Figure 6. Multistep growth of quantum dots by repeated reagent addition.

(a) Schematic showing a five-stage reactor used for multistep growth of CdSe quantum dots. (b) Normalized absorption and photoluminescence spectra of quantum dots obtained from the reactor following multistep reagent addition; spectra were measured offline using undiluted, unpurified solutions. (c) Peak emission wavelength (λ_max) vs reaction stage for multistep and single-step precursor addition; emission spectra were recorded inline using a bifurcated fibre-optic probe, and λ_max values were determined by averaging over multiple droplets. Indicative particle volumes may be inferred from the emission spectra and are shown on the right-hand y-axis (see main text). (d) Time-resolved data showing, for each of the five reaction stages during the multi-addition synthesis, the variation in the peak emission wavelength (λ_max) over a 90-s acquisition period. Spectra were acquired inline, and each data point corresponds to a measurement on an individual droplet. (e) Absorption spectra of the final as-produced quantum dots for multistep and single-step precursor addition; spectra were measured offline using undiluted, unpurified solutions.