Atomically thin layers of transition metal dichalcogenides (TMDs) are of great interest to the photonics community because of their unique optical properties. For example, in conjunction with microring or photonic crystal microresonators, they readily form microcavity light emitters. A number of configurations are now presented that apparently meet the conditions for lasing, yet there is considerable debate in the community as to whether lasing is actually achieved. By employing a very comprehensive set of assessment criteria, herein is shown that none of the TMD devices meet all the conditions for lasing, despite some very convincing data being presented. These findings are examined in the context of microcavity lasers based on III–V gain materials. Applications of TMD light emitters in the areas of quantum information and biosensing are also discussed to highlight areas where lasing action is not necessarily required.

Diagnosis and early assessment of the treatment response of rheumatoid arthritis (RA) necessitates a reliable bioanalytical method for rapid, sensitive, and specific detection of the hypochlorous acid (HOCl) biomarker in inflammatory diseases. Herein, two fluorescence probes, Probe‐1 and Probe‐2 are developed for quantitative monitoring and visualization of inflammatory response–related HOCl levels in vitro and in vivo. In the presence of HOCl, fluorescence “OFF–ON” response is obtained for both the probes as a result of specific HOCl‐triggered C=N bond cleavage reaction. Probe‐1 and Probe‐2 feature rapid response (<4 s), a high degree of sensitivity and selectivity toward HOCl, which allow them to be used for quantification of HOCl in a simulated physiological condition. Using Probe‐2 as the probe, fluorescence imaging and flow cytometry analysis of HOCl levels in lysosome of inflammatory mimic cells, visualization of HOCl generation in endotoxin‐induced inflammation of adult zebrafish and RA of mice are possible. Probe‐2 exhibits high effectiveness for early assessment of the treatment response of HOCl‐mediated RA in mice with an antiarthritic drug, methotrexate (MTX). The results demonstrate that Probe‐2 is a powerful tool for future studies on diagnosis and monitoring treatment efficiency in a broad range of inflammatory diseases, including RA.

Article:Safdar, Amna, Wang, Yue orcid.org/0000-0002-2482-005X and Krauss, Thomas F. orcid.org/0000-0003-4367-6601 (2018) Random lasing in uniform perovskite thin films. Optics Express. A75-A84. ISSN 1094-4087 https://doi.org/10.1364/OE.26.000A75eprints@whiterose.ac.uk https://eprints.whiterose.ac.uk/ Reuse Items deposited in White Rose Research Online are protected by copyright, with all rights reserved unless indicated otherwise. They may be downloaded and/or printed for private study, or other acts as permitted by national copyright laws. The publisher or other rights holders may allow further reproduction and re-use of the full text version. This is indicated by the licence information on the White Rose Research Online record for the item. TakedownIf you consider content in White Rose Research Online to be in breach of UK law, please notify us by emailing eprints@whiterose.ac.uk including the URL of the record and the reason for the withdrawal request. Abstract: Following the very promising results obtained by the solar cell community, metal halide perovskite materials are increasingly attracting the attention of other optoelectronics researchers, especially for light emission applications. Lasing with both engineered and selfassembled resonator structures, such as microcrystal networks, has now been successfully observed, with the low cost and the simple solution-based process being a particular attraction. The ultimate in simplicity, however, would be to observe lasing from a continuous thin film, which has not been reported yet. Here, we show random lasing action from such a simple perovskite layer. Our lasers work at room temperature; they are deposited on unpatterned glass substrates and they exhibit a minimum threshold value of 10 µJ/cm 2 . By carefully controlling the solution processing conditions, we can determine whether random lasing occurs or not, using identical precursors. A rather special feature is that some of the films exhibit single and dual mode lasing action, which is rarely observed in random lasers. Our work fully exploits the simplicity of the solution-based process and thereby adds an important capability into the emerging field of perovskite-based light emitters. Heiss, and M. V. Kovalenko, "Low-threshold amplified spontaneous emission and lasing from colloidal nanocrystals of caesium lead halide perovskites," Nat. Commun. 6, 8056-8064 (2015). 12. J. Xing, F. Yan, Y. Zhao, S. Chen, H. Yu, Q. Zhang, R. Zeng, H. V. Demir, X. Sun, A. Huan, and Q. Xiong, "High-Efficiency Light-Emitting Diodes of Organometal Halide Perovskite Amorphous Nanoparticles," ACS Nano 10(7), 6623-6630 (2016). Brenner, M. Stulz, D. Kapp, and T. Abzieher, "Highly stable solution processed metal-halide perovskite lasers on nanoimprinted distributed feedback structures," Appl. Random lasing in uniform perovskite

Optical vortex beams are at the heart of a number of novel research directions, both as carriers of information and for the investigation of optical activity and chiral molecules. Optical vortex beams are beams of light with a helical wavefront and associated orbital angular momentum. They are typically generated using bulk optics methods or by a passive element such as a forked grating or a metasurface to imprint the required phase distribution onto an incident beam. Since many applications benefit from further miniaturization, a more integrated yet scalable method is highly desirable. Here, we demonstrate the generation of an azimuthally polarized vortex beam directly by an organic semiconductor laser that meets these requirements. The organic vortex laser uses a spiral grating as a feedback element that gives control over phase, handedness, and degree of helicity of the emitted beam. We demonstrate vortex beams up to an azimuthal index l = 3 that can be readily multiplexed into an array configuration.

Keratinase has attracted increasing attention in the field of biocatalysis in recent years because of its critical role in keratin resource exploitation and keratin waste degradation. However, conventional studies focused on keratinases from bacterial and fungal strains, especially those of the Bacillus genus, keratinase resources from actinomycetes are far from being fully explored. In this study, a novel keratinase-producing strain was isolated with wool as the sole carbon and nitrogen source and identified as Streptomyces aureofaciens K13. The keratinase was purified to electrophoretic homogeneity with a molecular mass of 46 kDa. The purified enzyme exhibited optimum activity at 75 C and pH of 12.0. It remained extremely stable at alkaline pH values between 6 and 12 and at a high reaction temperature of 65 C. The keratinase displayed significant activity toward casein, keratin, BSA and wool. It could be activated in the presence of K + , Cu 2+ , Mn 2+ , Ca 2+ , Li + , and Sr 2+ . The keratinase was completely inhibited by PMSF and moderately inhibited by EDTA, indicating that this keratinase is a metallo-serine keratinase. This enzyme could remain stable and even be promoted in the presence of surfactants, including SDS, Tween, and Triton; especially, 1% of Tween 80 and Triton X-100 could substantially enhance the activity by 46% and 38%, respectively. These results indicated certain advantages over conventional keratinases. The keratinase can completely remove blood stains when combined with detergents. The improvement effect of S. aureofaciens K13 keratinase by various surfactants and the favourable washing performance might indicate its significant application potential in the detergent industry. There are rare reports on keratinase production from S. aureofaciens.

Halide perovskite materials have rapidly emerged as outstanding optoelectronic materials for solar cells, light-emitting diodes (LEDs), and lasers. Compared to hybrid organic-inorganic perovskites, all-inorganic perovskites have shown unique merits that may contribute to the ultimate goal of developing electrically-pumped lasers. In this paper, we demonstrate a distributed feedback (DFB) resonator using an all-inorganic perovskite thin film as the gain medium. The film has a gain coefficient of 161.1 cm and a loss coefficient of 30.9 cm. Excited by picosecond pulses, the microstructured all-inorganic perovskite film exhibits a single-mode emission at 654 nm with a threshold of 33 μJ/cm. The facile fabrication process provides a promising route towards low-cost single-mode visible lasers for many practical applications.

Many bacterial species readily develop biofilms that act as a protective matrix against external challenge, e.g., from antimicrobial treatment. Therefore, biofilms are often responsible for persistent and recurring infections. Established methods for studying biofilms are either destructive or focus on the biofilm’s surface. A non-destructive method that is sensitive to the underside of the biofilm is highly desirable, as it allows studying the penetration of antibiotics through the film. Here, we demonstrate that the high surface sensitivity of resonant hyperspectral imaging provides this capability. The method allows us to monitor the early stages of Escherichia coli biofilm formation, cell attachment and microcolony formation, in-situ and in real-time. We study the response of the biofilm to a number of different antibiotics and verify our observations using confocal microscopy. Based on this ability to closely monitor the surface-bound cells, resonant hyperspectral imaging gives new insights into the antimicrobial resistance of biofilms.

Resonant photonic sensors are enjoying much attention based on the worldwide drive toward personalized healthcare diagnostics and the need to better monitor the environment. Recent developments exploiting novel concepts such as metasurfaces, bound states in the continuum, and topological sensing have added to the interest in this topic. The drive toward increasingly higher quality (Q)-factors, combined with the requirement for low costs, makes it critical to understand the impact of realistic limitations such as losses on photonic sensors. Traditionally, it is assumed that the reduction in the Q-factor sufficiently accounts for the presence of loss. Here, we highlight that this assumption is overly simplistic, and we show that losses have a stronger impact on the resonance amplitude than on the Q-factor. We note that the effect of the resonance amplitude has been largely ignored in the literature, and there is no physical model clearly describing the relationship between the limit of detection (LOD), Q-factor, and resonance amplitude. We have, therefore, developed a novel, ab initio analytical model, where we derive the complete figure of merit for resonant photonic sensors and determine their LOD. In addition to highlighting the importance of the optical losses and the resonance amplitude, we show that, counter-intuitively, optimization of the LOD is not achieved by maximization of the Q-factor but by counterbalancing the Q-factor and amplitude. We validate the model experimentally, put it into context, and show that it is essential for applying novel sensing concepts in realistic scenarios.