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We employed a microwave-assisted two-pot in-situ deposition technique to incorporate zinc oxide particulates in the structure of filter paper to produce antimicrobial paper. The process involved successive immersion of filter paper samples in ZnSO4 (precursor solution) and NaOH (precipitating agent) to form Zn(OH)2, which transformed into ZnO during microwave treatment. Successful deposition of ZnO particles on the filter paper was confirmed via X-ray diffraction and the corresponding morphologies were observed using field emission scanning electron microscopy. The ZnO-deposited papers were tested for antimicrobial activity and were found to be more effective against Staphylococcus aureus (gram-positive) than Escherichia coli (gram-negative). Bacterial populations were reduced by up to 92 ± 2% and 57 ± 4% for S. aureus and E. coli, respectively. Also, it was found that the samples prepared using higher concentrations of ZnSO4 and NaOH exhibited better antimicrobial properties.

This study used a simple and efficient dipping method to prepare oleophilic calcium stearate-coated kapok fibers (CaSt2-KF) with improved hydrophobicity. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) confirmed the deposition of calcium stearate particles on the surface of the kapok fibers. This led to higher surface roughness and improved static water contact angle of 137.4°. The calcium stearate-coated kapok fibers exhibited comparable sorption capacities for kerosene, diesel, and palm oil. However, the highest sorption capacity of 59.69 g/g was observed for motor oil at static conditions. For motor oil in water, the coated fibers exhibited fast initial sorption and a 65% removal efficiency after 30 s. At equilibrium, CaSt2-KF attained a sorption capacity of 33.9 g/g and 92.5% removal efficiency for motor oil in water. The sorption kinetics of pure motor oil and motor oil in water follows the pseudo-second-order kinetic model, and the Elovich model further described chemisorption. Intraparticle diffusion and liquid film diffusion were both present, with the latter being the predominant diffusion mechanism during motor oil sorption.

Carbonized natural fibers show great promise as sorbents because of their low fabrication costs, high surface area, high sorption capacity, and improved oil selectivity. Pyrolysis was performed on cotton and kapok fiber blends to produce carbon fiber sorbents. The carbon sponges showed improved mechanical properties with the addition of cotton. Pure carbonized kapok fibers were quite brittle, leading to challenges in recovery after use. The static water contact angle of carbonized kapok fibers, carbonized kapok-cotton blend (50K50C), and carbonized cotton fibers were determined to be 137.0°, 135.0°, and 135.9° respectively. This was an observed improvement from 127.9° for raw kapok and 0° for raw cotton. Sorption experiments revealed that the 50K50C fibers have sorption capacities about 25-27 times its original weight at 27.77 g/g, 25.72 g/g, and 26.01 g/g for motor oil, palm oil, and diesel, respectively.

Hollow tubular structured kapok fibers (Ceiba pentandra) were coated with polyaniline (PANI) molecules using an in situ oxidative polymerization technique. The tubular morphology of the kapok fibers was retained after PANI coating. The Fourier transform infrared (FT-IR) spectrum of the PANI-coated kapok fibers illustrated the vibration modes associated with the presence of PANI molecules. The PANI-treated kapok fibers achieved complete wettability with water molecules (zero water contact angle) from initially being highly hydrophobic (contact angle = 120°). In the present work, the removal of contaminants such as methyl orange dye and Cu(II) from aqueous solution using polyaniline-coated kapok fibers was investigated. Isotherm studies show that the removal of methyl orange dye (R2 ≥ 0.959) and Cu(II) (R2 ≥ 0.972) using PANI-coated kapok fibers follow the Langmuir isotherm model with maximum sorption capacities determined to be 75.76 and 81.04 mg/g, respectively. Based from thermodynamic studies, the sorption of methyl orange dye and Cu(II) are endothermic, feasible and spontaneous. Furthermore, kinetic studies show that the both processes follow a pseudo-second-order model, implying that the rate-determining step is chemisorption.

The photochemical grafting of methyl groups onto an n-type Si(1 1 1) substrate was successfully achieved using a Grignard reagent. The preparation involved illuminating a hydrogen-terminated Si(1 1 1) that was immersed in a CH3MgBr-THF solution. The success was attributed to the ability of the n-type hydrogenated substrate to produce holes on its surface when illuminated. The rate of grafting methyl groups onto the silicon surface was higher when a larger illumination intensity or when a substrate with lower dopant concentration was used. In addition, the methylated layer has an atomically flat structure, has a hydrophobic surface, and has electron affinity that was lower than the bulk Si.

Nearly 100% Pb-doped Bi-2223 was synthesized from Pb-doped Bi-2212, Ca 2 CuO 3 and CuO. The partially melted materials show a lamellar structure whose extent correlates with the amount of Bi-2223 phase. The fluid-like movement is attributed to the breaking of the BiO bonds and the rapid formation of the Bi-2223 phase attributed to the activation of the structure that enhances intercalation.

Water-triggered release of antimicrobial solutions is advantageous in inhibiting the growth of bacteria and fungi in moist and wet environments. In this study, we fabricated a composite, by mixing polyvinyl acetate adhesive with copper sulfate solution, which exhibits antimicrobial activities against bacteria. Polyvinyl acetate adhesive serves as the binder and water soluble substance while copper sulfate serves as the antimicrobial agent. The composite was coated in an acetate film and air-dried. To monitor the rate of release of copper ions, the composite was submerged in water and the conductivity was measured. The conductivity saturation time was determined. The composite showed antimicrobial activity against Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive).

Copper-based particles were synthesized using an electroless deposition technique. The said synthesis was done in an aqueous solution by reducing copper oxide powders using hydrazine. In this technique, gelatin was used as protective agent. X-ray Diffraction (XRD) measurement shows that the synthesized sample is composed of cuprous oxide (Cu2O) and copper (Cu) particles. Scanning Electron Microscopy (SEM) shows the morphology of the synthesized copper-based particles. Antimicrobial test shows that the number of Escherichia coli organisms reduced to 62.06% after 2 minutes of contact with the sample. Likewise, SEM micrographs of the Escherichia coli organisms show that the said organism underwent morphological changes in the presence of the synthesized copper-based particles.

Hydrophobic surfaces were created by coating various substrates (aluminum sheet, soda-lime glass, silicon carbide polishing paper, glass with double-sided adhesive) with paint containing functionalized oxide particles. The paint was created by functionalizing oxide particles (ground ZnO, TiO2 nanoparticles, or TiO2 microparticles) with fluorosilane molecules in absolute ethanol. Water contact angle of samples shows that the coated substrate becomes hydrophobic (water contact angle ≥ 90°). Among the oxides that were used, ground ZnO yielded contact angle exemplifying superhydrophobicity (water contact angle ≥ 150°). Scanning electron micrograph of paint-containing TiO2 nanoparticles shows rough functionalized oxides structures which probably increase the hydrophobicity of the surface.

Copper sulfate salts were embedded on multipurpose paper using simple soaking technique while copper oxide particles were embedded using in-situ technique. In simple soaking technique, the papers were simply soaked in copper sulfate solution in order for the copper salts to be incorporated in the paper. In the in-situ technique, the copper sulfate-embedded papers were soaked in sodium hydroxide solution for reactions to occur that will lead to the formation of copper oxide. Copper sulfate-embedded papers have blue green color while copper oxide-embedded papers have brown color. The copper sulfate-embedded paper shows excellent antimicrobial property against Staphylococcus aureus. Meanwhile, the copper oxide-embedded paper shows small zone of inhibition against Escherichia coli and Staphylococcus aureus.

The current-voltage characteristics of copper oxide (CuO) - zinc oxide (ZnO) heterojunctions under different illumination intensities were observed in this study. ZnO and CuO films were deposited on separate graphite electrodes via electrophoretic deposition (EPD). The films underwent heat treatment and were physically joined to form the p-n junction. The current-voltage characteristics of the junctions were obtained under forward and reverse bias under different illumination intensities. It was observed that the ZnO-CuO junctions exhibited diode-like behavior in the dark, indicated by the passing of current in forward bias and restricting in reverse bias. Under illumination, the junctions exhibited photodiode-like behavior, with increasing reverse current at greater illumination intensities.

Polyaniline-coated kapok (Ceiba pentandra) fibers that were embedded with Cu-based particles were fabricated for antimicrobial application. Kapok fibers were coated with polyaniline molecules using oxidative polymerization. The coated fibers were embedded with copper-based particles using soaking method in prepared CuO suspension. X-ray diffraction (XRD) pattern shows presence of Cu and Cu2O particles on the modified fibers. Scanning electron microscopy (SEM) supports the presence of embedded particles on the modified fibers. The samples showed antimicrobial activity against Escherichia coli and Staphylococcus aureus.

Polyaniline molecules are embedded on adhesive tape using successive ionic layer adsorption and reaction (SILAR) technique. The infrared spectrum shows the existence of molecular vibrational modes associated with the presence of polyaniline molecules on the sample. With the addition of polyaniline molecules, the conductivity of adhesive tape increases. Surface conductivity increases with number of dipping cycle until it reaches a certain value. Beyond this value, surface conductivity begins to decrease. The surface conductivity of the sample is associated with the connectivity of the embedded polyaniline molecules. The connectivity increases as the number of dipping cycle progresses. Meanwhile, the decrease in surface conductivity is attributed to the eroding of existing embedded structure at higher number of dipping cycle.

Flexible substrates have many promising applications in sensing, electronics, and electromagnetic shielding and energy storage among many others. Paper can serve as substrate for these kinds of technologies offering a cheaper alternative. In this study, Zinc oxide (ZnO) was successfully deposited on graphite drawn on paper using electrophoretic deposition (EPD). Graphite from commercially-available pencil was drawn on paper. Graphite drawn on paper was used as electrodes for the EPD process. High-voltage power supply was used as source while ground ZnO in acetone was used as suspension in the deposition process. Scanning electron microscopy (SEM) and Energy dispersive x-ray spectroscopy (EDX) results reveal the deposition of ZnO on Graphite. In addition, the electrical contact of the ZnO-graphite interface showed Ohmic behaviour by two-point probe method.

Coupling of copper oxide (CuO) and zinc oxide (ZnO) was done by chemical precipitation method. In this method, copper sulfate pentahydrate and zinc sulfate heptahydrate salt precursors were separately dissolved in distilled water; then were mixed together. The copper sulfate-zinc sulfate solution was then combined with a sodium hydroxide solution. The precipitates were collected and washed in distilled water and ethanol several times, then filtered and dried. The dried sample was grounded, and then undergone heat treatment. After heating, the sample was grounded again. Zinc oxide powder and copper oxide powder were also fabricated using chemical precipitation method. X-Ray Diffraction measurements of the coupled CuO/ZnO powder showed the presence of CuO and ZnO in the fabricated sample. Furthermore, other peaks shown by XRD were also identified corresponding to copper, copper (II) oxide, copper sulfate and zinc sulfate. Results of the photocatalytic activity investigation show that the sample exhibited superior photocatalytic degradation of methyl orange under visible light illumination compared to copper oxide powder and zinc oxide powder. This may be attributed to the lower energy gap at the copper oxide-zinc oxide interface, compared to zinc oxide, allowing visible light to trigger its photocatalytic activity.

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