RESUMO
Recently, deep-red-emitting phosphors that can be excited by ultraviolet (UV) and near-ultraviolet (NUV) light have been extensively investigated for plant growth LED applications. However, due to the harmful effects of these high-energy rays on plants, violet- or blue-excited deep-red-emitting phosphors are considered a more appropriate solution. In this work, SrAl12O19:Cr3+ phosphors were synthesized using a simple solid-state reaction, revealing a strikingly sharp deep-red emission band centered at 694 nm and effective excitation by violet light. The optimal SrAl12O19:1.0%Cr3+ phosphor, annealed at 1500°C, exhibits an extended lifetime of 0.549 ms, an energy activation level of 0.239 eV, a good quantum efficiency (QE) of 36.2%, and superior color purity at 100%. Further, an LED prototype with a precise absorption spectrum for far-red phytochrome (Pfr) has been demonstrated. These results indicate that the synthesized SrAl12O19:1.0%Cr3+ phosphors could be used as a promising deep-red-emitting phosphor for plant growth LED.
Assuntos
Cromo , Cromo/química , Desenvolvimento Vegetal , Substâncias Luminescentes/química , Substâncias Luminescentes/síntese química , Estrôncio/químicaRESUMO
BACKGROUND AND OBJECTIVE: Alpinia, the largest genus of Zingiberaceae, includes ca. 250 species. The A. coriandriodora D. Fang was recognized for Vietnamese flora. However, the systematic position of this species within Alpinia genus was unclear. The study aimed to understand the phylogenetic placement of A. coriandriodora based on the molecular data and interpret evolution of the key morphological characters. MATERIALS AND METHODS: The phylogenetic analysis were conducted by using the combined dataset of two DNA regions by both Maximum Likelihood (ML) and Bayesian Inference (BI) methods. Seven morphological characters were selected for morphological character evolution and the analysis was performed in Mesquite. RESULTS: Alpinia coriandriodora was supported closely related to southern Chinese species of Alpinia. Morphological character optimizations suggest that the presence/absence of tomentum in leaf, inflorescence rachis and ovary is an important character for the taxonomy of Alpinia. The character evolution analyses indicated that panicle is ancestral character in Alpinia. The A. coriandriodora shares different evolutionary histories based on our character re-construction to most members of Southeast Asian Alpinia. The presence of filament is supposed to be an adaptation to the pollination by insects for species of Alpinia. CONCLUSION: The present study revealed the molecular phylogenetic relationship of A. coriandriodora within Alpinia. The presence of filament could be an adaptation to the pollination by insects for species of Alpinia. Some reasonable conservation strategies are proposed to protect the species including maintenance of the plant's natural habitats, seeds or seedlings collection for germplasm storage and artificial breeding using biotechnology.
Assuntos
Alpinia/genética , Evolução Biológica , Conservação dos Recursos Naturais , Genes de Plantas , Filogenia , Alpinia/crescimento & desenvolvimento , Regulação da Expressão Gênica de Plantas , Especificidade da EspécieRESUMO
Nanostructuring is considered one of the key approaches to achieve highly efficient thermoelectric alloys by reducing thermal conductivity. In this study, we investigated the effect of oxide (ZnO and SnO2) nanolayers at the grain boundaries of polycrystalline In0.2Yb0.1Co4Sb12 skutterudites on their electrical and thermal transport properties. Skutterudite powders with oxide nanolayers were prepared by atomic layer deposition method, and the number of deposition cycles was varied to control the coating thickness. The coated powders were consolidated by spark plasma sintering. With increasing number of deposition cycle, the electrical conductivity gradually decreased, while the Seebeck coefficient changed insignificantly; this indicates that the carrier mobility decreased due to the oxide nanolayers. In contrast, the lattice thermal conductivity increased with an increase in the number of deposition cycles, demonstrating the reduction in phonon scattering by grain boundaries owing to the oxide nanolayers. Thus, we could easily control the thermoelectric properties of skutterudite materials through adjusting the oxide nanolayer by atomic layer deposition method.
RESUMO
Point defect or doping in Strontium titanium oxide (STO) largely determines the thermoelectric (TE) properties. So far, insufficient knowledge exists on the impact of double Schottky barrier on the TE performance. Herein, we report a drastic effect of double Schottky barrier on the TE performance in undoped STO. It demonstrates that incorporation of Reduced Graphene Oxide (RGO) into undoped STO weakens the double Schottky barrier and thereby results in a simultaneous increase in both carrier concentration and mobility of undoped STO. The enhanced mobility exhibits single crystal-like behavior. This increase in the carrier concentration and mobility boosts the electrical conductivity and power factor of undoped STO, which is attributed to the reduction of the double Schottky barrier height and/or the band alignment of STO and RGO that allow the charge transfer through the interface at grain boundaries. Furthermore, this STO/RGO interface also enhances the phonon scattering, which results in low thermal conductivity. This strategy significantly increases the ratio of σ/κ, resulting in an enhancement in ZT as compared with pure undoped STO. This study opens a new window to optimize the TE properties of many candidate materials.
RESUMO
Using macrophage recruitment in tumors, we develop active, transportable, cancer theragnostic macrophage-based microrobots as vector to deliver therapeutic agents to tumor regions. The macrophage-based microrobots contain docetaxel (DTX)-loaded poly-lactic-co-glycolic-acid (PLGA) nanoparticles (NPs) for chemotherapy and Fe3O4 magnetic NPs (MNPs) for active targeting using an electromagnetic actuation (EMA) system. And, the macrophage-based microrobots are synthesized through the phagocytosis of the drug NPs and MNPs in the macrophages. The anticancer effects of the microrobots on tumor cell lines (CT-26 and 4T1) are evaluated in vitro by cytotoxic assay. In addition, the active tumor targeting by the EMA system and macrophage recruitment, and the chemotherapeutic effect of the microrobots are evaluated using three-dimensional (3D) tumor spheroids. The microrobots exhibited clear cytotoxicity toward tumor cells, with a low survivability rate (<50%). The 3D tumor spheroid assay showed that the microrobots demonstrated hybrid actuation through active tumor targeting by the EMA system and infiltration into the tumor spheroid by macrophage recruitment, resulting in tumor cell death caused by the delivered antitumor drug. Thus, the active, transportable, macrophage-based theragnostic microrobots can be considered to be biocompatible vectors for cancer therapy.