Tooth enamel comprises parallel microscale and nanoscale ceramic columns or prisms interlaced with a soft protein matrix. This structural motif is unusually consistent across all species from all geological eras. Such invariability-especially when juxtaposed with the diversity of other tissues-suggests the existence of a functional basis. Here we performed ex vivo replication of enamel-inspired columnar nanocomposites by sequential growth of zinc oxide nanowire carpets followed by layer-by-layer deposition of a polymeric matrix around these. We show that the mechanical properties of these nanocomposites, including hardness, are comparable to those of enamel despite the nanocomposites having a smaller hard-phase content. Our abiotic enamels have viscoelastic figures of merit (VFOM) and weight-adjusted VFOM that are similar to, or higher than, those of natural tooth enamels-we achieve values that exceed the traditional materials limits of 0.6 and 0.8, respectively. VFOM values describe resistance to vibrational damage, and our columnar composites demonstrate that light-weight materials of unusually high resistance to structural damage from shocks, environmental vibrations and oscillatory stress can be made using biomimetic design. The previously inaccessible combinations of high stiffness, damping and light weight that we achieve in these layer-by-layer composites are attributed to efficient energy dissipation in the interfacial portion of the organic phase. The in vivo contribution of this interfacial portion to macroscale deformations along the tooth's normal is maximized when the architecture is columnar, suggesting an evolutionary advantage of the columnar motif in the enamel of living species. We expect our findings to apply to all columnar composites and to lead to the development of high-performance load-bearing materials.

A systematic approach has been followed in the development of a high-efficiency hybrid photovoltaic device that has a combination of poly(3-hexylthiophene) (P3HT), [6,6]-phenyl C61-butyric acid methyl ester (PCBM), and silver nanowires (Ag NWs) in the active layer using the bulk heterojunction concept. The active layer is modified by utilizing a binary solvent system for blending. In addition, the solvent evaporation process after spin-coating is changed and an Ag NWs is incorporated to improve the performance of the hybrid photovoltaic device. Hybrid photovoltaic devices were fabricated by using a 1:0.7 weight ratio of P3HT to PCBM in a 1:1 weight ratio of o-dichlorobenzene and chloroform solvent mixture, in the presence and absence of 20 wt % of Ag NWs. We also compared the photovoltaic performance of Ag NWs embedded in P3HT:PCBM to that of silver nanoparticles (Ag NPs). Atomic force microscopy, scanning electron microscopy, transmittance electron microscopy, UV-visible absorption, incident photon-to-current conversion efficiency, and time-of-flight measurements are performed in order to characterize the hybrid photovoltaic devices. The optimal hybrid photovoltaic device composed of Ag NWs generated in this effort exhibits a power conversion efficiency of 3.91%, measured by using an AM 1.5G solar simulator at 100 mW/cm(2) light illumination intensity.

Enzyme inhibitors are ubiquitous in all living systems, and their biological inhibitory activity is strongly dependent on their molecular shape. Here, we show that small zinc oxide nanoparticles (ZnO NPs)-pyramids, plates, and spheres-possess the ability to inhibit activity of a typical enzyme β-galactosidase (GAL) in a biomimetic fashion. Enzyme inhibition by ZnO NPs is reversible and follows classical Michaelis-Menten kinetics with parameters strongly dependent on their geometry. Diverse spectroscopic, biochemical, and computational experimental data indicate that association of GAL with specific ZnO NP geometries interferes with conformational reorganization of the enzyme necessary for its catalytic activity. The strongest inhibition was observed for ZnO nanopyramids and compares favorably to that of the best natural GAL inhibitors while being resistant to proteases. Besides the fundamental significance of this biomimetic function of anisotropic NPs, their capacity to serve as degradation-resistant enzyme inhibitors is technologically attractive and is substantiated by strong shape-specific antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA), endemic for most hospitals in the world.

Nanoscale pyrite FeS2 is considered to be one of few potentially transformative materials for photovoltaics capable of bridging the cost/performance gap of solar batteries. It also holds promise for energy storage applications as the material for high-performance cathodes. Despite prospects, the synthesis of FeS2 nanostructures and diversity of their geometries has been hardly studied. Moreover, the state-of-the-art aqueous dispersions of nanoscale pyrite, which have special significance for solar energetics, are particularly disappointing due to low quality. There are no known methods to produce well-crystallized nanoparticles and other geometries of nanoscale pyrite in water or mixed aqueous solvents. Here, we describe a successful synthesis of single-phase pyrite nanoparticles with a diameter of 2–5 nm in polar solvent and aqueous dispersions. The particles display high uniformity and crystallographic purity. Moreover, the synthetic approach developed for nanoparticles was proven to be quite universal and can be modified to produce both nanowires and nanosheets, which also display high crystallinity. The diameter of the pyrite nanowires was 80–120 nm with the length exceeding 5 μm. The nanosheets displayed lateral dimensions of 100–200 nm with the thickness of 2 nm. Availability of single-phase FeS2 nanoscale aqueous dispersions is expected to stimulate further studies of these materials in green energy conversion technologies and drug delivery applications.

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This is the first report on the preparation of cardanol-containing methacrylate polymers having antibacterial properties for surface coating applications.

Detailed understanding of the mechanism of dielectrophoresis (DEP) and the drastic improvement of its efficiency for small size quantized nanoparticles (NPs) open the door for the convergence of microscale and nanoscale technologies. It was hindered however by the severe reduction of DEP force in particles with volume below few hundred nm3. We report here DEP assembly of size quantized CdTe nanoparticles (NPs) with a diameter of 4.2 nm under AC voltage of 4–10 V. Calculations of the nominal DEP force for these NPs indicate that it is several orders of magnitude smaller than the force of the Brownian motion destroying the assemblies even for the maximum applied AC voltage. Despite this theoretical background, very efficient formation of NP bridges between electrodes separated by a gap of 2μ was observed even for AC voltages of 6V and highly dilutes NP dispersions. The resolution of this conundrum was found in the intrinsic ability of CdTe NPs to self-assemble. The species being assembled by DEP are substantially bigger than the individual NPs. DEP assembly should be treated as a process taking place for NP chains with a length of ca 140 nm. The self-assembled chains increase the nominal volume where the polarization of the particles takes place, while retaining the size-quantized nature of the material. The produced NP bridges were found to be photoactive producing photocurrent upon illumination. DEP bridges of quantum confined NPs can be used in fast parallel manufacturing of novel MEMS components, sensors, optical, and optoelectronic devices. Purposeful engineering of self-assembling properties of NPs makes possible further facilitation of the DEP assemblies and increase of complexity of the produced nano- and microscale structures.

We synthesized gold nanonetwork using the amphiphilic polymer brush, poly(oxyethylene) containing decyltri(oxyethylene)thiomethyl (C 1 0 H 2 1 (OCH 2 CH 2 ) 3 SCH 2 -) side groups, as a stabilizer and/or a template. When tetrabutylammonium borohydride solution in THF was added to a mixture solution of the polymer and LiAuCl 4 in THF, 0-D gold nanomaterials were obtained. However, when an aqueous solution of sodium borohydride was added, gold nanonetworks were synthesized. The composites composed of polymer/0-D gold nanomaterials and polymer/ gold nanonetworks showed electrical conductivities of ~10 -9 and ~10 -3S/cm, respectively, which indicated that the gold nanonetworks increased the electrical conductivity.