DSpace Coleção:http://bdtd.uftm.edu.br/handle/tede/5212026-09-03T17:41:41Z2026-09-03T17:41:41ZDesenvolvimento de filmes automontados a partir de complexos de metais de transição derivados de um ligante aroilbis(tioureia)http://bdtd.uftm.edu.br/handle/123456789/21042026-08-29T02:03:09Z2025-02-27T00:00:00ZTítulo: Desenvolvimento de filmes automontados a partir de complexos de metais de transição derivados de um ligante aroilbis(tioureia)
Abstract: The fabrication of thin films has become an increasing demand in various fields of chemistry, enabling the construction of increasingly smaller and more precise devices. Among the self-assembly methods, the Layer-by-Layer (LbL) deposition technique is one of the most powerful tools for building nanoscale films. However, this technique generally employs water-soluble ionic compounds. Aiming to develop a method for constructing nanostructured films using neutral and water-insoluble compounds, this study focused on the synthesis and characterization of Cu(II), Ni(II), Zn(II), and Pd(II) complexes containing a ligand from the aroylbisthiourea class for application in film fabrication using the LbL technique. The ligand N¹,N⁴-bis(diethylcarbamothioyl)terephthalamide (H₂TBT) was used in complexation reactions with NiCl₂∙6H₂O, ZnCl₂, and CuCl₂∙2H₂O in the presence of triethylamine, forming [{M(TBT)}₃] (M = Ni (1), Cu (2) ou Zn (3)) complexes. The reaction of H₂TBT with the precursor [PdCl₂(MeCN)₂], without the addition of a base, resulted in the [{PdCl(HTBT)}₂] (4) complex, which forms the trimeric complex [{Pd(TBT)}₃] (5) upon addition of trietilamine. The synthesized compounds were characterized by techniques such as melting point determination, infrared spectroscopy (FTIR), UV-vis spectroscopy, and cyclic voltammetry. Characterization revealed that the Ni(II), Zn(II), and Cu(II) complexes exhibit a trimeric structure, whereas the Pd(II) complex has a dimeric structure. The compounds 1, 2, 4, and 5 exhibited square-planar geometry, while compound 3 presented tetrahedral geometry. These neutral and water-insoluble compounds 1, 2 and 4 were employed in the fabrication of nanostructured films using the LbL technique, applying sequential deposition of alternating layers to produce films with PAH/PSS/complex and PAH/GO/complex architectures. The UV-vis spectroscopy monitoring of film growth confirmed the feasibility of constructing LbL films with the synthesized compounds, demonstrating the potential of the proposed method. After film fabrication, their feasibility as electrochemical sensors for resorcinol and catechol was evaluated. The films derived from the Cu(II) and Pd(II) complexes exhibited electrochemical activity when used as working electrodes in the presence of catechol, confirming that the methodology developed in this study is suitable for the fabrication of potential sensors.
Tipo: Tese2025-02-27T00:00:00ZProdução e caracterização de carvão ativado proveniente de cascas de grãos de café e de cascas de grãos de girassolhttp://bdtd.uftm.edu.br/handle/123456789/19612025-07-18T02:02:49Z2024-09-12T00:00:00ZTítulo: Produção e caracterização de carvão ativado proveniente de cascas de grãos de café e de cascas de grãos de girassol
Abstract: The study of the use of biomass and lignocellulosic waste in the production of activated carbon
has shown positive results for the development of new technologies that are used to collaborate
with processes that involve the use of those adsorbents. Lignocellulosic residues from the
cultivation of different biomasses are materials that are produced on a large scale and, if
disposed of inappropriately in the environment, can cause environmental problems. Any
carbonaceous material can be used to produce activated carbon, as long as it has a low content
of inorganic components, low cost, high availability, does not suffer degradation during storage,
is easy to activate and produces good adsorbents. The aim of this work is to produce and
characterize activated carbon from coffee seed husks and sunflower seed husks, residual
biomass found on a large scale in Brazil due to the production of coffee and sunflower oil. The
method used consists of previously carbonizing the biomass at 700°C under an inert atmosphere
of nitrogen (N2), followed by an activation process using potassium hydroxide (KOH) in a dry
method. The activation parameters such as the activation temperature (600, 700 and 800°C) and
the impregnation mass ratio (1:1, 1:2 and 1:4) were evaluated during the production of the
adsorbents. The activated carbons produced were characterized using techniques such as:
Fourier transform infrared spectroscopy (FT-IR), surface area analysis, average pore volume
and pore distribution based on BET adsorption-desorption isotherms and scanning electron
microscopy (SEM). The microscopy analyses indicated the development of a porous structure
predominantly formed by mesopores and micropores, with a high carbon and oxygen content
in the composition of the adsorbents. The activated carbon sample that showed the best results
was the one produced from sunflower seed husks, activated at 700°C with an impregnation ratio
of 1:4 (coal:KOH), showing a surface area of 1326,54 m2.g-1, an average pore volume of
0,7947 cm3.g-1 and an average pore diameter of 2.34 nm. Based on the results obtained, it is
possible to state that both biomasses studied have favorable chemical and structural
characteristics for the production of activated carbon, and also that the activation method used
led to the development of a porous structure with a high surface area value when compared to
other materials in the literature.
Tipo: Dissertação2024-09-12T00:00:00ZFilmes nanoestruturados contendo óxido de grafeno reduzido e óxido de tungstênio: estudo em dispositivos supercahttp://bdtd.uftm.edu.br/handle/123456789/19482025-07-15T02:02:54Z2024-07-17T00:00:00ZTítulo: Filmes nanoestruturados contendo óxido de grafeno reduzido e óxido de tungstênio: estudo em dispositivos superca
Abstract: The research dedicated to the development of new nanocomposites plays a crucial role in the quest for supercapacitors with higher energy storage capacity. In this study, strategies employing nanostructured films through the Layer-by-Layer (LbL) self-assembly technique were employed. These films consist of the incorporation of tungsten oxide (WO3) and reduced graphene oxide (rGO) nanostructures combined with Poly(amidoamine) (PAMAM) on a glass substrate coated with ITO (indium tin oxide) for supercapacitor study. The growth of the films was monitored by (UV-VIS) spectroscopy, while images from atomic force microscopy (AFM) confirmed the formation of self-assembled PAMAM/GO-WO3 nanostructures. Cyclic voltammetry (CV) and galvanostatic charge-discharge measurements revealed the electrocapacitive characteristics of the PAMAM/GO LbL films, with capacitance values of 7.08 mF/cm² and 27.70 F/g, and values of 6.8 mF/cm² and 73.58 F/g for the PAMAM/GO-WO3 LbL films, respectively, at a current of 1.1x10-5 A and a scan rate of 100 mV/s. All films showed high capacitive retention performance, with no capacitance loss over 2000 charge-discharge cycles. These results demonstrate that the investigated films have suitable properties to be explored in nanostructured systems for energy storage.
Tipo: Dissertação2024-07-17T00:00:00ZInvestigação das propriedades ópticas de íons de Mn2+ com nanocristais de CsPbI3http://bdtd.uftm.edu.br/handle/123456789/19472025-07-12T02:02:56Z2024-08-06T00:00:00ZTítulo: Investigação das propriedades ópticas de íons de Mn2+ com nanocristais de CsPbI3
Abstract: The present work aimed to synthesize and characterize the optical, structural and electronic properties of Mn2+ ions and Perovskite - CsPbI3 nanocrystals in a glass matrix. To analyze the optical properties of nanocrystals, UV-Vis-NIR Optical Absorption Spectroscopy and Photoluminescence Spectroscopy experiments were carried out. Structural characterizations were carried out using X-ray Diffraction and Transmission Electron Microscopy. As results, experimental evidence was observed for energy transfer from CsPbI3 nanocrystals, synthesized by the fusion method, to Mn2+ ions embedded in glassy systems (SBNAPC: SiO2-B2O3–NaI–Al2O3–PbI2–Cs2CO3). The transfer of radiative and non-radiative energy between the Perovskite nanocrystals and the levels of Mn2+ ions were observed in the photoluminescence spectra. It is believed that these results can inspire further investigation of similar systems to enable possible laser devices or applications. Furthermore, a glass matrix analysis strategy protects the nanocrystals from chemical attack in a hostile environment, ensuring long-term stability, as they are easily oxidized or inactivated in the presence of oxygen, humidity or light irradiation.
Tipo: Dissertação2024-08-06T00:00:00Z