Intrinsic Ultralow-Threshold Laser Action from Rationally Molecular Design of Metal-Organic Framework Materials.

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/cm2) 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 ∼103 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.

Self-Sufficient and Highly Efficient Gold Sandwich Upconversion Nanocomposite Lasers for Stretchable and Bio-applications.

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.

Nanoscale Core-Shell Hyperbolic Structures for Ultralow Threshold Laser Action: An Efficient Platform for the Enhancement of Optical Manipulation.

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/cm2). 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.

Visual outcomes and associated risk factors of cataract surgeries in highly myopic Taiwanese.

AIMS: The purposes of this study were to describe the visual outcome of highly myopic eyes undergoing cataract surgery, to investigate associated risk factors for poor postoperative vision, and to assess postoperative complication frequency among the prevalent 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 of 26.0 mm. 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 registered between January 2002 and December 2004. Mean follow-up interval was 43.3 +/- 20.2 weeks (range 25-103). Thirty-two eyes (61.5%) had good postoperative visual improvement (> or =4 line 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 of 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.

Visual outcomes and associated risk factors of cataract surgeries in highly myopic Taiwanese.

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 > or =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 (> or =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.