116 research outputs found
Synergistic Formation of Radicals by Irradiation with Both Vacuum Ultraviolet and Atomic Hydrogen: A Real-Time In Situ Electron Spin Resonance Study
We report on the surface modification of polytetrafluoroethylene (PTFE) as an
example of soft- and bio-materials that occur under plasma discharge by
kinetics analysis of radical formation using in situ real-time electron spin
resonance (ESR) measurements. During irradiation with hydrogen plasma,
simultaneous measurements of the gas-phase ESR signals of atomic hydrogen and
the carbon dangling bond (C-DB) on PTFE were performed. Dynamic changes of the
C-DB density were observed in real time, where the rate of density change was
accelerated during initial irradiation and then became constant over time. It
is noteworthy that C-DBs were formed synergistically by irradiation with both
vacuum ultraviolet (VUV) and atomic hydrogen. The in situ real-time ESR
technique is useful to elucidate synergistic roles during plasma surface
modification.Comment: 14 pages, 4 figure
Studies of intermolecular interactions in solid dispersions using advanced surface chemical analysis
The aim of this study is to utilise an advanced surface chemical analysis based on X-ray photoelectron spectroscopy (XPS) to determine and characterise drug/polymer interactions in solid dispersions manufactured via hot melt extrusion (HME). Cetirizine HCl (CTZ) and verapamil HCl (VRP) were used as model cationic drugs while Eudragit® grade L100 and L100-55 polymers were used as anionic carriers. A molecular dynamics (MD) based simulation approach predicted drug/polymer interactions while scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS) mapping showed homogenous distribution of the drug particles onto the polymer matrices. Hot stage microscopy (HSM) characterised the solid state of the drugs in extruded formulations. XPS analysis revealed the strength and nature of interaction between the –NH3 groups of the APIs with the –COOH groups of the polymers. The results obtained from XPS were supported by XRD and NMR studies. The estimation of non-protonated/protonated N atom (N/N′) ratios using XPS revealed the strength of the intermolecular interaction in drug/polymer extrudates which can be used as an efficient tool to study the drug/polymer interaction
Fuel cell electrodes from organometallic Pt precursors: an easy atmospheric plasma approach
An organometallic powder (platinum (II) acetylacetonate) is decomposed in the
post-discharge of an atmospheric RF plasma torch to deposit Pt nanoparticles on
carbon black supports. The resulting nanohybrid materials are characterized by
FEG-SEM and XPS techniques to highlight their high content in Pt, their
oxidation degree, and the dispersion of the Pt nanoparticles on the substrate.
ICP-MS and electrochemical characterizations in a single fuel cell (cyclic
voltammetry, dynamic polarization curves) are also performed on electrodes
realized by treating the powder mixture overlaid on gas diffusion layers. The
comparison of the catalytic activity and the Pt loading with commercially
available electrodes shows the great potential of this simple innovative, fast,
and robust deposition method
Plasma treatment in textile industry
Plasma technology applied to textiles is a dry, environmentally- and worker-friendly method
to achieve surface alteration without modifying the bulk properties of different materials.
In particular, atmospheric non-thermal plasmas are suited because most textile materials
are heat sensitive polymers and applicable in a
continuous processes. In the last years plasma
technology has become a very active, high growth
research field, assuming a great importance among
all available material surface modifications in
textile industry. The main objective of this review
is to provide a critical update on the current state of
art relating plasma technologies applied to textile
industryFernando Oliveira (SFRH/BD/65254/2009) acknowledges Fundacao para a Cioncia e Tecnologia, Portugal, for its doctoral grant financial support. Andrea Zille (C2011-UMINHO-2C2T-01) acknowledges funding from Programa Compromisso para a Cioncia 2008, Portugal
Surface engineering and self-cleaning properties of the novel TiO2/PAA/PTFE ultrafiltration membranes
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