Volume 2, Issue 1, March 2011

Nanomedicine - bridging the gap between nanotechnology and medicine

Yi Ge; Ashutosh Tiwari;Songjun Li

Advanced Materials Letters, 2011, Volume 2, Issue 1, Pages 1-2
DOI: 10.5185/amlett.2011.3001

The application of science and technology at the nano-scale is redefining fields like imaging, diagnosis, drug delivery, regenerative medicine and biomaterials as well as underpinning the development of new generations of medical products. Many of these advances would offer vastly improved outcomes for patients, therapies for hitherto difficult-to-treat diseases or conditions, improved manufacturing efficiency, and better use of valuable medical professional resources. The technology has already found its way into multifarious applications in healthcare such as diagnostic imaging agents, drug delivery systems, pathogen detection systems, biosensors, tissue engineering, microfluidics, lab-on-a-chip, compact electronic systems.

On the problem of open circuit voltage in metal phthalocyanine/C60 organic solar cells

Ramchandra Pode

Advanced Materials Letters, 2011, Volume 2, Issue 1, Pages 3-11
DOI: 10.5185/amlett.2010.12186

The open circuit voltage (VOC) plays a crucial role in determining the efficiency of organic solar cells. Models of the VOC based on (i) the energy difference between the LUMO of the acceptor material and the HOMO of the donor material at the heterointerface and (ii) chemical potential gradient which depends on the carrier mobility in a bilayer cell, are inadequate to understand the exact origin of the  VOC.  In this review article,  the  VOC in various planar and non-planar metal phthalocyanine/C60 solar cells are analyzed. These results are compared in  CuPc/C60 and  SubPc/C60 solar cells as a representative case of the planar and non-planar metal phthalocyanine/C60 solar cells, respectively. Regardless of unfavorable characteristics of SubPc films, the VOC value of 0.92 to 0.98V in SubPc (13 nm)/C60 (33-32.5 nm) compared to 0.44 to 0.49V in CuPc (20-40 nm)/C60 (40-30 nm) solar cells was noticed. It is suggested that the structure, morphology,   and absorption properties of the evaporated film of the donor materials and the efficient separation of charges at the donor/acceptor interface in bilayer planar and non-planar metal phthalocyanine/C60 solar cells are also imperative in determining the VOC.

Effect of ultra-fine fly ash on the dielectric behavior of CFSC under stress

Wang Shoude; Lu Lingchao; Cheng Xin

Advanced Materials Letters, 2011, Volume 2, Issue 1, Pages 12-16
DOI: 10.5185/amlett.2010.9163

Small size particle of ultra-fine fly ash was contributed to the dispersion of carbon fiber in composite in the preparation process. The dispersibility of carbon fiber in composite was associated with self-sensing property of composite. The effect of ultra-fine fly ash on the change in relative dielectric constant of carbon fiber sulphoaluminate cement composite under stress was investigated. The sensitivity, accuracy and reversibility of the change in relative dielectric constant under stress have been improved when 10% content (by mass of cement) of ultra-fine fly ash was added into carbon fiber sulphoaluminate cement composite (CFSC). Besides promoting micro capacitor creation, ultra-fine fly ash could endow CFSC with excellent mechanical property and weaken the ions polarization effect. The combination of above three effects upgraded the dielectric behavior of CFSC under stress.

Sunn hemp cellulose graft copolymers polyhydroxybutyrate composites: morphological and mechanical studies

Susheel Kalia; Anil Kumar; B.S. Kaith

Advanced Materials Letters, 2011, Volume 2, Issue 1, Pages 17-25
DOI: 10.5185/amlett.2010.6130

For the synthesis of biocomposite materials for useful applications, it becomes necessary to modify the surface of natural fibers through chemical treatments. Morphology, structure and properties of natural fibers have an obvious effect on the mechanical properties of the biocomposite materials. It is thus necessary to know the morphology, thermal stability and crystalline behavior of original and modified fibers. In present paper, sunn hemp fibers (SHF) were chemically modified with ethyl acrylate and binary monomers (EA+MMA, EA+AA) through microwave radiations induced graft copolymerization. Various reaction parameters were optimized to get maximum grafting (91.8%). Morphology, thermal stability and crystalline behavior of original and modified fibers were investigated. Morphological and thermal studies showed that surface of sunn hemp fibers becomes rough and amorphous through graft copolymerization and thermal stability has been found to be increased. Microwave radiation induced grafting showed a diminutive effect on the crystalline behavior of the sunn hemp fibers as optimum time to get maximum grafting is very less (40 min) in comparison to conventional grafting. Synthesized graft copolymers were used as reinforcing material in preparation of polyhydroxybutyrate biocomposites. It has been observed that graft copolymers improved the interface between fiber and matrix and enhanced the mechanical strength of composites.

Structural, dielectric and electrical properties of Lead zirconate titanate and CaCu3Ti4O12 ceramic composite

Arun Chamola; Hemant Singh; U.C. Naithani; Shubhash Sharma; Uday Prabhat; Pratiksha Devi; Anuradha Malik; Alok Srivastava; R.K. Sharma

Advanced Materials Letters, 2011, Volume 2, Issue 1, Pages 26-31
DOI: 10.5185/amlett.2010.12182

In the present work, structural, dielectric and electrical properties of lead zirconate titanate and CaCu3Ti4O12 ceramic composite with composition (1-x)Pb(Zr0.65Ti0.35)O3 - xCaCu3Ti4O12 (where x = 0, 0.20, 0.40 and 0.60) has been reported. The sample was prepared by employing a high-temperature solid-state reaction technique. X-ray diffraction studies confirm the formation of pure phase for x = 0.00 concentration and composite phases for the x = 0.40, 0.60 compositions. Doublet of diffraction peaks suggests structural change for x = 0.20 composition. Scanning electron micrographs show a uniform grain distribution and the grain size and shape modified upon CaCu3Ti4O12 addition. Dielectric measurement demonstrates a decrease in the dielectric constant with increase in CaCu3Ti4O12 percentage. The prepared ceramic composites have high dielectric constant and low dielectric loss. The temperature dependence of the ac conductivity indicated that the conduction process is due to singly ionized (in ferroelectric region) and doubly ionized (in paraelectric region).

Implementation of statistical methods on LIBS data for classification of residues of energetic materials (nitro compounds)

Shikha Rai; A.K. Rai; I.M.L. Das; K.C. Tripathi

Advanced Materials Letters, 2011, Volume 2, Issue 1, Pages 32-37
DOI: 10.5185/amlett.2010.11184

Our key aim is to validate the use of statistical methods for analysis of Laser-Induced Breakdown Spectroscopy (LIBS) datasets of pure nitro compounds (4-nitroaniline and 4-nitrotoluene) and of test samples formed in Cu matrix. Laser-Induced Breakdown Spectroscopy (LIBS) provides the spectral lines of the constituent elements. The interest behind this study is to establish the essence behind the supplementation of LIBS analysis with statistical methods. When the energetic materials were doped with the interferents, such as Cu metal powder it leads to the alteration of the spectral profile of both the target samples, which have similar constituent elements such as C, H, N and O. So, for this situation, it is difficult to classify the test samples from their pure samples only on the basis of its spectral signatures. Hence, in order to classify these sets, we have applied sophisticated chemometric techniques such as linear correlation and Principal Components Analysis (PCA) to familiar LIBS datasets and found that 50% test samples of 4-nitroaniline and 70% test samples of 4-nitrotoluene were successfully discriminated. The causes for partial classification for both the samples have also been discussed in detail.

Optical properties of MAl12O19:Eu (M = Ca, Ba, Sr) nanophosphors

Abhay D. Deshmukh; S. J. Dhoble; N.S. Dhoble

Advanced Materials Letters, 2011, Volume 2, Issue 1, Pages 38-42
DOI: 10.5185/amlett.2010.10171

The MAl12O19:Eu (M = Ca, Ba, Sr) phosphor were synthesized by combustion method and systematically characterized by photoluminescence excitation and emission spectra, concentration quenching, morphology and X-ray mapping with scanning electron microscopy. In SrAl12O19:Eu phosphor two PL emission peaks are observed at about 389 nm and another around 420 nm as well as BaAl12O19:Eu phosphor shows blue emission around 460 nm is observed in the blue region of the spectrum and CaAl12O19:Eu shows only red emission at 592 as well as 615 nm. Both phosphors can be efficiently excited in the wavelength range of 250-425 nm, where the near UV (~320 nm) solid state excitation is matched. By combining MAl12O19:Eu (M = Ca, Ba, Sr) phosphor with near UV chops emitting intense blue green (Ba), yellow-red (Ca) and blue purple (Sr) LEDs white LEDs can be produced.

Performance of nanopolyaniline-fungal enzyme based biosensor for water pollution

B.S. Kushwah; S.C. Upadhyaya; Shipra Shukla; Apurva Singh Sikarwar; R.M.S. Sengar; Seema Bhadauria

Advanced Materials Letters, 2011, Volume 2, Issue 1, Pages 43-51
DOI: 10.5185/amlett.2010.8149

The Laccases are oxidoreductases belonging to the multinuclear copper-containing oxidases; they catalyse the monoelectronic oxidation of substrates at the expense of molecular oxygen. These essentially ecofriendly enzymes work with air and produce water as the only by-product. Their uses span from the textile to the pulp and paper industries, and from food applications to bioremediation processes. Laccases also have uses in organic synthesis, where their typical substrates are phenols and amines, and the reaction products are dimers and oligomers derived from the coupling of reactive radical intermediates. Laccase from Pleurotus ostreatus was extracted from the Shaken flask cultures of Pleurotus ostreatus and grown at 25°C with continuous agitation (110 rpm) in baffled Erlenmeyer flasks (1000 mL) containing 200 mL medium. The basal glucose yeast extract peptone agar medium (GYP medium) used for cultures unless otherwise stated contained 20 g glucose L -1 , 5 g yeast extract L -1 , 5 g peptone L −1 and 1 g MgSO4.7H2O L −1 . The pH was adjusted to 5±0 with H3PO4 prior to sterilization. The kinetics of oxidation reactions catalyzed by laccase was studied using 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid (ABTS). The laccase showed lower specific activity. Enzyme modified electrodes were fabricated with polyaniline. Electrochemical polymerization of aniline was performed to get the film of polymer on the surface of glass electrode. First, ITO/PANI electrode was reduced by a 15 min cathodic polarization of the sensor at -500 mV in 0.1 M acetate buffer, pH 5.5. After cathodic polarization, the film was immersed in 0.1 M of acetate buffer, pH 5.5 containing enzyme solution for the deposition of enzyme in polymer layer at +650 mV for 20 min. During this oxidation process laccase become electrostatically attached to polymer film. The ITO/PANI/LAC electrode was rinsed with deionised water to remove any loosely bounded enzyme, and stored in buffer solution at 4 o C, when not in use. Conducting polymer/enzyme modified electrodes prepared by immobilization of enzyme were tested for electrocatalytic activities towards amperometric sensing of phenol in industrial effluent.

Energy dispersive spectroscopy study of surface modified PEEK

Nitu Bhatnagar; Sangeeta Jha; Shantanu Bhowmik

Advanced Materials Letters, 2011, Volume 2, Issue 1, Pages 52-57
DOI: 10.5185/amlett.2010.12188

PEEK (polyether etherketone) polymer, is increasingly used in many industrial applications as a replacement for metal components. In this investigation, attention is given to understand the chemical changes that have been introduced on the surface of PEEK, when surface of the PEEK is modified by low pressure plasma under RF (radio frequency) glow discharge. The contact angle measurements show that the contact angle decreases after the plasma treatment which results in the increase in surface energy. This paper also discusses the common surface characterisation technique like Energy Dispersive Spectroscopy (EDS) analysis to determine the chemical changes that have been introduced on the surface.

Raman spectra of hot-pressed boron suboxide

Ronald Machaka; Bonex W. Mwakikunga; Elayaperumal Manikandan; Trevor E. Derry; Iakovos Sigalas

Advanced Materials Letters, 2011, Volume 2, Issue 1, Pages 58-64
DOI: 10.5185/amlett.2010.9167

Despite hot pressing being the most popular method of consolidating B6O powder, the Raman spectrum of polycrystalline hot-pressed B6O was until now poorly understood. Yet, recent reports have contributed to the understanding of only high-pressure and high-temperature sintered B6O. Using an automated method for subtraction of the fluorescence background from Raman measurements, the first- and second-order Raman spectra of B6O and their dependence on the wavelength of the excitation line from a green Argon ion (Ar + ) laser are reported. Our results confirm the existence of observable highly resolved first- and second-order Raman modes measured at ambient conditions using a green Ar + ion laser as the source of excitation. We also extend our study to present a comparative analysis of our recovered first-order Raman spectra and previously reported first-order Raman spectra other α-rhombohedral boron type based ultra-hard boron-rich ceramic materials. The results show an overall good agreement.

Fabrication of red organic light emitting diodes (OLEDs) using EuxY(1-x)(TTA)3Phen organic complexes for solid-state lighting

N. Thejo Kalyani; S.J. Dhoble; R.B. Pode

Advanced Materials Letters, 2011, Volume 2, Issue 1, Pages 65-70
DOI: 10.5185/amlett.2010.10169

The mechanism of energy transfer leading to electroluminescence (EL) of a lanthanide complex, EuxY(1-x)(TTA)3Phen (TTA= thenoyltrifluoro-acetone, phen=1,10-phenanthroline), doped into TPBi(1,3,5-tris(N-Phenyl-benzimidizol-2-yl) benzene host at 15 wt% of host is investigated. With the device structure of anode/hole transport layer/EuxY(1-x)(TTA)3Phen (15%): TPBi/electron transport layer/cathode, maximum luminescence of 185.6 cd/m2 and 44.72 cd/m2 was obtained from device I made of Eu0.4Y0.6(TTA)3Phen and device II made of Eu0.5Y0.5(TTA)3Phen, respectively at 18 volts. Saturated red Eu 3+ emission based on 5 D0→ 7 F2 transition is centered at a wavelength of 612 nm with a full width at half maximum of 5 nm. From the analysis of I-V, J-V-L characteristics and electroluminescent (EL) spectra, we conclude that direct trapping of holes and electrons and subsequent formation of the excitation occur on the dopant, leading to high quantum efficiencies at low current densities. These results show that fabricated OLED devices can successfully emit saturated red light and can be used in applications such as opto-electronic OLED devices, displays and solid-state lighting technology.

Study on synthesis of magnetic nanocomposite (Ni-Teflon) by swift heavy ion beam mixing

Jai Prakash; A. Tripathi; J.C. Pivin; Jalaj Tripathi; A.K. Chawla; Ramesh Chandra; S.S. Kim; K. Asokan; D.K. Avasthi

Advanced Materials Letters, 2011, Volume 2, Issue 1, Pages 71-75
DOI: 10.5185/amlett.2010.12187

The present work envisages synthesis of magnetic nanocomposites by ion beam mixing technique using swift heavy ion irradiation of Ni-Teflon bilayer system and its magnetic characterizations. The nanocomposite is characterized by Rutherford backscattering spectrometry (RBS), transmission electron microscopy (TEM), scanning probe microscopy (SPM) and superconducting quantum interference device (SQUID) magnetometer. Cross-sectional TEM and magnetic force microscopy (MFM) results confirm the formation of nanocomposite. Magnetic characterizations reveal that nanocomposite exhibits ferromagnetic behavior with an increase in the coercivity, which is attributed to the formation of Ni nanoparticles. The coercivity of the nanocomposite is found to be 112 Oe at room temperature which is two orders of magnitude larger than that of the bulk Ni (0.87 Oe).

X-ray and electrical properties of Ba(Gd0.5Nb0.5)O3 ceramic

Pritam Kumar; B.P. Singh; T.P. Sinha; N.K. Singh

Advanced Materials Letters, 2011, Volume 2, Issue 1, Pages 76-81
DOI: 10.5185/amlett.2010.11176

The complex perovskite oxide barium gadolinium niobate, Ba(Gd0.5Nb0.5)O3 (BGN) is synthesized by a solid-state reaction technique. The X-ray diffraction of the sample at room temperature shows a tetragonal phase. The scanning electron micrograph of the sample shows the average grain size of BGN ~ 1.92 mm. The frequency-dependent dielectric dispersion of BGN is investigated in the temperature range from 303 K to 463 K and in a frequency range from 50 Hz to 1 MHz by impedance spectroscopy. The logarithmic angular frequency dependence of loss peak is found to obey an Arrhenius law with activation energy of 0.70 eV. It is observed that: (i) the dielectric constant (e¢ ) and loss tangent (tan d) are dependent on frequency, (ii) the temperature of dielectric constant maximum shift toward lower temperature side, (iii) The scaling behavior of dielectric  loss spectra suggests that the relaxation describes the same mechanism at various temperatures.