Near-infrared (NIR) fluorescence is a well-established avenue for biomedical imaging. Fluorescent dyes are the primary choice for NIR bio-imaging, but not without notable drawbacks. Current challenges in this field include identifying candidate chromophores with sufficient quantum yield, improved biological stability, low susceptibility to photo bleaching, and amenability to introduced functionality. Ruby nanoparticles exhibit these traits, and thus are subject to extensive research. A preliminary survey of other minerals revelaed a handful of samples of Colorado tiger chert exhibiting similar far-red and NIR fluorescence. The fluorescence of these chert was characterized in order to illuminate a potential candidate for NIR biomedical imaging.<br/><br/>The IR fluorescence of the chert is superficial, with only a thin patina exhibiting fluorescence. The excitation and emission spectra of both synthetic ruby and the chert samples were obtained. The synthetic ruby yielded a sharp emissions peak at 695nm, while the chert featured a broad peak centered at 786nm. Tissues absorb less at longer wavelengths within the NIR; the longer maximum emission of the chert may provide better resolution or depth than that of synthetic ruby. The broadness of the chert emissions peak results in the visible far-red fluorescence, and may be attributed to the heterogeneity of the sample. Upon various treatments, none induced fluorescence in the non-fluorescent core sample, and only the heat treatment of 500 C for 2 days extinguished the fluorescence of the patina. The inactivity of the fluorescence towards a variety of conditions indicates biological stability. The composition of the patina was investigated using SEM-EDX and ICP-OES, yielding mixed results. While EDX indicated an appreciable iron content on the surface of the patina, an abundance of manganese was identified within the patina by OES. Future work may aim to resolve the origin of this fluorescence, and isolate or synthesize the responsible factors.

Characterization of Colorado tiger chert far-red and near IR fluorescence

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.