Stability of the Mn photoluminescence in bifunctional ZnS:0.05Mn nanoparticles

Abstract

We investigate the stability of the orange band photoluminescence (PL) of bifunctional nanoparticles of Mn2+-doped ZnS at 5% (ZnS:0.05Mn). These 4-nm nanoparticles are synthesized via a one-step inorganic chemical route under ambient conditions. The phase, crystallinity, and morphology are analyzed via X-ray and electron diffractions and high-resolution electron microscopy. Based on the thermally activated carrier-transfer model, it is found that orange emission is rather stable at low temperatures and possesses thermal activation energy of ∼18 meV. The analysis of the PL decay curves suggests the coexistence of multiple lifetimes, that the shortening observed in PL lifetime is not due to the Mn2+ ions, and that the orange band decay is stable in temperature range from 10 K to 300 K. The measured M-H hysteresis loops demonstrate that ZnS:0.05Mn nanoparticles exhibit ferromagnetic ordering below 30 K, unlike its bulk counterpart. No magnetic field dependence of the Mn2+ PL intensity is observed up to 1 T. The stability of the PL signal when subject to an applied magnetic field is discussed. This study offers experimental evidence to test low-dimensional dilute magnetic semiconductor models and widens the range of applications of ZnS:Mn nanostructures beyond optoelectronics.

Biocompatible ZnS:Mn quantum dots for reactive oxygen generation and detection in aqueous media

“…The well-defined peaks and rings found and the absence of parasitic phases and signal of ZnS wurtzite in the XRD and SAED patterns evidence that ZnS:Mn QDs are of high crystalline quality and purity. The calculated lattice constant of ZnS:Mn was a = 0.5384 ± 0.0007 nm consistent with its standard value (Beltran-Huarac et al 2013a , b ). The prominent broadening of the XRD diffraction peaks is ascribed to the nanocrystalline nature of the QDs.…”

“…Figure 4 a depicts the absorption profile of DPBF (400 μL of a 6.0 × 10 −5 M solution) in 2 mL of water in the presence of RB (1.0 × 10 −5 M). This spectrum shows the typical absorption band edges of DPBF centered at 264, 317, and 413 nm, and of RB peaking at 555 nm (Beltran-Huarac et al 2010 , 2013a , b ; Tuncel et al 2011 ). No photooxidation of RB was observed when the samples were exposed to light (10 mW) for 16 s, as expected.…”

“…Mn-doped ZnS QDs capped with 3-mercaptopropionic acid (MPA, ≥99 %, Sigma Aldrich, USA) were prepared by an inorganic wet chemical approach reported elsewhere (Beltran-Huarac et al 2013a , b ). Briefly, 1.705 g of ZnSO 4 ·H 2 O (≥99.9 %, Sigma Aldrich, USA), 0.085 g MnSO 4 ·H 2 O (≥ 99 %, Sigma Aldrich, USA), and 2.61 mL MPA were dissolved into 50-mL three-neck round-bottom flask using high-purity deionized water (HPDW), resulting in a 5 at.% Mn doping.…”

Cytocompatibility of direct water synthesized cadmium selenide quantum dots in colo-205 cells

“…Our observations indicate that the TGA-CdSe QDs are well-dispersed, near-spherical, and highly crystalline forming regular clusters. The statistical distributions of the particle size were modeled using standard Gaussian fits (Beltran-Huarac et al 2013), which reveal that the average sizes of particles are in the range of 2–4 nm for 10 mM and 6–8 nm for 15 mM with FWHM of 1.9 and 1.1 nm, respectively, partially consistent with the optical studies. The relatively uniform dispersion of CdSe QDs in water is correlated to the effective TGA capping process, although certain agglomeration was observed when selenium concentration was increased.…”

L-cysteine capped ZnS:Mn quantum dots for room-temperature detection of dopamine with high sensitivity and selectivity

“…The same spectral position of this band was observed for both ZnS and ZnS:Mn QDs, as expected. The phosphorescent spectrum shows a prominent orange emission band at $ 598 nm, which is associated to the internal Mn 2 þ ion transition between the 4 T 1 first excited state (spin 3/2) and the 6 A 1 ground state (spin 5/2) (Beltran-Huarac et al, 2013). Note that the blue band at $416 nm (ascribed to the nanostructure surface states) typically observed in dual-emitting ZnS:Mn QDs was not detected by the spectrometer since it was operated in phosphorescence mode (Ertas et al, 2015) The blue band of the QDs when the spectrometer is operated in fluorescence mode was reported in our previous work (Diaz-Diestra et al, 2015).…”