Submissões Recentes
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Adaptive optics systems
2025 - MORAIS, PAULO J.D. de; SILVA, RUBENS C. da; ROSSI, WAGNER de; MOTTA, CLAUDIO C.
This paper presents the implementation of a Lagrange-based processor extension for woofer-tweeter adaptive optics control. The approach leverages the complementary response of two deformable mirrors to compensate for a broad range of wavefront aberrations. Applications include high-energy laser propagation through the atmosphere, where adaptive optics mitigate distortions caused by turbulence, enabling improved beam focus and reduced scintillation in scenarios such as freespace optical communication and energy transmission.
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Exploring acid hydrolysis conditions and extended mechanical processing for producing cellulose nanocrystal and nanofibrils from pineapple leaf fibers
2025 - COSTA, FERNANDA A.T. da; DUFRESNE, ALAIN; SONG, TAO; PARRA, DUCLERC F.
This study investigates the potential of pineapple leaf fiber (PALF), as a renewable source, to produce cellulose nanofibrils (CNF) and cellulose nanocrystals (CNC), addressing a gap in the literature regarding optimal conditions for CNC extraction from PALF. Chemical analysis revealed a high α-cellulose content (78.14 %), making PALF suitable for nanocellulose production. MorFi analysis confirmed successful CNF production. Various hydrolysis conditions were explored to obtain CNC and some of them showed promising results. Characterization using FTIR, XRD, AFM, and TGA confirmed successful nanocellulose production. The CNCs exhibited a crystallinity index of 78.5 % and nanoscale dimensions (647–1105 nm, depending on the process), while CNF showed lengths of approximately 256 nm. TGA demonstrated that CNCs had lower thermal stability compared to cellulose and CNF due to reduced molecular weight and sulfate groups. CNC1 and CNC2, produced under optimized conditions (55 % acid concentration, 45 °C, 30 min), demonstrated superior properties, including high crystallinity and desirable nano-dimensions. This study highlights the novelty of using PALF for CNC production with tailored characteristics, paving the way for its application in biocomposites, drug delivery, and tissue engineering. PALF's availability and favorable composition make it a promising candidate for sustainable nanocellulose materials.
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New dye-sensitized solar cell (DSSC) based on BiVO4 film and bixin natural dye
2025 - COSTA, ANTONIO G.R.; SANTOS, LUZIA R.; MENESES, PAULO S.R.; VIANA, VICENTE G.F.; COSTA, ISOLDA; ANTUNES, RENATO A.; SILVA, REJANE M.P.; GUSMAO, GUSTAVO M.; LUZ JUNIOR, GERALDO E.; SANTOS, REGINALDO S.
A new pathway to develop dye-sensitized solar cells is presented using bixin, lithium perchloride (LiClO4) and bismuth vanadate (BiVO4) formed electrochemically. Optical analysis showed the BiVO4 film has a 2.37 eV band gap, suitable for visible sunlight. X-ray diffraction (XRD) revealed that the film is crystalline with a monoclinic phase. At the same time, morphological characterization carried out by Field Emission Scanning Electron Microscopy (FEG-SEM) showed that the film is porous and formed by particles measuring around 200 nm. Complete (photo)electrochemical studies were carried out for the photoanode, electrolyte, and bixin dye solution to evaluate the charge transfer energies of each solar cell component. BiVO4/bixin film photovoltaic devices were fabricated using iodide/triiodide redox mediators and compared with dye-free BiVO4 cells. Adding LiClO4 to the electrolyte enhanced solar cell performance. Thus, the results presented in this paper indicate that solar cells formed by BiVO4/bixin can be considered promising devices for converting solar energy into electrical current.
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Artigo IPEN-doc 31479 Influence of the deposition method on the characteristics of ZnO films for photocatalytic applications
2025 - COTINHO, S.P.; BENTO, R.T.; SANTOS, D.R. dos; CORREA, O.V.; PILLIS, M.F.
Contaminants of emerging concern have received considerable attention due to their potential adverse effects on aquatic systems, flora, fauna, and human health. Azo dyes represent a significant category of toxic organic contaminants. Heterogeneous photocatalysis offers an effective green alternative for the degradation of organic pollutants, particularly in wastewater treatment. This research aimed to synthesize and characterize nanostructured zinc oxide films to develop a UV-light activated photocatalyst capable of degrading organic compounds. The films were synthesized via the sol-gel method, and deposited on borosilicate glass substrates by spray coating and spray pyrolysis techniques. The samples underwent heat treatment at varying times and temperatures. The photocatalytic efficiency was evaluated by the methyl orange dye discoloration under UVA radiation. Wurtzite structure was observed in all conditions. Differences in surface morphology, band gap energies, and photocatalytic performance were also noted. Both methods enabled the production of UVA-photoactived films.