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Photo-catalytic activity of Zn1-xMnxS nanocrystals synthesized by wet chemical technique.

Chitkara M, Singh K, Sandhu IS, Bhatti HS - Nanoscale Res Lett (2011)

Bottom Line: Atomic absorption spectrometer has been used for qualitative and quantitative analysis of synthesized nanomaterials.Energy resolved luminescence spectra have been recorded for the detailed description of radiative and non-radiative recombination mechanisms.Photo-catalytic activity dependence on dopant concentration and luminescence quantum yield has been studied in detail.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Physics, Punjabi University, Patiala, Punjab 147 002, India. dhaliwalkaramjit@gmail.com.

ABSTRACT
Polyvinyl pyrrolidone capped Zn1-xMnxS (0 ≤ x ≤ 0.1) nanocrystals have been synthesized using wet chemical co-precipitation method. Crystallographic and morphological characterization of the synthesized materials have been done using X-ray diffraction and transmission electron microscope. Crystallographic studies show the zinc blende crystals having average crystallite size approx. 3 nm, which is almost similar to the average particle size calculated from electron micrographs. Atomic absorption spectrometer has been used for qualitative and quantitative analysis of synthesized nanomaterials. Photo-catalytic activity has been studied using methylene blue dye as a test contaminant. Energy resolved luminescence spectra have been recorded for the detailed description of radiative and non-radiative recombination mechanisms. Photo-catalytic activity dependence on dopant concentration and luminescence quantum yield has been studied in detail.

No MeSH data available.


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Photoluminescence spectra of Zn1-xMnxS nanocrystals.
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Figure 4: Photoluminescence spectra of Zn1-xMnxS nanocrystals.

Mentions: Figure 3 shows absorption spectra of synthesized nanocrystals, which lie in UV range. Energy resolved luminescence spectra shown in Figure 4 have been recorded at room temperature using 325-nm excitation. It is clear from the recorded spectrum that pure ZnS nanocrystals show only 425-nm emission peak, whereas dichromatic emission (λ1 = 425 nm and λ2 = 599 nm) has been observed in case of Mn2+-doped ZnS nanocrystals. Luminescence quantum yield of λ2 emission peak go on increasing with the increase of 'x' in Zn1-xMnxS nanocrystals, whereas λ1 emission intensity go on decreasing with increasing concentration of Mn2+ ions. More than six-fold increase and two-fold decrease has been observed in the emission intensities of λ2 and λ1 peaks, respectively, when the value of 'x' changes from 0.01 to 0.1 in Zn1-xMnxS nanocrystals. The Mn2+ ions substitute the Zn2+ ions in the ZnS nanocrystal acting as trap sites [22], where the electrons and holes can be trapped. Electrons after photo-excitation process in the host lattice subsequently decay via non-radiative process to the 4T1 localized state of manganese. The λ2 (599 nm) emission peak is attributed to the radiative decay between the 4T1 and 6A1 localized states of manganese inside the ZnS bandgap. The λ1 emission (425 nm) peak is assigned to the radiative transition of electrons from shallow trap states (ST) near the conduction band to sulfur vacancies (Vs) residing near the valence band. The increasing dopant concentration quenches the host related 425 nm emission. Detailed mechanism of various processes involved in Zn1-xMnxS nanocrystals upon excitation is shown in Figure 5. Photo-excited electrons from the conduction band transit spontaneously to the ST and 4T1 manganese trap sites via non-radiative processes. These ST electrons can recombine radiatively with Vs holes or further relaxed non-radiatively to the localized dopant trapping states. Radiative recombination of ST electrons and Vs holes is faster than the radiative transition between the 4T1 and 6A1 localized states [23].


Photo-catalytic activity of Zn1-xMnxS nanocrystals synthesized by wet chemical technique.

Chitkara M, Singh K, Sandhu IS, Bhatti HS - Nanoscale Res Lett (2011)

Photoluminescence spectra of Zn1-xMnxS nanocrystals.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211856&req=5

Figure 4: Photoluminescence spectra of Zn1-xMnxS nanocrystals.
Mentions: Figure 3 shows absorption spectra of synthesized nanocrystals, which lie in UV range. Energy resolved luminescence spectra shown in Figure 4 have been recorded at room temperature using 325-nm excitation. It is clear from the recorded spectrum that pure ZnS nanocrystals show only 425-nm emission peak, whereas dichromatic emission (λ1 = 425 nm and λ2 = 599 nm) has been observed in case of Mn2+-doped ZnS nanocrystals. Luminescence quantum yield of λ2 emission peak go on increasing with the increase of 'x' in Zn1-xMnxS nanocrystals, whereas λ1 emission intensity go on decreasing with increasing concentration of Mn2+ ions. More than six-fold increase and two-fold decrease has been observed in the emission intensities of λ2 and λ1 peaks, respectively, when the value of 'x' changes from 0.01 to 0.1 in Zn1-xMnxS nanocrystals. The Mn2+ ions substitute the Zn2+ ions in the ZnS nanocrystal acting as trap sites [22], where the electrons and holes can be trapped. Electrons after photo-excitation process in the host lattice subsequently decay via non-radiative process to the 4T1 localized state of manganese. The λ2 (599 nm) emission peak is attributed to the radiative decay between the 4T1 and 6A1 localized states of manganese inside the ZnS bandgap. The λ1 emission (425 nm) peak is assigned to the radiative transition of electrons from shallow trap states (ST) near the conduction band to sulfur vacancies (Vs) residing near the valence band. The increasing dopant concentration quenches the host related 425 nm emission. Detailed mechanism of various processes involved in Zn1-xMnxS nanocrystals upon excitation is shown in Figure 5. Photo-excited electrons from the conduction band transit spontaneously to the ST and 4T1 manganese trap sites via non-radiative processes. These ST electrons can recombine radiatively with Vs holes or further relaxed non-radiatively to the localized dopant trapping states. Radiative recombination of ST electrons and Vs holes is faster than the radiative transition between the 4T1 and 6A1 localized states [23].

Bottom Line: Atomic absorption spectrometer has been used for qualitative and quantitative analysis of synthesized nanomaterials.Energy resolved luminescence spectra have been recorded for the detailed description of radiative and non-radiative recombination mechanisms.Photo-catalytic activity dependence on dopant concentration and luminescence quantum yield has been studied in detail.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Physics, Punjabi University, Patiala, Punjab 147 002, India. dhaliwalkaramjit@gmail.com.

ABSTRACT
Polyvinyl pyrrolidone capped Zn1-xMnxS (0 ≤ x ≤ 0.1) nanocrystals have been synthesized using wet chemical co-precipitation method. Crystallographic and morphological characterization of the synthesized materials have been done using X-ray diffraction and transmission electron microscope. Crystallographic studies show the zinc blende crystals having average crystallite size approx. 3 nm, which is almost similar to the average particle size calculated from electron micrographs. Atomic absorption spectrometer has been used for qualitative and quantitative analysis of synthesized nanomaterials. Photo-catalytic activity has been studied using methylene blue dye as a test contaminant. Energy resolved luminescence spectra have been recorded for the detailed description of radiative and non-radiative recombination mechanisms. Photo-catalytic activity dependence on dopant concentration and luminescence quantum yield has been studied in detail.

No MeSH data available.


Related in: MedlinePlus