Halide perovskite quantum dots (Pe‐QDs) have been considered as outstanding candidates for photodetector, light‐emitting diode, and lasing applications, but these perspectives are being impeded by ...the severe stability, including both chemical and optical degradations. This study reports on amino‐mediated anchoring Pe‐QDs onto the surfaces of monodisperse silica to effectively depress the optical degradation of their photoluminescence (PL) and random lasing stabilities, hence achieving highly stable and low‐threshold lasing. An amination‐mediated nucleation and growth process is designed for the general and one‐pot synthesis of Pe‐QDs on the surfaces of silica spheres. The facile synthetic process, which can be finished within several minutes, insures scalable production. Surprisingly, almost no PL degradation is observed after 40 d storage under ambient conditions, even 80% PL intensity can be maintained after persistently illuminated by UV lamps for 108 h. Subsequently, extremely stable random lasing is achieved after storage for 2 months or over continuously optical pumping for 8 h. Such high PL and lasing stabilities originate from the isolation effects due to the effective anchoring, which separate the Pe‐QDs from each other and inhibit the photoinduced regrowth and deterioration. This work will also open the window of perovskite‐based multifunctional systems.
Amino‐mediated anchoring of perovskite quantum dots (QDs) onto the surfaces of monodisperse silica spheres separates the QDs from each other and inhibits the photoinduced regrowth and deterioration effectively, which also contributes to highly stable and low‐threshold random lasing. The general and one‐pot synthetic procedures ensure scalable production and open the window of perovskite‐based multifunctional systems.
Recently, newly engineered all‐inorganic cesium lead halide perovskite nanocrystals (IPNCs) (CsPbX3, X = Cl, Br, I) are discovered to possess superior optical gain properties appealing for ...solution‐processed cost‐effective lasers. Yet, the potential of such materials has not been exploited for practical laser devices, rendering the prospect as laser media elusive. Herein, the challenging but practically desirable vertical cavity surface emitting lasers (VCSELs) based on the CsPbX3 IPNCs, featuring low threshold (9 µJ cm−2), directional output (beam divergence of ≈3.6°), and favorable stability, are realized for the first time. Notably, the lasing wavelength can be tuned across the red, green, and blue region maintaining comparable thresholds, which is promising in developing single‐source‐pumped full‐color visible lasers. It is fully demonstrated that the characteristics of the VCSELs can be versatilely engineered by independent adjustment of the cavity and solution‐processable nanocrystals. The results unambiguously reveal the feasibility of the emerging CsPbX3 IPNCs as practical laser media and represent a significant leap toward CsPbX3 IPNC‐based laser devices.
All‐inorganic halide perovskite nanocrystals (IPNCs) (CsPbX3, X = Cl, Br, I) based vertical cavity surface emitting laser is realized for the first time. These laser devices operate at a very low threshold, such that quasi‐steady‐state pumping is feasible. The results highlight the emerging CsPbX3 IPNCs as practical laser media and represent a significant leap toward practically desirable laser devices.
Microlasers have experienced tremendous development in the past decade and become an essential part in laser evolution, as miniature lasers provide strong optical confinement and feature greatly ...enhanced light–matter interactions. Among all the configurations, whispering gallery mode (WGM) microcavities and microlasers exhibit outstanding optical performances with high quality factors and small mode volumes, thus ensuring low lasing thresholds. In addition, some unique properties inherent to WGM cavities, like bi‐directional propagation and an evanescent field that spans several hundred nanometers across the boundary, can be exploited for novel applications. Therefore, designing and engineering innovative WGM microcavities and microlasers has attracted increasing research interest. The fundamentals and characteristics of WGM are introduced here, and then the developments and current status of WGM microcavities and microlasers are reviewed in terms of the evolution of fabrication techniques and built‐up materials. In particular, the melting of glassy materials in early studies, top‐down and bottom‐up approaches with semiconductors, coating structures, as well as flexible, soft microresonators in recent years are presented. Finally, the application prospects of microlasers including the wavelength manipulation, sensing and microresonator coupling, are discussed.
Whispering gallery mode (WGM) microcavities and microlasers exhibit outstanding optical performances with high quality factors and small mode volumes, which ensure low lasing thresholds. The WGM fundamentals and advances in the fabrication methodologies, as well as the application prospects including wavelength modulation, sensitive biological and chemical sensors, and coupling mechanisms are presented.
CircRNA expression profiles for gastric cancer (GC) were screened using plasma samples from 10 GC patients with different TNM stages and 5 healthy individuals as controls. Results showed lower ...expression of circ-KIAA1244 in GC tissues, plasmas, and cells compare to normal controls. Further clinical data analysis demonstrated that a decreased expression of circ-KIAA1244 in plasmas was negatively correlated with TNM stage and lymphatic metastasis, and a shorter overall survival time of GC patients. Moreover, we found that circ-KIAA1244 could be detected in GC plasma exosomes and showed no obvious significance compared to the expression level in the corresponding plasmas. This study revealed a GC-tissues-derived circ-KIAA1244 could serve a novel circulating biomarker for detection of GC.
Circular RNAs (circRNAs), a novel class of long noncoding RNAs, are characterized by a covalently closed continuous loop without 5' or 3' polarities structure and have been widely found in thousands ...of lives including plants, animals and human beings. Utilizing the high-throughput RNA sequencing (RNA-seq) technology, recent findings have indicated thata great deal of circRNAs, which are endogenous, stable, widely expressed in mammalian cells, often exhibit cell type-specific, tissue-specific or developmental-stage-specific expression. Evidences are arising that some circRNAs might regulate microRNA (miRNA) function as microRNA sponges and play a significant role in transcriptional control. circRNAs associate with related miRNAs and the circRNA-miRNA axes are involved in a serious of disease pathways such as apoptosis, vascularization, invasion and metastasis. In this review, we generalize and analyse the aspects including synthesis, characteristics, classification, and several regulatory functions of circRNAs and highlight the association between circRNAs dysregulation by circRNA-miRNA-mRNA axis and sorts of diseases including cancer- related and non-cancer diseases."
Since the first observation of stimulated emission from colloidal quantum dots (CQDs) in year 2000, tremendous progress has been made in developing solution-processed lasers from colloidal ...semiconductor nanostructures in terms of both understanding the fundamental physics and improving the device performance. In this review paper, we will start with a brief introduction about the fabrication of CQDs and the corresponding electronic structures. The emphasis will be put on the discussion about the optical gain and lasing from colloidal nanostructures including the gain mechanism, the main hurdles against optical gain and lasing as well as strategies to optimize the lasing performance. Afterwards, the recent advances in CQD lasers, exemplified by the achievement of continuous wave lasing, will be presented. Finally, the challenges and a perspective of the future development of lasers based on the colloidal semiconductor nanostructures will be presented.
With regards to developing miniaturized coherent light sources, the temperature‐insensitivity in gain spectrum and threshold is highly desirable. Quantum dots (QDs) are predicted to possess a ...temperature‐insensitive threshold by virtue of the separated electronic states; however, it is never observed in colloidal QDs due to the poor thermal stability. Besides, for the classical II–VI QDs, the gain profile generally redshifts with increasing temperature, plaguing the device chromaticity. Herein, this paper addresses the above two issues simultaneously by embedding ligands‐free CsPbBr3 nanocrystals in a wider band gap Cs4PbBr6 matrix by solution‐phase synthesis. The unique electronic structures of CsPbBr3 nanocrystals enable temperature‐insensitive gain spectrum while the lack of ligands and protection from Cs4PbBr6 matrix ensure the thermal stability and high temperature operation. Specifically, a color drift‐free stimulated emission irrespective of temperature change (20–150 °C) upon two‐photon pumping is presented and the characteristic temperature is determined to be as high as ≈260 K. The superior gain properties of the CsPbBr3/Cs4PbBr6 perovskite nanocomposites are directly validated by a vertical cavity surface emitting laser operating at temperature as high as 100 °C. The results shed light on manipulating optical gain from the advantageous CsPbBr3 nanocrystals and represent a significant step toward the temperature‐insensitive frequency‐upconverted lasers.
Temperature‐insensitive optical gain is achieved by exploiting a novel lasing material composed of ligands‐free CsPbBr3 nanocrystals embedded in a wider band gap Cs4PbBr6 matrix based on low‐temperature solution‐phase synthesis. The unique electronic structures of CsPbBr3 nanocrystals enable a temperature‐insensitive gain profile while the lack of ligands and protection from Cs4PbBr6 matrix ensure the thermal stability and high temperature operation.
An ultra-wideband fiber optic acoustic sensor based on graphene diaphragm with a thickness of 10nm has been proposed and experimentally demonstrated. The two reflectors of the extrinsic Fabry-Perot ...interferometer is consist of fiber endface and graphene diaphragm, and the cavity is like a horn-shape. The radius of the effective area of the ultrathin graphene diaphragm is 1mm. Attributed to the strong van der Waals force between the diaphragm and the ceramic ferrule, the sensor head can be applied not only in the air but also underwater. Experimental results illustrate that ultra-wideband frequency response is from 5Hz to 0.8MHz, covering the range from infrasound to ultrasound. The noise-limited minimum detectable pressure level of 0.77Pa/Hz
@5Hz and 33.97μPa/Hz
@10kHz can be achieved, and the applied sound pressure is 114dB and 65.8dB, respectively. The fiber optic acoustic sensor may have a great potential in seismic wave monitoring, photoacoustic spectroscopy and photoacoustic imaging application due to its compact structure, simple manufacturing, and low cost.
The concept of point of darkness has received much attention for biosensing based on phase-sensitive detection and perfect absorption of light. The maximum phase change is possible at the point of ...darkness where the reflection is almost zero. To date, this has been experimentally realized using different material systems through the concept of topological darkness. However, complex nanopatterning techniques are required to realize topological darkness. Here, we report an approach to realize perfect absorption and extreme phase singularity using a simple metal-dielectric multilayer thin-film stack. The multilayer stack works on the principle of an asymmetric Fabry-Perot cavity and shows an abrupt phase change at the reflectionless point due to the presence of a highly absorbing ultrathin film of germanium in the stack. In the proof-of-concept phase-sensitive biosensing experiments, we functionalize the film surface with an ultrathin layer of biotin-thiol to capture streptavidin at a low concentration of 1 pM.
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