Keywords : Optical properties

Antifungal Activity of Iron-gold and Cobalt-gold co-doped ZnO Nanoparticles

A. Ferin Fathima; R. Jothi Mani; K. Sakthipandi

Advanced Materials Letters, 2021, Volume 12, Issue 6, Pages 1-5
DOI: 10.5185/amlett.2021.061636

Zn0.98Fe0.01Au0.01O and Zn0.98Co0.01Au0.01O nanoparticles (NPs) have been synthesized via poly ethylene glycol assisted route. The average crystallite size of Zn0.98Fe0.01Au0.01O and Zn0.98Co0.01Au0.01O NPs were estimated from X-ray diffraction results and the values are 31.38 nm and 36.14 nm respectively. The UV absorption spectra confirmed the formation of the NPs with the characteristic peaks at 374 and 366 nm respectively. This spectral observation indicates that the band gap of ZnO nanoparticles decreases by doping iron/gold and cobalt/gold nanoparticles. The morphology and elemental composition of Zn0.98Fe0.01Au0.01O and Zn0.98Co0.01Au0.01O NPs were investigated. The antifungal activity of synthesized Zn0.98Fe0.01Au0.01O and Zn0.98Co0.01Au0.01O NPs were found against four postharvest pathogenic fungi like Aspergillus niger, Aspergillus flavus, Rhizopus microsporus and Pencillium sp < /em>. The doping of iron and gold in ZnO nanoparticles enhances the zone of inhibition for the fungal pathogens compared to pure ZnO nanoparticles. Antifungal activity of Zn0.98Fe0.01Au0.01O and Zn0.98Co0.01Au0.01O nanoparticles were higher when compared with standard antibiotic mycostatin whose zone of inhibition is 18 mm against Aspergillus niger, Aspergillus flavus, Rhizopus microsporus and Pencillium sp.

Optical Characterization of Double Perovskite Ba2FeNbO6 Powders Derived from Molten Salt Method

Yao Lu; Xiangxiao Meng; Zhipeng Pei; Kai Leng; Weiren Xia; Xinhua Zhu

Advanced Materials Letters, 2020, Volume 11, Issue 9, Pages 1-6
DOI: 10.5185/amlett.2020.091554

Double perovskite Ba2FeNbO6 (BFN) powders were synthesized by molten salt method. Their optical properties were characterized by UV-Vis absorption spectra, and the band gaps (Eg) were determined to be 2.12 - 2.25 eV. The Eg values were tuned by adjusting the processing parameters of molten-salt route (e.g., annealing temperature, holding time as well as the molten salt ratios). The varied Eg values are ascribed to the different content ratios of Fe 3+ to Fe 2+ ions and the oxygen vacancies in the BFN powders. Oxygen vacancies in the BFN powders result in the distortions of FeO6 octahedrons, leading to different Fe-O bond lengths. Thus, the overlapping between the O-2p < /em> and Fe-3d orbitals is changed, making the Eg values changed. A small absorption shoulder with absorption edge at 650 nm (Eg ~ 1.91 eV) observed in the BFN powders, was ascribed to the d-d electronic transition from the Fe 3d-b2g to Fe 3d-b1g orbitals, which were formed by further splitting of Fe 3d orbitals in the distorted octahedral field. The present work offers an effective approach to tuning the Eg of BFN powders, which find promising applications in the fields of photovoltaic and photocatalytic devices.

Modulation of optical properties with multilayer thickness in antimonene and indiene   

Matko Mužević; Maja Varga Pajtler; Sanjeev Kumar Gupta; Igor Lukačević

Advanced Materials Letters, 2019, Volume 10, Issue 4, Pages 270-274
DOI: 10.5185/amlett.2019.2220

Optical properties of 2D materials can be effectively modulated by employing multilayer structures with different number of layers. Using the theoretical approach based on density functional theory we simulated relevant optical spectra of antimony and indium mono- and multilayers. We showed that the electronic band structures of antimonene and indiene possess numerous tracking bands enhancing the transition probability. Therefore, high absorption coefficients are found. Modelled multilayer nanostructures of antimonene and indiene experience a red-shift of absorption bands. Antimonene exhibits an optical directional anisotropy regarding the absorbance coefficient and reflectance spectrum for different nanolayer thicknesses. Indiene possesses very high reflectance and refractive index in the visible and IR spectrum which can be effectively modulated by the number of layers. Our work shows that antimonene and indiene multilayers harbour untapped potential for the optical applications at the nanoscale.

Synthesis and study of optical properties of microstructure flower-shaped ZnO 

Rajat K. Saha; Eeshankur Saikia;Mrinal K. Debanath

Advanced Materials Letters, 2018, Volume 9, Issue 7, Pages 494-498
DOI: 10.5185/amlett.2018.2066

In this study, we report the synthesis and optical properties of flower-shaped ZnO which is fabricated successfully using polyvinylpyrrolidone (PVP) as capping agent by wet chemical method at temperature 60 0 C. The structures and morphologies of flower-shaped ZnO is characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and Transmission Electron Microscopy (TEM) for nonlinear dynamical study of the system of particles. The studies of SEM and TEM have confirmed flower-shaped structure of the ZnO. The UV-vis absorption spectroscopy of the synthesized sample indicates the presence of blue shift. FTIR analysis shows the characteristic absorption of the Zn-O bond. It has been observed in room temperature photoluminescence (PL) spectroscopy of the sample exhibits emission peaks at near band edge (NBE) along with a weak blue emission peak. It is found from the present study that the phenomenon of flower-like microstructure is based on the size and shape of the particles as well as their aggregated forms. Moreover, their optical properties predict the factors responsible in inhibiting microorganisms for which it may lead to some biological applications. 

Determination of optimum cation to anion (Cd:S) ratio for the synthesis of mono sized CdS quantum dots through optical properties

Jai Kumar B; Sumanth Kumar D; Mahesh H. M

Advanced Materials Letters, 2017, Volume 8, Issue 4, Pages 386-392
DOI: 10.5185/amlett.2017.6918

The CdS quantum dots (QDs) were synthesized using double injection aqueous method and systematic studies were carried to determine optimum cation to anion (Cd:S) ratio to obtain mono sized CdS QDs. An efficient and convenient method is designed by utilizing the optical properties (absorbance and transmission spectra) as qualitative tool. CdS QDs was synthesized by varying cadmium and sulfur concentration from 0.01M to 0.1M and 0.01M to 0.05M respectively keeping MPA and other precursors constant. Through Concentration Optimization by Optical Spectra (COOS) method, it was found that for 0.02M sulfur and 0.04M MPA, 0.03 to 0.05M cadmium was the most favorable concentration and similarly for 0.04M cadmium and MPA the optimum concentration of sulfur was 0.02M. CdS QDs optical band gap varied from 3.09 eV to 3.69 eV with quantum dots size decreasing from 3.22 nm to 2.45 nm, respectively for Cadmium concentration from 0.02M to 0.07M. For Sulfur concentration variation, band gap varied from 3.55 eV to 3.03 eV, with size of QDs increasing from 2.58 nm to 3.33 nm, respectively for concentration 0.01M to 0.05M. All this results shows that synthesized quantum dots were well under quantum confinement effect. Further, the proposed COOS method can be extended to all QDs synthesis to obtain the optimum cation to anion ratio to synthesis QDs with narrow size distribution.

Optical properties of TiO2@C nanocomposites: Synthesized by green synthesis technique

Srikanta Karmakar; Subrata Biswas; Pathik Kumbhakar; Tapan Ganguly

Advanced Materials Letters, 2017, Volume 8, Issue 4, Pages 449-457
DOI: 10.5185/amlett.2017.1421

In this work, we have reported an eco-friendly and cost-effective technique of synthesis of TiO2@Carbon nanocomposites (TCNs) material by a facile solvothermal treatment of banana (Musa balbisiana) bract extract. Yellow-green photoluminescence (PL) feature and efficient catalytic activities of green synthesized TCNs have been demonstrated. X-ray diffraction (XRD) data has revealed the simultaneous presence of rutile and anatase phases of TiO2 in the synthesized TCNs. The presence of amorphous carbon and TiO2 is also confirmed by Raman spectroscopy. The light emission characteristics of TCNs are studied by PL emission spectroscopy which has confirmed the presence of defect levels caused by oxygen vacancies and surface hydroxyl groups localized within the band-gap. The photocatalytic performance of the synthesized material has been systematically evaluated by observing the degradation of Methylene Blue (MB) dye under the incidence of ultraviolet-visible (UV-Vis)/visible light irradiation and manifested a superior UV-Vis light photo-catalytic activity far over the commercial TiO2 powder (CTP) under the same experimental conditions. A relatively higher electrochemical performance and 52 times larger cathodic current density is obtained in TCNs in compared to that of CTP. TCNs exhibit extremely high hydrogen evolution reaction catalytic activity with very small onset over potential.

The Influence Of Incorporating Cobalt (Co) And Indium (In) Co-dopants On The Structural And Optical properties Of ZnO Nanoparticles

Mpho W. Maswanganye; Koena E. Rammutla; Thuto E. Mosuang; Bonex W. Mwakikunga; Sone T. Bertrand; Malik Maaza

Advanced Materials Letters, 2017, Volume 8, Issue 1, Pages 37-41
DOI: 10.5185/amlett.2017.6876

Co and In co-doped nanopowders of ZnO as well as In and Co singly doped ZnO were successfully prepared using sol-gel method. The synthesized samples were characterized using x-ray diffraction (XRD), UV-vis spectroscopy (UV-vis), Raman spectroscopy (RS), Transmission Electron Microscopy (TEM) and Energy Dispersive Spectroscopy (EDS). The effects of In and Co co-doping on the structural and optical properties were investigated. XRD results showed no peaks associated with In 3+ or Co 2+ ions indicating that In 3+ and Co 2+ ions substituted for Zn 2+ ions in the ZnO wurtzite structure, this was corroborated by the EDS results. Doping ZnO nanoparticles with In and Co significantly reduced the grain sizes whereas the lattice parameters were not significantly affected. TEM results confirmed that the nanoparticles were spherically shaped. Raman spectroscopy also confirmed that the ZnO nanoparticles were of a wurtzite hexagonal structure. Single doping reduced the energy band gaps and co-doping reduced them even further.

Optical, Electrical And Antimicrobial Studies Of Chemically Synthesized Graphite Oxide And Reduced Graphene Oxide

Alpana Thakur; Sunil Kumar; Manjula Sharma; V. S. Rangra

Advanced Materials Letters, 2016, Volume 7, Issue 12, Pages 1029-1034
DOI: 10.5185/amlett.2016.6810

Graphite oxide (GO) and reduced graphene oxide (RGO) have been synthesized using chemical methods. Prepared graphite oxide and reduced graphene oxide were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. XRD patterns, Raman spectra and FTIR spectroscopy confirms significant structural changes while reducing GO to RGO. The obtained products were further analyzed for their optical and electrical properties using UV-Vis spectroscopy, photoluminescence spectroscopy and four-point probe. RGO has shown excellent electrical conductivity of 1.363×10 4 S/m. The bactericidal action of prepared GO and RGO was also studied against Escherichia coli and Staphylococcus aureus bacteria.

Thickness Effect On Nano-multilayered Sb/As2S3 Chalcogenide Thin Films

Ramakanta Naik

Advanced Materials Letters, 2016, Volume 7, Issue 10, Pages 821-825
DOI: 10.5185/amlett.2016.6339

The nano multilayered thin films of Sb/As2S3 metal chalcogenide were prepared by thermal evaporation technique under high vacuum. The optical parameters such as optical band gap, tauc parameter, urbach energy were determined from the transmission spectra using Fourier Transform Infrared Spectroscopy. These properties are greatly influenced by the thickness of the nano layered Sb/As2S3 thin film. The Small Angle X-ray diffraction study reveals the amorphous nature of these films. The analysis reveals that the optical band gap decreases with increase in thickness due to Sb metal. The tauc parameter and urbach energy supports the optical property change. Such type of dependence is attributed to quantum size effect in semiconductors.

Single Oriented CeO2 Buffer Layer Deposition On Biaxially Textured Ni-W Substrate By RF Magnetron Sputtering

K.M.K. Srivatsa; Preetam Singh; Sourav Das

Advanced Materials Letters, 2015, Volume 6, Issue 10, Pages 883-887
DOI: 10.5185/amlett.2015.5884

Considerable attention has been gained on the deposition of CeO2 thin films with (200) single orientation as hetero-epitaxial buffer layer on (200) oriented biaxially textured flexible Ni substrates, in the fabrication of superconductor and semiconducting epitaxial thin films for device applications. In this work we have deposited (200) oriented CeO2 thin films on biaxially textured Ni-W substrate in a single-step process by RF magnetron sputtering, using CeO2 target. X-ray diffraction analysis shows that for the CeO2 thin film deposited at RF sputtering power below 200 W and for the substrate temperature of 700 o C, the film assumes single (200) orientation. For the substrate temperature below 700 o C and RF sputtering powers above 200 W the film shows polycrystalline nature with (111) and (200) orientations. The Raman spectrum of single oriented (200) CeO2 thin film shows only one sharp peak at about 464 cm -1 corresponds to the presence of F2g mode of CeO2. The ellipsometry studies reveal the value refractive index and optical band gap of single oriented film as 2.52 and 3.41 eV, respectively.

Preparation Of Epoxy Graphene And Its Structural And Optical Properties

Srinivasarao Yaragalla; Gopinathan Anilkumar; Vineeshkumar T. V.; Nandakumar Kalarikkal; Sabu Thomas

Advanced Materials Letters, 2015, Volume 6, Issue 10, Pages 848-852
DOI: 10.5185/amlett.2015.5914

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.

Investigations On Multiferroic, Optical And Photocatalytic Properties Of Lanthanum Doped Bismuth Ferrite Nanoparticles

Manpreet Kaur; K. L. Yadav; Poonam Uniyal

Advanced Materials Letters, 2015, Volume 6, Issue 10, Pages 895-901
DOI: 10.5185/amlett.2015.5861

Single phase Bi1-xLaxFeO3 nanoparticles have been successfully synthesized with varied concentration (0.0 ≤ x ≤ 0.2) for the photocatalytic degradation of an industrial dye. The room temperature X-ray diffraction (XRD) pattern of La 3+ doped BiFeO3 nanoparticles reveals the structural phase transition from rhombohedral (R3c) to orthorhombic (Pnma) at x=0.1, which is further analyzed via Rietveld refinement. The La 3+ doped BiFeO3 nanoparticles have much negative enthalpy of formation (ΔHf) than undoped BiFeO3. The particle size gradually decreases from ~132 to ~68 nm with La 3+ doping. Magnetic and ferroelectric transition temperatures are found to be slightly shifted towards room temperature upto x= 0.1 and then higher temperature side which could be attribute to the particle size effect. All compositions presented weak ferromagnetic ordering, which indicates that the La 3+ substitution in the BiFeO3 matrix released the latent magnetization. The increase in the energy band gap from 2.045 to 2.658 eV with cutoff wavelengths 639.58 and 513.061 nm for x=0.0 and 0.2 respectively, increases the visible light efficiency of photocatalytic activity in La 3+ doped BiFeO3 samples. The photodegradation efficiency of La 3+ doped BiFeO3 for azo-dye RB-5 is observed to be ~27% higher as compared to the undoped BiFeO3 (43% photodegradation efficiency), which makes it suitable for visible-light responsive photocatalysis for photocatalytic applications.

Structural, Electrical and Optical Properties Of Molybdenum Doped Zinc Oxide Films Formed By Magnetron Sputtering

R. Subba Reddy; K. Radhamma; A. Sivasankar Reddy; S. Uthanna

Advanced Materials Letters, 2015, Volume 6, Issue 9, Pages 834-839
DOI: 10.5185/amlett.2015.5920

Thin films of molybdenum doped (2.7 at.%) zinc oxide (MZO) were deposited on glass substrates held at room temperature by RF magnetron sputtering of mosaic target of Mo-Zn at different substrate bias voltages. The influence of substrate bias voltage on the structural, electrical and optical properties was investigated. The MZO films deposited on unbiased substrate were of amorphous, while those formed at substrate bias voltage of -40 V and above were of nanocrystalline. The crystallite size of the films improved with the applied bias voltage. At higher substrate bias voltage of -120 V the ion bombardment induced the high defect density in the films hence decrease in the crystallinity. The films formed at substrate bias voltage of -80 V exhibited low electrical resistivity of 1.2x10 -2 Ωcm and optical transmittance of about 79 %. These films showed optical band gap of 3.29 eV and figure of merit of 19 Ω -1 cm -1 .

Mechanisms Of Composite-hydroxide-mediated Approach For The Synthesis Of Functional ZnO Nanostructures And Morphological Dependent Optical Emissions

Taj Muhammad Khan; M. Zakria; Rana I. Shakoor; M. Raffi; Mushtaq Ahmad

Advanced Materials Letters, 2015, Volume 6, Issue 7, Pages 592-599
DOI: 10.5185/amlett.2015.5876

We report synthesis of the functional ZnO nanostructures (nanowires, nanorods) by a cost-effective and efficient method; called composite-hydroxide-mediated (CHM) approach. Effect of the processing temperature on the particle size, morphology, and subsequently morphological dependent optical emissions is investigated. Needle-shaped nanowires are obtained at 200 and 220 o C, of about (500-1500) nm in length, while at 250 o C; nanorods are formed with length in the range of (200-460) nm and width (10-30) nm. Optical study reveals that ZnO nanorods show only ultra-violet (UV) emission while bent nanowires demonstrate both UV and green emissions simultaneously. The week green emission at 2.4 eV indicates no efficient trapping of the photo-generated hole in the nanostructures. Phase purity, crystalline structure, size and chemical nature of the product are probed by XRD, EDX, Raman spectroscopy and FT-IR. The particle size estimated from the spatial correlation phonon confinement model for the E2 (high) phonon mode. The applied approach is believed to be efficient, and a direct route for the synthesis of a wide range of simple and complex oxide nanostructures for novel electro-optical nanodevices.

Plasmonic Resonance In Spray Deposited Au Nanoparticles Grown On TiO2 Thin Film

Promod Kumar; M. M. Ahmad

Advanced Materials Letters, 2015, Volume 6, Issue 7, Pages 628-632
DOI: 10.5185/amlett.2014.5745

Gold nanoclusters embedded in titania (TiO2) matrix were synthesized by thermal spray method followed by thermal annealing in an inert atmosphere. The effect of annealing temperature on the plasmonic response and optical properties of gold nanocluster in titanium dioxide matrices have been investigated by using UV-visible absorption spectroscopy. The surface plasmon resonance (SPR) at metal-dielectric interface for gold nanoparticles has been observed for as deposited samples at 561.8 nm which degrade as a function of post annealing temperature. Field emission scanning electron micrographs confirm the presence of spherical nanoparticles whose size increases with post annealing temperature. The plasmonic resonance of noble metals at nanoscale is fundamentally and technologically important for light trapping photovoltaic and other applications.

Structural, Optical And Magnetic Properties Of (Fe, Ag) Co-doped ZnO Nanostructures

B. Sankara Reddy; S. Venkatramana Reddy; N. Koteeswara Reddy; Y. Prabhakara Reddy

Advanced Materials Letters, 2014, Volume 5, Issue 4, Pages 199-205
DOI: 10.5185/amlett.2013.8529

The (Fe, Ag) co-doped ZnO nanostructures are developed through chemical precipitation method at various percentages of Fe. The X-ray diffraction studies suggest that all the as-synthesized (Fe, Ag) doped ZnO nanopowders have single phase wurtzite structure with no secondary phases. However, the positions of diffracted peaks slightly shifted towards lower (2θ) angles. Photoluminescence studies reveal that 1 mol% of Fe doped ZnO sample has the best ultra violet (UV) emission properties than the other samples. On the other hand, 5 mol% of Fe doped ZnO nanopowders consists of strong green emission band, which belongs to oxygen interstitial defect states. Magnetization analysis shows that 5 mol% of Fe doped ZnO nanopowders have highest room temperature ferromagnetism (RTFM) than the RTFM of other samples. The observed RTFM in co-doped ZnO nanopowders is discussed with the help of structural and emission studies. The results strongly suggest the future development of efficient luminescence and magnetic materials at normal laboratory temperatures with (Fe, Ag) co-doped ZnO nanostructures.

Enhanced White Light Emission And Energy Transfer Studies Of Dy3+/Ce3+ Co-doped YAl3(BO3)4 Phosphors For White Light Emitting Diodes

G.V. Lokeswara Reddy; L. Rama Moorthy; T. Chengaiah; B.C. Jamalaiah

Advanced Materials Letters, 2013, Volume 4, Issue 11, Pages 841-848
DOI: 10.5185/amlett.2013.3453

We reported the structure, photoluminescence and energy transfer studies of Dy 3+ /Ce 3+ co-doped YAl3(BO3)4 (YAB) phosphors prepared by solid-state reaction method at 1200 o C/3h. Upon 273 nm UV excitation, the YAB:Ce 3+ phosphor exhibits a sharp emission band with peak maximum at 380 nm related to the parity and spin allowed Ce 3+ : 5 d → 4 f transition. When excited with 352 nm, the broad emission band of Ce 3+ contains two components at 390 and 417 nm due to the electric dipole transitions from 5d excited state to the two splitting ground 2 F5/2,7/2 states, respectively. The incorporation of Ce 3+ enhances the luminescence intensity of Dy 3+ due to efficient energy transfer from Ce 3+ to Dy 3+ . The emission spectra of Dy 3+ /Ce 3+ co-doped phosphors under 273 nm excitation display the Dy 3+ : 4 F9/2 → 6 H15/2,13/2,11/2 and the Ce 3+ : 5 d → 4 f transitions. The emission colour can be tuned from blue-to-white as a function of Ce 3+ concentration and/or excitation wavelength. Colour perception has been analyzed by evaluating the Commission International de I’Eclairagein (CIE) chromaticity coordinates. The YAB:Dy 3+ /Ce 3+ phosphors can be significant for current generation UV excited white light emitting diodes.

Post-deposition Annealing Controlled Structural And Optical Properties Of RF Magnetron Sputtered MoO3 Films

S. Subbarayudu; V. Madhavi;S. Uthanna

Advanced Materials Letters, 2013, Volume 4, Issue 8, Pages 637-642
DOI: 10.5185/amlett.2012.11466

MoO3 films were deposited on Corning glass and silicon substrates held at room temperature (303 K) by RF magnetron sputtering of metallic molybdenum target at a fixed oxygen partial pressure of 4x10 -4 mbar and sputter pressure of 4x10 -2 mbar. The as deposited films were annealed in air at different temperatures in the range 473 – 673 K. X-ray diffraction studies suggest that the as-deposited and the films annealed at 473 K were amorphous in nature, while those annealed at 573 and 673 K were polycrystalline with mixed phases of α- orthorhombic and β- monoclinic MoO3. Scanning electron microscope images of the films annealed at 573 and 673 K exhibited nanoflower like and nanodisk like structures due to improvement in the crystallinity. Fourier transform infrared studies showed the characteristic vibrations of MoO3 with shift in the vibrational modes of Mo = O and Mo – O – Mo with increase of annealing temperature. The optical absorption edge of the films shifted towards lower wavelengths side with increase of annealing temperature. Optical band gap of as-deposited films was 2.98 eV with refractive index 2.01, while those annealed at 673 K showed the optical band gap of 3.15 eV and refractive index of 2.08. The MoO3 films annealed at 673 K were of nanocrystalline with crystallite size of 39 nm with optical band gap of 3.15 eV and refractive index of 2.08 were favorable for electron blocking and hole-selective layers in bulk-heterojuction solar cells.

A Convenient Noninjection One-pot Synthesis Of CdS Nanoparticles And Their Studies

M. Penchal Reddy; B.C. Jamalaiah; I.G. Kim; D.S. Yoo; R. Ramakrishna Reddy

Advanced Materials Letters, 2013, Volume 4, Issue 8, Pages 621-625
DOI: 10.5185/amlett.2012.12483

Water-dispersible CdS quantum dots (QDs) were synthesized in a simple one-pot noninjection route. The X-ray diffraction (XRD) pattern of the nanoparticles shows the cubic structure with particle size of the order 5-7 nm which was in good agreement with the transmission electron microscopic (TEM) studies. Selected area electron diffraction (SAED) recognized the cubic structure of CdS. The energy dispersive X- ray spectroscopy (EDAX) analysis confirms the presence of Cd and S elements in the samples. The optical properties are characterized by Ultraviolet-Visible (UV-Vis) absorption and Photoluminescence (PL) spectra. The synthesis parameters of this simple and rapid approach, including the reaction temperature and time, the pH of the reaction solution and the molar ratio of the 3-mercaptopropionic acid (MPA) stabilizer to Cd 2+ , have considerable influence on the particle size and photoluminescence of the CdS quantum dots. The 3-mercaptopropionic acid (MPA) stabilized CdS QDs can be used in solar cells, light emitting diodes, biological imaging etc.

New Synthetic Approach, Mesoporous properties And Photocatalytic Activity Of Titania adapted Chromium-niobate Nanocatalysts

Tanmay K. Ghorai; Prasanta Dhak

Advanced Materials Letters, 2013, Volume 4, Issue 2, Pages 121-130
DOI: 10.5185/amlett.2012.7382

Mesoporous titania adapted chromium-niobate nanocatalysts CrxNbxTi1-2xO2-x/2 (x = 0.01-0.2) were synthesized by a new synthetic approach, using N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine (edteH4) precursors and their photocatalytic activities were investigated. TiO2 nanomaterials have continued to be highly active in photocatalytic applications because these are useful to break down the organic molecules in water for endorsing the diffusion of reactants and products. CrxNbxTi1-2xO2-x/2 (x = 0.01)(CNT1) nanoparticles with the smaller particle sizes 12±1 nm and have mesoporous characteristics (SBET = 162 m 2 g −1 ). The energy band gap of CNT1 was found 1.85 eV obtained from optical emission spectrum. The XRD peaks revealed a mixture of anatase and rutile phases in the synthesized powders. EPR spectroscopy showed the characteristic features of Nb 5+ ions, whose existence was confirmed by XPS. The CNT1 powders display good (2.5 times greater) photocatalytic activity for degradation of Rhodamine B (RhB) as opposed to pure anatase TiO2 and other compositions of CrxNbxTi1-2xO2-x/2.

The Influence Of Substrate Temperature On The Structure, Morphology, And Optical Properties Of ZrO2 thin Films Prepared By E-beam Evaporation

K. J. Patel; M. S. Desai; C. J. Panchal

Advanced Materials Letters, 2012, Volume 3, Issue 5, Pages 410-414
DOI: 10.5185/amlett.2012.5364

Zirconium dioxide thin films were prepared by e-beam evaporation method to study the effect of substrate temperature on the structural, surface morphology, compositional, and optical properties. X-ray diffraction measurement shows that the films grown at 400 ℃ substrate temperature have monoclinic crystal structure. The root mean square surface roughness of the film increases with increase in the substrate temperature. The optical transmittance spectra indicate an average 80% transmittance in the visible region of light. The optical energy band gap of ZrO2 thin film decreases from 5.68 to 5.63 eV as the substrate temperature increases from room temperature to 400 ℃, respectively.

Synthesis Of CdSe Nanoparticles By Solvothermal Route: Structural, Optical And Spectroscopic Properties

Punita Srivastava;Kedar Singh

Advanced Materials Letters, 2012, Volume 3, Issue 4, Pages 340-344
DOI: 10.5185/amlett.2012.5341

We have developed successfully the synthesis of highly yielded CdSe nanoparticles (NPs) at 60 0C by solvothermal route in which the cadmium and selenium precursors have been dissolved in deionized water, ethylene glycol and hydrazine hydrate. This route is very facile, inexpensive and less hazardous and ensures almost complete yield of the precursors. The powder product was well characterized by powder X- ray diffraction (XRD), Transmission electron microscopy (TEM), Scanning electron microscopy (SEM), UV-Vis spectroscopy, Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR) .It is investigated that as synthesized powder has a hexagonal (Wurtzite) structure of CdSe with diameters of the particles are in the range of 10-15 nm. The formation mechanism is also discussed.

Effect Of Film Thickness On The Structural Morphological And Optical Properties Of Nanocrystalline ZnO Films Formed By RF Magnetron Sputtering

R. Subba Reddy; A. Sreedhar; A. Sivasankar Reddy; S. Uthanna

Advanced Materials Letters, 2012, Volume 3, Issue 3, Pages 239-245
DOI: 10.5185/amlett.2012.3329

Zinc oxide (ZnO) thin films were formed by RF reactive magnetron sputtering onto p-type silicon and glass substrates held at room temperature. The thickness of the films deposited was in the range 160 – 398 nm. The thickness dependence structural, morphological and optical properties of ZnO films were systematically investigated. The maximum crystallite size of 21 nm observed at films thickness of 231 nm by X- ray diffraction. Scanning electron microscopic analysis revealed that the growth of nanowires in all the films. The root mean square roughness of the films increased from 7.3 to 53 nm in the thickness range of investigation. Fourier transform infrared analysis confirmed the Zn-O bonding located at wavenumber of 413 cm -1 . The average optical transmittance of the films was about 89 % in the visible region. The optical band gap of the ZnO films decreased from 3.14 to 3.02 eV with increase of film thickness from 160 to 398 nm respectively.

Influence Of ZnO Buffer Layer On Growth Of Sb Doped ZnO Nano Wires Using Nano Particle Assisted Pulsed Laser Deposition (NAPLD) Using Sb As Catalyst

I.A. Palani; D. Nakamura; K. Okazaki; T. Shimogaki; M. Higashihata; T. Okada

Advanced Materials Letters, 2012, Volume 3, Issue 2, Pages 66-70
DOI: 10.5185/amlett.2012.1302

Influence of ZnO buffer layer thickness on the structural and optical properties of the Sb catalyzed/doped ZnO nanowires synthesized using NAPLD has been investigated. Buffer layer with a thickness of 100 nm, 800 nm and 1600 nm coated with Sb are used as a substrate and pure ZnO was used as a target to synthesize Sb doped ZnO nanowires. Introduction of the buffer layer lead to the growth of vertically aligned along with horizontally grown ZnO nano wires. With the increase in buffer layer thickness, the core diameter of the vertically grown ZnO nano wires was subsequently increased. Nano wires synthesized with a buffer layer thickness of 1600 nm showed a significant change in the lattice constants, resulting in measurable lower angle of about 0.06º from XRD, widening of lattice fringe spacing of 0.54 nm from TEM and Suppression of A1T and E1(L0) modes in Raman Spectroscopic. In addition a strong UV emission with absence of visible emission was observed from the room temperature PL. This confirms the generation of Sb doped ZnO nano wire with high crystal quality.