Optical limiting applications of resonating plasmonic Au nanoparticles in a dielectric glass medium.

Plasmonic nanostructures exhibiting high optical nonlinearities are widely used in the rapidly growing modern nanotechnology of nonlinear optics including biomedical applications due to their tunable plasmonic behavior. In this work, we investigate the nonlinear optical properties of uniformly distributed Au nanoparticles (NPs) embedded in pre-synthesized sodium-zinc borate glass by the well-known ion-exchange technique for optical limiting (OL) applications. Various techniques such as optical absorption spectroscopy, x-ray photoelectron spectroscopy, Transmission Electron Microscope (TEM), Photoluminescence, Time of Flight secondary mass spectroscopy and the Z scan technique were used for the characterization of these NPs. TEM confirmed spherically shaped Au NPs with varying sizes of up to 16 nm, in agreement with optical absorption spectroscopy. Nonlinear optical (NLO) properties of these Au NPs were investigated by using an open as well as close aperture Z scan technique which exhibited enhanced optical nonlinearities. The two-photon absorption (2PA) coefficients demonstrated an increasing trend while the OL threshold values demonstrated a decreasing trend as a function of heat treatment. The improved 2PA coefficients and decreased OL threshold values endorsed the Au NPs containing glasses as contending materials for the fabrication of promising optical limiters for the protection of eyes and other sensitive instruments from laser induced damages.

Enhanced adsorption of As(V) and Mn(VII) from industrial wastewater using multi-walled carbon nanotubes and carboxylated multi-walled carbon nanotubes.

The presence of As(V) and Mn(VII) in water beyond the permissible concentration allowed by World Health Organization (WHO) standard affects human beings, animals and the environment adversely. Hence, there is need for an efficient material to remove these potentially toxic elements from wastewater prior to discharge into water bodies. This research focused on the application of response surface method (RSM) assisted optimization of Fe-Ni/Activated carbon (AC) catalyst for the synthesis of MWCNTs. Also, the MWCNTs was carboxylated and the adsorption behaviors of both nano-adsorbents in the removal of As(V) and Mn(VII) from industrial wastewater was investigated through experimental and computational techniques. The prepared Fe-Ni/AC, MWCNTs and MWCNTs-OCH2CO2H were characterized using BET, TGA, FTIR, HRSEM, HRTEM, XRD and XPS. The result showed the BET surface area of Fe-Ni/AC, MWCNTs and MWCNTs-OCH2CO2H were obtained as 1100, 1250 and 1172 m2/g, respectively. Due to the enhanced impact of carboxylation, the adsorption capacity of As(V) and Mn(VII) removal increased from 200 to 192 mg/g for MWCNTs to 250 and 298 mg/g for MWCNTs-OCH2CO2H. The isotherm and kinetic models were best fitted by Langmuir and pseudo-second order kinetics, while the thermodynamic investigation found that the adsorption process was endothermic, spontaneous and chemisorptions controlled. The regeneration potential of MWCNTs and MWCNTs-OCH2CO2H after six repeated applications revealed good stability of adsorption efficiency. The study demonstrated optimization importance of Fe-Ni/AC catalyst design for MWCNTs adsorbents and the potentials of utilizing both MWCNTs and MWCNTs-OCH2CO2H in the removal of selected heavy metals from water and soil.

Thermally induced structural metamorphosis of ZnO:Rb nanostructures for antibacterial impacts.

In this work, we report on the synthesis of pure and Rb doped ZnO (ZnO:Rb) nanoparticles by a simple combustion technique followed by thermal treatment in an open-air atmosphere. The prepared samples were characterized using UV-vis spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), photoluminescence, Raman spectroscopy and scanning electron microscopy. The wurtzite hexagonal phase structure of ZnO and a secondary phase of Rb2ZnO2 was observed after doping ZnO with Rb. FTIR and DSC confirmed the functional groups and the thermal stability of the ZnO samples. Field emission scanning electron microscope showed an irregular shaped agglomerated morphology for the ZnO:Rb samples. The chemical states of the undoped and Rb doped samples were identified using X-ray photoelectron spectroscopy for both pure and ZnO:Rb samples. In addition, ZnO:Rb samples exhibit good antimicrobial activities against Bacillus subtilis with a change in antibacterial behaviour as compared to pure ZnO structures indicating their multifunctional applications.

Photocatalytic degradation of local dyeing wastewater by iodine-phosphorus co-doped tungsten trioxide nanocomposites under natural sunlight irradiation.

In the present work, one-step green synthesis of WO3 based on the interaction of ammonium paratungstate and Spondias mombin leaves extract is reported. Different concentrations of iodine and phosphorus in the range of (2%, 5% and 10%) were firstly incorporated into the prepared WO3 nanoparticles to obtain Iodine doped and Phosphorus doped WO3 nanoparticles respectively. Subsequently, iodine and phosphorus co-doped WO3 nanocomposites was prepared using a wet impregnation method followed by calcination at high temperature. The nanomaterials were characterized by HRSEM, HRTEM, BET, UV-Visible, EDS, XRD and XPS. The photo-oxidation of dyeing wastewater by the synthesized WO3 nanomaterials were tested and assessed using Total organic carbon (TOC) and Chemical oxygen demand (COD) as indicator parameters. XRD and HRSEM analysis demonstrated the formation of only monoclinic phase of WO3 irrespective of the dopants. The UV-Visible diffuse reflectance spectroscopy showed the band gap energy of 2.61 eV for undoped WO3 and 2.02 eV for I-P co-doped WO3 nanocomposites. The surface area of I-P co-doped WO3 (416.18 m2/g) was higher than the undoped WO3 (352.49 m2/g). The XPS demonstrated interstitial and substitution of oxygen (O2-) vacancies in WO3 by I- and P3+ and formed I-P-WO(3-x). The I-P co-doped WO3 exhibited higher catalytic activities (93.4% TOC, 95.1% COD) than the undoped (54.9% TOC, 79.2% COD) due to the synergistic effects between the two dopants. The experimental data better fitted to pseudo-second order than first order and pseudo-first order model. This study demonstrated the enhanced photocatalytic performance of I-P co-doped WO3 nanocomposites under sunlight.