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Hydrazine-assisted Routes to 1D Nitride and Oxide Nanomaterials for Environmental and Energy Applications

English title Hydrazine-assisted Routes to 1D Nitride and Oxide Nanomaterials for Environmental and Energy Applications
Applicant Patzke Greta Ricarda
Number 127943
Funding scheme SCOPES
Research institution Institut für Chemie Universität Zürich
Institution of higher education University of Zurich - ZH
Main discipline Material Sciences
Start/End 01.12.2009 - 31.03.2012
Approved amount 100'000.00
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All Disciplines (2)

Discipline
Material Sciences
Inorganic Chemistry

Keywords (9)

Nanomaterials; Nitrides; Oxides; Gas phase methods; Hydrazine; Nanowires; Synthetic methods; Nanodevices; Nitridation, Photocatalysis

Lay Summary (English)

Lead
Lay summary
The development of new technologies for the synthesis of innovative one dimensional (1D) materials is a key issue for fabricating advanced nanodevices with unique surface-related effects and quantum phenomena. The nitride nanomaterials, particularly group III nitrides, have attracted great interest due to their blue light and UV emission properties, piezoelectricity, high stability etc. In contrast to oxides, the synthesis of stoichiometric nitrides is a considerably more complicated task due to the lower reactivity of nitrogen. Therefore, the development of new nitridation technologies operating at low synthesis temperatures is a key challenge for modern materials science. The purpose of this project is to develop a hydrazine-based simple and efficient new technology for fabricating new 1D nanomaterials (nitrides, oxynitrides, oxides of Ge and Ge-In, Ge-Sn, Ge-Zn, Ge-Ga systems) and to furthermore investigate the properties of the emerging novel nanomaterials in order to evaluate their application potential in different nanodevices. Our new technological approach is based on the application of hydrazine for producing nitride and oxide nanomaterials. The advantage of hydrazine over ammonia as the conventionally used agent is its low pyrolysis temperature. Semiconductor surfaces then serve as catalysts for the low temperature decomposition of hydrazine via a chain reaction. Due to the low pyrolysis temperature and the formation of active radicals, a decrease of nitridation temperatures with hydrazine as a nitrogen source is expected. Oxynitride 1D nanomaterials will be synthesized following a similar route based on water-hydrazine mixtures. Preliminary syntheses of germanium nitride nanowires by annealing a Ge source in hydrazine vapor containing 3 mol% of water molecules demonstrate the efficiency of our strategy as a simple, low-cost technology aiming for the mass production of functional nitride nanomaterials. Special emphasis will furthermore be placed on the application of the newly synthesized 1D nanomaterials in sensors for environmental control and on the fabrication of nano-sized photocatalysts for solar hydrogen production by water splitting. Germanium nitride was the first non-oxide photocatalyst which was used for water splitting. We suggest that the application of this material in the form of flat nanobelts can increase its catalytic efficiency, because a considerable fraction of the atoms are located at the surface of the nanobelts. The insights obtained from the project will lead to a deeper understanding of 1D nanomaterial growth mechanisms and they will facilitate the transition to the zero dimensional (0D) quantum-dot devices.
Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Publications

Publication
Hydrazine-Assisted Formation of Indium Phosphide (InP)-Based Nanowires and Core-Shell Composites
Patzke Greta R., Kontic R., Shiolashvili Z., Makhatadze N., Jishiashvili D. (2013), Hydrazine-Assisted Formation of Indium Phosphide (InP)-Based Nanowires and Core-Shell Composites, in Materials, 6(1), 85-100.

Associated projects

Number Title Start Funding scheme
114711 Targeted Synthesis of Functional Inorganic Materials 01.05.2007 SNSF Professorships

Abstract

The development of new technologies for the synthesis of innovative one dimensional (1D) materials is a key issue for fabricating advanced nanodevices, which in most cases have no macro-sized analogs. Modern ultrasensitive gas sensors, which can easily detect ppb amounts of toxic gases and sensors for bio-medicinal applications, such as DNA analyses, can serve as examples of advanced nanowire devices. The unique properties of 1D nanomaterials (nanowires, nanobelts, nanorods etc.) mainly arise from the increased influence of surface-related effects and quantum phenomena due to the low dimensionality of these nanostructures. The nitride nanomaterials, particularly group III nitrides, have attracted great interest due to their blue light and UV emission properties, piezoelectricity, high stability etc. In contrast to oxides, the synthesis of stoichiometric nitrides is a considerably more complicated task due to the lower reactivity of nitrogen. The development of new nitridation technologies operating at low synthesis temperatures is a key challenge for modern materials science. The purpose of this project is to develop a hydrazine-based simple and efficient new technology for fabricating new 1D nanomaterials (nitrides, oxynitrides, oxides of Ge and Ge-In, Ge-Sn, Ge-Zn, Ge-Ga systems) and to furthermore investigate the properties of the emerging novel nanomaterials in order to evaluate their application potential in different nanodevices. Our new technological approach is based on the application of hydrazine (N2H4) for producing nitride and oxide nanomaterials. Hydrazine has a low pyrolysis temperature in comparison with ammonia as the conventionally used agent. Semiconductor surfaces serve as catalysts for low temperature decomposition of hydrazine which proceeds as a chain reaction. In the initial stage, active radicals such as NH and NH2 are formed, and finally the stable N2, NH3 and H2 molecules are produced. Due to the low pyrolysis temperature and the formation of active radicals one might expect a decrease of nitridation temperatures with hydrazine as a nitrogen source. Hydrazine is a liquid at room temperature that is miscible with water. Our strategy for producing oxynitride 1D nanomaterials relies on the application of water-hydrazine mixtures. During the synthesis, the hydrazine will serve as a source for nitrogen precursors while water molecules will produce oxide materials. The water content in hydrazine will be controlled by measuring its refraction index. In order to prove the viability of the suggested technology, preliminary experiments were carried out regarding the synthesis of germanium nitride nanomaterials. The synthesis was performed by annealing a Ge source in hydrazine vapor containing 3 mol% of water molecules. This technology afforded single-crystalline germanium nitride nanowires and nanobelts with the alpha-Ge3N4 structure. These experiments confirmed our expectations, because the nitride was synthesized at 530 °C, which is by 320 °C lower than literature data. The presence of 3 mol% of water in hydrazine supports the formation of volatile GeO molecules instead of the solid germanium dioxide phase which is stabile up to 1230 °C. The whole mass transfer during the growth of nanowires was performed by volatile GeO molecules, because volatile germanium hydrides are unstable at temperatures exceeding 150 °C and mass transfer by Ge3N4 molecules should be excluded due to the high sublimation temperature of these molecules. It should be mentioned that the newly developed technology is quite simple as it requires only two components (Ge source and hydrazine) and relatively low synthesis temperatures (ca. 530 °C) in comparison with existing technologies, which start from four components and higher temperatures (above 800 °C). In addition, the growth process proceeds at a static pressure of hydrazine without any gaseous reagent flow and the applied power is also low (< 215 W). The yield of nanowires reaches values of 8.0-5.5 mg/h per cm2 and can be increased further. All these factors are essential for the development of a simple, low-cost technology aiming for the mass production of germanium nitride or other functional nitride nanomaterials. Orienting data were also obtained for the growth of 1D nanomaterials by annealing eutectic In-Ge solid sources in hydrazine vapor. Depending on the synthesis temperature, 1D nanomaterials with different morphologies were obtained including a variety of unusual particle shapes. The obtained variety of forms and morphologies provides strong evidence for the technological flexibility of our growth method that brings forward nanowires covering a wide range of morphologies, compositions and structures.These initial experiments demonstrate the potential of the hydrazine-based technology and prove the applicability of this technology for the low temperature synthesis of different 1D nanostructures. However, manifold investigations remain to be performed. In the course of the proposed project we intend to perform a joint study of the new nanomaterials and to evaluate their implementation in different nanodevices. Special emphasis will be placed on the application of the newly synthesized 1D nanomaterials in sensors for environmental control and on the fabrication of nano-sized photocatalysts for solar hydrogen production by water splitting.The specific resistance of nanowires used in gas sensors should be in the range of several tens of Ohm cm. For this purpose, the germanium nitride nanowires will be doped with Zn atoms during the synthesis to decrease their resistance and for further use in sensors. The nanowires synthesized using In-Ge, Ga-Ge and Sn-Ge sources will be also evaluated for gas sensor applications.The photocatalytic properties of the produced nanomaterials will be examined. Germanium nitride was the first non-oxide photocatalyst which was used for water splitting. We suggest that the application of this material in the form of flat nanobelts can increase its catalytic efficiency, because a considerable fraction of the atoms are located at the surface of the nanobelts. The photogenerated holes will immediately participate in water splitting instead of being captured by bulk traps, thereby increasing the activity and durability of nanocatalysts. As a result of the project implementation, the simple and inexpensive new pyrolytic technology will be developed for the synthesis of known and new nitride, oxynitride and oxide nanomaterials. The developed technology will enable the flexible control and tailoring of nanomaterials properties. The structure, composition and parameters of these 1D nanomaterials will be studied and the prospects for application of these nanomaterials in sensors and photocatalysts will be evaluated. The insights obtained from the proposed project will lead to a deeper understanding of 1D nanomaterial growth mechanisms and they will facilitate the transition to the zero dimensional (0D) quantum-dot devices.
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