Measurement of Signal‐to‐Noise Ratio In Graphene‐based Passive Microelectrode Arrays

This work aims to investigate the influence of various electrode materials on the signal‐to‐noise ratio (SNR) of passive microelectrode arrays (MEAs) intended for use in neural interfaces. Noise reduction substantially improves the performance of systems which electrically interface with extracellular solutions. The MEAs are fabricated using gold, indium tin oxide (ITO), inkjet printed (IJP) graphene, and chemical vapor deposited (CVD) graphene. 3D‐printed Nylon reservoirs are adhered to glass substrates with identical MEA patterns and filled with neuronal cell culture media. To precisely control the electrode area and minimize the parasitic coupling of metal interconnects and solution, SU‐8 photoresist is patterned to expose only the area of the electrode to solution and cap the remainder of the sample. Voltage signals with varying amplitude and frequencies are applied to the solution using glass micropipettes, and the response is measured on an oscilloscope from a microprobe placed on the contact pad external to the reservoir. The time domain response signal is transformed into a frequency spectrum, and SNR is calculated. As the magnitude or the frequency of the input signal gets larger, a significantly increased signal‐to‐noise ratio was observed in CVD graphene MEAs compared to others. This result indicates that 2‐dimensional nanomaterials such as graphene can provide better signal integrity and potentially lead to improved performance in hybrid neural interface systems.     

Protein electrochemistry using aligned carbon nanotube arrays

The remarkable electrocatalytic properties and small size of carbon nanotubes make them ideal for achieving direct electron transfer to proteins, important in understanding their redox properties and in the development of biosensors. Here, we report shortened SWNTs can be aligned normal to an electrode by self-assembly and act as molecular wires to allow electrical communication between the underlying electrode and redox proteins covalently attached to the ends of the SWNTs, in this case, microperoxidase MP-11. The efficiency of the electron transfer through the SWNTs is demonstrated by electrodes modified with tubes cut to different lengths having the same electron-transfer rate constant.     

Complex interface and growth analysis of single crystalline epi‐Si(111)/Y2O3/ Pr2O3/Si(111) heterostructures: Strain engineering by oxide buffer control

Complex oxide heterostructures on Si gain in the field of engineered Si wafers increasing interest as flexible buffer systems for developing virtual Si substrates. Strain engineering of thin epitaxial Si thin films on insulating oxide buffers is of special interest to boost charge carrier mobility for Silicon‐on‐Insulator (SOI) technologies. The single crystalline Si(111)/Y₂O₃ (111)/Pr₂O₃ (111)/Si(111) heterostructure offers, in principle, the opportunity to grow strain‐engineered epitaxial Si(111) layers, realizing compressed, fully relaxed, as well as tensile‐strained Si films. This flexibility is based on a thickness‐dependence of the Y₂O₃ lattice constant in the oxide bi‐layer buffer: In theory, the Y₂O₃ buffer lattice constant on Pr₂O₃/Si(111) can change from pseudomorphism (bigger than Si) over the Si lattice constant towards a fully relaxed status (smaller than Si). By a detailed interface analysis, using TEM‐EELS in combination with an in‐situ RHEED–XPS study of the isomorphic Y₂O₃ growth on Pr₂O₃/Si(111), the physical origin of this Y₂O₃ buffer lattice constant variation is identified. It is possible to discriminate between the contributions from chemical mixing effects between the isomorphic oxides Y₂O₃ and Pr₂O₃ on the one hand and true misfit strain relaxation mechanisms in stoichiometric Y₂O₃ on the other hand. Copyright © 2010 John Wiley & Sons, Ltd.     

Valence Isomerization in the Solid State: From 1,3-Diphosphacyclobutane-2,4-diyl to 1,2-Dihydro-1,2-diphosphete

The butadiene-like phosphanylcarbene 2 is, according to ab initio calculations, the intermediate in the conversion of 1 into 3 in the solid state [Eq. (a)]; it is only 1.3 kJ mol⁻¹ higher in energy than 1 . For this conversion, only minor changes in the endocyclic bonds are required throughout the entire reaction. R₂N=2,2,6,6-Me₄C₅H₆N.     

Catalytic Copolymerization of Ethene and Carbon Monoxide on Nickel Complexes

Can palladium be replaced by nickel? For the industrial copolymerization of carbon monoxide and ethene a palladium catalyst is used which cannot be recovered—a cheaper procedure would be desirable. The presented complex 1 is the first structurally characterized nickel compound which does not polymerize ethene but a mixture from carbon monoxide and ethene unter mild conditions to give a perfectly alternating polyketone.     

Polymers,additives, surfactants and their mixtures: Computer-based search with special ftir libraries

This investigation was done with a PC of 850 MB/33 MHz, Windows 3.1 and the SPECTACLE program of LabControl/Cologne. The libraries contained standardized FTIR spectra of 3061 defined polymers, 530 industrial polymers and resins, 1969 additives (pigments, stabilizers, plasticizers etc.) 1190 surfactants and 1614 monomers, pyrolyzates and educts. For searches, the data density was reduced to 4/cm. Similarity search with standardized full spectra yields quantitative dissimilarity figures; it allows an experimental definition of identity. The derivative functions 3 and 4 of Lowry and Huppler increase the gap between identical and similar spectra. With the LH2 algorithm spectra are defined as identical if their dissimilarity values are within 10³. Since all organic matter has some spectral similarity the LH2 dissimilarity for organics will not go far beyond 10⁵. - The quality of IR preparation has a strong impact on search results. If a library contains spectra with false-light, Christiansen effect, high noise or other artefacts, peak search yields better results than similarity search with full spectra. Multicomponent systems can be searched successfully for their constituents with an algorithm combining peak and similarity searches. This algorithm is superior to all other algorithms if a library contains spectra with artefacts.     

Ueber Vorkommen und Nachweis von Morphin in thierischen Geweben und Ausscheidungen

Ohne Zusammenfassung