Frequently Asked Questions
Here are answers to the most frequently asked technical questions about Nanoco's Products.
- How do I ligand exchange?
Surface derivatization of the Quantum dots is very much a ligand-specific process and the procedure varies according to the desired ligand. For example, ligand exchange might be achieved by prolonged exposure of the dots to an excess of a competing capping group and in this case the exchange is driven through mass action.
The procedure consists of stirring a mixture of HDA-capped dots with a 10-20-fold excess of the competing ligand at room temperature for at least 72 hours. Mild heating can speed up the process of surface exchange however, depending on the ligand, heat treatment can cause a substantial decrease of the PLQY.
- What does FWHM mean?
Typically the emission spectra of quantum dots have the shape of a Gaussian curve. The width of the Gaussian is defined to be the full width at half-maximum (FWHM) and gives an idea of the size distribution of the particles. The narrower the FWHM, the narrower the size distribution. FWHM is also dependent upon the emission wavelength maximum
- What does QY mean?
Quantum yield or also quantum efficiency is the percentage of photons absorbed by the Quantum dots to those emitted. The ideal scenario would be 100% energy going into the quantum dot with an output of 100%. Typically QYs are between 30-50% depending on the material, however it is also possible to achieve much higher quantum yields
- How much material should I use for my application?
- How many particles do I get in 1mg?
The number of quantum dots present in 1mg of dry sample depends on the particle size and can be established by using the extinction coefficient. To measure the number of particles in 1mg of dots, Beer’s law can be used. According to Beer’s Law, A = εb[c] where A = absorbance of the solution of dots measure by UV-vis spectrometry, ε is the extinction coefficient, b is the cell path length and [C] is the concentration of the particles in the solution.
