Question: Would the desktop spectrometry kit work for measuring fluorescent responses?

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ICSK asked on November 20, 2017 18:11
244 | 3 answers | #15210


I'll primarily be using uv light sources (365, 275, 265, & 253.7nm) for measuring the response for fluorescent minerals. My concern is that the DVD grating would fluoresce and skew the result

https://youtu.be/ADled_4Z1F8?t=4m15s shows an example of how I intend on using it



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Does the diffraction slit that is offered also fluoresce? Any other thing I might not be thinking of for measuring fluorescent responses?

Only part of my question was posted. Here's the other part

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Hi! Here's a good place to post questions about fluorescence: https://publiclab.org/wiki/oil-testing-kit#Questions

Or, just at https://publiclab.org/tag/fluorescence -- there's a button there -- and it's helpful to keep questions separate so we don't mix all the answers together. Don't be afraid to post several!


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3 Answers

Hi, there's been a lot of work on fluorescence and there's still a lot to do -- you can read up at #fluorescence - and on this page:

https://publiclab.org/wiki/oil-testing-kit


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That's a good question about the DVD plastic fluorescing. I don't know of anyone who has raised that question about the Public Lab spectrometers. If you have access to those pure UV light sources, you could answer the question. Shine only the pure UV source on a DVD and take a photo with a good camera. Good cameras have UV block filters, and the glass in the lens will block most UV, so if the photo is black then the DVD does not fluoresce in that UV light.

If the slit fluoresces in UV light, just make a slit with two razor blades or utility blades. That will work better then the printed slits.

The web camera in the Desktop Spectrometry kit won't resolve the peaks as well as the Ocean Optics spectrometer, but if you use a good camera to take photos of the diffraction patterns your wavelength resolution will be much better.

Comparing the intensity of different peaks in a spectrum is fraught with error when using a DIY spectrometer based on a consumer camera, so identifying the minerals responsible for the peaks might require some guess work.

Chris


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For anyone wishing to know in the future this kit is not adequate for this task. I purchased the Desktop Spectrometry 3.0 Kit after not receiving a satisfactory answer from anyone. The camera's sensitivity to light is nowhere near great enough with even my most powerful UV sources. In my case it did not register fluorescent reactions of calcite from a 20W LED source right next to the specimen.


Hi, what does your setup look like? Can you upload a photo of how you're arranging the light and the samples?

I've gotten plenty of light while using a UV laser, but that's definitely a stronger source:

https://publiclab.org/notes/warren/01-05-2016/testing-high-brightness-405nm-leds-in-fluorescence-spectroscopy-of-oils https://publiclab.org/notes/mathew/09-23-2014/graded-oils-using-uv-fluorescence

If you're looking for a much more sensitive camera, a number of people have upgraded their spectrometers with a Raspberry Pi camera, which is a relatively simple and affordable upgrade:

https://publiclab.org/wiki/raspberry-pi-spectrometer

As this gets proven out, we're hoping to begin carrying this as a more sensitive variant.

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There was no setup. I struggled to get a reading with a fluorite from the Rogerley Mine. This specimen is incredibly bright. The issue probably lies in the fact that I had to bounce the light off of the fluorescer rather than through it. If I was measuring contamination content in water I'm sure I could get a reading too. They don't make laser diodes for some of the wavelengths I intend on using so something like a timed capture might work? Here's a reference graph for what my spectra should have looked like. http://www.fluomin.org/galeriespectre/FLUORITE12spectre.jpg

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