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Surface interactions between Y2O3 nanocrystals and organic molecules—an experimental and quantum-chemical study
Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.ORCID-id: 0000-0002-7171-5383
Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan.
Linköpings universitet, Institutionen för fysik, kemi och biologi, Sensorvetenskap och Molekylfysik. Linköpings universitet, Tekniska högskolan.
Linköpings universitet, Institutionen för fysik, kemi och biologi, Sensorvetenskap och Molekylfysik. Linköpings universitet, Tekniska högskolan.
Visa övriga samt affilieringar
2005 (Engelska)Ingår i: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 592, nr 1-3, s. 124-140Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

The surface interactions between Y2O3 nanocrystals and the organic molecules formic acid, diethylene glycol (DEG), and tetramethoxy silane (TMOS), have been studied experimentally and by quantum chemical calculations with the intent to elucidate the chemisorption characteristics such as adsorbate vibrational spectra and adsorption structures. Nanocrystal synthesis was performed by a colloidal method based on polyols and by a rapid combustion method. The products were experimentally characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS).

In the quantum chemical calculations, the B3LYP hybrid density functional ab initio method was used to study the chemisorption of formic acid, DEG and TMOS at the surface of Y12O18 clusters. From a comparison of calculated and experimental vibrational spectra, the binding mode for formic acid on Y2O3 was inferred to be of bridge or bidentate type. The XPS and FT-IR experiments showed that DEG is chemisorbed on the particle surface. The experimental IR spectra of DEG chemisorbed on Y2O3 were consistent with an adsorption mode where the hydroxyl groups are deprotonated according to the quantum-chemical computations. The adsorption energy is of the order of 370 kJ mol−1 for formic acid, 550 kJ mol−1 for DEG, and 60 kJ mol−1 for TMOS, according to the quantum chemical calculations.

Ort, förlag, år, upplaga, sidor
2005. Vol. 592, nr 1-3, s. 124-140
Nyckelord [en]
Ab initio quantum chemical methods and calculations; X-ray photoelectron spectroscopy; Chemisorption; Yttrium; Alcohols; Carboxylic acid; Silane
Nationell ämneskategori
Kemi
Identifikatorer
URN: urn:nbn:se:liu:diva-13296DOI: 10.1016/j.susc.2005.07.027ISI: 000232461700015OAI: oai:DiVA.org:liu-13296DiVA, id: diva2:18245
Tillgänglig från: 2008-05-21 Skapad: 2008-05-21 Senast uppdaterad: 2017-12-13Bibliografiskt granskad
Ingår i avhandling
1. Colloidal synthesis of metal oxide nanocrystals and thin films
Öppna denna publikation i ny flik eller fönster >>Colloidal synthesis of metal oxide nanocrystals and thin films
2008 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

A main driving force behind the recent years’ immense interest in nanoscience and nanotechnology is the possibility of achieving new material properties and functionalities within, e.g., material physics, biomedicine, sensor technology, chemical catalysis, energy storing systems, and so on. New (theoretical) possibilities represent, in turn, a challenging task for chemists and physicists. An important feature of the present nanoscience surge is its strongly interdisciplinary character, which is reflected in the present work.

In this thesis, nanocrystals and thin films of magnetic and ferroelectric metal oxides, e.g. RE2O3 (RE = Y, Gd, Dy), GdFeO3, Gd3Fe5O12, Na0.5K0.5NbO3, have been prepared by colloidal and sol-gel methods. The sizes of the nanocrystals were in the range 3-15 nm and different carboxylic acids, e.g. oleic or citric acid, were chemisorbed onto the surface of the nanoparticles. From FT-IR measurements it is concluded that the bonding to the surface takes place via the carboxylate group in a bidentate or bridging fashion, with some preference for the latter coordination mode. The magnetic properties of nanocrystalline Gd2O3 and GdFeO3 were measured, both with respect to magnetic resonance relaxivity and magnetic susceptibility. Both types of materials exhibit promising relaxivity properties, and may have the potential for use as positive contrast enhancing agents in magnetic resonance imaging (MRI). The nanocrystalline samples were also characterised by transmission electron microscopy (TEM), x-ray photoelectron spectroscopy (XPS), and quantum chemical calculations.

Thin films of Na0.5K0.5NbO3, GdFeO3 and Gd3Fe5O12 were prepared by sol-gel methods and characterized by x-ray powder diffraction (XRPD) and scanning electron microscopy (SEM). Under appropriate synthesis conditions, rather pure phase materials could be obtained with grain sizes ranging from 50 to 300 nm. Magnetic measurements in the temperature range 2-350 K indicated that the magnetization of the perovskite phase GdFeO3 can be described as the sum of two contributing terms. One term (mainly) due to the spontaneous magnetic ordering of the iron containing sublattice, and the other a susceptibility term, attributable to the paramagnetic gadolinium sublattice. The two terms yield the relationship M(T)=M0(T)+χ(T)*H for the magnetization. The garnet phase Gd3Fe5O12 is ferrimagnetic and showed a compensation temperature Tcomp ≈ 295 K.

Ort, förlag, år, upplaga, sidor
Institutionen för fysik, kemi och biologi, 2008
Serie
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1182
Nyckelord
nanoparticles, synthesis, contrast agents, functionalization, thin films
Nationell ämneskategori
Kemi
Identifikatorer
urn:nbn:se:liu:diva-11831 (URN)978-91-7393-899-0 (ISBN)
Disputation
2008-06-10, Planck, Fysikhuset, Campus Valla, Linköpings Universitet, Linköping, 10:15 (Engelska)
Opponent
Handledare
Tillgänglig från: 2008-05-21 Skapad: 2008-05-21 Senast uppdaterad: 2009-05-15
2. Experimental and quantum-chemical studies of the surface interactions between organic molecules and nanocrystals of (a) RE2O3 (RE = Y or Gd); and (b) TiOb2
Öppna denna publikation i ny flik eller fönster >>Experimental and quantum-chemical studies of the surface interactions between organic molecules and nanocrystals of (a) RE2O3 (RE = Y or Gd); and (b) TiOb2
2005 (Engelska)Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

The increasing interest for using nanocrystals in bio-medical and optical applications has highlighted the need of molecular functionalisation of nanocrystals. Knowledge of how to attach molecules to the nanocrystal surface is a key factor. This thesis focuses on the surface interactions between nanocrystals of (a) RE2O3 (RE = Y or Gd); and (b) TiO2 and organic molecules, which have been studied experimentally and by quantum-chemical calculations with the intent to elucidate the chemisorption characteristics such as adsorption geometries and energies.

(a) RE2O3 nanocrystal synthesis was performed by a colloidal method based on polyols and by a rapid combustion method. The products were experimentally characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), infrared spectroscopy (IR), Raman, and X-ray photoelectron spectroscopy (XPS). By quantum chemical calculations the chemisorption of formic acid, DEG, water and TMOS at the surface of RE12O18 clusters was studied. From comparison between calculated and experimental vibrational spectra, the binding mode for formic acid on RE2O3 was inferred to be of bridge or bidentate type. XPS and IR showed that DEG chemisorbs on the particle surface and experimental IR spectra of DEG chemisorbed on RE2O3 were consistent with an adsorption mode where the hydroxyl groups are deprotonated according to the quantum-chemical computations.

(b) Synthesis of single-phase rutile TiO2 nanocrystals was done by a sol-gel method and the nanocrystals was subsequently functionalized by organic acids and glycine. Quantum-chemical studies indicate that formic- and acetic acid adsorbs in a bridge or monodentate binding mode, while glycine is suggested to adsorb as a zwitterion with bridge bonded carboxylic group and a hydrogen bonded amino group. However, spectroscopic data showed that the amino acid, unlike the other acids did not adsorb on TiO2 under the given experimental conditions.

Ort, förlag, år, upplaga, sidor
Linköping: Linköpings universitet, 2005. s. 67
Serie
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1198
Nationell ämneskategori
Oorganisk kemi Fysikalisk kemi
Identifikatorer
urn:nbn:se:liu:diva-29720 (URN)LiU-TEK-LIC-2005:53 (Lokalt ID)91-85457-33-7 (ISBN)LiU-TEK-LIC-2005:53 (Arkivnummer)LiU-TEK-LIC-2005:53 (OAI)
Presentation
(Engelska)
Opponent
Handledare
Tillgänglig från: 2009-10-09 Skapad: 2009-10-09 Senast uppdaterad: 2015-03-11Bibliografiskt granskad

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HalvledarmaterialTekniska högskolanInstitutionen för fysik, kemi och biologiSensorvetenskap och MolekylfysikFysikalisk Kemi
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