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Synthesis and characterization of one-dimensional oxide nanotubes encapsulated with platinum metal nanoparticles [Elektronische Ressource] / von Catherine Aresipathi

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136 Pages
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Synthesis and Characterization of One - dimensional Oxide Nanotubes Encapsulated with Platinum Metal Nanoparticles Von der Naturwissenschaftlichen Fakultät der Gottfried Wilhelm Leibniz Universität Hannover Zur Erlangung des Grades einer DOKTORIN DER NATURWISSENSCHAFTEN Dr. rer. nat. genehmigte Dissertation Von M.Sc. Catherine Aresipathi Geboren am 06.04.1978, in Vijayawada, India 2008 Dem Promotionsausschuß vorgelegt im November 2008 Tag des öffentlichen Kolloquiums : 23. 01. 2009 Gutachter : Prof. Dr. Juergen Caro Prof. Dr. Josef - Christian Buhl Synthesis and Characterization of One - dimensional Oxide Nanotubes Encapsulated with Platinum Metal Nanoparticles A dissertation submitted to the Institute of Physical Chemistry and Electrochemistry Leibniz University of Hannover For the degree of Doctor of Science (Dr. rer. nat.

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Synthesis and Characterization of
One - dimensional Oxide Nanotubes Encapsulated
with Platinum Metal Nanoparticles







Von der Naturwissenschaftlichen Fakultät der Gottfried Wilhelm Leibniz
Universität Hannover

Zur Erlangung des Grades einer

DOKTORIN DER NATURWISSENSCHAFTEN

Dr. rer. nat.

genehmigte Dissertation











Von

M.Sc. Catherine Aresipathi

Geboren am 06.04.1978, in Vijayawada, India

2008

































Dem Promotionsausschuß vorgelegt im November 2008


Tag des öffentlichen Kolloquiums : 23. 01. 2009


Gutachter : Prof. Dr. Juergen Caro

Prof. Dr. Josef - Christian Buhl Synthesis and Characterization of
One - dimensional Oxide Nanotubes Encapsulated
with Platinum Metal Nanoparticles







A dissertation submitted to the

Institute of Physical Chemistry and Electrochemistry
Leibniz University of Hannover


For the degree of

Doctor of Science
(Dr. rer. nat.)




by
Catherine Aresipathi





Hannover, November 2008










































With love to my parents






Erklärung zur Dissertation I



Hierdurch erkläre ich, dass die Dissertation ‚Synthesis and Characterization of One -
dimensional Oxide Nanotubes Encapsulated with Platinum Metal Nanoparticles’
selbstständig verfasst und alle benutzten Hilfsmittel sowie evtl. zur Hilfeleistung
herangezogene Institutionen vollständig angegeben wurden.

Die Dissertation wurde nicht schon als Diplom- oder ähnliche Prüfungsarbeit verwendet.












Hannover



(Catherine Aresipathi) Acknowledgements II
Acknowledgements

I would like to express my deepest gratitude to Prof. Dr. Michael Wark for his valuable
guidance, thought provoking suggestions, inspiring reviews and constant encouragement to
carry out the present work. I will remain highly indebted to him for his support and timely
advice all throughout my work. The guidance and discussions with the head of the Physical
Chemistry and Electrochemistry group and my co – supervisor, Prof. Dr. Juergen Caro has
helped me enlighten myself about many facts in the field of Chemistry. His dynamic thoughts,
broad and profound knowledge, patient instructions have given me a great aid in completing
this project. I owe my gratitude also to Prof. Dr. Josef – Christian Buhl for his acceptance to
be a reviewer of this work and for his immediate readiness to be part of the examination
committee. His valuable suggestions are highly commendable.

I wish to thank Dr. Armin Feldhoff for his assistance on working with electron microscopy
and for his help in various aspects of my research. My special thanks go to Mr. Frank
Steinbach who performed measurements on Transmission Electron Microscopy and Dr.
Thorsten M. Giesing for his help in Rietveld analysis measurements. I would also like to
thank Mr. Marco Lange and Mr. Falk Heinroth for their collaboration in carrying out
Thermogravimetric and Inductive coupled plasma spectroscopy analysis. I am thankful to all
my colleagues at Institute of Physical Chemistry, University Hannover especially Ms. Inga
Bannat, Ms. Katrin Wessels, Ms. Julia Martynczuk, Mr. Roland Marschall, Ms. Britta
Seelandt, Ms. Kerstin Janze and Mrs. Yvonne – Uebe – Gabbey for their perpetual
contributions that helped me a lot to achieve my goals. Financial help from Deutsche
Forschungsgemeinschaft (DFG) and University of Hannover for this research are highly
acknowledged.

I am also grateful to my present colleagues at RENA GmbH, Gütenbach, Germany
exclusively for their motivation and support. I take this opportunity to thank my friends Mr.
Santosh Rao Kanjarkar, Ms. Anna Glyk, Mrs. Jinu John, Mr. Gautam Sagar, Mr. Rejish nath,
Mrs. Preeti Matthew Anil, Ms. Garima Jain and my friends in India for their moral support
throughout my work.

Above all, I thank Almighty and my family for giving me strength and courage throughout
my thesis and during my stay in Germany. My special gratitude to my brother for his
encouragement and love. Abstract III
Abstract

The present work focuses on the synthesis and characterization of metal oxide nanotubes
employing metal salt fibers as templating structures. Metal salt fibers when used as templating
structures together with sol – gel technique to coat the fibers with suitable metal alkoxides can
lead to the formation of template filled nanotubes which upon subsequent subjection to auto –
reduction by heat treatment results in metal filled nanotubes. The objective of thesis lies in
embedding platinum metal inside SiO , TiO and SnO nanotubes. Hence, templating fibers 2 2 2
from two different platinum salts were investigated for synthesis namely [Pt(NH ) (HCO ) ] 3 4 3 2
and [Pt(NH ) ][PtCl ], while the latter is popularly termed as Magnus green salt (MGS). 3 4 4
The samples were analyzed using electron microscopy, X - Ray diffractometry (XRD),
thermogravimetric analysis technique, Dynamic light scattering spectroscopy, and Inductively
coupled plasma emission – Mass spectrometry within the laboratory limitations.
Using fibers from [Pt(NH ) (HCO ) ] salt as template, SiO , TiO and SnO nanotubes were 3 4 3 2 2 2 2
synthesized in presence of tetraethylorthosilicate (TEOS) as capping agent which gave rise to
monodisperse nanotubes with approximately 38 - 40 wt.- % of Pt incorporated inside the
tubes. While Pt doped SiO nanotubes (Pt – SiO NTs) exhibited considerable yield of tubes 2 2
with diameter in range of 200 – 800 nm and lengths upto 20 µm long, Pt – SnO NTs 2
demonstrated short length tubes (2 – 5 µm) with diameter in broad range of 200 – 800 nm. On
the other hand, synthesis of Pt – TiO NTs under similar reaction conditions failed to produce 2
tubular morphologies and resulted in particles with minute traces of titanium alkoxide that
was utilized in the synthesis.
On contrary, templating fibers from [Pt(NH ) ][PtCl ] under optimized synthesis conditions 3 4 4
could give rise to monodisperse and high aspect ratios of Pt - SiO (600) and Pt - TiO NTs 2 2
(500) with higher incorporation of Pt (around 48 - 51 wt.- %) inside the tubes at lower
°temperatures (280 C). It is worthy to point out that synthesis of metal filled nanotubes using
MGS as templating structures could be performed at lower molar ratios of salt thereby making
the synthesis approach a cost effective technique comparatively. The experimental
investigation indicates that nanotubes with a diameter range of 300 – 700 nm and lengths upto
60 µm long for Pt – SiO NTs and an average diameter of 500 nm with lengths in the wide 2
range of 4 - 15 µm for Pt – TiO NTs can be realized from fibers of MGS. 2

Keywords: Oxide Nanotubes, Templating structures, Nanofibers, Magnus salt, Sol-gel
Process Kurzfassung IV
Kurzfassung

Diese Arbeit konzentriert sich auf die Synthese und Charakterisierung von Metalloxid-
Nanoröhren durch die Verwendung von Metallsalzfasern als Templatstrukturen.
Metallsalzfasern können, wenn sie als Vorlagestrukturen verwendet werden und mittels der
Sol - Gel - Technik mit geeigneten Metallalkoxiden beschichtet werden, zur Bildung gefüllter
Nanoröhren dienen. Durch Autoreduktion entstehen dann während einer Wärmebehandlung
mit Metall gefüllte Nanoröhren. Das Ziel dieser Arbeit ist Platin-Metall in Metalloxide wie
SiO , TiO , und SnO Nanoröhren einzubetten. Daher wurden Templatfasern aus zwei 2 2 2
verschiedenen Platinsalzen für die Synthese untersucht, nämlich [Pt(NH ) (HCO ) ] und 3 4 3 2
[Pt(NH ) ][PtCl ]; letzteres wird auch als Magnus - Salz bezeichnet. 3 4 4
Die Proben wurden mit Elektronenmikroskopie, Röntgenbeugung (XRD),
Thermogravimetrischer Analyse, Dynamischer Lichtstreuspektroskopie und Induktiv
gekoppelter Plasmaemmisionen Massenspektroskopie untersucht.
Mit Fasern aus [Pt(NH ) (HCO ) ] als Vorlage und in Anwesenheit von Tetraethylorthosilicat 3 4 3 2
(TEOS) als Additiv wurden SiO , TiO , und SnO Nanoröhren hergestellt. Die erzielten 2 2 2
monodispersive Nanoröhren enthielten ungefähr 38 - 40 Gewichtsprozent in den Röhren
eingebautes Pt. Pt - SiO Nanoröhren erreichten beachtliche Ausbeuten an Röhren mit 2
Durchmessern im Bereich von 200 - 800 nm und Längen bis zu 20 µm, Pt - SnO Nanoröhren 2
zeigten kurze Rohrlängen (2 - 5 µm) mit Durchmessern im Bereich von 200 - 800 nm. Auf
der anderen Seite konnten im Pt - TiO - System unter ähnlichen Reaktionsbedingungen keine 2
röhrenförmigen Morphologien erzeugt werden, man erhielt nur unstrukturierte Partikel mit
geringen Spuren von Titanalkoxid welches bei der Synthese verwendet wurde.
Im Gegensatz dazu führten Templatfasern aus [Pt(NH ) ][PtCl] unter optimierten 3 4 4
Synthesebedingungen zu monodispersiven Röhren mit einem hohen Längenverhältnis von
600 bei Pt - SiO und 500 bei Pt - TiO und höherem Pt Einbau in die Röhren bei niedrigeren 2 2
Temperaturen (280 °C). Es ist erwähnenswert, dass die Synthese mit Magnus Salz als Vorlage
bei kleineren molaren Mengen des Salzes durchgeführt werden konnte und damit eine
vergleichsweise kostengünstige Methode darstellt. Die experimentellen Untersuchungen
zeigen, dass Nanoröhren mit Durchmessen von 300 - 700 nm und Längen von bis zu 60 µm
für Pt - SiO und ein mittlerer Durchmesser von 500 nm mit Längen im Bereich von 4 - 15 2
µm für Pt - TiO aus Fasern aus Magnus Salz hergestellt werden können. 2

Stichwörter: Oxide-Nanoröhren, Templat, Nanofasern, Magnus salz, Sol – gel Prozess Table of Contents V


Erklärung zur Dissertation………………………………………………………………......I

Acknowledgements…………………….…………………………………………………….II

Abstract………………………………………….…………………………………………..III

Kurzfassung…………………………………………………………………………………IV


1. Introduction…………………………………………………………………………...........1


1.1 Introduction………………………………………………………………………………...1

1.2 Nanotubes…………………………………………………………………………………..2

1.2.1 Inorganic nanotubes…………………………………………………………................4

1.3 Scope of Thesis..............................................................................................................…...5

1.4 Organization of this work…………………………………………………………………..7

1.5 References………………………………………………………………………….………9

2. Scientific Background…………………………………………………………………….14

2.1 Crystallographic concepts………………………………………………………………...14

2.1.1 Crystal and its characteristics…………………………………………………………14

2.1.2 Growth of crystals…………………………………………………………………….15

2.1.3 Crystal Defects………………………………………………………………………..20

2.1.4 Crystal habit…………………………………………………………………………..22

2.1.5 Formation mechanism of nanotube…………………………………………………...23

2.2 Coating of Templates……………………………………………………………………..23

2.2.1 Sol – gel method……………………………………………………………………...24

2.2.2 Advantages and limitations of sol –gel method………………………………………29

2.3 References………………………………………………………………………………...30
Table of Contents VI
3. Physico – Chemical Characterizations Techniques……………………………………..32


3.1 Introduction……………………………………………………………………………….32

3.1.1 Electron Microscopy………………………………………………………………….32

3.1.2 X- Ray Diffractometry………...……………………………………………………...37

3.1.3 Inductively Coupled Plasma Emission – Mass spectrometry………………………...39

3.1.4 Dynamic Light Scattering Spectroscopy………………………………………….….40

3.1.5 Thermogravimetric Analysis………………………………………………………….42

3.2 References………………………………………………………………………………...44

4. Formation of Pt incorporated metal oxide nanotubes using Pt(NH ) (HCO ) fibers as 3 4 3 2
templates……………………………………………………………………………………..45

4.1 Introduction and objective………………………………………………………………..45

4.2 Templating structures from Pt(NH ) (HCO ) salt……………………………………….47 3 4 3 2

4.2.1 Introduction…………………………………………………………………………...47

4.2.2 Experimental details…………………………………………………………………..47

4.2.3 Mechanistic pathway for formation of template fibers……………………………….48

4.3 Pt – SiO NTs……………………………………………………………………………..51 2

4.3.1 Introduction and Objective……………………………………………………………51

4.3.2 Experimental details…………………………………………………………………..52

4.3.3 Results and discussion………………………………………………………………..53

4.3.4 Conclusions…………………………………………………………………………...55

4.4 Pt – TiO NTs……………………………………………………………………………..56 2

4.4.1 Introduction and Objective……………………………………………………………56

4.4.2 Experimental details…………………………………………………………………..57

4.4.3 Results and discussion………………………………………………………………..58

4.4.4 Conclusions…………………………………………………………………………...59