Mn-doped CdS Nanoparticles Research Articles

Facile synthesis of Mn-doped CdS nanoparticles on carbon quantum dots: towards efficient photocatalysis

Facile synthesis of Mn-doped CdS nanoparticles on carbon quantum dots: towards efficient photocatalysis

Study of structural, morphological and optical properties of Mn+2 doped CdS nanoparticles synthesized at various doping concentration

Manganese-doped cadmium sulphide semiconductor nanoparticles (CdS: Mn) NPs have been created utilizing a microwave-assisted solvothermal technique at different Mn concentrations (0, 1%, 3%, and 5%). The chemicals utilized for the preparation of Mndoped CdS nanoparticles were sodium sulphide (Na2S.xH2O), manganese chloride (MnCl2.4H2O), and cadmium acetate (CH3COO)2Cd., H2O). To determine the structural dimensions of the generated nanoparticles, the Debye-Scherer equation was used to calculate the average crystallite size at the full-width half maximum (FWHM) of the diffraction peaks. FTIR spectra analysis was used to look at the various functional and vibrational groups present in the Mn-doped CdS nanoparticle sample. The structure features of the produced nanoparticles have been examined using X-ray diffraction patterns. Energy dispersive X-rays were employed to ascertain the chemical composition of the synthesized nanoparticles. The optical properties and quantification of the energy band gap of the nanoparticles have been done using UV-V spectroscopy. According to XRD calculations, the cubic zinc-blend structure of the generated NPs had a crystal size of between 4 and 7 nm. By using EDX spectroscopy, the incorporation of Mn at the CdS lattice was confirmed.

Synthesis of Z-type heterojunction bifunctional composites with Mn-doped CdS nanoparticles supported on NH2-MIL-125(Ti) for hydrogen evolution and antibiotic degradation under visible light

In this paper, a novel Mn-doped CdS@NH2-MIL-125(Ti) (MC@NT) photocatalytic composites was synthetized through hydrothermal method. Hydrogen desorption and tetracycline and oxytetracycline degradation were performed under visible light to test their photocatalytic activities. The composites were characterized by XRD, FTIR, SEM, TEM, XPS, UV–Vis diffuse reflectance spectroscopy (DRS), EPR, EIS, and transient photocurrent response. From the characterization consequence, it could be seen that Mn-doped CdS was tightly attached to the surface of tetragonal NT in the form of nanoparticles. The MC@NT composites exhibited more promising catalytic activity than pristine monomeric materials. The photocatalytic hydrogen evolution rate reached 3.61 mmol g−1 h−1. Within 110 min, the degradation efficiencies of TC and OTC were 90% and 88%, respectively. The free radical trapping experiments proved that ·O2− and h+ were decisive role for degrading pollutants in the degradation catalysis process. Radical trapping experiments and electron spin resonance (ESR) indicated that the Z-scheme heterojunction was formed between Mn-doped CdS and NT, leading to facilitate the migration and shift of photogenerated carriers and holes. Cycling experiments showed that the as-prepared composites have good stability and have good prospects for practical applications. We believe this work will offer new ideas on the future development of efficient heterojunction catalysts for light energy conversion and other applications.

Enhanced nonlinear optical properties of reduced graphene oxide modified by Mn-doped semiconductor CdS nanoparticles as photonic materials

Graphene has broad prospects for application in photonic devices. However, its zero-band gap limits its nonlinear optical (NLO) properties, and thus, its application. In this study, we synthesized reduced graphene oxide modified by Mn-doped semiconductor CdS nanoparticles (RGO/CdS:Mn) via a solvothermal method to study the development of NLO properties of graphene. The structures, morphologies and basic physical properties of RGO, CdS, RGO/CdS, and RGO/CdS:Mn were characterized. The third-order optical nonlinearities were tested by the Z-scan technique using a mode-locked Nd:YAG laser operating at 532 nm with a 30 ps pulse width. The results showed that the nonlinear susceptibility and saturation absorption of RGO/CdS:Mn were 15.3 and 26 times higher than those of RGO, respectively. The mechanism of the enhancement was analyzed based on the charge transfer between and within the components, and Mn doping produced trapping effect. The significantly improved optical nonlinearity of RGO/CdS:Mn lays a foundation for its applications in photonic devices.

Efficient photocatalytic inactivation of E. coli by Mn-CdS/ZnCuInSe/CuInS2 quantum dots-sensitized TiO2 nanowires

A novel visible light-driven photocatalyst (represented as Mn-CdS/ZCISe/CIS/TiO2) for the passivation of E. coli was prepared with TiO2 nanowires as support and using CuInS2 (CIS) and ZnCuInSe (ZCISe) quantum dots (QDs), as well as Mn-doped CdS (Mn-CdS) nanoparticles (NPs) as sensitizers. The use of CIS and ZCISe QDs and Mn-CdS NPs extends the light harvest region to visible light. The photoelectric conversion efficiency was consequently improved, with a photocurrent density of 12.5 mA cm−2, about 60 times that of pure TiO2 nanowires. The germicidal efficiency of the photocatalyst was assessed by passivation of E. coli, 96% bacteria in 50 ml 105 colony forming units (CFU) ml−1 solution were killed within 50 min. Besides the high efficiency, the composite has good stability and satisfactory recycling performance. The antibiotic mechanism was also performed by using photoluminescence and a scavenging agent of different active matter, revealing that the photo-generated holes play a major role in the sterilization process.

Study of Hopping Conduction in Mn Doped CdS Nanoparticles

Study of Hopping Conduction in Mn Doped CdS Nanoparticles

A Novel Thermochemical Method for Fabrication and Theoretical Explanation of High Luminescent Mn-Doped CdS Nanoparticles

In this paper, fabrication and characterization of bare and doped CdS nanoparticles as well as investigating the luminescence properties of these particles as an important II-VI semiconductor are presented. A novel Thermochemical method was used for synthesis of these quantum dots. Thiols were used as the capping agent to prevent further growth during fabrication process. The application of TGA as a capping agent instead of TG was studied as a novel idea in this paper and was used practically in the synthesis of semiconductor nanoparticles. Using this process resulted in particles with sizes between 3 - 7 nm. Several samples were synthesized and characterized under various Mn ions doping ratio from 1:10 to 1:180, different temperatures from 40℃ to 96℃ and different pH values from 6 to 10. Synthesis of CdS nanoparticles with high Mn ions concentration resulted in luminescence decrement, while luminescence of nanoparticles was increased by decreasing Mn/Cd doping ratio until Mn:Cd = 1:180. The best fabrication temperature was obtained at 96℃ and the highest luminescence was observed at the pH value of 9. A theoretical explanation for the behavior of fabricated high luminescent quantum dots is presented based on the principles of quantum mechanics.

A strategy to improve the energy conversion efficiency and stability of quantum dot-sensitized solar cells using manganese-doped cadmium sulfide quantum dots.

This article describes the effect of manganese (Mn) doping in CdS to improve the photovoltaic performance of quantum dot sensitized solar cells (QDSSCs). The performances of the QDSSCs are examined in detail using a polysulfide electrolyte with a copper sulfide (CuS) counter electrode. Under the illumination of one sun (AM 1.5 G, 100 mW cm(-2)), 10 molar% Mn-doped CdS QDSSCs exhibit a power conversion efficiency (η) of 2.85%, which is higher than the value of 2.11% obtained with bare CdS. The improved photovoltaic performance is due to the impurities from Mn(2+) doping of CdS, which have an impact on the structure of the host material and decrease the surface roughness. The surface roughness and morphology of Mn-doped CdS nanoparticles can be characterised from atomic force microscopy images. Furthermore, the cell device based on the Mn-CdS electrode shows superior stability in the sulfide/polysulfide electrolyte in a working state for over 10 h, resulting in a highly reproducible performance, which is a serious challenge for the Mn-doped solar cell. Our finding provides an effective method for the fabrication of Mn-doped CdS QDs, which can pave the way to further improve the efficiency of future QDSSCs.

Structural And Magnetic Properties Of Undoped And Mn Doped CdS Nanoparticles Prepared By Chemical Co-precipitation Method

Undoped and Mn doped CdS nanoparticles with varying Mn concentration of 10,15 and 20 mol % have been prepared by chemical co-precipitation method with polyvinylpyrrolidone (PVP) as capping agent at room temperature. EDAX has shown that no foreign impurities are present in the synthesized nanoparticles and X-ray diffraction (XRD) revealed that undoped and Mn doped CdS nanoparticles possess cubic phase with crystallite size ranging from 4-6 nm. Transmission electron microscopy (TEM) images indicated that nanoparticle sizes are between 2-6 nm and exhibits polycrystalline nature as seen from selected area electron diffraction (SAED) pattern. Raman spectra of undoped and Mn-doped CdS nanoparticles have shown 1LO and 2LO phonon modes and their intensity ratio decreases as Mn concentration increases. Magnetic susceptibility clearly pointed out that undoped CdS behaves as diamagnetic whereas Mn doped CdS as paramagnetic and varies nonlinearly with Mn concentration in CdS. Rapid increase in magnetization below 50 K temperature is observed in M-T curves which can be assigned to Mn ions isolated in CdS crystal field or extrinsic defects. The M-H curve at 5 K and 300 K for 20% Mn doped CdS nanoparticles at different magnetic fields showed no hystersis. In near future Mn doped CdS nanoparticles can be used for application in dilute magnetic semiconductor and fabrication of solar cells. The result and discussion drawn from this work are elaborated in detail in the paper. Copyright © 2014 VBRI press.

Synthesis and study of optical and thermal properties of Mn doped CdS nanoparticles using polyvinylpyrrolidone

High quality and monodispersed CdS:Mn (1–5%) nanoparticles were synthesized by chemical precipitation method using PVP as surfactant. The structure and morphology of the CdS:Mn were investigated by means of XRD, FT-IR, TEM, UV–visible, PL, EPR and TG-DTA. XRD study was confirmed the formation cubic structured CdS:Mn nanoparticles. The optical absorption of Mn doped CdS nanoparticles was found to be 420–432nm, which is significantly decreased from the bulk CdS material. Photoluminescence spectroscopy of the CdS:Mn nanocrystals showed a strong emission peak at 535nm near the band edge along with a week green emission around 575nm. The PL property of annealed (255°C–850°C) samples was also investigated under different excitations. The presence of PVP on the CdS:Mn surface and incorporated the Mn ion into CdS lattice were identified by FT-IR and EPR spectroscopy, respectively. TEM result showed spherical with monodispersed particles with typical size of 3.8–4.3nm, which is a favorable characteristic for many applications. The major weight loss and gain were found in the thermogravimetric analysis (TGA) which corresponds to the decomposition and oxidation of the samples.

Understanding of ferromagnetism in thiol capped Mn doped CdS nanocrystals

The evolution of ferromagnetism has been investigated in thiol (2-mercaptoethanol) capped Mn doped CdS nanoparticles synthesized at various temperatures by sol-gel reverse micelle mechanism. X-ray diffraction measurements reveal a structural phase transformation from wurtzite to zinc blende structure with the increase in synthesis temperature of Mn doped nanocryatals. Magnetic measurements suggest that the antiferromagnetic interactions of Mn2+ ions within Mn—cluster in Mn doped CdS nanocrystals synthesized at lower temperature (∼17 °C) reduce the total magnetic moment at ambient temperature. Whereas the isolated Mn2+ ions in nanocrystals synthesized above 70 °C enhance the magnetic moment due to the sp-d exchange interaction at ambient temperature. It has been observed that the magnetic moments in all samples synthesized at various temperatures do not saturate even at lowest temperature, 5 K. The core diamagnetism in doped nanocrystals synthesized at low temperature (∼17 °C) is mostly due to the presence of magnetic ions around the surface, whereas these ions exist randomly throughout the crystal for samples synthesized at high temperature (∼70 °C), as a result core diamagnetism vanishes.

Preparation of Manganese Doped Cadmium Sulfide Nanoparticles in Zincblende Phase and Their Magnetic Properties

In this study, the random dope of Mn into CdS nanoparticles in zincblende phase has been carried out under the mild reaction condition. The resulting nanoparticles were characterized by energy dispersive X-ray analysis (EDX), transmission electron microscopy (TEM), X-ray diffractometer (XRD), UV-Vis spectrometer, PL spectrometer, and SQUID. EDX showed that the compositions of Mn doped CdS nanoparticles were readily controlled. TEM showed the particle sizes were not significantly affected by the compositions, retaining to be ca. 3 nm with a narrow size distribution. UV-Vis and PL spectra of the resulting nanoparticles showed the intra-Mn level may be affected by the quantum size effect. SQUID measurement showed that the resulting nanoparticles showed diamagnetism, paramagnetism and superparamagnetism dependent on Mn content.

Synthesis and characterization of CdS and Mn doped CdS nanoparticles and their catalytic application for chemoselective synthesis of benzimidazoles and benzothiazoles in aqueous medium

Abstract CdS and Manganese doped CdS nanoparticles of ~ 2 nm have been prepared at room temperature by a wet chemical technique. The heterogeneous catalysts were fully characterized by XRD, TEM, EDAX, ICP-AES and UV/VIS. These nanoparticles were exploited to study their catalytic activities towards the chemoselective aqueous mediated synthesis of 2-aryl benzimidazoles and benzothiazoles. Doping of Mn promotes the activity and selectivity of CdS nanoparticles indicated by high TOF value, providing the products in good to excellent yields, and with good chemoselectivity. The catalyst could also be recovered easily and used repetitively four times without significantly affecting the catalytic activity.

Synthesis, structural and photocatalytic studies of Mn-doped CdS nanoparticles

Mn-doped CdS nanoparticles (Cd1−xMnxS; where x = 0.00–0.10) were synthesized by a chemical precipitation method. The synthesized products were characterized by X-ray diffraction (XRD), scanning electron microscope, transmission electron microscope (TEM), and UV–Vis spectrometer. The XRD and TEM measurements show that the size of crystallites is in the range of 10–40 nm. Optical measurements indicated a red shift in the absorption band edge upon Mn doping. The direct allowed band gaps of undoped and Mn-doped CdS nanoparticles measured by UV–Vis spectrometer were 2.3 and 2.4 eV at 400 °C, respectively. Photocatalytic activities of CdS and Mn-doped CdS were evaluated by irradiating the solution to ultraviolet light and taking methyl orange (MO) as organic dye. It was found that 5 mol% Mn-doped CdS bleaches MO much faster than undoped CdS upon its exposure to the ultraviolet light. The experiment demonstrated that the photo-degradation efficiency of 5 mol% Mn-doped CdS was significantly higher than that of undoped CdS.

Structural, Optical and Magnetic Properties of Mn-doped CdS Diluted Magnetic Semiconductor Nanoparticles

Diluted magnetic CdS:Mn nanoparticles were synthesized by the aqueous solution method with different manganese (Mn2+) concentrations (x=7–10 atom %) at room temperature in nitrogen atmosphere and capped with Thiogelycerol. The X-ray diffraction patterns of CdS nanoparticles with different Mn doping concentration indicated that samples have hexagonal structure at room temperature. Energy dispersive X-ray spectroscopy confirmed incorporative of Mn ions in CdS nanoparticles. UV-Visible spectroscopy is used to investigate optical absorption of Mn-doped CdS. From photoluminescence measurement it was found that the intensity of the luminescence spectra decreases by increasing Mn2+ dopant ions at high precursor concentration. Also, the room temperature ferromagnetic behavior of Mn-doped CdS nanoparticles is discussed by using hysteresis measurement results.

Structural, optical and photoconductivity characteristics of manganese doped cadmium sulfide nanoparticles synthesized by co-precipitation method

Mn-doped CdS nanoparticles (NPs) have been synthesized by co-precipitation method and effect of Mn concentration on the structural, photoluminescence and photoconductivity properties have been studied. The X-ray diffraction (XRD) patterns show that the synthesized NPs have a cubical (zinc blende) phase. The clear lattice fringes in the high-resolution transmission electron microscopy (HRTEM) image, and selected area electron diffraction (SAED) patterns with bright circular rings with spots further confirms cubical nature. The estimated average particle size is found to be ∼3.1 nm by TEM image. UV–visible (UV–vis) absorption spectroscopy is used to calculate band-gap of material and blue shift in absorption peak indicates quantum size confinement effect. In photoconductivity study, variation of photocurrent with voltage on ln–ln scale is found to follow power law superlinearly due to injection of additional charge carriers from one of the electrodes. The growth and decay in photocurrent spectra exhibit anomalous behaviors which may be attributed to photo-induced chemisorptions of oxygen molecules on surface of NPs. A significant improvement in photocurrent has been observed in Mn-doped CdS NPs with concentration of Mn as 3 mol% as compared to un-doped CdS NPs. Photoluminescence (PL) spectra of un-doped as well as Mn-doped CdS NPs have one emission peak centered at ∼526 nm whereas Mn-doped CdS NPs show one additional emission peak centered at ∼575 nm which may be assigned to 4T 1 → 6A 1 transitions of Mn 2+.

Self-assembled one-pot synthesis of red luminescent CdS:Mn/Mn(OH) 2 nanoparticles

We report a novel method of growing red luminescent (635 nm) Mn-doped CdS (CdS:Mn) nanoparticles capped by an inorganic shell of Mn(OH) 2. CdSO 4, Na 2S 2O 3 and Mn(NO 3) 2 were used as the precursors, and thioglycerol (C 3H 8O 2S) was employed as the capping agent and also the catalyst of the reaction. Using these materials resulted in very slow rate of the reaction and particles growth. The self-assembled one-pot process was performed at pH of 8 and Mn:Cd ratio of 10, and took about 10 days for completion. CdS:Mn nanoparticles are slowly formed in the first day of the process; however, the luminescence is weak. After 7 days, the solution turns white turbid through the formation of additional particles, which precipitate on the walls on the next day. At this stage, a relatively strong red luminescence at 635 nm appears from transparent solution of the CdS:Mn nanoparticles. The white deposit on the walls turns to dark-brown color and luminescence increases on the 9th day. Finally, the CdS:Mn nanoparticles agglomerate and precipitate out of the solution on 10th day. X-ray diffraction and optical spectroscopy showed crystalline phase CdS nanoparticles with an average size of 3.6 nm. We explain the luminescence enhancement based on the formation of a Mn(OH) 2 shell on the surface of the CdS:Mn nanoparticles during the precipitation stage. This can passivate the S dangling bonds located on the particles surface. As the surface Cd sites are previously capped with thioglycerol molecules, a complete surface passivation is achieved and results in emergence of high-intensity luminescence.

Thermochemical growth of Mn-doped CdS nanoparticles and study of luminescenceevolution

We report a new method of growing Mn-doped CdS (CdS:Mn) nanoparticles in anaqueous solution at boiling temperature. The idea is to use precursors that reactonly at high temperature, in order to gain crystalline luminescent nanoparticles.CdSO4,Mn(NO3)2 andNa2S2O3 wereused as the precursors, and thioglycerol was employed as the capping agent and also the reaction catalyst.Na2S2O3 is thermally sensitiveand it releases S2− ions upon heating. The CdS:Mn nanoparticles obtained are about 4 nm in size andshow both cubic and hexagonal crystalline phases with a ratio of 35% to 65%.The luminescence of nanoparticles contains a peak at 580 nm, which is related toMn2+ ions. Prolonged reaction time results in a decrease of the Mn luminescence peak to about35% of the maximum value. We discuss the possible causes of the Mn peak reduction andattribute it to preferential dissolution of Mn ions into the solution due to shapereconfiguration of the nanoparticles.

Synthesis of TOPO-capped Mn-doped ZnS and CdS quantum dots

TOPO (tri-n-octylphosphine oxide) capped Mn-doped ZnS and Mn-doped CdS nanoparticles have been prepared from bis(diethyldithiocarbamato)zinc(II) or bis(methylhexyldithiocarbamato)cadmium(II) and manganese dichloride. The nanoparticles obtained all show quantum size effects in their optical spectra with respect to the parent CdS and ZnS. There are clear differences in the photoluminescence of the ZnS (448 nm) and ZnS∶Mn (510 nm) samples. The level of Mn-doping can be differentiated by the photoluminescence intensity, all of the doped samples show an emission maximum at 510 nm. EPR spectra and ICP results confirm the quantitative incorporation of manganese into the ZnS quantum dots. Selected area electron diffraction (SAED), X-ray diffraction (XRD) and transmission electron microscopy (TEM) show the material to be hexagonal. The crystallinity of the material was also evident from high resolution transmission electron microscopy (HRTEM) which gave well-defined images of particles with clear lattice fringes. The PL spectrum of the doped CdS nanoparticles has an emission maximum at 585 nm as is usually attributed to the 4T1–6A1 electronic transition of manganese in a tetrahedral site. However the PL spectrum changes over time (weeks) to give a spectrum typical of the deep trap emission of CdS. SAED and XRD show both CdS and the Mn-doped CdS particles to be in the hexagonal phase. TEM and high resolution TEM show images of nanosize particles with clear lattice fringes. EPR spectra and ICP results confirm the presence of manganese in the CdS nanoparticles. EPR spectra showed that CdS∶Mn was not stable over longer periods of time with segregation of manganese at the surface of particles in older samples of CdS. By contrast, the ZnS∶Mn samples were quite stable for several weeks.

Electroluminescence Devices with CdS and CdS:Mn Nanoparticles and Polymer Blends

ABSTRACTWe have investigated the photophysical properties of surface capped CdS and CdS:Mn nanoparticles in the form of spin coated thin films of the pure nanoparticles and nanoparticle -polymer blends. The organic capping reagent was p-thiocresol. Electroluminescence (EL) devices were fabricated and characterized by their current/voltage characteristics and EL emission performance. This is to our knowledge the first report on Mn doped CdS nanoparticles applied in EL devices with a single layer device structure (ITO/CdS:Mn/Al). Photoluminescence (PL) and PL excitation measurements were performed on CdS:Mn nanoparticles in pyridine dispersion and on thin films. The PL excitation spectrum shows a narrow peak at 390nm. Excitation at this wavelength yields a broad PL spectrum spanning from about 450 to 700nm, which is dominated by a strong emission band at 585nm. This emission is attributed to transitions involving Mn levels in previous works. The EL emission peak is shifted to the red compared to the PL emission spectra. The characteristics and performance of these new types of EL devices will be presented and discussed.