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Solomon, G., Mazzaro, R., You, S., Natile, M. M., Morandi, V., Concina, I. & Vomiero, A. (2019). Ag2S/MoS2 Nanocomposites Anchored on Reduced Graphene Oxide: Fast Interfacial Charge Transfer for Hydrogen Evolution Reaction. ACS Applied Materials and Interfaces, 11(25), 22380-22389
Åpne denne publikasjonen i ny fane eller vindu >>Ag2S/MoS2 Nanocomposites Anchored on Reduced Graphene Oxide: Fast Interfacial Charge Transfer for Hydrogen Evolution Reaction
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2019 (engelsk)Inngår i: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 11, nr 25, s. 22380-22389Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Hydrogen evolution reaction through electrolysis holds great potential as a clean, renewable, and sustainable energy source. Platinum-based catalysts are the most efficient to catalyze and convert water into molecular hydrogen; however, their large-scale application is prevented by scarcity and cost of Pt. In this work, we propose a new ternary composite of Ag2S, MoS2, and reduced graphene oxide (RGO) flakes via a one-pot synthesis. The RGO support assists the growth of two-dimensional MoS2 nanosheets partially covered by silver sulfides as revealed by high-resolution transmission electron microscopy. Compared with the bare MoS2 and MoS2/RGO, the Ag2S/MoS2 anchored on the RGO surface (the ternary system Ag2S/MoS2/RGO) demonstrated a high catalytic activity toward hydrogen evolution reaction (HER). Its superior electrochemical activity toward HER is evidenced by the positively shifted (−190 mV vs reversible hydrogen electrode (RHE)) overpotential at a current density of −10 mA/cm2 and a small Tafel slope (56 mV/dec) compared with a bare and binary system. The Ag2S/MoS2/RGO ternary catalyst at an overpotential of −200 mV demonstrated a turnover frequency equal to 0.38 s–1. Electrochemical impedance spectroscopy was applied to understand the charge-transfer resistance; the ternary sample shows a very small charge-transfer resistance (98 Ω) at −155 mV vs RHE. Such a large improvement can be attributed to the synergistic effect resulting from the enhanced active site density of both sulfides and to the improved electrical conductivity at the interfaces between MoS2 and Ag2S. This ternary catalyst opens up further optimization strategies to design a stable and cheap catalyst for hydrogen evolution reaction, which holds great promise for the development of a clean energy landscape.

sted, utgiver, år, opplag, sider
American Chemical Society (ACS), 2019
Emneord
electrocatalyst, hydrogen evolution, silver sulfide, molybdenum sulfide, reduced graphene oxide
HSV kategori
Forskningsprogram
Experimentell fysik
Identifikatorer
urn:nbn:se:ltu:diva-75551 (URN)10.1021/acsami.9b05086 (DOI)000473251100036 ()2-s2.0-85068008830 (Scopus ID)
Merknad

Validerad;2019;Nivå 2;2019-08-16 (johcin)

Tilgjengelig fra: 2019-08-16 Laget: 2019-08-16 Sist oppdatert: 2019-08-16bibliografisk kontrollert
Gilzad Kohan, M., Mazzaro, R., Morandi, V., You, S., Concina, I. & Vomiero, A. (2019). Plasma assisted vapor solid deposition of Co3O4 tapered nanorods for energy applications. Journal of Materials Chemistry A, 7(46), 26302-26310
Åpne denne publikasjonen i ny fane eller vindu >>Plasma assisted vapor solid deposition of Co3O4 tapered nanorods for energy applications
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2019 (engelsk)Inngår i: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 7, nr 46, s. 26302-26310Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Self-standing, 1-dimensional (1D) structures of p-type metal oxide (MOx) have been the focus of considerable attention, due to their unique properties in energy storage and solar light conversion. However, the practical performance of p-type MOx is intrinsically limited by their interfacial defects and strong charge recombination losses. Single crystalline assembly can significantly reduce recombination at interface and grain boundaries. Here, we present a one-step route based on plasma assisted physical vapor deposition (PVD), for the rational and scalable synthesis of single crystalline 1D vertically aligned Co3O4 tapered nanorods (NRs). The effect of PVD parameters (deposition pressure, temperature and duration) in tuning the morphology, composition and crystalline structure of resultant NRs is investigated. Crystallographic data obtained from X-ray diffraction and high-resolution transmission electron microscopy (TEM) indicated the single crystalline nature of NRs with [111] facet preferred orientation. The NRs present two optical band gaps at about 1.48 eV and 2.1 eV. Current–voltage (I–V) characteristic of the Co3O4 NRs electrodes, 400 nm long, present two times higher current density at −1 V forward bias, compared to the benchmarking thin film counterpart. These array structures exhibit good electrochemical performance in lithium-ion adsorption–desorption processes. Among all, the longest Co3O4 NRs electrodes delivers a 1438.4 F g−1 at current density of 0.5 mA cm−2 and presents 98% capacitance retention after 200 charge–discharge cycles. The very low values of charge transfer resistance (Rct = 5.2 Ω for 400 nm long NRs) of the NRs testifies their high conductivity. Plasma assisted PVD is demonstrated as a facile technique for synthesizing high quality 1D structures of Co3O4, which can be of interest for further development of different desirable 1D systems based on transition MOx.

sted, utgiver, år, opplag, sider
Royal Society of Chemistry, 2019
HSV kategori
Forskningsprogram
Experimentell fysik
Identifikatorer
urn:nbn:se:ltu:diva-77120 (URN)10.1039/c9ta08055d (DOI)2-s2.0-85075789051 (Scopus ID)
Merknad

Validerad;2019;Nivå 2;2019-12-10 (johcin)

Tilgjengelig fra: 2019-12-10 Laget: 2019-12-10 Sist oppdatert: 2019-12-10bibliografisk kontrollert
Ghamgosar, P., Rigoni, F., Gilzad Kohan, M., You, S., Morales, E. A., Mazzaro, R., . . . Vomiero, A. (2019). Self-Powered Photodetectors Based on Core-Shell ZnO-Co3O4 Nanowire Heterojunctions. ACS Applied Materials and Interfaces, 11(26), 23454-23462
Åpne denne publikasjonen i ny fane eller vindu >>Self-Powered Photodetectors Based on Core-Shell ZnO-Co3O4 Nanowire Heterojunctions
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2019 (engelsk)Inngår i: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 11, nr 26, s. 23454-23462Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Self-powered photodetectors operating in the UV–visible–NIR window made of environmentally friendly, earth abundant, and cheap materials are appealing systems to exploit natural solar radiation without external power sources. In this study, we propose a new p–n junction nanostructure, based on a ZnO–Co3O4 core–shell nanowire (NW) system, with a suitable electronic band structure and improved light absorption, charge transport, and charge collection, to build an efficient UV–visible–NIR p–n heterojunction photodetector. Ultrathin Co3O4 films (in the range 1–15 nm) were sputter-deposited on hydrothermally grown ZnO NW arrays. The effect of a thin layer of the Al2O3 buffer layer between ZnO and Co3O4 was investigated, which may inhibit charge recombination, boosting device performance. The photoresponse of the ZnO–Al2O3–Co3O4 system at zero bias is 6 times higher compared to that of ZnO–Co3O4. The responsivity (R) and specific detectivity (D*) of the best device were 21.80 mA W–1and 4.12 × 1012 Jones, respectively. These results suggest a novel p–n junction structure to develop all-oxide UV–vis photodetectors based on stable, nontoxic, low-cost materials.

sted, utgiver, år, opplag, sider
American Chemical Society (ACS), 2019
Emneord
ZnO−CoO core−shell, all-oxide p−n heterojunction, nanowire geometry, photovoltaic photodetector, self-powered photodetector
HSV kategori
Forskningsprogram
Experimentell fysik
Identifikatorer
urn:nbn:se:ltu:diva-75216 (URN)10.1021/acsami.9b04838 (DOI)000474670100061 ()31252456 (PubMedID)2-s2.0-85068447779 (Scopus ID)
Merknad

Validerad;2019;Nivå 2;2019-07-04 (svasva)

Tilgjengelig fra: 2019-07-04 Laget: 2019-07-04 Sist oppdatert: 2019-08-30bibliografisk kontrollert
Di Mauro, A., Landström, A., Concina, I., Impellizzeri, G., Privitera, V. & Epifani, M. (2019). Surface Modification by Vanadium Pentoxide Turns Oxide Nanocrystals into Powerful Adsorbents of Methylene Blue. Journal of Colloid and Interface Science, 533, 369-374
Åpne denne publikasjonen i ny fane eller vindu >>Surface Modification by Vanadium Pentoxide Turns Oxide Nanocrystals into Powerful Adsorbents of Methylene Blue
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2019 (engelsk)Inngår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 533, s. 369-374Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Hypothesis: If nanocrystals of such semiconductor as SnO2 and TiO2, which are not known as powerful adsorbents, have their surface modified by layer of V2O5, how will the adsorption properties be affected? Answering this question would provide a new set of surface properties to be designed by surface engineering of oxide nanocrystals.

Experiments: SnO2 and TiO2 colloidal nanocrystals were prepared by coupling sol-gel and solvothermal synthesis. By co-processing with V chloroalkoxide and subsequent heat-treatment at 400-500 °C, surface deposition of V2O5 layers was obtained. The methylene blue adsorption onto the prepared materials was tested and compared with the pure oxide supports. Cycling of the materials and analysis of the adsorption process was also investigated.

Findings: The V-modified nanocrystals extracted ∼ 80% methylene blue from 1.5 x 10-5 M aqueous solution after 15 min only, contrarily to pure materials, which took up only 30% of the dye even after 120 min. Comparison with pure commercial V2O5 showed that the peculiar adsorption properties were imparted by the surface deposition of the V2O5-like layers. This report demonstrates that new classes of adsorbing materials can be conceived by suitably coupling different metal oxides.

sted, utgiver, år, opplag, sider
Elsevier, 2019
HSV kategori
Forskningsprogram
Experimentell fysik
Identifikatorer
urn:nbn:se:ltu:diva-70622 (URN)10.1016/j.jcis.2018.08.070 (DOI)000447815200038 ()30172147 (PubMedID)2-s2.0-85052435735 (Scopus ID)
Merknad

Validerad;2018;Nivå 2;2018-09-04 (andbra)

Tilgjengelig fra: 2018-08-28 Laget: 2018-08-28 Sist oppdatert: 2018-11-15bibliografisk kontrollert
Landström, A., Soldatov, A., Vomiero, A. & Concina, I. (2019). Thermal Defect Modulation and Functional Performance: A Case Study on ZnO–rGO Nanocomposites. Physica status solidi. B, Basic research, 256(12), Article ID 1900239.
Åpne denne publikasjonen i ny fane eller vindu >>Thermal Defect Modulation and Functional Performance: A Case Study on ZnO–rGO Nanocomposites
2019 (engelsk)Inngår i: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 256, nr 12, artikkel-id 1900239Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Herein, a reduced graphene oxide–zinc oxide (rGO–ZnO) hybrid nanocomposite (1 wt% rGO) is synthesized and heat treated at different temperatures, aimed at modulating the intrinsic bulk/surface defects naturally present in nano‐ZnO. The correlation of both the dispersion of rGO within the metal oxide scaffold and the defects present on the semiconductor crystalline lattice with the photocatalytic performance toward the degradation of a molecular dye in water is investigated and discussed. It is shown that several processes compete to determine the catalytic skill of the nanocomposite, which can be enhanced by a simple thermal treatment at moderate temperatures.

sted, utgiver, år, opplag, sider
John Wiley & Sons, 2019
Emneord
crystalline defects, hybrid nanocomposites, photocatalysis, photoluminescence, reduced graphene oxide, thermal treatment, zinc oxide
HSV kategori
Forskningsprogram
Experimentell fysik
Identifikatorer
urn:nbn:se:ltu:diva-76877 (URN)10.1002/pssb.201900239 (DOI)000495784800001 ()2-s2.0-85075015324 (Scopus ID)
Merknad

Validerad;2020;Nivå 2;2019-12-16 (johcin)

Tilgjengelig fra: 2019-11-27 Laget: 2019-11-27 Sist oppdatert: 2019-12-16bibliografisk kontrollert
Ghamgosar, P., Rigoni, F., You, S., Dobryden, I., Gilzad Kohan, M., Pellegrino, A. L., . . . Vomiero, A. (2018). ZnO-Cu2O core-shell nanowires as stable and fast response photodetectors. Nano Energy, 51, 308-316
Åpne denne publikasjonen i ny fane eller vindu >>ZnO-Cu2O core-shell nanowires as stable and fast response photodetectors
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2018 (engelsk)Inngår i: Nano Energy, ISSN 2211-2855, E-ISSN 2211-3282, Vol. 51, s. 308-316Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

In this work, we present all-oxide p-n junction core-shell nanowires (NWs) as fast and stable self-powered photodetectors. Hydrothermally grown n-type ZnO NWs were conformal covered by different thicknesses (up to 420 nm) of p-type copper oxide layers through metalorganic chemical vapor deposition (MOCVD). The ZnO NWs exhibit a single crystalline Wurtzite structure, preferentially grown along the [002] direction, and energy gap Eg=3.24 eV. Depending on the deposition temperature, the copper oxide shell exhibits either a crystalline cubic structure of pure Cu2O phase (MOCVD at 250 °C) or a cubic structure of Cu2O with the presence of CuO phase impurities (MOCVD at 300 °C), with energy gap of 2.48 eV. The electrical measurements indicate the formation of a p-n junction after the deposition of the copper oxide layer. The core-shell photodetectors present a photoresponsivity at 0 V bias voltage up to 7.7 µA/W and time response ≤0.09 s, the fastest ever reported for oxide photodetectors in the visible range, and among the fastest including photodetectors with response limited to the UV region. The bare ZnO NWs have slow photoresponsivity, without recovery after the end of photo-stimulation. The fast time response for the core-shell structures is due to the presence of the p-n junctions, which enables fast exciton separation and charge extraction. Additionally, the suitable electronic structure of the ZnO-Cu2O heterojunction enables self-powering of the device at 0 V bias voltage. These results represent a significant advancement in the development of low-cost, high efficiency and self-powered photodetectors, highlighting the need of fine tuning the morphology, composition and electronic properties of p-n junctions to maximize device performances.

sted, utgiver, år, opplag, sider
Elsevier, 2018
HSV kategori
Forskningsprogram
Experimentell fysik
Identifikatorer
urn:nbn:se:ltu:diva-69838 (URN)10.1016/j.nanoen.2018.06.058 (DOI)000440682100034 ()2-s2.0-85049324019 (Scopus ID)
Merknad

Validerad;2018;Nivå 2;2018-08-02 (rokbeg)

Tilgjengelig fra: 2018-06-25 Laget: 2018-06-25 Sist oppdatert: 2019-04-19bibliografisk kontrollert
Memarian, N., Rozati, S. M., Vomiero, A. & Concina, I. (2017). Deposition of nanostructured Cds thin films by thermal evaporation method: Effect of substrate temperature. Materials, 10(7), Article ID 773.
Åpne denne publikasjonen i ny fane eller vindu >>Deposition of nanostructured Cds thin films by thermal evaporation method: Effect of substrate temperature
2017 (engelsk)Inngår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 10, nr 7, artikkel-id 773Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Nanocrystalline CdS thin films were grown on glass substrates by a thermal evaporation method in a vacuum of about 2 × 10-5 Torr at substrate temperatures ranging between 25 °C and 250 °C. The physical properties of the layers were analyzed by transmittance spectra, XRD, SEM, and four-point probe measurements, and exhibited strong dependence on substrate temperature. The XRD patterns of the films indicated the presence of single-phase hexagonal CdS with (002) orientation. The structural parameters of CdS thin films (namely crystallite size, number of grains per unit area, dislocation density and the strain of the deposited films) were also calculated. The resistivity of the as-deposited films were found to vary in the range 3.11-2.2 × 104 Ω·cm, depending on the substrate temperature. The low resistivity with reasonable transmittance suggest that this is a reliable way to fine-tune the functional properties of CdS films according to the specific application.

sted, utgiver, år, opplag, sider
Basel: MDPI, 2017
HSV kategori
Forskningsprogram
Experimentell fysik
Identifikatorer
urn:nbn:se:ltu:diva-65048 (URN)10.3390/ma10070773 (DOI)000406683000090 ()28773133 (PubMedID)2-s2.0-85023743510 (Scopus ID)
Merknad

Validerad; 2017; Nivå 2; 2017-08-14 (andbra)

Tilgjengelig fra: 2017-08-14 Laget: 2017-08-14 Sist oppdatert: 2018-11-26bibliografisk kontrollert
Milan, R., Selopal, G. S., Cavazzini, M., Orlandi, S., Boaretto, R., Caramori, S., . . . Pozzi, G. (2017). Dye-sensitized solar cells based on a push-pull zinc phthalocyanine bearing diphenylamine donor groups: computational predictions face experimental reality. Scientific Reports, 7, Article ID 15675.
Åpne denne publikasjonen i ny fane eller vindu >>Dye-sensitized solar cells based on a push-pull zinc phthalocyanine bearing diphenylamine donor groups: computational predictions face experimental reality
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2017 (engelsk)Inngår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, artikkel-id 15675Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Computational studies have suggested that the integration of secondary amine as donor groups in the structure of unsymmetrical zinc phthalocyanine (ZnPc) should have positive effects on photovoltaic performance, once the molecule is integrated as light harvester in dye sensitized solar cells (DSSCs). Aiming at obtaining experimental confirmation, we synthesized a peripherally substituted push-pull ZnPc bearing three electron donating diphenylamine substituents and a carboxylic acid anchoring group and integrated it as sensitizer in TiO2-based DSSCs. Detailed functional characterization of solar energy converting devices resulted in ruling out the original hypothesis. The causes of this discrepancy have been highlighted, leading to a better understanding of the conditions for an effective design of push-pull diarylamino substituted ZnPcs for DSSCs.

sted, utgiver, år, opplag, sider
Nature Publishing Group, 2017
HSV kategori
Forskningsprogram
Experimentell fysik
Identifikatorer
urn:nbn:se:ltu:diva-66626 (URN)10.1038/s41598-017-15745-3 (DOI)000415266100024 ()29142212 (PubMedID)2-s2.0-85034445753 (Scopus ID)
Merknad

Validerad;2017;Nivå 2;2017-11-17 (svasva)

Tilgjengelig fra: 2017-11-17 Laget: 2017-11-17 Sist oppdatert: 2017-12-08bibliografisk kontrollert
Epafini, M., Kaciulis, S., Mezzi, A., Altamura, D., Giannini, C., Díaz, R., . . . Concina, I. (2017). Inorganic Photocatalytic Enhancement: Activated RhB Photodegradation by Surface Modification of SnO2 Nanocrystals with V2O5-like species. Scientific Reports, 7, Article ID 44763.
Åpne denne publikasjonen i ny fane eller vindu >>Inorganic Photocatalytic Enhancement: Activated RhB Photodegradation by Surface Modification of SnO2 Nanocrystals with V2O5-like species
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2017 (engelsk)Inngår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, artikkel-id 44763Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

SnO2 nanocrystals were prepared by precipitation in dodecylamine at 100 °C, then they were reacted with vanadium chloromethoxide in oleic acid at 250 °C. The resulting materials were heat-treated at various temperatures up to 650 °C for thermal stabilization, chemical purification and for studying the overall structural transformations. From the crossed use of various characterization techniques, it emerged that the as-prepared materials were constituted by cassiterite SnO2 nanocrystals with a surface modified by isolated V(IV) oxide species. After heat-treatment at 400 °C, the SnO2 nanocrystals were wrapped by layers composed of vanadium oxide (IV-V mixed oxidation state) and carbon residuals. After heating at 500 °C, only SnO2 cassiterite nanocrystals were obtained, with a mean size of 2.8 nm and wrapped by only V2O5-like species. The samples heat-treated at 500 °C were tested as RhB photodegradation catalysts. At 10-7 M concentration, all RhB was degraded within 1 h of reaction, at a much faster rate than all pure SnO2 materials reported until now.

sted, utgiver, år, opplag, sider
Nature Publishing Group, 2017
HSV kategori
Forskningsprogram
Experimentell fysik
Identifikatorer
urn:nbn:se:ltu:diva-62573 (URN)10.1038/srep44763 (DOI)000396534800001 ()28300185 (PubMedID)2-s2.0-85015710811 (Scopus ID)
Merknad

Validerad; 2017; Nivå 2; 2017-03-20 (andbra)

Tilgjengelig fra: 2017-03-20 Laget: 2017-03-20 Sist oppdatert: 2018-11-20bibliografisk kontrollert
Epafini, M., Kaciulis, S., Mezzi, A., Altamura, D., Giannini, C., Tang, P., . . . Concina, I. (2017). Solvothermal Synthesis, Gas-Sensing Properties, and Solar Cell-Aided Investigation of TiO2-MoOx Nanocrystals. ChemNanoMat, 3(11), 798-807
Åpne denne publikasjonen i ny fane eller vindu >>Solvothermal Synthesis, Gas-Sensing Properties, and Solar Cell-Aided Investigation of TiO2-MoOx Nanocrystals
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2017 (engelsk)Inngår i: ChemNanoMat, ISSN 2199-692X, Vol. 3, nr 11, s. 798-807Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Titania anatase nanocrystals were prepared by sol-gel/solvothermal synthesis in oleic acid at 250 °C, and modified by co-reaction with Mo chloroalkoxide, aimed at investigating the effects on gas-sensing properties induced by tailored nanocrystals surface modification with ultra-thin layers of MoOx species. For the lowest Mo concentration, only anatase nanocrystals were obtained, surface modified by a disordered ultra-thin layer of mainly octahedral MoVI oxide species. For larger Mo concentrations, early MoO2 phase segregation occurred. Upon heat treatment up to 500 °C, the sample with the lowest Mo concentration did not feature any Mo oxide phase segregation, and the surface Mo layer was converted to dense octahedral MoVI oxide. At larger Mo concentrations all segregated MoO2 was converted to MoO3. The two different materials typologies, depending on the Mo concentration, were used for processing gas-sensing devices and tested toward acetone and carbon monoxide, which gave a greatly enhanced response, for all Mo concentrations, to acetone (two orders of magnitude) and carbon monoxide with respect to pure TiO2. For the lowest Mo concentration, dye-sensitized solar cells were also prepared to investigate the influence of anatase surface modification on the electrical transport properties, which showed that the charge transport mainly occurred in the ultra-thin MoOx surface layer.

sted, utgiver, år, opplag, sider
John Wiley & Sons, 2017
HSV kategori
Forskningsprogram
Experimentell fysik
Identifikatorer
urn:nbn:se:ltu:diva-65740 (URN)10.1002/cnma.201700160 (DOI)000417743700004 ()
Merknad

Validerad;2017;Nivå 2;2017-11-27 (rokbeg)

Tilgjengelig fra: 2017-09-20 Laget: 2017-09-20 Sist oppdatert: 2017-12-29bibliografisk kontrollert
Organisasjoner
Identifikatorer
ORCID-id: ORCID iD iconorcid.org/0000-0003-1785-7177