processed CuSe Nanocrystal Films with Bulk-Like Thermoelectric Performance.

Thermoelectric power generation can play a key role in a sustainable energy future by converting waste heat from power plants and other industrial processes into usable electrical power. Current thermoelectric devices, however, require energy intensive manufacturing processes such as alloying and spark plasma sintering. Here, we describe the fabrication of a p-type thermoelectric material, copper selenide (CuSe), utilizing solution-processing and thermal annealing to produce a thin film that achieves a figure of merit, ZT, which is as high as its traditionally processed counterpart, a value of 0.

Poly(vinylidene fluoride) (PVDF) Binder Degradation in Li-O Batteries: A Consideration for the Characterization of Lithium Superoxide.

We show that a common Li-O battery cathode binder, poly(vinylidene fluoride) (PVDF), degrades in the presence of reduced oxygen species during Li-O discharge when adventitious impurities are present. This degradation process forms products that exhibit Raman shifts (∼1133 and 1525 cm) nearly identical to those reported to belong to lithium superoxide (LiO), complicating the identification of LiO in Li-O batteries. We show that these peaks are not observed when characterizing extracted discharged cathodes that employ poly(tetrafluoroethylene) (PTFE) as a binder, even when used to bind iridium-decorated reduced graphene oxide (Ir-rGO)-based cathodes similar to those that reportedly stabilize bulk LiO formation.

Carrier Scattering at Alloy Nanointerfaces Enhances Power Factor in PEDOT:PSS Hybrid Thermoelectrics.

Unlabelled: This work demonstrates the first method for controlled growth of heterostructures within hybrid organic/inorganic nanocomposite thermoelectrics. Using a facile, aqueous technique, semimetal-alloy nanointerfaces are patterned within a hybrid thermoelectric system consisting of tellurium (Te) nanowires and the conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (

Pedot: PSS). Specifically, this method is used to grow nanoscale islands of Cu1.

Engineering Synergy: Energy and Mass Transport in Hybrid Nanomaterials.

An emerging class of materials that are hybrid in nature is propelling a technological revolution in energy, touching many fundamental aspects of energy-generation, storage, and conservation. Hybrid materials combine classical inorganic and organic components to yield materials that manifest new functionalities unattainable in traditional composites or other related multicomponent materials, which have additive function only. This Research News article highlights the exciting materials design innovations that hybrid materials enable, with an eye toward energy-relevant applications involving charge, heat, and mass transport.

Ligand coupling symmetry correlates with thermopower enhancement in small-molecule/nanocrystal hybrid materials.

We investigate the impact of the coupling symmetry and chemical nature of organic-inorganic interfaces on thermoelectric transport in Cu2-xSe nanocrystal thin films. By coupling ligand-exchange techniques with layer-by-layer assembly methods, we are able to systematically vary nanocrystal-organic linker interfaces, demonstrating how the functionality of the polar headgroup and the coupling symmetry of the organic linkers can change the power factor (S(2)σ) by nearly 2 orders of magnitude. Remarkably, we observe that ligand-coupling symmetry has a profound effect on thermoelectric transport in these hybrid materials.

Mapping Li(+) Concentration and Transport via In Situ Confocal Raman Microscopy.

We demonstrate confocal Raman microscopy as a general, nonperturbative tool to measure spatially resolved lithium ion concentrations in liquid electrolytes. By combining this high-spatial-resolution technique with a simple microfluidic device, we are able to measure the diffusion coefficient of lithium ions in dimethyl carbonate in two different concentration regimes. Because lithium ion transport plays a key role in the function of a variety of electrochemical devices, quantifying and visualizing this process is crucial for understanding device performance.

Structure and optical function of amorphous photonic nanostructures from avian feather barbs: a comparative small angle X-ray scattering (SAXS) analysis of 230 bird species.

Non-iridescent structural colours of feathers are a diverse and an important part of the phenotype of many birds. These colours are generally produced by three-dimensional, amorphous (or quasi-ordered) spongy β-keratin and air nanostructures found in the medullary cells of feather barbs. Two main classes of three-dimensional barb nanostructures are known, characterized by a tortuous network of air channels or a close packing of spheroidal air cavities.

Assembly of optical-scale dumbbells into dense photonic crystals.

We describe the self-assembly of nonspherical particles into crystals with novel structure and optical properties combining a partial photonic band gap with birefringence that can be modulated by an external field or quenched by solvent evaporation. Specifically, we study symmetric optical-scale polymer dumbbells with an aspect ratio of 1.58.

Stimuli-responsive smart gels realized via modular protein design.

Smart gels have a variety of applications, including tissue engineering and controlled drug delivery. Here we present a modular, bottom-up approach that permits the creation of protein-based smart gels with encoded morphology, functionality, and responsiveness to external stimuli. The properties of these gels are encoded by the proteins from which they are synthesized.

High-yield synthesis of monodisperse dumbbell-shaped polymer nanoparticles.

We describe a method for producing highly monodisperse dumbbell-shaped polymer nanoparticles with dimensions on the order of a few hundred nanometers in extremely high yields. Our technique is based on seeded polymerization, where suspended core-shell particles (linear polystyrene core with polystyrene-co-trimethoxysilylpropylacrylate shell) are used as seeds. When an aqueous suspension of seed particles is mixed with monomer solution, the core-shell particles display dramatic changes in their morphology.

Cell stimulation with optically manipulated microsources.

Molecular gradients are important for various biological processes including the polarization of tissues and cells during embryogenesis and chemotaxis. Investigations of these phenomena require control over the chemical microenvironment of cells. We present a technique to set up molecular concentration patterns that are chemically, spatially and temporally flexible.

Synthesis of colloidal particles with the symmetry of water molecules.

We describe a method for synthesizing "colloidal water": monodisperse micrometer-sized polymer particles with the symmetry of water molecules. Our approach is based on multistep seeded polymerization with variation of cross-linker concentration in each step. This enables precise control of swelling selectivity and phase-separation, which control the particle morphology.