Search results for "Porosity"

Influence of initial treatments of aluminium on the morphological features of electrochemically formed alumina membranes

2003

Abstract The fabrication of alumina membranes by electrochemical oxidation of annealed aluminium was investigated. Porous layers were grown in 0.4 M H3PO4 at −1 and 5 °C at different anodising times. The morphology of the outer surface was found to be dependent on temperature and charge density, with both determining the extent of chemical dissolution of the anodic oxide. The inner-surface morphology was found to depend on the applied voltage only. The chemical dissolution rate of anodic oxide grown on annealed aluminium was found to be lower than that formed on unannealed aluminium under otherwise identical conditions. Such a difference in behaviour is explained in terms of a higher finish…

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…

Characterization of porous alumina membranes for efficient, real-time, flow through biosensing

2015

Abstract Nanofluidic sensing devices promise high performance by overcoming issues of mass transport of analyte molecules to the sensing surface, whilst micro-porous membranes promise high sensitivity due to a large surface for their capture. Anodic alumina (AAO) filter membranes allow the flow through of samples, and could be used as a convenient and readily available fluidic platform for the targeted delivering of analytes to bioreceptors immobilized on the pore walls. The relatively small pore dimensions, compared to fluidic diffusion lengths, promise highly efficient capture of analytes from the whole sample volume, enabling relatively fast sensing response times and the use of small sa…

Comparison of the solid-phase extraction efficiency of a bounded and an included cyclodextrin-silica microporous composite for polycyclic aromatic hy…

2016

Solid-phase extraction is one of the most important techniques for sample purification and concentration. A wide variety of solid phases have been used for sample preparation over time. In this work, the efficiency of a new kind of solid-phase extraction adsorbent, which is a microporous material made from modified cyclodextrin bounded to a silica network, is evaluated through an analytical method which combines solid-phase extraction with high-performance liquid chromatography to determine polycyclic aromatic hydrocarbons in water samples. Several parameters that affected the analytes recovery, such as the amount of solid phase, the nature and volume of the eluent or the sample volume and …

X-ray analysis on the nanogram to microgram scale using porous complexes

2012

X-ray single-crystal diffraction (SCD) analysis has the intrinsic limitation that the target molecules must be obtained as single crystals. Here we report a protocol for SCD analysis that does not require the crystallization of the sample. In our method, tiny crystals of porous complexes are soaked in a solution of the target, such that the complexes can absorb the target molecules. Crystallographic analysis clearly determines the absorbed guest structures along with the host frameworks. Because the SCD analysis is carried out on only one tiny crystal of the complex, the required sample mass is of the nanogram–microgram order. We demonstrate that as little as about 80 nanograms of a sample …

Host Solids Containing Nanoscale Anion-Binding Pockets and Their Use in Selective Sensing Displacement Assays

2005

Porosities and dimensions of measures

1999

We introduce a concept of porosity for measures and study relations between dimensions and porosities for two classes of measures: measures on $R^n$ which satisfy the doubling condition and strongly porous measures on $R$.

Tailored syntheses of nanostructured silicas: Control of particle morphology, particle size and pore size

1998

Ordered mesoporous silicas with spherical morphology and average particle size in the range between 100 nm and 2 μm were synthesised according to two novel routes. Both synthesis routes used tetraethoxysilane, water, alcohol and aqueous ammonia for producing spherical silica beads. The porosity was created by adding two different kinds of pore structure directing agents to the starting solution: one was an n-alkyltrialkoxysilane which was covalently bonded to the silica framework, the other was an n-alkylamine which acted as a nonionic template. After calcination and post treatment the resulting particles showed a specific surface area up to 1000 m2 g-1, a specific pore volume of up to 0.8 …

Generalised syntheses of ordered mesoporous oxides: the atrane route

2000

Abstract A new simple and versatile technique to obtain mesoporous oxides is presented. While implying surfactant-assisted formation of mesostructured intermediates, the original chemical contribution of this approach lies in the use of atrane complexes as precursors. Without prejudice to their inherent unstability in aqueous solution, the atranes show a marked inertness towards hydrolysis. Bringing kinetic factors into play, it becomes possible to control the processes involved in the formation of the surfactant–inorganic phase composite micelles, which constitute the elemental building blocks of the mesostructures. Independent of the starting compositional complexity, both the mesostructu…

Fabrication of metal nano-structures using anodic alumina membranes grown in phosphoric acid solution: Tailoring template morphology

2007

Abstract The influence of experimental parameters on the morphology of the porous structure and on the formation kinetics has been investigated for anodic alumina membranes (AAM) grown in aqueous H 3 PO 4 at 160 V. It was found that pore aspect ratio and membrane porosity on the solution-side surface are influenced by tensiostatic charge, bath temperature and the presence of Al 3+ ions in solution. Morphological and kinetic data, recorded in different conditions, give useful information on the growth mechanism of pore channels in phosphoric acid solution. Nickel nano-structures have been fabricated using AAM as template. Electroless deposition, performed by adding the reducing agent to a su…