nacre is a technologically remarkable organic-inorganic composite biomaterial. It consists of an ordered multilayer structure of crystalline calcium carbonate platelets separated by porous organic layers. This microstructure exhibits both optical iridescence and mechanical toughness, which transcend those of its constituent components. Replication of nacre is essential for understanding this complex biomineral, and paves the way for tough coatings fabricated from cheap abundant materials. Fabricating a calcitic nacre imitation with biologically similar optical and mechanical properties will likely require following all steps taken in biogenic nacre synthesis. Here we present a route to artificial nacre that mimics the natural layer-bylayer approach to fabricate a hierarchical crystalline multilayer material. Its structure-function relationship was confirmed by nacre-like mechanical properties and striking optical iridescence. our biomimetic route uses the interplay of polymer-mediated mineral growth, combined with layer-by-layer deposition of porous organic films. This is the first successful attempt to replicate nacre, using CaCo 3 .

Gyroid‐structured calcite crystals are grown by templating though self‐assembled copolymer films. The remarkable triply periodic minimal surface is perfectly replicated on the nanometer scale, while single crystallinity is maintained. This is a wholly synthetic route to a crystal morphology found in biological systems, only on a smaller length scale.

Metal oxide nanoparticles (MONPs) have widespread usage across many disciplines, but monitoring molecular processes at their surfaces in situ has not been possible. Here we demonstrate that MONPs give highly enhanced (×10 4 ) Raman scattering signals from molecules at the interface permitting direct monitoring of their reactions, when placed on top of flat metallic surfaces. Experiments with different metal oxide materials and molecules indicate that the enhancement is generic and operates at the single nanoparticle level. Simulations confirm that the amplification is principally electromagnetic and is a result of optical modulation of the underlying plasmonic metallic surface by MONPs, which act as scattering antennae and couple light into the confined region sandwiched by the underlying surface. Because of additional functionalities of metal oxides as magnetic, photoelectrochemical and catalytic materials, enhanced Raman scattering mediated by MONPs opens up significant opportunities in fundamental science, allowing direct tracking and understanding of application-specific transformations at such interfaces. We show a first example by monitoring the MONPassisted photocatalytic decomposition reaction of an organic dye by individual nanoparticles. KEYWORDS: Metal oxide, plasmons, surface-enhanced Raman scattering, photocatalysis, interface T ransition-metal oxides, due to the strong correlations of their d electrons, give rise to a wide variety of phenomena such as magnetism, ionic conduction, metal−insulator transitions, multiferroicity, and superconductivity. 1 As a result, they have an extensive range of applications that include fuel cells, batteries, catalysts, sensors, and microelectronics. 1 Despite the resulting importance of molecular binding and surface reactivity, their utilization in plasmonic applications has been prevented by the tuning of their localized surface plasmon resonance (LSPR) into the infrared. 2−6 Surface-enhanced Raman scattering (SERS) is a popular plasmonic application utilizing ultraviolet (UV), visible (VIS), or near-infrared (NIR) excitation, which overcomes the extremely small scattering cross section (∼10 −30 cm 2 per molecule) in conventional Raman scattering 7 to yield a technique that offers noninvasive and nondestructive fingerprint characterization 8 with extensive applications in chemical and biological sensing. The amplification in SERS stems primarily from the electromagnetic (EM) enhancement (up to 10 14 ) 9 obtained by excitation of SPR. 10 This is accompanied by typically smaller and system-dependent chemical enhancement as a result of formation of chargetransfer complexes between adsorbate and the surface. 11 Therefore, for efficient and sensitive SERS detection of molecules, nanoscale structures fabricated entirely with coinage metals (especially Ag and Au) have been the materials of choice since their SPR is easily excited in the vis or NIR regions. On the other hand, use of metal oxide nanoscale materials for enhanced Raman scattering has remained confi...

Templating against atomically flat materials allows creation of smooth metallic surfaces. The process of adding the backing (superstrate) to the deposited metals has proven to be the most difficult part in producing reliable, large-area, solvent-resistant substrates and has been the subject of recent research. In this paper we describe a simple and inexpensive liquid glass template-stripping (lgTS) method for the fabrication of large area ultraflat gold surfaces. Using our lgTS method, ultraflat gold surfaces with normals aligned along the <111> crystal plane and with a root-mean-square roughness of 0.275 nm (over 1 μm(2)) were created. The surfaces are fabricated on silica-based substrates which are highly solvent resistant and electrically insulating using silicate precursor solution (commonly known as "liquid glass") and concomitant mild heat treatment. We demonstrate the capabilities of such ultraflat gold surfaces by imaging nanoscale objects on top and fabricating microelectrodes as an example application. Because of the simplicity and versatility of the fabrication process, lgTS will have wide-ranging application in imaging, catalysis, electrochemistry, and surface science.

Single crystals typically assume a crystallographically distinct shape. Many biological organisms, however, synthesize single crystals with an intricate mescoscopic morphology that does not reflect the crystal symmetry. The cover shows a calcite single crystal with a bicontinuous gyroid morphology, which was obtained by calcite nucleation in a self‐assembled polymer matrix in work reported by Ulli Steiner and co‐workers . The characteristic size of the biomimetic structure is ∼30 nm. The pattern in the title is the characteristic 211 plane of the gyroid morphology.

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