Development and Characterization of Gelatin-Based Hydrogels Containing Triblock Copolymer and Phytic Acid

In recent research, significant interest has been directed towards gelatin-based hydrogels due to their affordable price, extensive availability, and biocompatibility, making them promising candidates for various biomedical applications. The development and characterization of novel hydrogels formed from varying ratios of gelatin, triblock copolymer Pluronic F-127, and phytic acid have been presented. Swelling properties were examined at different pH levels. The morphology of hydrogels and their thermal properties were analyzed using scanning electron microscopy (SEM), thermogravimetric analysis (TG), and differential scanning calorimetry (DSC). Fourier-transform infrared (FTIR) analysis of the hydrogels was also performed. The introduction of phytic acid in the hydrogel plays a crucial role in enhancing the intermolecular interactions within gelatin-based hydrogels, contributing to a more stable, elastic, and robust network structure.

Integration of wood-based components - Cellulose nanofibrils and tannic acid - into a poly(vinyl alcohol) matrix to improve functional properties

Poly(vinyl alcohol) (PVA) biocomposite films reinforced with cellulose nanofibrils (CNF) and biologically active tannic acid (TA) were prepared. The influence of different concentrations of CNF and TA in the PVA polymer matrix was investigated in terms of mechanical properties, thermal properties and hydrophobicity improvement of the prepared films. The results showed that in all cases the addition of CNF and TA improved the values of tensile strength and elastic modulus. The PVA film with 10 % CNF exhibited a 30 % higher tensile strength, and the three-component PVA film with 2 % CNF and 10 % TA (P2C10T) exhibited a 40 % higher tensile strength compared to the neat PVA film. The thermal properties (Tg, Tonset) of the PVA biocomposite films were greatly improved, with a significant effect observed for the three-component PVA films. The Tg of the PVA film with 10 % CNF and 10 % TA was 87 °C, 12 °C higher than that of the neat PVA film. For three-component PVA biocomposites with 4 % and 6 % CNF and with all weight percentages of TA, the Tonset shifted to a higher temperature range by about 30 °C compared to the neat PVA film. The PVA film with 2 % CNF and 10 % TA exhibited about a 20° higher contact angle than the neat PVA film. Moreover, the addition of both fillers to the PVA matrix resulted in PVA biocomposites with lower water absorption. PVA film with 10 % TA absorbed about 90 % less water and PVA film with 10 % CNF and 10 % TA absorbed about 80 % less water than the neat PVA film after the films were soaked in water for one hour. The better properties of the composite films produced are due to hydrogen and ester bonds between the components of the composite, which was confirmed by FT-IR spectroscopy. Antioxidant effective films were also obtained due to the biologically active TA to the PVA and PVA/CNF systems.

The Role of Cerium Valence in the Conversion Temperature of H2Ti3O7 Nanoribbons to TiO2-B and Anatase Nanoribbons, and Further to Rutile

CeO2-TiO2 is an important mixed oxide due to its catalytic properties, particularly in heterogeneous photocatalysis. This study presents a straightforward method to obtain 1D TiO2 nanostructures decorated with CeO2 nanoparticles at the surface. As the precursor, we used H2Ti3O7 nanoribbons prepared from sodium titanate nanoribbons by ion exchange. Two cerium sources with an oxidation state of +3 and +4 were used to obtain mixed oxides. HAADF-STEM mapping of the Ce4+-modified nanoribbons revealed a thin continuous layer at the surface of the H2Ti3O7 nanoribbons, while Ce3+ cerium ions intercalated partially between the titanate layers. The phase composition and morphology changes were monitored during calcination between 620 °C and 960 °C. Thermal treatment led to the formation of CeO2 nanoparticles on the surface of the TiO2 nanoribbons, whose size increased with the calcination temperature. The use of Ce4+ raised the temperature required for converting H2Ti3O7 to TiO2-B by approximately 200 °C, and the temperature for the formation of anatase. For the Ce3+ batch, the presence of cerium inhibited the conversion to rutile. Analysis of cerium oxidation states revealed the existence of both +4 and +3 in all calcined samples, regardless of the initial cerium oxidation state.

Metal and Non-Metal Modified Titania: the Effect of Phase Composition and Surface Area on Photocatalytic Activity

The application of TiO2 photocatalysis in various environmental fields has been extensively studied in the last decades due to its ability to induce the degradation of adsorbed organic pollutants. In the present work, TiO2 powders doped and co-doped with sulfur and nitrogen and modified with platinum were prepared by particulate sol-gel synthesis. PXRD measurements revealed that the replacement of HCl with H2SO4 during synthesis reduced the size of the crystallites from ~ 30 nm to ~20 nm, increasing the surface area from ~44 m2/g to ~80 m2/g. This is consistent with the photocatalytic activity of the samples and the measured photocurrent behavior of the photocatalysts. The results showed that the properties of the powders (i.e., surface area, crystallite size, photocurrent behavior) depend strongly not only on the type but also on the amount of acid and dopants used in the synthesis. Doping, co-doping and modification of TiO2 samples with nitrogen, sulfur and platinum increased their photocatalytic activity up to 6 times.

Preparation and characterization of innovative electrospun nanofibers loaded with pharmaceutically applicable ionic liquids

Keeping up with cutting edge research in the field of drug delivery, the overall goal of this study was to develop innovative electrospun nanofibers loaded with ionic liquids (ILs) as active pharmaceutical ingredients (APIs). For the first time, a novel approach was examined by combining biocompatible polymer, poly (ethylene oxide) (PEO), and pharmaceutical ILs in an electrospinning process to develop nanofibers with high drug loading (up to 47%). Firstly, two well-known local anaesthetic drugs, lidocaine and procaine, were modified into ILs with the salicylate, forming lidocaine salicylate and procaine salicylate. Its dual-functional nature and increased water solubility for 4- to 10-fold depending on the drug used contribute to overcoming current hurdles encountered by APIs such as poor solubility, low bioavailability, and polymorphism of the solid-state. Nanofibers were formulated using solutions tested for density, viscosity, electrical conductivity, and small-angle X-ray scattering by varying PEO molecular weight and the PEO to IL mass ratio. Scanning electron microscopy showed the surface morphology of the obtained nanofibers, while Fourier transform infrared spectroscopy and differential scanning calorimetry confirmed IL in the nanofibers in an amorphous state. Thus, nanofibers with incorporated IL represent well-known drugs in the new form and a novel dermal application delivery system.

Highly active and efficient Cu-based hydrotalcite-like structured materials as reusable heterogeneous catalysts used for transcarbonation reaction

A series of robust and efficient Cu-Al hydrotalcite-like compounds (HTLc) as catalysts were prepared by the simple precipitation method with different Cu/Al molar ratios and investigated for the transcarbonation of glycerol with dimethyl carbonate (DMC) for glycerol carbonate (GC) synthesis in a batch reactor. The structural and textural properties of the Cu-Al (HTLc) catalysts were analyzed by several methods like N₂-sorption, SEM-EDX/TEM, XRD, FTIR, CO₂-TPD, TGA/DTA and ICP-OES. It was found that the transcarbonation of glycerol is directly dependent on the strong basic sites of the catalysts. The Cu/Al molar ratio has easily tuned the glycerol conversion and the GC yield. Among all synthesized catalysts, the Copper-Aluminum (3Cu-Al@500) catalyst showed excellent catalytic activity for a glycerol conversion (96%) and a GC yield (86%) with reaction rate (irrespective to glycerol) of approximately 0.106 mol L^-1 h^-1. Furthermore, the optimization of the reaction conditions (i.e. molar ratio of the reactants, catalyst mass, reaction time and temperature) and the reusability of the 3Cu-Al@500 catalyst for glycerol conversion and GC yield with TOF value were studied. In addition, the effect of stirring speed and particle size on the minimization of external and internal mass transfer resistance, respectively, was investigated.

Acrylate-Based Hybrid Sol-Gel Coating for Corrosion Protection of AA7075-T6 in Aircraft Applications: The Effect of Copolymerization Time

Pre-hydrolysed/condensed tetraethyl orthosilicate (TEOS) was added to a solution of methyl methacrylate (MMA) and 3-methacryloxypropyltrimethoxysilane (MAPTMS), and then copolymerised for various times to study the influence of the latter on the structure of hybrid sol-gel coatings as corrosion protection of aluminium alloy 7075-T6. The reactions taking place during preparation were characterised using real-time Fourier transform infrared spectroscopy, dynamic light scattering and gel permeation chromatography. The solution characteristics were evaluated, using viscosimetry, followed by measurements of thermal stability determined by thermogravimetric analysis. The optimal temperature for the condensation reaction was determined with the help of high-pressure differential scanning calorimetry. Once deposited on 7075-T6 substrates, the coatings were evaluated using a field emission scanning electron microscope coupled to an energy dispersive spectrometer to determine surface morphology, topography, composition and coating thickness. Corrosion properties were tested in dilute Harrison's solution (3.5 g/L (NH4)2SO4 and 0.5 g/L NaCl) using electrochemical impedance spectroscopy. The copolymerization of MMA and MAPTMS over 4 h was optimal for obtaining 1.4 µm thick coating with superior barrier protection against corrosion attack (Z10 mHz 1 GΩ cm2) during three months of exposure to the corrosive medium.

3-Amino-1-propanol and N-methylaminoethanol: coordination to zinc(ii) vs. decomposition to ammonia

The coordination of amino alcohols 3-amino-1-propanol and N-methylaminoethanol to zinc(ii) and their decomposition to ammonia were investigated.

Sulfur-, nitrogen- and platinum-doped titania thin films with high catalytic efficiency under visible-light illumination

Titanium dioxide photocatalysts have received a lot of attention during the past decades due to their ability to degrade various organic pollutants to CO₂ and H₂O, which makes them suitable for use in environmental related fields such as air and water treatment and self-cleaning surfaces. In this work, titania thin films and powders were prepared by a particulate sol-gel route, using titanium tetrachloride (TiCl₄) as a precursor. Afterwards, the prepared sols were doped with nitrogen (ammonium nitrate, urea), sulfur (thiourea) and platinum (chloroplatinic acid), coated onto glass substrates by dip-coating, and thermally treated in a muffle furnace to promote crystallization. The resulting thin films were then characterized by various techniques (i.e., TGA-DSC-MS, XRD, BET, XPS, SEM, band gap measurements). The photocatalytic activity of the prepared thin films was determined by measuring the degradation rate of plasmocorinth B (PB), an organic pigment used in the textile industry, which can pose an environmental risk when expelled into wastewater. A kinetic model for adsorption and subsequent degradation was used to fit the experimental data. The results have shown an increase in photocatalytic activity under visible-light illumination of nonmetal and metal doped and co-doped titania thin films compared to an undoped sample.

Molecular dynamics of 1-ethyl-3-methylimidazolium triflate ionic liquid studied by 1H and 19F nuclear magnetic resonances

The molecular dynamics of an ionic liquid (IL) composed of a 1-ethyl-3-methylimidazolium cation and a triflate (trifluoromethanesulfonate) anion, abbreviated as [Emim][TfO], were studied by NMR spectroscopy. By measuring the temperature-dependent high-field 1H and ¹⁹F spin-lattice relaxation (SLR) rates, the frequency-dependent ¹H and ¹⁹F SLR dispersion curves using fast-field-cycling relaxometry, and the temperature-dependent 1H and ¹⁹F diffusion constants, and by utilizing the fact that the primary NMR-active nucleus on the Emim cation is ¹H, whereas on the TfO anion it is ¹⁹F, the cationic and anionic dynamics were studied separately. A single theoretical relaxation model successfully reproduced all the experimental data of both types of resonant nuclei by fitting all the data simultaneously with the same set of fit parameters. Upon cooling, [Emim][TfO] exhibited a supercooled liquid phase between T_SL = 256 K and the crystallization temperature T_Cr ≈ 227-222 K, as confirmed by differential scanning calorimetry (DSC) experiments. Theoretical analysis revealed that within the liquid and the supercooled liquid states of [Emim][TfO], the ¹H and ¹⁹F relaxation rates are affected by both the rotational and translational diffusional processes with no discontinuous change at T_SL. While the rotational diffusion is well described as an Arrhenius thermally activated process, the translational diffusion undergoes strong freezing dynamics that are well described by the Vogel-Fulcher model assuming a freezing temperature of T₀ = 157 K. The existence of the supercooled liquid region in the [Emim][TfO] IL should be taken into account when using this IL for a specific application.

Structural properties and thermal stability of cobalt- and chromium-doped α-MnO2 nanorods

α-MnO₂ nanorods were synthesized via the hydrothermal decomposition of KMnO₄ in an acidic environment in the presence of Co²⁺ and Cr³⁺ ions. Reactions were carried out at three different temperatures: 90, 130 and 170 °C. All prepared samples exhibit a tetragonal MnO₂ crystalline phase. SEM-EDS analysis shows that cobalt cations are incorporated to a higher degree into the MnO₂ framework than chromium ions, and that the content of the dopant ions decreases with increasing reaction temperature. The oxidation of Co²⁺ to Co³⁺ during the reaction was proved by an XANES study, while EXAFS results confirm that both dopant ions substitute Mn⁴⁺ in the center of an octahedron. The K/Mn ratio in the doped samples synthesized at 170 °C is significantly lower than in the undoped samples. Analysis of an individual cobalt-doped α-MnO₂ nanorod with HAADF-STEM reveals that the distribution of cobalt through the cross-section of the nanorod is uniform. The course of thermal decomposition of the doped nanorods is similar to that of the undoped ones. Dopant ions do not preserve the MnO₂ phase at higher temperatures nor do they destabilize the cryptomelane structure.

Encapsulation of (-)-epigallocatechin gallate into liposomes and into alginate or chitosan microparticles reinforced with liposomes

BACKGROUND

(-)-Epigallocatechin gallate (EGCG) was encapsulated into liposomes that were further incorporated into alginate and chitosan microparticles. The stability of free and encapsulated EGCG in all three systems was evaluated at different pH values and in fruit nectar. Furthermore, the interactions between EGCG and the compounds of the microparticles were studied using Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC).

RESULTS

All three encapsulation systems showed high encapsulation efficiency (>97%) and sustained release; in 14 days, no more than 15% of EGCG was released. The encapsulation systems successfully protected EGCG against degradation at alkaline pH. For non-encapsulated EGCG, >70% was degraded after 14 days, while there was no significant degradation of encapsulated EGCG in these three systems. In fruit nectar, >30% of non-encapsulated EGCG was degraded in 14 days, while only 6% of EGCG encapsulated into liposomes or chitosan microparticles reinforced with liposomes was degraded at that time. The DSC and FTIR analyses showed that the main interactions occurred between the liposomes and the EGCG.

CONCLUSION

This study demonstrates that liposomes as well as alginate and chitosan microparticles reinforced with liposomes have the potential to enhance EGCG stability in food products during storage. © 2016 Society of Chemical Industry.

Transformation of hydrogen titanate nanoribbons to TiO2 nanoribbons and the influence of the transformation strategies on the photocatalytic performance

The influence of the reaction conditions during the transformation of hydrogen titanate nanoribbons to TiO2 nanoribbons on the phase composition, the morphology, the appearance of the nanoribbon surfaces and their optical properties was investigated. The transformations were performed (i) through a heat treatment in oxidative and reductive atmospheres in the temperature range of 400-650 °C, (ii) through a hydrothermal treatment in neutral and basic environments at 160 °C, and (iii) through a microwave-assisted hydrothermal treatment in a neutral environment at 200 °C. Scanning electron microscopy investigations showed that the hydrothermal processing significantly affected the nanoribbon surfaces, which became rougher, while the transformations based on calcination in either oxidative or reductive atmospheres had no effect on the morphology or on the surface appearance of the nanoribbons. The transformations performed in the reductive atmosphere, an NH3(g)/Ar(g) flow, and in the ammonia solution led to nitrogen doping. The nitrogen content increased with an increasing calcination temperature, as was determined by X-ray photoelectron spectroscopy. According to electron paramagnetic resonance measurements the calcination in the reductive atmosphere also resulted in a partial reduction of Ti(4+) to Ti(3+). The photocatalytic performance of the derived TiO2 NRs was estimated on the basis of the photocatalytic oxidation of isopropanol. After calcinating in air, the photocatalytic performance of the investigated TiO2 NRs increased with an increased content of anatase. In contrast, the photocatalytic performance of the N-doped TiO2 NRs showed no dependence on the calcination temperature. An additional comparison showed that the N-doping significantly suppressed the photocatalytic performance of the TiO2 NRs, i.e., by 3 to almost 10 times, in comparison with the TiO2 NRs derived by calcination in air. On the other hand, the photocatalytic performance of the hydrothermally derived TiO2 NRs was additionally improved by a subsequent heat treatment in air.

Hydroxyl radical scavenging-based method for evaluation of TiO₂ photocatalytic activity

A novel hydroxyl radical scavenging method was developed to establish the photocatalytic activity of TiO₂ thin films. Transparent TiO₂ thin films were prepared on soda-lime glass substrates using the sol-gel method and characterized using X-ray diffraction. During photoirradiation in aqueous buffered solutions, activity of the films was followed using the substituted nitrobenzene N,N'-(5-nitro-1,3-phenylene)bisglutaramide as a hydroxyl radical scavenger and its hydroxylated products were quantified using HPLC. The yield of hydroxyl radicals was evaluated at various pH of the reaction media, and reflected the dependence of the rate of the hydroxylation reaction on the experimental conditions and on the different qualities of the TiO₂ thin films. The proposed method allows for direct assessment of hydroxyl radical production, it is straightforward and is proposed for routine use.