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Drug nanocarriers have been continuously improved to promote satisfactory release control. In this sense, luminescent materials have become an alternative option in clinical trials due to their ability to monitor drug delivery. Among the nanocarriers, silica stands out for structural stability, dispersibility, and surface reactivity. When using ceramic nanocarriers, one of the challenges is their interaction and selectivity capability for organic molecules, such as drugs. In order to overcome such adversity, superficial modifications can be carried out to enable a higher affinity for the desired drug. Thus, the present study aimed to obtain silica nanoparticles (NPs) doped with low concentrations of europium (III) superficially modified by (3-aminopropyl)triethoxysilane (APTES) to assess their interaction with the model drug cloxacillin benzathine. This drug was chosen because it is part of the ampicillin family and is commonly used in several treatments. Near-spherical and homogeneous silica NPs were obtained via sol-gel synthesis, with particle sizes of approximately 21 nm. It was possible to verify the fluorescence capacity of the silica NPs when doped with europium (III) in a mole percent that varied from 0.5 to 3.0%. A 10% volume percent of APTES caused the silica nanoparticles to increase the degree of hydrophobicity, with a shift in the contact angle from 8° to 51°. After surface modification by APTES, the silica nanocarrier (10 g·L-1) achieved a satisfactory degree of CLOX incorporation (25 g·L-1), increasing the adsorptive capacity to values above 50%. Therefore, silica NPs doped with europium (III) in a low percent of 0.5% (mole) modified by APTES showed promising results as an alternative option for trials and clinical studies of drug incorporation.

Here, we investigated the feasibility of immobilizing phytase onto zeolite modified with iron(II) ions, for application in the feed and food sectors. Zeolites have excellent physical-chemical characteristics, ion exchange capacity, and can act as dietary supplements. The phytase immobilization yield was up to 73 % at pH 7 and ionic strength of 100 mM, with recovered activity higher than 100 %, representing a gain in catalytic activity. The immobilized phytase could be reused, retaining 80 % of its activity in the seventh cycle of phytate hydrolysis, indicating its potential for use in industrial processes. For use in animal feed, the immobilized phytase hydrolyzed the phytate of soybean meal and wheat bran, retaining >50 % of its activity in gastric simulation tests with pH varying from 2 to 7. The results highlighted the innovative combined benefits of phytase, zeolite, and iron for animal nutrition. For application in the food industry, the immobilized phytase could hydrolyze the phytate in soybean milk and be reused in the reaction, retaining ∼50 % of its catalytic activity after 6 cycles. These results indicated the excellent potential of zeolite/iron-immobilized phytase for use in animal feed and the food industry.

Hydroxyapatite (HA) is an inorganic material with high ability to interact with proteins and has been recently explored as a support for enzyme immobilization. However, there are still some drawbac...

Nanotechnology has been studied on environmental remediation processes to foster greater photocatalysts efficiency and reuse in wastewater. This study investigated the photocatalytic efficiency and viability of niobium pentoxide (Nb2O5) nanoparticles decorated with magnetic ferrite (cobalt ferrite (CoFe2O4) or magnesium ferrite (MgFe2O4)) for atrazine photodegradation. Thus, the decorated Nb2O5 was synthesized by the polymeric precursor method, forming nanoparticles with sizes ranging from 25 to 50 nm. Nanocomposite elementary analyses showed a homogeneous distribution of elements on all particles surface. Efficient magnetic saturation was observed for pure CoFe2O4 (53 emu g−1) and MgFe2O4 (19 emu g−1) nanoparticles, promoting the magnetic removal of Nb2O5:CoFe2O4 and Nb2O5:MgFe2O4 nanocomposites. Photocatalytic assays showed 88% efficiency for atrazine photodegradation with all nanomaterials, which represented a 21% increase compared to photolysis in the 1st cycle. The magnetic nanocomposites when applied to a 5th cycle maintained the atrazine photodegradation activity. In this way, magnetic Nb2O5-based nanocomposites decorated with ferrite nanoparticles showed an efficient photocatalytic response, in addition to posterior magnetic removal from the aqueous medium. Therefore, the evaluated magnetic Nb2O5 nanocomposites may be an alternative to enhance the wastewater removal process and foster the reuse in advanced oxidative processes.

Water pollution caused by heavy metals ions has been gaining attention in recent years, increasing the interest in the development of methodologies for their efficient removal focusing on the adsorption process for these purposes. The current challenge faced by adsorption processes is the adequate adsorbent immobilization for removal and reuse. Thus, the present work aimed at producing a faujasite zeolite nanocomposite decorated with cobalt ferrite nanoparticles for Pb2+ ions adsorption in an aqueous medium improving magnetic removal and reuse. As a result, a high surface area (434.4 m2·g−1) for the nanocomposite and an 18.93 emu·g−1 saturation magnetization value were obtained, indicating magnetic removal in a promising material for adsorption process. The nanocomposite regeneration capacity evaluated by magnetic recovery after 24 h suspension presented a high Pb2+ ion adsorptive capacity (98.4%) in the first cycle. Around 98% of the Pb2+ ions were adsorbed in the second cycle. In this way, the synthesized faujasite:cobalt ferrite nanocomposite reveals itself as a promising alternative in adsorption processes, aiming at a synergic effect of FAU zeolite high adsorptive activity and the cobalt ferrite nanoparticles magnetic activity, allowing for adsorbent recovery from the aqueous medium via magnetic force and successive adsorptive cycles.

Three different synthesis methods were applied to obtain TiO2 nanoparticles: microwave-assisted hydrothermal (TiO2-MW), sonochemical (TiO2-US), and polymeric precursor (TiO2-PP). The nanoparticles thus obtained presented 93% (TiO2-MW) and 92% (TiO2-US) anatase phase, and TiO2-PP 93% rutile phase. The TiO2-US sample performed best during the Prozac® photodegradation assays because of its lipophilic surface, attributable to the C-H groups therein. Additionally, adsorption rate and photodegradation were optimized by adjusting Prozac® solution to pH ~ 8. Following Prozac® photodegradation, quantitative monitoring of its by-products (PPMA, MAEB, and TFMP) was done using HPLC. This quantitative approach led us to conclude that semiconductor photoactivity cannot be discussed solely in terms of the main compound. Lastly, it was seen that these by-products compete with each other in the degradation mechanisms and are influenced by different materials.

Made available in DSpace on 2022-04-08T11:02:03Z (GMT). No. of bitstreams: 1 P-Electrospun-polylactic-acid-nanofibers-loaded-with-silver-....pdf: 2312409 bytes, checksum: 31e2f3d9af7ba66efcdd1a834713a40e (MD5) Previous issue date: 2020

Zinc oxide nanoparticles (ZnO NPs) have been widely employed in technological applications due to their appealing properties for catalytic, optoelectronic and antimicrobial applications. Moreover, ZnO NPs can also be employed in fertilizers as a source of zinc micronutrient, which is a primary element for enzymes and proteins synthesis in plants, allowing their regular growth and improving crop productivity. However, the extensive use of nanoparticles as a source of fertilizers in agricultural activities also raises concerns once nanoparticle features including surface charge, chemical fucntionalittes, size and shape can alter the toxicity of NPs. In this scenario, the toxicity of distinct ZnO NPs towards microalgae Pseudokirchneriella subcapitata, which is the base microorganism for the aquatic food chain, was evaluated and compared. ZnO NPs employed here were obtained by co-precipitation method and co-precipitation followed by hydrothermal method using different times. After characterizing the physical-chemical properties of ZnO NPs, they were employed in toxicity biossays in order to evaluate their ability to inhibit algal growth as well as to induce changes in algae morphology. Our results indicate that ZnO NPs concentrations below 10 mg L-1 presented low toxicity towards P. subcapitata microalgae. Higher concentrations of ZnO NPs, however, presented significant toxic effects, and revealed changes in morphology of the algae cells, and therefore, should be avoided for agri-related applications.

Photocatalysis is a promising alternative for the decontamination of effluents. In this paper, immobilized ZnO-based photocatalysts were obtained by pressing and by slip casting. The cylindrical pieces were heat-treated at 800°C. The samples were characterized by the method based on the principle of Archimedes, XRD, FTIR, Raman, diffuse reflectance and SEM. The samples obtained by slip casting presented lower apparent density (3.12 ± 0.04 g/cm

This research investigated the production of porous zinc oxide (ZnO) ceramics obtained by the replica method for water depollution by photocatalytic processes. Five photo-decolorization cycles were performed to analyze the reuse potential of the ceramics. Statistical analyses using R programming were conducted to investigate possible significant differences between them. The ceramics porosities were between 46.74 and 62.50% (depending on the composition). The most successful results were achieved in prepared ceramics from slurries containing 65% ZnO and 1% carboxymethylcellulose, in which the dye decolorization results reached 90.5% after 5 cycles, indicating a high reuse potential of these ceramics. Multivariate analysis proved the negative effect of increasing the heat treatment temperature on the evaluated properties. The best processing conditions to obtain porous ZnO ceramics by the replica technique were established through statistical tools, with very satisfactory results in the photo-decolorization potential of the investigated dye.

The increase in global warming due to NOx, CO2, and CH4 harmfully different ecosystems and significantly prejudice world life. A promising methodology in this sense is the pollutant conversion into valuable chemicals from photocatalytic processes by reusable photocatalyst. In this way, the present work aimed to produce a Nb2O5 photocatalyst nanofibers system to convert CO2 by the electrospinning method. Based on the collected data, the nanofibers calcination at 600°C for 2 h resulted in the best condition to obtain a homogeneous surface with an average diameter of 84 nm. As a result, the Nb2O5 nanofibers converted CO2 mostly into CO and CH4, reaching values around 8.5 μmol g−1 and 0.55 μmol g−1, respectively.

α-Fe2O3 samples were manufactured by means of the polymeric precursor method. The powders were sintered and calcined at temperatures of 300-700 °C for 2 h, respectively. In the X-ray diffraction results, the formation of the rhombohedral phase without secondary phases was exhibited. The size of the particle increased after calcination at 700 °C, exhibiting a slightly more irregular morphology for the samples calcined with the addition of NH4OH in the synthesis process. From the field-emission scanning electron microscopy measurements, the particle size was determined, showing a smaller size for the samples without NH4OH in the synthesis process. The samples calcined at 600 °C had a size of 100 nm, with the sizes for lower temperatures being smaller. The size of the nanoparticle agglomerates was largest for the samples with NH4OH; however, the zeta potential was slightly lower over time for these samples. The phase study of the α-Fe2O3 nanoparticles was confirmed by means of Raman spectroscopy, without additional bands of another crystal structure. In addition, the synthesized nanoparticles exhibited good photocatalytic activity in the degradation of rhodamine B (RhB) and atrazine (ATZ) within 40 min, with a maximum degradation of 59% for ATZ and 40% for rhodamine. The best responses in the degradation were for the samples without the addition of NH4OH in the synthesis process and in proportions lower than 0.1 g. The cytotoxic effects of the nanoparticles obtained at 600 °C were evaluated in apical cells of onion roots. The results are promising for future applications because no changes were observed in the mitosis of the cells.

espanolEn este trabajo se presenta un estudio comparativo de tres metodos en la obtencion de muestras a bajo costo. Las muestras obtenidas son nanopaticulas de oxido de Hierro, oxido de Cobre y nanotubos de Titanio. Las dos primeras fueron obtenidas por el metodo Sol-Gel, precursores polimericos y la tercera muestra por el metodo de anodizacion quimica. Las muestras fueron caracterizadas por metodos opticos como Raman, Rayos X y microscopia electronica de barrido. Los metodos usados para la obtencion de las muestras son metodos quimicos de los cuales se pueden obtener excelentes muestras a un costo bajo y con el uso de laboratorios simples, sobre todo en Colombia donde las inversiones en laboratorios de investigacion es baja hasta el momento. EnglishThe samples obtained are nanopaticules of Iron oxide, copper oxide and Titanium nanotubes. The first two were obtained by the Sol-Gel, polymeric precursors and the third sample by the chemical anodization method. The samples were characterized by optical methods such as Raman, X-rays and scanning electron microscopy. The methods used to obtain the samples are chemical methods from which excellent samples can be obtained at a low cost and with the use of simple laboratories, especially in Colombia where the investment in research laboratories is low so far.

The importance of fertilizers in boosting crop production has motivated the development of novel high-performance systems capable of improving the phosphorus release in the soil. For instance, methods capable of increasing the surface area of fertilizer particles and promoting the solubilization of low-solubility compounds, including phosphates, are highly pursued. This study was aimed at synthesizing hydroxyapatite nanoparticles and investigating their solubility in relation to crystallinity, size, and morphology for phosphorous fertilizer applications. To improve the phosphate ions release, the hydroxyapatite nanoparticles were storage in biodegradable sachets composed of thermoplastic starch/pectin blends with different polymer ratios. The results showed that the smallest and less crystalline hydroxyapatite nanoparticles presented the highest solubility. After storage in polymeric thermoplastic starch:pectin sachets, solubility for all samples was greatly improved, enhancing the phosphorus release due to pH decrease, independent on the nanoparticle size, shape, and crystallinity. The results highlight that the use of acidic sachets is a valuable approach for enhancing phosphorus and other macronutrients release from fertilizers with basic surface properties, aiming at increasing agricultural crop productivity.

Due to the pollution caused by different organic pollutants, various photocatalytic nanomaterials for environmental remediation have been promoted. In this study, Nb2O5 nanofibers were obtained by electrospinning technique, presenting controlled crystallinity and high specific surface area to improve the photoactivity response. The structural characterization indicated Nb2O5 nanofibres with orthorhombic phase formation, and the photoluminescence measurements showed different energy levels contributing to the electronic transition events. The nanofibers with a bandgap up to 3.6 eV were applied to photocatalysis of dyes [Rhodamine B (RhB) or Methylene Blue (MB)], and Prozac®, listed as an emergent pollutant. In the optimized condition (pH = 9), the RhB and MB photocatalysis was 59% and 93% more efficient than photolysis due to ζ = − 50 ± 5 mV for EtOH_550 sample that increased the interaction with MB (cationic) compared to RhB unprotonated (pKa = 3.7). Therefore, Prozac® (pKa = 10.7) was selected due to protonated form at pH = 9 and showed 68% ±1 adsorption in 30 min for EtOH_550. The Prozac® photocatalytic degradation under UV light irradiation was up to 17% higher than the photolytic degradation. The formation of hydroxyl radicals in the photocatalytic system (EtOH_550) was proven by the Coumarine probe assay, corroborating with the greater amount of α-[2-(Methylamino)ethyl]benzylalcohol (MAEB), a by-product obtained after Prozac® oxidation. Additionally, the material achieved specific catalytic activity for the different organic compounds (RhB, MB, or Prozac®), showing that only using dyes may not be ideal to conclude the great material applicability in environmental remediation studies. Therefore, Nb2O5 nanofibers were efficient for the degradation of three different pollutants under UV light, proving to be a viable alternative for environmental remediation.

The textile industry is responsible for most of the consumption and inappropriate disposal of organic and highly toxic pollutants, such as dyes. Therefore, it is necessary to remediate polluting molecules before returning the water to the environment. Photocatalysis is a promising method for dye molecule degradation as it can provide complete mineralization through an efficient photocatalytic process. CuWO4 exhibits a band gap of 2.40 eV and can be excited with visible light, making it economically advantageous for industrial-scale applications. In this work, CuWO4 was synthesized by coprecipitation (CM), microwave-assisted hydrothermal (HM), and polymeric precursor (PPM) methods to evaluate the photocatalytic behavior in response to the different characteristics obtained from the synthesis routes. In photocatalytic measurements for OH· radical generation, the sacrificial agent H2O2 was used, and in order to delay the recombination process sodium oxalate and silver nitrate scavengers were applied under visible light. CuWO4 synthesized by PPM was more efficient in the dye degradation when the Ag+ scavenger was used, indicating that the predominant reaction mechanism was by direct oxidation or hydroxyl radicals. The surface charge (− 38.5 (PPM), − 29.7 (CM), and − 16.2 mV (HM)) influence was more relevant than the specific surface area (1 (PPM), 22 (CM), and 21 m2 g−1 (HM)) of the samples in the photocatalytic process. The complete degradation occurred in 80 min for the samples obtained by CM and HM and only 20 min were necessary for the sample synthesized by PPM.

Various photocatalytic nanomaterials for environmental remediation have been promoted due to the pollution caused by different organic pollutants. In this study, Nb2O5 nanofibers were obtained by electrospinning technique, presenting controlled crystallinity and high specific surface area to improve the photoactivity response. The structural characterization indicated Nb2O5 nanofibers with orthorhombic phase formation. The photoluminescence measurements showed different energy levels contributing to the electronic transition events. The nanofibers with a bandgap up to 3.6 eV were applied to photocatalysis of dyes (rhodamine B (RhB) or methylene blue (MB)) and fluoxetine (FLX), listed as an emergent pollutant. In the optimized condition (pH = 9), the RhB and MB photocatalysis was 59% and 93% more efficient than photolysis due to ζ = - 50 mV ± 5 for EtOH_550 sample increased interaction with MB (cationic) compared to RhB unprotonated (pKa = 3.7). Therefore, FLX (pKa = 10.7) was selected due to protonated form at pH = 9 and showed 68% ± 1 adsorption in 30 min for EtOH_550. The FLX photocatalytic degradation under UV light irradiation was up to 17% higher than the photolytic degradation. The formation of hydroxyl radicals in the photocatalytic system (EtOH_550) was proven by the Coumarine probe assay, corroborating with the greater amount of α-[2-(methylamino)ethyl]benzylalcohol (MAEB), a by-product obtained after FLX oxidation. Additionally, the material achieved specific catalytic activity for the different organic compounds (RhB, MB, or FLX). Therefore, Nb2O5 nanofibers were efficient for degrading three different pollutants under UV light, proving a viable alternative for environmental remediation.

Made available in DSpace on 2021-06-25T10:21:09Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-01-01 This study reports the preparation of TiO2 and CeO2 doped with different quantities of terbium and discusses the influence of this dopant on the photocatalytic activity of the semiconductors, with respect to the degradation of methylene blue, under ultraviolet and solar radiations. The oxides obtained were characterized by X-ray diffraction, infrared vibrational spectroscopy, diffuse reflectance spectroscopy, scanning electron microscopy, and dispersive energy spectroscopy. The results indicate that the presence of the dopant in TiO2 favored the formation of the anatase crystalline phase to the detriment of rutile, increased the band gap energy, and decreased the size of the nanoparticles. Doping CeO2 with Tb resulted in a fluorite-type crystalline structure, reduced band gap, and smaller particle size. The photocatalytic activity decreases as the concentration of terbium increases regardless of the radiation source and nature of the oxide. Furthermore, a better performance was observed for all semiconductors excited by solar radiation in comparison to ultraviolet light. The samples of pure TiO2 and TiO2 doped with 0.5 and 1% terbium showed total removal of the dye after less than 120 min of reaction, while the samples of pure CeO2 and CeO2 doped with 0.5% terbium showed approximately 80% and 57% of dye removal after 120 min, suggesting that these materials can be promising for the treatment of industrial effluents. Sao Paulo State University (Unesp) Institute of Science and Technology Sorocaba, 511 Três de Março Avenue Federal Institute of Education Science and Technology of São Paulo (IFSP) Campus São Roque, 2100 Major Quintino de Lima Highway Sao Paulo State University (Unesp) Institute of Chemistry Araraquara, 55 Prof. Francisco Degni Avenue National Nanotechnology Laboratory for Agriculture (LNNA) Embrapa Instrumentação, 1452 XV de Novembro Street Sao Paulo State University (Unesp) Institute of Science and Technology Sorocaba, 511 Três de Março Avenue Sao Paulo State University (Unesp) Institute of Chemistry Araraquara, 55 Prof. Francisco Degni Avenue

Three different synthesis methods were applied to obtain TiO

TiO2 nanoparticles were efficiently doped with Mn applying microwave-assisted synthesis method. Anatase phase was confirmed by XRD pattern, which did not exhibit the peaks associated with MnOx contamination. Raman spectroscopy showed a displacement of up to 5 cm−1 in the O-Ti-O vibrational mode, suggesting that Ti was replaced by Mn. Oxidation state (Mn3+) was confirmed via high-resolution XPS spectrum of Mn 2p energy level. Incorporation of Mn into the TiO2 network resulted in increased surface area (64.6 m2 g−1), average particle size up to 16 nm, and bandgap reduction of up to 43 %. The photocatalytic properties of the materials were investigated through Prozac® degradation and improvement of up to 14 % (Ti-0.73 Mn) and 26 % (Ti-0.38 Mn) was seen on comparing doped TiO2 versus pure TiO2 during photocatalysis. Furthermore, after Prozac® photodegradation, TFMP was identified as the main by-product while MAEB and PPMA (other by-products) were seen to compete with each other in the degradation mechanism. In addition to the quantitative analysis done for Prozac®, TFMP, MAEB, and PPMA, LC MS-Q-TOF analysis was performed, confirming that in the presence of Mn-doped TiO2, specific by-products were formed, probably due to more oxidizing species being present in this reaction system. The present study has shown unprecedented evidence that the application of TiO2 nanoparticles efficiently doped with Mn promotes Prozac® degradation by specific mechanisms.

Copper oxide (CuO) has been broadly used in different technological and biological applications. However, based on the literature review, there are few reports describing the synthesis of tungsten doped copper oxide and its biological applications, although CuO and W (tungsten) based nanomaterials have been reportedly already synthesized. In this study we synthesized novel CuO and CuO/W (at.1%, 2% and 4%) nanoparticles and explored their tungsten content-dependent bactericide activity. In order to obtain the materials, was used a co-precipitation method which is of low cost. The synthesized materials were characterized by x-ray diffraction (XRD); XRD results indicated that only the sample with at.1% of W presented pure Tenorite phase. Diffuse reflectance spectroscopy (DRS) allowed to obtain the band gap energy values; CuO/W (at.2%) sample exhibited the minimum value of 2.62 eV. Grains sizes ranging from 39.78 to 53.47 nm were established through field emission-scanning electronic microscopy (FE-SEM), and these sizes were confirmed by transmission electron microscopy (TEM). Doping with W also influenced the morphology obtained in all cases. BET (Brunauer, Emmett, Teller) analysis allowed to establish an increase in specific surface area and pore size with W doping. The particle size was determined by dynamic light scattering (DLS). The bactericidal properties were tested using well diffusion method for Escherichia coli and Staphylococcus aureus bacteria. Bactericide response of CuO nanoparticles was improved by the inclusion of W dopant into the CuO structure, leading to an expansion in the inhibition zone for the CuO/W (at.1%) sample; inhibition halo diameters were 1.5 and 12 mm for CuO and CuO/W (at.1%), respectively. Hence, it was possible to infer the remarkable importance of the crystalline phase, morphology, particle size and specific superficial area of the CuO/W (at.1%) nanoparticles in its bactericide performance. WO3 secondary phase affected the bactericide response of the materials obtained at at.2% and at.4% of tungsten content.

N-doped ZnO is a prospective material for photocatalytic reactions. However, only oxidative paths are well investigated in the literature. This paper describes a comparative study about ZnO and ZnO:N potential for oxidative and reductive reactions, probed by rhodamine B dye photodegradation and CO2 photoreduction. The materials were prepared by the polymeric precursor method, using urea as a nitrogen source, and different heat treatments were used to observe their effects on surface decontamination, crystallinity, particle sizes and shapes, and photocatalytic performance. ZnO and ZnO:N presented a wurtzite crystalline structure and nanometric-scale particles. Samples submitted to higher temperatures showed lower specific surface areas, but higher crystallinity and lower contents of species adsorbed on their surfaces. On the other hand, the photocatalysts annealed in shorter times presented smaller crystallite sizes and lower crystallinity. These factors influenced the photoactivity in both conditions, i.e., oxidation and reduction reactions, under the ultraviolet and visible light, indicating that structural factors influenced the adequate charge separation and consequent photocatalytic activity since the as-synthesized samples were versatile photocatalysts in both redox reactions.

This paper aims to evaluate the effects of calcination temperature and manganese doping on optical properties and phase evolution of Mn-doped TiO2 pigments. The powders were prepared by the polymeric precursor method at Mn contents of 0, 1, 2 and 3 % and calcined at 600, 700 and 800 °C. The results demonstrated that crystalline powders were produced in all conditions evaluated. It was further noted that the samples calcined at 600 °C were composed of rutile and anatase TiO2 polymorphs. However, the anatase phase was completely converted into rutile at temperatures above 700 °C. The particle size increased with increasing temperature. The same behavior was observed for the measured crystallite sizes. The Mn3+ ion charge was determined as the main valence for manganese ions in the TiO2 host. Oxygen vacancies are the probable crystal defects formed for charge balancing in the Mn-doped rutile structure. The results obtained for the powder with 3 % Mn and calcined at 800 °C demonstrated dopant cation segregation to form Mn2O3. It is important to emphasize that the absorbance values of the powders increase in the visible range when adding manganese compared to the absorbance values of pure TiO2. The band gap of the powders was reduced in accordance with the content of doping: from 3.04 eV (0 % Mn) to 2.05–2.20 eV (3 % Mn), with small differences depending on the calcination temperature. The increase in visible light absorbance led to a brown color in Mn-doped materials. Thus, the color intensity varied with the Mn content, ranging from light brown to dark brown powders. In conclusion, the temperature of 700 °C was established in this paper as the best condition to produce Mn-doped TiO2 pigments, based on the absence of anatase polymorph, small contents of residual carbon, and undetectable amounts of Mn2O3 due to segregation.

The advance of nanotechnology has enabled the development of materials with optimized properties for applications in agriculture and environment. For instance, nanotechnology-based fertilizers, such as the candidate hydroxyapatite (HAp) nanoparticles (Ca10(PO4)6(OH)2), can potentially increase the food production by rationally supplying phosphorous to crops, although with inferior mobility in the environment (when compared to the soluble counterparts), avoiding eutrophication. Nonetheless, the widespread consumption of nanofertilizers also raises concern about feasible deleterious effects caused by their release in the environment, which ultimately imposes risks to aquatic biota and human health. Nanoparticles characteristics such as size, shape, surface charge and chemical functionality strongly alter how they interact with the surrounding environment, leading to distinct levels of toxicity. This investigation aimed to compare the toxicity of different HAp nanoparticles, obtained by two distinct chemical routes, against algae Pseudokirchneriella subcapitata, which composes the base of the aquatic trophic chain. The as synthesized HAp nanoparticles obtained by co-precipitation and co-precipitation followed by hydrothermal method were fully characterized regarding structure and morphology. Toxicity tests against the microalgae were carried out to evaluate the growth inhibition and the morphological changes experienced by the exposition to HAp nanoparticles. The results showed that high concentrations of coprecipitated HAp samples significantly decreased cell density and caused morphological changes on the algal cells surface when compared to HAp obtained by hydrothermal method. HAp nanoparticles obtained with dispersing agent ammonium polymethacrylate (APMA) indicated negligible toxic effects for algae, due to the higher dispersion of HAp in the culture medium as well as a reduced shading effect. Therefore, HAp nanoparticles obtained by the latter route can be considered a potential source of phosphorous for agricultural crops in addition to reduce eutrophication.

Zinc oxide nanoparticles (ZnO NPs) have been widely employed in technological applications due to their appealing properties for catalytic, optoelectronic and antimicrobial applications. Moreover, ZnO NPs can also be employed in fertilizers as a source of zinc micronutrient, which is a primary element for enzymes and proteins synthesis in plants, allowing their regular growth and improving crop productivity. However, the extensive use of nanoparticles as a source of fertilizers in agricultural activities also raises concerns once nanoparticle features including surface charge, chemical fucntionalittes, size and shape can alter the toxicity of NPs. In this scenario, the toxicity of distinct ZnO NPs towards microalgae

The elucidation of photocatalysis and adsorption mechanisms in the pollutant removal, as well as the efficiency for each process, provide key information for polluted water remediation. In this respect, the present study analyzed the application of nanomaterials based on niobium pentoxide (Nb2O5) and hydroxyapatite (HAP) during Prozac® and 4-(trifluoromethyl)phenol (TFMP) photodegradation. Removals for Prozac® and TFMP were respectively 93% after 2 min and 64% after 5 min. The photodegradation kinetic constants by Nb2O5 nanoparticles were 2.1 min‐1 (R2 = 0.943) and 0.185 min‐1 (R2 = 0.994), respectively, for Prozac® and TFMP, using a Hg-MDEL reactor operating at 70 W microwave power. A detailed study of the mechanisms for Prozac® and TFMP photodegradation was carried out, confirming that the adsorptive, oxidative, and photolytic processes work together to remove and/or convert the compounds into by-products. Therefore, Prozac® and the main by-products were quantified, and the cytotoxicity response was evaluated using the Lepidium sativum and Allium cepa plants. The results showed that 3-phenyl-propyl-methylamine (PPMA) by-product was more toxic than Prozac® to plant growth, exhibiting seed seability of 4% (PPMA), 33% (Prozac®), 77% (α-[2-(Methylamino) ethyl] benzyl-alcohol, MAEB), and 81% (TFMP). Furthermore, the presence of these contaminants may increase phytotoxicity at the cellular level, fostering mutation, and cell death.

Several studies reported that modifying CuO with CuWO4 can increase its photoactivity. In this study, copper and tungsten heterostructure materials were synthesized via a simple sol-gel method using ammonium paratungstate. The temperature’s influence (300, 500, 700, and 900 °C) was analyzed in the structural, morphological, microstructural, and optical properties of Cu and W materials using X-ray diffraction, infrared spectroscopy, field emission-scanning electron microcopy, transmission electron microscopy, diffuse reflectance spectroscopy, and dynamic light-scattering studies. The CuO diffraction patterns exhibited a tenorite phase formation, and the copper-tungsten materials diffractograms demonstrated the formation of CuO/CuWO4 at 300 and 500 °C and CuO/CuWO4/Cu2WO4/WO3 materials at 700 and 900 °C with crystallite sizes from 25 to 56 nm. Intense vibrational modes obtained at 300 °C for the CuWO4 phase decreased at 500 °C. Therefore, 500 °C is not a temperature that promotes CuO/CuWO4 heterostructure formation. Analyses conducted using microscopy techniques demonstrated the morphology of the CuO/CuWO4 heterostructure obtained at 300 °C, where CuWO4 nanoparticles covered the CuO polyhedral; microstructural analysis verified the heterostructure’s formation. The synthesized materials at 300 °C had an optical band gap of 2.66 eV (direct gap) and 1.35 eV and 2.11 eV (indirect gap), which were lower values than those of the CuO and CuWO4. The temperature at 300 °C proved to be optimal for the formation of the CuO/CuWO4 heterostructure. Only the material obtained at 300 °C exhibited a photocatalytic response in the rhodamine B degradation due to a possible interfacial charge transfer between the CuWO4 and CuO. The synthesis process used to obtain the CuO/CuWO4 heterostructure was novel, with a short processing time, low energy consumption and cost, and environmentally friendly properties.

Developing synthetic routes that lead to the formation of zeolites with small porous systems, such as GIS zeolites, has attracted great interest since these structures have unique properties in catalysis and adsorption, but are still underused. In this study, GIS type zeolite nanoparticles were synthesized by the microwave-assisted hydrothermal method. Two synthesis routes were evaluated using two different silica precursor sources. Silicon dioxide was used in crystalline and amorphous forms. The material was characterized by X-ray diffraction (XRD), nitrogen physisorption, zeta potential (ZP), high-resolution scanning electron microscopy (SEM-FEG), high-resolution transmission electron microscopy (HRTEM) and by energy dispersive X-ray spectroscopy (EDS). The obtained crystalline phase was the Na–P1 type zeolite (GIS structure). The BET surface area of the particles was 17 m2/g and the average pore size was 4 nm. These zeolites were used for Mn(II) ions adsorption in aqueous medium. Considering the studied adsorption conditions, adsorption was higher at pH 8, using an adsorbent concentration of 1 g/L and with 30 min of contact time. The kinetic model that best described the process was the pseudo-second order model and the isotherm model that best fitted to the experimental data was the Langmuir model, which indicates adsorption in monolayers and high affinity between the adsorbate and the adsorbent. The maximum adsorption capacity was 44.05 mg/g.

β-Glucosidase is an enzyme of great industrial interest that is used in biorefineries and in the pharmaceutical, food, and beverage sectors, among others. These industrial processes would benefit from the use of immobilized enzyme systems that allow several reuses of the enzyme. A promising inorganic and nontoxic material for such application is hydroxyapatite (HA), which can be synthesized at nanometric scale, hence providing good accessibility of the substrate to the catalyst. Here, we carried out a systematic study to evaluate the feasibility of immobilizing β-glucosidase on HA nanoparticles. The immobilization process was highly effective over wide ranges of pH and ionic strength, resulting in immobilization yields and recovered activities up to 90%. Investigation of the type of interaction between β-glucosidase and HA (using FT-IR, zeta potential measurements, and desorption tests with different salts) indicated the formation of coordination bonds between Ca2+ sites of HA and COO− of amino acids. Even after 10 cycles of reuse, the immobilized β-glucosidase retained about 70% of its initial activity, demonstrating the operational stability of the immobilized enzyme. The results showed that β-glucosidase could be efficiently immobilized on HA nanoparticles by means of a very simple adsorption protocol, offering a promising strategy for performing repeated enzymatic hydrolysis reactions.

This article reports a simple one-pot route to synthesize TiO 2 /WO 3 nano-heterostructures applied as photocatalysts to the degradation of water contaminants. The method was based on the formation of a polymeric structure from Ti and W complexes that were evenly distributed in the precursor to avoid phase separation during calcination steps. This strategy was shown to effectively produce the desired heterostructures, which were well-distributed and possessed interesting photocatalytic activities when compared with pristine oxides. Characterization of the heterostructures showed possible doping of each oxide, which may interfere with electronic properties. Additionally, an increase in surface area was observed according to TiO 2 proportions. However, high-resolution electron microscopy confirmed that the heterostructures were properly obtained, and photoluminescence experiments were well correlated to catalytic activities. The results indicated higher efficiencies for heterostructures with higher contents of WO 3 , although improved activity was observed for the material with 50 wt% of each oxide. This facile synthesis, and the remarkable properties observed for this heterostructured catalytic material, confirmed that this route is a candidate for high production, allowing its application in solving real environmental problems.

Heterostructured nanomaterials have attracted increasing interest because of their novel and distinct optical and electrical properties, finding applications in devices and chemical sensors. Here we report a new electrochemical platform based on the modification of fluorine doped tin oxide (FTO) electrodes with polyamide 6/polyaniline (PA6/PANI) electrospun nanofibers decorated with ZnO nanoparticles. The nanoparticles were synthesized by a co-precipitation method, followed by hydrothermal treatment; the route was optimized in order to obtain particles of small average diameter (45 nm). Polymeric nanofibers were obtained by the electrospinning technique and further subjected to ZnO modification by nanoparticle impregnation. SEM images confirmed the uniform distribution of ZnO nanoparticles adsorbed onto the nanofiber surface, the amount of which was estimated to be 4% w/w, according to thermal gravimetric analysis (TGA). According to the electrochemical characterization, an improvement in electron transfer kinetics and increase in electroactive area was observed for the ZnO-modified FTO electrode. The modified electrode was employed for monitoring hydrazine, and yielded a detection limit of 0.35 μmol L−1. Our results indicate that the novel sensing platform based on the adsorption of ZnO nanoparticles onto the surface of electrospun nanofibers can be potentially harnessed for electrochemical sensor and biosensor applications.

This article describes a study of the influence of parameters of the hydrothermal synthesis on the structural characteristics and photocatalytic activity of the materials synthesized from peroxytitanium complex precursor. The materials were characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning and transmission electron microscopy (SEM and TEM). The active oxidative species produced on the photocatalyst surface were investigated by measuring the fluorescence derived from their reaction with terephthalic acid (TPA). Also, the photocatalytic efficiency of the synthesized materials was assessed by monitoring the degradation of the methylene blue (MB) dye. The morphological characteristics and photocatalytic efficiency of the synthesized materials exhibited greater dependence on temperature than time of synthesis. The photocatalytic results show that the main factor for the effectiveness of the synthesized materials was crystallinity. Furthermore, it was observed that the photodegradation process occurred by the attack of active radicals on the MB molecules and not by the direct oxidation of adsorbed MB molecules on the photocatalyst surface.

This paper presents the development and optimization of the synthesis of magnetic nanoparticles composed of iron oxides by a solvothermal method with benzyl alcohol using iron(III) chloride hexahydrate as a metallic precursor in the substitution of iron(III) acetylacetonate. The synthesis parameters were studied and varied to obtain a high yield of magnetite. Metallic iron was evaluated as a reducing agent and iron source. Furthermore, the use of urea as a precipitation agent was crucial to increasing the yield of magnetite, at once reducing the acidity of the medium and inducing the precipitation of Fe2+ ions. Longer treatment times and no stirring led to an increase in the yield of magnetite, whose formation process followed the Ostwald step rule. The particles were characterized by X-ray diffraction, M¨ossbauer spectroscopy, FTIR, TEM, SEM-FEG and VSM (Vibrating Sample Magnetometry). The phases were quantified by the Rietveld method and M¨ossbauer spectroscopy, and a 97% maximum yield of magnetite was achieved. The polymerization of benzyl alcohol during the solvothermal treatment was shown to play an important role in the nanoparticle capping. The polymerized resin was characterized by FTIR and NMR-1H, and a mechanism for the polymerization reaction was proposed to elucidate the synthetic route and its relationship to particle formation and stability.

This paper evaluates the influence of the hydrothermal treatment temperature on the phase formation, structure and photocatalytic potential of Nb2O5 nanoparticles obtained by the oxidant-peroxo method (OPM). The materials were characterized by X-ray diffraction (XRD), Raman spectroscopy, UV–vis diffuse reflectance spectroscopy (DRS), scanning and transmission electron microscopy (SEM and TEM), thermogravimetry (TGA), Fourier transform infrared spectrometry (FTIR) and N2 adsorption isotherms. The photocatalytic efficiency of the Nb2O5 nanoparticles and the mechanism of degradation were evaluated with respect to the degradation of the contaminants: rhodamine B (RhB) and atrazine under UV and visible radiation. The synthesized nanoparticles presented mixed phases of Nb2O5 orthorhombic and Nb2O5·nH2O, with particle size ranging from 30 to 40 nm and specific surface area ranging from 129 to 199 m2/g. The results showed that the nanoparticles can be applied as catalysts for photoactivated reactions. The rate constant of RhB photodegradation in the reaction catalyzed by the Nb2O5 samples was approximately 5 times higher than the rate observed for RhB direct photolysis (RhB self-photolysis), and approximately 2 times higher than RhB photodegradation catalyzed by TiO2 (reference). The surface hydroxylation and crystallinity were the most important parameters for the photoactivity per unit area of the Nb2O5 nanoparticles obtained at lower (100 and 125 °C) and higher (150 and 175 °C) hydrothermal temperatures, respectively. Furthermore, under UV radiation, the main photodegradation mechanism occurred by the attack of OH radicals on the molecules (RhB and atrazine) and not by the direct oxidation of adsorbed molecules on the photocatalyst surface. Dye-sensitized photocatalysis was the main mechanism for RhB degradation under visible radiation.

Resumo A gestão do uso da água no ambiente agrícola é fator decisivo para a construção de métodos produtivos ambientalmente sustentáveis. A fotocatálise é um método promissor para a descontaminação de águas. Este artigo teve como proposta avaliar o potencial fotocatalítico de partículas de ZnO puro e dopado com manganês. Estes materiais foram produzidos pelo método dos precursores poliméricos e caracterizados por difratometria de raios X, adsorção de N2 em baixa temperatura, espectroscopia na região do infravermelho e do ultravioleta e fotoluminescência. Para avaliação da eficiência dos fotocatalisadores obtidos, ensaios de fotodegradação foram realizados utilizando-se o corante azul de metileno sob radiação UVC. As partículas apresentaram-se monofásicas, porém com baixa área superficial específica. A amostra de ZnO com teor de dopagem de 0,25% de Mn apresentou maior eficiência no processo fotocatalítico para a degradação do corante azul de metileno. Esta eficiência foi relacionada com o maior valor de energia de band gap e menor taxa de recombinação eletrônica, o que permite maior formação de radicais de hidroxila, compostos estes responsáveis pela degradação do corante. Abstract The management of water use in the agricultural environment is a key factor to build new environmentally sustainable productive methods. Photocatalysis is a promising method for water decontamination. This research paper aimed to evaluate the photocatalytic potential of pure and Mn-doped ZnO particles. The materials were obtained by the polymeric precursor method, and characterized by X-ray diffraction, N2 adsorption in low temperature, infrared and ultraviolet spectroscopy, and photoluminescence. In order to evaluate ZnO:Mn particles photoefficiency, experiments were carried out by applying the methylene blue dye solution to photodegradation under UVC exposure. The particles had ZnO single-phase, but low specific surface area. The sample ZnO:0.25% Mn presented higher efficiency in the methylene blue photocatalytic degradation test. This efficiency was related to a higher band gap energy value and a lower rate of electron recombination, which allows greater formation of hydroxyl radicals, which are responsible for dye degradation.

This paper shows a comparison between different nanostractured oxides, obtained by polymeric precursor method, regarding their activity for biodiesel conversion from oil-methanol mixtures. The basicity/acidity and surface area (SA) of the oxides were taken in account to analyze the catalytic activity in the transesterification reaction. The temperature dependence for the heterogeneous catalysts was analyzed, where only CaO showed activities at 70 °C (β-98% of conversion), while the other oxides, SnO2, ZnO, TiO2, CaTiO3, were observed active only at 150 °C for the reaction parameters adopted. The results revealed that the highest activity observed is not associated to SA only but mainly with the surface basicity. This suggest that, for oxides synthesized by the polymeric precursor method, the surface basicity surpasses the particle size effects in catalysis in a way to promote the transesterification reaction.

Summary: This work evaluated the influence of the synthesis temperature on the polyaniline (PANI) properties obtained by in-situ polymerization onto a poly (terephthalate) (PET) substrate. The residual mass of these syntheses was dried under vacuum, obtaining PANI powders for each temperature investigated. PANI/PET thin films and PANI powders were characterized by atomic force microscopy (AFM), field emission scanning electron microscopy (FEG-SEM), X-ray diffraction (XRD), ultraviolet-visible spectroscopy (UV-Vis) and four-point probe techniques. The UV-Vis results showed that the synthesized PANI presents the emeraldine oxidation state. By means of XRD technique, it was possible to verify that the PANI powders present crystalline form. The AFM and FEG-SEM techniques showed that the decrease in PANI/PET and PANI powders electrical conductivity with increasing of the synthesis temperature is related to the polymeric aggregates morphology.

This paper reports the synthesis of Eu-doped hydroxyapatite (HA:Eu) resulting in particles with nanorod diameters from 9 to 26 nm using the microwave hydrothermal method (HTMW). Eu 3+ ions were used as a marker in the HA network by basic hydrolysis followed by the HTMW treatment. The crystalline HA:Eu nanorod nature in a short-range order was detected by photoluminescence (PL) measurements from Eu 3+ emission into the HA matrix. Thus, was possible to verify that HA crystallization is favored in a short structural order when the HTMW treatment time was increased from 0 to 40 min and that the Eu 3+ substitution in the HA lattice is site-selective.

Lead Titanate Zirconate (PZT) perovskite powders were synthesized by microwave hydrothermal method (M-H) at 180 °C for different time periods (2, 4, 8 and 12 h) with the presence of aqueous polyvinyl alcohol (PVA) solution 0.36 g L−1. The X-Ray diffraction (XRD), SE-FEG as well as the measurements of photoluminescence (PL) emission were used for monitoring the formation of a perovskite phase with random polycrystalline distortion in the structure. Emission spectra with fixed excitation wavelength of 350 nm showed higher value for the powder obtained after undergoing 8 h of treatment. A theoretical model derived from previous calculations allows us to discuss the origin of photoluminescence emission in the powders, which can be further related to the local disorder in the network of both ZrO6 and TiO6 octahedral, and dodecahedral PbO12. The new morphology initially observed from the PZT perovskite crystal growth bearing the shape of fine plates is found to be directly related to photoluminescence emission with energy lower than that present in the PZT with cube-like morphology that emits in 560 nm.

Nanostructural β-nickel hydroxide (β-Ni(OH) 2 ) plates were prepared using the microwave–hydrothermal (MH) method at a low temperature and short reaction times. An ammonia solution was employed as the coordinating agent, which reacts with [Ni(H 2 O) 6 ] 2+ to control the growth of β-Ni(OH) 2 nuclei. A trigonal β-Ni(OH) 2 single phase was observed by X-ray diffraction (XRD) analyses, and the crystal cell was constructed with structural parameters and atomic coordinates obtained from Rietveld refinement. Field emission scanning electron microscopy (FE-SEM) images revealed that the samples consisted of hexagonal-shaped nanoplates with a different particle size distribution. Broad absorption bands assigned as transitions of Ni 2+ in oxygen octahedral sites were revealed by UV–vis spectra. Photoluminescence (PL) properties observed with a maximum peak centered in the blue-green region were attributed to different defects, which were produced during the nucleation process. We present a growth process scheme of the β-Ni(OH) 2 nanoplates.

CaxSr1−xTiO3 samples were synthesized by the microwave-assisted hydrothermal method. The X-ray diffraction results indicate that strontium calcium titanates powders show two crystalline structures: perovskite cubic and orthorhombic. The ultraviolet-visible spectra show that the band gap energies decrease with the Ca addition, suggesting imperfections or defects in the forbidden band of the titanates. The photoluminescence spectra show a broad band, which is usually observed at low temperatures in perovskite-type crystals. The nanoparticles show a nonuniform distribution with polyhedral morphology and spherical agglomerates, which change to faceted surfaces suggesting that the sample can reach other morphologies which ensure symmetry of lowest energy.

This article reports a theoretical study based on experimental results for barium zirconate, BaZrO3 (BZ) thin films, using periodic mechanic quantum calculations to analyze the symmetry change in a structural order-disorder simulation. Four periodic models were simulated using CRYSTAL98 code to represent the ordered and disordered BZ structures. The results were analyzed in terms of the energy level diagrams and atomic orbital distributions to explain and understand the BZ photoluminescence properties (PL) at room temperature for the disordered structure based on structural deformation and symmetry changes. V C 2009 Wiley Periodicals, Inc. Int J Quantum Chem 111: 694-701, 2011