ALLAN BERECZKI
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Artigo IPEN-doc 30047 Direct nanoplastics detection below the diffraction limit using micro Raman2023 - BERECZKI, ALLAN; DIPOLD, JESSICA; FREITAS, ANDERSON Z.; WETTER, NIKLAUSRaman spectra of polystyrene nanoparticles of 50 nm diameter were directly measured using micro-Raman spectroscopy. Data analysis demonstrated that particles as small as 20 nm could be directly measured with this simple and robust technique.Artigo IPEN-doc 30037 Sub-10 nm nanoparticle detection using multi-technique-based micro-raman spectroscopy2023 - BERECZKI, ALLAN; DIPOLD, JESSICA; FREITAS, ANDERSON Z.; WETTER, NIKLAUS U.Microplastic pollution is a growing public concern as these particles are ubiquitous in various environments and can fragment into smaller nanoplastics. Another environmental concern arises from widely used engineered nanoparticles. Despite the increasing abundance of these nanosized pollutants and the possibility of interactions with organisms at the sub cellular level, with many risks still being unknown, there are only a few publications on this topic due to the lack of reliable techniques for nanoparticle characterization. We propose a multi-technique approach for the characterization of nanoparticles down to the 10 nm level using standard micro-Raman spectroscopy combined with standard atomic force microscopy. We successfully obtained single-particle spectra from 25 nm sized polystyrene and 9 nm sized TiO2 nanoparticles with corresponding mass limits of detection of 8.6 ag (attogram) and 1.6 ag, respectively, thus demonstrating the possibility of achieving an unambiguous Raman signal from a single, small nanoparticle with a resolution comparable to more complex and time-consuming technologies such as Tip-Enhanced Raman Spectroscopy and Photo-Induced Force MicroscopyArtigo IPEN-doc 29353 Raman Spectroscopy of irradiated and non-irradiated plastics2022 - DIPOLD, JESSICA; BERECZKI, ALLAN; PINHEIRO, GUSTAVO; VASCONCELOS, KAMILLA; FREITAS, ANDERSON Z. de; WETTER, NIKLAUS U.Understanding radiation damage to plastic is of great interest for possible construction applications. Two different plastics were gamma irradiated and their property changes were studied with micro-Raman spectroscopy, showing promising results in increasing its toughness.Artigo IPEN-doc 27334 Polydispersed Nd3+:YVO4+SiO2 powders for highly efficient random lasers2020 - DIPOLD, JESSICA; SILVA, DANILO A.A. da; BERECZKI, ALLAN; JIMENEZ-VILLAR, E.; WETTER, NIKLAUS U.Random lasers are cheap and easy to fabricate, having several different applications such as early cancer detection, encryption and Speckle-free imaging. However, few fabricated random lasers present high efficiency, which limits their possible applications. In a recent work, our group achieved a record efficiency by developing random lasers that use compacted, polydispersed yttrium vanadate doped with neodymium (Nd3+:YVO4 ) powders to create separate regions for gain and light diffusion. Large particles are responsible for the light diffusion, while the small particles that occupy the spaces between them create gain pockets, absorbing the pumped light. In this work, this strategy is refined by using passive particles (SiO2) for light diffusion, restricting the laser active particles to the gain pockets. The first attempt with this strategy used 30% of Nd3+:YVO4 small powders and 70% of large SiO2 particles. Without any further optimization, the result achieved is already 40% of the highest obtained efficiency in the previously studied Nd3+:YVO4 polydisperse sample, showing a promising result to further improve this new strategy and reach even larger efficiencies with less laser active material.