Some Experiments with Phosphors in UVIVF

[colinbm]

It has taken me at least a year to get this far & probably another year before I can be confident in what I am doing.....?
I have made many lights, some LED & some others, from 222nm to 940nm.
I have spent the last year looking for Phosphor Powders for UVIVF, & containing them to photograph.
In frustration trying to find a white phosphor, I have cleaned out a few 5000K Tri-Phosphor fluorescent tubes & contained a thin layer between UV fused silica windows & sealed it.
I have managed to get the layers to between 0.5mm & 0.25mm thin.
The initial goal was to find a WB target for UVIVF & a UV yellow aka 350nm, the search will continue.....
Here are the results of 5000K Tri-Phosphor & a Disco white phosphor pigments without any binders, & comparing with white PTFE, under 6500K LED, filtered 365nm LED & filtered 222nm Excimer lights. I have plenty of other lights, but this is just a sample, & baby steps.

 

This one is a problem, I wasn't able to get it, as I saw it, The PTFE was grey to my eye & the colours of the Tri-Phosphor & Disco white were, the other way around, to my eyes...!

 

This is a good representation of what I saw in a dark room.

[OlDoinyo]

Your tri-phosphor target seems to have a hue highly dependent on excitation wavelength--this is one of the maddening complications of this topic. Exactly what is a "standard" excitation? The other target varies less but still is not really white-looking.

[Andy Perrin]

Interesting experiment. Colin, when you photograph them, make sure none of the channels are saturated. That second photo looks "white" on the Tri-phosphor because it's overexposed I think. It's hard to know what color it would have been if it wasn't overexposed. I think you have to check the RGB histogram in camera if yours has that option to make sure, otherwise play it safe by deliberately UNDERexposing and then increase it later in post processing?

[colinbm]

48 minutes ago, OlDoinyo said:

Your tri-phosphor target seems to have a hue highly dependent on excitation wavelength--this is one of the maddening complications of this topic. Exactly what is a "standard" excitation? The other target varies less but still is not really white-looking.

Thank you, it is all new to me & a steep learning on a poor old brain.
I have more phosphors coming.

[colinbm]

10 minutes ago, Andy Perrin said:

Interesting experiment. Colin, when you photograph them, make sure none of the channels are saturated. That second photo looks "white" on the Tri-phosphor because it's overexposed I think. It's hard to know what color it would have been if it wasn't overexposed. I think you have to check the RGB histogram in camera if yours has that option to make sure, otherwise play it safe by deliberately UNDERexposing and then increase it later in post processing?

Thank you, The 365nm excitation one has been difficult to get right.
There is a light leak into the PTFE from the Tri-Phosphor, I need to seal the edges of the PTFE with aluminium foil tape & photograph again.

[dabateman]

Colin this is a brilliant start. But I question your choice of phosphor. 

Why not buy a G8T5E bulb,  which is coated with special phosphor coating to take 254nm (low pressure mercury)  and output primarily 306nm and look whitish. 

Also grab a white BL Mercury bulbs with special phosphor coating to make 365nm mercury line look white.

 

The triphosphor is interesting: 

http://www.lamptech.co.uk/Documents/FL Phosphors.htm

[colinbm]

56 minutes ago, dabateman said:

Colin this is a brilliant start. But I question your choice of phosphor. 

Why not buy a G8T5E bulb,  which is coated with special phosphor coating to take 254nm (low pressure mercury)  and output primarily 306nm and look whitish. 

Also grab a white BL Mercury bulbs with special phosphor coating to make 365nm mercury line look white.

 

The triphosphor is interesting: 

http://www.lamptech.co.uk/Documents/FL Phosphors.htm

Thanks Dave & the useful link too.
I'll look for the G8T5E bulb & BL Mercury bulb.

 

[colinbm]

1 hour ago, dabateman said:

Colin this is a brilliant start. But I question your choice of phosphor. 

Why not buy a G8T5E bulb,  which is coated with special phosphor coating to take 254nm (low pressure mercury)  and output primarily 306nm and look whitish. 

Also grab a white BL Mercury bulbs with special phosphor coating to make 365nm mercury line look white.

 

The triphosphor is interesting: 

http://www.lamptech.co.uk/Documents/FL Phosphors.htm

Dave what is the ' E ' mean in G8T5E bulb please ?

[dabateman]

7 hours ago, colinbm said:

Dave what is the ' E ' mean in G8T5E bulb please ?

The E is very important,  its that this germacidal bulb has been coated with a coating and only outputs mostly 302nm and larger wavelengths,  down energy from the main 254nm of the germacidal bulb. 

It some internal company code from ushio. I have seen another code for the 302nm bulbs from another company,  but I can't remember it as easy.

G is germacidal bulb 

8 is 8 watts

T is a straight tube bulb

5 is with the special T5 end pins

E is special coating. 

No e and just germacidal. No g and F and then not germacidal. 

[colinbm]

1 minute ago, dabateman said:

The E is very important,  its that this germacidal bulb has been coated with a coating and only outputs mostly 302nm and larger wavelengths,  down energy from the main 254nm of the germacidal bulb. 

It some internal company code from ushio. I have seen another code for the 302nm bulbs from another company,  but I can't remember it as easy.

G is germacidal bulb 

8 is 8 watts

T is a straight tube bulb

5 is with the special T5 end pins

E is special coating. 

No e and just germacidal. No g and F and then not germacidal. 

Thanks very much Dave.

[dabateman]

More expensive but in the US we also have G15T8E

G germacidal

15 for 15 Watts 

T8, straight tube bulb with T8 plug

E for coatings. 

I am not sure what standard bulbs you have in Australia, might be similar but different and cheap there too using your fluorescent bulb codes.

[colinbm]

5 minutes ago, dabateman said:

More expensive but in the US we also have G15T8E

G germacidal

15 for 15 Watts 

T8, straight tube bulb with T8 plug

E for coatings. 

I am not sure what standard bulbs you have in Australia, might be similar but different and cheap there too using your fluorescent bulb codes.

Are these the same / similar to UVB Reptile tubes ?

[dabateman]

No the reptile bulbs are not germacidal.  They are mixtures of coating and different pressure and heat.

The 254nm germacidal wavelength comes from low pressure low heat.

The others I am rusty on, but each of the 185nm, 302, 313, 365 and 405 can be selected more dominantly based on pressure and heat.

185nm very low pressure very high heat.

313nm comes from medium pressure low heat.

365nm high pressure higher heat.

 

[colinbm]

Thanks Dave
 

[colinbm]

Dave this is the only narrow band UVB that I can find at the moment in Australia ?
https://www.lightonline.com.au/medical-lamps/philips-uvb-narrowband-phototherapy-lamp-20w

[dabateman]

12 minutes ago, colinbm said:

Dave this is the only narrow band UVB that I can find at the moment in Australia ?
https://www.lightonline.com.au/medical-lamps/philips-uvb-narrowband-phototherapy-lamp-20w

Thats a bit too expensive to smash open just for the coatings. 

I even see the g8t5e bulb at B&H:

https://www.bhphotovideo.com/c/product/1634249-REG/ushio_3000318_g8t5e_germicidal_uvb_t5.html

 

There must be a cheap one from China  or Europe that could ship to you.

[colinbm]

Yep, that is much better, thanks Dave.

[Alaun]

Colin, how do you handle the mercury, that comes with the bulbs?

[Andy Perrin]

6 minutes ago, Alaun said:

Colin, how do you handle the mercury, that comes with the bulbs?

Whoa, yes, somehow this point passed me by, but definitely breaking a bulb with mercury open seems like a bad idea in any living quarters (and it's not good for the environment either). 

[lukaszgryglicki]

I have 1kg of liquid mercury - nice to play with, but it is sealed most of the time.

 

[colinbm]

8 hours ago, Andy Perrin said:

Whoa, yes, somehow this point passed me by, but definitely breaking a bulb with mercury open seems like a bad idea in any living quarters (and it's not good for the environment either). 

Unless the Mercury fell out without me noticing, the Phosphor powder has passed through 0.5mm gauze to make the target disc & is now sealed inside the 2mm JGS1 discs at 0.5mm thin.

[Andy Perrin]

It did most likely fall out without you knowing. The total amount of mercury in those bulbs is a few milligrams. It’s not a lot, but it’s also not good to have any mercury at all in your environment. 
 

You can probably buy the phosphor directly if you know what you want. Or at least don’t do this anywhere it can get in your water supply. 

[colinbm]

I will be careful with the Mercury, I have been opening the fluoro tube in the back yard above a cement floor, being careful of glass & mercury. 
My work shorts glow nicely under UV now.
I have other phosphors coming soon, next year I can search more & learn what to be specific about.

[Andy Perrin]

If you got the phosphors on your clothes, the mercury is too. I know you usually are very safety conscious, but needless mercury exposure is seriously bad. The mercury is not necessarily in liquid form. It evaporates easily at room temp. Discontinuing this line of experiments using light bulbs seems like a smarter choice. 

 

This was with a far more dangerous form of mercury than the metal, but please remember what happened to Karen Wetterhahn, the chemist who spilled just a few drops of dimethylmercury on her GLOVED hand, and several months later died a horrific death. She was one of the world experts on mercury poisoning, and died of it at age 48.

 

MaxMax sells a lot of different phosphors, there may be a way to buy them or find them locally. Could different proportions of red, green and blue phosphors be combined to make a "white"?

 

[colinbm]

Thanks Andy
" Could different proportions of red, green and blue phosphors be combined to make a "white"? "
I have some 'known' kelvin phosphor coming & some R G B too.
I will look at what MaxMax has too thanks.