PDA

View Full Version : singlet oxygen


orcafood
09/08/2017, 08:00 AM
Would it be feasible to generate singlet oxygen and bleed it into the skimmer air intake? Would it be beneficial to the reef tank or no net overall? Photo irradiation of a porphyrin on silica gel or something along those lines

bertoni
09/08/2017, 03:01 PM
I'm not sure what the goal would be. Monatomic oxygen is highly reactive, so it'd oxidize organics in the air. It'd be easier to generate ozone, which would have a very similar effect, but either requires a bit of care.

orcafood
09/08/2017, 05:40 PM
Singlet O2 while in gas phase has around a half life of an hour while in liquid it has a half life of microseconds. I figured this might be better than the longer lived O3 which has a half life of 24 hours in gas at room temperature. Singlet O2 can participate in diels alder cycloadditions as well as react with alkenes such as certain lipids which triplet O2 cannot do without the help of some catalyst (palladium chloride for instance). Also singlet O2 favors the formation of hydroxyl moities rather than ketones like with O3, perhaps they would skim out more efficiently being a more polar surfectant. I was curious if anyone had looked into using this in a similar fashion, as you mentioned, to ozone.

Ozone is usually generated via a UV beam, the only modification to that would include the necessary photosensitizer doped gel to form triplet O2 instead of ozone.

bertoni
09/08/2017, 07:56 PM
I don't have enough chemistry background to help much with this issue. I think you mean singlet oxygen, not singlet O<sub>2</sub>. If you want to bias the end results of the reaction, then singlet oxygen might be required. On the other hand, the ozone as applied in our systems might be forming a fair amount of singlet oxygen:

http://www.jbc.org/content/266/14/9039.short

I'd have to do more research to check on this effect, though.

orcafood
09/09/2017, 06:43 AM
Hey no I mean singlet spin (one up one down) dioxygen, same stuff that microorganisms use to tear up organic molecules. https://en.wikipedia.org/wiki/Singlet_oxygen

Ozone must have a semi-stable singlet state to interact with alkenes, if I remember correctly I think ozone can spin flip between its singlet and triplet state much easier than singlet oxygen to triplet oxygen which is a forbidden transition. I think your right too ozone must form singlet O2 during certain reactions. But why use ozone at all when one could just use singlet O2 instead? Same basic ozone generating design with a little included photo active dye to form singlet O2 over O3

Thanks for taking the time bertoni

bertoni
09/10/2017, 05:25 PM
That's interesting. After a look at singlet oxygen papers, the primary issue would be the lifetime. At only a few microseconds, I don't know that the oxygen would be around long enough to do much, but it seems interesting enough to be worth a shot.

Tripod1404
09/10/2017, 07:55 PM
One issue might be generation of other reactive oxygen species with higher half-lives. Such as generation of superoxide, hydrogen peroxide or hydroxyly radical through singlet oxygen's reactions with molecular O2, H+, H2O, OH- etc. In long term thee can generate oxidative stress on livestock.

bertoni
09/10/2017, 09:06 PM
That's an interesting point. I would use activated carbon after the skimmer to try to handle any reactive species. I have no idea how effective it would be, though. I'm not a chemist.

orcafood
09/11/2017, 08:04 AM
Very interesting point tripod I will look into some of the lifetimes. With the long lifetime of ozone it is amazing that it can be used successfully in a reef tank.

Also would the singlet o2 really be dissolved in tank water? In a skimmer it would seem that there is quite a bit of gas compared with dissolving the singlet o2 in water, so the half life would be quite a bit longer. Also all of the organics congregate their non-polar parts into the inside of the bubbles in the skimmer so the singlet o2 would be decently exposed to the organics/proteins.

Doesn't peroxide breakdown very quickly in the presence of light? Perhaps a strongly lit refugium after the skimmer would provide some buffer area for the radicals to react. I was hoping that better surfectants could be produced with singlet o2 so that the skimmer could work more efficiently. Some polymerization between organics via free radical routes would make the skimmers job much easier.

orcafood
09/11/2017, 08:20 AM
How about getting leds that match the exact excitation wavelengths of the different radicals, one for superoxide, one for peroxide... then water proof them and send the skimmer output down a tube blasting the excitation spectrum

bertoni
09/11/2017, 05:24 PM
The oxygen can react with things in the water only if it is dissolved. I think the lifespan will be very short, but it might be long enough for some effect to occur. As far as the effectiveness of submerged LEDs, that's beyond my knowledge.

orcafood
09/12/2017, 07:06 AM
I liked your idea about using activated carbon, I'm still researching. I bet a uv sterilizer would do exactly what I was trying to describe with the leds. Carbon is even easier though. Thanks everyone for your insights!

orcafood
09/12/2017, 07:11 AM
I thought that the organic parts of skimmate became trapped in the interior of the bubble while the polar groups stick to the bubble surface in a skimmer. In that case the singlet o2 would be surrounded by mostly nonpolar singlet carbon bonds which it can react with very quickly in gas phase. This is why some makeups can photosensitize skin cancer of the face I think

bertoni
09/12/2017, 02:42 PM
I see what you mean. I'm not sure that the organics will get stuck so quickly to the bubbles, and if they do, they are likely to be highly skimmable in any case. Maybe not, though.

orcafood
09/14/2017, 08:37 AM
Great points! In gas phase singlet o2 has a half life closer to an hour so that might really work out. I found this device called the oxydator.

http://www.aquariumoxygenator.com/

Interesting little device and they claim to be producing reactive oxygen, I bet that it just 1O2. So they are generating 1O2 via a ceramic catalyst (probably with immobilized metal on it) and H2O2. How about hooking one of these up to a T to the skimmer line? 2L bottle, H2O2 and maybe some shards of iron or some reactive catalyst?

Or just bubble it into the tank water, seems like what they are doing.

http://pubs.acs.org/doi/abs/10.1021/es00162a012

H2O2 is found in seawater at concentrations of 10^-7 M and expected to be formed from organics by sunlight

bertoni
09/14/2017, 01:38 PM
I don't know whether that setup is producing singlet oxygen. I'm going to have to read the papers, but dosing hydrogen peroxide can be safe if there's method of scrubbing the output of the reactor.

orcafood
09/14/2017, 02:19 PM
Please link the papers you find to here! It is definetly feasible to make singlet oxygen from peroxide. I would use the peroxide, bleach reaction but chlorine gas is just so nasty. Their must be a chemical that can be used instead of hypochlorite, ugh.

Mr. Wiggles
09/14/2017, 08:42 PM
Also with your lifetimes so short and the organic compounds being in much lower concentration than water or oxidizable anions.

Consider this as a bimolecular reaction so the rate would be the kobs*[substrate]*[singlet O2]. If we pretend that two rate constants are the same, the substrate in the highest concentration will have a higher rate than the substrate at lower concentration. I just don't see this being worth the energy to set it up, the longer residency time of ozone makes it more attractive for the organic oxidations here.

orcafood
09/15/2017, 06:10 AM
Makes sense, I was mostly wondering how feasible it was. Seems very feasible but maybe not long lived enough. Definitely seems there isn't much of a clear cut answer and some experimentation is in order!

bertoni
09/15/2017, 04:00 PM
I agree that the lifetime is very short, so the approach seems like a long shot. It might be interesting and educational to try, though, even if it fails. As long as output is neutralized before it gets to the tank, it should be safe. Lots of carbon! That's what I'd use.

orcafood
09/15/2017, 05:56 PM
I was thinking of depositing some rose bengal or methylene blue onto a sheet of thin Plexiglas. I run my skimmer line outside so I could attach the end of the line to a box with this Plexiglas piece as the top and a thin area for the air to travel. This would expose alot of the incoming air to conditions which might generate singlet o2 via sunlight

ronaldwil
09/16/2017, 01:55 AM
Its very interesting. I would use activated carbon after the skimmer to try to handle any reactive species. How it effects?

bertoni
09/16/2017, 05:27 PM
I was thinking of depositing some rose bengal or methylene blue onto a sheet of thin Plexiglas. I run my skimmer line outside so I could attach the end of the line to a box with this Plexiglas piece as the top and a thin area for the air to travel. This would expose alot of the incoming air to conditions which might generate singlet o2 via sunlight
Do you know what the corresponding wavelength range is for absorption by the oxygen molecule's shared electrons? I'm not sure I'd trust sunlight to do much, especially after going through tubing.

bertoni
09/16/2017, 05:38 PM
I'm not finding much in the way of practical approaches to produce singlet oxygen from hydrogen peroxide. There is at least one catalyst:

http://pubs.acs.org/doi/abs/10.1021/ic00042a024

but most of the methods involving using chlorine gas or hypochlorite.

Hydrogen peroxide naturally decays to water and a single oxygen molecule, but how one could accelerate the process in a practical way is a bit of a challenge.

orcafood
09/17/2017, 06:33 AM
That is exactly how I was thinking that ceramic catalyst might work. High surface area ceramic functionalized with molybdate, lead, or copper. I am pretty sure a few different metals or metal oxides will produce singlet o2. Interesting that peroxide forms 1O2 at room temperature but that the reaction is kinetically unfavorable. I think MoO4^2- has a great affinity to be bound to a support much like in the catalyst support wiki.

https://en.wikipedia.org/wiki/Catalyst_support

Perhaps using pure O2 to produce the 1O2 over air would give better yields for the photocatalysis method

Also looking at the absorbance spectrum for rose bengal and methylene blue, around 300-330 nm light is what is required to form the necessary dye excited state to form 1O2.

orcafood
09/18/2017, 07:42 AM
https://commons.wikimedia.org/w/index.php?title=File%3ATiCrPt_micropump3.webm

bertoni
09/18/2017, 04:49 PM
I would be very cautious about having a pure oxygen source in a house. Oxygen can cause a lot of damage.