Optical and Photochemical Properties of Nonstoichiometric Cadmium Sulfide Nanoparticles:  Surface Modification with Copper(II) Ions

Abstract

Nonstoichiometric cadmium sulfide nanoparticles ([Cd 2+ ]/[S 2-] ) 3) in 2-propanol were surface-modified with Cu 2+ ions. Addition of copper(II) perchlorate to CdS nanoparticles leads to binding of copper ions onto the surface of the semiconductor, accompanied by rapid reduction of Cu 2+ to Cu + , as confirmed by EPR and absorption spectra. Copper(II) perchlorate also quenches the recombination luminescence of CdS nanoparticles effectively. The quenching data obey a static interaction model, which confirms the binding of copper ions onto CdS. The latter was confirmed also by ultrafiltration and ICP spectroscopy. Copper ions bound onto the surface of CdS lead to formation of a new, red-shifted, luminescence band. The maximum of the new band is at 14 700 cm -1 compared to that of the original band at 17 900 cm -1 . It is suggested that, at low copper ion concentrations, copper ions bound onto the surface of CdS nanoparticles exist as isolated Cu + ions. They create a new energy level in the bandgap at about 1.2 eV below the conduction band, which is responsible for the new emission band (14 700 cm -1 ). Higher copper(II) perchlorate concentrations give rise to the formation of ultrasmall particles of CuxS (x ) 1-2) on the surface of CdS, which eventually lead to precipitation. Both isolated Cu + ions and ultrasmall particles of CuxS quench the original recombination luminescence of CdS nanoparticles by facilitating e -/h + nonradiative annihilation. The presence of copper ions bound onto the surface of CdS nanoparticles retard both the photocorrosion of the latter and the photodecomposition of copper(II) tetraphenylporphyrin induced by CdS nanoparticles. Appropriate mechanisms are presented.

One-pot aqueous synthesis of composition-tunable near-infrared emitting Cu-doped CdS quantum dots as fluorescence imaging probes in living cells

“…Cu(II) may be reduced to Cu(I) by the sulfide ions during the diffusion of Cu into the host. 22,24,[34][35][36][37] Fig . 1c gives the mechanism of the emission broadening of the Cu:CdS d-dots, which has also been discussed in some literature for organic synthesis of the copper-doped d-dots.…”

Mn-Doped ZnSe Quantum Dots as Fluorimetric Mercury Sensor

“…The formed particles of HgSe, both isolated and aggregated, can quench the luminescence of QDs by facilitating non-radiative annihilation of charge carriers, which act as electron-hole Nonmagnetic and Magnetic Quantum Dotsrecombination centres [59]. However, mere K sp values are not the sole factors in fluorescence quenching.…”

The Composites of Cationic Polyelectrolyte and Glutathione‐capped Quantum Dots for Selective Fluorescence Detection of Cu2+

“…29 The formation of Cu + induces the effective quenching of the fluorescence of QDs through facilitating nonradiative recombination of excited electron in the conduction band and holes in the valence band. On the other hand, Cu 2+ displaces the Zn and/or Hg in the ZnHgSe QDs, leading to forming extremely low soluble particles of CuSe onto the surface of QDs.…”