Resumo em Inglês:

In this work, the surfactant cetyltrimethylammonium bromide (CTAB) was applied to observe how increasing the surfactant's concentration will affect the MgO characteristics, such as the increase in vacancies. The samples were characterized by X-ray diffraction (XRD). For the MgO-0.025CTAB sample, the intensity of the (200) peak of MgO decreased by three. However, the MgO-2.5CTAB showed an increase in the peaks intensity. In addition to using Rietveld refinement, it is possible to observe the textural characteristics of the samples, with the introduction of CTAB, oxygen vacancies increased, and from the MgO to the MgO-0.025CTAB sample, there was a decrease in oxygen occupancy from 94% to 82% in the unit cell. Thermogravimetry (TG) analyses were used to understand the interactions between the support and the surfactant as the CTAB concentration increased. With the physisorption of N2, the behavior of the sample pores and specific area determination are verified. The introduction of CTAB caused the decrease of the specific area from 32 m2/g to 9 m2/g for the MgO and MgO-0.025CTAB samples. However, for a more concentrated surfactant, MgO-2.5CTAB, the specific area was 25 m2/g. Scanning electron microscopy made it possible to observe the increase in the roughness with CTAB presence.

Resumo em Inglês:

Geopolymers are inorganic polymers obtained through the alkaline activation of aluminosilicates. Due to their cementitious properties, they are being studied as a sustainable alternative to Portland cement. Red ceramic waste (RCW), being a source of silica and alumina, can serve as a precursor for producing geopolymers. In this work, we evaluated the feasibility of producing geopolymers from hollow brick (HB) and hydrated lime, using only sodium hydroxide as an alkaline activator. The test specimens were prepared replacement HB by up to 30 wt% of hydrated lime, aiming to evaluate the compressive strength after 7 and 28 curing days of the geopolymer produced. The results showed that samples with 30 wt% of hydrated lime, achieved the highest compressive strength (11.26 MPa) after 28 days of curing, although all values found were above the limit established by Brazilian standards for modular geopolymer bricks. The results therefore show a sustainable and widely viable implementation alternative to reduce the environmental impacts caused by the production of Portland cement.

Resumo em Inglês:

This study focuses on the preparation and characterization of silver-doped calcium titanate (CaTiO3) photocatalysts for the degradation of Rhodamine B (RhB) dye. Utilizing a hydrothermal microwave-assisted method, efficient photocatalysts of pure CaTiO3 (CT) and 3% (CT3%) and 5% (CT5%) Ag-doped CaTiO3 were prepared. X-ray diffraction confirmed the orthorhombic phase of CaTiO3 with residual TiO2, more pronounced in the CT3%. Micro-Raman and FTIR spectra verified the presence of TiO2, while SEM images revealed distinctive morphologies. The band gap energy was lower in Ag-doped samples, particularly in the CT3% sample. Photocatalytic tests demonstrated superior RhB degradation with the CT3% catalyst. A 22 factorial design was used to determine the ideal condition for the photocatalysis. Photocatalysis with CT3% was efficient in toxicity removal, but stability tests indicated a decline in performance over multiple cycles. These findings suggest the potential of Ag-doped CaTiO3 as efficient photocatalysts for dye degradation.

Resumo em Inglês:

Poly(3-decylthiophene) is a polymer with conductive characteristics due to its conjugated polymeric chain. With the search for new applications and improvements of these materials, in sensors, and OPVs, there is a great demand for deeper knowledge about them. This work aims to characterize the P3DT, through analysis of optoelectrical measurements. Using the drop casting technique, thin films were made onto solid substrates. The films were subjected to optical characterization by UV-Vis and optical microscopy. The electrical characterization was obtained by IxV curves and then measuring the photoconductivity through Ixt curves, with a solar simulator. With UV-Vis measurements, it was observed that the absorption of light in the visible spectrum reached a peak of 520 nm in the film, blue-shifted in the solution attributed to the differences in the organization of the polymer chains. The optical microscopy measurements indicate the formation of aggregates with a higher concentration of aggregates observed for the film obtained with a more concentrated solution. Finally, the photoconductivity measurements carried out obtained a positive response to the photo-excitation of the material due to exposure to light, with an increase in current in the film as the photo-exposure cycles were repeated.

Resumo em Inglês:

Conjugated polymers have attracted considerable attention to the organic electronics field, due to their properties and a variety of potential areas of application, such as solar cells, OLEDs, sensors, and transistors. In the sensor area, the study of chloroform gained prominence due to its toxicity and effects on the human body, such as damage to the liver and kidneys. This work aims to study thin films of P3DT in different concentrations, perform their optical, morphological, and electrical characterization, and verify their applicability as chloroform sensors. The thin films and devices are characterized using various techniques: optical characterization is performed through UV-vis spectroscopy, morphological characterization is performed through optical microscopy and electrical characterization is performed in direct current by studying the current vs. voltage curves. Electrical measurements of current vs. time are also performed in order to verify the electrical response of the active layer when exposed to a saturated chloroform atmosphere. Characterization shows expected results, similar to other P3ATs, while gas response initially shows a release in trapped charges, increasing the current, however, as the measure is repeated, the current started to decrease when exposed to the current, caused by a swelling in the polymer’s chain.

Resumo em Inglês:

Titanium dioxide (TiO2) is an n-type oxide semiconductor, where the electron donors are usually associated with oxygen vacancies and interstitial titanium ions, whereas quinoline derivatives (QD) are usually p-type semiconductors with light emission in the blue range. We report a broad emission band centered at 485 nm, and temperature induced electrical properties of the QD 4-(6-(diethylamino)-4-phenylquinolin-2-yl)benzoic acid and TiO2 films. The combination of QD with TiO2, both layers in the form of thin film, forms a heterostructure in a very convenient format for integration in optoelectronics. Due to the techniques used for film deposition, both sort of films present defects, which are responsible for the electrical characteristics. The dominant level for TiO2 is located about 760 meV from the conduction band bottom, inside the bandgap, whereas for the QD film the activation energy is about 328 meV. Both levels show up for a range above room temperature. In the first case, it suggests the second ionization level of oxygen vacancies (VO2+) or the third ionization level of interstitial titanium ions (Ti3+), considering that both are electron donors, whereas in the case of QD it suggests a mechanism of small polaron tunneling (SPT).When combined as a heterostructure and explored under transport profile perpendicular to the films (transverse contacts) it leads to current-voltage (I-V) rectifying behavior similar to a p-n junction, which is evidence of the p-type-like electrical behavior of the QD, even though this I-V behavior may be destroyed for repetitive I-V measurement, which seems to be related with aging and the presence of defects at the heterostructure interface.

Resumo em Inglês:

The medical research community continues to search for effective technologies to treat diseases such as cancer, with photodynamic therapy (PDT) being a notable advancement. PDT combines light, oxygen, and a photosensitizer (PS) to target diseased cells. This study addresses the advancement of PDT in medical science for the treatment of diseases such as cancer, emphasizing the development of an efficient PS with desirable properties such as non-toxicity in the dark, high singlet oxygen yield, and selective targeting capabilities. Zinc oxide nanoparticles (NPs-ZnO), recognized for their unique catalytic and photochemical properties, are emerging as a potential next-generation PS for PDT. The research uniquely employs an eco-friendly synthesis approach using Glycine max (soybean) extract, in line with green chemistry principles. This novel method not only ensures the synthesis of NPs-ZnO, but also promotes environmental sustainability. The synthesized NPs-ZnO were evaluated for their ability to generate reactive oxygen species (ROS), which are essential for the degradation of methylene blue dye and serve as a proxy for their efficacy in PDT. In particular, NPs-ZnO synthesized using zinc acetate, zinc chloride at 180°C, and zinc nitrate at 100°C were identified as the most promising candidates for PDT applications. Their significant performance in ROS generation underscores the potential of these nanoparticles to enhance the efficacy of PDT in cancer treatment, paving the way for further research and development in this promising field.

Resumo em Inglês:

This work evaluates how adding cetyltrimethylammonium bromide (CTAB) in the synthesis affects the physical and chemical features of Ni/CeO2 catalysts. The samples were characterized by the Rietveld refinement from X-ray diffraction (XRD) and showed a decrease in the crystallite size and an increase in the microstrain from 5.9 to 7.5 x 10-3. Nitrogen physisorption analysis was used to obtain the pore size distribution by the BJH method, varying the pore size between 8 and 12 nm. Raman spectroscopy was employed to confirm the fluorite structure arrangement of ceria and the number of vacancies in the bulk phase, where the ratio from vibrational modes related to defects and oxygen vacancies increased from 0.488 to 0.516 ratio. With the spectra obtained from X-ray photoelectron spectroscopy (XPS), it was possible to observe the distribution of metals on the surface of the samples and their oxidative states, providing clues about the quantity of vacancies. Samples with higher concentrations of CTAB obtained higher values of Ce3+, reaching a 0.45 ratio on the surface. The scanning electron microscopy (SEM) analysis showed that the addition of CTAB formed more irregular shape grains, reaching 20 μm of medium size for all the samples.

Resumo em Inglês:

Nowadays, few studies have reported on the sensitivity of thin films of Al-doped ZnO to ozone. This gas can become harmful to health depending on its environmental concentration. This work presents the sensor response to ozone gas of pure ZnO and Al-doped thin films, prepared by sputtering with varying deposition times. Ceramic targets prepared by SSR, compacted at 65MPa, sintered at 950°C, with densities ranging from 74-97% of the theoretical density, depending on the dopant content were used. The films showed an increase in thickness with deposition time and a preferential growth in the (002) plane of the ZnO structure. Slight changes in the band gap value occurred with increasing Al, whose presence in the ZnO lattice was confirmed by XPS. The sensitivity results to ozone showed that the performance of the films decreased with the Al-doping, which could be attributed to the defects formation related to oxygen in the lattice during Zn-Al substitution or to the greater densification of the films. Although the results showed a decrease in the sensor properties, all films are sensitive to ozone, including the low concentrations of 50 ppb, a limit considered for a maximum daily average for human exposure, established by the WHO.

Resumo em Inglês:

The innovative work shows a new strategy to modify the physicochemical properties of medicines and improve patients' lives. The mechanochemical synthesis and characterization of the first Norfloxacin nanocrystal are described. In recent decades, nanotechnology has gained significant attention in the scientific field through the study of the design, formation and application of materials at the nanoscale level. In the pharmaceutical sector, nanotechnology has been the focus of studies on systems that allow increased bioavailability. The present work investigated the formation of pharmaceutical nanocrystals. Nanocrystals are crystalline nanoparticles ranging in size from a few nanometers to 1,000 nm, composed of 100% of the drug and stabilized by surfactants or polymeric stabilizers. They have a safe formulation and are well tolerated compared to conventional medicines. The drug used in this study was Norfloxacin, a broad-spectrum antibiotic that has low bioavailability. Several nanocrystallization techniques are found in the literature, among which the mechanochemical method stands out. Mechanochemistry is an approach that allows the reduction of particle size through the mechanical energy provided in the reaction medium. Thus, it was possible to obtain nanomaterials and explore the influence of surfactants in controlling the particle size and morphology of the materials obtained.

Resumo em Inglês:

Biopolymers such as PLA, ZnO nanoparticles and chitosan are materials that have some properties in common, such as oxidizing action, antimicrobial activity, biocompatibility and formation of a mechanical barrier, which make them promising for application in food packaging, as they ensure safety in contact with food. In this study, the antibacterial activity of pure PLA films and those incorporating chitosan, ZnO nanoparticles and both was analyzed for four strains (two Gram-positive and two Gram-negative bacteria) by the agar diffusion method, aiming to verify the action of each substance and their combination. The characterization of ZnO NPs was performed by XRD, FTIR, Raman spectroscopy, UV-Vis, SEM and Zeta potential (ZP) methods. The results showed that the ZnO nanoparticles synthesized by the Pechinhi method, with calcination temperatures of 600 and 800ºC, presented a predominant morphology of nanorods and nanospheres, according to SEM images, with high purity and crystallinity. The PLA-based films presented a rough structure, with small pores, and the incorporation of chitosan and ZnO NPs was effective, which was proven by the SEM/EDS technique. The results showed that the films incorporated with ZnO NPs presented inhibition for Gram-positive bacteria in the range of 12.5 to 14 mm.

Resumo em Inglês:

In this study, electrospun nanofibers of poly(vinylidene fluoride) (PVDF) were produced with the addition of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) and poly(3-hexylthiophene) (P3HT), for application as a nanostructured active layer of bulk heterojunction polymer with fullerene and polythiophene derivatives in third-generation photovoltaic devices. The electrospinning technique was used to favor the formation of the β phase, exhibiting ferroelectric properties, improving the electrical performance of the device. The morphological, structural and electrical characteristics of the nanofibers were investigated using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and DC electrical measurements. The synergism between nanofiber processing and the addition of P3HT and PCBM improved electrical conductivity by up to three orders of magnitude, furthermore, the nanofibers incorporating P3HT exhibited responses to solar stimuli.

Resumo em Inglês:

Organic solar cells offer significant advantages over traditional inorganic solar cells, including their lightweight nature, ease of fabrication, low cost, and low energy investment. Recent advances have shown that oligo and poly(fullerene)s play an important role in both types of devices, either as additives or interlayers, significantly improving stability and charge extraction. There is considerable room for further progress in understanding the properties of these novel materials. Here, we examine OPCBMMB, an oligo(fullerene) based on PCBM, and study its changes in photoconductivity when combined with thiophenes. The OPCBMMB:P3HT and OPCBMMB:P3OT composites are formed from drop casting, with optical and electronic characterizations being performed. UV characterizations confirm a difference in macromolecular conformation of the P3HT and P3OT going from solution to film, as would be expected. More interesting is the great improvement in the films conductivities when studied under direct current when compared to pristine OPCBMMB. Differences arise due to the variations in thiophene alkyl chains. The combination of OPCBMMB:P3HT and OPCBMMB:P3OT also proved to be an effective combination of acceptor-donor, with a visible increase in conductivity when exposed to light. A fact that can be correlated to the UV spectra, which shows the blends have a strong interaction with visible light.