Helsinki University of Technology

About: Helsinki University of Technology is a based out in . It is known for research contribution in the topics: Artificial neural network & Finite element method. The organization has 8962 authors who have published 20136 publications receiving 723787 citations. The organization is also known as: TKK & Teknillinen korkeakoulu.

Transport spectroscopy of single phosphorus donors in a silicon nanoscale transistor.

Abstract: We have developed nanoscale double-gated field-effect-transistors for the study of electron states and transport properties of single deliberately implanted phosphorus donors. The devices provide a high-level of control of key parameters required for potential applications in nanoelectronics. For the donors, we resolve transitions corresponding to two charge states successively occupied by spin down and spin up electrons. The charging energies and the Lande g-factors are consistent with expectations for donors in gated nanostructures.

Genetic Engineering of Biomimetic Nanocomposites: Diblock Proteins, Graphene, and Nanofibrillated Cellulose

Abstract: Nature has materials with extraordinary stiffness, strength, and toughness that is based on aligned, tailored self-assemblies. They have inspired biomimetic nanocomposites with drastically better properties than synthetic composites. Herein we show a new approach to making biomimetic nanocomposites based on the exfoliation of graphite into a matrix of genetically engineered proteins and native nanofibrillated cellulose. The protein was genetically engineered to incorporate a hydrophobin block, which binds to graphene, and a cellulose-binding block, which binds to nanofibrillated cellulose, thereby bringing about both the self-assembly and adhesion between the nanoscale components. The aligned co-assembly leads to remarkably good mechanical properties (modulus: 20.2 GPa, strength: 278 MPa, strain-to-failure: 3.1 %, and work-of-fracture 57.9 kJ m ). The bifunctional protein was crucial for the excellent mechanical properties. This concept shows how high-performance biomimetic composites can be built through the binding and self-assembly of advanced biomolecules that have been genetically tailored. Biology shows numerous composite materials wherein aligned hard and soft self-assembled components are bound together to result in excellent mechanical properties such as the combination of toughness, strength, and stiffness. Such materials are, for example, nacre, plant tissue, bone, silk, and tendon. Factors contributing to their advantageous properties include the chemical nature of the hard-reinforcing and soft-dissipating components, their molecular interactions, their mechanical interlocking, dimensions, and alignment, which contributes to the mechanics of crack propagation. The soft matrix is especially interesting as it acts as glue that keeps the hard components together and allows dissipation of fracture energy. Still, very little is known about, for example, how the matrix proteins of nacre function. A rational route towards a controlled interconnectivity between the self-assembled domains in biomimetic composites is suggested by the design principles of block copolymers, which are used in materials science, for example, to interface two different polymers in mixtures or to stabilize colloidal systems, even for responses or functions. In this work we show the feasibility of genetically engineered proteins having two well-defined binding blocks, denoted as diblock proteins, that bind and assemble the structural components for biomimetic composites. Previously we have shown that the adhesive surfactantlike proteins, hydrophobins, allow exfoliation of graphite to give singleor few-layer flakes of graphene in aqueous solutions. Here, the same route to disperse singleor fewlayer flakes of graphene using proteins in a cellulose matrix was employed to form biomimetic nanocomposite materials. The dispersions of the singleor few-layer flakes of graphene are referred to herein simply as graphene dispersions, although there may be a range of flake thicknesses present. A genetically modified hydrophobin was used to combine graphene and native nanofibrillated cellulose (NFC), also called nanocellulose or microfibrillated cellulose. The structure of the resulting composite resembles that of nacre where self-assembled, aligned platelet-like aragonite reinforcements are embedded in a protein matrix containing nanofibrillar chitin. By using engineered molecules that contain unusual combinations of binding abilities, it is possible to build composites from components that do not occur in natural materials. This technique allowed us to combine flakes of graphene, one of the strongest materials presently known, and nanofibrillated cellulose having a modulus approaching the one of steel 16] in a nanocomposite material. The protein was genetically engineered to connect graphene and NFC, so that it self-assembles at the interfaces, thus leading to cohesion and alignment (Figure 1 a). Binding to graphene was achieved by a hydrophobin, more specifically the class II hydrophobin HFBI, which self-assembles on various interfaces and surfaces, including graphene. Binding to cellulose was achieved by using a protein denoted as a cellulose-binding domain (CBD) found in cellulose[*] Dr. P. Laaksonen, J.-M. Malho, Prof. M. B. Linder Nanobiomaterials, VTT Technical Research Centre of Finland P.O. Box 1000, 02044 VTT (Finland) E-mail: paivi.laaksonen@vtt.fi Homepage: http://www.vtt.fi/research/technology/nanobiotechnology.jsp

Functional porous structures based on the pyrolysis of cured templates of block copolymer and phenolic resin

Abstract: Porous materials with controlled pore sizes have been investigated for different applications such as filters, separation, sensors, supports for catalysis, and controlled drug release. Proper selection of chemical groups lining the pore walls, as well as detailed control of the pore size and size distribution, can lead to selectivity and various functions. In this work we describe a facile method to construct porous films by crosslinking phenolic resin in the presence of a self-assembled block-copolymer template, followed by pyrolysis at moderate temperature. This enables us to transfer the ordered block copolymer self-assembly into porosity, with a fine control of the pore size and distribution. These materials have large surface area (in excess of 300 m 2 g –1 ), with a high number of phenolic hydroxyl groups at the matrix and pore walls, which can be used for, e.g., selective absorption or for further functional