Microstructure, electronic structure and optical properties of combustion synthesized Co doped ZnO nanoparticles

We report on the microstructure, electronic structure and optical properties of nanocrystalline Zn1-xCoxO (x=0, 0.01, 0.03, 0.05 and 0.07) particles prepared by solution combustion technique using L-Valine as fuel. The detailed structural and micro-structural studies were carried out by XRD, HRTEM and TEM-SAED respectively, which confirms the formation of single phased, nano-sized particles. The electronic structure was determined through NEXAFS and atomic multiplet calculations/simulations performed for various symmetries and valence states of 'Co' to determine the valance state, symmetry and crystal field splitting. The correlations between the experimental NEXAFS spectra and atomic multiplet simulations, confirms that, 'Co' present is in the 2+ valence state and substituted at the 'Zn' site in tetrahedral symmetry with crystal field splitting, 10Dq =-0.6 eV. The optical properties and 'Co' induced defect formation of as-synthesized materials were examined by using diffuse reflectance and Photoluminescence spectroscopy, respectively. Red-shift of band gap energy (Eg) was observed in Zn1-xCoxO samples due to Co (0.58 à ) substitution at Zn (0.60 à ) site of the host ZnO. Also, in PL spectra, a prominent pre-edge peak corresponds to ultraviolet (UV) emission around 360-370 nm was observed with Co concentration along with near band edge emission (NBE) of the wide band gap ZnO and all samples show emission in the blue region. © 2015 Elsevier B.V. All rights reserved

Effect of Fe doping on the structural, optical and magnetic properties of combustion synthesized nanocrystalline ZnO particles

In the present study, the effect of Fe substitution in nanocrystalline Zn1�xFexO (x = 0, 0.01, 0.03, 0.05 and 0.07) particles synthesized through solution combustion are reported. The detailed structural and microstructural studies of as-synthesized samples were carried out through X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Further, the optical and magnetic properties were investigated respectively through Diffuse Reflectance Spectroscopy and Superconducting Quantum Interference Device (SQUID). The XRD results as well as the Rietveld refinement on XRD data reveals the single phase, polycrystalline nature of the prepared materials and no impurities such as ZnFe2O4, Fe2O3, Fe3O4 were seen, which confirms the substitution of Fe at Zn site. SEM and TEM studies reveal that, the samples are porous and agglomerated due to the evolution of large amount of gases during the combustion and also as-formed particles are found to be in nano-range with an particle size varies from 20�25 nm. Optical studies show that, the absorption edge shifts to lower energy/higher wavelength. Room temperature magnetic (SQUID) studies shows that the undoped ZnO exhibit diamagnetic property where as Fe doped ZnO exhibit intrinsic room temperature ferromagnetism (RTFM) with increasing coercivity with Fe concentration and is attributed to the incorporation of Fe into ZnO host matrix. © 2017 The Society of Powder Technology Japa

The effect of fuel and fuel-oxidizer combinations on ZnO nanoparticles synthesized by solution combustion technique

We report on the synthesis of nanocrystalline ZnO particles by solution combustion technique using new organic fuels such as l-Glutamine, Leucine and l-Valine. The thermal decomposition and combustion of nitrate-organic fuels (precursors) were investigated through TG-DTA and XRD techniques. The results show that, the nitrate-organic fuel (precursor) gels exhibit self-propagating behavior at 400 °C after ignition in air. The effect of fuel and fuel to oxidizer ratio on structural properties of as-synthesized ZnO powder was investigated. It was observed that, the particle size of as-synthesized ZnO powder depends on F/O ratio, which influences the combustion process. The detailed analysis on the structure of as-synthesized ZnO powder was carried out by Rietveld refinement on XRD data and through TEM studies. Further, adiabatic temperature (Tad) was calculated through thermodynamic theoretical calculations for different fuel to oxidizer ratios. The results were discussed on the basis of the correlations established between the Tad, nature of the combustion and structural properties of the resulting powders

Effect of RF power on the structural, optical and gas sensing properties of RF-​sputtered Al doped ZnO thin films

The effect of Radio Frequency (RF) power on the properties of magnetron sputtered Al doped ZnO thin films and the related sensor properties are investigated. A series of 2 wt​% Al doped ZnO; Zn0.98Al0.02O (AZO) thin films prepd. with magnetron sputtering at different RF powers, are examd. The structural results reveal a good adhesive nature of thin films with quartz substrates as well as increasing thickness of the films with increasing RF power. Besides, the increasing RF power is found to improve the crystallinity and grain growth as confirmed by X-​ray diffraction. On the other hand, the optical transmittance is significantly influenced by the RF power, where the transparency values achieved are higher than 82​% for all the AZO thin films and the estd. optical band gap energy is found to decrease with RF power due to an increase in the crystallite size as well as the film thickness. In addn., the defect induced luminescence at low temp. (77 K) and room temp. (300 K) was studied through photoluminescence spectroscopy, it is found that the defect d. of electronic states of the Al3+ ion increases with an increase of RF power due to the increase in the thickness of the film and the crystallite size. The gas sensing behavior of AZO films was studied for NO2 at 350 °C. The AZO film shows a good response towards NO2 gas and also a good relationship between the response and the NO2 concn., which is modeled using an empirical formula. The sensing mechanism of NO2 is discussed

The quantum cryptographic switch

We illustrate using a quantum system the principle of a cryptographic switch, in which a third party (Charlie) can control to a continuously varying degree the amount of information the receiver (Bob) receives, after the sender (Alice) has sent her information. Suppose Charlie transmits a Bell state to Alice and Bob. Alice uses dense coding to transmit two bits to Bob. Only if the 2-bit information corresponding to choice of Bell state is made available by Charlie to Bob can the latter recover Alice's information. By varying the information he gives, Charlie can continuously vary the information recovered by Bob. The performance of the protocol subjected to the squeezed generalized amplitude damping channel is considered. We also present a number of practical situations where a cryptographic switch would be of use.Comment: 7 pages, 4 Figure

Kitozanski umetci za periodontitis: Utjecaj količine lijeka, plastifikatora i umrežavanja na oslobađanje metronidazola in vitro

Chitosan based metronidazole (MZ) inserts were fabricated by the casting method and characterized with respect to mass and thickness uniformity, metronidazole loading and in vitro metronidazole release kinetics. The fabricated inserts exhibited satisfactory physical characteristics. The mass of inserts was in the range of 5.63 ± 0.42 to 6.04 ± 0.89 mg. The thickness ranged from 0.46 ± 0.06 to 0.49 ± 0.08 mm. Metronidazole loading was in the range of 0.98 ± 0.09 to 1.07 ± 0.07 mg except for batch CM3 with MZ loading of 2.01 ± 0.08 mg. The inserts exhibited an initial burst release at the end of 24 h, irrespective of the drug to polymer ratio, plasticizer content or cross-linking. However, further drug release was sustained over the next 6 days. Cross-linking with 10% (m/m) of glutaraldehyde inhibited the burst release by ~30% and increased the mean dissolution time (MDT) from 0.67 to 8.59 days. The decrease in drug release was a result of reduced permeability of chitosan due to cross-linking.Umetci metronidazola na bazi kitozana napravljeni su kasting metodom. Proučavana je ujednačenost mase i debljine, količina ljekovite tvari i kinetika oslobađanja metronidazola in vitro. Fizičke karakteristike umetaka bile su zadovoljavajuće: masa je bila u rasponu 5,63 ± 0,42 – 6,04 ± 0,89 mg, debljina od 0.46 ± 0.06 – 0.49 ± 0.08 mm with, količina metronidazola od 0,98 ± 0,09 – 1,07 ± 0,07 mg. Nakon 24 h iz svih umetaka, neovisno o omjeru ljekovite tvari i polimera, količini plastifikatora ili umrežavanju, dio metronidazola se naglo oslobodio. Međutim, daljnje oslobađanje je bilo polagano tijekom 6 dana. Umrežavanje s 10% (m/m) otopinom glutaraldehida spriječilo je naglo oslobađanje za ~30% i povećalo je srednje vrijeme oslobađanja (MDT) s 0,67 na 8,59 dana. Smanjenje u oslobađanju ljekovite tvari posljedica je smanjenja permeabilnosti umreženog kitozana

Structural and optical studies on spin coated ZnO-graphene conjugated thin films

ZnO-Graphene conjugated thin films were prepared using spin coating technique for different spin rates. Prior to the deposition, ZnO-Graphene nanoparticles were synthesized and their particle size and conjugation was studied through Transmission electron microscope (TEM). The deposited films were characterized using grazing incidence x-ray diffractometer (GIXRD), atomic force microscope (AFM) and UV-Visible spectrometer for their crystallinity, surface topographic features and optical properties. GIXRD patterns confirms the presence of both ZnO and Graphene related crystalline peaks supports the TEM results, which shows the quasi core-shell type conjugation of ZnO-Graphene particles. The crystallinity as well as thickness of the films found to decrease with increase of spin rate. AFM results reveal the uniform, smooth and homogeneity of films and also good adhesivity of ZnO-Graphene with glass substrates. No significant change in the transmittance and absorption with spin rate is observed, while the band gap energy found to decrease due to the reduction in the thickness of the films and conjugation of ZnO-Graphene. All films exhibit∼90 % transmittance in the visible wavelength region, could be potential candidates for optoelectronics and transparent conducting oxide (TCO) applications

Spin-coated Al-doped ZnO thin films for optical applications: Structural, micro-structural, optical and luminescence studies

Zn1�xAlxO (x = 0, 0.01, 0.02, 0.03) thin films were deposited on glass substrate using sol-gel spin coating method and the effect of Al doping on their structural, micro-structural, optical and photoluminescence properties were investigated. The XRD results confirm the single phase nature and the successful substitution of Al at Zn site in ZnO thin films. Further with Al doping, the crystallite size, lattice parameters and film thickness were found to decrease. Also, both AFM and SEM results confirm the formation of spherical grains with lower roughness of the films. Al doped (>2) films shows � 90 transparency in the visible wavelength region. Widening of band gap (3.18�3.34 eV) was observed with increase in Al doping concentration, which was attributed to the Burstein�Moss band-filling effect. The defect induced luminescence at room temperature was studied by photoluminescence spectroscopy. PL spectra of AZO films show sharp peaks in the visible wavelength region. A detailed analysis of photoluminescence of undoped and Al doped ZnO films indicates the inhibition of defect density of electronic states due to substitution of Al3+. The observed emission peaks were attributed to the defect related deep-level emissions. Results suggest possible use of Al doped ZnO films for transparent conducting oxide (TCO) electrodes and light emitting diodes (LED's) applications. © 2017 Elsevier B.V

Studies on the thin films of zinc oxide–carbon 60 core–shell quantum dots

Thin films of zinc oxide–carbon 60 (ZnO–C60) core–shell quantum dots (QDs) prepared by a simple chemical method were deposited on to a cleaned glass substrate using the spin-coating method with different deposition speeds. Prior to the deposition, ZnO–C60 QDs (in powder form) were studied using a transmission electron microscope (TEM) to determine average particle size and core–shell structure. The lattice parameters and unit cell volumes were determined by analyzing the TEM–selected area electron diffraction pattern. The deposited films of ZnO–C60 were characterized using atomic force microscopy (AFM) and profilometry for the surface topography and an ultraviolet–visible spectroscope for their optical behaviour. AFM micrographs show the decrease in the root mean square roughness with an increase in the deposition speed and the films exhibit blue shift in Eg value due to the molecular interaction of the ZnO and C60 layer and the quantum confinement effect