Stable Aqueous Suspensions Research Articles

Proflavine binding to La-Sr perovskite manganite nanoparticles at temperatures above and below the Сurie temperature

The magnetic properties of La1-xSrxMnO3 (LSMO) nanoparticles within the ferromagnetic region (x ≈ 0.2–0.5) enable their application in two types of cancer treatment: chemotherapy drug delivery and self-controlled hyperthermia. Single-phase La0.80Sr0.20MnO3 nanoparticles were prepared by the sol-gel process followed by mechanical processing. Sample characterization was performed by using XRD, TEM, EPR, and DLS techniques. The encapsulation efficiency of proflavine to the nanoparticles was determined via spectrophotometry. The mean size of crystallites of LSMO nanoparticles is 18 nm, and the Curie temperature is 319 K. Bare LSMO particles do not form a colloidally stable aqueous suspension; they exhibit a zeta potential close to zero and provide micro-sized aggregates. Application of sodium citrate for their stabilization leads to a decrease in the size of agglomerates and to a highly negative zeta potential of –33 mV. The efficiency of proflavine sorption by LSMO nanoparticles increases significantly above the Curie temperature, from 16.1 % at 298 K to 26.2 % at 333 K. This increase is attributed to the partial disruption of nanoparticle agglomerates in suspension after the LSMO phase loses its ferromagnetic order. In summary, heating LSMO nanoparticles above the Curie temperature increases the degree of drug loading on the nanoparticles.

In-situ upgrading of Egyptian heavy crude oil using matrix polymer carboxyl methyl cellulose/silicate graphene oxide nanocomposites

This study delves into catalytic aquathermolysis to enhance the economic viability of heavy oil production by in-situ upgrading technique. It is known that introducing nanocatalysts would promote the aquathermolysis reaction. Therefore, in this study, the effect of matrix polymer carboxyl methyl cellulose/silicate graphene oxide nanocomposites (CSG1 and CSG2) in the catalytic aquathermolysis of Egyptian heavy crude oil was studied. Characterization techniques including Fourier-transform infrared (FTIR), X-ray diffraction (XRD), Dynamic light scattering (DLS), Brunauer–Emmett–Teller (BET) surface area analysis, Scanning electron microscopy (SEM), and thermogravimetric analysis (TGA) were used to evaluate the structure of the synthesized nanocomposites. Results reveal CSG2 has higher crystallinity and superior dispersion compared to CSG1, and both exhibited a good stability in aqueous suspensions. CSG2 enriched with graphene oxide, demonstrates superior thermal stability, suitable for high-temperature applications such as catalytic aquathermolysis process. Single factor and orthogonal tests were used to assess the catalytic aquathermolysis performance of the prepared nanoparticles. The obtained results revealed that the optimum conditions to use CSG1 and CSG2 are 40% water concentration, 225 °C temperature, and 0.5 wt% catalyst percentage. Where, CSG2 showed better viscosity reduction (82%) compared to CSG1 (62%), highlighting its superior performance in reducing the viscosity of heavy oil. Numerical results from SARA analysis, gas chromatography, and rheological testing confirmed the catalytic aquathermolysis's efficacy in targeting asphaltene macromolecules and producing lighter hydrocarbon fractions.

Aggregation and Sedimentation Stability of Nanoscale Zeolitic Imidazolate Framework (ZIF‐8) Nanocomposites for Antimicrobial Agent Delivery Applications

ABSTRACTThe applications of nanoscale zeolitic imidazolate frameworks (ZIF‐8) for antimicrobial drug delivery depend on the aqueous suspension stability of the ZIF‐8 which is influenced by their crystallinity, size, shape, aggregation, and surface chemistry. This study evaluated the stability of ZIF‐8 nanoparticles in terms of their aggregation and sedimentation characteristics. ZIF‐8 nanocomposites were synthesized with methanol via sonication at 30°C for 1 h. The effect of drying methods (oven drying at 80°C, and vacuum drying at 35°C), number of washing steps (0 = no wash, 1, 2, 3), and washing medium (washing with water and ethanol instead of methanol, and redispersion in water and ethanol) on the suspension stability was evaluated. The impact of added xanthan gum (XG) and poly‐L‐lysine (PL) as suspension media was also evaluated. ZIF‐8 nanoparticles were also synthesized using ethanol and suspended in PL. % transmittance and zeta potential were measured for freshly prepared ZIF‐8 suspensions in PL and after freeze‐drying and resuspending in water. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and x‐ray diffraction (XRD) analysis were utilized for the assessment of the crystallinity, structure, and morphology of the samples. Antibacterial activity was evaluated by disc diffusion test against Escherichia coli. Dried methanol‐synthesized ZIF‐8 nanoparticles did not suspend in water; only the ZIF‐8 nanoparticles synthesized with reduced washing times and no drying treatment were resuspended in the water, XG and PL solutions. Instead, the ethanol‐synthesized ZIF‐8 nanoparticles were resuspended in water even after being washed three times and dried in a vacuum oven. SEM and TEM images and XRD patterns showed that alcohol can form well‐defined ZIF‐8 nanoparticles. FTIR spectra showed that ZIF‐8 had typical peaks of ZIF‐8 reported by others. Although particle size increased, the PL coating provided a 32.22% increase in zeta potential of ZIF‐8 nanoparticles from 36.25 to 47.93 mV (p < 0.05) and prevented aggregation and sedimentation of the nanoparticles without changing their morphology. All the tested ZIF‐8 nanoparticles showed antibacterial activity with the PL‐coated ZIF‐8 having the highest effect followed by the ZIF‐8 nanoparticles synthesized in ethanol.

Antibacterial efficacy of decorated carbon nanotubes by nano silver against pseudomonas aeruginosa

Carbon nanotubes (CNTs) are considered as a promising nanomaterial for a variety of applications. It has desirable physicochemical characteristics of high surface area, superior mechanical and thermal strength, and electrochemical activity. In this study, CNTs decorated with silver nanoparticles (AgNPs) were manufactured by an arc discharge technique. As a result, etching produces stable AgNPs-CNTs aqueous suspensions of pure silver and carbon electrodes in ethanol vapor condensed in water. UV- visible photometer, x-ray Diffraction, transmission electron microscope, and energy dispersive x-ray characterized the synthesized AgNPs-CNTs. The synthesized AgNPs-CNTs crystals showed CNTs formation of an average 9.5 nm, with intermediate length position of about 75.8 nm decorated by homogeneous spherical AgNPs of average size 15.2 nm. The antibacterial efficiency of AgNPs-CNTs against Pseudomonas aeruginosa was established at a series of concentrations (45 g ml−1: 0.0879 g ml−1) while values for the MIC and MBC were determined. The MIC and MBC levels were found to be (>5.625 μg ml−1) and (>11.25 μg/ml) respectively. The bacteria cytotoxicity was evaluated through LDH and protein leakage levels. Treated samples with 3.2 μg ml−1 AgNPs-CNTs revealed significant injuries in the cell membrane by two times greater in LDH and protein leakage levels than samples treated by 5.0 μg ml−1 AgNPs. Results in this work substantiate the synergistic effect of combining AgNPs with CNTs to enhanced antibacterial properties and performance compared to AgNPs alone. The efficiency of using synthesized AgNPs-CNTs showed high antibacterial potential against Pseudomonas aeruginosa in a concentration-dependent manner. The arc discharge method can be adapted to incorporate different materials or change the synthesis conditions, allowing for the production of AgNPs-CNTs with tailored properties for specific applications.

Tunable X-ray-induced luminescence in lanthanide-doped LaPO4 nanoparticles

X-ray luminescent nanoparticles have gained significant attention as promising tools for implementing multimodal imaging and radiation-based treatments in theragnostics. The intricate comprehension of their properties and the underlying mechanisms driving the conversion of X-rays into light is critical for their success in various applications. LaPO4 nanoparticles doped with various individual luminescence centers, gadolinium (Gd3+), europium (Eu3+), dysprosium (Dy3+), and terbium (Tb3+), were produced via co-precipitation and investigated for their behavior upon X-ray excitation using energies of up to 225 kV. These materials evidenced a radioluminescent response dependent on the dopant concentrations, with emission lines from 300 to 700 nm, providing insights into the luminescence quenching effect in these structures. The luminescent characteristics of the nanoparticles were studied under continuous irradiation, evidencing the materials’ ability to withstand high absorbed doses and preserve their properties. Furthermore, the influence of dopant concentrations on crystallite size and the dependence of luminescence on thermal treatments was investigated. The assessment of nanoparticle stability in aqueous suspension was evaluated over a broad pH range, revealing a tendency of the LaPO4 surface to selectively interact with electropositive species. This insight enhances our comprehension of the colloidal stability of the material, positioning it for extended applications and in vitro evaluations, along with further surface functionalization.

L‐Cysteine‐Encapsulated MXene Nanosheet Possessing Ultra‐Antioxidation in Aqueous Suspension for Electrophoretic Deposition Assisted Carbon‐Fiber‐Surface Modification

AbstractWith recent progress in 2D materials, Ti3C2Tx MXene featured high metallic electrical conductivity, high electromagnetic interference shielding effectiveness, and super in‐plane stiffness, exhibits unique advantages in many fields, but is rarely applied as a sizing agent in long‐time continuous processing of carbon fiber sizing because of its poor ambient stability in aqueous suspension. Herein, a new strategy to chemically encapsulate the reactive sites of MXene nanosheet with l‐cysteine for restricting the attacking of water and/or oxygen in aqueous suspension is proposed. Based on the ultra‐antioxidation, polarity, and electrical properties of l‐cysteine‐encapsulated Ti3C2Tx MXene (LC‐MX) nanosheet, the LC‐MX, even if aging for weeks in aqueous suspension, can be deposited on the surface of high‐modulus carbon fiber (HMCF) uniformly via the electrophoretic deposition assisted sizing. Benefiting from the enhanced surface energy, wettability, and roughness of LC‐MX‐sized HMCF (HMCF‐LCMX) relative to that of unsized one (U‐HMCF), the interfacial property of HMCF‐LCMX/epoxy (EP) composites is also improved, for which the interlayer shear strength (ILSS) of the composite reached 88.5 MPa, 52.8% higher than that of U‐HMCF/EP composite (57.9 MPa). This work makes an essential step toward the application of ultra‐stable MXene nanosheet suspension in large‐scale continuous carbon fiber sizing.

Study on the stability of high solid content polyether‐ether‐ketone aqueous suspension

AbstractCarbon fiber (CF) reinforced polyether‐ether‐ketone (PEEK) composite is found extensive application in various industries. Efforts have been made to enhance the interfacial binding between the resin and fibers. Herein, we report a green CF surface modification suspension coating method that could resist high process temperature by optimizing the stability of the aqueous suspension, which contains PEEK resin particles and a mixture of sodium dodecyl sulfate (SDS) and polyethylene glycol monostearate (stPEG). The optimized suspension (PEEK: SDS mass ratio= 5:1) that can meet around 500°C process requirement was then used to improve the physical interfacial binding between CF and PEEK. Based on the suspension colloidal stability, the process was optimized by tensile tests of the CF/PEEK monofilaments. The results show that the colloidal stability of the PEEK aqueous suspension with a total solid content of 20 wt.% containing stPEG‐SDS (stPEG: SDS mass ratio= 1:2) surfactant blend (PEEK: stPEG‐SDS mass ratio= 5:1) reached the optimum at a stirring rate of 750 rpm. The maximum tensile strength of the CF/PEEK monofilaments reached ~4.968 GPa at a coating diameter of 8.54 μm. This PEEK aqueous suspension provides a non‐toxic, environmentally friendly and high temperature resistant aqueous material to produce high‐performance fiber reinforced PEEK composites.

Cobalt Ferrite Nanoparticles Capped with Perchloric Acid for Life-Science Application

Among the modern oncological therapies, one of the most promising is based on tumor hyperthermia with magnetic nanoparticles resulting from the crystallization of iron and cobalt oxides. We synthesized core–shell magnetic nanoparticles of perchlorate-CoxFe3−xO4 (x = 0; 0.5; 1.0) via the co-precipitation method and stabilized them in aqueous suspensions. Fine granulation of the dispersed ferrophase was revealed by Transmission Electron Microscopy and Dynamical Light Scattering, with FTIR data detailing the surface-interaction phenomena. X-ray diffractometry revealed specific crystallization features of inverse spinel lattice, providing crystallite size and lattice parameters dependent on the cobalt content. The results of the Vibrating Sample Magnetometry investigations indicated that cobalt doping has reduced the magnetic core size and increased the nanoparticle dimension, which could be the result of crystallization defects at the nanoparticle surface related to the presence of cobalt ions. A mathematical model was applied with a focus on the quantitative description of the temperature distribution around magnetic nanoparticles. Further development of our research will consider new cobalt ferrite nanoparticles with new cobalt contents and different organic coatings to contribute to their biocompatibility and stability in aqueous suspensions, as required by administration in living organisms.

Creation of a ready-to-use brexpiprazole suspension and the inflammation-mediated pharmacokinetics by intramuscular administration

Brexpiprazole (BPZ), which is approved for the treatment of schizophrenia and major depressive disorder, has the potential to meet diverse clinical needs. This study aimed to develop a long-acting injectable (LAI) formulation of BPZ that could provide sustained therapeutic benefits. A library of BPZ prodrugs was screened through esterification, and BPZ laurate (BPZL) was identified as an optimal candidate. To achieve stable aqueous suspensions, a pressure- and nozzle size-controlled microfluidization homogenizer was utilized. The pharmacokinetics (PK) profiles, considering dose and particle size modulation, were investigated following a single intramuscular injection in beagles and rats. BPZL treatment resulted in sustained plasma concentrations above the median effective concentration (EC50) for 2 ∼ 3 weeks, without exhibiting an initial burst release. Histological examination of foreign body reaction (FBR) in rats revealed the morphological evolution of an inflammation-mediated drug depot, confirming the sustained release mechanism of BPZL. These findings provide strong support for the further development of a ready-to-use LAI suspension of BPZL, which could potentially enhance treatment outcomes, improve patient adherence, and address the clinical challenges associated with long-term regimens of schizophrenia spectrum disorders (SSD).

Surface Potential Modulation in Boronate-Functionalized Magnetic Nanoparticles Reveals Binding Interactions: Toward Magnetophoretic Capture/Quantitation of Sugars from Extracellular Matrix.

Phenylboronic acids (BAs) are important synthetic receptors that bind reversibly to cis-diols enabling their use in molecular sensing. When conjugated to magnetic iron oxide nanoparticles, BAs have potential for application in separations and enrichment. Realizing this will require a new understanding of their inherent binding modes and measurement of their binding capacity and their stability in/extractability from complex environments. In this work, 3-aminophenylboronic acid was functionalized to superparamagnetic iron oxide nanoparticles (MNPs, core diameter 8.9 nm) to provide stable aqueous suspensions of functionalized particles (BA-MNPs). The progress of sugar binding and its impact on BA-MNP colloidal stability were monitored through the pH-dependence of hydrodynamic size and zeta potential during incubation with a range of saccharides. This provided the first direct observation of boronate ionization pKa in grafted BA, which in the absence of sugar shifted to a slightly more basic pH than free BA. On exposure to sugar solutions under MNP-limiting conditions, pKa moved progressively to lower pH as maximum capacity was gradually attained. The pKa shift is shown to be greater for sugars with greater BA binding affinity, and on-particle sugar exchange effects were inferred. Colloidal dispersion of BA-MNPs after binding was shown for all sugars at all pHs studied, which enabled facile magnetic extraction of glucose from agarose and cultured extracellular matrix expanded in serum-free media. Bound glucose, quantified following magnetophoretic capture, was found to be proportional to the solution glucose content under glucose-limiting conditions expected for the application. The implications for the development of MNP-immobilized ligands for selective magnetic biomarker capture and quantitation from the extracellular environment are discussed.

Formation of stable microporous core-shell V2O5/SiO2 colloidal particles potential for heterogeneous catalysis

An approach for the synthesis of stable core-shell V2O5/SiO2 colloidal particles has been proposed. First, ammonium vanadate particles ∼ 300 nm in size, which act as a precursor for vanadium pentoxide synthesis, are obtained from NH4VO3 saturated solution. To prevent possible changes in morphology of the obtained particles during the synthesis of V2O5 they are coated with silica shell via hydrolysis of tetraethoxysilane. The formed SiO2 shell possesses microporous structure with an average size of pores ∼ 1.5 nm and specific surface area 170 m2/g. It is shown that the presence of pores makes it possible to provide efficient removal of decomposition products during conversion of NH4VO3 to V2O5 during annealing at 550 °C and preserve the shape and size of the core-shell particles. The obtained V2O5/SiO2 particles are of ∼ 700 nm in size have an almond-like shape and form a stable aqueous suspension. It is found that they exhibit intense broadband room-temperature photoluminescence with maximum intensity at 660 nm. The shell retains its porous structure after annealing and gives access to the core of particles – V2O5, which allows complete conversion of V2O5 to, for example, V2O3 and makes the core-shell particles promising for use in heterogeneous catalysis.

High-yield preparation of ultrahigh-hydrophilicity MWCNTs by highly controllable oxidation with concentrated HNO3/HClO4 mixture

Functionalization of carbon nanotubes (CNTs) by an oxidation method is the essential step for many applications of CNTs. Herein, concentrated HNO3/HClO4 mixture is used to oxidize multi-walled carbon nanotubes (MWCNTs). The results show that the MWCNTs functionalization level is readily adjusted by regulating both the HNO3/HClO4 molar ratio of 1:(0.5–2) and the reaction temperature. The results for the yield, chemical structure and morphology of the MWCNTs show that the oxidation takes place in two stages. In the initial stage, the intense introduction of oxygen-containing groups dominates the oxidation reactions thereby obtaining functionalized MWCNTs in an unexpectedly high yield of 110% and carbon conversion of >98%. The second stage is characteristic of an obvious decrease in the yield of products, the carbon conversion and apparent damage to the MWCNTs. The carboxyl, hydroxyl and ether-like linkages are the predominant functional groups introduced with a total content of 3–7 mmol/g. Moreover, the high-yield functionalized CNTs exhibit excellent aqueous hydrophilicity thereby achieving stable MWCNTs aqueous suspensions of >40 mg/mL. It is affirmed that, in the mixture, HNO3 and HClO4 play a role in oxidizing and increasing the oxidizing ability of the HNO3, respectively.

Hydroxyl Boron Nitrid e/Natural Rubber Composites with Enhanced Mechanical and Thermal Conduction Properties: Implications for Heat Dissipative Tires or Conveyor Belts

For its significant technological interest, a systematic investigation on mechanical and thermal conduction properties of natural rubber reinforced by functionalized hexagonal boron nitride nanosheets is highly desirable. We herein first demonstrate a unique synthesis of hydroxyl-functionalized boron nitride nanosheets (OH-BNNSs) via a simple one-pot reduction reaction. This involves negative charging by treating BNNSs with lithium in liquid ammonia and subsequent bubbling of oxygen into dispersion of BNNS salts. Subsequently, a series of functionalized boron nitride nanosheets/natural rubber (NR) composites were fabricated by latex mixing and co-coagulation. Co-coagulating a stable aqueous suspension of OH-BNNSs with natural rubber latex afforded a weblike morphology consisting of platelet networks between the latex particles. Compared to pure rubber, the tensile strength and storage modulus at 25 °C for OH-BNNSs/NR (5 wt %) are increased by 466% and 1 order of magnitude, respectively. Benefiting from the unique structure, the composite at 5 wt % shows a 40% improvement in thermal conductivity relative to pure rubber. This latex-based method provides a facile and effective strategy to design and fabricate advanced functional BNNS-based polymeric nanocomposites with a segregated filler network morphology and considerable property enhancements in direct competition with graphene sheets. The composites could be potentially used in heat dissipative tires or conveyor belts.

Niobium pentoxide as an adsorbent for methylene blue removal: Synthesis, characterization and thermal stability

This study investigated the synthesis of niobium pentoxide (Nb2O5) by peroxide oxidation with hydrothermal treatment and evaluated its application for adsorption of the organic pollutant methylene blue (MB) in aqueous medium. Hydrothermal treatment was performed at 150 °C for different times (4, 12, and 24 h). The resulting materials were characterized by X-ray diffractometry, Raman spectroscopy, thermogravimetry, differential scanning calorimetry, Fourier-transform infrared spectroscopy (FTIR), N2 adsorption isotherm analysis, zeta-potential analysis, and scanning electron microscopy (SEM). Nb2O5 samples had high surface area (174 m2 g−1) and orthorhombic crystal structure. FTIR revealed that an increase in synthesis time produced an increase in surface hydroxylation. Particles dispersed in water had zeta-potential values lower than −31.3 mV, suggesting colloidal stability in aqueous suspension. SEM analyses showed no significant variation in nanoparticle morphology as a function of synthesis time. MB adsorption studies using the sample treated at 150 °C for 24 h showed that the adsorption was higher at pH 6.0, and the process follows pseudo-second order kinetics, suggesting chemical diffusion as the dominant process. The Freundlich isotherm model provided the best fit to experimental data. Thermal analyses indicated a phase transition at about 600 °C, corroborated by analysis of samples after calcination at 500 and 700 °C. Thus, the obtained materials have high specific surface area, adsorption capacity, suspension stability, and thermal stability.

Unintentional formation of nitrate and nitrite ions during nanodiamonds sonication: A source of radical and electron scavengers

Ever since studies on diamond nanoparticles (NDs) expanded, their exceptional colloidal stability was investigated as it is a key parameter for their further use in many applications. While a sonication step is required to deaggregate NDs and obtain stable aqueous suspensions, few works focused on the impact of the sonication process on the suspension composition. High-powered sonication induces the formation of a variety of species by radical pathways including nitrite and nitrate ions, which may act as radical or electron scavengers. Such effect may significantly affect the expected photocatalytic or radiolytic properties of NDs. This work aims to warn about the formation of these ionic species during the deagglomeration of NDs by sonication. Our investigation reveals for the first time that for oxidized detonation NDs, such treatment promotes the formation of additional NO2- ions and hydroxyl radicals, suggesting an increase in cavitation bubbles formation. Hydrogenated particles on the opposite present no overproduction of nitrite ions. Our results also show that these species can be avoided in suspension by sonicating under controlled atmosphere with no significant perturbation of NDs colloidal stability or surface chemistry.

Biosynthesis, Characterization, and Augmented Anticancer Activity of ZrO2 Doped ZnO/rGO Nanocomposite.

Fabrication of ZnO nanoparticles (NPs) via green process has received enormous attention for its application in biomedicine. Here, a simple and cost-effective green route is reported for the synthesis of ZrO2-doped ZnO/reduced graphene oxide nanocomposites (ZnO/ZrO2/rGO NCs) exploiting ginger rhizome extract. Our aim was to improve the anticancer performance of ZnO/ZrO2/rGO NCs without toxicity to normal cells. The preparation of pure ZnO NPs, ZnO/ZrO2 NCs, and ZnO/ZrO2/rGO NCs was confirmed by transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), photoluminescence (PL), and dynamic light scattering (DLS). XRD spectra of ZnO/ZrO2/rGO NCs exhibited two distinct sets of diffraction peaks, ZnO wurtzite structure, and ZrO2 phases (monoclinic + tetragonal). The SEM and TEM data show that ZrO2-doped ZnO particles were uniformly distributed on rGO sheets with the excellent quality of lattice fringes without alterations. PL spectra intensity and particle size of ZnO decreased after ZrO2-doping and rGO addition. DLS data demonstrated that green prepared samples show excellent colloidal stability in aqueous suspension. Biological results showed that ZnO/ZrO2/rGO NCs display around 3.5-fold higher anticancer efficacy in human lung cancer (A549) and breast cancer (MCF7) cells than ZnO NPs. A mechanistic approach suggested that the anticancer response of ZnO/ZrO2/rGO NCs was mediated via oxidative stress evident by the induction of the intracellular reactive oxygen species level and the reduction of the glutathione level. Moreover, green prepared nanostructures display good cytocompatibility in normal cell lines; human lung fibroblasts (IMR90) and breast epithelial (MCF10A) cells. However, the cytocompatibility of ZnO/ZrO2/rGO NCs in normal cells was better than those of pure ZnO NPs and ZnO/ZrO2 NCs. Augmented anticancer potential and improved cytocompatibility of ZnO/ZrO2/rGO NCs was due to ginger extract mediated beneficial synergism between ZnO, ZrO2, and rGO. This novel investigation emphasizes the significance of medicinal herb mediated ZnO-based NCs synthesis for biomedical research.

Synthesis of a stabilized colloidal suspension of PEGylated ceria nanoparticles for biomedical applications

In this study, a simple way to produce pegylated ceria nanoparticles (CNPs) with the use of low-cost and biofriendly starting reagents, such as low molecular Polyethylene Glycol (PEG) and Tris base buffer was attempted. Via this route, a highly stable aqueous suspension of ceria nanocrystals was synthesized. The synthesis of the suspension was performed at room temperature from a cerium nitrate solution. PEG was added as a dispersing agent and aqueous tris(hydroxymethyl)aminomethane (TRIS) solution 20% w/v was poured dropwise in order to achieve ceria precipitation. The CNPs had an average size of 5 nm and were almost monodispersed or formed loose agglomerates with short chainlike patterns of the size of 20 to 25 nm. The CNPs were characterized by TEM, XRD and DLS. PEGylation of the CNPs was confirmed via FT-IR analysis, while their surface chemistry was further investigated by XPS analysis. Finally, the stability of the ceria suspension was characterized with z-potential analysis.

Degradable Vinyl Copolymer Nanoparticles/Latexes by Aqueous Nitroxide-Mediated Polymerization-Induced Self-Assembly

The synthesis of degradable vinyl polymer nanoparticles/latexes in aqueous dispersed media is receiving much attention, particularly for biomedical applications and plastic pollution control, as it can circumvent the severe limitations associated with the emulsification of preformed degradable polymers. Polymerization-induced self-assembly (PISA), which enables the in situ formation of aqueous suspensions of diblock copolymer nano-objects of high solids content, has become a very popular polymerization process due to its many advantages in terms of simplicity, robustness, scalability, and versatility. However, the preparation of degradable vinyl polymer nanoparticles by direct aqueous PISA has never been reported. This severely limits the use of PISA in biomedical and environmental applications. Herein, we report the first aqueous emulsion PISA able to generate degradable vinyl polymer nanoparticles. It relies on radical ring-opening polymerization-induced self-assembly (rROPISA) of traditional vinyl monomers (n-butyl acrylate or styrene) with dibenzo[c,e]oxepane-5-thione (DOT), a thionolactone that features high stability in protic solvents and favorable reactivity with many vinyl monomers and is a precursor of labile thioester groups in the main chain. Stable aqueous suspensions of thioester-containing diblock copolymer nanoparticles were obtained with both vinyl monomers. Extensive degradation of the copolymers and the nanoparticles was successfully demonstrated under aminolytic or basic conditions. Given the success of the PISA process within the polymer community, this work has the potential to greatly expand its use in many areas, from nanomedicine (providing applicability to biocompatible vinyl polymers) to degradable coatings and sustained materials.

Cerium dioxide nanoparticles synthesized via precipitation at constant pH: Synthesis, physical-chemical and antioxidant properties

Cerium oxide nanoparticles (CeO2 NPs) are well known for their application in various fields of industry, as well as in biology and medicine. Knowledge of synthesis schemes, physicochemical and morphological features of nanoscale CeO2 is important for assessing their antioxidant behavior and understanding the mechanism of oxidative stress and its consequences. The choice of the method of synthesis should be based on the possibility to choose the conditions and parameters for obtaining CeO2 with controlled dimensions and a ratio of Се3+/Се4+ on their surface. In this study, CeO2 NPs are synthesized by precipitation in mixed water-alcohol solutions at constant pH = 9. The properties of obtained NPs are studied using various methods of physical-chemical characterization such as X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and dynamic light scattering. The size of CeO2 NPs varied from 14 to 4.2 nm with increasing alcohol concentration, while the effect of constant pH during synthesis on the morphology of the particles was insignificant. The synthesized nanoparticles form highly stable aqueous suspensions since their zeta-potential is higher than + 40 mV. It is found that the ability of CeO2 NPs to self-stabilize is associated with the presence of hydrated Ce4+ ions on their surface. In vitro biological studies have shown that, regardless of particle size, CeO2 NPs have antioxidant potential, but smaller NPs with a higher percentage of Ce3+ on the surface had a more effective antioxidant effect. In addition, the size-depended activity of CeO2 NPs to inhibit the amyloid formation of insulin is demonstrated.

Stability of Aqueous Suspensions of COOH-Decorated Carbon Nanotubes to Organic Solvents, Esterification, and Decarboxylation.

Carbon nanotubes are among the most widely used nanosystems, and stability of carbon nanotube suspensions is critical for nanotechnology and environmental science. Remaining in aqueous environment alone misses important factors that regulate colloidal stability in the presence of electrolytes. Indeed, introduction of (80-95) vol % organic solvents leads to sharp changes in suspension properties depending on the solvent. For example, the critical coagulation concentrations for a given inorganic or organic coagulating ion can change by 2 orders of magnitude when going from dimethyl sulfoxide to acetonitrile. We establish and explain these trends by Lewis acid-base interactions and show that a strong interaction extending beyond the standard theory of aggregation plays an important role.