• Flexibility—excited by 405 nm or 488 nm, maximizing violet laser use
  • Compatibility—combine with existing organic dyes, increase the number of detectable parameters
  • Stability—does not degrade over time like tandem conjugates, for greater reproducibility
  • Minimal single laser compensation—narrow emission spectra allow for minimal compensation when using a single excitation source

View all Qdot probe conjugates

What are Qdot probes and how are they used in flow cytometry?

What are Qdot probes?

Invitrogen Qdot probes are nanometer-scale semiconductor particles with unique fluorescence properties that differ from those of typical dye molecules. The color of light that the Qdot probe emits is strongly dependent on the particle size, creating a common platform of labels from green to red, all manufactured from the same underlying semiconductor material (Figure 1).

Qdot probes have broad absorbance spectra that increase dramatically at shorter excitation wavelengths. Their emission peaks are narrow and symmetrical, and do not change with variations in the excitation source (Figure 2). Qdot probes are optimally excited by a UV or violet (405–407 nm) laser, although sufficient excitation can also be obtained with other sources as discussed below.


Figure 1. Nanocrystals absorb light and then re-emit the light in a different color; the size of the nanocrystal determines the color. Seven different nanocrystal solutions are shown excited with the same long-wavelength UV lamp.

Figure 2. Extinction coefficients and emission profiles for selected Qdot probes. Excitation is presented as extinction coefficient; emission is normalized to maximum peak height.

Take your flow cytometry to the next level

Qdot probe conjugates are increasingly used in multispectral flow cytometry. The use of these conjugates will allow the addition of one to six colors, all excited from the violet laser. Qdot probes provide the additional advantages of brightness and photostability.

Because of their physical properties, Qdot probes are brighter than most organic fluorophores when compared to conventional dyes; Qdot conjugates remain fluorescent under constant illumination, while conventional dyes photobleach to varying degrees. The fluorescence stability of a Qdot probe translates to better stability of the reagent, and consequently of the stained sample, and also permits additional analysis steps after sorting.

How Qdot probes benefit your flow cytometry

Greater flexibility and precision for flow cytometry

With new flow cytometry instrumentation allowing ever-expanding detection capabilities, Qdot probes add an exciting new array of fluorescent labels for use in flow cytometry. Qdot probes provide fluorescent labels that can be excited with UV or violet light as well as longer-wavelength light sources, and exhibit long effective Stokes shifts and relatively narrow emission peaks. The result: greater flexibility and precision in designing multicolor flow cytometry panels.

Maximize your flow cytometry

As the exclusive provider of Qdot probe technology for life science research, we offer the full range of tools, from our new primary antibody conjugates to secondary detection reagents, required to maximize the use of your flow cytometer by combining Qdot probe technology with existing organic fluorophores.

For Research Use Only. Not for use in diagnostic procedures.