Frequently Asked Questions
Here are answers to the most frequently asked technical questions about Nanoco's Products.
- How do I get QYs?
PLQYs of quantum dots are measured relative to a number of standard fluorescence dyes according to the formula:
PLQY = PLQYst(I/Ist)(Ast/A)(n/nst)²
Where I (sample) and Ist (standard) are the integrated emission peak areas, A (sample) and Ast (standard) are the absorbances at the excitation wavelength, n (sample) and nst (standard) are the refractive indices of the solvents and PLQYst is the PLQY of the standard. The commercial dyes DPA-diphenylanthracene, Rhodamine 123 and Rhodamine 6G can be used as fluorescence standards to measure PLQYs across the whole visible region.
- What excitation should I use?
The best excitation source for visible emitting quantum dots is UV light (360-380nm). It is important that the excitation source has a higher frequency than the desired emission maximum.
- How were the extinction coefficients determined
Extinction coefficients were determined according to the method illustrated by Peng et al., ‘Experimental Determination of the Extinction Coefficient of CdTe, CdSe, and CdS Nanocrystals’, Chem. Mater. 2003, 15, 2854-2860.
- What solvents are quantum dots soluble in?
Quantum dots are soluble in a variety of solvents but some tend to be more aggressive towards the material. The surface of the Quantum dots is coated with organic ligands, and because of this the dots are soluble in a range of non-polar organic solvents such as Toluene, Chloroform and Hexane.
- How do I store quantum dots?
Ideal storage conditions would be in a dark room at a temperature of 4 degrees Celsius. The samples are air-sensitive and the optical properties might be affected if exposed to air for a long time. Solutions should be stored and handled under nitrogen.
