Electronic spectroscopy

26 Jun 2013

Kool-Aid analysis: Visible Spectroscopy and Paper Chromatography

Submitted by Megan Strayer, The Pennsylvania State University
Evaluation Methods: 

Students are able to work with their lab partners to answer the questions throughout the laboratory. Questions (including Excel graphs) are due at the end of the second laboratory period. Also, a follow-up laboratory quiz is given the laboratory period after the experiment is completed which includes questions from both concepts and data analysis for the laboratory.

Description: 

This lab experiment is designed to introduce the electromagnetic spectrum to non-science majors in a food chemistry course by using everyday food (i.e. Kool-Aid packets). Students will use a spectrophotometer to correlate wavelength to color, as well as determine the mass percent of certain colored dyes in a Kool-Aid sample. Paper chromatography is also introduced to determine the number of dyes in a Kool-Aid sample. This lab is adapted from Sigmann, S; Wheeler, D. J. Chem. Ed., 2004, 81, p. 1475.

Course Level: 
Prerequisites: 
Corequisites: 
Learning Goals: 

After completing this experiment, the student will be able to:

  • Correlate color to wavelength of light
  • Analyze Kool-Aid packets to find the number of dyes present by paper chromatography
  • Generate a Beer's law calibration curve
  • Calculate the percent mass of dye in Kool-aid
Equipment needs: 

Supplies:

  • White Chalk
  • Strawberry, Ice Blue Raspberry, Grape, Cherry Kool-Aid packets
  • Coffee Filters
  • Q-tips
  • Drinking water
  • Red Dye #40
  • Blue Dye #1
  • Gallon jugs
  • Micropipettes

Glassware:

  • 25mL, 50mL, 100mL, and 200mL volumetric flasks
  • Cuvettes
  • Test tubes
  • Beakers

Instruments:

  • Balance
  • Spectrophotometer
Implementation Notes: 

This lab experiment was designed for a lab class of non-science majors taking a food chemistry course. The students worked in pairs for the experiment. Half the class started with paper chromatography while the other half began with correlating wavelength and color if instrument access is limited. To decrease the overall time of the experiment, the students could graph the calibration curves and complete calculations outside of class time.

Unknown Kool-aid samples for day 2 of the experiment should be diluted at least 5:1 to fall inside the calibration curve. The unknown samples used in the  experiment are Kool-aid packets with only one dye.

Time Required: 
Two 3-hour laboratory periods
26 Jun 2013

Literature summary through student presentation - free choice of topic.

Submitted by Cameron Gren, University of North Alabama
Evaluation Methods: 

I typically weight this assignment as one-half of an exam, i.e. 50 points when exams are worth 100 points each. The question should be worth a portion, perhaps 10 points with the remaining points coming from the presentation. Another option could be, if it would be appropriate for your class, to dedicate a few points to students preparing questions of other presenters. For large classes, they need not all be asked, but simply handed in to you prior to each presentation. then YOU could ask a few of them. As far as a rubric for the presentations, this could vary greatly. I typically count off for things like incorrect information, extremely vague descriptions, or very weak question answering. Specific deductions may vary. Other evaluation options could include student evaluations on each other's presentations, giving a post-presentation quiz (covering all presentations), or possibly including questions on the final exam over the presentations.

Evaluation Results: 

I generally give good grades for this assignment if I can tell the students put in an appropriate amount of work. Students tend to enjoy this assignment (more so after completing it, of course), as they can truly take ownership of their work. They seem to have a good sense of accomplishment after tackling a difficult journal article and breaking it down so they can understand it.

Description: 

(1) Student choses and reads a journal article of his/her choice that is related to a topic we have discussed during the semester. (i.e. atomic structure, MO theory, group theory, solid state structure, band theory, coordination chemistry, organometallics, catalysis). Suggested journals include, but are not limited to JACS, Inorg. Chem., Organometallics, Angew. Chem., JOMC, Chem. Comm.)

(2) Student answers the following questions regarding their chosen article:

    (a) Describe, in 1 or 2 sentences the goal of this work. 

    (b) Define the primary topic(s) from our course that relate to this work. 

    (c) Do you feel the authors achieved their goal? Why or why not?

    (d) What questions remained about the work?

(3) Student prepares a brief (~15 min) PowerPoint (or equivalent program) presentation describing the article. The question set should aid the student in developing the presentation.

(4) Students are encouraged to ask questions following each other student’s presentation.

Course Level: 
Learning Goals: 

• Students will improve their overall reading comprehension with regards to chemical literature.

• Students will be able to identify the relationship between current chemical literature and key concepts in inorganic chemistry.

• Students will improve their ability to present chemical research in a concise but detailed manner.

• Students will become critical observers of other’s presentations, being able to formulate and ask insightful questions.

Implementation Notes: 

I have this assignment due the last few days of the semester. It may be valuable for the students to see the professor summarize an article in this manner first, although I do not do this. It may be valuable to make the journal articles available to the other students prior to the presentations. This might help them formulate insightful questions for the presenters.

Time Required: 
I usually assign this at the beginning of the semester, although ~ 2 weeks might be sufficient prep time. In-class time is about 20 mins per student.
25 Jun 2013

X-ray absorption spectroscopy and its applications to LFT

Submitted by Karen McFarlane Holman, Willamette University
Description: 

This series of (not five) slides introduces X-ray absorption spectroscopy (XAS), specifically XANES (X-ray absorption near-edge structure).  There is background in basic theory, the general technique including synchrotron radiation sources, and two specific examples from the literature that apply XANES spectra to (1) oxidation state and effective nuclear charge of sulfur in various compounds such as sulfates, and (2) measurement of energy levels in MO diagrams of coordination compounds (i.e., LFT).  Point (2) is analogous to showing PES peaks alongside MO diagrams for diatomics.  This is a fun slide series with some cool animations!  Note that you can extract some of the slides and re-vamp them to teach other techniques such as EDS.

 

Corequisites: 
Prerequisites: 
Learning Goals: 

After assimilating the information provided in these slides, the students will:

1.     Understand the fundamental ideas of synchrotron radiation, XAS, the K-edge of an element, and the pre-edge region of an XAS spectrum.

2.     Recognize the parallels between XAS and other basic spectroscopic techniques such as UV/Vis.

3.     Identify the unique features (utility) of XANES.

4.     Compare XANES spectra for different compounds and correlate oxidation states and effective nuclear charge with the K-edge energy and/or pre-edge features.

5.     Identify pre-edge features in XANES spectra as indicators of metal-ligand mixing and determine information regarding the electronic structure of the d-manifold. 

Note that there is a lot more information that can be determined from XANES spectra regarding orbital energies, quantitation of M-L mixing, covalency, and site symmetry, especially when spectral analysis is done alongside DFT.  Students who have a strong background in symmetry and quantum would be able to go into significantly more depth than what is provided here, but these slides are only meant to serve as a basic introduction.  I wrote up notes for the instructor, so if you don’t know XAS, you’ll learn some cool stuff too!

Implementation Notes: 

These slides are meant to introduce XAS to your students.  You could go through them in 15 minutes but to really have fun with it, I would take 30.  From here, they should be able to make some interpretations of spectra - comparing oxidation states, the degree of M-L orbital overlap, etc.

I tried to make good notes... please let me know if any of the slides are unclear or if you'd like anything expanded upon, etc.

Time Required: 
15-30 min
Evaluation
Evaluation Methods: 

You'd want to follow up with an in-class assignment or problem set to assess their understanding.  I hope to create one or both for submission to VIPEr, and hopefully others will as well!

Evaluation Results: 

My students have done fairly well on exam questions after teaching this level of introduction.  The questions have never been overly difficult, but I do have the sense that they have a fundamental understanding of the technique.  As I teach it more, I hope to have more to report in this section.

25 Jun 2013

I created this Collection of Learning Objects (LOs) at the IONiC VIPEr TUES 2013 Workshop: Solid State Materials for Alternative Energy Needs held at Penn State University.  The overall theme of the Collection is electronic and optical properties of metals, semiconductors, and insulators.  Most of the learning objects either require knowledge of or explicitly refer to band structures, either at a basic level or a more advanced level.  Some LOs also deal with extended structures, un

Prerequisites: 
Corequisites: 
24 Jun 2013
Evaluation Methods: 

Student performance on Preliminary Questions (PQs) and reports are assessed

Percent yield and percent purity from UV-Vis and titration analyses

Accuracy in completion of table of IR bands/assignments

Answers to Thought Questions

Evaluation Results: 

Percent Yield across two years: average 80%+/-11% for 21 students

Percent Purity via titration analysis in first year: -12% error (less than theoretical); implemented improved estimation of endpoint – see Instructor Notes

Added IR Spectroscopy Tables (given values, and a blank one to fill in on report). Without these 'lead by the nose' guides, students did a poor job demonstrating understanding of the meaning of the IR spectra. This is most likely due to the fact that this is their first exposure to IR spectroscopy (second-semester freshman level).

Description: 

Synthesis of ammonium decavanadate, and analysis via IR, UV-Vis and quantitative titration. Time: 1.5 lab periods

 

Purpose

            The purpose of this lab experiment is to expose students to the synthesis of a colored POM, and to connect the use of standard analytical techniques to this new type of compound. It introduces the use of IR spectroscopy of inorganic materials.

 

Introduction

            Ammonium decavanadate ((NH4)6V10O28•6H2O) is an example of a polyoxometallate (POM). POMs are a large and diverse group, containing various metal cations, including, but not limited to, vanadium, molybdenum, chromium and iron. They are formed spontaneously in solution through what is called ‘self-assembly’. Essentially, they come together in solution through unknown mechanisms. In the lab, we can isolate various POMs by controlling conditions to favor one form over another, by varying concentration, pH or counter-ion. In the phase diagram of vanadates (Figure 1), one can see how varying pH and vanadium concentration can yield monomeric vanadate (VO43-), or POMs containing 2-10 vanadium atoms.

Decavanadate in Geology

            The decavanadate anion occurs naturally in minerals, huemulite Na4Mg2V10O28•24H2O, hummerite (KMg)2V10O28•16H2O, lasalite (NaMg)2V10O28•20H2O , pascoite Ca3V10O28•16H2O, magnesiopascoite Ca2MgV10O28•16H2O, and rauvite Ca(UO2)2V10O28•16H2O, which differ in the cations and amount of hydration. As you can see from Figure 3, the dominant color is yellow-orange. This is due to the presence of the decavanadate anion, which is yellow-orange. All of the vanadium POMs and vanadate are yellow-orange due to charge-transfer bands in the 200 – 500 nm range.

Decavanadate in Biology

            Vanadate (VO43-) is isostructural and isoelectronic with phosphate (PO43-). For this reason, vanadate has found interest with researchers studying the role of phosphate in biological systems, such as in insulin uptake in cells. In addition, decavanadate has been used to bind to biologically relevant molecules, such as gelatin, cytosine, estrogen receptor, and myosin.

 

Laboratory Experiment

In this experiment, students synthesize ammonium decavanadate, and analyze the resulting product via UV-Vis and IR spectroscopy as well as by permanganate titration.

Corequisites: 
Prerequisites: 
Learning Goals: 
  1. The student will define polyoxometallates (POMs).
  2. The student is able to interpret a concentration-pH diagram to determine conditions suitable for formation of the desired product.
  3. The student will apply IR spectroscopy to identify inorganic compounds.
  4. The student will use Beer’s Law to analyze the purity of a colored compound.
  5. The student will use redox titration to analyze a compound for purity.
Course Level: 
Equipment needs: 

Materials for a class of 20:

Ammonium metavanadate (NH4VO3, CAS#7803-55-6, Aldrich 99%): 6.0g

50% acetic acid solution: 100 mL

95% ethanol: 360 mL

Oxalic acid dihydrate (H2C2O4•2H2O, CAS#6153-56-6, Aldrich 99%):  2.5g

1.0 M sulfuric acid: 1.2 L

Sodium bisulfite (NaHSO3, CAS#7631-90-5, Aldrich):   2.0g

0.10 M potassium permanganate (KMnO4): 100 mL

50 mL beakers, 100 mL volumetric flasks, funnels and erlenmeyers

50 mL burets, 10.0 mL and 20.0 mL transfer pipettes

UV-Vis (Spec 20 is fine) and IR spectrophotometers

Implementation Notes: 

Because the synthesis is quick, but the crystals should be allowed to dry, I pair this experiment with another synthesis and analysis experiment, and spend the first lab period on the two syntheses, then the subsequent lab periods on analyses. If you have another experiment that takes 1.5 lab periods, then you can pair appropriately. The 0.5 lab period part is the synthesis. See Instructor Notes for other comments.

Time Required: 
1.5 - 4 hour lab periods (0.5 lab period for synthesis, 1 lab period for analyses)
1 Apr 2013

Online Courses Directory

Submitted by Adam R. Johnson, Harvey Mudd College
Description: 

This website is a free and comprehensive resource that is a collection of open college courses that spans videos, audio lectures, and notes given by professors at a variety of universities. The website is designed to be friendly and designed to be easily accessed on any mobile device.

Course Level: 
Prerequisites: 
Corequisites: 
20 Jul 2012

Soluble Methane Monooxgenase Spectroscopy

Submitted by Gerard Rowe, University of South Carolina Aiken
Evaluation Methods: 

The activities are collected and graded based on how reasonable and well-supported their answers are.

Students also receive a question about inorganic spectroscopy on their final exam.

Evaluation Results: 

Students were generally successful at identifying the right spectroscopic technique for the job.  The most challenging problem was the one concerning spin states, especially because they have to consider all the coupling possibilities for each diiron species and remember what makes a compound EPR active/silent.

 

The final exam question had somewhat more mixed results, probably due to the fact that two weeks had elapsed in between this activity and the exam.

Description: 

Determining the reactive intermediates in metalloenzymes is a very involved task, and requires drawing from many different spectroscopies and physical methods.  The facile activation and oxidation of methane to produce methanol is one of the "holy grails" of inorganic chemistry.  Strategies exist within materials science and organometallic chemistry to activate methane, but using the enzyme methane monooxygenase, nature is able to carry out this difficult reaction at ambient temperatures and pressures (and in water, too!).  This activity asks students to look at the proposed catalytic cycle of soluble methane monooxygenase and choose an appropriate spectroscopic technique to provide different information about the various species in the process.

Learning Goals: 

The student will be able to identify the key features of a scheme describing a catalytic cycle's intermediates

The student will learn to think of spectroscopy as an experiment that operates within a specific time scheme instead of as a figure in a paper

The student will be able to explain the advantages and limitations of different spectroscopic techniques

The student will use their knowledge of spectroscopic techniques to decide the best method to obtain the desired information

Subdiscipline: 
Course Level: 
Corequisites: 
Implementation Notes: 

I give this activity to students towards the end of my advanced inorganic chemistry course.  By this point, they have already been exposed to most of the major spectroscopic techniques used in inorganic chemistry, and have had several lectures in bioinorganic chemistry.  

19 Jul 2012
Description: 

This is a great web resource for all types of nano materials.  There are lesson plans, demos, activites, labs and lots of background information.  It is very easy to navigate and there are videos of the labs so you can see each step - very useful when doing a type of synthesis or technique new to you.

Prerequisites: 
Corequisites: 
Implementation Notes: 

Students and instructors are able to watch videos and view safety info on a large number of nanomaterials labs and activities.  Truly a variety of skill and equipment levels but very well explained so you know what to expect.

I have used the ferrofluid synthesis proceedure and added some questions and information from the J. Chem. Ed. article listed on the site.  It works very well but pay attention to the notes they include - the iron II chloride needs to be fresh so buy small bottles.

Time Required: 
5 minutes if you know what you want, hours to read it all.
17 Jul 2012

Colored Note Cards as a Quick and Cheap Substitute for Clickers

Submitted by Chris Bradley, Mount St. Mary's University
Evaluation Methods: 

Use of the cards gives a rough "eyeball" evaluation of student learning throughout a lecture. Using the cards, for me at least, also provides a gauge of attendance as well and also if it waxes or wanes during the class period.

Description: 

For many years I have resisted using clickers, mainly because at our university there is no standard universal clicker. I wanted to keep student costs as low as possible but also desired the type of live feedback during a lecture that clicker questions can provide. In both my general chem. (200-300 students) and upper division courses (50-75 students), I now pass out 4 or 5 colored notecards on the first day of class and make sure everyone has one of each color. I then do clicker style questions and color code the different answer choices in powerpoint and ask them to hold up their choice after 15-60 seconds depending on the question. This has worked well to provide me instant feedback on difficult topics and doesn't end up singling out any particular student, which most students detest in larger lecture courses.   

 

Learning Goals: 

Students are able to provide feedback to the instructor on questions quickly and "anonymously" and allow one to adjust the direction of a lecture on the fly.   

Prerequisites: 
Corequisites: 
Equipment needs: 

NA

Implementation Notes: 

I typically use between 4-6 clicker questions during a 50 minute lecture. I'm sure someone could use more/less based on an individual's needs. I think the key is to use clicker style questions from the beginning of the class on a daily basis to remind students to bring the note cards in a book/binder/bag. This is really the only problem I have encountered- students often forget their cards. It is probably a wash though, as I'm sure students can also forget clickers.  

Time Required: 
1-5 minutes (depending on the problem)
15 Jun 2012

NMR Coin-Flip Game

Submitted by Adam Azman, Butler University
Description: 

A simple coin-flipping game to help students understand the origin of spin/spin splitting in 1H NMR.

  • A quarter is taken as 'set of equivalent protons' with a 'chemical shift' value of $0.25.
  • One penny is flipped 2000 times.
    • If the penny lands heads, $0.01 is added to the value of the quarter; value = $0.26
    • If the penny lands tails, $0.01 is subtracted from the value of the quarter; value = $0.24
    • Keep a running tally of the occurance of each outcome
  • By flipping one penny 2000 times, students will see a 1000:1000 ratio of the two outcomes ($0.24, $0.26). This mimics the origin of a doublet from one neighboring proton with j-value $0.02
  • Students can 'flip' up to 9 pennies to simulate up to 9 neighboring protons all with j-value $0.02
  • Students can also 'flip' up to 4 nickels to simulate additional neighbors with a second j-value of $0.10
  • After 5 trials, a link appears to an explanation page tying together the concepts of flipping coins and NMR splitting/j-value

It's actually pretty hard to distil into a set of simple, easy-to-understand, easy-to-follow rules. The intervention would be better suited for actually physically bringing pennies into class and run the demonstration physically with students (which I plan to do). The web resource can be used in class to simulate the statistical mixture (especially if the class contains too few students to practically achieve a statistical distribution manually). The web resource can also be provided to students after they leave the class to reinforce the concept.

NMR Coin-Flip Game Preview Image

Prerequisites: 
Corequisites: 
Learning Goals: 

A student should be able to explain the origin of NMR splitting, the meaning of a j-value, and predict the splitting pattern of simple systems with up to two different j-values.

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