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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
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
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
Benhouria, Y., Khossossi, N., Houmad, M., Essaoudi, I., Ainane, A. & Ahuja, R. (2019). Dynamic magneto-caloric effect of a multilayer nanographene: Dynamic quantum Monte Carlo. Physica. E, Low-Dimensional systems and nanostructures, 105, 139-145
Open this publication in new window or tab >>Dynamic magneto-caloric effect of a multilayer nanographene: Dynamic quantum Monte Carlo
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2019 (English)In: Physica. E, Low-Dimensional systems and nanostructures, ISSN 1386-9477, E-ISSN 1873-1759, Vol. 105, p. 139-145Article in journal (Refereed) Published
Abstract [en]

Using the dynamic quantum Monte Carlo simulation, the dynamic magnetocaloric effect of a ferromagnetic multilayer nanographene (MNG) is studied within the dynamic Ising model under the applied of a time-dependent oscillating (h(t)) magnetic field. The influence of the amplitude h(0) and the period tau of the h(t) and the transverse field Omega on the thermal behavior of the dynamic order parameter and the dynamic magnetocaloric properties (the dynamic isothermal Delta S-T (T, h(t)) entropy change and the dynamic Delta T-ad (T, h(t)) adiabatic change of temperature), the dynamic specific heat, the dynamic entropy and as well as the dynamic relative cooling power (RCP(t)) ferrimagnetic MNG are studied. Our predicted results may be a reference for future experiment and theoretical studies of the nanostructures.

Keywords
Quantum Monte Carlo, Multilayer nanographene, Magnetocaloric effect
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-374109 (URN)10.1016/j.physe.2018.09.008 (DOI)000454899600018 ()
Funder
Swedish Research Council, dnr-348-2011-7264
Available from: 2019-01-21 Created: 2019-01-21 Last updated: 2019-01-21Bibliographically approved
Hussain, T., Singh, D., Gupta, S. K., Karton, A., Sonvane, Y. & Ahuja, R. (2019). Efficient and selective sensing of nitrogen-containing gases by Si2BN nanosheets under pristine and pre-oxidized conditions. Applied Surface Science, 469, 775-780
Open this publication in new window or tab >>Efficient and selective sensing of nitrogen-containing gases by Si2BN nanosheets under pristine and pre-oxidized conditions
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2019 (English)In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 469, p. 775-780Article in journal (Refereed) Published
Abstract [en]

Motivated by the promise of two-dimensional nanostructures in the field of gas sensing, we have employed van der Waals corrected density functional theory calculations to study the structural, electronic and gas sensing propensities of the recently designed Si2BN monolayer. Our rigorous simulations reveal that the representative members of nitrogen-containing gases (NCGs) such as NO, NO2 and NH3 binds extremely strongly on pristine Si2BN monolayer. However, a strong dissociative adsorption in case of NO and NO2 would poison the Si2BN and ultimately reversibility of the monolayer would be compromised. Exploring the sensing mechanism in more realistic pre-oxidized conditions, the binding characteristics of O2@Si2BN changed dramatically, resulting into much lower adsorption in associative manner for all NO, NO2 and NH3. A visible change in work function indicates the variation in conductivity of O2@Si2BN upon the exposure of incident gases. Sustainable values of binding energies would also ensure a quick recovery time that makes O2@Si2BN an efficient nano sensor for pollutants like NCGs.

Keywords
Monolayer, Adsorption, Work function, Conductivity, Recovery time
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-374416 (URN)10.1016/j.apsusc.2018.11.020 (DOI)000454617200090 ()
Funder
Swedish Research CouncilCarl Tryggers foundation StandUpAustralian Research Council, FT170100373
Available from: 2019-01-31 Created: 2019-01-31 Last updated: 2019-01-31Bibliographically approved
Edin, E., Luo, W., Ahuja, R., Kaplan, B. & Blomqvist, A. (2019). First principles study of C diffusion in WC/W interfaces observed in WC/Co tools after Ti-alloy machining. Computational materials science, 161, 236-243
Open this publication in new window or tab >>First principles study of C diffusion in WC/W interfaces observed in WC/Co tools after Ti-alloy machining
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2019 (English)In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 161, p. 236-243Article in journal (Refereed) Published
Abstract [en]

Ti-alloys have many qualities making them ideal for use in aerospace applications, medical implants and chemical industries such as high strength to weight ratio, good high temperature strength and chemical stability. One downside to Ti-alloys is, however, that they are considered difficult to machine. Several investigations have been made in order to understand the wear mechanisms present in machining of Ti-alloys and the most common understanding is a combination of attrition and dissolution-diffusion. Observations by Odelros et al. [1] have shown that there exists a small layer of pure bcc W on top of the outermost WC grains after turning of Ti-6Al-4V. In order for such a layer to form C has to diffuse away from the WC leaving behind only W. In this work Density Functional Theory (DFT) is used together with Harmonic Transition State Theory (HTST) to investigate the prefactors and barriers for C diffusion into and within two different WC/W interfaces, [0001]/[111] and [10 (1) over bar0]/[100]. The diffusion into the interfaces show that the barrier for the [0001]/[111] interface is more than twice as high as the barrier for the [10 (1) over bar0]/[100] interface. Diffusion within the interfaces show, on average, slightly higher barriers for the [0001]/[111] interface.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE BV, 2019
Keywords
W, WC, Interface, First principles, Diffusion
National Category
Manufacturing, Surface and Joining Technology
Identifiers
urn:nbn:se:uu:diva-381106 (URN)10.1016/j.commatsci.2019.01.051 (DOI)000462165100027 ()
Available from: 2019-04-05 Created: 2019-04-05 Last updated: 2019-04-05Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0003-1231-9994

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