We report the successful fabrication of layers of functionalized nanoparticles using a novel infrared, laser-based
deposition technique. A frozen suspension of nanoparticles was ablated with a laser tuned to a vibrational mode of the
solvent, resulting in the disruption of the matrix and ejection of the nanoparticles. The solvent was pumped away and
the nanoparticles collected by a receiving substrate in a conformal process. Photoluminescence measurements of
nanoparticles containing two common dyes showed no significant change to the emission properties of either dye,
suggesting that no damage occurred during the laser ablation process. The process is generally applicable to particles of
various sizes, shapes, and chemistries provided that an appropriate solvent is chosen. Deposition through shadow masks
turned out to be straightforward using this technique, suggesting its potential utility in preparing designer sensor
structures using functionalized nanoparticles.
We report on monodisperse fluorescent core-shell silica nanoparticles (C dots) with enhanced brightness and photostability as compared to parent free dye in aqueous solution. Dots containing either tetramethylrhodamine or 7-nitrobenz-2-oxa-1,3-diazole dyes with diameters ranging from tens of nanometers to microns are discussed. The benefits of the core-shell architecture are described in terms of enhanced fluorescent yield of the fluorophores in the quasi-solid-state environment within the particle as compared with parent free dye in water. Several applications of these particles in the fields of photonics and the life sciences are discussed. Specifically, fluorescent core-shell silica nanoparticles are investigated as an active medium for photonic building blocks assembled on zinc sulfide-based seed particles. Initial assembly results for these composite raspberry structures are shown. Finally, applications in the life sciences are explored, including targeting of specific antibody receptors using these single-emission nanoparticles. We expand on single-emission core-shell architecture to incorporate environmentally-sensitive fluorophores to create quantitative ratiometric nanoscale sensors capable of interrogating chemical concentrations on the sub-cellular to molecular levels and demonstrate initial results of intracellular pH imaging. The concept of a single particle laboratory (SPL) is introduced as an active investigator of its environment.
We present the initial results of entraining colloidal quantum dots emitting at wavelengths from 0.5um through 1.2um, in various micro-structured optical fibers. Conventional and non-conventional, micro-structured optical fibers fabricated at Virginia Tech’s Fiber & ElectroOptics Research Center (FEORC) have been combined with semiconductor, colloidal quantum dots fabricated by the VT Advanced Biomedical Center (VTabc). The results are presented primarily in the form of visual verification and analysis of entrainment phenomena, for a cross-section of colloidal dot and micro-structured fiber forms. Unique optical, electro-optical and material properties resulting from the combinations are visibly suggested in the results. Core/clad/free space propagation properties and effects of emitted and absorbed light fields are observed to be dependent on the structure, aspect ratio and materials of the fibers as well as the properties of the colloidal quantum dots. Basic spectral data on representative free-space materials will be presented in the current paper. The presentation will explore in passing, the research options available to such quantum dot-fiber combinations, including advanced sensors, sources and filters.
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