Temperature and pressure behavior of the emission bands from Mn-, Cu-, and Eu-doped ZnS nanocrystals

Abstract

The temperature and pressure dependence of the photoluminescence from ZnS:Mn 2ϩ , ZnS:Cu 2ϩ , and ZnS:Eu 2ϩ nanocrystals were investigated in the temperature range from 10 to 300 K and under hydrostatic pressure up to 6 GPa at room temperature. The orange emission ͑590 nm͒ from the 4 T 1-6 A 1 transition of Mn 2ϩ ions, the green emission ͑518 nm͒ from the 4 f 6 5d 1-4 f 7 transition of Eu 2ϩ ions and the blue emission ͑460 nm͒ related to the transition from the conduction band of ZnS to the t 2 level of Cu 2ϩ ions were observed in the Mn-, Eu-, and Cu-doped samples, respectively. It was found that all of these emission bands decrease in intensity with increasing temperature. Among them the intensity of the Mn-orange emission dropped faster. The activation energies were estimated to be 58, 16, and 42 meV for the Mn-orange, Eu-green, and Cu-blue emissions, respectively. A negative pressure coefficient of Ϫ26 meV/GPa was obtained for the Mn-orange emission, which agrees with the value calculated from the crystal field theory. The pressure coefficient of the Cu-blue emission was found to be 62 meV/GPa, which is almost same as the value of the band gap of bulk ZnS. However, the pressure coefficient of the Eu-green emission is 23 meV/GPa, which is contrary to the predication by the crystal field theory. The strong interaction between the 4 f 6 5d 1 state of the Eu 2ϩ ions and the conduction band of ZnS may be the origin for the positive pressure coefficient and the small thermal activation energy of Eu-green emission.

Doped quantum dots for chemo/biosensing and bioimaging

“…The Mn 2+ and defect-related emissions in Mn-doped ZnS QDs are also pressure-dependent, [112][113][114] while the size of QDs also has a significant effect on the pressure behavior of Mn 2+ emission. For instance, the Mn 2+ emission intensity decreases substantially as pressure increases for 3-and 1 nm-sized Mn-doped QDs.…”

Photoluminescence and field emission properties of ZnS:Mn nanoparticles synthesized by rf-magnetron sputtering technique

“…Recently, ZnS nanobelts synthesis via chemical bath deposition (CBD) within the self-organized pores of PVA was reported by us [19]. The luminescence properties of doped ZnS have also been studied by different workers [20][21][22][23][24][25][26][27][28][29][30][31][32] synthesized via different routes. But to our knowledge there is no reports on the preparation of Mn doped ZnS nanoparticles via rf-magnetron sputtering technique and also the finding of its field emission property.…”

Visible emission characteristics from different defects of ZnS nanocrystals

“…[8][9][10][11] For example, ZnS : Cu 2+ , ZnS : Eu 2+ , and ZnS : Mn 2+ nanocrystals show blue (460 nm), green (518 nm) and orange emission (590 nm), respectively. 12 With the fast development of nanotechnology, ZnS unique nanostructures, such as nanowires, nanobelts and nanotubes, have been successfully synthesized. 13 ZnS nanostructures exhibit various optical properties, because the optical properties are sensitive to size, shape, crystal structure, and defects.…”