LABORATORY EXPERIMENTS Au Nanoparticles (3+4)
The study of Au nanoparticles using UV-vis-IR spectroscopy and SEM
You will need a Labbook and a USB data key to save your data. Make sure it is
exported in a format you can read in Excel.
1. Literature search – What are the technological applications of small Au
particles (there are quite a lot, from Surface-Enhanced Raman Spectroscopy
(SERS) to catalysis and changing the colour in stained glass windows).
a. Most introductions of papers will specify why people look at Au
particles.
b. Do a search for Au AND nanoparticle* AND SERS in Web of
Knowledge http://wok.mimas.ac.uk/ to check for some of the most
referenced papers (sort by number of citations) and have a look at a
few of them to get an idea of how Au particles are obtained and what
they are used for.
c. To help you along, i've attached a number of papers in the selfextracting archive.
Limit yourselves to no more than 5-6 papers and maybe one or two of the papers
referenced in. Give precedence to the papers containing or detailing UV-vis-IR
spectroscopy and SEM studies of Au particles.
2. You are going to prepare Au colloidal particles using the excimer laser
from AuCl4 and study their optical properties (UVvisIR) as a function of
particle size (SEM). Please read the Additional Laser Safety Assessment
from the self-extracting archive.
Formulate a hypothesis, having read the papers you looked up and also the ones
attached, about what you think you will observe and why.
This is a description of a typical route to obtaining small Au particles: “A gold metal
nanoparticle solution was synthesized with a laser-based technique using the pulses
from a Lambda-Physik LPX 210i excimer laser operating at 248 nm, with pulse
duration of 25 ns. The technique used to produce the Au nanoparticles involved the
UV photo-reduction of an aqueous auric chloride solution. A 4 mm depth of a 0.12
mM AuCl4- solution was placed in a vessel mounted on a computer-controlled
motorized X-Y translation stage. The 15 mJ laser pulses were defocused to produce a
rectangular spot of area 0.4 cm2. The laser spot was raster scanned over the whole
area of the vessel, during the 9000 laser shot irradiation, scanning across the whole
area 40 times. This method produced red-colored Au nanoparticle solutions.
Nanoparticle coalescence occurred rapidly, giving the solution a blue-purple color.”
a. Firstly, you have to fill in a COSHH form for using AuCl4. Use the
Materials Data Sheet provided and a form from the ATI Intranet link
(you will have to go through the log on to go further)
http://www.ati.surrey.ac.uk/safety. You cannot start the lab without
it.
b. Generate a number of solutions using different irradiation times. (what
should happen if the irradiation time varies? - see literature search).
3. UV-vis-IR
a. What does UV-vis-IR measure and what would you typically observe
in spectra of these solutions (check literature).
b. Read the SOP provided. What experimental set-up should you use and
what spectral range is of interest (check with literature for similar
experiments).
4. SEM.
a. You should formulate an idea of what conditions you want to image at,
also by looking at the detail in SEM images from your literature search.
b. Read Chapters 4 and 5 in the operation manual.
Reading again the paragraph about the preparation of Au particles in this document,
can you think of some practical issues/problems that might arise?
If this is what you choose to write up as an APL (Applied Physics Letters) article,
think of how the techniques complement each other and see if you can establish
relationships between the observations. The document will be submitted via Turn-itin.