Minute Papers Due 10/02/2009
Please post this week's minute papers as "comments" to this post. Minute papers should be posted by 5 pm on Friday. Feel free to read your classmate's posts.
Please post this week's minute papers as "comments" to this post. Minute papers should be posted by 5 pm on Friday. Feel free to read your classmate's posts.
On Monday, we'll finish the notes from last Wednesday's class and discuss the posted waveguide paper.
There are two Analytical Chemistry A-Pages articles to read for the classical optics section of class.
You should read "Planar Integrated Optical Waveguide Spectroscopy" by John T. Bradshaw and coworkers before class on 09/28/09.
You should read "Mid-IR Fiber-Optic Sensors" by Boris Mizaikoff and coworkers before class on 09/30/09.
Please post this week's minute papers as "comments" to this post. Minute papers should be posted by 5 pm on Friday. Feel free to read your classmate's posts.
These are the files for last Friday and this Monday's lectures.
**You can either turn your assignment in via email or to my Chemistry Department mailbox (A14). However, I would like an electronic copy of all answers to question #3.**
Please post this week's minute papers as "comments" to this post. Minute papers should be posted by 5 pm on Friday. Feel free to read your classmate's posts.
There are two articles to read for the laser section of class.
You should read "25 years of lasers and analytical chemistry: A reluctant pairing with a promising future" by Ben Smith before class on 09/18/09.
You should read "Tunable Deep Blue Light for Laser Spectrochemistry" by Kay Niemax and coworkers before class on 09/21/09.
Download "Questions to consider while reading "Tunable Deep Blue Light...".
We'll start Monday's lecture with the remaining slides from the first day of class. If time permits, we will start the material below:
Please post this week's minute papers as "comments" to this post. Minute papers should be posted by midnight on Friday. Feel free to read your classmate's posts.
Download the powerpoint file.
Download the pdf file.
Please choose one of these two papers to read thoroughly before Friday's class meeting:
ac901390j.pdf
Minute Paper #1 (09/04/2007) - Christy L. Haynes
Title: In Vivo Detection of Gold-Imidazole Self-Assembly Complexes: NIR-SERS Signal Reporters
By: G. R. Souza et al.
Journal: Analytical Chemistry
In this paper, the authors attempt to control aggregation of Au nanoparticles by adding imidazole in order to shift the nanoparticle optical properties so that high surface-enhanced Raman scattering (SERS) enhancement factors can be achieved with near-IR laser excitation. The techniques used in this work include: nanoparticle synthesis, UV-vis extinction spectroscopy, transmission electron microscopy, dynamic light scattering, and near-IR SERS.
The authors claim that adding specific concentrations of imidazole (with 2 available nitrogens for covalent attachment to Au) to Au nanoparticles generates nanoparticle aggregates with discrete sizes and optical properties. Individual Au nanoparticles absorb and scatter light at 520 nm; however, the authors need the optical properties to shift to the NIR in order to achieve large SERS enhancement factors in the "water window" (700 - 900 nm) for biological imaging. SERS enhancement factors are largest when the laser excitation wavelength matches the surface-enhancing substrate's optical properties. After aggregating the nanoparticles, the authors calculate their SERS enhancement factors to be as large as 10^9. This is a much larger than expected enhancement factor for spherical gold nanoparticles. The authors then inject the nanoparticle aggregates into mouse tumors and demonstrate that they can collect SERS spectra through the skin of the mouse.
The authors leave many questions unanswered in this work. In figure 1a, you see that the normal Raman scattering and SERS spectra are very different. This is expected because normal Raman scattering reports the vibrational structure of the bulk imidazole in solution while the SERS spectrum reveals the molecules covalently bound to the Au surface. In figure 1b, you can not see the red-shift in the optical properties very easily because the post-aggregation spectrum has very low intensity. This suggests that the nanoparticles are aggregating to the point where they precipitate out of solution. Also, the authors continually report the nanoparticles extinction at 520 nm (the absorption band for the original unaggregated Au nanoparticle solution) even though the most useful information would be the extinction efficiency at 785 nm (since this is the laser excitation they plan to use). Further, the calculated enhancement factors seem way too high based on previous literature precedent - this leads me to believe that their molecular coverage calculations are not correct. They should do a quantitative coverage measurement in order to conclusively demonstrate the claimed enhancement factor. Finally, while the authors show that you can collect SERS spectra through skin, the signals are very small and they do not explain how this will be used in actual biological imaging.
The purpose of the "Minute Paper" assignments is to promote your exposure to the scientific literature. Each week, you will choose an article from the ASAP alerts that is relevant to this class to read critically. Then, you will write a short summary of the paper you chose and post it as a "comment" under that week's minute paper blog post. It is OK if multiple people choose the same paper but your minute papers must be written individually.
The minute paper should be grammatically correct, written in your own words, and no longer than 500 words. Make sure to include the title, authors, and a link to the journal article. You should emphasize the technique that was used and the major findings of the work. Every minute paper should also include your own ideas about other experiments that could be done to continue or improve the presented work.
Each week, a minute paper is due by Friday at 5 pm (though I will accept them until midnight the first week). I will read the minute papers and give feedback. There will be a total of 14 minute papers during the course of the semester - you must complete at least 10 of them on time in order to receive full credit.
Please inform me about your availability for a 2 hour exam during the week of 10/19/2009 by Thursday evening. You can do this either via email (chaynes@umn.edu) or by posting a comment on this blog entry. If you do not send me your schedule, I will assume that you can make it at any time.
Please subscribe to the ASAP alerts for the journals most relevant to you in addition to Analytical Chemistry. This can be accomplished through the link at: http://pubs.acs.org/page/benefits-services/alerts.html
Download the pdf file.
Download the ppt file.
**Please bring a scientific calculator with you to each class.**
Please go over these notes on your own. The first slides emphasize important logistical information for the course. The remainder review some basic physics concepts about electromagnetic radiation. You will find slides titled "Are You Getting the Concept?" that ask you to do a short calculation to check your understanding. Please do these, and we will go over them during the first class meeting on Wednesday, September 9th. If you need more information on any of these topics, most slides include references to text books that are listed fully at the beginning of the notes.
In this course, we will survey both the fundamental and practical aspects of spectroscopies commonly used in analytical chemistry. First, a few logistical details:
Our class lectures are scheduled for Monday, Wednesday, and Friday from 9:05 am - 9:55 am in Smith Hall 111.
Ahead of our first class meeting on Wednesday, September 9th, I would like you to read over the course syllabus and be ready with any questions. Also, I will forgo reviewing the basic physics behind electromagnetic radiation so that we can jump right into other material. Please review the "Pre-lecture notes" that will be posted on this topic. This material should be familiar to all of you and will be necessary for the remainder of the class. I am happy to meet with you individually to discuss this material if necessary.