2-(2,6-Dimethoxy­phen­yl)-5-hydr­oxy-7-meth­oxy-4H-1-benzopyran-4-one

In the title compound, C18H16O6, the dimethoxy­phenyl ring is rotated by 61.8 (1)° from the plane of the benzopyran system. The mol­ecule is stabilized by an intra­molecular O—H⋯O hydrogen bond

Structural and photoluminescence properties of Zn1-xMnxO nanoparticles for optoelectronic device applications

High intense photoluminescence Zn1-xMnxO powder samples were prepared by simple solid state reaction method. All the samples were studied for their morphological, structural and photoluminescence properties. X-ray diffraction (XRD) results showed that all the samples were polycrystalline with wurtzite structure. The lattice parameters ‘a’ and ‘c’ varied linearly with composition following Vegard’s law in this composition range. Scanning Electron Microscopy (SEM) studies showed that all the samples investigated were in nanoparticles form with the particle size lying in the range 25 – 50 nm. The room temperature photoluminescence spectra show that the UV emission gradually shifted towards the higher energy side. A blue-shift in the position along with an intense blue emission band was observed with the Mn concentrations, which are ascribed to the quantum confinement effect

Structural and Electrical Properties of Resistive Thermal Evaporated Cd1−xMnxSCd_{1-x}Mn_xS Nano-Crystalline Films

Thin films of $Cd_{1-x}Mn_xS$ $(0\leq x \leq 0.5)$ were prepared on window glass substrates by resistive vacuum thermal evaporation. All the films were deposited at 300 K and the films annealed at 373 K, 473 K and 573 K for 1 hour in a vacuum of $10^{-6} m$. bar. The as-deposited and the annealed films were characterized by EDAX, XRD, AFM, electrical conductivity and Hall Effect studies

Structural and photoluminescence properties of thermally evaporated Cd1−xMnxSCd_{1-x}Mn_xS nano-crystalline films

Thin films of $Cd_{1-x}Mn_xS (0\leq x \leq 0.5)$ were formed on glass substrates by resistive vacuum thermal evaporation. All the films were deposited at 300 K and the films were annealed at 373, 473 and 573 K for 1 h in a vacuum of $10^{-6}$ mbar. Atomic force microscopy (AFM) studies showed that all the films investigated were in nano-crystalline form with a grain size in the range 36–82 nm. All the films exhibited a wurtzite structure of the host material. The lattice parameters varied linearly with composition following Vegard’s law in the entire composition range. Photoluminescence studies showed that two distinct emission bands were observed for each $Cd_{1-x}Mn_xS$ compound. One corresponds to internal transition and the other one is due to the transition of $Mn^{2+}$ ions in interstitial sites or in small ‘Mn’ chalcogenic clusters

Structural and morphological properties of thermally evaporated Zn1−xMnxSZn_{1-x}Mn_xS nanocrystalline films

In recent years the dilute magnetic semiconductors have received much attention due to the complementary properties of semiconductor and ferromagnetic behaviour. Nanostructured $Zn_{1-x}Mn_xS$ films $(0 \leq x \leq 0.25)$ were deposited on glass substrates at room temperature (300 K) using simple resistive thermal evaporation technique. All the deposited films were characterized by chemical, structural and morphological studies. Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) studies showed that all the films investigated were in nanocrystalline form with the grain size lying in the range 8 – 22 nm. All the films exhibited cubic structure and the lattice parameter varied linearly with composition

Synthesis and dc magnetic susceptibility of the diluted magnetic semiconducting Cd1−xMnxSCd_{1-x}Mn_xS nanocrystalline films

Nanocrystalline films of $Cd_{1-x}Mn_xS(0\leq x \leq0.5)$ with grain size of 36–58 nm were deposited on glass substrates at a substrate temperature of 300K using resistive thermal evaporation. All the films exhibited wurtzite structure and the lattice parameters varied linearly with composition.The magnetic susceptibility increased sharply with Mn content 'x' and decreased with increase of the temperature

Electrical Properties of Thermal Evaporated Cd1−xMnxS Nanocrystalline Films

Thin films of Cd1−xMnxS (0<=x<=0.5) were deposited on glass substrates by thermal evaporation. All the films were deposited at 300 K and annealed at 373, 473, and 573 K for 1 h in a high vacuum in the range 10−4 Pa. The as-deposited and the annealed films were characterized for composition, structure, and microstructure by using energy-dispersive X-ray, X-ray diffraction, scanning electron microscopy, and atomic force microscopy (AFM). The electrical properties were studied by Hall effect measurement. Electrical conductivity was studied in the temperature range 190–450 K. AFM studies showed that all the films were in nanocrystalline form with grain size varying in the range between 36 and 82 nm. Grain size studies showed a definite increase with annealing temperature. All the films exhibited wurtzite structure of the host material. The lattice parameter varied linearly with composition, following Vegard's law in the entire composition range. Grain size, electrical conductivity, Hall mobility, carrier concentration, and activation energy varied, exhibiting either maxima or minima at x=0.3

Strain, luminescence, and electrical properties of Zn1−xMnxSZn_{1-x}Mn_xS nanocrystalline films prepared on silicon wafers

Nanocrystalline $Zn_{1−x}Mn_xS$ films (0 \leq x \leq 0.25) were deposited on silicon wafers at 473 K using a simple resistive thermal evaporation technique. Morphological and structural measurements revealed that all the films investigated were nanocrystalline with a cubic structure. The lattice parameter increased linearly with Mn concentration. The surface roughness of all the films was shown to be in the range 1.2–3.5 nm. A blueshift in the photoluminescence was observed in the films with increasing Mn concentration along with an intense ultraviolet emission and orange-yellow emission, which are ascribed to the quantum confinement effect. The composition had a significant influence on the orange-yellow emission intensity as well as peak positions. The excitation wavelength of all the samples was 330 nm and emission wavelengths were observed around 410–560 nm. The presence of many recombination sites, surface areas, and defect types leads to broad band photoluminescence emission lines instead of sharp bands. The electrical resistivity as well as activation energy decreased with increasing Mn concentration

Room temperature ferromagnetism and white light emissive CdS:Cr nanoparticles synthesized by chemical co-precipitation method

Undoped and Cr (3% and 5%) doped CdS nanoparticles were synthesized by chemical co-precipitation method. The synthesized nanocrystalline particles are characterized by energy dispersive X-ray analysis (EDAX), scanning electron microscope (SEM), X-ray Diffraction (XRD), transmission electron microscopy (TEM), diffuse reflectance spectroscopy (DRS), photoluminescence (PL), Electron paramagnetic resonance (EPR), vibrating sample magnetometer (VSM) and Raman spectroscopy. XRD studies indicate that Cr doping in host CdS result a structural change from Cubic phase to mixed (cubic + hexagonal) phase. Due to quantum confinement effect, widening of the band gap is observed for undoped and Cr doped CdS nanoparticles compared to bulk CdS. The average particle size calculated from band gap values is in good agreement with the TEM study calculation and it is around 4-5 nm. A strong violet emission band consisting of two emission peaks is observed for undoped CdS nanoparticles, whereas for CdS:Cr nanoparticles, a broad emission band ranging from 420 nm to 730 nm with a maximum at similar to 587 nm is observed. The broad emission band is due to the overlapped emissions from variety of defects. EPR spectra of CdS:Cr samples reveal resonance signal at g = 2.143 corresponding to interacting Cr3+ ions. VSM studies indicate that the diamagnetic CdS nanoparticles are transform to ferromagnetic for 3% Cr3+ doping and the ferromagnetic nature is diminished with increasing the doping concentration to 5%. (C) 2015 Elsevier B.V. All rights reserved