SAJID FAROOQ
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Artigo IPEN-doc 30236 Quantitative analysis of high performance plasmonic metamolecules for targeted deep tissues applications2023 - FAROOQ, SAJID; RATIVA, DIEGO; ARAUJO, RENATO E. deRationally designed gold nanoparticles (Au NPs) show a great potential for biomedical applications. Specifically, for optically induced heating of deep tissues facilitated by plasmonic-assisted lasers, nanostructures with high optical absorption coefficient in biological window are required. Plasmonic metamolecules, such as gold nanodimers (NDs), exhibit a robust localized field enhancement with strong infrared optical absorption. However, an exclusive investigation of the optical/ thermal features of high-performance Au NDs for optical infrared heating remains a challenge. Here, we focus on Au NDs for optothermal characteristics in deep tissues heating procedures. Our analysis encompasses parameters such as absorption cross-sections, field enhancement, and temperature rise with a systematic methodology selecting optimal NDs. Our findings reveal a non-uniform spatial distribution of temperature at the nano-scale and show that short-pulsed laser excitation enhances the temperature near the dimerās junction. Remarkably, when compared to monomeric gold nanorods under the same excitation resonance mode, optically generated heating of Au NDs leads a threefold higher temperature increase. These results evidence valuable insights for using Au NDs as efficient plasmonic nanoheaters in photothermal-assisted applications.Artigo IPEN-doc 29715 Selecting plasmonic nanoshells for colorimetric sensors2023 - BALTAR, RAPHAEL M.S.M.; FAROOQ, SAJID; ARAUJO, RENATO E. deIn this work, the use of gold and silver nanoshells was evaluated as a starting point for the establishment of colorimetric sensor platforms. The sensitivity and linearity of the nanoplatforms (SiO2 coreāmetallic shell nanoparticles) were assessed under the influence of the nanoshell configuration, color space, and light source illuminant. A computational procedure for selecting high-performance plasmonic colorimetric sensor platforms is described. The evaluation methodology involves considering five different color spaces and 15 different color components. By exploring crucial figures of merit for sensing, the performance of the plasmonic nanoplatforms was evaluated, exploring Mie theory. We determined that gold nanoshells are highly efficient on colorimetric sensing, while silver nanoshells are a better choice for spectroscopic sensors. Plasmonic nanoplatforms based on nanoshells with 10 nm SiO2 core radii and 5 nm thick Au shells presented sensitivity values up to 4.70 RIUā1 , considering the hue angle of the HSV color space. Color variation of up to 40% was observed, due to the adsorption of a 10 nm thick molecular layer on the gold nanoshell surface. In the search for advances in colorimetric biosensors, the optimization approach used in this work can be extended to different nanostructures.Artigo IPEN-doc 29000 High performance blended nanofluid based on gold nanorods chain for harvesting solar radiation2023 - FAROOQ, SAJID; RATIVA, DIEGO; SAID, ZAFAR; ARAUJO, RENATO E. deColloids composed of metallic nanoparticles are promising working fluids for solar radiation harvesting using Direct Absorption Solar Collectors (DASC), due to a high thermal conductivity characteristic and a broad optical absorption that can be tuned to match the solar spectrum. Recently, different studies report gold nanorod (Au-NR) chains for biosensing and photothermal applications, which have broadband and high absorption cross-section and potential possibilities to orientate the nanoparticle using electromagnetic fields. Moreover, colloids with nanoparticles blended configuration show an efficient solar radiation absorption characteristics. Here, working fluids for DASC based on gold nanorod chains in an unblended and blended configuration are evaluated using numerical simulations. The results indicate that the solar absorption increases proportional to the size of the Au-NR assembly, and the best configuration is obtained for a tetramer structure. By using different blended arrangements such as single Au monomers, dimers, trimmers, and tetramers nanorods, it is possible to obtain solar weighted absorption coefficients close to an ideal solar thermal collector, even obtained at low volume fraction (1Ć10(ā5)). Moreover, the results show an enhancement of the temperature of 58.45 Ā°C for tetramer compared with a monomer structure, both under one sun excitation. Therefore, the Au-NR assembly shows a high potentiality to be explored as a high-performance working fluid for solar thermal collectors.