Hi
why we are using refractive index of solvents when calculating quantum yield in solvent. What is the effect of refractive index to quantum yield?
Hi Emrah Özcan , This is a very important fundamental question when it comes to fluorescence world.
The simplest answer to your question is: The fluorescence intensity of a substance is dependent on the solvent which you used for acquiring the spectrum. For example, if you use exact similar concentration of a probe with identical instrument set up ( excitation, gain etc..) you will get two different fluorescent intensities in two different solvent. This is where the refractive index comes to the picture. When two solvents have two distinct refractive indexes, the detector will not receive the same amount of photon budget during the analysis. Therefore, the relative fluorescence quantum yield of a probe is solvent dependent.
Now if we think about why this is important in quantum yield calculation. We typically calculate fluorescence quantum yield with reference to a standard. There standards have their QY reported in a defined solvent with a defined excitation wavelength. So, when you calculate the quantum yield of a material with respect to a standard, you will use same excitation wavelength for both. But you may need to use two different solvents. For example Rhodamine 6G has a reported quantum yield of 0.95 in ethanol (excitation at 490 nm). Now lets say I need to calculate my compound (lets hypothetically assume it excites close to 490 nm) with respect to RhD 6G. I may need to calculate the QY of my compound in many different solvents such as Ethanol, DCM, MeOH, Water etc. During the calculation of the QY with respect to the standard, I need to make sure I keep all other conditions identical. When I have two different solvents (For example RHD in Ethanol and My compound in DCM), I need to mitigate the effect of the solvent which can affect the detector input. This is where we do the simplification by using the ratio of the square of the refractive indexes of two solvents.
I hope this will give you some insight. Thanks for bringing up an interesting question.
Hi Emrah Özcan , This is a very important fundamental question when it comes to fluorescence world.
The simplest answer to your question is: The fluorescence intensity of a substance is dependent on the solvent which you used for acquiring the spectrum. For example, if you use exact similar concentration of a probe with identical instrument set up ( excitation, gain etc..) you will get two different fluorescent intensities in two different solvent. This is where the refractive index comes to the picture. When two solvents have two distinct refractive indexes, the detector will not receive the same amount of photon budget during the analysis. Therefore, the relative fluorescence quantum yield of a probe is solvent dependent.
Now if we think about why this is important in quantum yield calculation. We typically calculate fluorescence quantum yield with reference to a standard. There standards have their QY reported in a defined solvent with a defined excitation wavelength. So, when you calculate the quantum yield of a material with respect to a standard, you will use same excitation wavelength for both. But you may need to use two different solvents. For example Rhodamine 6G has a reported quantum yield of 0.95 in ethanol (excitation at 490 nm). Now lets say I need to calculate my compound (lets hypothetically assume it excites close to 490 nm) with respect to RhD 6G. I may need to calculate the QY of my compound in many different solvents such as Ethanol, DCM, MeOH, Water etc. During the calculation of the QY with respect to the standard, I need to make sure I keep all other conditions identical. When I have two different solvents (For example RHD in Ethanol and My compound in DCM), I need to mitigate the effect of the solvent which can affect the detector input. This is where we do the simplification by using the ratio of the square of the refractive indexes of two solvents.
I hope this will give you some insight. Thanks for bringing up an interesting question.
Hi Chathura S. Abeywickrama
Thank you very much for your informative answer.! It inspired me to focus more intimately.
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