Study of composition dependent structural, optical, and magnetic properties of Cu-doped Zn1−xCdxS nanoparticles
TL;DR: In this paper, a coprecipitation technique was used to synthesize Zn1-xCdxS nanoparticles in ice bath at 280 K. The band gap energy of Zn 1-xcdxS was shown to be lower by increasing the t...
Abstract: Cu-doped Zn1-xCdxS nanoparticles were synthesized by coprecipitation technique in ice bath at 280 K. The band gap energy of Zn1-xCdxS:Cu nanoparticles can be tuned to a lower energy by increasing t ...
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TL;DR: The Zn1-xCdxS/CdS heterostructure with small Cd content (10 at%) derived from ethylenediamine shows very high H2-evolution rate and shows an excellent photocatalytic stability over 100 h.
Abstract: Various porous Zn1–xCdxS/CdS heteorostructures were achieved via in situ synthesis method with organic amines as the templates Because of the larger radius of Cd2+ than that of Zn2+, CdS quantum dots are formed and distributed uniformly in the network of Zn1–xCdxS The Zn1–xCdxS/CdS heterostructure with small Cd content (10 at%) derived from ethylenediamine shows very high H2-evolution rate of 6675 μmol/h per 5 mg photocatalyst under visible light (λ ≥ 420 nm) with an apparent quantum efficiency of 501% per 5 mg at 420 nm Moreover, this Zn1–xCdxS/CdS heterostructure photocatalyst also shows an excellent photocatalytic stability over 100 h
56 citations
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TL;DR: This work designed and successfully fabricated a ZnS/CdS 3D mesoporous heterostructure with a mediating Zn1–xCdxS interface that is compatible with high-performance liquid chromatography platforms.
Abstract: We designed and successfully fabricated a ZnS/CdS 3D mesoporous heterostructure with a mediating Zn1−xCdxS interface that serves as a charge carrier transport channel for the first time. The H2-production rate and the stability of the heterostructure involving two sulfides were dramatically and simultaneously improved by the careful modification of the interface state via a simple post-annealing method. The sample prepared with the optimal parameters exhibited an excellent H2-production rate of 106.5 mmol h−1 g−1 under visible light, which was 152 and 966 times higher than CdS prepared using ethylenediamine and deionized water as the solvent, respectively. This excellent H2-production rate corresponded to the highest value among the CdS-based photocatalysts. Moreover, this heterostructure showed excellent photocatalytic stability over 60 h.
53 citations
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TL;DR: In this article, size-dependent structural, optical and magnetic properties of monodispersed CeO2 nanoparticles were investigated by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), high resolution transmission electron microscopy (HR-TEM), ultra-violet visible (UV-VIS) spectroscopy and vibrating sample magnetometer (VSM) measurements.
Abstract: In the present study, monodispersed CeO2 nanoparticles (NPs) of size 8.5 ± 1.0, 11.4 ± 1.0 and 15.4 ± 1.0 nm were synthesized using the sol-gel method. Size-dependent structural, optical and magnetic properties of as-prepared samples were investigated by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), high resolution transmission electron microscopy (HR-TEM), ultra-violet visible (UV-VIS) spectroscopy, Raman spectroscopy and vibrating sample magnetometer (VSM) measurements. The value of optical band gap is calculated for each particle size. The decrease in the value of optical band gap with increase of particle size may be attributed to the quantum confinement, which causes to produce localized states created by the oxygen vacancies due to the conversion of Ce4+ into Ce3+ at higher calcination temperature. The Raman spectra showed a peak at ∼461 cm-1 for the particle size 8.5 nm, which is attributed to the 1LO phonon mode. The shift in the Raman peak could be due to lattice strain developed due to variation in particle size. Weak ferromagnetism at room temperature is observed for each particle size. The values of saturation magnetization (Ms), coercivity (Hc) and retentivity (Mr) are increased with increase of particle size. The increase of Ms and Mr for larger particle size may be explained by increase of density of oxygen vacancies at higher calcination temperature. The latter causes high concentrations of Ce3+ ions activate more coupling between the individual magnetic moments of the Ce ions, leading to an increase of Ms value with the particle size. Moreover, the oxygen vacancies may also produce magnetic moment by polarizing spins of f electrons of cerium (Ce) ions located around oxygen vacancies, which causes ferromagnetism in pure CeO2 samples.
37 citations
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TL;DR: In this article, the effects of different doping concentrations of In have been investigated and the effect of In doping on the properties of CdSe:In 1% and CdS:In 5% thin films were obtained by thermal evaporation using the Inert Gas Condensation method.
Abstract: Nanocrystalline thin films of CdSe:In 1% and CdSe:In 5% are prepared by thermal evaporation using the Inert Gas Condensation method. The effects of different doping concentrations of In have been investigated. X-ray diffraction, optical absorption, Photoluminescence (PL) and electrical techniques are used to characterize the films. X-ray diffraction measurements indicate that the nc-CdSe:In 1% and nc-CdSe:In 5% thin films possess hexagonal structure. The crystallinity of the films and the grain size decreases as the In doping concentration increases. The results of PL measurements indicate that the PL intensity decreases as the In doping concentration increases. The optical band gap values increase as the In doping concentration increases. The dc electrical conductivity increases from undoped nc-CdSe to nc-CdSe:In 1% and decreases for nc-CdSe:In 5%. The density of the states near Fermi level N ( E F ), degree of disorder ( T o ), hopping distance ( R ) and hopping energy ( W ) near the Fermi level are calculated using dc conductivity measurements at low temperatures. The effect of In doping concentration on these parameters is discussed. Hall measurements are performed on nc-CdSe, nc-CdSe:In 1% and nc-CdSe:In 5% to calculate the carrier concentration, carrier type and mobility of charge carriers.
34 citations
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TL;DR: In this article, a nanoscale sample of Pb0.90La0.10(Ti1−xMnx)0.975O3 (x = 0.0, 0.04, 0.,07, and 0.10) compounds were prepared using high-energy ball-milling method.
Abstract: The nanoscale samples of Pb0.90La0.10(Ti1−xMnx)0.975O3 (x = 0.0, 0.04, 0.07, and 0.10) compounds were prepared using high-energy ball-milling method. Thermo-gravimetric analysis and high-resolution X-ray diffraction studies were carried out to verify the phase formation. Single-phase compounds were formed exhibiting tetragonal system. The presence of impedance and modulus spectroscopic data was used to gain an insight into the electrical properties of the samples and with a view to observing the relaxations in them. Impedance studies show non-freq-type behavior and the relaxation frequency shift toward higher frequency side with increase in temperature. An equivalent circuit has been used to provide a complete picture of the material. The difference between localized (i.e., dielectric relaxation) and non-localized conduction (i.e., long-range conductivity) processes within the bulk of the material may be discerned by the presence or the absence of a peak in the imaginary impedance and modulus versus frequency plot.
31 citations
References
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TL;DR: The magnetic coupling in all semiconductor ferromagnetic/nonmagnetic layered structures, together with the possibility of spin filtering in RTDs, shows the potential of the present material system for exploring new physics and for developing new functionality toward future electronics.
Abstract: REVIEW Semiconductor devices generally take advantage of the charge of electrons, whereas magnetic materials are used for recording information involving electron spin. To make use of both charge and spin of electrons in semiconductors, a high concentration of magnetic elements can be introduced in nonmagnetic III-V semiconductors currently in use for devices. Low solubility of magnetic elements was overcome by low-temperature nonequilibrium molecular beam epitaxial growth, and ferromagnetic (Ga,Mn)As was realized. Magnetotransport measurements revealed that the magnetic transition temperature can be as high as 110 kelvin. The origin of the ferromagnetic interaction is discussed. Multilayer heterostructures including resonant tunneling diodes (RTDs) have also successfully been fabricated. The magnetic coupling between two ferromagnetic (Ga,Mn)As films separated by a nonmagnetic layer indicated the critical role of the holes in the magnetic coupling. The magnetic coupling in all semiconductor ferromagnetic/nonmagnetic layered structures, together with the possibility of spin filtering in RTDs, shows the potential of the present material system for exploring new physics and for developing new functionality toward future electronics.
4,189 citations
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TL;DR: In this paper, the excited electronic states of semiconductor crystallites sufficiently small (∼50 A diam) that the electronic properties differ from those of bulk materials were modeled, and an approximate formula was given for the lowest excited electronic state energy.
Abstract: We model, in an elementary way, the excited electronic states of semiconductor crystallites sufficiently small (∼50 A diam) that the electronic properties differ from those of bulk materials. In this limit the excited states and ionization processes assume a molecular‐like character. However, diffraction of bonding electrons by the periodic lattice potential remains of paramount importance in the crystallite electronic structure. Schrodinger’s equation is solved at the same level of approximation as used in the analysis of bulk crystalline electron‐hole states (Wannier excitons). Kinetic energy is treated by the effective mass approximation, and the potential energy is due to high frequency dielectric solvation by atomic core electrons. An approximate formula is given for the lowest excited electronic state energy. This expression is dependent upon bulk electronic properties, and contains no adjustable parameters. The optical f number for absorption and emission is also considered. The same model is applied to the problem of two conduction band electrons in a small crystallite, in order to understand how the redox potential of excess electrons depends upon crystallite size.
4,069 citations