Volume 4 Edition 3

DEAR READERS


We had this email from Dr John Clarkson, University of Leeds, UK…..His suggestion has of course been added to our ever growing bookshelf page. 

I’d like to recommend to your readers: “Symmetry and Spectroscopy” by Daniel C. Harris and Michael D. Bertolucci, which is available from Dover Publications : ISBN 0-486-66144-X. Dover have reprinted the original 1978 Oxford University Press edition.

Dan Harris writes in the preface: “This book was written with the goal of introducing the student to vibrational and electronic spectroscopy and taking her or him to a rather sophisticated (albeit qualitative) level……. Taking the approach that group theory is essential to the modern practise of spectroscopy…….we believe that this book may be used as a primary text for a course on the applications of symmetry in chemistry, as well as for a course in spectroscopy.”

I find the text very helpful in getting the graduate students up to speed on the basics of vibrational spectroscopy and electronic spectroscopy, and would recommend it to all as an excellent undergraduate text. As it is published by Dover, it’s also very cheap!

This email came in from John Clarke of Borden Chemical, Toronto, Ontario..

I came across your site while searching for a means of removing the darkening from my IR cells. I think they’re silver “bromide” but they may be “chloride”. They’re quite soft. As I’m sure you’re aware these cells darken over time, sometimes from the samples I put on them. I’ve tried various methods of cleaning, what I assume are silver deposits, but have never found anything that is both effective and easy. Any ideas?

This is a well known and very old problem. The salts of silver are all photochemically sensitive. Photons to the blue of about 600 nm cause the reaction Ag+ → Ag. Clusters of silver atoms throughout the crystalline salts gradually darken them through purple to black. The process is, of course, used in photographic emulsions. Since the silver deposits are within the window material, there isn’t much you can do. Surface deposits might be removed with nitric acid, but these would, I think, be rare and arise from strong reducing agents in contact with the window surfaces.
For the future – always keep silver halide windows in the dark and try to expose them as little as possible to visible light in use. Silver halides were popular as window material because they are not water soluble but the introduction of the Irtron materials and then later ZnSe have tended to reduce their use.

Michael Nichols sent us his comments back in August…

This is a great site. I love reading the articles. I am preparing some of my work to hopefully get published. I have a question: Bacterial cell walls consist of many polymer layers of peptidoglycan (an alternating sequence of N-acetylglucosamine  and N-acety-muraminic acid). I would like to follow chemical changes in the polymer or its subunits with FTIR. Have you heard of anyone doing this or FTIR in general on bacteria or other cell walls?

Michael, nice to hear from you, particularly with such compliments! And we hope that you send us a paper very soon. Cellwall studies – I think there is considerable effort using micro Raman. The snag with IR is the poor spatial resolution of IR microscopes. The diffraction limit lies around 10m in the fingerprint region. If you use ATR on an IR microscope, the penetration into the cell wall multilayer will again be 10m. I wonder if SERS would be an answer? Have a look at the last edition (Vol 4 Edition 2) of IJVS and/or contact Prof. ZQ Tian at the University of Xiamen, China. His email is zqtian@xmu.edu.cn. Has anyone else got any ideas? Please contact Michael at plasmanick@msn.comand copy any correspondence to us at the IJVS office.

A tricky question now from Michelle Pataki from Melbourne, Australia.

I need to find an injection mouldable resin that will absorb IR at the frequency 2.94 nanometers. Can you recommend or suggest where I can start to look?

Michelle, I presume you mean 2.94 micrometers which translate to 3400 cm-1. [2.94nm lies in the soft X-Ray region]. Absorbers in this region are really only materials with OH groups and there are relatively few familiar commercial thermoplastics that contain much OH. Could I suggest polyvinyl alcohol and cellulose as starters. I am fairly certain that cellulose rich blends are available that will mould freely.

Out there someone must have other ideas, so please contact Michelle – again copy to Editorial Office please – Michelle’s email is mpataki@norwoodabbey.com.au.

We also heard from Siddhartha Seth in the States.

I am doing a project which involves use of vibration (sound waves) to decrease the deposition of wax. Could you suggest some articles or books which would contain information regarding the effect of sound waves on motion of particles?

I can’t help – can any of you? The email address to contact Siddhartha issidharthseth@usa.net.

Next, an email from Hugo Totozintle…

I am a master science student working with silica doped with cobalt. One of the characterisations is using Raman Spectroscopy, but I cannot find the reference. Could you send me, if you have it, the Raman spectra of cobalt silicate and the spectra of the cobalt oxide.

Hugo, thanks for your request. I don’t know of an extensive collection of Raman spectra of inorganics but some were published in Spectrochimica Acta a few years ago in one of the Special Editions on F-T Raman Spectroscopy. [Does anyone know of another source?] Perhaps cobalt silicate was included. Trying to remember my undergraduate analytical chemistry, I think CoIII silicate is insoluble, so why not make a small sample and run the spectrum? The reaction Na2SiO3 + CoCl3 in aq  Co2(SiO3)3 + NaCl should do the trick. 
Cobaltic oxide is available from lab supplies, so why not run this as well?

A recent email request came in from Lawrence Hudson, London, UK…

I am an amateur who was first introduced to Raman at a seminar at Kingston University several months ago. It struck me that one could build a Raman micro-spectroscope with off-the-shelf components for much less than the Renishaw price tag. I am slowly assembling the components and have gotten important clues from your journal. As a hobbyist, one consideration is that every piece of equipment must do many tasks. My microscope of choice would be a modular stereo (eg Nikon SMZ). Do you know anyone who has successfully condensed their laser beam elsewhere than via the objective? Can you tell me who manufactures the AIRE ENT-IR 800R microscope?

I’m sure you are correct particularly if you are prepared to build equipment yourself. Several points do however need emphasising – the microscope is not an efficient way of collecting scattered light hence you must have a highly efficient detector of which the CCD is paramount. Although the resolution is dismal, the most cost effective solution to the spectrograph CCD combination is the Ocean Optics system from the States. This is marketed as a monochromator/CCD/electronics all on a  PCB. If you were to take a hacksaw to the monochromator you might produce what you want.

Your specific question – all the NON microscope instruments use different optics to focus the laser and collect the light [see my paper in section 1 , particularly Figure 4]. They all use a mirror in front of the collection lens or in the Nicolet have a hole in the collection mirror. Using a microscope the mirror would be absurdly small so people use the object to focus the laser AND collect the light.

Finally, remember the filter problem – easy to solve but expensive.

Sorry I know nothing of the AIRE ENT microscope. However in a Special Edition a couple of years ago on Raman microscopy – there was a paper by Bernard Cook which features the AIRE ENT microscope – you may be able to contact him direct to ask your question. Can anyone help please? Lawrence’s email address is lawrence.m.hudson@attglobal.net, but don’t forget to copy the Editorial Office with any information you may have.

This request for help from Lai Chan..

Can you help ? I am interested in finding out how successful Raman Spectroscopy have been used to monitored either chemical reactions or crystallisation on-line.  Are there any articles/reviews on this subject that you can recommend ?

I know of papers on using Raman to make kinetic measurements and have seen
industrial plant with on-line Raman monitoring both levels of concentration
and crystallization. However, I don’t know of a review, so we passed your email onto Dr Neil Everall from ICI here in the UK and he’s come up with the following…

There are a number of review articles on this topic – it really is very
broad. For example, see F Adar, R Geiger and J Noonan, Appl. Spectrosc.
Rev. 32, 45 (1997), M A Leugers and E D Lipp, Chapter 5, pp 139-164
“Spectroscopy in Process Analysis”, Ed J M Chalmers, Sheffield Academic
Press, Sheffield, UK. A number of upcoming review articles are currently
“in press”, e.g. (1) I R Lewis, “Handbook of Raman Spectroscopy”, Marcel
Dekker,  (2) N Everall, B King and I Clegg, “Process Raman Analysis” in “The
Handbook of Vibrational Spectroscopy”, Eds P Griffiths and J Chalmers, J
Wiley and Sons (due 2001).

Some specific examples of polymerisation and crystallisation monitoring
were given by Everall and King, Macromol Symp. 141, 103-116 (1999). A
description of monitoring calcination of an inorganic and crystallisation
of a polymer appeared in Chemistry in Britain, 40-43 (July 2000) (Everall,
Clegg and King). A specific review of polymer examples was given by Everall, 
“Raman Spectroscopy of Synthetic Polymers”, pp 127-192 in “Analytical
Applications of Raman Spectroscopy”, M J Pelletier (Ed), Blackwell Science,
1999

Hope this helps. If you perform a literature search on process Raman spectroscopy he will find hundreds of examples!

If anyone else has any more information for Lai. Lai’s email address isLai.Chan@astrazeneca.com . And many thanks to Neil for his very speedy answer.

Tom Salvesen emailed the following…

I have a quick question which may display a certain amount of ignorance. Do you know of anyone who can supply software that can quickly predict IR spectra? I have been looking around and I can’t really find anyone. 

I’m sure that someone out there can help. Tom’s email address is Thomas.Salvesen@aguk.zeneca.com and please don’t forget to copy IJVS.

And Finally…….

My name is Chris Leggett [legch201@student.otago.ac.nz] and I am a University student in Dunedin, New Zealand. I am currently helping in research here in the university over summer and require information on FTIR spectra of lactitol and isomalt. If you know of any spectra and information on these then could you please get in touch with me via e-mail so I can go about getting hold of it if possible.

Chris, I don’t know of any data. I presume you have looked at the various libraries – Aldrych, Sadtler etc.  So can anyone help Chris? If so copy us.

Please keep your queries and comments coming in. We know that recently it’s been a few weeks until we’ve responded, but now the holiday period is over we should be a bit more efficient!