Shahidan Radiman

Synthesis and characterization of conducting polyaniline-coated cadmium sulphide nanocomposites in reverse microemulsion

Abstract II–VI group of semiconductor cadmium sulphide (CdS) nanocrystalline, which were coated with conducting polyaniline (PANI), have been prepared by microemulsion processing technique. The synthesized polyaniline-coated CdS nanocomposites were characterized by UV–Vis absorption spectroscopy, energy filter transmission electron microscopy (EFTEM), FTIR spectroscopy and TGA analysis. The UV–Vis spectrums revealed the enhancement of doping level for the nanocomposites, which is assigned to the existence of greater number of charges on the polymer backbone. The FTIR spectra indicated that the polymers were highly doped and existed in conducting emeraldine salt form. The as-prepared PANI/CdS nanocomposites were polydispersed and have an average size of ca. 17.8 nm. The obtained CdS/PANI nanocomposites showed significant improvement in the thermal behavior as indicated in the TGA thermograph.

Mild hydrothermal synthesis of Ni-Cu nanoparticles

Magnetic Ni-rich Ni-Cu nanoparticles with Ni : Cu mass ratio (S) of 2.0 and 2.6 were prepared using a mixture of polyoxyethylene (10) isooctylphenyl ether (Triton X-100) and sodium dodecyl sulfate (SDS) in a mild hydrothermal condition at 95°C. X-ray diffractometry (XRD) showed that the nanoparticles prepared at S = 2.0 possessed Ni-Cu alloy characteristic whereas the characteristic was absent at S = 2.6. The XRD data was enhanced by Fourier transform infrared spectroscopy (FTIR) which exhibited metal-metal (Ni-Cu) band at 455 cm-1. Based on transmission electron microscopy (TEM), the average particle sizes for the nanoparticles prepared at S = 2.0 and 2.6 were in the range of 19-23 nm. The as-prepared nanoparticles exhibited paramagnetic behaviour measured using a vibrating sample magnetometer (VSM) and the specific saturation magnetization decreased at the higher concentration of Ni.

Studies on the growth and characterization of CdS and PbS nanoparticles using sugar-ester nonionic water-in-oil microemulsion

The nanometer-sized semiconductors of CdS and PbS were prepared in the nonionic water-in-oil microemulsion system formed by sucrose monoester, 1-butanol, cyclohexane and water. The surfactant that has been employed in the present study is commercial food grade additive, in which is biodegradable and nonhazardous to the environment. The resultant nanoparticles were characterized by X-ray diffraction measurements in order to determine the crystalline phase of the products. The structural and morphological features of the nanoparticles have been investigated by energy filter transmission electron microscopy, X-ray photoelectron spectroscopy and UV-Vis absorption spectroscopy. The experimental results showed that the synthesized nanoparticles exhibited strong quantum confinement effect as the optical band gap increased significantly as compared to the bulk molecules. In addition, the as-prepared nanoparticles were found in spherical shape with a reasonably narrow size distribution.

Single w/o microemulsion templating of CdS nanoparticles

We report the synthesis of monodispersed CdS nanoparticle with tunable size by controlling the reaction aging time in a single water in oil (w/o) microemulsion system. The w/o microemulsion system consists of nonionic surfactant poly (oxyethylene)5 nonyl phenol ether (NP5), poly (oxyethylene)10 nonyl phenol ether (NP10), cyclohexane and aqueous solution (cadmium salt and thioacetamide). Thioacetamide (TAA) has been utilized as a source for slow release of sulfur ions in the in situ synthesis of CdS. UV-Visible spectra shows obvious blue shift for the CdS nanoparticles as compared to the bulk material due to quantum size effect. CdS nanoparticle size depends on the reaction aging time where longer reaction aging time yields bigger particles. CdS nanoparticles growth behaviour as a function of reaction aging time in the microemulsion system was characterized by UV-Visible spectroscopy. The particle growth follows a power law with an exponential in the order of 0.17. Energy Filter Transmissions Electron Microscopy (EFTEM) reveals monodispersed CdS nanoparticles with standard deviation, σ less than 8%.

The design of new magnetic-photocatalyst nanocomposites (CoFe2O4–TiO2) as smart nanomaterials for recyclable-photocatalysis applications

The current study reports the synthesis and characterisation of a new magnetic-photocatalyst (CoFe2O4–TiO2) and tests its feasibility to be used as smart magnetically-recoverable nanomaterial in the photodegradation of methylene blue (MB). 3D urchin-like TiO2 microparticles are hydrothermally prepared and decorated with CoFe2O4 magnetic nanoparticles (NPs) through a co-precipitation method. The as-prepared CoFe2O4–3D TiO2 nanocomposites show an enhancement in the photodegradation of MB as compared to the commercial rutile-phase TiO2 and the pure urchin-like TiO2 (3D TiO2) microparticles. Such an enhancement could be accredited to the lower recombination rate of the photoexcited charge carriers of the CoFe2O4–3D TiO2 nanocomposites. Furthermore, the CoFe2O4–3D TiO2 nanocomposite is magnetically-retrievable for sequential recycling, and the results indicate that the nanocomposite shows a relatively consistent photocatalytic performance with negligible degradation. Thus, the current study would offer a potential route for the design and processing of a value-added photocatalyst nanocomposite that will contribute to the advancement of photocatalysis studies.

Modified microwave method for the synthesis of visible light-responsive TiO2/MWCNTs nanocatalysts

Recently, TiO2/multi-walled carbon nanotube (MWCNT) hybrid nanocatalysts have been a subject of high interest due to their excellent structures, large surface areas and peculiar optical properties, which enhance their photocatalytic performance. In this work, a modified microwave technique was used to rapidly synthesise a TiO2/MWCNT nanocatalyst with a large surface area. X-ray powder diffraction, field-emission scanning electron microscopy, transmission electron microscopy and Brunauer-Emmett-Teller measurements were used to characterise the structure, morphology and the surface area of the sample. The photocatalytic activity of the hybrid nanocatalysts was evaluated through a comparison of the degradation of methylene blue dye under irradiation with ultraviolet and visible light. The results showed that the TiO2/MWCNT hybrid nanocatalysts degraded 34.9% of the methylene blue (MB) under irradiation with ultraviolet light, whereas 96.3% of the MB was degraded under irradiation with visible light.

Environmental Synthesis of Few Layers Graphene Sheets Using Ultrasonic Exfoliation with Enhanced Electrical and Thermal Properties

In this paper, we report how few layers graphene that can be produced in large quantity with low defect ratio from exfoliation of graphite by using a high intensity probe sonication in water containing liquid hand soap and PVP. It was founded that the graphene powder obtained by this simple exfoliation method after the heat treatment had an excellent exfoliation into a single or layered graphene sheets. The UV-visible spectroscopy, FESEM, TEM, X-ray powder diffraction and Raman spectroscopy was used to analyse the graphene product. The thermal diffusivity of the samples was analysed using a highly accurate thermal-wave cavity photothermal technique. The data obtained showed excellent enhancement in the thermal diffusivity of the graphene dispersion. This well-dispersed graphene was then used to fabricate an electrically conductive polymer-graphene film composite. The results demonstrated that this low cost and environmental friendly technique allowed to the production of high quality layered graphene sheets, improved the thermal and electrical properties. This may find use in the wide range of applications based on graphene.

Enhanced Photocatalytic Performance of NiO-Decorated ZnO Nanowhiskers for Methylene Blue Degradation

ZnO nanowhiskers were used for photodecomposition of methylene blue in aqueous solution under UV irradiation. The rate of methylene blue degradation increased linearly with time of UV irradiation. 54% of degradation rate was observed when the ZnO nanowhiskers were used as photocatalysts for methylene blue degradation for 80 min under UV irradiation. The decoration of p-type NiO nanoparticles on n-type ZnO nanowhiskers significantly enhanced photocatalytic activity and reached 72% degradation rate of methylene blue by using the same method. NiO-decorated ZnO was recycled for second test and shows 66% degradation from maximal peak of methylene blue within the same period. The increment of photocatalytic activity of NiO-decorated ZnO nanowhiskers was explained by the extension of the electron depletion layer due to the formation of nanoscale p-n junctions between p-type NiO and n-type ZnO. Hence, these products provide new alternative proficient photocatalysts for wastewater treatment.

Ternary phase behaviour and vesicle formation of a sodium N-lauroylsarcosinate hydrate/1-decanol/water system

The phase behaviour of a system composed of amino acid-based surfactant (sodium N-lauroylsarcosinate hydrate), 1-decanol and deionised water was investigated for vesicle formation. Changing the molar ratio of the amphiphiles, two important aggregate structures were observed in the aqueous corner of the phase diagram. Two different sizes of microemulsions were found at two amphiphile-water boundaries. A stable single vesicle lobe was found for 1∶2 molar ratios in 92 wt% water with vesicles approximately 100 nm in size and with high zeta potential value. Structural variation arises due to the reduction of electrostatic repulsions among the ionic headgroups of the surfactants and the hydration forces due to adsorbed water onto monolayers. The balance of these two forces determines the aggregate structures. Analysis was followed by the molecular geometrical structure. These findings may have implications for the development of drug delivery systems for cancer treatments, as well as cosmetic and food formulations.

Self-Assembled Potential Bio Nanocarriers for Drug Delivery

Self-assembled nanocarriers attract increasing attention due to their wide application in various practical fields; among them, one of the most focused fields is drug delivery. Appropriate selection of surfactant is the basis for preparing a successful nanocarrier. Until now, from phospholipid to synthetic surfactants, many surfactants have been used to explore a suitable drug delivery vehicle for the complex in-vivo environment. Among all, bio surfactants are found to be more suitable due to their bio-origin, less-toxicity, biodegradability, cheaper rate and above all, their versatile molecular structures. This molecular property enables them to self assemble into fascinating structures. Moreover, binding DNA, enhancing pH sensitivity and stability allows novelty over their synthetic counterparts and phospholipid. This review paper focuses on the properties and applications of bio-nano-carriers for drug delivery. Micelle, microemulsion, and vesicle are the three nanocarriers which are discussed herein.