Volume 1, Issue 3, December 2010

Molecularly Imprinted Sensors

Ashutosh Tiwari;Songjun Li

Advanced Materials Letters, 2010, Volume 1, Issue 3, Pages 178-178
DOI: 10.5185/amlett.2010.1201

There is tremendous interest by society in reliable and affordable sensors and sensing systems, ranging from environmental monitoring and protection to pharmaceutical separation and analysis, and from defense and security to medicine and healthcare. The emerging challenges associated with public exposure to pollution and hazardous substances have fuelled an urgent need for novel sensors and detection technologies. Scientists in this field have been working under pressure to meet these challenges over the past few years.

Spatially Controlled Cell Growth Using Patterned Biomaterials

Murugan Ramalingam; Ashutosh Tiwari

Advanced Materials Letters, 2010, Volume 1, Issue 3, Pages 179-187
DOI: 10.5185/amlett.2010.9160

Development of functional tissues often requires spatially controlled growth of cells over 2D surfaces or 3D substrates to maintain their distinct cellular functions; particularly it is essential for culturing anchorage-dependent cells. In this regard, development of new surfaces/substrates with superior surface properties that could control the cell behavior is of great important and extremely necessary for functional tissue engineering as well as to study how the cells spatially recognize and interact with synthetic material systems. Surface patterning is an approach to modify the surface of biomaterials, either chemically or topographically. Both the approaches are well demonstrated in manipulating cell behaviors such as shape, size, orientation, migration, proliferation, and differentiation. In this article, we review various commonly employed methodologies for use in patterning of biomaterial surfaces/substrates and their suitability in controlling cell behaviors.

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.

pH Dependant Fungal Proteins In The ‘green’ Synthesis Of Gold Nanoparticles

Rashmi Sanghi; Preeti Verma

Advanced Materials Letters, 2010, Volume 1, Issue 3, Pages 193-199
DOI: 10.5185/amlett.2010.5124

An efficient, simple and environment friendly biosynthesis of gold nanoparticles (GNPs), mediated by fungal proteins of Coriolus versicolor is reported. By altering the reaction conditions, the intracellular synthesis of GNPs on the fungal mycelium, could be well tailored to produce extracellular GNPs in the aqueous medium. The reaction rate and the morphology of the particles were found to depend on parameters such as pH, incubation temperature and concentration of gold solution. The gold nanoparticles were characterized by UV–Vis, SEM and AFM techniques, demonstrating high stability of gold nanoparticles in aqueous media, via the protein layer. The size of the gold nanoparticles using AFM studies was found to be in the range 5–30 nm. These nanoparticles were found to be highly stable as even after prolonged storage for over 6 months they do not show aggregation. A plausible mechanism explaining the role of different possible proteins under different conditions, in the formation of gold nanoparticles has been investigated using FTIR. This study represents an important advancement in the use of fungal protein for the extracellular synthesis of functional gold nanoparticles by a green and mild technique in one pot.

Effect Of Processing Parameters On Morphology And Thermal Properties Of Electrospun Polycarbonate Nanofibers

Advanced Materials Letters, 2010, Volume 1, Issue 3, Pages 200-204
DOI: 10.5185/amlett.2010.8148

In the present contribution, it has been reported about the effect of solvent, solvent concentration, flow rate and applied voltage on the fabrication of electrospun polycarbonate (PC) nanofibers. The morphology of fibers was studied by optical and scanning electron microscope. It is observed that morphology of fibers depends upon the concentration of PC or viscosity of the solution, vapor pressure and diffusion coefficient of solvent. In fact, when viscosity of the solution is very low, beads or droplets are formed instead of fibers. The same problem arises when the viscosity of the solution is too high due to high surface tension. In this case, jet formation will not be observed and the solution will coagulate at the tip of needle. Tetrahydrofuran (THF) easily diffuses with polymer, at higher concentration of PC and at higher flow rate of solution; fibers of micron size are formed because of high vapor pressure of THF. On the other hand, in case of mixed solvents (DMF and THF), by controlling processing parameters one can get fiber diameter up to 200 nm. The study of Differential Scanning Calorimetry (DSC) indicates that less amount of heat energy is absorbed during endothermic reaction and there is a slight increase in glass transition temperature of nanofibers. Thermogravimetric analysis (TGA) shows an increase in thermal stability of PC nanofibers by 40ºC as compared to PC granules. This is due to the alignment of PC polymeric chains during stretching and whipping that occurs while electro spinning process.

Fabrication Of Advanced Poly(etheretherketone)/ Clay Nanocomposites And Their Properties

R. K. Goyal; J.N. Sahu

Advanced Materials Letters, 2010, Volume 1, Issue 3, Pages 205-209
DOI: 10.5185/amlett.2010.8151

High performance polymer nanocomposites based on poly(etheretherketone) (PEEK) as matrix and modified clay as reinforcement were fabricated using hot pressing at 380 °C and 45 MPa. The clay was varied from 0 to 5 wt%. Nanocomposites were characterized by X-ray diffraction (XRD), Vickers hardness tester, high resistivity meter, and impedance analyzer to get information about morphology, microhardness, electrical conductivity and dielectric properties of nanocomposites, respectively. The experimental density was very close to the theoretical density. XRD showed exfoliation of clay up to 3 wt% and intercalation for 5 wt% nanocomposite. The water absorption decreased by 38 % at 1 wt% clay content. The microhardness increased up to 12 % for 2 wt% clay nanocomposite. Electrical conductivity was increased two orders of magnitude higher than pure PEEK. Dielectric constant was increased slightly with increasing clay content. The significant improvement in properties at lower clay loading might be attributed to the exfoliation of clay in the matrix.

Therapeutic Phytoelemental Profile Of Trichosanthes Dioica

Advanced Materials Letters, 2010, Volume 1, Issue 3, Pages 210-216
DOI: 10.5185/amlett.2010.7142

In India, Trichosanthes dioica is known as pointed gourd (in English), parwal (in Hindi) and potol (in Oriya) it is distributed in equatorial and subtropical regions and widely found in northern India. The present study is a unique example of interdisciplinary research as it deals not only with the phytochemical investigation of Trichosanthes dioica, using natural product technology but also correlates the presence of certain trace elements with its biological activities using Laser induced break down Spectroscopy (LIBS). The study reveals the isolation of one known and two unknown flavonoids and the presence of certain glycemic elements, responsible for the observed antidiabetic activity of Trichosanthes dioica. Hence, the presence of isolated flavonoids and trace elements can be very well correlated with its medicinal value.

Voltammetric Detection Of Microcystis Genus Specific-sequence With Disposable Screenprinted Electrode Modified With Gold Nanoparticles

Minbo Lan; Chen Chen; Qin Zhou; Yuanjie Teng; Hongli Zhao; Xiangheng Niu

Advanced Materials Letters, 2010, Volume 1, Issue 3, Pages 217-224
DOI: 10.5185/amlett.2010.

A disposable electrochemical biosensor for detection of DNA sequence related to Microcystis was described. After depositing gold nanoparticles (AuNPs) onto a screen-printed carbon electrode (SPCE) surface by electrodeposition, the DNA probe which is complementary to a specific gene sequence related to Microcystis was immobilized onto the AuNPs modified SPCE via a thiol linker at the 5’ end. On the electrode surface the immobilized single-stranded DNA could undergo hybridization in the solution containing DNA specific-sequence of Microcystis. Using methylene blue as the indicator, DNA immobilization and hybridization were characterized by cyclic voltammetry and differential pulse voltammetry. Parameters, such as the deposition conditions of gold nanopariticle and the preconcentration time of MB, were optimized. In addition, the control experiments with non-complementary and single base mismatch sequences were investigated and results demonstrated the high selectivity of the biosensor.

Preparation, Characterization And Application Studies Of Inorganic-organic Novel Polymer Composite

Vivek Singh Chauhan; M. Yunus; Nalini Sankararamakrishnan

Advanced Materials Letters, 2010, Volume 1, Issue 3, Pages 225-231
DOI: 10.5185/amlett.2010.6135

A novel iron doped chitosan coated activated alumna (IDCA) derivative was prepared and spectroscopic studies including FTIR, Elemental analysis (EA), XRD, and SEM were used for its characterization. Thermodynamic behavior of the adsorbent was evaluated by Thermogravimetric Analysis (TGA) and Differential Scanning calorimetry (DSC) analysis. The pore size distribution and nitrogen adsorption isotherm revealed the existence of micro porous structure. The applicability of the adsorbent towards the removal of arsenite and arsenate has been demonstrated.

Biogenic Synthesis Of Silver Nanocubes And Nanorods Using Sundried Stevia Rebaudiana Leaves

Ratnika Varshneya; Seema Bhadauriaa; Mulayam S.Gaur

Advanced Materials Letters, 2010, Volume 1, Issue 3, Pages 232-237
DOI: 10.5185/amlett.2010.9155

This work reports a novel biological method for the synthesis of rod shaped silver nanoparticles by exploiting sundried Stevia rebaudiana leaves at ambient conditions. On treatment of aqueous solutions of silver with leaf powder, not only the rod shaped silver nanoparticles ranging from 80-200 nm diameter and 400-800 nm height, but also cubes ranging from 55 to 80 nm in size, could be rapidly fabricated. The rate of reduction is much faster than those observed in earlier studies, highlighting the possibility that biological methodologies will achieve rates of synthesis comparable to those of chemical methods. The approach also appears to be a cost-efficient alternative to conventional methods, so it would be suitable for developing a biological process for large scale production. Instead of the boiled leaf broth used in previous studies, sundried leaf biomass could be preserved as an excellent bio-reductant, conveniently available any time for biosynthesis of the nanoparticles.

Thermal and Chemical Resistance Behavior of Cured Epoxy Based on Diglycidyl Ether of Bisphenol-A And Thiol Treated Liquid Polysulfide Blends

Reena Singhal; Arun Kumar Nagpal

Advanced Materials Letters, 2010, Volume 1, Issue 3, Pages 238-245
DOI: 10.5185/amlett.2010.10172

In the present study five blends of Diglycidyl ether of bisphenol-A and thiol terminated liquid polysulfide with varying amount of polysulfide (i.e. 10 to 50 phr) were synthesized by physical mixing at 90 o C and synthesized blends were cured with phthalic anhydride. Interaction among epoxide group of DGEBA, -SH group of polysulfide and anhydride group of curing agent discussed through FT-IR analysis. The TGA studies revealed a decrease in thermal stability and activation energy (114.35 - 73.04 kJ/mole) with increase in polysulfide content. Volume resistivity decreases from 5.34 × 10 15 to 3.83 × 10 11 ohm-cm with increase in polysulfide content in the blends. The study of chemical resistance for various acids, alkalies to distilled water, sea water, xylene, ethanol, methyl ethyl ketone and acetone indicated that chemical resistance of blends decreased with increase in polysulfide content. Scanning electron microscopy (SEM) indicated the presence of two-phase morphology in the blends.

Studies On Characterization Of Corn Cob Based Nanoparticles

Advanced Materials Letters, 2010, Volume 1, Issue 3, Pages 246-253
DOI: 10.5185/amlett.2010.9164

Corn cobs (central part of maize) are either treated as waste or burnt as fuel causing environmental concern. In order to achieve its value addition in new research areas, corn cob can be processed chemically to find ways to generate new end products with added values at very low price. Cellulose-based nanoparticles (CPNs) have an ability to remain intact in stomach environment and small intestine together with the presence of specific enzymes produced by cellulytic bacteria (ruminococus) for colon biodegradability and makes this biopolymer a suitable raw material for the biomedical field, particularly as a colon-specific drug carrier. Cellulose-based nanoparticles (CPNs) were prepared from corn cob raw material by treating it with sodium hydroxide in the range 0-24% of sodium hydroxide concentration, oven dry basis at 165oC for 1.5 h at liquor to solid ratio of 4.5:1. The sample obtained at the optimised condition (18% NaOH concentration, oven dry basis of raw materials) was washed with deionised water, disintegrated and filtered through 80 mesh screens. Powder thus obtained was delignified by acidified sodium chlorite and dried in a vacuum oven to constant weight. Dried powder was further separated by 270 mesh screens. An average particle size approximately equal to 22 nm was obtained by using Transmission Electron Microscopy (TEM). Its crystallinity, functional group and agglomerated particle size was determined by X-ray Diffraction (XRD), Fourier Transform Infrared (FT-IR) and Scanning Electron Microscopy (SEM) techniques respectively.

Influence Of Li+ Doping On Photoluminescence Properties Of Sr5(PO4)3F:Eu3+

K. N. Shinde;S. J. Dhoble

Advanced Materials Letters, 2010, Volume 1, Issue 3, Pages 254-258
DOI: 10.5185/amlett.2010.9161

In this article, the influence of lithium co-doped on Sr5(PO4)3F:Eu 3+ halophosphate based phosphor reported. The Sr5(PO4)3F:Eu 3+ and Sr5(PO4)3F:Eu 3+ , Li + phosphors were prepared by combustion synthesis route using urea as the fuel. The phosphors were characterized by X-ray diffraction (XRD) and photoluminescence (PL) techniques. The powders were annealed at 900 o C and 1200 o C and characterized by X-ray diffraction (XRD) which shows that the major crystalline phases from the as prepared or annealed powder samples were identical. The PL results show that the incorporation of Li + ions into the Sr5 (PO4)3F:Eu 3+ lattice could induce a remarkable improvement of the PL intensity in red region at 395 nm excitation wavelength. The highest emission intensity was observed with the compound of Eu 3+ 0.5 mol% and Li + 0.5 mol% co-doped Sr5(PO4)3F, whose brightness was increased by a factor of more than 3.0 in comparison with that of the Sr5(PO4)3F:Eu 3+ . The 300–400 nm is Hg free excitation (Hg excitation is 85% 254 nm wavelength of light and 15% other wavelengths), which is characteristic of solid-state lighting phosphors. Hence PL emission in trivalent europium co-doped with lithium may be efficient photoluminescent materials for solid-state lighting phosphors as a red component.

Structural, Dielectric And Ferroelectric Properties Of Y3+ Doped PZT (65/35)

K. L. Yadava

Advanced Materials Letters, 2010, Volume 1, Issue 3, Pages 259-263
DOI: 10.5185/amlett.2010.9159

Yttrium doped lead zirconium titanate (PYZT) was prepared by chemical co-precipitation technique using their nitrate salts. X-ray diffraction analysis was carried out to confirm the phase formation and to study the structural changes with Y doping in PZT. Scanning electron micrographs of the sample show uniform grain distribution with decreasing grain size with Y doping. The dielectric maxima was found to be enormously increased from 1791 to 2687 along with decreasing phase transition temperature from 335 to 400 o C with Y doping in PZT. The remnant polarization was also found to increase from ~11 to ~44 μC/cm 2 with Y doping.

SHG Relaxation Behaviour In M-nitroaniline Doped PMMA Guest-host System

R.K. Goyal; S.R. Damkale; U.P. Mulik; Y.S. Negi; J. W. Dadge; R.C. Aiyer

Advanced Materials Letters, 2010, Volume 1, Issue 3, Pages 264-268
DOI: 10.5185/amlett.2010.8150

In present work, we have reported the second harmonic generation (SHG) property on the Guest-Host system based on optical grade poly(methyl methacrylate) (PMMA) and m-Nitroaniline (m-NA) for their use in optoelectronic devices. SHG signal of the m-NA doped PMMA freestanding films was determined using Nd:YAG laser by varying input energy from 6 mJ to 18 mJ. For evaluating SHG, films were poled at various temperatures to align the m-NA guest molecules in PMMA host matrix. Doped films were also characterized isothermally by thermogravimetric analysis (TGA) to get the information about loss of m-NA molecules at poling temperatures. It was found that there is no change in glass transition temperature. SHG intensity increases as the poling temperature increases. However, SHG signal intensity decreases as the decay time of poled films increases. After one week of poling more than half of the original SHG intensity is retained. The decay in SHG intensity might be attributed to the relaxation of m-NA molecules from thermodynamic unstable state to the equilibrium state.

Synthesis, Characterization And Optical Properties Of Nanosized CdS Hollow Spheres

Radheshyam Rai; Seema Sharma

Advanced Materials Letters, 2010, Volume 1, Issue 3, Pages 269-273
DOI: 10.5185/amlett.2010.7140

In the present paper, we synthesized the CdS hollow spheres by using PMMA sphere templates of 298-301 nm diameters and 20-51 nm of shell thickness. A CdS hollow sphere was characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), optical absorption and photoluminescence technique. CdS products are all cubic face-centered structure with the cell constant a = 5.815 Å. We also explore the morphology, structure and possible synthesis mechanism. A possible template mechanism has been proposed for the production of the hollow CdS nano-particles. The band gap of bulk CdS is about 2.45 eV, showing an absorption onset of bulk at about 513 nm. This shows a blue shift in the absorption spectra due to the quantum size effect, which is quite possible due to the small size of the CdS nano crystals as is evident in XRD pattern. The diameter of the beads is about 265-310 nm. The change in beads size due to the CdS over-layer is not so apparent in structures, due to its small thickness. The average diameter of the sphere is similar to that of the beads. Therefore, the spherical shells were obtained after the removal of PMMA core.