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- ItemCharacterization and effect of Ag(0) vs. Ag(I) species and their localized plasmon resonance on photochemically inactive TiO 2(Basel : MDPI, 2019) Handoko, Chanel Tri; Moustakas, Nikolaos G.; Peppel, Tim; Springer, Armin; Oropeza, Freddy E.; Huda, Adri; Bustan, Muhammad Djoni; Yudono, Bambang; Gulo, Fakhili; Strunk, JenniferCommercial TiO 2 (anatase) was successfully modified with Ag nanoparticles at different nominal loadings (1%-4%) using a liquid impregnation method. The prepared materials retained the anatase structure and contained a mixture of Ag 0 and Ag I species. Samples exhibited extended light absorption to the visible region. The effect of Ag loading on TiO 2 is studied for the photocatalytic reduction of CO 2 to CH 4 in a gas-solid process under high-purity conditions. It is remarkable that the reference TiO 2 used in this work is entirely inactive in this reaction, but it allows for studying the effect of Ag on the photocatalytic process in more detail. Only in the case of 2% Ag/TiO 2 was the formation of CH 4 from CO 2 observed. Using different light sources, an influence of the localized surface plasmon resonance (LSPR) effect of Ag is verified. A sample in which all Ag has been reduced to the metallic state was less active than the respective sample containing both Ag 0 and Ag + , indicating that a mixed oxidation state is beneficial for photocatalytic performance. These results contribute to a better understanding of the effect of metal modification of TiO 2 in photocatalytic CO 2 reduction. © 2019 by the authors. Licensee MDPI, Basel, Switzerland.
- ItemMorphology, Optical Properties and Photocatalytic Activity of Photo- and Plasma-Deposited Au and Au/Ag Core/Shell Nanoparticles on Titania Layers(Basel : MDPI, 2018-7-6) Müller, Alexander; Peglow, Sandra; Karnahl, Michael; Kruth, Angela; Junge, Henrik; Brüser, Volker; Scheu, ChristinaTitania is a promising material for numerous photocatalytic reactions such as water splitting and the degradation of organic compounds (e.g., methanol, phenol). Its catalytic performance can be significantly increased by the addition of co-catalysts. In this study, Au and Au/Ag nanoparticles were deposited onto mesoporous titania thin films using photo-deposition (Au) and magnetron-sputtering (Au and Au/Ag). All samples underwent comprehensive structural characterization by grazing incidence X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Nanoparticle distributions and nanoparticle size distributions were correlated to the deposition methods. Light absorption measurements showed features related to diffuse scattering, the band gap of titania and the local surface plasmon resonance of the noble metal nanoparticles. Further, the photocatalytic activities were measured using methanol as a hole scavenger. All nanoparticle-decorated thin films showed significant performance increases in hydrogen evolution under UV illumination compared to pure titania, with an evolution rate of up to 372 μL H2 h−1 cm−2 representing a promising approximately 12-fold increase compared to pure titania.
- ItemTime Optimization of Seed-Mediated Gold Nanotriangle Synthesis Based on Kinetic Studies(Basel : MDPI, 2021) Podlesnaia, Ekaterina; Csáki, Andrea; Fritzsche, WolfgangThe synthesis of shape-anisotropic plasmonic nanoparticles such as gold nanotriangles is of increasing interest. These particles have a high potential for applications due to their notable optical properties. A key challenge of the synthesis is usually the low reproducibility. Even the optimized seed-based methods often lack in the synthesis yield or are labor- and time-consuming. In this work, a seed-mediated synthesis with high reproducibility is replicated in order to determine the necessary reaction time for each step. Online monitoring of the reaction mixtures by UV–VIS spectroscopy is used as a powerful tool to track the evolution of the synthesis. The kinetics of the individual stages is elucidated by real-time investigations. As a consequence, the complete synthesis could be optimized and can now be realized in a single day instead of three without any loss in the resulting sample quality.
- ItemA gold-nanotip optical fiber for plasmon-enhanced near-field detection(New York, NY : American Inst. of Physics, 2013) Uebel, P.; Bauerschmidt, S.T.; Schmidt, M.A.; Russell, P.St.J.A wet-chemical etching and mechanical cleaving technique is used to fabricate gold nanotips attached to tapered optical fibers. Localized surface plasmon resonances (tunable from 500 to 850 nm by varying the tip dimensions) are excited at the tip, and the signal is transmitted via the fiber to an optical analyzer, making the device a plasmon-enhanced near-field probe. A simple cavity model is used to explain the resonances observed in numerical simulations.