Silicon (Si) nanomaterials with bright luminescence in the visible region are promising materials for use as the nextgeneration light source in displays, lighting, and biomedical imaging. A scalable and cost-effective method for the synthesis of Si quantum dots (SiQDs) is essential for research and development in the field of quantum dots. Herein, we show a facile and costeffective method for controlling the structure and properties of SiQDs, obtained using the pyrolysis of hydrogen silsesquioxane (HSQ) polymer precursors synthesized using methanol. The amount of methanol added to trichlorosilane prior to the addition of water is a key factor that determines the structure and crosslinking density of the HSQ polymer used as the precursor. In turn, these features control the SiQD size, crystallinity, and luminescence efficiency. Dodecyl-passivated SiQDs of size 3−4 nm are obtained as a final product and show red photoluminescence (PL) at approximately 700−800 nm with the peak wavelength depending on the size of SiQDs. The PL quantum yield ranged from 10 to 25% with the highest value obtained for the smaller SiQDs with higher crystallinity. The present study provides new insight into the SiQD synthesis procedure and the understanding of the reaction mechanism. Furthermore, it was found that only methanol is the crucial reagent and the facile and cost-effective synthesis method can be controlled merely by changing the amount of methanol.

Nanomaterial toxicity and environmental concerns inspired us to develop a scalable method for fabricating quantum dots with a positive environmental impact. Milling rice creates billions of kilograms of rice husks yearly, which are an excellent source for high-quality silica (SiO 2 ) and value-added silicon (Si) powders. Herein, we synthesize SiO 2 , porous Si, and Si quantum dots (SiQDs) from rice husks containing 20 wt % SiO 2 using a conventional chemical synthesis method and investigate the structure, optical, and optoelectrical properties. The extraction yields of SiO 2 and Si powders from rice husks are 100 and 86%, respectively. The final product, decyl-passivated SiQDs, consists of 3 nm crystalline particles that are soluble in an organic solvent. A colloidal solution of the decyl-passivated SiQDs exhibits orange− red photoluminescence at a wavelength of 680 nm, with a 21% quantum yield. This colloidal solution is used to develop a SiQD LED, resulting in orange−red electroluminescence.

SUMMARYPre-messenger RNA (pre-mRNA) splicing is essential in eukaryotic cells. In animals and yeasts, the DEAHbox RNA-dependent ATPase Prp16 mediates conformational change of the spliceosome, thereby facilitating pre-mRNA splicing. In yeasts, Prp16 also plays an important role in splicing fidelity. Conversely, PRP16 orthologs in Chlamydomonas reinhardtii and nematode do not have an important role in general pre-mRNA splicing, but are required for gene silencing and sex determination, respectively. Functions of PRP16 orthologs in higher plants have not been described until now. Here we show that the CLUMSY VEIN (CUV) gene encoding the unique Prp16 ortholog in Arabidopsis thaliana facilitates auxin-mediated development including male-gametophyte transmission, apical-basal patterning of embryonic and gynoecium development, stamen development, phyllotactic flower positioning, and vascular development. cuv-1 mutation differentially affects splicing and expression of genes involved in auxin biosynthesis, polar auxin transport, auxin perception and auxin signaling. The cuv-1 mutation does not have an equal influence on pre-mRNA substrates. We propose that Arabidopsis PRP16/CUV differentially facilitates expression of genes, which include genes involved in auxin biosynthesis, transport, perception and signaling, thereby collectively influencing auxin-mediated development.

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Liver-on-a-Chip technology holds considerable potential for applications in drug screening and chemical-safety testing. To establish such platforms, functional hepatocytes are required; however, primary hepatocytes are commonly used, despite problems involving donor limitations, lot-to-lot variation, and unsatisfactory two-dimensional culture methods. Although human pluripotent stem cells (hPSCs) may represent a strong alternative contender to address the aforementioned issues, remaining technological challenges include the robust, highly efficient production of high-purity hepatic clusters. In addition, current Liveron-a-Chip platforms are relatively complicated and not applicable for high-throughput experiments. Here, we develop a very simple Liver-on-a-Chip platform with mature and functional hepatocyte-like cells derived from hPSCs. To establish a method for hepatic differentiation of hPSCs, cells were first treated by inhibiting the phosphoinositide 3-kinase-and Rho-associated protein kinase-signaling pathways to stop self-renewal and improve survival, respectively, which enabled the formation of a well-defined endoderm and facilitated hepatocyte commitment. Next, a simple microfluidic device was used to create a three-dimensional (3D) culture environment that enhanced the maturation and function of hepatocyte-like cells by increasing the expression of both hepatic maturation markers and cytochrome P450. Finally, we confirmed improvements in hepatic functions, such as drug uptake/excretion capabilities, in >90% of 3D-matured hepatocyte-like cells by indocyanin green assay. These results indicated that the incorporation of hPSC-derived hepatocytes on our Liver-on-a-Chip platform may serve to enhance the processes involved in drug screening and chemical-safety testing.

Silicon (Si) is a highly abundant, environmentally benign, and durable material and is the most popular semiconductor material; and it is used for the field enhancement of dielectric materials. Porous Si (PSi) exhibits high functionality due to its specific structure. However, the field enhancement of PSi has not been clarified sufficiently. Herein, we present the field enhancement of PSi by the fluorescence intensity enhancement of a dye molecule. The raw material used for producing PSi was rice husk, a biomass material. A nanocoral structure, consisting of spheroidal structures on the surface of PSi, was observed when PSi was subjected to chemical processes and pulsed laser melting, and it demonstrated large field enhancement with an enhancement factor (EF) of up to 545. Confocal microscopy was used for EF mapping of samples before and after laser melting, and the maps were superimposed on nanoscale scanning electron microscope images to highlight the EF effect as a function of microstructure. Nanocoral Si with high EF values were also evaluated by analyzing the porosity from gas adsorption measurements. Nanocoral Si was responsible for the high EF, according to thermodynamic calculations and agreement between experimental and calculation results as determined by Mie scattering theory.

Colloidal silicon quantum dots (SiQDs) may potentially minimize the environmental impact of commercial LEDs and advance next-generation light sources. Many studies have investigated the optical properties of SiQDs prepared by chemical synthesis, but the essential features of surface ligands have not fully been understood. Characterizing surface ligands should have a significant impact on optoelectronic research and ensuing applications. In this study, colloidal SiQDs were synthesized by pyrolyzing hydrogen silsesquioxane, followed by thermal hydrosilylation with 1-decene. Decyl-terminated SiQDs exhibited photoluminescence (PL) in a wavelength of 730 nm and PL quantum yields (QYs) of up to 38%. Seven decyl-terminated SiQDs with different ligand coverages were synthesized by varying the reaction time of hydrosilylation between 10 min and 9 h, and then these SiQDs were assembled into LEDs. The PL spectra, PLQYs, and performance of the SiQD LEDs were evaluated as a function of the decyl-ligand coverage. The PL properties (i.e., peak wavelength and PLQY) were insensitive to changes in decyl-ligand coverage, whereas the LED performance changed significantly. In particular, a 2-fold difference in decyl-ligand coverage exhibited a 4-fold difference in electroluminescence (EL) turn-on voltage and a 17-fold difference in EL external quantum efficiencies. In addition, the LED performance was characterized by quantifying the relationship between ligand coverage, the number of bonding sites, and the surface areas of the ligands. At greater than 25% coverage, the total surface area of the decyl-ligands was significantly larger than that of a single SiQD, and when decyl-ligands and Si–O groups covered 50% of the surface, the insulation effect impaired the LED performance. Therefore, ligand coverage significantly affected the performance of SiQD LEDs. Although this study was limited to decyl-terminated SiQDs, the same method can be applied to other ligands to further improve LED efficiency of next-generation light sources in displays, lighting, and biomedical imaging.

A microphysiological system (MPS) holds great promise for drug screening and toxicological testing as an alternative to animal models. However, this platform faces several challenges in terms of the materials used (e.g. polydimethylsiloxane; PDMS). For instance, absorption of drug candidates and fluorescent dyes into PDMS, as well as the effect elicited by materials on cultured cells, can cause inaccurate or misleading results in cell assays. The use of PDMS also poses challenges for mass production and long-term storage of fabricated MPSs. Hence, to circumvent these issues, herein we describe the development of a cyclo olefin polymer (COP)-based MPS using photobonding processes and vacuum ultraviolet (VUV), designated as COP-VUV-MPS. COP is an amorphous polymer with chemical/physical stability, high purity and optical clarity. Due to the thermostability and high modulus of COP, the metal molding processes was applied for mass production of MPSs without deformation of microstructures and with quick fabrication cycle time (approx. 10 min/cycle). Moreover, VUV photobonding process with an excimer light at a 172nm wavelength allowed assembling COP materials without the use of additional solvents and tapes, which might cause cell damages. In comparison with the conventional MPS made of PDMS (PDMS-MPS), COP-VUV-MPS showed improved chemical resistance without causing molecule absorption. Moreover, COP-VUV-MPS maintained the stemness of environmentally sensitive human-induced pluripotent stem cells without causing undesired cellular phenotypes or gene expression. These results suggest that COP-VUV-MPS may be broadly applicable for the advancement of MPS and applications in drug development, as well as in vitro toxicological testing.