I am a staff scientist at the Cornell High Energy Synchrotron Source, where I support x-ray fluorescence imaging and x-ray absorption spectroscopy experiments. I am especially interested in applications of synchrotron radiation for the study of material cultural heritage. I was awarded a 2016-2017 Andrew W. Mellon Foundation Postdoctoral Fellowship in the Department of Scientific Research at the Metropolitan Museum of Art to examine paintings and other objects with the Museum’s Bruker XRF scanner, and develop support materials for 2D XRF data analysis.
We present trace-element and composition analysis of azurite pigments in six illuminated manuscri... more We present trace-element and composition analysis of azurite pigments in six illuminated manuscript leaves, dating from the thirteenth to sixteenth century, using synchrotron-based, large-area x-ray fluorescence (SR-XRF) and diffraction (SR-XRD) mapping. SR-XRF mapping reveals several trace elements correlated with azurite, including arsenic, zirconium, antimony, barium, and bismuth, that appear in multiple manuscripts but were not always detected by point XRF. Within some manuscript leaves, variations in the concentration of trace elements associated with azurite coincide with distinct regions of the illuminations, suggesting systematic differences in azurite preparation or purification. Variations of the trace element concentrations in azurite are greater among different manuscript leaves than the variations within each individual leaf, suggesting the possibility that such impurities reflect distinct mineralogical/geologic sources. SR-XRD maps collected simultaneously with the SR-XRF maps confirm the identification of azurite regions and are consistent with impurities found in natural mineral sources of azurite. In general, our results suggest the feasibility of using azurite trace element analysis for provenance studies of illuminated manuscript fragments, and demonstrate the value of XRF mapping in non-destructive determination of trace element concentrations within a single pigment.
High-quality spatially-resolved measurements of electric fields are critical to understanding cha... more High-quality spatially-resolved measurements of electric fields are critical to understanding charge injection, charge transport, and charge trapping in semiconducting materials. Here, we report a variation of frequency-modulated Kelvin probe force microscopy (FM-KPFM) that enables spatially-resolved measurements of the electric field. We measure electric field components along multiple directions simultaneously by employing position modulation and lock-in detection in addition to numeric differentiation of the surface potential. We demonstrate the technique by recording linescans of the in-plane electric field vector in the vicinity of a patch of trapped charge in a DPh-BTBT organic field-effect transistor. This technique is simple to implement and should be especially useful for studying electric fields in spatially inhomogeneous samples like organic transistors and photovoltaic blends.
A poster presented at European Lacquer in Context Conference held in Brussels, January 2018
Inherently fragile, japanned surfaces are often in poor condition and heavily restored. This can ... more Inherently fragile, japanned surfaces are often in poor condition and heavily restored. This can obscure the intention of the craftsman and confuse both stylistic and technical analysis. This paper will explore the usefulness of scanning X-ray fluorescence (XRF) - a non-invasive technique commonly used to visualize pigment distribution in historical paintings – for the investigation of japanned surfaces.
Areas of two eighteenth century American japanned chests in the collection of the Metropolitan Museum of Art were scanned using a Bruker M6 Jetstream system. Data was processed to produce elemental distribution maps. A set of samples reproducing the typical stratigraphy of eighteenth century japanned surfaces was also scanned in order to further probe certain unexpected results.
The ability to overlay elemental maps made it possible to quickly see where elements were occurring separately and together, aiding the idenification of pigments and other inorganic material. Processing the data quanititavely made it possible to differentiate between areas where the same elements appear in different ratios, which was often helpful in distinguishing between original and restoration materials. The maps also made it easier to locate areas where only a small amount of original material remained. In one case, a siginificant part of the decorative scheme hidden beneath overpaint was revealed.
The limitations inherent to the technique will also be discussed. XRF does not provide information about organic materials or layer structure. The equipment is expensive and significant time and expertise is required both to scan and to process the data. Additionally, the technique is currently only suitable for two dimensional surfaces. Although it was possible to scan areas with raised decoration, the depth of field and spot size had to be increased, resulting in a less focused image.
The scanning XRF technique was found to be a significant improvement on conventional point XRF for the technical understanding of complicated, heavily restored japanned surfaces. The technique allowed the plausible attribution of pigments, metals and other inorganic material to regions, with areas of inconsistency often being immediately evident from the elemental maps.
We present trace-element and composition analysis of azurite pigments in six illuminated manuscri... more We present trace-element and composition analysis of azurite pigments in six illuminated manuscript leaves, dating from the thirteenth to sixteenth century, using synchrotron-based, large-area x-ray fluorescence (SR-XRF) and diffraction (SR-XRD) mapping. SR-XRF mapping reveals several trace elements correlated with azurite, including arsenic, zirconium, antimony, barium, and bismuth, that appear in multiple manuscripts but were not always detected by point XRF. Within some manuscript leaves, variations in the concentration of trace elements associated with azurite coincide with distinct regions of the illuminations, suggesting systematic differences in azurite preparation or purification. Variations of the trace element concentrations in azurite are greater among different manuscript leaves than the variations within each individual leaf, suggesting the possibility that such impurities reflect distinct mineralogical/geologic sources. SR-XRD maps collected simultaneously with the SR-XRF maps confirm the identification of azurite regions and are consistent with impurities found in natural mineral sources of azurite. In general, our results suggest the feasibility of using azurite trace element analysis for provenance studies of illuminated manuscript fragments, and demonstrate the value of XRF mapping in non-destructive determination of trace element concentrations within a single pigment.
High-quality spatially-resolved measurements of electric fields are critical to understanding cha... more High-quality spatially-resolved measurements of electric fields are critical to understanding charge injection, charge transport, and charge trapping in semiconducting materials. Here, we report a variation of frequency-modulated Kelvin probe force microscopy (FM-KPFM) that enables spatially-resolved measurements of the electric field. We measure electric field components along multiple directions simultaneously by employing position modulation and lock-in detection in addition to numeric differentiation of the surface potential. We demonstrate the technique by recording linescans of the in-plane electric field vector in the vicinity of a patch of trapped charge in a DPh-BTBT organic field-effect transistor. This technique is simple to implement and should be especially useful for studying electric fields in spatially inhomogeneous samples like organic transistors and photovoltaic blends.
A poster presented at European Lacquer in Context Conference held in Brussels, January 2018
Inherently fragile, japanned surfaces are often in poor condition and heavily restored. This can ... more Inherently fragile, japanned surfaces are often in poor condition and heavily restored. This can obscure the intention of the craftsman and confuse both stylistic and technical analysis. This paper will explore the usefulness of scanning X-ray fluorescence (XRF) - a non-invasive technique commonly used to visualize pigment distribution in historical paintings – for the investigation of japanned surfaces.
Areas of two eighteenth century American japanned chests in the collection of the Metropolitan Museum of Art were scanned using a Bruker M6 Jetstream system. Data was processed to produce elemental distribution maps. A set of samples reproducing the typical stratigraphy of eighteenth century japanned surfaces was also scanned in order to further probe certain unexpected results.
The ability to overlay elemental maps made it possible to quickly see where elements were occurring separately and together, aiding the idenification of pigments and other inorganic material. Processing the data quanititavely made it possible to differentiate between areas where the same elements appear in different ratios, which was often helpful in distinguishing between original and restoration materials. The maps also made it easier to locate areas where only a small amount of original material remained. In one case, a siginificant part of the decorative scheme hidden beneath overpaint was revealed.
The limitations inherent to the technique will also be discussed. XRF does not provide information about organic materials or layer structure. The equipment is expensive and significant time and expertise is required both to scan and to process the data. Additionally, the technique is currently only suitable for two dimensional surfaces. Although it was possible to scan areas with raised decoration, the depth of field and spot size had to be increased, resulting in a less focused image.
The scanning XRF technique was found to be a significant improvement on conventional point XRF for the technical understanding of complicated, heavily restored japanned surfaces. The technique allowed the plausible attribution of pigments, metals and other inorganic material to regions, with areas of inconsistency often being immediately evident from the elemental maps.
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Areas of two eighteenth century American japanned chests in the collection of the Metropolitan Museum of Art were scanned using a Bruker M6 Jetstream system. Data was processed to produce elemental distribution maps. A set of samples reproducing the typical stratigraphy of eighteenth century japanned surfaces was also scanned in order to further probe certain unexpected results.
The ability to overlay elemental maps made it possible to quickly see where elements were occurring separately and together, aiding the idenification of pigments and other inorganic material. Processing the data quanititavely made it possible to differentiate between areas where the same elements appear in different ratios, which was often helpful in distinguishing between original and restoration materials. The maps also made it easier to locate areas where only a small amount of original material remained. In one case, a siginificant part of the decorative scheme hidden beneath overpaint was revealed.
The limitations inherent to the technique will also be discussed. XRF does not provide information about organic materials or layer structure. The equipment is expensive and significant time and expertise is required both to scan and to process the data. Additionally, the technique is currently only suitable for two dimensional surfaces. Although it was possible to scan areas with raised decoration, the depth of field and spot size had to be increased, resulting in a less focused image.
The scanning XRF technique was found to be a significant improvement on conventional point XRF for the technical understanding of complicated, heavily restored japanned surfaces. The technique allowed the plausible attribution of pigments, metals and other inorganic material to regions, with areas of inconsistency often being immediately evident from the elemental maps.
Areas of two eighteenth century American japanned chests in the collection of the Metropolitan Museum of Art were scanned using a Bruker M6 Jetstream system. Data was processed to produce elemental distribution maps. A set of samples reproducing the typical stratigraphy of eighteenth century japanned surfaces was also scanned in order to further probe certain unexpected results.
The ability to overlay elemental maps made it possible to quickly see where elements were occurring separately and together, aiding the idenification of pigments and other inorganic material. Processing the data quanititavely made it possible to differentiate between areas where the same elements appear in different ratios, which was often helpful in distinguishing between original and restoration materials. The maps also made it easier to locate areas where only a small amount of original material remained. In one case, a siginificant part of the decorative scheme hidden beneath overpaint was revealed.
The limitations inherent to the technique will also be discussed. XRF does not provide information about organic materials or layer structure. The equipment is expensive and significant time and expertise is required both to scan and to process the data. Additionally, the technique is currently only suitable for two dimensional surfaces. Although it was possible to scan areas with raised decoration, the depth of field and spot size had to be increased, resulting in a less focused image.
The scanning XRF technique was found to be a significant improvement on conventional point XRF for the technical understanding of complicated, heavily restored japanned surfaces. The technique allowed the plausible attribution of pigments, metals and other inorganic material to regions, with areas of inconsistency often being immediately evident from the elemental maps.