Efficient Sorption of Basic Organic Dyes from Aqueous Solution Using Green Synthesized Silver Nanoparticles Beads

In this article, the potential of alginate stabilized silver nanoparticles beads for efficient sorption of methylene blue, malachite green, and rhodamine B from aqueous solutions was investigated. The adsorption data have been correlated with both Freundlich and Langmuir adsorption models. The kinetic studies for dyes adsorption showed rapid sorption dynamics by second-order kinetic model. The common problem of classical adsorbents towards efficient recyclability was overcome when alginate stabilized silver nanoparticles beads was used. The alginate stabilized silver nanoparticles beads were successfully recycled for 25 successive adsorption-desorption cycles indicating its high reusability.     

Temperature-Responsive Poly(N-Isopropylacrylamide-Acrylamide-Phenylboronic Acid) Microgels for Stabilization of Silver Nanoparticles

Poly(N-isopropylacrylamide-acrylamide-phenylboronic acid) [P(NIPAM-AAm-PBA)] microgels of uniform size were prepared by the chemical reaction of 3-aminophenylboronic acid with poly(N-isopropylacrylamide-acrylamide-acrylic acid) [P(NIPAM-AAm-AA)] microgels in aqueous medium in the presence of N-(3-dimethylaminopropyl)-N-ethylcarbodiimide hydrochloride catalyst via carbodiimide coupling. Silver (Ag) nanoparticles were prepared using seed-mediated growth method and stabilized in P(NIPAM-AAm-PBA)] microgels. Ag nanoparticles and hybrid microgels were characterized by transmission electron microscopy, UV–visible, and dynamic light scattering techniques. The temperature-responsive behavior of hybrid microgels was found to be similar to that of the pure microgels. The value of volume transition temperature of hybrid microgels was found to be slightly higher than that of pure microgels due to shielding effect of Ag nanoparticles present on the surface of microgel particle. The decrease in the size of hybrid microgels as compared to that of pure microgels in swollen state is due to physical cross-linking by Ag nanoparticles inside the network of microgels. The stable hybrid polymer microgel system has a potential to be used for different applications.     

Synthesis,Characterization, and Photocatalytic Properties of Ag/TiO2 Composite Nanofibers Prepared by Electrospinning

Ag nanoparticles (Ag NPs) embedded titanium dioxide (TiO₂) nanofibers were fabricated by colloidal sol process, electrospinning, and calcination technique. Calcination of the electrospun nanofibers were heat treated at 600°C for 180 minutes in air atmosphere. X-ray diffraction patterns exhibited that the anatase phase and silver coexisted in the resulted Ag NPs/TiO₂ nanofibers; transmission electron microscopy demonstrated Ag NPs well spread in the porous microstructure of composite fibers. The prepared nanofibers were utilized as photocatalyst for degradation of methyl orange. The degradation rate of methyl orange dye solution containing Ag/TiO₂ composite nanofibers is 99% only after irradiation for 3 hours. It is proposed that these new Ag NPs/TiO₂ composite nanofibers will have potential application in water pollution treatment.      

Tribological Characteristics of Protected Silver Nanoparticles in Oil

In recent years, there has been considerable interest in employing dispersed solid particles in the nanoscale range to enhance the friction and wear characteristics of liquid lubricants. Previous studies have suggested that tiny colloidal particles, under tribochemical conditions, deposit on rubbing surfaces influencing tribological characteristics of the contact. This article presents a study of the tribological behavior of stabilized silver nanoparticles dispersed in n-hexadecane. Friction and wear measurements are combined to investigate the extent to which colloidal solid particles influence a lubricated contact. It is shown that the silver nanoparticles studied contribute to reduce friction and wear only in the thin film regime. Nanoparticles help to reduce friction and wear down to a certain concentration value. Higher concentrations of nanoparticles do not bring any further contribution to reduce friction or wear, suggesting the existence of an optimum concentration of nanoparticles.     

Microwave-Assisted Synthesis and Characterization of Triton X 100 Capped Silver Nanospheres

In this article, we report the synthesis of silver nanospheres (Ag NS) by a simple microwave irradiation method using Triton X 100 (TX 100) as a capping agent. TX 100 was also observed to act as a reducing agent in the presence of microwave radiation. From the ultraviolet-visible spectrum, the formation of Ag NS was confirmed by observing surface plasmon resonance band at 414 nm. The emission band of Ag NS was observed at 482 nm from the photoluminescence (PL) spectrum. High-resolution transmission electron microscopy (HR TEM) was used to investigate the morphology of the synthesized sample. It shows that the synthesized sample has sphere-like morphology with an average diameter of 5 nm. Further, the elemental composition of the Ag NS was determined by energy dispersive x-ray analysis (EDX). Selected area electron diffraction (SAED) was used to find the crystalline nature of the Ag NS. The interaction between Ag NS and TX 100 was established by Raman spectroscopy. The electrochemical behaviour of the synthesized Ag NS was analyzed by cyclic voltammetry (CV).     

Efficiency of Superparamagnetic Nano Iron Oxide Loaded Poly(Acrylamide-co-Maleic acid) Hydrogel in Uptaking Cu2+ Ions from Water

A novel superparamagnetic iron oxide nanoparticles loaded poly(acrylamide-co-maleic acid) hydrogel (superparamagnetic PAM hydrogel) has been synthesized and cross-linked by methylene bisacrylamide for the investigation of its efficiency in uptaking copper ions from aqueous solution by batch method. The swelling behavior of the hydrogel was investigated. Metal ion uptake capacity of the adsorbent was evaluated in the light of varying pH, contact time, temperature, adsorbent dose, and different copper ion concentration. The synthesized superparamagnetic PAM was characterized by FTIR and XRD analysis. The structure and coating of the magnetic nanoparticles were characterized by XRD and FTIR analysis respectively. The adsorption data was fitted well in the Langmuir, Freundlich, and Temkin models and various static parameters were calculated. It is stated that this hydrogel could be regenerated efficiently (>97%) and used repeatedly.     

Biosynthesis of silver nanoparticles using <Emphasis Type="Italic">Carissa carandas</Emphasis> berries and its potential antibacterial activities

Metal nanoparticles synthesis using the biological material offers a simple, biocompatible, cost-effective and nontoxic in character. A number of plant materials have been utilized as resource material for the most favorable biosynthesis of active nanomaterials. This study involves the synthesis of active silver nanoparticles (Ag NPs) using the Carissa carandas (Karonda) berry water extract at room temperature. The nanoparticles characterized at several parameters including shape, size, mass and charge with help of electron microscopy (TEM), Fourier transforms IR (FTIR), UV-VIS spectroscopy and Raman spectroscopy which proved the efficient silver nanoparticles to be useful in several practical applications. The UV-visible spectra showed the surface plasmon resonance peak at ~440?nm, which is weel recognized attribute peak in case of silver nanoparticles. Avarage size of the biogenic silver nanoparticles ranged from ~10–60?nm, predominantly spherical in shape. The suggested possible mechanisms for the synthesis of silver nanoparticles relies on reduction of AgNO₃ due to occurrence of carinol (and related resonant compounds) in the berry extract with inductive effect of the proton of methoxy and allyl groups, present at ortho and para positions of the compounds. The biologically synthesized Ag NPs also showed efficient antibacterial activity against different pathogenic and non-pathogenic bacteria at par with the generic antibiotics.

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Synthesis,Characterization, and Silver Nanoparticles Fabrication in N-isopropylacrylamide-Based Polymer Microgels for Rapid Degradation of p-Nitrophenol

Multiresponsive poly(N-isopropylacrylamide-co-methacrylic acid) microgels were synthesized by precipitation polymerization in aqueous medium. Then silver-poly(N-isopropylacrylamide-co-methacrylic acid) hybrid microgels were prepared by in-situ reduction of silver ions. Formation of microgels was confirmed by Fourier transform infrared spectroscopic analysis. pH and temperature sensitivity of microgel was studied by dynamic light scattering. Hydrodynamic radius of microgels decreases with increase in temperature at pH 8.20 and show volume phase transition temperature around 45°C. At pH 2.65, hydrodynamic radius decreases with increase in temperatures upto 35°C but further increase in temperature causes aggregation and microgel becomes unstable due to increase of hydrophobicity. With increase in pH of medium, the hydrodynamic radius of microgels increases sigmoidally. Formation of silver nanoparticles inside microgel and pH dependence of surface plasmon resonance wavelength of the hybrid microgels were investigated by ultraviolet-visible spectroscopy. The value of surface plasmon resonance band and absorbance associated with surface plasmon resonance band increases with increases in pH of the medium. The apparent rate constant of reduction of p-nitrophenol was found to be linearly dependent on volume of hybrid microgels used as catalyst. The system has a potential to be used as effective catalyst for rapid degradation of industrial pollutant.     

Detection of Heavy Metal Ions Using Synthesized Amino Thiol Surfactants Assembled on Gold Nanoparticles

In this work, we synthesized amino thiol surfactants, namely, 10-(4-aminophenoxy)-decane-1-thiol and 12-(4-aminophenoxy)-dodecane-1-thiol. The self-assembling of the synthesized surfactants on gold nanoparticles (AuNPs) was investigated using different techniques such as ultraviolet analysis, x-ray diffraction, and transmission electron microscopy. The synthesized surfactants show the ability to assemble on gold nanoparticles and form stable nanostructure with it. We used the synthesized surfactants and their nanostructures with gold nanoparticles for the detection of Zn and Ni ions in aqueous solution using the ultraviolet spectrophotometer technique. The synthesized amino thiol surfactants showed the ability to detect Zn and Ni ions at low concentration. The results showed that gold nanoparticles can enhance the detection of Zn and Ni ions using the nanostructures of the synthesized surfactants.     

Pressure Drop and Performance Characteristics of Water-Based Al2O3 and CuO Nanofluids in a Triangular Duct

An experimental study is performed to determine the pressure drop and performance characteristics of Al₂O₃/water and CuO/water nanofluids in a triangular duct under constant heat flux where the flow is laminar. The effects of adding nanoparticles to the base fluid on the pressure drop and friction factor are investigated at different Reynolds numbers. The results show that at a specified Reynolds number, using the nanofluids can lead to an increase in the pressure drop by 35%. It is also found that with increases in the Reynolds number, the rate of increase in the friction factor with the volume fraction of nanoparticles is reduced. Finally, the performance characteristics of the two nanofluids are investigated using the data of pressure drop and convective heat transfer coefficient. The results show that the use of Al₂O₃/water nanofluid with volume fractions of 1.5% and 2% is not helpful in the triangular duct. It is also concluded that at the same volume fraction of nanoparticles, using Al₂O₃ nanoparticles is more beneficial than CuO nanoparticles based on the performance index.     

Removal of Phenol Dyes Using a Photocatalytic Reactor with SnO2/Fe3O4 Nanoparticles

In this study, we present kinetics of phenol dyes removal by SnO₂/Fe₃O₄ nanoparticles in a photocatalytic reactor for optimization of this process. The effect of different concentrations of SnO₂ 5, 10, 15, 20% w/w on the photocatalytic reactor during removal of phenol red was investigated. The SnO₂/Fe₃O₄ nanoparticles were synthesized by core–shell method. The results of XRD and TEM showed the successful synthesis of these nanoparticles. Several other methods were applied to synthesis of these nanoparticles but none of them succeeded. This process composed of two-stage. The first stage was absorption by iron oxide nanoparticles and second stage was photocatalytic by tin oxide nanoparticles that followed pseudo-second-order kinetic and first-order kinetic, respectively. Optimization of this process was done corresponding to the parameters affecting the process with design expert software. In order to determine the optimal values of each of the parameters and the optimal conditions of the process, parameters were introduced to response surface methodology.     

Fabrication of SPR Nanosensor Using Gold Nanoparticles and Self-Assembled Monolayer Technique for Detection of Cu2+ in an Aqueous Solution

In this work, we investigated the fabrication of surface plasmon resonance (SPR) nanosensor using gold nanoparticles (AuNPs) chemisorbed onto self assembled monolayer of 10-(3-amino phenoxy) decane-1-thiol on gold substrate. The fabrication process of SPR nanosensor was characterized using different techniques such as infrared reflection-absorption spectra (IRRAS), xX-ray photoelectron spectroscopy (XPS), and atomic force microscope (AFM). The fabricated SPR nanosensor was used for detection of Cu²⁺ in an aqueous solution using surface plasmon resonance refractometer. The results confirm the fabrication of new SPR nanosensor. The fabricated SPR nanosensor showed a good activity toward the detection of Cu²⁺. The detection of Cu²⁺ in an aqueous solution using the fabricated SPR nansensor was enhanced in the presence of gold nanoparticles.     

Preparation and Characterization of Polymeric Nanocapsules Produced by in Situ Polymerization From Nanoemulsions Produced by Direct Emulsification

Polymeric nanoparticles constitute an important drug delivery system with controlled release profile. This article describes a new way to produce polymeric nanocapsules using a vegetable oil nanoemulsion as template. The process occurs in two steps: First, a nanoemulsion was obtained with a low-energy method based on phase inversion emulsification, using 2-ethylhexyl acrylate as lipophilic monomer. The in situ polymerization of the nanoemulsion droplets is induced by the addition of polymerization catalyzers. The mean size of the polymeric nanoparticles was evaluated by photon correlation spectroscopy and atomic force microscopy. Both techniques showed the formation of polymeric nanocapsules with a mean particle size less than 300 nm.     

Utilization of Chitosan-Lactide Copolymer Nanoparticles as Controlled Release Pesticide Carrier for Pyraclostrobin Against Colletotrichum gossypii Southw

Low effective availability of modern pesticides places heavy burdens on both the environment and costs to farmers. Nano-augmented delivery systems seem to be more promising to address the present challenge modern pesticides are facing. In this article, biodegradable chitosan-lactide copolymer (CPLA) was prepared and characterized as hydrophobic pesticide-pyraclostrobin carrier. Nano-precipitation method was used to fabricate pyraclostrobin-loaded nanoparticles. Loading content (LC), encapsulation efficiency (EE), size, and size distribution of the resulting nanoparticles were investigated. The size of pesticide-loaded nanoparticles can be adjusted between 77 to 128 nm by varying the feed mass ratio of copolymer to pyraclostrobin from 50/1 to 5/1. Compounds contained within nanoparticles was protected from light compared with the technical material. The pyraclostrobin-loaded nanoparticles showed an initial burst, subsequent sustained and pH-controlled release profile. Compared to 25% pyraclostrobin emulsifiable concentrate (EC), the nanoparticles demonstrated better fungicidal activity against Colletotrichum gossypii Southw under long incubation time, which further exhibited sustained release characteristic.