Bio-initiated light addressable potentiometric sensor for unlabeled biodetection and its MEDICI simulation

A bio-mimetic anchoring strategy based on L-3,4-dihydroxyphenylalanine (L-DOPA) was exploited to activate the surface of light addressable potentiometric sensor (LAPS), with the structure of Si(3)N(4)/SiO(2)/Si. X-Ray photoelectron spectroscopy (XPS) measurements were carried out to ascertain its existence. The protein's immobilization on L-DOPA-initiated LAPS were also tested by our LAPS system. Then L-DOPA-activated LAPS were applied in the unlabeled rabbit anti-mouse immunoglobulin (IgG) detection. The maximum sensitivity of L-DOPA-activated LAPS to antigen (Ag) is about 5.68 nA/p[Ag]. LAPS responses in IgG measurements were from 95 to 180 nA, when the concentration was varied from 0-4 μg mL(-1). These experiments show that L-DOPA is an available material for LAPS surface modifications. At the same time, simulations based on MEDICI (Synopsys?) were performed. The simulated curves are in accordance with experimental data which demonstrate our theoretical analysis for the experimental phenomenon, and indicate the feasibility of simulating biological electronic devices with MEDICI.     

An adiabatic scanning calorimetry study of a chiral liquid crystal tolane with blue phases and twist grain boundary phases

High resolution adiabatic scanning calorimetry (ASC) was employed to study the phase behaviour exhibited by the chiral liquid crystal material (R)-1-methylheptyl 3-fluoro-4- (3-fluoro-4-octadecyloxybenzoyloxy)tolane-4-carboxylate (FH/FH/HH-18BTMHC). We report on the heat capacity of the different phases and phase transitions as well as the enthalpy changes of the material showing a phase sequence Cr-SmC*-TGBC-TGBA-BPI-BPIIBPIII-I. While the presence of the BPI phase was observed in previous DSC studies only on cooling the sample, our ASC measurements detected this phase also in the heating runs at sufficiently slow scanning rates. Indications of smectic order still present in the blue phases, as recently reported from X-ray scattering experiments, are also observed.     

X-ray photoelectron spectroscopic studies of hydrophilic surfaces modified via admicellar polymerization

Admicellar polymerization with styrene monomer was used to coat the surface of two porous solids: titanium dioxide and alumina. X-ray photoelectron spectroscopy (XPS) measurements clearly indicate that after admicellar polymerization, organic material and surfactant are present on the surface of the solids. Water washes, performed immediately after admicellar polymerization, were successful in removing approximately 30% of the organic material, presumably mostly surfactant. The water wash was followed by Soxhlet extraction with toluene, with no measurable removal of organic material according to ignition loss measurements of the solid, gel permeation chromatography of the extracting solvent and also UV/VIS spectroscopy of the extracting solvent. However, there was a 5-15% drop in organic material after Soxhlet extraction according to XPS measurements. This difference is attributed to the difference in sampling; XPS samples only the exterior surface area while these bulk measurements sample both the interior and exterior surface area. This study details the ability of different washing steps to remove materials from the porous substrates used in this study.     

Isotope abundance ratio measurements using femtosecond laser ablation ionization mass spectrometry

Accurate isotope ratio measurements are of high importance in various scientific fields, ranging from radio isotope geochronology of solids to studies of element isotopes fractionated by living organisms. Instrument limitations, such as unresolved isobaric inferences in the mass spectra, or cosampling of the material of interest together with the matrix material may reduce the quality of isotope measurements. Here, we describe a method for accurate isotope ratio measurements using our laser ablation ionization time‐of‐flight mass spectrometer (LIMS) that is designed for in situ planetary research. The method is based on chemical depth profiling that allows for identifying micrometer scale inclusions embedded in surrounding rocks with different composition inside the bulk of the sample. The data used for precise isotope measurements are improved using a spectrum cleaning procedure that ensures removal of low quality spectra. Furthermore, correlation of isotopes of an element is used to identify and reject the data points that, for example, do not belong to the species of interest. The measurements were conducted using IR femtosecond laser irradiation focused on the sample surface to a spot size of ~12 μm. Material removal was conducted for a predefined number of laser shots, and time‐of‐flight mass spectra were recorded for each of the ablated layers. Measurements were conducted on NIST SRM 986 Ni isotope standard, trevorite mineral, and micrometer‐sized inclusions embedded in aragonite. Our measurements demonstrate that element isotope ratios can be measured with accuracies and precision at the permille level, exemplified by the analysis of B, Mg, and Ni element isotopes. The method applied will be used for in situ investigation of samples on planetary surfaces, for accurate quantification of element fractionation induced by, for example, past or present life or by geochemical processes.     

Problems with the determination of heavy metals in precipitation

Summary Wet deposition is mostly determined by collecting precipitation in wet-only collectors equipped with funnels or buckets. During an intercomparison of wet-only collectors it has been found by preliminary experiments that appreciable amounts of heavy metals are adsorbed to the PE-funnel walls. Rinsing with HNO₃ and double-distilled water (equivalent height) was not sufficient to remove the material completely. From an investigation of succeeding measurements of rain water samples an increase of the metal concentration with decreasing pH-value demonstrates that a fraction of adsorbed metals appears to be removed during events with low pH. This adsorbed amount of material has to be considered as part of wet deposition and a procedure has to be developed how this amount can be determined reliably. The amounts of heavy metals analysed during our preliminary rinsing experiments was several times larger than the average concentration measured in the precipitation samples.     

Diamond microelectrodes for in vitro electroanalytical measurements: current status and remaining challenges

An emerging research field in electrochemistry today is the preparation, characterization and application of diamond microelectrodes for electroanalytical measurements in biological media. Interest in this new electrode material stems from its outstanding properties: (i) hardness, (ii) low, stable and pH-independent background current, (iii) morphological and microstructural stability over a wide range of potentials, (iv) good electrochemical responsiveness for multiple redox analytes without any conventional pre-treatment and (v) weak molecular adsorption of polar molecules that leads to a high level of resistance to response deactivation and electrode fouling. Diamond electrodes have advanced in recent years from being simply a scientific curiosity into a viable material for electroanalysis. In this article, we highlight the current state of progress by our laboratory and others on the preparation, study of the basic electrochemical properties, and application of this new type of microelectrode for in vitro electroanalytical measurements, and discuss some of the remaining challenges.     

Referencing strategies and techniques in stable isotope ratio analysis

Stable isotope ratios are reported in the literature in terms of a deviation from an international standard (delta-values). The referencing procedures, however, differ from instrument to instrument and are not consistent between measurement facilities. This paper reviews an attempt to unify the strategy for referencing isotopic measurements. In particular, emphasis is given to the importance of identical treatment of sample and reference material ('IT principle'), which should guide all isotope ratio determinations and evaluations. The implementation of the principle in our laboratory, the monitoring of our measurement quality, the status of the international scales and reference materials and necessary correction procedures are discussed.     

Dynamic surface tension measurements on surface active materials

Surface tension measurements by the Wilhelmy plate method are being done at our laboratory using an automatic balance. Surface-active material (surfactant) is spread as a monolayer on an air-water interface and a Pt plate, suspended from a micro-balance, is brought vertically into contact with the interface. The water is contained in a trough, two opposite sides of which can move independently, one producing a large variation in surface area and the other generating a longitudinal wave in the monolayer. This set-up is a new, asymmetric variant of the Benjamins-De Feyter method. Results of measurements on visco-elastic interfacial properties of model compounds of lung surfactant are reported.     

Refinements to the diastereoisomer-specific method for the analysis of hexabromocyclododecane

The emergence of hexabromocyclododecane (HBCD) as a bromine-based flame retardant of concern is partly attributable to recent measurements on the environmental occurrence of the individual diastereoisomers (alpha, beta and gamma). These measurements were fuelled by a newly developed liquid chromatography/tandem mass spectrometric (LC/MS/MS)-based analytical method. However, in the course of our recent studies on the environmental fate and behaviour of the diastereoisomers of HBCD, some interesting features of the LC/MS/MS method became apparent. For example, the ion signal of the native ions was found to be dependent on the final extract volume. This was true for both biotic and sediment samples and was found to arise from the suppression of the ion signal due to endogenous material in the extracts that escape clean-up. We have also found differences in the stability of the diastereoisomers in different solvents. If left unaccounted for, both factors can compromise analytical measurement data. By way of a series of controlled experiments conducted at our two laboratories [Department of Fisheries & Oceans Canada (DFO) and Environment Canada (EC)], we illustrate these features and demonstrate that use of newly synthesized labelled HBCD isomers [(13-carbon (13C) and deuterium (d18)] can minimize and often circumvent matrix-related effects.     

Understanding and Manipulating Inorganic Materials with Scanning Probe Microscopes

Scanning probe microscopies, such as scanning tunneling microscopy and atomic force microscopy, are uniquely powerful tools for probing the microscopic properties of surfaces. If these microscopies are used to study low-dimensional materials, from two-dimensional solids such as graphite to zero-dimensional nanostructures, it is possible to elucidate atomic-scale structural and electronic properties characteristic of the bulk of a material and not simply the surface. By combining such measurements with chemical synthesis or direct manipulation it is further possible to elucidate relationships between composition, structure, and physical properties, thus promoting an understanding of the chemical basis of material properties. This article illustrates that the combination of scanning probe microscopies and chemical synthesis has advanced our understanding of charge density waves, high-temperature superconductivity, and nanofabrication in low-dimensional materials. This new approach to studying materials has directly contributed to our knowledge of how metal dopants interact with charge density waves and elucidated the local crystal chemistry of complex copper oxides, microscopic details of the superconducting states in materials with a high superconducting transition I_c, and new approaches to the fabrication of multi-component nanostructures. Coupling scanning probe microscopy measurement and manipulation with chemical synthesis should provide an approach to understanding material properties and creating complex nanostructures in general.     

The nature of surface barriers on nanoporous solids explored by microimaging of transient guest distributions

Nanoporous solids are attractive materials for energetically efficient and environmentally friendly catalytic and adsorption separation processes. Although the performance of such materials is largely dependent on their molecular transport properties, our fundamental understanding of these phenomena is far from complete. This is particularly true for the mechanisms that control the penetration rate through the outer surface of these materials (commonly referred to as surface barriers). Recent detailed sorption rate measurements with Zn(tbip) crystals have greatly enhanced our basic understanding of such processes. Surface resistance in this material has been shown to arise from the complete blockage of most of the pore entrances on the outer surface, while the transport resistance of the remaining open pores is negligibly small. More generally, the revealed correlation between intracrystalline diffusion and surface permeation provides a new view of the nature of transport resistances in nanoporous materials acting in addition to the diffusion resistance of the regular pore network, leading to a rational explanation of the discrepancy which is often observed between microscopic and macroscopic diffusion measurements.     

Determination of the sulphur content of a lunar sample by neutron capture gamma-ray spectrometry

The technique of prompt neutron capture gamma-ray spectroscopy has been used to determine sulphur concentrations in extraterrestrial materials. In particular an effort was made to resolve reported discrepancies in the sulphur assays for the lunar rock sample 70215. While the validity of chemical analysis techniques are often influenced by the chemical form of the sulphur, particularly when in low concentration, the method used here is independent of such effects. The lunar and a bulk Allende meteorite sample were analyzed for sulphur, iron and silicon. The latter material, being well documented, was analyzed in order to verify the techniques of measurement and the subsequent methods of data reduction. Based upon our measurements and the acceptance of the silicon and iron content of the lunar sample the sulphur content was found to be 1741±112 ppm by weight.     

What is the technical and environmental interest in reusing a recycled polypropylene-hemp fibre composite?

The integration of the environmental problem in the design of industrial products leads us to incorporate vegetal fibres and recycled polymers into composite materials. The aim of this work is to study the behaviour and the environmental interest of a recycled PP/hemp fibre after several injection cycles. The mechanical and rheological behaviour of recycled PP/hemp composite was first studied by using tensile, dynamical mechanic analysis and rheological measurements. Then, to better understand the influence of the recycling, a morphology study was carried out on composites by using optical and electron microscopy. Finally, we investigated the environmental advantages of our composite thanks to a simplified environmental assessment. Our results highlighted the environmental interest of using a recycled matrix to prepare composites reinforced with vegetal fibres and the interesting properties of this material after recycling.     

K4Fe4P5O20: a new mixed valence microporous compound with elliptical eight-ring channels

A new small-pore compound K(4)Fe(4)P(5)O(20) was obtained by conventional solid-state reaction in a closed crucible. The crystal structure is constructed by Fe(4)P(5)O(20) units forming chains along the c axis and elliptical eight-ring channels on the a-b plane in which K cations locate inside. Such structural characteristics seem to be quite similar to those seen in the natrolite family. However, Fe ions in K(4)Fe(4)P(5)O(20) have trigonal-bipyramidal instead of common tetrahedral coordination. Furthermore, our experimental results combined from magnetic susceptibility and (57)Fe M?ssbauer spectrum measurements show mixed valence Fe(3+)/Fe(2+) in the titled material. To the best of our knowledge, this is the first example that contains mixed valence iron ions in a so-called natrolite framework.     

Investigating the Time Dependent Behavior of Thermoplastic Polymers under Tensile Load

The relationship between the results of the tensile and the stress relaxation tests of polypropylene specimens were analyzed and an attempt was made to find a way to estimate the former from the latter based on the measurements and the theory of linear viscoelasticity. The mechanical response of real polymers are basically of nonlinear character, therefore their behavior patterns do not meet the idealized (linear) ones. Experiments were performed on poly(propylene) (PP) as a test material and the stress relaxation behavior, as well as the linear elastic and linear viscoelastic approximation of the tensile load-time curve were analyzed. To demonstrate the applicability of our idea and to perform the numerical calculations we have chosen a flexible function with three parameters to realize the nonlinear behavior.     

Intrinsic Artefacts in Optical Oxygen Sensors—How Reliable are our Measurements?

Optical oxygen sensing is of broad interest in many areas of research, such as medicine, food processing, and micro‐ and marine biology. The operation principle of optical oxygen sensors is well established and these sensors are routinely employed in lab and field experiments. Ultratrace oxygen sensors, which enable measurements in the sub‐nanomolar region (dissolved oxygen), are becoming increasingly important. Such sensors prominently exhibit phenomena that complicate calibration and measurements. However, these phenomena are not constrained to ultratrace sensors; rather, these effects are inherent to the way optical oxygen sensors work and may influence any optical oxygen measurement when certain conditions are met. This scenario is especially true for applications that deal with high‐excitation light intensities, such as microscopy and microfluidic applications. Herein, we present various effects that we could observe in our studies with ultratrace oxygen sensors and discuss the reasons for their appearance, the mechanism by which they influence measurements, and how to best reduce their impact. The phenomena discussed are oxygen photoconsumption in the sensor material; depletion of the dye ground state by high‐excitation photon‐flux values, which can compromise both intensity and ratiometric‐based measurements; triplet–triplet annihilation; and singlet‐oxygen accumulation, which affects measurements at very low oxygen concentrations.     

Highly Luminescent N-Benzylcarbazole Compound Immobilized in Amino-functionalized Mesoporous SBA-15

An inorganic-organic photoluminescence solid material was obtained by immobilizing N-benzylcarbazole compound to an amino-functionalized mesoporous SBA-15(designated as N-benzylcarbazole-amino-SBA-15).XRD,SEM,and N2 adsorption-desorption measurements indicate that the mesostructure of parent material SBA-15 was preserved after introducing amino and N-benzylcarbazole groups.The absorbance and emission studies reveal that the fluorescent N-benzylcarbazole-amino-SBA-15 exhibited red-shift character in comparis...     

Crystallization of aqueous ammonium sulfate particles internally mixed with soot and kaolinite: crystallization relative humidities and nucleation rates

Using optical microscopy, we investigated the crystallization of aqueous ammonium sulfate droplets containing soot and kaolinite, as well as the crystallization of aqueous ammonium sulfate droplets free of solid material. Our results show that soot did not influence the crystallization RH of aqueous ammonium sulfate particles under our experimental conditions. In contrast, kaolinite increased the crystallization RH of the aqueous ammonium sulfate droplets by approximately 10%. In addition, our results show that the crystallization RH of aqueous ammonium sulfate droplets free of solid material does not depend strongly on particle size. This is consistent with conclusions made previously in the literature, based on comparisons of results from different laboratories. From the crystallization results we determined the homogeneous nucleation rates of crystalline ammonium sulfate in aqueous ammonium sulfate droplets and the heterogeneous nucleation rates of crystalline ammonium sulfate in aqueous ammonium sulfate particles containing kaolinite. Using classical nucleation theory and our experimental data, we determined that the interfacial tension between an ammonium sulfate critical nucleus and an aqueous ammonium sulfate solution is 0.064 +/- 0.003 J m(-2) (in agreement with our previous measurements), and the contact angle between an ammonium sulfate critical nucleus and a kaolinite surface is 59 +/- 2 degrees. On the basis of our results, we argue that soot will not influence the crystallization RH of aqueous ammonium sulfate droplets in the atmosphere, but kaolinite can significantly modify the crystallization RH of atmospheric ammonium sulfate droplets. As an example, the CRH50 (the relative humidity at which 50% of the droplets crystallize) ranges from about 41 to 51% RH when the diameter of the kaolinite inclusion ranges from 0.1 to 5 microm. For comparison, the CRH50 of aqueous ammonium sulfate droplets (0.5 microm diameter) free of solid material is approximately 34.3% RH under atmospheric conditions.     

A study of the silver form of a natural zeolitic material of the clinoptilolite type

The silver forms of a natural zeolitic material (from the East Slovakian deposit) on the clinoptilolite type has been prepared. The silver forms of the natural zeolitic material were investigated by X-ray powder diffractometry, IR spectroscopy, ESCA measurements, scanning electron microscopy and conductivity measurements. Depending on the preparation conditions, the content of silver ions in the zeolitic products was found to be in the range from 16 to 24%. In the sample with a silver loading of 18.6%, the silver uptake is due to an ion exchange process, mostly involving Na(I), Ca(II) and Mg(II) ions.