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Fluorescein as a gain medium regent here at Plab

by dhaffnersr | April 06, 2016 14:58 | 1,157 views | 6 comments | #12926 | 1,157 views | 6 comments | #12926 06 Apr 14:58

I am experimenting with fluorescein in NaOH3 (sodium bi-carbonate) as a gain medium for use as a regent for oil sampling. This series of tests are not done on an oil sample yet, but were done using my Prolight 1W UV LED.

fluorescein was aquired from consolidated chemical and solvents LLC and prepared in a solution of NaOH3 0.1M at a Ph of 8.4 (calibrated with a digital Ph meter.)

Fig.1 shows the raw data aquisition before processing

baseln_crrtcd_prolight_fluorscn_1ml_apr5.png

Fig.2 shows data after processing (subtracted from Blank.)

Prolight_fluorscn_ready_to_plot_apr5.png

Fig.3 shows the data plots

1ml_fluorscn_prolight_apr5.png

What is a gain medium? Dyes

Laser dyes consist of organic molecules, which in most cases are contained in a liquid solution. (Users often make them by dissolving dye powders in some solvents.) The optical transitions of dyes are relatively broad: tens of nanometers or more – roughly comparable to those of ion-doped glasses – resulting in good wavelength tunability. A big difference between dyes and ion-doped glasses, however, is that these transitions in dyes are not forbidden; they exhibit large transition cross sections, and the upper-state lifetime is correspondingly short (a few nanoseconds). Particularly for pulsed pumping, the gain can easily become rather high, leading to amplified spontaneous emission. The saturation fluence is very low, which implies that high pulse energies can be realized only with very large beam cross sections. Despite the short energy storage time, energetic pulses can be produced if a dye is pumped with a Q-switched laser shortly before it generates or amplifies a pulse itself.

A large number of laser dyes are available, and together they cover huge wavelength regions – the full visible range and also substantial areas in the ultraviolet and infrared region (Figure 3). A dye laser can be operated with various dyes; ideally, different cuvettes and circulation systems are used for different dyes so that an easy change is possible.

Gain_Figure3.jpg Figure 3. Wavelengths that are accessible with dye lasers and additional nonlinear frequency conversion. Basically, any wavelength in a very wide range can be provided. SFM = sum-frequency mixing; MAD = (nonlinear) mixing after doubling; THU = third-harmonic unit; SHG = single-harmonic generation; DFM = difference-frequency mixing; MIR = mid-infrared.

A notorious problem with dyes is their limited lifetime; they degrade during laser operation. Dye circulation systems are usually required, enabling use of a larger volume of dye solution, which may have a lifetime of a few hundred operation hours. Also, the circulation gives the used dye the time needed to recover from so-called triplet states, where it cannot be used.

The handling of dye solutions can be somewhat tedious and involves various hazards, particularly health hazards resulting from both the dyes and the solvents. Particularly, these substances can be carcinogenic.

Solid dyes would be simpler to use, but their very limited lifetimes and the triplet state problem present serious obstacles for most applications. Source- http://www.photonics.com/Article.aspx?AID=53768

Some discussion and conclusions, I'm hoping that with this particular dye, I can come up with an adequate regent for bonding with various oil samples that seem to have a lower fluorescent threshold, without the problem of getting close or matching their wavelengths (which can be a problem, because your only going to see the fluorescence of the dye in your signal.)

I know that most gain mediums are so called "laser dyes," but I think that they can be adapted for use with UV LED's, if this is already begin done I haven't found it yet, but would love some feedback on it.

Another observation is with the regent I used (NaOH3,) is standard and the Ph was darn close,(mine was 8.4)(typical Ph for this regent at a Ph of 9 is EX:490nm EM:514nm)

my data was obviously different, I think 1 factor is the FWHM data for the LED, slit width, camera sampling rate and instrument precision problems.

Also, this is the first time ever that I have made a plot from excel, or any other program for that matter, so please just cut me a little slack...please.


6 Comments

A few questions!

  1. Ah, is sodium bicarbonate just baking soda?
  2. Cool -- what's the purpose of a gain medium, i.e. what's the purpose of the baking soda?
  3. Where do you get fluorescein?
  4. Are you using fluorescein in combination with baking soda as your reagent, or do they play different roles?
  5. how did you choose to use baking soda?
  6. If I understand, you're hoping the reagent will bind with oils so that they fluoresce more strongly, right?
  7. But this might destroy information about the type of oil, at the benefit of making a test for any oil more sensitive, correct?
  8. How do we know that the reagent is binding with oil pollutants -- what else does it bind with?

Can you share any background research which led you to try these techniques?

Thanks Dave! Very interesting, just a lot to process, and I need help understanding the big picture here.

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hey jeff, NaOH3, is used as a regent for fluorescein because of the Ph level of 8.44, which at that level free's up more hydrogen bonds causing a higher energy state. Also it's the standard regent for fluorescein, but I just wanted to let you know why it works.

The purpose of a gain medium is tuning of primarily of a laser source at a specific wavelength, but I found it useful as a tracer in very small concentrations in order to increase the intensity of the fluorescing material, no it does not react in anyway on a molecular level with the sample, bonding to the substance is just my musings into this possibility.

If you keep the concentration of the fluorescein at the same level as the sample it won't drown out the sample data, but you'll be able to "see" it more clearly after data capture.

This is the source for all my chemicals, www.consolidated-chemical.com, including the fluorescein.

I have a lot of data on all my research, I only post some of it, it would be a little much if I posted it all at once, so I try and string it out, but I'm doing research everyday, I love it.

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Ah, so you're not adding fluorescin AND baking soda to oil samples, but the baking soda may increase fluorescence of either fluorescin or oils?

If so, I'd love to see a simple example of this. A test which shows a motor oil with different amounts of bakig soda, spectra overlaid. Would that be possible?

Thanks Dave!

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Hey jeff, nah man, that's kinda funny though, I might try that! Fluorescein is Ph dependent, the baking soda maximizes the dye's energy transfer. As far as the oils go, the specific regent of NaOH (sodium hydroxide Ph of 12.38) is necessary for the 20 percent ethanol mixture, to break apart the aromatic double bonds.

I will set up a series of experiments with the fluoresein and oils since this is really my primary focus, very soon, I just needed to get the spectrometer running the way that I want it to. I am happy with it's operation as of now, so it's good.

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Ah, i see -- i mixed up NaOH3 with NaOH from your other post, sorry! Maybe another reason to provide a brief explanation of what each is and what it's used for.

I apologize, but just so I can follow exactly what you're doing, could you try answering the questions I had posted above? I'm still not clear on what roles NaOH, NaOH3, and fluorescein play in your research here, can you help me? Thanks!

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1)Ah, is sodium bicarbonate just baking soda? 2)Cool -- what's the purpose of a gain medium, i.e. what's the purpose of the baking soda? 3)Where do you get fluorescein? 4)Are you using fluorescein in combination with baking soda as your reagent, or do they play different roles? 5)how did you choose to use baking soda? 6)If I understand, you're hoping the reagent will bind with oils so that they fluoresce more strongly, right? 7)But this might destroy information about the type of oil, at the benefit of making a test for any oil more sensitive, correct? 8)How do we know that the reagent is binding with oil pollutants -- what else does it bind with?

answers:

1) typo on my part, NaOH3 is ammonium nitrate, NaHCO3 is baking soda, sorry my mistake. I will have to correct that on my data graphs. Yes, it's just baking soda.

2) The purpose of a gain medium is for laser "tuning," Fluorescein in a pH of 9.0 has an excitation at:490 nm and an emission at:514 nm, knowing this information I can use an appropriate excitation wavelength for emission maxima. it also helps knowing the excitation wavelengths of the samples, hence the utilization of differing dyes. The baking soda is merely for raising the pH level (hydrogen molecule transfer,) in the solution.

3) this is where I got my fluorescien from- http://www.hvchemical.com/?gclid=CKS5waTticwCFZaEaQodhaQFTQ

4) Yes I am using both baking soda and sodium hydroxide as a regent, they both play the same role.

5) I chose baking soda as an experimental pH buffer.

6) Yes, I am working that problem out, I have a software program called Chemsketch, where I can edit and manipulate any chemical structure I want, I am hoping that I can use some of these dyes, especially fluorescein as more than just a gain medium and more of a tracer agent, which I would need it to bond to certain organic molecules in order to use it in that manner, I think it is possible.

7) No, fluorescein will not interfere with any samples chemical data structure.

8) You would know that bonding has occurred when you process the data, as a fluorescent amplifier, you would notice a closer molecular migration of the 2 elements on the data graph, both in absorption and concentration.

I hope this helped explain things, at least a little. Please don't hesitate to ask questions, I am more than happy to answer them.

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