Synthesis of newly cationic surfactant based on dimethylaminopropyl amine and their silver nanoparticles: Characterization; surface activity and biological activity

The chemical structure of newly synthesized cationic surfactants based on Schiff base was confirmed using Fourier transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, and mass spectroscopy. The synthesized surfactants were used in the synthesis of silver nanoparticles by a simple one-step method. The silver nanoparticle (AgNPs) formation was confirmed using transmission electron microscopy (TEM), electron diffraction (SAED), dynamic light scattering (DLS), and energy dispersive X-ray spectroscopy (EDX). The structure of the surfactant played an important role in the synthesis process. Increasing the hydrophobic chain length, the stability, and the amount of surfactant increased the quantity of AgNPs formed. The surface activity of the synthesized cationic surfactants was determined using surface tension measurements at three different temperatures. The synthesized surfactants showed a high tendency toward adsorption and micellization. Increasing the hydrophobic chain length of the synthesized surfactant increased its adsorption. Screening the synthesized cationic surfactants and their nano-form against bacteria and fungi showed that they are highly effective. The silver nanoparticles enhanced the biological activity of the synthesized cationic surfactants.     

Dissipative particle dynamics simulations of polymer-protected nanoparticle self-assembly

Dissipative particle dynamics simulations were used to study the effects of mixing time, solute solubility, solute and diblock copolymer concentrations, and copolymer block length on the rapid coprecipitation of polymer-protected nanoparticles. The simulations were aimed at modeling Flash NanoPrecipitation, a process in which hydrophobic solutes and amphiphilic block copolymers are dissolved in a water-miscible organic solvent and then rapidly mixed with water to produce composite nanoparticles. A previously developed model by Spaeth et al. [J. Chem. Phys. 134, 164902 (2011)] was used. The model was parameterized to reproduce equilibrium and transport properties of the solvent, hydrophobic solute, and diblock copolymer. Anti-solvent mixing was modeled using time-dependent solvent-solute and solvent-copolymer interactions. We find that particle size increases with mixing time, due to the difference in solute and polymer solubilities. Increasing the solubility of the solute leads to larger nanoparticles for unfavorable solute-polymer interactions and to smaller nanoparticles for favorable solute-polymer interactions. A decrease in overall solute and polymer concentration produces smaller nanoparticles, because the difference in the diffusion coefficients of a single polymer and of larger clusters becomes more important to their relative rates of collisions under more dilute conditions. An increase in the solute-polymer ratio produces larger nanoparticles, since a collection of large particles has less surface area than a collection of small particles with the same total volume. An increase in the hydrophilic block length of the polymer leads to smaller nanoparticles, due to an enhanced ability of each polymer to shield the nanoparticle core. For unfavorable solute-polymer interactions, the nanoparticle size increases with hydrophobic block length. However, for favorable solute-polymer interactions, nanoparticle size exhibits a local minimum with respect to the hydrophobic block length. Our results provide insights on ways in which experimentally controllable parameters of the Flash NanoPrecipitation process can be used to influence aggregate size and composition during self-assembly.     

A Universal Approach for the Reversible Phase Transfer of Hydrophilic Nanoparticles

The ability to engineer the surface properties of magnetic nanoparticles is important for their various applications, as numerous physical and chemical properties of nanoscale materials are seriously affected by the chemical constitution of their surfaces. For some specific applications, nanoparticles need to be transferred from a polar to a nonpolar environment (or vice versa) after synthesis. In this work we have developed a universal method for the phase transfer of magnetic nanoparticles that preserves their shape and size. Octadecyltrimethoxysilane was used to cap the surfaces of the aqueous magnetic nanoparticles, thereby allowing their transfer into nonpolar solution. The resulting hydrophobic magnetic nanoparticles were transferred back into aqueous solution by subsequently covering them with an egg‐PC lipid monolayer. The superparamagnetic properties of the particles were retained after the phase transfer. The maximum transfer yields are dependent on their particle size with a maximum value of 93.16±4.75 % for magnetic nanoparticles with a diameter of 100 nm. The lipid‐modified magnetic particles were stable over 1 week, and thus they have potential applications in the field of biomedicine. This work also provides a facile strategy for the controllable engineering of the surface properties of nanoparticles.     

Immobilization of lipases on hydrophobilized zirconia nanoparticles: highly enantioselective and reusable biocatalysts

Our study has demonstrated for the first time that zirconia nanoparticles modified by a simple carboxylic surfactant of a very long alkyl chain can significantly enhance the activity of the immobilized lipases for asymmetric synthesis in organic media. Zirconia nanoparticles of ca. 20 nm diameter were grafted with carboxylic surfactant modifiers from Tween 85 and erucic acid. The surface of nanoparticles was successfully changed from hydrophilic to hydrophobic. Lipases from Candida rugosa and Pseudomonas cepacia were immobilized on the modified zirconia nanoparticles by adsorption in aqueous solution. The immobilized lipases were used for the resolution of ( R, S)-ibuprofen and ( R, S)-1-phenylethanol through esterification and acylation, respectively, in isooctane organic solvent. When immobilized on erucic acid-modified zirconia, both lipases gave significantly higher activity and enantioselectivity compared with those from their corresponding crude lipase powders. The nanohybrid biocatalysts are stable and can be reused for eight cycles without loss in activity and selectivity. The interaction between the hydrophobic surface of zirconia support and lipases probably induces the conformational rearrangement of lipases into an active, stable form.     

Hydrophobically modified polyelectrolytes used as reducing and stabilizing agent for the formation of gold nanoparticles

This paper is focused on the synthesis and characterization of hydrophobically modified polyelectrolytes and their use as reducing as well as stabilizing agents for the formation of gold nanoparticles. Commercially available poly(acrylic acid) has been hydrophobically modified with various degrees of grafting of butylamine introduced randomly along the chain. Different analytical methods are performed, i.e., IR and ¹H-NMR spectroscopy in combination with elemental analysis to determine the degree of grafting. The modified polymers can successfully be used for the controlled single-step synthesis and stabilization of gold nanoparticles. The process of nanoparticle formation is investigated by means of UV-vis spectroscopy. The size and shape of the particles obtained in the presence of unmodified or modified polyelectrolytes are characterized by dynamic light scattering, zeta potential measurements and transmission electron microscopy. The polyelectrolytes were involved in the crystallization process of the nanoparticles, and in the presence of hydrophobic microdomains at the particle surface, a better stabilization at higher temperature can be observed.     

Synthesis of β‐Cyclodextrin Containing Copolymer via “Click” Chemistry and Its Self‐Assembly in the Presence of Guest Compounds

We report the synthesis of a hydrophilic copolymer with one polyethylene glycol (PEG) block and one β‐cyclodextrin (β‐CD) containing block by a “click” reaction between azido‐substituted β‐CD and propargyl flanking copolymer. ¹H NMR study suggested a highly efficient conjugation of β‐CD units by this approach. The obtained copolymer was used as a host macromolecule to construct assemblies in the presence of hydrophobic guests. For assemblies containing a hydrophobic polymer, their size can be simply adjusted by simply changing the content of hydrophobic component. By serving as a guest molecule, hydrophobic drugs can also be loaded accompanying the formation of nanoparticles, and the drug payload is releasable. Therefore, the copolymer synthesized herein can be employed as a carrier for drug delivery.     

Surface-modulated and thermoresponsive polyphosphoesternanoparticles for enhanced intracellular drug delivery

The chemical structure of end groups influenced the phase transition temperature of thermoresponsive polymers. We demonstrated a strategy for the preparation of the pH/thermo-responsive polymeric nanoparticles via subtle modification of end groups of thermoresponsive polymer segments with a carboxyl group and revealed its potential application for enhanced intracellular drug delivery. By developing a polymeric nanoparticle composed of poly(aliphatic ester) as the inner core and thermoresponsive polyphosphoester as the outer shell, we showed that end groups of thermoresponsive polyphosphoester segments modified by carboxyl groups exhibited a pH/thermo-responsive behavior due to the hydrophilic to hydrophobic transitions of the end groups in response to the pH. Moreover, by encapsulating doxorubicin into the hydrophobic core of such pH/thermo-responsive polymer nanoparticles, their intracellular delivery and cytotoxicity to wild-type and drug-resistant tumor cells were significantly enhanced through the phase-transition-dependent drug release that was triggered by endosomal/lysosomal pH. This novel strategy and the multi-responsive polymer nanoparticles achieved by the subtle chain-terminal modification of thermoresponsive polymers provide a smart platform for biomedical applications.     

Proapoptotic Peptide Brush Polymer Nanoparticles via Photoinitiated Polymerization-Induced Self-Assembly

Herein, we report the photoinitiated polymerization-induced self-assembly (photo-PISA) of spherical micelles consisting of proapoptotic peptide–polymer amphiphiles. The one-pot synthetic approach yielded micellar nanoparticles at high concentrations and at scale (150 mg mL⁻¹) with tunable peptide loadings up to 48 wt. %. The size of the micellar nanoparticles was tuned by varying the lengths of hydrophobic and hydrophilic building blocks. Critically, the peptide-functionalized nanoparticles imbued the proapoptotic “KLA” peptides (amino acid sequence: KLAKLAKKLAKLAK) with two key properties otherwise not inherent to the sequence: 1) proteolytic resistance compared to the oligopeptide alone; 2) significantly enhanced cell uptake by multivalent display of KLA peptide brushes. The result was demonstrated improved apoptosis efficiency in HeLa cells. These results highlight the potential of photo-PISA in the large-scale synthesis of functional, proteolytically resistant peptide–polymer conjugates for intracellular delivery.     

Synthesis of P(AA‐SA)/ZnO composite latex particles via inverse miniemulsion polymerization and its application in pH regulation and UV shielding

Poly(acrylic acid‐co‐sodium acrylate)/zinc oxide, P(AA‐SA)/ZnO, composite latex particles were synthesized by inverse miniemulsion polymerization. The ZnO nanoparticles were prepared by hydrothermal synthesis and undergone oleic acid (OA) surface treatment. The X‐ray diffraction pattern and FT‐IR spectra characterized the crystal structure and functional groups of OA‐ZnO nanoparticles. An appropriate formulation in preparing P(AA‐SA) latex particles, ensuring the dominant in situ particle nucleation and growth, was developed in our experiment first. Sodium hydroxide was chosen as a costabilizer, because of its ability to increase the deprotonation of acylic acid and enhance the hydrophilicity of monomer, acrylic acid besides providing osmotic pressure. The growth mechanism of P(AA‐SA)/ZnO composite particles was proposed. The OA‐ZnO nanoparticles were adsorbed on or around the surface of P(AA‐SA) latex particles by hydrophobic interaction, thus enhanced the interfacial tension over latex particles. The P(AA‐SA)/ZnO composite latex particles owned better thermal stability than pure latex particles. The pH regulation capacity was excellent for both ZnO and P(AA‐SA) particles. Combining P(AA‐SA) and ZnO nanoparticles into composite particles, the performance in pH regulation and UV shielding was discussed from our experimental results. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 8081–8090, 2008     

Fabrication of superhydrophobic filter paper and foam for oil–water separation based on silica nanoparticles from sodium silicate

Journal of Sol-Gel Science and Technology - We demonstrate the synthesis of hydrophobic silica nanoparticles from sodium silicate and their application in separation of the oil–water mixture....     

Impact of Thermal Treatment on the Starch-Protein Interplay in Red Lentils: Connecting Molecular Features and Rheological Properties

Thermal treatments are widely applied to gluten-free (GF) flours to change their functionality. Despite the interest in using pulses in GF formulations, the effects of thermal treatment at the molecular level and their relationship with dough rheology have not been fully addressed. Raw and heat-treated red lentils were tested for starch and protein features. Interactions with water were assessed by thermogravimetric analysis and water-holding capacity. Finally, mixing properties were investigated. The thermal treatment of red lentils induced a structural modification of both starch and proteins. In the case of starch, such changes consequently affected the kinetics of gelatinization. Flour treatment increased the temperature required for gelatinization, and led to an increased viscosity during both gelatinization and retrogradation. Regarding proteins, heat treatment promoted the formation of aggregates, mainly stabilized by hydrophobic interactions between (partially) unfolded proteins. Overall, the structural modifications of starch and proteins enhanced the hydration properties of the dough, resulting in increased consistency during mixing.     

Soluble IF-ReS2 nanoparticles by surface functionalization with terpyridine ligands

A major drawback in the application of layered chalcogenide nanoparticles/tubes is their inertness to chemical and biological modification and functionalization. Their potential use in composite materials might be greatly enhanced by improving the chalcogenide/matrix interface bonding. A novel modification strategy for layered chalcogenide nanoparticles based on the chalcophilic affinity of metals and the chelating terpyridine is reported. The terpyridine anchor group can be conjugated to fluorescent tags or hydrophilic/hydrophobic groups that confer solubility in various solvents to the otherwise insoluble chalcogenide nanoparticles. The functionalized particles are characterized using TEM/HRTEM, optical and vibrational spectroscopy, and confocal laser scanning microscopy.     

Antibacterial Effectiveness of Rice Water (Starch)‐Capped Silver Nanoparticles Fabricated Rapidly in the Presence of Sunlight

Green synthesized silver nanoparticles (AgNPs) have enormous applications. Hence, there is an increasing demand to explore diverse bioresources for AgNP fabrication to make the process more cost‐effective and rapid as possible. Due to the abundantly present hydroxyl groups of rice starch, it provides ideal sites for metal ion complexation and thereby synthesis of nanoparticles with promising activity. So the study was designed to develop rapid, eco‐friendly and cost‐effective method for green AgNP synthesis using boiled rice water starch in the presence of sunlight irradiation. The starch‐capped nanoparticles (sAgNPs) formed in the study were found to have the surface plasmon absorbance at 439 nm. The study showed optimum yield of sAgNPs when 25% rice starch was treated with aqueous 1 mM AgNO₃ for 15 min in the presence of sunlight. Fourier transform infrared spectroscopy analysis provided mechanistic insight into the role of –OH groups of starch in the reduction of AgNO₃ to sAgNPs. On further characterization by X‐ray diffraction analysis, the sAgNPs were identified to have FCC crystal structure. At the same time, high‐resolution transmission electron microscopic analysis showed majority of sAgNPs to have spherical morphology, and dynamic light scattering study revealed the average particle size as 36.3 nm. Further confirmation on presence of AgNPs was carried out by energy‐dispersive X‐ray spectroscopy. Moreover, the sAgNPs exhibited promising antibacterial activity against foodborne pathogens, Salmonella Typhimurium and Staphylococcus aureus.     

溶剂效应制备核壳纳米银及荧光素金属增强荧光

直链或支链高分子可用来制备和稳定纳米材料,具有丰富羟基的高分子通过分子间和分子内氢键作用形成分子级别的"胶囊",用作生长纳米颗粒的模板[1].可溶性淀粉主要是直链淀粉,是由多个葡萄糖单元构成的含有丰富羟基的高分子,同时具有疏水性和亲水性[2].     

纳米银修饰的超疏水界面用于农药的超灵敏检测

采用化学还原法,在具有不同微观结构的规整的不锈钢网和聚纤维素酯薄膜表面合成了银纳米颗粒.利用氟化试剂对复合界面进行处理,形成超疏水性能的界面,能有效地浓缩目标分子.以罗丹明6G(R 6G)为分析物,纳米银修饰聚纤维素酯薄膜为基底,采用表面增强拉曼散射(SERS)分析了氟化处理前后基底对目标分子的检测能力.实验结果表明,具有超疏水性能的复合基底对R 6G分子的检出限为1 ×10-16 mol/L.以纳米银修饰的不锈钢网和聚纤维素酯两种复合材料为基底,对常用杀虫剂敌百虫的检出限分别为1×10-15 mol/L和1×10-16 mol/L.     

Spacer-mediated synthesis of size-controlled gold nanoparticles using geminis as ligands

We report a new methodology for the size-controlled aqueous synthesis of gold nanoparticles using geminis with different spacers as ligands. Geminis possess a unique structure in which two hydrophobic chains and two polar headgroups are combined via a spacer. We herein demonstrate that the spacer can be used as a tool to control particle size when geminis are used as ligands for gold nanoparticles. Varying the spacer length of geminis yields facile control over the size and size distribution of nanoparticles. For the 18-s-18-capped gold nanoparticles, FTIR and TGA experiments indicate that the geminis form bilayers on the surface of gold nanoparticles, which serve as templates that control the formation of nanoparticles. The smallest particles are obtained with a moderate spacer length (s = 8) because in that case the gemini bilayers interdigitate to the fullest degree to reach the maximum chain-chain interaction, thus yielding the most compact coating on the surface of gold nanoparticles. This work provides a new approach to the size control of nanoparticles.     

Pure green chemical approach for synthesis of Ag2O nanoparticles

In this study, a green chemistry method is reported for the synthesis of Ag₂O nanoparticles with the utilization of starch molecules as a stabilizing agent. In particular, by simply adjusting the concentration of starch in the reaction media, the structure of A₂O nanoparticles can be engineered in disc and faceted shapes, which has been analyzed by transmission electron microscopy, UV-Vis spectroscopy, and X-ray diffraction technique. In addition, antibacterial activity of the prepared Ag₂O nanoparticles had been evaluated against food poisoning and pathogenic bacteria.     

W/O型微乳法制备淀粉基纳米粒

在正己烷、Span-60和NaOH水溶液的W／O型淀粉微乳液中,进行淀粉与环氧氯丙烷交联反应制备淀粉微球,用质量分数为1％的淀粉水浆液制备出微球的流体力学半径Rb为7．08—113nm,其中粒径不超过100nm的纳米粒在整个微粒体系中占69％,平均粒径为92．2nm。TEM和DLS结果表明,制得的微粒呈圆球形,且微粒的流体力学半径随淀粉水浆液浓度的增加而增大并分布变宽,淀粉水浆液的浓度低有利于淀粉基纳米粒的形成。     

Silica‐Coated Metal Nanoparticles

The advanced high‐quality synthesis of dense and porous silica‐coated nanostructures is enjoying ever‐increasing research interests for their important properties and diverse applications, especially for catalytic, controlled release, colorimetric diagnostics, photothermal therapy, surface enhanced Raman scattering (SERS) detection, and so forth. In this timely Focus Review, we summarize the up‐to‐date synthesis strategies, improved properties, and emerging applications of silica‐coated metal nanoparticles. In particular, the large scale synthesis of silica‐coated metal nanoparticles and the recent development of hollowed‐out silica‐coated metal nanoparticles by silica dissolution are emphasized for new and practical applications.     

Effect of different capping agents on physicochemical and antimicrobial properties of ZnO nanoparticles

This research aims to investigate the influence of soluble starch; lactose; carboxymethyl cellulose; urea; and polyvinylpyrrolidone on synthesis of zinc oxide nanoparticles (ZnO-NPs). Zinc acetate was used as a precursor under alkaline conditions to produce ZnO-NPs as a low-cost and efficient antimicrobial and UV-blocking agent. Characterization and antimicrobial functional properties of prepared nanoparticles were investigated and reported using FTIR, TGA, XRD, TEM, analysis, as well as antimicrobial assay, respectively. The results revealed that the thermal decomposition profile, size of ZnO-NPs, IR spectra, as well as antimicrobial activity of the prepared ZnO-NPs is governed by the type of capping agents. Crystallinity analysis showed identical patterns in peak intensities and width irrespective of the used capping agents. On the other hand, the obtained results disclosed that using soluble starch as a capping agent results in attaining lower particle size of 3–5 nm and higher antimicrobial efficacy as compared with the other capping agents.