TJIIRRS: Number 10c of an Ongoing Series;

Naturally Occurring Compounds Suitable for Use as Laser Dyes

Although most organic materials fluoresce at least a little, there are very few naturally-occurring compounds with quantum efficiency above 0.5 or so. This page discusses some of them, and a few with lower efficiency that have nonetheless been lased.

1: Aesculin

(04 September, 2006)

Aesculin (the modern spelling is Esculin) has been known for many years. It is a hydroxycoumarin compound, related to the umbelliferones. Aesculin can be extracted from the bark and probably the seed husks of Horse-Chestnuts (of which the most commonly grown kind seems to be Aesculus hippocastanum), and presumably also from closely-related species like the various kinds of Buckeye.

Aesculin is brightly fluorescent, particularly in basic solutions. It has been lased and reported in the literature, though only once that I’m aware of. It is a hemolytic toxin, so you shouldn’t eat any horse-chestnuts that you haven’t first crushed and soaked in several changes of boiling water.

I obtained a small quantity of Aesculin Sesquihydrate, and was able to lase it in 95% Ethanol with a small amount of ammonia. Here is a photo:

(The dye cuvette is on the right, its output on a paper target on the left. The “dye” was pumped by the [focused] output of a nitrogen laser I built.) I will post a tuning curve here, if and when I have one.

I should note that I have not yet lased any aesculin extracts that I’ve made myself, but I hope to do so at some point. (I have access to a small buckeye bush and possibly to some horse chestnut trees.)

2: Quinine

(04 September, 2006)

Quinine has fluorescence quantum efficiency of about 0.55 in slightly acid solutions. This makes it at best a mediocre candidate for lasing, but in fact it has been lased. (If you want a comparison, Fluorescein has quantum efficiency of about 0.96 in slightly basic solutions.) Quinine is commonly available in the form of tonic water, which is sold in supermarkets. If you want to lase it, you will need to get the bubbles out and add some acid. (In laboratory demonstrations people use about 0.1N sulfuric acid; I strongly suspect that other acids will also work.) Unfortunately, the concentration of quinine in tonic water is very low, and it is not suitable, as purchased, for nitrogen laser pumping, though it may be nearly concentrated enough for flashlamp pumping. (If you want to concentrate it by evaporating some of the water, I would suggest that you use diet tonic water, so you don’t end up with a thick sticky syrup. You should also be careful to prevent dust from getting into it.)

(Note, added 2008 December 13 and extended 2011 March 06)

It is sometimes possible to obtain quinine sulfate on eBay; it is used by aquarists to treat some sort of disease in tropical fish. It is also possible to pursue a far more DIY approach; at several local supermarkets I have found this:

As you can see, there isn’t much Cinchona bark (misspelled on the label) in the package, but I don’t think it was particularly pricy. If you extract the quinine from this material you will have to purify it somehow, which should be an interesting exercise. (If I do that I’ll report it here, and I will provide some sort of method, or at least some suggestions.)

3: Chlorophylls and Related Compounds

(04 September, 2006)

There are two common forms of Chlorophyll in higher plants; these are called “A” and “B”. Chlorophyll A has relatively low fluorescence quantum efficiency, but has nonetheless been lased. As far as I am aware, the fluorescence efficiency of Chlorophyll B is so low that it has not been lased. When chlorophylls lose their magnesium ions, which they do regrettably easily, they become the corresponding pheophytins. Mitsuo Maeda, in his book on Laser Dyes, mentions both these and the closely-related phycobilins, of which there are several. (Phycobilins seem to occur extensively in cyanobacteria and red/brown algae.)

It may be possible to purchase various of these in reasonably pure form, and some of them, particularly the phycoerythrins (which are actually proteins with attached chromophors), have significantly better quantum efficiency than Chl A, which suggests that they are worth taking a look at — typical reported phycoerythrin quantum efficiencies are 0.82 to 0.98. Some may also be more stable. One drawback of all of these, though is that they tend to occur with other compounds, and it is often difficult to separate and purify them. There are, however, extraction and purification protocols in the literature.

[[Note: In the process of extracting chlorophyll from some dark kale, I noticed that one of the layers of my extract had a fairly bright blue fluorescence. At some point I hope to try to figure out what is responsible and whether it can be lased.]]

4: Oat Roots

(05 September, 2006)

I have seen a report of two fluorescent substances that were obtained from oat (Avena sativa) roots. If memory serves, these compounds are coumarins, which would make them related to Aesculin and also several synthetic laser dyes. I hope to look into this at some point in the future.

5: Molds; Kojic Acid

(27 December, 2008)

In the course of investigating a particularly fluorescent mold that I found in my refrigerator —

— I started looking for information on the Web about mold fluorescences. I have yet to identify the mold, which I am attempting to culture, but I did find a mention of Kojic Acid, which forms an intensely fluorescent derivative when it is oxidized. I will be attempting to look into this at some point. In the meanwhile we will see whether I can grow more mold; whether the fluorescent compound can be extracted (and, if necessary, purified); whether it is stable in solution; and, if all of those conditions are met, whether it can be lased.

6: Riboflavin

Riboflavin (Vitamin B2) fluoresces about as efficiently as Chl A, and there is a limited chance that it might work as a laser dye. It is quite unstable, however, and does not have particularly strong absorption, so it probably cannot be pumped transversely by a nitrogen laser. (This does not entirely rule it out, just means that it will be nontrivial if it can be lased at all.)

7: Other Materials

I am always on the lookout for more natural compounds with strong fluorescence, and I will add them to the page as I find them or manage to obtain results with them.

There may also be relatively easy and nontoxic ways to improve some of the compounds that have low efficiency (for example, the fluorescent material[s] in turmeric) or are difficult to dissolve, but this gets into actual chemistry, and may be difficult for DIYers because of the difficulties involved in acquiring materials and equipment.

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Last modified: Thu Jun 23 15:46:25 CDT 2016