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Waqqar Ahmed (promotion date: 24 November 2010)

Synthesis and field control of non-spherical bare coated gold nanoparticles

Promotion date: 24. November 2010

Promotors: Prof. dr. ir. Bene Poelsema

Assistant Promotor: Dr. . E. Stefan Kooij

Development of the synthesis methods for bare and magnetically coated gold nanoparticles with tuneable optical and magnetic properties. It addresses ways to achieve control over their orientation and spatial positions both in solution and during the assembly at interfaces.

Was your research application oriented?

Gold nanoparticles possess very interesting and diverse optical properties, steerable by varying in shape, patterning and orientation. At the Physics of Interfaces and Nanomaterials Group (formally known as Solid State Physics), I synthesized these particles following pure chemical routines, which are much easier and better controllable than current techniques. The research is rather fundamental. In order to use these nano entities in devices, fundamental work has to be done first.

What kind of special properties are we talking about?

Gold nanoparticles have characteristic plasmon extinction peaks that can be tuned by varying the size and shape of the particles. For example, we were able to tune the extinction peak in a wide range in infrared by changing the shape of the particle from star-shaped to spherical.

Furthermore, tuning the orientation of anisotropic nanoparticles, such as nanorods, with respect to incident light also results in modification of their optical properties. Therefore, the size and shape controlled synthesis combined with the control of the orientation of particles, is imperative for the application of these nonentities in devices.

Did you manage to enter some nice publications?

Yes, indeed I did. The alignment technique was published in the journal Nano Letters. The story about the morphology of the star-shaped particles was a cover story in Nanotechnology. The self-assembly of nanorings, using nano-magnetic properties of gold and nickel, was published in Chemical Communication. Right now, articles are submitted to Physical Review Letters B and the Journal of Colloid Interface Science, and I am working on one more.

How did you develop personally, as a researcher and scientist during your thesis project?

I learned to question things in a constructive way, solving the problems coming out of that, and managing the research project by making sensible priorities and also by interacting with the people who can broaden your vision.

Being a physicist originally, I learned a lot on chemistry. I learned to appreciate the multidisciplinary approach, and now I know that in my field of research physics and chemistry are hard to distinguish.

It is interesting to discover what other researchers are doing, and learn from their expertise. At Mesa+ the collaboration between people and groups is open and easy to accomplish. The whole institute is like a family, which I liked very much.

What are your future plans?

First, I like to continue being a researcher. In the future, I would like to contribute to the educational system of my homeland, Pakistan.