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The study of energy transfer mechanism from different capping agents to intrinsic luminescent vacancy centres of zinc sulphide
(ZnS) has been reported in the present work. Nanoparticles of capped and uncapped ZnS are prepared by co-precipitation reaction.
These nanoparticles are sterically stabilized using organic polymers—poly vinyl pyrrolidone, 2...
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Context 1
... order to find the band gap of uncapped and capped ZnS NPs, UV-visible absorption spectra were recorded, which is given in Fig. 3. Table 2 presents the absorption edge and band gap values along with excitation wavelengths corresponding to peaks observed in Figs. 3 and 6 (discussed later), respec- tively. For uncapped, TG-capped, ME-capped and PVP-capped ZnS NPs, the estimated band gap values are 3.73, 3.86, 3.78 and 3.75 eV corresponding to absorption edge at 332, 321, 328 and 330 nm, respectively. ...
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... main difference in these three organic capping agents is the number of carbon atoms present in the molecule. In spite of these differences, when the synthesis conditions are same, all the passivating agents give rise to excitonic peak at almost the same position with ±5 nm deviation, which is confirmed from UV-visible and excitation studies (Table 2). ...
Context 3
... spectra corresponding to fixed emission in the range of 400-461 nm have been shown in Fig. 6 for uncapped and capped samples. Table 2 shows all excitation wavelengths corresponding to all possible emission sites. It also shows energy gap of all samples estimated from excitation and UV-visible absorption spectra. ...
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... shows excitonic peak at 329 nm with small peak at 275 nm. Figure 6d shows TG-capped ZnS NPs having excitonic peak at 329 nm. The absorption energies corresponding to these excitation peaks are calculated and given in Table 2, which are in close agreement with those estimated by UV- visible absorption spectra. This small variation can be attributed due to multiple excitations in all samples, which are showing excitations in band to band, band to defects and band to polymer energy levels in some cases. ...
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Citations
... The use of FTIR as a sensitive, high throughput and non-destructive mechanism for monitoring the vibrational frequency changes in functional groups of PAHs during biodegradation pathway mapping has been well documented [28]. The observed spectral absorption peaks at 3202 cm −1 -3340 cm −1 in both the control sample and fungal inoculated flasks could attribute to the O-H broad stretching of the alcohol rings due to the presence of ethyl-acetate used in during the extraction process [50,51]. The shift in adsorption peak of the control sample at wavelength 1610 cm −1 to 1650-1730 cm −1 is linkable to the presence of C=O rings of the quinone compounds [52]. ...
Two indigenous ascomycetes fungi, Trichoderma lixii strain FLU1 (TlFLU1) and Talaromyces pinophilus strain FLU12 (TpFLU12), were isolated from benzo(b)fluoranthene-enriched activated sludge and tested for bio-catalytically degrade fluoranthene as a sole carbon source. TlFLU1 and TpFLU12 degraded 98 and 99% of 400 mg/L of fluoranthene after 16 and 12 d incubation period, respectively. Degradation correlated with the upregulation of expression of ligninolytic enzymes. The GC-MS and FTIR analysis of the degradation products suggest that the degradation is initiated at the C1-C2 position of the compound ring via oxygenation and ring cleavage to form 9-oxo-9H-fluorene-1-carboxylic acid before undergoing ring cleavage to yield fluorenone, which then proceeds through the ß-Ketoadipate pathway via benzene-1,2,3-tricarboxylic acid. The degradation rate is better fitted in the first-order and zero-order kinetic model for TlFLU1 and TpFLU12, respectively. The metabolites from the TlFLU1 degradation media are shown to be toxic in Vibryo parahaemolyticus after 6 h of exposure with effective concentration (EC50) and toxicity unit (TU) values of 14.25 mg/L and 7.018%, respectively, while also being observed as non-toxic from TpFLU12 degradation media with an EC50 and TU values of 197.1 mg/L and 0.507%, respectively. Results from this study show efficient metabolism of fluoranthene into an innocuous state by TlFLU1 and TpFLU12.
... Zn-carboxylate group, respectively; broad band around 900-1500 cm −1 is commonly attributed to frequencies of oxygen bending and stretching [19,[31][32][33]. Synthesised ZnS QDs exhibit a C-C stretching doublet peak at 1339 cm −1 , absence of which in the prepared ZnS@ZnO samples can be an indicator of surface modification of the ZnS QDs by ZnO [34]. Synthesised ZnS QDs also exhibit the following peaks: O-H bending peak at 670 cm −1 ; characteristic Zn-S stretching peak at 615 cm −1 , which is absent in the FTIR spectra of the prepared ZnS@ZnO samples; and characteristic metal-oxide stretching mode at 485 cm −1 [35,36]. ...
... Broad peak common to all the samples around 1623 cm −1 is attributed to the vibration of the C=O bond in the Zn-carboxylate group; broad peaks around 1560 cm −1 and 1423 cm −1 are attributed to the antisymmetric and symmetric stretching of the COO − in the Zn-carboxylate group, respectively; broad band around 900-1500 cm −1 is commonly attributed to frequencies of oxygen bending and stretching [19,39]. Synthesised Zn 0.99 Mn 0.01 S QDs exhibit a C-C stretching doublet peak at 1340 cm −1 , absence of which in the prepared Zn 0.99 Mn 0.01 S@ZnO samples can be an indicator of surface modification of the Zn 0.99 Mn 0.01 S QDs by ZnO [34]. Synthesised Zn 0.99 Mn 0.01 S QDs also exhibit the following peaks: intense peak at 1106 cm −1 , whose absence in the FTIR spectra of the undoped ZnS QDs indicates the effect the doped Mn 2+ ions have on the host ZnS; O-H bending peak at 671 cm −1 ; characteristic Zn-S stretching peak at 617 cm −1 , which is absent in the FTIR spectra of the prepared Zn 0.99 Mn 0.01 S@ZnO samples; and characteristic metal-oxide stretching mode at 486 cm −1 [35,36,40,41]. ...
... Figure 7 shows the FTIR spectra of the prepared Zn 0.99 Mn 0.01 S@SiO 2 samples. Preliminary analysis reveals that the FTIR spectra of all the samples are similar and share a lot of common peaks: broad peaks around 1556 cm −1 and 1406 cm −1 are attributed to the antisymmetric and symmetric stretching of the COO − in the Zn-carboxylate group, respectively; weak peak around 1340 cm −1 is attributed to the doublet of C-C stretching; broad band around 900-1500 cm −1 is commonly attributed to frequencies of oxygen bending and stretching; peak around 672 cm −1 is attributed to O-H bending; and broad peak around 495 cm −1 is attributed to the metal-oxide stretching mode [18,19,[31][32][33][34][35][36]. However, FTIR spectrum of the synthesised Zn 0.99 Mn 0.01 S QDs exhibits some key differences: broad peak at 1616 cm −1 is attributed to the vibration of the C=O bond in the Zn-carboxylate group; intense peak at 1106 cm −1 , whose absence in the FTIR spectra of the undoped ZnS QDs indicates the effect the doped Mn 2+ ions have on the host ZnS; and characteristic Zn-S stretching peak at 617 cm −1 ; decreased intensity of these peaks in the FTIR spectra of the prepared Zn 0.99 Mn 0.01 S@SiO 2 samples can be an indicator of surface modification of the Zn 0.99 Mn 0.01 S QDs by SiO 2 [35,36,[39][40][41].The weak bands around 1100-1200 cm −1 are characteristic of inorganic ions, and the weak bands around 600-900 cm −1 are attributed to vibrational frequencies arising ...
To investigate a potential new antibacterial agent to combat increasing antimicrobial resistance, undoped and 1% manganese doped Zinc Sulphide quantum dots (ZnS and Zn0.99Mn0.01S QDs, respectively) were synthesised by co-precipitation method and capped with increasing amounts of Zinc Oxide and Silica in aqueous media to prepare ZnS@ZnO, Zn0.99Mn0.01S@ZnO, and Zn0.99Mn0.01S@SiO2 nanostructures. P-XRD analysis confirmed the cubic zinc-blende phase of the seed ZnS QDs, Zn0.99Mn0.01S QDs, and Zn0.99Mn0.01S@SiO2 nanostructures, and the wurtzite phase of the ZnO in the ZnS@ZnO and Zn0.99Mn0.01S@ZnO nanostructures, further confirmed using TEM studies, which also revealed the size of the largest nanostructures to be in the range of a hundred nanometres. FTIR spectroscopy illustrated the quenching of characteristic ZnS peaks with increasing capping material. UV–Visible absorption spectroscopy and subsequent Tauc analysis illustrated the strong size confinement of the synthesised ZnS and Zn0.99Mn0.01S QDs; Brus equation calculations revealed that the particle size of the samples increases with increasing capping material. Photoluminescent emission spectroscopy illustrated the tuneable emission properties of the prepared nanostructures; manganese doping induced the characteristic orange emission in the Zn0.99Mn0.01S QDs, which was enhanced by ZnO, but quenched by SiO2. The antimicrobial activity of all the prepared samples was qualitatively evaluated using well known Agar well diffusion method against six human pathogenic bacteria: Gram positive Bacillus subtilis and Staphylococcus aureus; Gram negative Salmonella Typhi, Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa. Qualitative antibacterial assay confirmed the high antibacterial potential of the synthesised ZnS and Zn0.99Mn0.01S QDs, especially against E. coli. Increasing ZnO amount improves the antibacterial activity of the nanostructures against different Gram-positive bacterial strains, while increasing SiO2 amount improves the antibacterial activity of the nanostructures against both Gram positive strains and three of the four Gram negative bacterial strains. Thus, the positive results suggest that the prepared ZnS@ZnO, Zn0.99Mn0.01S@ZnO, and Zn0.99Mn0.01S@SiO2 nanostructures should be further studied as antimicrobial agents.
... In order to synthesize doped (8 mol% Zn) and co-doped (4 mol % Y, 4 mol % Zn) CeO 2 nanoparticles (NPs), Zn(NO 3 ) 3 .6-H 2 O, and Y(NO 3 ) 3 .6H 2 O were dissolved in 30 ml of ethanol. The concentration of mother solution was maintained at 0.3 M. For the preparation of capped samples, known amount of thioglycerol (TG) was added after the addition of metal nitrate salts to avoid agglomeration [28]. Ammonia as a precipitating agent was added dropwise to the above solution until pH 7.5 was attained followed by overnight aging. ...
... The peak at 1630 cm -1 is attributed to adsorbed water from the atmosphere [54]. The absence of peak for TG at 2555 cm -1 is due to of TG molecule de-protonation and attachment to metal atom [28]. Thus, FTIR results confirmed the presence of both CeO 2 and CdS in the synthesized sample. ...
... Apparently, it seems that ZCCDS-1:2 sample may provide higher degradation but it may also provide recombination center for photogenerated charge carrier [9]. S-H group from 1-TG [28] J Mater Sci: Mater Electron Figure 5a shows the TEM image of ZCCDS-1:1 sample and the corresponding HRTEM shows the lattice fringes of ZCCDS-1:1, as shown in Fig. 5b. Figure 6a represents the TEM image of ZYCCDS-1:1 sample and Fig. 6b represents HRTEM image of the same. The morphological results reveal agglomeration of particles in both samples. ...
In the present work, CdS heterostructures are successfully synthesized with Zn-doped and (Y, Zn)-co-doped CeO2 via co-precipitation route using different molar concentrations of sodium sulfide. The synthesized samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy to study their structural, morphological, and elemental composition, respectively. XRD results confirmed the cubic phase for CeO2 and wurtzite structure for CdS with average crystallite size in the range of 3–5 nm. The crystallite size of CdS heterostructures with (Y, Zn)-co-doped CeO2 sample is found to be slightly larger than Zn-doped CeO2. The different modes of vibrations are observed in Raman spectra. The absorbance spectra and calculated band gap exhibited the formation of UV–visible active compound. TEM image depicted the formation of agglomerated nanoparticles (NPs) with irregular shapes. The photoluminescence spectra exhibited the charge recombination in synthesized samples. XRD, FTIR, UV, PL, and Raman techniques confirmed the formation of CdS in the synthesized heterostructures. Further, chemical composition and valence state of different elements were confirmed from XPS spectra. The photocatalytic activity was studied via UV–visible spectroscopy technique by examining the absorbance spectra using crystal violet dye. The present work elucidates the photocatalytic activity of CdS heterostructures synthesized with undoped, Zn-doped, and (Y, Zn)-co-doped CeO2 samples. Among the various samples, CdS heterostructures which were synthesized using Zn-doped CeO2 exhibited the quick removal of CV dye within 2 h under UV–visible illumination. The role of oxygen vacancies in alerting the photocatalytic activity of CdS heterostructures with doped and co-doped CeO2 NPs Zn-doped and (Y, Zn)-co-doped CeO2/CdS heterostructures for the removal of crystal violet dye has been studied in detail.
... ZnS has been prepared by different methods in other to achieve specific structures and properties [9], and different chemical and physical methods have been reported for the synthesis of ZnS [13,14]. Earlier, it has been mostly prepared using precipitation or coprecipitation methods [15,16]. However, in recent times, the single-source precursor methods have been widely used and Zn(II) complexes have been utilised as precursor compounds for the preparation of ZnS nanoparticles [17,18]. ...
Zinc sulphide nanoparticles represented as ZnS1, ZnS2 and ZnS3 have been prepared from Zn( ii ) N -methyl- N -ethanoldithiocarbamate (1) complex and its 2,2′-bipyridine (2) and 1,10′-phenanthroline (3) adducts, respectively. Both the parent complex (1) and the adducts (2) and (3) were characterised by spectroscopic techniques and elemental analysis. In the solid state, the structures of complexes (1) and (2) were established using single-crystal X-ray analysis. Complex (1) possessed a distorted trigonal bipyramidal geometry about the zinc centre, whilst forming a dimer via bidentate bridging coordination between two opposite dithiocarbamate motifs. On the other hand, complex (2) formed a trigonal prismatic geometry about the Zn centre with a ZnS4N2 chromophore. The decomposition of the complexes in hexadecylamine afforded spherical-shaped ZnS nanoparticles of the cubic sphalerite crystal phase. The transmission electron microscopy (TEM) micrographs showed that the average particles size of ZnS1, ZnS2 and ZnS3 were 2.63, 5.27 and 6.52 nm, respectively. In the optical study, the estimated bandgap energies were found in the range between 4.34 and 4.08 eV, which indicated a blue shift when compared with the bandgap energy of bulk ZnS.
... It is observed that the calcined samples exhibited enhanced photocatalytic activity due to the increased crystallinity and better absorption toward UVvisible light. The capped samples also showed better photocatalytic activity due to decrease in agglomeration and higher charge-transfer rate between metal-ligand interface resulting in better catalytic activity [18,19]. The samples that are synthesized using ethanol as a solvent medium also showed enhanced photocatalytic activity. ...
... For the synthesis of CeO 2 [18]. To this solution, ammonia (precipitating agent) was added drop-wise until pH 7.5 was obtained followed by overnight aging. ...
... The small bands around 725 and 840 cm −1 are associated with Ce-O-Ce bridging oxygen that is originated after calcination [34]. The absence of S-H vibration at 2555 cm −1 in the capped samples may infer the de-protonation of TG molecule and attachment with CeO 2 [18]. The peak present around 3300-3450 cm −1 is attributed to the surface hydroxyl group that in turn plays a vital role in the photocatalytic reaction to provide dye sensitization [35][36][37]. ...
The present work reports the synthesis of CeO2 nanoparticles (NPs) via chemical route by optimizing synthesis parameters such as solvent, capping agent, and calcination temperature. The prepared samples were characterized via X-ray diffraction (XRD), transmission electron microscopy, Fourier-transformed infrared spectroscopy, Raman spectroscopy, and UV-visible spectroscopy for structural, morphological, and optical studies. The XRD results confirmed the formation of cubic fluorite structured CeO2 with an average crystallite size ~5–11 nm. The enhancement in crystallite size was observed along with agglomerated irregular spherical-shaped NPs after calcination at higher temperatures. The use of capping agent (thioglycerol; TG) led to the reduced aggregation of NPs. With the help of UV-visible spectroscopy, a redshift was observed in the maximum absorbance peak as an effect of calcination. The NPs synthesized in ethanol as solvent exhibited better degradation efficiency for crystal violet dye than that synthesized in water medium due to high surface to volume ratio and surface functionalities inducing more active sites for the creation of electrons hole pair. It was observed that (TG) capped samples exhibited more photocatalytic activity toward the degradation of crystal violet dye than uncapped samples due to less agglomeration of particles. Furthermore, in the presence of the optimum amount of H2O2 the catalytic activity was achieved up to 97% within 90 min only.
... Figure 3 represents the FTIR transmission spectrum of (a) uncapped and (b) EDTA capped ZnS nanoparticles. From the FTIR spectrum of uncapped ZnS nanoparticles (Fig. 3a), the absorption peak at 1431 cm -1 is assigned to C-H bonding and weak band observed at 3460 cm -1 corresponds to O-H stretching [26]. The absorption peak at 662 cm -1 is assigned to the Zn-S stretching vibration [27]. ...
In the present study, ZnS nanoparticles have been synthesized via a simple and cost effective facile chemical co-precipitation method using ethylenediaminetetraaceticacid (EDTA) as capping or stabilizing agent. The role of EDTA was to stabilize the nanoparticle against aggregation and also to provide chemical passivation that leads to a significant influence on the improved structural, optical and photoluminescence properties of nanoparticles. The average grain size of the prepared nanoparticles calculated from the XRD pattern using Scherrer’s formula is about 3–5 nm, which exhibit cubic zinc blende structure. The SAED pattern exhibits three rings corresponding to (111), (220) and (311) planes respectively, which are in good agreement with the cubic phase of ZnS. The UV–Vis absorption results revealed that the EDTA capped ZnS nanoparticles exhibit strong quantum confinement effect as the optical band gap energy increased significantly compared to the uncapped and bulk ZnS. From FTIR analysis, the formation of EDTA capped ZnS nanoparticles were confirmed. Fluorescence spectra show that the EDTA capping increases the PL intensity compared to uncapped ZnS nanoparticles. From the Raman studies, the appearance of multiple resonance raman peaks show that the prepared EDTA capped ZnS nanoparticles exhibit good optical quality.
... Recent research on different nanosized structures has demonstrated the extraordinary optical, electrical, magnetic and mechanical properties of nanomaterials, which are different from their corresponding bulk counterparts [1][2][3][4][5][6][7][8][9][10][11]. In particular, semiconductor nanocrystals show excellent physical properties due to their large band gap and different defect related states [12][13][14][15]. CdS is the most promising material of II-VI group semiconductors which has a direct wide band gap of 2.42 eV at 300 K, high melting point of 1760°C and both cubic and hexagonal structure [16,17]. ...
In this work, jagged spherical CdS nanocrystals have been synthesized by chemical method to study their elastic properties. The synthesized CdS nanocrystal has been characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The transmission electron microscope images show that the average size of the nanocrystal is 100 nm approximately. X-ray diffraction (XRD) study confirms that the CdS nanocrystals are in cubic zinc blende structure. The size calculated from the XRD is consistent with the average size obtained from the TEM analysis. The XRD data have been analyzed to study the elastic properties of the jagged spherical CdS nanocrystals, such as intrinsic strain, stress and energy density, usingWilliamson- Hall plot method.Williamson-Hall method and size-strain plot (SSP) have been used to study the individual effect of crystalline size and lattice strain on the peak broadening of the jagged spherical CdS nanocrystals. Size-strain plot (SSP) and root mean square (RMS) strain further confirm the results obtained from W-H plots.
... The removal of organic pollutants in waste water using semiconductor nanomaterials has attracted a lot of attention as an important environmental protection procedure. Wide and direct band gap semiconductors are of great interest in photocatalysis with ZnS representing an important role [1]. In recent years, biosynthesis of nanoparticles for removal of organic pollutants in waste water has gained much attention to develop clean and renewable materials. ...
In this present work, improved photocatalytic activity and antibacterial properties of zinc sulfide (ZnS) nanoparticles using plant extract of Acalypha indica (A:ZnS) and Tridax procumbens (T:ZnS) via novel green synthesis route had been reported. X-ray diffraction (XRD), transmission electron microscopy (TEM), and Energy dispersive X-ray spectroscopy (EDX) were used to investigate the crystal structure, surface morphology, and elemental composition analysis, respectively. The optical properties and functional group analysis of the samples were done using UV–visible, photoluminescence, and Fourier transform infrared spectroscopy (FTIR). The influence of Acalypha indica (A:ZnS) and Tridax procumbens (T:ZnS) plant extract concentration on the structural, surface morphology, optical, antibacterial, and photocatalytic activity has been systematically investigated. XRD results are suggested that ZnS hexagonal wurtzite crystal structure formed during biosynthesis process. TEM and SAED images show the hexagonal- and spherical-shaped structure in morphology with average diameter around 5–20 nm which is good agreement with the grain size calculated from XRD. Optical properties were found to have considerable red shift in the absorption edge and decreasing band gap was observed for A:ZnS/T:ZnS (2.96 eV) when compared to pure ZnS (3.36 eV). The antibacterial properties of ZnS/A:ZnS/T:ZnS nanoparticles were investigated using in vitro disk diffusion method against human pathogenic microorganisms. The inhibition zone of biosynthesized ZnS nanoparticles increased by increasing plant extracts concentration. This result conformed that A:ZnS/T:ZnS nanoparticles have more potential as antibiotic when compared with pure ZnS. Besides, Biosynthesized T:ZnS (40 ml) nanoparticles showed high surface area (131.84 m2/g) and larger pore size (12.15 nm) than pure ZnS sample; this high surface area may offer more active sites to enhance photocatalytic ability. The dye degradation properties of methylene blue dye (MBD) were investigated using the ZnS/A:ZnS/T:ZnS nanoparticles under visible light irradiation. The results show that T:ZnS (40 ml) has excellent photocatalytic performance towards MBD such as high degradation efficiency (98%) and more cyclic stability than other ZnS samples. The role of plant extract on dye degradation properties was discussed based on the possible inhibition of photogenerated electron–hole pair recombination during dye degradation under visible light irradiation.
... [30] The most intense band at around 1463-1500 cm −1 and the weak band at 2936-2837 cm −1 were assigned to C-H bonding of PVP. [38] In pure PVP, absorption peaks at 1659, 1295 cm −1 corresponded to C=O bonding and C-N stretching respectively, these peaks were shifted to 1642 cm −1 and 1282 cm −1 ...
Zinc sulfide (ZnS) doped with transition metal has been used as phosphor for various optoelectronic applications. In the present report, ZnS:Mn doped and ZnS:Mn,Ni co‐doped were prepared using chemical co‐precipitation method using polyvinyl pyrolidone as a surfactant. The structural studies were carried out using an X‐ray diffraction technique; optical studies have been performed using ultraviolet–visible light absorption and photoluminescence (PL) spectroscopy. The presences of functional groups were confirmed using Fourier transform infrared spectroscopy. The X‐ray diffraction study and Reitveld analysis confirms the formation of cubic phase with crystalline size 2–3 nm for undoped and doped ZnS nanoparticles. A novel and enhanced luminescence characteristic have been observed in PL spectra. The luminescence intensity of Mn,Ni co‐doped ZnS in the blue region is much higher of that of ZnS. The PL results indicate that the doping of Ni creates shallow trap states or luminescence centres in the forbidden energy gap, which quenches the Mn states emission. Concentration quenching has been observed in Mn‐doped ZnS nanoparticles. From CIE coordinates, it is seen that the yellow and blue light emission of ZnS:Mn,Ni co‐doped nanophosphor may be a promising candidate for display devices and phosphor converted light‐emitting diode applications.
... Although, this is expected that in the absence of capping agent uncontrolled nucleation and growth of the particles occurred, then due to Ostwald ripening and vander Waals interaction between particles they agglomerate and settle down [29]. Capping of these nanoparticles with a suitable surfactants (PVP, Mercaptoethanol, Thioglycerol) act as a barrier to aggregate them and passivate the surface by removing the dangling bond present on the surface and reduces reactivity of the surface [30,31]. Agglomeration without capping agent has also been reported by Deshpande et al. [32] for ZnSe nanoparrticles. ...
... For the sample M2, the green emission centered at 488 nm (2.54 eV) that may be mainly due to existence of zinc defects in the CdZnS matrix [49]. However, for the sample M3 the emission at 458 nm (2.70 eV) is appearing, which corresponds to the transition from sulfur vacancy to the zinc vacancy [31]. Further, it has also been observed that with the increase in concentration of Mn 2+ ions, the emission has shifted towards lower wavelength side by ∼ 30 nm. ...
