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The activity of “fueled” NiGa2S4/ITO photodetector is described. The presence of ethanol boosts the performances of the photodetector increasing its responsivity and spectral response.

MXenes, a family of two-dimensional (2D) transition metal carbides, nitrides and carbonitrides based on earth-abundant constituents, are prospective candidates for energy conversion applications, including photocatalysis. While the activity of individual MXenes towards various photocatalytic processes is still debatable, these materials were proved to be excellent co-catalysts, accelerating the charge separation and suppressing the exciton recombination. Titanium-containing MXenes are well compatible with the classical TiO2 photocatalyst. The TiO2 component can be directly grown on MXene sheets by in situ oxidation, representing a mainstream processing approach for such composites. In this study, an essentially different approach has been implemented: a series of TiO2–MXene composite materials with controlled composition and both reference end members were prepared, involving two different strategies for mixing sol–gel-derived TiO2 nanopowder with the Ti3C2Tx component, which was obtained by HF etching of self-propagating high-temperature synthesis products containing modified MAX phase Ti3C2Alz (z > 1) with nominal aluminium excess. The prospects of such composites for the degradation of organic pollutants under simulated solar light, using benzene as a model system, were demonstrated and analysed in combination with their structural, microstructural and optical properties. A notable photocatalytic activity of bare MXene under near infrared light was discovered, suggesting further prospects for light-to-energy harvesting spanning from UV-A to NIR and applications in biomedical imaging and sensors.

The "Gold Dust Defect" affects the surface quality of AISI 430 ferritic stainless steels. However, there is a very limited number of studies focusing on it. To better understand its nature, we have combined several techniques, such as x-ray photoelectron spectroscopy, atomic force microscopy, and transmission electron microscopy, in order to extract a maximum of structural and compositional information. Our results show that the surface quality, microstructure, and chemistry of the samples are strongly affected by the aluminum content, the severity of the defect being the highest at the lowest Al concentration. Not only is the concentration of the defects at the surface strongly reduced when increasing the Al. at.% but the depth of the cavities is also reduced by a factor of 3 when the Al content is increased from 0.09 at.% to 0.59 at.%. Our results provide new information on the nature of this defect, and show that an increase of the aluminum content allows the Cr concentration to be maintained in the range of values required to maintain the passivity of the steel, thus improving the surface quality.

Two-dimensional (2D) silicene-germanene alloy - siligene (SixGey), a novel single-phase material has attracted increased attention due to its two-elemental low-buckled composition and unique physics and chemistry. This new 2D material has the potential to address the challenges caused by low electrical conductivity and the environmental instability of corresponding monolayers. Yet, siligene structure was studied in theory, demonstrating the material’s great electrochemical potential for energy storage applications. The synthesis of free-standing siligene remains challenged and therefore hinders the research and application of this material. Herein we pioneer non-aqueous electrochemical exfoliation of a few-layer siligene from Ca1.0Si1.0Ge1.0 Zintl phase precursor. The procedure was conducted in an oxygen-free environment applying 3.8 V potential. The obtained silicene exhibits a high-quality, high uniformity, and excellent crystallinity; the individual flake is within the micrometer lateral size. The 2D SixGey was further explored as an anode material for lithium-ion storage. Two types of anode have been fabricated and integrated into lithium-ion battery cells, namely 1) siligene_graphene oxide sponge, and 2) siligene_multi-walled carbon nanotubes. The as-fabricated batteries both with/without siligene exhibit similar behaviour, however referring to the increase in the electrochemical characteristics of SiGe-integrated batteries by 10%. The corresponding batteries exhibit 1145.0 mAh·g-1 specific capacity at 0.1 A·g-1. The SiGe-integrated batteries demonstrate a very low polarization confirmed by their good stability after 50 working cycles and a decrease in the solid electrolyte interface level that occurs after the first discharge/charge cycle. We anticipate the growing potential of emerging two-component 2D materials and their great promise for energy storage and beyond.

Modern life-style is creating an indoor generation: human beings spend approximately 90% of their time indoors, almost 70% of which is at home – this trend is now exacerbated by the lockdowns/restrictions imposed due to the COVID-19 pandemic. That large amount of time spent indoors may have negative consequences on health and well-being. Indeed, poor indoor air quality is linked to a condition known as sick building syndrome. Therefore, breathing the freshest air possible is of outmost importance. Still, due to reduced ventilation rates, indoor air quality can be considerably worse than outdoor. Heating, ventilation, and air conditioning (HVAC), air filtration systems and a well-ventilated space are a partial answer. However, these approaches involve only a physical removal. The photocatalytic mineralization of pollutants into non-hazardous, or at least less dangerous compounds, is a more viable solution for their removal. Titanium dioxide, the archetype photocatalytic material, needs UVA light to be ‘activated’. However, modern household light emitting diode lamps irradiate only in the visible region of the solar spectrum. We show that the surface of titanium dioxide nanoparticles modified with copper oxide(s) and graphene has promise as a viable way to remove gaseous pollutants (benzene and nitrogen oxides) using a common light emitting diode bulb, mimicking real indoor lighting conditions. Titanium dioxide, modified with 1 mol% CuxO and 1 wt% graphene, proved to have a stable photocatalytic degradation rate, three times higher than that of unmodified titania. Materials produced in this research work are thus strong candidates for offering a safer indoor environment. published

Correction for ‘Photocatalytic removal of benzene over Ti3C2Tx MXene and TiO2–MXene composite materials under solar and NIR irradiation’ by Sergii A. Sergiienko et al., J. Mater. Chem. C, 2022, 10, 626–639, https://doi.org/10.1039/D1TC03826E.

Modern life-style is creating an indoor generation: human beings spend approximately 90% of their time indoors, almost 70% of which is at home – this trend is now exacerbated by the lockdowns/restrictions imposed due to the COVID-19 pandemic. That large amount of time spent indoors may have negative consequences on health and well-being. Indeed, poor indoor air quality is linked to a condition known as sick building syndrome. Therefore, breathing the freshest air possible it is of outmost importance. Still, due to reduced ventilation rates, indoor air quality can be considerably worse than outdoor. HVAC, air filtration systems and a well-ventilated space are a partial answer. However, these approaches involve only a physical removal. Photocatalytic mineralisation of pollutants into non-hazardous, or at least less dangerous compounds, is a more viable solution for their removal. Titanium dioxide, the archetype photocatalytic material, needs UVA light to be “activated”. However, modern household light emitting diode lamps irradiate only in the visible region of the solar spectrum. In this short-communication, we show that the surface of titanium dioxide nanoparticles modified with copper oxide(s) and graphene shows promise as a viable way to remove gaseous pollutants (benzene and NOx) by using a common light emitting diode bulb, mimicking real indoor lighting conditions. Titanium dioxide, modified with 1 mol% CuxO and 1 wt% graphene, proved to have a stable photocatalytic degradation rate, three times higher than that of unmodified titania. Materials produced in this research work are thus strong candidates for offering a safer indoor environment.

Electrochemical synthesis of NH3 is a carbon-free alternative to the traditional Haber–Bosch process. Obtaining NH3 from environmental pollutants, such as nitrates or nitrites, is a more practical route than from the nitrogen reduction reaction (NRR) due to the difficult cleavage of the inert triple bond of nitrogen gas. Here, a novel heterogeneous catalyst is reported based on iron (Fe) single-atoms supported on 2D MoS2 (Fe-MoS2) for the nitrate reduction reaction (NO3RR). Fe-MoS2 exhibits remarkable performance with a maximum Faradaic efficiency of 98% for NO3RR to NH3 at an onset potential of −0.48 V versus the reversible hydrogen electrode (RHE) as confirmed by the isotopic nuclear magnetic resonance (NMR) analyses. Density functional theory (DFT) calculations reveal that the enhanced selectivity for the production of NH3 from single Fe atoms supported on MoS2 is attributed to a reduced energy barrier of 0.38 eV associated with de-oxidation of *NO to *N. The catalysts are coupled to an InGaP/GaAs/Ge triple-junction solar cell to demonstrate a solar-to-ammonia (STA) conversion efficiency of 3.4% and a yield rate of 510 µg h−1 cm−2. The results open new avenues for the design of single-atom catalysts (SAC) for the realization of solar-driven ammonia production.

Electrochemical synthesis of NH3 is a carbon-free alternative to the traditional Haber-Bosch process. The challenge with nitrogen reduction reaction (NRR) to NH3 is cleavage of the inert N≡N triple bond of nitrogen gas. Obtaining NH3 from environmental pollutants, such as nitrates or nitrites, is a more practical route than NRR. However, reduction of nitrates or nitrites to ammonia is currently hampered by modest Faradaic efficiencies, typically below 10 %. Here, we report a novel heterogeneous catalyst based on iron (Fe) single-atoms supported on two-dimensional MoS2 (Fe-MoS2) for the nitrate reduction reaction (NO3RR). We have found that Fe-MoS2 exhibits remarkable performance with a maximum Faradaic efficiency of 98 % for NO3RR to NH3 at an overpotential of -0.48 V vs. the reversible hydrogen electrode (RHE) as confirmed by our isotopic nuclear magnetic resonance (NMR) analyses. Density function theory (DFT) calculations reveal that the enhanced selectivity for the production of NH3 from single Fe atoms supported on MoS2 is attributed to a reduced energy barrier of 0.38 eV associated with de-oxidation of *NO to *N – the usual potential limiting step in NO3RR. We assembled our catalyst in a two-electrode electrolyzer coupled to an InGaP/GaAs/Ge triple-junction solar cell to demonstrate a solar-to-ammonia (STA) conversion efficiency of 3.4 % and a yield rate of 0.03 mmol h-1 cm-2 equivalent to 510 µg h-1 cm-2. Our results open new avenues for design of single-atom catalysts (SAC) for the realization of solar-driven ammonia production.

In this study, substochiometric hole-selective molybdenum oxide (MoOx) contacts in crystalline silicon (c-Si) solar cells were investigated by a combination of transmission electron microscopy (TEM) and spatially resolved electron energy-loss spectroscopy (SR-EELS). It was observed that a ≈ 4 nm SiOx interlayer grows at the MoOx/c-Si interface during the evaporation of MoOx over a c-Si substrate. SR-EELS analyses revealed the presence of a 1.5 nm diffused MoOx/indium tin oxide (ITO) interface in both as-deposited and annealed samples. Moreover, the presence of a 1 nm thin layer with a lower oxidation state of Mo was detected at the SiOx/MoOx interface in an as-deposited state, which disappears upon annealing. Overall, it was evident that no hole-blocking interlayer is formed at the MoOx/ITO interface during annealing and homogenization of the MoOx layer takes place during the annealing process. Furthermore, device simulations revealed that efficient hole collection is dependent on MoOx work function and that reduction in the work function of MoOx results in loss of band bending and negatively impacts hole selectivity.

Multifunctional materials working under solely visible-light are expected to play a significant role in photoelectronics, in particular photoswitches, photo-optical sensors, smart windows, displays, optical storage memories, and self-cleaning materials. We have modified the surface of a versatile semiconductor material (TiO2) with a noble metal (copper) and simultaneously doped its structure with a rare-earth element (neodymium). Exploiting the ability of a semiconductor to generate an exciton upon excitation, a multifunctional material working with visible-light and showing photochromic and photocatalytic activity was engineered. A combination of high-resolution (scanning) transmission electron microscopy (including image simulations), spatially resolved electron spectroscopies, and X-ray analyses were used to characterize the structure and local chemical environment of the modified material. We showed that Nd entered the TiO2 structure in a substitutional fashion, and when at 1 mol %, neodymium atoms we...

In this study, we grew 5-layered SrBi4.25La0.75Ti4FeO18 (SBLFT) polycrystalline thin films (80–330 nm thick) via pulsed-laser deposition to study their ferroelectric and magnetoelectric response. Structural/microstructural analysis confirmed the formation of orthorhombic SBLFT with good crystallinity and randomly oriented Aurivillius phases. Detailed scanning transmission electron microscopy analysis of 120 nm film revealed a predominantly five-layered structure with the coexistence of four-layer stacking. Such stacking defects are found to be pertinent to the high structural flexibility of Bi-rich Aurivillius phases, alleviated by lattice strain. Raman spectral features at ambient temperatures depict the signature of the orthorhombic-tetragonal phase transition. SBLFT films have a strong ferroelectric nature (remanent polarization 2Pr of 35 μC cm−2) with a fatigue endurance up to 1010 cycles and strongly improved, switchable magnetization as opposed to its antiferromagnetic bulk counterpart. The scaling behavior of dynamic hysteresis reveals that ferroelectric domain reversal has good stability and low energy consumption. We observed the presence of SBLFT nanoregions (1–5 nm), distributed across the film, with Bi and Fe-rich compositions and oxygen vacancies that contribute to the weak ferromagnetic behavior mediated by the Dzyaloshinskii–Moriya interactions. Subtle changes in the structural strain and lattice distortions of thin films with varied thicknesses led to distinct ferroic properties. Stronger ferroelectric polarization of 80 nm and 120 nm films compared to that of thicker ones can be due to structural strain and the possible rearrangement of BO6 octahedra. The observation of the improved magnetoelectric coefficient of 50 mV cm−1 Oe−1 for 120 nm film, as compared to that of several Aurivillius oxides, indicates that the structural strain modification in SBLFT is beneficial for the fatigue-free magnetic field switching of ferroelectric polarization. The structural strain of the unit cell as well as the presence of Bi- and ferromagnetic Fe-rich nanoregions was found to be responsible for the improved multiferroic behaviour of the SBLFT films.

The conversion of CO2 into desirable multicarbon products such as ethylene and ethanol via the carbon dioxide reduction reaction (CO2RR) hold promise to achieve a circular carbon economy. The develop of such a technology is currently hampered by the lack of catalysts, which can drive the reaction at industrially relevant current densities with high efficiency and selectivity. Here, we report a novel strategy for increasing the conversion of CO2 into hydrocarbon molecules with two or more carbon atoms (C2+) by modifying the surface of bimetallic silver-copper (Ag-Cu) catalyst with aromatic heterocycles such as thiadiazole and triazole derivatives. By combining operando Raman and X-ray absorption spectroscopy with electrocatalytic measurements and analysis of the reaction products, we identified that the electron withdrawing nature of functional groups orients the reaction pathway towards the production of C2+ species such as ethanol and ethylene and enhances the reaction rates on the surface of the catalyst. As a result, we achieve a maximum Faradaic efficiency for the formation of C2+ of ≈ 80% and full-cell energy efficiency of 20.3% with a specific current density of 261.4 mA cm-2 for C2+ using functionalized Ag-Cu electrodes, compared to only 33.8% and 70.6 mA cm-2 for the pristine Ag-Cu electrodes. We anticipate that our strategy can further be extended in order to improve the selectivity of the reaction towards the production of specific multicarbon molecules.

International audience; The CO2 reduction reaction using a renewable energy source is a promising strategy for its utilization. Such a technology however requires the development of catalysts with optimized activity and selectivity that can be integrated into the device architectures. Flow electrolyzers have recently been proposed for facilitating the electrochemical CO2 reduction reaction thanks to their unique ability to perform electroreduction at high reaction rates via the creation of three-phase interface. While some examples of flow electrolyzers for the conversion of CO2 has recently been reported, the influence of the CO2 and electrolyte streams on the overall catalytic mechanism is remained ambiguous. Here, we synthesized single-atom nickel on two-dimensional nitrogen-doped carbon nanosheets (SA Ni-NC) for the CO2-to-CO conversion. Taking advantage of this model catalyst, we explored the correlation between the applied potential and the feeds in both

Outdoor and indoor air pollution is a global environmental concern in modern society. Although many policies and regulations on air quality have been promulgated worldwide over the past decades, airborne pollution still negatively affects health and therefore the life-style of human beings. One of the strategies to challenge this problem might be reducing the amount of airborne pollutant by mineralising them via photoinduced reactions. Photocatalytic oxidation of gaseous pollutants via titanium dioxide is one of the most investigated solar photochemical reactions. In this research work, by means of a green sol-gel procedure, we have coupled titania to graphene (0.5 and 1.0 wt%) aiming to increase the solar photocatalytic activity of the produced hybrid materials. The photocatalytic reactions were assessed by monitoring the removal of nitrogen oxides and two different volatile organic compounds (benzene and isopropanol). Photocatalytic mechanism was investigated by means of EPR spin trapping experiments.Our results highlight the exceptional characteristics of the TiO2/graphene hybrid material (1.0 wt% graphene), and its suitability for multi-purpose applications in the field of environmental remediation. Compared to unmodified titania, the hybrid material with 1.0 wt% graphene shows a clear enhancement in the photocatalytic removal of those hazardous pollutants – corresponding to more than twice the photocatalytic degradation rate. In addition, the same material is highly stable and shows fully recyclability over repeated tests. Hybrid titania-graphene materials could thus be exploited to grant a safer outdoor and indoor environments, having a beneficial impact on public health and thus on the quality of our lives.

Indoor and outdoor air pollution remains a major health risk for human beings. Nitrogen oxides and volatile organic compounds are amongst the major pollutant found outdoor. Thus, actions to diminish such risks and to provide safer outdoor / indoor environment are required. In this research work, we have decorated the surface of TiO2 with noble-metal oxides (Ag and/or CuxO) to improve the photocatalytic performances (removal of nitrogen oxides and benzene) under simulated solar-light irradiation. By means of advanced X-ray methods it has been shown that noble metals did not enter the TiO2 crystal structure, although they retarded the anatase-to-rutile phase transition and crystal growth. Photocatalytic activity was assessed in the gas-solid phase, monitoring the degradation of NOx and benzene, using a lamp simulating the solar radiation. Results showed that TiO2 modified with an Ag:Cu molar ratio equal to 1:1 (with Ag+Cu = 0.5+0.5 mol% = 1 mol%), was that exhibiting best de-NOx and benzene removal performances.

Electrochemical sensors for monitoring biochemical substances are attracting considerable attention. These devices are usually based on enzymes that are sensitive and very specific. Still, the activity of those enzymes is lost with changes in temperature or pH. Non-enzymatic electrochemical sensors – fabricated via the modification of the electrode surface with metal oxide nanoparticles – are a judicious answer. In this study, we investigated the photo-electrochemical properties of CuO–TiO2 heterojunctions for glucose sensing in alkaline media. A combination of high-resolution (scanning) transmission electron microscopy, spatially resolved electron energy-loss spectroscopy, energy-dispersive X-ray spectroscopy and X-ray powder diffraction, was used to study in detail the microstructures of the prepared specimens. These results highlighted the strong intertwining between the TiO2 nanoparticles and the Cu-based nanoparticles, which present a metallic core with a CuO rich surface. In addition, we showed that CuO, joint to TiO2, has smaller size compared to pure CuO, which entails larger surface area available for the glucose electro-oxidation, which consequently enhanced the electrochemical features. The influence of Cu loading over the sensing performance of TiO2 was examined in detail carrying out electrochemical sensing tests under dark, laboratory and halogen lamp irradiation. Results demonstrated that, under halogen lamp irradiation, modified CuO–TiO2 electrodes showed a higher specific response signal than that of pure CuO. Those increased photo-electrochemical properties in CuO–TiO2 heterojunctions are likely due to a synergistic effect between the microstructural characteristics and effective separation of photo-generated exciton created at the heterojunction interface. Results of this study offer applicable guidelines for designing photo-electrochemical screen-printed electrodes based on nano-sized CuO on titania for an efficient detection of glucose.

Hydrogen, as energy carrier, is a zero-emission fuel. Being green and clean, it is considered to play an important role in energy and environmental issues. Photocatalytic water splitting is a process used to generate hydrogen from the dissociation of water. Titanium dioxide is still the archetype material for photocatalytic water splitting. However, because of the fast recombination of the photo-generated exciton, the yield of the reaction is typically low. In this work, we have modified the surface of titanium dioxide with copper and copper/graphene to sensitise it to visible light, and to increase the spatial charge carrier separation, thus extending the quantum yield of H2 production from methanol/water mixtures. Results showed that, in the analysed system, exists an optimum amount of copper plus graphene (i.e. 0.5 mol% copper plus 0.5 wt% graphene) to grant a two-fold increase in the photocatalytic hydrogen generation compared to that of bare titania. That system proved itself to be complex and dynamic. This was attributed to the increased spatial charge carrier separation exploited by graphene (under 365 and 405 nm irradiation), and to the continuous reduction of Cu(II) to Cu(I) due to IFCT that has proven to be an excellent visible-light sensitiser in the copper/graphene-titania system.Hybrid titania-copper-graphene materials could therefore be exploited in the field of light-to-energy applications.

Introduction Primitive extraterrestrial materials like carbonaceous chondrite matrices and interplanetary dust particles contain tiny dust grains that were formed in the winds of red giant branch, or asymptotic giant branch stars (AGB) and in the ejecta of novae and supernovae (SNe) explosions before the formation of our solar system. Following their formation, these tiny stardust grains of submicron size traversed through the interstellar medium before being incorporated into the cloud of gas and dust that collapsed and created our solar system. Presolar grains survived the high energy processes that created our solar system and, in their isotopic compositions, preserved the fingerprints that are the nucleosynthetic signatures of the parent stellar sources of the grains.1 Correlating isotopic data of individual presolar silicates with microstructural and chemical analyses obtained by (S)TEM, provides a unique opportunity to provide better insights into physiochemical conditions of grain formation in stellar environments, grain alteration in the interstellar and parent body processes and also helps constraining various astrophysical grain condensation models. In this work, isotopic, structural and chemical analysis of nine presolar silicate grains from the CH3/CBb3 chondrite Isheyevo and CR2 chondrite NWA801 are reported. The grains studied here are found within the lithic clasts in Isheyevo and fine grained chondrule rims in NWA801 that have experienced lower amount of parent body alteration and hence the chemical compositions of presolar grains studied here are minimally altered. Experimental Presolar oxygen anomalous grain search using oxygen isotope imaging was done in-situ using NanoSIMS50 ion microprobe and five grains from AGB and four grains from SNe, were selected for (S)TEM investigations. The TEM lamellas were prepared using a TESCAN LYRA3 FIB-SEM at Curtin University. Structural and chemical analysis of presolar grains were performed by combining high-resolution scanning TEM imaging, spatially-resolved electron energy-loss spectroscopy (EELS) and spatially-resolved energy-dispersive X-ray spectroscopy (EDS) by using a FEI Titan Cubed Themis 60-300 microscope at the University of Cádiz which was operated at 200 kV. EDS quantification was corrected by using a standard reference sample of known composition and density and by taking into account the thickness of the probed area as determined by using low-loss EELS. EELS spectrum images for fine structures (mostly, O-K, Si-L2,3 and Fe-L2,3 edges) analyses were acquired with the monochromator excited allowing an energy resolution of about 0.4 eV. After denoising using principal components analysis and removal of the multiple scattering, we were able to map the heterogeneities related to the Fe oxidation states and to the oxygen local chemical environment. For the chemical mapping of the Fe3+/ ∑Fe ratios, we have used a home-made Python routine based on the determination of the modified white-lines ratio.2 It allowed us to compare the degree of aqueous alteration of the grain with the surrounding rim and matrix grains. Results TEM and STEM data have revealed a strong heterogeneity and a broad range of structural and chemical compositions of the grains that enabled us to compare the stellar grain condensation environments (e.g. AGB stars and SNe), and suggest widely varying formation conditions for the presolar silicates identified in this study. Only one of the grains originally condensed as an amorphous grain has shown preferential sputtering of Mg, indicating that Mg-rich amorphous grains are not preferentially destroyed. Several grains are found with signatures that represent interstellar, nebular and parent body alteration. An oldhamite-like grain (Figure 1) within a presolar enstatite grain is probably the first observation of an oldhamite grain as a seed grain for the condensation of an enstatite grain in stellar atmospheres. This grain corresponds to a local increase in Mg and a local decrease in Fe with respect to the surrounding matrix. The surface of the grain surface of up to ~40 nm is composed of higher amounts of Ca and S. Below the surface of the grain and on the left side, diffusion streaks rich in Ca can be observed up to the lower boundary of the grain (on about 250 nm). The diffusion of Ca could be related to thermal processes and/or aqueous alterations undergone by the grain. Figure 2 shows typical EELS chemical maps acquired on the same grain. A very thin Fe-rich rim is also seen around the enstatite grain with a Fe3+/ΣFe ratio of about 0.6-0.7. The presence of several spherical nodules of Fe and Ni sulfide can also be highlighted in the matrix around the grain in the EDS and EELS chemical maps (red arrows in Figures 8 and 9). They have a diameter of about 30-45 nm and are similar to GEMS-like materials. Interestingly, they present a core/shell structure All these results, which will be discussed in detail, point out the importance of coordinated isotopic, microstructural and chemical studies of presolar silicates to investigate the processes that may have played a role in shaping our solar system. Zinner, E., (2014) Treatise on Geochemistry, Vol. 1 2nd ed. ed AM Davis Van Aken, P. A., B. Liebscher, and V. J. Styrsa. "Quantitative determination of iron oxidation states in minerals using Fe L 2, 3-edge electron energy-loss near-edge structure spectroscopy." Physics and Chemistry of Minerals 25.5 (1998): 323-327 Figure 1. a) STEM-HAADF micrograph of the grain Isheyevo_9. The red dashed lines line highlights the boundary of the grain. b) Superposition of HAADF micrograph and Ca chemical maps derived from EDS analysis. Chemical maps derived from EDS analyses corresponding to c) Fe, d) Ni, e) Mg and f) S elements. The red arrows highlight the presence of GEMS-like materials. Figure 2. Chemical maps derived from the EELS analysis for the grain Isheyevo_9 and corresponding to a) Fe, b) O, c) the O-K pre-peak, d) F and e) the Fe+3/ΣFe ratio. The black scale bar represents 0.1 µm. The red arrows highlight the presence of GEMS-like materials.

Nanostructured systems showing reversible colour switching are envisaged to play a significant role in photo-switches, photo-optical sensors, smart windows, displays, optical storage memories. Most of the materials exhibiting reversible colour switching are organic compounds. However, their UV-light activation, low thermal and chemical stability, as well as harmful synthesis methods, are of limit for their extensive use. In this research, we have created an inorganic switchable photochromic material exploiting: (i) TiO2 ability of creating an exciton upon excitation, (ii) copper as the chromophore, and (iii) graphene’s extraordinarily high electron mobility. Our material showed itself to be able to work under visible-light, its photochromic property being three times faster than conventional titania based photochromic materials, reaching a stable change in colouration after only 30 mins of visible-light irradiation (versus > 120 min in conventional Cu-TiO2). With the addition of just 1 wt% graphene, the material exhibited a staggeringly stable photochromic switching over repeated cycles. These results relate to the best previously reported values for any form of TiO2-based photochromic material. This is therefore an excellent candidate for smart self-cleaning windows, and other chromic devices and applications.

Nanostructured systems showing reversible color switching are envisaged to play a significant role in photo-switches, photo-optical sensors, smart windows, displays, optical storage memories. Most of the materials exhibiting reversible color switching are organic molecules. However, their UV-light activation, low thermal and chemical stability, as well as harmful synthesis methods, limit their extensive use. In this research, we have created an inorganic switchable photochromic material exploiting TiO2 ability of creating an exciton upon excitation, copper as the chromophore, and graphene's extraordinarily high electron mobility. Spatially-resolved electron energy-loss spectroscopy and aberration-corrected transmission electron microscopy imaging highlight the high sp2 content of the graphene flakes as well as the presence of few-layers nanocage graphene decorating the surface of the flakes. Our material showed itself to be able to work under visible-light, its photochromic property being three times faster than conventional titania based photochromic materials, reaching a stable change in coloration after only 30 min of visible-light irradiation (vs. > 120 min in conventional Cu–TiO2). With the addition of just 1 wt% graphene, the material exhibited a staggeringly stable photochromic switching over repeated cycles. These results relate to the best previously reported values for any form of TiO2-based photochromic material. This is therefore an excellent candidate for smart-windows, light-sensitive information and energy storage devices, and other chromic devices and applications.

We report the structural and chemical investigation of nine presolar silicate grains from the CH3/CBb3 chondrite Isheyevo and CR2 chondrite Northwest Africa (NWA) 801. Five of these grains belong to group 1, likely condensed in low- to intermediate-mass asymptotic giant branch (AGB) stars, super-AGB stars, or core-collapse supernovae, while the remaining four grains belong to group 4 and have a supernova origin. The advanced transmission electron microscopy and associated electron spectroscopy analyses show a diverse range of chemical and structural compositions for presolar silicates. Two GEMS (glass with embedded metal and sulfide)-like silicates, each from different groups, condensed under nonequilibrium conditions in stellar outflows. Two nonstoichiometric silicates from group 1 have dissimilar formation and alteration histories. An amorphous silicate from group 1 with olivine-like [(Mg,Fe)2SiO4] composition likely formed as a crystalline olivine that subsequently amorphized in the interstellar medium. An oldhamite (CaS) grain within a stoichiometric enstatite (MgSiO3) from group 1 probably formed by heterogeneous condensation in circumstellar outflows. Of the two crystalline grains from group 4, one is an antigorite [(Mg,Fe)3Si2O5(OH)4], while the other is a nontronite [Na,Fe2(Si,Al)4O10(OH)2.nH2O], both formed as a crystalline forsterite and later altered to have hydrated silicate composition. A group-4 silicate has a chemical composition similar to a low Ca-pyroxene [(Ca,Mg)(Si,Al)2O6]. Our data imply that presolar grains from different groups can have a similar range of grain-formation conditions.

We have synthesized quaternary chalcogenide-based misfit nanotubes LnS(Se)-TaS2(Se) (Ln = La, Ce, Nd, and Ho). None of the compounds described here were reported in the literature as a bulk compound. The characterization of these nanotubes, at the atomic level, has been developed via different transmission electron microscopy techniques, including high-resolution scanning transmission electron microscopy, electron diffraction, and electron energy-loss spectroscopy. In particular, quantification at sub-nanometer scale was achieved by acquiring high-quality electron energy-loss spectra at high energy (∼between 1000 and 2500 eV). Remarkably, the sulfur was found to reside primarily in the distorted rocksalt LnS lattice, while the Se is associated with the hexagonal TaSe2 site. Consequently, these quaternary misfit layered compounds in the form of nanostructures possess a double superstructure of La/Ta and S/Se with the same periodicity. In addition, the interlayer spacing between the layers and the interatom...

A new and original method, based on a non-aqueous sol–gel process, has been successfully established to produce quasi-spherical monodispersed TiO 2 nanoparticles (NPs) and also noble metals (NM) @TiO 2 heterostructures (NM = Au, Pt, Ag, 2 wt%), in one-pot and at low temperature. This has been achieved by using titanium oxyacetylacetonate as new single source precursors. This system has been deeply investigated by advanced characterization techniques. By using NMR, we have demonstrated the relatively complex mechanism behind this apparently simple synthesis, mediated by the reaction of the solvent and generated species, with many separate organic and organometallic molecules identified as being involved in the mechanism. The morphology and structure of the NM@TiO 2 heterostructures were investigated by advanced scanning transmission electron microscopy while the chemical state of the noble metal nanoparticles was check by X-ray photoelectron spectroscopy (XPS). Undoped and noble metal (Au, Pt, Ag) decorated quasi/spherical TiO 2 nanoparticles worked also as sensing interfaces, leading to the development of a highly sensitive conductometric NO gas sensor under both dark and UV–vis light irradiation, in the first result of its kind. Furthermore, the photocatalytic activity (PCA) was also evaluated, in the gas–solid phase, by monitoring the degradation of NO x under solar-light irradiation. Au-modified TiO 2 showed improved photocatalytic efficiencies, compared to unmodified TiO 2 .

The texture, structure, composition, and electronic state of new and used monolithic Mn-Cu catalysts were studied. Characterisation was performed at different scales and spatial resolution by combining STEM-FIB and imaging techniques (STEM-HAADF) and spectroscopy (STEM-EDX and EELS of space resolution). A thickness of the alumina layer that varies between 1 and 2 µm was observed, while the thickness of the Mn-Cu catalyst layer varies linearly with the number of charges between 1 µm and 2 µm, for 1 and 2 charges, respectively. In both fresh and used catalysts, the migration of both phases was observed to a different extent, depending on the number of charges of the Mn-Cu phase. This was associated with the synthesis conditions or the catalytic behaviour in the combustion of the n -hexane. The STEM-EDX analyses showed a homogeneous distribution of Mn and Cu, with values like the theoretical one. At the nanoscale, the SR-EELS analyses detected the presence of nanometric patches with lower Cu content, chemically inhomogeneous with a higher Mn oxidation state than the rest of the material. The advanced characterisation techniques used in this work allowed the precise identification of part of the constitutive phases of the Mn-Cu system generated in-situ on the monolith. Among them, manganese oxides with different oxidation states (MnO, Mn3O4, Mn2O3), Mn3Cu3O8 and CuO were detected.

Low-dimensional misfit layered compounds have been found to have ultralow thermal conductivity, which is attributed to their unique structure and the low dimensionality. There are a few studies reporting the preparation of sulfide-based misfit nanotubes but only one study on oxide-based analogs. In this investigation, we report a new oxide-based misfit nanotube derived from misfit layered strontium cobaltite. Thorough structural investigation by electron microscopy techniques, including electron diffraction, aberration corrected high-resolution (scanning) transmission electron microscopy, and electron energy-loss spectroscopy along with density functional theory calculations show that these nanotubes consist of alternating layers of SrCoO2 and CoO2. We have studied systematically the effect of base concentration on the structure and composition of the nanotubes, which reveals the importance of misfit stress to tightly roll the structure into tubular form and thus control the synthesis. Electronic structure calculations find that the structures are semiconducting with a ferrimagnetic ground state. Our studies further extend the family of bulk misfit layered oxides into the 1D realm with potential applications in thermoelectric and electronic devices.

This article belongs to the Special Issue Characterization of Disorder in Carbons., Multiwavelength Raman spectroscopy (325, 514, 633 nm) was used to analyze three different kinds of samples containing sp2 and sp3 carbons: chemical vapor deposited diamond films of varying microstructure, a plasma-enhanced chemical vapor deposited hydrogenated amorphous carbon film heated at 500 °C and highly oriented pyrolytic graphite exposed to a radio-frequent deuterium plasma. We found evidence that the lower part of the phonon density of states (PDOS) spectral region (300–900 cm−1) that rises when defects are introduced in crystals can give more information on the structure than expected. For example, the height of the PDOS, taken at 400 cm−1 and compared to the height of the G band, depends on the sp2 content, estimated by electron energy-loss spectroscopy. This ratio measured with 633 nm laser is more intense than with 514 nm laser. It is also correlated for diamond to the relative intensity ratio between the diamond band at 1332 cm−1 and the G band at ≈1500–1600 cm−1 when using 325 nm laser. Moreover, it is found that the shape of the PDOS of the exposed graphite samples is different when changing the wavelength of the laser used, giving evidence of a double resonance mechanism origin with the rise of the associated D3, D4 and D5 bands, which is not the case for a-C:H samples., R.A. gratefully acknowledges the support from the Spanish Ministerio de Economia y Competitividad (MAT2016-79776-P) and from the European Union H2020 program “ESTEEM3” (823717).".

Multifunctional materials working under solely visible-light are expected to play a significant role in photo-electronics, in particular photo-switches, photo-optical sensors, smart windows, displays, optical storage memories, and self-cleaning materials.In this work, we have modified the surface of a versatile semiconductor material (TiO2) with a noble metal (copper), and simultaneously doped its lattice with a rare-earth element (neodymium). Exploiting the ability of a semiconductor to generate an exciton upon excitation, a multifunctional material working with visible-light and showing photochromic, photoluminescent and photocatalytic activity was engineered. Advanced transmission electron microscopy techniques – aberration-corrected imaging combined with image simulation, statistical analyses and electron energy-loss spectroscopy – were used to characterise thoroughly the structure and local chemical environment as a function of the Nd3+ content, as well as to link the variation of these aspects to the evolution of the physico-chemical properties. Combined X-ray, spectroscopic and microscopy technique results showed that Nd entered the TiO2 lattice in a substitutional fashion. When at 1 mol%, neodymium atoms were ultra-dispersed inside the TiO2 (anatase) structure. On the contrary, when the neodymium mol% was higher than 1 mol%, neodymium atoms mostly clustered at the surface of the grains, forming a dense network. Furthermore, the Cu-modified / Nd-doped TiO2 exhibited faster (two times), as well as a reversible photoswitching that was remarkably more stable compared to standard Cu-TiO2 photochromic material. The same material also displayed visible-light and solar-light induced photocatalytic activity in the gas-solid phase (degradation of benzene, one of the most hazardous pollutants found indoor) superior to unmodified titania (1.35 and nearly 3.00 times higher, with a LED visible- and solar-light lamps, respectively). It was demonstrated that the optimum amounts of copper and neodymium, for both photochromic and photocatalytic performances, were 1 mol%.

Multifunctional materials working under solely visible-light are expected to play a significant role in photo-electronics, in particular photo-switches, photo-optical sensors, smart windows, displays, optical storage memories, and self-cleaning materials.In this work, we have modified the surface of a versatile semiconductor material (TiO2) with a noble metal (copper), and simultaneously doped its lattice with a rare-earth element (neodymium). Exploiting the ability of a semiconductor to generate an exciton upon excitation, a multifunctional material working with visible-light and showing photochromic, photoluminescent and photocatalytic activity was engineered. Advanced transmission electron microscopy techniques – aberration-corrected imaging combined with image simulation, statistical analyses and electron energy-loss spectroscopy – were used to characterise thoroughly the structure and local chemical environment as a function of the Nd3+ content, as well as to link the variation of these aspects to the evolution of the physico-chemical properties. Combined X-ray, spectroscopic and microscopy technique results showed that Nd entered the TiO2 lattice in a substitutional fashion. When at 1 mol%, neodymium atoms were ultra-dispersed inside the TiO2 (anatase) structure. On the contrary, when the neodymium mol% was higher than 1 mol%, neodymium atoms mostly clustered at the surface of the grains, forming a dense network. Furthermore, the Cu-modified / Nd-doped TiO2 exhibited faster (two times), as well as a reversible photoswitching that was remarkably more stable compared to standard Cu-TiO2 photochromic material. The same material also displayed visible-light and solar-light induced photocatalytic activity in the gas-solid phase (degradation of benzene, one of the most hazardous pollutants found indoor) superior to unmodified titania (1.35 and nearly 3.00 times higher, with a LED visible- and solar-light lamps, respectively). It was demonstrated that the optimum amounts of copper and neodymium, for both photochromic and photocatalytic performances, were 1 mol%.

Titanium dioxide is by far the most utilised semiconductor material for photocatalytic applications. Still, it is transparent to visible-light. Recently, it has been proved that a type-II band alignment for the rutile−anatase mixture would improve its visible-light absorption.In this research paper we thoroughly characterised the real crystalline and amorphous phases of synthesised titanias – thermally treated at different temperatures to get distinct ratios of anatase-rutile-amorphous fraction – as well as that of three commercially available photocatalytic nano-TiO2. The structural characterisation was done via advanced X-ray diffraction method, namely the Rietveld-RIR method, to attain a full quantitative phase analysis of the specimens. The microstructure was also investigated via an advanced X-ray method, the whole powder pattern modelling. These methods were validated combining advanced aberration-corrected scanning transmission microscopy and high-resolution electron energy-loss spectroscopy. The photocatalytic activity was assessed in the liquid- and gas-solid phase (employing rhodamine B and 4-chlorophenol, and isopropanol, respectively, as the organic substances to degrade) using a light source irradiating exclusively in the visible-range.Optical spectroscopy showed that even a small fraction of rutile (2 wt%) is able to shift to lower energies the apparent optical band gap of an anatase-rutile mixed phase. But is this enough to attain a real photocatalytic activity promoted by merely visible-light?We tried to give a reply to that question.Photocatalytic activity results in the liquid-solid phase showed that a high surface hydroxylation led to specimen with superior visible light-induced catalytic activity (i.e. dye and ligand-to-metal charge transfer complexes sensitisation effects). That is: not photocatalysis sensu-strictu.On the other hand, the gas-solid phase results showed that a higher amount of the rutile fraction (around 10 wt%), together with less recombination of the charge carriers, were more effective for an actual photocatalytic oxidation of isopropanol.

Hydrogen, as an energy carrier, is a zero-emission fuel. Being green and clean, it is considered to play an important role in energy and environmental issues. Photocatalytic water splitting is a process used to generate hydrogen from the dissociation of water. Titanium dioxide is the archetype material for photocatalytic water splitting. However, because of the fast recombination of the photo-generated exciton, the yield of the reaction is typically low. To overcome this limit, in this work, the surface of the TiO2 nanoparticles was modified with copper and graphene to give hybrid nanostructures. Synthesized materials were tested in the photocatalytic hydrogen generation using methanol as the sacrificial agent. X-ray diffraction and spectroscopic results showed that copper did not enter the TiO2 structure, and that neither copper nor graphene substantially altered the optical band-gap of prepared photocatalysts. Detailed aberration-corrected high-resolution electron transmission electron imaging and spatially resolved energy-loss spectroscopy experiments showed the oxidation and amorphization of graphene nanoplatelets, probably due to the combined action of the acidic media of the solution with the thermal treatment necessary to produce the hybrid materials. Hydrogen generation from methanol/water mix proved that exists an optimum concentration of both copper and graphene (i.e. 0.5 mol% copper plus 0.5 wt% graphene) to grant a two-fold increase in hydrogen production compared with that of unmodified titania when using UVA irradiation. A higher amount of initial graphene (i.e. 1.0 wt% graphene and 0.5 mol% copper) was instead necessary for granting higher H2 generation on visible-light exposure. Hybrid materials based on titania modified with both copper oxide and carbon-based materials could therefore be exploited as ideal candidates for light-to-energy applications.

Graphical abstract, Highlights • High throughput low-cost sol–gel graphene-TiO2 nanocomposites. • EPR proved different radicals upon excitation: complex reaction pathways. • Stable and high performance photocatalytic removal of VOCs and NOx. • 1 wt% graphene gave 2-fold increase in photocatalytic VOCs & NOx removal. • Graphene to increase electric transport; decrease exciton recombination., Outdoor and indoor air pollution has become a global concern in modern society. Although many policies and regulations on air quality have been promulgated worldwide over the past decades, airborne pollution still negatively affects health and therefore the life-style of human beings. One of the strategies to challenge this problem might be reducing the amount of airborne pollutant by mineralising them via photoinduced reactions. Photocatalytic oxidation of gaseous pollutants via titanium dioxide is one of the most promising solar photochemical reactions. In this research work, by means of a green sol–gel procedure, we have coupled titania to graphene (0.5 and 1.0 wt%) aiming to increase the solar photocatalytic activity of the produced hybrid materials. Transient paramagnetic species formed upon UV-A irradiation were detected by means of EPR spectroscopy. The photocatalytic reactions were assessed by monitoring the removal of nitrogen oxides and two different volatile organic compounds (benzene and isopropanol), which has never been assessed before. Our results highlight the exceptional characteristics of the TiO2/graphene hybrid material synthesised with 1.0 wt% graphene, and its excellent suitability for multi-purpose applications in the field of environmental remediation. Compared to unmodified titania, it shows a clear enhancement in the photocatalytic removal of those hazardous pollutants, having a photocatalytic degradation rate twice higher. In addition, the same material is highly stable and shows fully recyclability over repeated tests. Hybrid titania-graphene materials could thus be exploited to grant safer outdoor and indoor environments, having thus a beneficial impact on public health and on the quality of our lives.

The non-stoichiometric misfit layered compounds (MLC) of the general formula ((MX)1+y)m(TX2)n (abbreviated herein as MX-TX2) have been investigated quite extensively over the last 30 years. Here MX is a atomic slab of a material with distorted rocksalt structure and TX2 is a layered compound with hexagonal (octahedral) coordination between the metal T atom and the chalcogen X atom. Recognizing the mismatch between the two (MX and TX2) sublattices, nanotubes from the MLC of different compositions were described in the past. In particular, semimetallic nanotubes belonging to the family LnX-TaX2 with Ln = rare earth atom and X = S, Se, Te have been studied in the past. While some of them, like LaS-TaS2 were obtained with moderately high yields, others like YbS-TaS2 were scarce. In the present study, a new strategy for promoting the yield of such MLC nanotubes by alloying the LaS sublattice with another Ln atom is proposed. Detailed transmission electron microscopy investigation of the (mixed) LnxLa(1-x)S-TaS2 (Ln = Pr, Sm, Ho, Yb) nanotubes show clearly that the substituting Ln atom resides in the rocksalt LaS sublattice of the nanotubes. Raman measurements show distinct differences between mixed tubes with open-shell (Pr, Sm, Ho) and close-shell (La, Yb) rare-earth atoms. Density functional calculations show that the interplay between two important factors determine the enhanced stability of the mixed nanotubes- the size and electronic structure of the substituting rare-earth atom. The smaller is the substituting rare-earth atom (larger Z number), the more dissimilar it is to the original La atom. This dissimilarity enhances the incommensurability between the LnxLa(1-x)S and the TS2 subunits, promoting thereby the stability of the mixed MLC. However, the electronic structure of the Ln atom was found to play a more significant role. The MLC lattice of the LaS-TaS2 is electron-rich and consequently the 4dz2 level of Ta is full. The unoccupied 4f levels of the substituent open-shell atoms (Pr, Sm, Ho), which are positioned below the Fermi level, serve as electron acceptors. Consequently, the Ln substitution is found to enhance the stability of the mixed lattice and nanotubes thereof. This strategy can be employed for enhancing the yield of these and other misfit nanotubes using different substituents of the right size and energy profile.

Strontium hafnium oxide (SrHfO3) has great potential as a high-k gate dielectric material, for use in memories, capacitors, CMOS and MOSFETs. We report for the first time the dielectric properties (relative permittivity and capacitance) of SrHfO3 nanoparticles (NPs), as opposed to thin films or sintered bulk ceramics. These monodisperse, ultra-small, perovskite-type SrHfO3 nanocrystals were synthesised through a non-aqueous sol-gel process under solvothermal conditions (at only 220 degrees C) using benzyl alcohol as a solvent, and with no other capping agents or surfactants. Advanced X-ray diffraction methods (whole powder pattern modelling, WPPM), CS-corrected high-resolution scanning transmission electron microscopy (HRSTEM), dielectric spectroscopy, and optical (UV-vis, Raman) and photoluminescent spectroscopy were used to fully characterise the NPs. These SrHfO3 NPs are the smallest reported and highly monodisperse, with a mean diameter of 2.5 nm, a mode of 2.0 nm and a small size distribution. The formation mechanism of the NPs was determined using NMR and GC-MS analysis of the species involved. Our SrHfO3 nanoparticles had a dielectric constant of 17, which is on par with literature data for bulk and thin film samples, and they also had a relatively large capacitance of 9.5 nF cm(-2). As such, they would be suitable for applications as gate dielectrics for capacitors and in metal-oxide semiconductor field-effect transistor (MOSFET) technology.

International audience; A new Ag@m-Ag2Mo2O7 plasmonic hybrid nanostructure was designed by an easy two-step synthesis method. Firstly, very thin photosensitive monoclinic m-Ag2Mo2O7 nanowires (NWs) were synthesized under ambient pressure and at low temperature by using Ag2Mo3O10·2H2O NWs as a pre-nanostucturated starting material. This innovative soft chemistry route offers some precise control over the purity, the structure and the nanostructuration of the m-Ag2Mo2O7 NWs that exhibit a very thin diameter of around 100 nm and a superior specific surface area compared to previously reported synthesis methods. Secondly, the plasmonic hybrid nanostructure Ag@m-Ag2Mo2O7 was easily in situ obtained via an all solid-state photodeposition method, by irradiating the m-Ag2Mo2O7 NWs under low energy and low-power UV-light. The composition, morphology and plasmonic properties of the nanocomposite were investigated by a combination of energy-dispersive X-ray spectroscopy, high-resolution scanning transmission electron microscopy, X-ray photoelectron spectroscopy and Auger spectroscopy, and near-infrared, Raman and UV-vis spectroscopies as well as spatially-resolved electron energy-loss spectroscopy. A plausible mechanism explaining the formation of the nano-heterostructure under irradiation was also discussed. The Ag@m-Ag2Mo2O7 nanostructure manifests interesting plasmonic properties particularly high surface-enhanced Raman scattering (SERS) sensitivity probed using 2,2′-bipyridine.

As nanomaterials are dominating 21st century''s scene, multiple functionality in a single (nano)structure is becoming very appealing. Inspired by the Land of the Rising Sun, we designed a bifunctional (gas-sensor/photochromic) nanomaterial, made with TiO2 whose surface was simultaneously decorated with copper and silver (the Cu/Ag molar ratio being 3:1). This nanomaterial outperformed previous state-of-the-art TiO2-based sensors for the detection of acetone, as well as the Cu-TiO2-based photochromic material. It indeed possessed splendid sensitivity toward acetone (detection limit of 100 ppb, 5 times lower than previous state-of-the-art TiO2-based acetone sensors), as well as reduced response/recovery times at very low working temperature, 150 °C, for acetone sensing. Still, the same material showed itself to be able to (reversibly) change in color when stimulated by both UV-A and, most remarkably, visible light. Indeed, the visible-light photochromic performance was almost 3 times faster compared to the standard Cu-TiO2 photochromic material - that is, 4.0 min versus 10.8 min, respectively. It was eventually proposed that the photochromic behavior was triggered by different mechanisms, depending on the light source used.

Misfit layered compounds (MLC) with the composition (LaS)1.15TaS2 (for simplicity denoted as LaS-TaS2) and LaS-NbS2 were prepared and studied in the past. Nanotubes of LaS-TaS2 could be easily synthesized, while tubular structure of the LaS-NbS2 were found to be rather rare in the product. To understand this riddle, quaternary alloys of LaS-NbxTa(1–x)S2 with ascending Nb concentration were prepared herein in the form of nanotubes (and platelets). Not surprisingly, the concentration of these quaternary nanotubes shrank (and the relative density of platelets increased) with increasing Nb content in the precursor. The structure and chemical composition of such nanotubes was elucidated by electron microscopy. Conceivably, the TaS2 in the MLC compounds LnS-TaS2 (Ln = lanthanide atom) crystallizes in the 2H polytype. High resolution transmission electron microscopy showed however that, invariably, MLC nanotubes prepared from 80 at% Nb content in the precursor belonged to the 1T polytype. Raman spectroscopy of individual tubes revealed that up to 60 at% Nb, they obey the standard model of MLC, while higher Nb lead to large deviations, which are discussed in brief. The analysis indicated also that such nanotubes do not exhibit the pattern assigned to charge density wave transition so typical for binary 1T-TaS2. The prospect for revealing interesting quasi-1D behavior of such quaternary nanotubes is also briefly discussed., R.A. gratefully acknowledges the support from the Spanish Ministry of Economy and Competitiveness (MINECO) through project Grant No. MAT2016-79776-P (AEI/FEDER, UE). We acknowledge the support of the Irving and Cherna Moskowitz Center for Nano and Bio-Nano Imaging; the Perlman Family Foundation; the Kimmel Center for Nanoscale Science Grant No. 43535000350000; and the Irving and Azelle Waltcher Foundations in honor of Prof. M. Levy Grant No. 720821. Funding from the MINECO/FEDER (Project Refs: MAT2017-87579-R and MAT2016-81118-P) is also acknowledged.

We have synthesized quaternary chalcogenide-based misfit nanotubes LnS(Se)-TaS