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Nanotechnology case study
Many people see the advantages of using solar panels for energy as other forms of energy may impact
the environment. Solar panels consist of solar cells which collect the sun's energy and convert it to
electricity. These are called photovoltaic devices (PV devices).
Figure 1: Solar panels in Burlington, Ontario (Burlington Post).
The majority of solar cells are still being built with silicon (Si). Silicon is the second most abundant
element in the earth's crust but to be useful as a semiconductor material in solar cells it must be refined
to a purity of 99.9999%.
As a result, the cost of producing silicon as a
semiconductor material for solar cells is expensive. In
the past, other elements have been experimented with
but they were found to be either too expensive or
unable to have high enough conductivity to be effective.
Definition:
Conductivity - a measure of a material's ability
to conduct an electric current.
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1. Research in nanotechnology
Figure 2: National Institute for Nanotechnology (NINT) at the University of Alberta
Advances in nanotechnology knowledge have offered a possible solution to solar cell development.
Researchers at the National Institute for Nanotechnology (NINT) at the University of Alberta have been
investigating the conductivity of different elements at the nanoscale.
Did you know that the properties of gold when investigated at the nanoscale are different than when
you see it as bulk gold? For example, gold is not actually the colour “gold” at the nanoscale. It turns out
the optical properties are different depending on the size of the gold particle. This can be seen when
gold is observed as a chemical mixture called a colloid. Figure 2 shows the colour of various gold
nanoparticles in colloid mixtures.
Figure 3: Gold nanoparticles showing various sizes (Wikipedia).
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As you can see, the smallest gold particles create a red colour and the larger gold particles create a
purplish colour. This is due to an effect called localized surface plasmon resonance (LSPR). An
experiment showing how to perform the above colloids can be seen at the Nanoyou website at this link.
Here is a video of the synthesis of a gold colloid if you do not have the materials to perform the
experiment yourself.
Other nanoproperties
But the colour isn't the only thing that changes at the nanoscale. NINT researchers are also investigating
the conductivity of other various elements. It turns out that gold is also a very good conductor of
electricity, so the question for researchers is to investigate the conductivity of gold to see how its
conductivity changes at the nano-level.
Here are some images of the tools that researchers at NINT use to investigate these questions. You can
find more images and explanations of each tool on the NINT website.
Figure 4: Diode array detector (DAD) and Sedex model 75 evaporative light scattering detector (ELSD) (NINT).
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Figure 5: Waters PrepLC 4000 system with tunable absorbance detector for purification of organic compounds (NINT).
Figure 6: Multi-angle Light Scattering System for both dynamic light scattering (DLS) and static light scattering (SLS), (NINT).
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Figure 7: Circular Dichroism Chiroptical Spectrometer (NINT).
Figure 8: Thermo Nicolet Almega XR Raman Microscope with stage resolution of 0.1 micron (NINT).
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Figure 9: Imaging System DTGS detector for bulk sample measurement (NINT).
2. The data
Once the materials have been measured, the researchers at NINT begin their careful analysis. For this
investigation you will be looking at actual data obtained at NINT. Let's begin with the data set for gold
(Au). The tools above provide the information in a data set that can be analyzed in Microsoft Excel.
While much of the scientists’ time is spent using the tools shown above, being able to use data tables
and performing computer analysis is one of the most common scientific tools used in research labs
today. This investigation will give you practice it analyzing data.
Double click on the Excel icon for the Excel data
Microsoft Excel
Worksheet
When you open the data you will see two columns. The first is the conductivity of the gold element
measured in voltage (V). The second column is the density of the gold material measured in mg/mL (in
other words the amount of gold nanoparticles in the colloid mixture).
Remember, we are working with very small numbers here as these measurements are done at the nanolevel. For example, the conductivity for the first sample of gold is 0.0048828 V at 0.0000305 mg/mL.
Using the data provided create a scatter graph. Help pages at Microsoft office can assist you with this.
Your scatter graph may look like a thick, fuzzy line at first glance, but if you look really closely or change
the marker options to make each mark smaller, you will see that the line is actually many data points
plotted on the same graph.
Add an X-axis title for conductivity and a Y-axis title for density.
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Question: does the data show a linear relationship between the conductivity and density of gold
nanoparticles?
Question: as the conductivity increases, what trend in the density to you observe?
Question: if we continued to increase the density to be greater and greater what would eventually
happen to the conductivity measurements?
Comparing the conductivity of gold to other elements or compounds
In order for us to know if gold is an effective conductor at the nano-level we also want to compare it to
other elements or compounds. Researchers at NINT performed the same analysis on both zinc (Zn) and
cadmium sulfide (CdS).
Double-click on the Excel icon for the Excel data for
that order)
Microsoft Excel
Worksheet
gold, zinc, and cadmium sulfide (in
For this data you will want to look at all three scatter plots on the same chart to make it easier to
compare to one another. You can do this by using the “Select data” function under the design menu and
clicking the “Add” button under the “Legend Entries”.
Below are the specific instructions from Microsoft Office on how to do this:
Add data to an existing chart
You can use one of several ways to include additional source data in an existing chart. You can
quickly add another data series, drag the sizing handles of ranges to include data on a chart that
is embedded on the same worksheet, or copy additional worksheet data to an embedded chart or
to a separate chart sheet.
Add a data series to a chart
1. Click the chart to which you want to add another data series.
This displays the Chart Tools, adding the Design, Layout, and Format tabs.
2. On the Design tab, in the Data group, click Select Data.
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3. In the Select Data Source dialog box, under Legend Entries (Series), click Add.
4. In the Edit Series dialog box, do the following:
 In the Series name box, type the name that you want to use for the series, or select the
name on the worksheet.
 In the Series values box, type the reference of the data range of the data series that you
want to add, or select the range on the worksheet.
Tip You can click the Collapse Dialog button , at the right end of the Series name or Series
values box, and then select the range that you want to use for the table on the worksheet. When
you finish, click the Collapse Dialog button again to display the whole dialog box.
3. Comparing conductivity to cost
You should now have a graph showing the relationship between conductivity and density for gold, zinc,
and cadmium sulfide.
Question: based on this data, which nanoparticle is the most conductive?
Question: how would you describe the similarities between the three particles?
Question: how would you describe the differences between the three particles?
We next want to look at another variable in our analysis. We know that gold, zinc, and cadmium sulfide
have different conductivity at different densities. As we mentioned earlier in our case study, silicon is
expensive to refine. We will now use data from the United States Geological Survey (USGS ) that shows
the prices of metal in the United States through to 2010. The prices shown in the table below are the
prices per milligram (mg) of metal (we will use just cadmium instead of cadmium sulfide) for the years
2000 to 2010. To see the full report from the USGS click here.
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
Gold
$ 280.10
$ 272.22
$ 311.33
$ 364.80
$ 410.52
$ 446.20
$ 605.83
$ 698.95
$ 873.50
$ 974.68
$ 1,227.51
Zinc
$
$
$
$
$
$
$
$
$
$
$
0.03
0.03
0.02
0.03
0.03
0.04
0.10
0.10
0.06
0.05
0.06
Cadmium
$
0.01
$
0.01
$
0.02
$
0.04
$
0.03
$
0.09
$
0.08
$
0.22
$
0.17
$
0.08
$
0.11
Table 1: Price of metals per mg from 2000-2010
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Question: what do you notice when comparing the prices of the three metals?
Question: has the price of gold changed much between 2000 and 2010? What about the price of zinc?
What about the price of cadmium?
Question: do the prices of gold, zinc, and cadmium remain consistent between 2000 and 2010 or do
they fluctuate up and down?
Question: in another 10 years, what would you predict will be the price of gold? The price of zinc? The
price of cadmium?
4. Evaluating the most cost-effective solar cell alternative
Use all of the information above and analyze the graph you have created to answer the following
questions.
Create a table to show your answers to the next three questions:
1. Question: what is the approximate conductivity of each of the three particles at 0.002 mg/mL?
2. Question: what is the approximate conductivity of each of the three particles at 0.003 mg/mL?
3. Question: what is the approximate conductivity of each of the three particles at 0.004 mg/mL?
Final analysis:
It is now time to present your final analysis
of the data. If you were asked to make
decisions on the direction to pursue solar
cell panel particle research, think about
how you would present your
recommendation.
You receive a letter from a nanotechnology
company that wishes to pursue solar cell
development and requires your advice.
How would you respond to this letter?
Dear researcher,
We are a Canadian company hoping to create solar cells for
use in solar panels. We understand you have been
investigating three different particles at the nano-level that
can possibly be used in solar cell production.
Could you please provide us with information on which of
the three particles you would recommend using and why?
Also, can you recommend the size of particle, that is, what
density in mg/mL that you would recommend we produce
our nanoparticles?
Sincerely,
John Doe, President and CEO
Canada Nanoparticle Solar Cells Inc.
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