Ligand‐triggered self‐assembly of flexible carbon dot nanoribbons for optoelectronic memristor devices and neuromorphic computing

Carbon dots (CDs) are widely utilized in sensing, energy storage, and catalysis due to their excellent optical, electrical and semiconducting properties. However, attempts to optimize their optoelectronic performance through high-order manipulation have met with little success to date. In this study, through efficient packing of individual CDs in two-dimensions, the synthesis of flexible CDs ribbons is demonstrated technically. Electron microscopies and molecular dynamics simulations, show the assembly of CDs into ribbons results from the tripartite balance of π–π attractions, hydrogen bonding, and halogen bonding forces provided by the superficial ligands. The obtained ribbons are flexible and show excellent stability against UV irradiation and heating. CDs ribbons offer outstanding performance as active layer material in transparent flexible memristors, with the developed devices providing excellent data storage, retention capabilities, and fast optoelectronic responses. A memristor device with a thickness of 8 µm shows good data retention capability even after 104 cycles of bending. Furthermore, the device functions effectively as a neuromorphic computing system with integrated storage and computation capabilities, with the response speed of the device being less than 5.5 ns. These properties create an optoelectronic memristor with rapid Chinese character learning capability. This work lays the foundation for wearable artificial intelligence

Insights into the function of silver as an oxidation catalyst by ab initio, atomistic thermodynamics

To help understand the high activity of silver as an oxidation catalyst, e.g., for the oxidation of ethylene to epoxide and the dehydrogenation of methanol to formaldehyde, the interaction and stability of oxygen species at the Ag(111) surface has been studied for a wide range of coverages. Through calculation of the free energy, as obtained from density-functional theory and taking into account the temperature and pressure via the oxygen chemical potential, we obtain the phase diagram of O/Ag(111). Our results reveal that a thin surface-oxide structure is most stable for the temperature and pressure range of ethylene epoxidation and we propose it (and possibly other similar structures) contains the species actuating the catalysis. For higher temperatures, low coverages of chemisorbed oxygen are most stable, which could also play a role in oxidation reactions. For temperatures greater than about 775 K there are no stable oxygen species, except for the possibility of O atoms adsorbed at under-coordinated surface sites Our calculations rule out thicker oxide-like structures, as well as bulk dissolved oxygen and molecular ozone-like species, as playing a role in the oxidation reactions.Comment: 15 pages including 9 figures, Related publications can be found at http://www.fhi-berlin.mpg.de/th/paper.htm

Sub-surface Oxygen and Surface Oxide Formation at Ag(111): A Density-functional Theory Investigation

To help provide insight into the remarkable catalytic behavior of the oxygen/silver system for heterogeneous oxidation reactions, purely sub-surface oxygen, and structures involving both on-surface and sub-surface oxygen, as well as oxide-like structures at the Ag(111) surface have been studied for a wide range of coverages and adsorption sites using density-functional theory. Adsorption on the surface in fcc sites is energetically favorable for low coverages, while for higher coverage a thin surface-oxide structure is energetically favorable. This structure has been proposed to correspond to the experimentally observed (4x4) phase. With increasing O concentrations, thicker oxide-like structures resembling compressed Ag2O(111) surfaces are energetically favored. Due to the relatively low thermal stability of these structures, and the very low sticking probability of O2 at Ag(111), their formation and observation may require the use of atomic oxygen (or ozone, O3) and low temperatures. We also investigate diffusion of O into the sub-surface region at low coverage (0.11 ML), and the effect of surface Ag vacancies in the adsorption of atomic oxygen and ozone-like species. The present studies, together with our earlier investigations of on-surface and surface-substitutional adsorption, provide a comprehensive picture of the behavior and chemical nature of the interaction of oxygen and Ag(111), as well as of the initial stages of oxide formation.Comment: 17 pages including 14 figures, Related publications can be found at http://www.fhi-berlin.mpg.de/th/paper.htm

Offshore accident and incident statistics report 1997 (provisional data)

Report also numbered as OIAC 97/24Available from British Library Document Supply Centre-DSC:6244.385(97/951) / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo

Hydrogen production by tuning the photonic band gap with the electronic band gap of TiO2

Tuning the photonic band gap (PBG) to the electronic band gap (EBG) of Au/TiO2 catalysts resulted in considerable enhancement of the photocatalytic water splitting to hydrogen under direct sunlight. Au/TiO2 (PBG-357 nm) photocatalyst exhibited superior photocatalytic performance under both UV and sunlight compared to the Au/TiO2 (PBG-585 nm) photocatalyst and both are higher than Au/TiO2 without the 3 dimensionally ordered macro-porous structure materials. The very high photocatalytic activity is attributed to suppression of a fraction of electron-hole recombination route due to the co-incidence of the PBG with the EBG of TiO2 These materials that maintain their activity with very small amount of sacrificial agents (down to 0.5 vol.% of ethanol) are poised to find direct applications because of their high activity, low cost of the process, simplicity and stability.Peer Reviewe

Ethanol photoreaction to Hydrogen over Au/TiO(2) catalysts: Effect of Au particle size and TiO(2) bulk structure

Solar hydrogen production from renewables such as ethanol and water is potentially a key means of fuel generation either for direct combustion or to power fuel cells. To achieve this few methods are possible among them are those involving photocatalytic processes on semiconductor materials due to the simplicity of the concept and its technical feasibility. However, no materials have been found, to date, that can be used for this process. Among the most promising photo-catalysts are those composed of TiO2 based material in presence of a transition metal such as Au or Pd because of the simplicity of their structure and the present industrial knowledge. Gold catalysts with finite nanoparticle size have been found to be very active for specific reactions in dark conditions such as CO oxidation , . Yet, their potential as active materials for photoreactions has only received sporadic attention , , , and considerable work is needed because the size of Au, the size of the TiO2 particulate support and the nature of TiO2 can each, in turn, influence the photo-reaction rate. The rate of H2 production from water is so far very small to be used as a model system for materials study. Alcohol are known however to act as hole scavengers and when used in the appropriate environment (i.e., in presence of only traces of O2 as in the liquid phase) can be used in a systematic way to test for materials properties and help the design of the better photo-catalysts. We have opted for ethanol as an alternative feedstock to methanol for two main reasons. Firstly, ethanol is produced from renewable sources and secondly it is a realistic prototype for larger molecules as it has a carbon-carbon bond and thus serves as a prototype for larger organic compounds. In this work we are focusing on the effect of TiO2 polymorphs and size while keeping the Au particle size constant in order to extract information on the reaction rate. In addition we compare the effect of the polymorph of TiO2: Anatase and rutile separately and together.Preprin

Ethanol photoreaction to Hydrogen over Au/TiO(2) catalysts: Effect of Au particle size and TiO(2) bulk structure

Solar hydrogen production from renewables such as ethanol and water is potentially a key means of fuel generation either for direct combustion or to power fuel cells. To achieve this few methods are possible among them are those involving photocatalytic processes on semiconductor materials due to the simplicity of the concept and its technical feasibility. However, no materials have been found, to date, that can be used for this process. Among the most promising photo-catalysts are those composed of TiO2 based material in presence of a transition metal such as Au or Pd because of the simplicity of their structure and the present industrial knowledge. Gold catalysts with finite nanoparticle size have been found to be very active for specific reactions in dark conditions such as CO oxidation , . Yet, their potential as active materials for photoreactions has only received sporadic attention , , , and considerable work is needed because the size of Au, the size of the TiO2 particulate support and the nature of TiO2 can each, in turn, influence the photo-reaction rate. The rate of H2 production from water is so far very small to be used as a model system for materials study. Alcohol are known however to act as hole scavengers and when used in the appropriate environment (i.e., in presence of only traces of O2 as in the liquid phase) can be used in a systematic way to test for materials properties and help the design of the better photo-catalysts. We have opted for ethanol as an alternative feedstock to methanol for two main reasons. Firstly, ethanol is produced from renewable sources and secondly it is a realistic prototype for larger molecules as it has a carbon-carbon bond and thus serves as a prototype for larger organic compounds. In this work we are focusing on the effect of TiO2 polymorphs and size while keeping the Au particle size constant in order to extract information on the reaction rate. In addition we compare the effect of the polymorph of TiO2: Anatase and rutile separately and together

Ethanol photoreaction to Hydrogen over Au/TiO(2) catalysts: Effect of Au particle size and TiO(2) bulk structure

Solar hydrogen production from renewables such as ethanol and water is potentially a key means of fuel generation either for direct combustion or to power fuel cells. To achieve this few methods are possible among them are those involving photocatalytic processes on semiconductor materials due to the simplicity of the concept and its technical feasibility. However, no materials have been found, to date, that can be used for this process. Among the most promising photo-catalysts are those composed of TiO2 based material in presence of a transition metal such as Au or Pd because of the simplicity of their structure and the present industrial knowledge. Gold catalysts with finite nanoparticle size have been found to be very active for specific reactions in dark conditions such as CO oxidation , . Yet, their potential as active materials for photoreactions has only received sporadic attention , , , and considerable work is needed because the size of Au, the size of the TiO2 particulate support and the nature of TiO2 can each, in turn, influence the photo-reaction rate. The rate of H2 production from water is so far very small to be used as a model system for materials study. Alcohol are known however to act as hole scavengers and when used in the appropriate environment (i.e., in presence of only traces of O2 as in the liquid phase) can be used in a systematic way to test for materials properties and help the design of the better photo-catalysts. We have opted for ethanol as an alternative feedstock to methanol for two main reasons. Firstly, ethanol is produced from renewable sources and secondly it is a realistic prototype for larger molecules as it has a carbon-carbon bond and thus serves as a prototype for larger organic compounds. In this work we are focusing on the effect of TiO2 polymorphs and size while keeping the Au particle size constant in order to extract information on the reaction rate. In addition we compare the effect of the polymorph of TiO2: Anatase and rutile separately and together

Evolution of thiolate-stabilized Ag nanoclusters from Ag-thiolate cluster intermediates

10.1038/s41467-018-04837-xNature Communications91237