Bio-nanophotonics is a wide field in which advanced optical materials, biomedicine, fundamental optics, and nanotechnology are combined and result in the development of biomedical optical chips. Silk fibers or synthetic bioabsorbable polymers are the main light-guiding components. In this work, an advanced concept of integrated bio-optics is proposed, which is based on bioinspired peptide optical materials exhibiting wide optical transparency, nonlinear and electrooptical properties, and effective passive and active waveguiding. Developed new technology combining bottom-up controlled deposition of peptide planar wafers of a large area and top-down focus ion beam lithography provides direct fabrication of peptide optical integrated circuits. Finding a deep modification of peptide optical properties by reconformation of biological secondary structure from native phase to β-sheet architecture is followed by the appearance of visible fluorescence and unexpected transition from a native passive optical waveguiding to an active one. Original biocompatibility, switchable regimes of waveguiding, and multifunctional nonlinear optical properties make these new peptide planar optical materials attractive for application in emerging technology of lab-on-biochips, combining biomedical photonic and electronic circuits toward medical diagnosis, light-activated therapy, and health monitoring.
mostly based on fluorescent (FL) agents of high brightness and combines exceptional optical properties with biocompatibility, biodegradability, and precise targeting both in vivo and in vitro. This includes inorganic semiconductor quantum dots, [2] carbon nanodots, [3] organic molecular dyes, [4] and genetically encoded universal FL proteins. [5] Additional specific class of extrinsic FL nanoprobes is amyloidbinding small molecule ligands (thioflavin T, Congo red and more) employed for tracking the kinetics of amyloid fibrils growth. [6] Each of the imaging agents has its inherent mechanism of photon emission, which defines its figures of merit for bioimaging: FL spectral region, quantum yield (QY), and photobleaching. [7,8] For instance, quantum dots and organic dye molecules exhibit FL in the visible range and have very high QY exceeding 90%. However, the organic molecular dyes are limited for long-term bioimaging applications because of photobleaching issues. The biocompatibility is another basic parameter of any biolabels, which is especially critical for some organic dyes and inorganic semiconductor quantum dots, containing heavy metals. Recently found FL carbon nanodots are biocompatible but have a low QY. [9] The green fluorescence protein (GFP) and its homologues are the only molecules, known until today, having biological origin FL and providing unique biocompatibility. These proteins exhibit pronounced FL with QY reaching 90% covering the entire visible spectrum, which makes them unique FL tags [10] among unlimited number of nonfluorescent peptide and protein biomolecules. [1,2,5,7] Alternative composition-insensitive visible FL was recently found in biological and bioinspired nanostructures characterized by specific ordering of biomolecules into antiparallel β-sheets structures. This includes a wide variety of diverse biomolecular compositions, such as amyloidogenic proteins, [11,12] PEGylated peptides, [13,14] nonaromatic biogenic, and synthetic peptides [15] and recently natural silk fibrils. [16] The basic features of these FL nanostructures are similar fibrillar morphology, original β-sheets secondary structure, and identical visible FL optical spectrum. These common structural and optical properties enable to relate all of them to a wide class of thermodynamically stable disease-and nondiseased-related amyloid structures. [17][18][19] Such β-sheet structures and visible FL can also Nanoscale bioimaging is a highly important scientific and technological tool, where fluorescent (FL) proteins, organic molecular dyes, inorganic quantum dots, and lately carbon dots are widely used as light emitting biolabels. In this work, a new class of visible FL bioorganic nanodots, self-assembled from short peptides of different composition and origin, is introduced. It is shown that the electronic energy spectrum of native nonfluorescent peptide nanodots (PNDs) is deeply modified upon thermally mediated refolding of their biological secondary structure from native metastable to stable β-sheet rich structure. This ...
A detailed simulation of the fringing-field effect in liquid-crystal (LC)-based blazed-grating structures has been carried out. These studies are aimed at clarifying the relationship between the width of the fringing-field-broadened phase profile of the blazed grating and the LC cell thickness. This fringing-field broadening of the blazed grating's phase profile is shown to affect mostly the 2pi phase-step zone (fly-back zone) of the blazed grating. The results of the simulations carried out on the blazed-grating structure indicate two main effects of the fringing field: (1) reduction in the attainable diffraction efficiency and (2) limitation of the maximum deflection angle of the device. Both effects are shown to be directly linked to the broadening of the fly-back zone, which is shown to be proportional to the LC cell thickness.
Localized surface plasmons-polaritons represent collective behavior of free electrons confined to metal particles. This effect may be used for enhancing efficiency of solar cells and for other opto-electronic applications. Plasmon resonance strongly affects optical properties of ultra-thin, island-like, metal films. In the present work, the Finite Difference Time Domain (FDTD) method is used to model transmittance spectra of thin gold island films grown on a glass substrate. The FDTD calculations were performed for island structure, corresponding to the Volmer-Weber model of thin film growth. The proposed simulation model is based on fitting of experimental data on nanostructure of ultra-thin gold films, reported in several independent studies, to the FDTD simulation setup. The results of FDTD modeling are then compared to the experimentally measured transmittance spectra of prepared thin gold films and found to be in a good agreement with experimental data.
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