Laser-generated plasmas by graphene nanoplatelets embedded into polyethylene

AbstractGraphene micrometric particles have been embedded into polyethylene at different concentrations by using chemical–physical processes. The synthesized material was characterized in terms of mechanical and optical properties, and Raman spectroscopy. Obtained targets were irradiated by using a Nd:YAG laser at intensities of the order of 1010 W/cm2 to generate non-equilibrium plasma expanding in vacuum. The laser–matter interaction produces charge separation effects with consequent acceleration of protons and carbon ions. Plasma was characterized using time-of-flight measurements of the accelerated ions. Applications of the produced targets in order to generate carbon and proton ion beams from laser-generated plasma are presented and discussed

Functionalization of Polyhydroxyalkanoates (PHA)-Based Bioplastic with Phloretin for Active Food Packaging: Characterization of Its Mechanical, Antioxidant, and Antimicrobial Activities

: The formulation of eco-friendly biodegradable packaging has received great attention during the last decades as an alternative to traditional widespread petroleum-based food packaging. With this aim, we designed and tested the properties of polyhydroxyalkanoates (PHA)-based bioplastics functionalized with phloretin as far as antioxidant, antimicrobial, and morpho-mechanic features are concerned. Mechanical and hydrophilicity features investigations revealed a mild influence of phloretin on the novel materials as a function of the concentration utilized (5, 7.5, 10, and 20 mg) with variation in FTIR e RAMAN spectra as well as in mechanical properties. Functionalization of PHA-based polymers resulted in the acquisition of the antioxidant activity (in a dose-dependent manner) tested by DPPH, TEAC, FRAR, and chelating assays, and in a decrease in the growth of food-borne pathogens (Listeria monocytogenes ATCC 13932). Finally, apple samples were packed in the functionalized PHA films for 24, 48, and 72 h, observing remarkable effects on the stabilization of apple samples. The results open the possibility to utilize phloretin as a functionalizing agent for bioplastic formulation, especially in relation to food packaging

Optical Nanoantennas for Multiband Surface-Enhanced Infrared and Raman Spectroscopy

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A Raman Study of MMP2 and MnSOD, Two Pathology Biomarkers

International audienceMatrix Metalloproteinases (MMPs) are cell-secreted soluble and membranetethered enzymes that degrade extracellular matrix (ECM) proteins. These proteases play a key role in diverse physiological and pathological processes, including embryonic development, wound repair, inflammatory diseases and cancer [1]. On the other hand, Superoxide Dismutases (SODs) are metalloenzymes that defend biological systems against oxidative damage mediated by the superoxide anion [2]. The vibrational spectra of MMPs and SODs can provide crucial information about conformational changes induced by external factors, e.g. the interaction with metal ions, drugs, others proteins or peptides. On the other side, Raman spectroscopy can be used as a tool for non-invasive and non-ambiguous spectral detection of these proteins at very low concentration (10-8-10-12 M), with potential applications in early diseases diagnosis [3]. At present, there is still insufficient knowledge on the Raman spectral fingerprints of these proteins. Here we present a complete Raman analysis of MMP2 and MnSOD using multiwavelength-excitation at 514, 633, and 785 nm

The Occurrence of Microplastics in <i>Donax trunculus</i> (Mollusca: Bivalvia) Collected along the Tuscany Coast (Mediterranean Sea)

Microplastics (MPs) (0.1 µm–5 mm particles) have been documented in oceans and seas. Bivalve molluscs (BMs) can accumulate MPs and transfer to humans through the food chain. BMs (especially mussels) are used to assess MPs’ contamination, but the genus Donax has not been thoroughly investigated. The aim of this study was to detect and characterize MPs in D. trunculus specimens collected along the Tuscan coast (Italy), and to assess the potential risk for consumers. The samples (~10 g of tissue and intervalval liquid from 35 specimens) were digested using a solution of 10% KOH, subjected to NaCl density separation, and filtered through 5 μm pore-size filters. All items were morphologically classified and measured, and their mean abundance (MA) was calculated. Furthermore, 20% of them were analyzed by Raman spectroscopy and, based on the obtained results, the MA was recalculated (corrected MA) and the annual human exposure was estimated. In the 39 samples analyzed, 85 items fibers (n = 45; 52.94%) and fragments (n = 40; 47.06%) were found. The MA was 0.23 ± 0.17 items/grww. Additionally, 83.33% of the items were confirmed as MPs (polyethylene and polyethylene terephthalate). Based on the correct MA (0.18 MPs/grww), D. trunculus consumers could be exposed to 19.2 MPs/per capita/year. The health risk level of MPs was classified as level III (moderate)

Scaling of optical forces on Au-PEG core-shell nanoparticles

Optical trapping of hybrid core\u2013shell gold\u2013polymer particles is studied. Optical forces are measured for different gold core size and polymer shell thickness, revealing how a polymer shell increases the trapping efficiency with respect to the bare gold nanoparticles. Data are in agreement with calculations of optical trapping based on electromagnetic scattering theory in the T-matrix approach. The scaling behaviour of optical forces with respect to the ratio between polymer layer thickness and the whole particle radius is found and discussed

Optical Aggregation of Gold Nanoparticles for SERS Detection of Proteins and Toxins in Liquid Environment: Towards Ultrasensitive and Selective Detection

Optical forces are used to aggregate plasmonic nanoparticles and create SERS–active hot spots in liquid. When biomolecules are added to the nanoparticles, high sensitivity SERS detection can be accomplished. Here, we pursue studies on Bovine Serum Albumin (BSA) detection, investigating the BSA–nanorod aggregations in a range from 100 µM to 50 nM by combining light scattering, plasmon resonance and SERS, and correlating the SERS signal with the concentration. Experimental data are fitted with a simple model describing the optical aggregation process. We show that BSA–nanorod complexes can be optically printed on non-functionalized glass surfaces, designing custom patterns stable with time. Furthermore, we demonstrate that this methodology can be used to detect catalase and hemoglobin, two Raman resonant biomolecules, at concentrations of 10 nM and 1 pM, respectively, i.e., well beyond the limit of detection of BSA. Finally, we show that nanorods functionalized with specific aptamers can be used to capture and detect Ochratoxin A, a fungal toxin found in food commodities and wine. This experiment represents the first step towards the addition of molecular specificity to this novel biosensor strategy