Volume 9, Issue 9, September 2018

There is plenty of room at the bottom: New Insights into old observations

Abraham Marmur

Advanced Materials Letters, 2018, Volume 9, Issue 9, Pages 610-613
DOI: 10.5185/amlett.2018.2002

Three case studies are analysed to demonstrate (1) the usefulness of fundamental understanding and theoretical modelling in systems with small dimensions, for which interfacial phenomena are crucial; (2) The possibility of advancing our understanding even in areas that are considered old; and (3) The advantages of simple theories.

Facile synthesis of graphene quantum dots based on electrochemical method and their application for specific Fe3+ detection

Yang Fu; Runze Liu; Jinfang Zhi

Advanced Materials Letters, 2018, Volume 9, Issue 9, Pages 614-618
DOI: 10.5185/amlett.2018.2052

A novel electrochemical strategy for economical, environmental-friendly, simple and facile synthesis of glycine functionalized graphene quantum dots (GQDs) based on direct exfoliation and oxidation from graphite rods was reported. The average diameter of as-synthesized GQDs is 30 nm. Due to the rich nitrogen and oxygen functional groups on the surface of GQDs, the GQDs dispersion was bright yellow and further applied in selective detection of ferric ion (Fe 3+ ). A sensor based on photoluminescence quenching of GQDs after adding Fe 3+  has a limit of detection of 3.09 μM, which is lower than the maximum level (0.3 mg/L, equivalent to 5.4 µM) of Fe 3+ permitted in drinking water by the U.S. Environmental Protection Agency (EPA). The fluorescent sensor has a wide linear range of 10–150 μM. Moreover, due to the low cytotoxicity of as-prepared GQDs, this study may provide a new analytical platform for further applications of GQDs in real environmental and biological system.

Understanding the applicability of natural fibre composites in hybrid folded structures

Avishek Chanda; Debes Bhattacharyya

Advanced Materials Letters, 2018, Volume 9, Issue 9, Pages 619-623
DOI: 10.5185/amlett.2018.2073

One of the important by-products of wood is veneer sheets which can be pressed together to form plywood. Also known as radiata pine veneer, plywood has been increasingly used in different engineering applications and its unique thin structure, with significant mechanical properties, has increased its demand for hybrid deformed structures. The main scope of the present work is to understand the formability characteristics of the plywood with multiple bend axis on the same plane. The properties of wood nullify the normal bending process due to the significant amount of spring-back for the inherent properties of the constituent natural fibres bounded by a predominant lignin component. The process of in-situ curing and post-forming curing were used to achieve the desired folds. Experiment was performed on various plywood samples, with 4-point bending rig, to understand the variation in stress and strain due to variable distances between the bends and the maximum post-curing time. Finally, the overall spring-back analytically varied by 1.96%. 

Remote photonic sensing of glucose concentration via analysis of time varied speckle patterns

Nisan Ozana; Roy Talman; Amir Shemer; Ariel Schwartz; Sagi Polani; Ran Califa; Yevgeny Beiderman; Joaquin Ruiz-Rivas; Javier Garc

Advanced Materials Letters, 2018, Volume 9, Issue 9, Pages 624-628
DOI: 10.5185/amlett.2018.2054

The ability to perform a remote sensing of glucose in the blood stream can be very applicable. The novel method presented in this paper is based on two optical approaches both based on the extraction and analysis of the changes in the collected speckle field. The first physical effect used for the detection is the temporal changes of the back scattered secondary speckles produced in the skin due to the changes of the blood stream parameters as a function of the glucose concentration in the blood. These cardio related changes can be analyzed with different machine learning algorithms to enhance the sensitivity of the measurements. The second physical effect assisting in performing the remote glucose sensing is the Faraday rotation effect in which the polarization of linearly polarized light is rotated when scattered from materials exhibiting this effect while being exposed to a magnetic field.

Work function and induced band bending characterization for engineering of selective contact for solar cells

Marshall Wilson; Jie Cui;Jacek Lagowski; Alexandre Savtchouk; Ziv Hameiri

Advanced Materials Letters, 2018, Volume 9, Issue 9, Pages 629-631
DOI: 10.5185/amlett.2018.2084

This work demonstrates the effectiveness of non-contact Kelvin-probe and surface photovoltage characterization of the work function (WF) induced barriers formed in silicon (Si) by thin 5nm carrier selective contact films of MoOx, TiO2 and MgF2.  The calibrated Kelvin probe in the dark and under strong illumination where used to determine the dark WF of the deposited films and the band bending in the Si, FBB = WFDark – WFLight.  The ac-surface photo voltage provided an independent measurement of the Si depletion layer width.  Whole wafer mapping of all parameters can be performed.  For n-type Si the high work function oxides MoOx (WF~5.7eV) and TiO2 (WF~5.0eV) are found to induce a depletion barrier with the height increasing with WF as FBB[eV] = 0.23WF – 0.77, i.e. quite similar to the well-known relationship for metal-silicon contacts.  For the low work function MgF2 film, a depletion barrier was induced only in p-type Si.  For this case, full wafer mapping revealed a lower WF pattern coinciding with larger band bending giving the slope, DFBB/DWF ~ -0.52.  The slopes of 0.23 and 0.52 for n- and p-type Si deviates significantly from the ideal slope of 1.  This result implies that the barrier formation at the Film-Si heterojunction is limited by the effect of interfacial layers and interface states in analogy to the well-known effects in Metal-Si contacts. It is believed that this demonstrated very fast, preparation-free, non-contact characterization technique can benefit research and engineering of selective contacts for solar cells. 

Development of advanced aerogel-based composite material with high performance for building industry

Marina Stipetic

Advanced Materials Letters, 2018, Volume 9, Issue 9, Pages 632-637
DOI: 10.5185/amlett.2018.2087

According to the European Commission's plan, greenhouse gas emissions in the European Union must be reduced by 80% compared to the level from year 1990 (see [1]). In order to reduce the energy consumption of the buildings, an optimization of the building insulation is an effective measure. Super-insulating materials are promising materials to fulfil these objectives. Present work describes development of advanced aerogel-based composite material with small thickness. Such composite materials based on silica aerogel can be extremely efficient with regard to their thermal insulation properties. In this study, the experimental investigations of hydrothermal and mechanical performance were conducted on the aerogel-based insulation blanket and its constituents (core material and aerogel granules). Furthermore, the effect of ageing to performance of such material is assessed. The developed aerogel-based insulation material is characterized by very low thermal conductivity (under 18.0 mW/(m·K)) and good hydrothermal properties. It has been shown here that the thermal conductivity of an insulating material made of glass fibre can be reduced to more than half with using of aerogel granules. This aerogel-based composite material is characterized by good hydric properties. The material is both hydrophobic and water vapor permeable. In addition, mechanical properties of new composite material fulfil the multifunctional application of this promising insulating material. New product can be used for external thermal insulation system (ETICS) as well as for internal thermal insulation system.

Effect of the substrate bias in diamond deposition during hot filament chemical vapor deposition: Approach by non-classical crystallization 

Jin-Woo Park; Kwang-Ho Kim; Nong-Moon Hwang

Advanced Materials Letters, 2018, Volume 9, Issue 9, Pages 638-642
DOI: 10.5185/amlett.2018.2082

The effect of the substrate bias on the diamond deposition was studied using a hot filament chemical vapor deposition (HFCVD) reactor. Both growth rate of diamonds and sp < sup > 3 /sp < sup > 2 ratio increased with increasing the substrate bias from – 200 V to + 45 V. At + 60 V where the DC glow discharge occurred, however, the data deviated significantly from the tendency. These results were explained by the new concept of non-classical crystallization, where a building block of diamond growth is a charged nanoparticle rather than an atom. Based on the previously reported experimental confirmation of the gas phase generation of negatively-charged diamond nanoparticles, the bias effect on the diamond deposition behavior could be consistently explained.

Palm oil fatty acids and carotenoids extraction with lipase immobilized in magnetic nanoparticles 

Tamires Carvalho; Adejanildo Pereira; Priscilla V. Finotelli; Priscilla F. F. Amaral

Advanced Materials Letters, 2018, Volume 9, Issue 9, Pages 643-646
DOI: 10.5185/amlett.2018.2059

Magnetite nanoparticles have unique properties including superparamagnetism and low toxicity. They have been used as supports for immobilization of enzymes because of the advantage including easy separation and effective recycle under external magnetic field. Therefore, the present study aimed at developing a new enzymatic biocatalyst from the immobilization of Yarrowia lipolytica’s (IMUFRJ 50682) lipase on magnetic nanoparticles for its use in free fatty acids and carotenoids extraction from palm oil (Elaeis guineenses). The lipase production conducted in a 4 L benchtop bioreactor generated a crude enzyme extract with hydrolytic p-nitrophenyl laurate activity of 58 U/ml after 24 h. Lipase was immobilized by adsorption on magnetite nanoparticles (Fe3O4). The crude enzymatic extract, both free and immobilized, were used in the hydrolysis of palm oil. Temperature, reaction time and substrate ratio (water/palm oil) were evaluated in a central composite experimental design. The initial concentration of fatty acids and carotenoids present in palm oil obtained via traditional extraction (using organic solvents) were 82.45% and 1892.3 mg/kg, respectively. Using crude lipase extract immobilized in nanoparticles, after 120 min, temperature of 24°C and water/oil ratio of 2, it was possible to obtain similar values, with the advantage of easily removing the catalyst from reaction media and reusing it.

Microwave-assisted synthesis and mechanistic study of multicolor emissive Au nanoclusters using thiol-containing biomolecules  

Yong Yu; Preston Yi Jie Ching; Yen Nee Tan

Advanced Materials Letters, 2018, Volume 9, Issue 9, Pages 647-651
DOI: 10.5185/amlett.2018.2081

Developing effective synthesis method for few-atom gold nanoclusters (AuNCs) with tunable emissions is vitally important to gain better understanding of their formation mechanism and provide more design flexibilities to suite for various applications such as multiplex cellular imaging and/or light-emitting diodes. This paper reports a fast method (<30 minutes) of preparing multicolour (red, orange, near infrared) emissive AuNCs via a microwave-assisted biotemplating synthesis approach. A series of analytical tools such as UV-vis and photoluminescence spectroscopies, transmission electron microscopy (TEM) and polyacrylamide gel electrophoresis (PAGE) have been utilized to characterize the resultant AuNCs and unravel the formation mechanism that lead to their multicolour emissive properties. It was found that the surface charge of the thiol-containing peptide reagent and the peptide-to-Au ratio are crucial factors to control the size and emission colour of the resultant AuNCs. By bringing the solution pH to near the isoelectric point of peptide ligand (~3), the red (lem = 725 nm) emissive AuNC which is initially stable at alkaline conditions (pH-12) tends to aggregate due to deficiency of surface charge, thus forming a larger and orange (lem = 640 nm) emissive AuNC. By further applying an even lower peptide-to-Au ratio to fine-tune the protection power of thiolate ligands, a near-infrared (lem = 846 nm) emissive AuNC has been synthesized. Compared to other microwave-assisted synthesis of AuNCs, current study is featured by its simplicity, rapidity, and versatility to tune the emission wavelength of resultant AuNCs in a much broader range (up to 206 nm).

Metal matrix nano composites using graphene nano platelets indented on copper particles in aluminium matrix

Rachit Ranjan; Nirmal Kumar Singh; Anand Prakash Jaiswal; Vivek Bajpai

Advanced Materials Letters, 2018, Volume 9, Issue 9, Pages 652-655
DOI: 10.5185/amlett.2018.2078

Aluminium matrix composite was prepared by using an innovative approach of using graphene indent on copper particles as inforcement material. The reinforcement was mixed and ball milled for 30 and 60 min respectively to get proper sight of copper fracture where graphene (GNP) can be embedded. The reinforcement was also milled for 30 minutes to get uniform distribution of reinforcement in powder state. Casting technique was used with argon gas environment and mechanical stirrer to get final composite material. The morphological analysis has shown proper indent of graphene with Al-Cu and Cu-GNP interface. The composite so formed has micro hardness of 87 HV with an increment of 36.78% whereas yield strength and ultimate tensile strength have increased by 36.67% and 37.162% respectively.

Improved electrical and photoluminescence properties in Nd substitution of 0.94(Na0.5Bi0.5TiO3)-0.06BaTiO3 lead free multi-functional ceramics 

Kumara Raja Kandula; Sai Santosh Kumar Raavi; Saket Asthana

Advanced Materials Letters, 2018, Volume 9, Issue 9, Pages 656-659
DOI: 10.5185/amlett.2018.2038

Nd 3+ -substituted lead free 0.94(Na0.5Bi0.5-XNdXTiO3)-0.06BaTiO3 (x=0, 0.01) ceramics were synthesized by using conventional solid state route. The XRD studies revealed the phase purity and existence of the monoclinic (Cc), cubic (Pm3m) along with the minor tetragonal phases confirmed with help of structural refinement. The electrical poling field induces the structural modification to rhombhohedral (R3c), cubic (Pm3m) along with the minor tetragonal phase (P4mm). The dielectric measurements revealed the relaxor behavior. The coercive field drops remarkable and there is slight improvement in the polarization with the substitution of Nd as compared to the pure 0.94(Na0.5Bi0.5TiO3)-0.06BaTiO3. The luminescence occurred from the optically active element Nd 3+ under the influence of the average crystal symmetry of 0.94(Na0.5Bi0.5TiO3)-0.06BaTiO3. The luminescence quenching observed without any shift in position upon the poling supports the observation of higher symmetric structure.

Evaluation of mild steel hollow and foam filled circular tubes under axial loading

Dipen Kumar Rajak; Sushrut A. Gawande; L. A. Kumaraswamidhas

Advanced Materials Letters, 2018, Volume 9, Issue 9, Pages 660-664
DOI: 10.5185/amlett.2018.2041

AAF (Aluminium alloy foam) has turned out to be a beneficiary content in the automotive sector across the globe. It has been in applications due its light weight tendency and providing high strength and energy absorbing capacity. The content of paper marks a plot on the energy absorption capability of the AAF filled circular tubes. AlSi10Mg has been produced by the melt route method. Aluminium foam filled circular tubes, mild steel (MS) thin walled hollow tubes were tested under compression loading to note the energy absorption and deformation behavior. The compression was carried out with a strain rate of 0.1/s. FESEM tests was conducted to obtain the data at micro and macro levels. The test results portray that the foam filled circular tubes shows more energy absorption than the hollow (ERW) tubes at 0.1/s strain rate.