Silica-modified polyaniline (SM-PANI) thin films were prepared on glass substrates by oxidative polymerization.Zinc oxide (ZnO) nanostructures were grown on top of SM-PANI thin films by chemical bath deposition using zinc sulphate and varying concentrations of ammonium hydroxide.SM-PANI and ZnO nanostructures were characterized by scanning electron microscopy (SEM).SEM images revealed surface morphology of the nanostructures: SM-PANI forming rod-like nanostructures, and ZnO forming sea-urchin-like nanostructures grown on top of SM-PANI.Characterization results also revealed that ammonium hydroxide concentration can modify ZnO nanostructures grown on top of SM-PANI.For 1M concentration, hexagonal rod-like SM-PANI and sea-urchin-like ZnO nanostructures were present; for 3M concentration, flake-like ZnO nanostructures were grown with deformed rod-like SM-PANI.This mechanism can be explained via competition between growth of SM-PANI and ZnO nanostructures, and etching process during the chemical bath deposition of ZnO at different concentrations of ammonium hydroxide.
ZnO nanostructures grown on glass (SiO2) substrates have been successfully fabricated for ethanol gas sensor. These ZnOnanostructures were prepared by chemical bath deposition with various ammonium hydroxide concentrations. The response of ZnO- based ethanol gas sensor exhibited higher response at lower NH4OH concentration; this might be attributed to the uniform morphology of the ZnOnanostructures which facilitates easier interaction with the ethanol gas. On the other hand, at higher NH4OH concentration showed drastic decrease in sensor response. This might be due to the growth of broken nanorods. Scanning electron microscope (SEM) images confirmed the formation of uniform and vertically grown nanostructures with lower concentration of NH4OH. On the other hand, at higher NH4OH concentration, broken nanorodsand agglomerations were present as revealed in the SEM micrographs. Energy dispersive x-ray spectroscopy (EDS) measurements suggested that the grown nanostructures were most likely composed of ZnO. The calculated energy band gap from the UV-Vis spectra confirmed that the grown Zn Onanostructures.
Biological hydroxyapatite (BHAp) derived from thermally-treated fish bones was successfully produced. However, the obtained biological HAp was amorphous and thus making it unfavorable for medical application. Consequently, this research exploits and engineers the crystallinity of BHAp powders by addition of CaCO3 and investigates its degree of crystallinity using XRD and IR spectroscopy. On XRD, the HAp powders with [Ca]/[P] ratios 1.42, 1.46, 1.61 and 1.93 have degree of crystallinity equal to 58.08, 72.13, 85.79, 75.85% and crystal size equal to 0.67, 0.74, 0.75, 0.72 nm, respectively. The degree of crystallinity and crystal size of the obtained calcium deficient biological HAp powders increase as their [Ca]/[P] ratio approaches the stoichiometric ratio by addition of CaCO3 as source of Ca2+ ions. These results show the possibility of engineering the crystallinity and crystal size of biological HAp by addition of CaCO3. Moreover, the splitting factor of PO4 vibration matches the result with % crystallinity on XRD. Also, the area of phosphate-substitution site of PO4 vibration shows linear relationship (R2 = 0.994) with crystal size calculated from XRD. It is worth noting that the crystallinity of the biological HAp with [Ca]/[P] ratios 1.42 and 1.48 fall near the range 60-70% for highly resorbable HAp used in the medical application.
Polyanilinefilms doped with varying HClconcentrations (0.2 M, 0.6 M and 1.0 M) were synthesized on glass substrates via oxidative polymerization of aniline. The films were treated with supercritical carbon dioxide (SC-CO2) at 30 MPa and 40°C for 30 minutes. Their structural, optical and morphological properties were studied and compared to conventionally prepared polyanilinefilms using FTIR analysis, UVVisspectroscopy and scanning electron microscopy. It was observed that supercritical carbon dioxide (SC-CO2) could interact with PANI films that consequently altered the bandgapsand changed the film thickness. SC-CO2 treatment also increased the oxidation level of polyanilinefilms and modified the morphology of polyanilinefilm doped with 1M HCl.
Ce travail traite de la synthese et de la caracterisation structurale de nanoparticules d'oxyde de zirconium (ZrO2) ainsi que de leurs relations taille/structure. Nous avons elabore des nanoparticules de taille inferieure a 5 nm avec une distribution de taille etroite en utilisant une voie sol-gel non hydrolytique solvothermale. La diffraction des rayons X classique a ete utilisee pour evaluer la taille des cristallites via des affinements de Rietveld et la diffusion totale des rayons X pour extraire les fonctions de distribution des paires (PDF) des echantillons et effectuer leur analyse structurale.Nous avons reussi a synthetiser des nanoparticules cristallines de ZrO2 d'une taille d'environ 3 nm et quasi mono-disperses. Nous avons montre qu'une addition d'hydroxyde de sodium dans le melange reactionnel etait pertinente pour obtenir des nanoparticules bien cristallisees et monophasees presentant une structure moyenne soit monoclinique soit tetragonale en fonction du solvant utilise, respectivement dans le benzaldehyde ou dans l'alcool benzylique. Enfin, la dilution de l'alcool benzylique par l'anisole, un solvant inerte, conduit au controle fin de la taille moyenne des nanoparticules de 3,2 nm a 2 nm selon l'etude MET.Ces trois echantillons principaux prepares dans le benzaldehyde alcalinise, l'alcool benzylique ou l'anisole ont ete soumis a une analyse structurale complete. Selon leur analyse PDF, ces trois echantillons offrent un apercu de la comprehension des proprietes structurales de ces petites particules.La PDF experimental de l'echantillon prepare avec du benzaldehyde coincide avec la PDF affinee d'un modele structural monoclinique. Cependant, la PDF experimentale de l'echantillon prepare avec de l'alcool benzylique n'est conforme a aucun des polymorphes connus de ZrO2 ayant une structure derivee de la fluorine, mais presente plutot une structure tetragonale moyenne avec des distorsions monocliniques a l'ordre local. Enfin, la PDF experimentale de l'echantillon prepare avec de l'anisole presente de fortes distorsions structurales dans le domaine de l'ordre a moyenne distance, mais aussi une structure de type monoclinique a l'ordre local.Ensuite, l'echantillon prepare avec l'anisole a ete soumis a un vieillissement assiste thermiquement (3 a 24 jours) et on a ajoute des quantites variables d'eau ex-situ (teneur en volume de 0,3 a 5%). Nous avons observe que les nanoparticules evoluaient d'une phase contenant un desordre eleve (3 jours) a une structure mieux cristallisee (24 jours) correspondant a une structure tetragonale moyenne tout en maintenant une distorsion monoclinique a l'ordre local. De maniere similaire, l'addition d'eau ex-situ sur le melange reactionnel favorise une cristallisation plus rapide et favorise l'apparition de pics typiques de la structure monoclinique. Cependant, la formation de phase monoclinique a ete inhibee par la presence d'hydroxyde de sodium, mais limitee a environ 2% en volume d'eau, et une valeur plus elevee que cette quantite conduit a la formation de grandes particules de structure monoclinique.
In this work, the phase purity and size of zirconia nanocrystals samples were studied in terms of zirconium concentration, added water content, and subsequent use of a post solvothermal treatment. The progressive tetragonal-to-monoclinic transformation of zirconia sample was observed to be strongly related to the water content of the alcoholic medium. But more surprisingly, it has been shown that even under initially anhydrous conditions and for particle size below 5 nm, the phase purity of the samples was deteriorated by a side-reaction of alcohol dehydration catalyzed by the surface of the nanoparticles (NPs). Since the phase transformation is essentially driven by the water content of the reaction mixture, we have shown that it was possible to recover an excellent phase purity without the help of any usual dopants by adding a strong alkaline desiccating agent. Provided that a sufficient sodium to zirconium ratio was ensured, the formation of the monoclinic phase was not observed whatever the zirconium precursor concentration. The effectiveness of this cure was related to the ability of sodium metal to generate reactive alkoxide able to neutralize water and to catalyze an alternative sol-gel mechanism leading to the formation of the t-ZrO2 NPs.
Zinc oxide (ZnO) on silica modified polyaniline (SM-PANI) was prepared via chemical bath deposition and in situ polymerization. The optical characteristics of the nanocomposites were investigated using ultraviolet-visible (UV-Vis) spectroscopy. The bands showed higher absorbance in the visible region. Fourier transform infrared (FTIR) spectroscopy revealed that there is an interaction between SM-PANI and ZnO.
ZnO-SiO 2 nanostructures were grown on both bare Si and Pt-coated Si substrates via chemical bath deposition (CBD). The grown nanostructures were characterized using Scanning Electron Microscope with Energy Dispersive X-ray Spectroscopy (SEM-EDS), Fourier Transform Infrared (FTIR) measurement and Ultraviolet-Visible (UV-Vis) absorption spectroscopy. Surface morphology results revealed that Pt-coated Si substrate have promoted the growth of ZnO-SiO 2 nanostructures by providing more active sites for nucleation thus formation ZnO-SiO 2 nanostructures were observed. It is believed that SiO 2 will adhere to the non-polar sides of the grown ZnO nanostructures. This result is manifested in the FTIR spectra which showed a pronounced peak corresponding to ZnO-SiO 2 grown on bare Si suggesting that more Si-O bonds are present. However, Pt-coating did not significantly affect the band gap of the grown ZnO-SiO 2 nanostructures.
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