Why so Bright?

With immense visual brightness (which signifies the sensitivity in detection) and a high degree of photostability, CPNs™ offer revolutionary photonic properties that can enhance a variety of R&D.

Quantum yield (Φ) is thought to be an indication of brightness, however, this is incorrect. A true and accurate measurement of brightness is measured in the units, lumens (lu), and is given by the extinction coefficient (ε), multiplied by the quantum yield.

Brightness = Quantum Yield x Extinction Coefficient


  • Brightness is the fluorescence output per fluorophore, measured in lumens (lu);
  • Quantum Yield (Φ) is the number of fluorescence photons emitted for every excitation photon absorbed;
  • Extinction coefficient (ε) is the capacity for light absorption at a specific wavelength.

Exact measurements are influenced by a variety of environmental conditions. As Stream’s specially developed CPNs™ contain iron oxide for magnetic manipulation, it is likely that the true brightness is only slightly diminished from the 175x brighter Qdots and 1400x brighter AF488-dex in cells. 1

Quantum yields and extinction coefficients measured during the course of early CPN™ development can be found in various academic papers 2, 3, 4 and provide an initial insight into the potential of Stream’s CPNs™. Research investigating the true brightness of Stream’s CPNs™ is on going, with these results expected to be published in the near future.


1. The relative brightness of PEG lipid-conjugated polymer nanoparticles as fluid-phase markers in live cells, Lawrence P. Fernando et al.

2. Gd-containing conjugated polymer nanoparticles: bimodal nanoparticles for fluorescence and MRI imaging, Zeina Hashim, Mark Green et al.

3. Phospholipid Encapsulated Semiconducting Polymer Nanoparticles: Their Use in Cell Imaging and Protein Attachment, Philip Howes, Mark Green et al.

4. Luminescent quantum-dot-sized conjugated polymer nanoparticles – nanoparticle formation in a miniemulsion system Zeina Hashim, Philip Howes and Mark Green.