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Zinc oxide nanowires in chemical bath on seeded substrates: Role of hexamine
2006 (engelsk)Inngår i: Journal of Sol-Gel Science and Technology, ISSN 0928-0707, E-ISSN 1573-4846, Vol. 39, nr 1, s. 49-56Artikkel i tidsskrift (Fagfellevurdert) Published
sted, utgiver, år, opplag, sider
2006. Vol. 39, nr 1, s. 49-56
Identifikatorer
URN: urn:nbn:se:kth:diva-13234DOI: 10.1007/s10971-006-6969-yISI: 000239432100006Scopus ID: 2-s2.0-33746931705OAI: oai:DiVA.org:kth-13234DiVA, id: diva2:322532
Merknad
QC20100614Tilgjengelig fra: 2010-06-07 Laget: 2010-06-07 Sist oppdatert: 2022-06-25bibliografisk kontrollert
Inngår i avhandling
1. Photochemical and Photoelectric Applications of II-VI Semiconductor Nanomaterials
Åpne denne publikasjonen i ny fane eller vindu >>Photochemical and Photoelectric Applications of II-VI Semiconductor Nanomaterials
2010 (engelsk)Licentiatavhandling, med artikler (Annet vitenskapelig)
Abstract [en]

In this work we investigated fabrication of semiconductor nanomaterials and evaluated their potential for photo-chemical and photovoltaic applications. We investigated two different II-VI semiconductor nanomaterial systems; (i) ZnO oriented nanowire arrays non-epitaxially grown from a substrate; and (ii) colloidal CdTe nanotetrapods synthesized by solution-based thermal decomposition of organo-metallic precursors. In both the cases our main focus has been optimizing material synthesis for improving potential applications based on photon-electron interactions.

We have studied the synthesis of vertically aligned ZnO nanowire arrays (NWA), by a wet chemical process on various substrates. The synthesis is based on epitaxial growth of ZnO seed-layer on a substrate in a chemical bath consisting of an aqueous solution of zinc nitrate and hexamethylenetetramine (HMT). We have suggested an additional role played by HMT during the synthesis of ZnO nanowire arrays. We have also extended this synthesis method to fabricate hierarchical nanostructures of nanofibers of poly-L-lactide acting as a substrate for the radially oriented growth of ZnO nanowires. The combination of high surface area of the nanofibrous substrate with the flexibility of the PLLA-ZnO hierarchical nanostructure enabled the proof-of-principle demonstration of a ‘continuous-flow’ water treatment system that could effectively decompose single and combination of known organic pollutants in water, as well as render common waterborne bacteria nonviable.

We have studied another chemical synthesis that is commonly used for size controlled synthesis of colloidal quantum dots, which was modified to obtain anisotropic nanocrystals mainly for CdE (E=S, Se, Te) compositions. In this work we demonstrate by use of oleic acid (instead of alkylphosphonic acids) it is possible to synthesize CdTe and CdSe nanotetrapods at much lower temperatures (~180 ºC) than what is commonly reported in the literature, with significantly different  formation mechanism in the low-temperature reaction.

Finally, we have performed preliminary photoconduction measurements with CdTe nanotetrapods using gold ‘nanogap’ electrodes fabricated in-house, and obtain up to 100 times enhancement in current levels in the I–V measurements under illumination with a white light source.

sted, utgiver, år, opplag, sider
Stockholm: KTH, 2010. s. v, 47
Serie
Trita-ICT/MAP AVH, ISSN 1653-7610 ; 2010:03
Emneord
ZnO, Nanowire arrays, Photocatalysis, Nanofibers, CdTe, Nanotetrapods, Ostwalds ripening, Photoconduction, Nano-gap electrodes
Identifikatorer
urn:nbn:se:kth:diva-12808 (URN)978-91-7415-624-9 (ISBN)
Presentation
2010-05-05, C2, Electrum, Isafjordsgatan 22, Kista, 10:30 (engelsk)
Opponent
Veileder
Merknad
QC20100607Tilgjengelig fra: 2010-06-07 Laget: 2010-05-11 Sist oppdatert: 2022-09-07bibliografisk kontrollert
2. Fabrication and Photoelectrochemical Applications of II-VI Semiconductor Nanomaterials
Åpne denne publikasjonen i ny fane eller vindu >>Fabrication and Photoelectrochemical Applications of II-VI Semiconductor Nanomaterials
2012 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

In this work we investigated fabrication of semiconductor nanomaterials and evaluated their potential for photo-chemical and photovoltaic applications. We investigated different II-VI semiconductor nanomaterial systems; (i) ZnO oriented nanowire arrays non-epitaxially grown from a substrate; and (ii) colloidal CdE (E=Te,Se,S) quantum structures synthesized by solution-based thermal decomposition of organo-metallic precursors.

We have studied the synthesis of vertically aligned ZnO nanowire arrays (NWA), by a wet chemical process on various substrates. We have extended this method wherein nanofibers of poly-L-lactide act as a substrate for the radially oriented growth of ZnO nanowires. By combining the large surface area and the flexibility of the PLLA-ZnO hierarchical nanostructure we have shown the proof-of-principle demonstration of a ‘continuous-flow’ water treatment system to decompose known organic pollutants in water, as well as render common waterborne bacteria non-viable.

We have studied synthesis of colloidal quantum dots (QD), and show size, morphology and composition tailored nanocrystals for CdE (E=S, Se, Te) compositions. We have studied the influence of crystal growth habits of the nanocrtsyals on the final morphology. Furthermore we have synthesized core-shell, CdSe-CdS QDs with spherical and tetrahedral morphologies by varying the reaction conditions. We show that these core-shell quantum dots show quasi-type II characteristics, and demonstrate with I-V measurements, the spatial localization of the charge carriers in these hetero-nanocrystals. For this purpose, we developed hybrid materials consisting of the core-shell quantum dots with electron acceptors (ZnO nanowires) and hole acceptors (polymeric P3HT nanofibers).

In addition we have also compared the synthesis reaction when carried out with conventional heating and microwave-mediated heating. We find that the reaction is enhanced, and the yield is qualitatively better when using microwave induced heating.

sted, utgiver, år, opplag, sider
Stockholm: KTH Royal Institute of Technology, 2012. s. viii, 55
Serie
Trita-ICT/MAP AVH, ISSN 1653-7610 ; 2012:09
Emneord
ZnO, nanowire arrays, photocatalysis, CdTe, CdSe, CdS, nanotetrapods, nanotetrahedrons, photoconduction, nano-gap electrodes, Type-II QDs, P3HT nanofibers, microwave synthesis.
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-95410 (URN)978-91-7501-382-4 (ISBN)
Disputas
2012-05-31, Sal/Hall C2, KTH-ICT Electrum, Isafjordsgatan-22, Kista, 10:00 (engelsk)
Opponent
Veileder
Merknad
QC 20120525Tilgjengelig fra: 2012-05-25 Laget: 2012-05-24 Sist oppdatert: 2022-06-24bibliografisk kontrollert

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