| 1. |
- Avila, Marta, et al.
(författare)
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Surface functionalized nanofibers for the removal of chromium(VI) from aqueous solutions
- 2014
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Ingår i: Chemical Engineering Journal. - : Elsevier BV. - 1385-8947 .- 1873-3212. ; 245, s. 201-209
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Tidskriftsartikel (refereegranskat)abstract
- Polyacrylonitrile (PAN) nanofibers functionalized with amine groups (PAN-NH2) were prepared using a simple one-step reaction route. The PAN-NH2 nanofibers were investigated for the removal of chromium(VI) from aqueous solutions. The adsorption and the kinetic characteristics were evaluated in batch process. The adsorption process showed pH dependence and the maximum Cr(VI) adsorption occurred at pH = 2. The Langmuir adsorption model described well the experimental adsorption data and estimated a maximum loading capacity of 156 mg/g, which is a markedly high value compared to other adsorbents reported. The kinetics studies indicated that the equilibrium was attained after 90 min and the experimental data followed a pseudo-second order model suggesting a chemisorption process as the rate limiting step. X-ray Photoelectron Spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR) revealed that the adsorption of Cr(VI) species on PAN-NH2 was facilitated through both electrostatic attraction and surface complexation. High desorption efficiency (> 90%) of Cr(VI) was achieved using diluted base solutions that may allow the reuse of PAN-NH2 nanofibers.
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| 2. |
- Burks, Terrance, 1969-, et al.
(författare)
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Studies on the adsorption of chromium(VI) onto 3-Mercaptopropionic acid coated superparamagnetic iron oxide nanoparticles
- 2014
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 425, s. 36-43
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Tidskriftsartikel (refereegranskat)abstract
- Chromium (Cr) in the form of Cr(VI) is deemed toxic in water due to its mutagenic and carcinogenic properties. For the successful removal of Cr(VI), we demonstrate a novel adsorbent consisting of superparamagnetic iron oxide nanoparticles (SPION) functionalized with 3-Mercaptopropionic acid (3-MPA). Fourier transform infrared spectroscopy (FT-IR) confirmed the functionalization of nanoparticles and presence of sulfonate groups. Batch adsorption experiments showed that the functionalized adsorbent recovered 45 mg of Cr(VI)/g of 3-MPA coated SPION at initial concentration of 50 mg/L aqueous solution at pH 1 with less than 1% of Fe dissolution from SPION. The results from X-ray photoelectron spectroscopy confirmed that Cr(VI) chemisorbed onto the adsorbent. Hence, the XPS spectra did not indicate any reduction of Cr(VI) to Cr(III) upon adsorption. The adsorption data were better fitted for the Freundlich model. Moreover, the Cr(VI) adsorption kinetics on functionalized SPION followed a pseudo-second order rate, revealing chemisorption as the dominant mechanism. The high Cr(VI) removal, rapid adsorption kinetics and stability of adsorbent indicate that 3-MPA coated SPION could be an efficient adsorbent for the removal of Cr(VI). (C) 2014 Elsevier Inc. All rights reserved.
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| 3. |
- Cindemir, Umut, et al.
(författare)
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Sputter-Deposited Indium-Tin Oxide Thin Films for Acetaldehyde Gas Sensing
- 2016
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Ingår i: Coatings. - : MDPI AG. - 2079-6412. ; 6:2
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Tidskriftsartikel (refereegranskat)abstract
- Reactive dual-target DC magnetron sputtering was used to prepare In-Sn oxide thin films with a wide range of compositions. The films were subjected to annealing post-treatment at 400 degrees C or 500 degrees C for different periods of time. Compositional and structural characterizations were performed by X-ray photoelectron spectroscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, Rutherford backscattering and scanning electron microscopy. Films were investigated for gas sensing at 200 degrees C by measuring their resistance response upon exposure to acetaldehyde mixed with synthetic air. We found that the relative indium-to-tin content was very important and that measurable sensor responses could be recorded at acetaldehyde concentrations down to 200 ppb, with small resistance drift between repeated exposures, for both crystalline SnO2-like films and for amorphous films consisting of about equal amounts of In and Sn. We also demonstrated that it is not possible to prepare crystalline sensors with intermediate indium-to-tin compositions by sputter deposition and post-annealing up to 500 degrees C.
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| 4. |
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| 5. |
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| 6. |
- Lansåker, Pia C., et al.
(författare)
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Au-Based Transparent Conductors for Window Applications : Effect of Substrate Material
- 2010
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Ingår i: Advances in Science and Technology. - 1662-0356. ; 75, s. 25-30
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Tidskriftsartikel (refereegranskat)abstract
- Thin films of Au were made by sputter deposition onto glass substrates with and without transparent and electrically conducting layers of SnO2:In. The Au films were up to ~11 nm in thickness and covered the range for thin film growth from discrete islands, via large scale coalescence and formation of a meandering conducting network, to the formation of a more or less “holey” film. Scanning electron microscopy and atomic force microscopy showed that the SnO2:In films were considerably rougher than the glass itself. This roughness influenced the Au film formation so that large scale coalescence set in at a somewhat larger thickness for films on SnO2:In than on glass. Measurements of spectral optical transmittance and electrical resistance could be reconciled with impeded Au film formation on the SnO2:In layer, leading to pronounced “plateaus” in the near infrared optical properties for Au films on SnO2:In and an accompanying change from such two-layer films having a lower resistance than the single gold film at thicknesses below large scale coalescence to the opposite behavior for larger film thicknesses.
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| 7. |
- Lansåker, Pia C, et al.
(författare)
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Au thin films deposited on SnO2:In and glass : Substrate effects on the optical and electrical properties
- 2011
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Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 519:6, s. 1930-1933
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Tidskriftsartikel (refereegranskat)abstract
- We report on a detailed study on the optical and electrical properties of Au films made by sputter deposition onto glass substrates with and without transparent and electrically conducting layers of SnO2:In. The Au films had thicknesses up to 10.7 nm and hence spanned the range for thin film growth from discrete islands, via large scale coalescence and formation of a meandering conducting network, to the formation of a more or less "holey" film. Scanning electron microscopy and atomic force microscopy demonstrated that the SnO2:In films were considerably rougher than the glass itself, and this roughness influenced the Au film formation so that large scale coalescence set in at a somewhat larger thickness for films on SnO2:In than on glass. Measurements of spectral optical transmittance and reflectance and of electrical resistance gave a fully consistent picture that could be reconciled with impeded Au film formation on the SnO2:In layer; this led to pronounced "plateaus" in the near infrared optical spectra for Au films on SnO2:In and a concomitant change from such two-layer films having a lower resistance than the single gold film at thicknesses below large scale coalescence to the opposite behavior for larger film thicknesses. Our work highlights the importance of the substrate roughness for transparent conductors comprising coinage metal films backed by wide band gap transparent conducting oxides.
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| 8. |
- Lansåker, Pia C, et al.
(författare)
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Characterization of gold nanoparticle films : Rutherford backscattering spectroscopy, scanning electron microscopy with image analysis, and atomic force microscopy
- 2014
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Ingår i: AIP Advances. - : AIP Publishing. - 2158-3226. ; 4:10, s. 107101-
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Tidskriftsartikel (refereegranskat)abstract
- Gold nanoparticle films are of interest in several branches of science and technology, and accurate sample characterization is needed but technically demanding. We prepared such films by DC magnetron sputtering and recorded their mass thickness by Rutherford backscattering spectroscopy. The geometric thickness d(g)-from the substrate to the tops of the nanoparticles-was obtained by scanning electron microscopy (SEM) combined with image analysis as well as by atomic force microscopy (AFM). The various techniques yielded an internally consistent characterization of the films. In particular, very similar results for d(g) were obtained by SEM with image analysis and by AFM.
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| 9. |
- Lansåker, Pia C, et al.
(författare)
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Thin gold films on SnO2:In : Temperature-dependent effects on the optical properties
- 2012
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Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 520:9, s. 3688-3691
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Tidskriftsartikel (refereegranskat)abstract
- Gold films with thicknesses of 5 +/- 0.5 nm were sputter deposited onto SnO2:In-coated glass kept at different temperatures up to 140 degrees C, and similar films, deposited onto substrates at 25 degrees C, were annealing post treated at the same temperatures. Nanostructures and optical properties were recorded by scanning electron microscopy and spectrophotometry in the 0.3 to 2.5 mu m wavelength range, respectively. Annealing had a minor influence on the optical transmittance despite significant changes in the scale of the nanostructure, whereas deposition onto substrates heated to 140 degrees C yielded granular films with strong plasmon absorption of luminous radiation. These results are of considerable interest for optical devices with gold films prepared at elevated temperature or operating at such temperature.
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| 10. |
- Lansåker, Pia C., et al.
(författare)
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Thin sputter deposited gold films on In2O3:Sn, SnO2:In, TiO2 and glass : Optical, electrical and structural effects
- 2013
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Ingår i: Solar Energy Materials and Solar Cells. - : Elsevier BV. - 0927-0248 .- 1879-3398. ; 117:SI, s. 462-470
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Tidskriftsartikel (refereegranskat)abstract
- Thin gold films are promising transparent conductors with many actual and potential uses in "green" technologies, transparent electronics, etc. These applications require different substrate materials, and hence it is important to understand the role of the substrate on Au thin film growth. Such effects have been studied in this work wherein Au films ranging from island structures, via large scale coalescence into meandering metal networks, to thin homogenous layers were deposited by DC magnetron sputtering onto glass substrates and In2O3:Sn (ITO), SnO2:In and TiO2 base layers backed by glass. Optical, electrical and structural properties were recorded for films deposited onto unheated substrates. We found distinct and characteristic differences in Au growth on the various backings. Thus ITO and SnO2:In base layers yielded gold films with island features remaining to larger thicknesses than for deposition directly onto glass, and the sheet resistance was lower for gold deposition onto SnO2:In and ITO only when the gold films were less than similar to 5 nm in thickness. Our results highlight the complexity of substrates' influence on thin film formation.
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