Fluorescence images approaching sub-micron resolution are formed in thin nanocrystalline phosphor films. The images are created with UV exposure of the films under chrome-coated quartz masks. The UV light locally changes the valence state of the samarium ions in the nanocrystalline phosphors to activate fluorescence properties. The red fluorescence images are then read-out with blue-violet light. With an imaging resolution approaching the diffraction limit, this technology has potential for anti-counterfeiting labelling or optical data storage applications.
KEYWORDS: Nanoparticles, Quantum dots, Glasses, Medical research, In vivo imaging, In vitro testing, Image sensors, Sensors, Optical sensors, Semiconductors
Nanoparticles with various properties and functions are of growing interest for biomedical research, such as in vivo and in vitro sensors, imaging agents and delivery vehicles of therapeutics. An effective method to deliver nanoparticles into the intracellular environment is still a major challenge and critical to many biological studies. Current techniques, such as intracellular uptake, electroporation and microinjection, have different benefits and limitations (e.g., aggregation and endosomal degradation of nanoparticles, high cell mortality and low throughput). We demonstrate application of the well-established microelectrophoresis technique for the first time to deliver nanoparticles into target cells using fine-tipped micropipettes, which overcomes some of these delivery difficulties. Semiconductive quantum dots were selected as the nanoparticles in this study as they are widely used for biomedical imaging and sensing due to having functionalized surfaces suitable for bioconjugation, adaptable photophysical properties for multiplexed detection, and superior stability for longer investigation times. We developed a method to prepare monodisperse suspensions of quantum dots with average hydrodynamic diameter of ~20nm, which demonstrated sufficient colloidal stability to prevent aggregation and blockages in the tip of micropipettes during ejection while enabling sufficient electrical conductivity for ejection and recording electrical activity of cells. Fine-tipped glass micropipettes with an average tip inner diameter of 206 nm for ejection but less than 500 nm to minimize the cell membrane damage and cell distortion were successfully fabricated. Finally, quantum dots were successfully delivered into living human embryonic kidney cells using small electrical currents through fine-tipped glass micropipettes. The delivered quantum dots were found to stay monodispersed within the cells for 2 hours. We believe that microelectrophoresis technique may serve as a simple and general strategy for delivering a variety of biocompatible nanoparticles intracellularly in various biological systems.
In this paper, a novel and efficient approach to digital optical data storage using rare-earth ion doped inorganic insulators is demonstrated. More specifically, the nanocrystalline alkaline earth halide BaFCl:Sm is shown to hold great potential for multilevel optical data storage. Proof-of-concept demonstrations show that these phosphors could be used for rewritable, multilevel optical data storage down to the physical dimensions of a single nanocrystal. Multilevel information storage is based on the highly-efficient and reversible conversion of Sm3+ to Sm2+ ions upon exposure to UV-C light. The stored information is efficiently read-out by employing the photoluminescence of the Sm 2+ ions in the nanocrystals, with the signal strength being dependent on the UV-C intensity used during the write step. This serves as the mechanism for multilevel data storage in the individual nanocrystals. This data storage platform has the potential to be extended to 2D and 3D memory for storage densities that could approach tera- or even petabyte/cm3 levels.
In this paper, an egg-shaped microbubble is proposed and analyzed firstly, which is fabricated by the pressure-assisted arc discharge technique. By tailoring the arc parameters and the position of glass tube during the fabrication process, the thinnest wall of the fabricated microbubble could reach to the level of 873nm. Then, the fiber Fabry–Perot interference technique is used to analyze the deformation of microbubble that under different filling pressures. It is found that the endface of micro-bubble occurs compression when the inner pressure increasing from 4Kpa to 1400KPa. And the pressure sensitivity of such egg-shaped microbubble sample is14.3pm/Kpa. Results of this study could be good reference for developing new pressure sensors, etc.
A general model of excitation and fluorescence recapturing by the forward and backward modes of filled microstructured
optical fibres (MOFs) is developed for fluorecence-based fibre optic sensors. It is demonstrated
that the light-matter overlap alone does not determine the optimal fibre choice for maximum sensing efficiency.
Fibre designs with sub-wavelength features and high-index glasses exhibit localised regions of high intensity, and
we show that these regions can lead to approximately two orders of magnitude enhancement of fluorescence recapturing.
We demonstrate higher efficiency of fluorescence recapturing into backward modes in comparison with
that of forward modes. We present experimental results for both backward and forward flourescence recapturing
and demostrate a good qualitative agreement between the numerical model and experimental results.
Glass microstructured optical fibers have been rendered biologically active for the first time active via the
immobilization of antibodies within the holes in the fiber cross-section. This has been done by introducing coating layers
to the internal surfaces of soft glass fibers. The detection of proteins that bind to these antibodies has been demonstrated
experimentally within this system via the use of fluorescence labeling. The approach combines the sensitivity resulting
from the long interaction lengths of filled fibers with the selectivity provided by the use of antibodies.
We report integrated devices in chalcogenide glass for all-optical signal processing, based on pure Kerr (near instantaneous) optical nonlinearities. We demonstrate an integrated 2R optical regenerator operating through a combination of nonlinear self-phase modulation followed by spectral filtering, with a potential to reach bit rates in excess of 1Tb/s. It consists of a low loss As2S3 chalcogenide rib waveguide incorporating a high quality Bragg grating written by an ultra-stable Sagnac interferometer. We achieve a nonlinear power transfer curve using 1.4ps pulses, sufficient for suppressing noise in an amplified link. In addition, we report photonic crystal structures fabricated by focused ion beam (FIB) milling in AMTIR-1 (Ge33As12Se55) chalcogenide glass. We realize high quality free-standing photonic crystal membranes, and observe optical "Fano" resonances in the transmission spectra at normal incidence. We achieve good agreement with theoretical results based on 3D finite difference time-domain calculations. Finally, we achieve resonant evanescent coupling to photonic crystal waveguides via tapered microstructured optical fibre (MOF) nanowires.
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