“Study of quasi-fractal many-particle-systems and percolation networks by zero-loss spectroscopic imaging, electron energy-loss spectroscopy and digital image analysis”. Oleshko V, Kindratenko V, Gijbels R, van Espen P, Jacob W, Mikrochimica acta: supplementum 13, 443 (1996)
Abstract: Submicron colloidal Ag particles and nano-sized filaments forming a statistical percolation network during ''in situ'' development of double structure tabular microcrystals of AgRr(I) emulsions have been studied by electron energy-loss spectroscopy and zero-loss electron spectroscopic imaging (EELS/ZLESI). Image analysis has shown that random quasi-fractal clusters were formed in the colloid. ZLESI has been applied to characterise the morphology and defect structure of aggregated particles and filaments. Their energy-loss spectra revealed plasmon excitations and interband 4d electron transitions between 4-32 eV energy-loss. To study the cluster structure and its relation to the physical properties, fractal analysis including estimations of cluster fractal dimensions and of density autocorrelation functions has been performed. Mechanisms of fractal aggregation based on known models of diffusion limited aggregation, cluster-cluster aggregation and percolation are discussed.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT); Chemometrics (Mitac 3)
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“Study of the main physical processes contributing to image formation in emission radiography using mathematical modeling”. Leyva Pernia D, Cabal Rodríguez AE, Schalm O, van Espen P, Piñera Hernández I, Abreu Alfonso Y, (2013)
Keywords: P3 Proceeding; Engineering sciences. Technology; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Antwerp Cultural Heritage Sciences (ARCHES)
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“Study of the uniformity of aerosol filters by scanning MA-XRF”. Cabal A, Legrand S, Van den Bril B, Tote K, Janssens K, van Espen P, X-ray spectrometry
T2 –, 17th European Conference on X-Ray Spectrometry (EXRS), JUN 19-24, 2016, Univ Gothenburg, Univ Gothenburg, Gothenburg, SWEDEN 46, 461 (2017). http://doi.org/10.1002/XRS.2767
Abstract: Energy-dispersive X-ray fluorescence (XRF) is an attractive analytical method to determine the level of air pollution by heavy metals. The concentration of the filter in ng/cm(2) is obtained by direct comparison of the net characteristic line intensity of an element with that of a thin film standard. As the sampled area on the filter and the area of the standard are larger than the area analysed by the instrument, the distribution of the elements on the surface of both samples and standards have to be sufficiently uniform. If this is not the case, biased concentration estimates are obtained. Two scanning macro-XRF setups with a beam diameter of similar to 0.5 mm were used to investigate the distribution of elements in (1) commercially available (Micromatter) standards, (2) in-house quartz filter standards obtained with an aerosol generator and (3) particulatematter (PM10) collected on quartz filters by a Leckel SEQ 47/50 sampler. The uniformity of the Micromatter standards was better than 2%. At least some in-house standards showed a concave distribution with less material at the edges. The maximum bias introduced by this is less than 5%. Because of the limited sensitivity of scanning XRF compared with conventional XRF, the distribution of only a few common elements like Ca and Fe could be determined reliably in aerosol filters. The distribution of some heavy elements could only be measured in filters sampled in polluted regions. In general, the loading of particulate matter over the filters was uniform. Copyright (C) 2017 John Wiley & Sons, Ltd.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 1.298
Times cited: 4
DOI: 10.1002/XRS.2767
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“Studying aerosol samples by non-linear mapping of electron probe microanalysis data”. Treiger B, van Malderen H, Bondarenko I, van Espen P, Van Grieken R, Analytica chimica acta 284, 119 (1993). http://doi.org/10.1016/0003-2670(93)80014-C
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Chemometrics (Mitac 3)
DOI: 10.1016/0003-2670(93)80014-C
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“Sulfur and heavy metals over the Atlantic Ocean : comparison with other marine data”. Maenhaut W, Selen A, van Espen P, Van Grieken R, Winchester JW, (1980)
Keywords: P3 Proceeding; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Chemometrics (Mitac 3)
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“The development process of an expert system for the automated interpretation of large epma data sets”. Janssens K, Dorrine W, van Espen P, Chemometrics and intelligent laboratory systems 4, 147 (1988). http://doi.org/10.1016/0169-7439(88)80086-8
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Chemometrics (Mitac 3)
DOI: 10.1016/0169-7439(88)80086-8
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“The elemental composition of airborne particulate matter in the Atacama desert, Chile”. Rojas CM, Figueroa L, Janssens KH, Van Espen PE, Adams FC, Van Grieken RE, The science of the total environment 91, 251 (1990). http://doi.org/10.1016/0048-9697(90)90302-B
Abstract: Air particulate samples were collected at Chapiquiña near Arica (Chile) with a six-stage cascade impactor for about 17-day periods during a 31 month interval. Sixteen elements were determined by energy dispersive X-ray fluorescence analysis, and the elemental concentrations were subjected to principal factor analysis. The variability with time of the coarse particles was described by two factors both related to soil dispersion, whereas the fine particle variations could be explained by a third factor related to marine influence. Enrichment factors were compared with those obtained in other remote continental areas, in particular those of air particulate matter sampled at Chacaltaya, Bolivia. Results point to a negligible anthropogenic influence.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
DOI: 10.1016/0048-9697(90)90302-B
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“The primary energy dependence of backscattered electron images up to 100 keV”. Geuens I, Nys B, Naudts J, Gijbels R, Jacob W, van Espen P, Scanning microscopy 5, 339 (1991)
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT); Chemometrics (Mitac 3)
Times cited: 3
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“Three-dimensional chemical characterization of complex silver halide microcrystals by scanning ion microprobe mass analysis”. Verlinden G, Janssens G, Gijbels R, van Espen P, Geuens I, Analytical chemistry 69, 3773 (1997). http://doi.org/10.1021/ac970010r
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT); Chemometrics (Mitac 3)
Impact Factor: 6.32
Times cited: 6
DOI: 10.1021/ac970010r
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“Unlocking the full potential of voltammetric data analysis : a novel peak recognition approach for (bio)analytical applications”. Van Echelpoel R, de Jong M, Daems D, van Espen P, De Wael K, Talanta 233, 122605 (2021). http://doi.org/10.1016/J.TALANTA.2021.122605
Abstract: Bridging the gap between complex signal data output and clear interpretation by non-expert end-users is a major challenge many scientists face when converting their scientific technology into a real-life application. Currently, pattern recognition algorithms are the most frequently encountered signal data interpretation algorithms to close this gap, not in the least because of their straight-forward implementation via convenient software packages. Paradoxically, just because their implementation is so straight-forward, it becomes cumbersome to integrate the expert's domain-specific knowledge. In this work, a novel signal data interpretation approach is presented that uses this domain-specific knowledge as its fundament, thereby fully exploiting the unique expertise of the scientist. The new approach applies data preprocessing in an innovative way that transcends its usual purpose and is easy to translate into a software application. Multiple case studies illustrate the straight-forward application of the novel approach. Ultimately, the approach is highly suited for integration in various (bio)analytical applications that require interpretation of signal data.
Keywords: A1 Journal article; Engineering sciences. Technology; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 4.162
DOI: 10.1016/J.TALANTA.2021.122605
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“XRS activities at the Micro &, Trace Analysis Centre (MiTAC), University of Antwerp, Belgium”. Padilla R, Janssens K, van Espen P, Van Grieken R, IAEA XRF newsletter 12, 13 (2006)
Keywords: A3 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Chemometrics (Mitac 3)
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