Amorphous AlN films grown by ALD from trimethylaluminum and monomethylhydrazine

The great interest in aluminium nitride thin films has been attributed to their excellent dielectric, thermal and mechanical properties. Here we present the results of amorphous AlN films obtained by atomic layer deposition. We used trimethylaluminum and monomethylhydrazine as the precursors at a deposition temperature of 375-475 °C. The structural and mechanical properties and chemical composition of the synthesized films were investigated in detail by X-ray diffraction, X-ray photoelectron spectroscopy, electron and probe microscopy and nanoindentation. The obtained films were compact and continuous, exhibiting amorphous nature with homogeneous in-depth composition, at an oxygen content of as low as 4 at%. The mechanical properties were comparable to those of AlN films produced by other techniques

Iridium wire grid polarizer fabricated using atomic layer deposition

In this work, an effective multistep process toward fabrication of an iridium wire grid polarizer for UV applications involving a frequency doubling process based on ultrafast electron beam lithography and atomic layer deposition is presented. The choice of iridium as grating material is based on its good optical properties and a superior oxidation resistance. Furthermore, atomic layer deposition of iridium allows a precise adjustment of the structural parameters of the grating much better than other deposition techniques like sputtering for example. At the target wavelength of 250 nm, a transmission of about 45% and an extinction ratio of 87 are achieved

Atomic layer deposition of nanostructured materials

Atomic layer deposition, formerly called atomic layer epitaxy, was developed in the 1970s to meet the needs of producing high-quality, large-area fl at displays with perfect structure and process controllability. Nowadays, creating nanomaterials and producing nanostructures with structural perfection is an important goal for many applications in nanotechnology. As ALD is one of the important techniques which offers good control over the surface structures created, it is more and more in the focus of scientists. The book is structured in such a way to fi t both the need of the expert reader (d

Tuning the tensile strength of cellulose through vapor-phase metalation

The infiltration of transition metals into biopolymers by means of vapor-phase processes has been shown to unusually change the bulk mechanical properties of those materials. Here, for the first time, a novel, single precursor infiltration process was applied to cellulose. The mechanical properties, as measured through uniaxial tensile testing, showed improvement as a function of the total number of infiltration cycles as well as the precursor used. For cellulose infiltrated with diethyl zinc with only four infiltration cycles, the ultimate tensile strength was seen to nearly double from ∼160 to ∼260 MPa. A significant increase was also seen in the elastic modulus, with values increasing ∼2.5×, from ∼1.8 to ∼4.5 GPa. In contrast, cellulose infiltrated with trimethyl aluminum showed very little improvement in mechanical properties. By choosing the appropriate precursor and/or number of cycles, the mechanical properties become tunable. The chemical changes in the cellulose structure were measured with Raman spectroscopy and a novel semi in situ X-ray photoelectron spectroscopy experiment. The results of both spectroscopic techniques were used to propose a reaction scheme.K.E.G. and M.K. acknowledge financial support by the Spanish ministry of economy and competitivity (MINECO) through project no. MAT2012-38161 and the Basque government through project no. PI2013-56. D.F.P. acknowledges the MPC for financial support. C.R. and D.F.P. acknowledge support from the Basque Department of Education, UPV/EHU grant no. IT-621-13.Peer Reviewe

Coupling enzymes and inorganic piezoelectric materials for electricity production from renewable fuels

Sustainable electricity generation is one of the major current challenges for our society. In this context, the evolution of nanomaterials and nanotechnologies has enabled the fabrication of microscopic devices to produce clean energy from a great variety of renewable sources. To expand the possibilities of energy generation, we have designed and fabricated bioinorganic generators capable to produce electricity by conversion of chemical energy from renewable fuel sources. Unlike traditional generators, the systems described herein produce mechanical energy through enzyme-driven gas production which generates vibration and pressure that are thus converted into electricity by the action of a piezoelectric component properly integrated into the device. Our generators are able to produce an electric ernergy from different renewable sources like glucose, ethanol, and amino acids, attaining energy outputs around 250 nJ cm–2 and reaching maximum open-circuit voltages of up to 1 V. In addition, the produced energy can be easily regulated by adjusting both enzyme and fuel concentration which can tune the electrical output according to the application. The systems described herein propose a new concept for self-sufficient energy harvesting that bridges biocatalysis and piezoelectricity, where the energy production is based on the piezoelectric effect triggered by enzymatic action rather than on the enzyme-driven electron transfer that governs biofuel cells. Although the electric output is too low yet to be considered an alternative for energy production, this technology opens the door to power small devices. We envision the utilization of this technology in such remote locations where mechanical energy is lacking but there are chemical energy reservoirs.We would like to acknowledge Marie-Curie Actions (NANOBIENER project), IKERBASQUE foundation for funding F.L.-G., and the support of COST Action CM1303 Systems Biocatalysis. We also acknowledge HERGAR foundation for the funding.Peer reviewe

Functionalization of defect sites in graphene with RuO2 for high capacitive performance

Graphene is an attractive material for its physicochemical properties, but for many applications only chemically synthesized forms such as graphene oxide (GO) and reduced graphene oxide (rGO) can be produced in sufficient amounts. If considered as electrode material, the intrinsic defects of GO or rGO may have negative influence on the conductivity and electrochemical properties. Such defects are commonly oxidized sites that offer the possibility to be functionalized with other materials in order to improve performance. In this work, we demonstrate how such ultimately efficient functionalization can be achieved: namely, through controlled binding of very small amount of materials such as RuO2 to rGO by atomic layer deposition (ALD), in this way substituting the native defect sites with RuO2 defects. For the example of a supercapacitor, we show that defect functionalization results in significantly enhanced specific capacitance of the electrode and that its energy density can be stabilized even at high consumption rates.We acknowledge financial support by the Spanish Ministry of Economy and Competitivity (MINECO) through Project MAT2012-38161 and the Basque government through Project PI2013-56. M.K. acknowledges financial support through Marie Curie Actions (CIG) within Project 322158 (ARTEN). C.R. acknowledges financial support from the Basque Department of Education (Grant No. IT-621-13) and the Spanish Government (Grant No. MAT2013-46593-C6).Peer Reviewe

Carrierless Immobilization Route for Highly Robust Metal–Organic Hybrid Enzymes

The absence of a universal enzyme immobilization method that fulfils the needs of each biocatalytic system has boosted the development of new approaches to the fabrication of heterogeneous biocatalysts. Herein, we present a protocol for the synthesis of a novel sort of catalytically responsive hybrid biomaterials, named metal–organic enzyme aggregates (MOEAs). The formation of MOEAs is triggered by the coordination of divalent metal cations to imidazole-decorated enzyme nanogels in a fast and effective assembly mechanism. The size and morphology of MOEAs can be tailored from small individual particles to macroscopic aggregates, which are stable in water and disassemble in the presence of a complexing agent. Finally, the extensive compositional and catalytic characterization of the hybrids showed high transformation rates, significant protein loads, and great thermostability. These features revealed MOEAs as an excellent alternative as carrierless immobilization system