Rapid Removal and Mineralization of Bisphenol A by Heterosupramolecular Plasmonic Photocatalyst Consisting of Gold Nanoparticle-Loaded Titanium(IV) Oxide and Surfactant Admicelle

The establishment of technology for rapid and complete removal and mineralization of harmful phenolic compounds from water is of great importance for environmental conservation. Visible-light irradiation (λ > 430 nm, light intensity integrated from 420 to 485 nm = 6.0 mW cm^–2) of Au nanoparticle (NP)-loaded TiO₂ (Au/TiO₂) in dilute aqueous solutions of bisphenol A (BPA) and <i>p</i>-cresol (PC) causes degradation of the phenols. The addition of trimethylstearylammonium chloride (C₁₈TAC) enhances the adsorption of BPA on Au/TiO₂ to greatly increase the rate of reaction. Consequently, 10 μM phenols are completely removed from the solutions within 2.5 h irradiation, and prolonging irradiation time to 24 h quantitatively oxidizes BPA to CO₂. Dynamic light scattering ζ-potential measurements indicate that a C₁₈TAC bilayer or admicelle is formed on the Au/TiO₂ particle surface at C₁₈TAC concentration >50 μM. The action spectrum for reaction shows that this reaction is driven by the Au NP localized surface plasmon resonance excitation-induced interfacial electron transfer from Au to TiO₂. We propose a possible reaction scheme on the basis of the experimental results including intermediate analysis

Rapid Removal and Mineralization of Bisphenol A by Heterosupramolecular Plasmonic Photocatalyst Consisting of Gold Nanoparticle-Loaded Titanium(IV) Oxide and Surfactant Admicelle

The establishment of technology for rapid and complete removal and mineralization of harmful phenolic compounds from water is of great importance for environmental conservation. Visible-light irradiation (λ > 430 nm, light intensity integrated from 420 to 485 nm = 6.0 mW cm^–2) of Au nanoparticle (NP)-loaded TiO₂ (Au/TiO₂) in dilute aqueous solutions of bisphenol A (BPA) and <i>p</i>-cresol (PC) causes degradation of the phenols. The addition of trimethylstearylammonium chloride (C₁₈TAC) enhances the adsorption of BPA on Au/TiO₂ to greatly increase the rate of reaction. Consequently, 10 μM phenols are completely removed from the solutions within 2.5 h irradiation, and prolonging irradiation time to 24 h quantitatively oxidizes BPA to CO₂. Dynamic light scattering ζ-potential measurements indicate that a C₁₈TAC bilayer or admicelle is formed on the Au/TiO₂ particle surface at C₁₈TAC concentration >50 μM. The action spectrum for reaction shows that this reaction is driven by the Au NP localized surface plasmon resonance excitation-induced interfacial electron transfer from Au to TiO₂. We propose a possible reaction scheme on the basis of the experimental results including intermediate analysis

Number of needle stick injuries and mean incidence rate per 100 beds per year (n = 67 hospitals).

<p>Number of needle stick injuries and mean incidence rate per 100 beds per year (n = 67 hospitals).</p

Annual incidence rates of needle stick injuries per 100 beds in hospitals of three different sizes.

<p>Annual incidence rates of needle stick injuries per 100 beds in hospitals of three different sizes.</p

Phylogenetic relationships of <i>Bradyrhizobium</i> sp. DOA9 and related bacteria based on 16S rRNA gene sequences.

<p>Bootstrap values are expressed as percentages of 1,000 replications. Evolutionary distances were computed using the Kimura two-parameter method. The bar represents one estimated substitution per 100-nucleotide positions. Strains capable of Nod factor-dependent and -independent nodulation are marked with (ND) and (NI), respectively. Photosynthetic strains are highlighted in gray.</p

Comparative genomic analysis among <i>Bradyrhizobium</i> sp. DOA9, <i>B</i>. <i>japonicum</i> USDA110, and <i>Bradyrhizobium</i> sp. BTAi1.

<p>Each genome is represented by a circle, and the numbers of shared and unique genes are shown by the overlapping and nonoverlapping regions. The proportion of total genes represented by each area of the diagram is shown in parentheses. The total number of genes in each genome is shown in square brackets.</p

Phylogenetic relationships of pDOA9 and related plasmids.

<p>Bootstrap values are expressed as percentages of 1,000 replications. Evolutionary distances were computed using the Kimura two-parameter method. The bar represents one estimated substitution per 100-nucleotide positions.</p

Pulse-field gel electrophoresis of <i>Bradyrhizobium</i> sp. DOA9 genomic DNA.

<p>DOA9 cells were digested in 1% pulse field grade (PFG) agarose plugs with proteinase K, as described in the <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0117392#sec002" target="_blank">Materials and Methods</a>, and run 0.8% certified megabase agarose in TAE buffer to separate fragments of 225–6,000 kb (A), or 1% certified megabase agarose in 0.5 x TBE buffer (B) to separate fragments of 225–2,200 kb, respectively. Closed arrowheads and open arrowheads indicate the putative chromosome and the plasmid, respectively. Lane M1: PFGE marker, 3.5–5.7 Mb, <i>Saccharomyces pombe</i> chromosomal DNA. Lane M2: low-range (2.03–194 kb) PFG marker DNA ladder. DOA9: DOA9 genomic DNA.</p

Comparison of nodulation gene clusters in <i>Bradyrhizobium</i> sp. DOA9 and related bacteria.

<p>Double slash marks represent DNA regions that are not shown. Colored strips represent the conserved gene regions between the compared strains, and the color indicates the percentage similarity, as detailed in the key. T: region where the transposase genes were located.</p

Genome Analysis of a Novel <i>Bradyrhizobium</i> sp. DOA9 Carrying a Symbiotic Plasmid

<div><p><i>Bradyrhizobium</i> sp. DOA9 isolated from the legume <i>Aeschynomene americana</i> exhibited a broad host range and divergent nodulation (<i>nod</i>) genes compared with other members of the <i>Bradyrhizobiaceae</i>. Genome analysis of DOA9 revealed that its genome comprised a single chromosome of 7.1 Mbp and a plasmid of 0.7 Mbp. The chromosome showed highest similarity with that of the <i>nod</i> gene-harboring soybean symbiont <i>B. japonicum</i> USDA110, whereas the plasmid showed highest similarity with pBBta01 of the <i>nod</i> gene-lacking photosynthetic strain BTAi1, which nodulates <i>Aeschynomene</i> species. Unlike in other bradyrhizobia, the plasmid of DOA9 encodes genes related to symbiotic functions including nodulation, nitrogen fixation, and type III/IV protein secretion systems. The plasmid has also a lower GC content (60.1%) than the chromosome (64.4%). These features suggest that the plasmid could be the origin of the symbiosis island that is found in the genome of other bradyrhizobia. The <i>nod</i> genes of DOA9 exhibited low similarity with those of other strains. The <i>nif</i> gene cluster of DOA9 showed greatest similarity to those of photosynthetic bradyrhizobia. The type III/IV protein secretion systems of DOA9 are similar to those of <i>nod</i> gene-harboring <i>B. elkanii</i> and photosynthetic BTAi1. The DOA9 genome exhibited intermediate characteristics between <i>nod</i> gene-harboring bradyrhizobia and <i>nod</i> gene-lacking photosynthetic bradyrhizobia, thus providing the evidence for the evolution of the <i>Bradyrhizobiaceae</i> during ecological adaptation. <i>Bradyrhizobium</i> sp. DOA9 isolated from the legume <i>Aeschynomene americana</i> exhibited a broad host range and divergent nodulation (<i>nod</i>) genes compared with other members of the <i>Bradyrhizobiaceae</i>. Genome analysis of DOA9 revealed that its genome comprised a single chromosome of 7.1 Mbp and a plasmid of 0.7 Mbp. The chromosome showed highest similarity with that of the <i>nod</i> gene-harboring soybean symbiont <i>B. japonicum</i> USDA110, whereas the plasmid showed highest similarity with pBBta01 of the <i>nod</i> gene-lacking photosynthetic strain BTAi1, which nodulates <i>Aeschynomene</i> species. Unlike in other bradyrhizobia, the plasmid of DOA9 encodes genes related to symbiotic functions including nodulation, nitrogen fixation, and type III/IV protein secretion systems. The plasmid has also a lower GC content (60.1%) than the chromosome (64.4%). These features suggest that the plasmid could be the origin of the symbiosis island that is found in the genome of other bradyrhizobia. The <i>nod</i> genes of DOA9 exhibited low similarity with those of other strains. The <i>nif</i> gene cluster of DOA9 showed greatest similarity to those of photosynthetic bradyrhizobia. The type III/IV protein secretion systems of DOA9 are similar to those of <i>nod</i> gene-harboring <i>B. elkanii</i> and photosynthetic BTAi1. The DOA9 genome exhibited intermediate characteristics between <i>nod</i> gene-harboring bradyrhizobia and <i>nod</i> gene-lacking photosynthetic bradyrhizobia, thus providing the evidence for the evolution of the <i>Bradyrhizobiaceae</i> during ecological adaptation.</p></div