Showing papers in "Journal of Nanoscience and Nanotechnology in 2011"
TL;DR: This review of recent research on nanomaterials including design, synthesis, fabrication and functionalization based on the nanoarchitectonics concept is summarized.
Abstract: Nanomaterials have been prepared over a wide range of length scales from nanoscopic objects to bulk structural materials. Recent investigations have been focused on the regulation and control of nanoscopic structures for the modulation of the properties of even macroscopic objects. As an emerging concept, nanoarchitectonics has been proposed as a technology system to be used for arranging nanoscale structural units--i.e., the nanostructure unit as a group of atoms or molecules--in a predesignated configuration. In this review, we summarize recent research on nanomaterials including design, synthesis, fabrication and functionalization based on the nanoarchitectonics concept. Examples are roughly classified according to their dimensionalities: (i) OD nanomaterials (quantum dots, nanocrystals, nanoparticles and nanospheres); (ii) 1D nanomaterials (nanorods, nanowires, nanobelts, nanowhiskers and nanotubes), (iii) 2D nanomaterials (nanosheets, graphene, self-assemble monolayers, Langmuir-Blodgett films, layer-by-layer assemblies and interfacial structures), and (iv) 3D nanomaterials (bulk materials with nanoscale structural control, nanohybrids, nanocomposites and mesoporous materials).
419 citations
TL;DR: Halloysite morphology, structure and properties were characterized by using SEM, TEM, XRD, FT-IR spectroscopy, surface electrokinetic (zeta) potential and nitrogen adsorption isotherms.
Abstract: Halloysite is a naturally occurring clay mineral with submicron sized hollow cylindrical morphology. Halloysite morphology, structure and properties were characterized by using SEM, TEM, XRD, FT-IR spectroscopy, surface electrokinetic (zeta) potential and nitrogen adsorption isotherms. Comparison of the halloysite structure with imogolite was also provided. Halloysite toxicological studies revealed that it is environmentally friendly and biocompatible material. Due to its unique tubular shape and availability in thousands of tons halloysite has potential to be applied as nanocontainers for encapsulation of chemically and biologically active agents such as medicines, pharmaceuticals, antiseptics, corrosion inhibitors, antifouling agents, and doped with them plastics producing smart polymeric nanocomposites with improved mechanical strength. Finally possibility to synthesize metal nanorods within the halloysite lumen was demonstrated.
277 citations
TL;DR: It was found that the heterogeneous Ag-TiO2 composite showed a higher activity than the pure TiO2 nanofiber; the enhanced activity can be attributed to the excellent distribution and interaction of Ag nanoparticles with the TiO1 nan ofiber support.
Abstract: A novel chemical method has been developed for the fabrication of Ag nanoparticles-coated TiO2 nanofiber composites. The method involves dispersion of TiO2 nanofibers in silver salt solution under ultrasonication, followed by addition of sodium citrate as a reducing agent. The Ag-coated TiO2 composites were characterized by high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and X-ray photoelectron microscopy (XPS). Furthermore, the photocatalytic performance was evaluated by the photocatalytic degradation of methyl orange under UV-light irradiation. It was found that the heterogeneous Ag-TiO2 composite showed a higher activity than the pure TiO2 nanofiber; the enhanced activity can be attributed to the excellent distribution and interaction of Ag nanoparticles with the TiO2 nanofiber support. A plausible mechanism for the formation of the Ag-coated TiO2 composite and reasons for the enhancement of photocatalytic activity are also discussed.
257 citations
TL;DR: Results from this study contribute to the fundamental understanding and knowledge on how particle shape affects the transport and targeting efficiency of nanocarriers, which will provide mechanistic insights on the design of shape-specific nanomedicine for targeted drug delivery applications.
Abstract: One of the major challenges in nanomedicine is to improve nanoparticle cell selectivity and adhesion efficiency through designing functionalized nanoparticles of controlled sizes, shapes, and material compositions. Recent data on cylindrically shaped filomicelles are beginning to show that non-spherical particles remarkably improved the biological properties over spherical counterpart. Despite these exciting advances, non-spherical particles have not been widely used in nanomedicine applications due to the lack of fundamental understanding of shape effect on targeting efficiency. This paper intends to investigate the shape-dependent adhesion kinetics of non-spherical nanoparticles through computational modeling. The ligand-receptor binding kinetics is coupled with Brownian dynamics to study the dynamic delivery process of nanorods under various vascular flow conditions. The influences of nanoparticle shape, ligand density, and shear rate on adhesion probability are studied. Nanorods are observed to contact and adhere to the wall much easier than their spherical counterparts under the same configuration due to their tumbling motion. The binding probability of a nanorod under a shear rate of 8 s(-1) is found to be three times higher than that of a nanosphere with the same volume. The particle binding probability decreases with increased flow shear rate and channel height. The Brownian motion is found to largely enhance nanoparticle binding. Results from this study contribute to the fundamental understanding and knowledge on how particle shape affects the transport and targeting efficiency of nanocarriers, which will provide mechanistic insights on the design of shape-specific nanomedicine for targeted drug delivery applications.
177 citations
TL;DR: It is demonstrated that ZnO nanoparticles are internalized by the human epidermal keratinocytes and elicit a cytotoxic and genotoxic response and caution should be taken while using consumer products containing nanoparticles as any perturbation in the skin barrier could expose the underlying cells to nanoparticles.
Abstract: Zinc oxide (ZnO) nanoparticles are widely used in cosmetics and sunscreens. Human epidermal keratinocytes may serve as the first portal of entry for these nanoparticles either directly through topically applied cosmetics or indirectly through any breaches in the skin integrity. Therefore, the objective of the present study was to assess the biological interactions of ZnO nanoparticles in primary human epidermal keratinocytes (HEK) as they are the most abundant cell type in the human epidermis. Cellular uptake of nanoparticles was investigated by scanning electron microscopy using back scattered electrons imaging as well as transmission electron microscopy. The electron microscopy revealed the internalization of ZnO nanoparticles in primary HEK after 6 h exposure at 14 microg/ml concentration. ZnO nanoparticles exhibited a time (6-24 h) as well as concentration (8-20 microg/ml) dependent inhibition of mitochondrial activity as evident by the MTT assay. A significant (p < 0.05) induction in DNA damage was observed in cells exposed to ZnO nanoparticles for 6 h at 8 and 14 microg/ml concentrations compared to control as evident in the Comet assay. This is the first study providing information on biological interactions of ZnO nanoparticles with primary human epidermal keratinocytes. Our findings demonstrate that ZnO nanoparticles are internalized by the human epidermal keratinocytes and elicit a cytotoxic and genotoxic response. Therefore, caution should be taken while using consumer products containing nanoparticles as any perturbation in the skin barrier could expose the underlying cells to nanoparticles.
146 citations
TL;DR: Analysis of the self-assembly of meso-tetraphenylporphine on the surfaces of highly oriented pyrolytic graphite and single-walled carbon nanotubes shows preferred arrays assure the interaction of every porphyrin unit with as many neighbors as possible, thus lowering the potential energy of the adsorption complexes.
Abstract: The self-assembly of porphyrins into highly organized functional arrays supported on appropriate solid substrates is an area of research with multiple potential applications in the "bottom-up" approach to manufacturing. In order to analyze the self-assembly of meso-tetraphenylporphine (H2TPP) on the surfaces of highly oriented pyrolytic graphite (HOPG) and single-walled carbon nanotubes (SWNTs), we performed molecular mechanics modeling (by MM+ force field) and scanning tunneling microscopy (STM) imaging. Molecular modeling predicted an energetic preference of the H2TPP molecules to adsorb in monolayers on the surfaces of graphite and SWNT sidewall, rather than their stacking or separation. On graphite, the most favorable arrays were predicted to be ribbons composed of interacting parallel chains of H2TPP molecules. On the SWNT sidewall, the energetic preference pointed toward the formation of parallel and interacting long-period helixes, resulting in an almost full coverage of the SWNT surface. These preferable arrays on both carbon materials assure the interaction of every porphyrin unit with as many neighbors as possible, thus lowering the potential energy of the adsorption complexes. STM imaging results are in good agreement with molecular modeling predictions. The formation of self-assembled ribbons was a frequently observed phenomenon on the HOPG surface, while on the SWNT surface a full coverage of the exposed portion of the sidewalls was observed, suggesting the formation of interacting long-period helixes. A preferential adsorption of H2TPP molecules near graphite topographic defects was also observed.
125 citations
TL;DR: The results obtained suggest that biosynthesized gold and silver nanoparticles can be used as effective antimicrobial agents against some of the potential harmful pathogenic microorganisms.
Abstract: In the present study we investigated the extra cellular synthesis of gold and silver nanoparticles by using the yeast Candida guilliermondii. The formation of noble metal nanoparticles was monitored by the UV-Visible spectroscopy. As prepared gold and silver nanoparticles showed distinct surface plasmon peaks at 530 nm and 425 nm respectively. Phase and morphology of the as synthesized materials were investigated by X-ray diffraction and electron microscopy techniques respectively. XRD patterns confirmed the formation of gold and silver nanoparticles with face centered cubic structures. Bio-TEM images showed the formation of near spherical, well dispersed gold and silver nanoparticles in the size range of 50-70 nm and 10-20 nm respectively. The biosynthesized nanoparticles were tested for their antimicrobial activity against five pathogenic bacterial strains. The highest efficiency for both gold and silver nanoparticles was observed against Staphylococcus aureus. A comparative study was also done to find the effect of chemically synthesized noble metal nanoparticles against the above test strains. Chemically synthesized particles had no antimicrobial activity against any of the pathogenic strains. The results obtained suggest that biosynthesized gold and silver nanoparticles can be used as effective antimicrobial agents against some of the potential harmful pathogenic microorganisms.
97 citations
TL;DR: Property such as porosity, biodegradation and mechanical properties of composite electrospun nanofibers along with their utilization for nerve, cardiac, bone, skin, vascular and cartilage tissue engineering are discussed in this review.
Abstract: Nanotechnology assists in the development of biocomposite nanofibrous scaffolds that can react positively to changes in the immediate cellular environment and stimulate specific regenerative events at molecular level to generate healthy tissues. Recently, electrospinning has gained huge momentum with greater accessibility of fabrication of composite, controlled and oriented nanofibers with sufficient porosity required for effective tissue regeneration. Current developments include the fabrication of nanofibrous scaffolds which can provide chemical, mechanical and biological signals to respond to the environmental stimuli. These nanofibers are fabricated by simple coating, blending of polymers/bioactive molecules or by surface modification methods. For obtaining optimized surface functionality, with specially designed architectures for the nanofibers (multi-layered, core-shell, aligned), electrospinning process has been modified and simultaneous 'electrospin-electrospraying' process is one of the most lately introduced technique in this perspective. Properties such as porosity, biodegradation and mechanical properties of composite electrospun nanofibers along with their utilization for nerve, cardiac, bone, skin, vascular and cartilage tissue engineering are discussed in this review. In order to locally deliver electrical stimulus and provide a physical template for cell proliferations, and to gain an external control on the level and duration of stimulation, electrically conducting polymeric nanofibers are also fabricated by electrospinning. Electrospun polypyrrole (PPy) and polyaniline (PAN) based scaffolds are the most extensively studied composite substrates for nerve and cardiac tissue engineering with or without electrical stimulations, and are discussed here. However, the major focus of ongoing and future research in regenerative medicine is to effectively exploit the pluripotent potential of Mesenchymal Stem Cell (MSC) differentiation on composite nanofibrous scaffolds for repair of organs.
89 citations
TL;DR: G gadolinium-based particles can be designed to enter efficiently into the human glioblastoma cell line U87 in quantities that can be tuned by modifying the incubation conditions, giving promising opening to a particle-assisted radio-therapy by using irradiation systems already installed in the majority of hospitals.
Abstract: Since radiotherapy is widely used in cancer treatment, it is essential to develop strategies which lower the irradiation burden while increasing efficacy and become efficient even in radio resistant tumors. Our new strategy is relying on the development of solid hybrid nanoparticles based on rare-earth such as gadolinium. In this paper, we then evidenced that gadolinium-based particles can be designed to enter efficiently into the human glioblastoma cell line U87 in quantities that can be tuned by modifying the incubation conditions. These sub-5 nm particles consist in a core of gadolinium oxide, a shell of polysiloxane and are functionalized by diethylenetriaminepentaacetic acid (DTPA). Although photoelectric effect is maximal in the [10-100 keV] range, such particles were found to possess efficient in-vitro radiosensitizing properties at an energy of 660 keV by using the "single-cell gel electrophoresis comet assay," an assay that measures the number of DNA damage that occurs during irradiation. Even more interesting, the particles have been evidenced by MTT assays to be also efficient radiosensitizers at an energy of 6 MeV for doses comprised between 2 and 8 Gy. The properties of the gadolinium-based particles give promising opening to a particle-assisted radio-therapy by using irradiation systems already installed in the majority of hospitals.
86 citations
TL;DR: Graphene has attracted a great deal of attention from varied fields of condensed matter physics, materials science and chemistry in recent times as discussed by the authors, which makes it an attractive material for many applications and its high carrier mobility, high electrical and thermal conductivity make it an exciting material.
Abstract: Graphene-the wonder material has attracted a great deal of attention from varied fields of condensed matter physics, materials science and chemistry in recent times. Its 2D atomic layer structure and unique electronic band structure makes it attractive for many applications. Its high carrier mobility, high electrical and thermal conductivity make it an exciting material. However, its applicability cannot be effectively realised unless facile techniques to synthesize high quality, large area graphene are developed in a cost effective way. Besides that a great deal of effort is required to develop techniques for modifying and opening its band structure so as to make it a potential replacement for silicon in future electronics. Considerable research has been carried out for synthesizing graphene and related materials by a variety of processes and at the same time a great deal of work has also taken place for manipulating and opening its electronic band structure. This review summarizes recent developments in the synthesis methods for graphene. It also summarizes the developments in graphene nanoribbon synthesis and methods to open band gap in graphene, in addition to pointing out a direction for future research and developments.
82 citations
TL;DR: Analysis of the surface structure of autogenous tooth bone grafting material (AutoBT) showed that AutoBT is composed of low-crystalline hydroxyapatite and possibly other calcium phosphate minerals, which is similar to the minerals of human bone tissues.
Abstract: This study was performed to identify the calcium phosphate minerals, chemical element and Ca/P ratio and to examine the surface structure of autogenous tooth bone grafting material (AutoBT) which recently developed and applied clinically as a bone graft materials. The analytical results showed that AutoBT is composed of low-crystalline hydroxyapatite (HA) and possibly other calcium phosphate minerals, which is similar to the minerals of human bone tissues. And the dental crown portion was composed of high-crystalline calcium phosphate minerals (mainly HA) with higher Ca/P ratio while the root portion was mainly composed of low-crystalline calcium phosphates with relatively low Ca/P ratio.
TL;DR: The controllable synthesis of silver nanomaterials including nanorods, nanowires, nanotubes, nanoprisms, nanoplates, nanodisks, nanospheres, and nanopolyhedrons, etc are reviewed.
Abstract: Silver nanomaterials have lots of peculiar and exciting physical and chemical properties that are different from massive silver, so the synthesis and applications of silver nanomaterials have attracted a great deal of attention in the last decade. Currently, all kinds of silver nanomaterials having different shapes and sizes have been synthesized by many ingenious methods, and silver nanomaterials have exhibited extensive application prospects in many fields especially in biomedical aspect. In this article, the controllable synthesis of silver nanomaterials including nanorods, nanowires, nanotubes, nanoprisms, nanoplates, nanodisks, nanospheres, and nanopolyhedrons, etc. are reviewed. Silver nanomaterials are most utilized in the form of nanoparticles, so the main biomedical applications of silver nanoparticles, such as antibacterial and antiviral applications, antitumor applications, biosensors and biological labels, optical imaging and imaging intensifier, are discussed. Although antibacterial applications are still the most important aspects of silver nanomaterials at present, antitumor, optical sensors and imaging applications of silver nanomaterials have also shown good potential perspectives. More biomedical applications of silver nanomaterials still need to be exploited for the future, and the biological safety of silver nanomaterials also should be paid enough attention before their practical applications.
TL;DR: The results suggest that all the three types of CeO2 particles have antibacterial activity, and both the NPs are more toxic than b-CeO2.
Abstract: Due to the unique physical and chemical properties, nanosized cerium oxide (n-CeO(2)) has attracted considerable interest in many fields of research. The potential, the growing use and the mass production of n-CeO(2) have stimulated research on their potential impact on the environment and human health. However, the toxicological definition for CeO(2) nanoparticles (NPs) is still quite controversial. In the present work, we evaluated the antibacterial activity of CeO(2) NPs sized ca. 7 nm (7-CeO(2)), ca. 25 nm (25-CeO(2)) and their bulk counterpart (b-CeO(2)), using gram-negative Escherichia coli (E. coli). Our results suggest that all the three types of CeO(2) particles have antibacterial activity, and both the NPs are more toxic than b-CeO(2). The rise in intracellular ROS level induced by direct contact of particles with the surface of E. coli was involved in the mechanism for the antibacterial activity of CeO(2) NPs. Exposure to 25-CeO(2) could also impair the integrity of the outer membrane within E. coli cells. Due to agglomeration and negligible effect on membrane integrity, 7-CeO(2) did riot exhibit greater antibacterial activity than 25-CeO(2).
TL;DR: It is shown that the observed FM data fits well with the BMP model involving localised carriers and magnetic cations, based on the bound magnetic polaron (BMP) model.
Abstract: Structural, optical and magnetic studies have been carried out for the Co-doped ZnO nanoparticles (NPs). ZnO NPs are doped with 3% and 5% Co using ball milling and ferromagnetism (FM) is studied at room temperature and above. A high Curie temperature (Tc) has been observed from the Co doped ZnO NPs. X-ray diffraction and high resolution transmission electron microscopy analysis confirm the absence of metallic Co clusters or any other phase different from wurtzite-type ZnO. UV-visible absorption and photoluminescence studies on the doped samples show change in band structure and oxygen vacancy defects, respectively. Micro-Raman studies of doped samples shows defect related additional strong bands at 547 and 574 cm(-1) confirming the presence of oxygen vacancy defects in ZnO lattice. The field dependence of magnetization (M-H curve) measured at room temperature exhibits the clear M-H loop with saturation magnetization and coercive field of the order of 4-6 emu/g and 260 G, respectively. Temperature dependence of magnetization measurement shows sharp ferromagnetic to paramagnetic transition with a high Tc = 791 K for 3% Co doped ZnO NPs. Ferromagnetic ordering is interpreted in terms of overlapping of polarons mediated through oxygen vacancy defects based on the bound magnetic polaron (BMP) model. We show that the observed FM data fits well with the BMP model involving localised carriers and magnetic cations.
TL;DR: Natural halloysite nanotubes with a 15-nm internal lumen and a 50 nm outer diameter were investigated as a nanocontainer for the loading and extended release of glycerol for cosmetic applications.
Abstract: Natural halloysite nanotubes with a 15-nm internal lumen and a 50 nm outer diameter were investigated as a nanocontainer for the loading and extended release of glycerol for cosmetic applications. Cytotoxicity testing of the halloysite was conducted on 3T3 and MCF-7 cells, and the tubules showed no toxic effect on the cells for over 48 h. The capability of halloysite for loading glycerol was higher with the USA halloysite than with the New Zealand's, being approximately 20% and 2.3% by weight, respectively. The total elapsed time for releasing glycerol from the nanotubes exceeded 20 h. To further retard the glycerol release rate, the halloysite samples filled with glycerol were coated with several alternate layers of polyethyleneimine and polyacrylic acid. The release rate remained at the same level, however, probably due to the low molecular weight of the polyelectrolytes and the high solubility of glycerol in water.
TL;DR: A review of the previous work on metalcone MLD and a variety of new metalcone systems can be found in this article, where the relative number of cycles of atomic layer deposition and molecular layer deposition can be tuned from pure metalcone ALD to pure metal oxide ALD.
Abstract: Hybrid organic-inorganic films can be deposited using atomic layer deposition (ALD) and molecular layer deposition (MLD) techniques. A special set of hybrid organic-inorganic films based on metal precursors and various organic alcohols yields metal alkoxide films that can be described as "metalcones." Many metalcone films are possible such as the "alucones" and "zincones" based on the reaction of trimethylaluminum and diethylzinc, respectively, with various organic alcohols such as ethylene glycol (EG). This paper reviews the previous work on metalcone MLD and discusses a variety of new metalcone systems. "Titanicones" are grown using TiCl4 and glycerol or EG and "zircones" are grown using zirconium tetra-tert-butoxide and EG. In addition, the organic alcohol can also be varied to change the properties within one metalcone family. For example, the glycerol triol precursor allows for more cross-linking and higher toughness in alucones than the EG diol precursor. Alloys can also be formed by combining metalcone MLD and metal oxide ALD. By varying the relative number of cycles of MLD and ALD, the composition and properties of the hybrid organic-inorganic films can be tuned from pure metalcone MLD to pure metal oxide ALD.
TL;DR: Among the four prepared catalysts, the Mn3O4/SNPs nanocomposite had the highest monomer yield and may be explained by the high surface area, amorphous and porous structure, and existence of numerous active sites on the nanocomPOSite catalyst.
Abstract: Polyethylene terephthalate (PET) was depolymerized to monomer bis(2-hydroxyethyl) terephthalate (BHET) using excess ethylene glycol (EG) in the presence of metal oxides that were impregnated on different forms of silica support [silica nanoparticles (SNPs) or silica microparticles (SMPs)] as glycolysis catalysts. The reactions were carried out at 300 degrees C and 1.1 MPa at an EG-to-PET molar ratio of 11:1 and a catalyst-to-PET-weight ratio of 1.0% for 40-80 min. Among the four prepared catalysts (Mn3O4/SNPs, ZnO/SNPs, Mn3O4/SMPs, and ZnO/SMPs), the Mn3O4/SNPs nanocomposite had the highest monomer yield (> 90%). This high yield may be explained by the high surface area, amorphous and porous structure, and existence of numerous active sites on the nanocomposite catalyst. The BHET yield increased with time and reached the highest level where equilibrium was established between BHET and its dimer. The catalysts were characterized by their SEM, TEM, and BET surface areas, and via XRD, whereas the monomer BHET was characterized by HPLC and FT-IR. The glycolysis with the Mn3O4/SNPs nanocomposite as the glycolysis catalyst produced a maximum BHET in a short reaction time.
TL;DR: Results indicate that functionalization of MWCNTs with aromatic polyamide dendrimers and successive deposition of Ag nanoparticles could play an important role in the enhancement of antimicrobial activity.
Abstract: The nanohybrids composed of silver nanoparticles and aromatic polyamide functionalized multiwalled carbon nanotubes (MWCNTs) is successfully synthesized and tested for their antibacterial activity against different pathogens. Prior to deposition of silver nanoparticles, acid treated MWCNTs (MWCNTs-COOH) were successively reacted with p-phenylenediamine and methylmethacrylate to form series of NH2-terminated aromatic polyamide dendrimers on the surface of MWCNTs through Michael addition and amidation. Existence of high abundance of amine groups on the surface of functionalized MWCNTs (f-MWCNTs) provided sites for formation of silver nanoparticles by the reduction of aqueous solution of AgNO3. The silver nanoparticles formed in the resulted f-MWCNTs-Ag nanohybrids were determined to be face centered cubic (fcc) symmetry. The structure and nature of f-MWCNTs and f-MWCNTs-Ag nanohybrids were characterized by UV-vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction analysis (XRD), Raman spectroscopy and thermogravimetric analysis (TGA). The dispersion state of f-MWCNTs and immobilization of silver nanoparticles on the surface of f-MWCNTs were investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Elemental composition of f-MWCNTs-Ag nanohybrids was determined by energy dispersive X-ray spectroscopy (EDS). The antimicrobial activity of f-MWCNTs-Ag nanohybrids were estimated against E. coli, P. aeruginosa and S. aureu and compared with MWCNTs-COOH and f-MWCNTs. The results indicate that functionalization of MWCNTs with aromatic polyamide dendrimers and successive deposition of Ag nanoparticles could play an important role in the enhancement of antimicrobial activity.
TL;DR: TEM images showed that amount of platelets formed were predominant at lower temperature where as more number of monodispersed spherical particle of size 1-10 nm were perceived at high temperatures.
Abstract: Cumin seed was investigated for synthesis of gold nanoparticles. Polydispersed particles were obtained at pH 3 and 30 degrees C, and the effect of temperature and pH on synthesis of gold nanoparticles was analyzed. TEM images showed that amount of platelets formed were predominant at lower temperature where as more number of monodispersed spherical particle of size 1-10 nm were perceived at high temperatures. The gold nanoparticles particles formed at higher pH were stable, uniform and spherical in shape. XPS analysis showed the presence of pure gold nanoparticles.
TL;DR: Thiourea with both sulfur and diamine structure is used to synthesize reduced graphene oxide by the general wet chemical reduction method and is of low toxicity and nonvolatile, which makes the reduction much safer.
Abstract: Various compounds with sulfur or diamine structure have been served as efficient reducing agents to convert graphene oxide to reduced graphene oxide. In this work, we used thiourea with both sulfur and diamine structure to synthesize reduced graphene oxide by the general wet chemical reduction method. The effective deoxygenation of graphene oxide was confirmed by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy analysis and Raman spectroscopy. The as-prepared reduced graphene oxide is consisted of few-layered (no more than seven) and over 60% single-layered graphene sheet determined by atomic force microscopy and transmission electron microscopy. It also exhibits good dispersion in organic solvents such as ethanol and N,N-dimethylformamide, which is useful for the further modification of graphene and preparation of novel nanocomposites. This newly found reducing agent is of low toxicity and nonvolatile, which makes the reduction much safer.
TL;DR: It is reported that the synthesized calcium carbonate nanosized particles using polymer mediated growth technique are biocompatible and can be safely used for biomedical applications.
Abstract: The synthesis of nanoparticles and their functionalization to effectively utilize them in biological applications including drug delivery is currently a challenge. Calcium carbonate among many other inorganic nanosized particles offers promising results for such applications. We have synthesized calcium carbonate nanoparticles using polymer mediated growth technique, where one of the ions bound within polymer matrix and the other diffuses and reacts to form desired compound. The synthesized nanoparticles are characterized using X-ray diffraction, Scanning Electron Microscopy and spectroscopic techniques such as Fourier-Transform Infra-red spectroscopy and UV-Vis spectroscopy. The diameter of the calcium carbonate nanoparticles is estimated to be 39.8 nm and their biocompatibility studies showed no significant induction of oxidative stress or cell death even at higher concentrations (50 microg) upon exposure to HeLa and LE cells. Here, we report that the synthesized calcium carbonate nanosized particles using polymer mediated growth technique are biocompatible and can be safely used for biomedical applications.
TL;DR: The toxicity and biodistribution in vivo of various morphologies of Au nanoparticles (AuNPs) were studied by using KM mice and revealed all AuNPs were preferentially accumulated in organ of liver and spleen.
Abstract: The toxicity and biodistribution in vivo of various morphologies of Au nanoparticles (AuNPs) were studied by using KM mice. The quantitative analysis of Au in each tissue of mice was done by using the Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Sphere-shaped AuNPs displayed the best biocompatibility, compared with rod- and cube-shaped of AuNPs, and rod-shaped AuNPs was more toxic than cube-shaped AuNPs. In vivo biodistribution study revealed all AuNPs were preferentially accumulated in organ of liver and spleen. The findings from this study thus revealed that the toxicity and biodistribution in vivo of AuNPs are shape dependent.
TL;DR: It is indicated that the cytotoxicity of CdS QDs and the lack of it in ZnSQDs were probably due to the presence and absence of the toxic Cd element, respectively, and makes them favorable for in vivo imaging applications.
Abstract: Cytotoxicity tests of zinc sulfide (ZnS) and cadmium sulfide (CdS) quantum dots (QDs) synthesized via all-aqueous process with various surface conditions were carried out with human endothelial cells (EA hy926) using two independent viability assays, i.e., by cell counting following Trypan blue staining and by measuring Alamar Blue (AB) fluorescence. The ZnS QDs with all four distinct types of surface conditions were nontoxic at both 1 microM and 10 microM concentrations for at least 6 days. On the other hand, the CdS QDs were nontoxic only at 1 microM, and showed significant cytotoxicity at 10 microM after 3 days in the cell counting assay and after 4 days in the AB fluorescence assay. The CdS QDs with (3-mercaptopropyl)trimethoxysilane (MPS)-replacement plus silica capping were less cytotoxic than those with 3-mercaptopropionic acid (MPA) capping and those with MPS-replacement capping. Comparing the results of ZnS and CdS QDs with the same particle size, surface condition and concentration, it is indicated that the cytotoxicity of CdS QDs and the lack of it in ZnS QDs were probably due to the presence and absence of the toxic Cd element, respectively. The nontoxicity of the aqueous ZnS QDs makes them favorable for in vivo imaging applications.
TL;DR: Using finite-difference time-domain (FDTD) analysis, the role of different kinds of randomness in the structure of the Morpho butterfly's scale was investigated and revealed that incoherence in the incident light plays an essential role, which cannot be realized only by structural randomness.
Abstract: The blue coloration of Morpho butterflies has anomalously low angular dependence despite the production of color with a selected wavelength based on an interference effect. A key to the mechanism of the specific Morpho-color was suggested to be the randomness of its scale. Using finite-difference time-domain (FDTD) analysis, the role of different kinds of randomness in the structure of the Morpho butterfly's scale was investigated, which was impossible by conventional analytical calculations. The results revealed that incoherence in the incident light plays an essential role, which cannot be realized only by structural randomness. On the other hand, the lateral and vertical randomness, and the number of random components were found each to have an independent role to realize the specific Morpho-color preventing the sharp reflective angular dependence. The direction obtained by the numerical simulations to analyze optically complex random structures will serve not only to understand the scientific principles, but also to design the optical properties of artificial materials.
TL;DR: Ag nanoparticles capped by honey exhibited superior antimicrobial activity while Au nanoparticles revealed passable activity against pathogenic bacteria and Candida albicans, including multi-resistant strains for the first time.
Abstract: Biomolecules hosting the synthesis of nanoparticles has achieved considerable attention in recent decades due to their abundant availability, excellent biocompatibility and low toxicity. The present study demonstrates a rapid, cost-effective and eco-friendly fabrication of gold and silver nanoparticles at room temperature using natural honey as a source of stabilizing and reducing agent. The nanoparticles obtained were unambiguously characterized by using various characterization techniques such as transmission electron microscopy (TEM), UV-Visible absorption spectroscopy, X-ray diffraction and energy dispersive (EDX) X-ray analysis. The average size of Au and Ag nanoparticles are 10 and 12 nm respectively. Ag nanoparticles capped by honey exhibited superior antimicrobial activity while Au nanoparticles revealed passable activity against pathogenic bacteria and Candida albicans, including multi-resistant strains for the first time.
TL;DR: The biosynthesis of silver nanoparticles using Moringa oleifera leaf extract as reducing and stabilizing agent and its application in nonlinear optics is presented and it is shown that these biosynthesizedSilver nanoparticles possess very good nonlinear properties similar to those nanoparticles synthesized by chemical route.
Abstract: The Development of biologically inspired experimental processes for the synthesis of nanoparticles is evolving into an important branch of nanotechnology. The work presented here with the biosynthesis of silver nanoparticles using Moringa oleifera leaf extract as reducing and stabilizing agent and its application in nonlinear optics. The aqueous silver ions when exposed to Moringa oleifera leaf extract are reduced resulting in silver nanoparticles demonstrating the biosynthesis. The silver nanoparticles were characterized by UV-Visible, X-ray diffraction (XRD), Fourier transform infra-red spectroscopy (FT-IR) and transmission electron microscopy (TEM) techniques. TEM analysis shows a dispersion of the nanoparticles in a range of 5-80 nm with the average around 46 nm and are crystallized in face centred cubic symmetry. To show that these biosynthesized silver nanoparticles possess very good nonlinear properties similar to those nanoparticles synthesized by chemical route, we carried out the Z-scan studies with a 6 ns, 532 nm pulsed laser. We estimated the nonlinear absorption coefficient and compare it with the literature values of the nanoparticles synthesized through chemical route. The silver nanoparticles suspended in solution exhibited reverse saturable absorption with optical limiting threshold of 100 mJ/cm2.
TL;DR: The surface roughness of thin films is an important parameter related to the sticking behaviour of surfaces in the manufacturing of microelectomechanical systems (MEMS) and makes the TiO2 films candidates for adhesion engineering in MEMS.
Abstract: The surface roughness of thin films is an important parameter related to the sticking behaviour of surfaces in the manufacturing of microelectomechanical systems (MEMS). In this work, TiO2 films made by atomic layer deposition (ALD) with the TiCl4-H2O process were characterized for their growth, roughness and crystallinity as function of deposition temperature (110-300 degrees C), film thickness (up to approximately 100 nm) and substrate (thermal SiO2, RCA-cleaned Si, Al2O3). TiO2 films got rougher with increasing film thickness and to some extent with increasing deposition temperature. The substrate drastically influenced the crystallization behaviour of the film: for films of about 20 nm thickness, on thermal SiO2 and RCA-cleaned Si, anatase TiO2 crystal diameter was about 40 nm, while on Al2O3 surface the diameter was about a micrometer. The roughness could be controlled from 0.2 nm up to several nanometers, which makes the TiO2 films candidates for adhesion engineering in MEMS.
TL;DR: The present sensor shows a satisfactory response upon exposure to various concentrations of acetone vapor from 44 ppm to 352 ppm, and shows a significant change in sensitivity as compared with the POF probe without a graphene coating.
Abstract: Recently, many studies have been focused on the development of fiber optic sensor systems for various gases and vapors. In the present study, an intrinsic polymer optical fiber (POF) sensor using graphene is described for the purpose of acetone vapor sensing for the first time. Observations on the continuous measurement of acetone vapor in dehydrated air are presented. The principle of operation of sensor transduction relies on the dependence of the reflectance on the optical and geometric properties of the sensitive over layered when the vapor molecules are adsorbed on the graphene film. For the same purpose the CVD synthesized graphene film was transferred on the POF end. The synthesized graphene film thickness was evaluated using atomic force microscopy (AFM), Raman spectroscopy and transmission electron microscopy (TEM). For the preliminary evaluation using volatile organic compounds, we evaluated the sensor performance for acetone. Upon the interaction of the sensor with acetone vapor, the variation in the reflected light was monitored as a function of the acetone concentration. The sensor response shows a significant change in sensitivity as compared with the POF probe without a graphene coating. The present sensor shows a satisfactory response upon exposure to various concentrations of acetone vapor from 44 ppm to 352 ppm. To the best of our knowledge, the use of graphene film along with POF for the sensing of volatile organic compounds has not previously been reported.
TL;DR: Experimental results provided crucial insights into human serum proteins binding to different kinds of CNTs, which is important for understanding the safe application of carbon nanotubes.
Abstract: With more and more potential applications of carbon nanotubes (CNTs) in different fields, the risk of exposure to CNTs is increasing. The interaction between CNTs and protein in biological media can affect the way cells interact with, recognize and process the nanoparticles, and this has important implications for safety considerations. In this study, the interaction of single-walled and multiwall CNTs with various serum proteins was investigated. The adsorption kinetics of protein to CNTs was investigated and a semi-qualitative analysis was provided by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Matrix assisted laser desorption ionization/time of flight mass spectrometry (MALDI-TOF MS) was used to identify the protein species binding to CNTs and atomic force microscopy (AFM) was used to vividly demonstrate the adsorption model of protein on CNTs. All the experimental results showed that the adsorption capacity of CNTs for protein was highly dependent on the type, arrangement model, size and surface modification of CNTs. Significant quantity of proteins in serum could be quickly adsorbed by CNTs, mainly including albumin, prealbumin, transferrin, and immunoglobulin. Noncovalent functionalization of CNTs by polyethylene glycol (PEG) could decrease the protein adsorption on CNTs. These results provide crucial insights into human serum proteins binding to different kinds of CNTs, which is important for understanding the safe application of carbon nanotubes.
TL;DR: In this paper, the authors employed a simple process of anodizing Ti foils to prepare TiO2 nanotube arrays which show enhanced electrochemical properties for applications as Li-ion battery electrode materials.
Abstract: We have employed a simple process of anodizing Ti foils to prepare TiO2 nanotube arrays which show enhanced electrochemical properties for applications as Li-ion battery electrode materials. The lengths and pore diameters of TiO2 nanotubes can be finely tuned by varying voltage, electrolyte composition, or anodization time. The as-prepared nanotubes are amorphous and can be converted into anatase nanotubes with heat treatment at 480 degrees C. Rutile crystallites emerge in the anatase nanotube when the annealing temperature is increased to 580 degrees C, resulting in TiO2 nanotubes of mixed phases. The morphological features of nanotubes remain unchanged after annealing. Li-ion insertion performance has been studied for amorphous and crystalline TiO2 nanotube arrays. Amorphous nanotubes with a length of 3.0 microm and an outer diameter of 125 nm deliver a capacity of 91.2 microA h cm(-2) at a current density of 400 microA cm(-2), while those with a length of 25 microm and an outer diameter of 158 nm display a capacity of 533 microA h cm-2. When the 3-microm long nanotubes become crystalline, they deliver lower capacities: the anatase nanotubes and nanotubes of mixed phases show capacities of 53.8 microA h cm-2 and 63.1 microA h cm(-2), respectively at the same current density. The amorphous nanotubes show excellent capacity retention ability over 50 cycles. The cycled nanotubes show little change in morphology compared to the nanotubes before electrochemical cycling. All the TiO2 nanotubes demonstrate higher capacities than amorphous TiO2 compact layer reported in literature. The amorphous TiO2 nanotubes with a length of 1.9 microm exhibit a capacity five times higher than that of TiO2 compact layer even when the nanotube array is cycled at a current density 80 times higher than that for the compact layer. These results suggest that anodic TiO2 nanotube arrays are promising electrode materials for rechargeable Li-ion batteries.