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Experimental and quantum-chemical studies of the surface interactions between organic molecules and nanocrystals of (a) RE2O3 (RE = Y or Gd); and (b) TiOb2
Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology.ORCID iD: 0000-0002-7171-5383
2005 (English)Licentiate thesis, comprehensive summary (Other academic)
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.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet , 2005. , 67 p.
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1198
National Category
Inorganic Chemistry Physical Chemistry
Identifiers
URN: urn:nbn:se:liu:diva-29720Local ID: LiU-TEK-LIC-2005:53ISBN: 91-85457-33-7 (print)OAI: oai:DiVA.org:liu-29720DiVA: diva2:250537
Presentation
(English)
Opponent
Supervisors
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2015-03-11Bibliographically approved
List of papers
1. Synthesis and characterisation of Gd2O3 nanocrystals functionalised by organic acids
Open this publication in new window or tab >>Synthesis and characterisation of Gd2O3 nanocrystals functionalised by organic acids
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2005 (English)In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 288, no 1, 140-148 p.Article in journal (Refereed) Published
Abstract [en]

Nanocrystals of Gd2O3 have been prepared by various methods, using, e.g., trioctylphosphine oxide (TOPO), diethylene glycol (DEG) or glycine. The crystalline particles were of sizes 5 to 15 nm. Different carboxylic acids, e.g., oleic acid or citric acid, were adsorbed onto the surface of the particles made with DEG. IR measurements show that the molecules coordinate to the Gd2O3 surface via the carboxylate group in a bidentate or bridging manner. The organic-acid/particle complexes were characterised by XRPD, TEM, FTIR, Raman, and XPS.

Keyword
Nanocrystals; Synthesis; Functionalisation; IR; XPS
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-13295 (URN)10.1016/j.jcis.2005.02.089 (DOI)000229861600019 ()
Available from: 2008-05-21 Created: 2008-05-21 Last updated: 2015-03-11
2. Surface interactions between Y2O3 nanocrystals and organic molecules—an experimental and quantum-chemical study
Open this publication in new window or tab >>Surface interactions between Y2O3 nanocrystals and organic molecules—an experimental and quantum-chemical study
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2005 (English)In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 592, no 1-3, 124-140 p.Article in journal (Refereed) 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.

Keyword
Ab initio quantum chemical methods and calculations; X-ray photoelectron spectroscopy; Chemisorption; Yttrium; Alcohols; Carboxylic acid; Silane
National Category
Chemical Sciences
Identifiers
urn:nbn:se:liu:diva-13296 (URN)10.1016/j.susc.2005.07.027 (DOI)000232461700015 ()
Available from: 2008-05-21 Created: 2008-05-21 Last updated: 2015-03-11Bibliographically approved
3. Towards Biocompatibility of RE2O3 Nanocrystals − Water and Organic Molecules Chemisorbed on Gd2O3 and Y2O3 Nanocrystals Studied by Quantum-Chemical Computations
Open this publication in new window or tab >>Towards Biocompatibility of RE2O3 Nanocrystals − Water and Organic Molecules Chemisorbed on Gd2O3 and Y2O3 Nanocrystals Studied by Quantum-Chemical Computations
2006 (English)In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 6, no 9, 2004-2008 p.Article in journal (Refereed) Published
Abstract [en]

Nanocrystals of Gd2O3/Y2O3 and their interaction with water, formic acid, diethylene glycol (DEG), and tetramethoxy silane (TMOS) have been studied by quantum-chemical calculations at the B3LYP level using solvent-coated clusters of gadolinia and yttria. Adsorption energies, surface geometries, electronic structures, and excitation spectra were calculated. The results concerning adsorption strengths and superparamagnetic high-spin states can provide insight into the design of molecular-capped RE2O3 nanocrystals to be used in vivo.

National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-36184 (URN)10.1021/nl061185w (DOI)000240465100030 ()30419 (Local ID)30419 (Archive number)30419 (OAI)
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2015-03-11
4. IR and quantum-chemical studies of carboxylic acid and glycine adsorption on rutile TiO2 nanoparticles
Open this publication in new window or tab >>IR and quantum-chemical studies of carboxylic acid and glycine adsorption on rutile TiO2 nanoparticles
2006 (English)In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 296, no 1, 71-78 p.Article in journal (Refereed) Published
Abstract [en]

  Nanocrystalline TiO2 powders of the rutile polymorph, synthesized by a sol–gel method, were treated with water solutions containing, respectively, formic, acetic, and citric acid and glycine in order to study the adsorption properties of these organic species. The samples were characterized by FTIR, Raman, powder XRD, and TEM. It was found that HCOOH, CH3COOH and HOC(COOH)(CH2COOH)2—but not NH2CH2COOH—adsorbed onto TiO2. The adsorption of HCOOH, CH3COOH and NH2CH2COOH onto the (110) surface of rutile was also studied by quantum-chemical periodic density functional theory (DFT) calculations. The organic molecules were from the computations found to adsorb strongly to the surfaces in a bridge-coordinating mode, where the two oxygens of the deprotonated carboxylic acid bind to two surface titanium ions. Surface relaxation is found to influence adsorption geometries and energies significantly. The results from DFT calculations and ab initio molecular-dynamics simulations of formic acid adsorption onto TiO2 are compared and match well with the experimental IR measurements, supporting the bridge-binding geometry of carboxylic-acid adsorption on the TiO2 nanoparticles.

Keyword
Titanium oxide; Nanoparticle; Adsorption; Carboxylic acid; Glycine; FTIR; Raman; Quantum-chemical calculations
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-36193 (URN)10.1016/j.jcis.2005.08.037 (DOI)000236185600010 ()30468 (Local ID)30468 (Archive number)30468 (OAI)
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2015-03-11

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