Volume 4, Issue 10, October 2013


Editorial

Ashutosh Tiwari; Ashutosh Tiwari;Songjun Li

Advanced Materials Letters, 2013, Volume 4, Issue 10, Pages 720-720
DOI: 10.5185/amlett.2013.10001

We are pleased to publish the 4 volume, 10th issue, 2013 of Advanced Materials Letters, a monthly international journal that is intended to provide top-quality peer-reviewed articles in the fascinating field of materials science particularly in the area of structure, synthesis and processing, characterization, advanced-state properties, and applications of materials. The journal publishes review articles, research articles, notes and short communications. The peer-review and proof-ready editing is expected to be completed with-in 3 months and the online version will be published immediately. Advanced Materials Letters is fully committed to publish articles, all the published articles are indexed and are available for download for free.

Surface Affinity Of Graphene For Health, Energy And Environmental Safety Applications

Jyoti Tyagi;Rita Kakkar

Advanced Materials Letters, 2013, Volume 4, Issue 10, Pages 721-736
DOI: 10.5185/amlett.2013.3438

This review focuses on the applications of graphene, and the effects of doping and functionalization on its properties. Though known for several years, the potential applications of graphene in various fields have only been recently realized. Remarkable research is going on in the various application based fields of graphene, such as in hydrogen storage, Li batteries, catalysis and many more. Its use as a sensor to detect various species at the molecular level is fascinating. Also, on account of its 2D structure, graphene has found promising applications in several adsorption phenomena. Various adsorption studies have been done on the graphene surface resulting in the chemisorption of the chemical species. This review focuses on the application of graphene for removal of hazardous substances, such as heavy metal ions and drug metabolites, from waste waters. Another class of substances, known as disinfection by-products (DBPs), formed during the disinfection of drinking water using chlorine, ozone, chloramines and chlorine dioxide as disinfectants, and the use of graphene for their removal, is also discussed. Use of graphene based materials as chemical and biosensors and its applications in various other fields is also briefly discussed.

Application Of Mesoporous Anatase TiO2 Microspheres For Dye Sensitized Solar Cell On Flexible Titani

Advanced Materials Letters, 2013, Volume 4, Issue 10, Pages 737-741
DOI: 10.5185/amlett.2013.2423

In the preset study dye-sensitized solar cells (DSSC) have been fabricated on a flexible titanium metal foil substrate with mesoporous anatase Titania microsphers (TMS) as the electron transport layer for photo anode. These microspheres perform dual function of light scattering and efficient dye absorption. A light to electricity conversion efficiency of 2.93% is achieved with illumination through the counter electrode. Additionally electrochemical impedance spectroscopy (EIS) is used to analyze the electron transport processes occurring at the various interfaces. Copyright © 2013 VBRI press.  

Surface Modification Of Ramie Fibers Using Microwave Assisted Graft Copolymerization Followed By Brevibacillus Parabrevis Pretreatment

Susheel Kalia; Hemmant Mittal;Amit Kumar; Renu Sheoran

Advanced Materials Letters, 2013, Volume 4, Issue 10, Pages 742-748
DOI: 10.5185/amlett.2013.3441

Ramie fibers usually display poor interfacial adhesion when reinforced in hydrophobic polymer matrices. Hydrophilic nature of natural fibers becomes the most crucial issue in composites engineering. Surface modification of natural fibers has been found to be very effective in improving the fiber-matrix adhesion. In the present paper, we have reported the microwave assisted grafting of binary vinyl monomer mixtures on to ramie fibers (Boehmeria nivea) and bacterial cellulase assisted pre-treatment of ramie fibers using bacteria Brevibacillus parabrevis. The effects of these pretreatments on some properties of ramie fibers are discussed in the present paper. The modified fibers were characterized by scanning electron microscopy (SEM), X-ray diffraction, and TGA/DTA techniques to determine their morphology, crystallinity and thermal stability. Surface of ramie fiber becomes rough on grafting with synthetic polymers, whereas biologically modified ramie fibers showed the enhanced softness and smooth appearance due to the removal of gum materials and other impurities from the surface of fibers. Both the treatments have slightly changed the thermal stability and crystallinity of ramie fibers.

Synthesis And Characterization Of CuO Electrospum Nanofiber Using Poly(vinyl Acetate)/Cu(CH3COO)2 Annealing Method

Seema Sharma; Rashmi Rani; Radheshyam Rai; T. S. Natarajan

Advanced Materials Letters, 2013, Volume 4, Issue 10, Pages 749-753
DOI: 10.5185/amlett.2013.2425

One dimensional nanofibers of organic and inorganic materials have been used in filters, optoelectronic devices, sensors etc. It is difficult to obtain ultra fine fibers of inorganic materials having lengths in the order of millimeter as they tend to break during formation due to thermal and other mechanical stresses. In this study, we have investigated the mechanism to prevent the defect formation and the breaking of CuO nanofibers by using optimized heat flow rates. CuO nanofibers were obtained by heat treating the poly(vinyl acetate) PVA composite fibers formed by electrospinning. The morphology and structural characteristics of prepared samples were investigated by Scanning electron microscopy, Transmission electron microscopy and X-ray diffraction. It was found that the morphology of the composite and annealed nanofibers could be influenced by the concentration of the polymer content. A lower concentration favors the formation of defects along the fiber and the number of defects reduces when the concentration is increased.

Cyclic Oxidation Behavior Of Bare And Cr3C2-25 (NiCr) Coated Super Alloy At Elevated Temperature

Sanjeet Kumar; Deepa Mudgal; Surendra Singh; Satya Prakash

Advanced Materials Letters, 2013, Volume 4, Issue 10, Pages 754-761
DOI: 10.5185/amlett.2013.2428

High temperature oxidation is the main cause for the degradation of materials used at elevated temperature which is responsible for the major shut down of turbines, boilers and incinerators used in large units. An attempt has been made to use Cr3C2-25%NiCr coating deposited by D-gun technique on Superni 600 alloy. These coatings are generally used for wear applications. This coating has been studied for oxidation at 900C under cyclic conditions. Sound and adherent coatings of 150-250 μm can be obtained by D-gun process. The bare and coated alloys were subjected to cyclic oxidation in air for 100 cycles. Weight change/area has been plotted against number of cycles and to monitor the oxidation kinetics. The scale formed after oxidation both on the bare and coated alloys has been examined using FESEM/EDX, XRD, and Cross-sectional/Mapping analysis. The weight gain by coated Superni 600 was found to be about 80% less than that of bare Superni 600. D-gun sprayed Cr3C2-NiCr coating has contributed to increase in the oxidation resistance of coated superalloy. These types of coatings can be developed for high temperature applications for both corrosion and erosion resistance.

Photo-oxidative Degradation Of Polybenzimidazole Derivative Membrane

Omkar S. Kushwaha; C. V. Avadhani; R. P. Singh

Advanced Materials Letters, 2013, Volume 4, Issue 10, Pages 762-768
DOI: 10.5185/amlett.2013.3432

High temperature polymer electrolyte membrane fuel cells (HTPEMFCs) are energy efficient systems with the potential to address all energy issues of present and future generations. Polybenzimidazole (PBI) based high temperature fuel cells are subject of high importance because PBI membranes are proved to be one of the best candidates for high temperature fuel cell applications. The stability of PBI membranes has been identified as crucial issue for the long-term durability under oxidative conditions of fuel cells. The present investigation highlights the photo-oxidative degradation studies accomplished on polybenzimidazole based poly(2,2'-butylene-5,5'-bibenzimidazole) (PBIB) membranes. The PBIB polymer membranes are found suitable for both in high temperature fuel cells as well as other high temperature applications. In this research article, PBIB membranes were photoirradiated under polychromatic UV rays (λ > 290 nm). The photo-oxidative degradation of membranes was characterized by Fourier transform infrared spectroscopy (FT-IR) and Scanning electron microscopy (SEM). FT-IR results showed significant amount of photo-oxidation and chemical degradation in fuel cell membranes which is proposed to be initiated by free radical mechanism. SEM images revealed development of nano-dimensional cracks and holes on surface of membranes which indicate structural and morphological degradation. The present study showed better results of accelerated photo-degradation as compared to the oxidative degradation results already reported in literature obtained chemically and thermally. Hence, the proposed photo-oxidative degradation method may be useful in determining stability, life time expectancy and degradation mechanism of fuel cell and other high performance membranes.

Adsorption Studies Of Acetaldehyde On TiO2 Nanosurface

Ritu Gaba; Mamta Bhandari; Rita Kakkar

Advanced Materials Letters, 2013, Volume 4, Issue 10, Pages 769-778
DOI: 10.5185/amlett.2013.2424

The present work deals with the adsorption of acetaldehyde, one of the most harmful volatile organic compounds (VOCs), on the TiO2 anatase nanosurface. The research was undertaken due to environmental concerns, as the TiO2 nanosurface serves as an excellent catalyst for the adsorption and decomposition of VOCs. The chemistry of aldehydes on metal oxides is complex and elaborate, as it can result in a variety of reactions, such as selective oxidation, alcohols disproportionation, etherification and reductive coupling to higher olefins. The structural properties of the various nanosurfaces were first examined and finally adsorption studies were made on the (TiO2)17 cluster, as it shows least reconstruction and offers all kinds of coordination sites for the study. It is found that a myriad of different adsorption products are formed on the TiO2 nanosurface, depending upon the coordination site. The low coordination (3c) sites are highly reactive and form stronger bonds with the acetaldehyde molecule, whereas adsorption at the four coordination site leads to the reconstruction of the nanosurface. Acetaldehyde chemisorbs onto the surface producing zwitterionic four-membered rings, in which the carbonyl C=O bond is considerably weakened, or it adsorbs on the TiO2 surface in a H-bridge bonded form. The most feasible mode of adsorption on the TiO2 nanosurface is found to be methyl hydrogen migration resulting in the formation of [CH2-C(H)O] species, which may further undergo transformation by β-aldolization to yield crotonaldehyde and butane. Other products investigated in this work include oxidation to acetate and reduction to ethoxy species. The results obtained in this work can be of significant help in deciding the fate of reaction of acetaldehyde on the TiO2 nanosurface, and using it for decomposition of acetaldehyde to benign products.

Sunlight Induced Rapid Synthesis And Kinetics Of Silver Nanoparticles Using Leaf Extract Of Achyranthes Aspera L. And Their Antimicrobial Applications

T. Peter Amaladhas; M. Usha; S. Naveen

Advanced Materials Letters, 2013, Volume 4, Issue 10, Pages 779-785
DOI: 10.5185/amlett.2013.2427

Sunlight induced strategy for the rapid green synthesis of silver nanoparticles (AgNPs) is reported for the first time using aqueous leaf extract of Achyranthes aspera. On exposing a mixture of silver nitrate solution and aqueous leaf extract of A. aspera to sunlight, stable silver nanoparticles were obtained within few seconds. The water soluble biomolecules from the A. aspera served as both reducing and capping agents in the synthesis of silver nanoparticles. The nanoparticles were characterized using UV–Vis., Fourier transform infrared (FTIR), transmission electron microscopy (TEM), and EDAX techniques. The pseudo first order rate constant kobs, for the formation of AgNPs was found to be 3.49 x 10 -2 min -1 . The particles were stable for 3 months. The nanoparticles were mono-dispersed, spherical in shape with the average size of 12.82 nm. FT-IR analysis revealed that the -OH groups, possibly, from saponin were responsible for the reduction of silver ions to silver nanoparticles (AgNPs). Thus prepared AgNPs have desirable cytotoxicity towards bacterial strains and fungus and the effect was compared with standard drugs, Amikacin and fluconazole respectively. This green and mild technique can be used for the large scale extracellular synthesis of silver nanoparticles and the AgNPs thus prepared may be used for biological applications.

Morphological And Impedance Studies In Diluted Mn-doped CdS Nanocomposites

P. Venkatesu; K. Ravichandran; B. K. Reddy

Advanced Materials Letters, 2013, Volume 4, Issue 10, Pages 786-791
DOI: 10.5185/amlett.2013.2429

Nanocrystalline samples of Cadmium Sulphide (CdS) were prepared with different Manganese (Mn) doping concentrations (0-10 at.%) through chemical route using thiophenol as a capping agent. Fourier Tranform Infrared Spectroscopy (FT-IR) study disclosed the presence of capping agent on the surface of the samples. X-ray diffraction (XRD) analysis showed phase transition from hexagonal to cubic phase beyond 8 at.% of Mn doping and grain size in the range of 13-30 nm. Micro structural study by High Resolution Transmission Electron Microscopy (HRTEM) confirmed phase transition and quasi-spherical particles having size in 15-50 nm range with small grains distributed on the surface of the particles. A blue shift in the band gap energy of the samples was indicated in optical absorption study and the band gap was found to vary nonlinearly with Mn content. Studies on electrical properties of the samples using a complex impedance spectroscopy (CIS) technique showed a decrease in the bulk resistance with increase in Mn concentration. Further, the nature of cole-cole plots (Nyquist plots) revealed the presence of bulk and grain boundary effects in the samples in consistent with HRTEM results. These crystalline quasi-spherical nanoparticles of CdS:Mn seems to be one of the promising candidates for modern age opto-electronics and biomedical applications.

Trivalent Rare Earth Activated SrCaAl2O5 Phosphor For White Light-emtting Diode

A.N. Yerpude;S.J. Dhoble

Advanced Materials Letters, 2013, Volume 4, Issue 10, Pages 792-796
DOI: 10.5185/amlett.2013.2416

Eu 3+ , Dy 3+ activated SrCaAl2O5 phosphor were synthesized by the combustion method at 550°C. The prepared phosphor characterized by X-ray diffraction and photoluminescence measurements. The photoluminescence study of Eu 3+ doped phosphor shows that the intensity of electric dipole transition ( 5 D0→ 7 F2) at 615 nm dominates over that of magnetic dipole transition ( 5 D0→ 7 F1) at 596 nm under 395nm excitation. The PL emission spectrum of Dy 3+ ion at 350nm excitation gives an emission band at 484 nm (blue) and 575 nm (yellow). The optimum concentration of both the dopant having highest luminescence intensity is found to be 0.5 mole %. The obtained PL results indicated that prepared phosphor is suitable as near UV excited white light-emitting diodes.