Materials

781 KiB

Open AccessArticle

Preparation of Palladium-Supported Periodic Mesoporous Organosilicas and their Use as Catalysts in the Suzuki Cross-Coupling Reaction

by Jorge A. Corral, María I. López, Dolores Esquivel, Manuel Mora, César Jiménez-Sanchidrián and Francisco J. Romero-Salguero

Materials 2013, 6(4), 1554-1565; https://doi.org/10.3390/ma6041554 - 17 Apr 2013

Cited by 26 | Viewed by 6467

Abstract

Three periodic mesoporous materials, i.e., two organosilicas with either ethylene or phenylene bridges and one silica, have been used as supports for Pd nanoparticles. All Pd-supported samples (1.0 wt%) were prepared by the incipient wetness method and subsequently reduced in an H [...] Read more.

Three periodic mesoporous materials, i.e., two organosilicas with either ethylene or phenylene bridges and one silica, have been used as supports for Pd nanoparticles. All Pd-supported samples (1.0 wt%) were prepared by the incipient wetness method and subsequently reduced in an H₂ stream at 200 °C. Both hydrogen chemisorption and temperature programmed reduction experiments revealed significant differences depending on the support. Pd²⁺ species were more reducible on the mesoporous organosilicas than on their silica counterpart. Also, remarkable differences on the particle morphology were observed by transmission electron microscopy. All Pd-supported samples were active in the Suzuki cross-coupling reaction between bromobenzene and phenylboronic acid. Full article

(This article belongs to the Special Issue Advances in Mesoporous Materials)

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503 KiB

Open AccessArticle

Growth of Hexagonal Columnar Nanograin Structured SiC Thin Films on Silicon Substrates with Graphene–Graphitic Carbon Nanoflakes Templates from Solid Carbon Sources

by Xingfang Liu, Guosheng Sun, Bin Liu, Guoguo Yan, Min Guan, Yang Zhang, Feng Zhang, Yu Chen, Lin Dong, Liu Zheng, Shengbei Liu, Lixin Tian, Lei Wang, Wanshun Zhao and Yiping Zeng

Materials 2013, 6(4), 1543-1553; https://doi.org/10.3390/ma6041543 - 16 Apr 2013

Cited by 8 | Viewed by 6368

Abstract

We report a new method for growing hexagonal columnar nanograin structured silicon carbide (SiC) thin films on silicon substrates by using graphene–graphitic carbon nanoflakes (GGNs) templates from solid carbon sources. The growth was carried out in a conventional low pressure chemical vapor deposition [...] Read more.

We report a new method for growing hexagonal columnar nanograin structured silicon carbide (SiC) thin films on silicon substrates by using graphene–graphitic carbon nanoflakes (GGNs) templates from solid carbon sources. The growth was carried out in a conventional low pressure chemical vapor deposition system (LPCVD). The GGNs are small plates with lateral sizes of around 100 nm and overlap each other, and are made up of nanosized multilayer graphene and graphitic carbon matrix (GCM). Long and straight SiC nanograins with hexagonal shapes, and with lateral sizes of around 200–400 nm are synthesized on the GGNs, which form compact SiC thin films. Full article

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230 KiB

Open AccessArticle

Degradation of 2,4-Dichlorophenoxyacetic Acid (2,4-D) by Novel Photocatalytic Material of Tourmaline-Coated TiO₂ Nanoparticles: Kinetic Study and Model

by Xuesen Bian, Jianqiu Chen and Rong Ji

Materials 2013, 6(4), 1530-1542; https://doi.org/10.3390/ma6041530 - 15 Apr 2013

Cited by 36 | Viewed by 5771

Abstract

The novel complex photocatalytic material was prepared by coating TiO₂ nanoparticles on tourmaline using the sol-gel method, and used in the degradation of the herbicide 2,4-D. The results indicated that coating TiO₂ with tourmaline enhanced the photocatalytic activity significantly. Based on [...] Read more.

The novel complex photocatalytic material was prepared by coating TiO₂ nanoparticles on tourmaline using the sol-gel method, and used in the degradation of the herbicide 2,4-D. The results indicated that coating TiO₂ with tourmaline enhanced the photocatalytic activity significantly. Based on the research of a simplified model for the average light intensity in the photoreactor, the influence of the concentration of photocatalyst, and the initial concentration of 2,4-D, a model for the degradation of 2,4-D by the tourmaline-coated TiO₂ nanoparticles was established. Further tests showed that results calculated from this model were close to those obtained in the actual experiments. Full article

(This article belongs to the Special Issue Advances in Catalytic Materials)

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1217 KiB

Open AccessArticle

Enhanced Microwave Absorption Properties of α-Fe₂O₃-Filled Ordered Mesoporous Carbon Nanorods

by Yiming Wang, Liuding Wang and Hongjing Wu

Materials 2013, 6(4), 1520-1529; https://doi.org/10.3390/ma6041520 - 15 Apr 2013

Cited by 48 | Viewed by 6902

Abstract

A novel kind of α-Fe₂O₃-filled ordered mesoporous carbon nanorods has been synthesized by a facial hydrothermal method. Compared with dendritic α-Fe₂O₃ micropines, both a broader effective absorption range—from 10.5 GHz to 16.5 GHz with reflection loss [...] Read more.

A novel kind of α-Fe₂O₃-filled ordered mesoporous carbon nanorods has been synthesized by a facial hydrothermal method. Compared with dendritic α-Fe₂O₃ micropines, both a broader effective absorption range—from 10.5 GHz to 16.5 GHz with reflection loss (RL) less than −10 dB—and a thinner matching thickness of 2.0 mm have been achieved in the frequency range 2–18 GHz. The enhanced microwave absorption properties evaluated by the RL are attributed to the enhanced dielectric loss resulting from the intrinsic physical properties and special structures. Full article

(This article belongs to the Special Issue Microwave Processing of Materials)

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377 KiB

Open AccessArticle

Green Synthesis, Molecular Characterization and Associative Behavior of Some Gemini Surfactants without a Spacer Group

by Carla Villa, Sara Baldassari, Delia F. Chillura Martino, Alberto Spinella and Eugenio Caponetti

Materials 2013, 6(4), 1506-1519; https://doi.org/10.3390/ma6041506 - 12 Apr 2013

Cited by 14 | Viewed by 6459

Abstract

A series of new gemini surfactants without a spacer group, disodium 2,3-dialkyl-1,2,3,4-butanetetracarboxylates, were synthesized in a green chemistry context minimizing the use of organic solvents and applying microwaves (MW) when activation energy was required. Once the desired architecture was confirmed by means of [...] Read more.

A series of new gemini surfactants without a spacer group, disodium 2,3-dialkyl-1,2,3,4-butanetetracarboxylates, were synthesized in a green chemistry context minimizing the use of organic solvents and applying microwaves (MW) when activation energy was required. Once the desired architecture was confirmed by means of the nuclear magnetic resonance technique (¹H-NMR, ¹H-¹H COSY) for all the studied surfactants, the critical micellization concentration was determined by conductance measurements. The diffusion coefficient of micelles formed by the four compounds was characterized using pulsed field gradient (PFG)-NMR. Diffusion coefficients were found to be dependent on the concentration and on the number of carbon atoms in the alkyl chain. The absence of the spacer group, peculiar to this new series of gemini surfactants, may confer relatively low flexibility to the molecules, with potential implications on the interfacial properties, namely on micellization. These gemini surfactants might have interesting applications in the preparation of composite materials, in nanotechnology, in gene transfection and mainly, due to the low CMCs, as new interesting ingredients of cosmetics and toiletries. Full article

(This article belongs to the Special Issue Advances in Cosmetics)

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481 KiB

Open AccessArticle

Randomness and Statistical Laws of Indentation-Induced Pop-Out in Single Crystal Silicon

by Hu Huang, Hongwei Zhao, Chengli Shi, Lin Zhang, Shunguang Wan and Chunyang Geng

Materials 2013, 6(4), 1496-1505; https://doi.org/10.3390/ma6041496 - 12 Apr 2013

Cited by 23 | Viewed by 5947

Abstract

Randomness and discreteness for appearance of pop-out of the single crystal silicon with a (100) orientation were studied by a self-made indentation device. For a given maximum penetration load, the load P_po for appearance of pop-out fluctuates in a relatively large range, [...] Read more.

Randomness and discreteness for appearance of pop-out of the single crystal silicon with a (100) orientation were studied by a self-made indentation device. For a given maximum penetration load, the load P_po for appearance of pop-out fluctuates in a relatively large range, which makes it hard to study the effect of the loading/unloading rate on the load P_po. Experimental results with different maximum penetration loads indicate that the critical penetration load for appearance of pop-out is in the range of 15 mN~20 mN for the current used single crystal silicon. For a given maximum penetration load, the load P_po for appearance of pop-out seems random and discrete, but in the point of statistics, it has an obviously increasing trend with increase of the maximum penetration load and also the fraction P_po/P_max approximately keeps in the range of 0.2~0.5 for different maximum penetration loads changing from 15 mN to 150 mN. Full article

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777 KiB

Open AccessArticle

Mechanical Properties and Microstructure of Class C Fly Ash-Based Geopolymer Paste and Mortar

by Xueying Li, Xinwei Ma, Shoujie Zhang and Enzu Zheng

Materials 2013, 6(4), 1485-1495; https://doi.org/10.3390/ma6041485 - 9 Apr 2013

Cited by 105 | Viewed by 8743

Abstract

This paper presents workability, compressive strength and microstructure for geopolymer pastes and mortars made of class C fly ash at mass ratios of water-to-fly ash from 0.30 to 0.35. Fluidity was in the range of 145–173 mm for pastes and 131–136 mm for [...] Read more.

This paper presents workability, compressive strength and microstructure for geopolymer pastes and mortars made of class C fly ash at mass ratios of water-to-fly ash from 0.30 to 0.35. Fluidity was in the range of 145–173 mm for pastes and 131–136 mm for mortars. The highest strengths of paste and mortar were 58 MPa and 85 MPa when they were cured at 70 °C for 24 h. In XRD patterns, unreacted quartz and some reacted product were observed. SEM examination indicated that reacted product has formed and covered the unreacted particles in the paste and mortar that were consistent with their high strength. Full article

(This article belongs to the Special Issue Geopolymers and Geopolymeric Materials)

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603 KiB

Open AccessArticle

Organized Silica Films Generated by Evaporation-Induced Self-Assembly as Hosts for Iron Oxide Nanoparticles

by Ioanna Andreou, Heinz Amenitsch, Vlassis Likodimos, Polycarpos Falaras, Petros G. Koutsoukos and Epameinondas Leontidis

Materials 2013, 6(4), 1467-1484; https://doi.org/10.3390/ma6041467 - 9 Apr 2013

Cited by 7 | Viewed by 7191

Abstract

In this work, we prepared oriented mesoporous thin films of silica on various solid substrates using the pluronic block copolymer P123 as a template. We attempted to insert guest iron oxide (Fe_xO_y) nanoparticles into these films by two different [...] Read more.

In this work, we prepared oriented mesoporous thin films of silica on various solid substrates using the pluronic block copolymer P123 as a template. We attempted to insert guest iron oxide (Fe_xO_y) nanoparticles into these films by two different methods: (a) by co-precipitation—where iron precursors are introduced in the synthesis sol before deposition of the silica film—and subsequent oxide production during the film calcination step; (b) by preparing and calcining the silica films first then impregnating them with the iron precursor, obtaining the iron oxide nanoparticles by a second calcination step. We have examined the structural effects of the guest nanoparticles on the silica film structures using grazing incidence X-ray scattering (GISAXS), high-resolution transmission electron spectroscopy (HRTEM), spectroscopic ellipsometry, X-ray photoelectron spectroscopy (XPS), and Raman microscopy. Formation of nanoparticles by co-precipitation may induce substantial changes in the film structure leading, in our adopted process, to the appearance of lamellar ordering in the calcination stage. On the contrary, impregnation-based approaches perturb the film structures much more weakly, but are also less efficient in filling the pores with nanoparticles. Full article

(This article belongs to the Special Issue Advances in Sol-gel Derived Materials)

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981 KiB

Open AccessArticle

Dehydration Process of Hofmann-Type Layered Solids

by Omar Reyes-Martinez, Enelio Torres-García, Geonel Rodríguez-Gattorno and Edilso Reguera

Materials 2013, 6(4), 1452-1466; https://doi.org/10.3390/ma6041452 - 9 Apr 2013

Cited by 16 | Viewed by 5948

Abstract

In the present work the dehydration process of layered solids with formula unit M(H₂O)₂[Ni(CN)₄]·nH₂O, M = Ni, Co, Mn; n = 1, 2, 4 is studied using modulated thermogravimetry. The results show that [...] Read more.

In the present work the dehydration process of layered solids with formula unit M(H₂O)₂[Ni(CN)₄]·nH₂O, M = Ni, Co, Mn; n = 1, 2, 4 is studied using modulated thermogravimetry. The results show that water molecules need to overcome an energetic barrier (activation energy between 63 and 500 kJ/mol) in order to diffuse through the interlayer region. The related kinetic parameters show a dependence on the water partial pressure. On the other hand, X-ray diffraction results provide evidence that the dehydration process is accompanied by framework collapse, limiting the structural reversibility, except for heating below 80 °C where the ordered structure remains. Removal of water molecules from the interlayer region disrupts the long-range structural order of the solid. Full article

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2132 KiB

Open AccessArticle

Evaluation of Superficial and Dimensional Quality Features in Metallic Micro-Channels Manufactured by Micro-End-Milling

by Karla P. Monroy-Vázquez, Aldo Attanasio, Elisabetta Ceretti, Héctor R. Siller, Nicolás J. Hendrichs-Troeglen and Claudio Giardini

Materials 2013, 6(4), 1434-1451; https://doi.org/10.3390/ma6041434 - 3 Apr 2013

Cited by 28 | Viewed by 6840

Abstract

Miniaturization encourages the development of new manufacturing processes capable of fabricating features, like micro-channels, in order to use them for different applications, such as in fuel cells, heat exchangers, microfluidic devices and micro-electromechanical systems (MEMS). Many studies have been conducted on heat and [...] Read more.

Miniaturization encourages the development of new manufacturing processes capable of fabricating features, like micro-channels, in order to use them for different applications, such as in fuel cells, heat exchangers, microfluidic devices and micro-electromechanical systems (MEMS). Many studies have been conducted on heat and fluid transfer in micro-channels, and they appeared significantly deviated from conventional theory, due to measurement errors and fabrication methods. The present research, in order to deal with this opportunity, is focused on a set of experiments in the micro-milling of channels made of aluminum, titanium alloys and stainless steel, varying parameters, such as spindle speed, depth of cut per pass (a_p), channel depth (d), feed per tooth (f_z) and coolant application. The experimental results were analyzed in terms of dimensional error, channel profile shape deviation from rectangular and surface quality (burr and roughness). The micro-milling process was capable of offering quality features required on the micro-channeled devices. Critical phenomena, like run-out, ploughing, minimum chip thickness and tool wear, were encountered as an explanation for the deviations in shape and for the surface quality of the micro-channels. The application of coolant and a low depth of cut per pass were significant to obtain better superficial quality features and a smaller dimensional error. In conclusion, the integration of superficial and geometrical features on the study of the quality of micro-channeled devices made of different metallic materials contributes to the understanding of the impact of calibrated cutting conditions in MEMS applications. Full article

(This article belongs to the Special Issue Advances in Microelectromechanical Systems (MEMS) Materials)

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17 KiB

Open AccessCorrection

Correction: Daramola, M.O.; Aransiola, E.F.; Ojumu, T.V. Potential Applications of Zeolite Membranes in Reaction Coupling Separation Processes. Materials 2012, 5, 2101-2136.

by Michael O. Daramola, Elizabeth F. Aransiola and Tunde V. Ojumu

Materials 2013, 6(4), 1432-1433; https://doi.org/10.3390/ma6041432 - 2 Apr 2013

Cited by 1 | Viewed by 4231

Abstract

Due to an oversight by the authors, Table 4 in the aforementioned review article [1] should have been referred to as obtained from reference [2]: Khajavi, S. Separation of Process Water Using Hydroxy Sodalite Membranes. PhD Thesis, Delft University of Technology, Delft, The [...] Read more.

Due to an oversight by the authors, Table 4 in the aforementioned review article [1] should have been referred to as obtained from reference [2]: Khajavi, S. Separation of Process Water Using Hydroxy Sodalite Membranes. PhD Thesis, Delft University of Technology, Delft, The Netherlands, 2010. Furthermore, an additional affiliation for the first author of this review is added as follows: Catalysis Engineering Section, Delft University of Technology, Julianalaan 136, 2628 BL, Delft, The Netherlands The authors apologize for any inconvenience this may have caused. [...] Full article

523 KiB

Open AccessArticle

A Novel Hydrazinecarbothioamide as a Potential Corrosion Inhibitor for Mild Steel in HCl

by Ahmed A. Al-Amiery, Abdul Amir H. Kadhum, Abu Bakar Mohamad and Sutiana Junaedi

Materials 2013, 6(4), 1420-1431; https://doi.org/10.3390/ma6041420 - 2 Apr 2013

Cited by 107 | Viewed by 7476

Abstract

2-(1-methyl-4-((E)-(2-methylbenzylidene)amino)-2-phenyl-1H-pyrazol-3(2H)-ylidene)-hydrazineecarbothioamide (HCB) was synthesized as a corrosion inhibitor from the reaction of 4-aminoantipyrine, thiosemicarbazide and 2-methylbenzaldehyde. The corrosion inhibitory effects of HCB on mild steel in 1.0 M HCl were investigated using potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS). The results showed [...] Read more.

2-(1-methyl-4-((E)-(2-methylbenzylidene)amino)-2-phenyl-1H-pyrazol-3(2H)-ylidene)-hydrazineecarbothioamide (HCB) was synthesized as a corrosion inhibitor from the reaction of 4-aminoantipyrine, thiosemicarbazide and 2-methylbenzaldehyde. The corrosion inhibitory effects of HCB on mild steel in 1.0 M HCl were investigated using potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS). The results showed that HCB inhibited mild steel corrosion in acidic solution and inhibition efficiency increased with an increase in the concentration of the inhibitor. The inhibition efficiency was up to 96.5% at 5.0 mM. Changes in the impedance parameters suggested that HCB adsorbed on the surface of mild steel, leading to the formation of a protective film. The novel corrosion inhibitor synthesized in the present study was characterized using Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) spectral data. Full article

(This article belongs to the Special Issue Corrosion Monitoring and Control)

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763 KiB

Open AccessArticle

Extraction of Perchlorate Using Porous Organosilicate Materials

by Brandy J. Johnson, Iwona A. Leska, Brian J. Melde, Ronald L. Siefert, Anthony P. Malanoski, Martin H. Moore, Jenna R. Taft and Jeffrey R. Deschamps

Materials 2013, 6(4), 1403-1419; https://doi.org/10.3390/ma6041403 - 2 Apr 2013

Cited by 1 | Viewed by 5575

Abstract

Sorbent materials were developed utilizing two morphological structures, comprising either hexagonally packed pores (HX) or a disordered pore arrangement (CF). The sorbents were functionalized with combinations of two types of alkylammonium groups. When capture of perchlorate by the sorbents was compared, widely varying [...] Read more.

Sorbent materials were developed utilizing two morphological structures, comprising either hexagonally packed pores (HX) or a disordered pore arrangement (CF). The sorbents were functionalized with combinations of two types of alkylammonium groups. When capture of perchlorate by the sorbents was compared, widely varying performance was noted as a result of differing morphology and/or functional group loading. A material providing improved selectivity for perchlorate over perrhenate was synthesized with a CF material using N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride. Materials were applied in batch and column formats. Binding isotherms followed the behavior expected for a system in which univalent ligands of varying affinity compete for immobilized sites. Performance of the sorbents was also compared to that of commercial Purolite materials. Full article

(This article belongs to the Special Issue Advances in Mesoporous Materials)

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297 KiB

Open AccessArticle

Chitosonic^® Acid as a Novel Cosmetic Ingredient: Evaluation of its Antimicrobial, Antioxidant and Hydration Activities

by Shu-Mei Lee, Kun-Ho Liu, Yen-Yu Liu, Yen-Po Chang, Chih-Chien Lin and Yi-Shyan Chen

Materials 2013, 6(4), 1391-1402; https://doi.org/10.3390/ma6041391 - 28 Mar 2013

Cited by 23 | Viewed by 7516

Abstract

Chitosonic^® Acid, carboxymethyl hexanoyl chitosan, is a novel chitosan material that has recently been accepted by the Personal Care Products Council as a new cosmetic ingredient with the INCI (International Nomenclature of Cosmetic Ingredients) name Carboxymethyl Caprooyl Chitosan. In this study, we [...] Read more.

Chitosonic^® Acid, carboxymethyl hexanoyl chitosan, is a novel chitosan material that has recently been accepted by the Personal Care Products Council as a new cosmetic ingredient with the INCI (International Nomenclature of Cosmetic Ingredients) name Carboxymethyl Caprooyl Chitosan. In this study, we analyze several important cosmetic characteristics of Chitosonic^® Acid. Our results demonstrate that Chitosonic^® Acid is a water-soluble chitosan derivative with a high HLB value. Chitosonic^® Acid can form a nano-network structure when its concentration is higher than 0.5% and can self-assemble into a nanosphere structure when its concentration is lower than 0.2%. Chitosonic^® Acid has potent antimicrobial activities against gram-positive bacteria, gram-negative bacteria and fungus. Chitosonic^® Acid also has moderate DPPH radical scavenging activity. Additionally, Chitosonic^® Acid exhibits good hydration activity for absorbing and retaining water molecules with its hydrophilic groups. From a safety point of view, Chitosonic^® Acid has no cytotoxicity to L-929 cells if its concentration is less than 0.5%. Moreover, Chitosonic^® Acid has good compatibilities with various normal cosmetic ingredients. Therefore, we propose that Chitosonic^® Acid has the potential to be a widely used ingredient in various types of cosmetic products. Full article

(This article belongs to the Special Issue Advances in Cosmetics)

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1221 KiB

Open AccessArticle

Cellulose Perversions

by João P. Canejo and Maria H. Godinho

Materials 2013, 6(4), 1377-1390; https://doi.org/10.3390/ma6041377 - 28 Mar 2013

Cited by 21 | Viewed by 7264

Abstract

Cellulose micro/nano-fibers can be produced by electrospinning from liquid crystalline solutions. Scanning electron microscopy (SEM), as well as atomic force microscopy (AFM) and polarizing optical microscopy (POM) measurements showed that cellulose-based electrospun fibers can curl and twist, due to the presence of an [...] Read more.

Cellulose micro/nano-fibers can be produced by electrospinning from liquid crystalline solutions. Scanning electron microscopy (SEM), as well as atomic force microscopy (AFM) and polarizing optical microscopy (POM) measurements showed that cellulose-based electrospun fibers can curl and twist, due to the presence of an off-core line defect disclination, which was present when the fibers were prepared. This permits the mimicking of the shapes found in many systems in the living world, e.g., the tendrils of climbing plants, three to four orders of magnitude larger. In this work, we address the mechanism that is behind the spirals’ and helices’ appearance by recording the trajectories of the fibers toward diverse electrospinning targets. The intrinsic curvature of the system occurs via asymmetric contraction of an internal disclination line, which generates different shrinkages of the material along the fiber. The completely different instabilities observed for isotropic and anisotropic electrospun solutions at the exit of the needle seem to corroborate the hypothesis that the intrinsic curvature of the material is acquired during liquid crystalline sample processing inside the needle. The existence of perversions, which joins left and right helices, is also investigated by using suspended, as well as flat, targets. Possible routes of application inspired from the living world are addressed. Full article

(This article belongs to the Special Issue Advances in Cellulosic Materials)

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418 KiB

Open AccessArticle

Magnetic Graphene Oxide: Effect of Preparation Route on Reactive Black 5 Adsorption

by George Z. Kyzas, Nikolina A. Travlou, Orestis Kalogirou and Eleni A. Deliyanni

Materials 2013, 6(4), 1360-1376; https://doi.org/10.3390/ma6041360 - 28 Mar 2013

Cited by 105 | Viewed by 9885

Abstract

In this study, the effect of preparation route of magnetic graphene oxide (mGO) on Reactive Black 5 (RB5) adsorption was investigated. The synthesis of mGO was achieved both with (i) impregnation method (mGOi nanoparticles), and (ii) co-precipitation (mGOp nanoparticles). After synthesis, the full [...] Read more.

In this study, the effect of preparation route of magnetic graphene oxide (mGO) on Reactive Black 5 (RB5) adsorption was investigated. The synthesis of mGO was achieved both with (i) impregnation method (mGOi nanoparticles), and (ii) co-precipitation (mGOp nanoparticles). After synthesis, the full characterization with various techniques (SEM, FTIR, XRD, DTA, DTG, VSM) was achieved revealing many possible interactions/forces of dye-composite system. Effects of initial solution pH, effect of temperature, adsorption isotherms and kinetics were investigated in order to conclude about the aforementioned effect of the preparation method on dye adsorption performance of the magnetic nanocomposites. The adsorption evaluation of the magnetic nanoparticles presented higher adsorption capacity of mGOp derivative (188 mg/g) and lower of mGOi (164 mg/g). Equilibrium experiments are also performed studying the effect of contact time (pseudo-first and -second order equations) and temperature (isotherms at 25, 45 and 65 °C fitted to Langmuir and Freundlich model). A full thermodynamic evaluation was carried out, calculating the parameters of enthalpy, free energy and entropy (ΔH⁰, ΔG⁰ and ΔS⁰). Full article

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567 KiB

Open AccessReview

How Can Nanotechnology Help to Repair the Body? Advances in Cardiac, Skin, Bone, Cartilage and Nerve Tissue Regeneration

by Macarena Perán, María Angel García, Elena Lopez-Ruiz, Gema Jiménez and Juan Antonio Marchal

Materials 2013, 6(4), 1333-1359; https://doi.org/10.3390/ma6041333 - 28 Mar 2013

Cited by 53 | Viewed by 12946

Abstract

Nanotechnologists have become involved in regenerative medicine via creation of biomaterials and nanostructures with potential clinical implications. Their aim is to develop systems that can mimic, reinforce or even create in vivo tissue repair strategies. In fact, in the last decade, important advances [...] Read more.

Nanotechnologists have become involved in regenerative medicine via creation of biomaterials and nanostructures with potential clinical implications. Their aim is to develop systems that can mimic, reinforce or even create in vivo tissue repair strategies. In fact, in the last decade, important advances in the field of tissue engineering, cell therapy and cell delivery have already been achieved. In this review, we will delve into the latest research advances and discuss whether cell and/or tissue repair devices are a possibility. Focusing on the application of nanotechnology in tissue engineering research, this review highlights recent advances in the application of nano-engineered scaffolds designed to replace or restore the followed tissues: (i) skin; (ii) cartilage; (iii) bone; (iv) nerve; and (v) cardiac. Full article

(This article belongs to the Special Issue Advances in Nanoscale Biomaterials)

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188 KiB

Open AccessArticle

Half-Heusler (TiZrHf)NiSn Unileg Module with High Powder Density

by Sascha Populoh, Oliver C. Brunko, Krzysztof Gałązka, Wenjie Xie and Anke Weidenkaff

Materials 2013, 6(4), 1326-1332; https://doi.org/10.3390/ma6041326 - 27 Mar 2013

Cited by 36 | Viewed by 7347

Abstract

(TiZrHf)NiSn half-Heusler compounds were prepared by arc melting and their thermoelectric properties characterized in the temperature range between 325 K and 857 K, resulting in a Figure of Merit ZT ≈ 0.45. Furthermore, the prepared samples were used to construct a unileg module. [...] Read more.

(TiZrHf)NiSn half-Heusler compounds were prepared by arc melting and their thermoelectric properties characterized in the temperature range between 325 K and 857 K, resulting in a Figure of Merit ZT ≈ 0.45. Furthermore, the prepared samples were used to construct a unileg module. This module was characterized in a homemade thermoelectric module measurement stand and yielded 275 mW/cm² and a maximum volumetric power density of 700 mW/cm³. This was reached using normal silver paint as a contacting material; from an improved contacting, much higher power yields are to be expected. Full article

(This article belongs to the Section Advanced Materials Characterization)

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1295 KiB

Open AccessReview

Lithium Ion Battery Anode Aging Mechanisms

by Victor Agubra and Jeffrey Fergus

Materials 2013, 6(4), 1310-1325; https://doi.org/10.3390/ma6041310 - 27 Mar 2013

Cited by 344 | Viewed by 24792

Abstract

Degradation mechanisms such as lithium plating, growth of the passivated surface film layer on the electrodes and loss of both recyclable lithium ions and electrode material adversely affect the longevity of the lithium ion battery. The anode electrode is very vulnerable to these [...] Read more.

Degradation mechanisms such as lithium plating, growth of the passivated surface film layer on the electrodes and loss of both recyclable lithium ions and electrode material adversely affect the longevity of the lithium ion battery. The anode electrode is very vulnerable to these degradation mechanisms. In this paper, the most common aging mechanisms occurring at the anode during the operation of the lithium battery, as well as some approaches for minimizing the degradation are reviewed. Full article

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329 KiB

Open AccessReview

Alginate-Based Biomaterials for Regenerative Medicine Applications

by Jinchen Sun and Huaping Tan

Materials 2013, 6(4), 1285-1309; https://doi.org/10.3390/ma6041285 - 26 Mar 2013

Cited by 1053 | Viewed by 36436

Abstract

Alginate is a natural polysaccharide exhibiting excellent biocompatibility and biodegradability, having many different applications in the field of biomedicine. Alginate is readily processable for applicable three-dimensional scaffolding materials such as hydrogels, microspheres, microcapsules, sponges, foams and fibers. Alginate-based biomaterials can be utilized as [...] Read more.

Alginate is a natural polysaccharide exhibiting excellent biocompatibility and biodegradability, having many different applications in the field of biomedicine. Alginate is readily processable for applicable three-dimensional scaffolding materials such as hydrogels, microspheres, microcapsules, sponges, foams and fibers. Alginate-based biomaterials can be utilized as drug delivery systems and cell carriers for tissue engineering. Alginate can be easily modified via chemical and physical reactions to obtain derivatives having various structures, properties, functions and applications. Tuning the structure and properties such as biodegradability, mechanical strength, gelation property and cell affinity can be achieved through combination with other biomaterials, immobilization of specific ligands such as peptide and sugar molecules, and physical or chemical crosslinking. This review focuses on recent advances in the use of alginate and its derivatives in the field of biomedical applications, including wound healing, cartilage repair, bone regeneration and drug delivery, which have potential in tissue regeneration applications. Full article

(This article belongs to the Special Issue Advances in Multifunctional Materials)

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681 KiB

Open AccessArticle

Fabrication of Cellulose Film with Enhanced Mechanical Properties in Ionic Liquid 1-Allyl-3-methylimidaxolium Chloride (AmimCl)

by Jinhui Pang, Xin Liu, Xueming Zhang, Yuying Wu and Runcang Sun

Materials 2013, 6(4), 1270-1284; https://doi.org/10.3390/ma6041270 - 26 Mar 2013

Cited by 126 | Viewed by 10918

Abstract

More and more attention has been paid to environmentally friendly bio-based renewable materials as the substitution of fossil-based materials, due to the increasing environmental concerns. In this study, regenerated cellulose films with enhanced mechanical property were prepared via incorporating different plasticizers using ionic [...] Read more.

More and more attention has been paid to environmentally friendly bio-based renewable materials as the substitution of fossil-based materials, due to the increasing environmental concerns. In this study, regenerated cellulose films with enhanced mechanical property were prepared via incorporating different plasticizers using ionic liquid 1-allyl-3-methylimidazolium chloride (AmimCl) as the solvent. The characteristics of the cellulose films were investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM), thermal analysis (TG), X-ray diffraction (XRD), ¹³C Solid-state cross-polarization/magic angle spinning nuclear magnetic resonance (CP/MAS NMR) and tensile testing. The results showed that the cellulose films exhibited a homogeneous and smooth surface structure. It was noted that the thermal stability of the regenerated cellulose film plasticized with glycerol was increased compared with other regenerated cellulose films. Furthermore, the incorporation of plasticizers dramatically strengthened the tensile strength and improved the hydrophobicity of cellulose films, as compared to the control sample. Therefore, these notable results exhibited the potential utilization in producing environmentally friendly cellulose films with high performance properties. Full article

(This article belongs to the Special Issue Advances in Cellulosic Materials)

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443 KiB

Open AccessArticle

An Ultrasensitive Electrochemical Immunosensor for HIV p24 Based on Fe₃O₄@SiO₂ Nanomagnetic Probes and Nanogold Colloid-Labeled Enzyme–Antibody Copolymer as Signal Tag

by Ning Gan, Xiaowen Du, Yuting Cao, Futao Hu, Tianhua Li and Qianli Jiang

Materials 2013, 6(4), 1255-1269; https://doi.org/10.3390/ma6041255 - 25 Mar 2013

Cited by 56 | Viewed by 8316

Abstract

An ultrasensitive portable electrochemical immunosensor for human immunodeficiency virus p24 (HIV p24) antigen detection has been developed, whereby the detection sensitivity was 1000 times higher than that of the ELISA method. Firstly, a novel HRP enzyme–antibody copolymer (EV-p24 Ab2) was synthesized through an [...] Read more.

An ultrasensitive portable electrochemical immunosensor for human immunodeficiency virus p24 (HIV p24) antigen detection has been developed, whereby the detection sensitivity was 1000 times higher than that of the ELISA method. Firstly, a novel HRP enzyme–antibody copolymer (EV-p24 Ab2) was synthesized through an EnVision regent (EV, a dextrin amine skeleton anchoring more than 100 molecules of HRP and 15 molecules of anti IgG), then incubated in the secondary antibody of p24. Secondly, the copolymer was immobilized on the gold nanocolloids (AuNPs) to fabricate a novel signal tag (AuNPs/EV-p24 Ab2). Subsequently, a sandwich-type immunoreaction would take place between the capture probe (silicon dioxide-coated magnetic Fe₃O₄ nanoparticles (MNPs) labeled with the primary p24 antibody (MNPs-p24 Ab1)), p24 (different concentrations) and the signal tag [AuNPs/EV-p24 Ab2)] to form the immunocomplex. Finally, the immunocomplex was absorbed on the surface of screen printed carbon electrode (SPCE) by a magnet and immersed in the o-hydroxyl phenol (HQ) and H₂O₂. The large amounts of HRP on the signal tag can catalyze the oxidation of HQ by H₂O₂, which can induce an amplified reductive current. Moreover, the capture probe could improve the accumulation ability of p24 and facilitate its separation from the substrate through the magnet. Under optimal conditions, the proposed immunoassay exhibited good sensitivity to p24 within a certain concentration range from 0.001 to 10.00 ng/mL, with a detection limit of 0.5 pg/mL (S/N = 3). The proposed method can be used for real-time and early detection of HIV-infected people. Full article

(This article belongs to the Special Issue Advances in Nanoscale Biomaterials)

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818 KiB

Open AccessArticle

Characterization of an Exopolymeric Flocculant Produced by a Brachybacterium sp.

by Uchechukwu U. Nwodo, Mayowa O. Agunbiade, Ezekiel Green, Mutshinyalo Nwamadi, Karl Rumbold and Anthony I. Okoh

Materials 2013, 6(4), 1237-1254; https://doi.org/10.3390/ma6041237 - 25 Mar 2013

Cited by 30 | Viewed by 6933

Abstract

We evaluated the bioflocculant production potential of an Actinobacteria, which was isolated from a freshwater environment in the Eastern Cape province of South Africa. 16S rDNA nucleotide sequencing analyses revealed that the actinobacteria belongs to the Brachybacterium genus, and the sequences were deposited [...] Read more.

We evaluated the bioflocculant production potential of an Actinobacteria, which was isolated from a freshwater environment in the Eastern Cape province of South Africa. 16S rDNA nucleotide sequencing analyses revealed that the actinobacteria belongs to the Brachybacterium genus, and the sequences were deposited in the GenBank as Brachybacterium sp. UFH, with accession number HQ537131. Optimum fermentation conditions for bioflocculant production by the bacteria include an initial medium pH of 7.2, incubation temperature of 30 °C, agitation speed of 160 rpm and an inoculum size of 2% (vol/vol) of cell density 3.0 × 10⁸CFU/mL. The carbon, nitrogen and cation sources for optimum bioflocculant production were maltose (83% flocculating activity), urea (91.17% flocculating activity) and MgCl₂(91.16% flocculating activity). Optimum bioflocculant production coincided with the logarithmic growth phase of the bacteria, and chemical analyses of the bioflocculant showed 39.4% carbohydrate and 43.7% protein (wt/wt). The mass ratio of neutral sugar, amino sugar and uronic acids was 1.3:0.7:2.2. Fourier transform infrared spectroscopy (FTIR) indicated the presence of carboxyl, hydroxyl and amino groups, amongst others, typical for heteropolysaccharide and glycosaminoglycan polysaccharides. Bioflocculant pyrolysis showed thermal stability at over 600 °C, while scanning electron microscope (SEM) imaging revealed a maze-like structure of interlaced flakes. Its high flocculation activity suggests its suitability for industrial applicability. Full article

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1639 KiB

Open AccessReview

Synthetic Aspects and Electro-Optical Properties of Fluorinated Arylenevinylenes for Luminescence and Photovoltaics

by Carmela Martinelli, Gianluca M. Farinola, Vita Pinto and Antonio Cardone

Materials 2013, 6(4), 1205-1236; https://doi.org/10.3390/ma6041205 - 25 Mar 2013

Cited by 36 | Viewed by 6515

Abstract

In this review, the main synthetic aspects and properties of fluorinated arylenevinylene compounds, both oligomers and polymers, are summarized and analyzed. Starting from vinyl organotin derivatives and aryl halides, the Stille cross-coupling reaction has been successfully applied as a versatile synthetic protocol to [...] Read more.

In this review, the main synthetic aspects and properties of fluorinated arylenevinylene compounds, both oligomers and polymers, are summarized and analyzed. Starting from vinyl organotin derivatives and aryl halides, the Stille cross-coupling reaction has been successfully applied as a versatile synthetic protocol to prepare a wide series of π-conjugated compounds, selectively fluorinated on the aromatic and/or vinylene units. The impact of fluoro-functionalization on properties, the solid state organization and intermolecular interactions of the synthesized compounds are discussed, also in comparison with the non-fluorinated counterparts. Luminescent and photovoltaic applications are also discussed, highlighting the role of fluorine on the performance of devices. Full article

(This article belongs to the Section Energy Materials)

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Materials, Volume 6, Issue 4 (April 2013) – 24 articles , Pages 1205-1565

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