Advances in Natural Sciences: Nanoscience and Nanotechnology

Multi-walled carbon nanotubes (MWCNTs) were prepared by thermal chemical vapor deposition at 750 °C, and WO3nanobricks with an average size of 80 nm were synthesized by a hydrothermal route. MWCNTs and WO3 were mixed at different mass ratios in dimethylformamide solution to obtain composite materials. The WO3/MWCNT composite-based sensors were used for detection of NH3 gas. The gas-sensitive properties of the sensors were compared with those of pure CNT- and WO3-based sensors. The fabricated WO3/CNT composite sensors exhibited higher response, and faster response/recovery time than the other sensors at room temperature. In this work a possible mechanism conducting to the improvement of the hybrid sensors performance is proposed

Silver nanoparticles (AgNPs) are an important class of nanomaterials, which have used as antimicrobial and disinfectant agents due to their detrimental effect on target cells. In the present study it was explored to deliver a novel tamoxifen drug system that can be used in breast cancer treatment, based on chitosan coated silver nanoparticles on MCF-7 human breast cancer cells. AgNPs synthesized from Adenia hondala tuber extract were used to make the chitosan coated AgNPs (Ch-AgNPs), in which the drug tamoxifen was loaded on chitosan coated silver nanoparticles (Tam-Ch-AgNPs) to construct drug loaded nanoparticles as drug delivery system. The morphology and characteristics of the Ch-AgNPs were investigated by UV, FTIR, zeta potential and FESEM. Furthermore, the toxicity of AgNPs, Ch-AgNPs, Tam-Ch-AgNPs was evaluated through cell viability, lactate dehydrogenase leakage, reactive oxygen species generation, caspase-3, DNA laddering, and TUNEL assay in human breast cancer cells (MCF-7) and HBL-100 continuous cell line as a control. Treatment of cancer cells with various concentrations of AgNPs, Ch-AgNPs, Tam-Ch-AgNPs for 24 h revealed that Tam-Ch-AgNPs could inhibit cell viability and induce significant membrane leakage in a dose-dependent manner. Cells exposed to Tam-Ch-AgNPs showed increased reactive oxygen species and hydroxyl radical production when compared to AgNPs, Ch-AgNPs. Furthermore, the apoptotic effects of AgNPs, Ch-AgNPs, Tam-Ch-AgNPs were confirmed by activation of caspase-3 and DNA nuclear fragmentation. The present findings suggest that Tam-Ch-AgNPs could contribute to the development of a suitable anticancer drug delivery

The present work is devoted to the review of the methods to improve light trapping into polymer solar cells. After a discussion on the important role of the improvement of the light-trapping technique in the fabrication of solar cells by applying the plasmonic enhancement effect, we review the results of the study on this topic, which were obtained mainly during recent years. The light-trapping nanostructures usually comprised the following basic elements: antireflection coating, randomly distributed or symmetric–periodic monolayers of metallic spherical nanoparticles (NPs), metallic NPs with different shapes, spherical NPs with core–shell structure, nanovoids, plasmonic metallic grating, grating organic active layer, grating indium tin oxide (ITO) layer, dielectric grating, photonic structure, and plasmonic cavity with subwavelength hole array. Each light-trapping nanostructure may use either one or two of the above-mentioned basic elements

We have reported a novel method of synthesis of gold nanoparticles (GNPs), using two different peptides, e.g. glutathione (GSH) and glycyl-glycine (GG), as reducing agents. The formation of GNPs was observed with the development of the surface plasmon resonance (SPR) peak in UV-visible spectrum. The nanoparticles phase has been investigated using powder x-ray diffraction (XRD) method and has been seen to be single phase. The as-synthesized GNPs were not fully covered by the used peptides as seen by the thermogravimetry analysis (TGA), and therefore, trisodium citrate (TSC) has been used further as a 'filler' agent for GNPs to become well dispersible in aqueous medium. The Fourier transform infrared (FTIR) spectroscopy method has confirmed the presence of peptides and TSC coatings on the nanoparticles' surface. In comparison, the GNPs formed using GG have been observed to be more stable than those formed using GSH. The nanoparticle size was measured using XRD, dynamic light scattering (DLS) and transmission electron microscopy (TEM). These dispersions were further used to investigate the interaction between the GNPs and chitosan (CS) microparticles. The effects of this interaction were studied using UV-visible spectroscopy, DLS and FTIR. XRD and TEM showed that GNPs were uptaken by CS microparticles.

In this paper we present some research results on the micro and nano-photonic structures in the visible and near infrared spectral region for optical devices that have been done within the framework of Nanoscience and Nanotechnology Program of Institute of Materials Science. In the first part, we report the design and fabrication of 1D photonic structure based on porous silicon layers fabricated by electrochemical etching method and some of their potential applications such as optical filters, microcavity and optical sensors for distinguishing the content of bio-gasoline. In addition, we demonstrate some results on preparation of the 2D and 3D nanophotonic structures based on silica opal layers prepared by sol–gel and self-assembled methods. In the second part, we demonstrate the results of lasing emissions of erbium ions in the visible and near infrared zone from microcavity. The observation of emission of single-mode green light at the wavelength of 537 nm from erbium ions in the microcavity is interesting for the study of atom–photon interaction phenomenon. In the last part, we will show some new results of design and fabrication of nanocomposite based on nanoscale TiO2 and/or ZnO and nanoparticles of semiconductors and metals, which are oriented to the fabrication of energy conversion and photo-reactor devices

Large-size composite carbon nanotubes/polyaniline as supercapacitor electrode material has been investigated for optimization of the areal specific capacitance. Polyaniline, as conductive polymer, is synthesized on the structure of carbon nanotubes by an in situ method. Thicker the composite electrode and higher polyaniline loading increase the gravimetric and volumetric specific capacitance. It is noticeable that this report's areal specific capacitance can reach approximately 6.5 F cm−2

The control of the aging conditions for the aluminium alloys has been considered as an effective strategy to improve the properties of the alloy, especially in enhancement of the corrosion resistance. In this study, a detailed investigation of the effect of one-stage (T6) and two-stage (T76x) aging temper on mechanical properties, exfoliation and intergranular corrosion behaviours of 7075 Al–Zn–Mg–Cu alloy was implemented. Microstructures of the aged alloys were observed by optical microscopy and scanning electron microscopy (SEM), exfoliation and intergranular corrosion behaviours were investigated according to ASTM G34-2001 and ASTM G110-1992, respectively; the mechanical properties of the aged alloys were determined followed the standard methods. The microstructures of the sample aged with the T6 temper showed the finer particle size of precipitates than that of obtained from T76x tempers. Additionally, while the T6-aged sample revealed no appearance of the Precipitate Free Zones (PFZ), the PFZ with 40–50 nm in width was observed in the alloys treated with T76x tempers. The mechanical properties of the sample aged with T76x temper were negligibly reduced comparing to that of obtained with T6 temper, however, the exfoliation and intergranular corrosion behaviours were significantly improved by using two-stage aging conditions. The mechanism in enhancement of the corrosion resistance of the alloys treated with T76x temper over T6 temper was also discussed.

Phase separation of polymer mixtures is induced and controlled by photo-cross-link and photopolymerization using ultraviolet (UV) light. By taking advantage of the competition between phase separation and chemical reactions, a variety of morphologies such as co-continuous, spatially graded co-continuous and periodic structures with controllable periods, and hexagonal structures, etc, are obtained experimentally. The reaction kinetics (photo-cross-link or photopolymerization), reaction-induced elastic strain and phase separation kinetics are monitored, respectively, by UV–Vis spectroscopy, FTIR, Mach–Zehnder interferometry (MZI), light scattering (LS) and laser-scanning confocal microscopy (LSCM). Spatial modulation of light intensity generated by computer-assisted irradiation (CAI) is also used to induce phase separation of polymer blends. The correlation between the reaction-induced phase separation of polymer mixtures and the competing interactions is discussed with some perspectives on designing polymer materials with high performance

A comprehensive study of the effect of samarium nanoparticles on electrical transport properties of polyaniline has been reported. Samples are prepared by chemical oxidative polymerization of aniline in the presence of samarium nanoparticles and characterized by XRD, FESEM, EDS, HRTEM and UV-Vis spectrometer. When the samarium content in polyaniline matrix increases, energy band gap decreases and conductivity increases by four orders of magnitude. A transformation of negative to positive magnetoconductivity has been observed by incorporating samarium nanoparticles in polyaniline matrix. Two types of activation behavior have been observed from the dielectric relaxation behavior. AC conductivity strongly depends on magnetic field. Although, at present, no theoretical model is found in literature to explain directly the behavior of ac conductivity in the presence of magnetic field, it may be due to the change of grain and interfacial boundary resistances by magnetic field

An eco-friendly approach for the preparation of silver nanoparticles (AgNPs) from silver nitrate solution using aqueous Eriobotrya japonicaleaf extract was investigated. The reduction of silver ions in solution was monitored using UV–visible absorption spectroscopy, and the surface plasmon resonance of AgNPs at 435 nm was observed. The proper condition to biosynthesize AgNPs using E. japonica leaf extract was optimized by UV–visible absorption spectroscopy and dynamic light scattering measurement (DLS). The biosynthesised nanoparticles were characterised using transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDX), DLS, x-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). XRD and EDX analyses confirmed the crystalline character of AgNPs and the presence of elemental silver. The prepared AgNPs were spherical in shape, and their average particle size determined by TEM was about 20 nm. Furthermore the AgNPs were found to exhibit effective antibacterial activities against Escherichia coliand Staphylococcus aureus