Volume 4, Issue 7, July 2013

State-of-the-art Of Stimuli-responsive Materials

Ashutosh Tiwari

Advanced Materials Letters, 2013, Volume 4, Issue 7, Pages 507-507
DOI: 10.5185/amlett.2013.7001

Stimuli-responsive materials are widespread demand among researchers, customize them via chemistry which trigger to induce conformational changes in structures or to take advantage in the form of structural/molecular pedals. The size and dimension oriented materials are being formulated to sense precise environmental changes and can adjust in a predictable manner to make them effective tool for cutting-edge technology. A significant change in the size, structure and properties can be induced by a slight induction of stimulus due to changes in pH, ionic strength, temperature, light or other triggers. The responsive materials can be categorised on the basis of their responsive behaviours during the stimuli for example piezoelectric materials- a swift, linear shape change of materials in response to an electric field and find potential applications in the actuators; electrostrictive and magnetostrictive materials- change in materials size with response to either an electric or magnetic field, and conversely, producing a voltage during stretch and show promising applications for manufacturing of pumps and valves, aerospace wind tunnel, shock tube instrumentation, landing gear hydraulics, and further biomechanics force measurement of ortho-pedic gait and posturography, sports, ergonomics, neurology, cardiology and rehabilitation; rheological materials- electrorheological and magnetorheological fluids that can change state instantly using an electric or magnetic field and uses in vehicle seats, shock absorbers, exercise equipment, and optical finishing; thermo-responsive materials- the materials leading the change in shape with response to heat and/or cold and applicable in couplers, thermostats, automobile, plane and helicopter parts; pH-sensitive materials- materials change colours as a function of pH and promise in paints; electrochromic materials- material to change optical properties by applied voltage and can be used as antistatic layers, electrochrome layers in liquid crystal displays, and cathodes in lithium batteries; responsive gels- reply in term of shrinking or swelling of materials and can be programmed to absorb or release fluids with response to chemical or physical stimulus and applications in agriculture, food, drug delivery, prostheses, cosmetics, and chemical processing.

Recent Advancements On Warfare Agents/metal Oxides Surface Chemistry And Their Simulation Study

Neha Sharma;Rita Kakkar

Advanced Materials Letters, 2013, Volume 4, Issue 7, Pages 508-521
DOI: 10.5185/amlett.2012.12493

Chemical warfare agents (CWA) have been used in the World Wars and in terrorist attacks, and hence there is an urgent need to find means of their decontamination. Metal oxides offer a rapid means of their disposal, since they contain reactive Lewis acid and basic sites, on which adsorption of the CWA, and subsequent hydrolysis, can take place. Destructive adsorption of CWA on metal oxides yields non-toxic products. Nanoscale metal oxides display enhanced reactive properties toward warfare agents due to their high surface area, large number of highly reactive edges, corner defect sites, unusual lattice planes and high surface to volume ratio. Both experimental and theoretical studies have established that decomposition of nerve agents is facilitated on nanoscale Al2O3, MgO, CaO, TiO2, ZnO and small edge and corner clay mineral fragments. Compared to sulfur mustard, nerve agents are more potent. We first briefly describe their mode of action. Many experimental and theoretical studies have been performed to study their decomposition on various metal oxide surfaces, such as MgO, CaO, Al2O3, TiO2, V2O5, and clay minerals. The results of these studies are reviewed here. Photochemical degradation on TiO2 nanosurfaces has also yielded promising results. Because of the toxicity and risk involved, experimental studies have been mostly confined to the benign simulants, whereas theoretical studies have attempted to compare the real agents with their mimics. These studies establish a qualitative correlation between the G-agents and their simulant DMMP, and, hence, decomposition on metal oxide surfaces can be analyzed by observing the surface chemistry of DMMP on a wide variety of metal oxide surfaces. This review attempts to compile the literature concerning CWA and their simulants.

Ferrolectric Nanofibers: Principle, Processing And Applications

Seema Sharma

Advanced Materials Letters, 2013, Volume 4, Issue 7, Pages 522-533
DOI: 10.5185/amlett.2012.9426

Nanotechnology is one of the rapidly growing scientific disciplines due to its enormous potential in creating novel materials that have advanced applications. Electrospinning has been found to be a viable technique to produce materials in nanofiber form. Ferroelectric and/or piezoelectric materials in nanofiber and/or nanowire form have been utilized for producing energy harvesting devices, high frequency transducers, implanted biosensors, vibration absorbers and composite force sensors, etc. An in-depth review of research activities on the development of ferroelectric nanofibers, fundamental understanding of the electrospinning process, and properties of nanostructured fibrous materials and their applications is provided in this article. A detailed account on the type of fibers that have been electrospun and their characteristics is also elaborated. It is hoped that the overview article will serve as a good reference tool for nanoscience researchers in ferroelectric materials.

A New Statistical Point Of View To Choose A Better Linear Model For Reactivity And Microstructure Analysis In HEMA/furfuryl Acrylate Copolymerization Process

Gaston Fuentes Estevez; Oscar Valdes Lizama; Dionisio Zaldivar Silva; Lissette Aguero; Issa Katime

Advanced Materials Letters, 2013, Volume 4, Issue 7, Pages 534-542
DOI: 10.5185/amlett.2012.10441

Copolymers of 2–hydroxyethyl methacrylate (E) and furfuryl acrylate (A) were prepared by free radical polymerization in toluene at 80°C using benzoyl peroxide as initiator. Copolymers were analyzed by 1H–NMR in order to calculate the monomer composition in the copolymer. The monomer reactivity ratios were determined by four linear methods, Fineman–Röss, r1 = 1.33/r2 = 0.96; Fineman–Röss inverted, r1 = 1.27/r2 = 0.92; Kelen–Tüdos, r1 = 1.3/r2 = 0.96 and Kelen–Tüdos extended, r1 = 0.9982/r2 = 1.0004. Akaike Information Criterion was used to select the best r1–r2 pair of values. Dyads and triads confirm the average chain and copolymers type and lead to use a mathematical relationship to calculate a new r1–r2 par of values. The new values were r1 = 1.254/r2 = 1.08 from the dyads and r1 = 1.26/r2 = 1.07 from the triads. Other microstructure parameters such as run number (RN = 46.48, X = 1, one A units triads) and Q–e values for A, not reported before (e2 = 0.10 and Q2 = 1.68) were calculated.

Effect Of Al2O3 ceramic Filler On PEG-based Composite Polymer electrolytes For Magnesium Batteries

Anji Reddy Polu;Ranveer Kumar

Advanced Materials Letters, 2013, Volume 4, Issue 7, Pages 543-547
DOI: 10.5185/amlett.2012.9417

Composite polymer electrolyte films consisting of polyethylene glycol (PEG), Mg(CH3COO)2 and Al2O3 particles have been prepared by solution casting technique. The X-ray diffraction patterns of PEG-Mg(CH3COO)2 with Al2O3 ceramic filler, indicates the decrease in the degree of crystallinity with increasing concentration of the filler. The role of ceramic phase is to reduce the melting temperature which is ascertained from the DSC. The effect of ceramic filler on the conductivity of the polymer electrolyte was studied. The maximum ionic conductivity has been observed for 10 wt% of Al2O3 at room temperature (303 K). The transference number data indicated the dominance of ion-type charge transport in these composite polymer electrolytes. Using this (PEG-Mg(CH3COO)2-Al2O3) (85–15–10) electrolyte, solid-state electrochemical cell was fabricated and their discharge profiles were studied under a constant load of 100 kΩ. Several cell profiles associated with this cell were evaluated and are reported.

Green Synthetic Route For The Size Controlled Synthesis Of Biocompatible gold Nanoparticles Using Aqueous Extract Of Garlic (Allium Sativum) 

Lori Rastogi;J. Arunachalam

Advanced Materials Letters, 2013, Volume 4, Issue 7, Pages 548-555
DOI: 10.5185/amlett.2012.11456

A green synthetic approach for the highly stable, size controlled synthesis of gold nanoparticles is being described. The study explores the use of aqueous extract of garlic cloves as reducing/stabilizing agent for the synthesis of gold nanoparticles. The synthesis is achieved by heating the mixture of aqueous garlic extract and HAuCl4 at 95ºC in water bath at pH-10 for 2 hrs. The formation of gold nanoparticles was confirmed from the appearance of pink color and an absorption maximum at 530 nm. Further, extract concentration and type of alkali (NH4OH/NaOH) has been varied to tune the size of nanoparticles. The size of the synthesized gold nanoparticles was found to decrease (56.5 ± 13.6 to 24.7 ± 8.2) with increasing extract concentration (0.5%-1.0%) in the presence of NH4OH. In the presence of NaOH, the synthesis time was reduced to 20 min, with an average particle size of 5.5 ± 2.7. Transmission electron microscopy analysis indicated that non-aggregated gold nanoparticles of various sizes could be synthesized by simple change in reaction conditions. The synthesized gold nanoparticles were found to be pure face centered cubic crystals as suggested by selected area electron diffraction and X-ray diffraction patterns. Fourier transform infrared spectroscopy revealed possible role of S-allyl-cysteine as the major component responsible for reduction of Au 3+ to Au 0 and protein/amino acids as stabilizing agents. The gold nanoparticles were found to have remarkable in vitro stability: showed no sign of aggregation at room temperature storage for a long time (more than 6 months), could resist aggregation in aqueous media with high concentrations of NaCl, in various buffers including: cysteine, histidine, bovine serum albumin and at host of pH ranges. Further, cytotoxicity evaluations on S. cerevisiae have shown non-toxic nature of the synthesized gold nanoparticles up to 100 µM of concentration as assessed by well diffusion and inhibition of colony forming efficiency assay. Ease in size control, high stability and biocompatible nature of garlic extract reduced, stabilized gold nanoparticles suggests that they could be potential candidates for drug delivery applications.

Dielectric Relaxation And Electrical Properties Of ZnO1-xSx nanoparticle dispersed Ferroelectric Mesophase

Dharmendra Pratap Singh; A. C. Pandey;Rajiv Manohar; Swadesh Kumar Gupta

Advanced Materials Letters, 2013, Volume 4, Issue 7, Pages 556-561
DOI: 10.5185/amlett.2012.11463

The ZnO1-xSx, metal oxide nanoparticles (MNPs) have been dispersed in the ferroelectric mesophase (FLC). The electrical properties and dielectric relaxation processes have been studied for the MNPs dispersed FLC system with the variation of frequency and temperature. The dielectric measurements have been carried out in the frequency interval of 1Hz-10MHz to investigate different relaxation processes. Three different relaxation modes have been observed in the case of the pure FLC at frequency 2.5Hz, 20Hz and Goldstone relaxation mode at 200Hz. The addition of MNPs, suppressed the relaxation mode observed at 2.5 Hz for the pure FLC whereas the relaxation mode observed at 20 Hz is shifted to the higher frequency side. The conductivity and the relative permittivity of the pure FLC have also been enhanced by the dispersion of the MNPs. The present investigation establishes the MNPs as an intelligent material to tune the relaxation process and to enhance the conductivity of the materials.

Magnetically Tunable Superparamagnetic Cobalt Doped Iron Oxide Colloidal Nanocluster 

S. Ravi; A. Kartikeyan

Advanced Materials Letters, 2013, Volume 4, Issue 7, Pages 562-566
DOI: 10.5185/amlett.2012.11465

Magnetically tunable colloidal nano clusters (CNC’s) have been fabricated using superparamagnetic cobalt doped iron oxide CNCs for the first time. This has the regular interparticle spacing and strongly diffracts light, which is being controlled by an external field. The size of the nanoclusters varies from 10nm–200nm. It reveals that it can be used for wide magnetic tunability. The response to the magnetic field was studied using reflection spectra by varying field sample distance. This shows good response in the UV and visible region. We obtained eight prominent peaks in the UV region which enhances the prosperity of our CNC’s sensing the UV predominately. Hysteresis behavior shows the presence of superparamagnetic nature, which is promising candidate for drug delivery, bioseperation and magnetic resonance imaging.

An Experimental And Numerical Investigation Of Mechanical Properties Of Glass Fiber Reinforced Epoxy Composites

Satnam Singh; Pardeep Kumar;S.K. Jain

Advanced Materials Letters, 2013, Volume 4, Issue 7, Pages 567-572
DOI: 10.5185/amlett.2012.11475

Composites are one of the most advanced and adaptable engineering materials. The strength of any composite depends upon volume/weight fraction of reinforcement, L/D ratio of fibers, orientation angles and other factors. The present work focuses on determination of mechanical properties of pure epoxy and random oriented glass fiber (mat) reinforced epoxy at 10% and 20% weight fractions of glass fibers. The test specimens were prepared and tested according to ASTM standards. The experimental results revealed that with increase in weight fraction of reinforcement, the tensile strength and flexural strength increased by 14.5 % and 123.65% for 20 % glass reinforced composites over pure epoxy. The numerical results obtained were in good agreement to the experimental results. However increased reinforcement increases the brittleness of material which may results in low impact strength. This study further can be used to optimize the weight fraction of glass fibers, to achieve a combination of strength without compromising the impact strength of composites.

Liquid Petrolium Gas Sensor Based On Nanocrystallite Mg0.6Cd0.4Fe2O4

A. B. Gadkari; T.J. Shinde; P.N. Vasambekar

Advanced Materials Letters, 2013, Volume 4, Issue 7, Pages 573-576
DOI: 10.5185/amlett.2012.10430

The Mg0.6Cd0.4Fe2O4 ferrite powder was synthesized by oxalate co-precipitation method. The crystal structure and surface morphology were examined by XRD, SEM and FT-IR techniques. The nanocrystallite Mg0.6Cd0.4Fe2O4 sensor was tested for LPG, Cl2 and C2H5OH. The sensitivity was measured at various operating temperatures in the range of 100-400 o C. The sensor shows highest sensitivity at operating temperature 225 o C for LPG (~ 78%). It shows good sensitivity at operating temperature of 198 o C for Cl2 (~75%) and ethanol (~ 65%). The sensor exhibits a lower response and recovery time for LPG and Cl2 as compared to C2H5OH.

Thermal Analysis And Luminescent Properties Of Sr2CeO4 blue phosphor

Pradip Z. Zambare; K. V. R. Murthy;O. H. Mahajan; K. D. Girase

Advanced Materials Letters, 2013, Volume 4, Issue 7, Pages 577-581
DOI: 10.5185/amlett.2012.11457

In this paper we report Strontium Cerium Oxide (Sr2CeO4) blue phosphor was synthesized via solid state reaction method using strontium carbonate SrCO3 and cerium oxide CeO2 as raw materials. The samples were characterized by Thermo analytical techniques (TG, DTA, DTG and DSC) in nitrogen atmosphere, Fourier transformation infrared (FTIR) spectroscopy, and Photoluminescence at room temperature. Thermal analysis indicates that Sr2CeO4 phosphor can be prepared at temperature higher than 1100 °C. In excitation spectra two excitation peaks were located at 262 and 399 nm respectively. The emission spectrum was a broad band peaking at 470 nm, which was suitable for the doping of rare earth ions. The color co-ordinates for the pure Sr2CeO4 were x = 0.1918 and y = 0.2483. This material has potential for applications in the field of emission devices.

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.

Effect Of Sintering Temperature On Structural And Electrical Switching Properties Of Cadmium Ferrite 

S.P. Dalawai; A.B. Gadkari; T.J. Shinde; P.N. Vasambekar

Advanced Materials Letters, 2013, Volume 4, Issue 7, Pages 586-590
DOI: 10.5185/amlett.2012.10431

Cadmium ferrite was prepared by standard ceramic method and characterized by XRD, IR and SEM techniques. The X-ray analysis confirms the formation of single phase cubic spinel structure. The lattice constant decreases slightly and porosity increases with increase in sintering temperature. The crystallite size of the samples lies in the range of 22.83 to 24.44 nm. The IR study shows two absorption bands around 400 cm -1 and 600 cm -1 corresponding to octahedral and tetrahedral sites respectively. The grain size increases and switching field decreases with increases in sintering temperature.