Supplementary_Material-colorpixels-N - Plasmonic nanospherical dimers for color pixels

<p>Supplementary_Material-colorpixels-N for Plasmonic nanospherical dimers for color pixels by Salma Alrasheed, and Enzo Di Fabrizio in Nanomaterials and Nanotechnology</p

Large-Scale Plasmonic nanoCones Array For Spectroscopy Detection

Advanced optical materials or interfaces are gaining attention for diagnostic applications. However, the achievement of large device interface as well as facile surface functionalization largely impairs their wide use. The present work is aimed to address different innovative aspects related to the fabrication of large-area 3D plasmonic arrays, their direct and easy functionalization with capture elements, and their spectroscopic verifications through enhanced Raman and enhanced fluorescence techniques. In detail, we have investigated the effect of a Au-based nanoCone array, fabricated by means of direct nanoimprint technique over large area (mm²), on protein capturing and on the enhancement in optical signal. A selective functionalization of gold surfaces was proposed by using a peptide (AuPi3) previously selected by phage display. In this regard, two different sequences, labeled with fluorescein and biotin, were chemisorbed on metallic surfaces. The presence of Au nanoCones array consents an enhancement in electric field on the apex of cone, enabling the detection of molecules. We have witnessed around 12-fold increase in fluorescence intensity and SERS enhancement factor around 1.75 × 10⁵ with respect to the flat gold surface. Furthermore, a sharp decrease in fluorescence lifetime over nanoCones confirms the increase in radiative emission (i.e., an increase in photonics density at the apex of cones)

Charge Transport in Nanoscale “All-Inorganic” Networks of Semiconductor Nanorods Linked by Metal Domains

Charge transport across metal-semiconductor interfaces at the nanoscale is a crucial issue in nanoelectronics. Chains of semiconductor nanorods linked by Au particles represent an ideal model system in this respect, because the metal–semiconductor interface is an intrinsic feature of the nanosystem and does not manifest solely as the contact to the macroscopic external electrodes. Here we investigate charge transport mechanisms in all-inorganic hybrid metal–semiconductor networks fabricated <i>via</i> self-assembly in solution, in which CdSe nanorods were linked to each other by Au nanoparticles. Thermal annealing of our devices changed the morphology of the networks and resulted in the removal of small Au domains that were present on the lateral nanorod facets, and in ripening of the Au nanoparticles in the nanorod junctions with more homogeneous metal-semiconductor interfaces. In such thermally annealed devices the voltage dependence of the current at room temperature can be well described by a Schottky barrier lowering at a metal semiconductor contact under reverse bias, if the spherical shape of the gold nanoparticles is considered. In this case the natural logarithm of the current does not follow the square-root dependence of the voltage as in the bulk, but that of V^2/3. From our fitting with this model we extract the effective permittivity that agrees well with theoretical predictions for the permittivity near the surface of CdSe nanorods. Furthermore, the annealing improved the network conductance at cryogenic temperatures, which could be related to the reduction of the number of trap states

Directed Growth of Virus Nanofilaments on a Superhydrophobic Surface

The evaporation of single droplets of colloidal tobacco mosaic virus (TMV) nanoparticles on a superhydrophobic surface with a hexagonal pillar-pattern results in the formation of coffee-ring type residues. We imaged surface features by optical, scanning electron, and atomic force microscopies. Bulk features were probed by raster-scan X-ray nanodiffraction. At ∼100 pg/μL nanoparticle concentration, the rim of the residue connects to neighboring pillars via fibrous extensions containing flow-aligned crystalline domains. At ∼1 pg/μL nanoparticle concentration, nanofilaments of ≥80 nm diameter and ∼20 μm length are formed, extending normal to the residue-rim across a range of pillars. X-ray scattering is dominated by the nanofilament form-factor but some evidence for crystallinity has been obtained. The observation of sheets composed of stacks of self-assembled nanoparticles deposited on pillars suggests that the nanofilaments are drawn from a structured droplet interface

3D Hollow Nanostructures as Building Blocks for Multifunctional Plasmonics

We present an advanced and robust technology to realize 3D hollow plasmonic nanostructures which are tunable in size, shape, and layout. The presented architectures offer new and unconventional properties such as the realization of 3D plasmonic hollow nanocavities with high electric field confinement and enhancement, finely structured extinction profiles, and broad band optical absorption. The 3D nature of the devices can overcome intrinsic difficulties related to conventional architectures in a wide range of multidisciplinary applications

Dark to Bright Mode Conversion on Dipolar Nanoantennas: A Symmetry-Breaking Approach

The excitation of plasmonic dark modes via a radiative channel is a phenomenon strongly hindered in the subwavelength regime. Recently, for achieving this purpose it has been proposed to exploit near-field interactions between radiating (bright) modes and lossless dark modes. However, this approach unveils challenging difficulties related to the excitation of dark modes through the near-field coupling with a bright mode. Here, it is experimentally and numerically shown how symmetry breaking applied to a nanoantenna dimer can conversely induce the excitation of plasmonic resonances, which play a key role for the dark modes’ activation in more complex nanoassemblies. On the basis of this study, a T-shaped nanoantenna trimer has been introduced as an elemental unit for the energy transfer between bright and dark modes in plasmonic nanostructures. Finally, we implemented an analytical perturbative model to further investigate the plasmonic hybridization of subwavelength systems

Superhydrophobic Surfaces as Smart Platforms for the Analysis of Diluted Biological Solutions

The aim of this paper is to expound on the rational design, fabrication and development of superhydrophobic surfaces (SHSs) for the manipulation and analysis of diluted biological solutions. SHSs typically feature a periodic array or pattern of micropillars; here, those pillars were modified to incorporate on the head, at the smallest scales, silver nanoparticles aggregates. These metal nanoclusters guarantee superior optical properties and especially SERS (surface enhanced Raman scattering) effects, whereby a molecule, adsorbed on the surface, would reveal an increased spectroscopy signal. On account of their two scale-hybrid nature, these systems are capable of multiple functions which are (i) to concentrate a solution, (ii) to vehicle the analytes of interest to the active areas of the substrate and, therefore, (iii) to measure the analytes with exceptional sensitivity and very low detection limits. Forasmuch, combining different technologies, these devices would augment the performance of conventional SERS substrates and would offer the possibility of revealing a single molecule. In this work, similar SHSs were used to detect Rhodamine molecules in the fairly low atto molar range. The major application of this novel family of devices would be the early detection of tumors or other important pathologies, with incredible advances in medicine

The Role of Surface Tension in the Crystallization of Metal Halide Perovskites

The exciting intrinsic properties discovered in single crystals of metal halide perovskites still await their translation into optoelectronic devices. The poor understanding and control of the crystallization process of these materials are current bottlenecks retarding the shift toward single-crystal-based optoelectronics. Here we theoretically and experimentally elucidate the role of surface tension in the rapid synthesis of perovskite single crystals by inverse temperature crystallization. Understanding the nucleation and growth mechanisms enabled us to exploit surface tension to direct the growth of monocrystalline films of perovskites (AMX₃, where A = CH₃NH₃⁺ or MA; M = Pb²⁺, Sn²⁺; X = Br^–, I^–) on the solution surface. We achieve up to 1 cm²-sized monocrystalline films with thickness on the order of the charge carrier diffusion length (∼5–10 μm). Our work paves the way to control the crystallization process of perovskites, including thin-film deposition, which is essential to advance the performance benchmarks of perovskite optoelectronics

Increased NK susceptibility on mechanical stressed tumor cells.

<p>NK cell recognition of different tumor cell targets at different E/T (effector/target) ratio: 59c, 42a, 66b (melanoma cell lines), 293T (kidney carcinoma) and IM9 (lymphoblastoidcell lines) before (grey) and after (black) mechanical stress. The Mel 42a, Mel 66b, fibroblasts cells (panels B, E, and F) were treated with the micropump, the Mel 59c, IM9, 293 T cells (panels A, C and D) were stressed with the shock waves. As healthy target cells, in this case fibroblasts are shown. Representative experiments are reported for each cell type. Panels G and H show the statistics derived from three different functional assays, using NK lymphocytes as effectors cells (E) and IM9 and Melanoma cells as targets (T). The IM9 target cells were treated with the shock waves (panel G: n = 3, p = 0.0325), while the Melanoma target cells were stressed with the micropump (panel H, n = 3, p = 0.0186). E/T ratio 12/1, p<0.05.</p

Principal component analysis.

<p>PCA analysis on control and stress cells for various cell lines; Mel 42a, Mel 59c, Mel 103b and 293T. a) PC1 vs. PC2, b) PC2 vs. PC3 and c) PC1 vs. PC3.</p