Surface Of Solid Substrate Research Articles

Electrochemiluminescence Biosensor Based on Conducting Poly(5-formylindole) for Sensitive Detection of Ramos Cells

A signal-on electrochemiluminescence (ECL) biosensor devoted to the detection of Ramos cells was fabricated based on a novel conducting polymer, poly(5-formylindole) (P5FIn), which was synthesized electrochemically by direct anodic oxidation of 5-formylindole (5FIn). This ECL platform was presented by covalently coupling the 18-mer amino-substituted oligonucleotide (ODN) probes with aldehyde groups that are strongly reactive toward a variety of nucleophiles on the surface of solid substrates. The specific identification and high-affinity between aptamers and target cells, gold nanoparticles (AuNPs) enhanced ECL nanoprobes, along with P5FIn induced ECL quenching contributed greatly to the sensitivity and selectivity. The ECL signals were logarithmically linear with the concentration of Ramos cells in a wide determination range from 500 to 1.0 × 10(5) cells mL(-1), and the corresponding detection limit was 300 cells mL(-1).

AgAu Bimetallic Janus Nanoparticles and Their Electrocatalytic Activity for Oxygen Reduction in Alkaline Media

Bimetallic AgAu Janus nanoparticles were prepared by galvanic exchange reactions of 1-hexanethiolate-passivated silver (AgC6) nanoparticles with gold(I)-mercaptopropanediol complex. The AgC6 nanoparticles were deposited onto a solid substrate surface by the Langmuir-Blodgett method such that the galvanic exchange reactions were limited to the top face of the nanoparticles that was in direct contact with the gold(I) complex solution. The resulting nanoparticles exhibited an asymmetrical distribution not only of the organic capping ligands on the nanoparticle surface but also of the metal elements in the nanoparticle cores, in contrast to the bulk-exchange counterparts where these distributions were homogeneous within the nanoparticles, as manifested in contact angle, UV-vis, XPS, and TEM measurements. More interestingly, despite a minimal loading of Au onto the Ag nanoparticles, the bimetallic AgAu nanoparticles exhibited enhanced electrocatalytic activity in oxygen reduction reactions, as compared to the monometal AgC6 nanoparticles. Additionally, the electrocatalytic performance of the Janus nanoparticles was markedly better than the bulk-exchange ones, suggesting that the segregated distribution of the polar ligands from the apolar ones might further facilitate charge transfer from Ag to Au in the nanoparticle cores, leading to additional improvement of the adsorption and reduction of oxygen.

Preparation and probe analysis of Langmuir–Blodgett films with metal-containing dendritic and cluster structures

We aim to reveal the influence of pH values of the working solution on spatial arrangement of metal-containing inclusions in the monolayer coatings prepared by Langmuir–Blodgett (LB) technology and transferred to solid substrates with consequent modification of surface electrical properties. Consequently, films with inclusions in the form of dendrites and cluster shapes have been obtained. Submicron and micron lead-containing formations in Langmuir–Blodgett films have been characterized by using the atomic force microscopy, Kelvin probe microscopy, and scanning electron microscopy methods. The results show that increasing pH value of the subphase has caused the significant changes in the shape and composition of the inclusions in Langmuir–Blodgett films. The synthesized inclusions on the solid substrate surface resulted in formation of the regions with the local electric fields and, as consequence, to significant modification of the structure and electrical properties. The location and length of the regions with surface potential disturbance depend on the shape of inclusions, and consequently, on pH value of the subphase used in LB technology.

Heat resistance in Saccharomyces cerevisiae yeast

Saccharomyces cerevisiae yeast grow mainly on the surface of solid or liquid substrates. The life cycle of such microbial populations is substantially influenced by diurnal ambient temperature variation. The response of an unrestricted S. cerevisiae yeast culture to temperature changes has been studied in experiments. With the absence of environmental constraints on the operation of the cell chemiosmotic energy system, the culture remains heat-resistant when the growth temperature is switched from 12–36°C to 37.5–40°C. As a result, the yeast reproduction rate remained 1.5–2 times higher than under stationary conditions for one to four turnover cycles after the transition. This observation is explained by the adaptive potential of the chemiosmotic system acquired in the course of evolution. When the adaptive resource is exhausted, heat resistance is restored at 12–36°C within one generation with restricted or unrestricted nourishment. The adaptive significance of heat resistance is obvious: it keeps the reproduction rate high when the ambient temperature reaches a brief maximum shortly after noon.

(Invited) Advances in Si and Ge Millisecond Processing: From SOI to Superconductivity and Carrier-Mediated Ferromagnetism

This paper reviews the advances that millisecond thermal processing using flash lamps and lasers brings to the processing of the most advanced semiconductor materials, namely silicon and germanium, thus enabling the fabrication of novel microelectronic structures and materials. It will be demonstrated how such developments can translate into important practical applications leading to a wide range of technological benefits. Opportunities in ultra-shallow junction formation for silicon-on-insulator, superconducting Ge and Si, and diluted ferromagnetic Ge, along with the technical reasons for using annealing times in the ms range are discussed in the context of state-of-the-art materials processing. Whereas these examples are based on solid phase processing, the more sophisticated approach regards on working with the liquid phase at the surface of solid substrates. As a recent example the controlled surface melting of a Ge enriched silicon substrate is reported.

Photocontrollable Water Permeation on the Micro/Nanoscale Hierarchical Structured ZnO Mesh Films

Most research of responsive surfaces mainly focus on the wettability transition on different solid substrate surfaces, but the dynamic properties of the micro/nanostructure-enhanced responsive wettability on microscale pore arrays are lacking and still remain a challenge. Here we report the photocontrollable water permeation on micro/nanoscale hierarchical structured ZnO-coated stainless steel mesh films. Especially, for aligned ZnO nanorod array-coated stainless steel mesh film, the film shows good water permeability under irradiation, while it is impermeable to water after dark storage. A detailed investigation indicates that the special nanostructure and the appropriate size of the microscale mesh pores play a crucial role in the excellent controllability over water permeation. The excellent controllability of water permeation on this film is promising in various important applications such as filtration, microreactor, and micro/nano fluidic devices. This work may provide interesting insight into the design of novel functional devices that are relevant to surface wettability.

Ordered nano-structure of a stamped self-organized protein layer on a HOPG surface using a HFB carrier

A groundbreaking method for ordered molecular layer preparation on a solid surface employing the drop-stamp method has been developed by us taking advantage of the characteristics of the HFB molecule as a self-organizer/adsorption carrier. It is a smart method which can be used to prepare a self-organized protein layer on a solid surface without unspecific adsorption or defects. In our previous report, we clarified the self-organizing nature of HFB-tagged protein molecules on a surface of a solution droplet. In this report, a protein layer was prepared on a HOPG surface by using the drop-stamp method with a maltose binding protein (MBP)-tagged HFBII molecule. The structure of the stamped protein layer was investigated using frequency modulation atomic force microscopy (FM-AFM) in a liquid condition. The FM-AFM images show that the drop-stamp method can prepare an ordered protein layer on a solid surface smartly. The drop-stamp method using a HFB carrier is a practical method which can be used to prepare an ordered protein layer on a solid substrate surface without unspecific adsorption defects.

Stability of a plane jet of a highly viscous fluid impinging on a horizontal solid wall

In a plane formulation, we consider a viscous-fluid jet flowing out of a rectangular channel and interacting with a horizontal solid substrate surface in the presence of gravity. The mathematical problem is formulated within the creeping flow approximation. For the numerical solution, a boundary-element method is used. The kinematic parameters of the jet and the evolution of the free surface are studied for different values of governing parameters. The critical values of the distance from the channel outlet to the solid wall are found. For the heights, greater than the critical value, the jet loses stability, which is manifested in the periodic buckling of the jet. A flow regime characterized by damped oscillations is described.

Development of Film Sensors Based on Conjugated Polymers for Copper (II) Ion Detection

AbstractA fluorescent film sensor was prepared by chemical modification of a polyfluorene derivative on a glass‐plate surface. X‐ray photoelectron spectroscopy and ellipsometry measurements demonstrate the covalent attachment of the polyfluorene derivative to the glass‐plate surface. The sensor was used to detect Cu2+ ions in aqueous solution by a mechanism exploiting fluorescence quenching of conjugated polymers. Among the tested metal ions, the film sensor presents good selectivity towards Cu2+ ions. Further experiments show that the sensing process is reversible. Moreover, sensory microarrays based on conjugated polymers targeting Cu2+ ions are constructed, which display similar sensing performance to that of the film sensor. The structural motif in which conjugated polymers are covalently confined to a solid substrate surface offers several attractive advantages for sensing applications. First, in comparison with film sensors in which small fluorescent molecules are employed as sensing elements, the sensitivity of our new film sensor is enhanced due to the signal‐amplifying effect of the conjugated polymers. Second, the film sensors or microarrays can be used in aqueous environments, which is crucial for their potential use in a wide range of real‐world systems. Since the sensing process is reversible, the sensing materials can be reused. Third, unlike physically coated polymer chains, the covalent attachment of the grafted chains onto a material surface precludes desorption and imparts long‐term stability of the polymer chains.

On surfactant-enhanced spreading and superspreading of liquid drops on solid surfaces

The mechanisms driving the surfactant-enhanced spreading of droplets on the surface of solid substrates, and particularly those underlying the superspreading behaviour sometimes observed, are investigated theoretically. Lubrication theory for the droplet motion, together with advection–diffusion equations and chemical kinetic fluxes for the surfactant transport, leads to coupled evolution equations for the drop thickness, interfacial concentrations of surfactant monomers and bulk concentrations of monomers and micellar, or other, aggregates. The surfactant can be adsorbed on the substrate either directly from the bulk monomer concentrations or from the liquid–air interface through the contact line. An important feature of the spreading model developed here is the surfactant behaviour at the contact line; this is modelled using a constitutive relation, which is dependent on the local surfactant concentration. The evolution equations are solved numerically, using the finite-element method, and we present a thorough parametric analysis for cases of both insoluble and soluble surfactants with concentrations that can, in the latter case, exceed the critical micelle, or aggregate, concentration. The results show that basal adsorption of the surfactant plays a crucial role in the spreading process; the continuous removal of the surfactant that lies upon the liquid–air interface, due to the adsorption at the solid surface, is capable of inducing high Marangoni stresses, close to the droplet edge, driving very fast spreading. The droplet radius grows at a rate proportional to ta with a = 1 or even higher, which is close to the reported experimental values for superspreading. The spreading rates follow a non-monotonic variation with the initial surfactant concentration also in accordance with experimental observations. An accompanying feature is the formation of a rim at the leading edge of the droplet. In some cases, the drop spreads to form a ‘pancake’ or creates a ‘secondary’ front separated from the main droplet.

FA cellular automaton model of crystalline cellulose hydrolysis by cellulases

BackgroundCellulose from plant biomass is an abundant, renewable material which could be a major feedstock for low emissions transport fuels such as cellulosic ethanol. Cellulase enzymes that break down cellulose into fermentable sugars are composed of different types - cellobiohydrolases I and II, endoglucanase and β-glucosidase - with separate functions. They form a complex interacting network between themselves, soluble hydrolysis product molecules, solution and solid phase substrates and inhibitors. There have been many models proposed for enzymatic saccharification however none have yet employed a cellular automaton approach, which allows important phenomena, such as enzyme crowding on the surface of solid substrates, denaturation and substrate inhibition, to be considered in the model.ResultsThe Cellulase 4D model was developed de novo taking into account the size and composition of the substrate and surface-acting enzymes were ascribed behaviors based on their movements, catalytic activities and rates, affinity for, and potential for crowding of, the cellulose surface, substrates and inhibitors, and denaturation rates. A basic case modeled on literature-derived parameters obtained from Trichoderma reesei cellulases resulted in cellulose hydrolysis curves that closely matched curves obtained from published experimental data. Scenarios were tested in the model, which included variation of enzyme loadings, adsorption strengths of surface acting enzymes and reaction periods, and the effect on saccharide production over time was assessed. The model simulations indicated an optimal enzyme loading of between 0.5 and 2 of the base case concentrations where a balance was obtained between enzyme crowding on the cellulose crystal, and that the affinities of enzymes for the cellulose surface had a large effect on cellulose hydrolysis. In addition, improvements to the cellobiohydrolase I activity period substantially improved overall glucose production.ConclusionsCellulase 4D simulates the enzymatic hydrolysis of cellulose to glucose by surface and solution phase-acting enzymes and accounts for complex phenomena that have previously not been included in cellulose hydrolysis models. The model is intended as a tool for industry, researchers and educators alike to explore options for enzyme engineering and process development and to test hypotheses regarding cellulase mechanisms.

On the Thermal Stability of Surface-Assembled Viral-Metal Nanoparticle Complexes

Biological supramolecules offer attractive templates for nanoparticle synthesis and nanodevice fabrication because of their precise size and shape. Viruses in particular have gained significant attention in nanodevice fabrication for applications such as nanoelectronics, batteries, catalysis, and sensing. However, the performance range of these viral-nanoparticle complexes is not well known because of the lack of fundamental studies on their properties. In this work, we employ in situ grazing incidence small-angle X-ray scattering (GISAXS) to examine the thermal stability of viral-nanoparticle complexes composed of tobacco mosaic virus (TMV) and palladium nanoparticles. Specifically, we show that the stability of the Pd nanoparticles on TMV is significantly enhanced as compared to that of particles on the solid substrate surface. Furthermore, we show that the agglomeration of Pd nanoparticles and the degradation of the TMV templates are coupled and occur simultaneously. These results demonstrate a potent methodology toward the in situ analysis of subtle changes in viral-nanoparticle complexes in dynamic environments. We envision that the results and methodology demonstrated in this study could be applied to better understand the properties and dynamic behaviors of organic-inorganic hybrid materials and nanodevices in various applications.

Surfactant-Enhanced Rapid Spreading of Drops on Solid Surfaces

We study the surfactant-enhanced spreading of drops on the surfaces of solid substrates. This work is performed in connection with the unique ability of aqueous trisiloxane solutions to wet highly hydrophobic substrates effectively, which has been studied for nearly two decades. We couple a lubrication model to advection-diffusion equations for surfactant transport. We allow for micelle formation and breakup in the bulk and adsorptive flux at both the gas-liquid and liquid-solid interfaces and use appropriate equations of state to model variations in surface tension and wettability. Our numerical results show the effect of basal adsorption, kinetic rates, and the availability of surfactant on the deformation of the droplet and its spreading rate. We demonstrate that this rate is maximized for intermediate rates of basal adsorption and the total mass of surfactant.

Acceleration of the Enzymatic Hydrolysis of Corn Stover and Sugar Cane Bagasse Celluloses by Low Intensity Uniform Ultrasound

SouthernRegionalResearchCenter,1100RobertE.LeeBlvd,NewOrleans,LA70124,USThe cost-competitive production of bio-ethanol and other biofuels is currently impeded, mostly bythe high cost and the low efficiency of enzymatic hydrolysis of feedstock biomass and especiallyplant celluloses. Despite substantial reduction in the cost of production of cellulolytic enzymes inrecent times, the conversion of plant cellulose into sugars still remains an expensive and slow step.Our research has found that the introduction of a low energy, uniform ultrasound field into enzymeprocessing solutions greatly improved their effectiveness by significantly increasing their reactionrate. It has been established that the following specific features of combined enzyme/ultrasoundbio-processing are critically important: (a) cavitation effects caused by introduction of ultrasoundfield into the enzyme processing solution greatly enhance the transport of enzyme macromoleculestoward the substrate’s surface, (b) mechanical impacts, produced by the collapse of cavitation bub-bles, provide an important benefit of “opening up” the surface of solid substrates to the action ofenzymes, (c) the effect of cavitation is several hundred times greater in heterogeneous systems(solid substrate–liquid) than in homogeneous, and (d) in water, the maximum effects of cavitationoccur at ∼50 C, which is the optimum temperature for many enzymes. On a laboratory scale, intro-duction of low level, uniform ultrasonic energy in the reaction chamber during enzymatic hydrolysisof corn stover and sugar cane bagasse cellulose samples resulted in a significant improvement inenzyme efficiency. The combined enzyme/sonication hydrolysis of corn stover, bagasse and similarplant celluloses could significantly accelerate this critical step in the overall conversion of agriculturalwaste biomass into biofuels.

Monolayer and multilayer compact film formations on different substrates by physical deposition

AbstractDissipative particle dynamics simulations are applied to investigate the monolayer and multilayer film formations on different solid substrates by physical deposition. The influences of the polymer concentration, the polymer chain length, the solvent quality, and the interactions between the polymer solution and the solid substrate surface on the film formation dynamics and the mechanism are studied in detail. The results are analyzed in terms of the thickness and the shape of the deposited film, the kinetics of phase separation in the polymer solution, and the contact angle formed between the polymer aggregations and the substrate surface. Moreover, we suggest two strategies, designing a deposition process analogous to “chemical titration” and physically blocking interlayer diffusion by a simple crosslinked network barrier, to deposit the compact monolayer and multilayer films with better quality, respectively. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 353–365, 2009

Dynamics of surfactant-assisted spreading

The presence of surface-active molecules at interfaces reduces the surface tension, and this property is exploited to drive the spreading of fluid films on the surface of liquid and solid substrates. Surfactant-assisted spreading gives rise to fascinating phenomena that involve complex dynamics and pattern formation; as a result, it has received considerable attention in the literature. This article provides a review of previous work and highlights the important open problems in this area.

Borderline polymerization of aniline: Interpretation in the context of the electrical double layer model

The oxidative polymerization of aniline has been studied under heterophase conditions on the surface of solid and liquid substrates. It has been shown that the kinetic features and the structure of the products of heterophase synthesis differ appreciably from the corresponding characteristics of the process occurring in the bulk of the reaction solution. Formation of the polyaniline layer at the interface may be attributed to two independent reactions, namely, borderline and adsorption polymerizations. Only the first process is responsible for formation the ordered polymer coating. In the context of the electrical double layer model, the mechanism of the borderline polymerization best corresponds to the experimental data.

Plasma Modification of Solid and Porous Polyethylene

AbstractThe use of electron beam generated plasmas to modify the surface of solid and porous polyethylene substrates is discussed. In both cases, the hydrophobicity of the material was increased by exposing the substrates to electron beam generated plasmas produced in Ar/SF6 mixtures. The solid material studies served as a basis for understanding the plasma‐induced changes at the substrate surface, while the porous material was treated using a system designed for two‐sided processing applications and proved to be the best way to maximize treatment. Plasma diagnostics were used to characterize the ion and neutral fluxes at the substrates and thereby obtain a better understanding of the plasma–polymer interaction.magnified image

Scanning probe microscopic and optical detection of DNA integration within multicomponent structures on Si surfaces

Self-arrangement of DNA based structures on clean mica and modied Si surfaces is investigated by means of scanningprobe microscope (SPM) and spectroscopic ellipsometry (SE) method. DNA strands are deposited from a colloidal solutionon solid surfaces at room temperature. Surfaces of solid substrates and biomolecular structures are additionally modied byAg nanoparticles. The self-arranged surface structures are visualized by SPM. The effect of the multicomponent structureson the optical response of complex hybrid structures is studied. Changes in the optical response of the hybrid samples arerelated to the contributions of self-assembled DNA-based structures and Ag nanoparticles on the Si surfaces. Binding of Agnanoparticles to the DNA strands and formation of well-ordered structures on the surfaces with DNA are discussed.

Laser-Driven Acoustic Desorption of Organic Molecules from Back-Irradiated Solid Foils

Laser-induced acoustic desorption (LIAD) from thin metal foils is a promising technique for gentle and efficient volatilization of intact organic molecules from surfaces of solid substrates. Using the single-photon ionization method combined with time-of-flight mass spectrometry, we have examined the neutral component of the desorbed flux in LIAD and compared it to that from direct laser desorption. These basic studies of LIAD, conducted for molecules of various organic dyes (rhodamine B, fluorescein, anthracene, coumarin, BBQ), have demonstrated detection of intact parent molecules of the analyte even at its surface concentrations corresponding to a submonolayer coating. In some cases (rhodamine B, fluorescein, BBQ), the parent molecular ion peak was accompanied by a few fragmentation peaks of comparable intensity, whereas for others, only peaks corresponding to intact parent molecules were detected. At all measured desorbing laser intensities (from 100 to 500 MW/cm2), the total amount of desorbed parent molecules depended exponentially on the laser intensity. Translational velocities of the desorbed intact molecules, determined for the first time in this work, were of the order of hundreds of meters per second, less than what has been observed in our experiments for direct laser desorption, but substantially greater than the possible perpendicular velocity of the substrate foil surface due to laser-generated acoustic waves. Moreover, these velocities did not depend on the desorbing laser intensity, which implies the presence of a more sophisticated mechanism of energy transfer than direct mechanical or thermal coupling between the laser pulse and the adsorbed molecules. Also, the total flux of desorbed intact molecules as a function of the total number of desorbing laser pulses, striking the same point on the target, decayed following a power law rather than an exponential function, as would have been predicted by the shake-off model. To summarize, the results of our experiments indicate that the LIAD phenomenon cannot be described in terms of simple mechanical shake-off or direct laser desorption. Rather, they suggest that multistep energy-transfer processes are involved. Two possible (and not mutually exclusive) qualitative mechanisms of LIAD that are based on formation of nonequilibrium energy states in the adsorbate-substrate system are proposed and discussed.