Porous BiOBr/Bi₂MoO₆ Heterostructures for Highly Selective Adsorption of Methylene Blue

Porous BiOBr/Bi₂MoO₆ (Br/Mo) heterostructures were designed and successfully fabricated, in which BiOBr nanoparticles were deposited on the surface of the secondary nanoplate of three-dimensional porous Bi₂MoO₆ architectures through a deposition–precipitation process. The as-prepared Br/Mo heterostructures were used as an adsorbent to remove methylene blue (MB) from aqueous solution. The batch adsorption results indicated that 50.0 wt % Br/Mo heterostructures show an enhanced adsorption capacity compared with pure Bi₂MoO₆ and BiOBr. The effects of initial solution, initial concentration, and contact time were systematically investigated. The optimum adsorbent amount and the pH value were determined to be 0.8 g L^–1 and 2, respectively. Meanwhile, the experiments also revealed that porous Br/Mo heterostructures possess higher preferential adsorptivity for MB than that for methyl orange (MO^–) and rhodamine B (RhB⁺). The dynamic experimental result indicated that the adsorption process conforms to the pseudo-second-order kinetic model. Weber’s intraparticle diffusion model indicated that two steps took place during the adsorption process. Thermodynamic analysis results showed that the adsorption is a physisorption process, which conforms to the Langmuir isotherm model. Additionally, the possible adsorption mechanism was also investigated. The present study implied that Br/Mo heterostructures are promising candidates as adsorbents for MB removal. Therefore, fabrication of semiconductor-based heterostructures could be a strategy to design new efficient adsorbents for the removal of environmental pollutants

Dimethyl Sulfoxide: An Ideal Electrochemical Probe for Hydroxyl Radical Detection

In situ and real-time determination of hydroxyl radicals (•OH) in physiological and pathological processes is a great challenge due to their ultrashort lifetime. Herein, an electrochemical method was developed by using dimethyl sulfoxide (DMSO) as a trapping probe for rapid determination of •OH in aqueous solution. When DMSO reacted with •OH, an intermediate product methane sulfinic acid (MSIA) was formed, which can be electrochemically oxidized to methanesulfonic acid (MSA) on the glassy carbon electrode (GCE), resulting in a distinct voltammetric signal that is directly proportional to the concentration of •OH. Other commonly encountered reactive oxygen species (ROS), including hypochlorite anions (ClO–), superoxide anions (O2•–), sulfate radicals (SO4•–), and singlet oxygen (1O2), have showed no interference for •OH determination. Thus, an electrochemical method was developed for the determination of •OH, which exhibits a wide linear range (0.4–5120 μM) and a low limit detection of 0.13 μM (S/N = 3) and was successfully applied for the quantification of •OH in aqueous extracts of cigarette tar (ACT). Alternatively, the same reaction mechanism is also applicable for the determination of DMSO, in which a linear range of 40–320 μM and a detection limit 13.3 μM (S/N = 3) was achieved. The method was used for the evaluation of DMSO content in cell cryopreservation medium. This work demonstrated that DMSO can serve as an electrochemical probe and has valuable application potential in radical study, biological research, and environmental monitoring

Biomimetic Preparation of Hybrid Porous Adsorbents for Efficiently Purifying Complex Wastewater

Simulating the polymerization of polyphenol on a solid surface in nature, hybrid adsorbents were prepared by coating the hierarchically porous silica (HPS) with a poly­(pyrogallol) (PG) layer. Such material has a macroporous skeleton and well-defined mesopores. During a facile and mild reaction, the poly-PG membrane is strongly binded to the pore surface of HPS through covalent and noncovalent interactions. High-performance adsorbents, HPS/PG, was obtained. It exhibits a large capability to adsorb various pollutants in wastewater, such as heavy metal ions (Hg²⁺, Pb²⁺, Cu²⁺, Ni²⁺, and CrO₄^2–), organic dyes, and pesticides. Specifically, HPS/PG showed a good purifying capacity toward the Hg²⁺ ion and neutral red, which could reach 157.2 and 671.1 mg g^–1, respectively. More than that, HPS/PG showed a good recovering ability with simulated wastewater with complex components. The removal rate for any of the pollutants was more than 98%. The high adsorption capability of HPS/PG should be due to the hierarchically porous structure and ideal surface coating, which combine the benefits of both physical and chemical adsorptions

Copper-Catalyzed Cascade Reaction via Intramolecular Hydroamination Cyclization of Homopropargylic Amines and Intermolecular Povarov Reaction with Imines

A new one-pot cascade reaction of homopropargylic amines with simple imines is developed in the presence of Cu­(OTf)₂ and affords a series of hexahydro-1<i>H</i>-pyrrolo­[3,2-<i>c</i>]­quinoline derivatives in good to high yields. This reaction proceeds through an intramolecular hydroamination cyclization of homopropargylic amine to generate a highly reactive dihydropyrrole intermediate in situ. It subsequently reacts with imine via an intermolecular inverse-electron-demand aza-Diels–Alder reaction and a 1,3-H shift to give the fused pyrroloquinoline structures, forming two new C–C bonds and one C–N bond and one N–H bond

Rational Design of Magnetic Micronanoelectrodes for Recognition and Ultrasensitive Quantification of Cysteine Enantiomers

Driven by the urgent need for recognition and quantification of trace amino acids enantiomers in various biologic samples, we demonstrate for the first time an ultrasensitive electrochemical chiral biosensor for cysteine (Cys) based on magnetic nanoparticles (Fe₃O₄@PDA/Cu_<i>x</i>O) as electrode units. d-Cys-Cu²⁺-d-Cys formed in the presence of cysteine exhibits strong stability and a shielding effect on the redox current of indicator Cu²⁺, which can be used to quantify and recognize d-Cys by square wave voltammetry. Simultaneous detection of d-Cys and homocysteine (Hcy) is achieved in the presence of other amino acids, demonstrating an excellent selectivity of the sensor. Moreover, aided by the enrichment treatment effect of magnetic micronanoelectrodes, an ultrahigh sensitivity up to 102 μA μM^–1 cm^–2 was achieved, the detection limit is reduced to picomolar level (83 pM) for d-Cys and can be used for the recognition of cysteine enantiomers. The proposed method has been verified by real sample analysis with satisfactory results. The results highlight the feasibility of our proposed strategy for magnetic micronanoelectrode sensor, electrochemical recognition, and quantification of d-Cys, which can be more broadly applicable than that with traditional electrode structures and further advance the field of electrochemical sensors

Density Functional Theory Investigation on Thiophene Hydrodesulfurization Mechanism Catalyzed by ReS₂ (001) Surface

We present density functional theory calculations on the reaction mechanism of thiophene hydrodesulfurization (HDS) over ReS₂ (001) surface under typical HDS reaction conditions. It is found that thiophene adopts an “upright” adsorption configuration with the binding energy of 1.26 eV. Considering the factors such as Bader charge, two reaction mechanisms, named direct desulfurization (DDS) to the product of butadiene and hydrogenation (HYD) to 2-butene, 1-butene, and butane, are systematically investigated. Results show that H prefers to attack thiophenic C before the first C–S bond rupture but begins to hydrogenate S_T (S atom of thiophene) after ring-opening. Prehydrogenation has different effect on the activity of C–S bond breaking. When the ring is intact, it has nominal effect; but when the ring is open, appropriate prehydrogenation can dramatically decrease the energy barrier while complete hydrogenation makes the barrier rise again due to stereohindrance effect. The DDS mechanism is proved to be kinetically unfavorable while 2-butene is suggested to be a predominated product for HYD mechanism. The role of S_a (preadsorbed S) is a “ladder” which helps H approach the thiophenic molecule while S_T acts as an “intermediary” for H exchange. Changing reaction conditions through partial pressure of H₂ can only alter the rate-determining step but has nothing to do with the catalytic selectivity

Povarov Reaction of Cycloiminium Formed in Situ via Hydroamination Cycloisomerization of Homopropargylic Amines with Electron-Rich Olefins

A new, one-pot cascade reaction of homopropargylic amines with electron-rich olefins is developed in the presence of Cu­(OTf)₂ and affords a series of octahydrofuro­[3,2-<i>c</i>]­pyrrolo­[1,2-<i>a</i>]­quinoline derivatives in yields of 38–80%. This reaction proceeds through an intramolecular hydroamination cyclization of homopropargylic amine to generate a highly reactive cycloenamine intermediate in situ that subsequently isomerizes to the cycloiminium cation followed by the Povarov-type reaction with dihydrofuran, dihydropyran, or dihydropyrrole. Notably, the Al₂O₃ additive plays a key role for the effective inhibition of competitive self-dimerization of homoproargylic amines

The cell-cycle assay of keratocytes with or without VPA and VC.

<p>1 mM VPA and 50 ug/ml VC promoted cell-cycle entrance of keratocytes. Difference with P<0.05(*) was considered statistically significant.</p

RT-PCR analysed the expression of keratocan and lumican.

<p>RT-PCR was used to determine the expression of keratocan (206 bp), lumican (176 bp) with GAPDH (202 bp) as an internal control in keratocytes at day 8 of culture. Keratocytes cultured on the carriers of acellular bovine cornea under SMG (A) or on the carriers in static condition (B) expressed abundant amounts of keratocan transcript. However, keratocan not expressed in cells cultured on plastic with or without VPA and VC (C, D). Lumican and GAPDH were expressed in the cells from all groups.</p