| 1. |
- Samantara, Aneeya K., et al.
(författare)
-
Enhanced Oxygen Evolution Reaction with a Ternary Hybrid of Patronite-Carbon Nanotube-Reduced Graphene Oxide : A Synergy between Experiments and Theory
- 2021
-
Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 13:30, s. 35828-35836
-
Tidskriftsartikel (refereegranskat)abstract
- This work reports the hybridization of patronite (VS4) sheets with reduced graphene oxide and functionalized carbon nanotubes (RGO/FCNT/VS4) through a hydrothermal method. The synergistic effect divulged by the individual components, i.e., RGO, FCNT, and VS4, significantly improves the efficiency of the ternary (RGO/FCNT/VS4) hybrid toward the oxygen evolution reaction (OER). The ternary composite exhibits an impressive electrocatalytic OER performance in 1 M KOH and requires only 230 mV overpotential to reach the state-of-the-art current density (10 mA cm–2). Additionally, the hybrid shows an appreciable Tafel slope with a higher Faradaic efficiency (97.55 ± 2.3%) at an overpotential of 230 mV. Further, these experimental findings are corroborated by the state-of-the-art density functional theory by presenting adsorption configurations, the density of states, and the overpotential of these hybrid structures. Interestingly, the theoretical overpotential follows the qualitative trend RGO/FCNT/VS4 < FCNT/VS4 < RGO/VS4, supporting the experimental findings.
|
|
| 2. |
- Banerjee, Amitava, et al.
(författare)
-
Scrupulous Probing of Bifunctional Catalytic Activity of Borophene Monolayer : Mapping Reaction Coordinate with Charge Transfer
- 2018
-
Ingår i: ACS Applied Energy Materials. - : American Chemical Society (ACS). - 2574-0962. ; 1:8, s. 3571-3576
-
Tidskriftsartikel (refereegranskat)abstract
- We have envisaged the hydrogen evolution and oxygen evolution reactions (HER and OER) on two-dimensional (2D) noble metal free borophene monolayer based on first-principles electronic structure calculations. We have investigated the effect of Ti functionalization on borophene monolayer from the perspective of HER and OER activities enhancement. We have probed the activities based on the reaction coordinate, which is conceptually related to the adsorption free energies of the intermediates of HER and OER, as well as from the vibrational frequency analysis with the corresponding charge transfer mechanism between the surface and the adsorbate. Tifunctionalized borophene has emerged as a promising material for HER and OER mechanisms. We believe that our probing method, based on reaction coordinate coupled with vibrational analysis that has been validated by the charge transfer mechanism, would certainly become as a robust prediction route for HER and OER mechanisms in coming days.
|
|
| 3. |
- De Adhikari, Amrita, et al.
(författare)
-
Polyaniline-Stabilized Intertwined Network-like Ferrocene/Graphene Nanoarchitecture for Supercapacitor Application
- 2017
-
Ingår i: Chemistry - An Asian Journal. - : WILEY-V C H VERLAG GMBH. - 1861-4728 .- 1861-471X. ; 12:8, s. 900-909
-
Tidskriftsartikel (refereegranskat)abstract
- The present work highlights the effective H-p interaction between metallocenes ( ferrocene; Fc) and graphene and their stabilization in the presence of polyaniline ( PANI) through pi-pi interactions. The PANI-stabilized Fc@ graphene nanocomposite ( FcGA) resembled an intertwined network-like morphology with high surface area and porosity, which could make it a potential candidate for energy-storage applications. The relative interactions between the components were assessed through theoretical ( DFT) calculations. The specific capacitance calculated from galvanostatic charging/discharging indicated that the PANI-stabilized ter-nary nanocomposite exhibited a maximum specific capacitance of 960 Fg(-) at an energy density of 85 WhKg(-1) and a current density of 1 Ag-. Furthermore, electrochemical impedance spectroscopy (EIS) analysis confirmed the low internal resistance of the as-prepared nanocomposites, which showed improved charge-transfer properties of graphene after incorporation of Fc and stabilization with PANI. Additionally, all electrodes were found to be stable up to 5000 cycles with a specific capacitance retention of 86%, thus demonstrating the good reversibility and durability of the electrode material.
|
|
| 4. |
- Gadegaard, Ane Riis, et al.
(författare)
-
Spectroscopy and picosecond dynamics of aqueous NO2
- 2014
-
Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 141:6, s. 064310-
-
Tidskriftsartikel (refereegranskat)abstract
- We investigate the formation of aqueous nitrogen dioxide, NO2 formed through femtosecond photolysis of nitrate, NO3- ( aq) and nitromethane CH3NO2(aq). Common to the experiments is the observation of a strong induced absorption at 1610 +/- 10 cm(-1), assigned to the asymmetric stretch vibration in the ground state of NO2. This assignment is substantiated through isotope experiments substituting N-14 by N-15, experiments at different pH values, and by theoretical calculations and simulations of NO2-D2O clusters.
|
|
| 5. |
- Gond, Ritambhara, et al.
(författare)
-
Enabling the Electrochemical Activity in Sodium Iron Metaphosphate [NaFe(PO3)(3)] Sodium Battery Insertion Material : Structural and Electrochemical Insights
- 2017
-
Ingår i: Inorganic Chemistry. - : AMER CHEMICAL SOC. - 0020-1669 .- 1520-510X. ; 56:10, s. 5918-5929
-
Tidskriftsartikel (refereegranskat)abstract
- Sodium-ion batteries are widely pursued as an economic alternative to lithium-ion battery technology, where Fe- and Mn-based compounds are particularly attractive owing to their elemental abundance. Pursuing phosphate-based polyanionic chemistry, recently solid-state prepared NaFe(PO3)(3) metaphosphate was unveiled as a novel potential sodium insertion material, although it was found to be electrochemically inactive. In the current work, employing energy-savvy solution combustion synthesis, NaFe2+(PO3)(3) was produced from low-cost Fe3+ precursors. Owing to the formation of nanoscale carbon-coated product, electrochemical activity was enabled in NaFe(PO3)(3) for the first time. In congruence with the first principles density functional theory (DFT) calculations, an Fe3+/Fe2+ redox activity centered at 2.8 V (vs Na/Na+) was observed. Further, the solid-solution metaphosphate family Na(Fe1-xMnx)(PO3)(3) (x = 0-1) was prepared for the first time. Their structure and distribution of transition metals (TM = Fe/Mn) was analyzed with synchrotron diffraction, X-ray photoelectron spectroscopy, and Mossbauer spectroscopy. Synergizing experimental and computational tools, NaFe(PO3)(3) metaphosphate is presented as an electrochemically active sodium insertion host material.
|
|
| 6. |
- Jena, Naresh K., et al.
(författare)
-
Atomic level simulations of the interaction of asphaltene with quartz surfaces : role of chemical modifications and aqueous environment
- 2017
-
Ingår i: Materials and Structures. - : Kluwer Academic Publishers. - 1359-5997 .- 1871-6873. ; 50:1
-
Tidskriftsartikel (refereegranskat)abstract
- Understanding the properties of bitumen and its interaction with mineral aggregates is crucial for future strategies to improve roads and highways. Knowledge of basic molecular and electronic structures of bitumen, one out of the two main components of asphalt, poses a major step towards achieving such a goal. In the present work we employ atomistic simulation techniques to study the interaction of asphaltenes, a major constituent of bitumen, with quartz surfaces. As an effective means to tune adhesion or cohesion properties of asphaltenes and mineral surfaces, we propose chemical modification of the pristine asphaltene structure. By the choice of substituent and site of substitution we find that adhesion between the asphaltene molecule and the quartz surface can easily be improved at the same time as the cohesive interaction between the asphaltene units is reduced, while other substituents may lead to the opposite effect. We also provide insight at the molecular level into how water molecules affect interactions between asphaltenes and quartz. Our approach emphasizes a future role for advanced atomistic modeling to understand the properties of bitumen and suggest further improvements.
|
|
| 7. |
- Jena, Naresh K., et al.
(författare)
-
Borophane as a Benchmate of Graphene : A Potential 2D Material for Anode of Li and Na-Ion Batteries
- 2017
-
Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 9:19, s. 16148-16158
-
Tidskriftsartikel (refereegranskat)abstract
- Borophene, single atomic-layer sheet of boron (Science 2015, 350, 1513), is a rather new entrant into the burgeoning class of 2D materials. Borophene exhibits anisotropic metallic properties whereas its hydrogenated counterpart borophane is reported to be a gapless Dirac material lying on the same bench with the celebrated graphene. Interestingly, this transition of borophane also rendered stability to it considering the fact that borophene was synthesized under ultrahigh vacuum conditions on a metallic (Ag) substrate. On the basis of first-principles density functional theory computations, we have investigated the possibilities of borophane as a potential Li/Na-ion battery anode material. We obtained a binding energy of -2.58 (-1.08 eV) eV for Li (Na)-adatom on borophane and Bader charge analysis revealed that Li(Na) atom exists in Li+(Na+) state. Further, on binding with Li/Na, borophane exhibited metallic properties as evidenced by the electronic band structure. We found that diffusion pathways for Li/Na on the borophane surface are anisotropic with x direction being the favorable one with a barrier of 0.27 and 0.09 eV, respectively. While assessing the Li-ion anode performance, we estimated that the maximum Li content is Li0.445B2H2, which gives rises to a material with a maximum theoretical specific capacity of 504 mAh/g together with an average voltage of 0.43 V versus Li/Li+. Likewise, for Na-ion the maximum theoretical capacity and average voltage were estimated to be 504 mAh/g and 0.03 V versus Na/Na+, respectively. These findings unambiguously suggest that borophane can be a potential addition to the map of Li and Na-ion anode materials and can rival some of the recently reported 2D materials including graphene.
|
|
| 8. |
- Jena, Naresh K., et al.
(författare)
-
Solvent-Dependent Conformational States of a [2]Rotaxane-Based Molecular Machine : A Molecular Dynamics Perspective
- 2013
-
Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 117:47, s. 25059-25068
-
Tidskriftsartikel (refereegranskat)abstract
- Motion is an essential and fundamental feature of any living organism. The evolved organisms have developed sophisticated and perfect machineries and highly delicate mechanisms to carry out directional and coordinated movements which eventually lead to motion at the macroscopic length scale. By mimicking these natural machineries, attempts to design and synthesize similar molecular motors are made in relevance to their applications in drug delivery, data storage, and molecular sensing. It is highly desirable to establish the rules for controlling the conformational states of molecular motors by tuning some of the external variables which can be used for the design strategies. We contribute to this subject by looking into the solvent influence on the conformational states of a synthetic molecular rotor, namely, diketopyrrolopyrrole (DPP) based [2]rotaxane, using the force-field molecular dynamics approach. We study this system in three different solvents, and we report a strong solvent dependence in the population of three different translational isomers. In chloroform solvent we report the dominant population of the 2-P isomer which is in excellent agreement with experimental results based on H NMR spectra (Org. Lett. 2013, 15, 1274). However, there is a striking difference seen in the population of translational isomers in DMSO solvent, and we attribute these features to negligence of solvent hydrogen bonding induced upfield and downfield effects in the interpretation of experimental proton NMR spectra. In addition, we also report a solvent-polarity-induced fully unstretched to folded conformational transition in the [2]rotaxane system. On the basis of the molecular mechanics Poisson-Boltzmann (and generalized Born) surface area approach, we identify the driving force for the formation of the supramolecular guest-host [2]rotaxane system. Finally, we calculate the relative binding free energies for the macrocycle at different binding sites of the DPP skeleton using the molecular dynamics simulations performed for the macrocycle-rotaxane system in water solvent which suggests the increased stability of the 2-O isomer in polar solvent.
|
|
| 9. |
- Ji, Cheng, et al.
(författare)
-
Stability of Ar(H2)2 to 358 GPa
- 2017
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 114:14, s. 3596-3600
-
Tidskriftsartikel (refereegranskat)abstract
- "Chemical precompression" through introducing impurity atoms into hydrogen has been proposed as a method to facilitate metallization of hydrogen under external pressure. Here we selected Ar(H-2)(2), a hydrogen-rich compound with molecular hydrogen, to explore the effect of "doping" on the intermolecular interaction of H-2 molecules and metallization at ultrahigh pressure. Ar(H-2)(2) was studied experimentally by synchrotron X-ray diffraction to 265 GPa, by Raman and optical absorption spectroscopy to 358 GPa, and theoretically using the density-functional theory. Our measurements of the optical bandgap and the vibron frequency show that Ar(H-2)(2) retains 2-eV bandgap and H-2 molecular units up to 358 GPa. This is attributed to reduced intermolecular interactions between H-2 molecules in Ar(H-2)(2) compared with that in solid H-2. A splitting of the molecular vibron mode above 216 GPa suggests an orientational ordering transition, which is not accompanied by a change in lattice symmetry. The experimental and theoretical equations of state of Ar(H-2)(2) provide direct insight into the structure and bonding of this hydrogen-rich system, suggesting a negative chemical pressure on H-2 molecules brought about by doping of Ar.
|
|
| 10. |
- Lindblad, Rebecka, et al.
(författare)
-
Electronic Structure of CH3NH3PbX3 Perovskites : Dependence on the Halide Moiety
- 2015
-
Ingår i: The Journal of Physical Chemistry C. - American Chemical Society : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 119:4, s. 1818-1825
-
Tidskriftsartikel (refereegranskat)abstract
- A combination of measurements using photoelectron spectroscopy and calculations using density functional theory (DFT) was applied to compare the detailed electronic structure of the organolead halide perovskites CH3NH3PbI3 and CH3NH3PbBr3. These perovskite materials are used to absorb light in mesoscopic and planar heterojunction solar cells. The Pb 4f core level is investigated to get insight into the chemistry of the two materials. Valence level measurments are also included showing a shift of the valence band edges where there is a higher binding energy of the edge for the CH3NH3PbBr3 perovskite. These changes are supported by the theoretical calculations which indicate that the differences in electronic structure are mainly caused by the nature of the halide ion rather than structural differences. The combination of photoelectron spectroscopy measurements and electronic structure calculations is essential to disentangle how the valence band edge in organolead halide perovskites is governed by the intrinsic difference in energy levels of the halide ions from the influence of chemical bonding.
|
|
| 11. |
|
|
| 12. |
- Osella, Silvio, et al.
(författare)
-
Investigation into Biological Environments through (Non)linear Optics : A Multiscale Study of Laurdan Derivatives
- 2016
-
Ingår i: Journal of Chemical Theory and Computation. - : American Chemical Society (ACS). - 1549-9618 .- 1549-9626. ; 12:12, s. 6169-6181
-
Tidskriftsartikel (refereegranskat)abstract
- The fluorescent marker Laurdan and its new derivative, C-Laurdan, have been investigated by means of theoretical calculations in a DOPC lipid bilayer membrane at room temperature, and a comparison is made with results from fluorescence experiments. Experimentally, the latter probe is known to have a higher sensitivity to the membrane polarity at the lipid headgroup region and has higher water solubility. Results from Molecular Dynamics (MD) simulations show that C-Laurdan is oriented with the carboxyl group toward the head of the membrane, with an angle of 50 degrees between the molecular backbone and the normal to the bilayer, in contrast to the orientation of the Laurdan headgroup whose carbonyl group is oriented toward the polar regions of the membrane and which describes an angle of ca. 70-80 degrees with the membrane normal. This contrast in orientation reflects the differences in transition dipole moment between the two probes and, in turn, the optical properties. QM/MM results of the probes show little differences for one- (OPA) and two-photon absorption (TPA) spectra, while the second harmonic generation (SHG) beta component is twice as large in Laurdan with respect to C-Laurdan probe. The fluorescence anisotropy decay analysis of the first excited state confirms that Laurdan has more rotational freedom in the DOPC membrane, while C-Laurdan experiences a higher hindrance, making it a better probe for lipid membrane phase recognition.
|
|
| 13. |
- Philippe, Bertrand, Dr. 1986-, et al.
(författare)
-
Valence Level Character in a Mixed Perovskite Material and Determination of the Valence Band Maximum from Photoelectron Spectroscopy : Variation with Photon Energy
- 2017
-
Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 121:48, s. 26655-26666
-
Tidskriftsartikel (refereegranskat)abstract
- A better understanding of the electronic structure of perovskite materials used in photovoltaic devices is essential for their development and optimization. In this investigation, synchrotron-based photoelectron spectroscopy (PES) was used to experimentally delineate the character and energy position of the valence band structures of a mixed perovskite. The valence band was measured using PES with photon energies ranging from ultraviolet photoelectron spectroscopy (21.2 eV) to hard X-rays (up to 4000 eV), and by taking the variation of the photoionization cross sections into account, we could experimentally determine the inorganic and organic contributions. The experiments were compared to theoretical calculations to further distinguish the role of the different anions in the electronic structure. This work also includes a thorough study of the valence band maximum and its position in relation to the Fermi level, which is crucial for the design and optimization of complete solar cells and their functional properties.
|
|
| 14. |
- Sahoo, Laxminarayan, et al.
(författare)
-
5-Benzoyl triazole as new structural dimension in glycoconjugates
- 2018
-
Ingår i: Carbohydrate Research. - : ELSEVIER SCI LTD. - 0008-6215 .- 1873-426X. ; 469, s. 23-30
-
Tidskriftsartikel (refereegranskat)abstract
- In recent years, 1,4-triazole rings are being widely used for the synthesis of carbohydrate derived biomimetics, due to their easy synthesis and wide range of functional group compatibility. These triazole rings lead to synthetic molecules with improved enzymatic stability, bioavailability, and structural diversity. In this present work, a benzoyl group has been introduced at the C-5 position of the triazole ring present in the synthetic glycoconjugates providing further structural diversity to the molecule. 5-Benzoyl 1,4-triazole ring containing glycoconjugates were synthesized using Cu(I) catalyzed [3 + 2] cycloaddition reaction of per-O-acetylated glycopyranosyl azide and phenyl acetylene followed by in situ electrophilic addition of benzoyl group to the Cu (I) coordinated triazole intermediate. The X-ray crystal structure of one of the 5-benzoyl 1,4-triazole linked glycoconjugate derived from D-xylose {1-N-(2,3,4 tri-O-acetyl-beta-D-xylopyranosyl)-4-phenyl-5-benzoyl-1,2,3-triazole} showed unique pattern of intermolecular C-H center dot center dot center dot O interactions arranging the molecules in an anti-parallel orientation. The structure and morphology of the compounds were further explored using computational calculation and scanning electron microscopic (SEM) study which firmly established the uniqueness of 5-benzoyl 1,4-triazole linked glycoconjugates compared to that of 5-H 1,4-triazole linked derivative.
|
|
| 15. |
- Shukla, Vivekanand, et al.
(författare)
-
Borophene's tryst with stability : Exploring 2D hydrogen boride as an electrode for rechargeable batteries
- 2018
-
Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 20:34, s. 22008-22016
-
Tidskriftsartikel (refereegranskat)abstract
- Graphene's emergence can be viewed as a positive upheaval in 2D materials research. Along the same line, the realization of a related elemental 2D material, borophene, is another breakthrough. To circumvent the stability issues of borophene, which is reported to have been synthesized on metallic substrates under extreme conditions, hydrogenation of borophene (otherwise called as borophane or hydrogen boride or boron hydride) has been a plausible solution, but only proposed computationally. A recent report (H. Nishino, T. Fujita, N. T. Cuong, S. Tominaka, M. Miyauchi, S. Iimura, A. Hirata, N. Umezawa, S. Okada, E. Nishibori, A. Fujino, T. Fujimori, S. Ito, J. Nakamura, H. Hosono and T. Kondo, J. Am. Chem. Soc., 2017, 139(39), 13761-13769) brings to fore its experimental realization. Our current study delves into the possibilities of employing this intriguing 2D hydrogen boride as anodes in Li/Na ion batteries. Using first-principles density functional theory methods, we computed relevant properties such as the ion (Li/Na) adsorption behavior, the possible pathways of ionic diffusion with the estimation of barriers as well as the theoretical specific capacities and average voltages to uniquely demonstrate that this material is of particular significance for battery applications. It is noted that the use of hydrogen boride leads to a high specific capacity of 861.78 mA h g-1 for Li ions, which is remarkably higher than the value reported in relation to its computationally predicted structure. Furthermore, Na ion intercalation leads to negative voltage profiles, implying the unsuitability of 2D hydrogen boride for this particular ion. Our findings are timely and pertinent towards adding insightful details relevant to the progress of applications of 2D materials for energy storage.
|
|
| 16. |
- Shukla, Vivekanand, 1988-, et al.
(författare)
-
Electronic and Transport Properties of Bilayer Phosphorene Nanojunction : Effect of Paired Substitution Doping
- 2021
-
Ingår i: ACS APPLIED ELECTRONIC MATERIALS. - : AMER CHEMICAL SOC. - 2637-6113. ; 3:2, s. 733-742
-
Tidskriftsartikel (refereegranskat)abstract
- Electron transport in bilayer phosphorene is studied using the first-principles and nonequilibrium Green's function formalism. We have explored the interlayer properties of a vertically stacked bilayer structure with paired substitutional doping. The electron transport properties are calculated in bilayer phosphorene and compared with substitutional doping, which shows the tunable anisotropic nature of doped phosphorene in the I-V characteristics. Further, to understand the role played by dopants, the quantum transport properties of monolayer-bilayer monolayer (ML-BL-ML) nanojunction are studied with and without dopants. The interlayer direction-dependent current characteristics are discussed in different setups. This suggests that the dopants play a crucial role in the interlayer current and further provided rectifying behavior in the zigzag direction. Fano resonance is also observed as an effect that arises from the hydrogen-terminated edges interacting with the second layer. Our study demonstrates significant tuning of the electronic transport properties of the bilayer phosphorene implying its potential application in electronic devices.
|
|
| 17. |
- Shukla, Vivekanand, et al.
(författare)
-
Modelling high-performing batteries with Mxenes : The case of S-functionalized two-dimensional nitride Mxene electrode
- 2019
-
Ingår i: Nano Energy. - : Elsevier. - 2211-2855 .- 2211-3282. ; 58, s. 877-885
-
Tidskriftsartikel (refereegranskat)abstract
- Recent upsurge in the two-dimensional (2D) materials have established their larger role on energy storage applications. To this end, Mxene represent a new paradigm extending beyond the realm of oft-explored elemental 2D materials beginning with graphene. Here in, we employed first principles modelling based on density functional theory to investigate the role of S-functionalized Nitride Mxenes as anodes for Li/Na ion batteries. To be specific, V 2 NS 2 and Ti 2 NS 2 have been explored with a focus on computing meaningful descriptors to quantify these 2D materials to be optimally performing electrodes. The Li/Na ion adsorption energies are found to be high (>-2 eV) on both the surfaces and associated with significant charge transfer. Interestingly, this ion intercalation can reach up to multilayers which essentially affords higher specific capacity for the substrate. Particularly, these two 2D materials (V 2 NS 2 and Ti 2 NS 2 ) have been found to be more suitable for Li-ion batteries with estimated theoretical capacities of 299.52 mAh g −1 and 308.28 mAh g −1 respectively. We have also probed the diffusion barriers of ion migration on these two surfaces and these are found to be ultrafast in nature. All these unique features qualify these Mxenes to be potential anode materials for rechargeable batteries and likely to draw imminent attention.
|
|
| 18. |
- Shukla, Vivekanand, et al.
(författare)
-
Prospects of Graphene-hBN Heterostructure Nanogap for DNA Sequencing
- 2017
-
Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 9:46, s. 39945-39952
-
Tidskriftsartikel (refereegranskat)abstract
- Recent advances in solid-state nano-device-based DNA sequencing are at the helm of the development of a new paradigm, commonly referred to as personalized medicines. Paying heed to a timely need for standardizing robust nanodevices for cheap, fast, and scalable DNA detection, in this article, the nanogap formed by the lateral heterostructure of graphene and hexagonal boron nitride (hBN) is explored as a potential architecture. These heterostructures have been realized experimentally, and our study boasts the idea that the passivation of the edge of the graphene electrode with hBN will solve many of practical problems, such as high reactivity of the graphene edge and difficulty in controlled engineering of the graphene edge structure, while retaining the nanogap setup as a useful nanodevice for sensing applications. Employing first-principle density-functional-theory-based nonequilibrium Greens function methods, we identify that the DNA building blocks, nucleobases, uniquely couple with the states of the nanogap, and the resulting induced states can be attributed as leaving a fingerprint of the DNA sequence in the computed current-voltage (I-V) characteristic. Two bias windows are put forward: lower (1-1.2 V) and higher (2.7-3 V), where unique identification of all four bases is possible from the current traces, although higher sensitivity is obtained at the higher voltage window. Our study can be a practical guide for experimentalists toward development of a nanodevice DNA sensor based on graphene-hBN heterostructures.
|
|
| 19. |
- Shukla, Vivekanand, et al.
(författare)
-
Strain controlled electronic and transport anisotropies in two-dimensional borophene sheets
- 2018
-
Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 20:35, s. 22952-22960
-
Tidskriftsartikel (refereegranskat)abstract
- Two recent reports on realization of an elemental 2D analogue of graphene:borophene (Science, 2015, 350, 1513-1516; Nat. Chem., 2016, 8, 563-568) focus on the inherent anisotropy and directional dependence of the electronic properties of borophene polymorphs. Achieving stable 2D borophene structures may lead to some degree of strain in the system because of the substrate-lattice mismatch. We use first principles density functional theory (DFT) calculations to study the structural, electronic and transport properties of (12) and -borophene polymorphs. We verified the directional dependency and found the tunable anisotropic behavior of the transport properties in these two polymorphs. We find that strain as low as 6% brings remarkable changes in the properties of these two structures. We further investigate current-voltage (I-V) characteristics in the low bias regime after applying a strain to see how the anisotropy of the current is affected. Such observations like the sizeable tuning of transport and I-V characteristics at the expense of minimal strain suggest the suitability of 2D borophene for futuristic device applications.
|
|
| 20. |
- Shukla, Vivekanand, et al.
(författare)
-
The curious case of two dimensional Si2BN : A high-capacity battery anode material
- 2017
-
Ingår i: Nano Energy. - : Elsevier. - 2211-2855 .- 2211-3282. ; 41, s. 251-260
-
Tidskriftsartikel (refereegranskat)abstract
- The ubiquity of silicon in the semiconductor industry and its unique charge transport features has consistently fueled interest in this element and recent realization 2D silicene is a new feather in its cap. In what could be considered as opening up the Pandora's box with many possible virtues, buckled silicene, planar graphene and a host of other newly discovered 2D materials have redefined a whole new paradigm of research. To this end, the quest for new 2D materials and finding potential applications, particularly to the realm of energy storage, is a curiosity driven task. From first principle density functional theory studies, a newly reported graphene like 2D material Si2BN is investigated as a probable anode material for Li and Na ion batteries. In contrast to pristine silicene, which is inherently buckled, the material Si2BN is planar. However, an interesting transition from planar to buckled structure takes place upon subsequent adsorption of Li and Na ions. Concomitantly, this transition is associated with superior specific capacity (1158.5 and 993.0 mA h/g respectively for Li and Na) which is significantly higher than several other 2D analogues. Furthermore, the substrate Si2BN regains the planar structure on subsequent desorption of ions and stability of the material remains intact, as evidenced from ab initio molecular dynamics simulations. As we delve deep into the electronic structure and compute the diffusion pathways and barriers, it is observed that the ionic diffusion is very fast with significantly lesser barrier heights, particularly for Na-ion. These findings suggest that for the 2D Si2BN, there is no diminution in order to be a potential anode material for Li and Na ion batteries.
|
|
| 21. |
- Shukla, Vivekanand, et al.
(författare)
-
Toward the Realization of 2D Borophene Based Gas Sensor
- 2017
-
Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 121:48, s. 26869-26876
-
Tidskriftsartikel (refereegranskat)abstract
- To the league of rapidly expanding 2D materials, borophene is a recent addition. Herein, a combination of ab initio density functional theory (DFT) and nonequilibrium Green's function (NEGF) based methods is used to estimate the prospects of this promising elemental 2D material for gas sensing applications. We note that the binding of target gas molecules such as CO, NO, NO2, NH3, and CO2 is quite strong on the borophene surface. Interestingly, our computed binding energies are far stronger than several other reported 2D materials like graphene, MoS2, and phosphorene. Further rationalization of stronger binding is made with the help of charge transfer analysis. The sensitivity of the borophene for these gases is also interpreted in terms of computing the vibrational spectra of the adsorbed gases on top of borophene, which show dramatic shift from their gas phase reference values. The metallic nature of borophene enables us to devise a setup considering the same substrate as electrodes. From the computation of the transmission function of system (gas + borophene), appreciable changes in the transmission functions are noted compared to pristine borophene surface. The measurements of current-voltage (I-V) characteristics unambiguously demonstrate the presence and absence of gas molecules (acting as ON and OFF states), strengthening the plausibility of a borophene based gas sensing device. As we extol the extraordinary sensitivity of borophene, we assert that this elemental 2D material is likely to attract subsequent interest.
|
|
| 22. |
- Smazna, Daria, et al.
(författare)
-
Buckminsterfullerene hybridized zinc oxide tetrapods : defects and charge transfer induced optical and electrical response
- 2018
-
Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3364 .- 2040-3372. ; 10:21, s. 10050-10062
-
Tidskriftsartikel (refereegranskat)abstract
- Buckminster fullerene (C-60) based hybrid metal oxide materials are receiving considerable attention because of their excellent fundamental and applied aspects, like semiconducting, electron transfer, luminescent behaviors, etc. and this work briefly discusses the successful fabrication of C-60 decorated ZnO tetrapod materials and their detailed structure-property relationships including device sensing applications. The electron microscopy investigations indicate that a quite dense surface coverage of ZnO tetrapods with C-60 clusters is achieved. The spectroscopy studies confirmed the identification of the C-60 vibrational modes and the C-60 induced changes in the absorption and luminescence properties of the ZnO tetrapods. An increased C-60 concentration on ZnO results in steeper ZnO bandgap absorption followed by well-defined free exciton and 3.31 eV line emissions. As expected, higher amounts of C-60 increase the intensity of C-60-related visible absorption bands. Pumping the samples with photons with an energy corresponding to these absorption band maxima leads to additional emission from ZnO showing an effective charge transfer phenomenon from C-60 to the ZnO host. The density of states model obtained from DFT studies for pure and C-60 coated ZnO surfaces confirms the experimental observations. The fabricated C-60-ZnO hybrid tetrapod based micro- and nanodevices showed interesting ethanol gas sensing characteristics.
|
|
| 23. |
- Thogersen, Jan, et al.
(författare)
-
Hydration Dynamics of Aqueous Nitrate
- 2013
-
Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 117:12, s. 3376-3388
-
Tidskriftsartikel (refereegranskat)abstract
- Aqueous nitrate, NO3-(aq), was studied by 2D-IR, UV-IR, and UV-UV time-resolved spectroscopies in combination with molecular dynamics (MD) simulations with the purpose of determining the hydration dynamics around the anion. In water, the D-3h symmetry of NO3- is broken, and the degeneracy of the asymmetric-stretch modes is lifted. This provides a very sensitive probe of the ion-water interactions. The 2D-IR measurements reveal excitation exchange between the two nondegenerate asymmetric-stretch vibrations on a 300-fs time scale concomitant with fast anisotropy decay of the diagonal-peak signals. The MD simulations show that this is caused by jumps of the transition dipole orientations related to fluctuations of the hydrogen bonds connecting the nitrate ion to the nearest water molecules. Reorientation of the ion, which is associated with the hydrogen-bond breaking, was monitored by time-resolved UV-IR and UV-UV spectroscopy, revealing a 2-ps time constant. These time scales are very similar to those reported for isotope-labeled water, suggesting that NO3-(aq) has a labile hydration shell.
|
|
| 24. |
- Wang, Shujiang, et al.
(författare)
-
Saline Accelerates Oxime Reaction with Aldehyde and Keto Substrates at Physiological pH
- 2018
-
Ingår i: Scientific Reports. - : NATURE PUBLISHING GROUP. - 2045-2322. ; 8
-
Tidskriftsartikel (refereegranskat)abstract
- We have discovered a simple and versatile reaction condition for oxime mediated bioconjugation reaction that could be adapted for both aldehyde and keto substrates. We found that saline accelerated the oxime kinetics in a concentration-dependent manner under physiological conditions. The reaction mechanism is validated by computational studies, and the versatility of the reaction is demonstrated by cell-surface labeling experiments. Saline offers an efficient and non-toxic catalytic option for performing the bioorthogonal-coupling reaction of biomolecules at the physiological pH. This saline mediated bioconjugation reaction represents the most biofriendly, mild and versatile approach for conjugating sensitive biomolecules and does not require any extensive purification step.
|
|
| 25. |
- Wang, Shujiang, et al.
(författare)
-
Saline catalyse oxime reaction at physiological pH : overcoming a major limitation of bioorthogonal reaction
-
Tidskriftsartikel (refereegranskat)abstract
- We have discovered a simple and versatile reaction condition for oxime mediated bioconjugation reaction that could be adapted for both aldehyde and keto substrates. We found that saline accelerated the oxime kinetics in a concentration dependent manner under physiological conditions. The reaction mechanism is validated by computational studies, and the versatility of the reaction is demonstrated by cell-surface labeling experiments. Saline offers an efficient and non-toxic catalytic option for performing the bioorthogonal-coupling reaction of biomolecules at the physiological pH. This saline mediated bioconjugation reaction represents the most bio-friendly, mild and versatile approach for conjugating sensitive biomolecules and does not require any extensive purification step.
|
|
