The synthetic architectures of complex inorganic nanostructures, including multifunctional hollow capsules, are expected to play key roles in many different applications, such as drug delivery, photonic crystals, nanoreactors, and sensing. Implementation of novel strategies for the fabrication of such materials is needed because of the infancy of this knowledge, which still limits progress in certain areas. Herein we report a straightforward synthetic approach for the development of multifunctional submicron reactors comprising catalytic gold nanoparticles (2-3 nm) confined inside hollow silica capsules. Additionally, the confined growth of encapsulated metal nanoparticles was carried out to evidence the usefulness and functionality of these reactors in catalytic applications and as an approach for the development of novel complex nanostructures. Their potential and multifunctionality have been pointed out by fabrication of SERS-encoded submicrometer particles with shape and size uniformity for use in antigen biosensing; this was accomplished via codification of gold nanoparticle islands grown onto their inner surfaces.

Surface-enhanced Raman scattering (SERS) spectroscopy can be used for the label-free determination and quantification of relevant small biometabolites that are hard to identify by conventional immunological methods, in the absence of labelling. In this work, detection is based on monitoring the vibrational changes occurring at a specific biointerface (a monoclonal antibody, mAb) supported on silver-coated carbon nanotubes (CNT@Ag). Engineered CNT@Ag play a key role, as they offer a stable substrate to support the biointerface, with a high density of hot spots. Proof of concept is demonstrated through the analysis and quantification of the main cocaine metabolite benzoylecgonine. These results open a new avenue toward the generation of portable sensors for fast ultradetection and quantification of relevant metabolites. The use of discrete particles (CNT@Ag@mAb) rather than rough films, or other conventional SERS supports, will also enable a safe remote interrogation of highly toxic sources in environmental problems or in biological fluids.

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.

Herein we describe a one-step method for the preparation of single-crystal, dendritic Pt nanoparticles with no need of organic solvents, templates, or seeded growth. It is shown that Pt nanoparticles with two different shapesspherical or dendriticcan be efficiently supported onto the sidewalls of carbon nanotubes. Notably, the supported dendritic Pt nanostructrures yield unprecedented catalytic activity, evidenced through the lowest activation energy within an electron-transfer reaction as compared with those reported in the literature for Pt nanostructures.

No abstract