Effect of capping agent concentration on thermoluminescence and photoluminescence of copper‐doped zinc sulfide nanoparticles

Abstract

Copper-doped zinc sulfide (ZnS:Cu) nanoparticles with varying concentrations of capping agent were prepared using a chemical route technique. These particles were characterized by scanning electron microscopy (SEM), transmission electron microscopy and X-ray diffraction (XRD). Optical absorption studies showed that the absorption edge shifted towards the blue region as the concentration of the capping agent increased. Using effective mass approximation, calculation of the nanoparticle size indicated that effective band gap energy increases with decreasing particle size. The thermoluminescence (TL) properties of sodium hexameta phosphate (SHMP)-passivated ZnS:Cu nanoparticles were investigated after UV irradiation at room temperature. The TL glow curve of capped ZnS:Cu showed variations in TL peak position and intensity with the change in capping agent concentration. The photoluminescence (PL) spectra of ZnS:Cu nanoparticles excited at 254 nm exhibited a broad green emission band peaking around 510 nm, which confirmed the characteristic feature of Zn(2+) as well as Cu(2+) ions as the luminescent centres in the lattice. The PL spectra of ZnS:Cu nanoparticles with increasing capping agent concentrations revealed that the emission becomes more intense and shifted towards shorter wavelengths as the sizes of the samples were reduced.

Synthesis of ZnSe and ZnSe:Cu quantum dots by a room temperature photochemical (UV‐assisted) approach using Na2SeO3 as Se source and investigating optical properties

“…The PL intensity increased with copper doping concentration and reaches its maximum value at Cu:Zn (1.5% mole ratio) after which it decreased. This result has been observed previously in the other reported works on doped QDs . Actually by increasing the Cu concentration more than a particular value, the impurity ions may be act as a quencher and introduce non‐radiative transitions that kill PL intensity.…”

Biogenic Control of Manganese Doping in Zinc Sulfide Nanomaterial Using Shewanella oneidensis MR-1

“…The difference in the PL peak emission between the two methods may be a result of biogenic moieties altering the emission spectrum. Earlier work showed that PL emission wavelength of ZnS nanoparticles varied according to the capping agent used during the reaction (Warad et al, 2005; Wanjari et al, 2015).…”

Tuneable luminescence properties of EDTA‐assisted ZnS:Mn nanocrystals from a yellow‐orange to a red emission band

“…In addition, a series of the doping process as well as optical properties have been reported for different semiconductor nanocrystals. For instance, ZnS:Mn, ZnS:Eu, ZnS:Cu, CdS:Mn, CdS:Eu etc. have been described.…”

“…The better chemical stability and wide band gap energy (3.7 eV) of ZnS has made it a more efficient semiconductor among groups II–VI and thus it is considered to be a promising candidate to be the host material in the doping process. It has been observed that ZnS when used as host material has the ability to produced different emission bands in different regions with various dopants such as orange (Mn), green (Cu) and red emissions (Eu) . ZnS has been more successfully used as the host candidate with Mn as a dopant due to the chemical similarity between Zn 2+ and Mn 2+ and also due to the strong hybridization that takes place between the s‐p states of the ZnS host and the d states of the Mn 2+ ion.…”