Green Synthesis of Er-Doped ZnO Nanoparticles: An Investigation on the Methylene Blue, Eosin, and Ibuprofen Removal by Photodegradation

We present a study on the green synthesis of undoped and Er-doped ZnO compounds using Mangifera indica gum (MI). A set of tests were conducted to assess the structure of the material. The tests included X-ray diffraction, Raman, and Fourier-transform infrared spectroscopy. Optical properties were studied using diffuse reflectance and photoluminescence. Morphological and textural investigations were done using SEM images and N2 adsorption/desorption. Furthermore, photocatalytic tests were performed with methylene blue (MB), yellow eosin (EY), and the pharmaceutical drug ibuprofen (IBU) under UV irradiation. The study demonstrated that replacing the stabilizing agent with Mangifera indica gum is an effective method for obtaining ZnO nanoparticles. Additionally, the energy gap of the nanoparticles exhibits a slight reduction in value. Photoluminescence studies showed the presence of zinc vacancies and other defects in both samples. In the photocatalytic test, the sample containing Er3+ exhibited a degradation of 99.7% for methylene blue, 81.2% for yellow eosin, and 52.3% for ibuprofen over 120 min. In the presence of methyl alcohol, the degradation of MB and EY dyes is 16.7% and 55.7%, respectively. This suggests that hydroxyl radicals are responsible for the direct degradation of both dyes. In addition, after the second reuse, the degradation rate for MB was 94.08%, and for EY, it was 82.35%. For the third reuse, the degradation rate for MB was 97.15%, and for EY, it was 17%. These results indicate the significant potential of the new semiconductor in environmental remediation applications from an ecological synthesis.

Carbon Nanomaterial-Based Hydrogels as Scaffolds in Tissue Engineering: A Comprehensive Review

Carbon-based nanomaterials (CBNs) are a category of nanomaterials with various systems based on combinations of sp2 and sp3 hybridized carbon bonds, morphologies, and functional groups. CBNs can exhibit distinguished properties such as high mechanical strength, chemical stability, high electrical conductivity, and biocompatibility. These desirable physicochemical properties have triggered their uses in many fields, including biomedical applications. In this review, we specifically focus on applying CBNs as scaffolds in tissue engineering, a therapeutic approach whereby CBNs can act for the regeneration or replacement of damaged tissue. Here, an overview of the structures and properties of different CBNs will first be provided. We will then discuss state-of-the-art advancements of CBNs and hydrogels as scaffolds for regenerating various types of human tissues. Finally, a perspective of future potentials and challenges in this field will be presented. Since this is a very rapidly growing field, we expect that this review will promote interdisciplinary efforts in developing effective tissue regeneration scaffolds for clinical applications.

Substrate-Induced Changes on the Optical Properties of Single-Layer WS2

Among the most studied semiconducting transition metal dichalcogenides (TMDCs), WS2 showed several advantages in comparison to their counterparts, such as a higher quantum yield, which is an important feature for quantum emission and lasing purposes. We studied transferred monolayers of WS2 on a drilled Si3N4 substrate in order to have insights about on how such heterostructure behaves from the Raman and photoluminescence (PL) measurements point of view. Our experimental findings showed that the Si3N4 substrate influences the optical properties of single-layer WS2. Beyond that, seeking to shed light on the causes of the PL quenching observed experimentally, we developed density functional theory (DFT) based calculations to study the thermodynamic stability of the heterojunction through quantum molecular dynamics (QMD) simulations as well as the electronic alignment of the energy levels in both materials. Our analysis showed that along with strain, a charge transfer mechanism plays an important role for the PL decrease.

Study of Structural and Optical Properties of Titanate Nanotubes with Erbium under Heat Treatment in Different Atmospheres

Titanate nanotubes were synthesized and subjected to an ion exchange reaction with erbium salt aqueous solution to obtain titanate nanotubes exchanged with erbium (3+) ions. In order to evaluate the effects of the thermal treatment atmosphere on the structural and optical properties of erbium titanate nanotubes, we subjected them to heat treatment in air and argon atmospheres. For comparison, titanate nanotubes were also treated in the same conditions. A complete structural and optical characterizations of the samples was performed. The characterizations evidenced the preservation of the morphology with the presence of phases of erbium oxides decorating the surface of the nanotubes. Variations in the dimensions of the samples (diameter and interlamellar space) were promoted by the replacement of Na⁺ by Er³⁺ and the thermal treatment in different atmospheres. In addition, the optical properties were investigated by UV-Vis absorption spectroscopy and photoluminescence spectroscopy. The results revealed that the band gap of the samples depends on the variation of diameter and sodium content caused by ion exchange and thermal treatment. Furthermore, the luminescence strongly depended on vacancies, evidenced mainly by the calcined erbium titanate nanotubes in argon atmosphere. The presence of these vacancies was confirmed by the determination of Urbach energy. The results suggest the use of thermal treated erbium titanate nanotubes in argon atmosphere in optoelectronics and photonics applications, such as photoluminescent devices, displays, and lasers.

Biochar Obtained from Caryocar brasiliense Endocarp for Removal of Dyes from the Aqueous Medium

Given the increase in environmental pollution, especially of water, the emergence of studies that seek to develop strategies to mitigate/treat such effects have gained prominence in the world scientific community. Among the numerous adsorption processes, those made from biochar production stand out. This study analyzed the adsorption properties of the blue methylene model dye in the aqueous solution of biochar and activated biochar developed from pequi (Caryocar brasiliense) endocarp. The biochar was characterized, before and after adsorption, by infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffractometry (XRD), and thermogravimetric analysis (TG). The surface load of the materials was performed by the point of zero charge (pH_PZC) method. The study also included analyses of contact time parameters and adsorbed concentration in the adsorption process. Morphological analysis showed that a more significant and profound number of fissures and pores appeared in the activated biochar compared to the biochar. Residual mass analysis evidenced that biochar lost about 15% more mass than the activated biochar, indicating that activation occurred satisfactorily. The adsorption process was well adjusted by pseudo-second-order kinetics and Langmuir's isothermal model. The activated biochar achieved an excellent adsorption capacity of 476.19 mg.g^-1, thus demonstrating to be a sound system for removing dyes from an aqueous medium.

Amino-Functionalized Titanate Nanotubes: pH and Kinetic Study of a Promising Adsorbent for Acid Dye in Aqueous Solution

This work reports the functionalization of sodium titanate nanotubes with amine groups obtained from the reaction of titanate nanotubes with [3-(2-Aminoethylamino)propyl]trimethoxysilane, NaTiNT-2NH, and 3-[2-(2-Aminoethylamino)ethylamino]propyltrimethoxysilane, NaTiNT-3NH. It was verified that the crystalline and morphological structures of NaTiNT were preserved after the functionalization, spectroscopies showed that aminosilane interacted covalently with the surface of NaTiNT, and the incorporation of the aminosilane groups on the surface of NaTiNT can be confirmed. The adsorbent matrices NaTiNT-2NH and NaTiNT-3NH were used to remove the anionic dye from remazol blue R (RB) in aqueous medium, and the highest adsorption capacity was around 365.84 mg g-1 (NaTiNT-2NH) and 440.70 mg g-1 (NaTiNT-3NH) in the range of pH 5.0 to 10.0 and the equilibrium time was reached in 210 min (NaTiNT-2NH) and 270 min (NaTiNT-3NH). Furthermore, the Elovich model, which reports the adsorption in heterogeneous sites and with different activation energies in the chemisorption process, was the most appropriate to describe the adsorption kinetics. Thus, these adsorbent matrices can be used as an alternative potential for dye removal RB in aqueous solution.

Effects of the Incorporation of Distinct Cations in Titanate Nanotubes on the Catalytic Activity in NOx Conversion

Effects of the incorporation of Cr, Ni, Co, Ag, Al, Ni and Pt cations in titanate nanotubes (NTs) were examined on the NO_x conversion. The structural and morphological characterizations evidenced that the ion-exchange reaction of Cr, Co, Ni and Al ions with the NTs produced catalysts with metals included in the interlayer regions of the trititanate NTs whereas an assembly of Ag and Pt nanoparticles were either on the nanotubes surface or inner diameters through an impregnation process. Understanding the role of the different metal cations intercalated or supported on the nanotubes, the optimal selective catalytic reduction of NO_x by CO reaction (SCR) conditions was investigated by carrying out variations in the reaction temperature, SO₂ and H₂O poisoning and long-term stability runs. Pt nanoparticles on the NTs exhibited superior activity compared to the Cr, Co and Al intercalated in the nanotubes and even to the Ag and Ni counterparts. Resistance against SO₂ poisoning was low on NiNT due to the trititanate phase transformation into TiO₂ and also to sulfur deposits on Ni sites. However, the interaction between Pt²⁺ from PtO_x and Ti⁴⁺ in the NTs favored the adsorption of both NO_x and CO enhancing the catalytic performance.

Biomineralization inspired engineering of nanobiomaterials promoting bone repair

A biomineralization processes is disclosed for engineering nanomaterials that support bone repair. The material was fabricated through a hot press process using electrospun poly(lactic acid) (PLA) matrix covered with hybrid composites of carbon nanotubes/graphene nanoribbons (GNR) and nanohydroxyapatite (nHA). Various scaffolds were devised [nHA/PLA, PLA/GNR, and PLA/nHA/GNR (1 and 3%)] and their structure and morphology characterized through Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDS), and Atomic force microscope (AFM). Moreover, thorough biocompatibility and toxicity studies were performed. Here, in vivo studies on toxicity and cytotoxicity were conducted in aqueous dispersions of the biomaterials at concentrations of 30, 60, and 120 μg/mL using the Allium cepa test. Further toxicity studies were performed through hemolysis toxicity tests and genotoxicity tests evaluating the damage index and damage frequencies of DNAs through comet assays with samples of the animals' peripheral blood, marrow, and liver. Additionally, the regenerative activity of the scaffolds was analyzed by measuring the cortical tibiae of rats oophorectomized implanted with the biomaterials. Biochemical analyzes [glutamic pyruvic transaminase (GPT), glutamic oxaloacetic transaminase (GOT), urea, calcium, phosphorus, and alkaline phosphatase (ALP)] were also performed on blood samples. The results suggested a toxicity and cytotoxicity level for the GNR biomaterials at a concentration of 60 and 120 μg/mL, but non-toxicity and cytotoxicity for the 30 μg/mL concentration. The scaffolds obtained at a concentration of 0.3 mg/cm² were not toxic in the hemolysis test and demonstrated no cytotoxicity, genotoxicity, and mutagenicity in the blood, marrow, and liver analyzes of the animals, corroborating data from the biochemical markers of GPT, GOT, and urea. Tissue regeneration was performed in all groups and was more pronounced in the group containing the combination of nHA/GNR (3%), which is consistent with the data obtained for the calcium, serum phosphorus, and ALP concentrations. Consequently, the study indicates that the engineered nanobiomaterial is a promising candidate for bone tissue repair and regenerative applications. STATEMENT OF SIGNIFICANCE: The scientific contribution of this study is the engineering of a synthetic hybrid biomaterial, in nanoscale by a pressing and heating process. A biodegradable polymeric matrix was covered on both sides with a carbonated hybrid bioceramic/graphene nanoribbons (GNR), which has hydrophilic characteristics, with chemical elements stoichiometrically similar to bone mineral composition. The nanomaterial displayed promising bone regeneration ability, which is the first example to be used in an osteoporotic animal model. Moreover, detailed biocompatibility and toxicity studies were performed on the nanomaterials and their compositions, which is of great interest for the scientific community.

Temperature-dependent phonon dynamics and anharmonicity of suspended and supported few-layer gallium sulfide

Phonons play a fundamental role in the electronic and thermal transport of 2D materials which is crucial for device applications. In this work, we investigate the temperature-dependence of A[Formula: see text] and A[Formula: see text] Raman modes of suspended and supported mechanically exfoliated few-layer gallium sulfide (GaS), accessing their relevant thermodynamic Grüneisen parameters and anharmonicity. The Raman frequencies of these two phonons soften with increasing temperature with different [Formula: see text] temperature coefficients. The first-order temperature coefficients θ of A[Formula: see text] mode is ∼ -0.016 cm^-1/K, independent of the number of layers and the support. In contrast, the θ of A[Formula: see text] mode is smaller for two-layer GaS and constant for thicker samples (∼ -0.006 2 cm^-1 K^-1). Furthermore, for two-layer GaS, the θ value is ∼ -0.004 4 cm^-1 K^-1 for the supported sample, while it is even smaller for the suspended one (∼ -0.002 9 cm^-1 K^-1). The higher θ value for supported and thicker samples was attributed to the increase in phonon anharmonicity induced by the substrate surface roughness and Umklapp phonon scattering. Our results shed new light on the influence of the substrate and number of layers on the thermal properties of few-layer GaS, which are fundamental for developing atomically-thin GaS electronic devices.

A novel green approach based on ZnO nanoparticles and polysaccharides for photocatalytic performance

Novel green photocatalysts based on ZnO in the presence of arabic gum (AGZ) or karaya gum (KGZ) were synthesized by a sol-gel method for photocatalytic performance. The materials were characterized by XRD, FTIR spectroscopy, SEM, nitrogen adsorption/desorption, and PL and diffuse reflectance spectroscopy. Photocatalytic test was performed using methylene blue (MB) dye as the target pollutant under visible light. The reuse of photocatalysts and Artemia saline bioassays were investigated. The ZnO nanoparticles showed a hexagonal structure and the values of the band gaps were 2.95 (AGZ) and 2.98 eV (KGZ). The PL results demonstrated emission bands at 440, 473 or 478 and 549 nm. The textural properties indicated the presence of typically mesoporous materials. The MB discoloration efficiency was 81.5% and 91.0% for AGZ and KGZ, respectively. The photocatalytic activity of AGZ and KGZ was maintained after the third run. The ˙OH radicals are the main species involved in the MB discoloration. The MB discoloration from the photocatalysts showed no toxicity; therefore, they are considered to be promising materials for the degradation of the dye in the photocatalytic process.

Rotary-jet spun polycaprolactone/nano-hydroxyapatite scaffolds modified by simulated body fluid influenced the flexural mode of the neoformed bone

Polycaprolactone (PCL) is a biocompatible, biodegradable synthetic polymer which in combination with nanohydroxyapatite (nHAp) can give rise to a low cost, nontoxic bioactive product with excellent mechanical properties and slow degradation. Here we produced, characterized and evaluated in vivo the bone formation of PCL/nHAp scaffolds produced by the rotary jet spinning technique. The scaffolds produced were firstly soaked into simulated body fluid for 21 days to also obtain nHAp onto PCL/nHAp scaffolds. Afterwards, the scaffolds were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy and Raman spectroscopy. For in vivo experiments, 20 male Wistar rats were used and randomly divided in 4 experimental groups (n = 5). A critical defect of 3 mm in diameter was made in the tibia of the animals, which were filled with G1 control (clot); G2-PCL scaffold; G3-PCL/nHAp (5%) scaffold; G4-PCL/nHAp (20%) scaffold. All animals were euthanized 60 days after surgery, and the bone repair in the right tibiae were evaluated by radiographic analysis, histological analysis and histomorphometric analysis. While in the left tibias, the areas of bone repair were submitted to the flexural strength test. Radiographic and histomorphometric analyses no showed statistical difference in new bone formation between the groups, but in the three-point flexural tests, the PCL/nHAp (20%) scaffold positively influenced the flexural mode of the neoformed bone. These findings indicate that PCL/nHAp (20%) scaffold improve biomechanical properties of neoformed bone and could be used for bone medicine regenerative.

Synthesis of silver-cerium titanate nanotubes and their surface properties and antibacterial applications

Nano-heterostructures of titanate nanotubes were synthesized and they revealed a complex structure with the formation of TiO₂ (anatase), CeO₂, Ag₂O and metallic silver nanoparticles on the outer walls and intercalation of Ce⁴⁺ and Ag⁺ into the interlayer spaces of the nanotubes by microwave-assisted hydrothermal process and subjected to ion exchange reactions. To the best of our knowledge, this is the first reported silver and cerium co-exchanged titanate nanotubes for bio-applications. The co-ion exchange processes preserved the original tubular structure of titanate nanotubes with significant changes of the superficial as well as interlamellar environment. This study opens up possibility of synthesizing complex, functional nano-heterostructure with the scope of modification of the final structure, especially the amount and oxidation state of the intercalated cation (Ce⁴⁺, Ce³⁺ and Ag⁺) as well as the quantity and variety of the decorating nanoparticles (CeO₂, Ag₂O or metallic Ag). The interplay of which, in turn, can lead to important biological properties and applications, owing to their ion-liberation capacity. The samples were tested in antibacterial activity with two different kind of bacteria (gram positive and negative), cell cytotoxicity and adhesion, and it was found that the nano-heterostructure formed shows high antibacterial activity with low cytotoxicity and high cell adhesion, which makes it a promising material for further health applications.

Electrospraying Oxygen-Generating Microparticles for Tissue Engineering Applications

BACKGROUND

The facile preparation of oxygen-generating microparticles (M) consisting of Polycaprolactone (PCL), Pluronic F-127, and calcium peroxide (CPO) (PCL-F-CPO-M) fabricated through an electrospraying process is disclosed. The biological study confirmed the positive impact from the oxygen-generating microparticles on the cell growth with high viability. The presented technology could work as a prominent tool for various tissue engineering and biomedical applications.

METHODS

The oxygen-generated microparticles fabricated through electrospraying processes were thoroughly characterization through various methods such as X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) analysis, and scanning electron microscopy (SEM)/SEM-Energy Dispersive Spectroscopy (EDS) analysis.

RESULTS

The analyses confirmed the presence of the various components and the porous structure of the microparticles. Spherical shape with spongy characteristic microparticles were obtained with negative charge surface (ζ = -16.9) and a size of 17.00 ± 0.34 μm. Furthermore, the biological study performed on rat chondrocytes demonstrated good cell viability and the positive impact of increasing the amount of CPO in the PCL-F-CPO-M.

CONCLUSION

This technological platform could work as an important tool for tissue engineering due to the ability of the microparticles to release oxygen in a sustained manner for up to 7 days with high cell viability.

Modulation of antibiotic effect by Fe2(MoO4)3 microstrutures

In this study, we report the antibacterial activity and modulation of antibiotic activity by Fe₂(MoO₄)₃ microstructures obtained by the hydrothermal route without use of surfactants or organic additives. This material was characterized by X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy (SEM) images. The XRD pattern showed that the Fe₂(MoO₄)₃ crystallize in a monoclinic structure without secondary phases. Raman spectroscopy confirms the formation of Fe₂(MoO₄)₃. SEM images show that the Fe₂(MoO₄)₃ obtained have ball-of-yarn shaped morphology. In the antibacterial assays, strains of Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus were assayed by microdilution method to evaluate the antibacterial and modulatory-antibiotic activity with antibiotics as gentamicin, norfloxacin and imipenem. Against all bacteria, the Minimum Inhibitory Concentration (MIC) was Fe₂(MoO₄)₃ ≥ 1024 μg/mL. This high MIC result must be associated with the fact of the iron be an essential microelement to the bacterial growth. However, when the Fe₂(MoO₄)₃ was assayed in association with the antibiotics was observed an antagonistic effect demonstrated by an enhance of the MIC. This fact is associated directly with the pro-oxidative properties of metallic oxides. These compounds enhance the production of free radicals, as H₂O₂ and superoxide ions that can affect the cell structures as cell membrane and cell wall. Other effect is associated with the possible coordination of the metal, performing bonds with the chemical structure of the antibiotics, reducing their activity. Our results indicated that nanocompounds as Fe₂(MoO₄)₃ can not be used as antimicrobial products for clinical usage, neither directly and neither in association with antibiotics.

Physicochemical analysis of Permian coprolites from Brazil

In this paper we performed the study of two coprolites (fossilized feces) collected from the exposed levels of the Pedra de Fogo Formation, Parnaiba Sedimentary Basin, and Rio do Rasto Formation, Paraná Sedimentary Basin, both of the Palaeozoic era (Permian age). They were characterized using X-ray diffractometry, infrared, Raman and energy dispersive spectroscopy techniques in order to aid our understanding of the processes of fossilization and to discuss issues related to the feeding habits of the animals which generated those coprolites, probably cartilaginous fishes. The results obtained using a multitechnique approach showed that although these coprolites are from different geological formations, 3000km away from each other, they show the same major crystalline phases and elemental composition. The main phases found were hydroxyapatite, silica, calcite and hematite, which lead to infer that those coprolites were formed under similar conditions and produced by a similar group of carnivore or omnivore fishes.

Spectroscopic studies of the fish fossils (Cladocyclus gardneri and Vinctifer comptoni) from the Ipubi Formation of the Cretaceous Period

Fossils are mineralized remains or traces from animals, plants and other organisms aged to about 10(8)years. The chemical processes of fossilization are dated back from old geological periods on Earth. The understanding of these processes and the structure of the fossils are one of the goals of paleontology and geology in the sedimentary environments. Many researches have tried to unveil details about special kinds of biological samples; however, a lack of data is noticed for various other specimens. This study reports the investigations through infrared spectroscopy, X-ray fluorescence and X-ray diffraction measurements for two types of fish fossils from the Cretaceous Period. The sample of Cladocyclus gardneri and Vinctifer comptoni fossils were collected from the Ipubi Formation, being one of the less studied, among the formations that constitute the important Santana group in the Araripe Basin, Brazil. The results obtained through different techniques, showed that the C. gardneri fish fossil contains hydroxyapatite and calcite as constituents whereas its rock matrix was formed by calcite, quartz and pyrite. Regarding the V. comptoni, the measurements confirmed the presence of hydroxyapatite in the fossil and its rock matrix gypsum, pyrite, quartz and calcite. The above scientific data contributed to the understanding the fossil formation in the Ipubi Formation, an important environment of the Cretaceous Period, which is rich in well-preserved fossils from different species.

Spectroscopic analysis and X-ray diffraction of trunk fossils from the Parnaíba Basin, Northeast Brazil

The Parnaiba Sedimentary Basin is of the Paleozoic age and is located in Northeast Brazil, covering the states of Piauí, Maranhão and Tocantins and a small part of Ceará and Pará. In this work we applied several chemical analytical techniques to characterize trunk fossils found in the Parnaíba Sedimentary Basin, collected from four different sites, and discuss their fossilization process. We performed a study of the trunk fossils through X-ray diffraction, energy dispersive spectroscopy, infrared and Raman spectroscopy. The analysis allow us to identify the different compositions which are present in the trunk fossils: kaolinite (Al2Si2O5(OH)4), hematite (Fe2O3) and quartz (SiO2). Based in these results we were able to identify that the main fossilization mechanism of the trunk fossil was silicification. Furthermore, through Raman spectroscopy, we have observed the presence of carbonaceous materials in the Permian fossils, as evidenced by the D and G Raman bands. The relative intensities and bandwidths of the D and G bands indicated that the carbon has a low crystallinity. Thus, most of trunk fossils analyzed were permineralized and not petrified, because there is the presence of carbon that characterizes the partial decomposition of the organic matter in some trunks.

Spectroscopic studies of wood fossils from the Crato Formation, Cretaceous Period

In this work we study two types of wood fossils (Gymnosperms, Araucariaceae) from the Crato Formation of Araripe Basin in Brazil, from the Cretaceous Period. The samples were characterized by Raman and infrared spectroscopies, X-ray diffraction and scanning electron microscopy. The results obtained by different techniques showed that although the rocks surrounding the fossils have predominantly the same constitution - calcite - however, the formation processes of these types of wood fossils are quite different. One of the fossils, denominated as light wood, is predominantly composed of gypsum, while the other fossil, the dark wood, is rich in amorphous carbon, possibly the kerogen type. Implications relative to the environment where the plants lived millions years ago are also given. Finally, the results highlight the constitution of one of the most important paleontological sites of the Cretaceous Period in the South America.