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ZnO Nanoparticles Functionalized with Organic Acids: An Experimental and Quantum-Chemical Study
Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry. Linköping University, The Institute of Technology. (Beräkningskemi)
Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
Linköping University, Department of Physics, Chemistry and Biology, Inorganic Chemistry. Linköping University, Faculty of Science & Engineering.
Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
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2009 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 113, no 40, 17332-17341 p.Article in journal (Refereed) Published
Abstract [en]

Electrochemical synthesis and physical characterization of ZnO nanoparticles functionalized with four different organic acids, three aromatic (benzoic, nicotinic, and trans-cinnamic acid) and one nonaromatic (formic acid), are reported. The functionalized nanoparticles have been characterized by X-ray powder diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, UV−vis, and photoluminescence spectroscopy. The adsorption of the organic acids at ZnO nanoparticles was further analyzed and interpreted using quantum-chemical density-functional theory computations. Successful functionalization of the nanoparticles was confirmed experimentally by the measured splitting of the carboxylic group stretching vibrations as well as by the N(1s) and C(1s) peaks from XPS. From a comparison between computed and experimental IR spectra, a bridging mode adsorption geometry was inferred. PL spectra exhibited a remarkably stronger near band edge emission for nanoparticles functionalized with formic acid as compared to the larger aromatic acids. From the quantum-chemical computations, this was interpreted to be due to the absence of aromatic adsorbate or surface states in the band gap of ZnO, caused by the formation of a complete monolayer of HCOOH. In the UV−vis spectra, strong charge-transfer transitions were observed.

Place, publisher, year, edition, pages
2009. Vol. 113, no 40, 17332-17341 p.
Keyword [en]
nanoparticles, ZnO, organic acids, adsorption, synthesis, XPS, UV-vis, quantum chemical calculations
National Category
Physical Chemistry
Identifiers
URN: urn:nbn:se:liu:diva-50783DOI: 10.1021/jp905481vOAI: oai:DiVA.org:liu-50783DiVA: diva2:272172
Available from: 2009-10-14 Created: 2009-10-14 Last updated: 2017-12-12
In thesis
1. Theoretical Investigations of Water Clusters, Ice Clathrates and Functionalized Nanoparticles
Open this publication in new window or tab >>Theoretical Investigations of Water Clusters, Ice Clathrates and Functionalized Nanoparticles
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Nanosized structures are of intermediate size between individual molecules and bulkmaterials which gives them several unique properties. At the same time their relative limitedsizes make them suitable for studies by the methods of computational chemistry. In this thesiswater clusters, ice clathrates and functionalized metal-oxide nanoparticles have been studiedby quantum-chemical calculations and statistical thermodynamics.

The stabilities of water clusters composed of up to 100 molecules have been investigated. Themultitude of possible H-bonded topologies and their importance for determining theproperties of the clusters have been highlighted. Several structural characteristics of thehydrogen bonded network have been examined and the structural factors that determine thestability of an H-bonded network have been identified. The stability of two kinds of oxygenframeworks for water clusters have been analyzed, taking into account thermal energy andentropy corrections. Clusters with many 4-coordinated molecules have been found to be lowerin energy at low temperatures whereas the clusters with less-coordinated molecules dominateat higher temperatures. The equilibrium size distribution of water clusters as a function oftemperature and pressure has been computed using statistical thermodynamics. Themicroscopic local structure of liquid water has been probed by utilizing information from thestudied water clusters. The average number of H-bonds in liquid water has been predicted byfitting calculated average IR spectra for different coordination types in water clusters toexperimental IR spectra.

Water can form an ice-like structure that encloses various molecules such as methane. Thesemethane hydrates are found naturally at the ocean floor and in permafrost regions and canconstitute a large unemployed energy resource as well as a source of an effective green-housegas. The pressure dependencies of the crystal structures, lattice energies and phase transitionsfor the three methane hydrates with the clathrate structures I, II and H have been mapped out.

Zinc oxide is a semiconducting material with interesting luminescence properties that can beutilized in optical devices, such as photodetectors, light emitting devices and biomarkers. Theeffect of water molecules adsorbed on the ZnO surface when adsorbing organic acids havebeen investigated. Changes in optical properties by the adsorption of carboxylic acids havebeen studied and compared with experimental results. Aromatic alcohols at TiO2 metal-oxidenanoparticles have been studied as model systems for dye-sensitizied solar cells. Adsorptiongeometries are predicted and the influence from the adsorbed molecules on the electronicproperties has been studied.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2009. 52 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1254
National Category
Other Basic Medicine
Identifiers
urn:nbn:se:liu:diva-52746 (URN)978-91-7393-636-1 (ISBN)
Public defence
2009-06-09, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 10:15 (Swedish)
Opponent
Supervisors
Available from: 2010-01-18 Created: 2010-01-12 Last updated: 2015-03-09Bibliographically approved
2. Synthesis, Surface Modification, and Characterization of Metal Oxide Nanoparticles: Nanoprobes for Signal Enhancement in Biomedical Imaging
Open this publication in new window or tab >>Synthesis, Surface Modification, and Characterization of Metal Oxide Nanoparticles: Nanoprobes for Signal Enhancement in Biomedical Imaging
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis we investigate crystalline metal oxide nanoparticles of our own design to obtain nanoprobes for signal enhancement and bioimaging purposes. We report fabrication, surface modification and characterization of nanoparticles based on zinc (Zn), and rare earths (i.e. gadolinium (Gd) and europium (Eu)) singly and in combination. Our ZnO nanoparticles show high potential as fluorescent probes and Gd2O3 nanoparticles are promising as nanoprobes for MR signal enhancement. A combined Zn, Gd material is investigated as a potential dual probe. Interestingly, this nanoprobe shows, compared to the pure oxides, both increased fluorescent quantum yield and do induce improved relaxivity and by that enhanced MR signal. Nanoparticles composed of Eu doped Gd2O3 are also investigated in terms of their ability to interact with silicon surfaces. The presence of nanoparticles shows a catalytic effect on the annealing procedure of SiOx.

Surface modification of Gd and Zn based nanoparticles is performed, in a first step to improve stabilization of the nanoparticle core. Both carboxylic acids (paper I) and a thiol terminated silane (paper II and III) are used for this purpose. In a second step, a polyethylene glycol (PEG) is used for surface modification, to increase the biocompatibility of the nanoparticles. The Mal PEG NHS is chemically linked to thiol terminated silane groups via a maleimide coupling (Paper II). The presence of free NHS functional groups is intended to enable further linking of specific molecules for targeting purposes. The fluorescent dye rhodamine was, as a proof of concept, linked via the NHS functional group to the PEGylated Gd2O3 nanoparticles (Paper II). In Paper III, an alternative linking strategy is investigated, using iodized PEG2-Biotin for coupling via the iodide unit to the thiol terminated silane on ZnO nanoparticles. The resulting surface modified nanoparticles are investigated by means of coordination chemistry and coupling efficiency using X-ray photoelectron spectroscopy, near edge X-ray absorption fine structure  spectroscopy and infrared spectroscopy.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2013. 58 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1510
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-91849 (URN)978-91-7519-646-6 (ISBN)
Public defence
2013-05-24, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 10:15 (Swedish)
Opponent
Supervisors
Available from: 2013-05-03 Created: 2013-05-03 Last updated: 2015-06-03Bibliographically approved

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Lenz, AnnikaSelegård, LinneaSöderlind, FredrikLarsson, ArvidHoltz, Per-OlofUvdal, KajsaOjamäe, LarsKäll, Per-Olov

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