538 research outputs found
Self-assembly of latex particles for the creation of nanostructures with tunable plasmonic properties
In this short review we are discussing the creation of two dimensional
nanostructures based on self-assembly of latex particles. Furthermore we are
showing that optical properties of these structures can be controlled with
their morphology and materials used for their preparation. Two representative
structures, namely two dimensional arrays of triangles and holes are discussed
in detail, starting with the preparatory step, followed by the structural and
optical characterization, as well as the theoretical explanation of the
plasmonic properties
Plasmon resonances in coupled Babinet complementary arrays in the mid-infrared range
A plasmonic structure with transmission highly tunable in the mid-infrared spectral range is developed. This structure consists of a hexagonal array of metallic discs located on top of silicon pillars protruding through holes in a metallic Babinet complementary film. We reveal with FDTD simulations that changing the hole diameter tunes the main plasmonic resonance frequency of this structure throughout the infrared range. Due to the underlying Babinet physics of these coupled arrays, the spectral width of these plasmonic resonances is strongly reduced, and the higher harmonics are suppressed. Furthermore, we demonstrate that this structure can be easily produced by a combination of the nanosphere lithography and the metal-assisted chemical etching technique
Nanosphere lithography with variable deposition angle for the production of oneâdirectional transparent conductors
The production of high quality and cheap transparent electrodes is a fundamental step for a variety of optoelectronic devices. We present a method for the production of transparent conducting films optimised for electrical conduction in one direction. The deposition of a metal film through a perfectly aligned nanosphereâlithography mask at variable incidence angle gave origin to parallel nanowires with thin interconnections. This structure showed excellent conductivity in one direction and high optical transparency
Osteoarthritis severely decreases the elasticity and hardness of knee joint cartilage: A nanoindentation study
The nanoindentation method was applied to determine the elastic modulus and hardness of knee articular cartilage. Cartilage samples from both high weight bearing (HWB) and low weight bearing (LWB) femoral condyles were collected from patients diagnosed with osteoarthritis (OA). The mean elastic modulus of HWB cartilage was 4.46 ± 4.44 MPa in comparison to that of the LWB region (9.81 ± 8.88 MPa, p < 0.001). Similarly, the hardness was significantly lower in HWB tissue (0.317 ± 0.397 MPa) than in LWB cartilage (0.455 ± 0.434 MPa, p < 0.001). When adjusted to patientsâ ages, the mean elastic modulus and hardness were both significantly lower in the age group over 70 years (p < 0.001). A statistically significant difference in mechanical parameters was also found in grade 3 and 4 OA. This study provides an insight into the nanomechanical properties of the knee articular cartilage and provides a starting point for personalized cartilage grafts that are compatible with the mechanical properties of the native tissue
Composite spheres made of bioengineered spider silk and iron oxide nanoparticles for theranostics applications
Bioengineered spider silk is a biomaterial that has exquisite mechanical properties, biocompatibility, and biodegradability. Iron oxide nanoparticles can be applied for the detection and analysis of biomolecules, target drug delivery, as MRI contrast agents and as therapeutic agents for hyperthermia-based cancer treatments. In this study, we investigated three bioengineered silks, MS1, MS2 and EMS2, and their potential to form a composite material with magnetic iron oxide nanoparticles (IONPs). The presence of IONPs did not impede the self-assembly properties of MS1, MS2, and EMS2 silks, and spheres formed. The EMS2 spheres had the highest content of IONPs, and the presence of magnetite IONPs in these carriers was confirmed by several methods such as SEM, EDXS, SQUID, MIP-OES and zeta potential measurement. The interaction of EMS2 and IONPs did not modify the superparamagnetic properties of the IONPs, but it influenced the secondary structure of the spheres. The composite particles exhibited a more than two-fold higher loading efficiency for doxorubicin than the plain EMS2 spheres. For both the EMS2 and EMS2/IONP spheres, the drug revealed a pH-dependent release profile with advantageous kinetics for carriers made of the composite material. The composite spheres can be potentially applied for a combined cancer treatment via hyperthermia and drug delivery
Magnetic behaviour of non-interacting colloidal iron oxide nanoparticles in physiological solutions
Magnetic properties of colloidal nanoparticles (NPs) depend on various
parameters, such as size, size distribution, interparticle distance, shape,
condition of synthesis and stabilizing surfactants. Nowadays, those magnetic
nanoparticles (MNPs) are preferably produced in hydrophobic organic solvents,
while biomedical applications need hydrophilic properties. Thus, a major
challenge is the hydrophilization of the particles, while avoiding
destabilization and aggregation. Here we present magnetic characteristics of
non-interacting, highly crystalline iron oxide NPs in physiological solutions
that are coated with modified polyacrylic acid. The magnetic analysis
comprised both static and dynamic magnetic behaviour of 4 nm NPs. The NPs have
been further characterized by transmission electron microscopy (TEM) and
energy dispersive X-ray spectroscopy (EDX)
Observation of a hole-size-dependent energy shift of the surface-plasmon resonance in Ni antidot thin films
© 2015 AIP Publishing LLC. A combined experimental and theoretical study of the magneto-optic properties of a series of nickel antidot thin films is presented. The hole diameter varies from 869 down to 636 nm, while the lattice periodicity is fixed at 920 nm. This results in an overall increase of the polar Kerr rotation with decreasing hole diameter due to the increasing surface coverage with nickel. In addition, at photon energies of 2.7 and 3.3 eV, where surface-plasmon excitations are expected, we observe distinct features in the polar Kerr rotation not present in continuous nickel films. The spectral position of the peaks exhibits a red shift with decreasing hole size. This is explained within the context of an effective medium theory by a change in the effective dielectric function of the Ni thin films.H.F. gratefully acknowledges China Scholarship Council (CSC) for financial support and AndrĂ© Schirmeisen for the data of Ni film. A.G.-M. and B.C. acknowledge funding from Spanish Ministry of Economy and Competitiveness through grants âFUNCOATâ CONSOLIDER CSD2008-00023 and âMAPSâ MAT2011-29194-C02-01. J.C.C. acknowledges financial support from the Spanish Ministry of Economy and Competitiveness (Contract No. FIS2011-28851-C02-01) and from the Comunidad de Madrid (Contract No. S2013/MIT-2740). E.M.A. and M.G. acknowledge financial support by the European Union under the project CosmoPHOS with the number â3100337â.Peer Reviewe
Observation of a hole-size-dependent energy shift of the surface-plasmon resonance in Ni antidot thin films
A combined experimental and theoretical study of the magneto-optic properties of a series of nickel antidot thin films is presented. The hole diameter varies from 869 down to 636 nm, while the lattice periodicity is fixed at 920 nm. This results in an overall increase of the polar Kerr rotation with decreasing hole diameter due to the increasing surface coverage with nickel. In addition, at photon energies of 2.7 and 3.3 eV, where surface-plasmon excitations are expected, we observe distinct features in the polar Kerr rotation not present in continuous nickel films. The spectral position of the peaks exhibits a red shift with decreasing hole size. This is explained within the context of an effective medium theory by a change in the effective dielectric function of the Ni thin filmsH.F. gratefully acknowledges China Scholarship Council (CSC) for financial support and AndrĂ© Schirmeisen for the data of Ni film. A.G.-M. and B.C. acknowledge funding from Spanish Ministry of Economy and Competitiveness through grants âFUNCOATâ CONSOLIDER CSD2008-00023 and âMAPSâ MAT2011-29194-C02-01. J.C.C. acknowledges financial support from the Spanish Ministry of Economy and Competitiveness (Contract No. FIS2011-28851-C02-01) and from the Comunidad de Madrid (Contract No. S2013/MIT- 2740). E.M.A. and M.G. acknowledge financial support by the European Union under the project CosmoPHOS with the number â310337
Structural, spectroscopic and cytotoxicity studies of TbF3@CeF3 and TbF3@CeF3@SiO2 nanocrystals
Terbium fluoride nanocrystals, covered by a shell, composed of cerium fluoride
were synthesized by a co-precipitation method. Their complex structure was
formed spontaneously during the synthesis. The surface of these core/shell
nanocrystals was additionally modified by silica. The properties of TbF3@CeF3
and TbF3@CeF3@SiO2 nanocrystals, formed in this way, were investigated.
Spectroscopic studies showed that the differences between these two groups of
products resulted from the presence of the SiO2 shell. X-ray diffraction
patterns confirmed the trigonal crystal structure of TbF3@CeF3 nanocrystals.
High resolution transmission electron microscopy in connection with energy-
dispersive X-ray spectroscopy showed a complex structure of the formed
nanocrystals. Crystallized as small discs, âthe productsâ, with an average
diameter around 10 nm, showed an increase in the concentration of Tb3+ ions
from surface to the core of nanocrystals. In addition to photo-physical
analyses, cytotoxicity studies were performed on HSkMEC (Human Skin
Microvascular Endothelial Cells) and B16F0 mouse melanoma cancer cells. The
cytotoxicity of the nanomaterials was neutral for the investigated cells with
no toxic or antiproliferative effect in the cell cultures, either for normal
or for cancer cells. This fact makes the obtained nanocrystals good candidates
for biological applications and further modifications of the SiO2 shell
Carbon Nanotubes Interference with Luminescence-Based Assays
Carbon nanotubes (CNTs) are one of the most promising nanomaterials synthesized to date. Thanks to their unique mechanical, electronic, and optical properties, they have found a wide application in electronics in the production of biosensors and nanocomposites. The functionalization of multiwalled carbon nanotubes (MWCNTs) is aimed at making them biocompatible by adding hydrophilic groups on their surface, increasing their solubility and thus rendering them applicable in the regenerative medicine. So far, there is conflicting information about carbon nanotubes in biological systems. This paper investigates the effect of functionalized, oxidized, multiwalled carbon nanotubes (MWCNT-Ox) on the cytotoxicity of normal human articular chondrocytes (NHAC-kn cell line). Since absorbance-based and fluorescence-based assays were shown to interfere with carbon nanotubes, luminescence-based tests were carried out, as they work on a different method of detection and provide advantages over the mentioned ones. Cell viability and reactive oxygen species (ROS) tests were carried out. The cell viability assay showed that with the increasing MWCNTs concentration, the number of viable chondrocytes was significantly decreasing. Exposure to MWCNT-Ox indicated oxidative stress in the lowest investigated concentration with a decreased amount of ROS with higher concentrations. However, control experiments with adenosine triphosphate (ATP) and H2O2âmolecules that are detected by the assaysâshowed that carbon nanotubes interfere directly with measurement, thus rendering the results unreliable. To understand the exact interference mechanisms, further studies must be taken. In conclusion, this study shows that luminescence-based tests yield erroneous results, confirming that in vitro experiments in the literature concerning carbon nanotubes should be analyzed with caution
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