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This work reports the influence of precursor concentration on the thermal and optical properties of magnetic iron oxide nanoparticles (MIONPs) synthesized via the green synthesis route. A brown seaweed (Sargassum crassifolium) extract was used to mediate the reduction of iron precursors. Ultraviolet–visible spectra showed a sharp peak between 315 and 375 nm, which corresponds to the absorbance of MIONPs. This peak intensified with an increasing concentration of iron precursors. The Fourier transform infrared spectra revealed the presence of the transmittance bands around 557 cm−1 and 565 cm−1, which corresponds to Fe-O-Fe vibrational modes suggesting the successful formation of iron oxide nanoparticles. The dynamic light scattering technique revealed that the average hydrodynamic size of the MIONPs was 31.96 ± 15.61 nm and 147.40 ± 28.48 nm. Atomic force micrograph and scanning electron micrograph both showed quasi-spherical nanostructures with sizes ranging from 40 to 215 nm. Furthermore, X-ray diffraction and thermogravimetric analyses revealed the crystallinity and thermal stability of the synthesized MIONPs, respectively. This investigation on the effect of precursor concentration provides a valuable insight for the green- mediated synthesis of MIONPs that is vital for various environmental, biomedical, and industrial application.

The influence of cellulose fibers extracted from pineapple (Ananas comosus) leaf fibers on polyurethane foam’s mechanical properties (PUF) is reported. The PUFs were reinforced with different weight ratios (1, 3, and 5 wt%) of cellulose fibers. The surface morphology of the extracted cellulose fibers was determined using a scanning electron microscope (SEM). The functional groups and vibrational modes of the reinforced PUFs were measured using Fourier transform infrared spectroscopy (FTIR). The influence of cellulose fibers to the density and mechanical property of the PUFs were also investigated using universal testing Machine (UTM). Experimental results showed the absence of hemicellulose, lignin, and other soluble materials present in the pineapple leaves after alkaline treatment, suggesting high-quality cellulose fibers. Likewise, FTIR spectra revealed the presence of typical urethane linkages of PUFs suggesting the successful formation of PUFs with a varied amount of cellulose fibers. The mechanical properties of the PUFs with an increasing amount of cellulose fibers exhibit a decrease of the compressive strength of the fabricated PUFs may be due to the lack of cross-linking between the cellulose fibers and PUFs that will influence the reactivity in the system that eventually affects the polyurethane foam density expansion.

Cyanide ( CN - ) is a deleterious chemical and can cause serious health effects upon exposure even at low concentrations. Different sensors have been developed to monitor cyanide in water, which, however, suffers from complex mechanisms and high-cost. Curcuma longa or turmeric is a commercially available natural dye (usually in powder form) used as medicine. The phenolic substance curcumin is responsible for its yellow color and is capable of sensing environmentally significant analytes such as CN - . In this study, a colorimetric sensor for cyanide in aqueous solution was fabricated by the immobilization of crude curcumin on ordinary filter paper. The curcumin was extracted from locally available turmeric powder using a simple extraction method. Its successful integration in the filter paper was validated by FT-IR spectroscopy. UV–Vis analysis showed that the curcumin-based paper sensor was sensitive to CN - (down to 5.0 ppm), producing a visual change from yellow to dark red. The fabricated sensor also demonstrated high selectivity towards CN - in the presence of N a + , K + , and F - . Its response time was found to be inversely proportional to the concentration of the CN - in the solution. Assessment of reusability revealed that the sensor was reusable for up 8 cycles before significant changes in colorimetric response were observed. Importantly, the fabricated sensor exhibited applicability for actual cyanide monitoring in real water samples.

Increasing anthropogenic and industrial activities lead to the contamination of aquatic resources with organic pollutants such as dyes. In this work, a magnetic composite photocatalyst composed of Fe3O4, BiOCl, and Cu2O was fabricated for the degradation of organic dye pollutants. The composite was synthesized via a simple co-precipitation method. FT-IR and SEM-EDX analyses confirmed the formation of Fe3O4/BiOCI/Cu2O (FBC) composite. Photocatalytic degradation was tested under UV, and visible light using model organic dyes, methyl orange (MO), and methylene blue (MB), and was monitored using UV–Vis spectroscopy. The absorbance was found to decrease corresponding to the reduction of dye concentration during photocatalytic degradation. A plot of absorbance versus irradiation time for both model dyes exhibited exponential decay; faster degradation was observed with MO than with MB. Furthermore, the degradation of both dyes using the FBC photocatalyst was more efficient under UV light.

Kinetics of the step flow growth on the (16 × 2) reconstructed Si(110) surface has been studied experimentally and with computer simulations. It is shown that during Si growth under DC heating vicinal steps on the (16 × 2) reconstructed Si(110) surfaces undergo a kinetic step bunching and develop extended segments preferentially oriented along the (16 × 2) reconstruction domains. The final step configuration depends crucially on the direction of the applied electric field. In particular, when DC is applied in the [ 1 1 ¯ 2 ] direction, an array of straight multisteps parallel to the current direction and rotated in respect to the original orientation of the vicinal steps can be fabricated. Surprisingly, the observed step transformations are not affected by the polarity of the applied electrical field. Using a simple model of the Si/Si(110)-(16 × 2) growth and kinetic Monte Carlo simulations we show that the step bunching and step rotation on Si(110)-(16 × 2) might be induced by an incoherent matching of the (16 × 2) reconstruction domains across the vicinal steps on the surface.

The dark current–voltage ( J – V ) characteristics and the conversion efficiency of the solar cells with embedded stacked Ge islands in the intrinsic layer were investigated. These islands were grown by molecular beam epitaxy on Si substrates. We used a two-diode model to analyze the dark J – V characteristics of Ge island solar cells. Results showed that the minority carrier diffusion and the recombination current components increase as a function of the stacked Ge island layers. This increase of the minority carrier diffusion current was due to an increase of the intrinsic carrier density as a function of the number of stacked layers. Similarly, the increase in the recombination current components was due to the enormous recombination of carriers in the intrinsic region as the number of stacked layer increases. This phenomenon could lead to a decrease of the open circuit voltage, V oc . The decrease of V oc should be overcompensated by the increase of photocurrent, due to the presence of stacked Ge islands with higher absorption coefficient, in order to attain an optimum value of the conversion efficiency.

We investigated the effects of growth temperature on the surface morphology of silicon layers grown by liquid phase epitaxy method on a (1 1 1) oriented silicon substrate in a relatively low-temperature range from 600°C to 900°C using Au–Bi alloy solvent. Layers are formed in the following growth sequence: (1) commencing in the form of initial nuclei as starting points of growth, (2) these structures grow along lateral and vertical directions as island structures, and (3) coalesce each other. Moreover, it was made clear that flat layers tend to cover the substrate completely at high growth temperature, in order to clarify the main factor that influences the surface morphology, an empirical model of the growth process was constructed. As a result, the temperature dependence of the surface morphology mainly depends on the temperature dependence of the preferential growth direction of Si on Si (1 1 1).

We fabricated Si-based solar cell with stacked Ge islands grown via the Stranski-Krastanov growth mode in the intrinsic layer of pin diodes. The onset of the external quantum efficiency in the near infrared regime was extended up to approximately 1.4 μm for the solar cells with stacked Ge islands. The quantum efficiency was found to increase with increasing number of stacking, showing that a part of electron-hole pairs generated within Ge islands was separated by the internal electric field and contributed to the photocurrent. Increase of the processing temperature for the impurity diffusion was found to bring blue-shift of the band gap through the intermixing of Si and Ge as well as the deformation of Ge islands. Therefore, low-temperature process was suggested to be necessary for further enhancement of quantum efficiency in the near infrared regime.