Volume 2, Issue 2, June 2011

Biosensors And Bioelectronics

Advanced Materials Letters, 2011, Volume 2, Issue 2, Pages 82-83
DOI: 10.5185/amlett.2011.6001

Bioelectronics embodies the exploitation of biological or biologically-inspired molecules as an integral part of an electronic devices and biosensors are the analytical embodiment of this art. The world market for biosensors, in 2009, was just under US$13 billion, with nearly nine tenths of that still accounted for by glucose measurement. This extraordinary dominance by a single biosensor type is driven by the exceptional needs of people with diabetes combined with the success of biosensors in meeting their demands for an appropriate product. The overall in vitro diagnostics market is currently considered to be worth around $40 billion, while recent estimates suggest that the theranostics (companion diagnostics) market is potentially worth a staggering $72 billion. Diabetes is the fastest growing chronic disease in the World, with Asia now home to four of the five largest diabetic populations and 2% of the World‘s population afflicted. Heart disease and stroke kill around 17 million people each year, accounting for one-third of all deaths globally.

Dedication And Prominence: 31 Years In Biosensors And Bioelectronics Dedicated To Professor Anthony P.F. Turner‘ s 61st Birthday

Advanced Materials Letters, 2011, Volume 2, Issue 2, Pages 84-89
DOI: 10.5185/amlett.2010.12225

The name Anthony P. F. Turner, biosensor pioneer, is often considered synonymous with his chosen field. This 5th June will be his 61st birthday. We track here his professional footprint, in order to celebrate his upcoming birthday and to commemorate his 31-years of dedication to biosensors. Commemorating this pioneer’s achievements is a multidisciplinary celebration of his prominent contribution to biotechnology, chemistry, biomaterials and nanotechnology. Copyright © 2011 VBRI press.

Cartilage Tissue Engineering: Current Scenario And Challenges

Advanced Materials Letters, 2011, Volume 2, Issue 2, Pages 90-99
DOI: 10.5185/amlett.2011.1211

Cartilage is an avascular connective tissue found in many locations in the body, such as, in the joints between the bones, rib cage, ear, nose and intervertebral discs. Cartilage plays a vital role in our body by working as a cushion between joints so that rubbing of bones against each other is prevented. It also holds some bones together, for instance, rib cartilage, and makes the area shock-proof. Cartilage is composed of single type of cells called chondrocytes. There are several diseases associated with cartilage, e.g., osteoarthritis, traumatic rupture of cartilage. These defects are not easy to repair as cartilage possesses limited self repair capacity due to the lack of a sufficient supply of healthy chondrocytes to the defective sites. Tissue engineered cartilage can serve as a lifelong treatment to such problems. Reconstruction of the cartilage can be achieved by use of appropriate cell source, scaffold, and growth factors. Development of a 3D cartilaginous skeleton have challenged the researchers for decades as the pursuit for suitable cell source, biomaterials and growth factor combination is not yet over. Various composite biomaterials and multiple growth factor approach are applied nowadays to regenerate cartilage. Stem cell has emerged as a potent source of cells for cartilage regeneration. This review highlightens the advances in cartilage tissue engineering by throwing light on cell sources, scaffold materials as well as on growth factors used so far in cartilage tissue engineering. It also reflects a range of problems and future perspectives to overcome the existing hurdles in cartilage regeneration. Copyright © 2011 VBRI press.

Diphenylalanine Peptide Nanotube: Charge Transport, Band Gap And Its Relevance To Potential Biomedical Applications

Advanced Materials Letters, 2011, Volume 2, Issue 2, Pages 100-105
DOI: 10.5185/amlett.2010.12223

Peptide nanotubes (PNT) are emerging alternates frontier to carbon nanotubes (CNT). PNT’s can be engineered by solid phase synthesis with desired properties. Chemically PNT’s are reactive in sharp contrast to CNT’s and hence require less site specific functionalization for nanotechnology applications. In this paper we are reporting the electronic coupling between the Phe-Phe dipeptide which is calculated using the density functional theory method. The calculations are performed for linear and cyclic structures of diphenylalanine peptide. The calculated electronic coupling is sensitive to the peptide electronic structure and shows a significant dependence for conformations. The band gaps obtained for PNT are compared with Boron Nitride and CNT.  Peptide nanotubes (PNT) exhibit no cytotoxicity and hence offer tantalizing prospects in biomedical applications for example in drug delivery. Copyright © 2011 VBRI press.

High Temperature Tensile Properties Of 2D Cross-ply Carbon-carbon Composites

Advanced Materials Letters, 2011, Volume 2, Issue 2, Pages 106-112
DOI: 10.5185/amlett.2010.12189

High temperature tensile properties of 2D carbon-carbon composite made from high strength T700 carbon fibers were evaluated at different temperatures. Carbon-carbon composites were heat treated at different temperatures i.e., 750, 1000, 1500, 2000, 2500 °C and their tensile properties were measured at room temperature and at different high temperatures. It is observed that, maximum value of tensile strength at room temperature is  of composite heat treated at 1500 °C thereafter strength decreases with increasing processing temperature up to 2500 °C. The decreases in strength are related to degradation of fiber properties in composites and in-situ damage. On the other hand, tensile strength is higher at high temperature compared to room temperature.  It increases progressively with increasing the test temperature up to 2000 °C. Thereafter, strength decreases and ultimate value of tensile strength is less than that of the room temperature value of 2500 °C heat treated composites. Increase in strength up to 1500 °C is due to the improvement in fiber-matrix interactions, matrix properties due to relaxation of thermally induced stresses during high temperature test. Above 1500 °C enhancement in tensile strength is due to the enhancement in strength of carbon fibers and due to the creep deformation. Decrease in strength at measurement temperature 2500 °C is due to the additional in-situ degradation of fiber properties during high temperature test. Copyright © 2011 VBRI press.

Superplastic Deformation Of A Relatively Coarsegrained AZ80 Magnesium Alloy

Advanced Materials Letters, 2011, Volume 2, Issue 2, Pages 113-117
DOI: 10.5185/amlett.2010.12217

Superplastic deformation behaviors of a relatively coarse-grained AZ80 magnesium alloy sheet have been investigated at temperature ranging from 350 to 430 °C and at the strain rates ranging from 1.31 × 10 -4 to 1.31 × 10 -2 s -1 by uniaxial tensile tests. Superplasticity with the maximum elongation to failure of 239% was obtained at 430 °C and the strain rate of 6.56 × 10 -4 s -1 and its strain rate sensitivity exponent, the value of m is high up to 0.49. Fine interior dynamic recrystallized (DRX) grains distributed along primary grains were observed during superplastic deformation, but primary grains were not found significantly grown up. In addition, micro-cavities and their coalescences were also observed in the superplastic deformation of the relatively coarse-grained AZ80 magnesium alloy sheet. Grain boundary sliding (GBS) was considered to be the main deformation mechanism during the superplastic deformation. Dislocation creep controlled by atom diffusion through interior DRX and primary grains is suggested mainly to accommodate the GBS in superplastic deformation. Copyright © 2011 VBRI press.

Conversion Of Cellulosic Waste Materials Into Nanostructured Ceramics And Nanocomposites

Advanced Materials Letters, 2011, Volume 2, Issue 2, Pages 118-124
DOI: 10.5185/amlett.2011.1203

Cellulosic waste materials which include sawdust, wastepaper, corncob and sugarcane bagasse were converted into nanostructured ceramics and nanocomposites by submersion in silica colloidal suspension (sol) and subsequently by calcination of the cellulosic/SiO2 nanocomposites under controlled conditions. Depending on the calcination conditions used, nanostructured SiO2 ceramics and carbon/SiO2 nanocomposites were obtained. The morphology of resulting nanostructured ceramics and nanocomposites obtained from four types of cellulosic waste materials were characterized by Scanning Electron Microscopy (SEM), Fourier transformed infrared spectroscopy (FTIR), and CHN elemental analyzer. The effect of cellulosic materials on the properties of nanostructured ceramics and nanocomposites formed were investigated. Copyright © 2011 VBRI press.

Structural, Optical And Gas Evolution Studies Of 60 MeV Si5+ Ion Irradiated PoT-PVC Blends

Advanced Materials Letters, 2011, Volume 2, Issue 2, Pages 125-130
DOI: 10.5185/amlett.2010.1214

Swift Heavy Ion (SHI) irradiation induces chemical and structural changes in polymers by evolving various gases and gaseous fragments. The evolution of gases as a result of chain scissoring and bond breaking leads to cross-linking and cluster formation. Study of the evolved gases helps in understanding the various chemical and structural changes occurring within the polymer under the effect of SHI irradiation. In the present work, Poly (o-toluidine) (PoT), a derivative of polyaniline, is prepared by chemical oxidation polymerization and is blended with polyvinylchloride (PVC) to achieve self supported films. These PoT-PVC blend films were irradiated by 60 MeV Si 5+ ions at different fluences and evolved gases were monitored on-line by Residual Gas Analyzer (RGA). Pre and post irradiation FTIR, UV-Visible absorption and XRD studies have been carried out on these films to observe the changes in chemical/structural and optical properties. An effort has been made to correlate the evolved gases and structural properties after irradiation.Copyright © 2011 VBRI press.

Influence Of Temperature On Physical Properties Of Copper(I) Iodide

T. Prakash

Advanced Materials Letters, 2011, Volume 2, Issue 2, Pages 131-135
DOI: 10.5185/amlett.2011.1208

Copper (I) iodide (CuI) has been synthesized by wet chemical route at room temperature using freshly prepared copper oxide (CuO) as a precursor. The as-prepared CuI exists in g - phase and it undergoes two structural phase transition between room temperature and its melting point. Differential scanning calorimetry measurement in both heating and cooling cycles confirms its structural reversible phase transitions from g b phase then from b to a phase. In order to understand the underlying physical properties before and after transitions induced by temperature was studied by X-ray diffraction, scanning electron microscopy, fluorescence, fourier transformed infrared spectroscopy and thermal analysis using TGA, DTA and DSC.

Effect Of Preparation Processes On The Piezoresistivity Effect Of CFSC

Advanced Materials Letters, 2011, Volume 2, Issue 2, Pages 136-141
DOI: 10.5185/amlett.2010.12221

The preparation process of carbon fiber sulphoaluminate cement composite (CFSC) was intimately associated with its piezoresistivity effect. In this paper the piezoresistivity effects of CFSC prepared by different preparation processes were investigated. The experimental results indicated there was no significance difference of the variation amplitude for all specimens. Meanwhile, the good reversibility order of the piezoresistivity effect for all specimens was the specimen prepared by pressing, the specimen prepared by extrusion and the specimen prepared by casting. This phenomenon was related to the interfacial layer structure. Therefore, pressing and extrusion technology could improve the reversibility of the piezoresistivity effect of CFSC. Copyright © 2011 VBRI press.

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.

Study of Pb(Zr0.65Ti0.35)O3(PZT(65/35) doping on structural, dielectric and conductivity properties of BaTiO3(BT) ceramics

Arun Chamola; Hemant Singh; U.C. Naithani

Advanced Materials Letters, 2011, Volume 2, Issue 2, Pages 148-152
DOI: 10.5185/amlett.2010.11183

(1−x)BaTiO3–xPZT(65/35) ceramics were prepared by high temperature solid state reaction technique. Structural properties of the compounds were examined using an X-ray diffraction (XRD) technique to confirm the formation of phase at room temperature. Detailed studies of dielectric properties of (1−x) BaTiO3–xPZT(65/35) for all compositions were in temperature range 30-200 o C reveal that the compound have transition temperature well above at the room temperature. While pure BaTiO3 ceramics exhibited a sharp phase transformation expected for normal ferroelectrics, phase transformation behavior of the (1−x)BaTiO3–xPZT(65/35) solid solutions became more diffuse with increasing PZT(65/35) contents. The diffusivity of the dielectric peaks in the compound exhibited the values between 1 and 2 where the higher value indicates the greater disorder in the systems. This was primarily evidenced by an increased broadness in the dielectric peak, with a maximum peak width occurring at x = 0.5. The temperature dependence of ac conductivity indicated that the electrical conductivity decrease above Tc on increasing the PZT(65/35) contents. This increase in the conductivity is attributed to the increase in polarizability of the materials around Tc, due to oxygen vacancies.

Creep resistance of a cast Mg-3Er-0.2Mn alloy

Wang Zhongjun; Zhu Jing; Wang Zhaojing; Kang Baohua

Advanced Materials Letters, 2011, Volume 2, Issue 2, Pages 153-156
DOI: 10.5185/amlett.2010.12222

In this paper, the microstructure and creep properties of a cast Mg-3Er-0.2Mn alloy was investigated. The results showed that the cast alloy under both as-cast and solution treated conditions is mainly composed of α-(Mg) matrix and Mg24Er5 phase particles. The value of activation energy Q (240~244KJ/mol), for creep deformation of the solution treated alloy, was calculated in the temperature range of 190~210 o C, and in the stress range of 50~60 MPa, respectively, which can explain that the creep mode involved cross slip of dislocations from basal to prismatic planes in the hexagonal structure or climb.

Behaviour of ultrasonic velocities and elastic constants in Ag-Zn alloys

Pramod Kumar Yadawa

Advanced Materials Letters, 2011, Volume 2, Issue 2, Pages 157-162
DOI: 10.5185/amlett.2010.12190

The ultrasonic properties of the hexagonal closed packed structured Ag-Zn alloys have been studied at room temperature for their characterization. For the investigations of ultrasonic properties, I have also computed second order elastic constants using Lennard–Jones Potential. The velocities V1 and V2 have minima and maxima respectively with 45 0 with unique axis of the crystal, while V3 increases with the angle from unique axis. The inconsistent behaviour of angle dependent velocities is associated to the action of second order elastic constants. Debye average sound velocities of these alloys are increasing with the angle and has maximum at 550 with unique axis at room temperature. Hence when a sound wave travels at 55 0 with unique axis of these alloys, then the average sound velocity is found to be maximum. Ag0.2Zn0.8 alloy is more suitable for industrial and other uses, as it having highest elastic constants and lowest attenuation in comparison to other Ag-Zn samples. The mechanical and ultrasonic properties of these alloys will not be better than pure Ag and Zn due to their low SOEC and high ultrasonic attenuation. Achieved results have been discussed and compared with available experimental and theoretical results.

MgCl2 added triglycine sulphate crystals

V. Krishnakumar; M. Rajaboopathi; R. Nagalakshmi

Advanced Materials Letters, 2011, Volume 2, Issue 2, Pages 163-169
DOI: 10.5185/amlett.2010.12220

Single crystals of pure and MgCl2-added triglycine sulphate crystals were grown from aqueous solutions by low temperature solution growth technique. From the powder XRD technique crystal system remains same (Monoclinic) and the unit cell parameters are slightly different from the pure TGS. FTIR and FT-Raman spectra were recorded to identify the vibrational activity of the various functional groups present in the title crystals. To determine the concentration Mg 2+ ion in the MgCl2- added triglycine sulphate crystals inductively coupled plasma optical emission spectrometer (ICP-OES) study was carried out. The amount of MgCl2 (mol %) incorporated into the crystal is very low, a factor of 10 -2 in comparison to the actual amount taken in the solution. UV-VIS-NIR study shows that there is wide transparency in the visible region and the band gap energies were calculated. The mechanical strength of the grown crystals were known by hardness numbers and work hardening coefficient values. Dielectric constant and dielectric loss of the crystals were studied as function of frequency.