Metal−organic frameworks (MOFs) are superior for multiple applications including drug delivery, sensing, and gas storage because of their tunable physiochemical properties and fascinating architectures. Optoelectronic application of MOFs is difficult because of their porous geometry and conductivity issues. Recently, a few optoelectronic devices have been fabricated by a suitable design of integrating MOFs with other materials. However, demonstration of laser action arising from MOFs as intrinsic gain media still remains challenging, even though some studies endeavor on encapsulating luminescence organic laser dyes into the porous skeleton of MOFs to achieve laser action. Unfortunately, the aggregation of such unstable laser dyes causes photoluminescence quenching and energy loss, which limits their practical application. In this research, unprecedently, we demonstrated ultralow-threshold (∼13 nJ/cm 2 ) MOF laser action by a judicious choice of metal nodes and organic linkers during synthesis of MOFs. Importantly, we also demonstrated that the white random lasing from the beautiful microflowers of organic linkers possesses a porous network, which is utilized to synthesize the MOFs. The highly luminescent broad-band organic linker 1,4-NDC, which itself exhibits a strong white random laser, is used not only to achieve the stimulated emission in MOFs but also to reduce the lasing threshold. Such white lasing has multiple applications from bioimaging to the recently developed versatile Li-Fi technology. In addition, we showed that the smooth facets of MOF microcrystals can show Fabry−Perot resonant cavities having a high quality factor of ∼10 3 with excellent photostability. Our unique discovery of stable, nontoxic, high-performance MOF laser action will open up a new route for the development of new optoelectronic devices.

Multifunctional lanthanide-doped upconversion nanoparticles (UCNPs) have spread their wings in the fields of flexible optoelectronics and biomedical applications. One of the ongoing challenges lies in achieving UCNP-based nanocomposites, which enable a continuous-wave (CW) laser action at ultralow thresholds. Here, gold sandwich UCNP nanocomposites [gold (Au1)–UCNP–gold (Au2)] capable of exhibiting lasing at ultralow thresholds under CW excitation are demonstrated. The metastable energy-level characteristics of lanthanides are advantageous for creating population inversion. In particular, localized surface plasmon resonance-based electromagnetic hotspots in the nanocomposites and the huge enhancement of scattering coefficient for the formation of coherent closed loops due to multiple scattering facilitate the process of stimulated emissions as confirmed by theoretical simulations. The nanocomposites are subjected to stretchable systems for enhancing the lasing action (threshold ∼ 0.06 kW cm–2) via a light-trapping effect. The applications in bioimaging of HeLa cells and antibacterial activity (photothermal therapy) are demonstrated using the newly designed Au1–UCNP–Au2 nanocomposites.

Plasmonic material has emerged with multifunctionalities for its remarkable tailoring light emission, reshaping density of states (DOS), and focusing subwavelength light. However, restricted by its propagation loss and narrowband resonance in nature, it is a challenge for plasmonic material to provide a broadband DOS to advance its application. Here, we develop a novel nanoscale core−shell hyperbolic structure that possesses a remarkable coupling effect inside the multishell nanoscale composite owing to a higher DOS and a longer time of collective oscillations of the electrons than the plasmonic-based pure-metal nanoparticles. Subsequently, a giant localized electromagnetic wave of surface plasmon resonance is formed at the surface, causing pronounced out-coupling effect. Specifically, the nanoscale core−shell hyperbolic structure confines the energy well without being decayed, reducing the propagation loss and then achieving an unprecedented stimulated emission (random lasing action by dye molecule) with a record ultralow threshold (∼30 μJ/cm 2 ). Besides, owing to the radial symmetry of the nanoscale core−shell hyperbolic structure, the excitation of high wavevector modes and induced additional DOS are easily accessible. We believe that the nanoscale core−shell hyperbolic structure paves a way to enlarge the development of plasmonic-based applications, such as high optoelectronic conversion efficiency of solar cells, great power extraction of light-emitting diodes, wide spectra photodetectors, carrying the emitter inside the core part as quantitative fluorescence microscopy and bioluminescence imaging system for in vivo and in vitro research on human body.

Aims: The purposes of this study are to describe the visual outcome of highly myopic eyes undergoing cataract surgery, to investigate associated risk factors for poor postoperative vision and to assess the postoperative complication frequency among the myopic Taiwanese population. Methods: We conducted a retrospective, noncomparative case series study at the Department of Ophthalmology, Zhongxing Branch, Taipei City Hospital, Taiwan. High myopia was defined as axial length ≧26.0 mm. The main study outcomes were visual acuity for the initial 6-month postoperative period (including visual acuities and improvement of postoperative vision) and postoperative complications (including subsequent cataract formation and postoperative retinal detachment). Results: Fifty-two highly myopic eyes were enrolled between January 2002 and December 2004. The mean follow-up interval was 43.3 ± 20.2 weeks (range 25–103). Thirty-two eyes (61.5%) had good postoperative visual improvement (≧4 lines of Snellen chart). Thirty-seven eyes (71.2%) achieved good postoperative vision (20/40 or better). Fifteen eyes (28.8%) demonstrated poor postoperative vision. Pre-existing maculopathy was an independent risk factor for failure to achieve good postoperative vision [odds ratio (OR): 6.84, 95% confidence interval (CI): 1.12–41.8] and improvement (OR: 16.1, 95% CI: 2.2–119.9). Diabetic history was considered another independent risk factor for poor postoperative vision (OR: 15.6, 95% CI: 0.97–267.6). Six eyes (11.5%) developed subsequent posterior capsular opacification requiring Nd:YAG laser capsulotomy. Two eyes (3.8%) developed retinal detachment during follow-up. Conclusions: Most highly myopic eyes achieved good visual improvement and good postoperative visual acuity after cataract surgery. Pre-existing maculopathy was an independent risk factor of postoperative visual improvement and status. It is crucial to examine retinal status prior to cataract surgery to prevent poor vision improvement, poor postoperative vision or retinal complications.

Aluminum nitride (AlN) based resistance random access memory (RRAM) devices with TiN/AlN/Pt metal− insulator−metal (MIM) structures were fabricated in this study. To improve the characteristics of the RRAM such as high endurance operation and high resistance switching stability, silicon dopants were doped into AlN films by using the cosputtering method. Then, the influence of the concentration of silicon doping on the bipolar switching characteristics of AlN-based RRAM was studied. The research results show that the on/off ratio of the device after silicon doping has increased from 10 to about 1000, the set voltage has reduced from 2.5 to 1.9 V, and the reset voltage has reduced from −1.5 to −1.1 V. The stability of resistance switching (RS) is also improved. Besides, it is found that silicon doping helps to lower the instability caused by the oxygen ions and increased the endurance cycle (>2.5 × 10 6 cycles). Based on the results, the detailed mechanisms were also investigated systematically.

Stretchable optoelectronic devices are the need of the hour when it comes to making present day technologies user-friendly. These devices when placed conformably on the human skin or any other artificial intelligence products must function in all their capacities to get a durable and highly sensitive device performance. Stretchable photodetectors are the core fundamental constituents that fall under the umbrella of flexible optoelectronic devices. Although a significant amount of research has been reported on stretchable photodetectors, good performance still remains a challenge. Nanometer-sized methylammonium lead bromide ((MA)-PbBr 3 ) perovskite nanocrystals can significantly emit and absorb light in the visible spectrum. With high quantum yield and stable optical and electronic properties, when they are subjected to mechanically tunable two-dimensional (2D) composites, we obtain better performance from stretchable optoelectronic devices. Here, a hybrid photodetector composed of perovskite nanocrystals and graphene of rippled geometry is demonstrated, where a thin film of photon-absorbing perovskite nanocrystals is placed on rippled graphene that contributes to a photoresponsivity on the order of ∼6 × 10 5 A W −1 . The large photoresponsivity value places this hybrid stretchable device in the highest position among devices with similar functionality. It is found that the photoresponsivity of the perovskite nanocrystals and graphene hybrid rippled structure photodetector is strain tunable with a stretchability up to 100%. In addition, the hybrid rippled structure photodetector has wearability and durability. All of these superior functionalities lead the way toward fabricating stretchable optoelectronic devices suitable for applications in the fields of biomedicine, defense systems, fire detection, and flexible display panels.

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The integration of core-multishell nanostructure with upconversion nanoparticles achieve the ultralow pumping power density of 0.7 W cm-2 by continuous-wave infrared laser due to the formation of whispering gallery modes with diverse effective refractive indices.