Miquel Torras, PhD student at the N&N group, travelled to Madrid to attend the 3rd International Conference on Polyol Mediated Synthesis (ICPMS) held at the Instituto de Ciencia de Materiales de Madrid (ICMM). Miquel presented the talk “Fast and Simple Microwave Synthesis of Multicomponent Gold Nanoparticles”.
Abstract: The fabrication of small anatase titanium dioxide (TiO2) nanoparticles (NPs) attached to larger anisotropic gold (Au) morphologies by a very fast and simple two-step microwave-assisted synthesis is presented. The TiO2/Au NPs are synthesized using polyvinylpyrrolidone (PVP) as reducing, capping and stabilizing agent through a polyol approach. To optimize the contact between the titania and the gold and facilitate electron transfer, the PVP is removed by calcination at mild temperatures. The nanocatalysts activity is then evaluated in the photocatalytic production of hydrogen from water/ethanol mixtures in gas-phase at ambient temperature. A maximum value of 5.3 mmol·g−1cat⋅gcat-1·h−1 (7.4 mmol·g−1TiO2⋅gTiO2-1·h−1) of hydrogen is recorded for the system with larger gold particles at an optimum calcination temperature of 450°C. Herein we demonstrate that TiO2-based photocatalysts with high Au loading and large Au particle size (≈50 nm) NPs have photocatalytic activity.
Gold nanoparticles (AuNPs) are present in many man-made products and cosmetics, and are also used by the food and medical industries. Tight regulations regarding the use of mammalian animals for product testing can hamper the study of the specific interactions between engineered nanoparticles and biological systems. Invertebrate models, such as the nematode Caenorhabditis elegans (C. elegans), can offer alternative approaches during the early phases of nanoparticle discovery.
Here, we thoroughly evaluated the biodistribution of 11-nm and 150-nm citrate-capped AuNPs in the model organism C. elegans at multiple scales, moving from micrometric to nanometric resolution and from the organism to cellular level. We confirmed that the nanoparticles were not able to cross the intestinal and dermal barriers. We investigated the effect of AuNPs on the survival and reproductive performance of C. elegans, and correlated these effects with the uptake of AuNPs in terms of their number, surface area, and metal mass. In general, exposure to 11-nm AuNPs resulted in a higher toxicity than the larger 150-nm AuNPs. NP aggregation inside C. elegans was determined using absorbance microspectroscopy, which allowed the plasmonic properties of AuNPs to be correlated with their confinement inside the intestinal lumen, where anatomical traits, acidic pH and the presence of biomolecules play an essential role on NP aggregation. Finally, quantitative PCR of selected molecular markers indicated that exposure to AuNPs did not significantly affect endocytosis and intestinal barrier integrity.
This Friday 16th of December Laura González is going to defend her Doctoral Thesis entitled “Evaluating inorganic nanoparticles in the living organism Caenorhabditis elegans”, supervised by Dr. Anna Laromaine and Dr. Anna Roig.
Abstract: In this thesis, we have used the simple model organism Caenorhabditis elegans as an in vivo biological system to screen inorganic nanoparticles (NPs) with biomedical uses. In particular, we have assessed the behaviour of two types of particles with different composition, size and surface properties: iron oxide NPs coated with citrate and bovine serum albumin, and gold nanoparticles of two different sizes. We have studied their interactions with C. elegans including their uptake, fate, biological effects and NP-responsive molecular mechanisms, and compared our results with previous studies. To this end, we have combined toxicity tests, materials science and imaging techniques and gene expression analysis. We have been able to perform this biological evaluation in the synthetic laboratory where the particles were synthesized and characterised due to the advantageous experiments features of C. elegans.In summary, this thesis exploits the potential of C. elegans as a simple animal model to evaluate NPs in the initial stages of development and contributes to: (i) a systematic and comprehensive evaluation of NPs in C. elegans, in particular studying the influence of NP properties (size, surface coating and core composition) on their in vivo effects, (ii) extend the toolkit of techniques available to characterise nano-bio interactions in small organisms.
Miquel Torras, who was in the N&N Group during last semester to do his Degree’s Final Project, is back with us this year. He has started a MSc in Applied Materials Chemistry at Universitat de Barcelona (UB) and will do his MSc Thesis in the group, under the supervision of Anna Roig. He will be working on the synthesis and characterization of magnetic and plasmonic gold nanotriangles.
Jordi Llorca, from Institut de Tècniques Energètiques (INTE-UPC) explains in this video from the newspaper ara, one of the projects in which we collaborate: photocatalysis for hydrogen production from sunlight, a photocatalyst formed by TiO2/Au nanoparticles, and water:
In the video he says: “We obtain hydrogen -which is not in its free state in the Earth- to act as a source of energy, and to obtain it, we use use sunlight -completely clean-, a photocatalyst containing nanoparticles, and water.”
This paper describes a novel and convenient synthetic strategy for the preparation of magnetically responsive silica nanospheres decorated with mixed ligand protected gold nanoparticles. Gold nanoparticles are attached to the silica surface via stable amide bond formation. The hierarchical nanospheres show promising results as a reusable and efficient catalyst for esterification reactions and they can be recovered through a simple magnetic separation.
Figure: Schematic illustration of: (a) the partial ligand exchange of 3-mercapto-1-propanesulfonate (MPSA):1-octanethiol(OT) covered gold nanoparticles, (b) the synthesis of core-shell magnetic silica and (c) the synthesis of the magnetic silica decorated with gold nanoparticles hierarchical nanospheres.
The manuscript will be presented and discussed at a forthcoming Faraday Discussions meeting, this next summer. During the meeting, all delegates will be able to contribute to the debate, which will be included in the final volume. This will be a great opportunity to discuss the formation mechanism of the magnetic gold nanotriangles with some experts on this field.
The combination of iron oxide and gold in a single nanoparticle results in both magnetic and plasmonic properties that can stimulate novel applications in bio-sensing, medical imaging, or therapeutics. Microwave heating method allows the fabrication of multi-component, multi-functional nanostructures by promoting selective heating at desired sites. Recently, we reported a microwave-assisted polyol route yielding gold nanotriangles decorated with iron oxide nanoparticles (1). Here, we present an in-depth microstructural and compositional characterization of the system by using scanning transmission electron microscopy (STEM) and electron energy loss (EELS) spectroscopy. A method to remove the iron oxide nanoparticles from the gold nanocrystals and some insights on crystal nucleation and growth mechanisms are also provided.
Figure: (a) Schematic representation of the synthesis route. (b) HRTEM image of a Au NH-SPIONs and a Au NT-SPIONs. Characterization of the heterostructures: (c) UV-Vis-NIR spectra. (d) Hydrodynamic diameter of the Au-SPIONS measured by DLS. (e) Magnetization curve up to 6 T at 5K.