Versailles Project on Advanced Materials and Standards Interlaboratory Study on Measuring the Thickness and Chemistry of Nanoparticle Coatings Using XPS and LEIS

Belsey, Natalie A.; Cant, David J. H.; Minelli, Caterina; Araújo, Joyce R.; Böck, B.; Brüner, Philipp; Castner, David G.; Ceccone, Giacomo; Counsell, Jonathan; Dietrich, Paul; Engelhard, Mark H.; Fearn, Sarah; Galhardo, Carlos Eduardo Cardoso; Kalbe, Henryk; Kim, Jeong Won; Lartundo-Rojas, L.; Luftman, H. S.; Nunney, Tim; Pseiner, Johannes; Smith, Emily F.; Spampinato, Valentina; Sturm, Jacobus Marinus; Thomas, Andrew G.; Treacy, Jon; Veith, Lothar; Wagstaffe, Michael; Wang, Hai; Wang, Meiling; Wang, Yung-Chen; Werner, Wolfgang; Yang, Li; Shard, Alexander G.

doi:10.1021/acs.jpcc.6b06713

Cited by 34 publications

(25 citation statements)

References 31 publications

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“…In other words, the starting AuNPs should not be assumed to be completely "bare", which could be related to the presence of organic shells on solution-synthesized AuNPs and their interactions with PLL chains on the substrate. Assuming a well-defined state for as-received AuNPs that are nominally covered only with a weakly bound citrate shell is notoriously difficult, in part because they can easily become contaminated with other adsorbates at levels detectable by sensitive techniques [34][35][36]. Upon exposure to the ambient environment, adventitious organic contamination will be present on both nominally bare and peptide functionalized gold surfaces in the amounts at least comparable to those of the intentionally immobilized molecules [37,38], thus further diminishing the difference in refractive index surrounding the "bare" vs biofunctionalized AuNPs in the experiments.…”

Section: Ellipsometric Experimental Resultsmentioning

confidence: 99%

Adapting Bobbert-Vlieger model to spectroscopic ellipsometry of gold nanoparticles with bio-organic shells

Viegas

Fernandes

Queirós

et al. 2017

Biomed. Opt. Express

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Abstract:We investigate spectroscopic imaging ellipsometry for monitoring biomolecules at surfaces of nanoparticles. For the modeling of polarimetric light scattering off surfaceadsorbed core-shell nanoparticles, we employ an extension of the exact solution for the scattering by particles near a substrate presented by Bobbert and Vlieger, which offers insight beyond that of the Maxwell-Garnett effective medium approximation. Varying thickness and refractive index of a model bio-organic shell results in systematic and characteristic changes in spectroscopic parameters Ψ and Δ . The salient features and trends in modeled spectra are in qualitative agreement with experimental data for antibody immobilization and fibronectin biorecognition at surfaces of gold nanoparticles on a silicon substrate, but achieving a full quantitative agreement will require including additional effects, such as nanoparticle-substrate interactions, into the model.

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Section: Ellipsometric Experimental Resultsmentioning

confidence: 99%

Adapting Bobbert-Vlieger model to spectroscopic ellipsometry of gold nanoparticles with bio-organic shells

Viegas

Fernandes

Queirós

et al. 2017

Biomed. Opt. Express

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“…An interlaboratory comparison conducted by Belsey et al 73 . demonstrated the challenges associated with the movement of material from solution for XPS or other surface analysis.…”

Section: Provenance Information and Data Records For Nano-objectsmentioning

confidence: 99%

Provenance information as a tool for addressing engineered nanoparticle reproducibility challenges

2016

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Nanoparticles of various types are of increasing research and technological importance in biological and other applications. Difficulties in the production and delivery of nanoparticles with consistent and well defined properties appear in many forms and have a variety of causes. Among several issues are those associated with incomplete information about the history of particles involved in research studies, including the synthesis method, sample history after synthesis, including time and nature of storage, and the detailed nature of any sample processing or modification. In addition, the tendency of particles to change with time or environmental condition suggests that the time between analysis and application is important and some type of consistency or verification process can be important. The essential history of a set of particles can be identified as provenance information and tells the origin or source of a batch of nano-objects along with information related to handling and any changes that may have taken place since it was originated. A record of sample provenance information for a set of particles can play a useful role in identifying some of the sources and decreasing the extent of particle variability and the lack of reproducibility observed by many researchers.

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“…It is also desirable to have a consistent and standardised approach to calibration to enable the direct comparison of XPS data between different instruments and institutions. The fact that this is not done, and that different manufacturers adopt different procedures, was highlighted in two recent VAMAS interlaboratory studies on nanoparticle coating analysis and composition measurement in organic depth profiling . In these studies, the XPS composition values reported by participants varied by a factor of two from the mean.…”

Section: Introductionmentioning

confidence: 99%

Intensity calibration for monochromated Al Kα XPS instruments using polyethylene

Shard

Spencer

2019

Surface & Interface Analysis

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We describe a method for the intensity calibration of XPS instruments using polyethylene as the reference material. Previous methods have employed noble metals, such as gold, silver, and copper. Polyethylene has a number of advantages over these. It has far fewer photoelectron and Auger electron peaks than such metals, ie, the spectrum largely comprises inelastic background over a wide and continuous range of kinetic energies. The XPS spectrum can be described by a mathematical function enabling simple and noise-free implementation of the reference spectrum. Polyethylene can be cleaned ex situ using a sharp knife or razor blade to remove trace oxygen and, due to its chemical composition, should not be affected by adventitious carbon contamination. Thus, an ion source for sputter cleaning is not required, although an electron flood source for charge compensation is required. The drawback to using polyethylene is that the photoelectron yield is far lower than gold or silver, and this necessitates longer acquisition times and removal of dark noise. Longer acquisition times carry the risk of damaging the polyethylene surface, and we show that, even if damage does occur, it has a negligible effect on the XPS background intensity.The reference spectrum is valid for monochromated Al Kα XPS instruments with a monochromator-sample-analyser angle close to 60°. | INTRODUCTIONX-ray photoelectron spectroscopy is a widely used method to identify elements and their chemical states within the top few nanometres of a material surface. By correctly interpreting the intensity of peaks in an XPS spectrum, it is possible to measure the composition of a surface with excellent precision and reasonable accuracy. The accuracy of XPS composition measurements in a practical sense depends upon having appropriate sensitivity factors for each of the elemental peaks.However, because the efficiency of transmission through the analyser is a function of kinetic energy, instrument, illumination area, aperture settings, pass energies, and lens modes and may change slowly over time, it is not reasonable to maintain sensitivity factors for each condition. The approach taken by most manufacturers and operators is to measure a few reference materials, usually sputter-cleaned gold or silver, and, after dividing this by a reference spectrum of that material, obtain a version of the relative transmission function of the instrument operating at specified settings. Other spectra acquired using the same mode from samples of interest may be divided by the transmission function to obtain spectra that are consistent with anyone who uses the same reference spectra and reference material. If the reference spectra used for this purpose are, themselves, accurate, then this enables a direct comparison to theory, 1-3 for example the use of calculated photoionisation cross sections 4-7 and electron transport theory. [8][9][10] If an XPS instrument is used for quantitative analysis, or even to compare intensities between different operating modes or acquired at differe...

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Versailles Project on Advanced Materials and Standards Interlaboratory Study on Measuring the Thickness and Chemistry of Nanoparticle Coatings Using XPS and LEIS

Cited by 34 publications

References 31 publications

Adapting Bobbert-Vlieger model to spectroscopic ellipsometry of gold nanoparticles with bio-organic shells

Adapting Bobbert-Vlieger model to spectroscopic ellipsometry of gold nanoparticles with bio-organic shells

Provenance information as a tool for addressing engineered nanoparticle reproducibility challenges

Intensity calibration for monochromated Al Kα XPS instruments using polyethylene

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