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Nanomaterials, Volume 3, Issue 3 (September 2013), Pages 317-571

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Research

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Open AccessArticle A Strategy for Hydroxide Exclusion in Nanocrystalline Solid-State Metathesis Products
Nanomaterials 2013, 3(3), 317-324; doi:10.3390/nano3030317
Received: 23 May 2013 / Revised: 9 June 2013 / Accepted: 18 June 2013 / Published: 24 June 2013
Cited by 4 | PDF Full-text (424 KB) | HTML Full-text | XML Full-text
Abstract
We demonstrate a simple strategy to either prevent or enhance hydroxide incorporation in nanocrystalline solid-state metathesis reaction products prepared in ambient environments. As an example, we show that ZnCO3 (smithsonite) or Zn5(CO3)2(OH)6 (hydrozincite) forms extremely
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We demonstrate a simple strategy to either prevent or enhance hydroxide incorporation in nanocrystalline solid-state metathesis reaction products prepared in ambient environments. As an example, we show that ZnCO3 (smithsonite) or Zn5(CO3)2(OH)6 (hydrozincite) forms extremely rapidly, in less than two minutes, to form crystalline domains of 11 ±  2 nm and 6 ± 2 nm, respectively. The phase selectivity between these nanocrystalline products is dominated by the alkalinity of the hydrated precursor salts, which may in turn affect the availability of carbon dioxide during the reaction. Thus, unlike traditional aqueous precipitation reactions, our solid-state method offers a way to produce hydroxide-free, nanocrystalline products without active pH control. Full article
(This article belongs to the Special Issue New Developments in Nanomaterial Analysis)
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Open AccessArticle CO and NO2 Selective Monitoring by ZnO-Based Sensors
Nanomaterials 2013, 3(3), 357-369; doi:10.3390/nano3030357
Received: 21 May 2013 / Revised: 20 June 2013 / Accepted: 21 June 2013 / Published: 5 July 2013
Cited by 21 | PDF Full-text (1418 KB) | HTML Full-text | XML Full-text
Abstract
ZnO nanomaterials with different shapes were synthesized, characterized and tested in the selective monitoring of low concentration of CO and NO2 in air. ZnO nanoparticles (NPs) and nanofibers (NFs) were synthesized by a modified sol-gel method in supercritical conditions and electrospinning technique,
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ZnO nanomaterials with different shapes were synthesized, characterized and tested in the selective monitoring of low concentration of CO and NO2 in air. ZnO nanoparticles (NPs) and nanofibers (NFs) were synthesized by a modified sol-gel method in supercritical conditions and electrospinning technique, respectively. CO and NO2 sensing tests have demonstrated that the annealing temperature and shape of zinc oxide nanomaterials are the key factors in modulating the electrical and sensing properties. Specifically, ZnO NPs annealed at high temperature (700 °C) have been found sensitive to CO, while they displayed negligible response to NO2. The opposite behavior has been registered for the one-dimensional ZnO NFs annealed at medium temperature (400 °C). Due to their adaptable sensitivity/selectivity characteristics, the developed sensors show promising applications in dual air quality control systems for closed ambient such as automotive cabin, parking garage and tunnels. Full article
(This article belongs to the Special Issue Nanomaterials in Sensors)
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Open AccessArticle Alkyl and Aromatic Amines as Digestive Ripening/Size Focusing Agents for Gold Nanoparticles
Nanomaterials 2013, 3(3), 370-392; doi:10.3390/nano3030370
Received: 29 May 2013 / Revised: 22 June 2013 / Accepted: 26 June 2013 / Published: 5 July 2013
Cited by 4 | PDF Full-text (3917 KB) | HTML Full-text | XML Full-text
Abstract
Both long chain alkyl thiols and alkyl amines behave as size focusing agents for gold nanoparticles, a process that is under thermodynamic control. However, amines do not oxidize surface gold atoms while thiols do oxidize surface gold to gold(I) with evolution of hydrogen
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Both long chain alkyl thiols and alkyl amines behave as size focusing agents for gold nanoparticles, a process that is under thermodynamic control. However, amines do not oxidize surface gold atoms while thiols do oxidize surface gold to gold(I) with evolution of hydrogen gas. Therefore, alkyl amines participate in digestive ripening by a different mechanism. The efficiency of alkyl amines for this process is described and compared, and ultimate gold particle size differences are discussed. Reported herein is a detailed investigation of alkyl chain lengths for alkyl amines, aromatic amines (aniline), and unusually reactive amines (2-phenylethyl amine). Also, two methods of preparation of the crude gold nanoparticles were employed: gold ion reduction/inverse micelle vs. metal vaporization (Solvated Metal Atom Dispersion—SMAD). Full article
Open AccessArticle Synthesis of Microspherical LiFePO4-Carbon Composites for Lithium-Ion Batteries
Nanomaterials 2013, 3(3), 443-452; doi:10.3390/nano3030443
Received: 27 June 2013 / Revised: 16 July 2013 / Accepted: 17 July 2013 / Published: 22 July 2013
Cited by 5 | PDF Full-text (2572 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
This paper reports an “all in one” procedure to produce mesoporous, micro-spherical LiFePO4 composed of agglomerated crystalline nanoparticles. Each nanoparticle is individually coated with a thin glucose-derived carbon layer. The main advantage of the as-synthesized materials is their good performance at high
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This paper reports an “all in one” procedure to produce mesoporous, micro-spherical LiFePO4 composed of agglomerated crystalline nanoparticles. Each nanoparticle is individually coated with a thin glucose-derived carbon layer. The main advantage of the as-synthesized materials is their good performance at high charge-discharge rates. The nanoparticles and the mesoporosity guarantee a short bulk diffusion distance for both lithium ions and electrons, as well as additional active sites for the charge transfer reactions. At the same time, the thin interconnected carbon coating provides a conductive framework capable of delivering electrons to the nanostructured LiFePO4. Full article
(This article belongs to the Special Issue Nanomaterials in Energy Conversion and Storage)
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Open AccessArticle Nanostructure-Directed Chemical Sensing: The IHSAB Principle and the Effect of Nitrogen and Sulfur Functionalization on Metal Oxide Decorated Interface Response
Nanomaterials 2013, 3(3), 469-485; doi:10.3390/nano3030469
Received: 27 June 2013 / Revised: 26 July 2013 / Accepted: 29 July 2013 / Published: 7 August 2013
Cited by 6 | PDF Full-text (381 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The response matrix, as metal oxide nanostructure decorated n-type semiconductor interfaces are modified in situ through direct amination and through treatment with organic sulfides and thiols, is demonstrated. Nanostructured TiO2, SnOx, NiO and CuxO (x
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The response matrix, as metal oxide nanostructure decorated n-type semiconductor interfaces are modified in situ through direct amination and through treatment with organic sulfides and thiols, is demonstrated. Nanostructured TiO2, SnOx, NiO and CuxO (x = 1,2), in order of decreasing Lewis acidity, are deposited to a porous silicon interface to direct a dominant electron transduction process for reversible chemical sensing in the absence of significant chemical bond formation. The metal oxide sensing sites can be modified to decrease their Lewis acidity in a process appearing to substitute nitrogen or sulfur, providing a weak interaction to form the oxynitrides and oxysulfides. Treatment with triethylamine and diethyl sulfide decreases the Lewis acidity of the metal oxide sites. Treatment with acidic ethane thiol modifies the sensor response in an opposite sense, suggesting that there are thiol (SH) groups present on the surface that provide a Brønsted acidity to the surface. The in situ modification of the metal oxides deposited to the interface changes the reversible interaction with the analytes, NH3 and NO. The observed change for either the more basic oxynitrides or oxysulfides or the apparent Brønsted acid sites produced from the interaction of the thiols do not represent a simple increase in surface basicity or acidity, but appear to involve a change in molecular electronic structure, which is well explained using the recently developed inverse hard and soft acids and bases (IHSAB) model. Full article
(This article belongs to the Special Issue Nanomaterials in Sensors)
Open AccessArticle Magnetism of Amorphous and Nano-Crystallized Dc-Sputter-Deposited MgO Thin Films
Nanomaterials 2013, 3(3), 486-497; doi:10.3390/nano3030486
Received: 13 June 2013 / Revised: 20 July 2013 / Accepted: 26 July 2013 / Published: 7 August 2013
Cited by 4 | PDF Full-text (1335 KB) | HTML Full-text | XML Full-text
Abstract
We report a systematic study of room-temperature ferromagnetism (RTFM) in pristine MgO thin films in their amorphous and nano-crystalline states. The as deposited dc-sputtered films of pristine MgO on Si substrates using a metallic Mg target in an O2 containing working gas
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We report a systematic study of room-temperature ferromagnetism (RTFM) in pristine MgO thin films in their amorphous and nano-crystalline states. The as deposited dc-sputtered films of pristine MgO on Si substrates using a metallic Mg target in an O2 containing working gas atmosphere of (N2 + O2) are found to be X-ray amorphous. All these films obtained with oxygen partial pressure (PO2) ~10% to 80% while maintaining the same total pressure of the working gas are found to be ferromagnetic at room temperature. The room temperature saturation magnetization (MS) value of 2.68 emu/cm3 obtained for the MgO film deposited in PO2 of 10% increases to 9.62 emu/cm3 for film deposited at PO2 of 40%. However, the MS values decrease steadily for further increase of oxygen partial pressure during deposition. On thermal annealing at temperatures in the range 600 to 800 °C, the films become nanocrystalline and as the crystallite size grows with longer annealing times and higher temperature, MS decreases. Our study clearly points out that it is possible to tailor the magnetic properties of thin films of MgO. The room temperature ferromagnetism in MgO films is attributed to the presence of Mg cation vacancies. Full article
(This article belongs to the Special Issue Magnetic Nanomaterials)
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Open AccessArticle Influence of Nanoclay Dispersion Methods on the Mechanical Behavior of E-Glass/Epoxy Nanocomposites
Nanomaterials 2013, 3(3), 550-563; doi:10.3390/nano3030550
Received: 22 July 2013 / Revised: 19 August 2013 / Accepted: 23 August 2013 / Published: 28 August 2013
Cited by 12 | PDF Full-text (1054 KB) | HTML Full-text | XML Full-text
Abstract
Common dispersion methods such as ultrasonic sonication, planetary centrifugal mixing and magnetic dispersion have been used extensively to achieve moderate exfoliation of nanoparticles in polymer matrix. In this study, the effect of adding three roll milling to these three dispersion methods for nanoclay
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Common dispersion methods such as ultrasonic sonication, planetary centrifugal mixing and magnetic dispersion have been used extensively to achieve moderate exfoliation of nanoparticles in polymer matrix. In this study, the effect of adding three roll milling to these three dispersion methods for nanoclay dispersion into epoxy matrix was investigated. A combination of each of these mixing methods with three roll milling showed varying results relative to the unmodified polymer laminate. A significant exfoliation of the nanoparticles in the polymer structure was obtained by dispersing the nanoclay combining three roll milling to magnetic and planetary centrifugal mixing methods. This exfoliation promoted a stronger interfacial bond between the matrix and the fiber, which increased the final properties of the E-glass/epoxy nanocomposite. However, a combination of ultrasound sonication and three roll milling on the other hand, resulted in poor clay exfoliation; the sonication process degraded the polymer network, which adversely affected the nanocomposite final properties relative to the unmodified E-glass/epoxy polymer. Full article
Open AccessCommunication Hydrothermal Synthesis of Nanoclusters of ZnS Comprised on Nanowires
Nanomaterials 2013, 3(3), 564-571; doi:10.3390/nano3030564
Received: 29 July 2013 / Revised: 22 August 2013 / Accepted: 5 September 2013 / Published: 9 September 2013
Cited by 4 | PDF Full-text (535 KB) | HTML Full-text | XML Full-text
Abstract
Cetyltrimethyl ammonium bromide cationic (CTAB) surfactant was used as template for the synthesis of nanoclusters of ZnS composed of nanowires, by hydrothermal method. The structural and morphological studies were performed by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and high resolution transmission
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Cetyltrimethyl ammonium bromide cationic (CTAB) surfactant was used as template for the synthesis of nanoclusters of ZnS composed of nanowires, by hydrothermal method. The structural and morphological studies were performed by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) techniques. The synthesized ZnS nanoclusters are composed of nanowires and high yield on the substrate was observed. The ZnS nanocrystalline consists of hexagonal phase and polycrystalline in nature. The chemical composition of ZnS nanoclusters composed of nanowires was studied by X-ray photo electron microscopy (XPS). This investigation has shown that the ZnS nanoclusters are composed of Zn and S atoms. Full article

Review

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Open AccessReview Photoelectrochemical Properties of Graphene and Its Derivatives
Nanomaterials 2013, 3(3), 325-356; doi:10.3390/nano3030325
Received: 14 May 2013 / Revised: 20 June 2013 / Accepted: 20 June 2013 / Published: 3 July 2013
Cited by 29 | PDF Full-text (849 KB) | HTML Full-text | XML Full-text
Abstract
Graphene and its derivatives combine a numerous range of supreme properties that can be useful in many applications. The purpose of this review is to analyse the photoelectrochemical properties of pristine graphene, graphene oxide (GO) and reduced graphene oxide (rGO) and their impact
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Graphene and its derivatives combine a numerous range of supreme properties that can be useful in many applications. The purpose of this review is to analyse the photoelectrochemical properties of pristine graphene, graphene oxide (GO) and reduced graphene oxide (rGO) and their impact on semiconductor catalysts/quantum dots. The mechanism that this group of materials follows to improve their performance will be cleared by explaining how those properties can be exploited in several applications such as photo-catalysts (degradation of pollutants) and photovoltaics (solar cells). Full article
(This article belongs to the Special Issue Graphene Quantum Dots)
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Open AccessReview Theory of Carbon Nanotube (CNT)-Based Electron Field Emitters
Nanomaterials 2013, 3(3), 393-442; doi:10.3390/nano3030393
Received: 7 May 2013 / Revised: 24 June 2013 / Accepted: 27 June 2013 / Published: 17 July 2013
Cited by 12 | PDF Full-text (1788 KB) | HTML Full-text | XML Full-text
Abstract
Theoretical problems arising in connection with development and operation of electron field emitters on the basis of carbon nanotubes are reviewed. The physical aspects of electron field emission that underlie the unique emission properties of carbon nanotubes (CNTs) are considered. Physical effects and
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Theoretical problems arising in connection with development and operation of electron field emitters on the basis of carbon nanotubes are reviewed. The physical aspects of electron field emission that underlie the unique emission properties of carbon nanotubes (CNTs) are considered. Physical effects and phenomena affecting the emission characteristics of CNT cathodes are analyzed. Effects given particular attention include: the electric field amplification near a CNT tip with taking into account the shape of the tip, the deviation from the vertical orientation of nanotubes and electrical field-induced alignment of those; electric field screening by neighboring nanotubes; statistical spread of the parameters of the individual CNTs comprising the cathode; the thermal effects resulting in degradation of nanotubes during emission. Simultaneous consideration of the above-listed effects permitted the development of the optimization procedure for CNT array in terms of the maximum reachable emission current density. In accordance with this procedure, the optimum inter-tube distance in the array depends on the region of the external voltage applied. The phenomenon of self-misalignment of nanotubes in an array has been predicted and analyzed in terms of the recent experiments performed. A mechanism of degradation of CNT-based electron field emitters has been analyzed consisting of the bombardment of the emitters by ions formed as a result of electron impact ionization of the residual gas molecules. Full article
(This article belongs to the Special Issue CNT based Nanomaterials)
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Open AccessReview Inkjet Printing of Carbon Nanotubes
Nanomaterials 2013, 3(3), 453-468; doi:10.3390/nano3030453
Received: 1 July 2013 / Revised: 25 July 2013 / Accepted: 25 July 2013 / Published: 29 July 2013
Cited by 20 | PDF Full-text (387 KB) | HTML Full-text | XML Full-text
Abstract
In an attempt to give a brief introduction to carbon nanotube inkjet printing, this review paper discusses the issues that come along with preparing and printing carbon nanotube ink. Carbon nanotube inkjet printing is relatively new, but it has great potential for broad
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In an attempt to give a brief introduction to carbon nanotube inkjet printing, this review paper discusses the issues that come along with preparing and printing carbon nanotube ink. Carbon nanotube inkjet printing is relatively new, but it has great potential for broad applications in flexible and printable electronics, transparent electrodes, electronic sensors, and so on due to its low cost and the extraordinary properties of carbon nanotubes. In addition to the formulation of carbon nanotube ink and its printing technologies, recent progress and achievements of carbon nanotube inkjet printing are reviewed in detail with brief discussion on the future outlook of the technology. Full article
(This article belongs to the Special Issue CNT based Nanomaterials)
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Open AccessReview Conducting Polyaniline Nanowire and Its Applications in Chemiresistive Sensing
Nanomaterials 2013, 3(3), 498-523; doi:10.3390/nano3030498
Received: 1 July 2013 / Revised: 28 July 2013 / Accepted: 29 July 2013 / Published: 7 August 2013
Cited by 59 | PDF Full-text (999 KB) | HTML Full-text | XML Full-text
Abstract
One dimensional polyaniline nanowire is an electrically conducting polymer that can be used as an active layer for sensors whose conductivity change can be used to detect chemical or biological species. In this review, the basic properties of polyaniline nanowires including chemical structures,
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One dimensional polyaniline nanowire is an electrically conducting polymer that can be used as an active layer for sensors whose conductivity change can be used to detect chemical or biological species. In this review, the basic properties of polyaniline nanowires including chemical structures, redox chemistry, and method of synthesis are discussed. A comprehensive literature survey on chemiresistive/conductometric sensors based on polyaniline nanowires is presented and recent developments in polyaniline nanowire-based sensors are summarized. Finally, the current limitations and the future prospect of polyaniline nanowires are discussed. Full article
(This article belongs to the Special Issue Nanomaterials in Sensors)
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Open AccessReview Current Trends in Sensors Based on Conducting Polymer Nanomaterials
Nanomaterials 2013, 3(3), 524-549; doi:10.3390/nano3030524
Received: 18 July 2013 / Revised: 15 August 2013 / Accepted: 16 August 2013 / Published: 27 August 2013
Cited by 40 | PDF Full-text (5655 KB) | HTML Full-text | XML Full-text
Abstract
Conducting polymers represent an important class of functional organic materials for next-generation electronic and optical devices. Advances in nanotechnology allow for the fabrication of various conducting polymer nanomaterials through synthesis methods such as solid-phase template synthesis, molecular template synthesis, and template-free synthesis. Nanostructured
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Conducting polymers represent an important class of functional organic materials for next-generation electronic and optical devices. Advances in nanotechnology allow for the fabrication of various conducting polymer nanomaterials through synthesis methods such as solid-phase template synthesis, molecular template synthesis, and template-free synthesis. Nanostructured conducting polymers featuring high surface area, small dimensions, and unique physical properties have been widely used to build various sensor devices. Many remarkable examples have been reported over the past decade. The enhanced sensitivity of conducting polymer nanomaterials toward various chemical/biological species and external stimuli has made them ideal candidates for incorporation into the design of sensors. However, the selectivity and stability still leave room for improvement. Full article
(This article belongs to the Special Issue Nanomaterials in Sensors)
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