PL QY value obtained in comparison to a standard. Typically the standard used for CdSe QD fluorescence is rhodamine 6G, which has a known QY of 0.95. So we use the below formula to calculate QY for the CdSe QDs. Below is an example calculation. First the fluorescence absorbance and fluorescence spectrum of a rhodamine 6G solution was measured and the for the QD solution. I is the intensity of fluorescence, Abs is the absorbance units.

This text uses CdSe quantum dots as example, but i think it is applicable to anything else (as far as you measure the photoluminescence or other type of emission)

(this is copied from my course assignment)

Karim

PL QY value obtained in comparison to a standard. Typically the standard used for CdSe QD fluorescence is rhodamine 6G, which has a known QY of 0.95. So we use the below formula to calculate QY for the CdSe QDs. Below is an example calculation. First the fluorescence absorbance and fluorescence spectrum of a rhodamine 6G solution was measured and the for the QD solution. I is the intensity of fluorescence, Abs is the absorbance units.

This text uses CdSe quantum dots as example, but i think it is applicable to anything else (as far as you measure the photoluminescence or other type of emission)

(this is copied from my course assignment)

Karim

The method suggested by Stanislav is one of the good method to calculate quantum yield. There is one more method for which you need integrating sphere, whose walls are coated with completely reflecting coating. From this you can measure the power emitted by your sample and power absorbed the sample and then you can calculate the quantum yield. there are some links for your help

http://nvlpubs.nist.gov/nistpubs/jres/113/1/v113.n01.a03.pdf

http://www.usna.edu/Users/physics/mungan/Publications/QuantumEfficiency.pdf

Stanislav is correct, but it's important to reiterate that this calculation only works for calculating luminescence quantum yields, and even then it won't distinguish between phosphorescence and fluorescence.

Quantum yield measurements, by definition, require that you know the number of photons generated per unit time by your excitation source; this is why you need to identify an appropriate actinometer for you studies (i.e. a compound that undergoes a known, measurable response with a known occurrence per absorbed photon).

You'll then have to consider the system whose quantum yield you're trying to measure, and you'll have to identify a way to measure the quantum phenomenon you're interested in. If it's a non-equilibrium photochemical reaction, for instance, you can get the quantum yield from the number of moles of the photochemical product formed per absorbed photon (i.e. using your actinometry results) per mole of starting material.

It can be a bit more complex if you're trying to measure the amounts of a transient intermediate being generated (e.g. if you're trying to get a quantum yield of formation of a charge-separated species that rapidly undergoes charge recombination) or amounts of different photochemical reaction products generated in equilibrium, but the principal is the same.

Hi

The method described by Stanislav is indeed the most popular way of measuring fluorescence quantum yields. However, the equation shown above lacks the refractive indices of the two solvents in which the molecules are dissolved.

You can find a short guide for measuring fluorescence quantum yields, including a (free) software helping you do it, here:

http://www.fluortools.com/software/ae/documentation/qy

There is also a very similar thread on the topic here:

https://www.researchgate.net/post/How_does_one_find_the_quantum_efficiency_for_organic_compound_by_using_solvents_in_fluorescence_studies2

Best,

Søren

Thanks for giving valuable information