Browsing by Subject "Layer-by-layer assembly"
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Item Open Access Anisotropic Emission from Multilayered Plasmon Resonator Nanocomposites of Isotropic Semiconductor Quantum Dots(American Chemical Society, 2011-01-19) Ozel, T.; Nizamoglu, S.; Sefunc, M.A.; Samarskaya, O.; Ozel, I. O.; Mutlugun, E.; Lesnyak, V.; Gaponik N.; Eychmuller, A.; Gaponenko, S. V.; Demir, Hilmi VolkanWe propose and demonstrate a nanocomposite localized surface plasmon resonator embedded into an artificial three-dimensional construction. Colloidal semiconductor quantum dots are assembled between layers of metal nanoparticles to create a highly strong plasmon-exciton interaction in the plasmonic cavity. In such a multilayered plasmonic resonator architecture of isotropic CdTe quantum dots, we observed polarized light emission of 80% in the vertical polarization with an enhancement factor of 4.4, resulting in a steady-state anisotropy value of 0.26 and reaching the highest quantum efficiency level of 30% ever reported for such CdTe quantum dot solids. Our electromagnetic simulation results are in good agreement with the experimental characterization data showing a significant emission enhancement in the vertical polarization, for which their fluorescence decay lifetimes are substantially shortened by consecutive replication of our unit cell architecture design. Such strongly plasmon-exciton coupling nanocomposites hold great promise for future exploitation and development of quantum dot plasmonic biophotonics and quantum dot plasmonic optoelectronics.Item Open Access Layer-by-layer self-assembled semiconductor nanocrystal composites with nonradiative resonance energy transfer for innovative architectural precise color tuning and control(Bilkent University, 2009-08) Çiçek, NeslihanIn recent years semiconductor quantum dot nanocrystals (NC) have attracted significant interest and have found numerous important optoelectronic device applications mainly because of their highly tunable optical properties. For example, precisely tuning shades of color chromaticity is critically important in solid state lighting to achieve ultra-efficient, application-specific, spectrallyengineered illumination. To date such color tuning and control of NC emitters have been investigated and demonstrated only based on their composition, shape, and size (using the quantum confinement effect). All of these parameters are, however, limited to be controlled and set during the synthesis process. As a post-synthesis alternative, we proposed and demonstrated the precise and broad control and tuning of color chromaticity by strongly modifying photoluminescence decay kinetics of NC emitters solely based on nonradiative Förster resonance energy transfer (FRET) in layer-by-layer self-assembled NC composite structures. Locating NC emitters in such a layered architecture with a targeted gradient of bandgap in the close proximity (<10 nm) of each other and spatially interspacing them at the nanoscale (with a precision of <1 nm) enabled us to fine-tune and master FRET at a desired efficiency level of nonradiative energy transfer from electronically excited donor NCs to luminescent acceptor iv NCs. These proof-of-concept experimental demonstrations, combined with our numerical modeling and simulation results, proved a highly sensitive tuning capability based on FRET to span a broad color area in Commission Internationale De L’Eclairage (CIE) chromaticity diagram in principle beyond the limits of each of the commonly used LED epitaxial material systems. This innovative architectural tuning opens up a new direction for the photometric engineering of color-conversion LEDs.Item Open Access Nanoengineering hybrid supramolecular multilayered biomaterials using polysaccharides and self-assembling peptide amphiphiles(Wiley-VCH Verlag, 2017) Borges, J.; Sousa, M. P.; Cinar, G.; Caridade, S. G.; Güler, Mustafa O.; Mano, J. F.Developing complex supramolecular biomaterials through highly dynamic and reversible noncovalent interactions has attracted great attention from the scientific community aiming key biomedical and biotechnological applications, including tissue engineering, regenerative medicine, or drug delivery. In this study, the authors report the fabrication of hybrid supramolecular multilayered biomaterials, comprising high-molecular-weight biopolymers and oppositely charged low-molecular-weight peptide amphiphiles (PAs), through combination of self-assembly and electrostatically driven layer-by-layer (LbL) assembly approach. Alginate, an anionic polysaccharide, is used to trigger the self-assembling capability of positively charged PA and formation of 1D nanofiber networks. The LbL technology is further used to fabricate supramolecular multilayered biomaterials by repeating the alternate deposition of both molecules. The fabrication process is monitored by quartz crystal microbalance, revealing that both materials can be successfully combined to conceive stable supramolecular systems. The morphological properties of the systems are studied by advanced microscopy techniques, revealing the nanostructured dimensions and 1D nanofibrous network of the assembly formed by the two molecules. Enhanced C2C12 cell adhesion, proliferation, and differentiation are observed on nanostructures having PA as outermost layer. Such supramolecular biomaterials demonstrate to be innovative matrices for cell culture and hold great potential to be used in the near future as promising biomimetic supramolecular nanoplatforms for practical applications.