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DDC: 540 × Subject: Physicochemical methods ×

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    Comparability of Raman Spectroscopic Configurations: A Large Scale Cross-Laboratory Study
    (Columbus, Ohio : American Chemical Society, 2020) Guo S.; Beleites C.; Neugebauer U.; Abalde-Cela S.; Afseth N.K.; Alsamad F.; Anand S.; Araujo-Andrade C.; Aškrabić S.; Avci E.; Baia M.; Baranska M.; Baria E.; Batista De Carvalho L.A.E.; De Bettignies P.; Bonifacio A.; Bonnier F.; Brauchle E.M.; Byrne H.J.; Chourpa I.; Cicchi R.; Cuisinier F.; Culha M.; Dahms M.; David C.; Duponchel L.; Duraipandian S.; El-Mashtoly S.F.; Ellis D.I.; Eppe G.; Falgayrac G.; Gamulin O.; Gardner B.; Gardner P.; Gerwert K.; Giamarellos-Bourboulis E.J.; Gizurarson S.; Gnyba M.; Goodacre R.; Grysan P.; Guntinas-Lichius O.; Helgadottir H.; Grošev V.M.; Kendall C.; Kiselev R.; Kölbach M.; Krafft C.; Krishnamoorthy S.; Kubryck P.; Lendl B.; Loza-Alvarez P.; Lyng F.M.; Machill S.; Malherbe C.; Marro M.; Marques M.P.M.; Matuszyk E.; Morasso C.F.; Moreau M.; Muhamadali H.; Mussi V.; Notingher I.; Pacia M.Z.; Pavone F.S.; Penel G.; Petersen D.; Piot O.; Rau J.V.; Richter M.; Rybarczyk M.K.; Salehi H.; Schenke-Layland K.; Schlücker S.; Schosserer M.; Schütze K.; Sergo V.; Sinjab F.; Smulko J.; Sockalingum G.D.; Stiebing C.; Stone N.; Untereiner V.; Vanna R.; Wieland K.; Popp J.; Bocklitz T.
    The variable configuration of Raman spectroscopic platforms is one of the major obstacles in establishing Raman spectroscopy as a valuable physicochemical method within real-world scenarios such as clinical diagnostics. For such real world applications like diagnostic classification, the models should ideally be usable to predict data from different setups. Whether it is done by training a rugged model with data from many setups or by a primary-replica strategy where models are developed on a 'primary' setup and the test data are generated on 'replicate' setups, this is only possible if the Raman spectra from different setups are consistent, reproducible, and comparable. However, Raman spectra can be highly sensitive to the measurement conditions, and they change from setup to setup even if the same samples are measured. Although increasingly recognized as an issue, the dependence of the Raman spectra on the instrumental configuration is far from being fully understood and great effort is needed to address the resulting spectral variations and to correct for them. To make the severity of the situation clear, we present a round robin experiment investigating the comparability of 35 Raman spectroscopic devices with different configurations in 15 institutes within seven European countries from the COST (European Cooperation in Science and Technology) action Raman4clinics. The experiment was developed in a fashion that allows various instrumental configurations ranging from highly confocal setups to fibre-optic based systems with different excitation wavelengths. We illustrate the spectral variations caused by the instrumental configurations from the perspectives of peak shifts, intensity variations, peak widths, and noise levels. We conclude this contribution with recommendations that may help to improve the inter-laboratory studies. © 2020 American Chemical Society.
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    Characterizing photocatalysts for water splitting: from atoms to bulk and from slow to ultrafast processes
    (London : Royal Society of Chemistry (RSC), 2021) Kranz, Christine; Wächtler, Maria
    Research on light-driven catalysis has gained tremendous importance due to the ever-increasing power consumption and the threatening situation of global warming related to burning fossil fuels. Significant efforts have been dedicated to artificial photosynthesis mimicking nature to split H2O into H2 and O2 by solar energy. Novel semiconductor und molecular photocatalysts focusing on one-step excitation processes via single component photocatalysts or via two-step excitation processes mimicking the Z-scheme of natural photosynthesis are currently developed. Analytical and physicochemical methods, which provide information at different time and length scales, are used to gain fundamental understanding of all processes leading to catalytic activity, i.e., light absorption, charge separation, transfer of charges to the reaction centres and catalytic turnover, but also understanding degradation processes of the photocatalytic active material. Especially, molecular photocatalysts still suffer from limited long-Term stability due to the formation of reactive intermediates, which may lead to degradation. Although there is an overwhelming number of research articles and reviews focussing on various materials for photocatalytic water splitting, to date only few reviews have been published providing a comprehensive overview on methods for characterizing such materials. This review will highlight spectroscopic, spectroelectrochemical, and electrochemical approaches in respect to their potential in studying processes in semiconductor and (supra)molecular photocatalysts. Special emphasis will be on spectroscopic methods to investigate light-induced processes in intermediates of sequential electron transfer chains. Further, microscopic characterization methods, which are predominantly used for semiconducting and hybrid photocatalytic materials will be reviewed as surface area, structure, facets, defects, and bulk properties such as crystallinity and crystal size are key parameters for charge separation, transfer processes and suppression of charge recombination. Recent developments in scanning probe microscopy will also be highlighted as such techniques are highly suited for studying photocatalytic active material. © The Royal Society of Chemistry.