Preparation, characterization, and photocatalytic properties of silver carbonate

Silver carbonate (Ag₂CO₃) short rods were prepared using a precipitation method. It was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), diffuse reflective spectra (DRS) and photocatalytic degradation of organic pollutants and destruction of E. coli measurements. The results of DRS suggested that the optical transition of Ag₂CO₃ was indirectly allowed, and its band gap was determined to be 2.08 eV. The prepared Ag₂CO₃ displayed a high activity towards degradation of phenol and MB under visible light. The total organic carbon (TOC) value decreased during the photocatalytic process, which suggests that phenol was truly photodegraded. The stability of Ag₂CO₃ was greatly improved when Na₂CO₃ was added into the photocatalytic system. In addition, Ag₂CO₃ displayed enhanced photocatalytic activities for the destruction of E. coli due to its photogenerated electron-hole pairs.     

Modified cellulose morphologies and its composites; SEM and TEM analysis

The complex, multi-level super molecular architecture of cellulose has been the subject of interest for several decades. The mechanical, physical, and environmental properties of cellulose depend on the molecular, supramolecular and morphological structure of the cellulose. This paper gives a brief overview to micro structural analysis of cellulose, as studied using transmission electron microscopy and scanning electron microscopy. The application of these techniques to study the diverse morphology of cellulose and its composites is illustrated using several examples.     

Thermoplastic starch nanocomposites reinforced with cellulose nanocrystals: effect of plasticizer on properties

The objective of this study was to characterize cellulose nanocrystals /TPS-based nanocomposites. Nanocrystalline cellulose was isolated from cotton linters using sonochemical method and characterized through WXRD, TEM, and FTIR. These nanocrystals were then dispersed in glycerol and sorbitol plasticized starch using a Fluko high shear homogenizer in varying proportions and films were cast. The films were characterized using WXRD, SEM, and mechanical properties. TEM images of nanocrystals revealed a diameter of 20–30 nm and length 200–300 nm. XRD results for nanocomposite films for both the plasticizers showed 2θ peaks at 14.8°, 16.7,° and 22.5°. Elastic modulus increased with addition of cellulose nanocrystals and tan δ shifted toward higher temperature for both the plasticizers. Mechanical properties improved more than 200% for both glycerol and sorbitol plasticized nanocomposites.     

Synthesis and characterization of Fe3O4@C@Ag nanocomposites and their antibacterial performance

We synthesized Fe₃O₄@C@Ag nanocomposites through a combination of solvothermal, hydrothermal, and chemical redox reactions. Characterization of the resulting samples by X-ray diffraction, Fourier-transform infrared spectroscopy, field-emission scanning and transmission electron microscopy, and magnetic measurement is reported. Compared to Fe₃O₄@Ag nanocomposites, the Fe₃O₄@C@Ag nanocomposites showed enhanced antibacterial activity. The Fe₃O₄@C@Ag nanocomposites were able to almost entirely prevent growth of Escherichia coli when the concentration of Ag nanoparticles was 10 μg/mL. Antibacterial activity of the Fe₃O₄@C@Ag nanocomposites was maintained for more than 40 h at 37 °C. The intermediate carbon layer not only protects magnetic core, but also improves the dispersion and antibacterial activity of the silver nanoparticles. The magnetic core can be used to control the specific location of the antibacterial agent (via external magnetic field) and to recycle the residual silver nanoparticles. The Fe₃O₄@C@Ag nanocomposites will have potential uses in many fields as catalysts, absorbents, and bifunctional magnetic-optical materials.     

Synthesis and characterization of graphene-based nanocomposites with potential use for biomedical applications

In this paper, GaN nanoparticles were synthesized from the complex Ga(H₂NCONH₂)₆Cl₃ in the flow of NH₃ at a mild temperature (350 °C). Further purification was performed by the ethanol-thermal method. The ethanol-thermal method also prompted the GaN nanoparticles to grow into an anisotropic morphology. XRD patterns reveal that GaN nanoparticles have crystallized in a hexagonal wurtzite structure. TEM observation shows that the average size of the as-prepared nanoparticles is about 5–10 nm. The photoluminescence spectrum exhibits a broad green emission band with a peak at 510 nm. It can be known from the first-principle theoretic simulation by the TDDFT method that this fluorescence emission band is attributed to the hydride defects of V _N-H on the surface of GaN nanoparticles.     

Synthesis and characterisation: Zinc oxide–sulfide nanocomposites

A novel synthesis method is presented for the preparation of nanosized-semiconductor zinc oxide–sulphide (ZnO/ZnS) core–shell nanocomposites, both formed sequentially from a single-source solid precursor. ZnO nanocrystals were synthesized by a simple co-precipitation method and ZnO/ZnS core–shell nanocomposites were successfully fabricated by sulfidation of ZnO nanocrystals via a facile chemical synthesis at room temperature. The as-obtained samples were characterized by X-ray diffraction and transmission electron microscopy. The results showed that the pure ZnO nanocrystals were hexagonal wurtzite crystal structures and the ZnS nanoparticles were sphalerite structure with the size of about 10 nm grown on the surface of the ZnO nanocrystals. Optical properties measured reveal that ZnO/ZnS core–shell nanocomposites have integrated the photoluminescent effect of ZnO and ZnS. Based on the results of the experiments, a possible formation mechanism of ZnO/ZnS core–shell nanocomposites was also suggested. This treatment is suggested to improve various properties of optoelectronically valuable ZnO/ZnS nanocomposites. These nanosized semiconductor nanocomposites can form a new class of luminescent materials for various applications.     

Synthesis, thermal treatment and characterization of cobalt ferrite-based nanocomposites

We have used time-differential perturbed angular correlation (PAC) spectroscopy with ¹⁸¹Ta-probes to study the electric field gradient at Zr-sites in synthetic zircon and hafnon between room temperature and 1,200°C. PAC spectra are similar to those obtained from naturally occurring zircons. In particular, a change in slope of the quadrupole coupling vs. temperature is observed in the synthetic zircon at the same temperature as seen in natural zircons from the Mud Tank carbonatite (Australia). The synthetic hafnon data also shows this feature but at somewhat higher temperature. Low-temperature PAC spectra of both synthetic zircon and hafnon have a clearly reduced anisotropy. We believe that the cause for this is a electronic defect, possibly created during the β-decay of the probe parent nucleus.     

CdS-ZnO composite nanorods: Synthesis, characterization and application for photocatalytic degradation of 3,4-dihydroxy benzoic acid

Well-aligned arrays of CdS-ZnO composite nanorods were grown on indium tin oxide substrates. ZnO nanorods, deposited by a low temperature aqueous chemical growth technique, were dip coated with CdS. The CdS-ZnO nanorods were polycrystalline as confirmed from the low angle X-rays diffraction study. Photon to current conversion efficiency of CdS-ZnO composite nanorod was observed to be higher than that of CdS. In the micro-Raman spectrum, we observed longitudinal optical modes of CdS and ZnO showing their co-existence. The appealing application of CdS-ZnO nanorod as a visible photocatalyst was demonstrated and the possible mechanism was discussed.     

Synthesis and characterization of hydrophobic silica nanocomposites

Hydrophobically modified silica nanocomposites have been prepared using a low temperature sol-gel process. In this study, an alkyltriethoxysilane derivative, hexdecyltrimethoxysilane (HDTMS), was co-condensed with tetraethoxyorthosilicate (TEOS) with and without a cross-linking agent, 3-glycidoxypropyltrimethoxysilane (GPTMS), to produce the modified composites. The hydrophobic properties were determined using contact angle measurement. FESEM observations revealed a semispherical nanostructure of the composites with grain size of about 50-75 nm in diameter. The chemical modification was studied by FTIR and EDX, whereas the physicothermal properties were analyzed by DSC and TGA. These long-chain alkyl modified silica nanocomposites are promising materials for use in hydrophobic and water-resistant applications.     

Facile synthesis of multifunctional Ag/Fe3O4-CS nanocomposites for antibacterial and hyperthermic applications

Nanocomposites containing two or more functional constituents are attractive candidates for advanced nanomaterials. In this study, multifunctional Ag/Fe₃O₄-CS nanocomposites were successfully prepared, using chitosan as a stabilizing and cross-linking agent. The as-synthesized nanocomposites were characterized by Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), Energy-dispersive X-ray spectroscopy (EDS), UV–visible spectrophotometer (UV–Vis) and vibrating sample magnetometer (VSM). The results demonstrated that Ag/Fe₃O₄-CS composite nanoparticles (NPs) were composed of parent components, Fe₃O₄ and Ag NPs, which were uniformly dispersed in the chitosan matrix. The hybrid NPs exhibited strong antibacterial property against Pseudomonas aeruginosa. With high magnetization value (67 emu/g), the synthesized Ag/Fe₃O₄-CS composite can be easily separated or recycled in potential biomedical applications. Furthermore, the results showed that the multicomponent hybrid nanostructures appeared to be the promising material for local hyperthermia, which can be used as thermoseeds for localized hyperthermia treatment of cancers.     

Processing and characterization of new thermoset nanocomposites based on cellulose whiskers

In the present study, the processing and the mechanical properties of new thermoset nanocomposites prepared from aqueous suspensions of microcrystalline cellulose fillers and epoxy are described. The nature of cellulose fibers, which display a large aspect ratio and the ability to associate by means of H-bonds implies that the processing method chosen in this study avoids the problem of a high level of viscosity of the epoxy reactive system-whiskers mixture. The reinforcing effect of this type of natural fiber in an epoxy matrix is mainly shown from the dynamic mechanical properties in the rubbery state. This unusual reinforcement is due to (i) the strong interactions existing between the cellulose whiskers and the epoxy network and, (ii) the creation of a percolating network linked by H-bonds between cellulose fibers. The existence of such a percolation effect is evidenced from the analysis of the rubbery shear modulus of nanocomposites based on various volume fractions of whiskers with mechanical modeling such as Halpin-Kardos and percolation approaches.     

Synthesis and multifunctionality of (CeO2-NiO) nanocomposites synthesized via sonochemical technique

CeO₂, NiO and their nanocomposite were synthesized using facile sonochemical technique. XRD assure single phase CeO₂ and NiO while the nanocomposite consists of the two phases only. CeO₂ nanoparticles possess cubic shape, NiO was formed in nanorods, and CeO₂ decorated the NiO nanorods in the nanocomposite. The magnetic behavior of the nanocomposite lies between those of the two parents with a ferromagnetic tendency. Metal oxide nanoparticles acted as catalyst in the formation of carbon nanofibers (CNFs), while the nanocomposite leads to the production of carbon nanotubes. The photocatalyst (CeO₂-NiO) achieved complete dye degradation (100%) in light for the tested dye at 50 min. The decay products were analyzed using GC mass confirming mineralization of Bb red dye.     

Synthesis, characterization and photodegradation study of mixed-phase titania hollow submicrospheres with rough surface

Titania hollow submicrospheres with mixed phase (anatase-brookite or anatase-rutile) were synthesized via the combination of hydrothermal treatment and calcination of submicrospheres consisting of a polystyrene core and an amorphous TiO₂ shell. After hydrothermal treatment, amorphous titania shell could be transformed to anatase-brookite shell consisting of loose packed titania nanocrystals, which could be further converted to anatase-brookite (below 700 °C) or anatase-rutile titania (700-800 °C) hollow spheres with rough surface via calcination. The loose packing of titania nanocrystals not only inhibited the transformation temperature from anatase to rutile, but also provided titania hollow submicrospheres with high photodegradation activity of Rhodamine B. The photocatalytic activity of titania hollow spheres increased firstly then decreased when the calcination temperature was varied in the range of 450-800 °C, while hollow spheres obtained via calcinating at 700 °C exhibited the highest photocatalytic activity, which was five times higher than that of counterpart without hydrothermal treatment.     

Synthesis, characterization, and applications of shaped single crystals

In this paper we shall review techniques for the growth of single crystal, mostly of insulating material, which are shaped during the growth process. In particular, we shall focus on the growth of single-crystal fibers of optically activated materials; the emphasis will be placed on the so-called Laser Heated Pedestal Growth (LHPG) method of pulling crystalline fibers. LHPG offers a number of logistical advantages which can be exploited as a tool for materials research. Progress in the synthesis of materials using LHPG is described, as are spectroscopic techniques which are employed in characterizing the optical and physical properties of the crystal fibers obtained by this method. Fiz. Tverd. Tela (St. Petersburg) 41, 770–773 (May 1999) Published in English in the original Russian journal. Reproduced here with stylistic changes by the Translation Editor.     

Biosynthesis of nanoparticles: technological concepts and future applications

Nanotechnology involves the production, manipulation and use of materials ranging in size from less than a micron to that of individual atoms. Although nanomaterials may be synthesized using chemical approaches, it is now possible to include the use of biological materials. In this review, we critically assess the role of microorganisms and plants in the synthesis of nanoparticles.     

Fabrication and characterization of cellulose nanoparticles from maize stalk pith via ultrasonic-mediated cationic etherification

In this study, parenchyma cellulose, which was extracted from maize stalk pith as an abundant source of agricultural residues, was applied for preparing cellulose nanoparticles (CNPs) via an ultrasound-assisted etherification and a subsequent sonication process. The ultrasonic-assisted treatment greatly improved the modification of the pith cellulose with glycidyltrimethylammonium chloride, leading to a partial increase in the dissolubility of the as-obtained product and thus disintegration of sheet-like cellulose into nanoparticles. While the formation of CNPs by ultrasonication was largely dependent on the cellulose consistency in the cationic-modified system. Under the condition of 25% cellulose consistency, the longer sono-treated duration yielded a more stable and dispersible suspension of CNP due to its higher zeta potential. Degree of substitution and FT-IR analyses indicated that quaternary ammonium salts were grafted onto hydroxyl groups of cellulose chain. SEM and TEM images exhibited the CNP to have spherical morphology with an average dimeter from 15 to 55 nm. XRD investigation revealed that CNPs consisted mainly of a crystalline cellulose Ι structure, and they had a lower crystallinity than the starting cellulose. Moreover, thermogravimetric results illustrated the thermal resistance of the CNPs was lower than the pith cellulose. The optimal CNP with highly cationic charges, good stability and acceptable thermostability might be considered as one of the alternatively renewable reinforcement additives for nanocomposite production.     

Gd, N-codoped trititanate nanotubes: Preparation, characterization and photocatalytic activity

Trititanate nanotubes were prepared using hydrothermal method and then co-doped with Gd³⁺ and N through ion-exchanging with H⁺. They were characterized by X-ray photoelectron spectra (XPS), high-resolution transmission electronmicroscopy (HRTEM), X-ray diffraction (XRD), UV-vis diffusion reflection spectra (UV-vis DRS) and photoluminescence (PL) spectra. The photocatalytic activities were investigated with Rhodamine B as the model pollutant. The results indicated that synergistic reaction occurred when codoping with Gd³⁺ and N and the photocatalytic activities of TiO₂ were enhanced significantly under visible light irradiation.     

Synthesis, characterization and applications of nanostructural/nanodimensional metal oxides

Molybdenum oxide nanorods (MOx-NR) and vanadium oxide nanotubes (VOx-NT) have been prepared using MoO₃ and V₂O₅ powders as precursors and hexadecylamine as surfactant via hydrothermal route. Porous nanocrystalline MgO powder has been prepared by a simple and instantaneous solution combustion process using corresponding magnesium nitrate as oxidizer and glycine as fuel. The compounds are characterized by XRD, TG-DTA, SEM, TEM, surface area and porosity measurements. Because of the porous nature having large surface area (107 m²/g) with nanodimension (12-23 nm), MgO powder has been successfully employed as defluoridizing agent for the removal of fluoride (75%) in ground water     

Synthesis and optical characterization of Gd2O3:Eu nanocrystals: surface states and VUV excitation

This paper reports on the synthesis and characterization of Gd₂O₃:Eu³⁺ nanocrystals of different sizes. The particles have been synthesized by a sol-lyophilization process. This methods allows the synthesis of 7–100 nm diameter cubic-phase particles. The photoluminescence properties have been studied with different excitation from X-ray to VUV and visible wavelengths. Compared to the properties of the bulk materials, some important changes on the luminescence are observed. In particular some bands are strengthened when the size of the particles is diminished. We could therefore ascribe this bands to doping ions on a site close to the surface. Also a very low efficiency of excitation for small particles is observed when exciting with X-ray or high-energy VUV photons (i.e. when exciting the host matrix) compared to the efficiency obtained when exciting in the charge transfer band or in the doping ions related states.     

Synthesis and characterization of magnetic Fe/CNTs composites with controllable Fe nanoparticle concentration

Fe/CNTs composites, with different concentrations of Fe nanoparticles (NPs) on carbon nanotube (CNT) surfaces, were successfully fabricated via a facile solvothermal method. The lengths of CNTs are up to 10 μm and the mean diameter of the Fe nanoparticles is about 25 nm. The structures, composition and magnetic properties of the Fe/CNTs were characterized by XRD, FTIR, FE-SEM, TEM and PPMS. We found that the concentrations of Fe nanoparticles depositing on the CNTs could be controlled by adjusting the initial mass ratio of ferrocene to CNTs. The Fe/CNTs composites display good ferromagnetic properties at room temperature, with a saturation magnetization of 125 emu/g-Fe and a coercivity of 276 Oe. The Curie temperature of the sample is about 1038 K, slightly lower than that (1043 K) of the bulk iron.