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et al. ; The efficient conversion between thermal and electrical energy by means of durable, silent and scalable solid-state thermoelectric devices has been a long standing goal. While nanocrystalline materials have already led to substantially higher thermoelectric efficiencies, further improvements are expected to arise from precise chemical engineering of nanoscale building blocks and interfaces. Here we present a simple and versatile bottom-up strategy based on the assembly of colloidal nanocrystals to produce consolidated yet nanostructured thermoelectric materials. In the case study on the PbS-Ag system, Ag nanodomains not only contribute to block phonon propagation, but also provide electrons to the PbS host semiconductor and reduce the PbS intergrain energy barriers for charge transport. Thus, PbS-Ag nanocomposites exhibit reduced thermal conductivities and higher charge carrier concentrations and mobilities than PbS nanomaterial. Such improvements of the material transport properties provide thermoelectric figures of merit up to 1.7 at 850 K. ; At IREC, work was supported by European Regional Development Funds and the Framework 7 program under project UNION (FP7-NMP 310250). M.I. and S.O. thank AGAUR for their Beatriu i Pinos post-doctoral grant (2013 BP-A00344) and the PhD grant, respectively. A.G. thanks to the Turkish Ministry of National Education for the PhD grant. A.G. and J.A. acknowledge the Spanish MINECO MAT2014-51480-ERC (e-ATOM) and the ICN2 Severo Ochoa Excellence Program. Z.L. and Y.L. thanks the China Scholarship Council for their PhD grant. IREC and ICN2 groups acknowledge the funding from Generalitat de Catalunya 2014SGR1638. The work performed at Rutgers was supported by NSF grant number 1400246. M.V.K. acknowledges partial financial support by the European Union (EU) via FP7 ERC Starting Grant 2012 (Project NANOSOLID, GA No. 306733). ; Peer Reviewed

This study investigates the mechanisms of epitaxial development and functional properties of oxide thin films (Ce0.9Zr0.1O2−y, LaNiO3, and Ba0.8Sr0.2TiO3) grown on single crystal substrates (Y2O3:ZrO2, LaAlO3, and SrTiO3) by the chemical solution deposition approach. Rapid thermal annealing furnaces are very powerful tools in this study providing valuable information of the early stages of nucleation, the kinetics of epitaxial film growth, and the coarsening of nanocrystalline phases. Advanced transmission electron microscopies, X-ray diffraction, and atomic force microscopy are employed to investigate the film microstructure and morphology, microstrain relaxation, and epitaxial crystallization. This study demonstrates that the isothermal evolution toward epitaxial film growth follows a self-limited process driven by atomic diffusion, and surface and interface energy minimization. All investigated oxides experience a transformation from the polycrystalline to the epitaxial phase. This study unequivocally evidences that the film thickness highly influences the epitaxial crystallization rate due to the competition between heterogeneous and homogeneous nucleation barriers and the fast coarsening of polycrystalline grains as compared to epitaxial growth. The investigated films possess good functional properties, and this study successfully confirms an improvement at long annealing times that can be correlated with grain boundary healing processes. Thick epitaxial films can be crystallized by growing sequential individual epitaxial layers. ; We acknowledge financial support from Spanish Ministry of Economy and Competitiveness through the "Severo Ochoa" Programme for Centres of Excellence in R&D (SEV-2015-0496), CONSOLIDER Excellence Network (MAT2015-68994-REDC), COACHSUPENERGY project (MAT2014-56063-C2-1-R, co-financed by the European Regional Development Fund), and the projects MAT2011-28874-C02-01, ENE2014-56109-C3-3-R and Consolider Nanoselect (CSD2007-00041), and from the Catalan Government (2014-SGR-753 and Xarmae). AQ and MdlM are also grateful for JAE-Predoc fellowship from CSIC (E-08-2012-1321248 and E-08-2013-1028356, co-financed by the European Social Fund). ; Peer Reviewed

Resumen del trabajo presentado al Microscopy at the Frontiers of Science Congress Series (MFS), celebrado en el Parque de las Ciencias de Granada (España) del 11 al 13 de septiembre de 2019. ; This project has received funding the EU H2020 project CritCat (project ID: 686053). MCS has received funding from the European Union"s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 754510 (PROBIST). ICN2 acknowledge funding from Generalitat de Catalunya 2017 SGR 327 and the Spanish MINECO project ENE2017-85087-C3. ICN2 is supported by the Severo Ochoa program from Spanish MINECO (Grant No. SEV-2017-0706) and is funded by the CERCA Programme-Generalitat de Catalunya. ; Peer reviewed

Self-assembling approaches based on chemical solution deposition (CSD) are ideal methods for the cost-effective production of epitaxial nanostructures with high throughput. Therefore, an in-depth investigation of the nucleation and coarsening processes involved in the self-assembly of nanostructures is mandatory to achieve a good control over nanostructure shape, dimensions, and orientation. Heteroepitaxial Ce0.9Gd0.1O2-y (CGO) is an ideal model system to unveil the underlying nanostructure development mechanisms in addition to their promising properties for catalysis, gas sensors, and ionic conductivity. Rapid thermal annealing furnaces have been used to study separately the thermodynamic and kinetic nucleation and coarsening mechanisms of self-assembled CGO isotropic and anisotropic nanostructures based on strain-engineering and surface energies control. Different CGO nanoislands are obtained: isotropic (001)CGO nanodots are grown on (001)-oriented Y2O3:ZrO2 (YSZ) and LaAlO3 (LAO) substrates, whereas (011)LAO substrates promote the growth of elongated (011)CGO nanowires. HRTEM and RHEED analyses are used to study the early stages of nucleation, as well as the shape and interfacial structure of CGO nanostructures. A systematic study with the heating ramp, annealing temperature and time, and strain in combination with thermally activated theoretical models provides information on the nucleation behavior, nucleation barriers, and atomic diffusion coefficients along in-plane and out-of-plane island orientations. Highly anisotropic atomic diffusion constants have been shown to be at the origin of the high aspect ratios of some of the nanostructures. Overall, our study provides a general method for the evaluation of nucleation and coarsening of multiple CSD-derived oxide nanostructures and understanding the shape development by combining thermodynamic and kinetic approaches. ; We acknowledge financial support from Spanish Ministry of Economy and Competitiveness through the "Severo Ochoa" Programme for Centres of Excellence in R&D (SEV-2013-0295 and SEV-2015-0496), CONSOLIDER Excellence Network (MAT2015-68994-REDC), COACHSUPENERGY project (MAT2014-51778-C2-1-R, cofinanced by the European Regional Development Fund), and the projects MAT2011- 28874-C02-01, ENE2014-56109-C3-3-R and Consolider Nanoselect CSD2007-00041, and from the Catalan Government with 2014-SGR-753, 2014-SGR-1638, and Xarmae. A.Q. and M.d.l.M. are also grateful to CSIC and European Social Fund program for JAE-Predoc fellowships (E-08-2012-1321248 and E-08-2013-1028356). ; Peer reviewed

An optical in situ strategy for the analysis of oxygen diffusion in ultrathin ceria layers with a thickness of 2–10 nm at temperatures between 50 and 200 °C is presented, which allows for the determination of diffusion coefficients. This method is based on the sensitivity of the photoluminescence (PL) intensity of InGaN nanowires to adsorbed oxygen. The oxygen diffusion through an ultrathin CeO2 coating deposited on the InGaN nanowires is monitored by analyzing the transient PL behavior of the InGaN nanowires, which responds to changes of the oxygen concentration in the environment when the corresponding oxygen concentration is established at the CeO2/InGaN interface due to diffusion through the coating. Quantitative evaluation of the oxygen diffusion in CeO2 based on a model considering Langmuir Adsorption and recombination yields a diffusion coefficient D of (2.55 ± 0.05) × 10−16 cm2 s−1 at a temperature of 100 °C. Temperature‐dependent measurements reveal an Arrhenius type behavior of D with an activation energy of (0.28 ± 0.04) eV. In contrast, no oxygen diffusion is detected for an ultrathin layer (≥5 nm) of Al2O3, which is known as a poor oxygen ion conductor within the analyzed temperature regime. ; We thank Herbert Over from the Institute of Physical Chemistry at the JLU Giessen for sharing his knowledge and experience and helping improve the manuscript. Financial support was provided by the DFG via the GrK (Research training group) 2204 "Substitute Materials for sustainable Energy Technologies." M.C. thanks Ramón y Cajal program RYC‐2013‐12448. The authors also acknowledge financial support from the Spanish Ministry of Economy and Competitiveness, through the "Severo Ochoa" Programme for Centres of Excellence in R&D (SEV‐ 2015‐0496) and MAT2017‐83169‐R AEI/FEDER,UE. This article is based upon work from COST Action MP1402 "Hooking together European research in atomic layer deposition (HERALD)," supported by COST (European Cooperation in Science and Technology). S.M.S. acknowledges funding from "Programa Internacional de Becas 'la Caixa"'‐Severo Ochoa." ICN2 members acknowledge funding from Generalitat de Catalunya 2017 SGR 327 and the Spanish MINECO project ENE2017‐85087‐C3. ICN2 acknowledges support from the Severo Ochoa Programme (MINECO, grant no. SEV‐2013‐0295) and is funded by the CERCA Programme /Generalitat de Catalunya. Part of this work was performed in the framework of Universitat Autònoma de Barcelona Materials Science PhD program. This received funding from the European Union's Horizon 2020 Research and Innovation Programme under grant agreement no. 654360 NFFA‐Europe. ; Peer reviewed

The cost-effective conversion of low-grade heat into electricity using thermoelectric devices requires developing alternative materials and material processing technologies able to reduce the currently high device manufacturing costs. In this direction, thermoelectric materials that do not rely on rare or toxic elements such as tellurium or lead need to be produced using high-throughput technologies not involving high temperatures and long processes. BiSe is an obvious possible Tefree alternative to BiTe for ambient temperature thermoelectric applications, but its performance is still low for practical applications, and additional efforts toward finding proper dopants are required. Here, we report a scalable method to produce BiSe nanosheets at low synthesis temperatures. We studied the influence of different dopants on the thermoelectric properties of this material. Among the elements tested, we demonstrated that Sn doping resulted in the best performance. Sn incorporation resulted in a significant improvement to the BiSe Seebeck coefficient and a reduction in the thermal conductivity in the direction of the hot-press axis, resulting in an overall 60% improvement in the thermoelectric figure of merit of BiSe . ; M.L., Y.Z., T.Z. and K.X. thank the China Scholarship Council for their scholarship support. Y.L. acknowledges funding from the European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No. 754411. J.L. thanks the ICREA Academia program and projects MICINN/FEDER RTI2018-093996-B-C31 and G.C. 2017 SGR 128. ICN2 acknowledges funding from the Generalitat de Catalunya 2017 SGR 327 and the Spanish MINECO ENE2017-85087-C3.

Galceran, Regina et al. ; © 2015 American Physical Society. We report on magnetotransport properties on La0.7Sr0.3MnO3/MgO/Fe tunnel junctions grown epitaxially on top of (001)-oriented SrTiO3 substrates by sputtering. It is shown that the magnetoresistive response depends critically on the MgO/Fe interfacial properties. The appearance of an FeOX layer by the interface destroys the Δ1 symmetry filtering effect of the MgO/Fe system and only a small negative tunneling magnetoresistance (TMR) (∼-3%) is measured. However, in annealed samples a switchover from positive TMR (∼+25% at 70 K) to negative TMR (∼-1%) is observed around 120 K. This change is associated with the transition from semiconducting at high T to insulating at low T taking place at the Verwey transition (TV∼120K) in Fe3O4, thus suggesting the formation of a very thin slab of magnetite at the MgO/Fe interface during annealing treatments. These results highlight the relevance of interfacial properties on the tunneling conduction process and how it can be substantially modified through appropriate interface engineering. ; We acknowledge financial support from the Spanish MINECO through grants (MAT2012-33207, MAT2011-27470-C02, MAT2012-37638 and Consolider Ingenio 2010 - CSD2009-00013 (Imagine)), from CAM through Grant No. S2009/MAT-1756 (Phama) and Basque Government (PI2011-1). Financial support from EC through FEDER program and Marie Curie Actions (256470-ITAMOSCINOM) is also acknowledged. C.M.B. thanks the Spanish MINECO for the financial support through the RyC program ; Peer Reviewed

The surface of nanowires is a source of interest mainly for electrical prospects. Thus, different surface chemical treatments were carried out to develop recipes to control the surface effect. In this work, we succeed in shifting and tuning the semiconductivity of a Si nanowire-based device from n- to p-type. This was accomplished by generating a hole transport layer at the surface by using an electrochemical reaction-based nonequilibrium position to enhance the impact of the surface charge transfer. This was completed by applying different annealing pulses at low temperature (below 400 °C) to reserve the hydrogen bonds at the surface. After each annealing pulse, the surface was characterized by XPS, Kelvin probe measurements, and conductivity measured by FET based on a single Si NW. The mechanism and conclusion were supported experimentally and theoretically. To this end, this strategy has been demonstrated as an essential tool which could pave a new road for regulating semiconductivity and for other low-dimensional nanomaterials. ; M.B. is thankful for the MAOF Grant from the Council for Higher Education in Israel for new faculty members. A.S. is appreciative of the institutional scholarships for Ph.D. students that they received from Ben-Gurion University of the Negev. W.W. is thankful for the fundamental research funds from the Central Universities (JC2002). L.Z. is thankful for the support of a postdoctoral fellowship from the Jacob Blaustein Center for Scientific Cooperation, the National Natural Science Foundation of China (61904134), and the National Natural Science Foundation of Shaanxi Province (2019JQ-291). The computing resources and the related technical support used for this work have been provided by CRESCO/ENEAGRID High Performance Computing infrastructure and its staff, along with additional support from S. Migliori and S. Giusepponi. E.N.E.A. acknowledges funding from the European Union's Horizon 2020 research and innovation programme under grant agreement no. 824158 (EoCoE-II). J.A. acknowledges funding from Generalitat de Catalunya 2017 SGR 327 and the Spanish MINECO coordinated project ENE2017-85087-C3. ICN2 is supported by the Severo Ochoa program from Spanish MINECO (SEV-2017-0706) and is funded by the CERCA Programme/Generalitat de Catalunya. ; Peer reviewed

The crystallization process and physical properties of different functional oxide thin films (CeZrO, LaNiO, BaSrTiO, and LaSrMnO) on single crystal substrates (YO:ZrO, LaAlO, and SrTiO) are studied by pulsed laser annealing (PLA). A Nd:YAG laser source (λ = 266 nm, 10 Hz and τ ∼3 ns) is employed to crystallize chemical solution deposited (CSD) amorphous/nanocrystalline films under atmospheric conditions. We provide new insight on the influence of photochemical and photothermal interactions on the epitaxial crystallization kinetics of oxide thin films during the transformation from amorphous/polycrystalline material (i.e., atomic diffusion, epitaxial growth rates, and activation energies of nucleation and crystallization). The epitaxial growth is investigated by varying the laser fluence and the applied number of pulses. The morphology, structure, and epitaxial evolution of films are evaluated by means of atomic force and transmission electron microscopies and X-ray diffraction. Highly epitaxial oriented films of 20-40 nm in thickness are obtained by PLA. The crystallization kinetics of laser treatments is determined to be orders of magnitude faster than thermal treatments with similar activation energies (1.5-4.1 eV), mainly due to the large temperature gradients inducing modified atomic diffusion mechanisms derived mainly from photothermal interactions, as well as a minor contribution of photochemical effects. The fast heating rates achieved by PLA also contribute to the fast epitaxial growth due to reduced coarsening of polycrystalline material. The measurement of the physical properties (electrical resistivity and magnetism) of laser processed CSD films has revealed significantly good functionalities, close to those of thermally grown films, but with much shorter processing times. ; We acknowledge financial support from Spanish Ministry of Economy and Competitiveness through the "Severo Ochoa" Programme for Centres of Excellence in R&D (SEV-2013-0295 and SEV-2015- 0496), CONSOLIDER Excellence Network (MAT2015-68994-REDC), COACHSUPENERGY project (MAT2014-51778-C2-1-R, co-financed by the European Regional Development Fund), and the projects MAT2011-28874-C02-01, ENE2014-56109-C3-3-R and Consolider Nanoselect CSD2007-00041, and from the Catalan Government with 2014-SGR-753, 2014-SGR-1638 and Xarmae. AQ and MdlM are also grateful to CSIC and European Social Fund program for JAE-Predoc fellowships (E-08-2012-1321248 and E-08-2013-1028356). ; Peer Reviewed

A cost-effective and scalable approach was developed to produce monodisperse Ni2−xCoxP nanocrystals (NCs) with composition tuned over the entire range (0 ≤ x ≤ 2). Ni2−xCoxP NCs were synthesized using low-cost, stable and low-toxicity triphenyl phosphite (TPP) as a phosphorus source, metal chlorides as metal precursors and hexadecylamine (HDA) as a ligand. The synthesis involved the nucleation of amorphous Ni–P and its posterior crystallization and simultaneous incorporation of Co. The composition, size and morphology of the Ni2−xCoxP NCs could be controlled simply by varying the ratio of Ni and Co precursors and the amounts of TPP and HDA. Ternary Ni2−xCoxP-based electrocatalysts exhibited enhanced electrocatalytic activity toward the hydrogen evolution reaction (HER) compared to binary phosphides. In particular, NiCoP electrocatalysts displayed the lowest overpotential of 97 mV at J = 10 mA cm−2 and an excellent long-term stability. DFT calculations of the Gibbs free energy for hydrogen adsorption at the surface of Ni2−xCoxP NCs showed NiCoP to have the most appropriate composition to optimize this parameter within the whole Ni2−xCoxP series. However, the hydrogen adsorption energy was demonstrated not to be the only parameter controlling the HER activity in Ni2−xCoxP. ; J. David and J. Arbiol acknowledge funding from Generalitat de Catalunya 2017 SGR 327 and the Spanish MINECO project VALPEC (ENE2017-85087-C3). ICN2 acknowledges support from the Severo Ochoa Programme (SEV-2013-0295) and is funded by the CERCA Programme/Generalitat de Catalunya. J. David has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 665919. J. Llorca is a Serra Hunter Fellow and is grateful to the ICREA Academia program and grants MINECO/FEDER ENE2015-63969-R and GC 2017 SGR 128. J. Liu, J. Li and X. Yu thank the China Scholarship Council for scholarship support. M. Meyns acknowledges a Juan de la Cierva formación grant by the Spanish MINECO. ; Peer reviewed

In the quest for more efficient thermoelectric material able to convert thermal to electrical energy and vice versa, composites that combine a semiconductor host having a large Seebeck coefficient with metal nanodomains that provide phonon scattering and free charge carriers are particularly appealing. Here, we present our experimental results on the thermal and electrical transport properties of PbS-metal composites produced by a versatile particle blending procedure, and where the metal work function allows injecting electrons to the intrinsic PbS host. We compare the thermoelectric performance of composites with microcrystalline or nanocrystalline structures. The electrical conductivity of the microcrystalline host can be increased several orders of magnitude with the metal inclusion, while relatively high Seebeck coefficient can be simultaneously conserved. On the other hand, in nanostructured materials, the host crystallites are not able to sustain a band bending at its interface with the metal, becoming flooded with electrons. This translates into even higher electrical conductivities than the microcrystalline material, but at the expense of lower Seebeck coefficient values. ; This work was supported by the European Regional Development Funds, the Framework 7 program under project UNION (No. FP7-NMP-2012-310250), and the Spanish MINECO Project BOOSTER (No. ENE2013-46624-C4-3-R). Y.L. thanks the China Scholarship Council (No. CSC 201406500003) for the scholarship support. M.I., O.D., and S.O. thank AGAUR for their Beatriu de Pinós postdoctoral Grant No. (2013 BP-A00344) and Ph.D. grants. M.V.K. acknowledges the partial financial support from the European Union (EU) via FP7 ERC Starting Grant 2012 (Project NANOSOLID, GA No. 306733). Authors also acknowledge the funding from Generalitat de Catalunya 2014 SGR 1638. ; Peer Reviewed

ACS AuthorChoice - This is an open access article published under an ACS AuthorChoice License.-- et al. ; We report the fine-tuning of the localized surface plasmon resonances (LSPRs) from ultraviolet to near-infrared by nanoengineering the metal nanoparticle morphologies from solid Ag nanocubes to hollow AuAg nanoboxes and AuAg nanoframes. Spatially resolved mapping of plasmon resonances by electron energy loss spectroscopy (EELS) revealed a homogeneous distribution of highly intense plasmon resonances around the hollow nanostructures and the interaction, that is, hybridization, of inner and outer plasmon fields for the nanoframe. Experimental findings are accurately correlated with the boundary element method (BEM) simulations demonstrating that the homogeneous distribution of the plasmon resonances is the key factor for their improved plasmonic properties. As a proof of concept for these enhanced plasmonic properties, we show the effective label free sensing of bovine serum albumin (BSA) of single-walled AuAg nanoboxes in comparison with solid Au nanoparticles, demonstrating their excellent performance for future biomedical applications. ; J.A. and A.G. acknowledge the funding from Generalitat de Catalunya 2014 SGR 1638 and Spanish MICINN Project eATOM (MAT2014-51480-ERC). A.G. acknowledges the Turkish Ministry of National Education for the Ph.D. scholarship. J.P., N.G.B., and V.P. acknowledge financial support from the Generalitat de Catalunya 2014-SGR-612, Spanish MICINN (MAT2012-33330), and European Community (EU-FP7) through the FutureNanoNeeds project. N.G.B. thanks the Spanish MICINN for the financial support through the Juan de la Cierva program and European Commission for the Career Integration Grant (CIG)-Marie Curie Action. Some of the research leading to these results has received funding from the European Union Seventh Framework Program under Grant Agreement 312483 - ESTEEM2 (Integrated Infrastructure Initiative − I3). ; Peer Reviewed

Understanding the growth mechanisms of nanostructures obtained from chemical solutions, a high-throughput production methodology, is essential to correlate precisely the growth conditions with the nanostructures' morphology, dimensions and orientation. It is shown that self-organized (011)-oriented CeGdO (CGO) nanowires having a single in-plane orientation are achieved when an anisotropic (011)-LaAlO (LAO) substrate is chosen. STEM and AFM images of the epitaxial nanowires reveal the (001)CGO[0-11](011)LAO[100] growth orientation, with the enlargement occurring along the [0-11]CGO direction with (111) lateral facets. The chosen substrate allowed us to study a unique case where the resulting biaxial strain is isotropic, while the dissimilar lateral surface energies are the key factor to obtain an energetically imbalanced and non-degenerated nanowire configuration. Rapid Thermal Annealing (RTA) has allowed sorting of experimental nucleation from coarsening and analysis of the kinetic phenomena of the nanowires. A thermodynamic driving force is shown to exist for a continuous elongation of the nanowires while the coarsening rates are found to be strongly temperature dependent and so kinetic effects are the key factors to control the size and density of the self-organized nanowire system. A remarkably fast nanowire growth rate (14-40 nm min) is observed, which we associate with a high atomic mobility probably linked to a high concentration of oxygen vacancies, as detected by XPS. These nanowires are envisaged as model systems pushing forward the study of low energetic and highly oxygen deficient {111} lateral facets useful for catalysis, gas sensors and ionic conductivity applications. ; We acknowledge financial support from Spanish Ministry of Economy and Competitiveness through the "Severo Ochoa" Programme for Centres of Excellence in R&D (SEV-2013-0295 and SEV-2015-0496), CONSOLIDER Excellence Network (MAT2015-68994-REDC), COACHSUPENERGY project (MAT2014-51778-C2-1-R, co-financed by the European Regional Development Fund), and the projects MAT2011-28874-C02-01, ENE2014-56109-C3-3-R and Consolider Nanoselect (CSD2007-00041), and from the Catalan Government (2014-SGR-753, 2014-SGR-1638 and Xarmae). AQ and MdlM are also grateful for JAE-Predoc fellowship from CSIC (E-08-2012-1321248 and E-08-2013-1028356, co-financed by the European Social Fund). Authors also thank the INA-LMA facilities for the use of the advanced (S)TEM equipment. ; Peer Reviewed

The bottom-up assembly of colloidal nanocrystals is a versatile methodology to produce composite nanomaterials with precisely tuned electronic properties. Beyond the synthetic control over crystal domain size, shape, crystal phase, and composition, solution-processed nanocrystals allow exquisite surface engineering. This provides additional means to modulate the nanomaterial characteristics and particularly its electronic transport properties. For instance, inorganic surface ligands can be used to tune the type and concentration of majority carriers or to modify the electronic band structure. Herein, we report the thermoelectric properties of SnTe nanocomposites obtained from the consolidation of surface-engineered SnTe nanocrystals into macroscopic pellets. A CdSe-based ligand is selected to (i) converge the light and heavy bands through partial Cd alloying and (ii) generate CdSe nanoinclusions as a secondary phase within the SnTe matrix, thereby reducing the thermal conductivity. These SnTe-CdSe nanocomposites possess thermoelectric figures of merit of up to 1.3 at 850 K, which is, to the best of our knowledge, the highest thermoelectric figure of merit reported for solution-processed SnTe. ; This work was financially supported by the European Union (EU) via FP7 ERC Starting Grant 2012 (Project NANOSOLID, GA No. 306733). M.I. was supported by IST Austria, and by ETH Zurich via ETH career seed grant (SEED-18 16-2). Y.L. acknowledges funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No. 754411. IREC acknowledges funding from Generalitat de Catalunya (2014SGR1638). J.A. acknowledge funding from Generalitat de Catalunya 2017 SGR 327 and the Spanish MINECO coordinated projects between IREC and ICN2 ENE2017-85087-C3. ICN2 acknowledges support from the Severo Ochoa Program (MINECO, Grant SEV-2017-0706) and is funded by the CERCA Programme/Generalitat de Catalunya. ; Peer reviewed

The fabrication procedure of hollow iron oxide nanoparticles with a large surface to volume ratio by a single-step gas condensation process at ambient temperature is presented. Fe clusters formed during the sputtering process are progressively transformed into hollow cuboids with oxide shells by the Kirkendall mechanism at the expense of oxygen captured inside the deposition chamber. TEM and Raman spectroscopy techniques point to magnetite as the main component of the nanocuboids; however, the magnetic behavior exhibited by the samples suggests the presence of FeO as well. In addition, these particles showed strong stability after several months of exposure to ambient conditions, making them of potential interest in diverse technological applications. In particular, these hierarchical hollow particles turned out to be very efficient for both As(III) and As(V) absorption (326 and 190 mg/g, respectively), thus making them of strong interest for drinking water remediation. ; We kindly acknowledge the assistance of Guillaume Sauthier, from ICN2, for helping us with valuable X-ray photoelectron investigations. Financial support from the Spanish Ministry of Economy and Competitiveness, through the "Severo Ochoa" Program for Centres of Excellence in R&D (SEV- 2015-0496), MAT2015-71664-R, FEDER, and funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No. 645658 (DAFNEOX Project) is acknowledged. N.B. thanks the Spanish MINECO for financial support through the FPI program. ; Peer reviewed