Silicon nitride is the most commonly used passivation layer in biosensor applications where electronic components must be interfaced with ionic solutions. Unfortunately, the predominant method for functionalizing silicon nitride surfaces, silane chemistry, suffers from a lack of reproducibility. As an alternative, we have developed a silane-free pathway that allows for the direct functionalization of silicon nitride through the creation of primary amines formed by exposure to a radio frequency glow discharge plasma fed with humidified air. The aminated surfaces can then be further functionalized by a variety of methods; here we demonstrate using glutaraldehyde as a bifunctional linker to attach a robust NeutrAvidin (NA) protein layer. Optimal amine formation, based on plasma exposure time, was determined by labeling treated surfaces with an amine-specific fluorinated probe and characterizing the coverage using X-ray photoelectron spectroscopy (XPS). XPS and radiolabeling studies also reveal that plasma-modified surfaces, as compared with silane-modified surfaces, result in similar NA surface coverage, but notably better reproducibility.
Native American quillwork is well documented in art historical and anthropological literature. Methods for folding quills to create floral and abstract designs are addressed, but studies of the materials used to color the quills are conspicuously absent. This is particularly true for the pre-aniline dyes used by communities east of the Mississippi, as historical recipes tend to be more reflective of Plains and Pacific Northwest quillwork traditions. Research to derive quill dye baths from raw materials has and continues to be pursued, but no large-scale scientific analysis of existing quillwork has previously been undertaken. To address this literature gap, a liquid chromatography-mass spectrometry analysis project has been completed on early quillwork in the collections of the McCord Museum, the National Museum of the American Indian, and the Peabody Museum of Archaeology and Ethnology; reflectance spectroscopy and X-ray fluorescence were also used as complementary techniques and to investigate the use of metal salts as quill stains. An extensive literature review provides a historical understanding of pre-1856 quillwork dyes; this representation will be compared with the usage patterns suggested by the collections' analysis. A more complete understanding of Native dye technology, addressing assumptions currently made with regards to the use of mordants, mixing of multiple dyestuffs in a single bath, and incorporation of "Old World" dyes, will also be presented.
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