Solid-state Substrates Research Articles

Direct Observation of a Long-Lived Single-Atom Catalyst Chiseling Atomic Structures in Graphene

Fabricating stable functional devices at the atomic scale is an ultimate goal of nanotechnology. In biological processes, such high-precision operations are accomplished by enzymes. A counterpart molecular catalyst that binds to a solid-state substrate would be highly desirable. Here, we report the direct observation of single Si adatoms catalyzing the dissociation of carbon atoms from graphene in an aberration-corrected high-resolution transmission electron microscope (HRTEM). The single Si atom provides a catalytic wedge for energetic electrons to chisel off the graphene lattice, atom by atom, while the Si atom itself is not consumed. The products of the chiseling process are atomic-scale features including graphene pores and clean edges. Our experimental observations and first-principles calculations demonstrated the dynamics, stability, and selectivity of such a single-atom chisel, which opens up the possibility of fabricating certain stable molecular devices by precise modification of materials at the atomic scale.

Scanned stripping chronopotentiometry at bismuth film rotating disc electrodes: a method for quantitative dynamic metal speciation

Environmental context Electroanalytical methods have found wide application in trace metal speciation analysis in environmental systems. The need to find functional alternatives to mercury electrodes for in situ speciation studies has encouraged the use of bismuth as a solid-state electrode substrate. We demonstrate the utility of bismuth electrodes for quantitative dynamic speciation analysis. Abstract Bismuth film electrodes are employed for dynamic metal speciation analysis of PbII complexes by stripping chronopotentiometry at scanned deposition potential (SSCP). Their performance is found to be comparable to that of mercury-film electrodes. The quantitative SSCP expressions that describe the thermodynamic and kinetic complexation parameters are straightforwardly applicable to this solid electrode.

Substrate-Integrated Hollow Waveguides: A New Level of Integration in Mid-Infrared Gas Sensing

A new generation of hollow waveguide (HWG) gas cells of unprecedented compact dimensions facilitating low sample volumes suitable for broad- and narrow-band mid-infrared (MIR; 2.5-20 μm) sensing applications is reported: the substrate-integrated hollow waveguide (iHWG). iHWGs are layered structures providing light guiding channels integrated into a solid-state substrate material, which are competitive if not superior in performance to conventional leaky-mode fiber optic silica HWGs having similar optical pathlengths. In particular, the provided flexibility in device and optical design and the wide variety of manufacturing strategies, substrate materials, access to the optical channel, and optical coating options highlight the advantages of iHWGs in terms of robustness, compactness, and cost-effectiveness. Finally, the unmatched modularity of this novel waveguide approach facilitates tailoring iHWGs to almost any kind of gas sensor technology providing adaptability to the specific demands of a wide range of sensing scenarios. Device fabrication is demonstrated for the example of a yin-yang-shaped gold-coated iHWG fabricated within an aluminum substrate with a footprint of only 75 mm × 50 mm × 12 mm (L × W × H), yet providing a nominal optical absorption path length of more than 22 cm. The analytical utility of this device for advanced MIR gas sensing applications is demonstrated for the gaseous constituents butane, carbon dioxide, cyclopropane, isobutylene, and methane.

English

The main objectives of this study were to optimize the culture conditions for theproduction of lignin peroxidase by Ganoderma leucidum, economic utilization of waste corn cobs as inducers substrate by pollution free fermentation technology and to optimize the solid state fermentation (SSF) process for lignin peroxidase (LiP) production. Growth medium employed for the culture of G. leucidum for the production of LiP was supplied with fermentation conditions that were optimized before selection like incubation period, inoculum size, temperature, pH, substrate to water ratio, nitrogen source, yeast extract and cane molasses. Culture was harvested on the fourth day and diluted five times with distilled water and filtrate was stored in Eppendoff tubes for enzyme assay using 310 nm wave lengths in the spectrophotometer. Lignin peroxidase production was enhanced and maximum LiP activity (2807 U/ml) was found in the growth medium after 96 h, inoculum size 3 ml, pH 4.5 and temperature 35°C  with substrate to water ratio of 20 ml/5 g, yeast extract 4%, (NH4)2SO4, 2% and cane molasses 3%. Results indicate the excellent scope of corn cobs as solid state substrate for the production of lignin peroxidase by G. leucidum.   Key words: Lignin peroxidase (LiP), Ganoderma leucidum, fermentation, corn cobs, cane molasses.

Morphology of CD4+T Lymphocytes Bound on Nano-Patterened Substrates for Sensing the Size of Nanoholes

We report on direct finding of how the morphology (i.e. filopodia width) of <TEX>$CD4^+$</TEX> T lymphocytes correlates with the size of the quartz nanohohole arrays (QNHAs, 140, 200, 270, and 550 nm in diameter) via scanning electron microscopy (SEM). This research exhibits that the filopodia of <TEX>$CD4^+$</TEX> T-lymphocytes extended on the QNHA substrates were observed to increase in width by increasing the size of QNHA in diameter from 140 to 550 nm. This strong linear response (<TEX>$R^2$</TEX>=0.988, n = 6) in filopodia's width of surface-bound <TEX>$CD4^+$</TEX> T-cells with topographical structures of QNHA can be explained by contact guidance between the cells and solid-state substrates. Furthermore, this research suggests that the protruded filopodia of surface-bound T-lymphocytes can be used as a biosensor for sensing the topographical information of the nano-patterned substrates.

Biocompatibility of plasma nanostructured biopolymers

Many areas of medicine such as tissue engineering requires not only mastery of modification techniques but also thorough knowledge of the interaction of cells with solid state substrates. Plasma treatment can be used to effective modification, nanostructuring and therefore can significantly change properties of materials. In this work the biocompatibility of the plasma nanostructured biopolymers substrates was studied. Changes in surface chemical structure were studied by X-ray photoelectron spectroscopy (XPS). The morphology pristine and modified samples were determined using atomic force microscopy (AFM). The surface wettability was determined by goniometry from contact angle. Biocompatibility was determined by in vitro tests, the rat vascular smooth muscle cells (VSMCs) were cultivated on the pristine and plasma modified biopolymer substrates. Their adhesion, proliferation, spreading and homogeneous distribution on polymers was monitored. It was found that the plasma treatment leads to rapid decrease of contact angle for all samples. Contact angle decreased with increasing time of modification. XPS measurements showed that plasma treatment leads to changes in ratio of polar and non-polar groups. Plasma modification was accompanied by a change of surface morphology. Biological tests found that plasma treatment have positive effect on cells adhesion and proliferation cells and affects the size of cell’s adhesion area. Changes in plasma power or in exposure time influences the number of adhered and proliferated cells and their distribution on biopolymer surface.

Highly-Efficient Gating of Solid-State Nanochannels by DNA Supersandwich Structure Containing ATP Aptamers: A Nanofluidic IMPLICATION Logic Device

Integrating biological components into artificial devices establishes an interface to understand and imitate the superior functionalities of the living systems. One challenge in developing biohybrid nanosystems mimicking the gating function of the biological ion channels is to enhance the gating efficiency of the man-made systems. Herein, we demonstrate a DNA supersandwich and ATP gated nanofluidic device that exhibits high ON-OFF ratios (up to 10(6)) and a perfect electric seal at its closed state (~GΩ). The ON-OFF ratio is distinctly higher than existing chemically modified nanofluidic gating systems. The gigaohm seal is comparable with that required in ion channel electrophysiological recording and some lipid bilayer-coated nanopore sensors. The gating function is implemented by self-assembling DNA supersandwich structures into solid-state nanochannels (open-to-closed) and their disassembly through ATP-DNA binding interactions (closed-to-open). On the basis of the reversible and all-or-none electrochemical switching properties, we further achieve the IMPLICATION logic operations within the nanofluidic structures. The present biohybrid nanofluidic device translates molecular events into electrical signals and indicates a built-in signal amplification mechanism for future nanofluidic biosensing and modular DNA computing on solid-state substrates.

Graphene Oxides as Substrate for Enhanced Mammalian Cell Growth

Graphene Oxides as Substrate for Enhanced Mammalian Cell Growth Graphene oxides (GOs), widely used as precursors in the reduction for single-layer graphene materials (rGOs), have found application potentials independent of those for graphene. In particular, the excellent aqueous compatibility of GOs has attracted growing interest in their biological applications. Studies on cellular interactions of GOs have been centered on the cytotoxicity evaluations. Beyond cytotoxicity, however, the cellular interactions of GOs apparently have other consequences. In this work, GOs as coating on solid-state substrate were found to be significantly enhancing mammalian cell growth, despite the fact that GOs in a more concentrated aqueous suspension were somewhat toxic to the same cell lines. Results for a comparison of cell growth on other surfaces based on carbon nanomaterials, including rGOs, carbon nanotubes, and composites of GOs with carbon nanotubes, are presented and discussed.

Invest or Not to Invest … Not Always an Easy Question to Answer

Innovation fuels the in vitro diagnostics (IVD)6 industry. The introduction of new technologies has greatly changed the face of the clinical laboratory, and they will continue to impact the industry and the laboratory in the years ahead. Some advances have been evolutionary, building on established core technologies, whereas other advances have been game changers. For diagnostics industry research, business development, and product-development professionals, the question of what technologies will become the products of the future—and which ones will not—is a critical one. The search for the answer starts with a clear understanding of the customer and the clinical need, but the real question is more often not the needs of today but the true unmet needs of the clinical laboratory in the years ahead. What problems do laboratories work through today because no obvious technology solution exists? What new diagnostic information would improve the accuracy or speed of diagnosis? What new biomarker will provide a look to the future and facilitate clinical intervention and disease prevention? Let's take a trip back in time before the PCR, or even further back, before automated immunoassay systems. Innovation was planting the seeds for these important advances. Scientists and technologists were developing technologies to reach lower levels of clinical detection. Computer scientists and engineers were exploring how to tame the power of the microchip, fluidics, miniaturization, solid-state substrates, and informatics to build integrated clinical systems. While these changes were occurring, molecular biologists were exploring how to use the replication capability of DNA to create a new diagnostic field that has produced major advances in infectious disease testing, cancer diagnostics, and the detection and characterization of anomalies in our genetic code that are associated with disease. If you are an industry strategist, business-development manager, or investor, what technologies and breakthroughs occurring today would you …

Transport and Sensing in Nanofluidic Devices

Ion transport and sensing in nanofluidic devices are receiving a great deal of attention because of their unique transport properties and potential analytical applications. Some aspects of microscale transport transfer directly to the nanoscale, but nanofluidic systems can be significantly influenced by phenomena such as double-layer overlap, surface charge, ion-current rectification, diffusion, and entropic forces, which are either insignificant or absent in larger microchannels. Micro- and nanofabrication techniques create features with a wide range of well-defined geometries and dimensions in synthetic and solid-state substrates. Moreover, these techniques permit coupling of multiple nano- and microscale elements, which can execute various functions. We discuss basic nanofluidic architectures, material transport properties through single and multiple nanochannels, and characterization of single particles by resistive-pulse sensing.

Simulation of the Plasma Gas Condensation Based Synthesis and Extinction Spectra of Gold Nanoparticles

Nanoparticles can be synthesized using solution based or using ultra high vacuum based methods. Das et al.,[1] have already demonstrated nanoparticles of copper on solid state substrates using "plasma gas condensation", a vacuum based synthesis approach. This paper reports the simulation results for the synthesis of gold nanoparticles using plasma gas condensation and a study of their optical properties. The simulations as per [2] for process parameter control for the synthesis of gold nanoparticles using plasma gas condensation are discussed. The interaction of the nanoparticles with light is then studied. The electric field induced at the metal dielectric interface, which is relevant for SERS devices, is also calculated for different sizes of nanoparticles.

Production of haloduracin by Bacillus halodurans using solid-state fermentation

Bacillus halodurans was cultivated on wheat bran as a solid-state substrate and produced haloduracin, a bacteriocin, at about 245AU per wheat bran. Supplementation of the bran with Lauria-Bertani broth decreased haloduracin production. However, production was stimulated by addition of Mg(2)SO(4) and K(2)HPO(4). The highest production was achieved at a wheat bran/moisture ratio of 1:1.8 and in the presence of 10% (w/w) Na(2)CO(3). Under optimum conditions, the organism produced about 3,000AU per gram dry bran.

A comparative study on alkaline lipase production by a newly isolated Aspergillus fumigatus MTCC 9657 in submerged and solid-state fermentation using economically and industrially feasible substrate

A comparative study of solid-state fermentation (SSF) and submerged fermentation (SmF) for the production of alkaline lipase from a new isolate, Aspergillus fumigatus MTCC 9657, using defatted rice bran (DFRB) as a substrate was studied. Different process parameters, such as incubation period, initial pH and incubation temperature, were optimised to achieve the maximum yield of the alkaline lipase. Maximum enzyme production (8.13 U/mL) was obtained by day 7 of incubation in SSF compared to day 4 in SmF at an optimum pH of 8.5 and ambient temperature of 30 °C. Lipase produced by SSF was stable over a period of 15 days, whereas lipase production in SmF decreased by day 5. Lipase production in SSF with DFRB using sterile water as a moisture source exhibited more activity (577.5 U/70 mL) than that supplemented with mineral medium. Compared to the cost of culture medium, the solid-state substrate DFRB is inexpensive, and therefore this process is industrially and economically feasible. These results confirm the interesting potential of SSF in DFRB without any additional nutritional supplement.

Vapor-Phase Facile Coatings of Nanotextured Organic Biocompatible Films on Solid-State Substrates

Fluorinated coatings of solid surfaces are important for many applications ranging from corrosion resistance to low surface energy biological interfaces. We present a facile approach to coat solid-state surfaces directly from vapor phase without harsh chemical or plasma treatments. The coatings show nanostructures with high surface area, which is important for variety of surface functionalizations, for example, in molecule attachment and cell growth. The novel polymeric nanoporous film is achieved from the reaction and deposition of two molecules. The surface morphology and pore sizes of the coating on solid-state surfaces can be tuned with change in concentration of monomers in a simple reaction chamber. The X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy analyses show organic nature of the coating. Cell growth studies are done to gauge biocompatibility and adsorption of proteins and cells. The approach can be used to coat, functionalize, and treat nano- and microstructures for a variety of applications with minimal chemical footprint.

Production of Crude Xylanase from Thermoascus Aurantiacus CBMAI 756 Aiming the Baking Process

In recent years, the baking industry has focused its attention on substituting several chemical compounds with enzymes. Enzymes that hydrolyze nonstarch polysaccharides, such as xylanase, lead to the improvement of rheological properties of dough, loaf specific volume, and crumb firmness. The purpose of this study was to find a better solid-state fermentation substrate to produce high levels of xylanase and low levels of protease and amylase, which are enzymes involved in bread quality, from Thermoascus aurantiacus CBMAI 756. Wheat bran, corncob, and corn straw were used as energy sources. The enzyme extract of corncob showed high xylanase activity (130 U/mL) and low amylase and protease activity (<1 and 15 U/mL, respectively). This enzyme profile may be more profitable for the baking industry, because it results in a slower degradation of gluten. Our results confirm this finding, because the enzyme obtained by fermentation in corncob resulted in a gluten with a higher specific volume than all the other substrates that were tested. The crude xylanase presented maximum activity at a pH of 5, and the optimum temperature was 75 °C. It was stable up to 70 °C for an hour and at a pH range from 4 to 10.

Bending of purple membranes in dependence on the pH analyzed by AFM and single molecule force spectroscopy

The first AFM images of strongly bent purple membranes as well as the first single molecule force spectra of bacteriorhodopsins embedded therein are presented. AFM images of purple membranes to date always showed a flat membrane topology. Bacteriorhodopsin variants like BR-D85N and BR-D85T resemble an intermediate state of wild-type BR which is slightly 'wedge'-shaped. Due to the strong interaction within the 2-D crystalline lattice of the purple membrane, the geometrical anisotropy of the individual bacteriorhodopsins adds up to a macroscopic change in the geometry of the purple membranes. Instead of being flat they appear like domes at physiological conditions. Single molecule force spectroscopy was employed to determine the absolute sign of the membrane curvature. As the bacteriorhodopsins in the center of the dome-like purple membranes are not supported by any solid state substrate, the presented force spectra are the first of non-supported bacteriorhodopsin, resembling the natural occurrence in the halobacterial cell.

Jetting-Out Phenomenon Associated with Bonding of Warm-Sprayed Titanium Particles onto Steel Substrate

Titanium powder particles accelerated and simultaneously heated by the supersonic gas flow were deposited onto steel substrate by the warm spraying process. The sprayed particles were heavily deformed and bonded to the substrate in solid state. Especially, all the deposited particles showed jetting-out of materials out of the particle-substrate interface triggered by the adiabatic shear instability known to occur under such shock impact conditions. High-magnified images showed that grain refinement occurred in the jetting-out region by dynamic recrystallization. Furthermore, the elemental analysis using the electron energy loss spectrum showed jetting-outs of the substrate as well as the particle. Numerical simulation based on the Johnson-Cook plastic deformation model showed that the jetting-out phenomenon commences about 10 ns after the initial contact of the particle with the substrate and at a position away from the center bottom of particle, where the highest compressive stress is experienced.

Conduction Pathway of π-Stacked Ethylbenzene Molecular Wires on Si(100)

One of the most important challenges of molecular electronics is to enable systematic fabrication of molecular functional components on well-characterized solid-state substrates in a controlled manner. Recently, experimental techniques were developed to achieve such fabrication where lines of pi-stacked ethylbenzene molecules are induced to self-assemble on an H-terminated Si(100) surface at precise locations and along precise directions. In this work, we theoretically analyze charge transport properties of these ethylbenzene wires using a state-of-the-art first-principles technique where density functional theory (DFT) is used within the nonequilibrium Green's function formalism (NEGF). Our device model consists of ethylbenzene stacks bonded to an H-terminated Si(100) surface and bridging two metal leads. The electron transmission spectrum and its associated scattering states as well as the resistance of the molecular wire are determined by the self-consistent NEGF-DFT formalism. The transmission spectrum has a resonance nature for energies around the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the ethylbenzene wires. However, near the Fermi level of the device, which sits inside the HOMO-LUMO gap, the Si substrate is found to play an important role in providing additional pathways for conduction. It has emerged that, within our model system, the transmission peak nearest to the Fermi level corresponds to transport through the Si substrate and not the pi-stacked molecular line. The low-bias resistance R is found to increase exponentially with the length of the molecular line n, as R approximately e(betan), indicating a tunneling behavior in conduction. We further found that the exponential scaling has two regimes characterized by two different scaling parameters beta: a high value for conduction through the molecular stack in short lines and a lower value for conduction through the substrate in longer lines. Our results suggest that when the conduction of molecular wires bonded to semiconductor substrates is theoretically analyzed, conduction pathways through the substrate need to be taken into account.

The formation, imaging, and application of thin silicon-dioxide membrane

We have successfully formed and separated a very thin silicon-dioxide (SiO 2) film with a thickness of approx. 1 nm. The thin SiO 2 film was chemically grown on Si using a wet chemical treatment which is commonly used in semiconductor manufacturing. Highly selective etching of the underlying Si, through the native oxide, can be achieved using chlorine (Cl 2) gas. Such a unique phenomenon allows the formation and separation of native oxide from the Si surface. The native oxide film, which is suspended at its edges by thick-SiO 2, remains at the original level of the Si surface even after etching. The suspended Si-native oxide membrane is imaged using scanning electron microscopy (SEM). It is presumably the thinnest separated film ever recorded. The ∼1-nm-thickness SiO 2 membrane suspended by thick-SiO 2 can support subsequent film deposition. The sequential processes of native oxide formation on patterned Si, etching the Si by Cl 2 through the native oxide, and film deposition onto the native oxide membrane, can make a cavity in the solid-state substrate. This novel technique of creating a cavity by using a membrane of Si-native oxide can be applied to fabricate 3D micro-systems like pipes, diaphragms, tubes, and wave-guides on the solid-state circuits.

Structural and electronic properties of pentacene/pentacenequinone thin films prepared by Langmuir–Blodgett technique

Structural and electronic properties of pentacene/pentacenequinone thin films prepared on various solid-state substrates by the Langmuir–Blodgett technique are reported. Amorphous structure of the prepared films has been proved by XRD measurements. Oxygen-related defects have been identified in the Langmuir–Blodgett films as a consequence of the exposure of pentacene Langmuir layer to air. Crystallization induced by thermal treatment of the prepared amorphous thin films has been observed. Electronic properties of pentacene/ pentacenequinone Langmuir–Blodgett films have been investigated in the contact-less architecture using electrochemical techniques. The energy band diagram of the amorphous pentacene/pentacenequinone Langmuir–Blodgett film on a metallic surface was constructed from the obtained electrochemical data.