MoxC Heterostructures as Efficient Cocatalysts in Robust MoxC/g-C3N4 Nanocomposites for Photocatalytic H2 Production from Ethanol

In this work, we studied new materials free of noble metals that are active in photocatalytic H2 generation from ethanol aqueous solutions (EtOHaq), which can be obtained from biomass. MoxC/g-C3N4 photocatalysts containing hexagonal (hcp) Mo2C and/or cubic (fcc) MoC nanoparticles on g-C3N4 nanosheets were prepared, characterized, and evaluated for photocatalytic hydrogen production from EtOHaq (25% v/v). Tailored MoxC/g-C3N4 nanocomposites with MoxC crystallite sizes in the 4-37 nm range were prepared by treatment with ultrasound of dispersions containing MoxC and g-C3N4 nanosheets, formerly synthesized. The characterization of the resulting nanocomposites, MoxC/g-C3N4, by different techniques, including photoelectrochemical measurements, allowed us to relate the photocatalytic performance of materials with the characteristics of the MoxC phase integrated onto g-C3N4. The samples containing smaller hcp Mo2C crystallites showed better photocatalytic performance. The most performant nanocomposite contained nanoparticles of both hcp Mo2C and fcc MoC and produced 27.9 mmol H2 g-1 Mo; this sample showed the lowest recombination of photogenerated charges, the highest photocurrent response, and the lowest electron transfer resistance, which can be related to the presence of MoC-Mo2C heterojunctions. Moreover, this material allows for easy reusability. This work provides new insights for future research on noble-metal-free g-C3N4-based photocatalysts.

Influence of the Nature of Aminoalcohol on ZnO Films Formed by Sol-Gel Methods

Here we present comparative studies of: (i) the formation of ZnO thin films via the sol-gel method using zinc acetate dihydrate (ZAD), 2-methoxyethanol (ME) as solvent, and the aminoalcohols (AA): ethanolamine, (S)-(+)-2-amino-1-propanol, (S)-(+)-2-amino-3-methyl-1-butanol, 2-aminophenol, and aminobenzyl alcohol, and (ii) elemental analyses, infrared spectroscopy, X-ray diffraction, scanning electron microscopy, absorption and emission spectra of films obtained after deposition by drop coating on glass surface, and thermal treatments at 300, 400, 500 and 600 °C. The results obtained provide conclusive evidences of the influence of the AA used (aliphatic vs. aromatic) on the ink stability (prior to deposition), and on the composition, structures, morphologies, and properties of films after calcination, in particular, those due to the different substituents, H, Me, or ⁱPr, and to the presence or the absence of a -CH₂ unit. Aliphatic films, more stable and purer than aromatic ones, contained the ZnO wurtzite form for all annealing temperatures, while the cubic sphalerite (zinc-blende) form was also detected after using aromatic AAs. Films having frayed fibers or quartered layers or uniform yarns evolved to "neuron-like" patterns. UV and photoluminescence studies revealed that these AAs also affect the optical band gap, the structural defects, and photo-optical properties of the films.

Powder X-ray diffraction as a powerful tool to exploit in organic electronics: shedding light on the first N,N',N''-trialkyldiindolocarbazole

The first crystal structure of a fully N-alkylated diindolocarbazole derivative, namely, 5,8,14-tributyldiindolo[3,2-b;2',3'-h]carbazole (1, C₃₆H₃₉N₃), has been determined from laboratory powder X-ray diffraction (PXRD) data. A complex trigonal structure with a high-volume unit cell of 12987 ų was found, with a very long a(=b) [52.8790 (14) Å] and a very short c [5.36308 (13) Å] unit-cell parameter (hexagonal setting). The detailed analysis of the intermolecular interactions observed in the crystal structure of 1 highlights its potential towards the implementation of this core as a semiconductor in organic thin-film transistor (OTFT) devices. Since the molecule has a flat configuration reflecting its π-conjugated system, neighbouring molecules are found to stack atop each other in a slipped parallel fashion via π-π stacking interactions between planes of ca 3.30 Å, with a centroid-centroid distance between the aromatic rings corresponding to the shortest axis of the unit cell (i.e. c). The alkylation of the three N atoms proves to be a decisive feature since it favours the presence of C-H...π interactions in all directions, which strengthens the crystal packing. As a whole, PXRD proves to be a valuable option for the resolution of otherwise inaccessible organic crystal structures of interest in different areas.

Does Sb2Se3 Admit Nonstoichiometric Conditions? How Modifying the Overall Se Content Affects the Structural, Optical, and Optoelectronic Properties of Sb2Se3 Thin Films

Sb₂Se₃ is a quasi-one-dimensional (1D) semiconductor, which has shown great promise in photovoltaics. However, its performance is currently limited by a high V_oc deficit. Therefore, it is necessary to explore new strategies to minimize the formation of intrinsic defects and thus unlock the absorber's whole potential. It has been reported that tuning the Se/Sb relative content could enable a selective control of the defects. Furthermore, recent experimental evidence has shown that moderate Se excess enhances the photovoltaic performance; however, it is not yet clear whether this excess has been incorporated into the structure. In this work, a series of Sb₂Se₃ thin films have been prepared imposing different nominal compositions (from Sb-rich to Se-rich) and then have been thoroughly characterized using compositional, structural, and optical analysis techniques. Hence, it is shown that Sb₂Se₃ does not allow an extended range of nonstoichiometric conditions. Instead, any Sb or Se excesses are compensated in the form of secondary phases. Also, a correlation has been found between operating under Se-rich conditions and an improvement in the crystalline orientation, which is likely related to the formation of a MoSe₂ phase in the back interface. Finally, this study shows new utilities of Raman, X-ray diffraction, and photothermal deflection spectroscopy combination techniques to examine the structural properties of Sb₂Se₃, especially how well-oriented the material is.

Magnetic Propulsion of Recyclable Catalytic Nanocleaners for Pollutant Degradation

Electrochemically fabricated magnetic mesoporous CoNi@Pt nanorods are excellent nanomotors with controlled magnetic propulsion and excellent catalytic properties. The core-shell structure allows a double functionality: (i) controlled motion of the nanorods by applying rotating magnetic fields at different frequencies and field strengths and (ii) effective catalytic activity of the platinum shell for reactions involving sodium borohydride. The structure and magnetic properties of the CoNi core are not modified by the presence of the Pt shell. Nanorods were propelled via a tumbling-like dynamic by a rotating magnetic field. While in absence of NaBH₄, nanorods move at constant speed showing a linear path; in the presence of NaBH₄, they showed an intermittent trajectory. These catalytic nanorods can be used as nanocleaners with controlled directionality for pollutants degradation in the presence of borohydride. Their magnetic character allows control of the velocity and the direction throughout the contaminated solution by degrading the different pollutants in their path. The magnetic character of nanorods also allows their easy recycling.

(Z)-3-Methyl-N-(7-nitroacridin-3-yl)-2,3-dihydro-1,3-benzothiazol-2-imine from laboratory powder diffraction data

The title compound, C(21)H(14)N(4)O(2)S, belongs to a family of molecules possessing nonlinear optical properties in solution. Its structure has been solved from laboratory X-ray powder diffraction data using a new direct-space structure solution method, where the atomic coordinates are directly used as parameters and the molecular geometry is described by restraints. The molecular packing is controlled by two systems of π-π interactions and one weak edge-to-face interaction.

Round robin on Rietveld quantitative phase analysis of Portland cements

Interlaboratory studies on the precision and accuracy of Rietveld quantitative phase analysis (R-QPA) of mixtures of crystalline phases have already been carried out. However, cement-related materials are samples of variable complexity, ranging from three phases in white Portland clinkers to more than eight phases in grey cements, that need to be specifically investigated. Here, the results are reported from a round robin on the R-QPA of cement-related materials from laboratories with experience in this type of analysis. The aim of the work was to evaluate the levels of precision and accuracy associated with Portland clinkers and cements. Two sets of samples have been investigated, artificial mixtures and commercial samples. Artificial mixtures were prepared by mixing (weighing) synthesized single-crystalline phases in the appropriate proportions: (i) white clinker (Ca3SiO5, Ca2SiO4and Ca3Al2O6) and (ii) grey cement (Ca3SiO5, Ca2SiO4, Ca3Al2O6, Ca4Al2Fe2O10, CaCO3and CaSO4·2H2O). These two samples were used to assess the accuracy and uncertainty of the procedure, as an expected mineralogical phase fraction, the `true mineralogical percentage', is available under the assumption of negligible non-diffracting contents. In order to assess the validity and limitations of the Rietveld-based approach for cement materials, three commercial samples were measured: (i) white Portland clinker, (ii) grey Portland clinker and (iii) a type-I grey Portland cement. The samples studied have been chosen in order to cover most of the different typologies of binders. Reproducibilities and general uncertainty values, with a level of confidence of 95%, are reported and discussed.

Use of sorption and extraction tests to predict the dynamics of the interaction of trace elements in agricultural soils contaminated by a mine tailing accident

Over 2000 ha of agricultural soils were contaminated by a pyritic sludge and acidic waste waters coming from a spill from a mining exploitation. The affected soils were acidic with sandy-loam texture (SL), loamy with neutral pH (L), and calcareous, saline, with clay texture (Cs). The Cs soils were contaminated only with acidic waste waters. Sorption and extraction tests were applied to examine the medium-term dynamics of the interaction of trace elements (As, Cd, Cu, Pb and Zn) in the soils. The solid-soil solution distribution coefficient (KD) was determined in soil samples taken 3 months (initial stage, 3M samples) and then nearly 2 years (final stage, 21M samples) after the accident. Distribution coefficient values ranged from the lowest values in the SL samples (from 0.2 l kg(-1) for Cd and Zn to 25 l kg(-1) for As) to higher values in the L and Cs soils. Lead and As had the highest KD in all soils (over 10(5) l kg(-1) in the L soils). No clear dynamics pattern could be derived from these data because of the low heavy metal concentrations in the soil solution. As a complementary approach, four single extractions (0.01 and 1 mol l(-1) CaCl2; 0.05 mol l(-1) EDTA; 0.43 mol l(-1) CH3COOH) were applied to soil and sludge samples. Samples derived from submitting field 3M samples to drying-wetting (DW) cycles were included to define a complete laboratory approach to predict field dynamics. Results from extraction tests indicated that changes of the trace element interaction over time depended on the soil pH and on the source of contamination. For those soils affected only by the acidic waste waters, where an increase in fixation occurred, natural processes such as diffusion controlled dynamics. For those soils contaminated by a mixed source, the dynamics of the interaction was the resultant process of the combination of the natural attenuation and the oxidation of the pyritic sludge. This latter process led to an increase in the remobilization for those elements associated with soluble secondary minerals (Cd and Zn) and to an increase in the fixation for those elements coprecipitating with insoluble secondary minerals (Pb and As). Drying-wetting cycles were useful to predict the dynamics in the field at month-year scale. The CH3COOH was recommended as the best test among those studied here to derive conclusions about dynamics pattern because it provided significant desorption yields in most scenarios. Acidic soils with sludge contamination represented the scenarios with the highest risk, while calcareous soils better attenuated contamination. In a longer time scale, the depletion of calcareous components needs to be controlled.

Anisotropy of Intermolecular Interactions from the Study of the Thermal-Expansion Tensor

The anisotropy of the intermolecular interactions in the low-temperature ordered phases of three chemically and structurally related compounds [neopentylglycol, (CH3)2C(CH2OH)2, pivalic acid, (CH3)3C(COOH), and neopentylalcohol, (CH3)3C(CH2OH)], all of which display an orientationally disordered high-temperature phase, has been shown by means of the isobaric thermal-expansion tensor. The variation of the directions of the principal components of the thermal-expansion tensor as a function of temperature, as well as the variation of its principal coefficients, is evidence of the large differences in the intermolecular interactions for each compound; or, more precisely, between the strong intermolecular hydrogen bonds and the weak van der Waals interactions. In addition, the differences in the hydrogen-bonding schemes expecteda priorifrom the molecular structures of the studied compounds have been enhanced. Finally, the volume expansivity as well as the packing coefficient have been analysed in the orientationally disordered high-temperature phase of each of the three compounds.

Crystal data for p-chloroiodobenzene and p-bromochlorobenzene/p-chloroiodobenzene mixed crystals at 293 K

The powder data for p-chloroiodobenzene and p-bromochlorobenzene/p-chloroiodobenzene mixed crystals [pBCB] x [pCIB]1 − x at 293 K are reported; their stability at 293 K is given. The cell dimensions have been refined by least squares from accurate powder diffractometer data recorded at T = 293 (1) K (quartz as internal standard). Vertical diffractometer, graphite monochromator, Cu Kα 1−Cu Kα 2 correction so that λ = 1.54056 Å. They are all isomorphous, monoclinic, P21/a with Z = 2. a = 15.818(4), b = 5.912(2), c = 4.214(2) Å, β = 113.61(1)°, V = 361.1 Å3, Dx = 2.193 Mg m−3 for pCIB; JCPDS No. 37–2000. a = 15.210(5), b = 5.860(3), c = 4.091(2) Å, β = 112.64(2)°, V = 336.5 Å3, Dx = 1.936 Mg m−3 for [pBCB]0.90[pCIB]0.10; JCPDS No. 37–1989. a = 15.287(6), b = 5.870(3), c = 4.111(2) Å, β = 112.78(2)°, V = 340.1 Å3, Dx = 1.961 Mg m−3 for [pBCB]0.80[pCIB]0.20; JCPDS No. 37–1990. a = 15.360(5), b = 5.880(2), c = 4.126(1) Å, β = 112.87(2)°, V = 343.3 Å3, Dx = 1.988 Mg m−3 for [pBCB]0.70[pCIB]0.30; JCPDS No. 37–1991. a = 15.424(5), b = 5.889(3), c = 4.137(2) Å, β = 112.99(2)°, V = 346.0 Å3, Dx = 2.018 Mg m−3 for [pBCB]0.60[pCIB]0.40; JCPDS No. 37–1992. a = 15.493(4), b = 5.896(2), c = 4.155(2) Å, β = 113.09(2)°, V= 349.1 Å3, Dx = 2.045 Mg m−3 for [pBCB]0.50[pCIB]0.50; JCPDS No. 37–1993. a = 15.566(5), b = 5.901(3), c = 4.168(2) Å, β = 113.20(2)°, V = 351.9 Å3, Dx = 2.073 Mg m−3 for [pBCB]0.40[pCIB]0.60; JCPDS No. 37–1994. a = 15.623(5), b = 5.904(3), c = 4.178(3) Å, β = 113.26(2), V = 354.0 Å3, Dx = 2.105 Mg m−3 for [pBCB]0.30[pCIB]0.70; JCPDS No. 37–1995. a = 15.691(4), b = 5.913(3), c = 4.195(2)Å, β = 113.43(2)°, V = 357.1 Å3, Dx = 2.130 Mg m−3 for [pBCB]0.20[pCIB]0.80; JCPDS No. 37–1996. a = 15.759(4), b = 5.906(2), c = 4.204(2) Å, β = 113.55(2)°, V = 358.7 Å3, Dx = 2.164 Mg m−3 for [pBCB]0.10[pCIB]0.90; JCPDS No. 37–1999.