Concomitant paracentral acute middle maculopathy and acute macular neuroretinopathy in eyes post-blunt trauma.

Purpose: To analyze the imaging characteristics and the clinical course of patients showing concomitant paracentral acute middle maculopathy (PAMM) and acute macular neuroretinopathy (AMN) post-blunt trauma. Methods: PAMM and AMN lesions post-blunt trauma diagnosed on enhanced depth imaging optical coherence tomography (EDI-OCT) were recruited for the study. Results: : Thirteen eyes of 13 individuals with a history of blunt trauma were included in the study, of whom 11 (85%) were males. Mean age of the patients was 33.62 (range 16-67) years. Mean visual acuity at presentation and the last visit was 1.67 log of minimum angle of resolution (logMAR) and 0.82 logMAR, respectively. Mean interval between trauma and imaging was 5.08 (range 1-15) days. All patients had unilateral involvement, with the right eye being involved in 10 patients (77%). All patients had concomitant PAMM and AMN lesions. Conclusion: : Presence of coincident PAMM and AMN suggests a common pathophysiologic etiology, but the description of concomitant PAMM and AMN in the setting of blunt trauma to eye is hitherto unreported. Identifying AMN in a setting of PAMM requires meticulous examination of the OCT and OCTA images. It can be a cause of suboptimal visual recovery in such eyes.

Confined Excitons in Spherical-Like Halide Perovskite Quantum Dots.

Quantum dots (QDs) offer unique physical properties and novel application possibilities like single-photon emitters for quantum technologies. While strongly confined III-V and II-VI QDs have been studied extensively, their complex valence band structure often limits clear observations of individual transitions. In recently emerged lead-halide perovskites, band degeneracies are absent around the bandgap reducing the complexity of optical spectra. We show that for spherical-like CsPbBr3 QDs with diameters >6 nm, excitons confine with respect to their center-of-mass motion leading to well-pronounced resonances in their absorption spectra. Optical pumping of the lowest-confined exciton with femtosecond laser pulses not only bleaches all excitons but also reveals a series of distinct induced absorption resonances which we attribute to exciton-to-biexciton transitions and are red-shifted by the biexciton binding energy (∼40 meV). The temporal dynamics of the bleached excitons further support our exciton confinement model. Our study provides the first insight into confined excitons in CsPbBr3 QDs and gives a detailed understanding of their linear and nonlinear optical spectra.

Interfacial Manganese-Doping in CsPbBr3 Nanoplatelets by Employing a Molecular Shuttle.

Mn-doping in cesium lead halide perovskite nanoplatelets (NPls) is of particular importance where strong quantum confinement plays a significant role towards the exciton-dopant coupling. In this work, we report an immiscible bi-phasic strategy for post-synthetic Mn-doping of CsPbX3 (X=Br, Cl) NPls. A systematic study shows that electron-donating oleylamine acts as a shuttle ligand to transport MnX2 through the water-hexane interface and deliver it to the NPls. The halide anion also plays an essential role in maintaining an appropriate radius of Mn2+ and thus fulfilling the octahedral factor required for the formation of perovskite crystals. By varying the thickness of parent NPls, we can tune the dopant incorporation and, consequently, the exciton-to-dopant energy transfer process in doped NPls. Time-resolved optical measurements offer a detailed insight into the exciton-to-dopant energy transfer process. This new approach for post-synthetic cation doping paves a way towards exploring the cation exchange process in several other halide perovskites at the polar-nonpolar interface.

State of the Art and Prospects for Halide Perovskite Nanocrystals.

Metal-halide perovskites have rapidly emerged as one of the most promising materials of the 21st century, with many exciting properties and great potential for a broad range of applications, from photovoltaics to optoelectronics and photocatalysis. The ease with which metal-halide perovskites can be synthesized in the form of brightly luminescent colloidal nanocrystals, as well as their tunable and intriguing optical and electronic properties, has attracted researchers from different disciplines of science and technology. In the last few years, there has been a significant progress in the shape-controlled synthesis of perovskite nanocrystals and understanding of their properties and applications. In this comprehensive review, researchers having expertise in different fields (chemistry, physics, and device engineering) of metal-halide perovskite nanocrystals have joined together to provide a state of the art overview and future prospects of metal-halide perovskite nanocrystal research.

Coherent vibrational dynamics reveals lattice anharmonicity in organic-inorganic halide perovskite nanocrystals.

The halide ions of organic-inorganic hybrid perovskites can strongly influence the interaction between the central organic moiety and the inorganic metal halide octahedral units and thus their lattice vibrations. Here, we report the halide-ion-dependent vibrational coherences in formamidinium lead halide (FAPbX3, X = Br, I) perovskite nanocrystals (PNCs) via the combination of femtosecond pump-probe spectroscopy and density functional theory calculations. We find that the FAPbX3 PNCs generate halide-dependent coherent vibronic wave packets upon above-bandgap non-resonant excitation. More importantly, we observe several higher harmonics of the fundamental modes for FAPbI3 PNCs as compared to FAPbBr3 PNCs. This is likely due to the weaker interaction between the central FA moiety and the inorganic cage for FAPbI3 PNCs, and thus the PbI64- unit can vibrate more freely. This weakening reveals the intrinsic anharmonicity in the Pb-I framework, and thus facilitating the energy transfer into overtone and combination bands. These findings not only unveil the superior stability of Br-based PNCs over I-based PNCs but are also important for a better understanding of their electronic and polaronic properties.

Spin Polarization Dynamics of Free Charge Carriers in CsPbI3 Nanocrystals.

Lead halide perovskites (LHPs) exhibit large spin-orbit coupling (SOC), leading to only twofold-degenerate valence and conduction bands and therefore allowing for efficient optical orientation. This makes them ideal materials to study charge carrier spins. With this study we elucidate the spin dynamics of photoexcited charge carriers and the underlying spin relaxation mechanisms in CsPbI3 nanocrystals by employing time-resolved differential transmission spectroscopy (DTS). We find that the photoinduced spin polarization significantly diminishes during thermalization and cooling toward the energetically favorable band edge. Temperature-dependent DTS reveals a decay in spin polarization that is more than 1 order of magnitude faster at room temperature (3 ps) than at cryogenic temperatures (32 ps). We propose that spin relaxation of free charge carriers in large-SOC materials like LHPs occurs as a result of carrier-phonon scattering, as described by the Elliott-Yafet mechanism.

Transfer of Direct to Indirect Bound Excitons by Electron Intervalley Scattering in Cs2AgBiBr6 Double Perovskite Nanocrystals.

Lead-free halide double perovskites have emerged as a nontoxic alternative to the heavily researched lead-based halide perovskites. However, their optical properties and the initial charge carrier relaxation processes are under debate. In this study, we apply time-resolved photoluminescence and differential transmission spectroscopy to investigate the photoexcited charge carrier dynamics within the indirect band structure of Cs2AgBiBr6 nanocrystals. Interestingly, we observe a high energetic emission stemming from the direct band gap, besides the previously reported emission from the indirect band gap transition. We attribute this emission to the radiative recombination of direct bound excitons. This emission maximum redshifts nearly 1 eV within 10 ps due to electron intervalley scattering, which leads to a transfer of direct to indirect bound excitons. We conclude that these direct bound excitons possess a giant oscillator strength causing not only a pronounced absorption peak at the optical band gap energy but also luminescence to occur at the direct band gap transition in spite of the prevailing intervalley scattering process. These results expand the understanding of the optical properties and the charge carrier relaxation in double perovskites, thus, facilitating the further development of optoelectronic devices harnessing lead-free perovskites.

Manganese-Doping-Induced Quantum Confinement within Host Perovskite Nanocrystals through Ruddlesden-Popper Defects.

The concept of doping Mn2+ ions into II-VI semiconductor nanocrystals (NCs) was recently extended to perovskite NCs. To date, most studies on Mn2+ doped NCs focus on enhancing the emission related to the Mn2+ dopant via an energy transfer mechanism. Herein, we found that the doping of Mn2+ ions into CsPbCl3 NCs not only results in a Mn2+ -related orange emission, but also strongly influences the excitonic properties of the host NCs. We observe for the first time that Mn2+ doping leads to the formation of Ruddlesden-Popper (R.P.) defects and thus induces quantum confinement within the host NCs. We find that a slight doping with Mn2+ ions improves the size distribution of the NCs, which results in a prominent excitonic peak. However, with increasing the Mn2+ concentration, the number of R.P. planes increases leading to smaller single-crystal domains. The thus enhanced confinement and crystal inhomogeneity cause a gradual blue shift and broadening of the excitonic transition, respectively.

Iodine-Catalyzed Selenylation of 2H-Indazole.

A metal-free, environmentally friendly protocol for the arylselenylation of 2H-indazole has been developed using a catalytic amount of I2 under ambient conditions. A number of 3-(phenylselanyl)-2H-indazoles with wide functional group tolerance have been synthesized in good yields at room temperature. Mechanistic studies suggest that the reaction possibly proceeds through an ionic pathway.

Kinetics of Triplet Exciton Energy-Transfer Processes in Triplet Sensitizer-Doped Fluorescent Polymers.

Triplet sensitization is an important aspect for enhancing the performance of organic light-emitting diodes (OLEDs). The triplet-triplet annihilation (TTA) process is known to increase the efficiency of OLEDs. In this case, the time scale of triplet diffusion is an important parameter. In this paper, we have studied the triplet energy-transfer process as a function of time scale and temperature in pure and phosphorescent molecule FIrpic (bis[2-(4,6-difluorophenyl)pyridinato-C2, N](picolinato)iridium(III))-doped F8BT (poly(9,9-dioctylfluorene- alt-benzothiadiazole)) films. We have investigated the dynamics of triplet energy-transfer processes by probing the corresponding delayed fluorescence (DF) spectra (of the F8BT host system) generated from TTA. We have noticed that the dynamics of DF depends on the diffusion kinetics of the triplet excitonic state. We find that the successful triplet transfer to the host polymer system is directly proportional to the triplet lifetime of the guest molecule. We have further implemented doped F8BT films in polymer LEDs (PLEDs). A high triplet absorption (TA) signal (of the host triplets, i.e., F8BT) has been observed in doped PLEDs under electrical excitation. The high TA signal of the host triplets indicates the successful triplet transfer process from the FIrpic guest molecule to the F8BT host polymer system.

Metal-Free Synthesis of 2-Arylbenzothiazoles from Aldehydes, Amines, and Thiocyanate.

A highly efficient method for the synthesis of 2-arylbenzothiazoles has been developed using readily available aromatic amines, benzaldehydes, and NH4SCN as a sulfur source. A library of 2-arylbenzothiazoles with wide functional group compatibility has been synthesized in good yields through iodine-mediated oxidative annulation.

Role of Bimolecular Exciton Kinetics in Controlling the Efficiency of Organic Light-Emitting Diodes.

Here, we have carried out a spectroscopic investigation on the operational organic light-emitting diodes (OLEDs) to determine the role of emission layer thickness on the optoelectronic performance of OLEDs based on a poly(9,9-dioctylfluorene- alt-benzothiadiazole) (F8BT) copolymer system. Our study shows that delayed fluorescence (DF) via triplet-triplet annihilation (TTA) contributes significantly to boost the OLED efficiency through its fractional contribution. Interestingly, we note that DF contribution varies as a function of the emissive layer thickness. From the time-resolved electroluminescence (TREL) and triplet absorption (under electrical excitation) studies, we have seen that the emissive layer thickness controls triplet exciton generation and decay processes. From TREL, we have also shown that singlet-triplet annihilation (STA) is the dominant fluorescence quenching mechanism in bulk of the emissive layer, whereas thinner devices have significant exciton quenching at the interface of the injection layer/F8BT. The strength of STA differs in thin versus thick samples, which has been correlated with the spectral & spatial overlap integral of singlet and triplet states. Hence, STA strength and triplet population density are critical parameters for an explanation of high efficiency in unusually thick F8BT OLEDs.

Visible-Light-Induced Organophotoredox-Catalyzed Phosphonylation of 2 H-Indazoles with Diphenylphosphine Oxide.

A metal-free visible-light-induced phosphonylation of 2 H-indazoles with diphenylphosphine oxide has been developed using rose bengal as an organophotoredox catalyst under ambient air at room temperature. A library of diphenyl(2-phenyl-2 H-indazol-3-yl)phosphine oxide with broad functionalities has been synthesized in high yields. The experimental result suggests the radical pathway of the reaction.

Environment-Friendly Protocol for the Chlorination of Imidazoheterocycles by Chloramine-T.

An environment-friendly method for the chlorination of imidazoheterocycles has been developed using chloramine-T, a novel chlorinating reagent. A bunch of C-3 chloro-substituted imidazo[1,2-a]pyridines with variety of functionalities have been synthesized in good yields under neat condition at room temperature within very short time. This chlorination process is also applicable to imidazo[2,1-b]thiazole scaffolds. The present methodology is relevant to gram-scale synthesis. The major advantages of this system such as wide applicability, easy availability of reactants, open-air and metal- and solvent-free reaction conditions, no need of work-up, and simple purification technique represent a green synthetic protocol.

FeCl3/ZnI2-Catalyzed regioselective synthesis of angularly fused furans.

The FeCl3/ZnI2-catalyzed synthesis of angularly fused furans by intermolecular coupling between enols and alkynes has been developed in ambient air. The methodology is successfully applicable to 4-hydroxycoumarin, 4-hydroxyquinolinone and α-tetralone affording regioselective 2-aryl furans in good yields. The control experiments suggest the possibility of a radical reaction mechanism.

Copper-Catalyzed Regioselective Synthesis of Multisubstituted Furans by Coupling between Ketones and Aromatic Olefins.

A regioselective synthesis of multisubstituted furan derivatives has been developed via Cu(II)-catalyzed intermolecular annulation of aryl ketones with a wide range of aromatic olefins under ambient air in good yields. This protocol is applicable to both cyclic and acyclic aryl ketones.

Zn(OTf)2-Catalyzed Synthesis of Imidazole-Substituted Allenes.

A Zn(OTf)2-catalyzed simple and efficient method has been developed for the synthesis of imidazole-substituted allenes by the reaction of 1,1,3-triphenylprop-2-yn-1-ol and imidazoheterocycles. A library of tetrasubstituted allenes with broad functionalities have been prepared with excellent yields. The present methodology is also applicable to imidazo[1,2-a]pyrimidine, imidazo[2,1-b]thiazole and benzo[d]imidazo[2,1-b]thiazole.

Band Gap Tuning of CH3NH3Pb(Br(1-x)Clx)3 Hybrid Perovskite for Blue Electroluminescence.

We report on the structural, morphological and optical properties of AB(Br(1-x)Cl(x))3 (where, A = CH3NH3(+), B = Pb(2+) and x = 0 to 1) perovskite semiconductor and their successful demonstration in green and blue emissive perovskite light emitting diodes at room temperature. The bandgap of perovskite thin film is tuned from 2.42 to 3.16 eV. The onset of optical absorption is dominated by excitonic effects. The coulomb field of the exciton influences the absorption at the band edge. Hence, it is necessary to explicitly account for the enhancement of the absorption through the Sommerfield factor. This enables us to correctly extract the exciton binding energy and the electronic bandgap. We also show that the lattice constant varies linearly with the fractional chlorine content satisfying Vegards law.

Phytotherapy against insomnia: extravagant claims or an alternative medicine?

Insomnia or sleeplessness is a disorder characterized by a personal incapability to falling or staying asleep for a desirable period of time. Apart from Valeriana officinalis and Ziziphus jujuba most of the ethnobotanicals used for sleep disorders have not been evaluated for pharmacological or clinical efficacy against insomnia. Chinese herbal medicines involving polyherbal formulations are yet to be characterized and long-term side effects are yet to be evaluated. Anti insomniac phytotherapy opens up an exciting aspect of research which might benefit a large number of patients suffering from different degrees of insomnia.

Scorpion anti-venom activity of botanicals: a pharmacological approach.

Scorpion bite is considered as one of the common and dangerous phenomenon throughout the world. The clinical manifestations include pulmonary edema, myocardial damage, intracerebral haemorrhage, brachial plexopathy, renal failure etc. which sometimes leads to mortality. The common antivenin therapy includes anti-scorpion venom serum or prazosin. In the vast rural areas of the third world countries phytotherapy is considered as an alternative system of medicine and scorpion sting is treated with the help of medicinal botanicals. As the safety and efficacy are considered as important aspects of anti venin therapy, conventional treatment can be supported by the herbal remedy. The present review compiles a number of medicinal plants pharmacologically evaluated in vitro and/or in vivo for scorpion antivenin properties. Considering the aspects like cost effectiveness, availability, lesser side effects and development of drug resistance, plant based anti venin therapy may be considered as a possible remedy against scorpion envenomation.