Navegando por Palavras-chave "Green synthesis"
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- ItemSomente MetadadadosGreen synthesis of stable silver nanoparticles using Euphorbia milii latex(Elsevier B.V., 2011-09-20) Matos, Ricardo Almeida de [UNIFESP]; Cordeiro, Thiago da Silva; Samad, Ricardo Elgul; Vieira, Nilson Dias; Courrol, Lilia Coronato [UNIFESP]; Universidade Federal de São Paulo (UNIFESP); IPEN CNEN SPWe report a simple method to create silver nanoparticles that consists in the irradiation of a silver nitrate and Euphorbia milii solution by light from a xenon lamp followed by ultrashort laser pulses. the formation of silver nanoparticles has been confirmed with UV-visible and TEM microscopy, and no additives, such as solvents, surfactants or reducing agents, were used in the procedure. Nanoparticles are present after the xenon lamp illumination, and after the laser irradiation the silver nanoparticles sizes are reduced drastically to the range of 10-50 nm. A concentration variation study of silver nitrate and aqueous latex extract was carried out, as well as with the laser irradiation energy and time. the size reduction can be explained by a multiphoton process that promotes the photoexcitation of the surface plasmon band, breaking the particles due to charge accumulation. the utilization of environmentally friendly solvents is one of the key issues that merits important consideration in a green synthesis strategy. (C) 2011 Elsevier B.V. All rights reserved.
- ItemSomente MetadadadosSaliva and light as templates for the green synthesis of silver nanoparticles(Elsevier B.V., 2014-01-20) Matos, Ricardo Almeida de [UNIFESP]; Courrol, Lilia Coronato [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)We report a method for the synthesis of silver nanoparticles using an aqueous saliva solution and irradiation with light from a mercury metal halide lamp. Bi-deionized water was used as the solvent, and surfactants or reducing agents were substituted by saliva and light in the procedure, characterizing the process as a green synthesis. the light was used to reduce silver ions (Ag+) to metallic silver (Ag-0). the average size, size distribution, and morphology of the nanoparticles were determined by transmission electron microscopy (TEM), UV/visible absorption spectrophotometry and Fourier transform infrared spectroscopy (FTIR). Spherical nanoparticles of similar to 20 nm in size were present after the lamp illumination. This methodology represents a non-invasive approach for disease detection and possesses a good potential for diagnostics applications. (C) 2013 Elsevier B.V. All rights reserved.
- ItemAcesso aberto (Open Access)Síntese verde de nanopartículas de prata e ouro e sua aplicação na determinação de mercúrio(Universidade Federal de São Paulo, 2018-07-12) Lopes, Carla Regina Borges [UNIFESP]; Courrol, Lilia Coronato [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)Metal nanoparticles (MNP) has attracted great interest from the scientific community in recent years due to its large number of applications in various areas of science. In the environmental area, they stand out as an alternative to the traditional methods of quantification of pollutants, among them potentially toxic metals, such as mercury (Hg), which at high concentrations can cause damage to the brain, heart, kidneys, lungs and the immune system from human beings. The techniques traditionally used for the synthesis of metallic nanoparticles, involve the use of toxic chemical reagents, increasing the search for safer methods, among them, the green synthesis process has shown a sustainable alternative, it aims to use biological organisms to replace chemical reagents. In this project were synthesized spherical nanoparticles of silver (AgNP) and gold (AuNP) with average diameters between 10 and 50nm approximately. As reducing agents of the metallic ions and to avoid the aggregation of particles, the amino acid L-tryptophan (TrpAgNP/TrpAuNP) combined with exposure to the xenon lamp in a photoreduction process, or the aqueous extract obtained from leaves of Mimusops coriacea (McAgNP/McAuNP), plant of African origin with abundant presence on the coast of São Paulo, known as Abricó-de-Praia. Synthesized nanoparticles were characterized by different techniques, such as UV-vis optical absorption; emission (fluorescence); infrared (FTIR); transmission electron microscopy (TEM); dynamic light scattering (DLS) and zeta potential. Variations in the pH of the medium, concentration of the reagents and time of exposure to the lamp, were applied, aiming to optimize the synthesis processes, considering ideals that resulted in spherical nanoparticles with good stability, considering various parameters, such as: reagents and energy savings; lower cost; speed and yield. The synthesized nanoparticles have been tested for their potential for the detection and quantification of mercury in aqueous solution, through changes in the Superficial Plasmon of Resonance (SPR), with consequent alteration in the band of UV-vis optical absorption in the presence of different metal concentrations. The McAgNP presented the best result, with detection limit (LOD) from 6,5ng. mL -1, and quantification (LOQ) of 21,7ng. mL-1, showing high potential for the development of a simple and easy-to-operate method for the quantification of mercury. All the stages of this work were carried out so that the AgNPs/AuNPs obtained by these routes consisted of a material of interest in the development of new nanotechnological products with sustainable bases. The synthesis processes presented high reproducibility and are in accordance with the principles of green chemistry and sustainability, presenting as a low-cost alternative and biocompatible in the synthesis of AgNPs/AuNPs.
- ItemSomente MetadadadosSynthesis of silver nanoparticles using agar-agar water solution and femtosecond pulse laser irradiation(Elsevier B.V., 2013-04-20) Matos, Ricardo Almeida de [UNIFESP]; Cordeiro, Thiago da Silva; Samad, Ricardo Elgul; Sicchieri, Leticia Bonfante; Vieira Junior, Nilson Dias; Courrol, Lilia Coronato [UNIFESP]; Universidade Federal de São Paulo (UNIFESP); IPEN CNEN SPWe report a method to synthetize silver nanoparticles using an agar-agar solution illuminated by light from a xenon lamp, followed by irradiation by ultrashort laser pulses. Spherical nanoparticles of similar to 100 nm were created by the xenon lamp illumination, and after the ultrashort pulses irradiation their sizes were reduced to under 10 nm. Bideionized water was used as solvent and surfactants or reducing agents were substituted by agar-agar and light, characterizing the process as a green synthesis, a completely inoffensive procedure for the environment. the xenon light was used to reduce silver ions (Ag+) into metallic silver (Ag-0), and the laser irradiation was important to decrease the nanoparticles diameter. the average particles size, size distribution, morphology, and structure were determined by dynamic light scattering (DLS), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX) and UV/visible absorption spectrophotometry. (C) 2013 Elsevier B.V. All rights reserved.