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This study reports the synthesis of TiO2 nanoparticles through a bio-approach by Avicennia marina leaf extract to titanium source ratios of 0.03, 0.06, 0.125, 0.20, 0.25 and 0.5, and examines its a...

Ag/silver halides have recently received attention in the synthesis of heterostructured nanocomposites. Although important, the green biosynthesis of Ag/silver halide nanocomposites has not yet been reported. Herein, a simple, single-step biosynthesis process was implemented using aqueous leaf extract (ALE) of the mangrove Avicennia marina to synthesize Ag/AgCl@TiO2 plasmonic nanocomposites with enhanced visible light photoactivity. Characterization results showed that the ALE was necessary for nanocomposites preparation as a reducing and stabilizing agent. With increase in the ALE/AgNO3 ratio (R1) of the initial precursor from 0 to 1.63, the diffraction peaks of Ag/AgCl became visible slowly and their intensity increased. Besides, AgNO3/tetraethylorthotitanate ratio (R2) had a positive effect on increasing the intensity of Ag/AgCl diffraction peaks. The UV light absorption intensity of Ag/AgCl@TiO2 was improved and displayed stronger absorption by increasing R1 values. A broad absorption peak was recorded in the visible wavelength spectrum of the biosynthesized nanocomposites from 400 to 600 nm, centered at 500 nm, which could be associated with the surface plasmon resonance effect of spatially detained electrons in Ag/AgCl nanocrystals. This enhanced absorption showed the photoactivity of the biosynthesized nanocomposites in the visible light region, which was confirmed in a real application for degradation of eosin Y with 99.8% efficiency under sunlight. Thus, it seems that the biological procedure, which is environmentally friendly and inexpensive, could replace the conventional approaches to synthesize Ag/AgCl@TiO2 plasmonic nanocomposites with enhanced visible light photoactivity.

The green synthesis of nano-sized particles with specific functions is of great significance in the present bio-nanotechnology. In this study, the biosynthesis of silver nanoparticles (AgNPs) from the aqueous extract of stem, root and leaf of Rhizophora mucronata, one of the two native mangrove plants in southern Iran, and its activity against some bacterial pathogens are reported for the first time. A green procedure for the synthesis of AgNPs using the mangrove extract as reducing agent was used. Synthesized AgNPs were investigated using UV–visible spectrophotometry, transmission electron microscopy (TEM), field emission scanning electron microscopy, X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS) and Fourier transform infrared (FTIR) spectroscopy. Antibacterial effect of the biosynthesized AgNPs was investigated by agar well diffusion assay against pathogenic bacteria. The leaf extract yielded the highest production of biosynthesized AgNPs among the plant parts. UV–visible spectrophotometry at a wavelength of 420 nm confirmed the synthesis of AgNPs. The results from the XRD analysis approved the formation of crystalline AgNPs with crystallinity percentage of 88.54. As shown by TEM evaluation, AgNPs had the same spherical morphology. The size of the biosynthesized AgNPs was between 1 and 80 nm with average size of 32.44 nm. According to the size distribution histogram, nanoparticles in the size range of 20–25 nm were more than other size groups. SEM images identified silver nanoparticles ranging in size from 10 to 19 nm. Results of EDS showed the existence of carbon, silver, oxygen and chlorine in the nanoparticles synthesized from the leaf extract of R. mucronata. Silver was the major constituent element, 73.5%. FTIR analysis distinguished different functional groups such as aromatic loops, alcohol, phenol group, alkanes and alkyl halides in the biosynthesis process. The biosynthesized AgNPs had potential antibacterial activity against the bacterial pathogens. Out of the selected bacterial strains, the Gram-positive bacteria of Bacillus cereus with the maximum inhibition zone and the Gram-negative bacteria of Pseudomonas aeruginosa with the minimum inhibition zone were the most sensitive and resistant bacteria, respectively. The mangrove Rhizophora mucronata extract was found to be a suitable reducing agent for biosynthesis of AgNPs with approved antibacterial activity.

The development of eco-friendly and nontoxic processes for the synthesis of nanoparticles is one of the most important discussed issues in nanotechnology science. This study reports the green synth...

In the present study, we prepared silver nanoparticles immobilized on silica beads (Ag/TEPA-Den-SiO2) and examined their potential for removing luminous Vibrio sp. Persian1 from seawater used to culture Penaeus (Litopenaeus) vannamei post-larvae. The Ag/TEPA-Den-SiO2 sample was characterized by TEM, FE-SEM/EDS, FT-IR and ICP-OES and its antibacterial activity assayed by a test tube test and flow test using water filters filled with Ag/TEPA-Den-SiO2 as the filter media. The results of the test tube test indicated that no Vibrio sp. Persian1 was detectable after 2-h contact. The filter column that contained Ag/TEPA-Den-SiO2 + silver absorbent inactivated 100% of the bacteria after passage of seawater through the column for 12-h at a flow rate of 0.5 l/min. The survival rate and growth performance of post-larvae cultured in seawater treated with an antibacterial filter improved significantly compared with the control.

In this study, we prepared silver nanoparticles immobilized onto silica sand beads as an antibacterial material against pathogenic luminous Vibrio sp. Persian1. Silica beads were modified with 3-aminopropyltriethoxysilane (APTES), cyanuric chlorid and tetraethylene pentamine, and silver nanoparticles were generated in various concentrations (0.5, 1, and 2 mM g−1 of silica beads) of AgNO3 on the surface using chemical reduction. Ag/TEPA-Den-SiO2 samples were characterized by TEM, FE-SEM/EDS, FT-IR and ICP OES and their antibacterial activity assayed by zone of inhibition and test tube tests against pathogenic Vibrio sp. The results of the zone inhibitory test revealed that all the Ag/TEPA-Den-SiO2 samples had an antibacterial effect against luminous Vibrio sp. Persian1. In addition, the tube test results showed 100% killing of bacteria in 2 h contact period. Ag/TEPA-Den-SiO2 samples maintained their antibacterial activity after 14-day immersion in seawater by slow release of silver ions. These results suggest that Ag/TEPA-Den-SiO2 substrates could be effective antibacterial materials for disinfection of seawater used to culture Penaeid shrimp larvae.

The synthesis of photocatalysts revealing efficient performance under the visible light has recently broadened its appeal for the removal of environmental pollutants from the water and wastewater. Besides, the biosynthesis of nanostructured photocatalysts with the tunable surface plasmon band is eco-friendly and worth attending. In the same vein, this study was an endeavor to synthesize Ag/AgCl@TiO2 plasmonic photocatalyst, with an enhanced photoactivity under the sunlight by a facile biosynthesis method using aqueous leaf extract of mangrove plant Avicennia marina, as a reducing and stabilizing agent as well as a chlorine source. To this end, the plasmonic Ag/AgCl@TiO2 nanocomposite, with the particle size of ∼35 nm, the specific surface area of 31.94 m2 g−1, and the bandgap energy of 1.73 eV, was successfully synthesized with aqueous leaf extract/AgNO3 (R1) and AgNO3/TiO2 (R2) ratios of 0.31 and 1.61, respectively. Different techniques examined the effect of R1 and R2 on the characteristics of the products. Consequently, the results indicated that Ag/AgCl@TiO2 nanocomposite exhibited a swift degradation of the eosin Y dye in 60 min under the sunlight. A topmost dye photodegradation of 99% was attained at pH 4 with the photocatalyst concentration of 0.05 g/100 mL and the eosin Y concentration of 50 mg/L at the ambient temperature. The surface plasmon resonance and the effective charge separation due to the heterostructure developed among Ag, AgCl, and TiO2 could be accountable for the absorption band expansion to the visible light area and the significant photocatalytic activity of Ag/AgCl@TiO2 under the sunlight. Recycling experiments for the five cycles elucidated the magnificent long-term photocatalytic stability of the biosynthesized Ag/AgCl@TiO2. The operation simplicity and the potential of utilizing the sunlight energy prompted the biosynthesized Ag/AgCl@TiO2 to be a noteworthy reusable candidate for the photodegradation of the toxic organic pollutants in the aqueous solutions.