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ACS Applied Materials & Interfaces Mar 2013Photocatalysis is a promising advanced water treatment technology, and recently the possibility of using hydrogenation to improve the photocatalytic efficiency of...
Photocatalysis is a promising advanced water treatment technology, and recently the possibility of using hydrogenation to improve the photocatalytic efficiency of titanium dioxide has generated much research interest. Herein we report that the use of high-temperature hydrogenation to prepare black TiO2 primarily results in the formation of bulk defects in the material without affecting its electronic band structure. The hydrogenated TiO2 exhibited significantly worse photocatalytic activity under simulated sunlight compared to the unhydrogenated control, and thus we propose that high-temperature hydrogenation can be counterproductive to improving the photocatalytic activity of TiO2, because of its propensity to form bulk vacancy defects.
Topics: Catalysis; Hydrogenation; Photochemistry; Titanium; Water Purification
PubMed: 23465766
DOI: 10.1021/am302903n -
American Journal of Dentistry Nov 2000To review and connect the scientific background of light curing with clinical requirements and new technical opportunities in order to conclude the best technology for... (Comparative Study)
Comparative Study Review
PURPOSE
To review and connect the scientific background of light curing with clinical requirements and new technical opportunities in order to conclude the best technology for next generation light curing units.
RESULTS
Three conclusions are drawn for proper light curing: (1) A minimum dose of light is needed (wavelength dependent); (2) Internal stress can be reduced by giving the sample time to flow before gel point is reached; (3) An upper intensity limit has to be respected to limit temperature increase as well as light intensity dependent deactivation of activated photoinitiators. These conclusions can best be realized by using the softstart approach. A comparison of different light generation technologies shows that LEDs are most likely to shape the next generations of curing lights. Due to their superior power conversion rate as well as to their optimum spectral emission small and handy devices can be realized that work battery-powered and totally silent. The benefits for the dentist are improved reliability, handling, and hygiene.
Topics: Dental Materials; Electric Power Supplies; Electronics; Equipment Design; Humans; Light; Photochemistry; Radiation Dosage; Stress, Mechanical; Technology, Dental; Temperature; Viscosity
PubMed: 11763921
DOI: No ID Found -
Nature Communications Jan 2016Advances in photonics have stimulated significant progress in medicine, with many techniques now in routine clinical use. However, the finite depth of light penetration...
Advances in photonics have stimulated significant progress in medicine, with many techniques now in routine clinical use. However, the finite depth of light penetration in tissue is a serious constraint to clinical utility. Here we show implantable light-delivery devices made of bio-derived or biocompatible, and biodegradable polymers. In contrast to conventional optical fibres, which must be removed from the body soon after use, the biodegradable and biocompatible waveguides may be used for long-term light delivery and need not be removed as they are gradually resorbed by the tissue. As proof of concept, we demonstrate this paradigm-shifting approach for photochemical tissue bonding (PTB). Using comb-shaped planar waveguides, we achieve a full thickness (>10 mm) wound closure of porcine skin, which represents ∼ 10-fold extension of the tissue area achieved with conventional PTB. The results point to a new direction in photomedicine for using light in deep tissues.
Topics: Absorbable Implants; Medicine; Photochemistry; Polymers
PubMed: 26783091
DOI: 10.1038/ncomms10374 -
Photochemistry and Photobiology 2007To characterize photobiological and photochemical phenomena, standardized terms and units are required. Without a uniform set of descriptors, much of the scientific...
Radiometric quantities and units used in photobiology and photochemistry: recommendations of the Commission Internationale de L'Eclairage (International Commission on Illumination).
To characterize photobiological and photochemical phenomena, standardized terms and units are required. Without a uniform set of descriptors, much of the scientific value of publications can be lost. Attempting to achieve an international consensus for a common language has always been difficult, but now with truly international scientific publications, it is all the more important. As photobiology and photochemistry both represent the fusion of several scientific disciplines, it is not surprising that the physical terms used to describe exposures and dosimetric concepts can vary from author to author. There are, however, international organizations that were established to minimize the confusion produced by poor or inconsistent technical terminology. This note is to review the standardized terms and provide a background on how such terms are developed, with the hope that all readers will attempt to follow the standardized terminology.
Topics: International Agencies; Photobiology; Photochemistry; Radiometry
PubMed: 17115802
DOI: 10.1562/2006-11-14-RA-1081 -
Nature Materials Sep 2006Nanoscale systems are forecast to be a means of integrating desirable attributes of molecular and bulk regimes into easily processed materials. Notable examples include... (Review)
Review
Nanoscale systems are forecast to be a means of integrating desirable attributes of molecular and bulk regimes into easily processed materials. Notable examples include plastic light-emitting devices and organic solar cells, the operation of which hinge on the formation of electronic excited states, excitons, in complex nanostructured materials. The spectroscopy of nanoscale materials reveals details of their collective excited states, characterized by atoms or molecules working together to capture and redistribute excitation. What is special about excitons in nanometre-sized materials? Here we present a cross-disciplinary review of the essential characteristics of excitons in nanoscience. Topics covered include confinement effects, localization versus delocalization, exciton binding energy, exchange interactions and exciton fine structure, exciton-vibration coupling and dynamics of excitons. Important examples are presented in a commentary that overviews the present understanding of excitons in quantum dots, conjugated polymers, carbon nanotubes and photosynthetic light-harvesting antenna complexes.
Topics: Light; Nanostructures; Nanotechnology; Photochemistry
PubMed: 16946728
DOI: 10.1038/nmat1710 -
Inorganic Chemistry Mar 2008The photoredox reaction of ferrioxalate after 266/267 nm excitation in the charge transfer band has been studied by means of ultrafast extended X-ray absorption fine...
The photoredox reaction of ferrioxalate after 266/267 nm excitation in the charge transfer band has been studied by means of ultrafast extended X-ray absorption fine structure (EXAFS) analysis, optical transient spectroscopy, and quantum chemistry calculations. The Fe-O bond length changes combined with the transient spectra and kinetics have been measured and in combination with ultrahigh frequency density functional theory (UHF/DFT) calculations are used to determine the photochemical mechanism for the Fe(III) to Fe(II) redox reaction. The present data and the results obtained with 266/267 nm excitations strongly suggest that the primary reaction is the dissociation of the Fe-O bond before intramolecular electron transfer occurs. Low quantum yield electron photodetachment from ferrioxalate has also been observed.
Topics: Electrons; Kinetics; Oxalates; Photochemistry; Solvents; Spectrophotometry
PubMed: 18284192
DOI: 10.1021/ic7016566 -
Annual Review of Physiology 1990
Comparative Study Review
Topics: Acetates; Animals; Cations, Divalent; Chelating Agents; Chemical Phenomena; Chemistry; Egtazic Acid; Ethylenediamines; Photochemistry; Photolysis
PubMed: 2109966
DOI: 10.1146/annurev.ph.52.030190.004225 -
The Review of Scientific Instruments Mar 1972
Topics: Animals; Cell Biology; Cells; Chickens; Erythrocytes; Fluorescence; Photochemistry
PubMed: 5013444
DOI: 10.1063/1.1685647 -
Photochemistry of proteins. XV. Some observations on the ultraviolet absorption spectra of proteins.Biochimica Et Biophysica Acta Sep 1952
Topics: Photochemistry; Proteins
PubMed: 12997486
DOI: 10.1016/0006-3002(52)90158-3 -
Photochemistry and Photobiology Nov 1970
Topics: Alanine; Peptides; Photochemistry
PubMed: 5490480
DOI: 10.1111/j.1751-1097.1970.tb06071.x