www.sciencemag.org/cgi/content/full/337/6098/1056/DC1
Supplementary Materials for
Discovering Nanoscience
A. Colin Blair, Ellen R. Fisher, Dawn Rickey*
*To whom correspondence should be addressed. E-mail: [email protected]
Published 31 August 2012, Science 337, 1056 (2012)
DOI: 10.1126/science1215151
This PDF file includes:
Materials and Methods
Supplementary Materials:
Exploring Gold Nanoparticles Laboratory Module
Description
Table of contents
Student background knowledge, learning goals, and implementation suggestions
Student laboratory manual, including example grading rubrics
Supplies, chemicals, and laboratory preparation
Page(s)
i
ii
1–18
19–20
Additional information for instructors: Because providing more detailed information online
could compromise the implementation of the EGNP laboratory module, instructors wishing to
implement the module are encouraged to email the corresponding author at
[email protected] for further information including AFM image files used at Colorado
State University.
Exploring Gold Nanoparticles
© 2012 Colorado State University
i
Suggested Student Background Knowledge for the Exploring Gold Nanoparticles Module
The Exploring Gold Nanoparticles laboratory module is designed to be implemented prior to didactic instruction on the topics of colloidal mixtures and nanoparticles. The module assignments
assume that participating students have previously developed macroscopic and molecular-level
understandings of matter and basic chemical reactions. Thus, the module may be implemented
toward the end of a first-semester general chemistry course, during a second-semester general
chemistry course, or in other courses for which first-semester general chemistry is a prerequisite.
Learning Goals for Model-Observe-Reflect-Explain (MORE) Laboratory Modules
and Exploring Gold Nanoparticles
A key goal of Model-Observe-Reflect-Explain (MORE) laboratory modules is for students to
learn to construct, evaluate, and revise molecular-level models based on the experimental evidence they collect and analyze. Another goal is for students to develop robust understandings of
the systems they study, such that they are able to apply the models they develop in new contexts.
We have found that student engagement in three thinking processes during MORE instruction is
strongly correlated with subsequent successful reasoning in transfer contexts: (1) constructing
molecular-level models that are consistent with experimental evidence, (2) reflecting accurately
and completely on how molecular-level ideas have changed relative to previous ideas, and (3)
identifying evidence to justify personal model refinements as part of the reflection. Thus, engaging students in these specific thinking processes are also important goals.
Ideally, consideration of experimental evidence during a MORE laboratory module promotes
student model revisions toward progressively more correct ideas, so that students’ final refined
models are both consistent with the data and in line with scientifically-accepted views. Thus, for
the Exploring Gold Nanoparticles laboratory module, an additional learning goal is for students’
macroscopic and molecular-level models to progress toward a basic, scientifically-accurate model of colloidal gold nanoparticles.
Preparing to Teach the Exploring Gold Nanoparticles Laboratory Module
We suggest that first-time implementers (including teaching assistants) prepare to teach the Exploring Gold Nanoparticles laboratory module by participating in the module and associated assignments as if they were students. Ideally, multiple instructors participate in this process, allowing for discussion of how to best implement the module with students. We have found that using
the EGNP module in this way is effective for introducing teaching assistants to Model-ObserveReflect-Explain (MORE) Thinking Frame instruction. Supplies, chemicals, software, and laboratory preparation for the module are detailed on pages 19-20 of this document. Instructors are also
welcome to contact the corresponding author at [email protected] to discuss implementation.
Exploring Gold Nanoparticles
© 2012 Colorado State University
ii
Exploring Gold Nanoparticles
A. Colin Blair, Ellen R. Fisher, and Dawn Rickey
Department of Chemistry, Colorado State University, Fort Collins, CO 80523-1872
Construct Your Initial Model
During this laboratory module, you will synthesize gold nanoparticles, Au(s), and explore factors
that affect their properties. In the first week of the module, you will synthesize gold nanoparticles by mixing aqueous solutions of chloroauric acid (HAuCl4) and sodium citrate
(Na3C6H5O7). The net ionic equation for the reaction is:
4 HAuCl4(aq) + 3 C6H5O73–(aq) + 3 H2O(l) →
4 Au(s) + 6 CO2(g) + 3 C4H6O4(aq) + 7H+(aq) + 16 Cl–(aq)
succinic acid
Describe your understanding of what will happen in three experiments (labeled A, B, and C in
the table below) when different amounts of HAuCl4(aq) and Na3C6H5O7(aq) are mixed at an elevated temperature.
For each experiment, the table below shows the molarities and volumes of the reactant solutions
that will be mixed, as well as the resulting number of moles of each reactant that will be mixed
(calculated by multiplying the solution molarity by the solution volume).
A
B
C
Molarity of
HAuCl4(aq)
Volume of
HAuCl4(aq)
0.00050 M
0.00050 M
0.00050 M
0.0500 L
0.0500 L
0.0500 L
Moles
(=MxV) of
HAuCl4
0.000025 mol
0.000025 mol
0.000025 mol
Molarity of
Na3C6H5O7(aq)
Volume of
Na3C6H5O7(aq)
0.00375 M
0.00500 M
0.0250 M
0.0050 L
0.0050 L
0.0050 L
Moles
(=MxV) of
Na3C6H5O7
0.000019 mol
0.000025 mol
0.00013 mol
For the macroscopic aspect of your initial model, describe what you expect to observe for the
separate reactant solutions and for the resulting product mixtures for A, B, and C. For the molecular-level aspect, explain what you think the particles (e.g., molecules, atoms, ions) are doing
that results in your expected observations both before and after mixing these solutions for cases
A, B, and C. Be sure to include information about the nature and properties of the gold nanoparticles you will synthesize in both macroscopic and molecular-level aspects of your model.
Exploring Gold Nanoparticles
© 2012 Colorado State University
1
Score: __________ (out of 20)
Student Name:
Grading Rubric for Exploring Gold Nanoparticles Initial Model Assignment
Present your initial model (20)
Describes macroscopic model before
mixing for cases A, B, and C
Not present
(0)
Present but
incomplete
(_____)
Present
and complete
(4)
Describes macroscopic model after
mixing for cases A, B, and C
Not present
(0)
Present but
incomplete
(_____)
Present
and complete
(6)
Describes molecular-level model before mixing for cases A, B, and C
Not present
(0)
Present but
incomplete
(_____)
Present
and complete
(4)
Describes molecular-level model after mixing for cases A, B, and C
Not present
(0)
Present but
incomplete
(_____)
Present
and complete
(6)
Exploring Gold Nanoparticles
© 2012 Colorado State University
2
Part I: What are nanoparticles?
During this laboratory module, you will synthesize gold nanoparticles, Au(s), and explore the
factors that affect their properties. In the first week of the module, you will begin by investigating various mixtures, including the solutions you will subsequently use in synthesizing the gold
nanoparticles.
As you conduct your experiments, remember to think about how the evidence you collect relates
to your initial model.
Observe
1.
2.
3.
4.
5.
6.
7.
At your lab table, you have been provided with 8 vials containing various mixtures. Vials
1–4 contain: (1) aqueous solution of potassium permanganate (KMnO4); (2) aqueous solution of copper (II) sulfate (CuSO4); (3) finely ground charcoal, C(s); and (4) finely ground
charcoal in water.
Using the laser pointer provided, and being careful not to shake or jostle the vials, shine
the laser directly through the contents of these four vials, and record your observations.
Never look directly into the laser beam. Then shine the laser through the contents of each
vial from the bottom of the vial, aiming the laser beam toward the vial cap. Observe the
vial from the side. Then shine the laser pointer through the side of each vial, looking perpendicularly to the direction of the laser beam. Record all observations.
Next, shake vials 3 & 4 vigorously, immediately shine the laser pointer through the contents of each vial, and record your observations
Observe what happens when you shine the laser through vials 5 and 6, containing 0.0010
M aqueous silver nitrate (AgNO3) and 0.0010 M sodium chloride (NaCl), respectively.
Record your observations.
Removing the caps from vials 5 & 6, pour one solution into the other. Place the cap on
the vial that contains the mixture, shake the vial, and then shine the laser beam through the
mixture. Record your observations. Repeat these observations after letting the mixture
stand for 10 minutes.
Observe what happens when you shine the laser through vials 7 and 8, containing the
reactant solutions for the synthesis of gold nanoparticles, aqueous sodium citrate
(Na3C6H5O7) and aqueous chloroauric acid (HAuCl4) respectively. Record your observations.
Save all of your sample vials in case you wish to examine them again later.
Exploring Gold Nanoparticles
© 2012 Colorado State University
3
Reflect
As you reflect, discuss your thoughts with your classmates and record them in your laboratory
notebook.
¾ Compare and contrast the observations you made when shining the laser pointer through
the different samples. What was similar? What was different? What patterns do you notice?
¾ Draw a molecular-level picture for each sample. What do you think is happening on the
molecular level to account for your observations?
Synthesis of Gold Nanoparticles
In the next part of the laboratory module, you will synthesize gold nanoparticles by mixing
aqueous solutions of chloroauric acid (HAuCl4) and sodium citrate (Na3C6H5O7). The net ionic
equation is:
4 HAuCl4(aq) + 3 C6H5O73–(aq) + 3 H2O(l) →
4 Au(s) + 6 CO2(g) + 3 C4H6O4(aq) + 7H+(aq) + 16 Cl–(aq)
succinic acid
Each group will perform one of the three experiments (A, B, or C) that you considered in your
initial model assignment. Groups will then share samples of mixtures A, B, and C so that everyone in the class can make their own observations of the resulting mixtures.
A
B
C
Molarity of
HAuCl4(aq)
Volume of
HAuCl4(aq)
0.00050 M
0.00050 M
0.00050 M
0.0500 L
0.0500 L
0.0500 L
Exploring Gold Nanoparticles
© 2012 Colorado State University
Moles
(=MxV) of
HAuCl4
0.000025 mol
0.000025 mol
0.000025 mol
Molarity of
Na3C6H5O7(aq)
Volume of
Na3C6H5O7(aq)
0.00375 M
0.00500 M
0.0250 M
0.0050 L
0.0050 L
0.0050 L
Moles
(=MxV) of
Na3C6H5O7
0.000019 mol
0.000025 mol
0.00013 mol
4
Observe
1.
2.
3.
4.
5.
6.
7.
8.
9.
At your lab table, you should have three empty glass vials, a 100-mL beaker, a 100-mL
graduated cylinder, a hot plate, a magnetic stir bar, a Sharpie marker, and a plastic transfer
pipette.
Find out which concentration of Na3C6H5O7(aq) your group should use from your instructor and to which letter (A, B, or C) this corresponds (see Table above). Be sure to record
the concentration of Na3C6H5O7(aq) and the corresponding letter in your notebook.
Label all three of the glass vials with the letter corresponding to your assigned concentration of Na3C6H5O7(aq).
Using the graduated cylinder, measure out 50.0 mL of 5.0 × 10-4 M HAuCl4(aq), and pour
it into the 100-mL beaker. Add the magnetic stir bar and mark the bottom of the meniscus
with a Sharpie marker. Heat the solution to boiling on the hotplate. (Do not turn on the
magnetic stirring mechanism until the solution begins to boil.)
Once the solution begins to boil, turn the magnetic stirrer on, and add 5.0 mL of your assigned concentration of Na3C6H5O7(aq) to the beaker on the hotplate. Allow the mixture to
boil for 10 minutes; then turn the heat and magnetic stirrer off. Dilute the mixture in the
beaker by adding deionized water until the bottom of the meniscus reaches the marked line.
Once you have diluted the mixture, turn the magnetic stirrer back on at a low speed.
After the mixture has cooled, use a plastic pipette to carefully transfer an approximately 4mL aliquot (enough so that your vial is ¾ of the way full) of the mixture to each of your
three labeled glass vials. For each of these samples, try to obtain a representative sample
of your mixture.
Trade two of your samples for different samples from other groups so that you end up with
three vials containing mixtures A, B, and C.
Observe each of the mixtures in the three vials, and record your observations in your notebook. Shine the laser pointer through each of these mixtures and note what you observe.
Hold each of the samples up to an overhead light source and record your observations.
For groups that prepared mixture C, after you have allowed your classmates to obtain samples, transfer the remainder of your reaction mixture from the 100-mL beaker to a labeled
brown bottle. You will use this mixture during the second week of this laboratory module.
For groups that prepared mixture A or B, please dispose of your mixture in the appropriate
waste container.
Exploring Gold Nanoparticles
© 2012 Colorado State University
5
Reflect
As you reflect, discuss your thoughts with the other members of your group and record them in
your laboratory notebook.
¾ What similarities and differences did you observe for the mixtures you obtained at the end
of experiments A, B, and C? How do you think these similarities and differences relate to
the starting conditions for experiments A, B, and C?
¾ What evidence do your experiments using the laser pointer provide about what happens,
from both macroscopic and molecular-level perspectives, when you mix chloroauric acid
and sodium citrate?
¾ What effect does using different concentrations of sodium citrate have on the experiments’ outcomes? How can you explain this from macroscopic and molecular-level perspectives?
¾ Based on your experimental observations and evidence, what do you think a gold nanoparticle is? How do you think nanoparticles are similar to and different from other chemical species with which you are familiar?
¾ Sketch molecular-level views for the different product mixtures you obtained. How do
these depictions compare to your representations of the reactant solutions?
¾ How did your observations throughout the experiment compare to your initial expectations? Have your observations and data from this experiment prompted you to refine your
model? What changes will you make? What has prompted you to make these changes?
Explain
Participate in a class discussion about what happens when you react chloroauric acid and sodium
citrate. Be prepared to explain your refined model, how it differs from your initial model, and
what observations led you to revise your model.
Exploring Gold Nanoparticles
© 2012 Colorado State University
6
Refine Your Model
Develop a refined model of what happens when you mix HAuCl4(aq) and Na3C6H5O7(aq) at an
elevated temperature. Briefly present your refined macroscopic model (your observations) and
your refined molecular-level model that accounts for your observations. Be sure to address your
understanding of the nature of gold nanoparticles from both macroscopic- and molecular-level
perspectives in your model. Compare this model to your initial model, and identify the key aspects of your model that changed and remained the same for both the macroscopic and molecular
levels. Fully explain what revisions, if any, you made to your initial model, including what specific experimental evidence has caused you to make any revisions and what has supported your
initial model in aspects that you did not revise. What generalization(s) can you make based on
the experimental evidence you collected in lab this week?
Post-Laboratory Questions
Read page 9 of the introduction to next week’s experiments describing an atomic force microscope (AFM), and then answer the following question in your laboratory notebook.
1. Next week, samples of gold nanoparticles made via the procedures that you performed
this week will be made for you, deposited on glass microscope slides, and imaged with an
atomic force microscope, AFM (see page 9). Based on your refined model, predict what
you will see in AFM images for cases A, B, and C.
2. Sketch predicted AFM images for each of these, and explain what similarities and differences you expect to observe for cases A, B, and C. What trends or patterns do you expect?
Exploring Gold Nanoparticles
© 2012 Colorado State University
7
Score: ___________ (out of 50)
Student Name:
Grading Rubric for Exploring Gold Nanoparticles Week 1 & Refined Model
Lab notebook, data, observations, calcs (24)
Not present
(0)
Present but
incomplete
(_____)
Present
and complete
(24)
Present but
incomplete
(_____)
Present but
incomplete
(_____)
Partially
Consistent
(_____)
Present
and complete
(10)
Present
and complete
(10)
Fully Consistent
(4)
Present but
incomplete
(_____)
Present but
incomplete
(_____)
Present but
incomplete
(_____)
Present
and complete
(8)
Present
and complete
(8)
Present and
complete
(8)
Present your refined model (24)
Describes macroscopic model before and after
mixing for cases A, B, and C
Not present
(0)
Describes molecular-level model before and
after mixing for cases A, B, and C
Not present
(0)
Molecular-level model is consistent with experimental evidence
Not consistent
(0)
Explain why your model has changed (24)
For macroscopic model before and after mixing, identifies key aspects that changed & remained the same
For molecular-level model before and after
mixing, identifies key aspects that changed &
remained the same
Cites specific experimental evidence to justify
why molecular-level aspects remained the
same or changed
Generalize your model (16)
Not present
(0)
Not present
(0)
Not present
(0)
Provides macroscopic generalized model that
can be used to predict new situations
Not present
(0)
Present but
incomplete
(_____)
Present and
complete
(4)
Provides molecular-level generalized model
that can be used to predict new situations
Not present
(0)
Present but
incomplete
(_____)
Present and
complete
(4)
Cites specific evidence to support generalized
model
Not present
(0)
Present but
incomplete
(_____)
Present and
complete
(8)
Present but
incomplete
(_____)
Present but
incomplete
(_____)
Present and
complete
(6)
Present and
complete
(6)
Post-laboratory questions (12)
Sketch predicted AFM images for mixtures A,
B, and C.
Not present
(0)
Describe similarities/differences/patterns
among predicted AFM images
Not present
(0)
Exploring Gold Nanoparticles
© 2012 Colorado State University
8
Part II: Using atomic force microscope images to refine your model
In this portion of the module, you will employ atomic force microscope (AFM) images to observe samples of product mixtures like the ones you obtained when you synthesized gold nanoparticles last week. The AFM instrument is briefly described below.
Atomic Force Microscope
Once the samples have been deposited onto microscope slides, an atomic force microscope
(AFM) will be used to examine them. The AFM is a sensitive instrument that allows one to investigate the surface of a sample. The EasyScan AFM, whose use may be demonstrated for you
in lab, employs a silicon tip that moves across a sample’s surface, recording the height (in the z
direction, as indicated below) of each point on the surface. As shown in the diagrams below, the
tip traces the features found on the surface of the sample. A laser is used to monitor the position
of the AFM tip. Each trip the tip makes across the surface of the sample is called a “scan.” If
used properly, the EasyScan AFM can detect structures that are as small as one nanometer in
height.
Scan direction (along x-axis)
AFM tip
Particle on surface
z-axis
To convert these data to a 3-D image, the AFM software converts each scan across the sample
into a line along the x-direction of the image. When the AFM tip moves up one position along
the y-axis to record another scan, that scan appears as a second line in the image. Heights are
recorded along the z-axis. Viewing the image from top down looks like this:
y
x
Scan #2
Scan #1
z
For this part of the laboratory module, samples of gold nanoparticles made via the procedures
that you performed last week have been made for you, deposited on glass microscope slides, and
imaged with the AFM.
Exploring Gold Nanoparticles
© 2012 Colorado State University
9
Observe
1.
2.
Obtain electronic copies of the AFM images of mixtures A, B, and C.
To examine the AFM images, you will use a software program called Image SXM. Image SXM allows you to load, analyze, and print AFM images. Your laboratory instructor
will assign each group portions of the AFM images to analyze. Using the software instructions provided below, record the height of at least 10 of the structures in your assigned portion of each AFM image. Be sure to record this data in your laboratory notebook.
The button represented by this icon can be used to measure the height of structures on the surface of the slide. After selecting this option, click and drag to
draw a line over structures in your image, thus measuring the height of it. Be sure
to draw your lines vertically:
The zoom button allows you to make your AFM image larger.
3.
4.
If you would like to view the AFM images in color, choose Options > Color
Tables, and choose from a variety of color schemes.
Once you have recorded the heights of all of these images, share this data with the rest of
the class.
Using all of the class data, calculate the average structure height for each of the three images corresponding to mixtures A, B, and C.
Reflect
As you reflect, discuss your thoughts with the other members of your group and record them in
your laboratory notebook.
¾ What differences did you observe when you examined the AFM images of mixtures A, B,
and C? What does this evidence tell you about what happens when different amounts of
citrate are added to a fixed amount of chloroauric acid?
¾ What do the different colors in the AFM image mean – why are some portions red, other
portions yellow, and so on?
¾ How do your macroscopic observations of mixtures A, B, and C relate to your measurements of the AFM images? What does this evidence suggest about what happens on the
molecular level?
¾ The atomic radius of a gold atom is 144 picometers (pm). How does the size of a gold
atom compare to the sizes of the structures found in the AFM images? How does this relate to your molecular-level model?
Exploring Gold Nanoparticles
© 2012 Colorado State University
10
¾ Based on your observations from both weeks of this module, which solutions contained
the largest particles? What are the differences on both the macroscopic-level and molecular-level between the mixture(s) that contain(s) these large particles and the gold that
forms in the mixture(s) in which there are smaller particles?
¾ Based on your experimental observations and evidence, what do you think a gold nanoparticle is? How do you think nanoparticles are similar to and different from other chemical species with which you are familiar?
¾ How did your observations throughout the experiment compare to your initial expectations? Have your observations and data from this experiment prompted you to refine your
model? What changes will you make? What has prompted you to make these changes?
Explain
Participate in a class discussion about what happens when you react chloroauric acid and sodium
citrate, and the nature of gold nanoparticles. Be prepared to explain your refined model, how it
differs from your previous refined model, and what observations led you to revise your model.
Exploring Gold Nanoparticles
© 2012 Colorado State University
11
Part III: Use your refined model to predict how new systems behave
Predict Using Your Model
Consider two 1.0 M aqueous solutions: potassium iodide (KI) and dextrose (C6H12O6). Each of
these solutions will be added (separately) to portions of mixture C from last week. Based on
your refined model, what do you think will happen (from both macroscopic- and molecular-level
perspectives) when these solutions are added to mixture C? Explain.
Observe
1.
2.
3.
4.
5.
6.
7.
Obtain a 10-mL graduated cylinder, 3 disposable transfer pipettes, and four small glass
vials.
Into each of the four small glass vials, transfer 3.0 mL of gold nanoparticle mixture C.
Set one of these vials aside as a control.
Using a disposable transfer pipette, add 3 drops of KI(aq) to a second vial containing
gold nanoparticle mixture C. Cap the vial, shake it vigorously, and immediately shine
the laser pointer through the mixture. (Remember all of the different ways you used the
laser pointer to observe your mixtures last week.) Record your observations.
Repeat step 3 (in vials 3 and 4) with the dextrose solution and the unknown solution, respectively. Be sure to label each vial appropriately.
Add an additional 6 drops of the same solutions to the same vials. Record your observations.
Share your data with the other groups in your class.
Dispose of your mixtures, except for the control vial, in the appropriate waste container.
In preparation for the next part of the laboratory module, rinse each empty vial 3 times
with deionized water.
Reflect
As you reflect, discuss your thoughts with the other members of your group and record them in
your laboratory notebook.
¾ Draw molecular-level views of KI(aq) and C6H12O6(aq) before they are added to the gold
nanoparticle mixture?
¾ How does the addition of each solution affect the mixture? What does this evidence suggest about what happens on the molecular level?
¾ What can you determine about the identity of the unknown solution?
Exploring Gold Nanoparticles
© 2012 Colorado State University
12
¾ How do(es) the color change(s) that you have observed for the various additions of solutions to mixture C relate to the colors that you observed for mixtures A, B, and C during
the first week of experiments? What does this suggest about what happens on the molecular level when the various solutions are added to the gold nanoparticle mixture?
Explain
Participate in a class discussion about the effects of adding KI(aq) and C6H12O6(aq) solutions to
gold nanoparticle mixtures, and the implications for your molecular-level model.
Predict Using Your Model
The mixtures obtained from the experiments you just completed in Part III have been deposited
on glass microscope slides and imaged with the AFM. Based on your current model, what do
you expect to observe in these images? Sketch predicted AFM images for each of these, and explain what similarities and differences you expect to observe for the three different mixtures.
What trends or patterns do you expect to see?
Observe
Obtain electronic copies of the AFM images of mixture C + KI(aq) and mixture C +
C6H12O6(aq). Examine them to see whether they agree with your predictions, and record your
observations. (You do not need to measure the heights of features within these images.)
Reflect
As you reflect, discuss your thoughts with the other members of your group and record them in
your laboratory notebook.
¾ What differences did you observe when you examined the AFM images of mixture C with
the different added solutions? What does this evidence suggest about what happens on the
molecular level when the solutions are added to mixture C?
¾ Are your observations of the AFM images consistent with your molecular-level ideas
Exploring Gold Nanoparticles
© 2012 Colorado State University
13
about what happens when the different solutions are added to mixture C? Have your observations from this experiment prompted you to refine your model? What changes will
you make? What has prompted you to make these changes?
Explain
Participate in a class discussion about the effects of adding KI(aq) and C6H12O6(aq) to gold nanoparticle mixture C, and the implications for your molecular-level model.
Exploring Gold Nanoparticles
© 2012 Colorado State University
14
Part IV: How do gold-nanoparticle-based pregnancy tests work?
Early-detection pregnancy tests are based on the measurement of levels of human chorionic gonadotropin (hCG), a protein that is released by a developing embryo, in a women’s blood or
urine. Gold nanoparticles are used in some commercial pregnancy tests, such as the First Response® home pregnancy tests, to determine the presence or absence of high levels of hCG in
urine.
How do these pregnancy tests work? Human urine is an aqueous solution that contains moderate
levels of dissolved salts. The urine of women who are pregnant also contains higher concentrations of the protein hCG than the urine of women who are not pregnant. When urine containing
hCG is added to a gold nanoparticle mixture, hCG (which is a very large protein) wraps itself
around the gold nanoparticles and prevents the gold nanoparticles from clumping together to
form larger particles.
During the final portion of this laboratory module, you will conduct simulated pregnancy tests on
two synthetic urine samples. Both of these samples contain salt, but only one of them contains
protein. These samples have been submitted to your laboratory by two fictitious women, Lois
and Matilda. Your assignment is to develop a gold-nanoparticle-based pregnancy test, and then
determine who is pregnant.
The gold-nanoparticle-based pregnancy test that your class designs should 1) provide results that
clearly distinguish between the synthetic urine sample that contains protein and the sample that
does not contain protein, and 2) be as inexpensive as possible.
Observe
1.
2.
3.
4.
5.
For this part of the laboratory module, your entire laboratory section will be provided
with only 60 mL of a gold nanoparticle mixture for use in designing and carrying out the
pregnancy tests. Thus, you should begin with a whole-class discussion of how everyone
can work together to accomplish this task. The whole class should decide what specific
experiments each group of students will conduct (including amounts used).
Hints: (a) We suggest that you designate one student to come to the board/overhead and
facilitate the whole-class discussion. (b) We suggest that you use the small glass vials to
conduct your experiments. Be sure to rinse each vial three times with deionized water
and dry them with paper towel between experiments.
Remember to record the specific procedures you use in your laboratory notebook. Be
specific enough so that someone who was not involved in your class discussions would
be able to follow your instructions and carry out the procedures as you have designed
them.
Carry out your tests according to the procedures you outlined, and record your observations.
Share your results with the whole class, and assess how well you have accomplished your
goals.
Exploring Gold Nanoparticles
© 2012 Colorado State University
15
Reflect
As you reflect, discuss your thoughts with the other members of your group and record them in
your laboratory notebook.
¾ How does the addition of the gold nanoparticle mixture to each solution affect the resulting
mixture? What does this evidence suggest about what happens on the molecular level?
¾ How do the observations that you recorded during this part of the experiment compare to
your observations in part III? What does this suggest about the molecular-level species
that are present in each of the urine samples?
¾ Who do you think is pregnant, Lois or Matilda? Explain how the experimental evidence
supports your conclusions.
¾ How might a gold-nanoparticle-based pregnancy test result in a false positive? What
chemical species could account for this false positive?
¾ How did your observations throughout the experiment compare to your initial expectations? Have your observations and data from this experiment prompted you to refine your
model? What changes will you make? What has prompted you to make these changes?
Explain
Participate in a class discussion about the effects of adding the gold nanoparticle mixture to each
of the urine samples and the implications for your molecular-level model.
Exploring Gold Nanoparticles
© 2012 Colorado State University
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Refine Your Model
Develop a final refined model of the nature and properties of gold nanoparticles. Briefly present
your final macroscopic model (your observations) and your final molecular-level model that accounts for your observations. Compare your final refined model presented above with your initial model, and identify the key aspects of your model of gold nanoparticles that changed and
remained the same for both the macroscopic and molecular levels. [Note that in this model you
should focus on the nature and properties of gold nanoparticles, and how your ideas about these
have changed, not necessarily on the reaction to synthesize gold nanoparticles.]
Explain what revisions, if any, you made to your initial model, including what specific experimental evidence has caused you to make any revisions, and what has supported your initial model in aspects that you did not revise. Based on your experimental evidence from Parts III & IV,
what generalization(s) can you make? Propose a next experiment to inform your molecular-level
model of gold nanoparticles and/or similar chemical systems. Explain what the results of this
proposed experiment would tell you about what happens on the molecular level.
Exploring Gold Nanoparticles
© 2012 Colorado State University
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Score: __________ (out of 100)
Student Name:
Grading Rubric for Exploring Gold Nanoparticles Week 2 & Final Refined Model
Lab notebook, data, observations, calcs (24)
Not present
(0)
Present but
incomplete
(_____)
Present
and complete
(24)
Present but
incomplete
(_____)
Present but
incomplete
(_____)
Partially
Consistent
(_____)
Present
and complete
(10)
Present
and complete
(10)
Fully Consistent
(4)
Present but
incomplete
(_____)
Present but
incomplete
(_____)
Present but
incomplete
(_____)
Present
and complete
(8)
Present
and complete
(8)
Present and
complete
(8)
Present your refined model (24)
Describes macroscopic model of nature and
properties of gold nanoparticles
Not present
(0)
Describes molecular-level model of nature
and properties of gold nanoparticles
Not present
(0)
Molecular-level model is consistent with experimental evidence
Explain why your model has changed (24)
Identifies key aspects that changed & remained the same for macroscopic model of
nature & properties of Au nanoparticles
Identifies key aspects that changed & remained the same for molecular-level model of
nature & properties of Au nanoparticles
Cites specific experimental evidence to justify
why molecular-level aspects remained the
same or changed
Generalize your model (16)
Not consistent
(0)
Not present
(0)
Not present
(0)
Not present
(0)
Provides macroscopic generalized model that
can be used to predict new situations
Not present
(0)
Present but
incomplete
(_____)
Present and
complete
(4)
Provides molecular-level generalized model
that can be used to predict new situations
Not present
(0)
Present but
incomplete
(_____)
Present and
complete
(4)
Cites specific evidence to support generalized
model
Not present
(0)
Present but
incomplete
(_____)
Present and
complete
(8)
Present but
incomplete
(_____)
Present but
incomplete
(_____)
Present and
complete
(6)
Present and
complete
(6)
Propose a next experiment (12)
Proposes a specific new experiment
Not present
(0)
Explains how results of proposed experiment
would inform molecular-level understanding
of system
Not present
(0)
Exploring Gold Nanoparticles
© 2012 Colorado State University
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Chemicals and Supplies Required to Implement the Exploring Gold Nanoparticles Module
The following provides the requirements for implementing the Exploring Gold Nanoparticles
module with 6 groups of students.
Module Part I Supplies
Part I of the module requires 6 each of: red laser pointers, 100-mL beakers, 50-mL (or larger)
graduated cylinders, hot plate/stirrers, magnetic stir bars, markers or wax pencils, transfer pipettes. In addition, you will need 66 6-mL scintillation vials, and 2 50-mL storage bottles (for
groups of students synthesizing gold nanoparticle mixture C).
Module Part I Chemicals and Preparation Suggestions
Description
Vial 1
Vial 2
Vial 3
Vial 4
Vial 5
Vial 6
Vial 7 &
GNP syntheses
Vial 8 &
GNP syntheses
Chemical Name
(Formula)
Potasssium permanganate
(KMnO4)
Copper(II) sulfate
pentahydrate (CuSO4•5H2O)
Charcoal (C), finely ground
Charcoal (C), finely ground
Silver nitrate
(AgNO3)
Sodium chloride
(NaCl)
Sodium citrate dihydrate
(Na3C6H5O7•2H2O)
Gold (III) chloride
trihydrate
(HAuCl4•3H2O)
CAS
Number
Solution
Concentration
Preparation Suggestions
(all solutions are aqueous)
7722-64-7
0.005%
dissolve 0.05 g in 0.100 L sol’n and
dilute 1:10
7758-99-8
0.0200 M
2.50 g CuSO4•2H2O in 0.0500 L
sol’n
7440-44-0
N/A
0.10 g finely-ground charcoal
7440-44-0
N/A
0.01 g finely-ground charcoal in 4
mL of water
7761-88-8
0.0010 M
0.085 g in 0.500 L sol’n
7647-14-5
0.0010 M
0.058 g in 1.00 L sol’n
3 different
concentrations
for syntheses:
A: 0.00375 M
B: 0.0050 M
C: 0.0250 M
0.276 g in 0.500 L sol’n
0.368 g in 0.500 L sol’n
1.84 g in 0.500 L sol’n
6132-04-3
16961-25-4
0.00050 M
0.10 g in 0.500 L sol’n; make the
week of lab, store in brown bottle
Fill vials 1, 2, 4, 7, and 8 with 4 mL each of solution; fill vials 5 and 6 with 2.5 mL each of solution.
Exploring Gold Nanoparticles
© 2012 Colorado State University
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Module Parts II & III Software and Online Resources
The University of Virginia Virtual Lab Atomic Force Microscope provides a flash animation that
walks one through how an AFM takes images: http://virlab.virginia.edu/VL/easyScan_AFM.htm
Image SXM is the version of the public domain AFM image analysis software NIH Image referred to in the student laboratory manual. It is available for Macintosh computers at
http://www.liv.ac.uk/~sdb/ImageSXM/ImageSXM
ImageJ is a similar program that runs on the Macintosh, Windows, and Linux. It is available at:
http://rsb.info.nih.gov/ij/
Module Parts II, III, & IV Supplies
Part II of the module requires 6 each of: red laser pointers, 10-mL (or larger) graduated cylinders, and markers or wax pencils. In addition, you will need gold nanoparticle mixture C from
Part I of the module, 18 transfer pipettes, and 30 6-mL scintillation vials. Finally, you will need
computers with AFM image analysis software (see above) and the appropriate AFM image files
for students to analyze. (AFM image files from implementations at Colorado State University
may be obtained by contacting the corresponding author at [email protected].)
Module Parts III & IV Chemicals and Preparation Suggestions
Description
Part III
(known &
unknown)
Part III
(known &
unknown)
Part III
(unknown)
Part III
(unknown)
Part IV
“urine (not
pregnant)”
Part IV
“urine
(pregnant)”
Chemical Name
(Formula)
CAS
Number
Solution
Concentration
Preparation Suggestions
(all solutions are aqueous)
Potasssium iodide
(KI)
7681-11-0
1.0 M
8.3 g in 0.0500 L of sol’n
Dextrose
(C6H12O6)
50-99-7
1.0 M
9.0 g in 0.0500 L of sol’n
7647-14-5
1.0 M
2.9 g in 0.0500 L of sol’n
67-56-1
1.0 M
2.0 mL in 0.0500 L of sol’n
Sodium chloride
(NaCl)
7647-14-5
0.10 M
1.46 g NaCl in 0.250 L sol’n
Sodium chloride
(NaCl) & albumin
7647-14-5,
9048-46-8
0.10 M &
0.10% mass
1.46 g NaCl and 0.25 g albumin in
0.250 L sol’n
Sodium chloride
(NaCl)
Methanol
(CH3OH)
For Part III, fill vials with about 4 mL of each solution.
Exploring Gold Nanoparticles
© 2012 Colorado State University
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