| 1. |
- Arnalds, Unnar B., et al.
(author)
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Thermal transitions in nano-patterned XY-magnets
- 2014
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In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 105:4, s. 042409-
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Journal article (peer-reviewed)abstract
- We have fabricated ultra-thin disc shaped islands wherein shape anisotropy confines the moment to the island plane, creating XY-like superspins. At low temperatures, the superspins are blocked, and, as the temperature is increased, they undergo a transition into a superparamagnetic state. The onset of this dynamic superspin state scales with the diameter of the islands, and it persists up to a temperature governed by the intrinsic ordering temperature of the island material defining a range in temperature in which dynamic behavior of the magnetic islands can be obtained.
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| 2. |
- Aung, Soe Ko Ko, et al.
(author)
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Reduced hysteresis and enhanced air stability of low-temperature processed carbon-based perovskite solar cells by surface modification
- 2023
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In: Electrochimica Acta. - : Elsevier. - 0013-4686 .- 1873-3859. ; 443
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Journal article (peer-reviewed)abstract
- Low temperature processed carbon-based perovskite solar cells (C-PSCs) have gained great interest because of low cost and ease of fabrication. By replacing the Au electrode with carbon, stable solar cells suited for mass-production process can be made. However, power conversion efficiencies (PCEs) of C-PSCs still lag behind that of PSCs with Au contact.Here we explore low temperature (<= 150 degrees C) processed C-PSCs with, where a two-step method is used to prepare mixed-ion lead perovskite films, with tin oxide (SnO2) electron transport layer, poly(3-hexylthiophene-2,5-diyl) (P3HT) hole transport layer and carbon electrode, resulting in devices with a PCE of 14.0%. Moreover, hexyl trimethylammonium bromide (HTAB) was introduced to improve the interface between perovskite and P3HT. Perovskite grains were remarkably enlarged into micrometer-size and defects were reduced. As a result, a champion PCE of 16.1% was obtained, mainly due to enhanced fill factor from 0.67 to 0.73. The interface modification by HTAB molecule is an effective way to passivate the perovskite defects and facilitate the carrier transport at the perovskite/HTL interface. Unencapsulated devices showed excellent stability over 1500 h stored under ambient air (relative humidity -50 +/- 10%).
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| 3. |
- Kapaklis, Vassilios, et al.
(author)
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Melting artificial spin ice
- 2012
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In: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 14, s. 035009-
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Journal article (peer-reviewed)abstract
- Artificial spin ice arrays of micromagnetic islands are a means of engineering additional energy scales and frustration into magnetic materials. Here we demonstrate a magnetic phase transition in an artificial square spin ice and use the symmetry of the lattice to verify the presence of excitations far below the ordering temperature. We do this by measuring the temperature dependent magnetisation in different principal directions and comparing with simulations of idealised statistical mechanical models. Our results confirm a dynamical pre-melting of the artificial spin ice structure at a temperature well below the intrinsic ordering temperature of the island material. We thus create a spin ice array that has real thermal dynamics of the artificial spins over an extended temperature range.
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| 4. |
- Karimipour, Masoud, et al.
(author)
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A glassy carbon electrode modified with TiO2(200)-rGO hybrid nanosheets for aptamer based impedimetric determination of the prostate specific antigen
- 2019
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In: Microchimica Acta. - : SPRINGER WIEN. - 0026-3672 .- 1436-5073. ; 186:1
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Journal article (peer-reviewed)abstract
- TiO2(200)-rGO hybrid nanosheets were synthesized starting from TiO2, rGO and NaOH solid powders via a scalable hydrothermal process. The weight ratio of TiO2-GO was found to be crucial on the crystal growth and biosensor properties of the final hybrid nanosheets. They were characterized by means of SEM, FESEM-EDX, XRD, XPS, Raman and FTIR spectroscopies in order to verify the formation of very thin TiO2 anatase nanosheets with an orientation of the anatase crystal structure towards the (200) plane. The free active sites of TiO2 structure and the large surface of the 2D graphene structure strongly facilitate charge transport confirmed by BET-BJH analyses. Compared to pure AuNPs, rGO and TiO2, the hybrid nanosheet modified electrode represents the most sensitive aptasensing platform for the determination of PSA. The detection was based on that the variation of electron transfer resistance (Rct) at the modified electrode surface in a solution containing 3.0mmolL(-1) [Fe(CN)(6)](3-/4-) as a redox probe and 0.1molL(-1) KCl as supporting electrolyte. The detection limit of the sensor is 1pgmL(-1), and the sensor can be operated up to 30days. It was applied to the analysis of PSA levels in spiked serum samples obtained from patients with prostate cancer. Data compare well with those obtained by an immunoradiometric assay.
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| 5. |
- Karimipour, Masoud, et al.
(author)
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Effect of Annealing Temperature on the Structural and Magnetic Properties of Co-Doped TiO2 Nanoparticles via Complex-Polymer Sol-Gel Method
- 2012
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In: Journal of Nanoscience and Nanotechnology. - : American Scientific Publishers. - 1533-4880 .- 1533-4899. ; 12:2, s. 950-954
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Journal article (peer-reviewed)abstract
- Co-doped TiO2 nanoparticles were synthesized via non hydrous complex-polymer sol gel method. A series of Co-x:Ti1-xO2 samples with x = 0.01, 0.03, 0.05, 0.08 and 0.10, were prepared and subsequently annealed at 400 degrees, 600 degrees and 800 degrees C. Structural and magnetic properties of Co-x:Ti1-xO2 have been studied by means of X-ray diffraction and DC magnetometry. All samples annealed at 400 degrees C show a paramagnetic behavior with an average grain size of 11 nm. With increasing annealing temperatures a complete crystallization is seen with growth of the cluster size up to 31 nm with clear evidence of a presence of CoTiO3. For all concentrations and annealing conditions no sign of a metallic phase, even at x = 0.10, is seen.
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| 6. |
- Karimipour, Masoud, et al.
(author)
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Efficiency and Stability Enhancement of Perovskite Solar Cells Utilizing a Thiol Ligand and MoS2 (100) Nanosheet Surface Modification
- 2021
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In: ACS Applied Energy Materials. - : American Chemical Society (ACS). - 2574-0962. ; 4:12, s. 14080-14092
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Journal article (peer-reviewed)abstract
- Surface modification of perovskite films using a combination of 1-dodecanethiol (DT) and MoS2 nanosheets is investigated for perovskite solar cells. This surface modification is studied for two different types of perovskites, one with triple cations (CsFAMA) and one with double cations (FAMA), resulting in solar cell devices with power conversion efficiency (PCE) values of 18-19 and >20%, respectively. In both cases, stability enhancement is observed with DT and MoS2 surface modification using three different stability tracking protocols. The results reveal that by including DT and MoS2, the device retains 92% of its highest efficiency after 2200 h in dark (in air), while the standard device retained only 72%. Moreover, after light cycling, the device with DT and MoS2 retained 80%, and the standard device retained 55% of its maximum PCE. Moreover, these surface modifications gave rise to 58% decrease in the number of short-circuited devices and more reproducible results. Different characterizations revealed that the stability and efficiency enhancement is mainly due to reduced interface trap densities, improved charge transfer, and longer charge carrier lifetime. Moreover, the DT and MoS2 modifications induce hydrophobicity with an average contact angle over 80 degrees.
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| 7. |
- Karimipour, Masoud, et al.
(author)
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Efficient and bending durable flexible perovskite solar cells via interface modification using a combination of thin MoS2 nanosheets and molecules binding to the perovskite
- 2022
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In: Nano Energy. - : Elsevier. - 2211-2855 .- 2211-3282. ; 95
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Journal article (peer-reviewed)abstract
- In this work, efficient and bending durable flexible perovskite solar cells are obtained by modification of the perovskite film surface with 1- dodecanethiol (DT) followed by drop-casting of pre-dispersed thin nanosheets of MoS2. Our results show an enhancement in efficiency of the flexible device after the interface modification and revealed that the DT and MoS2 modified device recovers completely its initial values of PCE and FF, current density, and open-circuit voltage after 300 bending cycles while the standard device resembles only 50% of its PCE. Following a standard light cycling protocol for unencapsulated devices, it revealed an apparent PCE drop of the standard device up to 32% of its maximum value while the modified device recovers 95% of its highest PCE value. Different characterization methods suggest that the surface modification method induces hydrophobicity as well as significantly reduces the interface trap density.
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| 8. |
- Karimipour, Masoud, et al.
(author)
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Functionalized MXene/Halide Perovskite Heterojunctions for Perovskite Solar Cells Stable Under Real Outdoor Conditions
- 2023
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In: Advanced Energy Materials. - : WILEY-V C H VERLAG GMBH. - 1614-6832 .- 1614-6840. ; 13:44
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Journal article (peer-reviewed)abstract
- Despite the performance improvement in perovskite solar cells (PSCs) when MXenes are employed as transport layers, device stability studies are still missing. Especially under real outdoor conditions where devices are subjected to the synergy of multiple stressors. In this work, functionalized 2D titanium carbide (Ti3C2) MXene is employed in normal PSC configuration, at the interface between the halide perovskite and the hole transport layer. The functionalization of the Ti3C2 MXene is made utilizing the same organic additive passivating the halide perovskite layer. The functionalizing strategy creates a continuous link between the MXene and the halide perovskite layer. Champion MXene-based PSCs revealed a approximate to 22% efficiency, in comparison with the control device showing 20.56%. Stability analyses under ISOS protocols under different conditions (dark, continuous light irradiation and real outdoor analysis) reveal that the enhancement of the PSCs lifespan is always observed when the MXene layer is employed. Analysis under continuous light irradaition (ISOS-L) reveal an almost 100% retention of the efficiency for the MXene-modified device, and outdoor testing (ISOS-O) carried out for > 600 h reveals a T(80 )of approximate to 600 h, while the control device degrades completely. To the best of the authors knowledge, this is the first report of the stability assesment of MXene-based PSCs carried out under real outdoor (ISOS-O) conditions.
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| 9. |
- Karimipour, Masoud, et al.
(author)
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Nanoparticles of Ni/NiO embedded in TiO(2) synthesized by the complex-polymer sol-gel method
- 2011
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In: Physica Scripta. - : IOP Publishing. - 0031-8949 .- 1402-4896. ; 84:3, s. 035702-
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Journal article (peer-reviewed)abstract
- Ni-doped TiO(2) nanoparticles were synthesized by the non-hydrous complex-polymer sol-gel method. Titanium isopropoxide was used as precursor and acetyl acetone (AcAc) and citric acid were used as polymer and complex agent, respectively. A series of Ni(x) : Ti(1-x)O(2) samples with x = 0.01, 0.03, 0.05 and 0.10 were prepared and subsequently annealed at 400, 600 and 800 degrees C. The structural and magnetic properties of Ni(x) : Ti(1-x)O(2) were studied by means of x-ray diffraction (XRD) and dc magnetometery. Samples annealed at 400 degrees C attained a particle size of 12 nm with structural phases of anatase, rutile and cubic NiO. From the blocking temperatures of the zero-field-cooled and field-cooled measurements, similar particle sizes (as from XRD) were obtained. The presence of ferro- and antiferromagnetic (AFM) interactions further confirms that the particles have different structural compositions. At 800 degrees C the particles have grown to about 30 nm with either a rutile or NiTiO(3)-type structure. The presence of NiTiO(3) is also seen in the magnetic measurements, which show the characteristic AFM peak at 23 K.
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| 10. |
- Karimipour, Masoud, et al.
(author)
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Room temperature magnetization in Co-doped anatase phase of TiO2
- 2013
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In: European Physical Journal. - : EDP Sciences. - 1286-0042 .- 1286-0050. ; 61:1, s. 10601-
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Journal article (peer-reviewed)abstract
- CoxTi1-xO2 films were deposited by spray pyrolysis technique on Si(1 0 0) substrates at 475 degrees C. A hydro-alcoholic solution containing titanium (iv) isopropoxide and Co(NO3)(2) with various Co doping levels from x = 0-0.015 in solution was used as spray solution. Grazing incident angle of X-ray diffraction illustrates that the CoxTi1-xO2 films are single phase and polycrystal with mixed orientations. Study of surface morphology of the films by atomic force microscope reveals that the annealing atmosphere does not significantly affect the grain size and the microstructure of the films. This study provides further insight into the importance of annealing atmosphere on magnetization of the films. Room temperature magneto-optical Kerr measurement was employed in polar mode. A hysteresis loop and a paramagnetic behavior have been recorded for samples annealed in H-2 ambient gas and air, respectively. Chemical composition analysis by X-ray photo-electron spectroscopy showed that Co atoms are bounded to oxygen and no metallic clusters are present. Moreover, it indicates the formation of high spin Co2+ for the sample x = 0.008 annealed in H-2 ambient gas. The origin of magnetization can be attributed to the contribution of oxygen vacancies in the spin polarization of the structure.
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