Stable Colloidal Suspensions Research Articles

Microbial assisted date palm nanocellulose isolation and the fabrication of hydrophobic bioaerogel for oil absorption application

This study introduces a novel approach by utilizing Aspergillus niger for the isolation of nanocellulose from date palm sheath fibers (DPSF), achieving significant nano-scale reduction and high yield efficiency. The enzymatic breakdown by Aspergillus niger efficiently reduced the fibers' size, achieving an 81.3 % transition to nano-scale (<100 nm) after 96 hours, with an impressive 84 % yield using 72 hours of fungal treatment. The isolated nanocellulose demonstrated superior thermal stability and zeta potential value of −32.5 mV indicates a stable colloidal suspension due to the electrostatic repulsion between nanocellulose particles. Triethoxymethylsilane (TEMS) modification of nanocellulose aerogel significantly improved mechanical strength from 0.0194 to 0.03614 N/mm². Treatment with 5 % TEMS reduced water absorption from 41.7 g/g to 11.3 g/g, enhancing hydrophobicity (water contact angle 136.21°) and shifting material preference away from water. TEMS-treated samples showed increased absorption capacities of up to 44.3 g/g for cooking oil and 57.6 g/g for motor oil, highlighting improved compatibility with non-polar substances. These advancements underscore a sustainable solution for oil spill remediation, offering significant potential in environmental conservation and recovery efforts.

Synthesis and synergistic antibacterial efficiency of chitosan-copper oxide nanocomposites

Copper and chitosan are used for biomedical applications due to their antimicrobial properties. In this study, a facile method for the synthesis of chitosan-copper oxide nanocomposites (nCuO-CSs) was modified, yielding stable colloidal nCuO-CSs suspensions. Using this method, nCuO-CSs with different copper-to-chitosan (50–190 kDa) weight ratios (1:0.3, 1:1, 1:3) were synthesized, their physicochemical properties characterized, and antibacterial efficacy assessed against Gram-negative Escherichia coli and Pseudomonas aeruginosa, and Gram-positive Staphylococcus aureus. The nCuO-CSs with a primary size of ∼10 nm and a ζ-potential of >+40 mV proved efficient antibacterials, acting at concentrations around 1 mg Cu/L. Notably, against Gram-negative bacteria, this inhibitory effect was already evident after a 1-h exposure and surpassed that of copper ions, implying to a synergistic effect of chitosan and nano-CuO. Indeed, using flow cytometry and confocal laser scanning microscopy, we showed that chitosan promoted interaction between the nCuO-CSs and bacterial cells, facilitating the shedding of copper ions in the close vicinity of the cell surface. The synergy between copper and chitosan makes these nanomaterials promising for biomedical applications (e.g., wound dressings).

Aminated nanocellulose-mediated synthesis of polyaniline/nanocellulose hybrid materials for sustainable conductive and supercapacitors nanopapers

Diamine-functionalized cellulose nanocrystals (DamCNCs) prepared by periodate oxidation and reductive amination were used as a scaffold for the in-situ oxidative polymerization of polyaniline (PANI). Unlike unmodified CNCs, the hybrid PANI/DamCNC particles formed a stable colloidal suspension over a large pH domain, PANI particles having nucleated and grown from the nanocrystals. The hybridization of PANI was validated by transmission electron microscopy images, along with Fourier-transform infrared, Raman, and UV–Vis spectra. By taking advantage of the colloidal stability of the PANI/DamCNC nanohybrids, flexible and freestanding thin nanopapers were prepared, with different contents in PANI/DamCNCs, using cationic or anionic cellulose nanofibrils (CCNFs or ACNFs, respectively). Conductive nanopapers were obtained by mixing CCNFs with PANI/DamCNCs at a content higher than 20 wt%, exhibiting high flexibility, mechanical integrity, transparency, and stability over time. This work proposes a simple process to fabricate a novel class of biobased conductive hybrid nanofiller based on PANI grafted on DamCNCs, stable in water, that may be used as an additive in nanocellulose suspensions to produce green flexible thin nanopapers, with potential use in different types of electronic devices such as electronic displays, smart packaging, or paper-based supercapacitors for energy storage.

Toward Modeling the Structure of Electrolytes at Charged Mineral Interfaces Using Classical Density Functional Theory.

The organization of water molecules and ions between charged mineral surfaces determines the stability of colloidal suspensions and the strength of phase-separated particulate gels. In this article, we assemble a density functional that measures the free energy due to the interaction of water molecules and ions in electric double layers. The model accounts for the finite size of the particles using fundamental measure theory, hydrogen-bonding between water molecules using Wertheim's statistical association theory, long-range dispersion interactions using Barker and Henderson's high-temperature expansion, electrostatic correlations using a functionalized mean-spherical approximation, and Coulomb forces through the Poisson equation. These contributions are shown to produce highly correlated structures, aptly rendering the layering of counterions and co-ions at highly charged surfaces and permitting the solvation of ions and surfaces to be measured by a combination of short-range associations and long-ranged attractions. The model is tested in a planar geometry near soft, charged surfaces to reproduce the structure of water near graphene and mica. For mica surfaces, explicitly representing the density of the outer oxygen layer of the exposed silica tetrahedra allows water molecules to hydrogen-bond to the solid. When electrostatic interactions are included, water molecules assume a hybrid character, being accounted for implicitly in the dielectric constant but explicitly otherwise. The disjoining pressure between approaching like-charged surfaces is calculated, demonstrating the model's ability to probe pressure oscillations that arise during the expulsion of ions and water layers from the interfacial gap and predict strong interattractive stresses that form at narrow interfacial spacing when the surface charge is overscreened. This interattractive stress arises not due to in-plane correlations under strong electrostatic coupling but due to the out-of-plane structuring of associating ions and water molecules.

Synthesis of Silver‐Doped Titanium Dioxide Nanoparticles by Sol‐Gel and Coprecipitation Techniques: Evaluation of Antimicrobial Activity and Cytotoxic Effects

AbstractTiO2 nanoparticles are effective alternative to the antibiotics. The quick recombination of the photogenerated charges and the inefficient exploitation of visible light remain the major problems limiting their large‐scale applications. Modifying the TiO2 with Silver that acting as an electron trap, plays an important role in reducing the recombination of TiO2 charges and shift its photo‐response to the visible light region. The present work aims to synthesize AgTiO2 nanoparticles using sol‐gel and coprecipitation methods and evaluating the antimicrobial behavior of them. Also, to find the optimal conditions based on the anatase phase of TiO2 due to its higher antimicrobial activity than the rutile form. Among Ag‐TiO2 nanoparticles obtained, the one prepared by sol‐gel method at 450 °C and PH=8–8.5 exhibits the best antimicrobial property. AgTiO2 nanoparticles have been characterized by means X‐ray Diffraction (XRD), Fourier transform infrared spectroscopy (FTIR),scanning electron microscope (SEM), ζ‐potential, dynamic light scattering (DLS) that showing promising results. Zeta potential values −103 mV has been reported that is considered as a stable colloidal suspension system that prevents nanoparticles aggregation. Antimicrobial behavior of them were evaluated using Diffusion (Agar disk‐diffusion), Dilution (MIC) and Bacterial colony counting methods and diameter of the inhibitory zone 15 mm and minimum inhibitory concentration 5 mg/ml was observed.Colony count results indicated that AgTiO2 able to kill bacteria at the lowest concentration of 5 mg/ml. Outcomes of MTT assay (measure cell cytoxicity) suggesting the absence of toxicity in living Hfff cells (as a normal human fibroblast) while surviving L929 cells (as a cancer cell line originated from mouse fibroblast cells). After 24 and 48 h incubation from 100 % to 77.3 % and 57.2 % was reduced respectively. This indicates that Ag/TiO2 nanoparticles act as a anticancer drug and have inherent selective toxicity nature towards cancer cells while posing no effect to normal cells. AgTiO2 nanoparticles are synthesized using sol‐gel and coprecipitation methods. The sample prepared by the sol‐gel method at a temperature of 450 °C and pH=8.5, which corresponds to the anatase phase of TiO2 synthesis, shows the best antimicrobial properties and acts as an anticancer drug with inherent selective toxicity nature towards cancer cells while posing no effect on normal cells.

Synthesis and Characterization of Silica-Titanium Oxide Nano-Coating on NiTi Alloy

To functionalize the surface of the NiTi alloy, hybrid layers comprising nanometric silica and titanium oxides were synthesized. The TiO2–SiO2 nanosystem was chemically prepared and utilized for electrophoretic deposition (EPD) to create multifunctional layers on the alloy surface. The impact of pH on Zeta potential and ceramic particle size was explored to ensure a stable colloidal suspension for EPD, with optimal parameters established at a pH of approximately 6. A uniform layer was formed by applying a voltage of 40 V for 3 min, appearing as a thin film interspersed with regularly spaced larger agglomerates. The thin film primarily consisted of a minor fraction of defective rutile nanoparticles, accompanied by silica and carbon agglomerates from the nanosystem synthesis process. Heat treatment at 800 °C for 2 h induced significant structural changes, developing a novel-generation material with a different structure. An interlayer with strong Si–O–Ti connections was formed. Moreover, the mechanism of layer formation was extensively discussed.

Scalable and adaptable two-ligand co-solvent transfer methodology for gold bipyramids to organic solvents.

Large and faceted nanoparticles, such as gold bipyramids, presently require synthesis using alkyl ammonium halide ligands in aqueous conditions to stabilize the structure, which impedes subsequent transfer and suspension of such nanoparticles in low polarity solvents despite success with few nanometer gold nanoparticles of shapes such as spheres. Phase transfer methodologies present a feasible avenue to maintain colloidal stability of suspensions and move high surface energy particles into organic solvent environments. Here, we present a method to yield stable suspensions of gold bipyramids in low-polarity solvents, including methanol, dimethylformamide, chloroform, and toluene, through the requisite combination of two capping agents and the presence of a co-solvent. By utilizing PEG-SH functionalization for stability, dodecanethiol (DDT) as the organic-soluble capping agent, and methanol to aid in the phase transfer, gold bipyramids with a wide-range of aspect ratios and sizes can be transferred between water and chloroform readily and maintain colloidal stability. Subsequent transfer to various organic and low-polarity solvents is then demonstrated for the first time.

Multiscale Modeling of Aqueous Electric Double Layers.

From the stability of colloidal suspensions to the charging of electrodes, electric double layers play a pivotal role in aqueous systems. The interactions between interfaces, water molecules, ions and other solutes making up the electrical double layer span length scales from Ångströms to micrometers and are notoriously complex. Therefore, explaining experimental observations in terms of the double layer's molecular structure has been a long-standing challenge in physical chemistry, yet recent advances in simulations techniques and computational power have led to tremendous progress. In particular, the past decades have seen the development of a multiscale theoretical framework based on the combination of quantum density functional theory, force-field based simulations and continuum theory. In this Review, we discuss these theoretical developments and make quantitative comparisons to experimental results from, among other techniques, sum-frequency generation, atomic-force microscopy, and electrokinetics. Starting from the vapor/water interface, we treat a range of qualitatively different types of surfaces, varying from soft to solid, from hydrophilic to hydrophobic, and from charged to uncharged.

Flow and Heat Transfer of Micropolar Ferrofluid at Stagnation Point on a Horizontal Flat Plate in the Presence of Magnetic Field and Thermal Radiation

Ferrofluid demonstrates Newtonian or non-Newtonian fluid behaviour depending on the characteristics of ferrofluid. Generally, ferrofluid consists of a stable colloidal suspension of single-domain magnetic particles in a base fluid that can assume non-Newtonian fluid behaviour involving a spin vector and microinertia tensor in flow motion. These two properties possess the theory of micropolar fluid which exhibits microrotational motions and spin inertia in microscopic behaviour. Therefore, this theoretical study is focused to investigate the boundary layer of micropolar ferrofluid flow and heat transfer at the stagnation point on the horizontal flat plate. Magnetite (Fe3O4) nanoparticles and water (H2O) compose in ferrofluid exposed to the magnetic field and thermal radiation is considered. The influences of ferroparticles volume fraction and micropolar parameter on the ferrofluid flow and heat transfer are evaluated mathematically. The partial differential equations have been formulated based on purposed assumptions using Tiwari and Das model and are simplified into ordinary differential equations, which are then solved numerically by Runge-Kutta Fehlberg (RFK45) method. The numerical results of the velocity profile, temperature profile, angular velocity profile, reduced skin friction and reduced Nusselt number are scrutinised in different values of ferroparticles volume fraction and micropolar parameter to estimate the ferrofluid flow and heat transfer. It is found the velocity profile of micropolar ferrofluid flow increases when elevates the ferroparticles volume fraction but decreases when increasing the micropolar parameter. Meanwhile, enlarging ferroparticles volume fraction of micropolar ferrofluid also enhances the temperature profile, reduced skin friction and reduced Nusselt number in the presence of magnetic field and thermal radiation parameter.

Nanohydroxyapatite Loaded with 5-Fluorouracil and Calendula officinalis L. Plant Extract Rich in Myo-Inositols for Treatment of Ovarian Cancer Cells

In this study, the hydroxyapatite (HAp) in the form of nanoparticles was synthesized through the wet co-precipitation method and loaded with plant extract from Calendula officinalis L. rich in biologically active myo-inositol, and the 5-fluorouracil anticancer drug. The obtained nanomaterials have rod-like structures approx. 30 nm in diameter and 100 nm in length. FT-IR analysis results proved the immobilization of biologically active compounds. The loading of plant extract into the carrier improved the stability of colloidal suspension, which was confirmed with turbidimetry. The composite modified with calendula extract and drug (HAp@Cal@5-flu) effectively scavenges the DPPH radicals, with a radical scavenging activity (RSA) of about 20.0 ± 1.3%. The effect is supported by the DFT calculations of the HOMO-LUMO, presenting the chemical reactivity of the molecules loaded into the HAp. The in vitro cytotoxicity results on SKOV-3 ovarian cancer cells show the pronounced cytotoxic effect of the HAp@Cal@5-flu. The calendula extract loading into the carrier provided better interactions with the tumorous biomimetic membranes studied with a Langmuir trough, making it a promising material in nano-biomedicine, including drug delivery and targeted cancer treatment.

Molecular-Level Relation between the Intraparticle Glass Transition Temperature and the Stability of Colloidal Suspensions.

In many colloidal suspensions, the dispersed colloidal particles are amorphous solids, resulting from vitrification. A crucial open problem is understanding how colloidal stability is affected by the intraparticle glass transition. By dealing with the latter process from a solid-state perspective, we estabilish a proportionality relation between the intraparticle glass transition temperature, Tg, and the Hamaker constant, AH, of a generic suspension of nanoparticles. It follows that Tg can be used as a convenient parameter (alternative to AH) for controlling the stability of colloidal systems. Within the Derjaguin-Landau-Verwey-Overbeek theory, we show that the novel relationship, connecting Tg to AH, implies the critical coagulation ionic strength to be a monotonically decreasing function of Tg. We connect our predictions to recent experimental findings.

Nano-Bio Interface Engineering Using Cyclovoltammetry and Design of Nanostructured Lanthanide Oxysulfide Thin Films

Nanoparticles (NPs) in which magnetic and optical properties coexist have been intensively explored for diverse biomedical applications including diagnostic, in vivo imaging and therapy. Gadolinium oxysulfide (Gd2O2S) NPs are promising candidates for biotechnologies as they have been used as MRI contrast agent or X-ray absorbing materials. When doped with cerium, they gain an additional functionality as visible light absorber due to the decrease in the material bandgap from 4.7 eV non-doped to 2.5 eV with 5% of Ce. Further biomedical applications may be envisioned thanks to the combined antioxidant properties of cerium and the magnetic properties of gadolinium.Understanding the molecular-level interactions between organisms and nanoparticles to guide and enable the design of novel materials that are less toxic remains a challenge. In order to understand these interactions at the nanoscale, we studied the change in the physico-chemical properties of (Gd,Ce) oxysulfide NPs when they are immersed in a biological medium. In biological medium, pristine nanomaterials transform and acquire a corona of biomolecules, such as proteins, which can modify their identity. This is known as the nano-bio interface. A better understanding of how nanoparticles interaction with a biological system affect their properties is critical to the future development of multifunctional NPs.Our recent work provides us with a privileged access to composition-controlled nanoplates with a narrow size distribution for a large range of Ln. In particular, we mastered the preparation of mixed-lanthanide nanoplates with tunable band gap and magnetic properties while providing an in-depth understanding of their structural and surface features. The challenge addressed here is to prepare and characterize ligand-free nanostructured thin films made from the NPs suspension. Compared to studies realized in solution, thin films allow to reach the surface of the nanoparticles without any interaction from the ligands. Moreover, it allows spectroscopic and electrochemical methods to be used for the monitoring of the NPs intrinsic properties.The design and development of nanostructured thin films started with the colloidal synthesis of (Gd,Ce) oxysulfide NPs which provides a phase-pure powder. The nanoparticles were then dispersed into an optimized mix of solvents in order to get a stable colloidal suspension. Dip coating is an easy method to deposit matter on a substrate while having a fine control of the thickness and homogeneity. This process was optimized to obtain homogenous films with a withdrawal speed of 2 mm/s under low relative humidity. Thin films of optical quality with a thickness from 40 nm to 150 nm were obtained using single-layer and multilayer deposition on various substrates including silicon, FTO and kapton (Figure A). In situ UV and IR Spectroscopic Ellipsometry were used to monitor the variations of thickness and optical constants, together with the chemical species present at the surface, upon heating the films in different conditions. This study allowed to finely tune the thermal treatment in order to get rid of the stabilizing ligands while preserving the integrity of the nanoplates, as confirmed by Transmission Electron Microscopy (Figure B shows the scraped film). As a result, we have access to the bare surface of the NPs, which was hardly possible in solution. The change in the band gap of the material was monitored through UV-Variable Angle Spectroscopic Ellipsometry. This non-invasive technique is the gold-standard for the characterization of optical quality thin films and gives refractive index of the material (Figure C shows the Tauc plot with the linear fit giving the band gap of the material).The film can be immersed into a biological medium where proteins are expected to bind to the surface of the NP and significantly change their reactivity and mobility. Cyclovoltammetry helped us to probe the access to the NPs and monitor the position of the conduction band. We used redox probes of different standard potentials as electrolytes (Figure D). Electron exchange with the semiconductor electrode is supposed to occur through the conduction band as the valence band is too far in energy. For a redox couple with a standard potential negative to the conduction band edge, when the applied potential equals E0 redox, the semiconductor is accumulating electrons at its surface in a so-called space charge layer. Under these conditions, whether a positive or negative bias is applied (compared to E0 redox), the SC is maintained in an accumulation mode. This was very helpful to check whereas the electronical properties of the material changed upon exposition to biological medium. This could lead to a better understanding and prediction of the chemical interactions at the interface with biomolecular systems. Figure 1

Pickering emulsion stabilized by conjugated sodium caseinate-ascorbic acid nanoparticles: Synthesis and physicochemical characterization

This study investigated the effect of sodium caseinate (SC)-ascorbic acid (AA) interaction under thermal (as a Maillard reaction) treatment on the physicochemical properties of the SC-AA colloidal particles, as well as, the physical and oxidative stability of the prepared Pickering emulsion (PE) using colloidal particles as an aqueous phase with the volumetric ratio of 50:50 water and oil. The stable colloidal suspensions were obtained when the concentration of SC-AA solution was set at 10 and 1 mg/mL for SC and AA, respectively. The fluorescence and FT-IR results showed strong hydrophobic interaction in SC-AA complex, but after heat treatment of SC and AA (HSC-AA), the covalent Schiff base type bond formed. In the HSC-AA sample, the percentage of free amino group reduction (∼32%) confirmed the Maillard reaction occurrence, and the results of SDS-PAGE showed cross-linking between SC particles. A significant decrease in interfacial tension was observed in samples containing AA, which reached the lowest value in HSC-AA (6.5 mN/m). Also, the wettability of HSC-AA increased based on a three-phase contact angle analysis to θ ∼82°. In the case of physical stability, while SC, SC-AA, and HSC samples could not stabilize the PE, the HSC-AA showed the best physical stability for more than 90 days at 4 °C and 7 days at 37 °C. CLSM images showed HSC-AA particles were located around the oil droplet. Based on TBARS results, the value of advanced oxidation product was the lowest for HSC-AA stabilized PE, indicating the protective effect of HSC-AA solid particles against lipid oxidation. This research confirmed the HSC-AA effectiveness as a solid particle stabilizer for PE, especially in reduced fat formulations. These results are valuable due to the common use of SC and AA as food-grade additives.

Facile preparation of 3D interconnected macroporous CeF3

CeF3 is largely used due to its technological importance for applications in various domains such as photonics, sensors, energy and catalysis and its nanostructuration represents a real challenge. In this paper, we report on the novel and environmentally friendly synthetic route of monodisperse CeF3 nanoparticles (NP) with a diameter of about 10 nm and a high surface area (≈130 m2 g−1) by a surfactant-free aqueous precipitation route at room temperature (yield ≈ 90%). The dispersion of the NP as a stable colloidal suspension allows to prepare for the first time 3D interconnected macroporous CeF3 through the assembly of as-prepared NP and home-made poly(methyl methacrylate) (PMMA) beads as template. These Organized Porous Inorganic Fluorides (OPIF) materials have been deeply characterized at different synthesis stages by means of powder X-ray diffraction (XRD), N2 sorption, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses. CeF3 OPIF present a macroporosity (pore diameter ≈ 200 nm) as well as well as intergranular mesoporosity emerging from the voids between the CeF3 NP (DTEM ≈ 7 nm) composing the OPIF walls resulting in a surface area of 33 m2 g−1. The thermal stability under nitrogen of the CeF3 crystal structure is increased for the 3D interconnected macroporous materials in comparison with the NP as the CeF3 crystal structure remains stable until 550 °C for CeF3 OPIF and only 400 °C for CeF3 NP. Finally, the porous structuration of CeF3 materials considerably slows down the crystallite growth during thermal treatment under nitrogen. The crystallite size of CeF3 NP constantly increases from 10 nm (120 °C) to 30 nm (420 °C). At the opposite, the crystallite size of CeF3 OPIF remains unchanged until 460 °C (17 nm).

Characterization of pickering emulsion stabilized by colloidal sodium caseinate nanoparticles prepared using complexation and antisolvent method

The aim of this study was to investigate the effect of different treatments on sodium caseinate (SC) colloidal suspension physicochemical properties and their ability to act as a Pickering stabilizer for reduced-fat formulations. Heat-treated SC (HSC) particles were prepared by adding glucose (HSC-Glc) and tannic acid (HSC-TA), followed by precipitation with ethanol (EtOH) and ethyl cellulose (EC) dissolved in ethanol (EC/EtOH). Stable colloidal suspensions were prepared by adjusting SC, Glc, TA, and EC to 10, 4, 2, and 5 mg/mL respectively, and using a 5: 3 solvent/antisolvent (mL/mL). The stable Pickering emulsions (PEs) in the volumetric ratio of 50: 50 (mL/mL) oil: water were prepared using HSC/EtOH, HSC-Glc/EtOH, and HSC-Glc-TA-EC/EtOH particles as the aqueous phases. They showed higher contact angles and lower interfacial tensions in comparison with native SC and long-term physical stability. Heating and the addition of anti-solvent played the main role in stabilizing PEs with SC and the addition of Glc, TA or EC has only an auxiliary role that could be added or removed depending on its application purpose in the food or pharmaceutical industry. They especially had a major role in the oxidative and thermal stability of the emulsion.

Integration of surface modified aqueous ink for multi-functional material extrusion

The possibility to construct functional materials with designed shapes via 3d printing involves higher flexibility in the next-generation of our device. In order to formulate stable colloidal suspension with high solid loading, water-based ink allows particles dispersion by tuning surface chemistry. But it has been limited by material solubility in water. Moreover, tailoring ink formulation of different materials will increase the feasibility of wider materials combinations. Here, a facile method of polyvinylpyrrolidone coating of starting functional materials is been utilized, illustrating with zinc oxide as an example. Inks made with surface modified powder shows a typical shear thinning behavior. In addition, the printed samples are employed as adsorbents for removal of gaseous HCHO, and the sample with higher capping agent molecular weight offers better adsorption performance compared to other samples. Furthermore, compared with commercial Co Foam, the Tafel slope of the 3D Co is only 116.1 mV dec−1, exhibiting good hydrogen evolution reaction electrocatalytic kinetics, and demonstrating its wide potential in electrocatalytic field.

Optical-Quality Thin Films with Tunable Thickness from Stable Colloidal Suspensions of Lanthanide Oxysulfide Nanoplates.

In modern laser technologies, there is a need for coatings that would be compatible with flexible substrates while retaining the advantages of inorganic compounds in terms of robustness. As a first step in this direction, we developed here thin films of lanthanide oxysulfide, of optical quality, prepared by low-temperature dip coating. As a model compound in the family of oxysulfides, (Gd,Ce)2O2S anisotropic nanoplates were used. The films were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and in situ UV and IR spectroscopic ellipsometry, showing that the band gap of the materials was preserved through the deposition process. The thickness of the films was tuned in a broad range, from a few nanometers to 150 nm, using different concentrations of the colloidal suspensions as well as single-layer and multilayer deposition. Lastly, thermal treatment of the thin films was optimized to remove the stabilizing organic ligands of the nanoparticles while preserving their integrity, as confirmed by SEM and XRD.

Study of gallic acid antioxidant molecule in interaction with solvents, aiming its utilization as a stabilizer of magnetic nanoparticles in suspensions

Gallic acid (GA) molecule was studied by quantum-chemical and experimental approaches since it is a remarkable antioxidant product that could be used to improve the biocompatibility of magnetite nanoparticles in colloidal suspension. Computational modeling has evidenced significant dipolar character as well as good reactivity and stability. The preparation of magnetite nanoparticles capped with GA has resulted in stable colloidal suspension as revealed by Transmission Electron Microscopy investigation. A solvatochromic study was carried out on GA in binary and ternary solutions, evidencing the coexistence of the main types of universal solute–solvent interactions. Based on the spectral behavior in protic and polar solvents the dipole moment vector in the excited state was found.

Synthesis and Characterization of Alginate/Bentonite Hydrogels

AbstractThe use of bentonite for organic dyes removal in the water system is an economical and highly efficient alternative against the usually applied purification methods. However, during the post‐treatment stage bentonite swells and forms highly stable colloidal suspensions, being difficult to separate from the aqueous system. In this work, calcium alginate hydrogels beads with 5 and 10% w/w of bentonite are synthetized and their capacity to adsorb methylene blue, as model dye, from aqueous media is evaluated. Structure and mechanical properties of hydrogels beads are determined, showing that hydrogels beads with bentonite present higher viscosity and hardness. Regarding methylene blue adsorption capacity, the effect the contact time (0–32 h) and the initial cadmium ion concentration (0.2–3.0 mg L−1) are studied employing hydrogel beads. The equilibrium adsorption time is reached at 300 min for all studied hydrogels and experimental data are fitted well with a pseudo‐second order kinetic model. As conclusion, alginate/bentonite hydrogel beads are accepted as a promising candidate to remove methylene blue dye from aqueous solutions.

Solid-state synthesis of UV-plasmonic Cr2N nanoparticles.

Materials that exhibit plasmonic response in the UV region can be advantageous for many applications, such as biological photodegradation, photocatalysis, disinfection, and bioimaging. Transition metal nitrides have recently emerged as chemically and thermally stable alternatives to metal-based plasmonic materials. However, most free-standing nitride nanostructures explored so far have plasmonic responses in the visible and near-IR regions. Herein, we report the synthesis of UV-plasmonic Cr2N nanoparticles using a solid-state nitridation reaction. The nanoparticles had an average diameter of 9 ± 5nm and a positively charged surface that yields stable colloidal suspension. The particles were composed of a crystalline nitride core and an amorphous oxide/oxynitride shell whose thickness varied between 1 and 7nm. Calculations performed using the finite element method predicted the localized surface plasmon resonance (LSPR) for these nanoparticles to be in the UV-C region (100-280nm). While a distinctive LSPR peak could not be observed using absorbance measurements, low-loss electron energy loss spectroscopy showed the presence of surface plasmons between 80 and 250nm (or ∼5 to 15eV) and bulk plasmons centered around 50-62nm (or ∼20 to 25eV). Plasmonic coupling was also observed between the nanoparticles, resulting in resonances between 250 and 400nm (or ∼2.5 to 5eV).