Shape Control Synthesis and Microstructure Studies of Metal Nanoparticles
Doctoral thesis, 2020

Metal nanoparticles have been extensively studied in recent years due to their unique chemical, biological and physical properties. Gold (Au) and palladium (Pd) nanoparticles are two of the most popular materials because Au nanoparticles have a strong localized surface plasmon resonance effect and Pd nanoparticles have high hydrogen adsorption and chemical catalytic capacities. In the colloidal-chemical synthesis of gold (Au) and palladium (Pd) nanoparticles, capping agents are widely used to control the shape and size of nanoparticles. Capping agents are usually surfactants, polymers, organic ligands and dendrimers. In this work, an anionic surfactant, sodium oleate (NaOL) was mixed with common capping agents such as hexadecyltrimethylammonium bromide (CTAB), hexadecyltrimethylammonium chloride (CTAC) and polyvinylpyrrolidone (PVP) in order to tune the shapes of nanoparticles. Three mixtures of capping agent: CTAB-NaOL, CTAC-NaOL, and PVP-NaOL were applied to the synthesis of Pd nanoparticles, resulting in the formation of Pd nanodendrites under proper circumstances including temperature, pH value and ratio between the capping agents. The large surface area makes Pd nanodendrites advantageous in catalytic applications. However, the application of CTAB-NaOL mixture in the growth of Au nanorods plays a remarkably different role. It increased the rod-shape yield and narrowed the aspect ratio of Au nanorods. A growth-induced strain was discovered in the Au nanorods, leading to slight bending in a large percentage (≈ 47%) of the Au nanorods.

A variety of techniques were used to investigate the microstructure and properties of Au and Pd nanoparticles. Transmission electron microscopy including selected area electron diffraction and Kikuchi pattern methods, energy dispersive X-ray spectroscopy, and scanning transmission electron microscopy were employed to study microstructure and elemental composition. Ultraviolet-visible spectroscopy, dynamic light scattering and conductivity measurements were used to characterize the growth kinetics of metal nanoparticles. Through these techniques, the effects of the capping agent ratio, pH value and precursor types on the growth of Pd nanodendrites were investigated. Additionally, the growth-induced strain in Au nanorods was studied as well. Investigations of the shapes and microstructure of metal nanoparticles have the potential to expand their applications in the fields of surface plasmonic sensing and catalysis.

hexadecyltrimethylammonium bromide

sodium oleate


Gold nanorod

palladium nanodendrite

seed mediated growth

transmission electron microscopy

hexadecyltrimethylammonium chloride

Online Password: 088470
Opponent: Prof. Jorge Pérez-Juste, Department of Physical Chemistry, University of Vigo, Spain


Xin Wen

Chalmers, Chemistry and Chemical Engineering, Applied Chemistry

Xin Wen, Torben Nilsson Pingel, Lunjie Zeng, Gabriel Sanchez-Santolino, Shun Kondo, Nestor J. Zaluzec, Naoya Shibata, Yuichi Ikuhara, Sarah Lerch, Kasper Moth-Poulsen, Eva Olsson. Growth-Induced Strain in Single Crystal Gold Nanorods

Xin Wen, Jessica Orrego Hernandez, Sarah Lerch, Alicja Stolas, Eva Olsson, Kasper Moth-Poulsen. Performance of Palladium Nanodendrites Stabilized by Polyvinylpyrrolidone and Sodium Oleate in Sonogashira Reactions

Nanoscience and nanotechnology are gradually changing our world in the last decades. The study on metal nanoparticles is an important field in nanoscience. A metal nanoparticle is defined as a particle with a diameter less than 100 nm. When a material becomes as small as this size, it has many new physical and chemical properties. Nowadays, metal nanoparticles are widely applied in chemistry, physics and biology. For example, gold nanoparticles can be used in cancer treatment, silver nanoparticles are used as antimicrobial agents and palladium nanoparticles can catalyze organic reactions. All these applications are potentially promoting the quality of our life. Additionally, the development of electron microscopy opens a door to the microworld for human beings. Through an electron microscope, people can see the nanoscale materials by eyes directly. Electron microscopy is widely used to study microstructure and chemical composition of nanomaterials.

This thesis studies the shape control in the synthesis of metal nanoparticles. A variety of experimental parameters are tested to produce metal nanoparticles with a high synthetic yield and uniform size. The detailed microstructure studies aim to reveal the association between structures and properties. Therefore, it is expected that this thesis can contribute to promote applications of metal nanoparticles in real life and help us understand the microworld.

Areas of Advance

Nanoscience and Nanotechnology

Subject Categories

Materials Chemistry

Nano Technology



Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 4854



Online Password: 088470


Opponent: Prof. Jorge Pérez-Juste, Department of Physical Chemistry, University of Vigo, Spain

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