Papers by Keyword: Nanohybrid

Abstract: CuO/Rb₂CO₃ nanohybrid structures are fabricated, and their selectivity to CO over H₂ as well as related sensing mechanisms are investigated. A series of CuO/Rb₂CO₃ nanohybrid structures are deposited on alumina substrates by the bar-coating method. The chemical, morphological, and structural properties of the nanohybrid structures are examined by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and Raman spectroscopy. The best selectivity to CO over H₂ and highest CO response level are observed upon CuO/Rb₂CO₃ nanohybrid (5 wt.% Rb₂CO₃). The gas-sensing performance of the CuO/Rb₂CO₃ hybrid nanostructures is analyzed to prove that the catalytic properties of Rb2CO3 and its modulation ability to hole accumulation layer thickness of CuO determine the outstanding selectivity and high response level of CuO/Rb₂CO₃ nanohybrid structure compared to pristine CuO nanoparticles.

Abstract: This study provides accounts of the bonding character, electronic structure, and optical properties of the cellulose–polyaniline hybrid complex using principles of quantum mechanics. The calculations revealed cellulose and polyaniline binding energy per unit ranged from -0.52 eV to -0.68 eV. The electron localization function of the complex revealed that there was no value at the interface but deformed basins, indicating a physisorption type of interaction. The highest occupied molecular orbitals and lowest molecular orbitals are mainly dominated by the polyaniline, with minor hybridization of the orbitals of the cellulose in all configurations. These results indicate that the bonding between cellulose and polyaniline is characterized as an unshared electron interaction. Generally, the density of states of the cellulose and polyaniline complex can be considered a superposition of the states of isolated subsystems—the bandgap of the complex ranges from 2.30 eV to 2.87 eV. The lowest bandgap is observed when the prototype polyaniline is placed near the cellulose hydroxy and hydroxymethyl group. Further, the optical absorption spectra are calculated using time-dependent density functional theory. The results indicate that the prominent peak of the prototype polyaniline at 3.59 eV (345.36 nm) is suppressed at the complex. Meanwhile, in the higher energy region, the optical absorption spectra can be considered a superposition of the absorption spectra of the isolated constituents. The results presented here provide new information on the cellulose–polyaniline complex's bonding mechanism and give the resulting electronic–optical properties. The results will be helpful in the development of innovative biomaterials, fibers, and multifunctional composites based on cellulose and polyaniline.

Abstract: Background: The most frequently used monomer in commercial composite resins is bisphenol A glycidyl dimethacrylate. Bisphenol A glycidyl dimethacrylate free monomer and the long chain dimer acid based monomer were considered as an alternative method to improve mechanical and physical properties of composite resins. Objective: To study the surface roughness of different nanohybrid composites with different monomer compositions after finishing and polishing with different polishing systems. Materials and Methods: 72 composite disk specimens were prepared and divided into 3 groups (n=24) according to the resin composite that were used (harmonize kerr, venus diamond heraeus kulzer and n'durance septodont). Each group was subdivided into 4 subgroups (n=6) according to the polishing technique that was used (Jiffy natural universal wheels ultradent, sof-lex spiral wheels 3m espe, hiluster kerr or enhance system dentsply). Atomic force microscope was used to measure surface roughness. Results: There was statistical significant difference in surface roughness measuring among different n'durance, venus diamond and harmonize groups (Kruskal Wallis Test p<0.05). Post hock pairwise comparison revealed that venus diamond showed statistically significant higher surface roughness when compared with either n'durance and harmonize. Among the polishing systems, jiffy natural universal wheels produce the least surface roughness. Conclusion: Different monomer compositions may have direct effect on the final surface polish of the restorative materials. Clinical significance: The use of jiffy natural universal wheels may be found to result in the smoothest surface finish with the least clinical steps.

Abstract: Fe₃O₄/TiO₂ and Fe₃O₄/CuO nanohybrid nanohybrid materials have attracted widespread attention due to their scientific and technological importance as photocatalyst. Complicated process is usually used to synthesize these nanohybrid. In this study, we demonstrated a simple low-temperature sol-gel method to prepare Fe₃O₄/TiO₂/CuO nanohybrid as photocatalyst. Hexavalent chromium was used as a model pollutant to evaluate their photocatalytic activity. The results of the photoreduction of hexavalent chromium in aqueous solution indicated that with the incorporation of CuO content in Fe₃O₄/TiO₂ nanohybrid increasing the photocatalytic performance in ultraviolet and visible region. Moreover, it is found that hydroxyl radical has an important role in photocatalytic efficiency.

Abstract: Fe₃O₄/TiO₂ and CuO incorporated in Fe₃O₄/TiO₂ nanohybrid were successfully synthesized using sol-gel method. X-ray diffraction, Field emission scanning electron microscope, Fourier-transform infrared absorption, diffuse reflectance UV-visible spectrophotometer and Vibrating sample magnetometer were employed to investigate the structural, morphology and composition, optical and magnetic properties of the as prepared sample. The photocatalytic activity of as-prepared nanohybrids photocatalyst was tested by the photocatalytic reduction of Cr(VI) in aqueous solution under UV and visible light irradiation. Compared with Fe₃O₄/TiO₂, Fe₃O₄/TiO₂/CuO had better photocatalytic reduction efficiency. Furthermore, the possible primary species involved in the photocatalytic reduction of Cr(VI) was studied by examination the photocatalytic activity in the presence of scavengers.

Abstract: The intercalation of herbicide, 2,4,5-tricholorophenoxybutyrate (TBA) , into zinc-aluminium-layered double hydroxide (ZAL) for the formation of a new nanocomposite ZAT, was accomplished via anion exchange method. Due to the intercalation of TBA with ZAL interlayer domain, basal spacing expanded from 8.9Å in the ZAL to 23.3 Å in the ZAT. The percentage loading of TBA in the ZAT is 45.5 % (w/w). The FTIR spectra of the nanocomposite shows resemblance peaks of the TBA and Zn-Al-layered double hydroxide indicating the inclusion of TBA into the layered double hydroxide. Surface area of the resulting nanocomposite increased from 1.3 to 15.6 m²g^-1 with the nitrogen adsorption-desorption of type IV, indicating the mesopore type of material.

Abstract: Nanohybrids, based on a modified natural rubber,Epoxidized Natural Rubber (ENR-50), and organomodified montmorillonite (MMT) containing alkyl ammonium, were prepared by solvent casting technique. Morphology and non-isothermal degradation of ENR-50 and various ENR/MMT nanohybrids were characterized by POM, SEM and TG-DTG. In the hybrid materials,an increase MMT loading in the ENR-50 increased the maximum decomposition temperature (T_max) of thermal profiles. Kissinger and Ozawa plots deduced a trend of the decomposition activation energy, E_d, which is related to the agglomeration and heat transfer ability of MMT. A mechanism comprising of the degradation of ENR-50 via scission of epoxy-isoprene chains to shorter chains, ring opening reaction and the possible interactions of modified nanoclay and ENR-50 is discussed.

Abstract: Au nanoparticles of average size 3.0 nm have been deposited on SWCNT surfaces following a very lucid wet chemical process. The SWCNT/Au nanohybrid material has been characterized using field emission scanning electron microscopy (FESEM), energy dispersive x-ray analysis (EDAX), X-ray diffraction (XRD) study and Raman spectroscopy. Both optical and electrical characteristics of the hybrid sample have been studied. The PL emission intensity of the nanohybrid structure has been found to decrease on increasing the excitation wavelength in the plasmon absorption region. High temperature DC conductivity has increased appreciably when pristine SWCNT is treated with Au NPs. Such SWCNT- supported gold nanoparticles can serve as efficient catalysts in chemical industry. Also the tendency of gold-based nanoparticles to attach with biological molecules may make them useful in medical diagnostics. Increase in conductivity of SWCNT on decorating with Au NPs can find practical application as conducting filler in polymer composites.

Abstract: Poly(vinyl alcohol) (PVA) was introduced during in situ synthesis of hydroxyapatite (HA) in neutral collagen (COL) solution and final PVA-COL-HA nanohybrids were achieved via sequential steps including gelation by fibrillogenesis, freezing-thawing physical crosslinking, removal of unreacted residues and dehydration. This method is expected to endow the pure PVA with good bioactivity and meanwhile the presence of elastic PVA would improve the properties of COL-HA composites. The phase, microstructure and possible molecular interactions of the achieved PVA-COL-HA nanohybrids were analyzed by using X-ray diffraction, Fourier transform infra-red spectroscopy and scanning electron microscopy. The results indicate that the inorganic phase is poorly crystallized apatite with a nanometer size due to the confinement of organic macromolecules which forms a network structure.

Abstract: We have synthesized for the first time efficient visible light active photocatalysts of porous MOx-Ti1.83O4 (M = Ni, Cr) heterostructure through an exfoliation-restacking route. XRD, SEM, TEM, and XAS results reveal that the titanate nanosheets and the nanosized metal oxide particles are well ordered in layer-by-layer way. N2 adsorption-desorption isotherm and diffuse UV-vis spectroscopic analyses demonstrate that the present nanohybrids have a large surface area (~190-240 m2/g) and a narrow bandgap (~1.6-2.4 eV), which are ascribable to the formation of porous structure and a coupling of the wide bandgap titanate and the narrow bandgap metal oxide species, respectively. These nanohybrids show an enhanced photocatalytic activity to effectively decompose organic compounds under the irradiation of visible light. The present results highlight that the exfoliation-restacking route can provide a very powerful way of developing novel heterostructured materials with efficient visible light driven photocatalytic activity.