Blue-Emitting Copper Nanoclusters Synthesized in the Presence of Lysozyme as Candidates for Cell Labeling

Abstract

Highly fluorescent copper nanoclusters (Cu NCs) have been synthesized using single-step reduction of copper sulfate by hydrazine in the presence of lysozyme. The fluorescence quantum yield was measured to be as high as 18%. The emission was also found to be dependent on the excitation wavelength. Mass spectrometric analyses indicated the presence of species corresponding to Cu2 to Cu9. Transmission electron microscopic analyses indicated the formation of agglomerated particles of average diameter of 2.3 nm, which were constituted of smaller particles of average diameter of 0.96 nm. They were found to be stable between pH 4 and 10 and in addition having excellent chemical and photostability. The noncytotoxic NCs were used to successfully label cervical cancer HeLa cells.

All‐Copper Nanocluster Based Down‐Conversion White Light‐Emitting Devices

“…Reduction of Cu 2+ by GSH is evidenced by the absence of any satellite peaks around 942 eV. We note that the difference between 2p 3/2 peaks of Cu 0 and Cu + species is only 0.1 eV, so that the valence state of copper in Cu NCs may lie between zero (in the core) and one (at the surface where it is bound to sulfur), which is consent with the previous reports 13, 22. The ratio of S to Cu was estimated to be 4:1 from XPS measurements.…”

“…Along a similar concept, Liu et al fabricated WLEDs employing blue‐green emitting Cu sheets (PL QY of 4.6%) and red emitting Au sheets obtained by electrophoretic deposition of Cu and Au NCs 12. To the best of our knowledge, there have been no reports on WLEDs where solely Cu NCs as phosphors were employed, eventually due to their relatively low PL QY, which is commonly below 10% for clusters dispersed in solution12 and decreases further upon their processing as powders 13, 14. Emission quenching upon transfer of luminescent nanoparticles from solution to films or powders is a well‐known phenomenon, ascribed to the nonradiative Förster resonant energy transfer of excitons to the neighboring species with lower PL QY 15.…”

Copper nanocluster-based fluorescent probe for hypochlorite

“…As shown in Fig. 1d, a new peak at about 942 eV, which was assigned to Cu(II) [26], appeared after addition of hypochlorite to PVP-capped CuNCs.…”

Glutathione-stabilized Cu nanoclusters as fluorescent probes for sensing pH and vitamin B1

“…Importantly, the 2p 3/2 binding energy of Cu 0 was only 0.1 eV different from that of Cu + . Therefore, the presence of Cu 0 cannot be ruled out [43,44].…”