Reaction Mechanism of Aromatic Ring Amination of Benzene and Substituted Benzenes by Aqueous Ammonia over Platinum-Loaded Titanium Oxide Photocatalyst

The reaction mechanism of photocatalytic aromatic ring amination of benzene and the derivatives with aqueous ammonia was clarified by some reaction experiments and electron spin resonance spectroscopy as follows: a platinum-loaded titanium oxide photocatalyst oxidizes an ammonia to form an amide radical (·NH₂) and a proton, and the amide radical attacks an aromatic ring to produce an intermediate, followed by the abstraction of the hydrogen atom from it on the platinum sites to produce an aniline. Simultaneously, the photocatalyst also promotes the reduction of a proton to form a hydrogen radical on the platinum sites, and it reacts with the abstracted hydrogen to produce a molecular hydrogen. The photocatalytic aromatic ring amination proceeded for many kinds of monosubstituted benzenes except for phenol, and high selectivity was recorded for benzonitrile and halogenated benzenes. It is noted that the distributions of the aminated isomers were unique, i.e., the <i>para-</i>isomer was predominantly produced in the case of nitrobenzene, and <i>ortho-</i>isomers were preferentially produced in the case of the other substrates, which would depend on the approaching direction of the molecule to the photocatalyst surface

Bifunctional Rhodium Cocatalysts for Photocatalytic Steam Reforming of Methane over Alkaline Titanate

Photocatalytic steam reforming of methane (PSRM; 2 H₂O (g) + CH₄ → 4 H₂ + CO₂) was examined over metal-loaded K₂Ti₆O₁₃ photocatalysts. Although the production rate was improved by loading Pt cocatalyst on the K₂Ti₆O₁₃ photocatalyst, unfavorable formation of CO and gradual deactivation of photocatalyst were observed. On the other hand, a Rh-loaded K₂Ti₆O₁₃ sample showed two times higher activity than the Pt-loaded one did, and promoted the PSRM selectively without deactivation for many hours. In the highly active Rh-loaded photocatalyst, the Rh cocatalyst existed as a mixture of small metallic rhodium and large rhodium oxide particles. The photocatalytic activity tests for hydrogen evolution and oxygen evolution from each aqueous solution of sacrificial reagent (methanol and silver nitrate, respectively) revealed that the metallic rhodium particles and the rhodium oxide particles could function as cocatalysts preferably for reduction and oxidation, respectively. Also on a Na₂Ti₆O₁₃ photocatalyst, a mixture of rhodium metal and oxide similarly enhanced the photocatalytic activity. Thus, it is suggested that the Rh cocatalyst on these alkaline titanates bifunctionally promoted the PSRM

Reaction Mechanism of Aromatic Ring Hydroxylation by Water over Platinum-Loaded Titanium Oxide Photocatalyst

Direct aromatic ring hydroxylation of benzene derivatives by using water as an oxidant over platinum-loaded titanium oxide photocatalyst proceeded with high selectivity under the light of selected wavelength. Two kinds of electrophilic active species, which depended on the reaction condition, were proposed: a surface oxygen radical in neutral or acidic conditions and a hydroxyl radical in basic condition, both of which were produced by a photoformed hole on the surface of titanium oxide. In both cases, these active species can attack the aromatic ring to form an intermediate, followed by the formation of a hydroxylated product. Thus, the reaction proceeds through the addition–elimination mechanism. On the other hand, a photoformed electron reduces a proton to form a hydrogen radical, which reacts with the intermediate to produce a hydroxylated product and a molecular hydrogen or with another hydrogen radical to form a molecular hydrogen

Sites et monuments : bulletin de la Société pour la protection des paysages et de l'esthétique générale de la France

juillet 19841984/07 (N106)-1984/09

Additional file 2: of Available, Bed-sided, Comprehensive (ABC) score to a diagnosis of Methicillin-resistant Staphylococcus aureus infection: a derivation and validation study

Comparison of the two patient cohorts. (PDF 149 kb

Structural Characterization of 2D Zirconomolybdate by Atomic Scale HAADF-STEM and XANES and Its Highly Stable Electrochemical Properties as a Li Battery Cathode

The structural determination of nanomaterials and their application in energy storage and transfer are of great importance. Herein, a layered zirconomolybdate with a two-dimensional structure was synthesized. Atomic resolution electron microscopy was utilized for direct visualization of the structure that was further confirmed by powder X-ray diffraction and X-ray absorption near-edge structure analyses. The structure of the molecular sheet was stable at a high temperature in an oxidative atmosphere. The electrochemical performance of the material was evaluated with a Li battery composed of the calcined material as a cathode. Li ions were reversibly inserted and extracted between the layers without collapse of the structure of the material. The electrochemical properties of the material were derived from the reversible redox activity of the Mo ions and Zr ions in the material as well as the flexibility of the molecular layer of the material

Durability of immunity by hepatitis B vaccine in Japanese health care workers depends on primary response titers and durations

<div><p>Background</p><p>Health care workers (HCWs) are frequently exposed to hepatitis B virus (HBV) infection. The efficacy and safety of immunization with the hepatitis B (HB) vaccine are well recognized, but the durability of immunity and need for booster doses in those with secondary vaccine response failure remains controversial.</p><p>Methods</p><p>This was a retrospective cohort study performed at Osaka University Hospital, Japan. We examined antibodies against HB surface antigen (anti-HBs) titers annually after immunization for previously non-immunized HCWs. Primary responders were categorized by their sero-positive durations as short responders (those whose anti-HBs titers declined to negative range within 3 years), and long responders (those who retained positive anti-HBs levels for 3 years and more). We re-immunized short responders with either single or 3-dose boosters, the long responders with a single booster when their titers dropped below protective levels, and examined their sero-protection rates over time thereafter.</p><p>Results</p><p>From 2001 to 2012, data of 264 HCWs with a median age of 25.3 were collected. The rate of anti-HBs positivity after primary vaccination were 93.0% after three doses (n = 229), 54.5% after two doses (n = 11), and 4.2% after a single dose (n = 24). Of 213 primary responders, the anti-HBs levels of 95 participants (44.6%) fell below the protective levels, including 46 short responders and 49 long responders. HCWs with higher initial anti-HBs titers after primary vaccination had significantly longer durations of sero-positivity. For short responders, 3-dose booster vaccination induced a longer duration of anti-HBs positivity compared to a single-dose booster, whereas for long responders, a single-dose booster alone could induce prolonged anti-HBs positivity.</p><p>Conclusion</p><p>Our preliminary data suggested that it may be useful to differentiate HB vaccine responders based on their primary response durations to maintain protective levels of anti-HBs efficiently. A randomized, prospective, large-scale study is warranted to support our findings.</p></div

Initial anti-HBs titers of primary responders after full series of vaccination and its duration of positivity.

<p>(A) A box indicates a median and interquartile range, and error bars denote the 10th and 90th percentiles. (B) High (> 500 mIU/mL, n = 35), moderate (100–500 mIU/mL, n = 62), and low (< 100 mIU/mL, n = 46) titers. It was a significant trend that individuals with lower titers of initial anti-HBs experienced secondary vaccine response failure earlier.</p

Booster doses administered to short/long responders and duration of anti-HBs positivity.

<p>Booster doses administered to short/long responders and duration of anti-HBs positivity.</p

Doses of primary hepatitis B vaccine and rate of anti-HBs positivity.

<p>Doses of primary hepatitis B vaccine and rate of anti-HBs positivity.</p