| 1. |
- Arvizu, Miguel A, et al.
(författare)
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Electrochromic WO3 thin films attain unprecedented durability by potentiostatic pretreatment
- 2019
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Ingår i: Journal of Materials Chemistry A. - : ROYAL SOC CHEMISTRY. - 2050-7488 .- 2050-7496. ; 7:6, s. 2908-2918
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Tidskriftsartikel (refereegranskat)abstract
- Electrochromic windows and glass facades are able to impart energy efficiency jointly with indoor comfort and convenience. Long-term durability is essential for practical implementation of this technology and has recently attracted broad interest. Here we show that a simple potentiostatic pretreatment of sputterdeposited thin films of amorphous WO3-the most widely studied electrochromic material-can yield unprecedented durability for charge exchange and optical modulation under harsh electrochemical cycling in a Li-ion-conducting electrolyte and effectively evades harmful trapping of Li. The pretreatment consisted of applying a voltage of 6.0 V vs. Li/Li+ for several hours to a film backed by a transparent conducting In2O3: Sn layer. Associated compositional and structural modifications were probed by several techniques, and improved durability was associated with elemental intermixing at the WO3/ITO and ITO/glass boundaries as well as with carbonaceous solid-electrolyte interfacial layers on the WO3 films. Our work provides important new insights into long-term durability of ion-exchange-based devices.
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| 2. |
- Cindemir, Umut, 1986-, et al.
(författare)
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Characterization of nanocrystalline-nanoporous nickel oxide thin films prepared by reactive advanced gas deposition
- 2019
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Ingår i: Materials Chemistry and Physics. - : ELSEVIER SCIENCE SA. - 0254-0584 .- 1879-3312. ; 227, s. 98-104
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Tidskriftsartikel (refereegranskat)abstract
- Nanocrystalline-nanoporous Ni oxide is of much interest for gas sensors and other applications. Reactive advanced gas deposition (AGD) stands out as a particularly promising technique for making thin films of this material owing to the techniques ability to separate between the growth of individual nanoparticles and their subsequent deposition to create a consolidated material on a substrate. Here we report on the characterization of Ni oxide films, made by reactive AGD, by several methods. X-ray diffractometry showed that the films had a face centered cubic NiO structure, and scanning electron microscopy indicated a compact nanoparticulate composition. X-ray photoelectron spectroscopy showed the presence of Ni3+ and demonstrated that these states became less prominent upon heat treatment in air. Extended x-ray absorption fine structure analysis elucidated the local atomic structure; in particular, data on interatomic distances and effects of annealing on local disorder showed that the Ni oxide nanoparticles crystallize upon annealing while maintaining their nanoparticle morphology, which is a crucial feature for reproducible fabrication of Ni oxide thin films for gas sensors. Importantly, several techniques demonstrated that grain growth remained modest for annealing temperatures as high as 400 degrees C for 1700-nm-thick films. The present article is a sequel to an earlier one [U. Cindemir et al., Sensors and Actuators B 242 (2017) 132-139] in which we reported on fluctuation-enhanced and conductometric gas sensing with Ni oxide films prepared by AGD.
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| 3. |
- Ji, Yu -Xia, et al.
(författare)
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Synergistic TiO2/VO2 Window Coating with Thermochromism, Enhanced Luminous Transmittance, and Photocatalytic Activity
- 2019
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Ingår i: Joule. - : Elsevier. - 2542-4351. ; 3:10, s. 2457-2471
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Tidskriftsartikel (refereegranskat)abstract
- Modern buildings tend to be ‘‘energy guzzlers’’ and have indoor environments with unhealthy air. Glazing with TiO2/VO2 bilayer coatings (1) exhibits enhanced photocatalytic air purification compared with single-layer TiO2 due to heating from the underlying infrared-absorbing VO2 film, (2) is thermochromic thanks to the VO2 and admits less solar energy inflow when there is a cooling demand, and (3) has significantly improved luminous transmittance as a result of antireflection due to TiO2. These coatings were deposited by reactive DC magnetron sputtering onto heated glass; they were nanocrystalline, and the anatase phase prevailed in TiO2. The VO2 coatings showed well-developed thermochromism.The photocatalytic degradation rate of stearic acid was almost doubled for the TiO2/VO2 bilayer film compared with that for single-layer TiO2. Our results demonstrate an important, and hitherto unexplored, synergy between photocatalysis, thermochromism, and high luminous transmittance which exploits spectral-selective material properties for solar illumination.
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| 4. |
- Karlsson, Stefan, et al.
(författare)
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“Transparent Intelligence” for Sustainable Development
- 2018
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Ingår i: Abstracts. ; , s. 208-
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Konferensbidrag (refereegranskat)abstract
- Transparent materials are essential in everyone’s life. They enable daylight to reach the interior of buildings, thereby contributing to both our physical and mental well-being; they are the primary component for communication via optical fibers and a key component in electronic devices such as protective cover and/or dielectric material; and they enable clean energy production through solar panels or algae reactors by acting as protective and light transmitting barriers. Adding functions to transparent materials in an intelligent way creates further opportunities to use and enhance the beneficial impacts of transparency. The concept Transparent Intelligence covers transparent materials and products with integral intelligent functions – passive, active or interactive. By using Transparent Intelligence it is possible to embrace many of the societal challenges that we are facing today. The concept can be divided into five broad industrial sectors: Built Environment, Information and Communication Technologies (ICT), Solar Energy, Mobility, and Materials. A perspective on how Transparent Intelligence can improve the sustainable development of our world will be presented, using examples of electrochromic windows for energy-efficient buildings, photocatalytic coatings for improved indoor air quality, transparent conductive coatings for antennas, bandpass filters for mobile phone indoor coverage, UV down-converting components for efficient solar energy, hygienic surfaces for infection mitigation on electronic devices, printed electronics for sustainable glass packaging, and IR-reflecting coatings for fire safety.
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| 5. |
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| 6. |
- Qu, Hui-Ying, et al.
(författare)
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Cation/Anion-based electrochemical degradation and rejuvenation of electrochromic nickel oxide films
- 2018
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Ingår i: ChemElectroChem. - : Wiley. - 2196-0216. ; 5:22, s. 3548-3556
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Tidskriftsartikel (refereegranskat)abstract
- Ni oxide thin films are widely used in electrochromic (EC) devices with variable throughput of visible light and solarenergy. However, the mechanisms underlying the optical modulation – and its degradation under extended operationand subsequent rejuvenation – are poorly understood especially for Li+-conducting electrolytes. Here, we report a comprehensive study of the EC properties of sputter-deposited Ni oxide films immersed in an electrolyte of LiClO4 in propylene carbonate. Cyclic voltammetry and optical transmittance measurements were used to document degradation and subsequent potentiostatic rejuvenation. X-ray diffraction did not show evidence for accompanying changes in crystallinity, whereas vibrational spectroscopy indicated that degraded films had carbonaceous surface layers. Time-of-flight elastic recoil detection analysis demonstrated that both Li+ and Cl-based ions participate in the electrochromism and its degradation and rejuvenation. A major result was that degradation is associated with a reduced difference in the concentrations of Li+ and Cl based ions in the nickel oxide during extended electrochemical cycling, and rejuvenation of degraded films is achieved by removal of Li+ ions and accumulation of Cl-based anions to regain their initial concentration difference. Our work provides new insights into the use of ion-exchange-based devices incorporating nickel oxide.
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| 7. |
- Topalian, Zareh, et al.
(författare)
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Spectroscopic study of the photofixation of SO2 on anatase TiO2 thin films and their oleophobic properties
- 2012
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 4:2, s. 672-679
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Tidskriftsartikel (refereegranskat)abstract
- Photoinduced SO2 fixation on anatase TiO2 films was studied by in situ Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS). The TiO2 films were prepared by reactive DC magnetron sputtering and were subsequently exposed to 50 ppm SO2 gas mixed in synthetic air and irradiated with UV light at substrate temperatures between 298 and 673 K. Simultaneous UV irradiation and SO2 exposure between 373 and 523 K resulted in significant sulfur (S) deposits on crystalline TiO2 films as determined by XPS, whereas amorphous films contained negligible amounts of S. At substrate temperatures above 523 K, the S deposits readily desorbed from TiO2. The oxidation state of sulfur successively changed from S4+ for SO2 adsorbed on crystalline TiO2 films at room temperature without irradiation to S6+ for films exposed to SO2 at elevated temperatures with simultaneous irradiation. In situ FTIR was used to monitor the temporal evolution of the photoinduced surface reaction products formed on the TiO2 surfaces. It is shown that band gap excitation of TiO2 results in photoinduced oxidation of SO2, which at elevated temperatures become coordinated to the TiO2 lattice through interactions with O vacancies and form sulfite and sulfate surface species. These species makes the surface acidic, which is manifested in nondetectable adherence of stearic acid to the modified surface. The modified films show good chemical stability as evidenced by sonication and repeated recycling of the films. The results suggest a new method to functionalize wide band gap oxide surfaces by means of photoinduced reactions in reactive gases at elevated substrate temperatures. In the case of anatase TiO2 in reactive SO2 gas, we here show that such functionalization yields surfaces with excellent oleophobic properties, as probed by adhesion of stearic acid.
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| 8. |
- Österlund, Lars, 1967-, et al.
(författare)
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Novel multi-functional self-cleaning, air cleaning and thermochromic films for the built environment
- 2018
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Ingår i: FMNT Functional Materials and Nanotechnologies. ; , s. 63-
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Konferensbidrag (refereegranskat)abstract
- Spectrally selective photocatalytic multilayer films that exhibit dramatically enhanced photochemical reactivity upon solar light activation were fabricated. It is shown that synergistically enhanced physciochemcial properties can be achieved the surpass those of the constituting single-layer films. We present two case studies: TiO2/VO2 and TiO2/TiAlN bilayer films made by reactive dc magnetron sputtering. The TiO2/VO2 bilayer exhibits enhanced near-infrared light absorption, which thereby heats the TiO2 film by more than 15 degrees, resulting in an almost 2-fold increase of the reaction rate for photo-degradation of stearic acid layers. In addition, the TiO2/VO2 bilayer stack exhibited anti-reflective properties, and enhanced solar modulation (∼ 9%) compared to VO2, and ∼ 20% increased solar absorptance compared to TiO2. In the second example, bilayer TiO2/TiAlN films yielded an almost 10-fold enhancement of the quantum yield for acetaldehyde removal (on par with state-of-the-art, heterojunction photocatalysts), and an associated temperature rise larger than 120 degrees. Both findings can be understood by thermal activation to the increase the surface reaction kinetics, where water desorption from the oxide plays and important role. We generalize the results, and discuss their implications for green building technology and possible scenarios for their implementation.References1. Yu-Xia Ji, Andreas Mattsson, Gunnar A. Niklasson, Claes-Göran Granqvist, Lars Österlund TiO2/VO2 bilayer coatings for glazing: Synergetically enhanced photocatalytic, thermochromic, and luminous properties, submitted to Advanced Functional Materials 2018.2. Lars Österlund, Andreas Mattsson, Joel Martin, Spectrally selective heat absorptive bilayer photocatalyst with enhanced reactivity: TiO2/TiAlN, Topics in Catalysis, in press.
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| 9. |
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| 10. |
- Österlund, Lars, 1967-, et al.
(författare)
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Spectrally selective nanocoatings with synergistically enhanced photocatalytic and solar light modulation properties
- 2019
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Spectrally selective nanocoatings that exhibit synergistically enhanced solar light modulation, luminous transmittance and catalytic properties can be made by combining dielectric film stacks with complementary optical and structural properties. Here we show two case studies:1)TiO2/VO2 luminous transparent bilayers that exhibits enhanced near-infrared light absorption and heats the TiO2 film by up to ~ 30°C resulting in ~ 2-fold increase of the photocatalytic reaction rate. The TiO2/VO2 bilayer stack exhibits anti-reflective properties, and enhanced solar light modulation (∼ 9%) compared to VO2, and ∼ 20 times% increased solar absorptance compared to TiO2. In addition the TiO2 chemically protects the VO2 layer avoiding oxidation to vanadium pentoxide. 2)TiO2/TiAlN solar absorber bilayers that yield an almost ~ 10-fold enhancement of the quantum yield for acetaldehyde removal (on par with state-of-the-art, heterojunction photocatalysts), and an associated temperature rise ~120 °C.
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