Department Of Physics

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    Preparation and Energy Storage Assessment of Ti3C2 2d MXene and Its Possible Thinning Mechanism
    (Springer Nature, 2023-09-07T00:00:00) Singh, Diya; Rani, Pinki; Biswas, Sayani; Alegaonkar, Prashant S.
    Since after its discovery, MXene has captivated the focus of many researchers. In this work, we report on the low-temperature synthesis of Ti3AlC2 MAX phase at 800�? and its further etching to obtain Ti3C2 MXene. Initially, titanium (Ti), aluminium (Al), and graphite (C) precursors were taken in an appropriate volume proportion and add-mixed and grounded well via molten salt technique (Galvin et al. in J Eur Ceram Soc 38, 2018 [1]). The characterizations performed on powder such as FTIR, XRD, UV�Visible, SEM, and EDS confirmed Ti3AlC2 MAX phase. The MAX phase was subjected to the acid treatment (HF, concentration 40%) for ~ 80�h. The synthesized MXene was separated and investigated using FTIR, XRD, UV�Visible, SEM, and EDS techniques. The MXene was further employed to microwave treatment over the temperature 300�420�K at a discharge of power 120 W for 1�h. Analysis revealed that thickness of Ti3C2 layers is observed to be decreased with microwave treatment which can be a possible mechanism to obtain MXene quantum dots. In electrochemical analysis, specific capacitance for two electrode MXene@300�K and @400�K is reported to be 15 and 10�F/g, respectively, showing resistive nature of capacitance coupling for MXene. Analysis of electrochemical impedance spectroscopy together with bode showed the surface passivation effect of MXene layers to achieve different charge dynamics in both the systems. � 2023, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
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    Optoelectronic and photocatalytic properties of stable pentagonal B2S and B2Se monolayers
    (Elsevier B.V., 2022-06-01T00:00:00) Katoch, Neha; Kumar, Jagdish; Kumar, Ashok; Ahluwalia, P.K.; Pandey, Ravindra
    Boron-based 2D monolayers have attracted tremendous interest due to their unique physical and chemical properties. In this paper, we report novel pentagonal monolayers, B2S and B2Se, which are predicted to be energetically, dynamically, and thermally stable based on density functional theory. At the HSE06 level of theory, they exhibit a moderate indirect bandgap of (e.g., 1.82 eV for Penta-B2S and 1.94 eV for Penta-B2Se). Strain-induced indirect-to-direct bandgap transition, high hole mobility (~103 Cm2V-1S-1) and strong optical absorption (? ~105 Cm-1) in the visible region are observed for these monolayers. Moreover, the electronic band structures and optical spectra are tunable by mechanical strains suggesting their visible light-harvesting capabilities for optoelectronic applications. In this way, the pentagonal family of 2D materials is now expanded to include boron-containing photocatalytic materials for water splitting applications. � 2022
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    Engineering 2D Materials for Photocatalytic Water-Splitting from a Theoretical Perspective
    (MDPI, 2022-03-21T00:00:00) Jakhar, Mukesh; Kumar, Ashok; Ahluwalia, Pradeep K.; Tankeshwar, Kumar; Pandey, Ravindra
    Splitting of water with the help of photocatalysts has gained a strong interest in the scientific community for producing clean energy, thus requiring novel semiconductor materials to achieve highyield hydrogen production. The emergence of 2D nanoscale materials with remarkable electronic and optical properties has received much attention in this field. Owing to the recent developments in highend computation and advanced electronic structure theories, first principles studies offer powerful tools to screen photocatalytic systems reliably and efficiently. This review is organized to highlight the essential properties of 2D photocatalysts and the recent advances in the theoretical engineering of 2D materials for the improvement in photocatalytic overall water-splitting. The advancement in the strategies including (i) single-atom catalysts, (ii) defect engineering, (iii) strain engineering, (iv) Janus structures, (v) type-II heterostructures (vi) Z-scheme heterostructures (vii) multilayer configurations (viii) edge-modification in nanoribbons and (ix) the effect of pH in overall watersplitting are summarized to improve the existing problems for a photocatalytic catalytic reaction such as overcoming large overpotential to trigger the water-splitting reactions without using cocatalysts. This review could serve as a bridge between theoretical and experimental research on next-generation 2D photocatalysts. � 2022 by the authors. Licensee MDPI, Basel, Switzerland.
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    High-performance supercapacitor based on MoS2@TiO2 composite for wide range temperature application
    (Elsevier Ltd, 2021-06-07T00:00:00) Iqbal, Muzahir; Saykar, Nilesh G.; Arya, Anil; Banerjee, Indrani; Alegaonkar, Prashant S.; Mahapatra, S.K.
    Transition metal sulphide and their composites gain attention as electrode material in energy storage devices due to their superior properties like excellent conductivity, high surface area, and porosity. We report an evaluation of the electrochemical performance of MoS2@TiO2 binary composite in symmetric supercapacitor assembly at different temperatures. A facile hydrothermal technique is used to prepare MoS2@TiO2 binary composite. Structural and morphological analysis reveals that highly crystalline composite comprising MoS2 assembled in flower-like flake configuration, whereas, TiO2 in nanorods form are prepared. Among all three electrodes, MoS2@15%TiO2 demonstrates maximum specific capacitance 210 F/g at 10 mV/s with excellent cycling stability (98%, 2000 cycles) at ambient temperature. It may be concluded that the mono-phased, mesoporous structure is a key feature behind the improved performance over the other electrodes. Further, improvement in charge-discharge characteristics has been observed by a factor of 200% at 60 �C attributing to low activation energy and faster ion dynamics at elevated temperatures. The impedance spectroscopic analysis reveals a significant reduction in interfacial impedances that leads to a superior capacitance effect compounded with favourable electrolytic charge dynamics. The highest energy density is reported to be 21 Wh/kg with a power density of 1300 W/kg in symmetric configuration. Synergistic effect of the binary system along with unique surface morphology and charge storage followed by intercalation and capacitive mechanism results in enhanced performance of supercapacitor with MoS2@15%TiO2. Thus, binary MoS2@TiO2 composite seems to be an exceptional candidate for the energy storage device operating at a wide temperature range (25�60 �C). � 2021 Elsevier B.V.
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    Topological Insulators: An In-Depth Review of Their Use in Modelocked Fiber Lasers
    (John Wiley and Sons Inc, 2021-05-03T00:00:00) Mondal, Shyamal; Ganguly, Rounak; Mondal, Krishnakanta
    Topological insulators (TIs) exhibit exciting optical properties, which open up a new pathway to generate ultrashort pulses from fiber lasers. Layered TIs display distinct saturable absorption properties due to excited state absorption, as compared to their bulk structures. Moreover, the electronic structures of the TI films depend on the thickness of the films due to the quantum confinement of the electrons. By virtue of this, TI nanoparticles play a key role in all-fiber modelocked lasers. By tweaking the crystal structures of TIs, it is possible to generate ultrashort pulses across the visible, near-infrared, and mid-infrared wavelengths. Starting from the crystal structures and density of states calculations, how different topological insulators can be fabricated and integrated as an efficient passive saturable absorber in all-fiber modelocked lasers with the capability of producing fundamental to high-harmonic pulse generation are described clearly in this review report. Moreover, this report reviews the current state-of-art of TI-based saturable absorbers and their applications in different regimes of modelocked fiber�lasers. � 2021 Wiley-VCH GmbH