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A comprehensive and reliable view on the influence of UV light and heat on optical properties of ZnO shall be outlined mainly based on research conducted by scientists from Warsaw Pact countries throughout the twentieth century. The problems of language barrier and loss of knowledge are being addressed. An insight into processes of photodesorption and photoadsorption of oxygen and other gas phase molecules leading to changes in charge carrier states is outlined. While desorption of surface adsorbates leads to increased number of conduction electrons and thus increased absorbance of infrared light, adsorption of electronegative gas phase molecules leads to quenching in fluorescence.

In this study nitrogen-doped carbon quantum dots/graphitic carbon nitride nanosheet (CNQD) composites with different contents of nitrogen-doped carbon quantum dots (NCQDs; 2, 4, 6, and 8 wt%) were synthesized. The morphological, physicochemical, and photoelectrochemical properties were investigated using complementary methods such as scanning electron microscopy (SEM), powder X-ray diffraction (pXRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), UV/Vis spectroscopy in diffuse reflectance (DRS), photoluminescence (PL), nitrogen physisorption (BET), photocurrent response, and electrochemical impedance spectroscopy (EIS). The photocatalytic activity of the synthesized materials was assessed during diclofenac (DCF) degradation in an aqueous solution under visible light irradiation. As a result, improved photocatalytic efficiency in DCF degradation was observed for all the CNQD composites compared with bulk graphitic carbon nitride (bCN) and nanosheet g-C3N4 (CNS). The fastest DCF degradation was observed for the 6 wt% NCQD on the surface of CNS (CNQD-6), which removed 62% of DCF in 3 h, with an associated k value of 5.41 × 10−3 min−1. The performance test results confirmed the contribution of NCQDs to enhancing photocatalytic activity, leading to an improvement factor of 1.24 over bCN. The morphology of the CNS and the synergistic interaction between NCQDs and CNS were essential elements for enhancing photocatalytic activity. The photoelectrochemical data and photoluminescence analyses showed the efficient migration of photoexcited electrons from NCQDs to the CNS. The reduced charge recombination rates in CNQD photocatalysts might be due to the synergistic interaction between NCQDs and CNS and the unique up-conversion photoluminescence properties of NCQDs. Further investigations revealed that the photogenerated superoxide radicals (•O2−) predominated in the degradation of DCF, and this photocatalyst had good reusability and toxicity reduction abilities. This work provides insight into the effects of NCQDs on the CNS surface to enhance its potential to remove emerging organic pollutants from water and wastewater.

s This work describes the synthesis of porous hierarchical microspheres composed of amorphous SiO2 and crystalline β-Bi2O3 (BSO) via a simple solvothermal process and subsequent calcination. Complementary physicochemical methods were applied to study the function of amorphous SiO2, as well as the phase composition and morphology evolution of as-synthesized samples as a function of calcination temperature. The presence of amorphous SiO2 contributed to form hierarchically structured β-Bi2O3 with enhanced thermostability. Moreover, the degradation of tetracycline hydrochloride (TC) under visible light irradiation was employed as a model reaction to evaluate the photocatalytic activity of as prepared materials. In consequence, both phase composition and morphology were found to be significant parameters for adjusting the photocatalytic performance of the synthesized samples. The fastest TC degradation at a low dosage of catalyst (0.2 g L-1) was observed for the sample annealed at 400℃ which contains a highly crystalline β-Bi2O3 phase. The synergistic effect of the porous structure, excellent light absorption, and higher charge carrier separation and transfer efficiency is believed to be the reason for the optimal photocatalytic activity. This study offers a new method toward the fabrication of hierarchical porous structured β-Bi2O3 with enhanced thermostability for various applications.

Evidence is provided that in a gas-solid photocatalytic reaction the removal of photogenerated holes from a titania (TiO2 ) photocatalyst is always detrimental for photocatalytic CO2 reduction. The coupling of the reaction to a sacrificial oxidation reaction hinders or entirely prohibits the formation of CH4 as a reduction product. This agrees with earlier work in which the detrimental effect of oxygen-evolving cocatalysts was demonstrated. Photocatalytic alcohol oxidation or even overall water splitting proceeds in these reaction systems, but carbon-containing products from CO2 reduction are no longer observed. H2 addition is also detrimental, either because it scavenges holes or because it is not an efficient proton donor on TiO2 . The results are discussed in light of previously suggested reaction mechanisms for photocatalytic CO2 reduction. The formation of CH4 from CO2 is likely not a linear sequence of reduction steps but includes oxidative elementary steps. Furthermore, new hypotheses on the origin of the required protons are suggested.

A comprehensive and reliable view on the influence of UV light and heat on optical properties of ZnO shall be outlined mainly based on research conducted by scientists from Warsaw Pact countries throughout the 20th century. The problems of language barrier and loss of knowledge are being addressed. An insight into processes of photodesorption and photoadsorption of oxygen and other gas phase molecules leading to changes in charge carrier states is outlined. While desorption of surface adsorbates leads to increased number of conduction electrons and thus increased absorbance of infrared light, adsorption of electronegative gas phase molecules leads to quenching in fluorescence.

Evidence is provided that in a gas-solid photocatalytic reaction the removal of photogenerated holes from a titania (TiO

This work describes the synthesis of porous hierarchical microspheres composed of amorphous SiO

The solvated title salt, (C

Perovskites such as SrTiO3 are interesting for photocatalytic applications due to their structure-related and electronic properties. These properties are influenced by the presence of SrCO3 which is often formed simultaneously during the hydrothermal synthesis of SrTiO3. In this study, SrTiO3-SrCO3 composites with different contents of SrCO3 (5–24 wt%) were synthesized. Their morphological, structural, and optical properties were investigated using complementary methods such as scanning electron microscopy (SEM), X-ray diffraction (XRD), nitrogen sorption, and diffuse reflectance spectroscopy (DRS). Their photocatalytic activity was assessed during the degradation of diclofenac (DCFNa) in aqueous solution and CO2 photoreduction under Xe lamp irradiation. Improved photocatalytic efficiency in DCFNa degradation was observed for all the studied composites in comparison with SrTiO3, and the highest mineralization efficiency was obtained for the sample with 21 wt% SrCO3 content. The presence of SrCO3 led to an increased concentration of active species, such as •OH radicals. Otherwise, its presence inhibits CH4 and C2H6 production during CO2 photoreduction compared with pure SrTiO3.

The title mol­ecular salt, C5H12NO+·C4BN4− or (C5H12NO)[B(CN)4], was obtained as single crystals by slow evaporation of a solution of the compound in aceto­nitrile over several weeks. The asymmetric unit contains two (S)-alanine ethyl ester cations and two tetra­cyanidoborate anions, which are linked by N—H...N hydrogen bonds. The compound exhibits a relatively low melting point of 110°C and shows a solid–solid phase transition near room temperature (Ts–s = 29°C) on the basis of DSC measurements.

Ordered titanium dioxide nanotube arrays fabricated via electrochemical route are considered as a promising material for photocatalytic applications. Due to their amorphous character, a subsequent crystallization step is usually required. In this work, well-aligned nanotube arrays were annealed under flowing gas streams of different compositions (air/steam, air, N2/steam, N2, and O2/steam) in a temperature range from 140 to 543 °C. Under continuous gas flow, the morphology of the crystallized titanium dioxide is strongly affected by the gas atmosphere. When using a dry gas for annealing, the tube structure was almost destroyed after 1 h treatment at 473 °C. In contrast, when annealing the titania nanotube array in a water vapor/gas stream, the tube morphology can be maintained up to 543 °C and 10 h annealing time. Moreover, nanotube arrays crystallized in a flowing gas atmosphere containing water vapor showed a significantly higher photocatalytic activity for phenol degradation under UV irradiation than nanotube arrays crystallized in a dry gas stream. Reasons for this behavior might be the preservation of the tubular structure as well as a lower concentration or density of structural defects in presence of water vapor which leads to an enhanced generation of reactive oxygen species when the arrays are exposed to UV-light.

Im Jahr 1890 wechselte August Michaelis, ein Pionier der Heteroatomchemie, von der Technischen Hochschule Aachen an die Universitat Rostock. Wahrend er Phosphorhalogenide, phosphorige Saure und Aryl-Phosphor-Verbindungen untersuchte, erlebte die Chemie in Rostock einen kleinen Boom.

In this study we assess the general applicability of the widely used P25-TiO2 in gas-phase photocatalytic CO2 reduction based on experimentally determined reactivity descriptors from classical heterogeneous catalysis (productivity) and photochemistry (apparent quantum yield/AQY). A comparison of the results with reports on the use of P25 for thermodynamically more feasible reactions and our own previous studies on P25-TiO2 as photocatalyst imply that the catalytic functionality of this material, rather than its properties as photoabsorber, limits its applicability in the heterogeneous photocatalytic CO2 reduction in the gas phase. The AQY of IrOx/TiO2 in overall water splitting in a similar high-purity gas-solid process was four times as high, but still far from commercial viability.

In this study we assess the general applicability of the widely used P25-TiO

Commercial TiO2 (anatase) was successfully modified with Ag nanoparticles at different nominal loadings (1%&ndash, 4%) using a liquid impregnation method. The prepared materials retained the anatase structure and contained a mixture of Ag0 and AgI species. Samples exhibited extended light absorption to the visible region. The effect of Ag loading on TiO2 is studied for the photocatalytic reduction of CO2 to CH4 in a gas&ndash, solid process under high-purity conditions. It is remarkable that the reference TiO2 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/TiO2 was the formation of CH4 from CO2 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 Ag0 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 TiO2 in photocatalytic CO2 reduction.

A series of new ionic liquids of the formula Ax[CoII(NCO)4] with the [CoII(NCO)4]2 anion and nitrogen-based organic cations was synthesized. The single crystal structures of all compounds were determined by X-ray diffraction and reveal for all cases the existence of discrete ions. The magnetic behavior at room temperature is paramagnetic resulting from the high-spin tetrahedrally coordinated CoII ions. Melting points or glass transition temperatures are found in the range of ionic liquids for some of the compounds with singly charged cations, and above 100 °C for all compounds with doubly charged cations and the [PPN]+ salt. Each compound has been characterized by elemental analysis, NMR-, IR-, and UV/Vis- spectroscopy. Measurements of the density, dynamic viscosity, conductivity and surface tension for the low melting substance [EMIm]2[Co(NCO)4] show, that they differ slightly but are generally comparable to the corresponding values of the isothiocyanato complexes.

This Perspective highlights recent developments in methane conversion into different hydrocarbons and oxygenates (methanol, its derivatives, and formaldehyde) with the purpose to address the global demand for efficient and environmentally friendly production of these bulk chemicals. Our analysis identified possible directions for further research to bring the above approaches to a commercial level. As no progress in the development of catalysts for the oxidative coupling of methane could be identified, improvements are expected through reactor operation, cost- and energy-efficient methods for product separation and for providing pure oxygen. With respect to methane oxidation to methanol, further progress can also be achieved by proper catalyst design on the basis of fundamental knowledge especially gained from homogeneous and enzymatic catalysts as well as from theoretical calculations.

The synthesis of more than 10 new magnetic ionic liquids with [MnX4]2&minus, anions, X = Cl, NCS, NCO, is presented. Detailed structural information through single-crystal X-ray diffraction is given for (DMDIm)[Mn(NCS)4], (BnEt3N)2[Mn(NCS)4], and {(Ph3P)2N}2[Mn(NCO4)]&middot, 0.6H2O, respectively. All compounds consist of discrete anions and cations with tetrahedrally coordinated Mn (II) atoms. They show paramagnetic behavior as expected for spin-only systems. Melting points are found for several systems below 100 &deg, C classifying them as ionic liquids. Thermal properties are investigated using differential scanning calorimetry (DSC) measurements. The physicochemical properties of density, dynamic viscosity, electrolytic conductivity, and surface tension were measured temperature-dependent of selected samples. These properties are discussed in comparison to similar Co containing systems. An increasing amount of bromide impurity is found to affect the surface tension only up to 3.3%.

Dynamic crossover above Tg has been recognized as a characteristic feature of molecular dynamics of liquids approaching glass transition. Experimentally, it is manifested as a change in Vogel–Fulcher–Tammann dependence or a breakdown of the Stokes–Einstein and related relations. In this paper, we report the exception from this rather general pattern of behavior. By means of dielectric, ultrasonic, rheological, and calorimetric methods, dynamics of two good ionic conductors (BMIm)2[Co(NCS)4] and (EMIm)2[Co(NCS)4] of less common stoichiometry (2:1) was studied in a very broad temperature range. However, none of the mentioned dynamic changes was observed in the entire studied temperature range. On the contrary, the single VFT and the same fractional Walden coefficient were found for conductivity and viscosity changes over 12 decades. Moreover, ultrasonic studies revealed that the data at temperatures which cover the normal liquid region cannot be fitted by a single exponential decay, and the Cole–Cole functi...

It was a big surprise to see crystals of an ionic liquid (IL) forming by sublimation at room temperature. ILs are generally accepted to have negligible vapour pressures at elevated temperatures, making their sublimation or distillation very difficult. ILs that sublime easily contain silylimidazolium-based cations. In order to establish the details of the unusual behaviour of this subclass of ILs, a combined spectroscopic, X-ray crystallographic, physicochemical and theoretical characterization was performed. The results are compared with those of other easily vaporizable compounds, like ammonium chloride and naphthalene. The single-crystal X-ray structure analysis of one of these compounds, N-methyl-N′-dimethyl(phenyl)silylimidazolium chloride (monoclinic, C2/c), clearly shows the existence of isolated ions, demonstrating that the compound is an ionic liquid.

In preparation of the 600th anniversary of Rostock University the question arose who the first female students at the institute of chemistry were. With the help of digitized materials of the enrollments and printed lists of graduations in the beginning of the 20th century, the first female graduate, Else Hirschberg, was found. This article examines her life, her scientific career and her fate. After a short introduction about women’s studies in Germany, particular attention will be paid to the ancestry of Else Hirschberg´s Jewish family in the first part. Based on documents provided by several archives and the possibilities of ancestry.com in connection with online-access detailed information about Else, her family and her ancestors will be described – both her maternal and the paternal lineage. The second part of the paper informs about Else Hirschberg´s academic career. It is not possible to name the exact reasons for her decision to study chemistry, but an impressive picture of her scientific efforts will be drawn. Furthermore, a list of her papers and some information about the network that she used in her attempts to emigrate from Germany are available.

Polymeric carbon nitride (p-C3N4) based materials have shown great potential as photocatalysts for degradation of pollutants from wastewater. In this work p-C3N4 was synthesized from urea or ferric chloride/urea by pyrolysis followed by a post-treatment with hydrogen peroxide (H2O2). The prepared materials were characterized by physico-chemical methods in order to study their structural and electronic features. The characterization results revealed that iron was present in p-C3N4 as a Fe3O4 phase. The H2O2 treatment did not only modify the p-C3N4 framework through the generation of oxygen functional groups and defect sites but it also affected the size, distribution, and oxidation state of iron oxide. The photocatalytic activity of the catalysts was tested through the degradation of methyl orange under visible and white light irradiation. In comparison, the iron oxide containing p-C3N4 post-treated with H2O2 sample shows superior photocatalytic performance towards methyl orange degradation. This might be attributed to the valence and conduction band levels of the composite material, an inhibited recombination of photogenerated charge carriers as well as a synergistic effect of iron species and the oxygen containing functional groups or defects present in p-C3N4.

NaTaO3 compound prepared by (i) a solid state reaction (SSR) with crystallite sizes between 1–5 μm and (ii) by an exotemplate method (EM) with crystallite sizes of about 25 nm was tested as photocatalyst in light-driven water splitting. NaTaO3(EM) showed an 18 times higher photocatalytic hydrogen evolution rate than NaTaO3(SSR). A further improvement by a factor of 28 was achieved by mixing the EM derived material with multilayer reduced graphene oxide (m-rGO). Moreover, by depositing 0.2 wt % Au on the surface of NaTaO3(EM), the hydrogen production efficiency has been increased by a factor of 41. Surprisingly, the hydrogen production rate could not be significantly improved with NaTaO3(SSR) under the same conditions. By using in situ EPR spectroscopy, the electronic interactions between semiconductor, cocatalyst, and m-rGO have been investigated in detail. Plausible electron separation and transfer mechanisms from NaTaO3(SSR) or NaTaO3(EM), respectively, to m-rGO are discussed and compared to the catalyt...