Department Of Physics

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2D layered transition metal dichalcogenides (MoS2): Synthesis, applications and theoretical aspects
(Elsevier, 2018) Singh, Arun Kumar; Kumar, P.; Late, D.J.; Kumar, Ashok; Patel, S.; Singh, Jai
Recently, graphene and other two-dimensional (2D) transition metal dichalcogenides (TMDCs) have been widely explored due to their unique optical, mechanical, electrical and sensing properties for versatile electronic and optoelectronic applications. The atomically thin layers of TMDC materials have shown potential to replace state-of-the-art silicon-based technology. Graphene has already revealed an excess of new physics and multifaceted applications in several areas. Similarly, mono-layers of TMDCs such as molybdenum disulfide (MoS2) have also shown excellent electrical and optical properties possessing a direct band-gap of ∼1.8 eV combined with high mechanical flexibility. In contrast to semi-metallic graphene, the semiconducting behavior of MoS2 allows it to overcome the deficiencies of zero-band-gap graphene. This review summarizes the synthesis of 2D MoS2 by several techniques, i.e., mechanical and chemical exfoliation, RF-sputtering, atomic layer deposition (ALD) and chemical vapor deposition (CVD), etc. Furthermore, extensive studies based on potential applications of MoS2 such as the sensor, solar cells, field emission and as an efficient catalyst for hydrogen generation has been included. Theoretical aspects combined with the experimental observations to provide more insights on the dielectric, optical and topological behavior of MoS2 was highlighted.
2D layered transition metal dichalcogenides (MoS2): Synthesis, applications and theoretical aspects
(Elsevier Ltd, 2018) Singh, Arun Kumar; Kumar, P.; Late, D.J.; Kumar, Ashok; Patel, S.; Singh, Jai
Recently, graphene and other two-dimensional (2D) transition metal dichalcogenides (TMDCs) have been widely explored due to their unique optical, mechanical, electrical and sensing properties for versatile electronic and optoelectronic applications. The atomically thin layers of TMDC materials have shown potential to replace state-of-the-art silicon-based technology. Graphene has already revealed an excess of new physics and multifaceted applications in several areas. Similarly, mono-layers of TMDCs such as molybdenum disulfide (MoS2) have also shown excellent electrical and optical properties possessing a direct band-gap of ?1.8 eV combined with high mechanical flexibility. In contrast to semi-metallic graphene, the semiconducting behavior of MoS2 allows it to overcome the deficiencies of zero-band-gap graphene. This review summarizes the synthesis of 2D MoS2 by several techniques, i.e., mechanical and chemical exfoliation, RF-sputtering, atomic layer deposition (ALD) and chemical vapor deposition (CVD), etc. Furthermore, extensive studies based on potential applications of MoS2 such as the sensor, solar cells, field emission and as an efficient catalyst for hydrogen generation has been included. Theoretical aspects combined with the experimental observations to provide more insights on the dielectric, optical and topological behavior of MoS2 was highlighted.
2D-HfS 2 as an efficient photocatalyst for water splitting
(Royal Society of Chemistry, 2016) Singh, Deobrat; Gupta, Sanjeev K.; Sonvane, Yogesh; Kumar, Ashok; Ahuja, Rajeev
Two dimensional monolayer nanostructures for water splitting solar photocatalysts are drawing more attention due to their extraordinary properties. Using first principles calculations we have systematically investigated the structural, electronic and vibrational properties of corresponding HfS2 monolayers in both hexagonal (1H) and trigonal (1T) phases. The most stable adsorption configurations and adsorption energies are calculated. The adsorption energy of H2O on the substrate is 646.53 kJ mol−1 for the 1H-phase and 621.65 kJ mol−1 for the 1T-phase of HfS2. This shows that H2O molecules have a stronger interaction with the HfS2 substrate. The calculated redox potentials of H2O splitting lie properly astride the valence and conduction bands, suggesting that the monolayers of 1H- and 1T-HfS2 show the same characteristics as a photocatalyst for water splitting. Furthermore, we also calculated that the optical band gaps for the 1H and 1T phases of HfS2 are 2.60 eV and 3.10 eV, respectively. We have also calculated Raman spectrum signatures of the monolayer 1H and 1T-phase of the in-plane vibrational mode of the Hf and S atoms (E1g) and the out-of-plane vibrational mode of S atoms (A1g and A2u). Our work suggests that a lot more research and attention in this field is needed for the practical application of the material as visible light active photocatalysts.
Ab Initio Modeling of the ZnO-Cu(111) Interface
(American Chemical Society, 2021-12-31T00:00:00) Mondal, Krishnakanta; Megha; Banerjee, Arup; Fortunelli, Alessandro; Walter, Michael; Moseler, Michael
The morphology at the catalytically active interfacial site of ZnO/Cu in the commercial ZnO/Cu/Al2O3 catalyst for CO2 hydrogenation to methanol is still an open question. In the present study, we employ ab initio density functional theory based methods to gain insight into the structure of the ZnO-Cu interface by investigating the morphology of supported ZnO nano-ribbons at the interface with the Cu(111) surface in the presence of hydrogen and water molecules. We find that the stabilities of free-standing ZnO nano-ribbons get enhanced when they are supported on the Cu(111) surface. These supported nano-ribbons are further stabilized by the adsorption of hydrogen atoms on the top of O atoms of the nano-ribbons. Interestingly, the hydrogenated nano-ribbons are found to be equally stable and they appear to be an array of independent chains of ZnOH motifs, suggesting that the hydrogenated nano-ribbons are structurally fluxional. The edge of these fluxional nano-ribbons is stabilized via a triangular reconstruction with a basic composition of Zn6O7H7 in the presence of water molecules. Such a triangular structure gets further stabilized when it is attached to a bulk-like part of the ZnO/Cu(111) system. Furthermore, we find that the triangular reconstruction is energetically favorable even at the methanol synthesis conditions. Therefore, we propose that, under methanol synthesis conditions, the motif Zn6O7H7 represents a stable form at the interface between the bulk-like part of ZnO and the Cu(111) surface in the ZnO/Cu/Al2O3 based commercial catalyst. � 2021 American Chemical Society
Adsorption and activation of CO2 on a Au19Pt subnanometer cluster in aqueous environment
(Elsevier B.V., 2022-04-15T00:00:00) Mondal, Krishnakanta; Megha; Banerjee, Arup; Fortunelli, Alessandro
We employ ab initio density functional theory based method to investigate the ability of a subnanometer bimetallic Au19Pt cluster to adsorb and activate a CO2 molecule in an aqueous electrochemical environment. We find that, in water, Au19Pt gets negatively charged at zero bias and selectively promotes the adsorption and activation of the CO2 molecule via electron transfer and through the hybridization of oxygen p-orbitals and partially filled platinum d-orbitals. Notably, Pt acts as a collector of negative charge and behaves as a CO2-activating single-atom catalyst embedded within a robust Au20-like framework, thus suggesting Au19Pt as a potential candidate for CO2 mitigation. � 2022 Elsevier B.V.
Adsorption and Activation of CO2on Small-Sized Cu-Zr Bimetallic Clusters
(American Chemical Society, 2021-03-17T00:00:00) Megha; Mondal, Krishnakanta; Ghanty, Tapan K.; Banerjee, Arup
Adsorption and activation of CO2 is a key step in any chemical reaction, which aims to convert it to other useful chemicals. Therefore, it is important to understand the factors that drive the activation process and also search for materials that promote the process. We employ the density functional theory to explore the possibility of using small-sized bimetallic Cu-Zr clusters, Cu4-nZrn, with n = 1-3 for the above-mentioned key step. Our results suggest that after adsorption, a CO2 molecule preferably resides on Zr atoms or at the bridge and triangular faces formed by Zr atoms in bimetallic Cu-Zr clusters accompanied with its high degree of activation. Importantly, maximum activation occurs when CO2 is adsorbed on the CuZr3 cluster. Interestingly, we find that the adsorption energy of CO2 can be tuned by varying the extent of the Zr atom in Cu-Zr clusters. We rationalize the high adsorption of CO2 with the increase in the number of Zr atoms using the d-band center model and the concept of chemical hardness. The strong chemisorption and high activation of CO2 are ascribed to charge migration between Cu-Zr clusters and the CO2 molecule. We find an additional band in the infrared vibrational spectra of CO2 chemisorbed on all of the clusters, which is absent in the case of free CO2. We also observe that the energy barriers for the direct dissociation of the CO2 molecule to CO and O decrease significantly on bimetallic Cu-Zr clusters as compared to that on pure Cu4. In particular, the barrier heights are considerably small for Cu3Zr and CuZr3 clusters. This study demonstrates that Cu3Zr and CuZr3 clusters may serve as good candidates for activation and dissociation of the CO2 molecule. � 2021 American Chemical Society.
Adsorption of nucleobases on different allotropes of phosphorene
(American Institute of Physics, 2019) Jakhar, M; Kumar, Ashok; Srivastava, S; Parida, P; Tankeshwar, K.
There has been tremendous interest in low-dimensional quantum systems during past two decades, fueled by a constant stream of striking discoveries and also by the potential for, and realization of, new state-of-the-art electronic device architectures. In this paper, our work includes the structural, electronic and optical properties of nucleobase (Adenine(A), Cytosine(C), Guanine(G), Thymine(T)) adsorbed on different allotropes of phosphorene (α, β, γ). From the optical absorption spectra of different nucleobases when adsorbed on the surface of phosphorene, we could optically probe different Nucleobases. As phosphorene shows different spectra for different nucleobases, it behaves as a bio-sensor to detect various nucleobases. © 2019 Author(s).
Advanced cyclic stability and highly efficient different shaped carbonaceous nanostructured electrodes for solid-state energy storage devices
(Elsevier Ltd, 2022-07-12T00:00:00) Singh, Nirbhay; Tanwar, Shweta; Sharma, A.L.; Yadav, B.C.
The most reliant storage technologies are batteries and supercapacitors. While supercapacitors are more efficient in terms of faster energy delivery, sustainability, and high capacity retention. In supercapacitors, mostly utilized precursors are least abundant which are toxic and costly, as well as facing structural stability issues during the advanced charging-discharging cycles. So in the present work, we have studied the sustainability and capacity retention profile of shape-dependent carbonaceous materials in terms of cyclic stability. Here, we have prepared an environment-friendly, cost-effective carbon@FeOOH composite series by low-temperature hydrothermal method. The galvanostatic charge-discharge analysis shows a high power density of 5000 W kg?1 at a current density of 10 A g?1. The advanced capacity retention up to 92% is seen up to 15,000 cycles and 100% Coulombic efficiency till the last segment (30000th segment of charging-discharging) of galvanostatic charge-discharge (GCD) for optimized mesoporous carbon@FeOOH (MCF) sample. The symmetric solid-state device comprising MCF electrodes has been fabricated at the laboratory scale. It has been able to glow red LED for 18 min and a panel consisting of 16 LEDs for 5 min. A self-explanatory mechanism has also been proposed for a better understanding of readers. � 2022 Hydrogen Energy Publications LLC
Advanced sustainable solid state energy storage devices based on FeOOH nanorod loaded carbon@PANI electrode: GCD cycling and TEM correlation
(Elsevier Ltd, 2023-03-09T00:00:00) Singh, Nirbhay; Tanwar, Shweta; Kumar, Pradip; Sharma, A.L.; Yadav, B.C.
A cost-effective, environment-friendly polyaniline-wrapped activated carbon-FeOOH ternary composite electrode is developed by two steps facile method for the efficient and sustainable energy storage device. The HR-TEM analysis before and after cyclic stability (20 k cycles of charging-discharging) shows electrode structural stability and potentiality as an energy storage device. The ternary composite utilizes polyaniline (PANI) maximum, which reflects an increase in voltage window, and electrochemical performance. The voltammetry (cyclic) and galvanostatic charge-discharge (GCD) examination display specific capacitance of 213 F g?1 at 10 mV s?1 and 234 F g?1 at 2 mA sec?1 for 20 wt%. The drastic variation through EIS (electrochemical impedance spectroscopy) in equivalent series resistance is seen by the nyquist plot before and after cycling. The specific capacitance is 234.5 F g?1 at 1 Ag?1 for 20 wt% PANI composite. The energy(Ed) and power density (Pd) of the device are 45 W h kg?1 and 5997 W kg?1 at 2 mA and 20 mA, respectively. The fabricated device shows very advanced capacity retention of up to 89% and coulombic efficiency of 100% till the last 20 k cycles with a stable potential window. The fabricated device can glow LED panels (consisting of 26 LEDs) for up to 5.30 min. The device retention profile and stable potential window show its advanced structural stability up to commercial-scale cycling, which signifies the additional role of PANI. The HR-TEM and electrochemical results after cyclic stability are in correlation. � 2023 Elsevier B.V.
Aging impact of Se powder on the electrochemical properties of Molybdenum selenide: Supercapacitor application
(Elsevier Ltd, 2022-02-10T00:00:00) Tanwar, Shweta; Singh, Nirbhay; Sharma, A.L.
In the present report, we have studied the impact of aging on selenium (Se) powder in hydrazine hydrate (act as reducing agent) during synthesis of pure molybdenum selenide (MoSe2) material. The MoSe2 as electrode material is prepared via single-step hydrothermal technique with aging Se powder in reducing agent for zero, one, and three days. The structural, microstructural, and chemical nature analysis of the samples was done via XRD, FESEM, and FTIR tools whereas the electrochemical study was performed via CV, GCD, and EIS techniques. The optimized material coded as M 39 (three days aged sample with pH 9) shows a high specific capacitance (Cs) of 368 F g?1 at the current density of value 0.5 A g?1 along with an energy density of 51 Wh kg?1 and power density of 250 W kg?1. Based on the electrode's electrochemical outcomes, it may be indicated that the electrochemical performance of MoSe2 material upsurges as the aging of Se increases from zero to three days. From the obtained results it is could be predicted that the M 39 material may stand appropriate for commercial supercapacitors. � 2022
Aging impact on morphological and electrochemical performance of MoSe2 composite for supercapacitor application
(Elsevier Ltd, 2023-02-27T00:00:00) Tanwar, Shweta; Sharma, A.L.
The report is associated with the investigation of the impact of selenium powder aging in hydrazine hydrate acting as a reducing agent on the electrochemical performance of the molybdenum diselenide/activated carbon (MoSe2@AC) composite-based electrodes, and its supercapacitor application. The MoSe2@AC composite is formulated via the simple hydrothermal method. The composite formation is validated via structural, chemical bond, and morphology investigation. Among all synthesized samples, six days aged sample coded M6AC appears to exhibit the best electrochemical performance. The specific capacitance estimated for M6AC material-based fabricated symmetric cell is around 394 F g?1 at the 1 A g?1 using KOH (6 M) electrolyte. The energy and power density delivered by the same cell at 1 A g?1 is about 55 W h kg?1 and 845 W kg?1 correspondingly. Furthermore, we have tested the real-world usability of the M6AC symmetric cell by illuminating different voltage cum colors light emitting diodes (LEDs). The 26 red LEDs in the parallel connection illuminate for approximately 32 min with the aid of our fabricated symmetric cell as the power source. For easy understanding of the readers, we also report the self-proposed charge storage mechanism linked with the glowing LEDs using our obtained experimental results. Thereby, the observed outcomes associated with the M6AC material indicate that it has immense potential for scaling its performance at the industrial cum commercial level to resolve the energy crisis problem of the society. � 2023
All-redox hybrid supercapacitors based on carbon modified stacked zinc cobaltite nanosheets
(Royal Society of Chemistry, 2023-09-12T00:00:00) Kour, Simran; Kour, Pawanpreet; Sharma, A.L.
The role of energy in the present century has increased with the fast advancement of the global economy. In this regard, hybrid supercapacitors (HSCs) as energy storage systems have become an extensive research focus worldwide. This study reports the synthesis of carbon-loaded ZnCo2O4 stacked nanosheets via an in situ hydrothermal process followed by annealing. The electrochemical response was tested in a 2-electrode system. The optimized composite exhibited a capacitance of ?527.6 F g?1 at 5 mV s?1. The symmetric SC (SSC) possessed an energy density (Ed) of ?17.3 W h kg?1 corresponding to a power density (Pd) of 2.25 kW kg?1. Two asymmetric all-redox HSCs have also been fabricated using an optimized composite material as the positive electrode. The previously synthesized MnCo2O4/AC (HSC1) and MnO2/AC (HSC2) were taken as negative electrodes. HSC1 exhibited an Ed of ?24.4 W h kg?1 corresponding to a Pd of ?0.8 kW kg?1. On the other hand, HSC2 exhibited the highest Ed of ?30.8 W h kg?1 at 2.4 kW kg?1. The real-time application of the composite is tested with the fabricated HSCs. HSC1 exhibited a capacitive retention of ?72.2% after 10 000 cycles. On the other hand, HSC2 exhibited a capacitive retention of ?73.4% after 10 000 cycles. The SSC, HSC1, and HSC2 illuminated a 39 red LED panel for ?3 min, 7 min, and 13 min, respectively. The results suggested the promising performance of all-redox HSCs. The overall results present a sustainable approach for creating hierarchical energy materials for the construction of future energy-storage systems. � 2023 The Royal Society of Chemistry.
Alloyed monolayers of Cu, Ag, Au and Pt in hexagonal phase: A comprehensive first principles study
(Elsevier Ltd, 2018) Kapoor, Pooja; Kumar, Arun; Sharma, Munish; Kumar, Jagdish; Kumar, Ashok; Ahluwalia, P. K.
We present density functional theory (DFT) based comprehensive study of two-dimensional (2D) alloyed monolayers of noble metals (AgCu, AgPt, AgAu, AuCu, AuPt and CuPt) in hexagonal phase within numerical atomic orbitals and plane wave basis sets methods. The monolayers considered exhibit positive phonon frequencies suggesting them to be dynamically stable. The Pt containing alloyed monolayers have superior structural stability (binding energy and tensile strength) and exhibit metallic and ferromagnetic character amongst all the alloyed monolayers. Interestingly, alloying of Au monolayer with Cu and Ag show semiconducting behavior whereas alloyed AgCu monolayer posseses Dirac-cone like features at high symmetry points. These distinct features in electronic structures of alloyed 2D monolayers have been captured in STM like set up. An anisotropic behavior has been observed in dielectric spectra for all the considered structures. Tunneling characteristics show NDR region for Pt containing alloyed monolayers. The considered alloyed monolayers may potentially be useful as a building blocks for the applications in nano- and opto-electronics. ? 2017 Elsevier B.V.
Anisotropic short-range attractions precisely model branched erythrocyte aggregates
(Royal Society of Chemistry, 2023-10-17T00:00:00) Yadav, Megha; Vanshika, None; Singh, Chamkor
Homogeneous suspensions of red blood cells (RBCs or erythrocytes) in blood plasma are unstable in the absence of driving forces and form elongated stacks, called rouleaux. These erythrocyte aggregates are often branched porous networks - a feature that existing red blood cell aggregation models and simulations fail to predict exactly. Here we establish that alignment-dependent attractive forces in a system of dimers can precisely generate branched structures similar to RBC aggregates observed under a microscope. Our simulations consistently predict that the growth rate of typical mean rouleau size remains sub-linear - a hallmark from past studies - which we also confirm by deriving a reaction kernel taking into account appropriate collision cross-section, approach velocities, and an area-dependent sticking probability. The system exhibits unique features such as the existence of percolated and/or single giant cluster states, multiple coexisting mass-size scalings, and transition to a branched phase upon fine-tuning of model parameters. Upon decreasing the depletion thickness we find that the percolation threshold increases but the morphology of the structures opens up towards an increased degree of branching. Remarkably the system self-organizes to produce a universal power-law size distribution scaling irrespective of the model parameters. � 2023 The Royal Society of Chemistry.
Argon ion implanted CR-39 polymer: Optical and structural characterization
(Elsevier B.V., 2021-04-03T00:00:00) Chhokkar, Preeti; Kumar, V.; Goyal, Parveen K.; Kumar, Shyam; Tomar, A.K.; Gaur, Anurag; Arya, Anil
The samples of Polyallyl diglycol Carbonate (CR-39) were implanted with 100 keV argon ions at fluences 1 � 1015, 5 � 1015 and 1 � 1016 ions/cm2 to be employed for optical and structural studies. The changes in transmittance, reflectance, optical energy gap and refractive index have been studied through the UV�Vis�NIR spectroscopic technique. The enhancement in reflectivity and a strong reduction in transmittance, particularly in the UV region, are observed after Ar+ implantation in CR-39 samples. The absorbance value remains low ~0.10, 0.15 and 0.20 in the key communication wavelength region i.e. 800�1600 nm for sample implanted at the fluence of 1 � 1015, 5 � 1015, 1 � 1016 Ar+/cm2, respectively. The Optical energy gap (EOPT) is determined to be 0.92 eV for the implanted layer of the sample implanted at the fluence of 1 � 1016 Ar+/cm2, whereas 3.70 eV for the pristine sample. The surface electrical conductivity is increased from ~1.49 � 10?14 S (pristine sample) to ~8.34 � 10?10 S for sample implanted at the fluence of 1 � 1016 Ar+/cm2. The formation of conjugated ?-bond (-C[dbnd]C-) structure with Ar+ implantation is confirmed via FTIR and Raman measurements. TGA results are analysed in detail and are found to be in strong agreement with the changes observed in different properties of CR-39 after ion implantation. � 2021 Elsevier B.V.
Armchair and zigzag nanoribbons of gold and silver: A DFT study
(American Institute of Physics Inc., 2018) Kapoor, Pooja; Sharma, Munish; Kumar, Ashok; Ahluwalia, P. K.
This paper presents the results from a DFT-based computational study of structural and electronic properties of zigzag and armchair edge shaped nanoribbons of gold and silver in hexagonal phase. The cohesive energy of the considered nanoribbons are found to be more than the corresponding 2D counterpart, thereby, suggesting Au and Ag nanoribbons to be more stable in 1D as compared to 2D. All nanoribbons are found to be metallic with a modulation in quantum ballistic conductance with length and edge type of the nanoribbon. Au nanoribbons are found to have higher conductance than Ag nanoribbon. There is increase in conductance with increase in length of nanoribbon. ? 2018 Author(s).
Axial distribution of plasma fluctuations, plasma parameters, deposition rate and grain size during copper deposition
(Taylor and Francis Inc., 2017) Gopikishan, S.; Banerjee, I.; Pathak, Anand; Mahapatra, S. K.
Floating potential fluctuations, plasma parameters and deposition rate have been investigated as a function of axial distance during deposition of copper in direct current (DC) magnetron sputtering system. Fluctuations were analyzed using phase space, power spectra and amplitude bifurcation plots. It has been observed that the fluctuations are modified from chaotic to ordered state with increase in the axial distance from cathode. Plasma parameters such as electron density (ne), electron temperature (Te) and deposition rate (Dr) were measured and correlated with plasma fluctuations. It was found that more the deposition rate, greater the grain size, higher the electron density, higher the electron temperature and more chaotic the oscillations near the cathode. This observation could be helpful to the thin film technology industry to optimize the required film. ? 2017 Informa UK Limited, trading as Taylor & Francis Group.
Bi-phasic BiPO4 prepared through template-assisted hydrothermal method with enhanced electrochemical response for hybrid supercapacitor applications
(Springer Science and Business Media B.V., 2023-03-27T00:00:00) Monteles, Iara A.; Penha, Bruno V.; Fonseca, Weliton S.; Silva, Let�cia M. B.; Santos, Evelyn C. S.; de Souza, Luiz K. C.; Santos, C.C.; de Menezes, A.S.; Sharma, Surender K.; Javed, Yasir; Khawar, Muhammad R.; Tanaka, Auro A.; Almeida, Marcio A. P.
Abstract: We report the structural evolution of BiPO4 prepared in aqueous under different synthesis conditions viz., templates and temperatures to explore their electrochemical performance for supercapacitor applications. The templates [(hexadecyltrimethylammonium bromide (CTAB)), sodium dodecyl sulfate (SDS)] were added in bismuth precursor solution at 60��C, alternatively ethylene glycol (EG), a less toxic additive was incorporated at 90��C. BiPO4 exhibits a monoclinic phase, whereas a hexagonal structure was observed with the addition of the templates SDS and CTAB. Interestingly, both monoclinic and hexagonal phases were obtained by the addition of EG. The presence of mixed phase was thoroughly validated through Raman spectra, where vibrational modes for both monoclinic and hexagonal phases of BiPO4-EG were witnessed. The effect of template was clearly seen through electron microscopy with a rod-like morphology with (no template) and unfaceted (template). The electrochemical behavior of the synthesized materials was investigated, and it was found that the mixed structure of BiPO4-EG exhibited the highest specific capacity (167.15 C�g?1) at a scan rate of 5�mV�s?1, good capacitance retention at high current densities of up to 10 A�g?1 and the lowest electrochemical series resistance (ESR) of 57 ?. Graphical abstract: [Figure not available: see fulltext.]. � 2023, The Author(s), under exclusive licence to Springer Nature B.V.
BiOBr/ZnWO4 heterostructures: An important key player for enhanced photocatalytic degradation of rhodamine B dye and antibiotic ciprofloxacin
(Elsevier Ltd, 2022-11-07T00:00:00) Santana, Rafael W.R.; Lima, A.E.B.; Souza, Luiz K.C. de; Santos, Evelyn C.S.; Santos, C.C.; Menezes, A.S. de; Sharma, Surender K.; Cavalcante, L.S.; Maia da Costa, Marcelo E.H.; Sales, T.O.; Jacinto, Carlos; Luz, G.E.; Almeida, M.A.P.
We report a facile synthesis of p-BiOBr/n-ZnWO4 heterostructures by hydrothermal/precipitation method as an important key player to enhance the photocatalytic degradation of Rhodamine B (RhB) dye and ciprofloxacin antibiotic. The structural and microstructural features confirm that p-BiOBr/n-ZnWO4 heterostructures display a mixed tetragonal/monoclinic phase with the presence of several n-ZnWO4 nanocrystals on the surface of petals of flower-like p-BiOBr microcrystals. X-ray photoluminescence (XPS) analysis of BiOBr exhibits the existence of Bi, O, and Br, whereas BiOBr/ZnWO4-5%, in addition to Bi, O, and Br, consist of signature of Zn and W. UV�Visible spectra of p-BiOBr/n-ZnWO4-5% showed better absorption than p-BiOBr and n-ZnWO4, which displayed an enhanced collection of photons in the heterojunction. An intense photoluminescence emission at room temperature was observed for p-BiOBr microcrystals as compared to p-BiOBr/n-ZnWO4. We observed the best photocatalytic activity for p-BiOBr/n-ZnWO4-2.5% in the degradation of RhB dye at 99.4% in 25 min and CIP antibiotic at 58.2% in 170 min, which is assigned due to high surface area SBET (13 m2/g), pore size, providing active catalytic sites for bonding chemical and surface interaction and bonding chemical between the bromide/oxides. Finally, we have investigated the use of scavengers for isopropanol, benzoquinone, and sodium azide, which proves that the hydroxyl (�OH) and superoxide (O2?) radicals as the foremost reactive oxygen spicies (ROS) in photocatalytic degradation of RhB dye and antibiotic CIP. � 2022 Elsevier Ltd
Blast mitigation properties of porous nano-carbon
(Elsevier Ltd, 2021-11-03T00:00:00) Chinke, Shamal L.; Sandhu, Inderpal S.; Alegaonkar, Prashant S.
Designing and development of a superior shock mitigation nano�material shield is an emerging armour building technology. We report, the effect of Kolsky bar simulated blast waves, onto the shock damping characteristics of the porous nano�carbon (abbreviation: PNC), synthesized by pyrolysis of biomass precursor. Measurement of stress (?)�strain (?), constitutive variables reveal the elasto�plastic behaviour suggesting moderate built�up, and accumulation of stress; independent of applied strain before reaching a yield ~50 MPa. Gruneisen fatigue parameter is estimated to be less (~0.92) over a theoretical Rayleigh limit with >80% post impact damage of porous component. The loci of dictated shock states derived from Rankine�Hugoniot formulism demonstrates the hydrodynamic interplay between pressure (P), volume (V), shock (US) and particle (UP) velocity. For PNC, Rayleigh slope is observed to be reduced, whereas, US became pressure independent over 10 GPa. Behaviour of P�UP hydrodynamic equation displays 30% variation in shock states and predicts a reduction of sound speed by a factor of ~0.25 in porous matrix. Behind the shock wavefront, matrix particles attend a max�speed of 100 km�s?1. The value of elastic limit for PNC is ~8.62 GPa as obtained by analysing the actual shock profile, with an evidence of phase transformation. Electron and force microscopy studies show reduction in an area, effectively, by 20�30%, thickness by six�fold factors with a rise in topological disorder. Hydro�physical variables inferred from Raman, scanning electron, transmission electron, and atomic force microscopy is comparatively discussed for PNC and other nano�carbons. Shock topology obtained by pressure�time signal processing shows ~30% impact of the shock onto PNC and manifested as shock echo. Details of the analysis are presented. � 2021 Elsevier B.V.