Search results for " magnetic materials"
showing 10 items of 4666 documents
Convection, diffusion and reaction in a surface-based biosensor: Modeling of cooperativity and binding site competition on the surface and in the hyd…
2005
We study theoretically the transport and kinetic processes underlying the operation of a biosensor (particularly the surface plasmon sensor "Biacore") used to study the surface binding kinetics of biomolecules in solution to immobilized receptors. Unlike previous studies, we concentrate mainly on the modeling of system-specific phenomena rather than on the influence of mass transport limitations on the intrinsic kinetic rate constants determined from binding data. In the first problem, the case of two-site binding where each receptor unit on the surface can accommodate two analyte molecules on two different sites is considered. One analyte molecule always binds first to a specific site. Sub…
Direct gravimetric sensing of GBL by a molecular recognition process in organic cage compounds.
2013
Organic cages were identified as highly potent affinity materials for the tracing of γ-butyrolactone. The selectivity over ethanol and water is based on the interior functional groups which allow preferential hydrogen bonding to the target analyte.
Selection and characterization of adsorbents for the analysis of an explosive-related molecule traces in the air
2013
International audience; This study is focused on the development of a 3D micro-preconcentrator for a sensitive analysis of an explosive-related compound: orthonitrotoluene (ONT). A set of potentially efficient adsorbents for the pre-concentration of ONT was investigated here. An in-depth characterization of their textural properties was carried out in order to better understand their adsorption behavior toward the target analyte. More particularly, this study allowed highlighting the interesting adsorption features of a hydrophobic zeolite and a porous activated carbon in relation to their preconcentration performances toward ONT at the ppb level. Moreover, we found a difference in the adso…
A tailor-made nucleoside-based colourimetric probe of formic acid
2014
A ratiometric, specific probe of formic acid has been developed. It is based on intermolecular nucleobase-pairing of inosine-capped plasmonic nanoparticles to form nucleoside channels, which are destabilised by the analyte.
Evidence of tetraphenylporphyrin monoacids by ion-transfer voltammetry at polarized liquid|liquid interfaces
2008
We present a simple methodology to illustrate the existence of tetraphenylporphyrin monoacid based on ion-transfer voltammetry at a polarized water|1,2-dichloroethane interface and organic pK values are also estimated.
Transmembrane electrochemistry of erythrocytes: Direct electrochemical test for detecting hemolysis in whole blood
2016
A rapid method for detecting hemolysis in whole blood based on a direct electrochemical assay either in venous blood and finger blood, respectively at glassy carbon and screen-printed graphite electrodes is described. The presence of hemolysis is detected from characteristic voltammetric signatures associated to Fe-heme units in healthy and hemolyzed erythrocytes. The voltammetric response of blood was also investigated using scanning electrochemical microscopy (SECM) and scanning tunneling microscopy (STM) and involved transmembrane electrochemistry of erythrocytes superimposed to molecular electrochemistry of heme-containing proteins and heme fragments in the plasma. Voltammetric testing …
Low vacuum photo electron emitting thin films
2009
Impact ionisation is a standard procedure to ionise gaseous or vaporisable substances in organic mass spectrometry. In this work, a "softer" ionisation is introduced which seems to be an alternative ion source for reducing collision between substance molecules and the hot internal walls of the box. Through collision mainly found in impact ionisation sources, fragments are built especially from thermally sensitive substances falsifying the spectra. We present here photoelectron emitting materials for the soft ionisation using semiconducting compounds, galliumn nitride (GaN), and a representative of the borides, lanthanum hexaboride (LaB 6 ). They are evaluated by photoelectron spectroscopic …
Effect of sodium to barium substitution on the space charge implementation in thermally poled glasses for nonlinear optical applications
2009
Thermally poled niobium borophosphate glasses in the system 0.55(0.95-y) NaPO{sub 3}+y/2 Ba(PO{sub 3}){sub 2}+0.05Na{sub 2}B{sub 4}O{sub 7})+0.45Nb{sub 2}O{sub 5} were investigated for second order optical nonlinear (SON) properties. Bulk glasses were studied by Raman spectroscopy, thermal analysis, optical and dielectric measurements. The sodium to barium substitution does not lead to significant changes in optical properties, crystallization of glasses and coordination environment of polarizable niobium atoms. However, the ionic conductivity decreases drastically with the increase of barium concentration. Secondary ion mass spectroscopy has been used to determine the element distribution …
Thermodynamic Study of Small Hydrophobic Ions at the Water–Lipid Interface
2001
Abstract The thermodynamics of binding of two small hydrophobic ions such as norharman and tryptophan to neutral and negatively charged small unilamellar vesicles was investigated at pH 7.4 using fluorescence spectroscopy. Vesicles were formed at room temperature from dimyristoyl phosphatidylcholine (DMPC) or DMPC/dimyristoylphosphatidic acid and DMPC/dimyristoylphosphatidylglycerol. The changes in fluorescence properties were used to obtain association isotherms at variable membrane surface negative charge and at different ionic strengths. The binding of both ions was found to be quantitatively enhanced as the percentage of negative phospholipid increases in the membrane. Also, a decrease …
Graphene and ionic liquids new gel paste electrodes for caffeic acid quantification
2015
Abstract Graphene/ionic liquids nanocomposite gels were synthesized by an electrochemical etching approach and fully characterized under a morphological and structural point of view. For this purpose, several analytical techniques were applied, as HR-TEM/EDX (High Resolution-Transmission Electron Microscopy/Energy Dispersive X-Ray Analysis); FE-SEM/EDX (Field Emission-Scanning Electron Microscopy/Energy Dispersive X-Ray Analysis); XPS (X-Ray Photoelectron Spectroscopy); FT-IR (Fourier Transform-Infrared Spectroscopy) and electrochemical techniques. After the characterization study, nanocomposite-gel paste electrodes were assembled, exhibiting a selective and specific detection toward the ca…