lighting. [1] Typical phosphor-capped white LEDs are composed of GaN-based blue LED chips-for both phosphor excitation and blue color contribution-and phosphor materials with a wide emission bandwidth covering the rest of the visible range. [2] Mainstream phosphor development-to improve color conversion efficiency or to tune absorption/ emission bands-has so far been predominantly materials-oriented. [3] Quite recently, the authors' group proposed and demonstrated a paradigm-shifting concept in phosphor research, called photonic crystal (PhC) phosphors. [4] The basic idea behind PhC phosphors is to structurally engineer phosphor materials into periodic PhCs-with the associated photonic bandedge (PBE) modes tuned to the phosphor excitation wavelength-to induce an enhancement in phosphor excitation efficiency (and therefore color conversion efficiency). To demonstrate the viability and applicability of the technology, we stacked two batches of the PhC phosphor films emitting in red and green on top of a blue LED chip to efficiently and economically produce high-quality white light. [4d] The PhC phosphors employed in the previous conceptual demonstrations comprised simple 1D PhC film structures, in which parallel grating lines were arranged periodically in the lateral plane. [4c,d] Consequently, their response to vertically impinging excitation photons is inevitably polarizationsensitive, thereby limiting their overall efficiency when used with unpolarized excitation sources. Here in this study, we investigate a 2D square lattice PhC phosphor film as a more advanced PhC phosphor structure to eliminate the strong polarization dependence suffered by the previous 1D version. The implication and impact of the present experimental demonstration should be significant because phosphor excitation is commonly achieved with unpolarized excitation sources in most applications. Figure 1a schematically shows the proposed 2D PhC phosphor structure, in which a square lattice PhC backbone layer is sandwiched between a phosphor material (on top) and a transparent substrate (at the bottom). The fabrication began with the deposition of a waveguide backbone layer composed of a high refractive index material. For this purpose, we deposited As a continuing effort to improve the performance of photonic crystal (PhC) phosphors-an engineered nanophotonic phosphor structure developed by the authors' group-hereby 2D PhC phosphor films are introduced. In particular, the excitation polarization dependence inherent to and suffered by the precedent 1D PhC phosphors can be eliminated using a square lattice PhC structure due to its fourfold rotational symmetry. In addition, the thickness of the high index PhC backbone layer is intentionally increased so that dual excitation resonances occur for both the transverse-electric (TE) and transverse-magnetic (TM) waveguide modes, thereby effectively doubling the phosphor efficiency. 2D PhC phosphor structures are implemented and examined using colloidal quantum dots (CQDs) as phosphor material. Unli...
Photonic crystal (PhC) phosphor, in which the phosphor material is periodically modulated for an enhancement in color-conversion efficiency via resonant absorption of excitation photons, is a paradigm-shifting structural phosphor platform. Two-dimensional (2D) square-lattice PhC phosphor is currently considered the most advanced platform because of not only its high efficiency, but also its immunity to excitation polarization. In the present study, two major modifications are made to further improve the performance of the 2D PhC phosphor: increasing the refractive index contrast and planarizing the surface. The index contrast is improved by replacing the PhC backbone material with TiO2 whereas the surface planarization is achieved by removing excessive colloidal quantum dots from the surface. In comparison with the reference phosphor, the upgraded PhC phosphor exhibits ~59 times enhanced absorption (in simulations) and ~7 times enhanced emission (in experiments), both of which are unprecedentedly high. Our results not only brighten the viability and applicability of the PhC phosphor but also spur the phosphor development through structural engineering of phosphor materials.
Excessive preadipocyte differentiation/adipogenesis is closely linked to the development of obesity. LY3009120 is a pan-Raf kinase inhibitor and is known for its anticancer activities. In the present study, the effect of LY3009120 on 3T3-L1 cell adipogenesis was investigated. The differentiation of 3T3-L1 preadipocytes into adipocytes was measured by Oil Red O staining and AdipoRed assay. changes of cellular protein expression and phosphorylation levels in differentiating 3T3-L1 preadipocytes in the absence or presence of LY3009120 were determined by western blotting analysis. cell count assay was used to assess the cytotoxicity of LY3009120 on 3T3-L1 cells. At 0.3 µM, LY3009120 markedly inhibited lipid accumulation and decreased triglyceride content in differentiating 3T3-L1 cells. However, it had minimal effect on the elevated expression and phosphorylation of three Raf kinase isoforms (c-Raf, A-Raf, and B-Raf) observed in the cells. LY3009120 reduced not only the expression of ccAAT/enhancer-binding protein-α (c/EBP-α), peroxisome proliferator-activated receptor-γ (PPAR-γ), fatty acid synthase (FAS), acetyl coA carboxylase (Acc), and perilipin A, but also reduced the phosphorylation of signal transducer and activator of transcription-3 (STAT-3) in differentiating 3T3-L1 cells. LY3009120 also increased the phosphorylation of adenosine 3',5'-cyclic monophosphate (cAMP)-activated protein kinase (AMPK), but did not affect the phosphorylation or expression of liver kinase B1 in these cells. In summary, this is the first report, to the best of our knowledge, demonstrating that LY3009120 has an anti-adipogenic effect on 3T3-L1 cells, which may be mediated through control of the expression and phosphorylation of c/EBP-α, PPAR-γ, STAT-3, FAS, Acc, perilipin A, and AMPK.
Silk protein is being increasingly introduced as a prospective material for biomedical devices. However, a limited locus to intervene in nature-oriented silk protein makes it challenging to implement on-demand functions to silk. Here, we report how polymorphic transitions are related with molecular structures of artificially synthesized silk protein and design principles to construct a green-lithographic and high-performative protein resist. The repetition number and ratio of two major building blocks in synthesized silk protein are essential to determine the size and content of β-sheet crystallites, and radicals resulting from tyrosine cleavages by the 193 nm laser irradiation induce the β-sheet to α-helix transition. Synthesized silk is designed to exclusively comprise homogeneous building blocks and exhibit high crystallization and tyrosine-richness, thus constituting an excellent basis for developing a high-performance deep-UV photoresist. Additionally, our findings can be conjugated to design an electron-beam resist governed by the different irradiation−protein interaction mechanisms. All synthesis and lithography processes are fully water-based, promising green lithography. Using the engineered silk, a nanopatterned planar color filter showing the reduced angle dependence can be obtained. Our study provides insights into the industrial scale production of silk protein with ondemand functions.
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