liu.seSearch for publications in DiVA
Change search
Link to record
Permanent link

Direct link
BETA
Käll, Per-Olov
Publications (10 of 81) Show all publications
Ballem, M. A., Söderlind, F., Nordblad, P., Käll, P.-O. & Odén, M. (2013). Growth of Gd2O3 nanoparticles inside mesoporous silica frameworks. Microporous and Mesoporous Materials, 168, 221-224
Open this publication in new window or tab >>Growth of Gd2O3 nanoparticles inside mesoporous silica frameworks
Show others...
2013 (English)In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 168, p. 221-224Article in journal (Refereed) Published
Abstract [en]

Gadolinium oxide (Gd2O3) nanoparticles with very small size, and narrow size distribution were synthesized by infiltration of Gd(NO3)3.6H2O as an oxide precursor into the pores of SBA-15 mesoporous silica using a wet-impregnation technique. High resolution transmission electron microscopy and X-ray diffraction show that during the hydrothermal treatment of the precursor at 550 °C, gadolinium oxide nanoparticles inside the silica pores are formed. Subsequent dissolution of the silica template by NaOH resulted in well dispersed nanoparticles with an average diameter of 3.6 ± 0.9 nm.

Place, publisher, year, edition, pages
Elsevier, 2013
Keywords
Gd2O3; Nanoparticles; Nanocasting; Mesoporous silica; SBA-15
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-67918 (URN)10.1016/j.micromeso.2012.10.009 (DOI)000313839800030 ()
Note

At the time of the defence, this publication was an unsubmitted manuscript

Available from: 2011-05-02 Created: 2011-05-02 Last updated: 2017-12-11Bibliographically approved
Khan, Y., Tajammul Hussain, S., Abbasi, M. A., Käll, P.-O. & Söderlind, F. (2013). On the decoration of 3D nickel foam with single crystal ZnO nanorod arrays and their cathodoluminescence study. Materials letters (General ed.), 90, 126-130
Open this publication in new window or tab >>On the decoration of 3D nickel foam with single crystal ZnO nanorod arrays and their cathodoluminescence study
Show others...
2013 (English)In: Materials letters (General ed.), ISSN 0167-577X, E-ISSN 1873-4979, Vol. 90, p. 126-130Article in journal (Refereed) Published
Abstract [en]

Starting with an ammonical solution of zinc acetate, dense single crystal ZnO nanorod arrays were grown directly on high surface area porous 3D nickel foam substrates using a low temperature hydrothermal route. Heterogeneous nucleation of the nanorods with diameters around 100 nm can be conveniently and reproducibly Controlled by adjusting the amount of ammonia added to the growth solution. X-ray diffraction and HRTEM analysis confirmed the single phase wurtzite structure and c-axis orientation of the as grown ZnO nanorod arrays. Cathodoluminescence measurements indicate that the as-grown nanorod arrays were rich in atomic defects and gave strong orange emissions in the visible region. The nanorod arrays on unique 3D substrate are expected to improve the sensitivity and efficiency of ZnO based electrochemical sensors and heterogeneous catalysts.

Place, publisher, year, edition, pages
Elsevier, 2013
Keywords
ZnO, Nanostructures, Porous materials, Cathodoluminescence
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-86622 (URN)10.1016/j.matlet.2012.09.033 (DOI)000311260700032 ()
Available from: 2012-12-20 Created: 2012-12-20 Last updated: 2017-12-06
Darmastuti, Z., Bhattacharyya, P., Andersson, M., Kanungo, J., Basu, S., Käll, P.-O., . . . Lloyd Spetz, A. (2013). SiC-FET methanol sensors for process control and leakage detection. Sensors and actuators. B, Chemical, 187(SI), 553-562
Open this publication in new window or tab >>SiC-FET methanol sensors for process control and leakage detection
Show others...
2013 (English)In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 187, no SI, p. 553-562Article in journal (Refereed) Published
Abstract [en]

Two types of SiC based field effect transistor sensors, with Pt or Ir gate, were tested to detect methanol in the concentration range of 0–1600 ppm for both process control and leak detection applications. The methanol response was investigated both with and without oxygen, since the process control might be considered as oxygen free application, while the sensor is operated in air during leak detection. Pt sensors offered very fast response with appreciably high response magnitude at 200 °C, while Ir sensors showed both higher response and response time up to 300 °C, but this decreased considerably at 350 °C. Cross sensitivity effect in presence of oxygen, hydrogen, propene and water vapor was also investigated. The presence of oxygen improved the response of both sensors, which is favorable for the leak detection application. Hydrogen had a large influence on the methanol response of both sensors, propene had a negligible influence, while water vapor changed direction of the methanol response for the Pt sensor. The detection mechanism and different sensing behavior of Pt and Ir gate sensors were discussed in the light of model reaction mechanisms derived from hybrid density-functional theory quantum-chemical calculations.

Keywords
SiC-FET sensor, methanol, quantum-chemical calculation, Pt, Ir, gas sensor
National Category
Engineering and Technology Natural Sciences
Identifiers
urn:nbn:se:liu:diva-85636 (URN)10.1016/j.snb.2013.04.019 (DOI)000324298300081 ()
Available from: 2012-11-26 Created: 2012-11-26 Last updated: 2018-09-14Bibliographically approved
Ahrén, M., Selegård, L., Söderlind, F., Linares, M., Kauczor, J., Norman, P., . . . Uvdal, K. (2012). A simple polyol-free synthesis route to Gd2O3 nanoparticles for MRI applications: an experimental and theoretical study. Journal of nanoparticle research, 14(8)
Open this publication in new window or tab >>A simple polyol-free synthesis route to Gd2O3 nanoparticles for MRI applications: an experimental and theoretical study
Show others...
2012 (English)In: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 14, no 8Article in journal (Refereed) Published
Abstract [en]

Chelated gadolinium ions, e. g., GdDTPA, are today used clinically as contrast agents for magnetic resonance imaging (MRI). An attractive alternative contrast agent is composed of gadolinium oxide nanoparticles as they have shown to provide enhanced contrast and, in principle, more straightforward molecular capping possibilities. In this study, we report a new, simple, and polyol-free way of synthesizing 4-5-nm-sized Gd2O3 nanoparticles at room temperature, with high stability and water solubility. The nanoparticles induce high-proton relaxivity compared to Gd-DTPA showing r(1) and r(2) values almost as high as those for free Gd3+ ions in water. The Gd2O3 nanoparticles are capped with acetate and carbonate groups, as shown with infrared spectroscopy, near-edge X-ray absorption spectroscopy, X-ray photoelectron spectroscopy and combined thermogravimetric and mass spectroscopy analysis. Interpretation of infrared spectroscopy data is corroborated by extensive quantum chemical calculations. This nanomaterial is easily prepared and has promising properties to function as a core in a future contrast agent for MRI.

Place, publisher, year, edition, pages
Springer Verlag (Germany), 2012
Keywords
Gadolinium oxide, Synthesis, Relaxivity, XPS, IR, Toxicity
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-81505 (URN)10.1007/s11051-012-1006-2 (DOI)000307273400028 ()
Note

Funding Agencies|VINNOVA|2008-03011|Centre in Nanoscience and Technology at LiTH (CeNano)||Swedish research council|621-2010-5014|SERC (Swedish e-Science Research Center)||

Available from: 2012-09-18 Created: 2012-09-18 Last updated: 2017-12-07
Khan, Y., Hussain, S., Söderlind, F., Käll, P.-O., Abbasi, M. A. & Durrani, S. K. (2012). Honeycomb β-Ni(OH)2 films grown on 3D nickel foam substrates at low temperature. Materials letters (General ed.), 69, 37-40
Open this publication in new window or tab >>Honeycomb β-Ni(OH)2 films grown on 3D nickel foam substrates at low temperature
Show others...
2012 (English)In: Materials letters (General ed.), ISSN 0167-577X, E-ISSN 1873-4979, Vol. 69, p. 37-40Article in journal (Refereed) Published
Abstract [en]

A simple method is presented to grow thick honeycomb β-Ni(OH)2 films on 3D nickel foam substrates at80 °C using nickel sulfate and ammonia as the starting materials. The porous honeycomb network structureof the films with pore openings about 0.5–1 μm wide is built from seamlessly connected polycrystallinenanowalls, approximately 10–20 nm thick. The amount of ammonia added to the growth solution and thegrowth time were found to be critical parameters in determining the morphology and pore structure ofthe films. Air annealing of the as-prepared films resulted in polycrystalline NiO films with morphologiessimilar to those of their hydroxide precursors.

Keywords
β-Ni(OH)2, NiO, Thick films, Porous materials, Crystal growth, FTIR
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:liu:diva-72991 (URN)10.1016/j.matlet.2011.11.058 (DOI)000300190300012 ()
Note
funding agencies|HEC, Pakistan||Available from: 2011-12-14 Created: 2011-12-14 Last updated: 2017-12-08
Darmastuti, Z., Bhattacharyya, P., Basu, S., Käll, P.-O., Ojamäe, L. & Lloyd Spetz, A. (2012). SiC - FET Sensors for methanol leakage detection. In: Proceeding of the 14th International Meeting on Chemical Sensors (IMCS 2012): . Paper presented at 14th International Meeting on Chemical Sensors (IMCS 2012), 20-23 May 2012, Nürnberg, Germany (pp. 1579-1582).
Open this publication in new window or tab >>SiC - FET Sensors for methanol leakage detection
Show others...
2012 (English)In: Proceeding of the 14th International Meeting on Chemical Sensors (IMCS 2012), 2012, p. 1579-1582Conference paper, Published paper (Other academic)
Abstract [en]

Pt and Ir SiC based Field Effect Transistor sensors were tested to detect low concentration of methanol (<200 ppm) for both process control and leak detection applications. Pt sensors gave good and very fast response at 200°C, while Ir sensors gave larger but much slower response. The presence of oxygen improved the response of the sensor which was favorable for the leak detection application. The influence of hydrogen and propene to the sensor response was also studied. Beside the experimental work, the detection mechanism and different sensing behavior of Pt and Ir were studied by quantum chemical calculations.

National Category
Other Chemical Engineering
Identifiers
urn:nbn:se:liu:diva-92403 (URN)10.5162/IMCS2012/P2.5.3 (DOI)978-3-9813484-2-2 (ISBN)
Conference
14th International Meeting on Chemical Sensors (IMCS 2012), 20-23 May 2012, Nürnberg, Germany
Available from: 2013-05-10 Created: 2013-05-10 Last updated: 2015-03-09Bibliographically approved
Kanungo, J., Andersson, M., Darmastuti, Z., Basu, S., Käll, P.-O., Ojamäe, L. & Lloyd Spetz, A. (2011). Development of SiC-FET methanol sensor. Sensors and actuators. B, Chemical, 160(1), 72-78
Open this publication in new window or tab >>Development of SiC-FET methanol sensor
Show others...
2011 (English)In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 160, no 1, p. 72-78Article in journal (Refereed) Published
Abstract [en]

A silicon carbide based field effect transistor (SiC-FET) structure was used for methanol sensing. Due to the chemical stability and wide band gap of SiC, these sensors are suitable for applications over a wide temperature range. Two different catalytic metals, Pt and Ir, were tested as gate contacts for detection of methanol. The sensing properties of both Ir gate and Pt gate SiC-FET sensors were investigated in the concentration range 0.3–5% of methanol in air and in the temperature range 150–350 °C. It was observed that compared to the Ir gate sensor, the Pt gate sensor showed higher sensitivity, faster response and recovery to methanol vapour at comparatively lower temperature, with an optimum around 200 °C. Quantum-chemical calculations were used to investigate the MeOH adsorption and to rationalize the observed non-Langmuir behavior of the response functions. The methanol sensing mechanism of the SiC-FET is discussed.

Place, publisher, year, edition, pages
Amsterdam, Nederländerna: Elsevier B.V., 2011
Keywords
SiC, FET sensor, Pt, Ir, Methanol, Gas sensor, Solid state sensor
National Category
Engineering and Technology Natural Sciences
Identifiers
urn:nbn:se:liu:diva-72077 (URN)10.1016/j.snb.2011.07.015 (DOI)000298768100011 ()
Note

funding agencies|Swedish Research Council| VR 348-2007-6837 VR 621-2008-3229 VR 621-2008-4859 |

Available from: 2011-11-15 Created: 2011-11-15 Last updated: 2017-12-08
Gustafsson, H., Ahrén, M., Söderlind, F., Córdoba Gallego, J. M., Käll, P.-O., Nordblad, P., . . . Engström, M. (2011). Magnetic and Electron Spin Relaxation Properties of (GdxY1-x)2O3 (0 ≤ x ≤ 1) Nanoparticles Synthesized by the Combustion Method. Increased Electron Spin Relaxation Times with Increasing Yttrium Content. The Journal of Physical Chemistry C, 115(13), 5469-5477
Open this publication in new window or tab >>Magnetic and Electron Spin Relaxation Properties of (GdxY1-x)2O3 (0 ≤ x ≤ 1) Nanoparticles Synthesized by the Combustion Method. Increased Electron Spin Relaxation Times with Increasing Yttrium Content
Show others...
2011 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 115, no 13, p. 5469-5477Article in journal (Refereed) Published
Abstract [en]

The performance of a magnetic resonance imaging contrast agent (CA) depends on several factors, including the relaxation times of the unpaired electrons in the CA. The electron spin relaxation time may be a key factor for the performance of new CAs, such as nanosized Gd2O3 particles. The aim of this work is, therefore, to study changes in the magnetic susceptibility and the electron spin relaxation time of paramagnetic Gd2O3 nanoparticles diluted with increasing amounts of diamagnetic Y2O3. Nanoparticles of (GdxY1-x)2O3 (0 e x e 1) were prepared by the combustion method and thoroughly characterized (by X-ray di.raction, transmission electron microscopy, thermogravimetry coupled with mass spectroscopy, photoelectron spectroscopy, Fourier transform infrared spectroscopy, and magnetic susceptibility measurements). Changes in the electron spin relaxation time were estimated by observations of the signal line width in electron paramagnetic resonance spectroscopy, and it was found that the line width was dependent on the concentration of yttrium, indicating that diamagnetic Y2O3 may increase the electron spin relaxation time of Gd2O3 nanoparticles.

Place, publisher, year, edition, pages
United States: American Chemical Society, 2011
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-67439 (URN)10.1021/jp111368t (DOI)000288885900036 ()
Available from: 2011-04-13 Created: 2011-04-12 Last updated: 2017-12-11Bibliographically approved
Selegård, L., Khranovskyy, V., Söderlind, F., Vahlberg, C., Ahrén, M., Käll, P.-O., . . . Uvdal, K. (2010). Biotinylation of ZnO Nanoparticles and Thin Films: A Two-Step Surface Functionalization Study. ACS APPLIED MATERIALS and INTERFACES, 2(7), 2128-2135
Open this publication in new window or tab >>Biotinylation of ZnO Nanoparticles and Thin Films: A Two-Step Surface Functionalization Study
Show others...
2010 (English)In: ACS APPLIED MATERIALS and INTERFACES, ISSN 1944-8244, Vol. 2, no 7, p. 2128-2135Article in journal (Refereed) Published
Abstract [en]

This study reports ZnO nanoparticles and thin film surface modification using a two-step functionalization strategy. A small silane molecule was used to build up a stabilizing layer and for conjugation of biotin (vitamin B7), as a specific tag. Biotin was chosen because it is a well-studied bioactive molecule with high affinity for avidin. ZnO nanoparticles were synthesized by electrochemical deposition under oxidizing condition, and ZnO films were prepared by plasma-enhanced metal organic chemical vapor deposition. Both ZnO nanoparticles and ZnO thin films were surface modified by forming a (3-mercaptopropyl)trimethoxysilane (MPTS) layer followed by attachment of a biotin derivate. lodoacetyl-PEG2-biotin molecule was coupled to the thiol unit in MPTS through a substitution reaction. Powder X-ray diffraction, transmission electron microscopy, X-ray photoemission electron microscopy, atomic force microscopy. X-ray photoelectron spectroscopy, and near-edge X-ray absorption fine structure spectroscopy were used to investigate the as-synthesized and functionalized ZnO materials. The measurements showed highly crystalline materials in both cases with a ZnO nanoparticle diameter of about 5 nm and a grain size of about 45 nm for the as-grown ZnO thin films. The surface modification process resulted in coupling of silanes and biotin to both the ZnO nanoparticles and ZnO thin films. The two-step functionalization strategy has a high potential for specific targeting in bioimaging probes and for recognition studies in biosensing applications.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 1155 16TH ST, NW, WASHINGTON, DC 20036 USA, 2010
Keywords
ZnO nanoparticles, thin films XRD, TEM, XPS, NEXAFS, biotin, PEEM
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-58542 (URN)10.1021/am100374z (DOI)000280367000049 ()
Available from: 2010-08-13 Created: 2010-08-13 Last updated: 2015-05-29
Becker, R., Liedberg, B. & Käll, P.-O. (2010). CTAB promoted synthesis of Au nanorods - Temperature effects and stability consideration. Journal of Colloid and Interface Science, 343(1), 25-30
Open this publication in new window or tab >>CTAB promoted synthesis of Au nanorods - Temperature effects and stability consideration
2010 (English)In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 343, no 1, p. 25-30Article in journal (Refereed) Published
Abstract [en]

A systematic study is performed of the influence of surfactant and temperature on the aspect ratio and monodispersity of Au nanorods, synthesized by a seed-mediated growth technique in water using cetyltrimethylammonium bromide (CTAB) as surfactant. The changes in aspect ratio with temperature show an "anomalous" behaviour, where the aspect ratio first decreases with increasing temperature, reaching a minimum at about 55oC, and after that increases again reaching a maximum at about 80oC. A physical explanation of the observed behaviour is proposed. It has also been studied how the CTAB concentration in the cleansing water used in the post-synthesis treatment of the samples affected the stability of the gold suspension. It was found that without the presence of a surfactant such as CTAB in the washing medium, only very few centrifugations can be carried out without considerable loss of product. Characterization of prepared samples was performed with UV-Vis and TEM.

Keywords
Aspect ratio; CTAB; Gold; Nanorods; Stability; Synthesis
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-53753 (URN)10.1016/j.jcis.2009.10.075 (DOI)000274548900004 ()
Available from: 2010-02-02 Created: 2010-02-02 Last updated: 2017-12-12
Organisations

Search in DiVA

Show all publications