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Recently, oxide-based materials have proven to be potential thermoelectric materials at high temperatures. In this work, the thermoelectric properties of one-step solid-state sintered Sn1-xSbxO2 (x = 0, 0.005, 0.01, 0.02, 0.03, 0.04) ceramic pellets were investigated in detail. It was confirmed that the addition of Sb significantly alters the thermoelectric properties of SnO2 due to the increase in the carrier concentration, which increases the electrical conductivity. The Seebeck coefficient values of all the solid solutions were negative, which indicates that these samples have n-type conduction. The thermoelectric performance of the material was evaluated by determining the zT value and the best composition was Sn0·98Sb0·02O2 with zT ∼0.06 at 1073 K.

The same electrochemical process drives the preparation of supported and free-standing molybdenum disulfide monolayers.

In this paper, we report on a new path of ZnWO4 phase formation, synthesized by the polymerizable complex (PC) method. At 550 °C, we obtained a single phase of the ZnWO4 complex oxide. To explain the phase transformation processes, we propose a mechanism based on the coexistence of more than one amorphous phase after the pre-pyrolysis process. These amorphous metastable phases indicate a different phase formation path, which has not yet been described in the literature for multi-component oxides processed by the PC method. The formation path proposed here shows the relevance of the metastable phases in the reaction processes of complex oxides.

Summary Atomic-scale structure determination is crucial to the understanding of nanomaterial properties and development of new technologies. Although pair distribution function (PDF) analysis by neutrons and X-ray scattering profile has been used to study materials, electron diffraction can offer advantages to characterize the atomic structure of clusters, amorphous samples, and nanomaterials. Electrons have higher scattering power than X-rays, allowing the acquirement of PDF from electron diffraction (ePDF) for small sample amounts and with time-efficient data acquisition. Compared with synchrotron X-rays and neutrons as sources for PDF, the availability of electron microscopes worldwide is advantageous. Nowadays, with the rise of methodologies and specific software for ePDF data analysis, the scientific community can benefit from advanced transmission electron microscopy (TEM) structure determination integrating commonly available TEM analyses—size, distribution, shape, and high-resolution TEM atomic visualization—with ePDF atomic structure determination, both for bulk and surface configurations. Therefore, ePDF has the potential to become a routine and advanced characterization tool for nanomaterials science.

Electrocatalytic materials play a crucial role in the development of technologies for hydrogen production (hydrogen evolution reaction) from renewable and sustainable energy resources. Among these ...

Titanium dioxide (TiO2) is a semiconductor that can be applied in different technological areas. In this work, we investigated the modifications of the electrical properties of thin films composed of TiO2 nanoparticles produced with different morphologies. The solvothermal route used for the synthesis allowed the production of nanoparticles with functionalized surfaces due to oleate groups. It was possible to modulate nanocrystals shape and size due to the detachment crystal growth mechanism, by changing the reaction time. Nanorods were obtained using 4 h of synthesis, and an increase in the reaction time to 64 h led to a bipyramidal morphology. The functionalization by the organic ligand allowed the preparation of stable colloidal solutions, which were used to prepare thin films by the dip-coating method. The films presented a homogeneous surface, an average thickness around 100 nm, and no agglomerations were observed. The electrical resistance measurements indicated a typical behavior of semiconductors, and they were dependent on the nanoparticle morphology. An exploratory test indicated that the thin films prepared using nanorod particles presented a higher electrical response compared with isotropic particles, when exposed in a liquefied petroleum gas vapor atmosphere. Therefore, the morphology of the nanoparticles is a key factor for the further application of these thin films in gas sensing. Employing an easy methodology which required simple apparatus, and by using reaction time modulation only, it was possible to prepare homogeneous thin films with a tunable electrical response.

Made available in DSpace on 2020-12-12T01:30:24Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-01-01 Herein, to balance the overall performance of SPEEK membrane, the imidazolium hydrogen sulfate (Im.HSO4), 1-methylimidazolium hydrogen sulfate (MI.HSO4), and 1-butyl-3-methylimidazolium hydrogen sulfate (BMI.HSO4) ionic liquids (ILs) were used as dopants in polymer matrix. A series of SPEEK/ionic liquid composite membranes were successfully fabricated by casting method and evaluated. Comparative studies showed that the membranes doped with 5 wt.% of MI.HSO4 or BMI.HSO4 ILs showed an increase in the proton conductivity of 50% and 30% at 80 °C, respectively, compared with the pristine SPEEK membrane. The proton exchange membrane fuel cell (PEMFC) performance demonstrated that the membrane doped with 5 wt.% of BMI.HSO4 IL (SBMI5) has the highest current density value and the highest power density without loss of performance as temperature increases. This result indicates that this membrane is promising for fuel cells application. Chemistry Department Federal University of São Carlos, P. O. Box 676 Department of Chemistry Universidade Estadual Paulista–Unesp, P.O. Box 473 LRC-Institute of Chemistry Universidade Federal do Rio Grande do Sul, P. O. Box 15003 Department of Chemistry Universidade Estadual Paulista–Unesp, P.O. Box 473

Cu

Using a combination of in situ high-resolution transmission electron microscopy and density functional theory, we report the formation and rupture of ZrO_{2} atomic ionic wires. Near rupture, under tensile stress, the system favors the spontaneous formation of oxygen vacancies, a critical step in the formation of the monatomic bridge. In this length scale, vacancies provide ductilelike behavior, an unexpected mechanical behavior for ionic systems. Our results add an ionic compound to the very selective list of materials that can form monatomic wires and they contribute to the fundamental understanding of the mechanical properties of ceramic materials at the nanoscale.

Surface-initiated atom transfer radical polymerization in the presence of a Zn0 plate (SI-Zn0-ATRP) enables the rapid synthesis of chemically diverse polymer brushes from both planar inorganic supports, and fabrics made of natural fibers. This process enables the controlled formation of polymer-brush layers on a variety of substrates, without the need for either inert conditions or lengthy deoxygenation procedures of the reaction mixtures. © 2020 The Royal Society of Chemistry., Polymer Chemistry, 11 (44), ISSN:1759-9962, ISSN:1759-9954

The silver-based metal oxides have been considered good photocatalysts for the removal of organic dyes in wastewater treatments. In our knowledge, for the first time, the photoluminescence and photocatalytic properties of silver pyrophosphate (Ag4P2O7) synthesized by the precipitation method have been investigated. The long- and short-range structural ordering was analyzed by means of X-ray diffraction and, Raman and infrared spectroscopies, respectively. The broadband photoluminescence spectrum revealed a typical profile arising from electronic transitions involving intermediary energy levels in the band gap. The photocatalytic efficiency of Ag4P2O7 was monitored for the degradation of rhodamine B and 6G under ultraviolet light irradiation. The reusability and stability of this material as photocatalyst were checked by recycling tests. Different radical scavengers were introduced into reaction medium to detect the main active species involved in the degradation process of rhodamine 6G. Based on our results, a photodegradation mechanism for this synthetic organic dye by using Ag4P2O7 photocatalyst was proposed in detail.

Made available in DSpace on 2020-12-12T00:59:19Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-03-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Because of the socio-environmental and economic impacts of the use of fossil fuels, the demand for the diversification of the energy matrix has increased. Energy devices utilizing renewable energy such as solar cells stand out as a possible solution to this problem. Therefore, in order to realize the practical applications of solar cells, it is imperative to develop novel structural materials and to optimize the properties of the existing ones. In this study, we prepared a photoelectrode using hematite-decorated zinc oxide particles (ZnO/Fe2O3). The field-emission scanning electron microscopy and Brunauer–Emmett–Teller results confirmed that Fe2O3 coated the surface of the ZnO particles and improved their photoelectrochemical properties. The composite was found to be a promising photoelectrode for solar cells. Department of Chemistry Universidade Estadual Paulista – Unesp, P.O. Box 473 Institute of Marine Sciences UNIFESP LIEC – CDMF - Department of Chemistry Universidade Federal de São Carlos, P.O. Box 676 Department of Chemistry Universidade Estadual Paulista – Unesp, P.O. Box 473 FAPESP: 2013/07296-2

The structural, morphological and optical properties of silver pyrophosphate (Ag4P2O7) powders were investigated in detail. This material was synthesized by chemical precipitation (CP), conventional hydrothermal and microwave-assisted hydrothermal. The crystallization of hexagonal Ag4P2O7 phase presented a dependence with both temperature and synthesis approach. A system composed of doughnut/hexagonal-shaped microparticles was evidenced for the powders obtained by CP. The hydrothermal treatments modified these particle shapes. Ultraviolet–visible spectra revealed a band gap controlled by indirect electronic transitions. Broadband photoluminescence spectra with maximum emissions in blue region were detected, suggesting the participation of several intermediary energy levels in the band gap.

Perovskite-type metal oxides have emerged as important materials in renewable energy because the high electrocatalytic performance for oxygen evolution reaction (OER). Hence, we perform a study on the electrocatalytic properties of LaNi1-xFexO3 (x = 0.0, 0.3, 0.6, and 0.9 mol%) for OER, mainly analyzing the influence provoked by the incorporation of Fe3+ in the lattice as well as the use of pyrolytic graphite sheet (PGS) as a potential substrate for electrocatalysis. These perovskites were synthesized by the co-precipitation method. The thin film electrodes were prepared depositing the obtained powders on PGS substrates via drop-casting. Depending on the Fe3+ level, structural changes and morphological modifications were identified for these materials. The highest electrocatalytic activity for OER was detected for LaNi0.4Fe0.6O3. Besides the low charge transfer resistance, LaNi0.4Fe0.6O3 exhibited a lower overpotential (439 mV) and a smaller Tafel slope (52 mV dec−1) than the LaNiO3 (465 mV and 76 mV dec−1).

Novel two-dimensional non-van der Waals materials have been reported, boosting efforts to probe their properties and identify key applications. In this work, we report the synthesis, by means of a novel route via sonication of synthetic hematite, and characterization by transmission electron and atomic force microscopy of samples composed of two-dimensional hematite ([001]-cut layered α-Fe2O3). Microscopy images show a layered material with a handful of possible crystalline orientations, of which the [001] is the most abundant, presenting thickness of up to approximately 100 nm. Next, we employed first-principles calculations to study their structural stability and evaluate their thickness distribution. The stability of single, double, and triple layered structures is confirmed by phonon spectra and the formation energy is obtained, pointing out to the possibility of few layers, freestanding, stable samples. Further statistical modeling suggests that even though such thin samples are stable, their abundan...

Understanding the effects of atomic structure modification in hematite photoanodes is essential for the rational design of high-efficiency functionalizations. Recently it was found that interface modification with Sn/Sb segregates considerably increases hematite photocatalytic efficiency. However, the understanding of the different electronic effects of these modifications at the atomic level is still lacking. This letter describes the segregation effects of two different dopants-Sn and Sb-on both the solid-solid (grain-boundaries) and solid-liquid interfaces (surfaces) of hematite. Within an ab-initio approach, we quantitatively extract the potential barrier reduction on polycrystalline interfaces due to the dopant, which causes an increase in the inter-grain electron transport. Concomitantly, the dopants' segregation on hematite surfaces results in a decrease of the oxygen vacancy formation energy. Such vacancies lead to the experimentally observed rise of the flat-band potential. The comprehension of the electronic effects of dopants on both types of interfaces explains the experimental peak efficiency of interface-modified hematite with dopant segregates, also enabling the control and design of interfaces for different higher-efficiency applications.

In this communication, we describe a simple one-pot approach to exfoliate and functionalize MoS2 (f-MoS2) via liquid-phase exfoliation (LPE) starting from bulk MoS2 dispersed in styrene/N-methyl pyrrolidone (NMP) solution using azobisisobutyronitrile (AIBN) as a radical initiator. The colloidal stability of f-MoS2 is achieved due to an in situ radical polymerization of styrene and functionalization on the edge sites of MoS2. Thermogravimetric analysis (TGA) showed the presence of 8.23 wt% of functionalized MoS2. The f-MoS2 was then incorporated in polystyrene (PS) matrix at different loadings (15 wt%, 30 wt% and 60 wt%) by a solution-based process using toluene as solvent. The f-MoS2/PS nanocomposites exhibited a good polymer/nanofiller interfacial interaction and promoted significant thermal stabilization in PS increasing, in our best case, the T-5% and T-50% temperatures by 91 °C and 15 °C, respectively, compared to neat PS. When increasing the f-MoS2 loading, we also noticed a dramatic decrease on the glass transition temperature (Tg) of the f-MoS2/PS nanocomposites, which has a direct correlation on its mechanical properties. As f-MoS2 loading increases the Young's modulus decreases, compared to neat PS. However, at 60 wt% f-MoS2 loading, the nanocomposite showed basically the same Young's modulus of neat PS and the strain at break increased more than a 150%, which indicates a significant load transfer between the polymer-nanofiller interface. Therefore, the f-MoS2 is a potential candidate to overcome the brittleness of PS. In addition, this simple one-pot approach opens pathways for new developments of functionalized MoS2.

This work describes a colloidal deposition process that exploits the thermal spreading ability of Sb over a hematite surface to obtain a mesoporous film with extensive open porosity and high degree of Sb5+ dispersion. The addition of Sb increased the efficiency of water oxidation by a factor of 4.5 and photocurrent at 1.23 VRHE by a factor of 6.5 compared to those of an unmodified hematite film prepared under the same conditions. The overall efficiency increase for water oxidation is attributed to more efficient charge separation. Sb was found to be an excellent selective semimetal modifier with high dispersion over the material.

In this paper, we investigate the structural and morphological changes caused by the electron-beam irradiation that led to the growth of complex extruded filaments on the surfaces of α-Ag2WO4. To provide a complete description of this phenomenon, both scanning electron microscope (SEM) and transmission electron microscope (TEM) were employed in this study. Our experimental results evidenced that the extruded material was able to exhibit growth on different crystallographic faces, depending on the kind of microscope adopted during the electron-beam irradiation. For a more complete analysis, different electron-beam current densities in TEM were used to investigate all in situ modifications in the microcrystals. For the first time, besides the metallic silver, the presence of silver oxides (Ag2O and Ag3O4) were detected in the composition of extruded material. The diffusion mechanisms related to morphological modifications in the samples irradiated in SEM and TEM were discussed in detail. The coprecipitation...

Upcoming generation of smart windows requires simple design, fast stimulus response and cost-effective production. Aiming these features, we reported a new approach of switchable devices based on the thermosensitive polymer poly(N-vinylcaprolactam) (PNVCL) and facile assembly of the components (FTO layers and polymer). Its optical/color change from transparent to opaque is temperature-dependent and activated by induced Joule heating of conductive substrates. Therefore, the reported devices showed fast reversible response (less than 60 s) by small input power and adjustable opaqueness according to polymer concentration. In opposite to traditional electrochromic smart windows dependence of the kinetics charge-transfer reaction, the observed features are triggered by the thermodynamic mechanism of the reversible coil-globule transition from PNVCL suspension, which can lead to stable performance of the proposed device.

Materials presenting high photocatalytic performance and interesting photoluminescence emissions are promising candidates for photodegradation of organic pollutants discharged into natural waters as well as for development of new electro-optical devices, respectively. In this study, Ag3-2xCuxPO4 (x = 0.00, 0.01, 0.02, 0.04 and 0.08) powders were synthesized by the precipitation method. The long- and short-range structural ordering was affected when the copper (Cu) content was increased in the lattice, as identified by X-ray diffraction patterns, Fourier transform infrared spectroscopy and Raman spectroscopy, respectively. The field emission scanning electron microscope and transmission electron microscope revealed a particle system composed of irregular spherical-like microcrystals. The presence of Cu as well as its real amount in the samples were confirmed by means of X-ray photoelectron spectroscopy and inductively coupled plasma-atomic emission spectrometry, respectively. On increasing Cu level, a slight variation was noted on the photocatalytic activity of Ag3-2xCuxPO4 powders for degradation of rhodamine B under visible light irradiation. A photodegradation mechanism was proposed in details. The photoluminescence emissions were explained by electronic transitions involving intermediary energy levels in the band gap. The origin these energy levels was related to defects caused by the substitution of Ag by Cu in the crystalline structure.

Porous ceramics that exhibit porosity gradient are considered promising materials from the industrial point of view, especially for the production of ceramic membranes and filters. This paper describes a simple and versatile approach to produce ceramics with porosity gradient. In order to perform this study, MnO 2 /SnO 2 bi-layered pellets were conformed via uniaxial pressure and sintered at 1100 °C and 1300 °C for different times. MnO 2 layer had the role of sintering aid, while the SnO 2 layer was chosen as ceramic matrix subjected to the densification. The field emission scanning electron microscope (FE-SEM) was employed to obtain information on the microstructural features of these pellets. FE-SEM micrographs revealed that the overall percentage of porosity, pore size and shape in SnO 2 layer can be controlled by sintering variables (temperature and time). The results indicated a correlation between the porosity gradient in SnO 2 with the Mn concentration gradient in this matrix.

We here report the growth and structural characterization of Sb-doped SnO2 nanowires synthesized by Vapor-Liquid-Solid technique using X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray Photoelectron Spectroscopy (XPS) and Raman spectroscopy. Both X-ray diffraction and Raman spectroscopy exhibited typical features of the rutile phase of SnO2 nanowires for all samples. The analysis of XPS confirmed the Sb doping effectiveness. In addition, Raman spectra revealed inactive modes (242 and 284 cm−1) attributed to local structural disorder caused by the incorporation of the dopant into the SnO2 lattice and leading to the breakdown of the Raman selection rules.

In the current communication, the synthesis of metallic Bi nanoparticles with coexisting crystallographic structures (rhombohedral, monoclinic, and cubic) obtained via direct femtosecond laser irradiation of NaBiO3 is demonstrated for the first time. By exploring the use of high laser power values, it is revealed that the promoted laser-mediated reactions lead to the synthesis of coexisting phases in metal nanoparticles, which may be a widely occurring phenomenon in other materials under femtosecond laser irradiation, and a fundamental concern for laser-based nanofabrication.

The understanding on defect-related photoluminescence (PL) properties of hydroxyapatite (HA) particles has a fundamental importance in the technological field for the development of new non-toxic biomedical and optical devices. However, the mechanisms responsible for this intrinsic PL in HA are not completely elucidated in the literature yet. In the present paper, stoichiometric and calcium-deficient HA nano- and micro-particles were synthesized by chemical precipitation. The influence of structural and morphological features on the intrinsic PL and electronic structure of this material were investigated by varying the addition rate of the phosphate precursor (0.15, 7.00 or 600.00 mL/min) and pH (4.5–5.0 or 9.5–10.0) value adopted in the precipitation. The results indicated that the structural order at long- and short-range varied with the synthesis conditions and particle shapes (rods, needles, plates, and rices). The blue and green PL emissions were attributed to defects (bulk, surface and interface) in the samples. These defects promoted the formation of additional energy levels within the band gap, as revealed by using two distinct excitation wavelengths for photoemission measurements. The energies of these wavelengths (~ 3.54 and ~ 2.98 eV at 350 and 415 nm, respectively) were lower than the band gap energies of HA samples (from 5.59 to 5.72 eV). A general model was proposed to explain the occurrence of self-activated PL in HA structure.

Made available in DSpace on 2018-12-11T17:35:37Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-12-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Ministerio de Economía y Competitividad Universitat Jaume I Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) In recent years, complex nanocomposites formed by Ag nanoparticles coupled to an α-Ag2WO4 semiconductor network have emerged as promising bactericides, where the semiconductor attracts bacterial agents and Ag nanoparticles neutralize them. However, the production rate of such materials has been limited to transmission electron microscope processing, making it difficult to cross the barrier from basic research to real applications. The interaction between pulsed laser radiation and α-Ag2WO4 has revealed a new processing alternative to scale up the production of the nanocomposite resulting in a 32-fold improvement of bactericidal performance, and at the same time obtaining a new class of spherical AgxWyOz nanoparticles. CDMF-UFSCar Universidade Federal de São Carlos, P.O. Box 676, CEP Department of Inorganic and Organic Chemistry University Jaume i (UJI) Institute for Nanomaterials Advanced Technologies and Innovation Technical University of Liberec, Studentská 1402/2 GROC-UJI Institut de Noves Tecnologies de la Imatge (INIT University Jaume i (UJI), Castelló FOAr-UNESP Universidade Estadual Paulista, P.O. Box 1680 Department of Analytical and Physical Chemistry University Jaume i (UJI) FOAr-UNESP Universidade Estadual Paulista, P.O. Box 1680 FAPESP: 2013/07296-2 FAPESP: 2013/26671-9 CNPq: 304531/2013-8 Ministerio de Economía y Competitividad: CTQ2015-65207-P Ministerio de Economía y Competitividad: FIS2016-75618-R Ministerio de Economía y Competitividad: MAT2016-80410-P Universitat Jaume I: P11B2013-65 CAPES: PNPD-1268069 Universitat Jaume I: UJIB-2016-38

In recent years, cryogenic electron microscopy (Cryo-EM) has revolutionized the structure determination of wet samples and especially that of biological macromolecules. The glassy-water medium in which the molecules are embedded is considered an almost

Cyclodextrin (CD) is a conical compound used in food and pharmaceutical industry to complexation of hydrophobic substances. It is a product of microbial enzymes which converts starch into CD during their activity. We aim to detect CD using active-electrode biosensor of SnO

Dopant atoms can be incorporated into nanowires either via the vapor-liquid-solid mechanism through the catalyst droplet or by the vapor-solid growth on the sidewalls. Si is a typical n-type dopant for GaAs, but in nanowires it often suffers from a strongly amphoteric nature in the vapor-liquid-solid process. This issue can be avoided by using Te, which is a promising but less common alternative for n-type doping of GaAs nanowires. Here, we present a detailed investigation of Te-doped self-catalyzed GaAs nanowires. We use several complementary experimental techniques, such as atom probe tomography, off-axis electron holography, micro-Raman spectroscopy, and single-nanowire transport characterization, to assess the Te concentration, the free-electron concentration, and the built-in potential in Te-doped GaAs nanowires. By combing the experimental results with a theoretical model, we show that Te atoms are mainly incorporated by the vapor-liquid-solid process through the Ga droplet, which leads to both axial and radial dopant gradients due to Te diffusion inside the nanowires and competition between axial elongation and radial growth of nanowires. Furthermore, by comparing the free-electron concentration from Raman spectroscopy and the Te-atom concentrations from atom probe tomography, we show that the activation of Te donor atoms is 100% at a doping level of 4×1018cm-3, which is a significant result in terms of future device applications. acceptedVersion

In this Letter, the role of Ti addition in thick hematite mesoporous photoanodes was elucidated by performing intensity modulated photocurrent spectroscopy (IMPS) monitoring its charge carrier dynamics during water oxidation. Interface engineering associated with doping of hematite is crucial to develop highly efficient thick photoanodes. Photoelectrochemical data recorded under front- and back-side illumination show that Ti insertion mitigates the collection deficit faced by hematite due to an energy barrier decrease between the grains and a change in the surface chemistry. IMPS reveals that Ti clearly influences the hematite film performance by increasing the charge separation efficiency due to its segregation at the hematite interface. However, Ti insertion does not enhance the kinetics of water oxidation at the solid–liquid interface. These facts indicate that Ti mainly affects the hematite electronic properties instead of accelerating the surface processes. This comprehensive understanding of the electronic transport and charge carrier dynamics in Ti:hematite photoanodes enables the control and design of better interfaces for more efficient photoelectrochemical water splitting.

A magnetically recoverable catalyst [Fe 3 O 4 @SiO 2 -AEAPTMS-Pd(II)] was prepared, fully characterized and had its catalytic activity evaluated on the Suzuki cross-coupling reaction under microwave irradiation. The reaction conditions for the synthesis of biaryl compounds was optimized in two stages - an initial fractional design 2 4 , in which the parameters reaction time, temperature, solvent and catalyst loading were evaluated, followed by a Doehlert design. The factorial design proved to be a viable approach for obtaining the optimal reaction conditions based on a relatively small number of experiments. Additionally, the biaryl derivatives synthesized by this method were obtained with good to excellent yields (71–96%) and the recovery and reuse of the palladium catalyst was also evaluated.

Here, we describe a simple approach to control the oriented attachment process through selective ligand scavenging from the {100} facets of CeO2 nanoclusters. Aggregates of these nanoclusters smaller than 10 nm with controlled shapes and exposed facets were obtained. For the synthesis of the cuboctahedral CeO2 nanoclusters, we developed a solvent-controlled synthesis approach based on a non-hydrolytic sol–gel process and used an ester aminolysis reaction to control ligand scavenging from the {100} facets. First-principle calculations allowed us to understand and interpret, at the atomic level, the effects of shape control on the synthesis. Fine-tuning of the desired morphologies can be achieved by controlling the values of the surface energies, which leads to the formation of morphologies that the classic growth process does not allow.

HDS NiMo catalyst precursors supported on SiO 2 , SiO 2 -TiO 2 or SiO 2 -ZrO 2 , having high specific surface areas and highly dispersed Mo species were prepared using a one-pot sol-gel methodology or by wet impregnation. After the catalyst precursor sulfidation, HRTEM and Raman analyses evidenced the effective formation of MoS 2 slabs on the support. For the NiMoS-Si catalyst (precursor one-pot synthesized), there was a high formation of edge-bonded oriented MoS 2 slabs, whereas for the NiMoS/Si prepared by impregnation, basal-bonded MoS 2 slabs were more abundant. Coherent with the formation of MoS 2 slabs and the promoting effect of Ni, all of the prepared NiMoS catalysts were active in the HDS of thiophene, with those one-pot supported on SiO 2 or SiO 2 -ZrO 2 being the most active. Due to the strong interaction between Mo and Ti, the NiMoS-SiTi catalyst did not show consistent formation of MoS 2 slabs and consequently it presented the lowest activity. No observable effect in the HDS activity of the Zr incorporation into the SiO 2 framework was noticed. The considerable specific activity (SA) of the catalysts NiMoS-Si and NiMoS/Si, was respectively related to the formation of the most active edge-bonded MoS 2 slabs and to the well-active Type II HDS catalysts on multilayer basal-bonded MoS 2 slabs. The studied NiMoS-Si and NiMo-SiZr with high SA values evidences that the one-pot sol-gel synthesis methodology used to prepare the catalyst precursor leads to highly active HDS catalysts with the important advantages of reducing the preparation time, energy consumption, and consequently diminishing the catalyst production cost.