Cheap plastic band pass filters/Fluorescence Spectrascopy 1

[salukikev]

Hello,
On a project I am involved with, we are seeking to increase visual contrast/brightness in order to better distinguish objects of interest from background ambient light. There are two questions somewhat related to this task, and one involves consideration of band pass filters- of which I am only slightly familiar. Cost is a major element of this equation as this will be a retail product commonly available in your typical Walmart/Target. Current cost of this entire component assembly is around $.25 usd.
With that in mind- question 1 is whether there is a low cost (plastic) film material that can be manufactured in large quantity that will act to increase the apparent contrast or brightness when viewed through the filter. Similar to the diffusion gratings or tinted/semi-metallic acrylic plastics seen in sunglass lenses or the paper glasses for special effects. We wouldn't be concerned with clarity or scientific measure- we are merely concerned with the ability to distinguish fluorescing objects from the surrounding environment and reduce apparent ambient lighting in that pursuit.

Question 2:
With the same goal as the question above in mind, can a chemical be applied that would effectively act as a fluorescing catalyst? That is to say, not act as a typical fluorescing marker agent (flurophore) but rather as a non-or-low fluorescing agent that will cause a particular chemical to either fluoresce or amplify/differentiate the fluorescing output of a material?

If Q2 needs more explanation, consider this example: in a CSI-style crime investigation, suppose a detective is scanning a counter top in daytime with considerable ambient light. There is a small droplet of blood on this counter top. Can a chemical agent which is not just a dye be applied to the counter that will not fluoresce uniformly, but rather will react with the blood to increase its specific fluorescence/contrast?

Thanks for any help in either of these areas!
-kevin

 

[IRstuff]

Q1 -- You're just going to have to talk to a coating supplier like:

http://www.evaporatedcoatings.com/bandpass-optical-filters

Q2 -- That depends on the "material of interest" Had you done more research, you would know that CSIs use phenolphthalein:

http://en.wikipedia.org/wiki/Kastle-Meyer_test

TTFN
faq731-376

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[salukikev]

Q1: I have talked to several, but the ones I've ended up with tend to use glass substrates for precision medical/military applications, and so the cost is way out of line with our goals. I'll follow up with the company you cited as I see they have some "low cost" plastic options described. thanks!

Q2: I didn't want to get too narrow in my description, but I did want to create an example people would be familiar with- so the CSI/Blood works to that end. Phenolphthalein is a helpful citation, but as far as I know the reaction does not necessarily effect the overall fluorescence of the sample- which was specifically what I am interested in.

What I am asking in Q2 is if there is a chemical that will react with any "materials of interest" (in quotes because we prefer this be a fairly broad range of TBD materials), rather than just be a chemical fluorescent marker- an important distinction.

 

[salukikev]

I'm sorry it appears I've left out a critical element of my question, even if it was implied:

My application will be utilizing 340nm Ultraviolet (UV) light.

Sorry about any confusion!
Also- while I'm clarifying- the $.25/pc estimate would be overseas manufacturing costs.

 

[IRstuff]

My answer for Q2 remains the same. Without any specific's the answer is "it depends," i.e., there is no such chemical for general work, which should already have been obvious. I don't understand how you can get this far into a product development without actually doing the critical engineering. Do you seriously think that there is a chemical that you can use on, blood, that would work on steel?

TTFN
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[salukikev]

Well, so far we haven't conclusively given any examples of a reaction that will cause an increase in fluorescence in any substance. I don't know that color change is the same thing(as in your phenolphthalein example).
If there is no reaction when I broaden the search to "anything" then I'm not going to worry too much about narrowing to specific substances before crossing it off my research list. In any case, keeping it broad also allows for those with some relevant experience or examples to chime in with a lead to pursue.
If I was to only inquire on chemistry that reacts with blood, I cut down my respondents dramatically. In any case, we may be able to include an assortment of chemicals within a compound mixture, so collecting a list of chemicals to research or possibly a class of chemicals/reactions would help focus areas of further research. As stated initially, I am not a chemist, but a mechanical engineer- which is the reason I'm here having this conversation.
As you can see, we are still speaking in general terms- I'm not sure how you presume to know how far we are into this particular product development, but if you'd like me to explain where we are and why we'd take this approach, I'd be glad to PM you my phone #.

 

[IRstuff]

I presume, based on the fact that you claim to determined the cost of the product, yet actually have no working premise for the product.

TTFN
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[salukikev]

"Current cost" is the cost to manufacture the product that is selling in stores now. This indicates the price range we are in and what latitude we have to spend additional. We have a working prototype, and we are investigating technologies to improve it further such as filters and chemical catalysts/indicators. Neither of these is a primary feature, but either or both would support the premise.

I'm not sure how much background information you need to offer constructive feedback, but I've tried to keep conversation exploratory & on topic by considering all/any available options.

 

[rgaughan]

Q1 and Q2 are (perhaps unfortunately in regard to your wish to keep the discussion "general") linked not only to each other, but also linked to the specifics of the fluorescence of your target. Unfortunately each target compound has different fluorescence characteristics (directly tied to their different chemical characteristics). There is no "generally effective" chemical fluorescence catalyst. You can use proximity to a metal surface to enhance fluorescence, but you need to tightly control the target and imaging geometry, which is not only far from what you're doing, but also becomes very expensive.

It's not all bad news, though. If you do have a specific fluorophore of interest and you know the emission spectrum, you can find a very inexpensive surrogate for a "wratten filter" in either theatrical "gels" or colored cellophane. You just need to be sure the peak of your fluorescence is close enough to the relatively narrow passband of the cellophane. This is the same kind of material you find in the old-style (really cheap) 3-d glasses where one eye looks through a red filter while the other looks through a green. If your fluorescence is red, then it will show up with a red filter (for example), while other background is suppressed.

This does leave the open question, however, whether the distinctive color of the fluorescence or the brightness of the signal is more easily perceived. If it's the distinctive color, the filter might actually reduce the user's ability to distinguish the signal, because the filter will only let red light through, so there will be no other colors to contrast with the red. Depends upon the specific illumination environment and the strength of the signal, etc. But if you're trying to excite multiple fluorophores of different colors then none of this will be of any help.

http://www.mountainoptical.com/ScientificSeen/