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The possibility to precisely control reaction outcomes for pursuing materials with well-defined features is a main endeavor in the development of inorganic materials. Confining reactions within a confined space, such as nanoreactors, is an extremely promising methodology which allows to ensure control over the final properties of the material. An effective room temperature inverse miniemulsion approach for the controlled synthesis of undoped and Eu3+-doped calcium molybdate crystalline nanophosphors was developed. The advantages and the efficiency of confined space in terms of controlling nanoparticle features like size, shape, and functional properties are highlighted by systematically comparing miniemulsion products with calcium molybdate particles obtained without confinement from a typical batch synthesis. A relevant beneficial impact of space confinement by miniemulsion nanodroplets is observed on the control of size and shape of the final nanoparticles, resulting in 12 nm spherical nanoparticles with a narrow size distribution, as compared to the 58 nm irregularly shaped and aggregated particles from the batch approach (assessed by TEM analysis). Further considerable effects of the confined space for the miniemulsion samples are found on the doping effectiveness, leading to a more homogeneous distribution of the Eu3+ ions into the molybdate host matrix, without segregation (assessed by PXRD, XAS, and ICP-MS). These findings are finally related to the photoluminescence properties, which are evidenced to be closely dependent on the Eu3+ content for the miniemulsion samples, as an increase of the relative intensity of the direct f–f excitation and a shortening of the lifetime (from 0.901 ms for 1 at. % to 0.625 ms for 7 at. % samples) with increasing Eu3+ content are observed, whereas no relationship between these parameters and the Eu3+ content is evidenced for the batch samples. All these results are ascribed to the uniform and controlled crystallization occurring inside each miniemulsion nanodroplet, as opposed to the less controlled nucleation and growth for a classic nonconfined approach. [ABSTRACT FROM AUTHOR]

Local temperature determination is essential to understand heat transport phenomena at the nanoscale and to design nanodevices for biomedical, photonic, and optoelectronic applications. In particular, the detection of the local temperature of the intracellular environment is interesting for photothermal therapy. In the present work, nanoparticles consisting of an Ag core, covered by a TiO2 shell and Ag@TiO2 core–shell, were suitably synthesized through a one-pot method. Silver nanoparticles synthesized in DMF were coated by controlled hydrolysis of titanium tetrabutoxide in the same reaction environment. The synthesis led to nanocomposites where AgNPs were covered by a diffuse layer of anatase. The nanocomposites were characterized using UV/Vis spectroscopy and Raman spectroscopy. The samples obtained proved to be good Raman nanothermometers with a sensitivity comparable to that of simple anatase nanoparticles. [ABSTRACT FROM AUTHOR]

Enclosed nanoscale volumes, i.e., confined spaces, represent a fascinating playground for the controlled synthesis of inorganic materials, albeit their role in determining the synthetic outcome is currently not fully understood. Herein, we address the synthesis of MoO3 nano- and microrods with hexagonal section in inverse miniemulsion droplets and batch conditions, evaluating the effects of spatial confinement offered by miniemulsion droplets on their crystallization. Several synthetic parameters were systematically screened and their effect on the crystal structure of h-MoO3, as well as on its size, size distribution and morphology, were investigated. Moreover, a direct insight on the crystallization pathway of MoO3 in both synthetic conditions and as a function of synthetic parameters was provided by an in situ time-resolved SAXS/WAXS study, that confirmed the role of miniemulsion confined space in altering the stepwise process of the formation of h-MoO3. [ABSTRACT FROM AUTHOR]

The ongoing problems in western countries connected to the global energy supply urgently force the research community to strive in finding new methodologies for boosting the functional properties of earth‐abundant raw materials, for example, the largely available cupreous oxide. In this work, the authors focus on the surface sensitization of this metal oxide semiconductor with an argon plasma treatment, that promotes, during photoelectrochemical hydrogen evolution, the formation of metallic copper nanostructures. Interestingly, these copper‐based hierarchical nano‐branches, having inherent plasmonic properties, are at the origin of the improved shelf‐life of the modified Cu2O photocathode, as is demonstrated by advanced structural and photophysical analyses. This proposed photophysical mechanism for an operando electrode stabilization suggests that a self‐healing process can occur within the Cu2O/plasmonic Cu heterostructure. These findings pave the way to the implementation of new, easy‐to‐make strategies to improve the properties of low‐cost, low‐toxicity energy materials. [ABSTRACT FROM AUTHOR]

Zinc oxide is an extensively studied semiconductor with a wide band gap in the near-UV. Its many interesting properties have found use in optics, electronics, catalysis, sensing, as well as biomedicine and microbiology. In the nanoscale regime the functional properties of ZnO can be precisely tuned by manipulating its size, shape, chemical composition (doping), and surface states. In this review, we focus on the colloidal synthesis of ZnO nanocrystals (NCs) and provide a critical analysis of the synthetic methods currently available for preparing ZnO colloids. First, we outline key thermodynamic considerations for the nucleation and growth of colloidal nanoparticles, including an analysis of different reaction methodologies and of the role of dopant ions on nanoparticle formation. We then comprehensively review and discuss the literature on ZnO NC systems, including reactions in polar solvents that traditionally occur at low temperatures upon addition of a base, and high temperature reactions in organic, nonpolar solvents. A specific section is dedicated to doped NCs, highlighting both synthetic aspects and structure–property relationships. The versatility of these methods to achieve morphological and compositional control in ZnO is explicated. We then showcase some of the key applications of ZnO NCs, both as suspended colloids and as deposited coatings on supporting substrates. Finally, a critical analysis of the current state of the art for ZnO colloidal NCs is presented along with existing challenges and future directions for the field. [ABSTRACT FROM AUTHOR]

Costs and toxicity concerns are at the center of a heated debate regarding the implementation of perovskite solar cells (PSCs) into commercial products. The first bottleneck could be overcome by eliminating the top metal electrode (generally gold) and the underlying hole transporting material and substituting both with one single thick layer of conductive carbon, as in the so‐called carbon‐based PSCs (C‐PSCs). The second issue, related to the presence of lead, can be tackled by resorting to other perovskite structures based on less toxic metallic components. An interesting case is that of the double perovskite Cs2AgBiBr6, which at present still lacks the outstanding optoelectronic performances of the lead‐based counterparts but is very stable to environmental factors. In this work, the processing of carbon electrodes onto Cs2AgBiBr6‐based C‐PSCs was reported, starting from an additive‐free isopropanol ink of a carbon material obtained from the hydrothermal recycling of waste tires and employing a high‐throughput ultrasonic spray coating method in normal environmental conditions. Through this highly sustainable approach that ensures a valuable step from an end‐of‐life to an end‐of‐waste status for used tires, devices were obtained delivering a record open circuit voltage of 1.293 V, which might in the future represent ultra‐cheap solutions to power the indoor Internet of Things ecosystem. [ABSTRACT FROM AUTHOR]