Nanomaterials

668 KiB

Open AccessArticle

Effect of Nanotube Film Thickness on the Performance of Nanotube-Silicon Hybrid Solar Cells

by Daniel D. Tune and Joseph G. Shapter

Nanomaterials 2013, 3(4), 655-673; https://doi.org/10.3390/nano3040655 - 17 Dec 2013

Cited by 26 | Viewed by 7005

The results of measurements on solar cells made from randomly aligned thin films of single walled carbon nanotubes (SWCNTs) on n-type monocrystalline silicon are presented. The films are made by vacuum filtration from aqueous TritonX-100 suspensions of large diameter arc-discharge SWCNTs. The [...] Read more.

The results of measurements on solar cells made from randomly aligned thin films of single walled carbon nanotubes (SWCNTs) on n-type monocrystalline silicon are presented. The films are made by vacuum filtration from aqueous TritonX-100 suspensions of large diameter arc-discharge SWCNTs. The dependence of the solar cell performance on the thickness of the SWCNT film is shown in detail, as is the variation in performance due to doping of the SWCNT film with SOCl₂. Full article

(This article belongs to the Special Issue Nanomaterials in Energy Conversion and Storage)

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3437 KiB

Open AccessArticle

Study of the Effect of Grafting Method on Surface Polarity of Tempo-Oxidized Nanocellulose Using Polycaprolactone as the Modifying Compound: Esterification versus Click-Chemistry

by Abdelhaq Benkaddour, Khalil Jradi, Sylvain Robert and Claude Daneault

Nanomaterials 2013, 3(4), 638-654; https://doi.org/10.3390/nano3040638 - 12 Dec 2013

Cited by 27 | Viewed by 11086

Abstract

Esterification and click-chemistry were evaluated as surface modification treatments for TEMPO-oxidized nanocelluloses (TONC) using Polycaprolactone-diol (PCL) as modifying compound in order to improve the dispersion of nanofibers in organic media. These two grafting strategies were analyzed and compared. The first consists of grafting [...] Read more.

Esterification and click-chemistry were evaluated as surface modification treatments for TEMPO-oxidized nanocelluloses (TONC) using Polycaprolactone-diol (PCL) as modifying compound in order to improve the dispersion of nanofibers in organic media. These two grafting strategies were analyzed and compared. The first consists of grafting directly the PCL onto TONC, and was carried out by esterification between hydroxyl groups of PCL and carboxyl groups of TONC. The second strategy known as click-chemistry is based on the 1,3-dipolar cycloaddition reaction between azides and alkyne terminated moieties to form the triazole ring between PCL and TONC. The grafted samples were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and Thermogravimetry analysis (TGA). Further, the effects of the two treatments on the surface hydrophobization of TONC were investigated by contact angle measurements. The results show that both methods confirm the success of such a modification and the click reaction was significantly more effective than esterification. Full article

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776 KiB

Open AccessReview

Molecularly Imprinted Nanomaterials for Sensor Applications

by Muhammad Irshad, Naseer Iqbal, Adnan Mujahid, Adeel Afzal, Tajamal Hussain, Ahsan Sharif, Ejaz Ahmad and Muhammad Makshoof Athar

Nanomaterials 2013, 3(4), 615-637; https://doi.org/10.3390/nano3040615 - 26 Nov 2013

Cited by 58 | Viewed by 10207

Abstract

Molecular imprinting is a well-established technology to mimic antibody-antigen interaction in a synthetic platform. Molecularly imprinted polymers and nanomaterials usually possess outstanding recognition capabilities. Imprinted nanostructured materials are characterized by their small sizes, large reactive surface area and, most importantly, with rapid and [...] Read more.

Molecular imprinting is a well-established technology to mimic antibody-antigen interaction in a synthetic platform. Molecularly imprinted polymers and nanomaterials usually possess outstanding recognition capabilities. Imprinted nanostructured materials are characterized by their small sizes, large reactive surface area and, most importantly, with rapid and specific analysis of analytes due to the formation of template driven recognition cavities within the matrix. The excellent recognition and selectivity offered by this class of materials towards a target analyte have found applications in many areas, such as separation science, analysis of organic pollutants in water, environmental analysis of trace gases, chemical or biological sensors, biochemical assays, fabricating artificial receptors, nanotechnology, etc. We present here a concise overview and recent developments in nanostructured imprinted materials with respect to various sensor systems, e.g., electrochemical, optical and mass sensitive, etc. Finally, in light of recent studies, we conclude the article with future perspectives and foreseen applications of imprinted nanomaterials in chemical sensors. Full article

(This article belongs to the Special Issue Nanomaterials in Sensors)

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1371 KiB

Open AccessArticle

Fabrication and Characterization of SnO₂/Graphene Composites as High Capacity Anodes for Li-Ion Batteries

by Abirami Dhanabalan, Xifei Li, Richa Agrawal, Chunhui Chen and Chunlei Wang

Nanomaterials 2013, 3(4), 606-614; https://doi.org/10.3390/nano3040606 - 15 Nov 2013

Cited by 42 | Viewed by 8319

Abstract

Tin-oxide and graphene (TG) composites were fabricated using the Electrostatic Spray Deposition (ESD) technique, and tested as anode materials for Li-ion batteries. The electrochemical performance of the as-deposited TG composites were compared to heat-treated TG composites along with pure tin-oxide films. The heat-treated [...] Read more.

Tin-oxide and graphene (TG) composites were fabricated using the Electrostatic Spray Deposition (ESD) technique, and tested as anode materials for Li-ion batteries. The electrochemical performance of the as-deposited TG composites were compared to heat-treated TG composites along with pure tin-oxide films. The heat-treated composites exhibited superior specific capacity and energy density than both the as-deposited TG composites and tin oxide samples. At the 70th cycle, the specific capacities of the as-deposited and post heat-treated samples were 534 and 737 mA·h/g, respectively, and the corresponding energy densities of the as-deposited and heat-treated composites were 1240 and 1760 W·h/kg, respectively. This improvement in the electrochemical performance of the TG composite anodes as compared to the pure tin oxide samples is attributed to the synergy between tin oxide and graphene, which increases the electrical conductivity of tin oxide and helps alleviate volumetric changes in tin-oxide during cycling. Full article

(This article belongs to the Special Issue Nanomaterials in Energy Conversion and Storage)

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1848 KiB

Open AccessArticle

Formation of Gold Microparticles by Ablation with Surface Plasmons

by Quincy Garner and Pal Molian

Nanomaterials 2013, 3(4), 592-605; https://doi.org/10.3390/nano3040592 - 28 Oct 2013

Cited by 4 | Viewed by 5654

Abstract

The formation of gold microparticles on a silicon substrate through the use of energetic surface plasmons is reported. A laser-assisted plasmonics system was assembled and tested to synthesize gold particles from gold thin film by electrical field enhancement mechanism. A mask containing an [...] Read more.

The formation of gold microparticles on a silicon substrate through the use of energetic surface plasmons is reported. A laser-assisted plasmonics system was assembled and tested to synthesize gold particles from gold thin film by electrical field enhancement mechanism. A mask containing an array of 200 nm diameter holes with a periodicity of 400 nm was prepared and placed on a silicon substrate. The mask was composed of 60 µm thick porous alumina membrane sputter-coated with 100 nm thin gold film. A Nd:YAG laser with 1064 nm wavelength and 230 µs pulse width (free-running mode) was then passed through the mask at an energy fluence of 0.35 J/cm². The extraordinary transmission of laser light through alumina/gold micro-hole optical antenna created both extended and localized surface plasmons that caused the gold film at the bottom of the mask to fragment into microparticles and deposit on the silicon substrate that is in direct contact with the mask. The surface plasmon method is simpler, quicker, more energy efficient, and environmentally safer than existing physical and chemical methods, as well as being contamination-free, and can be extended to all types of materials that will in turn allow for new possibilities in the formation of structured surfaces. Full article

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581 KiB

Open AccessArticle

Tuning NaYF₄ Nanoparticles through Alkaline Earth Doping

by Xian Chen, Dengfeng Peng and Feng Wang

Nanomaterials 2013, 3(4), 583-591; https://doi.org/10.3390/nano3040583 - 24 Oct 2013

Cited by 25 | Viewed by 8886

Abstract

Phase and size of lanthanide-doped nanoparticles are the most important characteristics that dictate optical properties of these nanoparticles and affect their technological applications. Herein, we present a systematic study to examine the effect of alkaline earth doping on the formation of NaYF₄ [...] Read more.

Phase and size of lanthanide-doped nanoparticles are the most important characteristics that dictate optical properties of these nanoparticles and affect their technological applications. Herein, we present a systematic study to examine the effect of alkaline earth doping on the formation of NaYF₄ upconversion nanoparticles. We show that alkaline earth doping has a dual function of tuning particle size of hexagonal phase NaYF₄ nanoparticles and stabilizing cubic phase NaYF₄ nanoparticles depending on composition and concentration of the dopant ions. The study described here represents a facile and general strategy to tuning the properties of NaYF₄ upconversion nanoparticles. Full article

(This article belongs to the Special Issue Current Trends in Up-Converting Nanoparticles)

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1524 KiB

Open AccessArticle

Susceptibility of CoFeB/AlO_x/Co Magnetic Tunnel Junctions to Low-Frequency Alternating Current

by Yuan-Tsung Chen and Zu-Gao Chang

Nanomaterials 2013, 3(4), 574-582; https://doi.org/10.3390/nano3040574 - 15 Oct 2013

Cited by 2 | Viewed by 6586

Abstract

This investigation studies CoFeB/AlO_x/Co magnetic tunneling junction (MTJ) in the magnetic field of a low-frequency alternating current, for various thicknesses of the barrier layer AlO_x. The low-frequency alternate-current magnetic susceptibility (χ_ac) and phase angle (θ) of the [...] Read more.

This investigation studies CoFeB/AlO_x/Co magnetic tunneling junction (MTJ) in the magnetic field of a low-frequency alternating current, for various thicknesses of the barrier layer AlO_x. The low-frequency alternate-current magnetic susceptibility (χ_ac) and phase angle (θ) of the CoFeB/AlO_x/Co MTJ are determined using an c_ac analyzer. The driving frequency ranges from 10 to 25,000 Hz. These multilayered MTJs are deposited on a silicon substrate using a DC and RF magnetron sputtering system. Barrier layer thicknesses are 22, 26, and 30 Å. The X-ray diffraction patterns (XRD) include a main peak at 2θ = 44.7° from hexagonal close-packed (HCP) Co with a highly (0002) textured structure, with AlO_x and CoFeB as amorphous phases. The full width at half maximum (FWHM) of the Co(0002) peak, decreases as the AlO_x thickness increases; revealing that the Co layer becomes more crystalline with increasing thickness. χ_ac result demonstrates that the optimal resonance frequency (f_res) that maximizes the χ_ac value is 500 Hz. As the frequency increases to 1000 Hz, the susceptibility decreases rapidly. However, when the frequency increases over 1000 Hz, the susceptibility sharply declines, and almost closes to zero. The experimental results reveal that the mean optimal susceptibility is 1.87 at an AlO_x barrier layer thickness of 30 Å because the Co(0002) texture induces magneto-anisotropy, which improves the indirect CoFeB and Co spin exchange-coupling strength and the χ_ac value. The results concerning magnetism indicate that the magnetic characteristics are related to the crystallinity of Co. Full article

(This article belongs to the Special Issue Magnetic Nanomaterials)

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114 KiB

Open AccessEditorial

Nanomaterials in Sensors

by Joseph J. BelBruno

Nanomaterials 2013, 3(4), 572-573; https://doi.org/10.3390/nano3040572 - 14 Oct 2013

Cited by 16 | Viewed by 5070

Abstract

This Special Issue of Nanomaterials is focused on the continuing implementation of nanomaterials and nanostructures in the development of more sensitive and more specific sensing devices. As a result, these new devices employ smaller sensing elements and provide more “real time” capability. Often, [...] Read more.

This Special Issue of Nanomaterials is focused on the continuing implementation of nanomaterials and nanostructures in the development of more sensitive and more specific sensing devices. As a result, these new devices employ smaller sensing elements and provide more “real time” capability. Often, the inclusion of nanomaterials leads to sensing elements for targets that were previously inaccessible. [...] Full article

(This article belongs to the Special Issue Nanomaterials in Sensors)

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Nanomaterials, Volume 3, Issue 4 (December 2013) – 8 articles , Pages 572-673

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