Use of nano gold obtained by laser ablation for SEIRA analyses of colorants

The analysis of dyes in cultural heritage samples is a well-known challenging task, due to their inherent high tinting strength and consequent low concentration in the carrying matrix a fact that severely limits the number of analytical techniques that can be efficiently and micro-destructively employed for their detection and unambiguous identification. In the present study, an advanced and alternative SEIRA based analytical protocol for the analysis of small quantities of synthetic colorants has been proposed. The method has been set up for the identification of Acid Orange 7 (AO7) using Au nanoparticles obtained by laser ablation in solution (LASiS). Analyses have been performed applying a drop containing a mixture between the colorant and the Au colloidal solution in its unaggregated state on a gold coated glass slide for RAS (Reflection Absorption Spectroscopy) analysis. The first results showed that, thanks to the enhancement produced by the nanoparticles, it is possible to analyze small amount of diluted solutions containing the colorant. Thus, the method has been successfully applied for the analysis of few pieces of dyed wool, after the development of a suitable micro extraction procedure

Synthesis and Shape Manipulation of Anisotropic Gold Nanoparticles by Laser Ablation in Solution

Anisotropic gold nanostructures are attracting attention due to the strong correlation between their shape and the localized surface plasmon resonances, which allows tuning their optical responses through morphological optimizations. Laser ablation synthesis in solution usually produces stable gold nanospheres colloids without any surfactant, which is important for their easy functionalization. Nevertheless, obtaining anisotropic nanoparticles with this technique is still a challenge, and few examples show that a postsynthesis approach is usually required. We show that a single pulse laser ablation allows the synthesis of anisotropic branched gold nanoparticles through careful control of the number of laser pulses interacting with the generated nanoparticles. It is shown that the very first pulses considerably affect the morphology of the ablated nanomaterial. Moreover, also the fluence above the ablated target is found to have an important role in the final nanoparticle morphology. The study of the interaction between the nanostructures and the laser pulses is achieved using an inflow setup. The optical extinction behavior of the produced anisotropic gold nanostructures was rationalized using boundary element method (BEM) based calculations, by considering the contributions from several morphologies, which were found to be in good agreement with experimental observations

SERSTEM: An app for the statistical analysis of correlative SERS and TEM imaging and evaluation of SERS tags performance

Raman spectroscopy is becoming increasingly popular as an in vitro bioimaging technique, when coupled with plasmonic substrates such as gold nanoparticles (AuNPs). Plasmonic AuNPs not only display excellent biocompatibility but can also induce the surface-enhanced Raman scattering (SERS) effect, which can be exploited for cell labeling, as an interesting alternative to fluorescence-based techniques. SERS bioimaging requires the use of so-called SERS tags or SERS-encoded AuNPs. A remaining difficulty toward the general implementation of this method is the difficulty to correlate the SERS signal (spectral intensity) with the number of SERS tags. Therefore, a general correlation method, suitable for arbitrary AuNP morphologies and Raman-active molecules (Raman reporters or RaRs), should largely improve the quantitative character of SERS as an imaging technique. We propose a protocol, with an associated app (SERSTEM), which enables the user to determine the average SERS intensity per nanoparticle from transmission electron microscopy (TEM) and SERS data. As a proof of concept, we demonstrated the method for Au nanostars and nanorods, carrying four different RaRs, and implemented the SERSTEM app, which is publicly available from an open-source platform

Synthesis of magnetic nanoparticles by laser ablation of strontium ferrite under water and their characterization by optically detected magnetophoresis supported by BEM calculations

Measurement of the properties of magnetic nanoparticles is mandatory for their application and usually this is accomplished using magnetometers, like SQUIDs or VSMs. However, these techniques require amounts of materials that are not always available and do not allow exploration of new syntheses with low production. The tiny quantity of nanoparticles obtained by laser ablation of strontium ferrite necessitated the characterization of their magnetic properties using an alternative technique, optically detected magnetophoresis, which exploits the motion of nanoparticles in a fluid under a magnetic field gradient. Time dependent optical extinction of a colloidal solution of magnetic nanoparticles can be used for recording the collective motion of the nanoparticles in a fluid. The optical extinction of nanoparticles, with absorption and scattering contributions, depends on the particle material and on their morphologies. We report a new implementation of a magnetophoretic model with the extinction properties of nanoparticles calculated using the Boundary Element Method. The model is applied to estimate the magnetic properties of a challenging sample of mixed ferrite nanoparticles. The results show that, especially for polydisperse samples, the explicit consideration of the size dependent extinction properties of the nanoparticles is needed to characterize magnetic nanoparticles by optically detected magnetophoresis. The motion of magnetic nanoparticles in a fluid, exploited in many applications, is provided with an appropriate description using the present approach

High-Quality, Ligands-Free, Mixed-Halide Perovskite Nanocrystals Inks for Optoelectronic Applications

High-quality ligand-free Pb halides-based perovskites inks by laser ablation synthesis assisted in solution a technique known as an easy approach to generate nanomaterials with a plasma plume confined by a solution. It was shown that stable colloidal dispersions of PBI2 and PbBr2 in organic solvents can be prepared and that they can be entirely converted into mixed-halide perovskite inks. The acquired colloidal solutions and the fabrication of thin films did not show the formation of a rectifying junction when polarized between two symmetric contacts and are photostable when the semiconductor bandgap is tuned. The perovskite inks allow for a better control of the semiconductor quality prior deposition while keeping the possibility of making conductive thin films which are electrically photostable and will qurantee the possibility of producing solar cells with optimal optical band for multijunction applications