Department of Physics

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We present measurements of the first to fourth moments of the lepton mass squared q2 of B→Xcℓν¯ℓ decays for ℓ=e, μ and with Xc a hadronic system containing a charm quark. These results use a sample of electron-positron collisions at the ϒ(4S) resonance corresponding to 62.8 fb-1 of integrated luminosity and collected by the Belle II 2 experiment in 2019 and 2020. To identify the Xc system and reconstruct q2, one of the B mesons from an ϒ(4S)→BB¯ decay is fully reconstructed in a hadronic decay mode using a multivariate B tagging algorithm. We report raw and central moments for q2>1.5 GeV2/c4 up to q2>8.5 GeV2/c4, probing up to 77% of the accessible B→Xcℓν¯ℓ phase space. This is the first measurement of moments in the experimentally challenging range of [1.5,2.5] GeV2/c4. The results can be used for a new determination of |Vcb| using inclusive B→Xcℓν¯ℓ decays. © 2023 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the "https://creativecommons.org/licenses/by/4.0/"Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3.

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Physical Review D

Measurement of lepton mass squared moments in B →xcℓ ν ¯ ℓ decays with the Belle II experiment

We search for lepton-flavor-violating τ-→e-α and τ-→μ-α decays, where α is an invisible spin-0 boson. The search uses electron-positron collisions at 10.58 GeV center-of-mass energy with an integrated luminosity of 62.8 fb-1, produced by the SuperKEKB collider and collected with the Belle II detector. We search for an excess in the lepton-energy spectrum of the known τ-→e-ν¯eντ and τ-→μ-ν¯μντ decays. We report 95% confidence-level upper limits on the branching-fraction ratio B(τ-→e-α)/B(τ-→e-ν¯eντ) in the range (1.1-9.7)×10-3 and on B(τ-→μ-α)/B(τ-→μ-ν¯μντ) in the range (0.7-12.2)×10-3 for α masses between 0 and 1.6 GeV/c2. These results provide the most stringent bounds on invisible boson production from τ decays. © 2023 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the "https://creativecommons.org/licenses/by/4.0/"Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3.

Physical Review Letters

Search for Lepton-Flavor-Violating τ Decays to a Lepton and an Invisible Boson at Belle II

Fulltext

Journal of High Energy Physics

Erratum to: Combined analysis of Belle and Belle II data to determine the CKM angle ϕ 3 using B+ → D(K S 0 h+h−)h+ decays (Journal of High Energy Physics, (2022), 2022, 2, (63), 10.1007/JHEP02(2022)063)

Atomically thin semiconducting 2D transition metal dichalcogenides have garnered remarkable attention from the scientific community due to their prodigious contributions in the field of next-generation electronic and optoelectronic devices. In this continuation, we report a facile synthesis protocol of monolayer WSe2 films via the atmospheric-pressure chemical vapor deposition (APCVD) technique using hydrothermally synthesized hexagonal-phase tungsten oxide (h-WO3) nanorods. The as synthesized WSe2 crystal is a monolayer of ∼0.9 nm thickness as confirmed by atomic force microscopy. The confocal Raman and photoluminescence (PL) mapping suggests that the grown monolayer WSe2 triangles have lattice defects at edge sites, with a slight red-shift of ∼2 nm in PL, a blue-shift of ∼2 cm-1 in Raman peak and reduction in both the intensities. Confocal time-resolved PL mapping at edges reveals a fast-decay component of ∼582 ps and a slow-decay component of ∼2.18 ns that also signifies the presence of lattice defects, which serves as localized-states for photon-generated charge excitons. Furthermore, we have also investigated its electrical property by devising field-effect transistors (FETs). The fabricated WSe2 based FET shows intrinsic n-type behavior. WSe2 FET offers an electron mobility (μ) of ∼13.2 cm2 V-1 s-1, current ON/OFF ratio of ∼107 with a subthreshold slope (SS) of ∼397 mV/decade, which is relatable to the other reported works on WSe2 based FETs. In addition, the device exhibits very high on-current of order of ∼150 μA/μm. These results indicate that h-WO3 nanorod assisted APCVD synthesized WSe2 has prospective of being a competitor for next-generation optoelectronic, and valley-tronic devices. © 2022 Author(s).

Journal of Applied Physics

Unveiling the electrical and photo-physical properties of intrinsic n-type 2D WSe2 for high performance field-effect transistors

Electrocatalytic water splitting in alkaline media is greatly challenged by the lack of highly active bifunctional electrocatalysts to overcome the sluggish kinetics of the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively. In this regard, transition metal dichalcogenides (TMDs) have emerged as potential bifunctional catalysts for overall water splitting, but still suffer from high overpotentials. Herein, we report Mo and Co doped nanostructured 1T-VS2 directly grown on carbon cloth in a one step hydrothermal reaction as a binder free highly active bifunctional electrocatalyst for the HER and OER in alkaline media. The bifunctional electrocatalytic properties are tuned by optimizing the doping concentration of the heteroatoms. Various physicochemical results demonstrate that 10% molar doping of Mo and Co in VS2 (10:MoCo-VS2) leads to the highest bifunctional activities demanding HER and OER overpotentials of only 63 and 248 mV at a current density of 10 mA cm−2. Furthermore, a 10:MoCo-VS2 based electrolyzer fabricated using 10:MoCo-VS2 as both the anode and cathode also demonstrated high overall water splitting activity demanding a low cell potential of only 1.54 V to generate a current density of 10 mA cm−2 with long-term stability (35 h), which are attributed to its ultrathin and mesoporous nature, expanded interlayer spacing (∼63%), activated basal planes, and abundant active sites resulting from the synergistic effect of optimized Mo and Co dual doping into the 1T-VS2 host material. This study thus presents a facile approach for designing efficient bifunctional electrocatalysts based on heteroatoms doped VS2 for electrocatalytic water splitting in alkaline media. © 2022 The Royal Society of Chemistry

Journal of Materials Chemistry A

Mo/Co doped 1T-VS 2 nanostructures as a superior bifunctional electrocatalyst for overall water splitting in alkaline media

Sustainable supply of water and energy has always been essential for socio-economic development. Flocculation, adsorption, and membrane filtration are among the most cost-effective techniques for water purification. However, in today's world, hybrid technology has emerged as a potential alternative for membrane filtration water purification. Further, the hybrid system is more energy-efficient and takes up less space than membrane filtration alone, including double-pass Reverse Osmosis. The reuse of wastewater for the production of drinkable water has indeed been made possible due to rapid developments in membrane filtration technology. The potential applications of membrane technologies and their existing position in the realm of water and energy sustainability are discussed in this chapter. Further, the rapidly progressing hybrid membrane filtering technologies, as well as future research prospects are also discussed in this chapter. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.

Polymer-Based Advanced Functional Materials for Energy and Environmental {\ldots}

Polymeric Membranes and Hybrid Techniques for Water Purification Applications

Chalcogenide-based quantum dots are useful for the application of memory-switching devices because of the control in the trap states in the materials. The control in the trap states can be achieved using a hot-injection colloidal synthesis method that produces temperature-dependent size-variable quantum dots. In addition to this, formation of a nanoscale heterostructure with an insulating material adds to the charge-trapped switching mechanism. Here, we have shown that the colloidal monodispersed CdSe quantum dots and poly(4-vinylpyridine) (PVP) formed a nanoscale heterostructure between themselves when taken in a suitable ratio to fabricate a device. This heterostructure helps realize memory-switching in the device with a maximum on-off current ratio of 105. The switching in the device is mainly due to the trap states in the CdSe quantum dots. The conduction in the off state is due to thermal charge injection and space charge injection conduction and in the on state, due to the Ohmic conduction mechanism. © 2021 American Chemical Society.

ACS Applied Materials and Interfaces

Hot Injection-Based Synthesized Colloidal CdSe Quantum Dots Embedded in Poly(4-vinylpyridine) (PVP) Matrix Form a Nanoscale Heterostructure for a High On-Off Ratio Memory-Switching Device

Enhanced Ammonia Gas Sensing Properties of Graphene via Ion‑Beam‑Induced Fluorination

Curcumin (CUR), demethoxycurcumin (DMC) and bisdemethoxycurcumin (BDMC) - the class of natural compound derived from turmeric can exist as keto-enol and β-diketone tautomer form. The structure and dynamics of particular relevance CUR is reported in prior studies, whereas DMC and BDMC, by far, have not been scrutinized. In the present studies, we have investigated the detailed molecular structure of CUR, DMC and BDMC by employing NMR spectroscopy as a key tool. The bridging carbon as methylene in β-diketone form and methine in keto-enol form shows significant difference in NMR spectrum. The results justified that Curcuminoids (CC) has nearly 3% of β-diketone tautomer in DMSO solvent at 298 K. Further, results revealed that β-diketone form was favoured in alkaline pH condition whereas acidic and neutral pH conditions favour keto-enol tautomer. However, at higher temperature equilibrium shift towards β-diketone tautomer. Moreover, this is the first report by NMR for observing the presence of β-diketone tautomer. © 2021 Elsevier Ltd

Food Chemistry

Existence of β-diketone form of curcuminoids revealed by NMR spectroscopy

We used density functional theory (DFT) calculations to examine the various molecular properties of two coumarin derivatives, namely 4-(5-amino-[1,3,4]thiadiazol-2-ylsulfanylmethyl)-7-methyl-chromen-2-one and 4-(5-amino-[1,3,4]thiadiazol-2-ylsulfanylmethyl)-7-methoxy-chromen-2-one at different levels of theory and basis sets. The calculated highest occupied molecular orbital and lowest unoccupied molecular orbital energies revealed that the investigated molecules were chemically active with a tendency for molecular interactions. The theoretical vibrational frequencies of these molecules were found to be consistent with the experimentally obtained frequencies. Moreover, solvatochromic measurements indicated no significant change in absorption spectral peak by varying the polarity of solvent. Under the same conditions we found that there was a red shift of 39 nm in the fluorescence spectral peak with increase in solvent polarity. The solvatochromic data were used to estimate excited dipole moments and the change in dipole moment was interpreted based on resonance structure of molecules. © 2020 John Wiley & Sons, Ltd.