Two active electrochromic materials, vacancy-doped tungsten oxide (WO(3-x)) nanocrystals and amorphous niobium oxide (NbOx) glass are arranged into a mesostructured architecture. In a strategy applicable across electrochemical applications, the critical dimensions and interfacial connections in the nanocomposite are designed to optimize pathways for electrochemical charging and discharging. The result is an unprecedented optical range for modulation of visible and near-infrared solar radiation with rapid switching kinetics that indicate the WO(3-x) nanocrystal framework effectively pumps charge out of the normally sluggish NbOx glass. The material is durable for at least 2000 electrochemical cycles.

Regulating the complex environment accounting for the stability, selectivity, and activity of catalytic metal nanoparticle interfaces represents a challenge to heterogeneous catalyst design. Here we demonstrate the intrinsic performance enhancement of a composite material composed of gold nanoparticles (AuNPs) embedded in a bottom-up synthesized graphene nanoribbon (GNR) matrix for the electrocatalytic reduction of CO. Electrochemical studies reveal that the structural and electronic properties of the GNR composite matrix increase the AuNP electrochemically active surface area (ECSA), lower the requisite CO reduction overpotential by hundreds of millivolts (catalytic onset > -0.2 V versus reversible hydrogen electrode (RHE)), increase the Faraday efficiency (>90%), markedly improve stability (catalytic performance sustained over >24 h), and increase the total catalytic output (>100-fold improvement over traditional amorphous carbon AuNP supports). The inherent structural and electronic tunability of bottom-up synthesized GNR-AuNP composites affords an unrivaled degree of control over the catalytic environment, providing a means for such profound effects as shifting the rate-determining step in the electrocatalytic reduction of CO to CO, and thereby altering the electrocatalytic mechanism at the nanoparticle surface.

We report here the first solid-state, NIR-selective electrochromic devices. Critical to device performance is the arrangement of nanocrystal-derived electrodes into heteromaterial frameworks, where hierarchically porous ITO nanocrystal active layers are infiltrated by an ion-conducting polymer electrolyte with mesoscale periodicity. Enhanced coloration efficiency and transport are realized over unarchitectured electrodes in devices, paving the way towards new smart windows technologies.

Here we show that sub-micron coatings of zeolitic imidazolate frameworks (ZIFs) and even ZIF−ZIF bilayers can be grown directly on polymers of intrinsic microporosity from zinc oxide (ZnO) nanocrystal precursor films, yielding a new class of all-microporous layered hybrids. The ZnO-to-ZIF chemical transformation proceeded in less than 30 min under microwave conditions using a solution of the imidazole ligand in N,N-dimethylformamide (DMF), water, or mixtures thereof. By varying the ratio of DMF to water, it was possible to control the morphology of the ZIFon-polymer from isolated crystallites to continuous films. Grazing incidence X-ray diffraction was used to confirm the presence of crystalline ZIF in the thin films, and X-ray absorption spectroscopy was used to quantify film purity, revealing films with little to no residual ZnO. The role solvent plays in the transformation mechanism is discussed in light of these findings, which suggest the ZnO nanocrystals may be necessary to localize heterogeneous nucleation of the ZIF to the polymer surface.

Colloidal nanocrystal frameworks (CNFs) are a modular class of mesostructured porous materials, which are assembled from pre-formed nanocrystal building units using suitably designed block copolymer architecture-directing agents. The functional attributes of these frameworks are determined both by the physiochemical characteristics of the nanocrystal components as well as their ordered arrangements in space. It is noteworthy that their assembly schemes are readily amenable to more than one type of framework component, yielding a multivariate landscape to navigate mesoscale phenomena arising from the coupled interactions of different nanocrystals within the framework. Early reports indicate surprisingly efficient propagation of both matter and energy within and along the surfaces of these frameworks, although there remains much to be learned about the origins of their structural, electronic, and dynamic properties, and how they feed back across multiple length and time scales.

A framework is presented to control phase transformations in colloidal nanocrystal assemblies at liquid-liquid interfaces.

Preventing the permeation of reactive molecules into electronic devices or photovoltaic modules is of great importance to ensure their life span and reliability. This work is focused on the formation of highly functioning barrier films based on nanocrystals (NCs) of a water-scavenging metal-organic framework (MOF) and a hydrophobic cyclic olefin copolymer (COC) to overcome the current limitations. Water vapor transmission rates (WVTR) of the films reveal a 10-fold enhancement in the WVTR compared to the substrate while maintaining outstanding transparency over most of the visible and solar spectrum, a necessary condition for integration with optoelectronic devices.

Assembly of presynthesized nanocrystals by block copolymer micelles can be rationalized by the incorporation of nanocrystals into micellar coronas of constant width. As determined by quantitative analysis using small-angle X-ray scattering, high loading of small nanocrystals yields composites exhibiting order on two length scales, whereas intermediate loading of nanocrystals larger than the coronal width produces single nanocrystal networks. The resulting structures obey expectations of thermodynamically driven assembly on the nanocrystal length scale, whereas kinetically frozen packing principles dictate order on the polymer micelle length scale.