Very recently, perovskite based microdisk
lasers have attracted
considerable research attention. However, most of the researches are
focused on the lasing spectra in bottom-up synthesized microdisks
with regular shapes. The directionality, which is also essential for
practical applications, has not been explored. Here we demonstrate
unidirectional lasing emissions from perovskite microdisks for the
first time. We synthesized the rectangle-shaped microdisks connected
with straight waveguides and studied the lasing characteristics, where
unidirectional emissions along the waveguides have been observed.
Numerical calculations reveal that the unidirectional emissions are
formed by the breaking of total internal reflections at the joints
between waveguides and microdisks. Since waveguides are compatible
with other photonic elements, we believe that our finding will be
essential for the applications of perovskite microdisks in integrated
photonic circuits and networks.
Chronic
wounds are one of the most serious complications of diabetes
mellitus. Even though utilizing nitric oxide (NO) as a gas medicine
to repair diabetic wounds presents a promising strategy, controlling
the NO release behavior in the affected area, which is vital for NO-based
therapy, still remains a significant challenge. In this work, a copper-based
metal–organic framework, namely, HKUST-1, has been introduced
as a NO-loading vehicle, and a NO sustained release system with the
core–shell structure has been designed through the electrospinning
method. The results show that the NO is quantificationally and stably
loaded in the HKUST-1 particles, and the NO-loaded HKUST-1 particles
are well incorporated into the core layer of the coaxial nanofiber.
Therefore, NO can be controllably released with an average release
rate of 1.74 nmol L–1 h–1 for
more than 14 days. Moreover, the additional copper ions released from
the degradable HKUST-1 play a synergistic role with NO to promote
endothelial cell growth and significantly improve the angiogenesis,
collagen deposition as well as anti-inflammatory property in the wound
bed, which eventually accelerate the diabetic wound healing. These
results suggest that such a copper-based metal–organic framework
material as a controllable NO-releasing vehicle is a highly efficient
therapy for diabetic wounds.
Solution‐processed lead halide perovskites have shown good applicability in both solar cells and microlasers. Very recently, the nonlinear properties of perovskites have attracted considerable research attention. Second harmonic generation and two‐photon absorption have been successfully demonstrated. However, perovskite devices based on these nonlinear properties, such as micro‐ and nanolasers have thus far not been fabricated. Here we demonstrate two‐photon pumped microlasers from CH3NH3PbBr3 perovskite microwires. These CH3NH3PbBr3 perovskite microwires are synthesized through a one‐step solution precipitation method and dispersed on a glass substrate. Under optical excitation at 800 nm, two‐photon pumped lasing action with periodic peaks is successfully observed at around 546 nm. The obtained quality (Q) factors of the two‐photon pumped microlasers are around 682, and the corresponding thresholds are about 674 µJ cm‐2. Both the Q factors and thresholds are comparable to conventional whispering‐gallery modes in two‐dimensional polygon microplates. This work is the first demonstration of two‐photon pumped microlasers in CH3NH3PbBr3 perovskite microwires. We believe our finding will significantly expand the application of perovskites in low‐cost nonlinear optical devices, such as optical limiters, optical switches, and biomedical imaging devices.
The synthesized perovskites are randomly distributed and their optical properties are fixed after synthesis. Here we demonstrate the tailoring of lasing properties of perovskite microwire via micromanipulation. One microwire has been lifted by a tungsten probe and repositioned on a nearby perovskite microplate with one end suspended in air. Consequently, the conventional Fabry-Perot lasers are completely suppressed and a single laser peak has been observed. The numerical calculations reveal that the single-mode laser is formed by the whispering-gallery mode in the transverse plane of microwire. Our research provides a simple way to tailor the properties of microwire postsynthesis.
The control of photoluminescence and absorption of lead halide perovskites plays a key role in their applications in micro- and nano-sized light emission devices and photodetectors. To date, the wavelength controls of lead halide perovskite microlasers are mostly realized by changing the halide mixture in solution. Herein, we report the postsynthetic and selective control of the optical properties of lead halide perovskites with conventional semiconductor technology. By selectively exposing a CHNHPbBr microstructure with chlorine in inductively coupled plasma, we find that the wavelengths of absorption, photoluminescence, and laser emissions of exposed structures are blue-shifted around 50 nm. Most importantly, the device characteristics such as the photoluminescence intensities and laser thresholds are well maintained during the reaction process. We believe our finding will significantly boost the practical applications of lead halide perovskite based optoelectronics.
Impaired angiogenesis is one of the predominant reasons for non-healing diabetic wounds. Herein, a nanofiber/hydrogel core–shell scaffold with three-dimensional (3D) multilayer patterned structure (3D-PT-P/GM) was introduced for promoting diabetic wound healing with improved angiogenesis. The results showed that the 3D-PT-P/GM scaffolds possessed multilayered structure with interlayer spacing of about 15–80 μm, and the hexagonal micropatterned structures were uniformly distributed on the surface of each layer. The nanofibers in the scaffold exhibited distinct core–shell structures with Gelatin methacryloyl (GelMA) hydrogel as the shell and Poly (d, l-lactic acid) (PDLLA) as the core. The results showed that the porosity, water retention time and water vapor permeability of the 3D-PT-P/GM scaffolds increased to 1.6 times, 21 times, and 1.9 times than that of the two-dimensional (2D) PDLLA nanofibrous scaffolds, respectively. The in vitro studies showed that the 3D-PT-P/GM scaffolds could significantly promote cell adhesion, proliferation, infiltration and migration throughout the scaffolds, and the expression of cellular communication protein-related genes, as well as angiogenesis-related genes in the same group, was remarkably upregulated. The in vivo results further demonstrated that the 3D-PT-P/GM scaffolds could not only effectively absorb exudate and provide a moist environment for the wound sites, but also significantly promote the formation of a 3D network of capillaries. As a result, the healing of diabetic wounds was accelerated with enhanced angiogenesis, granulation tissue formation, and collagen deposition. These results indicate that nanofiber/hydrogel core–shell scaffolds with 3D multilayer patterned structures could provide a new strategy for facilitating chronic wound healing.
Graphical Abstract
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