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Publications (10 of 611) Show all publications
Wani, I. H., Jafri, S. H., Wärnå, J., Hayat, A., Li, H., Shukla, V. A., . . . Leifer, K. (2019). A sub 20 nm metal-conjugated molecule junction acting as a nitrogen dioxide sensor. Nanoscale, 11(14), 6571-6575
Open this publication in new window or tab >>A sub 20 nm metal-conjugated molecule junction acting as a nitrogen dioxide sensor
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2019 (English)In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 11, no 14, p. 6571-6575Article in journal (Refereed) Published
Abstract [en]

The interaction of a gas molecule with a sensing material causes the highest change in the electronic structure of the latter, when this material consists of only a few atoms. If the sensing material consists of a short, conductive molecule, the sensing action can be furthermore probed by connecting such molecules to nanoelectrodes. Here, we report that NO2 molecules that adhere to 4,4'-biphenyldithiol (BPDT) bound to Au surfaces lead to a change of the electrical transmission of the BPDT. The related device shows reproducible, stable measurements and is so far the smallest (<20 nm) gas sensor. It demonstrates modulation of charge transport through molecules upon exposure to nitrogen dioxide down to concentrations of 55 ppb. We have evaluated several devices and exposure conditions and obtained a close to linear dependence of the sensor response on the gas concentration.

National Category
Nano Technology
Identifiers
urn:nbn:se:uu:diva-381056 (URN)10.1039/c8nr08417c (DOI)000464454400007 ()30916070 (PubMedID)
Funder
Swedish Research CouncilKnut and Alice Wallenberg FoundationGöran Gustafsson Foundation for Research in Natural Sciences and MedicineCarl Tryggers foundation Swedish Energy AgencySwedish Foundation for Strategic Research
Available from: 2019-04-03 Created: 2019-04-03 Last updated: 2019-05-03Bibliographically approved
Qian, Z., Zhang, H., Jiang, G., Bai, Y., Ren, Y., Du, W. & Ahuja, R. (2019). Ab Initio Screening of Doped Mg(AlH4)(2) Systems for Conversion-Type Lithium Storage. Materials, 12(16), Article ID 2599.
Open this publication in new window or tab >>Ab Initio Screening of Doped Mg(AlH4)(2) Systems for Conversion-Type Lithium Storage
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2019 (English)In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, no 16, article id 2599Article in journal (Refereed) Published
Abstract [en]

In this work, we have explored the potential applications of pure and various doped Mg(AlH4)(2) as Li-ion battery conversion electrode materials using density functional theory (DFT) calculations. Through the comparisons of the electrochemical specific capacity, the volume change, the average voltage, and the electronic bandgap, the Li-doped material is found to have a smaller bandgap and lower average voltage than the pure system. The theoretical specific capacity of the Li-doped material is 2547.64 mAhg(-1) with a volume change of 3.76% involving the electrode conversion reaction. The underlying reason for property improvement has been analyzed by calculating the electronic structures. The strong hybridization between Lis-state with H s-state influences the performance of the doped material. This theoretical research is proposed to help the design and modification of better light-metal hydride materials for Li-ion battery conversion electrode applications.

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
conversion electrode, doping design, lithium storage, light metal hydrides, density functional theory, electronic structures
National Category
Condensed Matter Physics Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-394644 (URN)10.3390/ma12162599 (DOI)000484464800100 ()31443234 (PubMedID)
Funder
Swedish Research CouncilSwedish National Infrastructure for Computing (SNIC)
Available from: 2019-10-17 Created: 2019-10-17 Last updated: 2019-10-17Bibliographically approved
Khossossi, N., Banerjee, A., Benhouria, Y., Essaoudi, I., Ainane, A. & Ahuja, R. (2019). Ab initio study of a 2D h-BAs monolayer: a promising anode material for alkali-metal ion batteries. Physical Chemistry, Chemical Physics - PCCP, 21(33), 18328-18337
Open this publication in new window or tab >>Ab initio study of a 2D h-BAs monolayer: a promising anode material for alkali-metal ion batteries
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2019 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 21, no 33, p. 18328-18337Article in journal (Refereed) Published
Abstract [en]

The selection of a suitable two dimensional anode material is one of the key steps in the development of alkali metal ion batteries to achieve superior performance with an ultrahigh rate of charging/discharging capability. Here, we have used state of the art density functional theory (DFT) to explore the feasibility of two dimensional (2D) honeycomb boron arsenide (h-BAs) as a potential anode for alkali-metal (Li/Na/K)-ion batteries. The structural and dynamic stability has been confirmed from the formation energy and the non-negative phonon frequency. The h-BAs monolayer exhibits negative adsorption-energy values of -0.422, -0.321 and -0.814 eV, for the Li, Na, and K-ions, respectively. Subsequently, during the charging process the adsorption-energy increases considerably without an energy-barrier when any of the A-atoms achieve a crucial distance (similar to 8 angstrom). In addition, it has been observed that insertion of the mono alkali metal atom into the h-BAs surface results in the semi-conducting nature of the monolayer being transformed into a metallic-state. The low energy barriers for Li (0.522 eV), Na (0.248), and K (0.204 eV) active ion migration imply high diffusion over the h-BAs surface, hence suggesting it has a high charge/discharge capability. Moreover, we have obtained low average operating voltages of 0.49 V (Li), 0.35 V (Na) and 0.26 V (K) and high theoretical capacities of 522.08 mA h g(-1) (for Li and Na) and 209.46 mA h g(-1) (for K) in this study. The aforementioned findings indicate that a h-BAs monolayer could be a promising anode material in the search for low cost and high performance alkali metal ion batteries.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2019
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-394052 (URN)10.1039/c9cp03242h (DOI)000482471400031 ()31397457 (PubMedID)
Funder
Swedish Research Council, dnr-348-2011-7264Swedish Research Council, URAC: 08Swedish Research Council, 2016-06014
Available from: 2019-10-04 Created: 2019-10-04 Last updated: 2019-10-04Bibliographically approved
Poonia, E., Mishra, P. K., Kiran, V., Sangwan, J., Kumar, R., Rai, P. K., . . . Mishr, Y. K. (2019). Aero-gel based CeO2 nanoparticles: synthesis, structural properties and detailed humidity sensing response. Journal of Materials Chemistry C, 7(18), 5477-5487
Open this publication in new window or tab >>Aero-gel based CeO2 nanoparticles: synthesis, structural properties and detailed humidity sensing response
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2019 (English)In: Journal of Materials Chemistry C, ISSN 2050-7526, E-ISSN 2050-7534, Vol. 7, no 18, p. 5477-5487Article in journal (Refereed) Published
Abstract [en]

In this work, we present aero-gel based cerium oxide (CeO2) nanoparticles for the relative humidity (%RH) sensing application. X-ray diffraction (XRD) and N-2 adsorption-desorption isotherms revealed that the synthesized CeO2 nanoparticles (NPs) possessed a face centered cubic (fcc) structure with a high surface area (268 m(2) g(-1)). The high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), and selected area electron diffraction (SAED) studies confirmed that the shape of CeO2 NPs was spherical and they possessed a polycrystalline nature. X-ray photoelectron spectroscopy (XPS) studies revealed the presence of both trivalent (Ce3+) and tetravalent (Ce4+) oxidation states of ceria. The CeO2 NPs' response towards %RH was explored by measuring the important sensing attributes (response/recovery, linearity, hysteresis, repeatability and stability) at 11-98%RH and at room temperature. An impressive impedance change of 4.5 orders of magnitude was observed along with a swift response (4.6 s) time and rapid recovery (2.7 s) time. Moreover, the prepared sensor showed negligible hysteresis, excellent stability and good reversible response in the complete 11-98%RH range.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2019
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-390523 (URN)10.1039/c9tc01081e (DOI)000472443000030 ()
Funder
Swedish Research Council
Available from: 2019-08-14 Created: 2019-08-14 Last updated: 2019-08-14Bibliographically approved
Qian, Z., Jiang, G., Ren, Y., Nie, X. & Ahuja, R. (2019). Atomistic Modeling of Various Doped Mg2NiH4 as Conversion Electrode Materials for Lithium Storage. Crystals, 9(5), Article ID 254.
Open this publication in new window or tab >>Atomistic Modeling of Various Doped Mg2NiH4 as Conversion Electrode Materials for Lithium Storage
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2019 (English)In: Crystals, ISSN 2073-4352, Vol. 9, no 5, article id 254Article in journal (Refereed) Published
Abstract [en]

In this work, we have compared the potential applications of nine different elements doped Mg2NiH4 as conversion-type electrode materials in Li-ion batteries by means of state-of-the-art Density functional theory calculations. The electrochemical properties, such as specific capacity, volume change and average voltage, as well as the atomic and electronic structures of different doped systems have been investigated. The Na doping can improve the electrochemical capacity of the pristine material. Si and Ti doping can reduce the band gap and benefit the electronic conductivity of electrode materials. All of the nine doping elements can help to reduce the average voltage of negative electrodes and lead to reasonable volume changes. According to the computational screening, the Na, Si and Ti doping elements are thought to be promising to enhance the comprehensive properties of pure material. This theoretical study is proposed to encourage and expedite the development of metal-hydrides based lithium-storage materials.

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
conversion electrode materials, doping, metal hydrides, lithium storage, first-principles
National Category
Condensed Matter Physics Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-390537 (URN)10.3390/cryst9050254 (DOI)000472674400030 ()
Funder
Swedish Research Council
Available from: 2019-08-12 Created: 2019-08-12 Last updated: 2019-08-12Bibliographically approved
Chafai, A., Essaoudi, I., Ainane, A., Dujardin, F. & Ahuja, R. (2019). Binding energy of an exciton in a GaN/AlN nanodot: Role of size and external electric field. Physica. B, Condensed matter, 559, 23-28
Open this publication in new window or tab >>Binding energy of an exciton in a GaN/AlN nanodot: Role of size and external electric field
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2019 (English)In: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 559, p. 23-28Article in journal (Refereed) Published
Abstract [en]

We report the impact of an external electric field on the energy spectrum of an exciton inside a spherical shaped GaN/AlN core/shell nanodot. The modulation of the confined exciton lowest state energy by the nanodot size is also treated. Our theoretical approach, based on a variational calculation, predicts a remarkable decrease in the exciton's energy when the electric field is switched on. Furthermore, our investigation shows that for a fixed nanodot size, the energy redshift is a unique function of the external electric field strength. On the other hand, it was observed that as the nanodot size increases the lowest exciton energy decreases and vice versa.

Keywords
Exciton, Core/shell materials, Nanostructures, Quantum dots, Electric field
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-379325 (URN)10.1016/j.physb.2019.01.047 (DOI)000459824700004 ()
Funder
Swedish Research Council, dnr-348-2011-7264
Available from: 2019-03-28 Created: 2019-03-28 Last updated: 2019-03-28Bibliographically approved
Johansson, M. B., Philippe, B., Banerjee, A., Phuyal, D., Mukherjee, S., Chakraborty, S., . . . Johansson, E. (2019). Cesium Bismuth Iodide Solar Cells from Systematic Molar Ratio Variation of CsI and BiI3. Inorganic Chemistry, 58(18), 12040-12052
Open this publication in new window or tab >>Cesium Bismuth Iodide Solar Cells from Systematic Molar Ratio Variation of CsI and BiI3
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2019 (English)In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 58, no 18, p. 12040-12052Article in journal (Refereed) Published
Abstract [en]

Metal halide compounds with photovoltaic properties prepared from solution have received increased attention for utilization in solar cells. In this work, low-toxicity cesium bismuth iodides are synthesized from solution, and their photovoltaic and, optical properties as well as electronic and crystal structures are investigated. The X-ray diffraction patterns reveal that a CsI/BiI3 precursor ratio of 1.5:1 can convert pure rhombohedral BiI3 to pure hexagonal Cs3Bi2I9, but any ratio intermediate of this stoichiometry and pure BiI3 yields a mixture containing the two crystalline phases Cs3Bi2I9 and BiI3, with their relative fraction depending on the CsI/BiI3 ratio. Solar cells from the series of compounds are characterized, showing the highest efficiency for the compounds with a mixture of the two structures. The energies of the valence band edge were estimated using hard and soft X-ray photoelectron spectroscopy for more bulk and surface electronic properties, respectively. On the basis of these measurements, together with UV-vis-near-IR spectrophotometry, measuring the band gap, and Kelvin probe measurements for estimating the work function, an approximate energy diagram has been compiled clarifying the relationship between the positions of the valence and conduction band edges and the Fermi level.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2019
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-395308 (URN)10.1021/acs.inorgchem.9b01233 (DOI)000486565600024 ()31483638 (PubMedID)
Funder
Swedish Energy AgencySwedish Research CouncilSwedish Research Council FormasSwedish Foundation for Strategic Research
Available from: 2019-10-18 Created: 2019-10-18 Last updated: 2019-10-18Bibliographically approved
Klaa, K., Labidi, S., Banerjee, A., Chakraborty, S., Labidi, M., Amara, A., . . . Ahuja, R. (2019). Composition dependent tuning of electronic and magnetic properties in transition metal substituted Rock-salt MgO. Journal of Magnetism and Magnetic Materials, 475, 44-53
Open this publication in new window or tab >>Composition dependent tuning of electronic and magnetic properties in transition metal substituted Rock-salt MgO
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2019 (English)In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 475, p. 44-53Article in journal (Refereed) Published
Abstract [en]

Full potential linearized augmented plane wave (FP-LAPW) method based on the density functional theory (DFT) is used to investigate the structural, electronic and magnetic properties of Fe and Ni (3d transition metal) substituted Rock-salt wide band gap insulator Mg1-xMxO (M = Fe, Ni). We have performed spin polarized calculations throughout this work with generalized gradient approximation (GGA) type exchange correlation functional. Additionally, the electronic structures and density of states are computed using modified Becke-Johnson (mBJ) potential based approximation with the inclusion of coulomb energy (U = 7 eV). Based on the Vegard's law and structural optimization, the lattice parameter and bulk modulus are found to be in good agreement with experimental values. Moreover, the analysis of electronic band structures reveals an insulating character for Ni substituted MgO while semiconducting and half-metallic character for Fe substituted case. It has been found that the p-d super-exchange interaction provides a ferromagnetic character due to the 3d transition metal impurities and oxygen atom. The observed p-d hybridization at the top of the valence band edge in this investigations could be useful for magneto-optic and spintronic applications.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE BV, 2019
Keywords
FP-LAPW, mBJ plus U, P-d exchange interaction, Half-metallic, Magnetic moment
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-378617 (URN)10.1016/j.jmmm.2018.11.065 (DOI)000458152000008 ()
Funder
Swedish Research CouncilCarl Tryggers foundation
Available from: 2019-03-11 Created: 2019-03-11 Last updated: 2019-03-11Bibliographically approved
Watcharatharapong, T., T-Thienprasert, J., Chakraborty, S. & Ahuja, R. (2019). Defect formations and pH-dependent kinetics in krohnkite Na2Fe (SO4)2·2H2O based cathode for sodium-ion batteries: Resembling synthesis conditions through chemical potential landscape. Nano Energy, 55, 123-134
Open this publication in new window or tab >>Defect formations and pH-dependent kinetics in krohnkite Na2Fe (SO4)2·2H2O based cathode for sodium-ion batteries: Resembling synthesis conditions through chemical potential landscape
2019 (English)In: Nano Energy, ISSN 2211-2855, E-ISSN 2211-3282, Vol. 55, p. 123-134Article in journal (Refereed) Published
Abstract [en]

Thermodynamics and kinetics of intrinsic point defects in Na2Fe(SO4)(2)center dot 2H(2)O, a high-voltage cathode for Na-ion batteries, are studied by means of first-principles density functional theory. Electronic structures of charged defects are calculated to study their influences towards electronic and electrochemical properties as well as to probe hole polaron formation. As defect formation energy strongly depends on atomic chemical potentials, we initiate a systematic approach to determine their valid ranges for the pentrary Na-Fe-S-O-H compound under thermodynamic equilibria and correlate them with approximated pH parameters in solution-based synthesis. Given chemical potential landscape and formation energy, we find that Fe-Na(1+), V-Na(1-,0) and Na-Fe(1-,0) are dominant and their concentrations could be manipulated through pH condition and oxygen content in the precursor solution. It is predicted that the channel blockage due to Fe-Na would appear under strong acidic growth condition but could be diminished under weak acidic condition (4.7 <= pH <= 5.6) where Na-Fe facilitates a faster migration between each diffusion channel. Our results do not only explain the origin of intercalation mechanism and improved electronic conduction, but also demonstrates the pH influence towards conductivities in the cathode material.

Keywords
Chemical potentials, Defects, DFT, Diffusions, Sodium-ion batteries
National Category
Materials Chemistry Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-374115 (URN)10.1016/j.nanoen.2018.10.038 (DOI)000454636200012 ()
Funder
Swedish Research CouncilSwedish Research CouncilCarl Tryggers foundation
Available from: 2019-01-23 Created: 2019-01-23 Last updated: 2019-04-05Bibliographically approved
Benhouria, Y., Essaoudi, I., Ainane, A. & Ahuja, R. (2019). Dynamic magneto-caloric effect of a C70 fullerene: Dynamic Monte Carlo. Physica. E, Low-Dimensional systems and nanostructures, 108, 191-196
Open this publication in new window or tab >>Dynamic magneto-caloric effect of a C70 fullerene: Dynamic Monte Carlo
2019 (English)In: Physica. E, Low-Dimensional systems and nanostructures, ISSN 1386-9477, E-ISSN 1873-1759, Vol. 108, p. 191-196Article in journal (Refereed) Published
Abstract [en]

Using the dynamicMonte Carlo (DMC) simulation, the dynamic magnetocaloric effect of a ferrimagnetic C70 Fullerene-like structure is studied within the dynamic Ising model under of a magnetic (h(t)) field. The influences of the amplitude (h0) and the frequency (ω) of the h(t) magnetic field and bias field (hb) on the thermal behavior of the dynamic order parameter and the dynamic magnetocaloric properties (the dynamic isothermal ΔSiso(T,h(t)) entropy variation and the dynamic ΔTad (T,h(t)) adiabatic variation of temperature), the dynamic specific heat, the dynamic entropy and as well as the dynamic refrigerant capacity (RC(t)) ferrimagnetic C70 Fullerene-like structure are studied. Our results may be a reference for future experiment and theoretical studies of the nano-clusters.

Keywords
Dynamic Monte Carlo, C70 fullerene, Magnetocaloric effect
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-375791 (URN)10.1016/j.physe.2018.11.043 (DOI)000455988500030 ()
Available from: 2019-02-20 Created: 2019-02-20 Last updated: 2019-02-20Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0003-1231-9994

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