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    Twisted helical armchair graphene nanoribbons: mechanical and electronic properties
    (Springer Science and Business Media Deutschland GmbH, 2021-05-08T00:00:00) Thakur, Rajesh; Ahluwalia, P.K.; Kumar, Ashok; Sharma, Munish; Sharma, Raman
    Abstract: The Hydrogen and Fluorine planar armchairs graphene nanoribbons (H & F AGNRs), subjected to twist deformation within fixed periodic boundary conditions. H-AGNRs is highly elastic in nature, though passivation with Fluorine does induce the plasticity when twisted beyond threshold torsional strain. This plasticity attributes to the wider bond length distribution suggests distortion of benzo-rings. The bandgap response to the effective strain of narrow GNRs N= 6 , 7 , and 8 get arranged as (i) monotonously increasing for q= 0 , 2 and (ii) decreasing for q= 1 ; here, q= mod(N, 3) in effective strain space (?2?2). The effective strain space is found to be more appropriate for gauging the response of torsional strain. This trend has also been observed for Fluorine passivated AGNRs; however, because of higher sensitive response to torsional strain, the bandgap of N= 7 F-AGNRs drops from Eg? 0.95 eV to Eg? 0.05 eV at extreme torsional strain forming Dirac cone at � K allows dissipationless transport to charge carriers of high kinetic energy at low bias. Graphic abstract: [Figure not available: see fulltext.] � 2021, The Author(s), under exclusive licence to EDP Sciences, SIF and Springer-Verlag GmbH Germany, part of Springer Nature.
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    Enhanced capacitive behaviour of graphene nanoplatelets embedded epoxy nanocomposite
    (Springer, 2021-01-06T00:00:00) Raval, Bhargav; Sahare, P.D.; Mahapatra, S.K.; Banerjee, I.
    For the development of advanced polymer nanocomposite processability, high-quality and cost-efficiency plays a crucial role which combines mechanical robustness with functional electrochemical properties. In this study, we fabricated the epoxy/graphene nanocomposite (EGNC) with different wt% ratio of graphene nanoplatelets (GNPs). The EGNCs were fabricated through a solution mixing process and used it as an electrode to enhance electrochemical properties. The GNPs and EGNCs characterized using XRD, Raman spectroscopy, ATR FT-IR, and FE-SEM for the structural conformation and surface morphological study. The electrochemical analysis results show significant improvement in the specific capacitance in the EGNC samples as compared to the blank epoxy film. Specific capacitance 17.74 Fg?1 was recorded at 10 mVs?1 scan rate in 1.0�M KOH electrolyte solution for the 1.0 wt% EGNC film by cyclic voltammetry analysis. The Galvanostatic charge�discharge and Ragone plots also show mended results by the addition of GNPs. � 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC part of Springer Nature.
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    Reduced and oxidized rice straw biochar for hexavalent chromium adsorption: Revisiting the mechanism of adsorption
    (Elsevier Ltd, 2023-11-01T00:00:00) Dahiya, Amarjeet; Bhardwaj, Akanksha; Rani, Archana; Arora, Meenu; Babu, J. Nagendra
    Surface oxygen functional groups of biochar were tuned by oxidation and reduction of biochar for establishing Cr(VI) adsorption mechanism. Oxygen functional groups (OFGs) on the surface of leached rice straw biochar (LBC4-6) obtained from pyrolysis at 400, 500 and 600 �C, were oxidized to furnish OBC4-6 using modified Hummer's method. Reduced biochar RBC4-6 were obtained by esterification and NaBH4/I2 reduction of oxidized biochar (OBC4-6). The modified biochar were characterized by increase in O/C and H/C ratio, respectively, in case of OBC4-6 and RBC4-6. The Cr(VI) adsorption by modified biochar LBC4-6, OBC4-6, and RBC4-6 showed optimum conditions of pH 3 and dose 0.1 g/L with a good non-linear fit for Langmuir & Freundlich isotherm. The maximum adsorption (Qm) followed the trend: OBC4 (17.47 mg/g) > RBC4 (15.23) > OBC5 (13.23) > LBC4 (10.23) > RBC5 (9.83) > OBC6 (9.60) > RBC6 (7.24) > LBC5 (6.32) > LBC6 (5.98). The adsorption kinetics for adsorption of Cr(VI) on to modified biochar fits pseudo second order (PSO), Elovich and intraparticle diffusion kinetics, showing a chemisorptions in case of biochar L/O/RBC4-6. The lower temperature modified biochar O/RBC4 show better Cr(VI) adsorption. X-ray Photoelectron Spectroscopy (XPS) studies establish optimum OFGs for reduction of Cr(VI) and chelation of the reduced Cr(III). Adsorption and stripping cycles show the oxidized and reduced biochar as better adsorbents with excellent stripping of Cr up to >98 % upon desorption with 1 M NaOH. � 2023