Talal F. Qahtan

Synthesis of exfoliated polystyrene/anionic clay MgAl-layered double hydroxide: structural and thermal properties

Exfoliated polystyrene/layered double hydroxide (PS/LDH) nanocomposites were prepared by direct intercalation of PS into MgAl LDH at 60 °C. The MgAl LDH as the nanofiller was modified via the precipitation of the salt mixture of magnesium and aluminum metals by sodium dodecyl sulfate (SDS). Various techniques, Fourier Transformed Infrared Spectroscopy (FTIR), X-Ray-diffraction (XRD), Filed Emission Transmission Electron Microscopy (FETE) and thermo gravimetric analyses (TGA) were employed for structural properties and thermal stability of the nanocomposites. FTIR spectra indicated the presence of both functional groups of SDS–LDH and PS. XRD patterns and TEM images indicated the formation of amorphous dispersed and exfoliated nanocomposites. Increase in thermal stability with SDS–MgAl LDH content was observed by TGA and DTG through the T0.5 (T0.5 the degradation temperature at 50%) and Tmax (Tmax the maximum rate of change) with a maximum obtained for a loading of 2 and 4 wt%.

Detection of carcinogenic chromium in synthetic hair dyes using laser induced breakdown spectroscopy

A laser induced breakdown spectroscopic (LIBS) system, consisting of a pulsed 266 nm laser radiation, in conjunction with a high-resolution spectrograph, a gated intensified charge coupled device camera, and a built-in delay generator were used to develop a sensitive detector to quantify the concentration of toxic substances such as chromium in synthetic hair dyes available on the local market. The strong atomic transition line of chromium (Cr I) at 427.5 nm wavelength was used as a fingerprint wavelength to calibrate the detection system and also to quantify the levels of chromium in the hair dye samples. The limit of detection achieved by our LIBS detection system for chromium was 1.2 ppm, which enabled us to detect chromium concentration in the range of 5-11 ppm in the commercial hair dyes available on the local market. The concentrations of chromium in the hair dyes measured using our system were validated using a standard analytical technique such as inductively coupled plasma mass spectrometry (ICPMS), and acceptable agreement (nearly 8%) was found between the results obtained by the two methods (LIBS and ICPMS). This study is highly significant for human health, specifically for people using synthetic hair dyes for changing the color of their hair.

Fabrication of Water Jet Resistant and Thermally Stable Superhydrophobic Surfaces by Spray Coating of Candle Soot Dispersion

A facile synthesis method for highly stable carbon nanoparticle (CNP) dispersion in acetone by incomplete combustion of paraffin candle flame is presented. The synthesized CNP dispersion is the mixture of graphitic and amorphous carbon nanoparticles of the size range of 20–50 nm and manifested the mesoporosity with an average pore size of 7 nm and a BET surface area of 366 m2g−1. As an application of this material, the carbon nanoparticle dispersion was spray coated (spray-based coating) on a glass surface to fabricate superhydrophobic (water contact angle > 150° and sliding angle < 10 °) surfaces. The spray coated surfaces were found to exhibit much improved water jet resistance and thermal stability up to 400 °C compared to the surfaces fabricated from direct candle flame soot deposition (candle-based coating). This study proved that water jet resistant and thermally stable superhydrophobic surfaces can be easily fabricated by simple spray coating of CNP dispersion gathered from incomplete combustion of paraffin candle flame and this technique can be used for different applications with the potential for the large scale fabrication.

Fabrication and Wettability Study of WO 3 Coated Photocatalytic Membrane for Oil-Water Separation: A Comparative Study with ZnO Coated Membrane

Superhydrophilic and underwater superoleophobic surfaces were fabricated by facile spray coating of nanostructured WO3 on stainless steel meshes and compared its performance in oil–water separation with ZnO coated meshes. The gravity driven oil-water separation system was designed using these surfaces as the separation media and it was noticed that WO3 coated stainless steel mesh showed high separation efficiency (99%), with pore size as high as 150 µm, whereas ZnO coated surfaces failed in the process of oil-water separation when the pore exceeded 50 µm size. Since, nanostructured WO3 is a well known catalyst, the simultaneous photocatalytic degradation of organic pollutants present in the separated water from the oil water separation process were tested using WO3 coated surfaces under UV radiation and the efficiency of this degradation was found to be quite significant. These results assure that with little improvisation on the oil water separation system, these surfaces can be made multifunctional to work simultaneously for oil-water separation and demineralization of organic pollutants from the separated water. Fabrication of the separating surface, their morphological characteristics, wettability, oil water separation efficiency and photo-catalytic degradation efficiency are enunciated.

Photofabrication of Highly Transparent Platinum Counter Electrodes at Ambient Temperature for Bifacial Dye Sensitized Solar Cells

Platinum (Pt) counter electrodes (CEs) have consistently shown excellent electrocatalytic performance and holds the record of the highest power conversion efficiency (PCE) for dye-sensitized solar cells (DSSCs). However, its use for large-scale production is limited either by high temperature required for thermal decomposition of its precursor or by wastage of the material leading to high cost or sophisticated equipment. Here, we report a novel photofabrication technique to fabricate highly transparent platinum counter electrodes by ultraviolet (UV) irradiation of platinic acid (H2PtCl6.6H2O) on rigid fluorine-doped tin oxide (FTO) and flexible indium-doped tin oxide (ITO) on polyethylene terephthalate (PET) substrates. The photofabrication technique is a facile and versatile method for the fabrication of Pt CEs for dye sensitized solar cells (DSSCs). The photofabricated Pt CEs were used to fabricate bifacial DSSCs with power conversion efficiencies (PCEs) attaining 7.29% for front illumination and 5.85% for rear illumination. The highest percentage ratio of the rear illumination efficiency to the front illumination efficiency (ηR) of 85.92% was recorded while the least ηR is 77.91%.

Synthesis and characterization of copper oxides nanoparticles via pulsed laser ablation in liquid

Pulsed laser ablation in liquids is a simple synthesis process of nano-particles for the production of high purity material with no need for any expensive instrumentation except laser. The 532 nm wavelength laser beam with 5 ns pulse width and 10 Hz repetition rate was an ablating laser source. In order to control the size and stoichiometry of the nano particles, the laser ablation was done in the presence of 9% of H2O2. The optical properties and structure of the prepared samples were studied using different analytical techniques, such as energy dispersive X-ray spectroscope (EDS), X-ray Diffraction, UV-Visible absorption, Photoluminescence, FT-IR. In order to study the morphology of the prepared nano-sized powders, Field Emission Scanning Electron Microscope was used. From the above analytical studies it was found that the particle size was between 13 and 28 nanometer, while the band gap energy was estimated to be 2.46 eV.

Development of a laser induced breakdown sensor for detection of carcinogenic chemicals in cosmetic products

A highly sensitive Laser Induced Break down Sensor has been developed using a fourth harmonic Nd: YAG laser and a spectrograph with an ICCD camera to detect carcinogenic substances in cosmetic products especially hair dyes and Kohl available on the local market with in Saudi Arabia. For the hair dye, chromium (Cr) was detected using a spectral marker line of 427.5 nm and concentrations in the range of 5-11 ppm were detected by the LIBS sensor with a detection limit of 1.2 ppm. For Kohl eyeliners lead (Pb) and chromium (Cr) was detected using atomic transitions at wavelengths of 405.7 nm and 425.4 nm respectively as the spectral marker lines. Lead (Pb) and chromium (Cr) was detected in the concentration range of 5-14 ppm and 4-9 ppm with detection limits of lppm and 2 ppm respectively.