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Journal ArticleDOI

Growth and Stability of Titanium Dioxide Nanoclusters on Graphene/Ru(0001)

TL;DR: The studies demonstrate that highly thermally stable TiOx nanoclusters of controlled composition and morphology can be prepared on Gr supports, and show that cluster ripening proceeds via a Smoluchowski mechanism below 800 K and above 800 K.
Abstract: Titanium dioxide/graphene composites have recently been demonstrated to improve the photocatalytic activity of TiO2 in visible light. To better understand the interactions of TiO2 with graphene we have investigated the growth of TiO2 nanoclusters on single-layer graphene/Ru(0001) using scanning tunneling microscopy (STM) and Auger electron spectroscopy (AES). Deposition of Ti in the O2 background at 300 K resulted in the formation of nanoclusters nucleating on intrinsic defects in the graphene (Gr) layer. The saturation nanocluster density decreased as the substrate temperature was increased from 300 to 650 K, while deposition at 700 K resulted in the significant etching of the Gr layer. We have also prepared nanoclusters with Ti2O3 stoichiometry using lower O2 pressures at 650 K. Thermal stability of the TiO2 nanoclusters prepared at 300 K was evaluated with AES and STM. No change in oxidation state for the TiO2 nanoclusters or etching of the Gr layer was observed up to ∼900 K. Annealing studies revealed...
Citations
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Journal ArticleDOI
TL;DR: Mechanistic information is provided that can be applied to organotin EUV photoresists, where a significant increase in photoresist sensitivity may be obtained by varying the ambient conditions during EUV exposures.
Abstract: Organotin photoresists have shown promise for next-generation lithography because of their high extreme ultraviolet (EUV) absorption cross sections, their radiation sensitive chemistries, and their ability to enable high-resolution patterning. To better understand both temperature- and radiation-induced reaction mechanisms, we have studied a model EUV photoresist, which consists of a charge-neutral butyl-tin cluster. Temperature-programmed desorption (TPD) showed very little outgassing of the butyl-tin resist in ultrahigh vacuum and excellent thermal stability of the butyl groups. TPD results indicated that decomposition of the butyl-tin resist was first order with a fairly constant decomposition energy between 2.4 and 3.0 eV, which was determined by butyl group desorption. Electron-stimulated desorption (ESD) showed that butyl groups were the primary decomposition product for electron kinetic energies expected during EUV exposures. X-ray photoelectron spectroscopy was performed before and after low-energy electron exposure to evaluate the compositional and chemical changes in the butyl-tin resists after interaction with radiation. The effect of molecular oxygen during ESD experiments was evaluated, and it was found to enhance butyl group desorption during exposure and resulted in a significant increase in the ESD cross section by over 20%. These results provide mechanistic information that can be applied to organotin EUV photoresists, where a significant increase in photoresist sensitivity may be obtained by varying the ambient conditions during EUV exposures.

35 citations

Journal ArticleDOI
12 Jul 2018
TL;DR: A mild, inexpensive, and general photocatalytic initiation protocol for anti-Markovnikov hydrothiolation of olefins using carbon nanomaterial/metal oxide (carbon NM-MO) composites is reported in this paper.
Abstract: A mild, inexpensive, and general photocatalytic initiation protocol for anti-Markovnikov hydrothiolation of olefins using carbon nanomaterial/metal oxide (carbon NM-MO) composites is reported Graphene oxide (GO), nanodiamonds (ND), and carbon nano-onions (CNO) displaying bismuth or tungsten oxide nanoparticles adhered to the surface and function as highly efficient photocatalysts for thiol–ene ligation under both UV and visible-light-mediated conditions The straightforward catalyst preparation, excellent overall yields, ease of purification, and broad substrate scope render this a highly versatile method for bioconjugation

16 citations

Journal ArticleDOI
TL;DR: In this paper, the authors demonstrate the epitaxial growth of polycrystalline cubic Cu films on single-crystal monolayer graphene using thermal evaporation at an elevated substrate temperature of 250 °C.
Abstract: Quasi van der Waals epitaxial growth of face-centered cubic Cu (~100 nm) thin films on single-crystal monolayer graphene is demonstrated using thermal evaporation at an elevated substrate temperature of 250 °C The single-crystal graphene was transferred to amorphous (glass) and crystalline (quartz) SiO2 substrates for epitaxy study Raman analysis showed that the thermal evaporation method had minimal damage to the graphene lattice during the Cu deposition X-ray diffraction and electron backscatter diffraction analyses revealed that both Cu films are single-crystal with (1 1 1) out-of-plane orientation and in-plane Σ3 twin domains of 60° rotation The crystallinity of the SiO2 substrates has a negligible effect on the Cu crystal orientation during the epitaxial growth, implying the strong screening effect of graphene We also demonstrate the epitaxial growth of polycrystalline Cu on a commercial polycrystalline monolayer graphene consisting of two orientation domains offset 30° to each other It confirms that the crystal orientation of the epitaxial Cu film follows that of graphene, ie the Cu film consists of two orientation domains offset 30° to each other when deposited on polycrystalline graphene Finally, on the contrary to the report in the literature, we show that the direct current and radio frequency flip sputtering method causes significant damage to the graphene lattice during the Cu deposition process, and therefore neither is a suitable method for Cu epitaxial growth on graphene

9 citations

Journal ArticleDOI
01 Feb 2020-Carbon
TL;DR: In this paper, the photocatalytic activity of titania nanoparticles deposited on epitaxial graphene is proven to be significantly affected by the substrate on which graphene is supported, and it has been revealed that the addition of a two-dimensional TiO1.5 layer sandwiched between graphene and the supporting metal induces a p-doping of graphene itself and a consistent shift in the Ti d states.

8 citations

References
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Journal ArticleDOI
TL;DR: The origins, challenges and solutions of NIH Image and ImageJ software are discussed, and how their history can serve to advise and inform other software projects.
Abstract: For the past 25 years NIH Image and ImageJ software have been pioneers as open tools for the analysis of scientific images. We discuss the origins, challenges and solutions of these two programs, and how their history can serve to advise and inform other software projects.

44,587 citations

Journal ArticleDOI
24 Oct 1991-Nature
TL;DR: In this article, the authors describe a photovoltaic cell, created from low-to medium-purity materials through low-cost processes, which exhibits a commercially realistic energy-conversion efficiency.
Abstract: THE large-scale use of photovoltaic devices for electricity generation is prohibitively expensive at present: generation from existing commercial devices costs about ten times more than conventional methods1. Here we describe a photovoltaic cell, created from low-to medium-purity materials through low-cost processes, which exhibits a commercially realistic energy-conversion efficiency. The device is based on a 10-µm-thick, optically transparent film of titanium dioxide particles a few nanometres in size, coated with a monolayer of a charge-transfer dye to sensitize the film for light harvesting. Because of the high surface area of the semiconductor film and the ideal spectral characteristics of the dye, the device harvests a high proportion of the incident solar energy flux (46%) and shows exceptionally high efficiencies for the conversion of incident photons to electrical current (more than 80%). The overall light-to-electric energy conversion yield is 7.1-7.9% in simulated solar light and 12% in diffuse daylight. The large current densities (greater than 12 mA cm-2) and exceptional stability (sustaining at least five million turnovers without decomposition), as well as the low cost, make practical applications feasible.

26,457 citations

Journal ArticleDOI
TL;DR: In this article, the authors focus on interfacial processes and summarize some of the operating principles of heterogeneous photocatalysis systems, including the electron transfer and energy transfer processes in photocatalytic reactions.
Abstract: In 1972, Fujishima and Honda discovered the photocatalytic splitting of water on TiO{sub 2} electrodes. This event marked the beginning of a new era in heterogeneous photocatalysis. Since then, research efforts in understanding the fundamental processes and in enhancing the photocatalytic efficiency of TiO{sub 2} have come from extensive research performed by chemists, physicists, and chemical engineers. Such studies are often related to energy renewal and energy storage. In recent years, applications to environmental cleanup have been one of the most active areas in heterogeneous photocatalysis. This is inspired by the potential application of TiO{sub 2}-based photocatalysts for the total destruction of organic compounds in polluted air and wastewaters. There exists a vast body of literature dealing with the electron transfer and energy transfer processes in photocatalytic reactions. A detailed description of these processes is beyond the scope of this review. Here, the authors tend to focus on interfacial processes and to summarize some of the operating principles of heterogeneous photocatalysis. In section 2, the authors first look at the electronic excitation processes in a molecule and in a semiconductor substrate. The electronic interaction between the adsorbate molecule and the catalyst substrate is discussed in terms of the catalyzed ormore » sensitized photoreactions. In section 3, thermal and photocatalytic studies on TiO{sub 2} are summarized with emphasis on the common characteristics and fundamental principles of the TiO{sub 2}-based photocatalysis systems. In section 4, they address the research effort in the electronic modification of the semiconductor catalysts and its effect on the photocatalytic efficiency. Several representative examples will be presented including the Schottky barrier formation and modification at metal-semiconductor interfaces. Some concluding remarks and future research directions will be given in the final section. 160 refs.« less

10,719 citations

Journal ArticleDOI
Ulrike Diebold1
TL;DR: Titanium dioxide is the most investigated single-crystalline system in the surface science of metal oxides, and the literature on rutile (1.1) and anatase surfaces is reviewed in this paper.

7,056 citations

Journal ArticleDOI
TL;DR: The most relevant features of WSXM, a freeware scanning probe microscopy software based on MS-Windows, are described and some relevant procedures of the software are carried out.
Abstract: In this work we briefly describe the most relevant features of WSXM, a freeware scanning probe microscopy software based on MS-Windows. The article is structured in three different sections: The introduction is a perspective on the importance of software on scanning probe microscopy. The second section is devoted to describe the general structure of the application; in this section the capabilities of WSXM to read third party files are stressed. Finally, a detailed discussion of some relevant procedures of the software is carried out.

6,996 citations