Selective chemisorption of end-functionalized conjugated polymer on macro- and nanoscale surfaces

Linear and conjugated poly(p-phenylene ethynylene)s (PPEs) with three different types of functionalized end groups (thiolacetate, isocyanide, and carboxylic acid groups) were synthesized, and their selective chemisorption behavior on various substrate surfaces were investigated using UV/vis transmission absorption spectroscopy. The UV/vis spectra of the PPEs were clearly dependent on the chemical affinity between the PPE end group and the solid surfaces. Furthermore, regarding the chemisorption of thiolacetate modified polymer on a nanoscopic gold particle surface, we visualized novel polymer-colloid nanoarchitectures such as a barbell-type nanohybrid and interconnected polymer nanowire structures that are successively linked through gold nanoparticles.     

Electrodes in stripping voltammetry: from a macro- to a micro- and nano-structured surface

A correlation between the morphology of the solid surface and electrochemical response was found in microscopic and electrochemical investigations. A shift of the oxidation potentials of metals to more negative values was observed on electrodes with microstructured surface with respect to similar processes on macrostructured electrodes. The formation of passivating films, causing reverse current and deteriorating the analytical signal, was not observed, and the performance characteristics of voltammetric procedures were improved. The experimental data indicated the increased electrochemical activity of modifying metal particles with a decrease in the particle size. As a result of the deliberate change of the surface composition and the formation of a micro- and nano-structured surface, a new generation of electrodes was developed with excellent electroanalytical characteristics.     

Thermooptical detection in microchips: from macro- to micro-scale with enhanced analytical parameters

In this paper, we compared the methods of photothermal spectroscopy used in different spatial scales, namely thermal-lens spectrometry (TLS) and thermal-lens microscopy (TLM) to enhance the performance parameters in analytical procedures. All of the experimental results were confirmed by theoretical calculation. It was proven that the design for both TLM and TLS, despite a different scale for the effect, is governed by the same signal-generating and probing conditions (probe beam diameter at the sample should be equal to the diameter of the blooming thermal lens), and almost does not depend on the nature of the solvent. Theoretical and experimental instrumental error curves for thermal lensing were coincident. TLM obeys the same law of instrumental error as TLS and shows better repeatability for the same levels of thermal-lens signals or absorbances. TLS is more advantageous for studying low concentrations in bulk, while TLM shows much lower absolute LODs due to better repeatability for low amounts. The behavior of the thermal-lens signal with different flow rates was studied and optimum conditions, with the minimum contribution to total error, were found. These conditions are reproducible, are in agreement with the existing theory of the thermal response in thermal lensing, and do not significantly affect the design of the optimum scheme for setups. TLM showed low LODs in solvent extraction (down to 10(-8) M) and electrokinetic separation (10(-7) M), which were shown to be governed by discussed instrumental regularities, instead of by microchemistry.     

Ion current rectification: from nanoscale to microscale

Ion current rectification(ICR) is an electrodynamic phenomenon in electrolyte solution which is defined as the asymmetric potential-dependent ion flux through a confined environment, giving rise to asymmetric electrical current-voltage characteristics induced by the influence of an asymmetric electrical double layer structure. Since the discovery of the ICR phenomenon, the observation and application of ICR at nanoscale and microscale have been widely investigated experimentally and theoretically.Here, the recent progress of ICR from nanoscale to microscale is systematically reviewed. Nano/micropore structures of different materials, shapes and pore sizes are first discussed. Then, the factors influencing ICRs by thermodynamically or kinetically regulating the electrical double layer structure are introduced. Moreover, theoretical models are presented to explain the mechanism of ICRs. Based on the understanding of this phenomenon, the applications, especially in biosensors, are discussed.Finally, future developments of this area are briefly presented. This review covers the representative related literature published since 2010 and is intended to give a systematic introduction to this area.     

Confinement effects on the structure and dynamics of polymer systems from the mesoscale to the nanoscale

In this article, we review some of our recent progress in experimental and simulation methods for generating, characterizing, and modeling polymer microparticles and nanoparticles in a number of polymer and polymer‐blend systems. By using instrumentation developed for probing single fluorescent molecules in micrometer‐sized liquid droplets, we have shown that polymer particles of nearly arbitrary size and composition can be made with a size dispersion that is ultimately limited by the chain length and number distribution within the droplets. Depending on the timescale for solvent evaporation—a tunable parameter in our experiments—the phase separation of otherwise immiscible polymers can be avoided by confinement effects, and homogeneous polymer‐blend microparticles or nanoparticles can be produced. These particles have tunable properties that can be controlled by the simple adjustment of the size of the particle or the relative mass fractions of the polymer components in solution. Physical, optical, and mechanical properties of a variety of microparticles and nanoparticles, differing in size and composition, have been examined with extensive classical molecular dynamics calculations in conjunction with experiments to gain deeper insights into the fundamental nature of their structure, dynamics, and properties. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1571‐1590, 2005     

Advances in aqueous biphasic systems for biotechnology applications

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Adsorptive separation using self-assembly on graphite: from nanoscale to bulk processes

Adsorptive separation is a promising lower-energy alternative for traditional industrial separation processes. While carbon-based materials have a long history in adsorptive removal of organic contaminants from solution or gas mixtures, separation using an adsorption/desorption protocol is rarely considered. The main drawbacks are the limited control in bulk adsorption experiments, as often all organic molecules are adsorbed, and lack of desorption methods to retrieve the adsorbed molecules. Using high-resolution on-surface characterization with scanning tunneling microscopy (STM), an increased understanding of the on-surface adsorption behavior under different conditions was obtained. The insight obtained from the nanoscale experiments was used to develop a highly selective separation method using adsorption and desorption on graphite, which was tested for the separation of quinonoid zwitterions. These experiments on adsorptive separation using self-assembly on graphite show its potential and demonstrate the advantage of combining surface characterization techniques with bulk experiments to exploit different possible applications of carbon-based materials.

Insights from high-resolution on-surface characterization techniques are used to improve the control over adsorption and desorption on graphite in bulk adsorptive separation processes.     

Immobilization of nanofibrous metal oxides on microfibers: a macrostructured catalyst system functionalized with nanoscale fibrous metal oxides

Nanofibrous LaMnO(3) can be immobilized on macrostructured materials using carbon nanofibers as templates; their application as macro-nanostructured catalysts are also presented.     

Simulating molecular shuttle movements: towards computer-aided design of nanoscale transport systems

Molecular shuttles based on the motor protein kinesin and microtubule filaments have the potential to extend the lab-on-a-chip paradigm to nanofluidics by enabling the active, directed and selective transport of molecules and nanoparticles. Based on experimentally determined parameters, in particular the trajectory persistence length of a microtubule gliding on surface-adhered kinesin motors, we developed a Monte-Carlo simulation, which models the transport properties of guiding structures, such as channels, rectifiers and concentrators, and reproduces the properties of several experimentally realized systems. Our tool facilitates the rational design of individual guiding structures as well as whole networks, and can be adapted to the simulation of other nanoscale transport systems.     

Switch from intra- to intermolecular H-bonds by ultrasound: induced gelation and distinct nanoscale morphologies

During cooling of the ( R)-N-Fmoc-Octylglycine (Fmoc-OG)/cyclohexane solution, gelation is observed exclusively when ultrasound is used as an external stimulus, while deposit is obtained without sonication. The xerogel consists of entangled fibrous network made by interconnected nanofibers, while the deposit comprises large numbers of unbranched nanowires. It is found that the Fmoc-OG molecules form bilayer structures in both the deposit and the gel. However, the ratio ( R) between the Fmoc-OG molecules in a stable intramolecular H-bonding conformation and those in a metastable intermolecular H-bonding conformation can be tuned by the ultrasound, R (deposit) > R (gel). The increased population of the intermolecular H-bonding Fmoc-OG molecules induced by the ultrasonication facilitates to the interconnection of nanofibers for the formation of the fibrous network, and therefore gelation. The alteration in the morphologies and properties of the obtained nanomaterials induced by the ultrasound wave demonstrates a potential method for smart controlling of the functions of nanomaterials from the molecular level.     

Forces in nematic liquid crystals: from nanoscale interfacial forces to long-range forces in nematic colloids

In this paper we give an overview of experiments that provided an insight into the nature of forces between surfaces and objects in a nematic liquid crystal. These forces, also called ‘structural forces’, are the consequence of the long-range orientational order and orientational elasticity of nematic liquid crystals. Owing to their fundamental as well as technological importance, forces between objects in liquid crystals have been a subject of growing interest during the last decade. Experimental observations and studies of structural forces are described from nanoscale interfacial forces, measured by an atomic force microscope, to the micro-scale forces between colloidal particles in nematics, studied by laser tweezers and optical video microscopy.     

Immobilization of scandium and other chemical elements in systems with aquatic macrophyte

The possibility of immobilization of scandium and other chemical elements by biogenic materials derived from an aquatic macrophyte was explored. The concentrations of scandium and some other chemical elements were measured in the dried biomass (mortmass) of aquatic plants Myriophyllum aquaticum. In the experiments, the mortmass was incubated in aquatic systems where some chemical elements were added to the aquatic medium. After the incubation, the concentrations of these chemical elements in the mortmass were measured using inductively coupled plasma atomic emission spectroscopy (ICP-AES), also referred to as inductively coupled plasma optical emission spectrometry (ICP-OES). Increases in the concentrations of scandium and some other chemical elements (Ce, In, Se, Ru, Pd, U, and Zr) were observed in the biogenic material.     

Magnetic iron oxide nanoparticles for biorecognition: evaluation of surface coverage and activity

Modifying the surfaces of magnetic nanoparticles (MNPs) by the covalent attachment of biomolecules will enable their implementation as contrast agents for magnetic resonance imaging or as media for magnetically assisted bioseparations. In this paper we report both the surface coverage and the activity of IgG antibodies on MNPs. The antibodies were immobilized on gamma-Fe2O3 nanoparticles by conventional methods using aminopropyltriethoxy silane and subsequent activation by glutaraldehyde. Novel fluorescence methods were used to provide a quantitative evaluation of this well-known approach. Our results show that surface coverage can be stoichiometrically adjusted with saturated surface coverage occurring at approximately 36% of the theoretical limit. The saturated surface coverage corresponds to 34 antibody molecules bound to an average-sized MNP (32 nm diameter). We also show that the immobilized antibodies retain approximately 50% of their binding capacity at surface-saturated levels.     

SIMONA 1.0: An efficient and versatile framework for stochastic simulations of molecular and nanoscale systems

Molecular simulation methods have increasingly contributed to our understanding of molecular and nanoscale systems. However, the family of Monte Carlo techniques has taken a backseat to molecular dynamics based methods, which is also reflected in the number of available simulation packages. Here, we report the development of a generic, versatile simulation package for stochastic simulations and demonstrate its application to protein conformational change, protein–protein association, small-molecule protein docking, and simulation of the growth of nanoscale clusters of organic molecules. Simulation of molecular and nanoscale systems (SIMONA) is easy to use for standard simulations via a graphical user interface and highly parallel both via MPI and the use of graphical processors. It is also extendable to many additional simulations types. Being freely available to academic users, we hope it will enable a large community of researchers in the life- and materials-sciences to use and extend SIMONA in the future. SIMONA is available for download under http://int.kit.edu/nanosim/simona . © 2012 Wiley Periodicals, Inc.