The Nanopore Electrode

The fabrication and electrochemical characterization of truncated cone-shaped nanopore electrodes are reported. A nanopore electrode is a Pt disk electrode embedded at the bottom of a conical pore, the circular orifice of the pore having nanometer dimensions. The electrochemical properties of nanopore electrodes with orifice radii of 39 and 74 nm are presented. Both the steady-state and transient voltammetric behavior of the nanopore electrode are reported and compared to predictions obtained using finite-element simulations. The truncated cone-shaped pore electrode possesses a unique transport propertythe steady-state flux of molecules into a deep pore is limited by the restriction near the pore orifice, and thus, the steady-state current is independent of the pore depth. This characteristic is potentially useful in studying transport through nanometer-scale orifices

Steady-State Voltammetric Response of the Nanopore Electrode

The steady-state voltammetric response of the truncated conical-shaped glass nanopore electrode is presented. Analytical theory, finite-element simulations, and experimental measurement of the diffusive flux of a redox molecule through the pore orifice demonstrate that the steady-state current decreases rapidly as the pore depth increases and then asymptotically approaches a constant value when the pore depth is ∼50× larger than the pore orifice. The asymptotic limit of the steady-sate current is only a function of the pore orifice radius and the cone angle of the pore and has a finite value for all cone angles greater than zero. Experimental confirmation of the predicted dependence on pore depth is obtained using nanopore electrodes with 100−1000 nm orifice radii, by measuring the steady-state voltammetric current corresponding to the oxidation of ferrocene in acetonitrile solutions containing an excess of supporting electrolyte

Biological nitrogen fixation is mainly determined by <i>Nostocales</i> and correlates negatively to diazotrophic community evenness in rice paddy soils.

Biological nitrogen fixation (BNF) is carried out by diazotrophs and makes great contributions to maintaining paddy soil fertility. However, the linkage between diazotrophs and BNF in paddy soil is still unclear. In this study, twenty-seven paddy soil samples were collected from the southwest to the northeast in China. These soils with rice planting were incubated in a 15N2 enriched growth chamber to measure BNF amounts. After incubation, the diazotrophic and bacterial communities in 0–1 cm soil were measured by high-throughput sequencing of nifH and 16s rRNA genes. Results showed that the BNF amounts ranged from 0.66 to 12.36 kg ha-1 during the 77-days labelling period. The variation of BNF mainly came from 0–1 cm surface soil. The BNF amounts in 0–1 cm soil moved little downward to the 1–15cm soil. BNF amounts had a significant positive relationship with the difference between the relative abundance of cyanobacteria measured by the nifH gene and that by 16s rRNA gene but had no significant relationship with their relative abundances separately. The relative abundance of Nostocales assigned by 16s rRNA or nifH gene had significant positive correlation with BNF amounts in 0–1 cm. BNF amounts in 0-1cm soils were negatively correlated with diazotrophic community evenness. These results indicated that Nostocales determined the BNF, and higher BNF could result in a more uneven diazotrophic community in paddy soil.</p

Biological nitrogen fixation in rice paddy soils is driven by multiple edaphic factors and available phosphorus is the greatest contributor

 Various sole edaphic factor has been screened as controlling factor for paddy biological nitrogen fixation (BNF), however, no single factor can interpret different results from different experiments. Paddy BNF might be influenced by several factors simultaneously at various degrees, but we still lack a model to predict BNF as a function of multiple edaphic factors. Developing this model will help us to estimate BNF based on soil properties and improve policy decisions to enhance paddy BNF. In this paper, 27 paddy soil samples with different soil properties were collected from the southwest to the northeast in China. These soils with rice plantations were incubated for 77 days in an airtight, transparent, and 15N2 enriched growth chamber to measure BNF. Results showed that BNF amounts ranged from 0.66 to 12.3 kg ha-1 and had a lognormal distribution. A multiplicative model was developed, the R code and raw data were deposited in this project. This multiplicative model could explain 86% variance of the BNF in various soils. In each site, the controlling factors were screened and corresponding measures to enhance BNF were proposed. Our study provided a systematic framework on how BNF responded to a range of edaphic factors simultaneously in paddy soils, and this work might also give inspiration for the study of other ecological functions. </p

Highly Efficient, Mild, Bromide-Free and Acetic Acid-Free Dioxygen Oxidation of <i>p</i>-Nitrotoluene to <i>p</i>-Nitrobenzoic Acid with Metal Phthalocyanine Catalysts

Four metal tetracarboxyl phthalocyanines were synthesized and characterized by elemental analysis and mass spectrometry. p-Nitrobenzoic acid was efficiently prepared in high yield from bromide-free and acetic acid-free aerobic oxidation of p-nitrotoluene using metal phthalocyanines as catalysts under mild conditions in alkali−methanol solution. Up to 88.8% isolated yield of p-nitrobenzoic acid was obtained with the catalysis of tetracarboxyl phthalocyanine cobalt (0.13 mol %, based on the moles of p-nitrotoluene) optionally combined with a small amount of dimethylformamide in the presence of 2.0 MPa dioxygen at 30−60 °C. The effect on catalytic performance of a carboxyl group introduced into the phthalocyanine ring was further discussed on the basis of metal coordination chemistry theory

Graphene Transforms Wide Band Gap ZnS to a Visible Light Photocatalyst. The New Role of Graphene as a Macromolecular Photosensitizer

We report the assembly of nanosized ZnS particles on the 2D platform of a graphene oxide (GO) sheet by a facile two-step wet chemistry process, during which the reduced graphene oxide (RGO, also called GR) and the intimate interfacial contact between ZnS nanoparticles and the GR sheet are achieved simultaneously. The ZnS–GR nanocomposites exhibit visible light photoactivity toward aerobic selective oxidation of alcohols and epoxidation of alkenes under ambient conditions. In terms of structure–photoactivity correlation analysis, we for the first time propose a new photocatalytic mechanism where the role of GR in the ZnS–GR nanocomposites acts as an organic dye-like macromolecular “photosensitizer” for ZnS instead of an electron reservoir. This novel photocatalytic mechanism is distinctly different from all previous research on GR–semiconductor photocatalysts, for which GR is claimed to behave as an electron reservoir to capture/shuttle the electrons photogenerated from the semiconductor. This new concept of the reaction mechanism in graphene–semiconductor photocatalysts could provide a new train of thought on designing GR-based composite photocatalysts for targeting applications in solar energy conversion, promoting our in-depth thinking on the microscopic charge carrier transfer pathway connected to the interface between the GR and the semiconductor

Tuning the Optical Property and Photocatalytic Performance of Titanate Nanotube toward Selective Oxidation of Alcohols under Ambient Conditions

Titanate nanotube (TNT) represents one class of novel one-dimensional semiconducting nanomaterials that can be used as photocatalyst for given applications. However, TNT is only UV-light photoactive because of its intrinsic limitation of light absorption in the UV region. Here, we report a facile approach to tune the optical property and photocatalytic performance of TNT by doping various metal ions (Cu²⁺, Co²⁺, Ni²⁺, Fe²⁺, and Mn²⁺) via an ion-exchange method in an aqueous phase. The optical properties of TNT can be finely tuned by incorporating different kinds of metal ions into its tubular framework. In particular, the incorporation of metal ions into the matrix of TNT is able to extend its light absorption to the visible-light region, thus making TNT have the visible-light photoactivity. Activity testing on photocatalytic selective oxidation of a variety of benzylic and allylic alcohols under mild conditions demonstrates that these metal-ion-doped TNTs exhibit markedly enhanced catalytic performance as compared to the undoped TNTs under both the irradiation of UV light and visible light. Such an enhancement of photocatalytic activity with regard to metal-ion-doped TNT is primarily attributed to the prolonged lifetime of photogenerated electron–hole pairs in comparison with that of undoped TNT. Our current research work demonstrates the tunable optical property of TNT by doping metal ions and, more significantly, opens promising prospects of one-dimensional nanotubular TNT or TNT-based materials as visible-light-driven photocatalyst in the area of selective transformation using molecular oxygen as benign oxidant under ambient conditions

A Unique Silk Mat-Like Structured Pd/CeO₂ as an Efficient Visible Light Photocatalyst for Green Organic Transformation in Water

The charm embedded in nature is its inherent power to create a myriad of materials, for example, a spider web and lotus leaf, with ordinary composition but exhibiting fascinating functional property owing to their unique structures. Such intricate natural designs inspire immense research in synthesizing materials with controlled structure and morphology toward achieving novel or enhanced properties for target applications. Herein, we report a rotary vacuum evaporation and support-driven nanoassembly of tiny Pd noble metal particles on nanosized CeO₂, which features a remarkable unique silk “mat-like” morphology with significant anti-aggregation of Pd nanoparticles during a high temperature calcination process, whereas the obvious aggregation phenomenon of Pd nanoparticles occurs when using commercial CeO₂ as a support. This nanocomposite with unique structural and morphology composition is able to act as a highly selective and active visible light photocatalyst toward organic redox transformations in water, including aerobic oxidation of alcohols and anaerobic reduction of nitro-compounds under ambient conditions, representing a typical tenet of photocatalytic green chemistry

Graphene Oxide as a Surfactant and Support for In-Situ Synthesis of Au–Pd Nanoalloys with Improved Visible Light Photocatalytic Activity

Traditional ways for the synthesis of bimetallic alloyed nanoparticles involve successive or simultaneous reduction of metallic precursors either in an organic solvent phase or in an aqueous phase. However, these two approaches generally require the use of surfactants or polymers, dendrimers, or ligands as protecting or capping agents in order to achieve stable colloidal bimetallic nanoalloys for potential use, for example, loading them onto supports as heterogeneous catalysts. Here, we report the direct synthesis of stabilizing-molecules-free bimetallic Au–Pd nanoalloys promoted by graphene oxide (GO) in an aqueous phase. Formation of Au–Pd nanoalloys and loading onto the reduced GO (denoted as GR) are accomplished simultaneously. Controlled experiments suggest that GO vividly acts as a unique “solution processable macromolecular surfactant” and 2D “flat-mat” support to promote formation and loading of alloyed Au–Pd bimetallic nanoparticles onto the GR sheet. The as-formed Au–Pd/GR exhibits higher photocatalytic activity than both monometallic Au/GR and Pd/GR, prepared by the same approach toward degradation of dye, Rhodamine B (RhB), which thus demonstrates the promising potential of bimetallic nanoalloys rather than the monometallic one in promoting visible light photocatalysis. It is anticipated that our work could boost further interest for harnessing the versatile soft materials features of GO in solution to synthesize other bimetallic alloy catalysts and exploring their applications in photocatalysis

Table1_Neonatal cholestasis as the onset symptom of McCune–Albright syndrome: case reports and a literature review.pdf

AimThis study aimed to summarize and show the characteristics and evolutionary process of neonatal cholestasis caused by McCune–Albright syndrome (MAS), as neonatal cholestasis may be the initial manifestation of MAS before other classic clinical features appear.MethodsThe clinical characteristics, treatment methods, and outcomes of three neonatal cholestasis cases caused by MAS in our center were retrospectively studied. In addition, all the reported cases of MAS combined with cholestasis were reviewed and summarized to show the cholestatic features in them.ResultsWe have confirmed three MAS cases in our center, presenting onset symptoms of jaundice, pale stool, and neonatal cholestasis soon after birth. The cholestasis subsided spontaneously at around the sixth month. The literature review showed that the levels of total bilirubin, conjugated bilirubin, ALT, AST, and GGT in neonatal MAS cholestasis cases were 207 μmol/L (range 65–445 μmol/L), 162 μmol/L (range 46–412 μmol/L), 821 U/L (range 85–3,597 U/L), 532 U/L (range 127–3,633 U/L), and 244 U/L (range 79–3,800 U/L), respectively. Liver histology showed canalicular and hepatocellular cholestasis, giant hepatic cell transformation, and bile paucity. Extrahepatic manifestations such as café-au-lait pigmented skin lesions, Cushing's syndrome, hyperthyroidism, renal tubular dysfunction, and skeletal abnormalities could occur simultaneously when jaundice occurred. GNAS mutations had a high positive rate (83.3%–100%) in liver tissue with cholestasis. Neonatal cholestasis caused by MAS could be self-resolved, but hepatic lesions persist and have malignant potential.ConclusionMAS can be one of the causes of neonatal cholestasis, which may be the first manifestation of the disease. Extrahepatic coexisting symptoms of MAS and liver histology can help to distinguish MAS from other etiology of cholestasis. Detecting GNAS mutations in liver tissue may shorten diagnostic time and is of particular interest in the partial and atypical forms of MAS with neonatal cholestasis. Neonatal cholestasis in children with MAS can self-resolve, but liver dysfunction and malignant lesions persist.</p