Filtern
Erscheinungsjahr
- 2017 (9) (entfernen)
Dokumenttyp
- Vortrag (6)
- Zeitschriftenartikel (1)
- Sonstiges (1)
- Posterpräsentation (1)
Sprache
- Englisch (9)
Schlagworte
- NAP-XPS (7)
- Alginate (6)
- Biofilms (6)
- E. coli (4)
- Nanoparticles (2)
- Aqueous Solutions (1)
- Bacteria (1)
- Biofilm (1)
- Core-shell nanoparticles (1)
- FTIR (1)
Eingeladener Vortrag
- nein (6)
Near Ambient Pressure XPS opens up a new world of possibilities for measurements with XPS. While there are examples where NAP-XPS has been used to study electrochemical processes and heterogeneous catalysis, little attention has been paid to its potential use in biological materials. Until now, bacteria have only been characterised with conventional XPS, which requires tedious sample preparation usually involving freeze drying, a treatment that may degrade biological sample constituents. By studying biological samples in their native wet states, new insight about composition, absorption and transport of drugs through cell membranes and extracellular polymeric substance (EPS) layers can be obtained. Both artificial model-films of exopolysaccharides and biofilms of Escherichia Coli have been characterised at pressures ranging from ultra-high vacuum to 15 mbar by using SPECS’ EnviroESCA NAP-XPS instrument and conventional XPS. By applying antimicrobials to model biofilms, some of which are known to be resistant towards the antimicrobial in question, the distribution of antimicrobials in biofilms has been studied. Capabilities and limitations of the approach will be discussed.
Water and aqueous reagents are essential in any biological process or system. But apart from a few special low vapor-pressure cases, liquids have not been accessible to any technique requiring UHV conditions. EnviroESCA opens up this exciting field of applications.
In this paper first results from water based samples are presented as a proof of concept to demonstrate the special capabilities of EnviroESCA analyzing liquid samples. The following solutions were investigated under near ambient pressure conditions: i.) water, ii.) brine, iii.) an oil in water dispersion, iv.) aqueous iron(II) sulfate heptahydrate, and v.) a suspension of nano silver particles in water.
A drawback for X-ray photoelectron spectroscopy is that the measurements must be performed under ultra-high vacuum, which limits the type of samples which can be studied. However, by applying a differentially pumped aperture positioned close to the surface, even wet samples can be measured at near ambient pressure while the energy analyser is still under ultra-high vacuum, as illustrated below. Successful XPS-measurements with pressure up to 30 mbar have been reported using this approach, which opens up a new world of possibilities for ambient pressure measurements with XPS.
While there are examples where NAP-XPS has been used to study electrochemical processes and heterogeneous catalysis, little attention has been paid to its potential use in biological materials. Until now, bacteria have only been characterised with conventional XPS, which requires tedious sample preparation usually involving freeze drying, a treatment that may degrade biological sample constituents. By studying biological samples in their native wet states, new insight about composition, absorption and transport of drugs through cell membranes and extracellular polymeric substance (EPS) layers can be obtained.
Both artificial model-films of exopolysaccharides and biofilms of Escherichia Coli have been characterised at pressures ranging from ultra-high vacuum to 15 mbar by using SPECS’ EnviroESCA NAP-XPS instrument and conventional XPS. By applying antimicrobials to model biofilms, some of which are known to be resistant towards the antimicrobial in question, the distribution of antimicrobials in biofilms has been studied. Measurement capabilities and limitations of the approach will be discussed.
Detection of suspended nanoparticles with near-ambient pressure x-ray photoelectron spectroscopy
(2017)
Two systems of suspended nanoparticles have been studied with near-ambient pressure x-ray photoelectron spectroscopy: silver nanoparticles in water and strontium fluoride—calcium fluoride core-shell nanoparticles in ethylene glycol. The corresponding dry samples were measured under ultra high vacuum for comparison. The results obtained under near-ambient pressure were overall comparable to those obtained under ultra high vacuum, although measuring silver nanoparticles in water requires a high pass energy and a long acquisition time. A shift towards higher binding energies was found for the silver nanoparticles in aqueous Suspension compared to the corresponding dry sample, which can be assigned to a change of surface potential at the water-nanoparticle interface. The shell-thickness of the core-shell nanoparticles was estimated based on simulated spectra from the National Institute of Standards and Technology database for simulation of electron spectra for surface analysis. With the instrumental set-up presented in this paper, nanoparticle suspensions in a suitable Container can be directly inserted into the analysis chamber and measured without prior sample preparation.