Improvement of the optical, photocatalytic and antibacterial properties of ZnO semiconductor nanoparticles using different pepper aqueous extracts.

Peppers are fruits that grow on plants of the genus Capsicum and are popular for their use in gastronomy as a condiment and for their anti-inflammatory and anti-cancer properties due to their phytocompounds such as flavonoids, polyphenols, or alkaloids. Semiconductor zinc oxide (ZnO) nanoparticles (NPs) were synthesized using a green approach employing natural aqueous extracts of several varieties of peppers (jalapeño, morita, and ghost). The obtained NPs were characterized by different techniques, and their photocatalytic and antibacterial activity was studied. The signal at 620 cm-1 in the FTIR spectra belonging to the Zn-O bond, the appearance of the main peaks of a hexagonal wurtzite structure in the XRD pattern, and the characteristic signals in the UV-Vis spectra confirm the correct formation of ZnO NPs. The photocatalytic activity was analyzed against Methylene Blue (MB), Rhodamine B (RB), and Methyl Orange (MO) under UV and sunlight. All syntheses were able to degrade more than 93% of the pollutants under UV light. Antibacterial assays were performed against gram-positive and gram-negative bacteria. All syntheses exhibited antibacterial activity against all bacteria and maximum growth inhibition against Bacillus subtilis. The prominent results demonstrate that natural aqueous extracts obtained from peppers can be used to synthesize ZnO NPs with photocatalytic and biomedical applications.

SERS activity of hybrid nano/microstructures Ag-Fe3O4 based on Dimorphotheca ecklonis pollen grains as bio-template.

Nature provides remarkable examples of mass-produced microscale particles with structures and chemistries optimized by evolution for particular functions. Synthetic chemical tailoring of such sustainable biogenic particles may be used to generate new multifunctional materials. Herein, we report a facile method for the synthesis of hybrid nano/microstructures Ag-Fe3O4 based on Dimorphotheca ecklonis pollen grains as bio-template. Silver nanoparticles was biosynthesized using pollen grains as a reduction and stabilization agent as well as a bio-template promoting the adhesion of silver nanoparticles to pollen surface. Fe3O4 nanoparticles were synthesized by co-precipitation method from FeSO4. Hybrid nano/microstructures Ag-Fe3O4 based on Dimorphotheca ecklonis pollen grains as bio-template were obtained and characterized using Scanning Electron Microscopy and Transmission Electron Microscopy to study the morphology and structure; Energy-Dispersive X-ray Spectroscopy to determine the chemical composition distribution; and Confocal Fluorescence Microscopy to demonstrate the fluorescence properties of hybrid nano-microstructures. Furthermore, these hybrid nano-microstructures have been studied by Surface-Enhanced Raman Scattering (SERS), using methylene blue as a target molecule; the hybrid nano-microstructures have shown 14 times signal amplification.

Reuse of sustainable materials for xylenol orange dye and copper (II) ion ammoniacal removal.

Water pollution caused by heavy metals and organic compounds is an environmental problem with negative impact, making the restoration of water quality a priority. In this paper, the adsorption of xylenol orange dye (XO) on vitreous tuff mineral (VT) was studied. It was established that the adsorption capacity of VT was 45.17 mg/g. The removal was carried out by interactions between active sites on the surface of the material and the functional groups of the dye. The solid waste obtained from this process (VTXO) was reused as adsorbent material for Cu removal in the form of the complex Cu-NH3 because this process was done in an ammoniacal medium. It was found that the adsorption capacity of this new material was 33.09 mg/g. In a previous research, VT mineral was used to remove crystal violet (CV) instead of XO. The solid waste of this last process (VTCV) was also applied for Cu-NH3 removal, in order to compare the adsorption capacity of VT after the adsorption of two different kinds of dyes. The adsorption capacity of VTXO was lower than that of VTCV (71.23 mg/g). In both processes, adsorption kinetic was well described by a chemical adsorption onto a heterogeneous surface. The equilibrium time for XO removal was 50 min and 80 min for Cu-NH3. The experimental design stated that the maximum adsorption capacity was reached when the initial concentration was 6400 mg/L and the solid-liquid ratio was 10 g/L. The system that requires the least amount of adsorbent was the counter flow batch. Finally, it was possible to estimate the behavior of the system on a higher scale. This research provides an efficient and economical alternative to treat water contaminated with dyes and cooper in an ammoniacal medium using the same material in both processes, one after the other.

Study of the morphology of ZnS thin films deposited on different substrates via chemical bath deposition.

In this work, the influence of substrate on the morphology of ZnS thin films by chemical bath deposition is studied. The materials used were zinc acetate, tri-sodium citrate, thiourea, and ammonium hydroxide/ammonium chloride solution. The growth of ZnS thin films on different substrates showed a large variation on the surface, presenting a poor growth on SiO2 and HfO2 substrates. The thin films on ITO substrate presented a uniform and compact growth without pinholes. The optical properties showed a transmittance of about 85% in the visible range of 300-800 nm with band gap of 3.7 eV.

Biosynthesis of lead nanoparticles by the aquatic water fern, Salvinia minima Baker, when exposed to high lead concentration.

Salvinia minima Baker is a small floating aquatic fern that is efficient for the removal and storage of heavy metals such as lead and cadmium. In this study, we report that lead removal by S. minima causes large accumulation of lead inside the cells in the form of nanoparticles (PbNPs). The accumulation pattern of lead was analyzed in both, submerged root-like modified fronds (here named "roots"), and in its aerial leaf-like fronds ("leaves"). Analysis by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM) confirmed the biosynthesis of PbNPs by the plant. In both, roots and leaves, PbNPs were found to accumulate almost exclusively at the cell wall and closely associated to the cell membrane. Two types of PbNPs shapes were found in cells of both tissues, those associated to the cell wall were quasi-spherical with 17.2±4.2 nm of diameter, while those associated to the cell membrane/cytoplasm were elongated. Elongated particles were 53.7±29.6 nm in length and 11.1±2.4 nm wide. Infrared spectroscopy (IR) results indicate that cellulose, lignin and pectin are the major components that may be acting as the reducing agents for lead ions; these findings strongly suggest the potential use of this fern to further explore the bio-assisted synthesis of heavy metal nanostructures.

Citric acid modifies surface properties of commercial CeO2 nanoparticles reducing their toxicity and cerium uptake in radish (Raphanus sativus) seedlings.

Little is known about the mobility, reactivity, and toxicity to plants of coated engineered nanoparticles (ENPs). Surface modification may change the interaction of ENPs with living organisms. This report describes surface changes in commercial CeO2 NPs coated with citric acid (CA) at molar ratios of 1:2, 1:3, 1:7, and 1:10 CeO2:CA, and their effects on radish (Raphanus sativus) seed germination, cerium and nutrients uptake. All CeO2 NPs and their absorption by radish plants were characterized by TEM, DLS, and ICP-OES. Radish seeds were germinated in pristine and CA coated CeO2 NPs suspensions at 50mg/L, 100mg/L, and 200mg/L. Deionized water and CA at 100mg/L were used as controls. Results showed ζ potential values of 21.6 mV and -56 mV for the pristine and CA coated CeO2 NPs, respectively. TEM images showed denser layers surrounding the CeO2 NPs at higher CA concentrations, as well as better distribution and smaller particle sizes. None of the treatments affected seed germination. However, at 200mg/L the CA coated NPs at 1:7 ratio produced significantly (p ≤ 0.05) more root biomass, increased water content and reduced by 94% the Ce uptake, compared to bare NPs. This suggests that CA coating decrease CeO2 NPs toxicity to plants.

Green method to form iron oxide nanorods in orange peels for chromium(VI) reduction.

A green method for synthesizing iron oxide nanorods within orange peel pith has been developed. Orange peel pith functions as both a support and a reducing agent for iron ions. The nanorods were characterized using scanning electron microscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. Results of the characterization indicate that iron is deposited on the surface of orange peel primarily in the form of iron, iron(II) oxide and magnetite. The nanoparticles grow to form nanorods in the range of 20-40 nm of diameter. The biocomposite was then tested for Cr(VI) reduction and removal from aqueous solutions, exhibiting removals as high as 96% for concentrations of 10 mg/L and 76% for 50 mg/L, which is almost 4 times the removal capacity of orange peel alone.