mechanical strength, flexibility, and chemical stability. [1][2][3] However, the absence of a bandgap in graphene has limited its application in optoelectronics. [4] This has introduced a passive way of using graphene by integrating it with other functional materials. [5,6] Integration of graphene with 1D or 2D materials, such as inorganic semiconductors, [7,8] chalcogenides, [9][10][11] and hexagonal boron nitride (h-BN), [12][13][14] has created interesting and tunable optoelectronic properties suitable for multifunctional device applications. Particularly, 2D materials such as GaSe, InSe, and MoS 2 can be stacked or grown on graphene supported by the van der Walls (vdW) forces. [9,[15][16][17][18][19][20] GaSe is a 2D vdW chalcogenide semiconductor material with a direct bandgap of 2.1 eV in its bulk form. A single layer of GaSe possesses a larger and indirect bandgap (3.0 eV), which turns into a smaller and direct bandgap (2.1 eV) material upon increasing the number of vdW layers. [21,22] It makes the bulk GaSe a suitable material for photodetection and photovoltaic applications. Exfoliated GaSe flakes have been demonstrated for photodetector application with a responsivity of 2.8 A W -1 for 254 nm light. [21] Recently, photodetectors based on GaSe and graphene heterostructures have also been studied for various optical ranges. [23,15] Researchers have demonstrated graphene as an electrode in two terminals or gated photo detector devices. [16,21] Controlled growth of GaSe on 2D graphene has potential to fabricate multifunctional integrated devices. However, the direct growth of GaSe on patterned graphene has rarely been reported. [17] Position-controlled growth of GaSe on a prepatterned large-area graphene substrate can be advantageous for fabricating large-scale GaSe-based detector array and other integrated devices.This report demonstrates the growth and fabrication of GaSe photodetector array on prepatterned graphene. The GaSe was grown on top of graphene using a molecular beam epitaxy (MBE) technique. Physical properties of the grown GaSe layer were investigated using X-ray diffraction (XRD), absorption, and Raman spectroscopies. GaSe-based photodetector diodes were fabricated and studied under the exposure of lights of different wavelengths and incident powers. Furthermore, 16 × 16 detectors of 40 × 40 um 2 were also fabricated and examined to demonstrate the feasibility of addressable photodetector array and mapping capability.
γ-Aminobutyric acid (GABA) content in fermented plant products and their main plant materials (aerial part of Acanthopanax sessiliflorus, fruit of Crataegus pinnatifida, and whole plant of Morus alba) was determined by high-performance liquid chromatography. GABA was quantified using a reversephase column with a gradient elution program (water:acetonitrile =90:10 to 0:100 for 40 min). UV detection was conducted at 280 nm. GABA content was measured in fermented plant products (15.07 mg/g), aerial part of A. sessiliflorus (4.49 mg/g), fruit of C. pinnatifida (10.59 mg/g), and whole plant of M. alba (2.31 mg/g). The presence of GABA in fermented plant products, including A. sessiliflorus, C. pinnatifida, and M. alba is important in industrial application for health supplements.
We report laser emission from gallium nitride (GaN) microrods that are introduced into mammalian cells and the application of these microrods for cell labeling. GaN microrods were grown on graphene-coated SiO2/Si substrates by metal-organic vapor phase epitaxy. The GaN microrods are easily detached from the substrates because of the weakness of the van der Waals forces between GaN and graphene. The uptake of microrods into HeLa cells via endocytosis and viability after uptake were investigated. Normal cellular activities, including migration and division, were observed over 2 weeks in culture. Furthermore, the photoluminescence spectra of the internalized microrods exhibited sharp laser emission peaks with a low lasing threshold of 270 kW/cm2.
Species identification of wood provides important information for archaeology, restoration of cultural assets, preventing illegal logging, and more. Wood species are usually identified based on their anatomical features with the use of a microscope. However, this method may not be able to distinguish between anatomically similar species or subspecies. To overcome this problem, wood species need to be identified at the molecular level using DNA sequencing. However, unlike living plant cells, wood is difficult to pulverize using a mortar, and DNA extraction from dried wood is challenging.To solve these problems, we propose a pretreatment method in which wood is pulverized using 60-grit sandpaper and hydrated with water for 2 days. Using this method, we were able to stably amplify the rpoB gene from the extracted DNA of Pinus rigida. In addition, sequence analysis of the rpoB gene revealed six single nucleotide polymorphisms (SNPs), which classified the rpoB sequences in the genus Pinus into five groups. Our data indicate that although these SNPs were not suitable for species identification, they can potentially be used to determine the origin of different wood subspecies or individual samples of wood.
The julolidine based interfacial modifier (IM-J) for cathode buffer layer following the "donor-acceptor" design concept with julolidine substituent as an electron donating moiety was incoporated to improve the surface properties of ZnO. Simple treatment of metal oxide type cathode buffer materials with organic interfacial modifier induces the enhanced photovoltaic performance and could effectively overcome several interfacial problems in inverted organic photovoltaic cells (I-OPVs). We studied on the coverage of IM-J on ZnO surface with variation of solution concentrations to reduce charge recombination and macroscopic phase separation. At the optimum condition, ZnO/IM-J (0.05 w/v%), IM-J significantly decreased the surface tension (46.1 mN/m) and improved surface morphology (RMS roughness: 0.61 nm). As a result, compared to the unmodified ZnO based device, the ZnO/IM-J based I-OPVs showed significantly improved power conversion efficiency (PCE) from 7.41 to 8.07% due to the increased photocurrent density (Jsc) and fill factor (FF). It is concluded that IM-J is one of the promising candidates for controlling electronic property of ZnO buffer layer in inverted organic photovoltaic cells. Also, our interfacial modified system can be utilized in other optoelectronic devices.
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