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Highly efficient IR-blue light up-converting NaYF4: Yb3+, Eu2+ phosphors have been prepared by a template-free hydrothermal method under mild and reductive experimental conditions. It has been demonstrated that for a fixed reaction time and temperature (150 °C/4 h), the α → β NaYF4 conversion can be accurately controlled by modifying the F/Y ratio. UC emission spectroscopy reveals that IR-blue light emission efficiency is greatly improved when β-NaYF4 phase predominates. Under the experimental conditions set in this work, reaching full α → β conversion just by increasing fluoride content entails the co-crystallization of the secondary phase YF3 1.5NH3, but far from causing a detrimental effect on the optical properties, it has been found that the samples where both β-NaYF4 and YF3 1.5NH3 phases coexist, exhibit outstanding optical properties. Resumen: Fósforos anti-Stokes NaYF4: Yb3+, Eu2+ de alta eficiencia para la conversión de radiación infrarroja en luz azul han sido satisfactoriamente sintetizados mediante un procedimiento hidrotermal en medio reductor, en ausencia de «template» y bajo condiciones experimentales suaves. Se ha demostrado que, para un tiempo y temperatura de reacción dados (150 °C/4 h), el equilibrio entre las fases polimórficas α→β del NaYF4 puede ser controlado de manera precisa mediante la modificación de la relación F/Y en el medio de reacción. Los resultados obtenidos mediante espectroscopía de fluorescencia revelan que la eficiencia con la que los fósforos sintetizados transforman radiación IR en luz azul aumenta significativamente cuando la fase predominante es β-NaYF4. Bajo las condiciones experimentales establecidas en esta investigación, alcanzar una conversión α→β completa modificando únicamente el contenido de iones fluoruro conlleva la co-cristalización de la fase secundaria YF3 1.5NH3 pero, lejos de entrañar un efecto negativo, se ha comprobado que los materiales luminiscentes donde ambas fases β-NaYF4 e YF3 1.5NH3 coexisten, exhiben propiedades ópticas excepcionales.

Thin films of silver-doped zinc oxide (SZO) were deposited at room temperature using a DC reactive magnetron co-sputtering technique using two independent Zn and Ag targets. The crystallographic structure, chemical composition and surface morphology of SZO films with different silver concentrations were correlated with the photocatalytic (PC) properties. The crystallization of the SZO films was made using millisecond range flash-lamp-annealing (FLA) treatments. FLA induces significant structural ordering of the wurtzite structure and an in-depth redistribution of silver, resulting in the formation of silver agglomerates. The wurtzite ZnO structure is observed for silver contents below 10 at.% where Ag is partially incorporated into the oxide matrix, inducing a decrease in the optical band-gap. Regardless of the silver content, all the as-grown SZO films do not exhibit any significant PC activity. The best PC response is achieved for samples with a relatively low Ag content (2–5 at.%) after FLA treatment. The enhanced PC activity of SZO upon FLA can be attributed to structural ordering and the effective band-gap narrowing through the combination of silver doping and the plasmonic effect caused by the formation of Ag clusters.

The obtaining of BiFeO3 in the form of a thin film represents a critical issue for its application in electronic devices since this is the required geometry for the integration of this material in microelectronic circuits. There are several techniques for this purpose, from those that use a gas or plasma phase to transport the precursors to the substrate, which would be included within the PVD or CVD techniques (for its acronym Physical Vapor Deposition and Chemical Vapor Deposition) to those that use a phase liquid for this transport, which would be included under the CSD (Chemical Vapor Deposition) techniques. However, among the large number of published papers, there is much controversy about which of them would be most suitable. It has been clearly demonstrated that all of them have the sufficient capacity to produce uniform and homogeneous thin films in thickness throughout the entire substrate, and although in many articles pure BiFeO3 films have been obtained with an exploitable functional response, others have reported the typical drawbacks that usually entails the obtaining this material: appearance of secondary phases, high leakages or a poor functional response. Nevertheless, there is a common aspect in the specialized literature that seems to be in agreement: the first group of techniques require very sophisticated equipment that involves high energy consumption in terms of temperature and pressure (vaccum), while the techniques that are based on solutions are characterized by their higher simplicity. In this context, the purpose of the present review is to summarize the main aspects of each technique in the obtaining of BiFeO3 thin films, from those that are more sophisticated to the simplest and environmentally benevolent ones, in order to provide an easier understanding of them. Resumen: La obtención de BiFeO3 en forma de lámina delgada representa una cuestión crítica para su aplicación en dispositivos electrónicos ya que es la geometría requerida para la integración de este material en circuitos microelectrónicos. Existen varias técnicas para este fin, desde las que utilizan una fase gaseosa o plasmática para transportar los precursores al sustrato, que se englobarían dentro de las técnicas PVD o CVD (por sus siglas en inglés de Physical Vapor Deposition y Chemical Vapor Deposition) hasta las que utilizan una fase líquida para este transporte, que se englobarían dentro de las técnicas CSD (Chemical Vapor Deposition). Sin embargo, entre el gran número de trabajos publicados, hay mucha controversia sobre cuál de ellas sería la más adecuada. Se ha demostrado claramente que todas ellas tienen la capacidad suficiente para producir películas delgadas uniformes y homogéneas en espesor a lo largo de todo el sustrato, y aunque en muchos artículos se han obtenido películas puras de BiFeO3 con una respuesta funcional aprovechable, otros han reportado los típicos inconvenientes que suele conllevar la obtención de este material: aparición de fases secundarias, corrientes de fuga altas o una pobre respuesta funcional. Sin embargo, hay un aspecto común en la literatura especializada que parece coincidir: el primer grupo de técnicas requiere de equipos muy sofisticados que implican un consumo energético alto en términos de temperatura y presión (vacío), mientras que las técnicas que se basan en disoluciones se caracterizan por su mayor simplicidad. En este contexto, el propósito de la presente revisión es resumir los principales aspectos de cada técnica en la obtención de películas delgadas de BiFeO3, desde las más sofisticadas hasta las más sencillas y respetuosas con el medio ambiente, con el fin de facilitar su comprensión.

The conventional solid state processing of bulk Ti,Sm co-doped BiFeO3 ceramics typically produces a complex micro-nanostructure which exhibits an effective decrease of the leakage conductivity. This same nanostructured configuration however confines the mobility of the ferroelectric domains and in this way the potential piezoelectric response of the formulated composition remains restrained. Hereby, a two-step doping strategy based on a simple surface modification approach is proposed which eventually allows for suitably engineering the microstructural development of the material, leading to a coarsened configuration where the conductivity is kept in low levels while the piezoelectric response is satisfactorily released for practical purposes. Resumen: El procesamiento convencional en estado sólido de materiales cerámicos en volumen de BiFeO3 co-dopado con Ti y Sm, típicamente produce una compleja micro-nanoestructura que permite una reducción efectiva de la conductividad eléctrica del material (corrientes de fuga). Sin embargo, esta misma configuración nano-estructurada también reduce la movilidad de los dominios ferroeléctricos y por ello, la potencial respuesta piezoeléctrica de la composición formulada permanece confinada. En este trabajo se propone el empleo de una estrategia de dopado en dos etapas, basada en una sencilla aproximación de modificación superficial, con la cual es posible diseñar y controlar adecuadamente el desarrollo microestructural del sistema, dando lugar a un engrosamiento de la microestructura que permite mantener la conductividad del material en bajos niveles al tiempo que libera satisfactoriamente su respuesta piezoeléctrica. Keywords: BiFeO3, Processing, Microstructure, Electrical conductivity, Piezoelectricity, Palabras clave: BiFeO3, Procesamiento, Microestructura, Conductividad eléctrica, Piezoelectricidad

We highlight hereby recent developments in the emerging field of theranostics, which encompasses the combination of therapeutics and diagnostics in a single entity aimed for an early-stage diagnosis, image-guided therapy as well as evaluation of therapeutic outcomes of relevance to prostate cancer (PCa). Prostate cancer is one of the most common malignancies in men and a frequent cause of male cancer death. As such, this overview is concerned with recent developments in imaging and sensing of relevance to prostate cancer diagnosis and therapeutic monitoring. A major advantage for the effective treatment of PCa is an early diagnosis that would provide information for an appropriate treatment. Several imaging techniques are being developed to diagnose and monitor different stages of cancer in general, and patient stratification is particularly relevant for PCa. Hybrid imaging techniques applicable for diagnosis combine complementary structural and morphological information to enhance resolution and sensitivity of imaging. The focus of this review is to sum up some of the most recent advances in the nanotechnological approaches to the sensing and treatment of prostate cancer (PCa). Targeted imaging using nanoparticles, radiotracers and biomarkers could result to a more specialised and personalised diagnosis and treatment of PCa. A myriad of reports has been published literature proposing methods to detect and treat PCa using nanoparticles but the number of techniques approved for clinical use is relatively small. Another facet of this report is on reviewing aspects of the role of functional nanoparticles in multimodality imaging therapy considering recent developments in simultaneous PET-MRI (Positron Emission Tomography-Magnetic Resonance Imaging) coupled with optical imaging in vitro and in vivo, whilst highlighting feasible case studies that hold promise for the next generation of dual modality medical imaging of PCa. It is envisaged that progress in the field of imaging and sensing domains, taken together, could benefit from the biomedical implementation of new synthetic platforms such as metal complexes and functional materials supported on organic molecular species, which can be conjugated to targeting biomolecules and encompass adaptable and versatile molecular architectures. Furthermore, we include hereby an overview of aspects of biosensing methods aimed to tackle PCa: prostate biomarkers such as Prostate Specific Antigen (PSA) have been incorporated into synthetic platforms and explored in the context of sensing and imaging applications in preclinical investigations for the early detection of PCa. Finally, some of the societal concerns around nanotechnology being used for the detection of PCa are considered and addressed together with the concerns about the toxicity of nanoparticles–these were aspects of recent lively debates that currently hamper the clinical advancements of nano-theranostics. The publications survey conducted for this review includes, to the best of our knowledge, some of the most recent relevant literature examples from the state-of-the-art. Highlighting these advances would be of interest to the biomedical research community aiming to advance the application of theranostics particularly in PCa diagnosis and treatment, but also to those interested in the development of new probes and methodologies for the simultaneous imaging and therapy monitoring employed for PCa targeting.

As a primary goal, this review highlights the role of supramolecular interactions in the assembly of new sustainable materials incorporating functional porphyrins and carbon nanoplatforms as building blocks for photovoltaics advancements.

With the development of 5G, Internet of Things, and smart home technologies, miniaturized and compact multi-antenna systems and multiple-input multiple-output (MIMO) antenna arrays have attracted increasing attention. Reducing the coupling between antenna elements is essential to improving the performance of such MIMO antenna system. In this work, we proposed a graphene-assembled, as an alternative material rather than metal, film-based MIMO antenna array with high isolation for 5G application. The isolation of the antenna element is improved by a graphene assembly film (GAF) frequency selective surface and isolation strip. It is shown that the GAF antenna element operated at 3.5 GHz has the realized gain of 2.87 dBi. The addition of the decoupling structure improves the isolation of the MIMO antenna array to more than 10 dB and corrects the antenna radiation pattern and operating frequency. The isolation between antenna elements with an interval of 0.4λ is above 25 dB. All experimental results show that the GAF antenna and decoupling structure are efficient devices for 5G mobile communication.

This paper provides direct evidence to support the role of capping agents in controlling the evolution of TiO2 seeds into nanocrystals with a specific shape. Starting with Ti(OBut)4 and using oleid acid, oleylamine, dioleamide, 11-aminoundecanoic acid, arginine, trifluroacetic acid or HF as capping agents, mainly TiO2 truncated octahedrons enclosed by {1 0 1} and {0 0 1} facets were obtained. We could also selectively obtain square, rods and rounded rhombic-shaped nanoparticles by growing of {0 1 0} facets by adding oleic acid and oleylamine in ratio 6:4, respectively, while all other parameters were kept the same. This research not only offers new insights into the role played by a capping agent in shape-controlled synthesis but also provides, a versatile approach to controlling the shape of metal oxide nanocrystals.

Abstract We report on the design and testing of new graphite and graphene oxide‐based extended π‐conjugated synthetic scaffolds for applications in sustainable chemistry transformations. Nanoparticle‐functionalised carbonaceous catalysts for new Fischer Tropsch and Reverse GasWater Shift (RGWS) transformations were prepared: functional graphene oxides emerged from graphite powders via an adapted Hummer's method and subsequently impregnated with uniform‐sized nanoparticles. Then the resulting nanomaterials were imaged by TEM, SEM, EDX, AFM and characterised by IR, XPS and Raman spectroscopies prior to incorporation of Pd(II) promoters and further microscopic and spectroscopic analysis. Newly synthesised 2D and 3D layered nanostructures incorporating carbon‐supported iron oxide nanoparticulate pre‐catalysts were tested, upon hydrogen reduction in situ, for the conversion of CO2 to CO as well as for the selective formation of CH4 and longer chain hydrocarbons. The reduction reaction was also carried out and the catalytic species isolated and fully characterised. The catalytic activity of a graphene oxide‐supported iron oxide pre‐catalyst converted CO2 into hydrocarbons at different temperatures (305, 335, 370 and 405 °C), and its activity compared well with that of the analogues supported on graphite oxide, the 3‐dimensional material precursor to the graphene oxide. Investigation into the use of graphene oxide as a framework for catalysis showed that it has promising activity with respect to reverse gas water shift (RWGS) reaction of CO2 to CO, even at the low levels of catalyst used and under the rather mild conditions employed at atmospheric pressure. Whilst the γ‐Fe2O3 decorated graphene oxide‐based pre‐catalyst displays fairly constant activity up to 405 °C, it was found by GC‐MS analysis to be unstable with respect to decomposition at higher temperatures. The addition of palladium as a promoter increased the activity of the iron functionalised graphite oxide in the RWGS. The activity of graphene oxide supported catalysts was found to be enhanced with respect to that of iron‐functionalised graphite oxide with, or without palladium as a promoter, and comparable to that of Fe@carbon nanotube‐based systems tested under analogous conditions. These results display a significant step forward for the catalytic activity estimations for the iron functionalised and rapidly processable and scalable graphene oxide. The hereby investigated phenomena are of particular relevance for the understanding of the intimate surface morphologies and the potential role of non‐covalent interactions in the iron oxide‐graphene oxide networks, which could inform the design of nano‐materials with performance in future sustainable catalysis applications.

Abstract Three‐dimensional fluorescent graphene frameworks with controlled porous morphologies are of significant importance for practical applications reliant on controlled structural and electronic properties, such as organic electronics and photochemistry. Here we report a synthetically accessible approach concerning directed aromatic stacking interactions to give rise to new fluorogenic 3D frameworks with tuneable porosities achieved through molecular variations. The binding interactions between the graphene‐like domains present in the in situ‐formed reduced graphene oxide (rGO) with functional porphyrin molecules lead to new hybrids via an unprecedented solvothermal reaction. Functional free‐base porphyrins featuring perfluorinated aryl groups or hexyl chains at their meso‐ and β‐positions were employed in turn to act as directing entities for the assembly of new graphene‐based and foam‐like frameworks and of their corresponding coronene‐based hybrids. Investigations in the dispersed phase and in thin‐film by XPS, SEM and FLIM shed light onto the nature of the aromatic stacking within functional rGO frameworks (denoted rGOFs) which was then modelled semi‐empirically and by DFT calculations. The pore sizes of the new emerging reduced graphene oxide hybrids are tuneable at the molecular level and mediated by the bonding forces with the functional porphyrins acting as the “molecular glue”. Single crystal X‐ray crystallography described the stacking of a perfluorinated porphyrin with coronene, which can be employed as a molecular model for understanding the local aromatic stacking order and charge transfer interactions within these rGOFs for the first time. This opens up a new route to controllable 3D framework morphologies and pore size from the Ångstrom to the micrometre scale. Theoretical modelling showed that the porosity of these materials is mainly due to the controlled inter‐planar distance between the rGO, coronene or graphene sheets. The host‐guest chemistry involves the porphyrins acting as guests held through π‐π stacking, as demonstrated by XPS. The objective of this study is also to shed light into the fundamental localised electronic and energy transfer properties in these new molecularly engineered porous and fluorogenic architectures, aiming in turn to understand how functional porphyrins may exert stacking control over the notoriously disordered local structure present in porous reduced graphene oxide fragments. By tuning the porosity and the distance between the graphene sheets using aromatic stacking with porphyrins, it is also possible to tune the electronic structure of the final nanohybrid material, as indicated by FLIM experiments on thin films. Such nanohybrids with highly controlled pores dimensions and morphologies open the way to new design and assembly of storage devices and applications incorporating π‐conjugated molecules and materials and their π‐stacks may be relevant towards selective separation membranes, water purification and biosensing applications.