Mechanochemical Synthesis of New Praziquantel Cocrystals: Solid-State Characterization and Solubility

New cocrystals of praziquantel with suberic, 3-hydroxybenzoic, benzene-1,2,4,5-tetracarboxylic, trimesic, and 5-hydroxyisophthalic acids were obtained through ball milling experiments. The optimal conditions for the milling process were chosen by changing the solvent volume and the mechanical action time. Supramolecular interactions in the new cocrystals are detailed based on single-crystal X-ray diffraction analysis, confirming the expected formation of hydrogen bonds between the praziquantel carbonyl group and the carboxyl (or hydroxyl) moieties of the coformers. Different structural characterization techniques were performed for all samples, but the praziquantel:suberic acid cocrystal includes a wider range of investigations such as thermal analysis, infrared and X-ray photoelectron spectroscopies, and SEM microscopy. The stability for up to five months was established by keeping it under extreme conditions of temperature and humidity. Solubility studies were carried out for all the new forms disclosed herein and compared with the promising cocrystals previously reported with salicylic, 4-aminosalicylic, vanillic, and oxalic acids. HPLC analyses revealed a higher solubility for most of the new cocrystal forms, as compared to pure praziquantel.

Designing a cercosporin-bioinspired bifunctional algicide with flocculation and photocatalysis for efficiently controlling harmful cyanobacterial blooms

Harmful cyanobacterial blooms (HCBs) are spreading in freshwater ecosystems worldwide, adversely affecting drinking water supplies, aquatic production, recreational and tourism activities. Therefore, the efficient and environmentally friendly method is still of interest to be developed to effectively control HCBs. Inspired by the excellent algicidal activity of cercosporin (CP), a novel metal-free algaecide SiO2@EDU@CP (EDU, N-ethyl-N'-(3-dimethylaminopropyl)urea) with flocculation and photoremoval functions, was successfully designed and prepared in one-step to simultaneously introduce CP and EDU on SiO2 nanoparticles. It could rapidly form algae flocs in 20 min with 97.1% flocculation rate, and remove Microcystis aeruginosa within 12 h with 91.0% algicidal rate under 23 W compact fluorescent light irradiation without any leaked CP detected. Additionally, odorant β-cyclocitral and toxin microcystin-LR were both photodegraded after treatment of SiO2@EDU@CP. Further mechanistic studies showed that the introduction of EDU significantly reversed the zeta potential of SiO2-COOH to achieve the flocculation through neutral charge, and the photophysical characterization of SiO2@EDU@CP revealed the improved charge separation ability to generate reactive oxygen species. More importantly, the utility of SiO2@EDU@CP was well demonstrated by its effectiveness for algae from Taihu Lake under natural sunlight and inability to regrow after treatment. This study not only establishes a bifunctional algicide SiO2@EDU@CP to efficiently control HCBs, but also provides design possibilities to develop more novel and efficient algicides for the better control of practical HCBs.

Low-Temperature and UV Irradiation Effect on Transformation of Zirconia -MPS nBBs-Based Gels into Hybrid Transparent Dielectric Thin Films

Bottom-up approaches in solutions enable the low-temperature preparation of hybrid thin films suitable for printable transparent and flexible electronic devices. We report the obtainment of new transparent PMMA/ZrO2 nanostructured -building blocks (nBBs) hybrid thin films (61–75 nm) by a modified sol-gel method using zirconium ethoxide, Zr(OEt)4, and 3-methacryloxypropyl trimethoxysilane (MPS) as a coupling agent and methylmethacrylate monomer (MMA). The effect of low-temperature and UV irradiation on the nBBs gel films is discussed. The thermal behaviors of the hybrid sols and as-deposed gel films were investigated by modulated thermogravimetric (mTG) and differential scanning calorimetry (DSC) analysis. The chemical structure of the resulted films was elucidated by X-ray photoelectron (XPS), infrared (IR) and Raman spectroscopies. Their morphology and crystalline structure were observed by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), and grazing incidence X-ray diffraction. The cured films show zirconia nanocrystallites of 2–4 nm in the hybrid matrix and different self-assembled structures for 160 °C or UV treatment; excellent dielectric behavior, with dielectric constant values within 6.7–17.9, depending on the Zr(OEt)4:MMA molar ratio, were obtained.

One-Pot Synthesis of SiO2@Ag Mesoporous Nanoparticle Coating for Inhibition of Escherichia coli Bacteria on Various Surfaces

Silver nanoparticles (Ag NPs) as antibacterial agents are of considerable interest owing to their simplicity, high surface area to volume ratio, and efficient oligodynamic properties. Hence, we investigated the synthesis of silica-supported Ag NPs (SiO₂@Ag) as an effective antibacterial agent by using a wet-impregnation method. The formation of SiO₂@Ag with Ag NP (5–15 nm diameter) on the silica particle (100–130 nm diameter) was confirmed with transmission electron microscopy (TEM). The study on antibacterial activity was performed in a liquid culture to determine the minimum inhibitory concentration (MIC) against Escherichia coli (E. coli) and Bacillus subtilis (B. subtilis) bacteria. Both bacteria are chosen to understand difference in the effect of Ag NPs against Gram-negative (E. coli) and Gram-positive (B. subtilis) bacteria. SiO₂@Ag mesoporous nanoparticles had excellent antibacterial activity against E. coli bacteria and fully restricted the bacterial growth when the material concentration was increased up to 1.00 mg/mL. In addition, the obtained material had good adhesion to both steel and polyethylene substrates and exhibited a high inhibition effect against E. coli bacteria.

One-step fabrication of robust and durable superamphiphobic, self-cleaning surface for outdoor and in situ application on building substrates

HYPOTHESIS

Water and oil inhibition treatment is essential for protecting natural and artificial stone surfaces. Bioinspired super-antiwetting surfaces with "lotus effect", together with superoleophobic properties, can be achieved combining very low-surface-energy materials and suitable surface roughness. Exploiting the natural roughness of stone surfaces, the simple and inexpensive fabrication of superamphiphobic surfaces through the coating dispersion deposition is expected. It seems the ideal method for the safeguard of contemporary and historical constructions, since the physical, chemical and aesthetic properties can be maintained.

EXPERIMENTS

The new coating agent (3-perfluroether-amidopropylsilane) was synthesized via one-step amidation. Hydrophobicity, robustness and environmental durability were systematically studied on stone surfaces through several tests: contact angle (CA), contact angle hysteresis (CAH), water inhibition efficiency, vapor diffusivity, chemical and mechanical resistance, artificial and field-exposure ageing.

FINDINGS

The as-prepared coating demonstrated superamphiphobicity (oil and water CA > 150° with CAH < 10°) on stones with low and high porosity. Moreover, it manifested very high water inhibition efficacy while maintaining high vapor diffusivity and aesthetic properties of substrates. The superhydrophobic coating showed good robustness towards corrosive chemical agents, peeling, mechanical abrasion, water immersion and environmental weathering, thereby permitting various outdoor applications, including stone protection in rainy regions where acid rain is also present.

A novel green chemistry gelation method for polyvinyl pyrrolidone (PVP) and dimethylpolysiloxane (silicone): microwave-induced in-liquid-plasma

The focus of this article rests on our discovery that a water-soluble polymer could be cross-linked to form a gel using a novel Green Chemistry gelation method: the microwave-induced in-liquid-plasma (MILP) method that requires neither a cross-linking agent nor an initiator as are required in the conventional chemical method. For instance, the water-soluble polyvinyl pyrrolidone (PVP) polymer was gelled by MILP plasma irradiation within a few minutes without using toxic cross-linking agents and initiators. As well, the hydrophobic dimethylpolysiloxane macromolecule was dispersed in aqueous media to a colloidal sol, which could then also be easily gelled under MILP irradiation conditions within a few minutes, in comparison to the conventional method that often requires several hours to days for gelation to occur in the presence of cross-linking agents and initiators. The viscosity of the MILP silicone gel was greater than a similar gel formed by the conventional method. In contrast, the viscosity of the MILP-formed PVP gel was lower than the viscosity of the PVP gel obtained from the conventional method. Gels were characterized by ¹³C-NMR spectrometry, FT-IR spectroscopy, SEM microscopy, viscosity measurements, and dynamic light scattering for particle size distributions. Plausible mechanistic stages for the two gelation occurrences have been inferred as involving the synergistic effects from microwaves, together with the sound waves (cavitation microbubbles), heat, UV and ˙OH radicals resulting from the microwave-generated in-liquid-plasma.

The discovery of a water-soluble polymer that cross-links to form a gel using a novel green gelation method: the microwave-induced in-liquid-plasma method that requires neither a cross-linking agent nor an initiator as are required in the conventional chemical method.

New details of assembling bioactive films from dispersions of amphiphilic molecules on titania surfaces

Tailoring the surface properties of materials for biomedical applications is important to avoid clinical complications. Forming thin layers of amphiphilic molecules with apolar regions that facilitate attractive intermolecular interactions, can be a suitable and versatile approach to achieve hydrophobic surface modification and provide functional antibacterial properties. Aiming to correlate layer structure and properties starting from film formation, octadecylphosphonic acid (ODPA) and dimethyloctadecyl (3-trimethoxysilylpropyl) ammonium chloride (DMOAP) layers were adsorbed onto smooth titania surfaces. Then the films were studied by atomic force microscopy (AFM) and X-ray Photoelectron Spectroscopy (XPS), and their interactions with aqueous environments were characterized by contact angle and zeta potential measurements. In addition, antibacterial assays were performed using E. coli and S. mutants to reveal the antibacterial properties effected by the surface modification. Immediately after sputter deposition, titania was hydrophilic; however, after air storage and adsorption of DMOAP or ODPA, an increase in the water contact angle was observed. XPS investigations after layer formation and after antibacterial tests revealed that the attachment of layers assembled from ODPA on titania substrates is considerably stronger and more stable than that observed for DMOAP films. Heat treatment strongly affects DMOAP layers. Furthermore, DMOAP layers are not stable under biological conditions.

Structure–property relationship of amphiphilic molecules on smooth substrates was explored through a multi-step approach and its influence on biological activity.

New insights into the interactions between asphaltene and a low surface energy anionic surfactant under low and high brine salinity

HYPOTHESIS

The hyperbranched chains on the tail of low surface energy surfactants (LSES) causes lowering of surface free energy and rock wettability alteration, offering significant improvement in oil recovery in asphaltene oil reservoirs.

EXPERIMENTS

Oil sweep efficiency was determined by fluid displacement in pure brine and LSES-brine solutions in a microfluidic pattern that was representative of a sandstone cross-section. Interfacial tension (IFT), wettability alteration, Raman and X-ray photoelectron spectroscopy (XPS) were used to measure the changes of asphaltene interactions with oil-aged substrate after surface treating with brine and surfactant-brine solutions.

FINDINGS

The hyperbranched LSES yielded a significant increase in the original-oil-in-place (OOIP) recovery (58%) relative to brine flooding (25%), even in the presence of asphaltene. Raman spectra showed the LSES-brine solutions to be capable of causing change to the asphaltene aggregate size after centrifugation treatment.

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.

The Effect of the Methyl and Ethyl Group of the Acrylate Precursor in Hybrid Silane Coatings Used for Corrosion Protection of Aluminium Alloy 7075-T6

This study investigated polysiloxane hybrid sol-gel coatings synthesized from tetraethyl orthosilicate (TEOS), 3-(trimethoxysilyl)propyl methacrylate (MAPTMS) and two different precursors, i.e., methyl- or ethyl- methacrylate (MMA or EMA), as corrosion protection of aluminium alloy 7075-T6. The hypothesis was that the additional alkyl group might affect the chemical properties and, consequently, the corrosion properties. Synthesis of the sols proceeded in two steps, each involving either MMA or EMA in the same molar ratio. The resulting sols, siloxane-(poly(methyl methacrylate-co-MAPTMS)) or siloxane-(poly(ethyl methacrylate-co-MAPTMS)), were applied on aluminium alloy followed by characterization in terms of chemical structure and composition, topography, wettability, adhesion and corrosion resistance in 0.1 M sodium chloride solution. The chemical properties of sols, monoliths and coatings were investigated using Fourier transform infrared spectrometry, solid state nuclear magnetic resonance spectrometry, X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry. Coatings were similar in terms of surface topography, while the wettability of the coating with EMA showed 6° greater water contact angle compared to the coating with MMA. Both coatings were shown, by electrochemical impedance spectroscopy in 0.1 M NaCl solution, to act as barriers to protect the underlying substrate in which coating with EMA exhibits better protection properties after 2 months of immersion. Adhesion tests confirmed the highest grade of adhesion to the substrate for both coatings. Testing in a salt-spray chamber demonstrated excellent corrosion protection, where coatings remaining intact after more than 600 h of exposure.

Polymerizable Ceramic Ink System for Thin Inkjet-Printed Dielectric Layers

An innovative ceramic ink system for thin inkjet-printed dielectric layers is presented, with which it is possible to avoid undesired drying effects. This system contains surface-modified Ba_0.6Sr_0.4TiO₃ (BST) particles, a cross-linking agent, and a thermal radical initiator. The polymerization starts immediately after the ink drop contacts the heated substrate and therefore leads to very homogeneous topographies. Since an organic/inorganic composite ink is used, no sintering is needed after printing and thus printing on flexible substrates is possible. A comparison of the printing and drying behavior between modified and nonmodified BST with the described ink system is performed. The successful surface modification is confirmed via X-ray photoelectron spectroscopy (XPS). Topographies of different printed structures are compared by white light interferometry, the occurring polymerization is confirmed by measurements with an oscillatory rheometer, layer thicknesses are determined by scanning electron microscopy (SEM) images, and the capacitance of a printed capacitor is measured via impedance spectroscopy. It is successfully shown that the developed ink system enables the production of thin ceramic layers (<1 μm) with very homogeneous topographies since undesired drying effects can be avoided. The printed dielectric layers on flexible substrates have a high ceramic content and a high permittivity of 40.

Dual Role of Lithium on the Structure and Self-Healing Ability of PMMA-Silica Coatings on AA7075 Alloy

In this work, structural and active corrosion inhibition effects induced by lithium ion addition in organic-inorganic coatings based on poly(methyl methacrylate) (PMMA)-silica sol-gel coatings have been investigated. The addition of increasing amounts of lithium carbonate (0, 500, 1000, and 2000 ppm), yielded homogeneous hybrid coatings with increased connectivity of nanometric silica cross-link nodes, covalently linked to the PMMA matrix, and improved adhesion to the aluminum substrate (AA7075). Electrochemical impedance spectroscopy (EIS), performed in 3.5% NaCl aqueous solution, showed that the improved structural properties of coatings with higher lithium loadings result in an increased corrosion resistance, with an impedance modulus up to 50 GΩ cm², and revealed that the lithium induced self-healing ability significantly improves their durability. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS) suggest that the regeneration process occurs by means of lithium ions leaching from the adjacent coating toward the corrosion spot, which is restored by a protective layer of precipitated Li rich aluminum hydroxide species. An analogue mechanism has been proposed for artificially scratched coatings presenting an increase of the impedance modulus after salt spray test compared to the lithium free coating. These results evidence the active role of lithium ions in improving the passive barrier of the PMMA-silica coating and in providing through the self-restoring ability a significantly extended service life of AA7075 alloy exposed to saline environment.

Dual Role of Lithium on the Structure and Self-Healing Ability of PMMA-Silica Coatings on AA7075 Alloy

In this work, structural and active corrosion inhibition effects induced by lithium ion addition in organic-inorganic coatings based on poly(methyl methacrylate) (PMMA)-silica sol-gel coatings have been investigated. The addition of increasing amounts of lithium carbonate (0, 500, 1000, and 2000 ppm), yielded homogeneous hybrid coatings with increased connectivity of nanometric silica cross-link nodes, covalently linked to the PMMA matrix, and improved adhesion to the aluminum substrate (AA7075). Electrochemical impedance spectroscopy (EIS), performed in 3.5% NaCl aqueous solution, showed that the improved structural properties of coatings with higher lithium loadings result in an increased corrosion resistance, with an impedance modulus up to 50 GΩ cm², and revealed that the lithium induced self-healing ability significantly improves their durability. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS) suggest that the regeneration process occurs by means of lithium ions leaching from the adjacent coating toward the corrosion spot, which is restored by a protective layer of precipitated Li rich aluminum hydroxide species. An analogue mechanism has been proposed for artificially scratched coatings presenting an increase of the impedance modulus after salt spray test compared to the lithium free coating. These results evidence the active role of lithium ions in improving the passive barrier of the PMMA-silica coating and in providing through the self-restoring ability a significantly extended service life of AA7075 alloy exposed to saline environment.

Electrochemical Study of a Hybrid Polymethyl Methacrylate Coating using SiO2 Nanoparticles toward the Mitigation of the Corrosion in Marine Environments

The demand for hydrophobic polymer-based protective coatings to impart high corrosion resistance has increased recently. The increase of the hydrophobicity in a hybrid coating is a new challenge, for that reason and in order to protect a metallic surface of oxidant agents, a poly (methyl methacrylate) (PMMA) coating with the addition of a different amount of silicon dioxide (SiO₂) was developed. The hybrid coating was applied on a sample of stainless steel AISI 304 by the dip-coating method. The characterization of the coatings was determined by electrochemical impedance spectroscopy and with a scanning electrochemical microscopy. The best coatings were PMMA and PMMA + SiO₂ 0.01% that exhibits a real impedance in the Nyquist diagram of 760 and 427,800 MΩ⋅cm², respectively, and the modulus of the real impedance in the Bode diagram present values of 2.2 × 10⁸ and 3.3 × 10⁸ Ω⋅cm². Moreover, the phase angle presents constant values around 75° to 85° and 85° for the PMMA and PMMA + SiO₂ 0.01%, respectively. Moreover, the values of the real resistance for the PMMA + SiO₂ 0.01% coating present values in the order of Mega-ohms despite the coating exhibits an artificial defect in their surface. The contact angle test showed that the hydrophobicity of the hybrid PMMA + SiO₂ 0.01% coating is higher than that of the pure PMMA coatings. The hybrid PMMA + SiO₂ coatings developed in this work are a very interesting and promising area of study in order to develop efficient products to protect metallic surfaces from corrosion phenomenon.

Effect of Hydrothermal Treatment on Structural and Catalytic Properties of [CTA]-MCM-41 Silica

The [CTA]-MCM-41 hybrid silica is a useful and simply prepared heterogeneous basic catalyst for the transesterification reaction. Here, the effect of hydrothermal treatment during catalyst preparation was investigated, with the aim of improving the structural stability of this catalyst during the reaction. It was observed that the hydrothermal step led to the formation of a material with a higher degree of organization and a greater wall thickness, which improved its structural stability. However, the catalyst prepared using this treatment presented lower catalytic activity, due to the presence of fewer active sites.

Effects of sol–gel process parameters on the anticorrosive performance of phosphosilicate hybrid coatings for carbon steel: structural and electrochemical studies

The effects of several sol–gel process parameters such as acid catalyst addition and the heat treatment procedure on porosity and anticorrosive properties were investigated for phosphosilicate sol–gel hybrid coatings prepared from 3-[(methacryloyloxy)propyl] trimethoxysilane (MEMO) and bis-[2-(methacryloyloxy)ethyl] phosphate (BMEP).

A Comparative Study on Graphene Oxide and Carbon Nanotube Reinforcement of PMMA-Siloxane-Silica Anticorrosive Coatings

Carbon nanotubes (CNTs) and graphene oxide (GO) have been used to reinforce PMMA-siloxane-silica nanocomposites considered to be promising candidates for environmentally compliant anticorrosive coatings. The organic-inorganic hybrids were prepared by benzoyl peroxide (BPO)-induced polymerization of methyl methacrylate (MMA) covalently bonded through 3-(trimethoxysilyl)propyl methacrylate (MPTS) to silica domains formed by hydrolytic condensation of tetraethoxysilane (TEOS). Single-walled carbon nanotubes and graphene oxide nanosheets were dispersed by surfactant addition and in a water/ethanol solution, respectively. These were added to PMMA-siloxane-silica hybrids at a carbon (CNT or GO) to silicon (TEOS and MPTS) molar ratio of 0.05% in two different matrices, both prepared at BPO/MMA molar ratios of 0.01 and 0.05. Atomic force microscopy and scanning electron microscopy showed very smooth, homogeneous, and defect-free surfaces of approximately 3-7 μm thick coatings deposited onto A1020 carbon steel by dip coating. Mechanical testing and thermogravimetric analysis confirmed that both additives CNT and GO improved the scratch resistance, adhesion, wear resistance, and thermal stability of PMMA-siloxane-silica coatings. Results of electrochemical impedance spectroscopy in 3.5% NaCl solution, discussed in terms of equivalent circuits, showed that the reinforced hybrid coatings act as a very efficient anticorrosive barrier with an impedance modulus up to 1 GΩ cm(2), approximately 5 orders of magnitude higher than that of bare carbon steel. In the case of GO addition, the high corrosion resistance was maintained for more than 6 months in saline medium. These results suggest that both carbon nanostructures can be used as structural reinforcement agents, improving the thermal and mechanical resistance of high performance anticorrosive PMMA-siloxane-silica coatings and thus extending their application range to abrasive environments.