One of the main research lines in the nanoscience relies on the development and study of nanoparticles. In nanotechnology, a nanoparticle is defined as a small object that behaves as a whole unit with respect to its transport and properties with a diameter between 1 and 100 nanometers in size.
Nanoparticles are of great scientific interest as they are, in effect, a bridge between bulk materials and atomic or molecular structures. The properties of materials change as their size approaches the nanoscale and as the percentage of atoms at the surface of a material becomes significant. Often, these materials posse unexpected optical properties as they are small enough to confine their electrons and produce quantum effects. Other size-dependent property changes include quantum confinement in semiconductor particles, surface plasmon resonance in some metal particles and superparamagnetism in magnetic materials. For biological applications, Nanoparticles can be linked to biological molecules that can act as address tags, to direct the nanoparticles to specific sites within the body, specific organelles within the cell, or to follow specifically the movement of individual protein or RNA molecules in living cells. The surface coating of this kind of particles is so important to give high aqueous solubility and prevent nanoparticle aggregation and funtionallize the particle.
The characterization of nano materials: morphology, size distribution, coating, physical properties: optical, electrical and magnetic… is essential in order to define the nanotechnology applications of this new materials. The best and more complete technique to do that is the Transmission Electron Microscopy. Different techniques in TEM can provide all the information for a complete characterization of the nanoparticles:
Morphology, size distribution and coating: C-TEM
Crystalline information: HRTEM
Chemical information: Zcontrast-HAADF imaging, EDS, EELS
Chemical environment: EELS fine structure
Optical properties: Study of surface Plasmon
Magnetic properties: Lorentz microscopy and Holography
Electric properties: Holography
Nanoparticles 3D reconstruction: Tomography
Nanoparticles is one of the most important research lines in INA-LMA. Some examples of the work perfomed in nanoparticles in our lab are:
Au-NPs for biotechnology applications: A novel and straightforward wet-chemical synthetic route to produce biocompatible single-crystalline gold nanoparticles with specific shapes in order to obtain special optical properties for biotechnology applications has been designed. The method allows tune the edge length of NPs in the range of 100?170 nm by adjusting the final concentration/molar ratio of gold salt and reducing agent (thiosulfate), while the thickness of NPRs remained constant (9 nm). Thus, the surface plasmon band of NPRs can be set along the near-infrared (NIR) range. This new route supplies NPs which represent a significant advance in the biocompatibility of nanoparticles Due to their biocompatibility (avoiding CTAB), ease of production, ease of functionalization, and remarkable heating features, and serve as an attractive alternative to those currently in use as plasmonic photothermal agents. A complete characterization of the particles has been performed by TEM and STEM.
Tailoring the Synthesis and Heating Ability of Gold Nanoprisms for Bioapplications
B. Pelaz, V. Grazu, A. Ibarra, C. Magen, P. del Pino, and J. M. de la Fuente.
Langmuir, 2012, 28 (24), pp 8965-8970
3D reconstruction of hollow Au NPs: An exquisite control of synthesis parameters is generally required in nanomaterial synthesis to guarantee consistency in the essential characteristics such as size and shape. On the other hand, reliable scaled-up production of nanomaterials is required in order to achieve the production rates required for emerging nanotechnology applications while delivering a consistent product with the intended characteristics, avoiding the traditional batch-to-batch deviations. In this work, a continuous, scaled-up synthesis of high quality plasmonic hollow gold nanoparticles is reported for the first time together a complete characterization of the NP produced, including a complete 3d reconstruction of the particles.
Scaled-up production of plasmonic nanoparticles using microfluidics: from metal precursors to functionalized and sterilized nanoparticles
L. Gomez, V. Sebastian, S. Irusta, A. Ibarra, M. Arruebo and J. Santamaria.
Lab Chip, 2014,14, 325-332
Core-shell MnO/Mn3O4 nanoparticles: Here we show that spontaneous oxidation of MnO nanoparticles into MnO/Mn3O4 core/shell nanoparticles has the effect of a local pressure, decreasing the MnO cell parameter and increasing strain, resulting in the increase of the MnO antiferromagnetic/paramagnetic transition temperature TN. These effects are more severe in smaller nanoparticles. A complete study of the crystalline structure evolution throughout of the different MnO oxidation states has been performed.
Shell pressure on the core of MnO/Mn3O4 core/shell nanoparticles
N. J. O. Silva, M. Karmaoui, and V. S. Amaral, I. Puente-Orench and J. Campo, I. da Silva, A. Ibarra, R. Bustamante, A. Millán, and F. Palacio.
PHYSICAL REVIEW B 87, 224429 (2013)
Bio-functionalized nanoparticles have a huge interest due to their use in biotechnology and bio-nanomedicine. However, in order to achieve the functionalization in a more efficient way, a deep knowledge of the bio-functionalizing moieties and their spatial distribution on the nanoparticle surface is required. Thus, we have showed that cryo-spatial-resolved EELS (SR-EELS) is a very appropriate and powerful technique for providing very rich information at the sub-nanometer scale on complex hybrid nanomaterials. The nanostructures on which we focus in these works are magnetic nanoparticles functionalized with a Protein-G/antibody (PG-Ab) system [R. Arenal, et al., ACS Nano 7, 4006 (2013); R. Arenal, et al., Microscopy and Microanalysis, 19, 1628 (2013)]. SR-EEL spectra were recorded using a VG-HB501 dedicated STEM (At LPS, Orsay (Fr.)) and a FEI Low Base. Figure 1 displays an EEL spectrum-image recorded on PG/Ab-functionalized nanoparticles, where Figure 1 (a) and (b) correspond to the bright-field and high angular annular dark field (HAADF) images of the nanoparticles, respectively. Carbon and nitrogen maps, extracted, after background subtraction, from the EEL spectra displayed in Figure 1 (e), are shown in Figure 1 (c) and (d), respectively. From these maps, we can observe that there is a clear correspondence between the spatial distributions of these elements which are localized at the surface of the nanoparticles. This finding indicates that they correspond to the organic constituents (PG/Ab) bio-functionalizing the magnetic nanoparticles. Thus, we have showed that the functional moieties (i.e., the antibodies) are only anchored in specific areas of the surface of the nanoparticles. This result showing that the biological entities are discontinuously distributed over the nanoparticle shell is very relevant because validates our selective functionalization protocol. In fact, the use of a critical amount of amino groups on the nanoparticle shell could be tuned for achieving simultaneously good water particle stability and the proper protein G adsorption for the suitable antibody immobilization on the particle surface leading to a highly efficient immunorecognition.
R. Arenal, L. De Matteis, L. Custardoy, A. Mayoral, M. Tence, V. Grazu, J.M. de la Fuente, C. Marquina, M.R. Ibarra, Spatially-Resolved EELS Analysis of the Antibody Distribution on Bio-functionalized Magnetic Nanoparticles, ACS Nano, 7, 4006-4013 (2013).
R. Arenal, L. De Matteis, L. Custardoy, A. Mayoral, M. Tence, V. Grazu, J.M. de la Fuente, C. Marquina, M.R. Ibarra, Antibody Distribution on Bio-Functionalized Magnetic Nanoparticles Analyzed by Spatial-Resolved EELS, Micros. and Microanal. 19, 1628 (2013).