Bending-Induced Bidirectional Tuning of Whispering Gallery Mode Lasing from Flexible Polymer Fibers

Polymer microfibers with a circular cross-section are directly drawn from a solution. By encapsulating the dye-doped microfibers with polydimethylsiloxane (PDMS) elastomer, optically pumped lasing with enhanced photostability is achieved. The lasing characteristics as well as size-dependent lasing action are carefully analyzed, and the lasing phenomenon is ascribed to whispering gallery mode. The PDMS elastomer offers another degree of freedom to mechanically tune the lasing from microfibers. It is interesting to note that by different types of bending, bidirectional shifting of the laser wavelength is observed, which is due to strain-induced refractive index change of the fiber and PDMS matrix. Our studies not only show an effective method to passivate the microfibers, but also open up a new approach to manipulating the lasing, which allows for fine adjustment of laser emission to any desired wavelength within the tuning range

Compounds from the Fruits of the Popular European Medicinal Plant Vitex agnus-castus in Chemoprevention via NADP(H):Quinone Oxidoreductase Type 1 Induction

As part of our continuing efforts in the search for potential biologically active compounds from medicinal plants, we have isolated 18 compounds including two novel nitrogen containing diterpenes from extracts of the fruits of Vitex agnus-castus. These isolates, along with our previously obtained novel compound vitexlactam A (1), were evaluated for potential biological effects, including cancer chemoprevention. Chemically, the nitrogenous isolates were found to be two labdane diterpene alkaloids, each containing an alpha,beta-unsaturated gamma-lactammoiety. Structurally, they were elucidated to be 9 alpha-hydroxy-13(14)-labden-16,15-amide (2) and 6 beta-acetoxy-9 alpha-hydroxy-13(14)-labden-15,16-amide (3), which were named vitexlactams B and C, respectively. The 15 known isolates were identified as vitexilactone (4), rotundifuran (5), 8-epi-manoyl oxide (6), vitetrifolin D (7), spathulenol (8), cis-dihydro-dehydro-diconiferylalcohol-9-O-beta-D-glucoside (9), luteolin-7-O-glucoside (10), 5-hydroxy-3,6,7,4'-tetramethoxyflavone (11), casticin (12), artemetin (13), aucubin (14), agnuside (15), beta-sitosterol (16), p-hydroxybenzoic acid (17), and p-hydroxybenzoic acid glucose ester (18). All compound structures were determined/identified on the basis of 1D and/or 2D NMR and mass spectrometry techniques. Compounds 6, 8, 9, and 18 were reported from a Vitex spieces for the first time. The cancer chemopreventive potentials of these isolates were evaluated for NADP(H): quinone oxidoreductase type 1 (QR1) induction activity. Compound 7 demonstrated promising QR1 induction effect, while the new compound vitexlactam (3) was only slightly active

Nonlinear Absorption and Low-Threshold Multiphoton Pumped Stimulated Emission from All-Inorganic Perovskite Nanocrystals

Halide perovskite materials have attracted intense research interest due to the striking performance in photoharvesting photovoltaics as well as photoemitting applications. Very recently, the emerging CsPbX₃ (X = Cl, Br, I) perovskite nanocrystals have been demonstrated to be efficient emitters with photoluminescence quantum yield as high as ∼90%, room temperature single photon sources, and favorable lasing materials. Herein, the nonlinear optical properties, in particular, the multiphoton absorption and resultant photoluminescence of the CsPbBr₃ nanocrystals, were investigated. Notably, a large two-photon absorption cross-section of up to ∼1.2 × 10⁵ GM is determined for 9 nm sized CsPbBr₃ nanocrystals. Moreover, low-threshold frequency-upconverted stimulated emission by two-photon absorption was observed from the thin film of close-packed CsPbBr₃ nanocrystals. The stimulated emission is found to be photostable and wavelength-tunable. We further realize the three-photon pumped stimulated emission in green spectra range from colloidal nanocrystals for the first time. Our results reveal the strong nonlinear absorption in the emerging CsPbX₃ perovskite nanocrystals and suggest these nanocrystals as attractive multiphoton pumped optical gain media, which would offer new opportunities in nonlinear photonics and revive the nonlinear optical devices

Solvent-Assisted Surface Engineering for High-Performance All-Inorganic Perovskite Nanocrystal Light-Emitting Diodes

All-inorganic cesium halide perovskite nanocrystals have attracted much interest in optoelectronic applications for the sake of the readily adjustable band gaps, high photoluminescence quantum yield, pure color emission, and affordable cost. However, because of the ineluctable utilization of organic surfactants during the synthesis, the structural and optical properties of CsPbBr₃ nanocrystals degrade upon transforming from colloidal solutions to solid thin films, which plagues the device operation. Here, we develop a novel solvent-assisted surface engineering strategy, producing high-quality CsPbBr₃ thin films for device applications. A good solvent is first introduced as an assembly trigger to conduct assembly in a one-dimensional direction, which is then interrupted by adding a nonsolvent. The nonsolvent drives the adjacent nanoparticles connecting in a two-dimensional direction. Assembled CsPbBr₃ nanocrystal thin films are densely packed and very smooth with a surface roughness of ∼4.8 nm, which is highly desirable for carrier transport in a light-emitting diode (LED) device. Meanwhile, the film stability is apparently improved. Benefiting from this facile and reliable strategy, we have achieved remarkably improved performance of CsPbBr₃ nanocrystal-based LEDs. Our results not only enrich the methods of nanocrystal surface engineering but also shed light on developing high-performance LEDs

Fluorescent pH Sensor Based on Ag@SiO₂ Core–Shell Nanoparticle

We have demonstrated a novel method for the preparation of a fluorescence-based pH sensor by combining the plasmon resonance band of Ag core and pH sensitive dye (HPTS). A thickness-variable silica shell is placed between Ag core and HPTS dye to achieve the maximum fluorescence enhancement. At the shell thickness of 8 nm, the fluorescence intensity increases 4 and 9 times when the sensor is excited at 405 and 455 nm, respectively. At the same time, the fluorescence intensity shows a good sensitivity toward pH value in the range of 5–9, and the ratio of emission intensity at 513 nm excited at 455 nm to that excited at 405 nm versus the pH value in the range of 5–9 is determined. It is believed that the present pH sensor has the potential for determining pH real time in the biological sample

π‑Conjugated Discrete Oligomers Containing Planar and Nonplanar Aromatic Motifs

A new family of π-conjugated oligomers featuring a nonplanar polycyclic aromatic hydrocarbon, corannulene, and a planar aromatic unit, thiophene, is synthesized through an iterative metal-catalyzed coupling protocol. The two structural motifs are connected through an acetylene linkage. In the shorter oligomers, a thiophene unit is attached to one or two corannulenes. In the higher analogues, two, three, and four thiophene units are placed in an alternating fashion with three, four, and five corannulene units, respectively. Photophysical studies reveal extended π-effects that initially increase and then attenuate as a function of the oligomer length. Notably, longer oligomers are found to be highly active for nonlinear absorption and emission properties. The oligomer with three corannulene and two thiophene units exhibits a two-photon absorption cross section of 600 GM and two-photon-excited intense green luminescence. This work, therefore, introduces the concept of combining planar and nonplanar aromatic motifs in the design of π-conjugated discrete oligomers, establishes synthetic feasibility of such hybrid materials, reports on their photophysical properties that is anticipated to have significant implications for future research targets, and features the discovery that corannulene derivatives can exhibit excellent nonlinear optical activity when extended through π-bridges

Au Nanorod Decoration on NaYF₄:Yb/Tm Nanoparticles for Enhanced Emission and Wavelength-Dependent Biomolecular Sensing

We introduce gold nanorods (GNRs) decoration on NaYF₄:Yb/Tm upconversion nanocrystals (UCNCs) by functionalizing the UCNCs with polyamidoamine generation 1 (PAMAM G1) dendrimer, followed by a single-step seed-mediated growth of long-range GNRs to enhance “biological window” upconversion emission. The up-conversion emission of GNR-decorated UCNCs can be enhanced beyond the level typically obtainable using shell-like structures up to 27-fold enhancement. Also, the enhancement can be tuned at different wavelength regions by varying the GNR aspect ratio. The GNR-decorated UCNC is further modified with 2-thiouracil for nonenzymatic detection of uric acid, revealing a detection limit as 1 pM

Identification of a group of <i>ent</i>-Kaurane diterpenoids and triterpene dilactones as Hh pathway antagonists.

<p><b>(A)</b> Chemical structures of the <i>ent</i>-Kaurane diterpenoids and the triterpene dilactones. <b>(B)</b> Half maximal inhibitory concentrations (IC₅₀) of the HPAs in the Hh reporter assays activated by SAG. <b>(C)</b> The HPAs inhibit SAG activated expressions of the Hh target genes <i>Ptch1</i> and <i>Gli1</i>. <b>(D)</b> The HPAs suppress 20(S)-OHC-activated Hh signaling. <b>(E)</b> The HPAs do not compete with Bodipy-Cyc for Smo binding. Scale bar: 50 μm. <b>(F)</b> Quantitation of the intensities of bound Bodipy-Cyc to Smo-expressing cells treated with the HPAs. <b>(G)</b> Unlike GANT58, which targets Gli1 downstream of Sufu, the HPAs do not suppress the activation of the Hh pathway in Sufu^-/- MEFs. The relative expression levels of the Hh target genes <i>Ptch1</i> and <i>Gli1</i> were determined. The data in C, D, F and G are expressed as the mean ± SD, and the HPAs were used at 10 μM. Asterisks indicate <i>p</i> < 0.05 for individual compounds vs. DMSO or control.</p

The <i>ent</i>-Kauranoids remarkably elongate mature cilia.

<p><b>(A)</b> Representative images of the effects of HPAs on well-formed mature cilia. The cilia were visualized by staining acetylated α-tubulin (Ac Tubulin). <b>(B)</b> Quantitative analysis the length of cilia from the Ac Tubulin images. Asterisks indicate significance with one-way ANOVA analysis (****, <i>p</i> < 0.0001). The data are presented as the mean ± SD. <b>(C)</b> Representative images of observed cilia malformations. Asterisks indicate bulged tips. Scale bar: 5 μm.</p

Henryin inhibits Wnt/β-catenin signaling.

<p>(A) (B) Microarray assay and data analysis of differential gene expression under henryin treatment. SW480 cells were treated for 12h with 4µM of henryin with 0.5% DMSO used as a control in the assay. GO annotation and pathway analysis were employed from the BioCarta and KEGG databases, respectively. The genes with fold alteration of at least >2 (up-regulated) or <0.5(down-regulated) were taken as differentially expressed genes. Data analysis and the statistics were generated only when the hits > 5 in each signaling pathway. Representative pathways obtained after microarray data analysis are shown. (C) Henryin inhibits the Wnt reporter expression in a dose-dependent manner in wnt1 transfected HEK293T cells, and in colorectal cancer cells, SW480 and HCT116. Three hours after transfection of the Wnt1 and/or ST-Luc, DMSO or henryin with indicated dosage was added to the cells for additional 24h and luciferase activity was then measured. (D) Henryin (4µM) preferentially inhibits the Wnt signaling (ST-Luc) over the NF-κB signaling pathway (NF-κB-Luc) in HEK293T cells. Wnt signaling was stimulated by transfection of wnt1 and NF-κB signaling was stimulated with 25ng/mL TNFα. Each bar is the mean ± SD from three independent experiments. *P<0.05, **P<0.01, relative to vehicle control. NS, not significant.</p