Inverse Photonic Glasses by Packing Bidisperse Hollow Microspheres with Uniform Cores.

A major fabrication challenge is producing disordered photonic materials with an angle-independent structural red color. Theoretical work has shown that such a color can be produced by fabricating inverse photonic glasses with monodisperse, nontouching voids in a silica matrix. Here, we demonstrate a route toward such materials and show that they have an angle-independent red color. We first synthesize monodisperse hollow silica particles with precisely controlled shell thickness and then make glassy colloidal structures by mixing two types of hollow particles with the same core size and different shell thicknesses. We then infiltrate the interstices with index-matched polymers, producing disordered porous materials with uniform, nontouching air voids. This procedure allows us to control the light-scattering form factor and structure factor of these porous materials independently, which is not possible to do in photonic glasses consisting of packed solid particles. The structure factor can be controlled by the shell thickness, which sets the distance between pores, whereas the pore size determines the peak wave vector of the form factor, which can be set below the visible range to keep the main structural color pure. By using a binary mixture of 246 and 268 nm hollow silica particles with 180 nm cores in an index-matched polymer matrix, we achieve angle-independent red color that can be tuned by controlling the shell thickness. Importantly, the width of the reflection peak can be kept constant, even for larger interparticle distances.

Ag Nanoparticle/Polydopamine-Coated Inverse Opals as Highly Efficient Catalytic Membranes.

Polymeric three-dimensional inverse-opal (IO) structures provide unique structural properties useful for various applications ranging from optics to separation technologies. Despite vast needs for IO functionalization to impart additional chemical properties, this task has been seriously challenged by the intrinsic limitation of polymeric porous materials that do not allow for the easy penetration of waterborne moieties or precursors. To overcome this restriction, we present a robust and straightforward method of employing a dipping-based surface modification with polydopamine (PDA) inside the IO structures, and demonstrate their application to catalytic membranes via synthetic incorporation of Ag nanoparticles. The PDA coating offers simultaneous advantages of achieving the improved hydrophilicity required for the facilitated infiltration of aqueous precursors and successful creation of nucleation sites for a reduction of growth of the Ag nanoparticles. The resulting Ag nanoparticle-incorporated IO structures are utilized as catalytic membranes for the reduction of 4-nitrophenol to its amino derivatives in the presence of NaBH4. Synergistically combined characteristics of high reactivity of Ag nanoparticles along with a greatly enhanced internal surface area of IO structures enable the implementation of remarkably improved catalytic performance, exhibiting a good conversion efficiency greater than 99% while minimizing loss in the membrane permeability.

Highly efficient and recyclable nanocomplexed photocatalysts of AgBr/N-doped and amine-functionalized reduced graphene oxide.

Although silver bromide has recently drawn considerable attention because of its high photocatalytic activity, it tends to form agglomerated metallic silver under the irradiation of visible light. Therefore, photocatalytic activity decreases with time and cannot be applied for repeated uses. To overcome this limitation, in the present work, we complexed AgBr with nitrogen doped (N-doped) and amine functionalized reduced graphene oxide (GN). N-doped and/or amine functionalized graphene shows intrinsically good catalytic activity. Besides, amine groups can undergo complexation with silver ions to suppress its reduction to metallic Ag. As a result, these complexed catalysts show excellent photocatalytic activity for the degradation of methylene blue (MB) dye under the irradiation of visible light. Photocatalytic degradation of MB shows that the catalytic activity is optimized at a condition of 0.5 wt % GN, under which ∼99% of MB was degraded only after 50 min of visible light irradiation. Notably, the complexed catalyst is quite stable and retained almost all of its catalytic activity even after greater than 10 repeated cycles. Moreover, the catalyst can also efficiently decompose 2-chlorophenol, a colorless organic contaminant, under visible light exposure. Detailed experimental investigation reveals that hydroxyl (·OH) radicals play an important role for dye degradation reactions. A relevant mechanism for dye degradation has also been proposed.

Multiscale porous interconnected nanocolander network with tunable transport properties.

A nanocolander network is developed by embedding mesoporous block copolymers inside the structural frame of a macroporous inverse-opal structure. Spontaneously formed macroconduits interconnecting the macropores are utilized as internal bypasses for enhancing the bulk transport properties. A demonstrative application for the membrane of the nanocolander network is of perfect size-selectivity for nanoparticle separation without compromising the high permeability of the transporting medium.

Particle-nested inverse opal structures as hierarchically structured large-scale membranes with tunable separation properties.

A novel multiscale porous architecture where an individual particle is nested inside a hollow chamber of inverse-opal (IO) frame is created using a large scale self-assembly of core-shell structured colloidal particles and subsequent selective removal of the outer shells of the colloids. Since the nested particle is smaller than the size of individual IO chamber, the interconnected nanochannels are spontaneously formed within the structured frame. The size of internal nanochannels is readily tuned to have high permeability and size-selective separation capability, which is successfully tested for nanoparticle separation.

Al-C hybrid nanoclustered anodes for lithium ion batteries with high electrical capacity and cyclic stability.

Structurally regulated and hybridized Al-C nanoclusters are prepared from C60 and Al precursors by thermal evaporation-combined plasma-enhanced chemical vapour deposition. The resulting Al-C hybrid nanoclustered anodes for Li-ion batteries exhibit a high reversible capacity of >900 mA h g(-1) at an optimized current density of 6 A g(-1) for over 100 cycles.