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: dawn.rickey@colostate.edu This PDF file includes: Materials and Methods Published 31 August 2012, Science 337, 1056 (2012) DOI: 10.1126/science1215151
Supplementary Materials: Laboratory Module Description Page(s) Table of contents i Student background knowledge, learning goals, and implementation suggestions ii Student laboratory manual, including example grading rubrics 1 18 Supplies, chemicals, and laboratory preparation 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 dawn.rickey@colostate.edu for further information including AFM image files used at Colorado State University. i
Suggested Student Background Knowledge for the Module The 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 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 ly 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 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 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-Observe- Reflect-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 dawn.rickey@colostate.edu to discuss implementation. ii
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 (HAuCl 4 ) and sodium citrate (Na 3 C 6 H 5 O 7 ). The net ionic equation for the reaction is: 4 HAuCl 4 (aq) + 3 C 6 H 5 O 7 3 (aq) + 3 H 2 O(l) 4 Au(s) + 6 CO 2 (g) + 3 C 4 H 6 O 4 (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 HAuCl 4 (aq) and Na 3 C 6 H 5 O 7 (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). Molarity of HAuCl 4 (aq) Volume of HAuCl 4 (aq) Moles (=MxV) of HAuCl 4 Molarity of Na 3 C 6 H 5 O 7 (aq) Volume of Na 3 C 6 H 5 O 7 (aq) Moles (=MxV) of Na 3 C 6 H 5 O 7 A 0.00050 M 0.0500 L 0.000025 mol 0.00375 M 0.0050 L 0.000019 mol B 0.00050 M 0.0500 L 0.000025 mol 0.00500 M 0.0050 L 0.000025 mol C 0.00050 M 0.0500 L 0.000025 mol 0.0250 M 0.0050 L 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. 1
Student Name: Score: (out of 20) Grading Rubric for Initial Model Assignment your initial model (20) Describes macroscopic model before mixing for cases A, B, and C (4) Describes macroscopic model after mixing for cases A, B, and C (6) Describes molecular-level model before mixing for cases A, B, and C (4) Describes molecular-level model after mixing for cases A, B, and C (6) 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. At your lab table, you have been provided with 8 vials containing various mixtures. Vials 1 4 contain: (1) aqueous solution of potassium permanganate (KMnO 4 ); (2) aqueous solution of copper (II) sulfate (CuSO 4 ); (3) finely ground charcoal, C(s); and (4) finely ground charcoal in water. 2. 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. 3. Next, shake vials 3 & 4 vigorously, immediately shine the laser pointer through the contents of each vial, and record your observations 4. Observe what happens when you shine the laser through vials 5 and 6, containing 0.0010 M aqueous silver nitrate (AgNO 3 ) and 0.0010 M sodium chloride (NaCl), respectively. Record your observations. 5. 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. 6. 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 (Na 3 C 6 H 5 O 7 ) and aqueous chloroauric acid (HAuCl 4 ) respectively. Record your observations. 7. Save all of your sample vials in case you wish to examine them again later. 3
Reflect As you reflect, discuss your thoughts with your classmates and record them in your laboratory notebook. 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? 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 (HAuCl 4 ) and sodium citrate (Na 3 C 6 H 5 O 7 ). The net ionic equation is: 4 HAuCl 4 (aq) + 3 C 6 H 5 O 7 3 (aq) + 3 H 2 O(l) 4 Au(s) + 6 CO 2 (g) + 3 C 4 H 6 O 4 (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. Molarity of HAuCl 4 (aq) Volume of HAuCl 4 (aq) Moles (=MxV) of HAuCl 4 Molarity of Na 3 C 6 H 5 O 7 (aq) Volume of Na 3 C 6 H 5 O 7 (aq) Moles (=MxV) of Na 3 C 6 H 5 O 7 A 0.00050 M 0.0500 L 0.000025 mol 0.00375 M 0.0050 L 0.000019 mol B 0.00050 M 0.0500 L 0.000025 mol 0.00500 M 0.0050 L 0.000025 mol C 0.00050 M 0.0500 L 0.000025 mol 0.0250 M 0.0050 L 0.00013 mol 4
Observe 1. 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. 2. Find out which concentration of Na 3 C 6 H 5 O 7 (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 Na 3 C 6 H 5 O 7 (aq) and the corresponding letter in your notebook. 3. Label all three of the glass vials with the letter corresponding to your assigned concentration of Na 3 C 6 H 5 O 7 (aq). 4. Using the graduated cylinder, measure out 50.0 ml of 5.0 10-4 M HAuCl 4 (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.) 5. Once the solution begins to boil, turn the magnetic stirrer on, and add 5.0 ml of your assigned concentration of Na 3 C 6 H 5 O 7 (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. 6. After the mixture has cooled, use a plastic pipette to carefully transfer an approximately 4- ml 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. 7. 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. 8. 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. 9. 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. 5
Reflect As you reflect, discuss your thoughts with the other members of your group and record them in your laboratory notebook. 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? 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? 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? 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? Sketch molecular-level views for the different product mixtures you obtained. How do these depictions compare to your representations of the reactant solutions? 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. 6
Refine Your Model Develop a refined model of what happens when you mix HAuCl 4 (aq) and Na 3 C 6 H 5 O 7 (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? 7
Student Name: Score: (out of 50) Grading Rubric for Week 1 & Refined Model Lab notebook, data, observations, calcs (24) your refined model (24) Describes macroscopic model before and after mixing for cases A, B, and C Describes molecular-level model before and after mixing for cases A, B, and C Molecular-level model is consistent with experimental evidence 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) Provides macroscopic generalized model that can be used to predict new situations Provides molecular-level generalized model that can be used to predict new situations Not consistent Partially Consistent (24) (10) (10) Fully Consistent (4) (8) (8) and (8) and (4) and (4) Cites specific evidence to support generalized model Post-laboratory questions (12) Sketch predicted AFM images for mixtures A, B, and C. Describe similarities/differences/patterns among predicted AFM images and (8) and (6) and (6) 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 z-axis Particle on surface 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. 9
Observe 1. Obtain electronic copies of the AFM images of mixtures A, B, and C. 2. 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. If you would like to view the AFM images in color, choose Options > Color Tables, and choose from a variety of color schemes. 3. Once you have recorded the heights of all of these images, share this data with the rest of the class. 4. 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. 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? What do the different colors in the AFM image mean why are some portions red, other portions yellow, and so on? 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? 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? 10
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? 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? 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. 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 (C 6 H 12 O 6 ). 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. Obtain a 10-mL graduated cylinder, 3 disposable transfer pipettes, and four small glass vials. 2. 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. 3. 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. 4. Repeat step 3 (in vials 3 and 4) with the dextrose solution and the unknown solution, respectively. Be sure to label each vial appropriately. 5. Add an additional 6 drops of the same solutions to the same vials. Record your observations. 6. Share your data with the other groups in your class. 7. 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. Draw molecular-level views of KI(aq) and C 6 H 12 O 6 (aq) before they are added to the gold nanoparticle mixture? How does the addition of each solution affect the mixture? What does this evidence suggest about what happens on the molecular level? What can you determine about the identity of the unknown solution? 12
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 C 6 H 12 O 6 (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 d 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 + C 6 H 12 O 6 (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. 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? Are your observations of the AFM images consistent with your molecular-level ideas 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 C 6 H 12 O 6 (aq) to gold nanoparticle mixture C, and the implications for your molecular-level model. 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. 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). 2. 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. 3. 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. 4. Carry out your tests according to the procedures you outlined, and record your observations. 5. Share your results with the whole class, and assess how well you have accomplished your goals. 15
Reflect As you reflect, discuss your thoughts with the other members of your group and record them in your laboratory notebook. 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? 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? Who do you think is pregnant, Lois or Matilda? Explain how the experimental evidence supports your conclusions. How might a gold-nanoparticle-based pregnancy test result in a false positive? What chemical species could account for this false positive? 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. 16
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. 17
Student Name: Score: (out of 100) Grading Rubric for Week 2 & Final Refined Model Lab notebook, data, observations, calcs (24) your refined model (24) Describes macroscopic model of nature and properties of gold nanoparticles Describes molecular-level model of nature and properties of gold nanoparticles 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) Provides macroscopic generalized model that can be used to predict new situations Provides molecular-level generalized model that can be used to predict new situations Cites specific evidence to support generalized model Propose a next experiment (12) Proposes a specific new experiment Explains how results of proposed experiment would inform molecular-level understanding of system Not consistent Partially Consistent (24) (10) (10) Fully Consistent (4) (8) (8) and (8) and (4) and (4) and (8) and (6) and (6) 18
Chemicals and Supplies Required to Implement the Module The following provides the requirements for implementing the 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 (KMnO 4 ) Copper(II) sulfate pentahydrate (Cu- SO 4 5H 2 O) Charcoal (C), finely ground Charcoal (C), finely ground Silver nitrate (AgNO 3 ) Sodium chloride (NaCl) Sodium citrate dihydrate (Na 3 C 6 H 5 O 7 2H 2 O) Gold (III) chloride trihydrate (HAuCl 4 3H 2 O) CAS Number Solution Concentration 7722-64-7 0.005% 7758-99-8 0.0200 M Preparation Suggestions (all solutions are aqueous) dissolve 0.05 g in 0.100 L sol n and dilute 1:10 2.50 g CuSO 4 2H 2 O 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 6132-04-3 16961-25-4 0.00050 M 3 different concentrations for syntheses: A: 0.00375 M 0.276 g in 0.500 L sol n B: 0.0050 M 0.368 g in 0.500 L sol n C: 0.0250 M 1.84 g in 0.500 L sol n 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. 19
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 dawn.rickey@colostate.edu.) 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) Potasssium iodide (KI) Dextrose (C 6 H 12 O 6 ) Sodium chloride (NaCl) Methanol (CH 3 OH) Sodium chloride (NaCl) Sodium chloride (NaCl) & albumin CAS Number Solution Concentration Preparation Suggestions (all solutions are aqueous) 7681-11-0 1.0 M 8.3 g in 0.0500 L of sol n 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 7647-14-5 0.10 M 1.46 g NaCl in 0.250 L sol n 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 For Part III, fill vials with about 4 ml of each solution. 20