Flávio Junior Caires

Bio: Flávio Junior Caires is an academic researcher from Sao Paulo State University. The author has contributed to research in topics: Thermal decomposition & Thermogravimetry. The author has an hindex of 12, co-authored 81 publications receiving 510 citations.

Thermal behaviour of fumaric acid, sodium fumarate and its compounds with light trivalent lanthanides in air atmosphere

Abstract: Characterization, thermal stability and thermal decomposition of light trivalent lanthanide fumarates, as well as, the thermal behaviour of fumaric acid and its sodium salt were investigated employing simultaneous thermogravimetry and differential thermal analysis, differential scanning calorimetry, Fourier transform infrared spectroscopy (FTIR), TG–FTIR techniques, elemental analysis and complexometry. On heating, sublimation of fumaric acid is observed, while the thermal decomposition of the sodium fumarate occurs with the formation of a mixture of sodium carbonate and carbonaceous residue. The thermal decomposition of light trivalent lanthanide fumarates occurs in consecutive and/or overlapping steps with the formation of the respective oxides: CeO2, Pr6O11, and Ln2O3 (Ln = La, Nd, Sm, Eu, Gd).

Mechanochemical synthesis, characterization, and thermal behavior of meloxicam cocrystals with salicylic acid, fumaric acid, and malic acid

Abstract: A liquid-assisted grinding approach was used to synthesize three cocrystals between the coformers: salicylic acid, fumaric acid, and malic acid with meloxicam, a nonsteroidal anti-inflammatory drug. The spectroscopic techniques, Raman and Fourier transform infrared (FTIR), confirm the formation of these compounds by showing evidence of hydrogen bonds between NH or OH and CO groups. Powder X-ray diffraction verified the formation of the cocrystals by comparing the results with a crystallographic database. Differential scanning calorimetry (DSC), simultaneous thermogravimetry and differential scanning calorimetry (TG-DSC), evolved gas analysis (EGA by TG-FTIR), DSC-photovisual analysis, and videos of the cocrystals being heated were used to study the thermal behavior, analyze the composition, identify polymorphic transitions in meloxicam cocrystal with malic acid, and understand the decomposition phenomena of these solids. The malic acid compound shows a unique degradation step that was confirmed by TG-DSC data and FTIR analysis of the residue formed. A solubility test was performed: fumaric cocrystal showed an enhanced performance compared to pure drug, and malic and salicylic cocrystals showed a slower dissolution profile.

Power of Infrared and Raman Spectroscopies to Characterize Metal-Organic Frameworks and Investigate Their Interaction with Guest Molecules

Abstract: The variety of functionalities and porous structures inherent to metal-organic frameworks (MOFs) together with the facile tunability of their properties makes these materials suitable for a wide range of existing and emerging applications. Many of these applications are based on processes involving interaction of MOFs with guest molecules. To optimize a certain process or successfully design a new one, a thorough knowledge is required about the physicochemical characteristics of materials and the mechanisms of their interaction with guest molecules. To obtain such important information, various complementary analytical techniques are applied, among which vibrational spectroscopy (IR and Raman) plays an important role and is indispensable in many cases. In this review, we critically examine the reported applications of IR and Raman spectroscopies as powerful tools for initial characterization of MOF materials and for studying processes of their interaction with various gases. Both the advantages and the limitations of the technique are considered, and the cases where IR or Raman spectroscopy is preferable are highlighted. Peculiarities of MOFs interaction with specific gases and some inconsistent band assignments are also emphasized. Summarizing the broad analytical possibilities of the IR and Raman spectroscopies, we conclude that it can be applied in combinations with other techniques to explicitly establish the structure, properties, and reactivity of MOFs.

Resveratrol: a review of plant sources, synthesis, stability, modification and food application

Abstract: Resveratrol, a stilbene molecule belonging to the polyphenol family, is usually extracted from a great many natural plants. The technologies of preparation and extraction methods are developing rapidly. As resveratrol has many beneficial properties, it has been widely utilized in food and medicine industry. In terms of its structure, it is susceptible to degradation and can undergo chemical changes during food processing. Different studies have therefore given more attention to various aspects of resveratrol, including anti-aging, anti-oxidant, and anti-cancer activity. This review classifies the study of resveratrol, considers plant sources, synthesis, stability, common reactions, and food applications, and provides references to boost its food and medical utilization. © 2019 Society of Chemical Industry.

Iron-based metal organic framework, MIL-88A, as a heterogeneous persulfate catalyst for decolorization of Rhodamine B in water

Abstract: While Metal Organic Frameworks (MOFs) have been extensively investigated as photocatalysts to eliminate toxic pollutants in water, studies using MOFs as chemical oxidative catalysts to degrade contaminants are still limited. MOFs used as catalysts for chemical oxidation reactions were prepared in N,N-dimethylformamide (DMF), a potential carcinogenic solvent. If such MOFs are not well activated and have not properly undergone solvent exchange, DMF can still be encapsulated inside MOFs, leading to secondary pollution. Considering the essence of wastewater treatment and pollutant reduction, DMF-free MOFs which still exhibit the catalytic activity to activate oxidants should be developed. Thus, we selected an iron-based MOF, MIL-88A, which can be prepared using Fe3+ with fumaric acid just in water. The as-synthesized MIL-88A is evaluated as the heterogeneous catalyst to activate persulfate for the decolorization of Rhodamine B (RB) dye. Iron oxide clusters (i.e., Fe2O3) form within MIL-88A through the coordination of Fe3+ and fumaric acid. Fe3+ of Fe2O3 is expected to induce the generation of persulfate radicals which in turn lead to the formation of sulfate radicals to decolorize RB dye. Factors influencing the activation of persulfate and RB decolorization were examined including persulfate dosage, MIL-88A loading, temperature, pH, UV and US irradiation as well as inhibitors. MIL-88A was assessed for the multiple-cycle activation of persulfate without additional regeneration of spent MIL-88A. These features make MIL-88A an effective and recyclable heterogeneous catalyst for the activation of persulfate.