Tuning thermally treated graphitic carbon nitride for H₂ evolution and CO₂ photoreduction: The effects of material properties and mid-gap states

Graphitic carbon nitride (g-C3N4) is regarded as an attractive photocatalyst for solar fuel production, i.e., H2 evolution and CO2 photoreduction. Yet, its structural, chemical and optoelectronic properties are very much dependent on the synthesis method and are likely to contribute differently whether H2 evolution or CO2 reduction is considered. Little is known about this aspect making it difficult to tailor g-C3N4 structure and chemistry for a specific photoreaction. Herein, we create g-C3N4 of varying chemical, structural and optical features by applying specific thermal treatments and investigating the effects of the materials properties on solar fuel production. The samples were characterized across scales using spectroscopic, analytical and imaging tools, with particular attention given to the analyses of trap states. In the case of H2 evolution, the reaction is controlled by light absorption and charge separation enabled by the presence of trap states created by N vacancies. In the case of CO2 photoreduction, reactant adsorption appears as a dominating factor. The analyses also suggest that the thermal treatment leads to the formation of trap states located close to the valence band of g-C3N4

Artificial Intelligence Techniques Applied to Electromagnetic Interference Problems Between Power Lines and Metal Pipelines

European ecological regulations meant to protect nature and wild life along with construction cost reduction policies generated a set of government regulations that limit the access to new transmission and distribution corridors. As a result, gas, water or oil supply pipelines are forced to share the same distribution corridors with Electrical Power Lines (EPL), AC Railway Systems or Telecommunication Lines (figure 1)

Photovoltaic Power Plants as a Source of Electromagnetic Interference to Metallic Agricultural Pipelines

AbstractThe electromagnetic interference of power lines to nearby metallic pipelines has been a subject of research for many decades. Usually attention was given to gas or oil pipelines that shared the same rights-off-way with a power line for large distances. However, the recent advancement of renewable energy sources and specifically Photovoltaic (PV) power, due to generous incentives provided in many countries, has resulted in installations of large PV power stations even in agricultural areas. This brought up cases where such power stations in the MWp level, typically connected in medium voltage through buried cables, are located in the vicinity of metallic irrigation pipelines. Under certain conditions, these situations may result in induced voltages and currents on the pipeline that can pose threats to operating personnel. This work presents an analysis of the problems through a quasi-real case study adapted from a real case of a PV power station. The calculation methodology involves a hybrid method that is used in a way to reduced computational time. Results are presented both for normal operating conditions and faults in the power station and may be useful for both agriculture professionals and engineers

Photocatalytic Hydrogen Production: A Rift into the Future Energy Supply

Photocatalytic hydrogen (H2) production is a process that converts solar energy into chemical energy by means of a suitable photocatalyst. After the huge amount of systems that have been tested in the last forty years, the advent of nanotechnology and a careful design at molecular level, allow to obtain attractive activity, even using pure visible light. At the same time we are approaching reasonable photocatalyst stability in laboratory test, and the attention is paid to identify cost-effective photocatalysts that might find real applications. This Review provides a broad overview of the elementary steps of the heterogeneous photocatalytic H2 production, including an outline of the physico-chemical reactions occurring on semiconductors and cocatalysts. The use of different renewable oxygenates as sustainable sacrificial agent for the H2 production is outlined, in view of a transition from fossil fuels to pure water splitting. Finally, the recent advances in the development of photocatalyst are discussed focusing on the current progress in organic and hybrid organic/inorganic photocatalysts

Metal-free dual-phase full organic carbon nanotubes/g-C 3 N 4 heteroarchitectures for photocatalytic hydrogen production

Hydrogen generation from water using solar energy has grown into a promising approach for sustainable energy production. Over the last years, graphitic carbon nitrides (g-C3N4, CN), polymers based on the heptazine-group, have been widely applied as photocatalysts for H2 evolution. The poor charge separation efficiency of CN is considered the major drawback. Here, we investigated the effect of coupling CN with different types of carbon nanotubes on the charge transfer properties and the photocatalytic H2 evolution. We used carbon nanotubes (CNTs) of different wall number (single (SWCNTs), double (DWCNTs) and multi-walled (MWCNTs) CNTs) for the development of full-organic CN based composite photocatalysts. Photoactivity was drastically affected by the content but more importantly by the nature of the CNTs. The SWCNTs functionalized CN composites were the most active presenting approximately 2\u20135 times higher H2 evolution than the corresponding DWCNTs and MWCNTs functionalized CN under both solar and pure visible light irradiation. Photoactivity was primarily controlled by the improved electronic properties linked with the abundance and stability of photogenerated charges as evidenced by electron paramagnetic resonance spectroscopy. Transient absorption spectroscopy verified the transfer of reactive electrons from CN to CNTs. CNTs functioned as electron acceptors improving charge separation. The data suggest that charge transfer is inversely proportional to the wall number of the CNTs and that photoactivity is directly controlled by the size at the nanoscale of the CNTs used. In the CNTs/CN nanocomposites, photogenerated electrons are transferred more efficiently from CN when SWCNTs are used, providing more available electrons for H2 production

VEGF induces signalling and angiogenesis by directing VEGFR2 internalisation via macropinocytosis

Endocytosis plays critical role in receptor signalling. VEGFR2 and its ligand VEGFA are fundamental in neovascularization. Yet, our understanding of the role of endocytosis in VEGFR2 signalling remains limited. Despite the existence of diverse internalisation routes, the only known endocytic pathway of VEGFR2 is the clathrin-mediated. Here, we show that this pathway is the predominant internalisation route of VEGFR2 only in the absence of ligand. Intriguingly, VEGF introduces a novel internalisation itinerary for VEGFR2, the pathway of macropinocytosis, which becomes the prevalent endocytic route of the receptor in the presence of ligand, while the route of clathrin becomes minor. Macropinocytic internalisation of VEGFR2, which mechanistically is mediated via the small GTPase CDC42, takes place via macropinosomes generated at ruffling areas of the membrane. Interestingly, macropinocytosis plays critical role in VEGF-induced signalling, endothelial cell functions in vitro and angiogenesis in vivo, while clathrin-mediated endocytosis is not essential for VEGF signalling. These findings expand our knowledge on the endocytic pathways of VEGFR2 and suggest that VEGF-driven internalisation of VEGFR2 via macropinocytosis is essential for endothelial cell signalling and angiogenesis

Identification of TPM2 and CNN1 as Novel Prognostic Markers in Functionally Characterized Human Colon Cancer-Associated Stromal Cells

Stromal infiltration is associated with poor prognosis in human colon cancers. However, the high heterogeneity of human tumor-associated stromal cells (TASCs) hampers a clear identification of specific markers of prognostic relevance. To address these issues, we established short-term cultures of TASCs and matched healthy mucosa-associated stromal cells (MASCs) from human primary colon cancers and, upon characterization of their phenotypic and functional profiles in vitro and in vivo, we identified differentially expressed markers by proteomic analysis and evaluated their prognostic significance. TASCs were characterized by higher proliferation and differentiation potential, and enhanced expression of mesenchymal stem cell markers, as compared to MASCs. TASC triggered epithelial-mesenchymal transition (EMT) in tumor cells in vitro and promoted their metastatic spread in vivo, as assessed in an orthotopic mouse model. Proteomic analysis of matched TASCs and MASCs identified a panel of markers preferentially expressed in TASCs. The expression of genes encoding two of them, calponin 1 (CNN1) and tropomyosin beta chain isoform 2 (TPM2), was significantly associated with poor outcome in independent databases and outperformed the prognostic significance of currently proposed TASC markers. The newly identified markers may improve prognostication of primary colon cancers and identification of patients at risk