Keywords : nanostructures


Synthesis, Impedance and Current-Voltage Spectroscopic Characterization of Novel Gadolinium Titanate Nano Structures

Vinayak M Adimule; Debdas Bhowmik; Adarsha Haramballi Jagadeesha

Advanced Materials Letters, 2021, Volume 12, Issue 6, Pages 1-7
DOI: 10.5185/amlett.2021.061638

Gadolinium (Gd) doped titanate nanostructures (NS) with a new set of 10-50 wt. % of Gd were synthesized by microwave-assisted hydrothermal and reduction using hydrazine hydrate. The crystal structure has been evaluated with SEM (scanning electron microscopy) analysis exhibited rod like geometry of nanoparticles (NPs). XRD (X-ray diffraction spectroscopy) analysis of GdTiO3 and undoped titanate nanostructure (NS) intense peak exhibited crystal tetragonal structure. CV (cyclic voltammetry) exhibited an oxidation potential of 50 wt. % of GdTiO3 was found to be - 0.54 eV. UV-Visible spectroscopic revealed absorptivity of 50 wt. % of GdTiO3 was found to be 650 nm (visible region) and undoped titanate absorptivity at 320 nm (UV region). The pelletized nanostructures of GdTiO3 were investigated for current-voltage (I-V), capacitance-voltage (C-V), resistance-voltage (R-V) measurements, which showed frequency range in between 1 kHz to 2 MHz and 50 wt. % GdTiO3 NS showed a decreasing trend in admittance value with an increase in frequency. However, an increase in the conductance, power dissipation values with a decrease in resistivity, and increase in the frequency has been noticed which embark considerable variation in conductivity and power dissipation in GdTiO3 NS. The results from the plots of current-voltage (I-V), capacitance-voltage (C-V), and bias voltage with an applied frequency of the GdTiO3 NS has been discussed.

Synthesis of Rod-coil Molecules bearing Oligo-Phenylene Vinylene Motifs: Effect of PEO Chain Lengths on the Evolution of Nanostructures Morphology and their Photophysical Properties

Chetan J. Bhongale; Rahul Chaudhari;Yashwant Pandit

Advanced Materials Letters, 2019, Volume 10, Issue 10, Pages 731-736
DOI: 10.5185/amlett.2019.0024

The applications of nano-dispersed organic conjugated active compounds or materials as well as current research is concerned mainly with optimization and control of the optical properties, by particle size and supramolecular structure of the particles. The aromatic macromolecules consisting of conjugated rigid rod segment and hydrophilic flexible chain as coil in aqueous solution can aggregate into a variety of supramolecular structures through mutual interaction between aromatic rod and hydrophilic chains of molecules and water. Here we report the synthesis of newer oligo phenylene vinylene (OPV) based rod-coil molecules with varying chain-length polyethylene oxide (PEO) repeating units (n = 8, 17, 45). Formation and photophysical properties of their nanostructures in water are studied comparatively. The nanostructures evolution of these molecules is observed with simple reprecipitation method. The stable nanostructures were formed without addition of any surfactants. The fabricated nanostructures ultimately give the materials with ‘controlled’ aggregation induced enhanced photophysical properties. The self-assembly of such OPV type rod molecules in water without adding any surfactants, therefore, can provide a strategy for the construction of well-defined and stable nanostructures with certain chemical functionalities and physical properties as advanced materials for photonic, electronic and biological applications. Copyright © VBRI Press.

Pulsed-injection metal organic chemical vapour deposition for the development of copper silicate and silicide nanostructures   

Richard. O

Advanced Materials Letters, 2017, Volume 8, Issue 8, Pages 830-840
DOI: 10.5185/amlett.2017.1465

In this manuscript we report the production of copper silicate and silicide nanostructures: octahedral o-Cu(SiO3), wire w-Cu(SiO3) and wire w-Cu3Si (embedded in silicate shell) using copper bis(2,2,6,6-tetramethyl-3,5-heptanedionate) [Cu(tmhd)2] precursor and the pulsed injection metal organic chemical vapour deposition (PI-MOCVD) technique. In our experiments, particular attention has been paid to the structural composition and morphological analysis of the nanostructures which are dictated by the deposition parameters such as deposition temperature, carrier gas flow rate and injection time. Deposition processes were diffusion limited and various methods were used to show that by changing the amount of stress relaxation via the reaction time, concentration and flow rate, w-Cu(SiO3) and w-Cu3Si could be made to evolve. Nanostructures have been characterised by x-ray diffraction (XRD), Raman, scanning tunneling electron microscopy (STEM) and atomic force microscopy (AFM) techniques. It was found that the presence of oxygen (SiO2) in the silicon substrates and exposure of the nanostructures to ambient conditions results in the formation of copper silicate from initially produced copper silicide nanomaterials. This work outlines the potential for the manufacturing of various patterned copper nanostructures via PI-MOCVD. 

Synthesis of nanostructured TiO2 thin films with highly enhanced photocatalytic activity by atom beam sputtering

Jaspal Singh; Kavita Sahu; Sini Kuriakose; Nishant Tripathi; D. K. Avasthi; Satyabrata Mohapatra

Advanced Materials Letters, 2017, Volume 8, Issue 2, Pages 107-113
DOI: 10.5185/amlett.2017.6432

Nanostructured TiO2 thin films with highly enhanced photocatalytic activity were prepared by atom beam sputtering technique. The effects of thermal annealing on the structural, morphological and photocatalytic properties of TiO2 thin films were investigated using X-ray diffraction, atomic force microscopy, field emission scanning electron microscopy, Raman spectroscopy and UV-visible absorption spectroscopy. X-ray diffraction studies showed that the as-deposited TiO2 thin films made up of anatase TiO2 nanoparticles transformed into anatase/ rutile mixed-phase TiO2 nanoparticles upon annealing. Field emission scanning electron microscopy and atomic force microscopy studies revealed growth of TiO2 nanoparticles from 16 nm to 29 nm upon annealing at 600  o C. The photocatalytic activities of the nanostructured TiO2 thin films were studied by monitoring photocatalytic degradation of methylene blue in water. Our results showed that the as-deposited nanostructured TiO2 thin films exhibited highly enhanced photocatalytic efficiency as compared to the annealed samples. The mechanism underlying the enhanced photocatalytic activity of nanostructured TiO2 thin film is tentatively proposed.

Effects Of Solvent On Structural, Optical And Photocatalytic Properties Of ZnO Nanostructures

Sini Kuriakose; Biswarup Satpati; Satyabrata Mohapatra

Advanced Materials Letters, 2015, Volume 6, Issue 12, Pages 1104-1110
DOI: 10.5185/amlett.2015.6088

ZnO nanostructures were synthesized by a facile wet chemical method using water, ethanol and propanol as solvents. X-ray diffraction, field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) have been used to study the structural properties of the synthesized ZnO nanostructures, while their optical properties have been studied using UV-visible absorption spectroscopy and Raman spectroscopy. The photocatalytic activities of the as-synthesized ZnO nanostructures were evaluated by monitoring sunlight driven photocatalytic degradation of methylene blue (MB) and methyl orange (MO) dyes in water and it was observed that ZnO nanostructures prepared using propanol as a solvent exhibit highly enhanced photocatalytic activity as compared to those prepared using other solvents. The mechanism underlying the photocatalytic activity of ZnO nanostructures towards photocatalytic degradation of dyes is proposed. We attribute the highly enhanced photocatalytic activity of ZnO nanostructures prepared in propanol to the high surface area of nanosheets-like structures formed, which lead to enhanced adsorption of dye molecules resulting in efficient photocatalytic degradation of dyes upon sunlight irradiation.

Thermal Evolution Of Structural, Optical And Photocatalytic Properties Of TiO2 Nanostructures

Jaspal Singh; Satyabrata Mohapatra

Advanced Materials Letters, 2015, Volume 6, Issue 10, Pages 924-929
DOI: 10.5185/amlett.2015.6000

Nanostructures of TiO2 were synthesized by a facile sol-gel method using pentanol as solvent. The effects of thermal annealing on the structural, optical and photocatalytic properties of as-synthesized TiO2 nanostructures have been studied using X-ray diffraction (XRD), atomic force microscopy (AFM), Raman spectroscopy and UV-visible absorption spectroscopy. XRD and Raman spectroscopy results revealed that the synthesized TiO2 nanostructures exist in anatase phase for annealing at temperatures up to 300 o C, while annealing at 600 o C led to the formation of TiO2 nanostructures in anatase/rutile mixed-phase. AFM studies revealed the presence of TiO2 nanorods, which showed a small decrease in aspect ratio upon annealing. The photocatalytic activity of nanostructured TiO2 samples was evaluated through sun light driven degradation of methylene blue (MB) dye in water. TiO2 nanorods in anatase/rutile mixed-phase in the sample annealed at 600 o C were found to exhibit the highest photocatalytic activity towards degradation of MB dye. The mechanism underlying the enhanced photocatalytic activity of TiO2 nanostructures in anatase/rutile mixed-phase is tentatively proposed.

Multiferroic Properties In Nanostructured Multilayered Magnetic Semiconductor Bi0.9La0.1Fe0.9Co0.1O3-BiFeO3 Thin Films

V. Annapu Reddy; Navneet Dabra; K. K. Ashish; Jasbir S. Hundal; N. P. Pathak; R. Nath

Advanced Materials Letters, 2015, Volume 6, Issue 8, Pages 678-683
DOI: 10.5185/amlett.2015.5802

Multilayers with nanostructured thin films of Bi0.9La0.1Fe0.9Co0.1O3-BiFeO3 (BLFCO-BFO) were grown on Zn0.91Mn0.09O (ZMO) buffered Si (100) substrate by chemical solution deposition. Structural analysis indicates that rhombohedral crystal structure of BFO, changes to orthorhombic for BLFCO film. Increased ferroelectric saturation and reduced leakage current were obtained for bi-layered and four-layered thin films and are compared with those of BFO and BLFCO thin films.Improvement in ferroelectric properties, as well as induced ferromagnetism was enhanced for four-layered thin films than two-layered thin films. The interface coupling and interaction between the thin layers has led to the resultant improvements. Highly enhanced ferroelectric fatigue properties are observed in these multilayer films up to 10 8 switching cycles.

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.

 Shape Control Synthesis, Characterizations, Mechanisms And Optical Properties Of Larg Scaled Metal oxide Nanostructures Of ZnO And TiO2

Rajni Verma; Bhanu Mantri; Avanish Kumar Srivastava

Advanced Materials Letters, 2015, Volume 6, Issue 4, Pages 324-333
DOI: 10.5185/amlett.2015.5661

In the present study, ZnO and TiO2 nanostructures of different size have been synthesized in high yield with excellent repeatability by simple, economical and environmentally benign chemical route. ZnO quantum dots and nanorods of tuned aspect ratio were evolved by optimising the reaction conditions such as by varying solvent composition, precursor concentration and by using different additives. On the other hand, the synthesis of brookite, the rare phase, anatase and rutile, the stable phases of TiO2 were also achieved by just varying the annealing temperature from 400 to 615 °C.  The obtained nanostructures were rationalized by various characterization techniques such as XRD, FTIR, Raman, SEM, HR- TEM, UV-Vis and PL. The Phase formation and structure determination were identified by using XRD, FTIR and Raman Spectra, SEM and HR-TEM were performed to determine the morphology and particle size. The aspect ratio was calculated to be in the range of 3.2-9.4 in case of ZnO NRs, and particle size was found to be 2-5 nm for ZnO QDs of wurtzite phase and ~ 10 nm for TiO2 (anatase phase) NPs, respectively. The UV-Vis optical absorption spectrum demonstrates the band gap value of 3.60, 4.02 and 3.40 eV for ZnO NRs, QDs and TiO2 NPs respectively. The UV-Vis optical absorption spectrum demonstrates the band gap and room temperature PL spectra illustrates about the various defects present in the sample. Various chemical reactions and mechanism involved in producing these nanostructures are dealt in detail. The future prospective of these metal oxide nanostructures lie in photocatalysis, sensors and biomedical applications.

Structural And Optical Study Of MeV Cobalt Ion Implanted Silicon

Pramita Mishra; Vanaraj Solanki; Ashutosh Rath; Soumee Chakraborty; Himanshu Lohani; Pratap K. Sahoo; Biju Raja Sekhar

Advanced Materials Letters, 2014, Volume 5, Issue 12, Pages 699-705
DOI: 10.5185/amlett.2014.nib503

We report the optical tunability through defect states created in silicon by 1 MeV cobalt ion implantation at room temperature in the fluence range of 5 × 10 13 to 5 × 10 15 ions cm -2 . Atomic force microscopy studies reveal the surface nanostructures with maximum roughness of 0.9 nm at a critical fluence of 5 × 10 15 ions cm-2 which is reduced to 0.148 nm with further increase of fluence. The enhanced native oxide layers after Co ion implantation observed from X-Ray photoelectron spectroscopy studies confirm the presence of surface defects. The combined effect of nanostructures formation and amorphization leads to band gap tailoring. For low fluence, the nanostructures produced on the surface result in an enhanced absorption in the entire UV-Visible region with a simultaneous reduction in band gap of 0.2 eV in comparison to pristine Si whereas high fluence implantation results in interference fringes which signifies the enhancement in refractive index of the top implanted layer ensuing increase in band gap of 0.3 eV. Combined amorphous and crystalline phases of nanostructured surface with tunable optical absorption may have potential applications in solar cell, photovoltaics and optical sensors.

SHI Irradiation Induced Amorphization Of Nanocrystalline Tin Oxide Thin Film At Low Temperature

R.S. Chauhan; Vijay Kumar; Anshul Jain; Deepti Pratap; D.C. Agarwal; R.J. Chaudhary; Ambuj Tripathi

Advanced Materials Letters, 2014, Volume 5, Issue 11, Pages 666-670
DOI: 10.5185/amlett.2014.nib501

Nanocrystalline tin oxide (SnO2) thin films were fabricated using pulsed laser deposition (PLD) technique. The as-deposited films were irradiated at liquid nitrogen (LN2) temperature using 100 MeV Ag ions at different fluences ranging from 3×10 13 to 3×1014 ions/cm 2 and at 75o with respect to surface normal. Pristine and irradiated samples were characterized using XRD, AFM, Raman and I-V (current-voltage characteristics) for the study of modifications in structural, surface morphological, bond angle and resistivity respectively. XRD patterns show that the pristine film is highly polycrystalline and irradiation amorphizes the film systematically with increasing the irradiation fluence. The surface of the pristine film contains nanograins of tin oxide with roughness 5.2 nm. Upon irradiation at lower fluences agglomeration is seen and roughness increased to 10.8 nm. Highest fluence irradiation again develops nanograins with roughness 7.5 nm. Raman spectra and I-V characteristics also confirms the irradiation induced amorphization. The observed results are explained in the frame work of thermal spike model.

State-of-the-art Of Chemically Grown Vanadium Pentoxide Nanostructures With Enhanced Electrochemical Properties

Dimitra Vernardou

Advanced Materials Letters, 2013, Volume 4, Issue 11, Pages 798-810
DOI: 10.5185/amlett.2013.5485

This review begins by the principles that describe the intercalation properties of vanadium pentoxide. Recent developments in the chemical synthesis of vanadium pentoxide nanostructures including nanorod and nanotube arrays, nanowires, anhydrous and hydrous nanorolls and nanobelts, nanoribbons, nanocables and gels are examined. The objective of this review is to demonstrate the use of these nanostructures as cathodes for lithium batteries and electrochromics with high storage capacity and rate performance due to the large surface area and short distance for charge transport compared to the thin film cathodes.

A Convenient Route To Synthesize Hexagonal Pillar Shaped ZnO nanoneedles Via CTAB Surfactant

K. Kaviyarasu; Prem Anand Devarajan

Advanced Materials Letters, 2013, Volume 4, Issue 7, Pages 582-585
DOI: 10.5185/amlett.2012.10443

In this work we report the successful formation of hexagonal pillar shaped ZnO nanoneedles with high yield and by using simple cheap method with CTAB as the surfactant. SEM and TEM microscopic observation revealed that the ZnO nanorods were smooth and uniform throughout their length and the functional groups in the molecule were identified by FTIR analysis. PL properties of ZnO nannorods were found to be dependent on the growth condition and the resultant morphology revealed that ZnO nanorods were highly transparent in the visible region.

Modification Of Nanocrystalline RF Sputtered Tin Oxide Thin Film Using SHI Irradiation

Vijay Kumara; Anshul Jaina; Deepti Pratapa; D.C. Agarwalb; I. Sulaniab; V. V. Siva Kumarb; A. Tripathib; S. Varmac; R.S. Chauhan

Advanced Materials Letters, 2013, Volume 4, Issue 6, Pages 428-432
DOI: 10.5185/amlett.2012.ib.108

Nano crystalline tin oxide thin films were deposited on Si and quartz substrates using R. F. magnetron sputtering technique. A set of films was annealed in oxygen environment. These as-deposited and annealed films were irradiated using 100 MeV Ag ions at different fluences ranging from 3×10 11 to 3×10 13 ions/cm 2 . The structural, optical and surface morphological properties of films were studied using X-ray diffraction (XRD), UV-Vis spectroscopy, and atomic force microscopy (AFM) techniques. As deposited films showed the polycrystalline nature and annealing enhances the crystallinity along a particular plane. Upon irradiation at lower fluences up to 3×1012 ions/cm 2 , reduction in crystallinity is observed but at highest fluence 1×10 13 ions/cm 2 a small increase in crystallinity occurs as inferred from XRD spectra. UV-Vis study showed red shift at the lower fluences and blue shift at higher fluences. The pristine film, as observed in AFM micrograph, has randomly distributed surface nano structures with broader size distribution. Irradiation induces the formation of regular shape structures with narrow size distribution. These results may be attributed to the energy deposited by swift heavy ions in the film.

Doping Sensitive Optical Scattering In Zinc Oxide Nanostructured films For Solar Cells

Ratheesh R. Thankalekshmi; Samwad Dixit; A. C. Rastogi

Advanced Materials Letters, 2013, Volume 4, Issue 1, Pages 9-14
DOI: 10.5185/amlett.2013.icnano.137

The nanostructured ZnO thin films are used in solar cells as heterojunction window layer as well as to enhance the junction area. Nanostructures also offer advantage of light scattering property to transmit more light into the absorber layer of solar cells. The optical and light scattering property of the nanostructured ZnO thin films doped with Al and Cu have been studied. The homogeneously doped ZnO nanostructured films were synthesized by a flux sublimation technique at ~ 300°C temperature. The structural studies show hexagonal nanocrystal growth in Al doped ZnO film and nanowire structure in Cu doped ZnO film. These doped ZnO films consistently showed two direct band gaps. The low energy band gap of Al and Cu- doped ZnO films originates from the macroscopic structural feature in the film, and the higher energy band gap due to the quantum confinement of nanostructure clusters in the film. Increased transmission in the lower wavelength region is caused by the forward light scattering by the nanostructure. Simulation of the optical absorption spectra of the Al and Cu- doped ZnO films using the modified Mie scattering theory shows consistent match with the experimental absorption spectra. The results show that increased forward scattering of light could be harvested by increasing the nanoparticle density which will enhance the photocurrent generation from the thin film solar cells by using doped ZnO nanostructured film as a window layer or as a transparent conducting electrode.

Calculation Of Lattice Thermal Conductivity Of Suspended GaAs nanobeams: Effect Of Size Dependent Parameters

S. M. Mamand; M. S. Omar; A. J. Muhammed

Advanced Materials Letters, 2012, Volume 3, Issue 6, Pages 449-458
DOI: 10.5185/amlett.2012.icnano.102

Theoretical calculations of the magnitude and temperature variation of the measured thermal conductivity of undoped and doped GaAs nanobeams will present. The calculations have been performed by employing modified Callaway’s theoretical model. In the model, both longitudinal and transverse modes are explicitly taken into account. Scattering of phonons is assumed to be by nanobeam boundaries, imperfections, dislocations, electrons, and other phonons via both normal and Umklapp processes. A method is used to calculate the Debye temperature and phonon group velocities for undoped and doped nanobeams from their related melting points. Phonon confinement and size effects as well as the role of dislocation in limiting thermal conductivity are investigated. The drop in thermal conductivity of doped nanobeams compared to that of the undoped beams arises from electron-phonon scattering and additional phonon scattering from a large number of point impurities due to the presence of dopant atoms. Effect of Gruneisen parameter, surface roughness, and dislocations are successfully used to correlate the calculated values of lattice thermal conductivity to that of the experimentally measured curves.

Nanaostructured ZnO, ZnO-TiO2 And ZnO-Nb2O5 As Solid State Humidity Sensor

Richa Srivastava;B. C. Yadav

Advanced Materials Letters, 2012, Volume 3, Issue 3, Pages 197-203
DOI: 10.5185/amlett.2012.4330

Present paper deals with a comparative performance of n-type ZnO, ZnO-TiO2 and ZnO-Nb2O5 nanomaterials as humidity sensors. ZnO was synthesized through hydroxide route. TiO2 and then Nb2O5 were used as additives for improvement of sensitivity. Scanning electron micrograph of ZnO shows rod-like particles with average diameter 40 nm. Structural properties by X-Ray diffraction were studied. The minimum crystallite sizes of ZnO-TiO2 and ZnO-Nb2O5 calculated from Scherrer’s formula were found to be 19 and 17 nm respectively. The pellet of each sensing material was annealed at temperatures 150, 300, 450 and 550 ?C for 3 h and checked for its sensing efficiency. Each heat treated pellet was exposed to humidity under controlled condition and variations in resistance with the humidity were recorded. Comparative study of sensitivities of each sensing element was performed. Average sensitivity achieved was 8 MΩ/%RH for the n-type ZnO annealed at 550 ?C. After chemical mixing of TiO2, the sensitivity increased to 18 MΩ/%RH and after Nb2O5, it was found to be 19 MΩ/%RH. Activation energy of electrical transport and Kelvin radii of each sensing elements were also studied.

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.

Silver nanoparticles: preparation, characterization, and kinetics

Javed Ijaz Hussain; Sunil Kumar; Athar Adil Hashmi; Zaheer Khan

Advanced Materials Letters, 2011, Volume 2, Issue 3, Pages 188-194
DOI: 10.5185/amlett.2011.1206

In this paper we report the effect of aniline concentrations on the growth and size of silver nanocrystals using aniline and silver nitrate as reductant and oxidant, respectively. UV-Vis spectroscopy, transmission electron microscopy (TEM) and selected areas electron diffraction (SAED) have been employed to characterize silver nanoparticles. The TEM images show that silver nanocrystals are roughly spherical and of uniform particle size, and the average particle size is ca. 25 nm. A broad surface plasmon resonance band appears at 400 nm. The rings patterns are in good agreement with the standard values of the face-centered-cubic form of silver nanocrystals. This is attributed to the adsorption of aniline and /or interparticle interaction onto the surface of Ag-nanocrystals through electrostatic interactions between the lone-pairs electrons of –NH2 and positive surface of Ag- nanoparticles.

Shape selective growth of ZnO nanostructures: spectral and electrochemical response

A. K. Srivastava; M. Deepa; K. N. Sood; E. Erdem; R. A. Eichel

Advanced Materials Letters, 2011, Volume 2, Issue 2, Pages 142-147
DOI: 10.5185/amlett.2011.1201

Novel growth morphologies of sharp needle-shaped tetrapods and coexistent tetrapods and nanowires of ZnO have been prepared by sublimation of pure Zn utilizing a simple solid – catalyst free - vapor mechanism at the temperatures of 950 and 1100 ºC respectively. These striking differences in these microscopic objects, which evolved at two different process temperatures, were deduced from electron paramagnetic resonance and Raman spectra thereby revealing the role of microstructures, defects and oxygen vacancies in ZnO at lattice scale, which are receptive for luminescence, and electrochemical activity of this functional oxide.