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Synthesis and characterization of Zn/ZnO microspheres on indented sites of silicon substrate

Ahmed N., Majid A., Khan M. A., Rashid M., Umar Z. A., Baig M. A.

Materials Science Poland

2018

Vol. 36, No. 3

501--508

Self-assembled Zn/ZnO microspheres have been accomplished on selected sites of boron doped P-type silicon substrates using hydrothermal approach. The high density Zn/ZnO microspheres were grown on the Si substrates by chemical treatment in mixed solution of zinc sulfate ZnSO4·7H2O and ammonium hydroxide NH4 (OH) after uniform heating at 95 degrees C for 15 min. The Zn/ZnO microspheres had dimensions in the range of 1 pm to 20 pm and were created only on selected sites of silicon substrate. The crystal structure, chemical composition and morphology of as-prepared samples were studied by using scanning electron microscope SEM, X-ray diffraction XRD, energy dispersive X-ray spectroscopy EDS, Fourier transform infrared spectroscopy FT-IR and UV-Vis diffuse reflectance absorption spectra DRS. The energy band gap Eg of about 3.28 eV was obtained using Tauc plot. In summary, this study suggests that interfacial chemistry is responsible for the crystal growth on indented sites of silicon substrate and the hydrothermal based growth mechanism is proposed as a useful methodology for the formation of highly crystalline three dimensional (3-D) Zn/ZnO microspheres.

Nitrogen and phosphorous removal from leachate by duckweed (Lemna minor)

Iqbal J., Baig M. A.

Environment Protection Engineering

2017

Vol. 43, nr 4

123--134

Two separate experiments were conducted during the months of June and September, 2014 to investigate the nutrient (nitrogen and phosphorous) removal from leachate by growing duckweed, Lemna minor in various leachate dilutions under natural climatic conditions of Islamabad, Pakistan. The highest uptake of nitrogen and phosphorous by duckweed was 95% and 90%, respectively, whereas the highest growth rate of duckweed was 6.4 g·m–2·day–1 during both experiments. The highest rates of nitrogen and phosphorous removal from leachate media were 380 and 200 mg·m–2·day–1, respectively, during both experiments. Nutrient uptake by duckweed and its growth rate was rapid at more diluted leachate whereas the nutrient removal rates from leachate media were higher in more concentrated leachate. The duckweed growth and its nutrient uptake ability under natural climatic conditions were directly affected by seasonal climatic variations. Relatively higher temperature and more intense solar radiation were more favorable for the duckweed growth and its nutrient uptake ability. Both parameters can be improved by pre-acclimation of duckweed with leachate which prevents the lag phase of the duckweed growth.