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Important efforts are currently under way in order to implement plasmonic phenomena in the growing field of photocatalysis, striving for improved efficiency and reaction selectivity. A significant fraction of such efforts has been focused on distinguishing, understanding and enhancing specific energy transfer mechanisms from plasmonic nanostructures to their environment. Herein we report a synthetic strategy that brings together two of the main physical mechanisms driving plasmonic photocatalysis into an engineered system by rationally combining the photochemical features of energetic charge carriers and the electromagnetic field enhancement inherent to the plasmonic excitation. We do so by creating hybrid photocatalysts that integrate multiple plasmonic resonators in a single entity, controlling their joint contribution through spectral separation and differential surface functionalization. This strategy allows us to study the combination of different photosensitization mechanisms when activated simultaneously. Our results show that hot electron injection can be combined with an energy transfer process mediated by near-field interaction, leading to a significant increase of the final photocatalytic response of the material. In this manner, we overcome the limitations that hinder photocatalysis driven only by a single energy transfer mechanism, and move the field of plasmonic photocatalysis closer to energy-efficient applications. Furthermore, our multimodal hybrids offer a test system to probe the properties of the two targeted mechanisms in energy-related applications such as the photocatalytic generation of hydrogen and open the door to wavelength-selective photocatalysis and novel tandem reactions.

An alternative model to the well-established paradigm of the externally switchable drug delivery systems is herein proposed. In contrast to the on–off archetype, here the amount of released drug is pre-set by the application of an external stimulus, and is gradually released after the withdrawal of the exogenous signal. These attributes are achieved through an innovative approach featuring the integration of plasmonic nanovehicles in a polymer-based film. Such a platform is provided with optically responsive capabilities together with multiple diffusional barriers, allowing for an “on-demand” time-limited release where light acts as a therapeutic “starting shot”. These nanoarchitectured depots have great potential as implantable drug delivery systems in clinical scenarios where a recurrent, sustained, and yet, on–off administration of medication is required. The application of these hybrid materials may extend the implementation of nanomedicine strategies beyond the point-of-care setting.

Metal&ndash, semiconductor nanocomposites have become interesting materials for the development of new photocatalytic hybrids. Along these lines, plasmonic nanoparticles have proven to be particularly efficient photosensitizers due to their ability to transfer plasmonic hot electrons onto large bandgap semiconductors such as TiO2, thus extending the activity of the latter into a broader range of the electromagnetic spectrum. The extent of this photosensitization process can be substantially enhanced in those geometries in which high electromagnetic fields are created at the metal&ndash, semiconductor interface. In this manner, the formation of plasmonic hot spots can be used as a versatile tool to engineer the photosensitization process in this family of hybrid materials. Herein, we introduce the use of titanate nanowires as ideal substrates for the assembly of Au nanorods and TiO2 nanoparticles, leading to the formation of robust hybrids with improved photocatalytic properties. Our approach shows that the correct choice of the individual units together with their rational assembly are of paramount importance in the development of complex nanostructures with advanced functionalities.

The use of plasmonic metal nanoparticles as photosensitizers has undergone a strong development in the past few years given their ability to increase the activity of semiconductors into the visible and near-infrared regions. The present work reports an experimental and theoretical study on the critical influence that shape anisotropy of gold nanoparticles exerts on the photocatalytic performance of Au–TiO2 nanoarchitectures. The obtained results show that for a given amount of metallic material, Au nanostars endow titania with a strongly enhanced catalytic efficiency compared to that found in the presence of Au nanospheres or nanorods. This is ascribed to the ability of nanostars to locally create extremely large electromagnetic field enhancements around their spikes, which ensures an increased population of hot electrons close to the interface between the metal and the semiconductor. Therefore, these nanostructures exhibit a novel regime of photocatalytic activity that could be described as plasmonic hot...

Hollow inorganic nanostructures have attracted much interest in the last few years due to their many applications in different areas of science and technology. In this Feature Article, we overview part of our current work concerning the collective use of plasmonic and magnetic nanoparticles located in voided nanostructures and explore the more specific operational issues that should be taken into account in the design of inorganic nanocapsules. Along these lines, we focus our attention on the applications of silica-based submicrometer capsules aiming to stress the importance of creating nanocavities in order to further exploit the great potential of these functional nanomaterials. Additionally, we will examine some of the recent research on this topic and try to establish a perspective for future developments in this area.

Elena González-Domínguez,1,* Nerea Iturrioz-Rodríguez,2,* Esperanza Padín-González,2 Juan Villegas,2 Lorena García-Hevia,2 Moisés Pérez-Lorenzo,1 Wolfgang J Parak,3 Miguel A Correa-Duarte,1,* Mónica L Fanarraga2,* 1Department of Physical Chemistry, Biomedical Research Center (CINBIO), Southern Galicia Institute of Health Research (IISSG), Biomedical Research Networking Center for Mental Health (CIBERSAM), Universidade de Vigo, Vigo, Spain; 2Nanomedicine Group, Universidad de Cantabria-IDIVAL, Santander, Spain; 3Department of Physics, Philipps Universität Marburg, Marburg, Germany *These authors contributed equally to this work Abstract: Carbon nanotubes (CNTs) are likely to transform the therapeutic and diagnostic fields in biomedicine during the coming years. However, the fragmented vision of their side effects and toxicity in humans has proscribed their use as nanomedicines. Most studies agree that biocompatibility depends on the state of aggregation/dispersion of CNTs under physiological conditions, but conclusions are confusing so far. This study designs an experimental setup to investigate the cytotoxic effect of individualized multiwalled CNTs compared to that of identical nanotubes assembled on submicrometric structures. Our results demonstrate how CNT cytotoxicity is directly dependent on the nanotube dispersion at a given dosage. When CNTs are gathered onto silica templates, they do not interfere with cell proliferation or survival becoming highly compatible. These results support the hypothesis that CNT cytotoxicity is due to the biomimetics of these nanomaterials with the intracellular nanofilaments. These findings provide major clues for the development of innocuous CNT-containing nanodevices and nanomedicines. Keywords: MWCNTs, biomimetics, cytoskeleton, microtubules, apoptosis, migration, proliferation

A solar heat shield coating featuring the combination of plasmonic nanostructures in silica-based insulating materials has been developed and tested under conditions resembling natural sunlight exposure. Our results when implementing this coating on standard glazing reveal a blocking efficiency higher than 40%, compatible with a notable preservation of visible light transmittance above 75%. This strategy is (i) cost-effective, as only requires minute amounts of absorbent material in order to obtain the desired effect; (ii) straightforward, because no particular ordering of the plasmon resonators is needed onto the glass substrate; (iii) eco-friendly, as no metal leaching is observed once the gold is encapsulated; and (iv) retrofit-capable, given the fact that these nanostructures can be easily incorporated onto pre-installed glazing. All of these features emphasize the great potential of this approach in the search of more sustainable technologies for the fenestration industry.

The translocation of nanomaterials or complex delivery systems into the cytosol is a main challenge in nanobiotechnology. After receptor-mediated endocytosis, most nanomaterials are sequestered undergoing degradation, therapy inactivation or exocytosis. Here we explore a novel surface particle-coating made of adsorbed carbon nanotubes that provides coated materials with new properties that reproduce the viral cell invasive mechanisms, namely: receptor mediated endocytosis, endo-lysosomal escape and cytosolic particle release preserving intact cell viability. This novel biomimetic coating design will enable the intracytoplasmic delivery of many different functional materials endowed with therapeutic, magnetic, optical or catalytic functionalities thus, opening the door to a wide array of chemical and physical processes within the cytosolic or nuclear domains, and supporting the generation of new developments in the biotechnological, pharmaceutical and biomedical industries.

A hierarchically structured nanoplatform comprising the integration of enzymes into a hybrid carbon-nanotube-based magnetic nanocomposite was developed. By means of this complex support, laccases are endowed with exceptional performance even in fully denaturing environments. In this regard, up to 10-fold enhancements in the biocatalytic activity of the enzymes can be attained at different temperatures and pH conditions. Furthermore, these platforms are found to provide laccases with unprecedented recycling potential. In this line, these composites allow straightforward recovery and reuse of the biocatalysts with no loss of efficiency even after 10 successive runs. These outstanding operational capabilities make these nanocarriers a promising material to tackle the challenges associated with the implementation of enzymes in industrial biotechnology.

An experiment is described to introduce advanced undergraduate students to an exciting area of nanotechnology that incorporates nanoparticles onto carbon nanotubes to produce systems that have valuable technological applications. The synthesis of such material has been easily achieved through a simple three-step procedure. Students explore cutting-edge research and gain knowledge in nanoscience.

This work calls for a paradigm shift in order to change the operational patterns of self-regulated membranes in response to chemical signals. To this end, the fabrication of a retrofitting material is introduced aimed at developing an innovative generation of porous substrates endowed with symbiotic but fully independent sensing and actuating capabilities. This is accomplished by transferring carefully engineered plasmonic architectures onto commercial microfiltration membranes lacking of such features. The integration of these materials leads to the formation of a coating surface proficient for ultrasensitive detection and "on-command" gating. Both functionalities can be synergistically modulated by the spatial and temporal distribution of an impinging light beam offering an unprecedented control over the membrane performance in terms of permeability. The implementation of these hybrid nanocomposites in conventional polymeric porous materials holds great potential in applications ranging from intelligent fluid management to advanced filtration technologies and controlled release.

A synthetic strategy for the microencapsulation of ultra-small gold nanoparticles toward the development of a novel nanoreactor is reported. In this case, it is shown that the catalytic activity of Au nanoclusters as small as 0.8 nm remains unaffected after a thermal treatment up to 800 °C in air. This is accomplished through the deposition and further coating of the gold nanoparticles in a void/silica/Au/silica configuration where the nature of the alternate shells can be tuned regardless of each other's porosity and the size of the embedded metal nanoparticles. Such spatial confinement suppresses the growth of the gold nanoclusters and thus preserves their catalytic properties. In this way, a remarkable compromise between the immobilization and the accessibility to the metal nanocatalyst can be met. Furthermore, these nanoreactors are found to be colloidally stable in simulated body fluids which also makes them suitable for biomedical applications. The implementation of hollow nanoreactors containing highly dispersed and immobilized but accessible ultra-small metal nanoparticles constitutes a promising alternative in the search for model catalysts stable under realistic technical conditions.

The bioaccumulation of polycyclic aromatic compounds originating from textile processing industries is nowadays a major environmental problem worldwide. In order to tackle this situation, several inorganic semiconductors have been tested as photocatalysts for the degradation of these harmful pollutants in the search of sustainable and cost-effective solutions. Nevertheless, these semiconductor materials often involve important limitations, such as poor efficiency and selectivity, which, in the end, substantially restrict their implementation at the industrial scale. As an alternative, we herein report the fabrication and application of Au-decorated titanate nanotubes (TNTs) as high-performance architectures for the selective degradation of organic contaminants. This synthetic strategy is intended to establish a synergetic integration of the physicochemical and photocatalytic features of these hybrid nanostructures, by combining the remarkable adsorption capabilities of TNTs with the enhanced light-harvesting efficiency provided by the incorporation of a noble metal component. The obtained results evidence the great potential that rationally designed plasmonic composites may have for the development of selective environmental remediation technologies and in particular on the current challenges faced by the wastewater treatment sector.

Hollow-shelled nanoreactors have emerged as efficient structures to maximize the potential of nanoparticles in the field of catalysis. In this Concept article, we underline the importance of both the morphology of the active nanoparticles as well as the composition and porosity of the shell for the catalytic performance of the overall nanocomposite. Different configurations are discussed, with a focus on preparative methods and applications in organic synthesis. Perspectives on future designs that may offer new opportunities to improve the selectivity of the catalyzed transformations and add additional features are also addressed, in order to illustrate the potential of these unique nanostructures.

We report herein the design of plasmonic hollow nanoreactors capable of concentrating light at the nanometer scale for the simultaneous performance and optical monitoring of thermally activated reactions. These reactors feature the encapsulation of plasmonic nanoparticles on the inner walls of a mesoporous silica capsule. A Diels–Alder cycloaddition reaction was carried out in the inner cavities of these nanoreactors to evidence their efficacy. Thus, it is demonstrated that reactions can be accomplished in a confined volume without alteration of the temperature of the bulk solvent while allowing real-time monitoring of the reaction progress.

Hollow-shelled nanoreactors have emerged as efficient structures to maximize the potential of nanoparticles in the field of catalysis. In this Concept article, we underline the importance of both the morphology of the active nanoparticles as well as the composition and porosity of the shell for the catalytic performance of the overall nanocomposite. Different configurations are discussed, with a focus on preparative methods and applications in organic synthesis. Perspectives on future designs that may offer new opportunities to improve the selectivity of the catalyzed transformations and add additional features are also addressed, in order to illustrate the potential of these unique nanostructures.

Catalysis by metallic nanoparticles is certainly among the most intensely studied problems in modern nanoscience. However, reliable tests for catalytic performance of such nanoparticles are often poorly defined, which makes comparison and benchmarking rather difficult. We tackle in this tutorial review a subset of well-studied reactions that take place in aqueous phase and for which a comprehensive kinetic analysis is available. Two of these catalytic model reactions are under consideration here, namely the reduction of (i) p-nitrophenol and (ii) hexacyanoferrate (III), both by borohydride ions. Both reactions take place at the surface of noble metal nanoparticles at room temperature and can be accurately monitored by UV-vis spectroscopy. Moreover, the total surface area of the nanoparticles in solution can be known with high precision and thus can be directly used for the kinetic analysis. Hence, these model reactions represent cases of heterogeneous catalysis that can be modelled with the accuracy typically available for homogeneous catalysis. Both model reactions allow us to discuss a number of important concepts and questions, namely the dependence of catalytic activity on the size of the nanoparticles, electrochemistry of nanoparticles, surface restructuring, the use of carrier systems and the role of diffusion control.

Sintering of nanoparticles mediated by an Ostwald ripening mechanism is generally assessed examining the final particle size distributions. Based on this methodology, a general approach for depositing platinum nanoparticles onto carbon nanotubes in solution has been employed in order to evaluate the sintering process of these metallic nanoparticles at increasing temperatures in a carbon nanotube/silica-templated confined space.

It happens inside: highly active nanoreactors are prepared by encapsulating dendritic Pt nanoparticles (NPs) grown on a polystyrene template inside hollow porous silica capsules. The catalytic activity of these Pt NPs is preserved after encapsulation and template removal. Different metals, such as Ni, can thus be reduced inside the capsules, thereby leading to the formation of composites with tunable magnetic properties.