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Sidra Khalid,Saira Riaz,Samia Naeem,Aseya Akbar,S. Sajjad Hussain,YB Xu,Shahzad Naseem 한국공업화학회 2021 Journal of Industrial and Engineering Chemistry Vol.103 No.-
Production of single-phase materials with multifunctional properties is still a challenge faced by materialscientists. In addition, obtaining high spin polarization efficiency in the materials that exhibit multifunctionalproperties is a big issue. A novel approach is suggested in this work for obtaining multifunctionalityand spin polarization in the same material. This approach has combined the effect of microwave radiationsand aluminum (Al) doping in iron oxide thin films during synthesis. Combined effect of microwaveradiations and Al doping results in controlling / tuning the structural transitions in iron oxide thin films. Pristine and 2–10 wt% Al doped iron oxide thin films are prepared and studied in detail. Raman analysisshows that 2 and 4 wt% Al concentration results in c-Fe2O3 + Fe3O4 phase with 71.3% and 64.5% of c-Fe2O3content, respectively. XRD and Raman analyses confirm the transition from c-Fe2O3 to Fe3O4 thin films atAl concentrations of 6–10 wt%. Structural transformation shows that microwave radiations catalyzes thatAl3+ions to occupy the vacancies on B sites of iron oxide thus, lead to the formation of Fe3O4. Observationof Verwey transition ~ 126 K also supports the transition in phases of iron oxide with increase in saturationmagnetization from 251.3emu/cm3 (pristine films) to 405.6emu/cm3 (8 wt% Al concentration). Highdielectric constant of ~ 135.5 (log f = 5.0) is observed for 8 wt% Al concentration. Conductivity anddetailed impedance & modulus analyses depict Mott’s hopping phenomenon along with presence of differentrelaxation times. Coupling between magnetic and dielectric properties is observed at room temperature. Magnetoresistance curves indicate spin polarization efficiency of ~24%.
Sol–gel based phenolphthalein encapsulated heterogeneous silica–titania optochemical pH nanosensor
Shumaila Islam,Noriah Bidin,Saira Riaz,Shahzad Naseem 한국공업화학회 2016 Journal of Industrial and Engineering Chemistry Vol.34 No.-
Thermally stable phenolphthalein encapsulated silica–titania nanomatrix is fabricated by sol–gelmethod for optochemical pH sensing. The particle size 56–121 nm is obtained with average surfaceroughness of 3.95 nm after the encapsulation of dye which is highly appropriate for optical and sensingapplications. High surface area value 218 m2/g, pore volume of 0.16 cm3/g and pore diameter of31.49 A˚ is obtained after encapsulation. Furthermore, the sensor response is optimized at pH 10. Fastresponse time 1–2 s, sensitivity with good reproducibility identify that the fabricated optochemicalnanosensor is challenging for the detection of pH at room temperature.
Shumaila Islam,Rosly Rahman,ZULKAFLI OTHAMAN,Saira Riaz,Shahzad Naseem 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.6
Films of multi-organic indicators, encapsulated in silica–titania hybrid matrix with CTAB, have beensynthesized using sol–gel dip coating method. Two types of stable,dense and uniform matrices wereannealed at a 150 ℃ within two time intervals 1 h and 2 h by using 0.1 M and 0.5 M indicatorconcentrations. Nanoparticles are uniformly distributed with size in the range from 15–28 nm. Matriceshave high surface area (418.18–441.30 m2/g), which has more capability to sense the broader pH range. Spectroscopic studies showed the establishment of heterogeneous chemical bonding which indicative ofstability of matrices with 69% porosity. The response of the sensor is optimum at pH 9.
Synthesis and characterization of multilayered sol–gel based plastic-clad fiber optic pH sensor
Shumaila Islam,Rosly Abdul Rahman,Zulkafli Bin Othaman,Saira Riaz,Shahzad Naseem 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.23 No.-
The fabrication and characterization of an optical fiber pH sensor for the detection range 3–11 are described. The sensing element consists of a combination of indicators encapsulated in mesoporous surfactant based hybrid matrix, which are deposited onto an uncladed plastic optical fiber. Stable, dense and uniform sol–gel cladding with more than 90% transparency in the visible range are observed. Roughness value 9.7–6.57 nm is obtained by AFM. Film thickness, refractive index, and porosity are found to vary with number of coatings, 70% porosity is determined with 116 nm thickness. The response of the sensor with third layer is observed in acid and basic medium.