Nanomaterials

1760 KiB

Open AccessCommunication

Freestanding rGO-SWNT-STN Composite Film as an Anode for Li Ion Batteries with High Energy and Power Densities

by Taeseup Song, Junghyun Choi and Ungyu Paik

Nanomaterials 2015, 5(4), 2380-2390; https://doi.org/10.3390/nano5042380 - 18 Dec 2015

Cited by 5 | Viewed by 7014

Freestanding Si-Ti-Ni alloy particles/reduced graphene oxide/single wall carbon nanotube composites have been prepared as an anode for lithium ion batteries via a simple filtration method. This composite electrode showed a 9% increase in reversible capacity, a two-fold higher cycle retention at 50 cycles [...] Read more.

Freestanding Si-Ti-Ni alloy particles/reduced graphene oxide/single wall carbon nanotube composites have been prepared as an anode for lithium ion batteries via a simple filtration method. This composite electrode showed a 9% increase in reversible capacity, a two-fold higher cycle retention at 50 cycles and a two-fold higher rate capability at 2 C compared to pristine Si-Ti-Ni (STN) alloy electrodes. These improvements were attributed to the suppression of the pulverization of the STN active material by the excellent mechanical properties of the reduced graphene oxide-single wall carbon nanotube networks and the enhanced kinetics associated with both electron and Li ion transport. Full article

(This article belongs to the Special Issue Nanostructured Materials for Li-Ion Batteries and Beyond)

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2255 KiB

Open AccessArticle

Non-Cytotoxic Quantum Dot–Chitosan Nanogel Biosensing Probe for Potential Cancer Targeting Agent

by Tyler Maxwell, Tahmina Banu, Edward Price, Jeremy Tharkur, Maria Gabriela Nogueira Campos, Andre Gesquiere and Swadeshmukul Santra

Nanomaterials 2015, 5(4), 2359-2379; https://doi.org/10.3390/nano5042359 - 18 Dec 2015

Cited by 19 | Viewed by 7417

Abstract

Quantum dot (Qdot) biosensors have consistently provided valuable information to researchers about cellular activity due to their unique fluorescent properties. Many of the most popularly used Qdots contain cadmium, posing the risk of toxicity that could negate their attractive optical properties. The design [...] Read more.

Quantum dot (Qdot) biosensors have consistently provided valuable information to researchers about cellular activity due to their unique fluorescent properties. Many of the most popularly used Qdots contain cadmium, posing the risk of toxicity that could negate their attractive optical properties. The design of a non-cytotoxic probe usually involves multiple components and a complex synthesis process. In this paper, the design and synthesis of a non-cytotoxic Qdot-chitosan nanogel composite using straight-forward cyanogen bromide (CNBr) coupling is reported. The probe was characterized by spectroscopy (UV-Vis, fluorescence), microscopy (Fluorescence, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Dynamic Light Scattering. This activatable (“OFF”/“ON”) probe contains a core–shell Qdot (CdS:Mn/ZnS) capped with dopamine, which acts as a fluorescence quencher and a model drug. Dopamine capped “OFF” Qdots can undergo ligand exchange with intercellular glutathione, which turns the Qdots “ON” to restore fluorescence. These Qdots were then coated with chitosan (natural biocompatible polymer) functionalized with folic acid (targeting motif) and Fluorescein Isothiocyanate (FITC; fluorescent dye). To demonstrate cancer cell targetability, the interaction of the probe with cells that express different folate receptor levels was analyzed, and the cytotoxicity of the probe was evaluated on these cells and was shown to be nontoxic even at concentrations as high as 100 mg/L. Full article

(This article belongs to the Special Issue Nanoparticles Assisted Drug Delivery)

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546 KiB

Open AccessArticle

Size Effect of Ordered Mesoporous Carbon Nanospheres for Anodes in Li-Ion Battery

by Pei-Yi Chang, Kartick Bindumadhavan and Ruey-An Doong

Nanomaterials 2015, 5(4), 2348-2358; https://doi.org/10.3390/nano5042348 - 18 Dec 2015

Cited by 23 | Viewed by 8204

Abstract

The present work demonstrates the application of various sizes of ordered mesoporous carbon nanospheres (OMCS) with diameters of 46–130 nm as an active anode material for Li-ion batteries (LIB). The physical and chemical properties of OMCS have been evaluated by performing scanning electron [...] Read more.

The present work demonstrates the application of various sizes of ordered mesoporous carbon nanospheres (OMCS) with diameters of 46–130 nm as an active anode material for Li-ion batteries (LIB). The physical and chemical properties of OMCS have been evaluated by performing scanning electron microscopy (SEM), transmission electron microscopy (TEM), N₂ adsorption-desorption analysis; small-angle scattering system (SAXS) and X-ray diffraction (XRD). The electrochemical analysis of using various sizes of OMCS as anode materials showed high capacity and rate capability with the specific capacity up to 560 mA·h·g⁻¹ at 0.1 C after 85 cycles. In terms of performance at high current rate compared to other amorphous carbonaceous materials; a stable and extremely high specific capacity of 240 mA·h·g⁻¹ at 5 C after 15 cycles was achieved. Such excellent performance is mainly attributed to the suitable particle size distribution of OMCS and intimate contact between OMCS and conductive additives; which can be supported from the TEM images. Results obtained from this study clearly indicate the excellence of size distribution of highly integrated mesoporous structure of carbon nanospheres for LIB application. Full article

(This article belongs to the Special Issue Nanostructured Materials for Li-Ion Batteries and Beyond)

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827 KiB

Open AccessArticle

Facile and Eco-Friendly Synthesis of Finger-Like Co₃O₄ Nanorods for Electrochemical Energy Storage

by Shijiao Sun, Xiangyu Zhao, Meng Yang, Liqun Ma and Xiaodong Shen

Nanomaterials 2015, 5(4), 2335-2347; https://doi.org/10.3390/nano5042335 - 17 Dec 2015

Cited by 23 | Viewed by 6060

Abstract

Co₃O₄ nanorods were prepared by a facile hydrothermal method. Eco-friendly deionized water rather than organic solvent was used as the hydrothermal media. The as-prepared Co₃O₄ nanorods are composed of many nanoparticles of 30–50 nm in diameter, forming [...] Read more.

Co₃O₄ nanorods were prepared by a facile hydrothermal method. Eco-friendly deionized water rather than organic solvent was used as the hydrothermal media. The as-prepared Co₃O₄ nanorods are composed of many nanoparticles of 30–50 nm in diameter, forming a finger-like morphology. The Co₃O₄ electrode shows a specific capacitance of 265 F g⁻¹ at 2 mV s⁻¹ in a supercapacitor and delivers an initial specific discharge capacity as high as 1171 mAh g⁻¹ at a current density of 50 mA g⁻¹ in a lithium ion battery. Excellent cycling stability and electrochemical reversibility of the Co₃O₄ electrode were also obtained. Full article

(This article belongs to the Special Issue Nanostructured Materials for Li-Ion Batteries and Beyond)

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Open AccessArticle

Nanocarriers for DNA Vaccines: Co-Delivery of TLR-9 and NLR-2 Ligands Leads to Synergistic Enhancement of Proinflammatory Cytokine Release

by Johanna Poecheim, Simon Heuking, Livia Brunner, Christophe Barnier-Quer, Nicolas Collin and Gerrit Borchard

Nanomaterials 2015, 5(4), 2317-2334; https://doi.org/10.3390/nano5042317 - 17 Dec 2015

Cited by 11 | Viewed by 6601

Abstract

Adjuvants enhance immunogenicity of vaccines through either targeted antigen delivery or stimulation of immune receptors. Three cationic nanoparticle formulations were evaluated for their potential as carriers for a DNA vaccine, and muramyl dipeptide (MDP) as immunostimulatory agent, to induce and increase immunogenicity of [...] Read more.

Adjuvants enhance immunogenicity of vaccines through either targeted antigen delivery or stimulation of immune receptors. Three cationic nanoparticle formulations were evaluated for their potential as carriers for a DNA vaccine, and muramyl dipeptide (MDP) as immunostimulatory agent, to induce and increase immunogenicity of Mycobacterium tuberculosis antigen encoding plasmid DNA (pDNA). The formulations included (1) trimethyl chitosan (TMC) nanoparticles, (2) a squalene-in-water nanoemulsion, and (3) a mineral oil-in-water nanoemulsion. The adjuvant effect of the pDNA-nanocomplexes was evaluated by serum antibody analysis in immunized mice. All three carriers display a strong adjuvant effect, however, only TMC nanoparticles were capable to bias immune responses towards Th1. pDNA naturally contains immunostimulatory unmethylated CpG motifs that are recognized by Toll-like receptor 9 (TLR-9). In mechanistic in vitro studies, activation of TLR-9 and the ability to enhance immunogenicity by simultaneously targeting TLR-9 and NOD-like receptor 2 (NLR-2) was determined by proinflammatory cytokine release in RAW264.7 macrophages. pDNA in combination with MDP was shown to significantly increase proinflammatory cytokine release in a synergistic manner, dependent on NLR-2 activation. In summary, novel pDNA-Ag85A loaded nanoparticle formulations, which induce antigen specific immune responses in mice were developed, taking advantage of the synergistic combinations of TLR and NLR agonists to increase the adjuvanticity of the carriers used. Full article

(This article belongs to the Special Issue Nanoparticles Assisted Drug Delivery)

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Open AccessArticle

Mesoporous Silica Nanoparticles Loaded with Cisplatin and Phthalocyanine for Combination Chemotherapy and Photodynamic Therapy in vitro

by Juan L. Vivero-Escoto and Maram Elnagheeb

Nanomaterials 2015, 5(4), 2302-2316; https://doi.org/10.3390/nano5042302 - 16 Dec 2015

Cited by 55 | Viewed by 8136

Abstract

Mesoporous silica nanoparticles (MSNs) have been synthesized and loaded with both aluminum chloride phthalocyanine (AlClPc) and cisplatin as combinatorial therapeutics for treating cancer. The structural and photophysical properties of the MSN materials were characterized by different spectroscopic and microscopic techniques. Intracellular uptake and [...] Read more.

Mesoporous silica nanoparticles (MSNs) have been synthesized and loaded with both aluminum chloride phthalocyanine (AlClPc) and cisplatin as combinatorial therapeutics for treating cancer. The structural and photophysical properties of the MSN materials were characterized by different spectroscopic and microscopic techniques. Intracellular uptake and cytotoxicity were evaluated in human cervical cancer (HeLa) cells by confocal laser scanning microscopy (CLSM) and 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assays, respectively. The CLSM experiments showed that the MSN materials can be readily internalized in HeLa cells. The cytotoxic experiments demonstrated that, after light exposure, the combination of both AlClPc and cisplatin compounds in the same MSN platform potentiate the toxic effect against HeLa cells in comparison to the control AlClPc-MSN and cisplatin-MSN materials. These results show the potential of using MSN platforms as nanocarriers for combination photodynamic and chemotherapies to treat cancer. Full article

(This article belongs to the Special Issue Nanoparticles in Theranostics)

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3186 KiB

Open AccessFeature PaperArticle

Nanoscience Supporting the Research on the Negative Electrodes of Li-Ion Batteries

by Alain Mauger and Christian M. Julien

Nanomaterials 2015, 5(4), 2279-2301; https://doi.org/10.3390/nano5042279 - 16 Dec 2015

Cited by 17 | Viewed by 6719

Abstract

Many efforts are currently made to increase the limited capacity of Li-ion batteries using carbonaceous anodes. The way to reach this goal is to move to nano-structured material because the larger surface to volume ratio of particles and the reduction of the electron [...] Read more.

Many efforts are currently made to increase the limited capacity of Li-ion batteries using carbonaceous anodes. The way to reach this goal is to move to nano-structured material because the larger surface to volume ratio of particles and the reduction of the electron and Li path length implies a larger specific capacity. Additionally, nano-particles can accommodate such a dilatation/contraction during cycling, resulting in a calendar life compatible with a commercial use. In this review attention is focused on carbon, silicon, and Li₄Ti₅O₁₂ materials, because they are the most promising for applications. Full article

(This article belongs to the Special Issue Nanostructured Materials for Li-Ion Batteries and Beyond)

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1981 KiB

Open AccessArticle

Simulation of the Impact of Si Shell Thickness on the Performance of Si-Coated Vertically Aligned Carbon Nanofiber as Li-Ion Battery Anode

by Susobhan Das, Jun Li and Rongqing Hui

Nanomaterials 2015, 5(4), 2268-2278; https://doi.org/10.3390/nano5042268 - 15 Dec 2015

Cited by 4 | Viewed by 5490

Abstract

Micro- and nano-structured electrodes have the potential to improve the performance of Li-ion batteries by increasing the surface area of the electrode and reducing the diffusion distance required by the charged carriers. We report the numerical simulation of Lithium-ion batteries with the anode [...] Read more.

Micro- and nano-structured electrodes have the potential to improve the performance of Li-ion batteries by increasing the surface area of the electrode and reducing the diffusion distance required by the charged carriers. We report the numerical simulation of Lithium-ion batteries with the anode made of core-shell heterostructures of silicon-coated carbon nanofibers. We show that the energy capacity can be significantly improved by reducing the thickness of the silicon anode to the dimension comparable or less than the Li-ion diffusion length inside silicon. The results of simulation indicate that the contraction of the silicon electrode thickness during the battery discharge process commonly found in experiments also plays a major role in the increase of the energy capacity. Full article

(This article belongs to the Special Issue Nanostructured Materials for Li-Ion Batteries and Beyond)

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Open AccessReview

Electric Field-Responsive Mesoporous Suspensions: A Review

by Seung Hyuk Kwon, Shang Hao Piao and Hyoung Jin Choi

Nanomaterials 2015, 5(4), 2249-2267; https://doi.org/10.3390/nano5042249 - 15 Dec 2015

Cited by 26 | Viewed by 7468

Abstract

This paper briefly reviews the fabrication and electrorheological (ER) characteristics of mesoporous materials and their nanocomposites with conducting polymers under an applied electric field when dispersed in an insulating liquid. Smart fluids of electrically-polarizable particles exhibit a reversible and tunable phase transition from [...] Read more.

This paper briefly reviews the fabrication and electrorheological (ER) characteristics of mesoporous materials and their nanocomposites with conducting polymers under an applied electric field when dispersed in an insulating liquid. Smart fluids of electrically-polarizable particles exhibit a reversible and tunable phase transition from a liquid-like to solid-like state in response to an external electric field of various strengths, and have potential applications in a variety of active control systems. The ER properties of these mesoporous suspensions are explained further according to their dielectric spectra in terms of the flow curve, dynamic moduli, and yield stress. Full article

(This article belongs to the Special Issue Frontiers in Mesoporous Nanomaterials)

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1539 KiB

Open AccessReview

Magnetic Nanoparticles Cross the Blood-Brain Barrier: When Physics Rises to a Challenge

by Maria Antònia Busquets, Alba Espargaró, Raimon Sabaté and Joan Estelrich

Nanomaterials 2015, 5(4), 2231-2248; https://doi.org/10.3390/nano5042231 - 11 Dec 2015

Cited by 68 | Viewed by 9794

Abstract

The blood-brain barrier is a physical and physiological barrier that protects the brain from toxic substances within the bloodstream and helps maintain brain homeostasis. It also represents the main obstacle in the treatment of many diseases of the central nervous system. Among the [...] Read more.

The blood-brain barrier is a physical and physiological barrier that protects the brain from toxic substances within the bloodstream and helps maintain brain homeostasis. It also represents the main obstacle in the treatment of many diseases of the central nervous system. Among the different approaches employed to overcome this barrier, the use of nanoparticles as a tool to enhance delivery of therapeutic molecules to the brain is particularly promising. There is special interest in the use of magnetic nanoparticles, as their physical characteristics endow them with additional potentially useful properties. Following systemic administration, a magnetic field applied externally can mediate the capacity of magnetic nanoparticles to permeate the blood-brain barrier. Meanwhile, thermal energy released by magnetic nanoparticles under the influence of radiofrequency radiation can modulate blood-brain barrier integrity, increasing its permeability. In this review, we present the strategies that use magnetic nanoparticles, specifically iron oxide nanoparticles, to enhance drug delivery to the brain. Full article

(This article belongs to the Special Issue Nanoparticles in Theranostics)

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3462 KiB

Open AccessFeature PaperArticle

Structural and Morphological Tuning of LiCoPO₄ Materials Synthesized by Solvo-Thermal Methods for Li-Cell Applications

by Jessica Manzi, Mariangela Curcio and Sergio Brutti

Nanomaterials 2015, 5(4), 2212-2230; https://doi.org/10.3390/nano5042212 - 10 Dec 2015

Cited by 23 | Viewed by 6060

Abstract

Olivine-type lithium metal phosphates (LiMPO₄) are promising cathode materials for lithium-ion batteries. LiFePO₄ (LFP) is commonly used in commercial Li-ion cells but the Fe³⁺/Fe²⁺ couple can be usefully substituted with Mn³⁺/Mn²⁺, Co³⁺ [...] Read more.

Olivine-type lithium metal phosphates (LiMPO₄) are promising cathode materials for lithium-ion batteries. LiFePO₄ (LFP) is commonly used in commercial Li-ion cells but the Fe³⁺/Fe²⁺ couple can be usefully substituted with Mn³⁺/Mn²⁺, Co³⁺/Co²⁺, or Ni³⁺/Ni²⁺, in order to obtain higher redox potentials. In this communication we report a systematic analysis of the synthesis condition of LiCoPO₄ (LCP) using a solvo-thermal route at low temperature, the latter being a valuable candidate to overcome the theoretical performances of LFP. In fact, LCP shows higher working potential (4.8 V vs. 3.6 V) compared to LFP and similar theoretical capacity (167 mAh·g⁻¹). Our goal is to show the effect of the synthesis condition of the ability of LCP to reversibly cycle lithium in electrochemical cells. LCP samples have been prepared through a solvo-thermal method in aqueous-non aqueous solvent blends. Different Co²⁺ salts have been used to study the effect of the anion on the crystal growth as well as the effect of solution acidity, temperature and reaction time. Materials properties have been characterized by Fast-Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopies. The correlation between structure/morphology and electrochemical performances has been investigated by galvanostatic charge-discharge cycles. Full article

(This article belongs to the Special Issue Nanostructured Materials for Li-Ion Batteries and Beyond)

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Open AccessArticle

Hydrothermal Synthesis of Ultrasmall Pt Nanoparticles as Highly Active Electrocatalysts for Methanol Oxidation

by Wenhai Ji, Weihong Qi, Shasha Tang, Hongcheng Peng and Siqi Li

Nanomaterials 2015, 5(4), 2203-2211; https://doi.org/10.3390/nano5042203 - 8 Dec 2015

Cited by 41 | Viewed by 7664

Abstract

Ultrasmall nanoparticles, with sizes in the 1–3 nm range, exhibit unique properties distinct from those of free molecules and larger-sized nanoparticles. Demonstrating that the hydrothermal method can serve as a facile method for the synthesis of platinum nanoparticles, we successfully synthesized ultrasmall Pt [...] Read more.

Ultrasmall nanoparticles, with sizes in the 1–3 nm range, exhibit unique properties distinct from those of free molecules and larger-sized nanoparticles. Demonstrating that the hydrothermal method can serve as a facile method for the synthesis of platinum nanoparticles, we successfully synthesized ultrasmall Pt nanoparticles with an average size of 2.45 nm, with the aid of poly(vinyl pyrrolidone) (PVP) as reducing agents and capping agents. Because of the size effect, these ultrasmall Pt nanoparticles exhibit a high activity toward the methanol oxidation reaction. Full article

(This article belongs to the Special Issue Nanoparticles for Catalysis)

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2781 KiB

Open AccessArticle

Morphological, Chemical Surface, and Diffusive Transport Characterizations of a Nanoporous Alumina Membrane

by María I. Vázquez, Virgina Romero, Victor Vega, Javier García, Victor M. Prida, Blanca Hernando and Juana Benavente

Nanomaterials 2015, 5(4), 2192-2202; https://doi.org/10.3390/nano5042192 - 5 Dec 2015

Cited by 15 | Viewed by 4909

Abstract

Synthesis of a nanoporous alumina membrane (NPAM) by the two-step anodization method and its morphological and chemical surface characterization by analyzing Scanning Electron Microscopy (SEM) micrographs and X-Ray Photoelectron Spectroscopy (XPS) spectra is reported. Influence of electrical and diffusive effects on the NaCl [...] Read more.

Synthesis of a nanoporous alumina membrane (NPAM) by the two-step anodization method and its morphological and chemical surface characterization by analyzing Scanning Electron Microscopy (SEM) micrographs and X-Ray Photoelectron Spectroscopy (XPS) spectra is reported. Influence of electrical and diffusive effects on the NaCl transport across the membrane nanopores is determined from salt diffusion measurements performed with a wide range of NaCl concentrations, which allows the estimation of characteristic electrochemical membrane parameters such as the NaCl diffusion coefficient and the concentration of fixed charges in the membrane, by using an appropriated model and the membrane geometrical parameters (porosity and pore length). These results indicate a reduction of ~70% in the value of the NaCl diffusion coefficient through the membrane pores with respect to solution. The transport number of ions in the membrane pores (Na⁺ and Cl⁻, respectively) were determined from concentration potential measurements, and the effect of concentration-polarization at the membrane surfaces was also considered by comparing concentration potential values obtained with stirred solutions (550 rpm) and without stirring. From both kinds of results, a value higher than 0.05 M NaCl for the feed solution seems to be necessary to neglect the contribution of electrical interactions in the diffusive transport. Full article

(This article belongs to the Special Issue Frontiers in Mesoporous Nanomaterials)

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2586 KiB

Open AccessArticle

Utilization of Enzyme-Immobilized Mesoporous Silica Nanocontainers (IBN-4) in Prodrug-Activated Cancer Theranostics

by Bau-Yen Hung, Yaswanth Kuthati, Ranjith Kumar Kankala, Shravankumar Kankala, Jin-Pei Deng, Chen-Lun Liu and Chia-Hung Lee

Nanomaterials 2015, 5(4), 2169-2191; https://doi.org/10.3390/nano5042169 - 4 Dec 2015

Cited by 40 | Viewed by 8786

Abstract

To develop a carrier for use in enzyme prodrug therapy, Horseradish peroxidase (HRP) was immobilized onto mesoporous silica nanoparticles (IBN-4: Institute of Bioengineering and Nanotechnology), where the nanoparticle surfaces were functionalized with 3-aminopropyltrimethoxysilane and further conjugated with glutaraldehyde. Consequently, the enzymes could be [...] Read more.

To develop a carrier for use in enzyme prodrug therapy, Horseradish peroxidase (HRP) was immobilized onto mesoporous silica nanoparticles (IBN-4: Institute of Bioengineering and Nanotechnology), where the nanoparticle surfaces were functionalized with 3-aminopropyltrimethoxysilane and further conjugated with glutaraldehyde. Consequently, the enzymes could be stabilized in nanochannels through the formation of covalent imine bonds. This strategy was used to protect HRP from immune exclusion, degradation and denaturation under biological conditions. Furthermore, immobilization of HRP in the nanochannels of IBN-4 nanomaterials exhibited good functional stability upon repetitive use and long-term storage (60 days) at 4 °C. The generation of functionalized and HRP-immobilized nanomaterials was further verified using various characterization techniques. The possibility of using HRP-encapsulated IBN-4 materials in prodrug cancer therapy was also demonstrated by evaluating their ability to convert a prodrug (indole-3- acetic acid (IAA)) into cytotoxic radicals, which triggered tumor cell apoptosis in human colon carcinoma (HT-29 cell line) cells. A lactate dehydrogenase (LDH) assay revealed that cells could be exposed to the IBN-4 nanocomposites without damaging their membranes, confirming apoptotic cell death. In summary, we demonstrated the potential of utilizing large porous mesoporous silica nanomaterials (IBN-4) as enzyme carriers for prodrug therapy. Full article

(This article belongs to the Special Issue Frontiers in Mesoporous Nanomaterials)

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2863 KiB

Open AccessReview

Upconverting NIR Photons for Bioimaging

by Zhanjun Li, Yuanwei Zhang, Hieu La, Richard Zhu, Ghida El-Banna, Yuzou Wei and Gang Han

Nanomaterials 2015, 5(4), 2148-2168; https://doi.org/10.3390/nano5042148 - 4 Dec 2015

Cited by 61 | Viewed by 10851

Abstract

Lanthanide-doped upconverting nanoparticles (UCNPs) possess uniqueanti-Stokes optical properties, in which low energy near-infrared (NIR) photons can beconverted into high energy UV, visible, shorter NIR emission via multiphoton upconversionprocesses. Due to the rapid development of synthesis chemistry, lanthanide-doped UCNPscan be fabricated with narrow distribution [...] Read more.

Lanthanide-doped upconverting nanoparticles (UCNPs) possess uniqueanti-Stokes optical properties, in which low energy near-infrared (NIR) photons can beconverted into high energy UV, visible, shorter NIR emission via multiphoton upconversionprocesses. Due to the rapid development of synthesis chemistry, lanthanide-doped UCNPscan be fabricated with narrow distribution and tunable multi-color optical properties. Theseunique attributes grant them unique NIR-driven imaging/drug delivery/therapeuticapplications, especially in the cases of deep tissue environments. In this brief review, weintroduce both the basic concepts of and recent progress with UCNPs in material engineeringand theranostic applications in imaging, molecular delivery, and tumor therapeutics. The aimof this brief review is to address the most typical progress in basic mechanism, materialdesign as bioimaging tools. Full article

(This article belongs to the Special Issue Nanoparticles in Bioimaging)

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627 KiB

Open AccessArticle

Performance Evaluation of a Nanofluid-Based Direct Absorption Solar Collector with Parabolic Trough Concentrator

by Guoying Xu, Wei Chen, Shiming Deng, Xiaosong Zhang and Sainan Zhao

Nanomaterials 2015, 5(4), 2131-2147; https://doi.org/10.3390/nano5042131 - 4 Dec 2015

Cited by 62 | Viewed by 8215

Abstract

Application of solar collectors for hot water supply, space heating, and cooling plays a significant role in reducing building energy consumption. For conventional solar collectors, solar radiation is absorbed by spectral selective coating on the collectors’ tube/plate wall. The poor durability of the [...] Read more.

Application of solar collectors for hot water supply, space heating, and cooling plays a significant role in reducing building energy consumption. For conventional solar collectors, solar radiation is absorbed by spectral selective coating on the collectors’ tube/plate wall. The poor durability of the coating can lead to an increased manufacturing cost and unreliability for a solar collector operated at a higher temperature. Therefore, a novel nanofluid-based direct absorption solar collector (NDASC) employing uncoated collector tubes has been proposed, and its operating characteristics for medium-temperature solar collection were theoretically and experimentally studied in this paper. CuO/oil nanofluid was prepared and used as working fluid of the NDASC. The heat-transfer mechanism of the NDASC with parabolic trough concentrator was theoretically evaluated and compared with a conventional indirect absorption solar collector (IASC). The theoretical analysis results suggested that the fluid’s temperature distribution in the NDASC was much more uniform than that in the IASC, and an enhanced collection efficiency could be achieved for the NDASC operated within a preferred working temperature range. To demonstrate the feasibility of the proposed NDASC, experimental performances of an NDASC and an IASC with the same parabolic trough concentrator were furthermore evaluated and comparatively discussed. Full article

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Open AccessFeature PaperReview

Composites of Polymer Hydrogels and Nanoparticulate Systems for Biomedical and Pharmaceutical Applications

by Fuli Zhao, Dan Yao, Ruiwei Guo, Liandong Deng, Anjie Dong and Jianhua Zhang

Nanomaterials 2015, 5(4), 2054-2130; https://doi.org/10.3390/nano5042054 - 3 Dec 2015

Cited by 306 | Viewed by 26311

Abstract

Due to their unique structures and properties, three-dimensional hydrogels and nanostructured particles have been widely studied and shown a very high potential for medical, therapeutic and diagnostic applications. However, hydrogels and nanoparticulate systems have respective disadvantages that limit their widespread applications. Recently, the [...] Read more.

Due to their unique structures and properties, three-dimensional hydrogels and nanostructured particles have been widely studied and shown a very high potential for medical, therapeutic and diagnostic applications. However, hydrogels and nanoparticulate systems have respective disadvantages that limit their widespread applications. Recently, the incorporation of nanostructured fillers into hydrogels has been developed as an innovative means for the creation of novel materials with diverse functionality in order to meet new challenges. In this review, the fundamentals of hydrogels and nanoparticles (NPs) were briefly discussed, and then we comprehensively summarized recent advances in the design, synthesis, functionalization and application of nanocomposite hydrogels with enhanced mechanical, biological and physicochemical properties. Moreover, the current challenges and future opportunities for the use of these promising materials in the biomedical sector, especially the nanocomposite hydrogels produced from hydrogels and polymeric NPs, are discussed. Full article

(This article belongs to the Special Issue Nanoparticles Assisted Drug Delivery)

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3176 KiB

Open AccessReview

Recent Advance on Mesoporous Silica Nanoparticles-Based Controlled Release System: Intelligent Switches Open up New Horizon

by Ruijuan Sun, Wenqian Wang, Yongqiang Wen and Xueji Zhang

Nanomaterials 2015, 5(4), 2019-2053; https://doi.org/10.3390/nano5042019 - 25 Nov 2015

Cited by 69 | Viewed by 10851

Abstract

Mesoporous silica nanoparticle (MSN)-based intelligent transport systems have attracted many researchers’ attention due to the characteristics of uniform pore and particle size distribution, good biocompatibility, high surface area, and versatile functionalization, which have led to their widespread application in diverse areas. In the [...] Read more.

Mesoporous silica nanoparticle (MSN)-based intelligent transport systems have attracted many researchers’ attention due to the characteristics of uniform pore and particle size distribution, good biocompatibility, high surface area, and versatile functionalization, which have led to their widespread application in diverse areas. In the past two decades, many kinds of smart controlled release systems were prepared with the development of brilliant nano-switches. This article reviews and discusses the advantages of MSN-based controlled release systems. Meanwhile, the switching mechanisms based on different types of stimulus response are systematically analyzed and summarized. Additionally, the application fields of these devices are further discussed. Obviously, the recent evolution of smart nano-switches promoted the upgrading of the controlled release system from the simple “separated” switch to the reversible, multifunctional, complicated logical switches and selective switches. Especially the free-blockage switches, which are based on hydrophobic/hydrophilic conversion, have been proposed and designed in the last two years. The prospects and directions of this research field are also briefly addressed, which could be better used to promote the further development of this field to meet the needs of mankind. Full article

(This article belongs to the Special Issue Frontiers in Mesoporous Nanomaterials)

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Open AccessArticle

Nanostructuring of Palladium with Low-Temperature Helium Plasma

by P. Fiflis, M.P. Christenson, N. Connolly and D.N. Ruzic

Nanomaterials 2015, 5(4), 2007-2018; https://doi.org/10.3390/nano5042007 - 25 Nov 2015

Cited by 14 | Viewed by 5154

Abstract

Impingement of high fluxes of helium ions upon metals at elevated temperatures has given rise to the growth of nanostructured layers on the surface of several metals, such as tungsten and molybdenum. These nanostructured layers grow from the bulk material and have greatly [...] Read more.

Impingement of high fluxes of helium ions upon metals at elevated temperatures has given rise to the growth of nanostructured layers on the surface of several metals, such as tungsten and molybdenum. These nanostructured layers grow from the bulk material and have greatly increased surface area over that of a not nanostructured surface. They are also superior to deposited nanostructures due to a lack of worries over adhesion and differences in material properties. Several palladium samples of varying thickness were biased and exposed to a helium helicon plasma. The nanostructures were characterized as a function of the thickness of the palladium layer and of temperature. Bubbles of ~100 nm in diameter appear to be integral to the nanostructuring process. Nanostructured palladium is also shown to have better catalytic activity than not nanostructured palladium. Full article

(This article belongs to the Special Issue Plasma Nanoengineering and Nanofabrication)

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Open AccessArticle

Electrochemical Characterization of Graphene and MWCNT Screen-Printed Electrodes Modified with AuNPs for Laccase Biosensor Development

by Gabriele Favero, Giovanni Fusco, Franco Mazzei, Federico Tasca and Riccarda Antiochia

Nanomaterials 2015, 5(4), 1995-2006; https://doi.org/10.3390/nano5041995 - 20 Nov 2015

Cited by 49 | Viewed by 6935

Abstract

The aim of this work is to show how the integration of gold nanoparticles (AuNPs) into multi-wall-carbon-nanotubes (MWCNTs) based screen-printed electrodes and into graphene-based screen-printed electrodes (GPHs) could represent a potential way to further enhance the electrochemical properties of those electrodes based on [...] Read more.

The aim of this work is to show how the integration of gold nanoparticles (AuNPs) into multi-wall-carbon-nanotubes (MWCNTs) based screen-printed electrodes and into graphene-based screen-printed electrodes (GPHs) could represent a potential way to further enhance the electrochemical properties of those electrodes based on nanoparticles. Laccase from Trametes versicolor (TvL) was immobilized over MWCNTs and GPH previously modified with AuNPs (of 5 and 10 nm). The characterization of the modified electrode surface has been carried out by cyclic voltammetry. The results showed that the use of AuNPs for modification of both graphene and MWCNTs screen-printed electrode surfaces would increase the electrochemical performances of the electrodes. MWCNTs showed better results than GPH in terms of higher electroactive area formation after modification with AuNPs. The two modified nanostructured electrodes were successively proven to efficiently immobilize the TvL; the electrochemical sensing properties of the GPH- and MWCNT-based AuNPs-TvL biosensors were investigated by choosing 2,2′-Azino-bis(3-ethylbenzothiazoline-6-sulfonic-acid diammonium salt (ABTS), catechol and caffeic acid as laccase mediators; and the kinetic parameters of the laccase biosensor were carefully evaluated. Full article

(This article belongs to the Special Issue Nanomaterials for Biosensing Applications)

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Open AccessArticle

Lithium-Excess Research of Cathode Material Li₂MnTiO₄ for Lithium-Ion Batteries

by Xinyi Zhang, Le Yang, Feng Hao, Haosen Chen, Meng Yang and Daining Fang

Nanomaterials 2015, 5(4), 1985-1994; https://doi.org/10.3390/nano5041985 - 20 Nov 2015

Cited by 30 | Viewed by 7146

Abstract

Lithium-excess and nano-sized Li_2+xMn₁₋_x_/2TiO₄ (x = 0, 0.2, 0.4) cathode materials were synthesized via a sol-gel method. The X-ray diffraction (XRD) experiments indicate that the obtained main phases of Li_2.0MnTiO₄ and [...] Read more.

Lithium-excess and nano-sized Li_2+xMn₁₋_x_/2TiO₄ (x = 0, 0.2, 0.4) cathode materials were synthesized via a sol-gel method. The X-ray diffraction (XRD) experiments indicate that the obtained main phases of Li_2.0MnTiO₄ and the lithium-excess materials are monoclinic and cubic, respectively. The scanning electron microscope (SEM) images show that the as-prepared particles are well distributed and the primary particles have an average size of about 20–30 nm. The further electrochemical tests reveal that the charge-discharge performance of the material improves remarkably with the lithium content increasing. Particularly, the first discharging capacity at the current of 30 mA g⁻¹ increases from 112.2 mAh g⁻¹ of Li_2.0MnTiO₄ to 187.5 mAh g⁻¹ of Li_2.4Mn_0.8TiO₄. In addition, the ex situ XRD experiments indicate that the monoclinic Li₂MnTiO₄ tends to transform to an amorphous state with the extraction of lithium ions, while the cubic Li₂MnTiO₄ phase shows better structural reversibility and stability. Full article

(This article belongs to the Special Issue Nanostructured Materials for Li-Ion Batteries and Beyond)

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Open AccessArticle

Synthesis of Ordered Mesoporous CuO/CeO₂ Composite Frameworks as Anode Catalysts for Water Oxidation

by Vassiliki Markoulaki Ι, Ioannis T. Papadas, Ioannis Kornarakis and Gerasimos S. Armatas

Nanomaterials 2015, 5(4), 1971-1984; https://doi.org/10.3390/nano5041971 - 17 Nov 2015

Cited by 32 | Viewed by 8376

Abstract

Cerium-rich metal oxide materials have recently emerged as promising candidates for the photocatalytic oxygen evolution reaction (OER). In this article, we report the synthesis of ordered mesoporous CuO/CeO₂ composite frameworks with different contents of copper(II) oxide and demonstrate their activity for photocatalytic [...] Read more.

Cerium-rich metal oxide materials have recently emerged as promising candidates for the photocatalytic oxygen evolution reaction (OER). In this article, we report the synthesis of ordered mesoporous CuO/CeO₂ composite frameworks with different contents of copper(II) oxide and demonstrate their activity for photocatalytic O₂ production via UV-Vis light-driven oxidation of water. Mesoporous CuO/CeO₂ materials have been successfully prepared by a nanocasting route, using mesoporous silica as a rigid template. X-ray diffraction, electron transmission microscopy and N₂ porosimetry characterization of the as-prepared products reveal a mesoporous structure composed of parallel arranged nanorods, with a large surface area and a narrow pore size distribution. The molecular structure and optical properties of the composite materials were investigated with Raman and UV-Vis/NIR diffuse reflectance spectroscopy. Catalytic results indicated that incorporation of CuO clusters in the CeO₂ lattice improved the photochemical properties. As a result, the CuO/CeO₂ composite catalyst containing ~38 wt % CuO reaches a high O₂ evolution rate of ~19.6 µmol·h⁻¹ (or 392 µmol·h⁻¹·g⁻¹) with an apparent quantum efficiency of 17.6% at λ = 365 ± 10 nm. This OER activity compares favorably with that obtained from the non-porous CuO/CeO₂ counterpart (~1.3 µmol·h⁻¹) and pure mesoporous CeO₂ (~1 µmol·h⁻¹). Full article

(This article belongs to the Special Issue Frontiers in Mesoporous Nanomaterials)

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Open AccessArticle

Surface Properties and Photocatalytic Activities of the Colloidal ZnS:Mn Nanocrystals Prepared at Various pH Conditions

by Jungho Heo and Cheong-Soo Hwang

Nanomaterials 2015, 5(4), 1955-1970; https://doi.org/10.3390/nano5041955 - 11 Nov 2015

Cited by 11 | Viewed by 6256

Abstract

Water-dispersible ZnS:Mn nanocrystals (NC) were synthesized by capping the surface with mercaptoacetic acid (MAA) molecules at three different pH conditions. The obtained ZnS:Mn-MAA NC products were physically and optically characterized by corresponding spectroscopic methods. The UV-Visible absorption spectra and PL emission spectra showed [...] Read more.

Water-dispersible ZnS:Mn nanocrystals (NC) were synthesized by capping the surface with mercaptoacetic acid (MAA) molecules at three different pH conditions. The obtained ZnS:Mn-MAA NC products were physically and optically characterized by corresponding spectroscopic methods. The UV-Visible absorption spectra and PL emission spectra showed broad peaks at 310 and 590 nm, respectively. The average particle sizes measured from the HR-TEM images were 5 nm, which were also supported by the Debye-Scherrer calculations using the X-ray diffraction (XRD) data. Moreover, the surface charges and the degrees of aggregation of the ZnS:Mn-MAA NCs were determined by electrophoretic and hydrodynamic light scattering methods, indicating formation of agglomerates in water with various sizes (50–440 nm) and different surface charge values accordingly the preparation conditions of the NCs (−7.59 to −24.98 mV). Finally, the relative photocatalytic activities of the ZnS:Mn-MAA NCs were evaluated by measuring the degradation rate of methylene blue (MB) molecule in a pseudo first-order reaction condition under the UV-visible light irradiation. As a result, the ZnS:Mn-MAA NC prepared at the pH 7 showed the best photo-degradation efficiency of the MB molecule with the first-order rate constant (kobs) of 2.0 × 10−3·min−1. Full article

(This article belongs to the Special Issue Current Trends in Colloidal Nanocrystals)

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Open AccessArticle

Cytotoxicity, Uptake Behaviors, and Oral Absorption of Food Grade Calcium Carbonate Nanomaterials

by Mi-Kyung Kim, Jeong-A. Lee, Mi-Rae Jo, Min-Kyu Kim, Hyoung-Mi Kim, Jae-Min Oh, Nam Woong Song and Soo-Jin Choi

Nanomaterials 2015, 5(4), 1938-1954; https://doi.org/10.3390/nano5041938 - 10 Nov 2015

Cited by 44 | Viewed by 7839

Abstract

Calcium is the most abundant mineral in human body and essential for the formation and maintenance of bones and teeth as well as diverse cellular functions. Calcium carbonate (CaCO₃) is widely used as a dietary supplement; however, oral absorption efficiency of [...] Read more.

Calcium is the most abundant mineral in human body and essential for the formation and maintenance of bones and teeth as well as diverse cellular functions. Calcium carbonate (CaCO₃) is widely used as a dietary supplement; however, oral absorption efficiency of CaCO₃ is extremely low, which may be overcome by applying nano-sized materials. In this study, we evaluated the efficacy of food grade nano CaCO₃ in comparison with that of bulk- or reagent grade nano CaCO₃ in terms of cytotoxicity, cellular uptake, intestinal transport, and oral absorption. Cytotoxicity results demonstrated that nano-sized CaCO₃ particles were slightly more toxic than bulk materials in terms of oxidative stress and membrane damage. Cellular uptake behaviors of CaCO₃ nanoparticles were different from bulk CaCO₃ or Ca²⁺ ions in human intestinal epithelial cells, showing efficient cellular internalization and elevated intracellular Ca²⁺ levels. Meanwhile, CaCO₃ nanoparticles were efficiently transported by microfold (M) cells in vitro model of human intestinal follicle-associated epithelium, in a similar manner as Ca²⁺ ions did. Biokinetic study revealed that the biological fate of CaCO₃ particles was different from Ca²⁺ ions; however, in vivo, its oral absorption was not significantly affected by particle size. These findings provide crucial information to understand and predict potential toxicity and oral absorption efficiency of food grade nanoparticles. Full article

(This article belongs to the Special Issue Nanoparticles Assisted Drug Delivery)

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Open AccessReview

Smart Mesoporous Nanomaterials for Antitumor Therapy

by Marina Martínez-Carmona, Montserrat Colilla and Maria Vallet-Regí

Nanomaterials 2015, 5(4), 1906-1937; https://doi.org/10.3390/nano5041906 - 6 Nov 2015

Cited by 80 | Viewed by 10884

Abstract

The use of nanomaterials for the treatment of solid tumours is receiving increasing attention by the scientific community. Among them, mesoporous silica nanoparticles (MSNs) exhibit unique features that make them suitable nanocarriers to host, transport and protect drug molecules until the target is [...] Read more.

The use of nanomaterials for the treatment of solid tumours is receiving increasing attention by the scientific community. Among them, mesoporous silica nanoparticles (MSNs) exhibit unique features that make them suitable nanocarriers to host, transport and protect drug molecules until the target is reached. It is possible to incorporate different targeting ligands to the outermost surface of MSNs to selectively drive the drugs to the tumour tissues. To prevent the premature release of the cargo entrapped in the mesopores, it is feasible to cap the pore entrances using stimuli-responsive nanogates. Therefore, upon exposure to internal (pH, enzymes, glutathione, etc.) or external (temperature, light, magnetic field, etc.) stimuli, the pore opening takes place and the release of the entrapped cargo occurs. These smart MSNs are capable of selectively reaching and accumulating at the target tissue and releasing the entrapped drug in a specific and controlled fashion, constituting a promising alternative to conventional chemotherapy, which is typically associated with undesired side effects. In this review, we overview the recent advances reported by the scientific community in developing MSNs for antitumor therapy. We highlight the possibility to design multifunctional nanosystems using different therapeutic approaches aimed at increasing the efficacy of the antitumor treatment. Full article

(This article belongs to the Special Issue Frontiers in Mesoporous Nanomaterials)

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Nanoporous Carbon Nanofibers Decorated with Platinum Nanoparticles for Non-Enzymatic Electrochemical Sensing of H₂O₂

by Yang Li, Mingfa Zhang, Xiaopeng Zhang, Guocheng Xie, Zhiqiang Su and Gang Wei

Nanomaterials 2015, 5(4), 1891-1905; https://doi.org/10.3390/nano5041891 - 6 Nov 2015

Cited by 56 | Viewed by 8264

Abstract

We describe the preparation of nanoporous carbon nanofibers (CNFs) decorated with platinum nanoparticles (PtNPs) in this work by electrospining polyacrylonitrile (PAN) nanofibers and subsequent carbonization and binding of PtNPs. The fabricated nanoporous CNF-PtNP hybrids were further utilized to modify glass carbon electrodes and [...] Read more.

We describe the preparation of nanoporous carbon nanofibers (CNFs) decorated with platinum nanoparticles (PtNPs) in this work by electrospining polyacrylonitrile (PAN) nanofibers and subsequent carbonization and binding of PtNPs. The fabricated nanoporous CNF-PtNP hybrids were further utilized to modify glass carbon electrodes and used for the non-enzymatic amperometric biosensor for the highly sensitive detection of hydrogen peroxide (H₂O₂). The morphologies of the fabricated nanoporous CNF-PtNP hybrids were observed by scanning electron microscopy, transmission electron microscopy, and their structure was further investigated with Brunauer–Emmett–Teller (BET) surface area analysis, X-ray photoelectron spectroscopy, X-ray diffraction, and Raman spectrum. The cyclic voltammetry experiments indicate that CNF-PtNP modified electrodes have high electrocatalytic activity toward H₂O₂ and the chronoamperometry measurements illustrate that the fabricated biosensor has a high sensitivity for detecting H₂O₂. We anticipate that the strategies utilized in this work will not only guide the further design and fabrication of functional nanofiber-based biomaterials and nanodevices, but also extend the potential applications in energy storage, cytology, and tissue engineering. Full article

(This article belongs to the Special Issue Nanomaterials for Biosensing Applications)

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T₁-MRI Fluorescent Iron Oxide Nanoparticles by Microwave Assisted Synthesis

by Riju Bhavesh, Ana V. Lechuga-Vieco, Jesús Ruiz-Cabello and Fernando Herranz

Nanomaterials 2015, 5(4), 1880-1890; https://doi.org/10.3390/nano5041880 - 4 Nov 2015

Cited by 22 | Viewed by 7024

Abstract

Iron oxide nanoparticles have long been studied as a T₂ contrast agent in MRI due to their superparamagnetic behavior. T₁-based positive contrast, being much more favorable for clinical application due to brighter and more accurate signaling is, however, still limited [...] Read more.

Iron oxide nanoparticles have long been studied as a T₂ contrast agent in MRI due to their superparamagnetic behavior. T₁-based positive contrast, being much more favorable for clinical application due to brighter and more accurate signaling is, however, still limited to gadolinium- or manganese-based imaging tools. Though being the only available commercial positive-contrast agents, they lack an efficient argument when it comes to biological toxicity and their circulatory half-life in blood. The need arises to design a biocompatible contrast agent with a scope for easy surface functionalization for long circulation in blood and/or targeted imaging. We hereby propose an extremely fast microwave synthesis for fluorescein-labeled extremely-small iron oxide nanoparticles (fdIONP), in a single step, as a viable tool for cell labeling and T₁-MRI. We demonstrate the capabilities of such an approach through high-quality magnetic resonance angiographic images of mice. Full article

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Open AccessReview

Gold Nanotheranostics: Proof-of-Concept or Clinical Tool?

by Pedro Pedrosa, Raquel Vinhas, Alexandra Fernandes and Pedro V Baptista

Nanomaterials 2015, 5(4), 1853-1879; https://doi.org/10.3390/nano5041853 - 3 Nov 2015

Cited by 108 | Viewed by 12477

Abstract

Nanoparticles have been making their way in biomedical applications and personalized medicine, allowing for the coupling of diagnostics and therapeutics into a single nanomaterial—nanotheranostics. Gold nanoparticles, in particular, have unique features that make them excellent nanomaterials for theranostics, enabling the integration of targeting, [...] Read more.

Nanoparticles have been making their way in biomedical applications and personalized medicine, allowing for the coupling of diagnostics and therapeutics into a single nanomaterial—nanotheranostics. Gold nanoparticles, in particular, have unique features that make them excellent nanomaterials for theranostics, enabling the integration of targeting, imaging and therapeutics in a single platform, with proven applicability in the management of heterogeneous diseases, such as cancer. In this review, we focus on gold nanoparticle-based theranostics at the lab bench, through pre-clinical and clinical stages. With few products facing clinical trials, much remains to be done to effectively assess the real benefits of nanotheranostics at the clinical level. Hence, we also discuss the efforts currently being made to translate nanotheranostics into the market, as well as their commercial impact. Full article

(This article belongs to the Special Issue Nanoparticles in Theranostics)

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Open AccessArticle

Structural Stability of Diffusion Barriers in Cu/Ru/MgO/Ta/Si

by Shu-Huei Hsieh, Wen Jauh Chen and Chu-Mo Chien

Nanomaterials 2015, 5(4), 1840-1852; https://doi.org/10.3390/nano5041840 - 3 Nov 2015

Cited by 6 | Viewed by 6041

Abstract

Various structures of Cu (50 nm)/Ru (2 nm)/MgO (0.5–3 nm)/Ta (2 nm)/Si were prepared by sputtering and electroplating techniques, in which the ultra-thin trilayer of Ru (2 nm)/MgO (0.5–3 nm)/Ta (2 nm) is used as the diffusion barrier against the interdiffusion between Cu [...] Read more.

Various structures of Cu (50 nm)/Ru (2 nm)/MgO (0.5–3 nm)/Ta (2 nm)/Si were prepared by sputtering and electroplating techniques, in which the ultra-thin trilayer of Ru (2 nm)/MgO (0.5–3 nm)/Ta (2 nm) is used as the diffusion barrier against the interdiffusion between Cu film and Si substrate. The various structures of Cu/Ru/MgO/Ta/Si were characterized by four-point probes for their sheet resistances, by X-ray diffractometers for their crystal structures, by scanning electron microscopes for their surface morphologies, and by transmission electron microscopes for their cross-section and high resolution views. The results showed that the ultra-thin tri-layer of Ru (2 nm)/MgO (0.5–3 nm)/Ta (2 nm) is an effective diffusion barrier against the interdiffusion between Cu film and Si substrate. The MgO, and Ta layers as deposited are amorphous. The mechanism for the failure of the diffusion barrier is that the Ru layer first became discontinuous at a high temperature and the Ta layer sequentially become discontinuous at a higher temperature, the Cu atoms then diffuse through the MgO layer and to the substrate at the discontinuities, and the Cu₃Si phases finally form. The maximum temperature at which the structures of Cu (50 nm)/Ru (2 nm)/MgO (0.5–3 nm)/Ta (2 nm)/Si are annealed and still have low sheet resistance is from 550 to 750 °C for the annealing time of 5 min and from 500 to 700 °C for the annealing time of 30 min. Full article

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Effects of Annealing Temperature on Properties of Ti-Ga–Doped ZnO Films Deposited on Flexible Substrates

by Tao-Hsing Chen and Ting-You Chen

Nanomaterials 2015, 5(4), 1831-1839; https://doi.org/10.3390/nano5041831 - 3 Nov 2015

Cited by 24 | Viewed by 5470

Abstract

An investigation is performed into the optical, electrical, and microstructural properties of Ti-Ga–doped ZnO films deposited on polyimide (PI) flexible substrates and then annealed at temperatures of 300 °C, 400 °C, and 450 °C, respectively. The X-ray diffraction (XRD) analysis results show that [...] Read more.

An investigation is performed into the optical, electrical, and microstructural properties of Ti-Ga–doped ZnO films deposited on polyimide (PI) flexible substrates and then annealed at temperatures of 300 °C, 400 °C, and 450 °C, respectively. The X-ray diffraction (XRD) analysis results show that all of the films have a strong (002) Ga doped ZnO (GZO) preferential orientation. As the annealing temperature is increased to 400 °C, the optical transmittance increases and the electrical resistivity decreases. However, as the temperature is further increased to 450 °C, the transmittance reduces and the resistivity increases due to a carbonization of the PI substrate. Finally, the crystallinity of the ZnO film improves with an increasing annealing temperature only up to 400 °C and is accompanied by a smaller crystallite size and a lower surface roughness. Full article

(This article belongs to the Special Issue Nanomaterials for Flexible and Stretchable Devices: Synthesis, Processes, and Applications)

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Nanomaterials, Volume 5, Issue 4 (December 2015) – 47 articles , Pages 1556-2390

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