Volume 10, Issue 10, October 2019

Wearable Healthcare Devices

Ashutosh Tiwari

Advanced Materials Letters, 2019, Volume 10, Issue 10, Pages 675-675
DOI: 10.5185/amlett.2019.1010

As the prevalence of chronic ailments and diseases increase among the rapidly aging world population, the healthcare sector is looking more and more towards high-tech medical solutions and devices. This is the reason the world has seen a proliferation of advanced wearable electronics in the recent years. These devices have emerged as one of the most effective ways to improve patient outcomes and reduce medical costs.

Nano-Graphene and Its Derivatives for Fabrication of Flexible Electronic Devices: A Quick Review

Wee Siang Koh; Kiat Moon Lee; Pey Yi Toh; Swee Pin Yeap

Advanced Materials Letters, 2019, Volume 10, Issue 10, Pages 676-681
DOI: 10.5185/amlett.2019.0050

Along with technology development, the demand for flexible, foldable, and portable electronic devices has grew over the past few years. Successful fabrication of this flexible electronic devices relying on the internal electronic components which are also flexible and lightweight. In this regard, researchers are now working on using nanomaterials which exhibit the desired electronic properties to replace the conventional electronic components. Graphene nanosheet and its derivatives are known for their intrinsic electrical behaviour. Meanwhile, they are lightweight and consume small space in any design. Hence, recent research has been focussing on fabricating flexible and foldable electronic components by attaching the graphene and its derivatives on a thin film/substrate. In fact, this idea has been realized in year 2017 on the first flexible OLED panel that uses transparent graphene-based electrode. In view of the positive impact of this nanomaterial towards future design of electronic devices, the present paper aims to provide a quick review on the current stage of research, the challenges encountered, as well as the future outlook in the use of graphene nanomaterials for designing flexible electronics. Copyright © VBRI Press.

Natural Fibers as Viable Sources for the Development of Structural, Semi-Structural, and Technological Materials – A Review

Chioma E. Njoku; Kenneth K. Alaneme; Joseph A. Omotoyinbo; Michael O. Daramola

Advanced Materials Letters, 2019, Volume 10, Issue 10, Pages 682-694
DOI: 10.5185/amlett.2019.9907

A systematic and critical review on the potentials and viability of naturally occurring fibers as suitable reinforcements for the development of composite systems for structural, semi-structural and technological materials is presented in this article. Globally, the movement towards greater protection of the environment and the use of cost-saving technologies has led to a surge in the consideration of natural (biodegradable) products for the development of technological materials. In this regard, natural fibers have been proven to be good substitutes to synthetic fibers for the development of composites - because they possess similar mechanical and physical characteristics, to the synthetic fibers. In addition, natural fibers are lighter non-toxic and biodegradable. It is on this premise that several studies on their use in a number of applications where composites are desirable have been reported. Therefore, this article discusses various types of natural fibers, their properties, and their applications in different technological domains. The documentation of this review is thought-provoking and provides challenges and future prospects in the development and application of natural fibers and their composites. Copyright © VBRI Press.

Geometrical Characterization of Wire-and-Arc Additive Manufactured Steel Element

Vittoria Laghi; Michele Palermo; Giada Gasparini; Valentina Alena Girelli; Tomaso Trombetti

Advanced Materials Letters, 2019, Volume 10, Issue 10, Pages 695-699
DOI: 10.5185/amlett.2019.0019

In the last decades Additive Manufacturing has gained fundamental importance in the development of digital fabrication for the automotive, aerospace, biomedical and only lately civil engineering field. In particular, the technology of Wire-and-Arc Additive Manufacturing, based on a welding process adopted on a robotic arm, is the most suitable to realize structural elements which usually requires large dimensions of the printed outcome, with still a good mechanical response of the printed metal material. The authors have been part of a pioneering work which provides the first insight into the material and geometrical properties relevant to characterize 308LSi stainless steel elements to realize the first 3D-printed steel footbridge to be held in Amsterdam by 2020 and manufactured by the Dutch company MX3D. In detail, the work presents the first results of an intense geometrical study to characterize the intrinsic irregularities of the printed outcome, by means of hand measurements and high-precision 3D scan acquisition of different element types. Copyright © VBRI Press.

Plasma Activated Water Generation and its Application in Agriculture

N. Punith; R. Harsha; R. Lakshminarayana; M. Hemanth; M. S. Anand; S. Dasappa

Advanced Materials Letters, 2019, Volume 10, Issue 10, Pages 700-704
DOI: 10.5185/amlett.2019.0042

Use of fossil fuels to produce nitrogenous fertilizer contributes to global warming and climate change. The plasma activated water (PAW) provides an alternative option for nitrogen supply to plant by fixing the nitrogen available in the air into the water using plasma. The PAW is a mixture of nitrate, nitrite, and hydrogen peroxide as its major constituents. In this work, an attempt was made to generate PAW using an efficient and scalable PAW generator.  Then plasma is characterized by measuring the power, and OES spectrum. This is a study in which for the first-time arc plasma has been used to demonstrate enhanced plant growth on tomato plant. The results indicate that compared to control, the plants fed with PAW activated for 30 minutes (PAW-30) have 1.5 times higher shoot length, 4 times higher leaf count and more than twice the chlorophyll content in the leaves. The wet weight of the plants fed with PAW-30 was 61% higher than that of the control. Copyright © VBRI Press.

Development of Advanced Electrode Materials on Porous Silicon for Micropower Formic Acid-Oxygen Fuel Cells 

Nicolay A. Yashtulov; Alexander V. Ragutkin; Marina V. Lebedeva

Advanced Materials Letters, 2019, Volume 10, Issue 10, Pages 705-710
DOI: 10.5185/amlett.2019.9912

In this work, in order to create electrode materials for electrochemical energy converters, composites on porous silicon modified by palladium have been obtained. The functional characteristics of the electrodes have been studied by scanning electron microscopy, X-ray phase analysis, ex-situ and in-situ cyclic voltammetry. The electrode materials based on porous silicon had demonstrated high catalytic activity and specific characteristics in fuel cells with direct oxidation of formic acid. The fuel cell prototype with low palladium content showed the maximum specific power of about 30 mW/cm 2 at a current density of 95-100 mA/cm 2 . Copyright © VBRI Press.

Water Management within Tragacanth gum-g-polyitaconic Acid Hydrogels

Chetna Verma; Poonam Negi; Deepak Pathania; Sadiya Anjum; Bhuvanesh Gupta

Advanced Materials Letters, 2019, Volume 10, Issue 10, Pages 711-714
DOI: 10.5185/amlett.2019.4090

In our investigation, we have studied the interaction of the water molecules with the hydrophilic sites in itaconic acid grafted Tragacanth gum copolymer. The water existed in two different states within the hydrogel matrix. There is one fraction of water which has close interaction with functional groups and does not undergo freezing during cooling. Besides, this the other type of water undergoes thermal transitions and freezes at -50°C. The water management within the grafted matrix seems to be strongly governed by hydrophilicity, crosslinked density and functionality. The water uptake by the hydrogel increased significantly as the degree of grafting increased, in spite of the increasing crosslink density of the matrix. Results have been explained in terms of the carboxylic groups and their ionization which has an overriding influencing the hydrogel structure leading to a more amenable structure for the water diffusion. Copyright © VBRI Press.

Synthesis and Characterization of Humic Acid-coated Fe3O4 Nanoparticles for Methylene Blue Adsorption Activity

Geitu Yirga; H C Ananda Murthy;Eshetu Bekele

Advanced Materials Letters, 2019, Volume 10, Issue 10, Pages 715-723
DOI: 10.5185/amlett.2019.0049

Humic acid modified magnetite nanoparticles (HA-Fe3O4 NPs) were synthesized by co-precipitation method by varying the precursor magnetite to HA ratio of 10:1 and 20:1. The synthesized NPs were characterized by FTIR, XRD, SEM-EDX and UV-Vis DR Techniques. The appearance of C=O vibration at 1390 cm -1 confirms positive interaction of carboxylate anion of HA and Fe3O4. The XRD pattern and SEM image shows bare Fe3O4 and HA-Fe3O4 (10:1 and 20:1) exhibit cubic spinel structure and the spherical shape morphology, respectively. The crystallite sizes of NPs were found to be 11.50 nm, 9.17 nm and 12.65 nm for bare, 10:1 and 20:1 Fe3O4-NPs, respectively. The adsorption capacity for the dye was found to increase with increase in contact time, adsorbent dose and initial pH of the solution. The result was best fitted to pseudo 2 nd order kinetics model and Langmuir isotherm model. The methylene blue (MB) removal efficiency of bare, 10:1 and 20:1 Fe3O4-NPs from aqueous solutions was recorded to be 95.8%, 99.4%, and 97.6%, respectively. The study confirms the greater efficiency of HA-Fe3O4 NPs compared to bare Fe3O4 for the removal of MB dye. The MB removal efficiency of HA-Fe3O4 NPs was found to be proportional to amount of adsorbed HA. Copyright © VBRI Press.

Synthesis and characterization of thermally stable flame retardant thermoplastic polyphosphazenes

Krishna Pratap Singh; Anuradha Mishra; Nand Kumar; Trilok Chand Shami

Advanced Materials Letters, 2019, Volume 10, Issue 10, Pages 724-730
DOI: 10.5185/amlett.2019.0005

Different types of functionalized thermoplastic polyphosphazenes such as poly(bis(furfuroxy)phosphazenes) (PBFP), poly(bis(1-adamantanemethylamine)phosphazenes) (PBAP) and poly(bis(cyanophenoxy)phosphazenes) (PBCP) were synthesized and further characterized to study their flame retardant properties. Structural characterizations were carried out by using GPC, FTIR, 1 H & 31 P NMR and wide angle XRD. Beside this, the solubility behaviour of these synthesized polyphosphazenes was checked in various protic and aprotic solvents. Thermal analysis and combustion properties of synthesized polyphosphazenes were investigated using thermogravimetric analysis (TGA), differential scanning calorimetry, UL-94 (vertical burning test) and cone calorimetry. The Limiting Oxygen Index values of synthesized polyphosphazenes were also determined from their % char yield obtained in TGA. It was found that the LOI value was highest for PBCP and lowest for PBAP amongst all substituted polyphosphazenes. Further, all the polymeric samples showed high flame retardancy with UL-94 V-0 rating. The water uptake property of synthesized polyphosphazene polymers was also invested by measuring their water contact angles which showed that all the polymers were hydrophobic in nature with their water contact angles in the range of 137 o to 141 o . Copyright © VBRI Press.

Synthesis of Rod-coil Molecules bearing Oligo-Phenylene Vinylene Motifs: Effect of PEO Chain Lengths on the Evolution of Nanostructures Morphology and their Photophysical Properties

Chetan J. Bhongale; Rahul Chaudhari;Yashwant Pandit

Advanced Materials Letters, 2019, Volume 10, Issue 10, Pages 731-736
DOI: 10.5185/amlett.2019.0024

The applications of nano-dispersed organic conjugated active compounds or materials as well as current research is concerned mainly with optimization and control of the optical properties, by particle size and supramolecular structure of the particles. The aromatic macromolecules consisting of conjugated rigid rod segment and hydrophilic flexible chain as coil in aqueous solution can aggregate into a variety of supramolecular structures through mutual interaction between aromatic rod and hydrophilic chains of molecules and water. Here we report the synthesis of newer oligo phenylene vinylene (OPV) based rod-coil molecules with varying chain-length polyethylene oxide (PEO) repeating units (n = 8, 17, 45). Formation and photophysical properties of their nanostructures in water are studied comparatively. The nanostructures evolution of these molecules is observed with simple reprecipitation method. The stable nanostructures were formed without addition of any surfactants. The fabricated nanostructures ultimately give the materials with ‘controlled’ aggregation induced enhanced photophysical properties. The self-assembly of such OPV type rod molecules in water without adding any surfactants, therefore, can provide a strategy for the construction of well-defined and stable nanostructures with certain chemical functionalities and physical properties as advanced materials for photonic, electronic and biological applications. Copyright © VBRI Press.

Dielectric Properties of Cu based Polymeric Composites in X-band of Microwave Frequency

Azizurrahaman Ansari

Advanced Materials Letters, 2019, Volume 10, Issue 10, Pages 737-740
DOI: 10.5185/amlett.2019.0034

In this work, the microwave dielectric properties of Cu and PEO based composite sheets are studied in the X-band. The desired composites sheets (thickness ~ 250 μm) are prepared via solution casting method, one of the best methods for sheet preparation. Various characterization techniques including the X-ray diffraction and Scanning Electron Microscopy are used to analyze the presence and uniform dispersion of Cu particles into polyethylene oxide (PEO) matrix. Vector Network Analyzer is employed to obtain the scattering parameters (S21/S11), which are then used to extract the dielectric permittivity of the samples using cavity perturbation technique in the X-band of microwave frequency. The real and imaginary parts (dielectric constant and dielectric loss) of the complex permittivity of synthesized composite sheets are found to be increased with the addition of copper contents (10, 20, and 30 wt %). This enhancement of the dielectric properties in the X-band of microwave frequency may be attributed to the interfacial polarization mechanism. Copyright © VBRI Press.

Critical Association Concentration of Dansyl-Poly (acrylic acid) Synthetized by Redox Polymerization Followed by an Esterification in Aqueous Solution: Spectrophotometric and Tensiometric Studies

Fateh Eltaboni; Abdelkader Imragaa; Mansour Khuzkhaz; Nada Ali; Naziha Baayu

Advanced Materials Letters, 2019, Volume 10, Issue 10, Pages 741-745
DOI: 10.5185/amlett.2019.0006

In the present work, the critical concentration for self-assembly of dansyl-polyacrylic acid (DANS-PAA) in aqueous solution has been characterized by a combination of spectrophotometric and tensiometric techniques, number average molar mass, degree of polymerization, and average number of bonds were also determined. The normalized absorbance value for DANS-PAA (10 -4 wt%) as a function of PAA concentration was at maximum below a critical self-assembly concentration (CAC) of 0.0005 g·mL −1 and decreased dramatically with PAA concentration above this CAC. This supposes that upon adding more polymer, assembly occurs in a short concentration range about 0.0005 g·mL −1 . Similarly, surface tension measurements for DANS-PAA decreased markedly with concentration after a threshold of around 0.0005 g·mL −1 , above which it remained constant at ca. 20 dyne·cm −1 . Consequently, the binary techniques produced an equivalent estimation of the CAC. Additionally, surface tension studies showed that the DANS-PAA polymer miscible with water caused surface tension to decrease by 49 % over a concentration range of 0 to 0.0014 g·mL −1 , whereas marked reduction in surface tension (33 %) upon adding PAA, and slight decreasing (7%) was recorded upon adding acrylic acid monomer (AA) to water. © VBRI Press.

Influence of Iron Doping on Structural and Optical Properties of Nickel Oxide Nanoparticles

Nashiruddin Ahammed; M. Mehedi Hassan

Advanced Materials Letters, 2019, Volume 10, Issue 10, Pages 746-751
DOI: 10.5185/amlett.2019.0004

In this article, auto combustion prepared Ni1-xFexO (0≤x≤0.10) nanoparticles (NPs) have been investigated for their structural, morphological and optical properties. X-ray diffraction (XRD) studies reveal that all Fe doped NiO samples crystallize in single phase without any impurity. The crystallite size monotonically decreases from 20 nm to 10 nm with increasing Fe substitution. Transmission Electron Microscope images represent that the synthesized NiO NPs with size around 28 nm. A red shift in UV-Vis spectra indicates that band gap can be tuned by Fe doping from 3.76 eV to 2.51 eV because of the upward shifting of t2g level.  The broad transmittance peak in Fourier transform infra-red spectra at 500 cm -1 is assigned to Ni–O stretching vibration mode. Differential scanning calorimetry curve revealed that the transition at 250 o C was exothermic because of structural relaxation. Copyright © VBRI Press.