Band bending in semiconductors: chemical and physical consequences at surfaces and interfaces.

The formation of semiconductor composites comprising multicomponent or multiphase heterojunctions is a very effective strategy to design highly active photocatalyst systems. This review summarizes the recent strategies to develop such composites, and highlights the most recent developments in the fi eld. After a general introduction into the different strategies to improve photocatalytic activity through formation of heterojunctions, the three different types of heterojunctions are introduced in detail, followed by a historical introduction to semiconductor heterojunction systems and a thorough literature overview. Special chapters describe the highly-investigated carbon nitride heterojunctions as well as very recent developments in terms of multiphase heterojunction formation, including the latest insights into the anatase-rutile system. When carefully designed, semiconductor composites comprising two or three different materials or phases very effectively facilitate charge separation and charge carrier transfer, substantially improving photocatalytic and photoelectrochemical effi ciency.

https://faculty.missouri.edu/~glaserr/3700s15/Marschall_Strategies_adfm201303214.pdf

Semiconductor Composites: Strategies for Enhancing Charge Carrier Separation to Improve Photocatalytic Activity

Medical device-associated infections account for a large proportion of hospital-acquired infections. A variety of opportunistic pathogens can cause implant infections, depending on the type of the implant and on the anatomical site of implantation. The success of these versatile pathogens depends on rapid adhesion to virtually all biomaterial surfaces and survival in the hostile host environment. Biofilm formation on implant surfaces shelters the bacteria and encourages persistence of infection. Furthermore, implant-infecting bacteria can elude innate and adaptive host defences as well as biocides and antibiotic chemotherapies. In this Review, we explore the fundamental pathogenic mechanisms underlying implant infections, highlighting orthopaedic implants and Staphylococcus aureus as a prime example, and discuss innovative targets for preventive and therapeutic strategies.

Implant infections: adhesion, biofilm formation and immune evasion

Titanium dioxide (TiO2) has been the most intensively investigated binary transition metal oxide in the past four decades as indicated by Figure S1. Furthermore, the annual number of papers published on TiO2 has seen a continuous increase, particularly since the beginning of this century (Figure S2). This is understandable when one considers the wide range of applications of TiO2 from the conventional areas (i.e., pigment, cosmetic, toothpaste, and paint) to the later developed functional areas such as photoelectrochemical cell,(1-3) dye-sensitized solar cells (DSSCs),(4-11) photocatalysis,(12-24) catalysis,(25-31) photovoltaic cell,(32-34) lithium ion batteries,(35-41) sensors,(42-46) electron field emission,(47-51) microwave absorbing material, biomimetic growth, and biomedical treatments.(52-57) Nearly all these functional applications of TiO2 fall in the scope of energy, environment, and health, which are definitely the three most important and challenging themes facing the Human race that need to be addressed in this century. Besides the apparent merits including nontoxicity, elemental abundance, good chemical stability, and easy synthesis, TiO2 has attracted strong research interest worldwide due to its physicochemical properties for realizing various functions.(15, 58, 59) Especially, very encouraging progresses in photocatalysis and DSSCs with the involvement of TiO2 have greatly stimulated the rapid development of TiO2 crystals with controllable phase, size, shape, defect, and heteroatom.(58, 60-68)

Titanium dioxide crystals with tailored facets

Lixia Sang,† Yixin Zhao,‡ and Clemens Burda* †Key Laboratory of Enhanced Heat Transfer and Energy Conservation, Ministry of Education and Key Laboratory of Heat Transfer and Energy Conversion, Beijing Municipality, College of Environmental and Energy Engineering, Beijing University of Technology, Beijing 100124, China ‡School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China Center for Chemical Dynamics and Nanomaterials Research, Department of Chemistry, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio 44106, United States

TiO2 nanoparticles as functional building blocks.

In 1991, Bickley et al. proposed a synergetic effect between anatase and rutile in Degussa P25. Since then, there has been an intensive debate about the correctness of this proposal, the origin of the synergism, and the right polymorph composition. However, a comparison of pure titanium dioxide samples with various anatase-to-rutile ratios, but otherwise identical properties, is missing. In this paper, we report about a series of utterly pure, highly porous titanium dioxide films with identical grain sizes, surface areas, and crystallinity, but varying polymorph compositions. Photocatalytic oxidation of methylene blue was utilized to investigate the influence of the anatase-to-rutile ratio on the photoreactivity. We clearly observe the synergetic effect within a well-defined range of anatase-to-rutile ratios. A film with ∼60% anatase and ∼40% rutile exhibits optimal performance at a 50% improved activity compared with pure anatase.

How the Anatase-to-Rutile Ratio Influences the Photoreactivity of TiO2

Very high lateral ionic conductivities in epitaxial cubic yttria-stabilized zirconia (YSZ) synthesized on single-crystal SrTiO3and MgO substrates by reactive direct current magnetron sputtering are reported. Superionic conductivities (i.e., ionic conductivities of the order similar to 1 Omega(-1)cm(-1)) are observed at 500 degrees C for 58-nm-thick films on MgO. The results indicate a superposition of two parallel contributions - one due to bulk conductivity and one attributable to conduction along the film substrate interface. Interfacial effects dominate the conductivity at low temperatures (andlt;350 degrees C), showing more than three orders of magnitude enhancement compared to bulk YSZ. At higher temperatures, a more bulk-like conductivity is observed. The films have a negligible grain-boundary network, thus ruling out grain boundaries as a pathway for ionic conduction. The observed enhancement in lateral ionic conductivity is caused by a combination of misfit dislocation density and elastic strain in the interface. These very high ionic conductivities in the temperature range 150-500 degrees C are of great fundamental importance but may also be technologically relevant for low-temperature applications.

/pdf/low-temperature-superionic-conductivity-in-strained-yttria-58pzrd1uao.pdf

Low‐Temperature Superionic Conductivity in Strained Yttria‐Stabilized Zirconia

Accelerated bone ingrowth by local delivery of strontium from surface functionalized titanium implants.

α-Cr2O3 template-texture effect on α-Al2O3 thin-film growth

http://liu.diva-portal.org/smash/get/diva2:325579/FULLTEXT01.pdf

M. Sillassen

Papers

How the Anatase-to-Rutile Ratio Influences the Photoreactivity of TiO2

Low‐Temperature Superionic Conductivity in Strained Yttria‐Stabilized Zirconia

Accelerated bone ingrowth by local delivery of strontium from surface functionalized titanium implants.

α-Cr2O3 template-texture effect on α-Al2O3 thin-film growth

Texture and microstructure of Cr2O3 and (Cr,Al)2O3 thin films deposited by reactive inductively coupled plasma magnetron sputtering