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We investigate the hot carrier and exciton dynamics in two-dimensional (2D) metal halide perovskites using time-resolved spectroscopy. 2D perovskite films were prepared with and without dimethyl sulfoxide treatment to elucidate the effect of film processing techniques on optoelectronic properties. Femtosecond transient absorption measurements reveal that the charge carrier dynamics are different in the two samples, and excitons survive for a longer time in the treated sample than the untreated one. While the early-time carrier dynamics in the untreated sample are dominated by charges trapped by defect states, the hot free carriers govern the dynamics in the treated sample due to fewer defects in it. Morphological and other spectroscopic studies, including time-resolved photoluminescence, further suggest the formation of more defects in the untreated sample. These results can guide the future development of efficient 2D perovskite-based optoelectronic devices. [ABSTRACT FROM AUTHOR]

Optical emissions from two-dimensional transition metal dichalcogenides greatly differ from sample to sample due to their interactions with different substrates with variations in parameters such as the dielectric constant, absorption coefficient, growth conditions, strain, and defects. Often, the mechanisms of environmentally sensitive optical emission in 2D materials are lacking, and it is essential to perform the measurements on the same sample with different substrate backgrounds, which is a challenge. In this work, we explore photoluminescence engineering by comparing the optical properties of WS2 on SiO2, TiOx, and Pt by selectively creating different environments locally on the same sample. The PL-confocal map with good spatial resolution reveals that the emission of WS2 on TiOx and Pt is suppressed by charge transfer at the interface. While moving from WS2 on Pt toward WS2 on the TiOx region, a 3-fold enhancement in PL emission has been observed in agreement with a 20% increase in the trion-to-exciton ratio and calculated carrier densities. Further, the transient absorption spectroscopy shows faster exciton recombination in WS2/Pt (∼5.7 ps) and WS2/TiOx (∼7.2 ps) than WS2/SiO2 (∼48.5 ps), confirming the charge transfer in varied optical emission of the WS2 monolayer. Our method paves the way for using charge transfer and controlled carrier injection to design nanoantennas, optoelectronic devices, and quantum optical cavities in 2D materials. [ABSTRACT FROM AUTHOR]

Dinitroanilines group are persistent pesticides and important pollutants of soil and water. Their dissipation is needed to accurately predict the environmental risk entailing its use in different ecosystems. Degradation kinetics is not reported under subtropical conditions thus, kinetics of oryzalin under soybean field conditions at two application rate in texturally different Pantnagar soils were investigated for two cropping years. Oryzalin was extracted with acetone: methanol from soils followed by florisil SPE cleanup and residues were identified by HPLC-UV. Oryzalin persisted for more than 120 days in soils and slowly dissipated with biphasic first order kinetics. Dissipation was faster in sandy loam compared to silty clay loam soil. At 1.5 & 3.0 kg ha−1 initial half-life in silty clay loam and sandy loam soils were 5.892 & 5.675 and 6.015 & 5.770 days, while, in later phase it were 49.500 & 52.105 and 37.459 & 40.290 days, respectively. Recovery in soil, plant straw, seed husk, soybean oil, deoiled cake, and water samples varied from 77.50–88.85%, 79.50–89.25%, 78.05–88.20%, 75.45–83.92%, 77.40–84.75% and 81.75–93.75%, respectively. Minimum detection limit was 0.001 μg mL−1 and quantitation limit for soil, straw, oil, cake, husk and water were 0.007, 0.01, 0.04, 0.05, 0.03 µg g−1 and 0.005 µg mL−1, respectively. At harvest the oryzalin residues were below detection & MRL in all samples. Study revealed that under subtropical conditions oryzalin is safe for weed control in soybean fields and at harvest soybean crop could be used safely for human/animal consumption and would not create any residual/environmental problem. [ABSTRACT FROM AUTHOR]

In this paper, we study the uniqueness problems of fn(z)L(g) and gn(z)L(f) when they share a non-zero small function α(z) with finite weights, where L(h) represents any one of h(k)(z), h(z + c), h(z + c) - h(z) and h(k)(z + c), k ≥ 1 and c is a non-zero constant. Here f(z) and g(z) are transcendental meromorphic (or entire) functions and α(z) is a small function with respect to both f(z) and g(z). Our results improve and supplement the recent results due to Gao and Liu [Bull. Korean Math. Soc. 59 (2022), 155-166]. [ABSTRACT FROM AUTHOR]

The free vibration behavior of a bidirectional functionally graded rotating micro-disk that is subjected to uniform transverse pressure and high-temperature thermal loading has been studied. The micro-disk is functionally graded along the radial and thickness directions. The problem is mathematically formulated using two distinct but interrelated steps within the framework of Kirchhoff plate theory and modified couple stress theory. The first step determines the time-invariant deformed configuration of the micro-disk under centrifugal, pressure, and thermal loading using minimum potential energy principle. The second step determines the free vibration behavior of the micro-disk in the neighborhood of the deformed configuration using Hamilton's principle. The solutions of the governing equations for both these steps are obtained using the Ritz method. The mathematical model is successfully validated with various reduced problems. The numerical results for the first four axisymmetric bending vibration modes are presented to investigate the effects of wide range of parameters such as rotational speed, applied pressure, thermal loading, size-dependent thickness, volume fraction indices, and radius ratio. The mode shapes of vibration are illustrated through surface and contour plots. [ABSTRACT FROM AUTHOR]

Doping and alloying induce defect states in atomically thin transition metal dichalcogenides (TMDCs), leading to strong carrier–phonon interactions. The robust excitonic behavior of these layered materials can be modified by injecting a high density of charge carriers. However, comprehending the influence of carrier–phonon and carrier–carrier interactions on the optical properties of 2D materials is crucial for their optoelectronic and photonic applications. Here, transient absorption (TA) spectroscopy is employed to demonstrate the modulation of the transient optical behavior of TMDCs through doping and excitation near Mott density. The TA spectra reveal broadening attributed to carrier–carrier and carrier–phonon interactions, with the broadening being particularly pronounced in vanadium (V) doped TMDCs due to the hybridization of defect and exciton transitions. Analysis of TA kinetics suggests the involvement of various carrier species in the carrier dynamics of TMDCs, with the influence of mid‐gap carriers dominating at higher excitation densities. Nonetheless, the presence of strong carrier–phonon coupling in V‐doped TMDCs is demonstrated by temperature‐dependent Raman and photoluminescence spectroscopy. The results reveal that the enhanced coupling between acoustic phonons and carriers can lead to multiphonon emission. The findings of this study hold promise for controlling the optical response of TMDCs in ultrafast optoelectronic applications. [ABSTRACT FROM AUTHOR]

Transmissible Spongiform Encephalopathies are fatal neurodegenerative diseases caused by the misfolding of the cellular prion protein (PrP C ) into its pathological isoform (PrP Sc ). Efficient transmission of PrP Sc occurs within the same species, but a species barrier limits interspecies transmission. While PrP structure is largely conserved among mammals, variations at the β2-α2 loop are observed, and even minor changes in the amino acid sequence of the β2-α2 loop can significantly affect transmission efficiency. The present study shows that the introduction of the elk/deer-specific amino acid substitutions at positions 169 (Ser to Asn) and 173 (Asn to Thr) into the mouse prion protein, which are associated with the structural rigidity of the β2-α2 loop, has a substantial impact on protein dynamics as well as on the misfolding pathways of the protein. Native state hydrogen-deuterium exchange studies coupled with mass spectrometry, show that the rigid loop substitutions stabilize not only the β2-α2 loop but also the C-terminal end of α3, suggesting that molecular interactions between these two segments are strengthened. Moreover, the energy difference between the native state and multiple misfolding-prone partially unfolded forms (PUFs) present at equilibrium, is increased. The decreased accessibility of the PUFs from the native state leads to a slowing down of the misfolding of the protein. The results of this study provide important insights into the early events of conformational conversion of prion protein into β-rich oligomers, and add to the evidence that the β2-α2 loop is a key determinant in prion protein aggregation.

Two-dimensional (2D) transition metal dichalcogenides (TMDs) and perovskites hold substantial promise for various optoelectronic applications such as light emission, photodetection, and energy harvesting. However, each of these materials possesses certain limitations that can be overcome by synergistically combining them to form heterostructures, thereby unveiling intriguing optical properties. In this study, we present an uncomplicated technique for crafting a van der Waals (vdW) heterojunction comprising monolayer WS 2 and a Ruddlesden-Popper (RP) perovskite, namely (TEA) 2 PbI 4 . By utilizing ultrafast transient absorption (TA) spectroscopy, we explored the charge carrier dynamics within the WS 2 /(TEA) 2 PbI 4 heterostructure. Our findings uncover a type-II band alignment in the heterostructure, facilitating rapid (within 260 fs) hole transfer from WS 2 to the perovskite and leading to the formation of interlayer excitons (IXs) with a much longer lifetime (728 ps). This strategic approach has the potential to contribute to the development of hybrid systems aimed at achieving high-performance optoelectronic devices.