Coagulation performance of cationic polyelectrolyte/TiO2 nanocomposites prepared under LED irradiation

A series of acrylic-based cationic polyelectrolyte nanocomposites including water-soluble monomers acrylamide (AAm) and 2-acryloyloxyethyltrimethylammonium chloride (DAC) with different mole percent of DAC (30, 40, and 45%) in feed were produced using TiO₂ nanoparticles (0.018, 0.037, and 0.11 wt%) as photoinitiator in the aqueous solution of monomers and named as p(ADT)_1–9. The LED light at 365 nm was used for photocatalysis activation of TiO₂ nanoparticles. Structure and morphology of the synthetic polyelectrolyte were characterized by FT-IR, NMR, TGA, FESEM-EDX, and TEM. The other properties of synthetic polyelectrolyte such as molecular weight, viscosity, charge density, AAm/DAC molar ratio in copolymers, reactivity ratio values for the AAm and DAC monomers, and polymerization degree were measured. Furthermore, coagulation performance of these polyelectrolytes was investigated in soil suspension (1,000 ml, initial turbidity = 1,715 NTU). The prepared nanocomposites enhanced the coagulation of soil suspension up to 99.5% in low dosages. The best turbidity removal efficiencies (TRE) between 99.5–99.77% were achieved by p(ADT)₃ conatining 30% DAC and 0.11 wt% TiO₂. Decreasing the temperature from room temperature to 0°C led to an increase in TRE from 98 to 99.8%. Also, increasing the pH from 4 to 12 led to a decrease in TRE from 99.86 to 94%.     

Size-controllable gold nanoparticles stabilized by PDEAEMA-based double hydrophilic graft copolymer

Poly(N-isopropylacrylamide)-b-[poly(ethyl acrylate)-g-poly(2-(diethylamino)ethyl methacrylate)] (PNIPAM-b-(PEA-g-PDEAEMA)) double hydrophilic graft copolymers were employed to prepare stable colloidal gold nanoparticles in situ with controllable size in aqueous media without any external reducing agent. PDEAEMA side chains served as reduction agent and stabilizer and PNIPAM segment acted as a hydrated layer to enhance the stability of gold nanoparticles. These gold nanoparticles showed a remarkable colloidal stability without any observable flocculation or aggregation for at least 2 months and they were characterized by UV-vis, XRD, TEM and AFM in detail. The size of gold nanoparticles can be tuned by adjusting the length of PDEAEMA side chains and the molar ratio of [DEAEMA]/[AuCl₄⁻]. Both the increasing of the length of PDEAEMA side chains and the decreasing of [DEAEMA]/[AuCl₄⁻] molar ratio resulted in the fall of size.     

Size Controlled Synthesis of Gold Nanoparticles by Porphyrin with Four Sulfur Atoms

Tetradentate thioacetyl porphyrin ligand (1) was synthesized to protect gold nanoparticles. 1-protected gold nanoparticles were characterized by UV-vis spectroscopy and XPS. Analysis by XPS showed that all of four thioacetyl groups of 1 were dissociated and bound to the surface of gold nanoparticles in thiolate form. The size of 1-protected gold nanoparticles (GN:1) was controlled by thioacetyl group/HAuCl₄ molar ratio and approached to 2 nm. Compared with a protecting ligand without porphyrin plane (2) or dodecanethiol, 1 can control the size of gold nanoparticles efficiently probably due to the tetradentate ligation effect.     

Synthesis and characterization of Nafion-stabilized Pt nanoparticles for polymer electrolyte fuel cells

Platinum nanoparticles are synthesized by alcohol reduction method using Nafion as a stabilizer under various conditions such as the Nafion/Pt molar ratio and reflux temperature. Nafion-Pt nanoparticles are characterized by agglomeration and the particle size is typically in the range of 2-4 nm. The electrocatalytic activity of Nafion-Pt nanoparticles for polymer electrolyte and direct methanol fuel cells (PEFCs and DMFCs) is investigated in comparison to that of unsupported Pt black and carbon-supported Pt/C electrocatalysts. Nafion-Pt nanoparticles prepared with low Nafion/Pt ratios show higher and/or comparable activities towards O₂ reduction reaction in the absence and presence of methanol in comparison to that of Pt black and Pt/C electrocatalysts. In contrast, the electrocatalytic activity of the Nafion-Pt nanoparticles for the methanol oxidation reaction is very low. The results indicate that Pt nanoparticles embedded in Nafion polyelectrolyte are potential methanol tolerant electrocatalysts for the O₂ reduction reaction in DMFCs.     

Microwave irradiation synthesis and self-assembly of alkylamine-stabilized gold nanoparticles

The hydrophobic gold nanoparticles protected with octadecylamine, tetradecylamine and decylamine, respectively, were prepared by using ethanol reduction in reverse micelle through microwave dielectric heating. In this experiment, the commonly used toxic and highly volatile organic solvents such as chloroform, toluene and so on, which were an obstacle for preparing hydrophobic nanoparticles under microwave irradiation, were replaced by a safe organic mixed solvent n-heptane/ethanol used as an oil phase. The various alkylamine-stabilized gold nanoparticles obtained through this method were characterized and analyzed by ultraviolet visible spectroscopy (UV-vis), X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and elemental analysis. When the molar ratio of alkylamine to HAuCl₄ was 40 : 1, the average diameters and standard deviations for octadecylamine-, tetradecylamine- and decylamine-capped gold nanoparticles were 4.53 ± 0.79, 5.22 ± 1.66, and 4.09 ± 1.22 nm, respectively. Furthermore, the composition of octadecylamine-stabilized gold nanoparticles was determined to be (C₁₈H₃₇NH₂)₂₆₅·Au₂₈₂₂, and the experimental result showed that both the monodispersity and stability of these gold nanoparticles were beneficial to forming large areas of ordered two-dimensional arrangement at the air/water interface.     

Influence of sulfide ions on the formation and properties of gold nanoparticles in aqueous solutions

The influence of sulfide ions on the formation of gold nanoparticles during reduction of HAuCl₄ in an aqueous solution is studied using plasmon resonance spectroscopy and scanning tunneling microscopy. Upon the simultaneous addition of sodium citrate and sodium sulfide and for the molar ratios S/Au < 1, the nanoparticles have smaller sizes than those formed during the reduction only with sodium citrate under the same conditions; however, an increase in the sulfur content leads to an increase in the particle size. The gold nanoparticles are also obtained under microwave heating with a single-stage reaction of an AuCl ₄ ^? aqueous solution with sodium sulfide. The particle size decreases with an increase in the S/Au ratio.     

Mono- and bi-functional arenethiols as surfactants for gold nanoparticles: synthesis and characterization

Stable gold nanoparticles stabilized by different mono and bi-functional arenethiols, namely, benzylthiol and 1,4-benzenedimethanethiol, have been prepared by using a modified Brust's two-phase synthesis. The size, shape, and crystalline structure of the gold nanoparticles have been determined by high-resolution electron microscopy and full-pattern X-ray powder diffraction analyses. Nanocrystals diameters have been tuned in the range 2 ÷ 9 nm by a proper variation of Au/S molar ratio. The chemical composition of gold nanoparticles and their interaction with thiols have been investigated by X-ray photoelectron spectroscopy. In particular, the formation of networks has been observed with interconnected gold nanoparticles containing 1,4-benzenedimethanethiol as ligand.     

Tunability and stability of gold nanoparticles obtained from chloroauric Acid and sodium thiosulfate reaction

ABSTRACT: In the quest for producing an effective clinically relevant therapeutic agent, scalability, repeatability, and stability are paramount. In this paper, gold nanoparticles (GNPs) with precisely controlled near infrared (NIR) absorption are synthesized by a single step reaction of HAuCl4 and Na2S2O3, without assistance of additional templates, capping reagents or seeds. The anisotropy in the shape of gold nanoparticles offers high NIR absorption making it therapeutically relevant. The synthesized products consist of GNPs with different shape and size, including small spherical colloid gold particles and non-spherical gold crystals. The NIR absorption wavelengths and particle size increase with increasing molar ratio of HAuCl4/Na2S2O3. Non-spherical gold particles can be further purified and separated by centrifugation to improve the NIR absorbing fraction of particles. In-depth studies reveal that GNPs with good structural and optical stability only form in a certain range of the HAuCl4/Na2S2O3 molar ratio, whereas higher molar ratios result in unstable GNPs, which lose their NIR absorption peak due to decomposition and reassembly via Ostwald ripening. Tuning the optical absorption of the gold nanoparticles in the NIR regime via a robust and repeatable method will improve many applications requiring large quantities of desired NIR absorbing nanoparticles.     

Polyelectrolyte‐aided synthesis of gold and platinum nanoparticles: Implications in electrocatalysis and sensing

An electrochemical method for depositing redispersible, lower size gold nanoparticles from a novel polyelectrolyte‐gold complex is described. The size of gold nanoparticles is in the range 6.2–15.4 nm. The gold nanoparticles, first deposited on platinum surface are transferable into water. They can also be directly in situ‐electrodeposited on to materials like carbon, carbon nanotubes or conducting polymers for an end use as electro catalysts. The composites Au‐MWCNT, Pt‐MWCNT, Au‐Carbon, and Pt‐Carbon are synthesized and tested for their electrocatalytic activity. The composites exhibit good catalytic activity in sensing dopamine or electrooxidation of methanol. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Cationic polyelectrolytes,XI. Polymers with quaternary N-atoms in the main chain obtained by condensation polymerization of epichlorohydrin with amines

Water soluble cationic polyelectrolytes containing quaternary nitrogen atoms within the main chain were prepared via condensation polymerization of epichlorohydrin (ECH) with dimethylamine (DMA) and N,N-dialkylaminoalkylamines. The main parameters of the reaction that influence the polymer properties are: DMA/asymmetrical diamine molar ratio, the initial concentration of amine solution, NaOH/amine molar ratio, ECH/amine molar ratio, and asymmetrical diamine structure. The feature of flexible polyelectrolyte own to the investigated polymers was emphasized by the viscosimetric behaviour in dilute aqueous solutions with and without salt presence.     

Phase Transformation of Iron Oxide Nanoparticles by Varying the Molar Ratio of Fe2+:Fe3+

Co‐precipitation from a solution of ferrous/ferric mixed salt with the ratio of Fe²⁺:Fe³⁺ = 1:2 in air atmosphere is not a reliable method to synthesize magnetite (Fe₃O₄) nanoparticles because of the fact that Fe²⁺ oxidizes to Fe³⁺ and the molar ratio of Fe²⁺:Fe³⁺ changes. Therefore, the phase composition changes from magnetite to maghemite (γ‐Fe₂O₃). The influence of the initial molar ratio of Fe²⁺:Fe³⁺ on the phase composition of nanoparticles, their crystallinity and magnetic properties was studied. Experimental data from XRD, FTIR, SEM, and VSM reveal that the appropriate method to synthesize magnetite nanoparticles is reverse precipitation from only ferrous salt. It is found that by decreasing the synthesis temperature and by increasing the concentration of alkaline solution and the ratio of Fe²⁺:Fe³⁺ the crystallinity and the specific saturation magnetization (σ_s) are increased.     

低温油相合成金钯纳米粒子及其催化性能研究

采用低温油相法合成了不同金钯量比的双金属纳米催化剂,对其形貌和电催化性能进行了分析。透射电镜表征结果显示,金钯的量比对催化剂的分散性和纳米颗粒的尺寸有一定的影响。当金钯等量比时,分散性最好、纳米颗粒的粒径最小。而电化学测试表明,当金钯等量比时,高分散、小尺寸的金钯纳米催化剂更易于裸露有效活性位点,从而对甲酸和乙醇显示出较高的催化活性和稳定性。     

One-step preparation and characterization of PDDA-protected gold nanoparticles

Poly(diallyl dimethylammonium) chloride (PDDA), an ordinary and watersoluble cationic polyelectrolyte, was investigated for its ability to generate and stabilize gold colloids from a chloroauric acid precursor. In this reaction, PDDA acted as both reducing and stabilizing agents for gold nanoparticles (AuNPs). More importantly, PDDA is a quaternary ammonium polyelectrolyte, which shows that the scope of the reducing and stabilizing agents for metal nanoparticles can be extended from the amine-containing molecules to quaternary ammonium polyelectrolytes or salts. UV-vis spectroscopy, transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS) and Fourier transform infrared (FTIR) were used to characterize the synthetic AuNPs. The PDDA-protected AuNPs obtained are very stable and have relative narrow size distribution.     

Rheological behavior of multi-sized SiC inks containing polyelectrolyte complexes specifically for direct ink writing

In order to simultaneously improve both the solid loading and rheological behavior of ceramic ink during direct ink writing (DIW) process, the polyelectrolyte complexes have been used as rheological modifiers. Based on the Funk-Dinger function, the maximum solid loading of multi-sized SiC ink reached 63 vol%. The viscoelasticity of SiC inks with different [COOH]:[NH_x] molar ratios was investigated and the mechanism of polyionic chains on rheology was analyzed. When the [COOH]:[NH_x] molar ratio was 1:0.1, the SiC ink exhibited excellent thixotropic behavior and formability. The effect of particle size on rheological behavior of SiC ink was investigated to clarify the correlation between polyelectrolyte complexes and multi-sized SiC.     

Co-existance of various active gold species in Au-mordenite catalyst for CO oxidation

Different structural and electronic states of gold species in H-mordenite with SiO₂/Al₂O₃ molar ratio 206 and their transformations under redox treatments have been studied by the methods of diffuse reflectance UV–visible spectroscopy and FTIR spectroscopy of adsorbed CO. Different states of ionic and metallic gold were detected in the zeolite channels and on the external surface of the zeolite – Au⁺ and Au³⁺ ions, charged clusters ${\mathrm{Au}}_n^{\delta +}$, and neutral nanoparticles Au_m. Catalytic tests of the samples revealed the co-existence of several types of active species of gold in CO oxidation – gold clusters <1.5 nm (responsible for low-temperature activity) and gold nanoparticles (responsible for high-temperature activity).     

Decorating Au nanoparticles onto optimized P(tBA-co-DMAEMA) carriers for ameliorative catalytic capability

Gold nanoparticles are increasingly being explored as novel catalytic nanomaterials due to their great reductive capacity. However, the van der Waals forces between them would bring poor stabilities as well as attenuated catalytic properties in solution. Therefore, it is significant to find carriers that could prevent catalytic gold nanoparticles from agglomerating. Herein, hydrophilic dimethylaminoethyl methacrylate (DMAEMA) and hydrophobic tert-butyl acrylate (tBA) were used as co-monomers to synthesize copolymer P(tBA-co-DMAEMA) microspheres by one-step emulsifier-free emulsion polymerization. Afterward, the self-assembly behaviors of the amphiphilic polymers P(tBA-co-DMAEMA) under different conditions like molar ratio of DMAEMA/tBA and ethanol/water were explored to reveal an optimal condition for obtaining copolymer with appropriate size and morphology. These microspheres were used as carriers for gold nanoparticles, since HAuCl₄ could be simply reduced and stabilized on their surface. Furthermore, various conditions such as HAuCl₄ content, adding method of HAuCl₄, protonation time and reducing conditions were filtered for the decoration of gold nanoparticles on the shell of that assembled copolymer. This composite was applied as an excellent catalyst for hydrogenation of hazardous chemicals (4-nitrophenol and nitrobenzene). And it shows improved catalytic performance for both 4-nitrophenol in the aqueous system and nitrobenzene in the oil system. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48920.     

Chemical synthesis of nanosized BaCO3 with a pillar-like morphology

A procedure for the preparation of nanosized pillar-like BaCO₃ based on the aging of barium nitrate aqueous solutions in the presence of lactic acid, sodium carbonate, and polyvinylpyrrolidone. Using X-ray diffraction analysis, scanning electron microscopy, and transmission electron microscopy, the morphological characteristics of BaCO₃ were controlled by altering the molar ratio of lactic acid to barium ion, as well as the initial pH and barium ion concentration. The possible formation mechanism of the nanoparticles was also discussed.     

Synthesis, characterization, and antibacterial activity of metal nanoparticles embedded into amphiphilic comb-type graft copolymers

The synthesis, spectroscopic characterization, and antimicrobial efficiency of gold and silver nanoparticles embedded in novel amphiphilic comb-type graft copolymers having good film-forming properties have been described. Amphiphilic comb-type graft copolymers were synthesized by the reaction of chlorinated polypropylene (PP) (M _w = 140,000 Da) with polyethylene glycol (PEG) (M _n  = 2,000 Da) at different molar ratios. Metal nanoparticles embedded graft copolymers were prepared by reducing solutions of the salts of silver or gold and the copolymer in tetrahydrofuran. The optical properties of the metal nanoparticle embedded copolymers were determined by using UV–visible spectroscopy. Surface plasmon resonance (SPR) of the gold and silver nanoparticle embedded copolymers in toluene was observed at a maximum wavelength (λ_max) of 428 and 551 nm in the UV–VIS absorption spectra, respectively. The average particle diameters of the gold and silver nanoparticles were found to be 50 nm from the high resolution scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Amphiphilic polymer films containing silver and gold nanoparticles were found to be highly antimicrobial by virtue of their antiseptic properties to Escherichia coli and Staphylococcus aureus.     

Preparation of gold nanoparticles under presence of the diblock polyampholyte PMAA-<Emphasis Type="Italic">b</Emphasis>-PDMAEMA

The preparation of gold nanoparticles in presence of different weak polyampholytes is investigated. As diblock polyampholytes several poly(methacrylic acid)-block-poly((dimethylamino)ethyl methacrylate), PMAA-b-PDMAEMA, have been used, characterized by different molecular weight and block ratio. HAuCl₄ is used as gold precursor where LiBH₄ is acting as reductive agent to obtain the gold nanoparticles. The addition of gold precursors to aqueous solutions of PMAA-b-PDMAEMA polyampholytes leads to an acidification of the solution resulting in a change of the polyampholyte conformation through protonation of the PDMAEMA blocks. This modification of polyampholyte conformation also allows the tuning of the size and size distribution of the accordingly formed gold nanoparticles. Investigations presented, are performed mainly by AFM of the systems in thin film adsorbed on native oxide-terminated Si substrate. TEM was used to reveal the change in size of the obtained gold nanoparticles.     

Polyelectrolytes with sulfonic acid groups useful in the synthesis and stabilization of Au and Ag nanoparticles

Two novel polyelectrolytes were obtained by chemical modification of poly(4-acryloyloxybenzaldehyde) using o- and p-aminophenylsulfonic acid, the characterization shows a chemical modification of 24.38 and 63.33%, respectively. The study shows that the polyelectrolyte with sulfonic acid in para position reduces metal ions more rapidly than polyelectrolyte in ortho position. The obtained nanoparticles of Au and Ag were characterized by ultraviolet–visible absorption spectroscopy (UV–vis) and transmission electron microscopy. The results showed that these ionic polymers are not only capable of reducing gold and silver ions, but also can stabilize the nanoparticles in the colloidal solutions. With these polymers, the process of metallic ions reduction is very slow and they lead to the production of Au and Ag nanoparticles with quasi-spherical shapes which are stable in colloidal solutions for several months. The advantage of the method used here is that the reduction can be realized in water at room temperature.