How Fluorescence Works - The Science

In this video we explore the colorful science of fluorescence.
A really cool way to play with fluorescence at home is get a blue or violet laser pointer and shine it into a dish or jar of water where you have added a drop of fluorescent highlighter fluid. You'll clearly see the beam as the solution fluoresces in its path.
Now the common definition of fluorescent is something that glows a visible color when exposed to ultraviolet light. Fluorescence is actually much broader than that and you don't need ultraviolet light in particular. For example in the yellow fluorescent dye "rubrene" both violet and green lasers will activate it and glow yellow. This proves you don't always need ultraviolet light. But a red laser will not activate a yellow dye. Why is that?
What's happening in fluorescence is that the incoming light raises the energy of the electrons in the molecule to an excited state. The electrons then lose a bit of energy due to vibrations of the molecules. And finally the electrons return to the ground state by releasing light. Now since energy cannot be created or destroyed and a bit of energy was already lost as heat in the vibrations of the molecules, the energy of light emitted must have lower energy than the light absorbed.
So since the yellow fluorescent dye emits yellow light, we need to use light of higher energy like violet and green for it to glow. Red is lower energy than yellow light so it can't excite the dye.
It also won't work if you use the same color as the dye like a green laser onto a green dye. This is because you almost always lose a bit of energy and therefore it has to emit a different color or none at all.
Another restriction is that the dye has to also absorb the light to work.
For example Europium Tetrakis (Dibenzoylmethide)Triethylammonium will glow bright orange under violet light. But under green light it doesn't glow at all. This is because the substance simply doesn't absorb green light and so it can't reach an excited state where it can fluoresce. So you need both absorption and higher energy to get fluorescence. Higher energy does not automatically imply absorption.
A really cool trick with absorbance and fluorescence is to get multiple fluorescent dyes of differing colors and shining various wavelengths of light on them. If you start with short, high energy, wavelengths of light you will see all the dyes glow. But as you go to longer wavelengths of lower energy the high-energy dyes will go clear as they can no longer absorb or emit light. When you reach red light all the dyes may look "clear" even though you know they are actually multiple vivid colors in white light.
Now what happens if you mix fluorescent dyes? The results depend on the concentration, absorption and emission profile of the dyes. Sometimes the colors of the resulting fluorescence will simply add up and you get a mix of color. Other times the emission of the higher energy dye will get absorbed by the lower energy dye and the color you get at the end is exclusively the lower energy dye.
Moving on to a new topic now: I said fluorescence worked by first using light to push electrons into high-energy states. Well if we could just push these electrons into their higher energy levels then we don't necessarily need the light. We can do this in a glow stick. A glow stick reaction uses chemicals instead of light to excite the electrons in a fluorescent dye.
Now instead of using chemicals to excite those electrons we can also use direct mechanical grinding. A special range of compounds has this property called triboluminescence.
On a different note: Remember when i said way back that after an electron is excited it loses a bit of energy due to molecular vibrations? It follows that if we can alter or stop these vibrations then we can change the energy of fluorescence and thus its color.
A special dye called pyridine copper iodide exhibits a property called fluorescence thermochromism. It changes fluorescent color with temperature. At room temperature the color is yellow but under liquid nitrogen it changes to blue.
Finally a life saving application of fluorescence is in medical diagnostics. A dye is specially engineered to glow when it comes into contact with a pathogen. Since pathogens usually only occur in tiny invisible concentrations by using one of these special fluorescence dyes a sample to be tested quickly and accurately for the presence of such pathogens. The key point is that fluorescence can still be very bright even at these tiny concentrations.
So there you have it, a cool effect that helps us to understand light, have fun and save lives.

[@madelinesparks6145]

I love how he says Europium Tetrakis Dibenzoylmethide Triethylammonium like it's no problem to say.

[@ShaunVillafana]

What's the matter _you never had Europium Tetrakis Dibenzoylmethide Triethylammonium before?_ It's delicious. I drink it with my mountain dew so that when I use the bathroom at night I can see where I'm peeing.

[@svnhddbst8968]

"do not look into laser with remaining good eye" definitely a good old laser joke.

[@untelmorveux]

You can inject this into your veins right

[@Me-xk5tf]

no

[@mingmingandmikki]

So it's heavily implied that you can look into laser IF you have TWO good eyes.

[@michaelsmaragdakis4272]

Well, the consequences will not even nearly be as bad as if you do it with just one good eye :)

[@crisscrossam]

i am so glad this channel is somehow still going. i used to watch so much of it as a kid and was looking for this video specifically because it always amazes me and is a great demonstration. thank you nurdrage for helping people see the cool side of chemistry and make them want to learn! i'm more into computer science now but chemistry will always be fascinating to me.

[@SilentSnipest]

Best intro video on Fluorescence, HANDS DOWN. This is how every professor should introduce this topic in chemistry courses. This was interesting, simple and concise. Great job Nurdrage!

[@Alexander_Sannikov]

This is one of the coolest videos I've seen in a while. I really appreciate that you explained luminescence mechanism the proper way with energy diagrams without dumbifying it.

[@NurdRage]

most of the dyes i bought from sigma aldrich or alfa aesar. Most of the video used: 9,10-diphenylanthracene 9.10-bis(phenylethynyl)anthracene rubrene rhodamine B tetraphenyl porphyrin and the special dye at 8:00 is a type of FRET based molecular beacon coded to the DNA of e.coli. you can buy the kit online but the compound itself is propriety so even I don't know what it actually is.

[@petevenuti7355]

Is there such a thing as a single source of info, and encyclopedia of dyes, that shows all of their absorption and emission Spectra, compatibility ,chemical structure solubility etc... I would like to transfer animated gifs to t-shirts, the animation achieved by cycling long wave shortwave and RGB illumination.. 30 years ago I wanted to do animated flame effects on the hood of my car, but the one UV-c only activated red that I could find that was compatible with clear coat and had longevity was horrendously expensive.. If I can find a more imaginative artist to help me, perhaps a phosphorescent stegographic latent image you might see for a second before your eyes adjust 😜

[@sirflimflam]

NurdRage, I've watched a lot of science videos on youtube, but yours are some of my personal favorites. You cover not only interesting topics but actually teach something in the process. Kudos, man.

[@xeel224109]

Man, that's the best science video I've seen in my life. 10 years ago and today again.

[@souravzzz]

I love your videos but this one was something special! Keep up the awesome work!

[@SigEpBlue]

I really appreciate the more-thorough explanation of what's happening in this video. It's a bit longer than your other vids, but it's really a nice touch, and this is one of my favorite NurdRage videos so far. Good work, and thanks!

[@cup3r]

great video. i've been a fan of your videos for a couple of years now and i like how in this particular one you not only introduced some of the theory behind the demo but also some applications.

[@iwakunrock]

I loved this video. I really like the science-focused detailed explanations. For a lot of your videos I think, "That was awesome, but I'm not sure what it means, or what you can do with it." This really helped to show that and I learned a lot from it. Kudos!

[@SebastianGrans]

This is by far the best video you have ever made. Your other videos are by no means bad, they are great! I'm just saying that this one is exceptionally good. I find the short educational explanations very intriguing! Thank you NurdRage! You are one of the reasons that made me choose to study chemistry at the university.

[@BlackWolf18C]

Automotive Technicians also use fluorescent dyes to detect coolant leaks. A small amount of dye in a radiator and a UV light lets you see where coolant is coming from. It's a handy tool to have.

[@eliyawaters9075]

That's so cool! I have always found light fascinating, but your experiments make it look even cooler!!

[@karencwaldron]

I think this is a great video; just showed it to a group of first-year university students in a bioanalysis course after teaching the principles of fluorescence spectroscopy.

[@chaos1267]

wow thank you for this. ive always had an interest in flourescence but never really got into how it works. you made everything easy to understand. nice job.

[@gorillasapien]

very well done, thank you for what you do, even when some of the science goes over my head i still feel as if i got something from your videos, and i felt as if i needed to say thank you.

[@snorman1911]

This was better than any other description of fluorescence I've ever seen.

[@endimion17]

This might be your best video so far, judging by my preferences. It's quite informative. It goes beyond standard KZbin sci-videos, but remains in the safe zone of complexity so the amount of people capable of understanding it is not heavily reduced. Now if someone could make a similarly quirky video which extends into the procedures used in molecular biology (fluorescent DNA probes), that would be awesome. There are few videos about it, but they're too dull. Hope you have great holidays.

[@kolobian]

We had glow sticks at an event recently, and I was able to explain how they worked because of you. Thank you.

[@obviouslyblack]

One of your best videos. Very entertaining and educational. Thank you for taking the time to do this.

[@snixder]

I love how you tied in every other video you made regarding fluorescence. Excellent video :)

[@wanjockey]

Man that was freaking awesome. Thanks for sharing. I believe that you need to learn something new every day and you did it for me.

[@Jadinass]

This is awesome. I recently learnd about fluorescence in physics, but the chemical aspect and its usage is just as impressive.

[@NicholasOsto]

I think it makes your videos more memorable. Thanks NurdRage your videos are great.

[@wobblycogsyt]

Certainly one of your best videos. An excellent explanation of the effect.

[@jeebersjumpincryst]

This one is in a class of its own. like magicgonza said - flawless. NurdRage, these newer vids of yours are so so slick - professional even. I LOVED the diagrams. This one displayed a huge amount of your work - the products of so many different little projects u have done along the way. I know yr style is different, but I for one would love to see a collab by u and Brady(Periodic Videos, for anyone who doesnt know already) I love collabs between my KZbin heroes. merry xmas. best regards, J

[@KiwiTibb]

Very informative, and a very broad amount of information presented quickly and clearly. I love it.

[@rogerdotlee]

This is freaking huge. It's good to see the physics behind the chemistry. It makes a great deal of sense, and next time I see something with that detached blue-ish glow, I'm going to hit it with UV to see if it's florescence or if I just need to get my eyes checked again.

[@a380rockerfan]

Wow, this was so interesting! Thank you for uploading this - very nicely edited and I'm living that new intro! Keep it up!

[@XempireX18]

lol at the warning in the beginning. this video is well done. loved it.

[@codandmkfan]

my favourite 3 videos of yours: this one, thescience of glow stick, and the complete guide to hot ice, i really like videos like that

[@rogerdotlee]

Thanks, Dr. Rage. I've missed your stuff (obviously the chemistry that pays the bills has been a bumper crop of late). WONDERFUL video. Love the disclaimer.

[@terrattenfanger5571]

I just found this channel... possibly the best channel ever.

[@ispamalot]

One of your best (in my opinion), absolutely mind blowing.

[@cristianfcao]

One of your best videos, mate! Thanks a lot!

[@NurdRage]

Too be honest i don't know. Most amateurs i find get their equipment from ebay. I get mine from professional distributors like VWR. I also get glassware from chemglass. But to be really honest chemistry as a hobby is NOT cheap. Glassware is expensive and breaks easily and often. Chemicals get used up. And mistakes, even if you're unhurt, are a costly loss of chemicals. My "make luminol" video cost $2000 to make over the course of a year due to costly "exploration" of the science.

[@FourthRoot]

I LOVED this video. Don't know why, but it was surprisingly informative and very easy to grasp. Great job, you have altered my fluorescent paradigm.

[@TestEric]

I would love a video expanding on this, absolutely amazing.

[@dannieboy824]

This video was PERFECT! I only wish you uploaded more often

[@creasedjoker9996]

I'm in an chemical instrumentation laboratory and this literally helped me understand what I'm studying. Thanks!

[@_sunsor]

Outstanding, clear, and well thought out video. Merry Christmas NurdRage!

[@changer_of_ways_suspense_smith]

I was actually able to pick out the one with the microgram... but I wasn't entirely sure until you shined the light. This video is very helpful. I've been working with painting miniatures with florescent paint but wanted to know more of the specifics in order to use then better.

[@airtownSC2]

Added to my short list of favorite videos, THANKS FOR THIS!

[@Muscleduck]

This probably is my favorite clip you ever made. Very interesting!

[@JP129]

A+. Best video on the subject that I've seen so far.

[@stepb24]

Once I saw that this video was 9 minutes long, I almost clicked away but once I started watching it I thought it was very interesting. NurdRage, I appreciate these videos and I think you do a great job explaining the material.

[@DexLuther]

Thank you Mr. Rage (or is it Dr. Rage?). I love your videos. You make me feel like I'm sitting back in science class. I hope to see many more videos from you in the future.

[@1DangerRose]

I'm studying medical lab science and we use spectrofluorometer it works in the same process and this video helped me understanding the results. thank you :)

[@masterell99]

This vid deserves so many more views. Presented in an interesting, clear and precise manner, defiantly worth a sub :D

[@MrLollikus]

This is the best video so far! very exaustive and interesting. I really like this style, keep it up!

[@TonyHaluza]

THIS IS FRICKIN AMAZING!! Thank you!

[@Alumx]

This was best educational chemistry video I ever saw :D I understood many things that didn't got in normal school lessons Thank you NurdRage! Looking forward for more awesome video lessons like this one c:

[@xdoods]

This is incredibly fascinating, thank you very much!

[@StrokeMahEgo]

I very much enjoyed this video. It really helped me to understand the various other fluorescence videos you have on a better level

[@KiingCobra1]

Great job nurdrage.Thank's for the knowledge.

[@whatsername1020]

Please never stop making these videos

[@MagicGonza91]

This episode was flawless.

[@Nivekomi]

This sir was one of the best videos plus explanation i ever saw!

[@timmowarner]

I always like your videos, but this one was particularly informative! I learned a lot!

[@lukabotic]

Another phenomenal video loved it!

[@TheKingofRandom]

Will you tell me what dye is used to detect e-coli? Thanks in advance!

[@demoaccount2392]

Maybe that was quinine

[@instazx2]

This was probably one of my favorite videos :) Great presentation, fascinating topic. I've been subbed for a long time, and check back constantly to watch your videos.

[@LeifMaginnis]

Wow, what a lot of information, thank you!

[@AtlasStruggles]

You're so cool! Thanks for teaching me in such a fun way that was very digestible!! Amazing video!!

[@grutnip]

thanks for the vids, and happy holidays to you too

[@Erik_The_Viking]

Excellent video, as always. Keep up the good work!

[@morphles]

This is one kick ass video, spectacular job! Thank you!

[@zbret]

Fascinating. Thanks for the great work on this..

[@pwhiteOO]

I love these so much! I wish I could pay you to make them more frequently!

[@TheKingofRandom]

Thanks. Yes I would like to give it a try. Any more information you can send is helpful. Thanks again!

[@ockertoustesizem1234]

RIP Grant

[@DawsonTyson]

My friends I'm continuously impressed in the way your videos educate. If I had a child I would with out question use you're videos to help educate him or her

[@NurdRage]

The Jablonski diagram is used in many areas of physics and chemistry.

[@godcoffee07]

Once again, a fantastic video.

[@GeorgeC1andonly]

loving the greater stokes shift on the europium compound!

[@boswell255]

Fascinating. Nice indepth video too. Culd you maybe do a video on Thermochromic materials/inks? I've always been mystified, ever since a colour changing toothbrush I had as a kid. It would be great to know exactly what's going on with the chemistry (if anything, or if it's all just physical).

[@MikeWarren]

I really enjoyed the recap and science, and using your previous videos as reference was awesome. How about another with more of your videos? Maybe "All Things Gold" (with Aqua Regia and Chloroauric Acid), "Fun with Liquid Nitrogen", or "Potassium - coalesced spheres or explosive fears?"

[@mackenzietrzil]

This was awesome! Thanks for the video!

[@punknfunk]

It's nice to see these types of higher level chemistry demonstration videos on youtube. Your voice sounds a lot like Wes from Geoff's group...

[@JoeJoeTater]

Videos that explain the theory behind the awesomeness are my favorite kind.

[@MrLiquimatter]

IMO, this is the best video you have made!

[@harryzwiers7499]

Super informative and interesting, thank you!

[@ThePaulnavarro]

One of your best videos!!

[@MoralidadMty]

Those 9 minutes went by too fast, I didn't notice it until I read a comment about it. I really enjoyed and learned a couple of new things about fluorescence and I love your videos, they are really enlightening.

[@Dleger13]

very cool video! these honestly make my day when i see them in my sub box

[@bojandude]

I can't believe I actually understood that... great job!

[@JustinCglass]

I love your videos Always very informative and enjoyable to watch I watch these with my little girls and even do some of the safer experiments with them Thank you and keep it up!

[@omsingharjit]

Wow thanks for such informational video

[@catsfromhell1]

It looks like you put a lot of work into this video. And I must say it is a great video! Keep it up!

[@forestoak1063]

@Ali Jafri When the photon is absorbed, the molecule is excited to a higher vibrational state, as opposed to an electronic excitation. The energy required for excitation to the fist excited state (from the ground state) is discrete, so only one frequency of photon can do this. However, excitations can occur from the ground state to the second excited state, and the third, etc. These would require higher frequency photons. When the molecule relaxes, it does not relax to its initial state (due to it having the highest population), so the light emitted is of a lower frequency.

[@flagman57]

This was amazing. I just had a little epiphany about fluorescence... Now to go make some simulations :) You should do some of these informative videos more often! You're great at them.

[@whareyou]

This is better than any text book or class, love it. I like how easy and short this concept is explained. Wow i remember i work

[@KL00100]

Thanks you for making science understandable .

[@queenblurblab]

This an amazing video! Very well thought out, Taught me much more then chemistry class did on the topic.

[@Kaiju_Tea_Party]

Fantastic video. Really interesting and LOOK! Pretty colors!

[@mevansthechemist]

NR, this is a phenomenal overview of fluorescence. As a fellow chemistry teacher, I salute you! :-)

[@sean918]

Your best video yet.

[@EddioFabio]

Loved learning about this! Thanks for the education

[@Truthiness231]

Brilliant talk, I learned quite a bit from this.