Exciton dynamics in atomically thin MoS2: Interexcitonic interaction and broadening kinetics

We report ultrafast pump-probe spectroscopy examining exciton dynamics in atomically thin MoS2. Spectrally and temporally resolved measurements are performed to investigate the interaction dynamics of two important direct-gap excitons (A and B) and their associated broadening kinetics. The two excitons show strongly correlated interexcitonic dynamic, in which the transient blue-shifted excitonic absorption originates from the internal A-B excitonic interaction. The observed complex spectral response is determined by the exciton collision-induced linewidth broadening; the broadening of the B-exciton linewidth in turn lowers the peak spectral amplitude of the A exciton. Resonant excitation at the B-exciton energy reveals that interexcitonic scattering plays a more important role in determining the broadening kinetics than free-carrier scattering.Keywords: Relaxation, Monolayer MoS[subscript 2], Blue shift, Semiconductor, Transient absorption spectra, Layer, Femtosecond, Photoexcited carriers, Regenerative amplifier, Quantum well structur

Controllable synthesis of molybdenum tungsten disulfide alloy for vertically composition-controlled multilayer

The effective synthesis of two-dimensional transition metal dichalcogenides alloy is essential for successful application in electronic and optical devices based on a tunable band gap. Here we show a synthesis process for Mo<inf>1-x</inf>W<inf>x</inf>S<inf>2</inf> alloy using sulfurization of super-cycle atomic layer deposition Mo<inf>1-x</inf>W<inf>x</inf>O<inf>y</inf>. Various spectroscopic and microscopic results indicate that the synthesized Mo<inf>1-x</inf>W<inf>x</inf>S<inf>2</inf> alloys have complete mixing of Mo and Watoms and tunable band gap by systematically controlled composition and layer number. Based on this, we synthesize a vertically composition-controlled (VCC) Mo<inf>1-x</inf>W<inf>x</inf>S<inf>2</inf> multilayer using five continuous super-cycles with different cycle ratios for each super-cycle. Angle-resolved X-ray photoemission spectroscopy, Raman and ultraviolet-visible spectrophotometer results reveal that a VCC Mo<inf>1-x</inf>W<inf>x</inf>S<inf>2</inf> multilayer has different vertical composition and broadband light absorption with strong interlayer coupling within a VCC Mo<inf>1-x</inf>W<inf>x</inf>S<inf>2</inf> multilayer. Further, we demonstrate that a VCC Mo<inf>1-x</inf>W<inf>x</inf>S<inf>2</inf> multilayer photodetector generates three to four times greater photocurrent than MoS<inf>2</inf>-and WS<inf>2</inf>-based devices, owing to the broadband light absorption. © 2015 Macmillan Publishers Limitedopen1

Identification of a regulatory pathway governing TRAF1 via an arthritis-associated non-coding variant

TRAF1/C5 was among the first loci shown to confer risk for inflammatory arthritis in the absence of an associated coding variant, but its genetic mechanism remains undefined. Using Immunochip data from 3,939 patients with juvenile idiopathic arthritis (JIA) and 14,412 control individuals, we identified 132 plausible common non-coding variants, reduced serially by single-nucleotide polymorphism sequencing (SNP-seq), electrophoretic mobility shift, and luciferase studies to the single variant rs7034653 in the third intron of TRAF1. Genetically manipulated experimental cells and primary monocytes from genotyped donors establish that the risk G allele reduces binding of Fos-related antigen 2 (FRA2), encoded by FOSL2, resulting in reduced TRAF1 expression and enhanced tumor necrosis factor (TNF) production. Conditioning on this JIA variant eliminated attributable risk for rheumatoid arthritis, implicating a mechanism shared across the arthritis spectrum. These findings reveal that rs7034653, FRA2, and TRAF1 mediate a pathway through which a non-coding functional variant drives risk of inflammatory arthritis in children and adults

Pharmacological inhibition of Kv3 on oxidative stress-induced cataract progression

Oxidative stress is one of the most important risk factors for cataractogenesis. Previous studies have indicated that BDS-II, a Kv3 channel blocker, plays pivotal roles in oxidative stress-related diseases. This study demonstrates that BDS-II exerts a protective effect on cataractogenesis. Specifically, BDS-II was observed to inhibit lens opacity induced by H2O2. BDS-II was also determined to inhibit cataract progression in a sodium selenite-induced in vivo cataract model by inhibiting reduction of the total GSH. In addition, BDS-II was demonstrated to protect human lens epithelial cells against H2O2-induced cell death. Our results suggest that BDS-II is a potential pharmacological candidate in cataract therapy.N

Light Polarization-Controlled Conversion of Ultrafast Coherent-Incoherent Exciton Dynamics in Few-Layer ReS2

Coherent light-matter interaction can transiently modulate the quantum states of matter under nonresonant laser excitation. This phenomenon, called the optical Stark effect, is one of the promising candidates for realizing ultrafast optical switches. However, the ultrafast modulations induced by the coherent light-matter interactions usually involve unwanted incoherent responses, significantly reducing the overall operation speed. Here, by using ultrafast pump-probe spectroscopy, we suppress the incoherent response and modulate the coherent-to-incoherent ratio in the two-dimensional semiconductor ReS2. We selectively convert the coherent and incoherent responses of an anisotropic exciton state by solely using photon polarizations, improving the control ratio by 3 orders of magnitude. The efficient modulation was enabled by transient superpositions of differential spectra from two nondegenerate exciton states due to the light polarization dependencies. This work provides a valuable contribution toward realizing ideal ultrafast optical switches.11Nsciescopu