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Development of Concepts for the Size- and Shape-Controlled Synthesis of Metal Oxide Nanoparticles in Surfactant-Free Reaction Systems

English title Development of Concepts for the Size- and Shape-Controlled Synthesis of Metal Oxide Nanoparticles in Surfactant-Free Reaction Systems
Applicant Niederberger Markus
Number 119741
Funding scheme Project funding (Div. I-III)
Research institution Departement Materialwissenschaft ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Material Sciences
Start/End 01.04.2008 - 31.07.2011
Approved amount 289'942.00
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All Disciplines (2)

Discipline
Material Sciences
Inorganic Chemistry

Keywords (7)

metal oxide nanoparticles; sol-gel synthesis; crystal engineering; crystallization; surface science; formation mechanism; formation

Lay Summary (English)

Lead
Lay summary
The broad range of applications of metal oxide nanoparticles, especially in emerging technologies like medicine, energy storage and conversion, catalysis and functional ceramics made them the primary target of chemists and materials scientists. It is expected that a decrease of crystallite size into the nanometre regime will considerably improve their performance in many of these applications.In spite of the immense progress in nanoparticle research, the development of synthesis concepts based on a rational strategy has remained a primary objective, and yet we are far from achieving this goal. It is still impossible to prepare a certain compound on the nanoscale with a desired composition, structure, size and shape, or even properties, intentionally and in a predicted way. One of the main reasons for this major limitation is the fact that the role of the organic species during the growth of the inorganic nanoparticles is not yet understood on a molecular level. Whereas the size- and shape-controlling effect of organic species, mainly surfactants, has empirically been used for decades, the organic reaction pathways, i.e., the chemical transformation of the organic components in the reaction mixture with proceeding reaction time, have hardly been investigated. However, to gain new insights into the crystallization and formation mechanisms of inorganic nanoparticles, one has to study the interaction of all organic species, initially added to the starting solution as well as in-situ formed during the reaction course, with the growing nuclei. Only a detailed knowledge, which and how organic compounds adsorb on the surface of the metal oxide nanoparticles makes it possible to go a step beyond simple trial-and-error experiments toward the development of rational synthesis strategy for inorganic nanomaterials. The proposed research targets the main questions on the way to size- and shape-controlled synthesis of metal oxide nanoparticles in organic solvents:i)Which organic species form during the synthesis procedure?ii)Which of these species adsorb on the surface of the metal oxide nanoparticles?iii)Is it possible, eventually, to establish a relationship between a particular synthesis system (precursor and solvent) and the size and the shape of the final product?iv)Is it possible to find any predictable, generally valid concepts upon systematic variation of the reaction systems?Metal oxide powders with uniform particle size and shape play a fundamental role in industry and therefore, any results regarding size- and shape-control will have a direct impact on the technological application of metal oxide nanoparticles.
Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Publications

Publication
A comprehensive study of the crystallization mechanism involved in the nonaqueous formation of tungstite
Olliges-Stadler Inga, Rossell Marta D., Sueess Martin J., Ludi Bettina, Bunk Oliver, Pedersen Jan Skov, Birkedal Henrik, Niederberger Markus (2013), A comprehensive study of the crystallization mechanism involved in the nonaqueous formation of tungstite, in NANOSCALE, 5(18), 8517-8525.
Zinc oxide nanoparticles: Chemical mechanisms and classical and non-classical crystallization
Ludi Bettina, Niederberger Markus (2013), Zinc oxide nanoparticles: Chemical mechanisms and classical and non-classical crystallization, in Dalton Transactions, 42(35), 12554-12568.
Mechanistic aspects of molecular formation and crystallization of zinc oxide nanoparticles in benzyl alcohol
Ludi B, Suess MJ, Werner IA, Niederberger M (2012), Mechanistic aspects of molecular formation and crystallization of zinc oxide nanoparticles in benzyl alcohol, in NANOSCALE, 4(6), 1982-1995.
Study of the Chemical Mechanism Involved in the Formation of Tungstite in Benzyl Alcohol by the Advanced QEXAFS Technique
Olliges-Stadler I, Stotzel J, Koziej D, Rossell MD, Grunwaldt JD, Nachtegaal M, Frahm R, Niederberger M (2012), Study of the Chemical Mechanism Involved in the Formation of Tungstite in Benzyl Alcohol by the Advanced QEXAFS Technique, in CHEMISTRY-A EUROPEAN JOURNAL, 18(8), 2305-2312.
Extension of the benzyl alcohol route to metal sulfides: "nonhydrolytic'' thio sol-gel synthesis of ZnS and SnS2
Ludi B, Olliges-Stadler I, Rossell MD, Niederberger M (2011), Extension of the benzyl alcohol route to metal sulfides: "nonhydrolytic'' thio sol-gel synthesis of ZnS and SnS2, in CHEMICAL COMMUNICATIONS, 47(18), 5280-5282.
Interplay Between Size and Crystal Structure of Molybdenum Dioxide Nanoparticles-Synthesis, Growth Mechanism, and Electrochemical Performance
Koziej D, Rossell MD, Ludi B, Hintennach A, Novak P, Grunwaldt JD, Niederberger M (2011), Interplay Between Size and Crystal Structure of Molybdenum Dioxide Nanoparticles-Synthesis, Growth Mechanism, and Electrochemical Performance, in SMALL, 7(3), 377-387.
Co-operative Formation of Monolithic Tungsten Oxide-Polybenzylene Hybrids via Polymerization of Benzyl Alcohol and Study of the Catalytic Activity of the Tungsten Oxide Nanoparticles
Olliges-Stadler I, Rossell MD, Niederberger M (2010), Co-operative Formation of Monolithic Tungsten Oxide-Polybenzylene Hybrids via Polymerization of Benzyl Alcohol and Study of the Catalytic Activity of the Tungsten Oxide Nanoparticles, in SMALL, 6(8), 960-966.

Collaboration

Group / person Country
Types of collaboration
Aarhus University Denmark (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
ChinaNano Talk given at a conference Mechanistic Studies on Zinc Oxide Nanoparticle Formation within the Benzyl Alcohol Route 07.09.2011 Peking, China Ludi Bettina; Niederberger Markus;
XVIth International Sol-Gel Conference Talk given at a conference Comprehensive Study on Zinc Oxide Nanoparticle Formation Mechanism in Benzyl Alcohol 28.08.2011 Hangzhou, China Ludi Bettina; Niederberger Markus;
XVIth International Sol-Gel Conference Talk given at a conference In-Situ Studies of Tungstite Formation within a Nonaqueous Sol-Gel Process 28.08.2011 Hangzhou, China Olliges-Stalder Inga; Niederberger Markus;
Vortragstagung der Fachgruppe Materialforschung und Festkörperchemie der GDCh Poster Cooperative Formation of Monolithic Tungsten Oxide Polybenzylene Hybrids and Study of the Catalytic Activity of the Tungsten Oxide Particles 20.09.2010 Berlin, Germany Niederberger Markus; Olliges-Stalder Inga;
SCS Fall Meeting Poster Study of Zinc Oxide Nanoparticle Crystallization in Benzyl Alcohol 16.09.2010 Zürich, Switzerland Niederberger Markus; Ludi Bettina;
SCS Fall Meeting Poster Cooperative Formation of Monolithic Tungsten Oxide Polybenzylene Hybrids and Study of the Catalytic Activity of the Tungsten Oxide Particles 16.09.2010 Zürich, Switzerland Niederberger Markus; Olliges-Stalder Inga;
E-MRS Spring Meeting Talk given at a conference Cooperative Formation of Monolithic Tungsten Oxide Polybenzylene Hybrids 10.06.2010 Strasbourg, France Olliges-Stalder Inga; Niederberger Markus;
EMPA PhD Student Symposium Talk given at a conference Polymerization of Arylmethyl Alcohols using Tungsten Oxide Nanoparticles Synthesized in a Nonaqueous Sol-Gel Process 15.09.2009 Dübendorf, Switzerland Olliges-Stalder Inga; Niederberger Markus;
15th International Sol-Gel Conference Poster Polymerization of Arylmethyl Alcohols Using a Tungsten Oxide Catalyst Synthesized in a Nonaqueous Sol-Gel Process 23.08.2009 Porto de Galinhas, Brazil Olliges-Stalder Inga; Niederberger Markus;
15th International Sol-Gel Conference Poster Nonaqueous Sol-Gel Chemistry for the Synthesis of Zinc Oxide Nanoparticles 23.08.2009 Porto de Galinhas, Brazil Niederberger Markus; Ludi Bettina;
E-MRS Spring Meeting Poster A Study on the Morphology and Assembly Behavior of Zinc Oxide Nanoparticles Synthesized by Nonaqueous Sol-Gel Routes 08.06.2009 Strasbourg, France Ludi Bettina; Niederberger Markus;
NanoEurope Poster Solvent Effects and Organic Reaction Pathways in Nonaqueous Synthesis of Metal Oxide Nanoparticles 16.09.2008 St. Gallen, Switzerland Niederberger Markus; Olliges-Stalder Inga;
NanoEurope Poster Nonaqueous Sol-Gel Chemistry- A versatile Tool for the Synthesis of Metal Oxide Nanoparticles 16.09.2008 St. Gallen, Switzerland Ludi Bettina; Niederberger Markus;
SCS Fall Meeting Poster Nonaqueous Sol-Gel Synthesis of Nanocrystalline Zinc Oxide 11.09.2008 Zurich, Switzerland Ludi Bettina; Niederberger Markus;
SCS Fall Meeting Poster Solvent Effects and Organic Reaction Pathways in Nonaqueous Sol-Gel Processes 11.09.2008 Zürich, Switzerland Niederberger Markus; Olliges-Stalder Inga;
MRC Graduate Symposium Poster Size and Morphology Control via Nonaqueous Sol-Gel Synthesis - Zinc Oxide as a Case Study 14.05.2008 Zürich, Switzerland Niederberger Markus; Ludi Bettina;


Awards

Title Year
Best Poster Award, 15th International Sol-Gel Conference - Porto de Galinhas 2009
Best Poster Industrial Applications, NanoEurope, St. Gallen, 2008 2008

Associated projects

Number Title Start Funding scheme
128688 Dispersive Raman Spectroscopy for ex- and in-situ chemical analysis 01.12.2009 R'EQUIP
124632 Microwave-Assisted Nonaqueous Synthesis of Nanocrystalline Lithium Transition Metal Phosphates for Battery Applications 01.04.2009 Project funding (Div. I-III)

Abstract

Although metal oxides constitute one of the most important classes of functional materials, their synthesis on the nanoscale under mild reaction conditions and with control over particle size, shape, and crystallinity remains a challenging task. In the last few years, sol-gel routes to metal oxide nanoparticles in organic solvents under exclusion of water have become a versatile alternative to aqueous methods. In comparison to the complex aqueous chemistry, nonaqueous processes offer the possibility of better understanding and controlling the reaction pathways on a molecular level, enabling the synthesis of oxidic nanomaterials with high crystallinity and well-defined and uniform particle morphologies.Nonaqueous sol-gel routes are based on the chemical transformation of molecular metal oxide precursors such as metal halides, alkoxides, or acetylacetonates into an extended metal oxide network in various organic solvents such as alcohols, amines, or ketones under exclusion of water. Organic components and organic reaction pathways play a fundamental role in these processes, not only in determining the structural, compositional and morphological characteristics of the inorganic product, but also as oxygen source for the oxide formation.Although aqueous sol-gel approaches were highly successful in the synthesis of bulk metal oxides, they brought some major limitations forward when it came to the preparation of their nanoscale counterparts. Aqueous sol-gel chemistry is rather complex, mainly due to the high reactivity of the metal oxide precursors and the double role of water as ligand and solvent. Furthermore, the as-synthesized metal oxides are often amorphous and it is difficult to retain full control over the crystallization process during any additional annealing step. Nonaqueous sol-gel processes are able to overcome some of the major limitations of aqueous systems. The advantages are closely related to the manifold role of the organic components in the reaction mixture. The slow reaction rates, mainly a consequence of the moderate reactivity of the C-O bond, in combination with the stabilizing effect of the organic species leads to the formation of highly crystalline products that are often characterized by uniform particle morphologies and crystallite sizes in the range of just a few nanometers. Nonaqueous sol-gel processes clearly benefit from the fact that the chemistry of the C-O bond is well established in organic chemistry, which is of utmost significance considering the fundamental role of organic reaction pathways in these synthesis approaches. Parallel to the formation of the inorganic nanoparticles, also the initial organic species (i.e., solvent and organic constituent of the precursor) undergo transformation reactions that are often based on elementary organic chemistry principles. Identification and quantification of these organic by-products provides valuable information about the chemical reaction mechanisms leading to the nanoparticles. In spite of the immense progress in nanoparticle research, the development of synthesis concepts based on a rational strategy has remained a primary objective, and yet we are far from achieving this goal. It is still impossible to prepare a certain compound on the nanoscale with a desired composition, structure, size and shape, or even properties, intentionally and in a predicted way. One of the main reasons for this major limitation is the fact that the role of the organic species during the growth of the inorganic nanoparticles is not yet understood on a molecular level. Whereas the size- and shape-controlling effect of organic species, mainly surfactants, has empirically been used for decades, the organic reaction pathways, i.e., the chemical transformation of the organic components in the reaction mixture with proceeding reaction time, have hardly been investigated. However, to gain new insights into the crystallization and formation mechanisms of inorganic nanoparticles, one has to study the interaction of all organic species, initially added to the starting solution as well as in-situ formed during the reaction course, with the growing nuclei. Only a detailed knowledge, which and how organic compounds adsorb on the surface of the metal oxide nanoparticles makes it possible to go a step beyond simple trial-and-error experiments toward the development of rational synthesis strategy for inorganic nanomaterials.The proposed research targets the main questions on the way to size- and shape-controlled synthesis of metal oxide nanoparticles in organic solvents:i) Which organic species form during the synthesis procedure?ii) Which of these species adsorb on the surface of the metal oxide nanoparticles?iii) Is it possible, eventually, to establish a relationship between a particular synthesis system (precursor and solvent) and the size and the shape of the final product?iv) Is it possible to find any predictable, generally valid concepts upon systematic variation of the reaction systems?We will apply two complementary approaches to find answers to these four questions:1) Identification and quantification of the organic species present in the final synthesis solution: These investigations will provide information about the chemical reaction mechanisms leading to the nanoparticles, and about the formation of potential ligands that attach to the surface of the growing nanoparticles and thus influence the size and the shape of the crystallites.2) Systematic variation of the reaction system, i.e., use of precursors and solvents with variable chemical reactivity: These studies will reveal the fundamental trends that are the basis for the establishment of general reaction principles.We will focus our investigations on surfactant-free nonaqueous systems, because in comparison to the synthesis of metal oxides in the presence of surfactants, solvent-controlled approaches are considerably simpler. The initial reaction mixture just consists of two components, the metal oxide precursor(s) and a common organic solvent. The small number of reactants simplifies the characterization of the final reaction solution and, related to that, the elucidation of the chemical reaction mechanisms. However, in spite of the simplicity of the starting reaction solution, different particle morphologies ranging from spheres to platelets and nanowires can be obtained. The variety of particle sizes and shapes in combination with the simple synthesis protocol makes the surfactant-free and nonaqueous sol-gel routes particularly versatile for finding a relationship between a starting reaction system and the final particle morphology.In the proposed research we will investigate the influence of organic species on the size, shape, and assembly behavior of metal oxide nanoparticles prepared in organic solvents. In the absence of any additional morphology-controlling agents like surfactants, we will focus our interest on the role of the solvent, the organic constituent of the metal oxide precursor, and the organic species that potentially form in-situ during nanoparticle growth on the structural and morphological features of the inorganic nanomaterials.We want to achieve the following objectives:1) Investigation of the organic species i) in the final reaction solution and ii) adsorbed on the surface of the metal oxide nanoparticles2) Elaboration of a relation between surface-adsorbed organic species and the size, shape, and assembly behavior of the metal oxide nanoparticles3) Transfer of the knowledge gained to a rational synthesis planning of metal oxide nanoparticles with predictable size, shape, and assembly properties4) Preliminary evaluation of metal oxide nanoparticles in catalysis and gas sensing and of their performance in dependence of the size and shape.The requested funding for this project consists of two PhD students.
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