Jose L. Hueso

Beyond gold: rediscovering tetrakis-(hydroxymethyl)-phosphonium chloride (THPC) as an effective agent for the synthesis of ultra-small noble metal nanoparticles and Pt-containing nanoalloys

The use of tetrakis-(hydroxymethyl)-phosphonium chloride (THPC) as simultaneous reducing agent and stabilizing ligand has been extended to the single-step synthesis at room temperature of a wide variety of monometallic nanoparticles and bi-/tri- metallic nanoalloys containing noble metals with potential application in catalysis. The colloidal suspensions exhibit mean diameters below 4 nm with narrow size distributions and high stability in aqueous solution for long periods of time.

Carbon nanotubes—mesoporous silica composites as controllable biomaterials

A composite based on mesoporous ordered silica (SBA-15) and carbon nanotubes (CNTs), has been synthesized to be used in biomedical applications as a conductor composite for cell stimulation and regeneration. The influence of the CNT addition time on the SBA-15–CNTs composite synthesis has been studied and optimized attending to morphology and structure, to produce a homogeneous material with both structures preserved. With the addition of the CNTs, the electrical resistance has decreased 8 orders in magnitude in comparison to the SBA-15 itself. The potential of these materials to be used as bioimplants has been evaluated in vitro by soaking the composite in simulated body fluid (SBF) at 37 °C.

Use of a polyol liquid collection medium to obtain ultrasmall magnetic nanoparticles by laser pyrolysis

The present work addresses the main bottleneck in the synthesis of magnetic nanoparticles by laser pyrolysis. Since the introduction of laser pyrolysis for the production of nanoparticles nearly three decades ago, this method has been repeatedly presented as a highly promising alternative, on account of two main characteristics: (i) its flexibility, since nanoparticles can be formed from a wide variety of precursors in both gas and liquid phase, and (ii) its continuous nature, avoiding the intrinsic variability of batch processing. However, the results reported to date invariably show considerable aggregation of the obtained nanoparticles, which strongly limits their application in most fields. In this work, we have been able to circumvent this problem by collecting the particles in a polyol liquid medium. This method prevents the formation of aggregates and renders a uniform distribution of well dispersed ultrasmall nanoparticles (<4 nm) in a water-compatible solvent. We consider that the effectiveness of this novel collection method for the production of well-dispersed magnetic nanoparticles will be of high interest to a wide range of scientists working in the nanoparticle synthesis field and may enable new applications wherever there is a strict requirement for non-agglomerated nanoparticles.

Gold-coated halloysite nanotubes as tunable plasmonic platforms

We propose the use of natural Halloysite Hollow Nanotubes (HNTs) as supports to generate plasmonic platforms with remotely triggered heating capacity. The chemical modification and subsequent coating with nanostructured gold either in the form of individually dispersed particles or by forming a shell with variable thickness and interconnectivity has been studied. The dielectric nature of the silica in conjunction with the plasmonic gold layer allows a flexible optical response with tunable maximum absorptions within the visible to Near-Infrared (NIR) range. The generation of hollow gold nanotubes using halloysite as a sacrificial template is also demonstrated.

A Nanoarchitecture Based on Silver and Copper Oxide with an Exceptional Response in the Chlorine-Promoted Epoxidation of Ethylene

The selective oxidation of ethylene to ethylene epoxide is highly challenging as a result of competing reaction pathways leading to the deep oxidation of both ethylene and ethylene oxide. Herein we present a novel catalyst based on silver and copper oxide with an excellent response in the selective oxidation pathway towards ethylene epoxide. The catalyst is composed of different silver nanostructures dispersed on a tubular copper oxide matrix. This type of hybrid nanoarchitecture seems to facilitate the accommodation of chlorine promoters, leading to high yields at low reaction temperatures. The stability after the addition of chlorine promoters implies a substantial improvement over the industrial practice: a single pretreatment step at ambient pressure suffices in contrast with the common practice of continuously feeding organochlorinated precursors during the reaction.

Efficient and facile tuning of Vulcan XC72 with ultra-small Pt nanoparticles for electrocatalytic applications

In this work, we report the synergic combination of tiny, reproducible, and crystalline platinum nanoparticles with functionalized Vulcan XC72 support for the preparation of efficient electrocatalysts. The morphology and crystallinity of Pt NPs, the amination of carbon support and the Pt loading have been properly evaluated by TEM, STEM, ATR-FTIR, XPS and microwave plasma-atomic emission spectrometry MP-AES. The electrochemical performance of the as prepared powders has been evaluated and compared with the exhibited by commercial Pt-ETEK catalyst with similar Pt-loadings, i.e. 20% wt. The herein described electrocatalyst shows higher dispersion (98.2 m2 gPt−1) of Pt nanoparticles (1.5 ± 0.3 nm in size) and strong metal–support interaction than commercial Pt-ETEK counterpart, highlighting the elevated mass activity for methanol electrooxidation.

Nitrogen‐Induced Transformation of Vitamin C into Multifunctional Up‐converting Carbon Nanodots in the Visible–NIR Range

Water-soluble, biocompatible, and photoluminescent carbon nanodots have been obtained from the rationalized carbonization of vitamin C, a well-known antioxidant molecule in the presence of an amine co-reactant. Herein, we describe the positive influence of N-doping to induce a unique pH-dependent lifetime decay response that would be potentially attractive in biological backgrounds with intrinsic fluorescence fluctuations. In addition, the selectivity and sensitivity of the N-containing carbon nanoprobes towards the detection of copper ions at ppm levels is critically enhanced in comparison with the un-doped counterpart, especially in the near-infrared (NIR) range. Finally, the up-converting properties have been also successfully applied to image tumor cells in the visible range and remarkably, in the NIR region in which minimal tissue or water absorption and maximum penetration depth are expected.

Laser-Assisted Production of Carbon-Encapsulated Pt-Co Alloy Nanoparticles for Preferential Oxidation of Carbon Monoxide

C-encapsulated highly pure PtxCoy alloy nanoparticles have been synthesized by an innovative one-step in-situ laser pyrolysis. The obtained X-ray diffraction pattern and transmission electron microscopy images correspond to PtxCoy alloy nanoparticles with average diameters of 2.4 nm and well-established crystalline structure. The synthesized PtxCoy/C catalyst containing 1.5 wt% of PtxCoy nanoparticles can achieve complete CO conversion in the temperature range 125–175°C working at weight hourly space velocities (WHSV) of 30 L h−1g−1. This study shows the first example of bimetallic nanoalloys synthesized by laser pyrolysis and paves the way for a wide variety of potential applications and metal combinations.

Pumping Metallic Nanoparticles with Spatial Precision within Magnetic Mesoporous Platforms: 3D Characterization and Catalytic Application

The present work shows an efficient strategy to assemble two types of functional nanoparticles onto mesoporous MCM-41 silica nanospheres with a high degree of spatial precision. In a first stage, magnetite nanoparticles are synthesized with a size larger than the support pores and grafted covalently through a peptide-like bonding onto their external surface. This endowed the silica nanoparticles with a strong superparamagnetic response, while preserving the highly ordered interior space for the encapsulation of other functional guest species. Second, we report the finely controlled pumping of preformed Pt nanoparticles (1.5 nm) within the channels of the magnetic MCM-41 nanospheres to confer an additional catalytic functionality to the multiassembled nanoplatform. The penetration depth of the metallic nanoparticles can be explained as a result of the interplay between the particle-wall electrostatic attraction and the repulsive forces between neighboring Pt nanoparticles. A detailed transmission electron microscopy and a 3D high-resolution high-angle annular dark-field detector electron tomography study were carried out to characterize the material and to explain the assembly mechanism. Finally, the performance of these multifunctional nanohybrids as magnetically recoverable catalysts has been evaluated in the selective hydrogenation of p-nitrophenol, a well-known pollutant and intermediate in multiple industrial processes.