Paulo José Pereira de Oliveira; Fabielle Castelan Marques; Arlan da Silva Gonçalves; Greice Kelly dos Santos Brito; Enzo Victorio Andrade; Marcos Pedro Dalmaso Pinto
Abstract
Global warming has generated great concern worldwide. One way to control this problem is to use clean renewable energy new sources. Among the energy sources, we can mention hydrogen gas, produced by water photocatalysis by mean of a semiconductor material. In this work, we report a study about band gap ...
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Global warming has generated great concern worldwide. One way to control this problem is to use clean renewable energy new sources. Among the energy sources, we can mention hydrogen gas, produced by water photocatalysis by mean of a semiconductor material. In this work, we report a study about band gap and absorption spectra by mean of the density functional theory of the anatase allotropic form of titanium dioxide doped with Ruthenium. The results indicated systematic decrease of the band gap and increase of the absorbance at the visible region with the increase of the amount of dopant.
Nashiruddin Ahammed; M. Mehedi Hassan
Abstract
In this article, auto combustion prepared Ni1-xFexO (0≤x≤0.10) nanoparticles (NPs) have been investigated for their structural, morphological and optical properties. X-ray diffraction (XRD) studies reveal that all Fe doped NiO samples crystallize in single phase without any impurity. The crystallite ...
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In this article, auto combustion prepared Ni1-xFexO (0≤x≤0.10) nanoparticles (NPs) have been investigated for their structural, morphological and optical properties. X-ray diffraction (XRD) studies reveal that all Fe doped NiO samples crystallize in single phase without any impurity. The crystallite size monotonically decreases from 20 nm to 10 nm with increasing Fe substitution. Transmission Electron Microscope images represent that the synthesized NiO NPs with size around 28 nm. A red shift in UV-Vis spectra indicates that band gap can be tuned by Fe doping from 3.76 eV to 2.51 eV because of the upward shifting of t2g level. The broad transmittance peak in Fourier transform infra-red spectra at 500 cm -1 is assigned to Ni–O stretching vibration mode. Differential scanning calorimetry curve revealed that the transition at 250 o C was exothermic because of structural relaxation. Copyright © VBRI Press.
Elizabeta Stojcheva; Metka Benčina; Ita Junkar; Tomaž Lampe; Matjaz Valant; Veronika Kralj-Iglič; Aleš Iglič
Abstract
The photocatalytic activity of TiO2 nanotubes (NTs) makes these materials promising candidates for a variety of applications, including photocatalytic degradation, water splitting and biomedical devices. The large band gap of TiO2 (anatase ∼3.2 eV; rutile ∼ 3.0 eV) requires excitation with UV ...
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The photocatalytic activity of TiO2 nanotubes (NTs) makes these materials promising candidates for a variety of applications, including photocatalytic degradation, water splitting and biomedical devices. The large band gap of TiO2 (anatase ∼3.2 eV; rutile ∼ 3.0 eV) requires excitation with UV light, which accounts for only a small fraction of solar light. In order to increase the light absorption in the visible region, reduction of the band gap is required. Here, TiO2 nanotubes (NTs) were fabricated by electrochemical anodization of Ti foil. Scanning electron microscopy (SEM), X-ray diffraction analysis (XRD) and X-ray photoemission spectroscopy (XPS) were used to determine morphology, crystal structure and surface composition of the TiO2 NTs. Different synthesis conditions influenced TiO2 NTs properties that allowed the tuning of the band gap. UV-Vis analysis of 61.54 µm long NTs showed light absorption over the whole visible range, while NTs with the length up to 0.21 µm are able to absorb only UV light. 61.54 µm long NTs exhibited band tailing up to 1.43 eV.
Fazel Shojaei; Hong Seok Kang
Abstract
Based on the first-principles calculations, we identify four stacking patterns of the GeS bilayer, in which two most stable ones are almost equally stable. The most stable one corresponds to the experimental pattern in bulk GeS. Its interlayer binding is stronger than those in a-phosphorene and ...
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Based on the first-principles calculations, we identify four stacking patterns of the GeS bilayer, in which two most stable ones are almost equally stable. The most stable one corresponds to the experimental pattern in bulk GeS. Its interlayer binding is stronger than those in a-phosphorene and graphene, indicating that the material will rather exist in the form of bilayers or multilayers. Our HSE06 band structure calculations show that both patterns are semiconductors with indirect band gaps in the visible region, which are slightly smaller than that of the monolayer. For the monolayer, our refined calculation based on the deformation potential approximation indicates that the electron mobility along the armchair direction amounts to 4.62×10 4 cm 2 V -1 s -1 , which is ~40 times larger than that of the a-phosphorene. The electron mobility of the bilayer is dependent on the stacking pattern. The most stable pattern is expected to exhibit the mobility of 1.69×10 4 cm 2 V -1 s -1 , which is still ~30 times larger than that of the bilayer a-phosphorene. A detailed comparison of the carrier mobilities suggests that both of the mono- and bi-layer will be useful for n-type electronics.
Srinivasarao Yaragalla; Gopinathan Anilkumar; Vineeshkumar T. V.; Nandakumar Kalarikkal; Sabu Thomas
Abstract
Epoxy graphene (EG) was synthesized from graphite (GT) powder using meta chloroperbenzoic acid (mCPBA) as an oxidizing agent at room temperature. Structural properties of the prepared EG were investigated by Fourier transform infrared (FT-IR) spectroscopy, Raman spectroscopy and UV-visible spectroscopy. ...
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Epoxy graphene (EG) was synthesized from graphite (GT) powder using meta chloroperbenzoic acid (mCPBA) as an oxidizing agent at room temperature. Structural properties of the prepared EG were investigated by Fourier transform infrared (FT-IR) spectroscopy, Raman spectroscopy and UV-visible spectroscopy. Results of FT-IR and Raman spectroscopy confirmed that the epoxy groups are incorporated into graphene basal planes. The layered structure of EG was determined using transmission electron microscope (TEM). Optical properties of the prepared EG were analyzed using UV-visible spectroscopy and Photo luminescence (PL) spectroscopy. From the UV-visible spectroscopy data, the band gap of EG was found to be 4.1 eV and this energy gap was roughly correlated with the maximum photoemission behavior of EG and the fluorescence energy was found to be dependent on the excited wavelength. These novel functional materials could be used for applications in the field of opto-electronic and light emitting devices.
Soumya Mukherjee; Manoj Kumar Mitra
Abstract
Multiferroic materials are new class of multi-functional materials which possess both ferro-electric and magnetic properties. This type of material has wide range of applications like semi-conducting to sensors applications. Nanocomposite of equimolar perovskite-spinel is synthesized by chemical ...
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Multiferroic materials are new class of multi-functional materials which possess both ferro-electric and magnetic properties. This type of material has wide range of applications like semi-conducting to sensors applications. Nanocomposite of equimolar perovskite-spinel is synthesized by chemical route by blending of Nickel ferrite as second phase on Bismuth ferrite after heat treatment at 500 °C for 2, 3 and 4 hours soaking period. From the diffractogram data of XRD, the phase, and planes of orientation are analyzed of the synthesized materials. The crystallite size is calculated by Scherrer’s formula. FESEM studies reveal the morphological features having interconnected agglomerates with spherical, irregular polygonal or some elongated shape of the synthesized nanocomposite. FTIR result shows the molecular signature of the nanocrystalline material to verify the M-O coordination. Interplanar spacings and SAED pattern are revealed from HRTEM images which are very close to the experimental findings from XRD phase analysis. UV-VIS analysis is performed in the transmission mode of spectra within the scan range of 200-1100 nm. From the spectra, using Tauc relation band gap is calculated. Band gap are found of the order of 2.847 eV, 2.78 eV, 2.69 eV respectively for 2, 3 and 4 hours soaking period close to semiconducting material. With the increase of soaking time band gap is found to decrease following Arrhenius activation of electronic mobility overwhelming the energy barrier at respective lattice sites. M-H analysis of Nanocomposite at 500 °C for 2 hrs is closer towards ferromagnetic with incomplete loop but for sample at 500 °C for 4hrs it is closer towards superparamagnetic one. The property of this material reflects it has many interesting characteristics suitable for opto-electronic, photo-magnetic devices and other electronic applications.
S. Som; S. Dutta; Subrata Das; Mukesh Kumar Pandey; Ritesh Kumar Dubey; S. P. Lochab; S. K. Sharma
Abstract
Herein, a comparative study on the structural and luminescence properties of optimized Y2O3:Eu 3+ /Tb 3+ nanophosphor has been reported after 150 MeV Ni 7+ , 120 MeV Ag 9+ and 110 MeV Au 8+ ion beam irradiation at various fluences ranging from 1×10 11 to 1×10 13 ions/cm 2 . The X-ray diffraction ...
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Herein, a comparative study on the structural and luminescence properties of optimized Y2O3:Eu 3+ /Tb 3+ nanophosphor has been reported after 150 MeV Ni 7+ , 120 MeV Ag 9+ and 110 MeV Au 8+ ion beam irradiation at various fluences ranging from 1×10 11 to 1×10 13 ions/cm 2 . The X-ray diffraction results confirm the cubic phase in case of unirradiatedY 2 O 3 :Eu 3+ /Tb 3+ nanophosphor. The loss of crystallinity was observed after ion irradiation and Au ion is more effective to damage the crystal structure in these phosphors. The transmission electron microscopic results show the reduction of the particle size from 100 nm to 50, 30 and 20 nm after ion irradiation with the Ni 7+ , Ag 9+ and Au 8+ ions, respectively. Diffuse reflectance spectra show a blue shift in the absorption band owing to the increase in the band gap after ion irradiation. An increase in the photoluminescence intensity without any shift in the peak positions was observed with the increase in the ion fluence. The colour tunability was observed with ion irradiation as the colour coordinate varies from red to white chromaticity.
N. Bouazizi; R. Bargougui; A. Oueslati; R. Benslama
Abstract
CuO nanopowder oxide was synthesized by reflux condensation method without any surfactants or templates, using copper nitrate in deionized water and aqueous ammonia solution. The structural, optical and electrical properties of the sample were investigated using X-ray diffraction (XRD), FT-IR, UV–visible ...
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CuO nanopowder oxide was synthesized by reflux condensation method without any surfactants or templates, using copper nitrate in deionized water and aqueous ammonia solution. The structural, optical and electrical properties of the sample were investigated using X-ray diffraction (XRD), FT-IR, UV–visible spectroscopy and impedance spectroscopy measurements. The X-ray diffraction patterns revealed that CuO nanoparticles (NPs) was formed in pure monoclinic phase and good crystalline quality, whose NPs sizes were of the order 25 nm which an average size can be tailored by the synthesis time. FT-IR spectra of CuO NPs used to detect the possible adsorbed species on the CuO materials. In addition, the peaks at 529 and 604 cm-1 correspond to the characteristic stretching vibrations of Cu-O bond in the monoclinic CuO. The optical absorption property has been determined by UV–visible Spectroscopy in the wavelength range of 200–800 nm which indicate the energy gap (Eg). As result, Eg increases with increasing the synthesis time from 2.72 to 1.87 eV. The complex measurement has been investigated at room temperature, and in the frequency range 40 Hz–100 kHz, showing that Nyquist plots (Z' versus Z'') are well fitted to an equivalent circuit model which consists of a parallel combination of a bulk resistance Rb and constant phase elements CPE. On the other hand, the capacitance and the conductance of CuO NPs have a proportional relationship to the charge transfer and the surface electrode-pallet. These properties make these materials very promising electrode.
Gurpreet Kaur; Anirban Mitra; K.L. Yadav
Abstract
Al-doping of 1.5% by weight, in ZnO (Al:ZnO), thin films are deposited on glass substrates at temperature 400 °C and varying oxygen gas pressure (PO2) from 1.33 Pa to 5.32 Pa via Pulsed Laser Deposition (PLD) technique. The single crystalline nature of the thin films is confirmed from the X-ray diffraction ...
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Al-doping of 1.5% by weight, in ZnO (Al:ZnO), thin films are deposited on glass substrates at temperature 400 °C and varying oxygen gas pressure (PO2) from 1.33 Pa to 5.32 Pa via Pulsed Laser Deposition (PLD) technique. The single crystalline nature of the thin films is confirmed from the X-ray diffraction (XRD) pattern. The evaluated crystallite size is found to be <15 nm. Atomic Force Microscopy (AFM) study reveals the columnar grain formation in the thin films, with low surface roughness. The surface morphology of the grown thin films is significantly affected by PO2. Optical measurements depict that the thin films are highly transparent in the visible region with transmittance up to 80%. The optical band gap calculated from Tauc’s plot evinced that Al-doping results in band edge bending in Al:ZnO thin films, a red shift in the band gap is observed with increase in PO2 that is due to the contributing electrons from oxygen ions. Photoluminescence (PL) spectra of films indicate the visible emission peaks originating from defect states. Optical properties of the thin films confirm their applicability for optoelectronic devices. The room temperature, current-voltage (I-V) plots indicate low resistivity in the thin films ~ 10 -2 (Ω-cm).
R. Amutha
Abstract
Ultrathin (250 Å) initial deposit of copper on glass substrates were used for the subsequent deposition of ZnTe films under a pressure of 10 -5 m.bar by thermal evaporation method. The decrease of atomic percentage of copper with increase of the ZnTe film thickness is confirmed by EDAX analysis. ...
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Ultrathin (250 Å) initial deposit of copper on glass substrates were used for the subsequent deposition of ZnTe films under a pressure of 10 -5 m.bar by thermal evaporation method. The decrease of atomic percentage of copper with increase of the ZnTe film thickness is confirmed by EDAX analysis. The phase change from hexagonal to cubic structure is observed by XRD analysis. The strain (), grain size (D) and dislocation density ( ) were calculated and results are discussed. The transmittance and the optical bandgap energy were found decreases when increases of ZnTe film thickness. The optical transition of these films is found to be direct allowed.
Abstract
Peptide nanotubes (PNT) are emerging alternates frontier to carbon nanotubes (CNT). PNT’s can be engineered by solid phase synthesis with desired properties. Chemically PNT’s are reactive in sharp contrast to CNT’s and hence require less site specific functionalization for nanotechnology ...
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Peptide nanotubes (PNT) are emerging alternates frontier to carbon nanotubes (CNT). PNT’s can be engineered by solid phase synthesis with desired properties. Chemically PNT’s are reactive in sharp contrast to CNT’s and hence require less site specific functionalization for nanotechnology applications. In this paper we are reporting the electronic coupling between the Phe-Phe dipeptide which is calculated using the density functional theory method. The calculations are performed for linear and cyclic structures of diphenylalanine peptide. The calculated electronic coupling is sensitive to the peptide electronic structure and shows a significant dependence for conformations. The band gaps obtained for PNT are compared with Boron Nitride and CNT. Peptide nanotubes (PNT) exhibit no cytotoxicity and hence offer tantalizing prospects in biomedical applications for example in drug delivery. Copyright © 2011 VBRI press.
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