4 Conclusion
The conventional NPs such as AuNPs have been known to show the
measurement uncertainty in ES-SMPS system because of the addition of
surfactant, and the surfactant-depended uncertainty is more serious
especially for the NPs with sub-10 nm diameter. In this experiment, two
treatments including centrifugation and heating were used to remove the
surfactant while both were found to present little effect on the
detected diameter. Instead of working on the size improvement of AuNPs,
the self-disperse biological macromolecules were considered for the
sub-10 nm RM. Bio-NPs of four proteins were examined and the BSA and
ubiquitin were characterized to have the similar charging efficacy with
the conventional NPs, where the monomer, dimer and trimer could be seen
among their size distributions. The representative diameter of BSA was
6.9 nm and ubiquitin was 3.6 nm. The suspense stability of these bio-NPs
was monitored and the consistence in the detected size was approved. In
conclusion, the BSA and ubiquitin were suggested as the sub-10 nm RM for
the ES-SMPS calibration.