Keywords : sol

Effect of Nd-concentration in Nd(2-x)FexO3 System on the Crystal Structure and Microwave Absorption Characteristics

Wisnu Ari Adi

Advanced Materials Letters, 2020, Volume 11, Issue 7, Pages 1-4
DOI: 10.5185/amlett.2020.071540

Effect of Nd-concentration in Nd(2-x)FexO3 system on the structure and microwave absorption characteristics have been studied. Nd(2-x)FexO3 system is one of perovskite based system which has a relative high permittivity. Nd(2-x)FexO3  (x=0.5; 1.0 and 1.2) samples were synthesized by Fe(NO3)3 and Nd(NO3)3 in mole ratio using sol–gel method and then sintered at 800°C for 5 hours. All of the samples were characterized using XRD to identify the phase, SEM to observe the morphology and VNA was used to measure the microwave absorption. Phase identification of XRD data shows that single phase of NdFeO3 have been formed for x = 1.0 composition (ABO3). While multiphase have been formed which is indicated by the appearance of NdFeO3 and Nd2O3 phase for x = 0.5, and then NdFeO3 and Fe2O3 phase for x = 1.2. SEM image shows the samples of Nd(2-x)FexO3 have homogenous morphology with particle size is approximately 200 nm. The results of microwave absorbing properties measured by using VNA (Vector Network Analyzer) shows the best ability of microwave absorption is x = 1.0 composition is around 96.27% at frequency of 10.46 GHz.

Fabrication and magnetic properties of Sol-Gel derived NiZn ferrite thin films for microwave applications

Shauna Robbennolt; Stephen S. Sasaki; Tylisia Wallace; Marquise Bartholomew; Sarah H. Tolbert

Advanced Materials Letters, 2018, Volume 9, Issue 5, Pages 345-352
DOI: 10.5185/amlett.2018.1996

We present a new solution-phase, sol-gel based spin-coating method to fabricating high quality, nickel zinc ferrite (NZFO) thin films. The effect of annealing temperature on the microstructure, static magnetic properties and X-band FMR linewidth and resonance field was investigated. Furthermore, the effect of composition on these properties was explored in films with the formula NixZn(1-x)Fe2O4 (where x = 0 to 1 in 0.1 increments). Films annealed at the highest annealing temperature of 1100 ?C were found to have the highest saturation magnetization and coercivity, as well as the lowest FMR linewidths. Films with the composition Ni0.3Zn0.7Fe2O4 were found to have the lowest linewidths along with favorable magnetic properties for microwave applications. The champion film showed an FMR linewidth of 93 G, corresponding to a low Gilbert damping coefficient of α = 0.003, a saturation magnetization of 330 emu/cm 3 , and a coercivity and anisotropy field of 14 and 62 Oe respectively.

Study of the properties of La-doped ZnS thin Films synthesized by Sol-gel method

Amel Tounsi; Djahida Talantikite-Touati; Hamid Merzouk; Hadjira Haddad; Roumaïssa Khalfi

Advanced Materials Letters, 2018, Volume 9, Issue 3, Pages 216-219
DOI: 10.5185/amlett.2018.1963

The thin layers of undoped ZnS and ZnS doped La with different concentrations (2, 4, 6, 8 and 10%) were deposited on glass substrates using sol-gel and dip-coating methods. The structural characterization of these samples was carried out by the  X-rays diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). UV-visible and Fourier Transform Infrared spectroscopy (FTIR) have been used to study the effect of dopant on the optical properties of ZnS doped La thin films. Atomic force microscopy images of the films have revealed homogeneous and granular structure and the SEM micrographies show deposit films with uniform and porous structure. The optical transmission spectra in the UV - visible range have shown that all the doped films present a good optical transmission in the visible domain.

Magnetic and dielectric properties of divalent Ca2+ and Ba2+ ions co-doped BiFeO3 nanoparticles

N. Manjula; S. Ramu; K. Sunil Kumar; R. P. Vijayalakshmi

Advanced Materials Letters, 2018, Volume 9, Issue 3, Pages 175-181
DOI: 10.5185/amlett.2018.1411

Pristine BiFeO3 (BFO) and Ca doped BiFeO3: Ba nanoparticles (NPs) were synthesized in aqueous solution by sol-gel method with Tartaric Acid as a chelating agent. EDAX measurements confirmed the presence of Ca, Ba in the BiFeO3 host lattice. X-ray diffraction analysis showed that the average grain size of the prepared samples was in the range of 09–28 nm. The lattice structure of the nanoparticles transformed from rhombohedral to tetragonal phase with Ca 2+ ions substitution increased. TEM images indicated that sphere and square shape of nanoparticles through a size ranging from 10 to 15 nm. Diffusion reflectance spectra of BiFeO3 NPs showed a substantial blue shift of ~100 nm (630 nm -> 530 nm) on Ca, Ba co-doping which corresponds to increase in band gap by 0.47 eV. Dielectric constant (ε’) and dielectric loss (ε’’) were measured in the frequency range 1 Hz to 1 MHz at room temperature. Dielectric constant and loss are increased with Ca concentration except for Ca (4 at. %). The bulk conductivity (σ) increases from 3.07 x 10 -6 S/m to 1.64 x 10 -5 S/m as the Ca concentration increased from 0.00 to 0.03. Magnetic measurements revealed the ferromagnetic character of Pristine BFO and Ca doped BiFeO3: Ba samples. It is observed that by increasing the Ca concentration the value of Mr and magnetization are varied irregularly upto Ca (4 at. %). But for x = 0.01 Mr and magnetization are highest. The values of magnetization and Mr for 1% Ca doped BiFeO3: Ba NPs are 2.99 emu/g, 1.54 emu/g, respectively, which are quite significant at room temperature. These materials have potential applications in data storage, switching devices, spintronics, sensors and microelectronic. 

Optical and structural characteristics of ZnO nanopowders for different preparation methods

Advanced Materials Letters, 2017, Volume 8, Issue 12, Pages 1193-1198
DOI: 10.5185/amlett.2017.1581

Zinc oxide (ZnO) nanoparticles (NPs) were synthesized by different methods known as Pechini and Sol-Gel. It was observed during the experiments significant differences comparing these methods as: particle size, time applied, crystallinity and chemical residues generated by-products. The NPs were analysed by X-ray diffraction (XRD), ultraviolet-visible (UV-Vis.) absorption and Raman spectroscopy techniques. X-Ray Difractograms showed peaks corresponding to hexagonal wurtzite crystalline structure. It was observed that NPs obtained by the Pechini showed better homogeneity and crystallinity; these presented average size of 115 nm. The NPs produced by Sol-Gel method showed crystallites with smaller average size of 8 nm. The band gap energy (Eg) obtained using UV-Vis for ZnO NPs synthesized by Pechini was 3.39 eV. Still, the results for Sol-Gel method with 5 and 10 hours of reactions were 3.53 eV and 3.55 eV respectively. Raman data obtained by Pechini and Sol-Gel Methods showed characteristics peaks. The obtained data confirmed the ZnO phase samples and the proportional relationship to the enlargement with the intensity of peaks E2 High ˜ 438 cm -1 , as evidenced by literature. These results lead to the applicability of both NPs in optoelectronic and fluorescent applications. 

Europium doped silicate phosphors: Synthetic and characterization techniques

Devender Singh; Suman Sheoran; Vijeta Tanwar

Advanced Materials Letters, 2017, Volume 8, Issue 5, Pages 656-672
DOI: 10.5185/amlett.2017.7011

In this review article, different synthetic procedures and characterization techniques used for the development of materials are discussed briefly. The stability and high luminous intensity of silicate materials makes them practically important in the field of white light emitting diodes (WLEDs). During the experimental designing of our research, we have understood carefully the theoretical and methodological strategy regarding the synthesis of phosphors and then, a large number of silicate-based luminescent materials have been prepared using sol-gel technology. Among them, a series of silicate materials having composition M(2-x)EuxSi2O7 (M = Y, Gd, La and x = 0.03 moles) have been described in this review prepared with sol-gel process. Intense peak in europium (III) doped M2Si2O7 silicates originate from 5 D0→ 7 F2 transition of Eu 3+ ion available in crystal lattices. X-ray diffraction pattern have triclinic structure for Y2Si2O7 and Gd2Si2O7 silicate phosphors. However, hexagonal and monoclinic structures are obtained for La2Si2O7 material at different temperatures employed for further annealing. Transmission electron microscopic analysis is used to study the morphology and particle size of prepared phosphors. Excellent luminescence response of these silicate phosphors make them suitable for photonic applications and also open up new avenues for solid-state lighting, cathode ray tubes, fluorescent lamps and scintillators etc.

Titanium dioxide (TiO2) and silver/titanium dioxide (Ag/TiO2) thin films with self-cleaning properties

Ana Flávia R. Silva; Nelcy D. S. Mohallem; Marcelo M. Viana

Advanced Materials Letters, 2017, Volume 8, Issue 4, Pages 444-448
DOI: 10.5185/amlett.2017.7093

In this work, TiO2 and Ag/TiO2 thin films were synthesized on glass by combination of sol-gel method and dip-coating deposition technique. Thermal treatment in temperatures ranging from 100 °C to 500 °C was used to evaluate changes in structure, morphology and texture of these materials. Adherent and microcrack-free films were obtained. The structural and morphological evolution with temperature was studied by X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). Average particle size and roughness were determined by atomic force microscopy (AFM). The films were tested for wettability by measuring the contact angle between a drop of distilled water and the material surface. Results of hydrophobic/hydrophilic tests using UV-C irradiation showed that the films change their hydrophobic character to hydrophilic reaching even the superhydrophilic character which indicates their potential application as self-cleaning coatings. 

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.

Adsorption Of Mercury From Aqueous Solution Using Gum Acacia-silica Composite: Kinetics, Isotherms And Thermodynamics Studies

Somit Kumar Singh; Ananda Murthy H. C; Vandana Singh

Advanced Materials Letters, 2016, Volume 7, Issue 8, Pages 673-678
DOI: 10.5185/amlett.2016.6189

In the present investigation, the remediation of mercury by using the gum acacia-silica composite as an adsorbent has been studied. Experiments revealed optimum parameters which were found to be pH 6, contact time 2 hours, Hg(II) concentration of 100 ppm, reflux temperature 30 0 C and adsorbent dosage of 50 mg. The experimental data was subjected to modeling using the Langmuir and Freundlich isotherms. It was found that the data very well fitted to the Freundlich model. The pseudo second order kinetics confirms chemisorption with rate constant 3.1 × 10-4 gmg-1min-1. The calculated thermodynamic parameters (?G 0 , ?S 0 , ?H 0 ) revealed the exothermic and spontaneous nature of adsorption process at the solid–solution interface. The adsorbent could be recycled for six successive cycles with 31.5% loss in its efficiency. The adsorbent is found to be highly effective and economical for mercury remediation from water.

Relaxations In Gelatin Hydrogels Probed By Dynamic Light Scattering

Nitin Kumar; Vinay Kumar; Jitendra Sharma

Advanced Materials Letters, 2016, Volume 7, Issue 2, Pages 136-143
DOI: 10.5185/amlett.2016.6012

The relaxation behavior of gelatin aqueous solutions has been investigated by time resolved dynamic light scattering (TRDLS) measurements at different temperatures spanning the entire sol to gel phase transition behavior of the system (i.e. from 5 min to 1440 min after a sudden quench from high temperature sol to low temperature gel state), when the chosen gelatin concentration in water was maintained at 5 % (w/v), well over the overlap threshold. The quantity of interest, structure factor S (q,τ), has been obtained from the experimentally measured autocorrelation function,  g2(τ), allowing appropriate heterodyne contribution. The nonlinear regression analysis of the obtained scattering profiles (variation of structure factor vs. delay time) exhibited good fits to the function S(q,τ) ~A exp(-Dq 2 τ) + B exp(-(τ/τc) β ), up tosystem evolution time of 360 min, whereas the data obtained after 360 min showed appropriate fits to S(q,τ) ~A exp(-Dq 2 τ)+ Cτ -α + B exp(-(τ/τc) β ). The temporal behavior of different fit parameters defining the transient structural network formed in the system has been quantified and analyzed under the purview of well-defined theories. Furthermore, the evolution of particle dynamics from fast to slow and then to almost frozen behavior has been explored through the continuous evaluation of ‘Gelation factor (κ)’ at different stages of system evolution times during the measurements.

Aqueous Phase Photodegradation Of Rhodamine B And P-nitrophenol Desctruction Using Titania Based Nanocomposites

Suranjan Sikdar; Sayantan Pathak; Tanmay K Ghorai

Advanced Materials Letters, 2015, Volume 6, Issue 10, Pages 867-873
DOI: 10.5185/amlett.2015.5858

Heterogeneous photocatalysts offer great potential for converting photon energy into chemical energy for decomposition and destruction of organic contaminants from organic molecules i.e. Rhodamine B (RhB) and p-nitophenol (p-NP) under UV light. The titania based novel MxNbxTi1-2xO2-x/2 (M = Cr, Fe; x = 0.01-0.2) was prepared by tetra and tri-podal amine type binder with iron or chromium support using sol–gel method followed by calcination at 150 o C in an auto generated pressure. The photodegradation performance of the optimized catalyst was compared with synthesized nano-compositions, P-25 titania with RhB and p-NP. The particle sizes, surface area, mesopore sizes of CrxNbxTi1-2xO2-x/2 (x = 0.01) (CNT1) and FexNbxTi1-2xO2-x/2 (x = 0.01) (FNT1) are 12±1 and 10±2 nm, SBET=162 and 145 m 2 g −1 , 4.9 and 4-5 nm, respectively. The energy band gap of CNT1, FNT1 and NT was found to be 1.85, 2.06 and 2.1 eV, respectively. The importance of CNT1 powders is that it shows good photocatalytic activity for the degradation of Rhodamine B (RhB) within only 180 min and the importance of FNT1 powders is that it reduces the p-NP to p-aminophenol using a little bit of NaBH4 (0.054 g) within 10 min as compared to pure anatase TiO2 and other compositions of MxNbxTi1-2xO2-x/2 (M = Cr, Fe).

SHI Induced Thermoluminescence Properties Of  sol-gel Derived Y2O3:Er3+ Nanophosphor

N.J. Shivaramu; B.N. Lakshminarasappa; K.R. Nagabhushana; Fouran Singh

Advanced Materials Letters, 2015, Volume 6, Issue 4, Pages 342-347
DOI: 10.5185/amlett.2015.5713

Nanocrystalline erbium doped yttrium oxide (Y2O3:Er 3+ ) was synthesized by the sol-gel technique using citric acid as complexing agent. The synthesized samples were characterized by X-ray diffraction (XRD), Field emission scanning electron microscope (FE-SEM) techniques for phase-purity and microstructure. Er 3+ doped Y2O3 crystallizes in cubic phase with an average crystallite size of 24.3 nm. The pellets of Y2O3:Er 3+ were irradiated with 100 MeV swift Si 8+ ions with fluence in the range of 3×10 11 - 3×10 13 ions cm -2 .  Three well resolved thermoluminescence (TL) glows with peaks at ~422, 525 and 620 K were observed in Er 3+ doped Y2O3 samples. It was observed that the TL intensity was found to increases with increasing Er 3+ concentration up to 0.4 mol% in Y2O3 and thereafter it decreases with further increase of Er 3+ concentration. Also, the intensity of low temperature TL glow peak (~422 K) increases with increasing ion fluence up to 1×10 12 ions cm -2 and decreases with further increase of ion fluences. The TL trap parameters were calculated by glow curve shape method and the deconvoluted glows were exhibit of second order kinetics.

Structural, Dielectric And Magnetic Properties Of Nanocrystalline BaFe12O19 Hexaferrite Processed Via Sol-gel Technique

Virender P. Singh; Gagan Kumar; Pooja Dhiman; R. K. Kotnala; Jyoti Shah; Khalid M. Batoo; M. Singh

Advanced Materials Letters, 2014, Volume 5, Issue 8, Pages 447-452
DOI: 10.5185/amlett.2014.554

In the present work BaFe12O19 nano-hexaferrite had been synthesized by sol-gel method and then characterized for its structural, electric, dielectric and magnetic properties. X-ray diffraction studies confirmed the hexagonal structure of the prepared nanohexaferrite with no secondary phase and the particle size was found to be of the order of 49 nm. Further, the morphology of the sample has been studied by using transmission electron microscopy (TEM). A high value of the DC resistivity (5.5 × 106 Ω cm), has been obtained at room temperature. The dielectric properties such as dielectric constant (ε′), dielectric loss tangent (tan δ) and ac electrical conductivity (σac) are investigated as a function of frequency. The dielectric constant and loss tangent are found to be decreasing with the increase in frequency while ac electrical conductivity is observed to be increasing with the increase in frequency. The dielectric properties have been explained on the basis of Maxwell-Wagner’s two-layer model and hopping of the charge. The magnetic properties such as initial permeability (µi) and relative loss factor (RLF) have been investigated as a function of frequency in the range 75 kHz to 30 MHz .Fairly constant value of initial permeability and low values of RLF of the order of 10-4 over a wide frequency range are the cardinal achievements of the present work. The room temperature M-H study shows that present nanohexaferrite has high value of coercivity (2151.3 Oe) and high saturation magnetization (32.5 emu/gm), which make present nanohexaferrite very suitable for magnetic applications. The M-T study shows that prepared nano-hexaferrite has high Tc (746 K).

Diastase α-amylase immobilization on sol-gel derived guar gum-gelatin-silica nanohybrid

Vandana Singh; Devendra Singh

Advanced Materials Letters, 2014, Volume 5, Issue 1, Pages 17-23
DOI: 10.5185/amlett.2013.7513

In the present communication, we report on diastase alpha amylase immobilization at guar gum-silica nanohybrid material (H5). The immobilized amylase (H5-Amyl) showed significantly higher bioactivity (21.62 U mg -1 ) as compared to free amylase (15.59 U mg -1 ) in solution at pH 5 and temperature 40°C. The kinetic parameters of the free (Km = 10.66 mg L -1 ; Vmax = 1.36 µmolemL -1 .min -1 ) and the immobilized enzyme (Km = 6.11 mg mL -1 ; Vmax = 1.45 µmolemL -1 .min -1 ) revealed that the immobilization has increased the overall catalytic property of the enzyme. The immobilized enzyme on recycling could show 87% of initial activity even in the sixth cycle. Since immobilization did not hamper the enzymatic reaction rate, the biocatalyst may be suitably exploited in food and pharmaceutical industries.

Synthesis Of Porous Titania And Its Application To Dye-sensitized Solar Cells

Ammar Elsanousi; Kamal Khalifa Taha; Nazar Elamin

Advanced Materials Letters, 2013, Volume 4, Issue 12, Pages 905-909
DOI: 10.5185/amlett.2013.5472

Nanocrystalline porous titania with rutile and anatase bi-phase structure has been fabricated by the sol-gel method without the introduction of any surfactant, using tetrabutile titanate as precursor. The porous material was integrated as an electrode in a dye-sensitized solar cell as an electrode and its photoelectrical parameters were measured. Experimental measurements showed that the cell exhibits higher values of short-circuit current density and overall conversion efficiency compared to P25 (typical commercial titania powder) cells. The overall conversion efficiency of both samples was calculated to be 2.81 and 1.57 for the prepared and commercial (P-25) sample respectively. This drastic increase in the conversion efficiency of the prepared sample was attributed to its high surface area and porous structure, allowing more sensitizer dye to be chemically anchored in the electrode and, as a consequence, improved the light harvesting drastically. These results indicate that it is possible to achieve commendable conversion efficiencies using porous bi-phase titania.

Effect Of Swift Heavy Ion On Structural And Optical Properties Of Undoped And Doped Nanocrystalline Zinc Oxide Films

Vinod Kumar; L. P. Purohit;Fouran Singh; R. G. Singh

Advanced Materials Letters, 2013, Volume 4, Issue 6, Pages 423-427
DOI: 10.5185/amlett.2012.ib.107

Swift heavy ion (SHI) induced modification in structural and optical properties of undoped and doped nanocrystalline (nc) ZnO films deposited by sol-gel method are investigated. These nanocrystalline films were irradiated by MeV ions of Au, Ag and Ni at various ion fluences. The structural properties were studied using X-ray diffraction and it shows that the average crystallite size of ZnO films is observed to increase by the irradiation. The atomic force microscopy (AFM) study of films shows that the roughness of the films varies with increase in the fluence. A maximum transmittance is observed to be 85% in the visible region for doped films. It is also shown that the bandgap of undoped and doped ZnO films is varied using SHI irradiation. The modifications of structural and optical properties are explained in terms of thermal spikes induced by SHIs.

Characterization And Evaluation Of Nano-sized α-Fe2O3 pigments synthesized Using Three Different Carboxylic Acid

M. F. R. Fouda; M. A. Wahba;M. F. El-Shahat; M. B. ElKholy; S. A. Mostafa; A. I. Hussien

Advanced Materials Letters, 2013, Volume 4, Issue 5, Pages 347-353
DOI: 10.5185/amlett.2012.9421

AnchorUniform α-Fe2O3 nanoparticles have been prepared by sol gel method using three different carboxylic acids citric, tartaric and succinic acids as chelating agents. The structure and morphology of α-Fe2O3 samples were characterized using (TGA), (XRD), (TEM), (IR) and diffuse reflectance spectroscopy (DRS) techniques. The TEM images revealed that in all cases, the products consisted of 18–25 nm sized particles close to the average crystallite size calculated from XRD data by the Scherrer’s formula. Among the prepared samples, the sample that has the best thermal stability, the smallest particle size and the reddest color is that prepared in presence of tartaric acid. The prepared samples were evaluated as pigments according to the American Society for Testing and Materials (ASTM) standard methods for evaluation of pigments.

Microstructure And Photo-catalytic Dye Degradation Of Silver- Silica Nano Composites Synthesised By Sol-gel Method

Surender Duhan; B.S. Dehiya;Vijay Tomer

Advanced Materials Letters, 2013, Volume 4, Issue 4, Pages 317-322
DOI: 10.5185/amlett.2012.8414

Sol–gel chemistry has recently attracted a large attention with a view of preparation of silver-silica nano-composites for photo-catalytic applications. This method of synthesis allows glassy materials to be prepared at a much lower temperature than the traditional melt-glass techniques. Moreover, it enables higher doping concentrations and a more uniform distribution of silver in the glass host matrix to be achieved. This method produces large quantities of amorphous gels that are thermal treated in air at the temperature of 500°C for one hour. The silver-silica samples were investigated through X-ray diffraction (XRD for the determination of their microstructure, phase and compositions. It is found that the microstructure depends closely on the solution pH and the extent of silver-doping. MB dye degradation by undoped and Ag doped SiO2 was studied under UV and Visible light irradiation. The results are intriguing as the doping by Ag produces opposite effects on photocatalytic degradation rates under the two conditions.

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.

Neodymia-silica Nanocomposites: Sythesis and Structural Properties

Saruchi Surbhi; Praveen Aghamkar; Sushil Kumar

Advanced Materials Letters, 2013, Volume 4, Issue 1, Pages 78-81
DOI: 10.5185/amlett.2013.icnano.109

Nanomaterials and nanostructures have received steadily growing interests as a result of their peculiar and fascinating properties and applications. Neodymia-silica nanocomposites were prepared by sol-gel route followed by calcination. The samples were prepared with different concentration of dopant (Nd2O3) and calcined in a programmable furnace at 1000 °C for 5 h. The structural evolution of samples was investigated by employing techniques such as XRD, FTIR and TEM. X-ray diffraction patterns showed that the samples were nanocrystalline and the size of crystallites has been determined using Debye-Scherrer relation. The FTIR spectra confirmed the presence of functional groups of prepared material. The particle size of samples was also estimated through TEM analysis. It has been observed that crystallinity as well as particle size of the samples increases with increase in dopant concentration.

Co And Fe Doped SnO2 nanorods By Ce Co-doping And Their Electrical And Magnetic Properties

Jasneet Kaur; Jaspreet Kaur; R. K. Kotnala; Vinay Gupta; Kuldeep Chand Verma

Advanced Materials Letters, 2012, Volume 3, Issue 6, Pages 511-514
DOI: 10.5185/amlett.2012.icnano.142

In the present work, the self-assembly of Co 2+ and Fe 3+ doped SnO2 nanoparticles (Co and Fe = 5 mol% each) into nanorods by co-doping of Ce 3+ (4 mol%) ions is studied. The nanorods are prepared by a chemical route using polyvinyl alcohol as surfactant with the composition Sn0.91Co0.05Ce0.04O2 (SCC54) and Sn0.91Fe0.05Ce0.04O2 (SFC54). The X-ray diffraction (XRD), transmission electron microscopy (TEM), magnetic and electrical measurements are used to characterize these nanorods. The XRD pattern show the tetragonal rutile and polycrystalline nature of SnO2 nanorods which is also confirmed by TEM. The TEM images exhibit that the diameter of SCC54 nanorods lie in the range of 15-20 nm, length~100-200 nm whereas for SFC54 specimen, diameter ~5-15 nm and length ~50-100 nm. In our previous work, we fabricated Co and Fe (3 and 5 mol% each) doped SnO2 nanoparticles which exhibited high ferromagnetism. It is observed that on Ce 3+ co-doping, nanoparticles assembled themselves into rod like structures and the values of saturation magnetization and dielectric properties have further enhanced. Thus the nature and the concentration of dopants are found to play crucial role in tuning the morphology, magnetic and electrical properties of nanostructures. The values of saturated magnetization (Ms) are 1.14 and 0.14 emu/g and coercive field are 112 and 42 Oe, in SCC54 and SFC54 specimen, respectively, at room temperature. The variation in dielectric behavior is attributed due to the interface polarization. However, in lower frequency regime, the decreasing trend of dielectric permittivity with increasing frequency is explained by the Maxwell-Wagner theory and Koops’ model, whereas, in higher frequency region, the resonant behavior is observed due to nano size effect.

Low Temperature Synthesis And Magneto Resistance Study Of Nano La1-xSrxMnO3 (x = 0.3, 0.33, And 0.4) Perovskites

Maneesha Gupta; Poonam Yadav; Wasi Khan; Ameer Azam; Alim H. Naqvi; R. K. Kotnala

Advanced Materials Letters, 2012, Volume 3, Issue 3, Pages 220-225
DOI: 10.5185/amlett.2012.1309

We have synthesized La1-xSrxMnO3 (with x=0.3, 0.33 & 0.4) perovskite nanoparticles using mild sol-gel technique at low temperature and thereby studied the effect of nanosize on magnetoresistance. These samples were characterized using TGA/DSC, XRD, TEM, FTIR and temperature dependent magnetoresistance (MR) measurements. Powder X-ray diffraction (XRD) result confirms the formation of pure crystalline phase with rhombohedral symmetry in R-3C space group. Crystallite size increases with increase in Sr concentration. TEM analysis further supports the nanosized particles in the samples which lie in the range of 20-30 nm. Fourier transform infrared (FTIR) spectroscopy shows a broad peak at 615 cm -1 for all the samples gives an evidence for the formation of metal oxygen bond organized in to MnO6 octahedral. The steep change in magnetoresistance (MR) at low field at low temperature is observed which is attributed to the alignment of the spins, while in the high field MR is due to the grain boundaries effect at low temperature. In the series studied, 33% Sr doped sample shows higher MR both at low temperature (-17.15) and room temperature (-3.07) than their counter parts.

Citrate–nitrate Derived Sr0.5Ba0.5Ta2O6 Tetragonal Tungsten Bronze Nanorods: Investigation Of Their Optical And Dielectric Properties

Yogesh Kumar Sharma; Krishna Kumar; Chandrashekhar Sharma; R. Nagarajan

Advanced Materials Letters, 2012, Volume 3, Issue 2, Pages 118-125
DOI: 10.5185/amlett.2011.6278

First time novel complex strontium barium tantalate, Sr0.5Ba0.5Ta2O6 was successfully synthesized in 1D structure (nanorods) by citrate-nitrate gel route. Their structural properties were examined via X-ray diffractometry (XRD) and revealed the formation of tetragonal tungsten bronze (TTB) structure at as low as 1100ºC. Also, FT-IR, FT-Raman, UV-vis, SEM, TEM and PL were used to identify the structure and properties of powders. Well isolated nanorods of the average diameter of ~200nm can be fabricated by this route. PL spectrum showed strong and broad visible emission band around 439nm due to particles with little surface defects. The frequency dependent dielectric dispersion of SBT50 powders sintered at 1300°C/4 h was investigated in a frequency range from 1 kHz-1MHz and at different temperatures (25°C- 450°C). It is observed that: (i) the dielectric constant (ε') and loss tangent (tan δ) are dependent on frequency, (ii) the temperature of dielectric constant maximum shift toward lower temperature side and the maximum dielectric constant (ε) was observed to be 2400 at 1 kHz. The Tc was found to be ~444-449°C and ferroelectric relaxor or diffuse phase transition like behavior was observed at around 449°C.

Sol-gel Processing and characterization Of nanometersized (Ba, Sr) TiO3 ceramics

Kavita Verma; Seema Sharma; Dhananjay K Sharma; Raju Kumar; Radheshyam Rai

Advanced Materials Letters, 2012, Volume 3, Issue 1, Pages 44-49
DOI: 10.5185/amlett.2011.5264

 Ba0.5Sr0.3TiO3 (BST 70/30) nanopowders have been prepared by the modified sol-gel method using barium acetate, strontium acetate and titanium isopropoxide as the precursor. The formation mechanism, phase evolution, and particle size have been investigated using TG/DTA, XRD, and SEM. The fine particles of the nano-powders calcined are homogeneous and well-dispersed and their narrow size distribution is about 15–25 nm. The as-formed gel was dried at 2000 C and then calcined in the temperature range 6500 C to 8500 C for crystallization. Phase evolution during calcination was studied using X-ray diffraction (XRD) technique which exhibited cubic crystal structure with perovskite phase. Sintering of the pellet was performed at 9500 C and the study on the dielectric relaxation and the ac electrical conductivity behavior of modified Barium titanate, Ba0.5Sr0.3TiO3 ferroelectric ceramic exhibit that these are thermally activated process.

Preparation And Characterization Of Molecularly Imprinted SiO2-TiO2 and Photo-catalysis For 2,4-dichlorophenol

Deman Han; Yongmin Li; Wenping Jia

Advanced Materials Letters, 2010, Volume 1, Issue 3, Pages 188-192
DOI: 10.5185/amlett.2010.7137

A novel 2, 4-dichlorophenol imprinted TiO2-SiO2 catalyst was prepared by molecular imprinting technique in combination with sol-gel method. The prepared material was characterized by X-ray diffraction (XRD), infrared spectroscopy (IR), scanning electron-microscopy (SEM), transmission electron microscopy (TEM) and N2 adsorption measurement. The effect of the preparation condition on the degradation behavior, the photo-catalytic ability and selectivity of the prepared material were evaluated. The results show that the imprinted material has good photo-degradation capacity and selectivity toward the target pollutant, which was shown to be promising for selective removal of 2, 4-dichlorophenol from environmental samples.

In-situ Coating Of MWNTs With Solgel TiO2 Nanoparticles

Li Chen; Guangshui Yua;Jianming Zhanga; Xiujiang Pangb

Advanced Materials Letters, 2010, Volume 1, Issue 1, Pages 75-78
DOI: 10.5185/amlett.2010.4117

Multi-walled carbon nanotubes (MWNTs) were in-situ coated with anatase TiO2 via sol-gel process followed by annealing of the composites using infrared (IR) lamp. SEM results showed that MWNTs were coated with 15-45 nm thick TiO2 layer depending on the composite ratios. Based on the XRD results, MWNTs were found to show heterogeneous nucleation for anatase TiO2 and promote the formation of larger anatase TiO2 crystalline particles with higher crystalline degree. The UV-Vis- NIR characterization indicated the MWNTs also enhanced the sensitivity of TiO2 matrix for both UV and visible light, and the bond edge absorption position of the TiO2  composites shifted toward higher wavelengths with the decrease of MWNTs content. The method could be utilized to fabricate MWNTs /TiO2 composites conveniently.

Adsorption Behavior of Potato Starch-silica Nanobiocomposite

Vandana Singha; Sadanand Pandeya;Rashmi Sanghib; Somit Kumar Singha

Advanced Materials Letters, 2010, Volume 1, Issue 1, Pages 40-47
DOI: 10.5185/amlett.2010.4107

In continuation to our recent study on the synthesis and characterization of starch-silica nanocomposite, in the present study the nanocomposite has been evaluated for the removal of Cd(II) from the aqueous solution. The conditions for the sorption have been optimized and kinetic and thermodynamic studies were performed to understand the adsorption behaviour of the composite. Though the cadmium sorption by the nanocomposite takes place in wide pH range, pH 7.5 was found most favorable and at this pH the adsorption equlibrium data were modeled using the Langmuir and Freundlich isotherms at 10°C, 20°C, 30°C and 40°C. At all the temperatures, the data fitted more satisfactorily to Langmuir isotherm indicating unilayer adsorption. Based on Langmuir model, Qmax was calculated to be 769.23 mg/g. The adsorption showed pseudo second order kinetics with a rate constant of 5.65 × 10 -5 g mg -1 min -1 (at 100 mg/L initial Cd(II) concentration) indicating chemisorption. The thermodynamic study revealed the endothermic and spontaneous nature of the adsorption. Effect of electrolyte on the adsorption was also studied. The nanocomposite was sucessfully recycled for six consecutive adsorption-desorption cycles with only a marginal loss in its efficiency indicating its high reusability. The composite was found to be a highly stable photoluminescent Cd(II) adsorbent which may be suitable for sensor applications in detecting the metal ions both in vivo and vitro as the material is natural polymer based.