Stabilization Of Ag Nanoparticles Research Articles

Fabrication of silver nanoparticles by a diethylene triamine-hyaluronic acid derivative and use as antibacterial coating

In this work a synthetic protocol for the functionalization of hyaluronic acid with diethylenetriamine (DETA) was standardized. HA-DETA derivatives were characterized by NMR and proton carbon correlation analysis HSQC and HMBC to confirm chemical structure. A selected derivative was used to set up a green fabrication procedure for HA-DETA capped silver nanoparticles with the aim to achieve a polymeric based coating with potential application in the treatment of medical devices associated infections. Data from UV–visible spectroscopy, electron scanning and transmission microscope (STEM), photoelectric spectroscopy (XPS) and rheological characterization were combined to characterize the HA-DETA/Ag nanocomposites. HA-DETA stabilized Ag nanoparticles (10–30 nm) were obtained through an UV accelerated production. The viability of MC3T3-E1 was analyzed with the aim of designing a cytocompatible antimicrobial coating. Antibacterial and antibiofilm activity of HA-DETA/Ag nanocomposites have been tested in vitro against Staphylococcus aureus and Pseudomonas aeruginosa both in culture plates than on titanium specimens.

Supramolecular DNA sensor based on the integration of host-guest immobilization strategy and WP5-Ag/PEHA supramolecular aggregates

Primary liver cancer, mostly hepatocellular carcinoma (HCC) is the most common cause of cancer-related deaths around the world. Hepatitis B virus (HBV) DNA is the dominant factor that influences the progression of HCC. In this work, a novel electrochemical sensor triggered by a sandwich hybridization reaction has been developed for the ultrasensitive detection of HBV DNA. The multi-walled carbon nanotubes (MWCNTs) and hydroxylatopillar [5]arene (HP5) stabilized Au nanoparticles are used to modify the electrode to immobilize Rhodamine B-labeled DNA probes and improve the electron transfer efficiency. A supramolecular aggregate was synthesized based on pentaethylenehexamine (PEHA) induced self-assembly behavior of water-soluble pillar [5]arene (WP5) stabilized Ag nanoparticles through host-guest interaction, which serves as signal materials. The sensitivity of the sensor has enhanced on account of the electrochemical oxidation from Ag to Ag+ to yield an electrochemical response greater than that of the single silver nanoparticle. Linear sweep voltammetry (LSV) curves illustrate that the response has a good linear relationship with the logarithm of HBV-DNA concentration in a wide range from 0.1 fmol/L to 0.1 nmol/L, and the detection limit is 0.19 fmol/L according to the 3σ rule. Besides, the sensor shows good reproducibility, stability and selectivity, providing a promising prospect for application in disease diagnosis and prognosis.

D-Mannitol based surfactants for cosmetic and food applications and hydrogels to produce stabilized Ag nanoparticles

A novel synthetic approach for lipid modification of mannitol for hydrogelation, cosmetic and food application.

Ag nanoparticles immobilized on new magnetic alginate halloysite as a recoverable catalyst for reduction of nitroaromatics in aqueous media

Amines can be applied in the synthesis of various important compounds such as dyes, drugs, polymers, pharmaceutical products, and biologically active materials. The significant subject in the preparation of amines is the selection of the most effective heterogeneous catalyst to get the best catalytic efficiency, stability, recoverability, and reusability. For this target, we prepared new alginate magnetically recoverable nanocatalyst by stabilization of Ag nanoparticles on the surface of the halloysite (HS) [HS-Alginate-Ag/Fe3O4]. Several detection methods confirmed the production of HS-Alginate-Ag/Fe3O4 nanocatalyst and the results obtained were well explained in the context. HS-Alginate-Ag/Fe3O4 presented good catalytic performance for the hydrogenation of nitro compounds using NaBH4 as the reducing agent and hydrogen donor. The good activity and durability of this catalyst can be attributed to the good dispersion and nano-sized particle of silver nanoparticles.

Role of polystyrene microplastics in sunlight-mediated transformation of silver in aquatic environments: Mechanisms, kinetics and toxicity

Sunlight-oxidative ageing is a common and critical process for microplastics (MPs) in aquatic environments. O2•−, 1O2, and •OH generation has been widely proven in this process, which can alter metal speciation based on its reduction and oxidation potential. Herein, chemical speciation of Ag mediated by polystyrene (PS) MPs was determined under simulated sunlight irradiation. The O2•− generation on the PS MPs surfaces is the vital factor for Ag+ reduction, regardless of acid or base conditions. The 1O2 and •OH are dominant factors, and 1O2 played a more important role than •OH for its higher formation amount, causing oxidative dissolution of newly formed Ag0 nanoparticles (NPs). The Ag NPs can hetero-aggregate with PS MPs through electrostatic interactions with O–containing groups (C–O, C–OH and CO), and co-precipitate from the water phase. This hetero-aggregation can stabilize Ag NPs by inhibiting Ag NPs surface photooxidation and suppressing Ag+ release. Transformation of Ag species (from Ag+ to Ag0 NPs) mediated by sunlight with PS MPs significantly suppressed acute toxicity of Ag+ to Escherichia coli, Selenastrum capricornutum, Daphnia magna and zebrafish. This study emphasized that PS MPs play an important role in the speciation, migration and toxicity of Ag+ in freshwater environments.

Track formation in nuclear emulsion plates for cosmic-ray imaging with stabilized Ag nanoparticles

In cosmic-ray imaging system with nuclear emulsions, silver halide (AgX) grains capture muon-created electrons to form a latent image composed of small Ag nanoparticles (latent image centers), which could be as small as three atoms. Since it needs such a long time as several months for the grains to capture sufficient number of muon-created electrons for imaging, the stabilization of latent image is inherently important. There are two kinds of latent image fading; the first- and second-order reactions. The former is the oxidation of latent image centers by oxidants, which are not formed by cosmic-ray irradiation, and the latter is the re-halogenation of latent image centers by irradiation-created X2. It was revealed that the latter became to be predominant over the former within several days after irradiation as the volume ratio of gelatin in emulsion layers decreased, indicating that gelatin is very effective to depress this type of latent image fading. Following the previous paper, we have extended our study on the property and behavior of new additives by means of photoelectron spectroscopy to prove the mechanism of the latent image fading with the first-order reaction, according to which a latent image center with electric charge of +1/2 degrades via the repetition of the ionic process (detachment of an Ag+ion) and the electronic process (losing of an electron) one after the other, its electric charge changing to -1/2 and back. The mechanism thus proved has provided several ideas to depress latent image fading in nuclear emulsions for cosmic-ray imaging.

An efficient Ag/MIL-100(Fe) catalyst for photothermal conversion of CO2 at ambient temperature

The conversion of CO2 under mild condition is of great importance because these reactions involving CO2 can not only produce value-added chemicals from abundant and inexpensive CO2 feedstock but also close the carbon cycle. However, the chemical inertness of CO2 requires the development of high-performance catalysts. Herein, Ag nanoparticles/MIL-100(Fe) composites were synthesized by simple impregnation-reduction method and employed as catalysts for the photothermal carboxylation of terminal alkynes with CO2. MIL-100(Fe) could stabilize Ag nanoparticles and prevent them from aggregation during catalytic process. Taking the advantages of photothermal effects and catalytic activities of both Ag nanoparticles and MIL-100(Fe), various aromatic alkynes could be converted to corresponding carboxylic acid products (86%–92% yields) with 1 atm CO2 at room temperature under visible light irradiation when using Ag nanoparticles/MIL-100(Fe) as photothermal catalysts. The catalysts also showed good recyclability with almost no loss of catalytic activity for three consecutive runs. More importantly, the catalytic performance of Ag nanoparticles/MIL-100(Fe) under visible light irradiation at room temperature was comparable to that upon heating, showing that the light source could replace conventional heating method to drive the reaction. This work provided a promising strategy of utilizing solar energy for achieving efficient CO2 conversion to value-added chemicals under mild condition.

Phytobiological-facilitated Production of Silver Nanoparticles From Selected Non-cultivated Vegetables in Nigeria and Their Biological Potential.

Plant-mediated synthesis [silver (Ag) to form Ag nanoparticles (AgNPs)] is becoming progressively well accepted in many scientific and pharmaceutical fields. The aim of this study was to synthesize AgNPs using air-dried leaves of four neglected vegetables, i.e. Ceratotheca sesamoides, Ceiba pentandra, Crassocephalum crepidioides, and Launaea taraxacifolia. Ultraviolet-visible (UV-Vis) spectroscopy, fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM) were used for characterization. Cell stabilization membrane and lipoxidase assays were used to determine used to assess the antiinflammatory activities while 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS+) assays were used to assess the antioxidant activities of AgNPs [L. taraxacifolia-AgNPs, C. sesamoides Ag nanoparticles (CS-AgNPs), C. pentandra Ag nanoparticles (CP-AgNPs), and C. crepidioides AgNPs (CC-AgNPs)]. The UV-Vis spectra of the synthesized NPs displayed absorption bands at around 360-440 nm, which is a characteristic band for AgNPs. The SEM image showed that the AgNPs formed were spherical in morphology. CC-AgNPs exhibited the most significant inhibitory activity against human red blood cell membrane stabilizasyonu [median inhibitory concentration (IC50): 32.2 μg/mL] while CS-AgNPs displayed the most significant inhibitory activity against lipoxygenases (IC50: 32.8 μg/mL). CP-AgNPs exhibited the most significant antioxidant effect against both ABTS and DPPH (IC50: 5.5 and 6.4 μg/mL) when compared to ascorbic acid (IC50: 4.7 μg/mL). The synthesized AgNPs were found to be stable and the FTIR evidence suggested that the phytochemicals in the vegetables might have played an important role in the reduction and stabilization of AgNPs. This work showed that the synthesized AgNPs from non-cultivated vegetables can find relevance and application in health, drugs, food and environmental science. The evidences herein further confirmed their ethnopharmacological applications.

Stabilizing Ag Nanoparticles Using Anatase TiO2 and Cu on Al Surface

Chemical adsorption of anatase TiO2, silver nanoparticles (Ag NPs), and Cu particles (Cu Ps) on aluminum (Al) surface yielded an active surface-enhanced Raman scattering (SERS) substrate. TiO2 is known to reduce both silver (Ag) and copper (Cu). In an oxidizing environment, Ag NPs remain unoxidized since Cu has a more negative redox potential than Ag. Ag is therefore protected by Cu from getting oxidized. Although Ag NPs exhibit better SERS activity than Au NPs, Ag is relatively easier to oxidize, limiting the development of Ag-based nanomaterials. Therefore, despite the poor SERS activity of Au nanoparticles than that of Ag nanoparticles, Au nanoparticles have been widely used. Herein, the stabilization of Ag nanoparticles by incorporating a reductive process using anatase TiO2 is reported. The fabricated substrates bearing anatase, Ag NPs, and Cu Ps were stable, as seen by Raman spectra, and remained unchanged for more than 2 months.

Synthesis and characterization of starch stabilized Ag nanoparticles. Effect of the crystalline structure of starch.

Silver nanoparticles (AgNps) are known for their antimicrobial activity and other physicochemical properties that can be applied in several fields. Most of their synthesis methods include chemical reduction and the use of stabilizing agents such as starch. In recent years, several green methods have been developed such as using carbohydrates as reducing agents. On the other hand, starch is a semi crystalline structure formed by mixtures of the linear glucan, amylose and the branched glucan amylopectin. In this work we studied the effect of the semi crystalline structure on the physicochemical properties (particle size and surface plasmon resonance). Three types of starch were selected (corn, potato and banana) representing the three types of semi crystalline structures of the starch granule (A, B and C). Results showed that banana starch allowed larger particle sizes and broader size distribution, while there was not significant difference between nanoparticles stabilized with A and B type starches.

Synthesis and antibacterial activity of cellulose acetate sheets modified with flower-shaped AlOOH/Ag

Modified cellulose acetate antibacterial material was obtained by immobilizing Al/Ag nanoparticles on fabric fibres in water and subsequent hydrolysis of this nanoparticles under mild reaction condition. AlOOH/Ag self-assembled flower-shaped nanostructures consist of AlOOH nanoplates and Ag inclusions. The AlOOH nanosheets size is of 150–300 nm, thickness is 5–7 nm. The silver inclusions were from 5 to 30 nm in size. Flower-shaped AlOOH/Ag nanostructures change the charge of fibres and stabilize Ag nanoparticles against agglomeration. The positive charge of the modified fibres improves the bacteria adsorption due to electrostatic interaction. The antibacterial activity of the nanoparticles and modified material arise due to the slow Ag+ migration into the medium from stabilized Ag nanoparticles. The nanoparticles and modified cellulose acetate sheets were characterized by transmission and scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction analysis, FTIR spectroscopy. The release of silver ions to the medium remains low for 70 h with AlOOH/Ag@CA reducing all the tested bacterial strains below the limit of detection (102 CFU/mL) within 3 h for Escherichia coli and 6 h for MRSA due to local effects of silver on adsorbed bacteria. The antibacterial activity of modified cellulose acetate fabric allows this method of modification to be exploited to produce materials for biomedical applications.

Modification of poly (ethylene glycol) with a multifunctional silane ligand, stabilization of Ag nanoparticles and its catalytic activity toward nitro-aromatics reduction

The modification of poly (ethylene glycol) (PEG) with (3, 3′-bis-(3-triethoxysilylpropyl)-2, 2′-dithioxo [5, 5′] bithiazolidinylidene-4, 4′-dione) ligand was performed in the presence of Et3N in toluene (MPEG). With the addition of AgNO3, MPEG with obtained spherical nanoparticles on the surface could interact with Ag + under ultrasonic. Finally, the MPEG-Ag + complex were reduced with hydrazine under reflux to obtain MPEG-Ag nanocomposite. The structure of MPEG-Ag nanocomposite was characterized by different techniques. The nanocomposite was used as an efficient catalyst for the reduction of nitro-aromatic compounds using NaBH4 in the water at room temperature. The catalyst was recovered, and applied for subsequent reactions without any substantial loss of efficiency for five runs.

Using a Brush Copolymer as Efficient Dispersant for the Preparation of Highly Stabilized Ag Nanoparticles in Aqueous Suspensions

AbstractSilver (Ag) nanoparticle has extremely high surface energy and it is difficult to find an efficient dispersant to prevent its agglomeration in suspensions. A new brush copolymer, succinic anhydride modified epoxy‐amine poly[(propylene oxide)‐co‐(ethylene oxide)]‐grafted polymer (EPOA), which can efficiently disperse concentrated aqueous suspensions of Ag nanoparticles is revealed. The dispersion efficiency of EPOA for the dispersion of a 60 nm‐Ag nanoparticles in aqueous suspension is studied by measuring its sedimentation and rheological behavior, and the results are compared with those of a commercially available dispersant, ammonium poly(acrylic acid) (PAA‐NH4). Interactions between the dispersants and the Ag nanoparticles are characterized by zeta potential and adsorption analyses. Theoretical calculations are conducted to clarify the adsorption and the dominant dispersion stabilization mechanisms of the dispersants. Compared with PAA‐NH4, EPOA obtains a higher stable suspension of Ag nanoparticles with less significant sedimentation over 1 month. The dispersion homogeneity of the suspension remains excellent even at an extremely high solid loading of 30–40 wt%. According to adsorption analysis, it is suggested that both EPOA and PAA‐NH4 adsorb via single‐point attachment through the carboxyl group on the Ag surface. Based on theoretical calculations, the Ag nanoparticles are better stabilized by EPOA via an electrosteric dispersion mechanism.

Unification of Surface Enhanced Raman Spectroscopy of Dyes Using One Pot Synthesized Stabilized Ag Nanoparticles

Unification of Surface Enhanced Raman Spectroscopy of Dyes Using One Pot Synthesized Stabilized Ag Nanoparticles

Preparation and stabilization of Ag nanoparticles with N-vinyl-2-pyrrolidone grafted-poly(vinyl alcohol) in an organic medium and investigation of their usability in the catalytic dye decolorization

To obtain a copolymer with different substituent groups, N-vinyl-2-pyrrolidone (NVP) was grafted onto certain appendages of vinyl methacrylate introduced-poly(vinyl alcohol) PVA using AIBN. Then, PVA-g-NVP copolymer was used in the formation and stabilization of Ag nanoparticles in an organic medium without the use of reducing agents. The effects of volume ratio of the solvents, temperature, and concentrations of reactants were investigated for the formation of Ag nanoparticles. The particle size distribution of the Ag particles was determined using the TEM technique. The dispersions of the Ag nanoparticles were used in the decolorization of Congo Red (CR) and Methylene Blue (MB), in the presence of an electron donor NaBH4. Satisfactory catalytic activity results (>85%) were obtained with lower amounts of Ag dispersions according to the dye concentration, and it was observed that the performance of the Ag nanoparticles changed depending on the type of dye and preparation conditions.

Porous Carbon Nitride Frameworks Derived from Covalent Triazine Framework Anchored Ag Nanoparticles for Catalytic CO2 Conversion

Porous carbon nitride frameworks (PCNFs) with uniform and rich nitrogen dopants and abundant porosity were successfully fabricated through the direct carbonization of the covalent triazine frameworks (CTFs) at different pyrolysis temperatures and used as supports to anchor and stabilize Ag nanoparticles (NPs) for catalytic CO2 conversion. Importantly, the pyrolysis temperature plays a crucial role in the properties of porous carbon nitride frameworks. The material carbonized at 700 °C showed the highest surface area and micro- and mesoporous structure with a certain interlayer distance. Taking advantage of their unique surface characteristics, PCNF-supported Ag NP catalysts (Ag/PCNF-T, T=pyrolysis temperature) were prepared by a simple chemical method. A series of characterizations revealed that Ag NPs are embedded in the porous carbon nitride frameworks and confined to a relatively small size with high dispersion owing to the assistance of the abundant surface groups and porous structures. The as-obtained Ag/PCNF-T catalysts, especially Ag/PCNF-700, showed excellent catalytic activity, selectivity, and stability for the carboxylation of CO2 with terminal alkynes under mild conditions. This can be due to the existence of abundant nitrogen atoms and diverse porosity, which resulted in highly efficient catalytic activity and stability.

Room‐Temperature Metallic Fusion‐Induced Layer‐by‐Layer Assembly for Highly Flexible Electrode Applications

AbstractTo fabricate flexible electrodes, conventional silver (Ag) nanomaterials have been deposited onto flexible substrates, but the formed electrodes display limited electrical conductivity due to residual bulky organic ligands, and thus postsintering processes are required to improve the electrical conductivity. Herein, an entirely different approach is introduced to produce highly flexible electrodes with bulk metal–like electrical conductivity: the room‐temperature metallic fusion of multilayered silver nanoparticles (NPs). Synthesized tetraoctylammonium thiosulfate (TOAS)‐stabilized Ag NPs are deposited onto flexible substrates by layer‐by‐layer assembly involving a perfect ligand‐exchange reaction between bulky TOAS ligands and small tris(2‐aminoethyl)amine linkers. The introduced small linkers substantially reduce the separation distance between neighboring Ag NPs. This shortened interparticle distance, combined with the low cohesive energy of Ag NPs, strongly induces metallic fusion between the close‐packed Ag NPs at room temperature without additional treatments, resulting in a high electrical conductivity of ≈1.60 × 105 S cm−1 (bulk Ag: ≈6.30 × 105 S cm−1). Furthermore, depositing the TOAS–Ag NPs onto cellulose papers through this approach can convert the insulating substrates into highly flexible and conductive papers that can be used as 3D current collectors for energy‐storage devices.

Acid hydrogel matrixes as reducing/stabilizing agent for the in-situ synthesis of Ag-nanocomposites by UV irradiation: pH effect

Synthetic methods to obtain Ag-nanocomposites are widely studied in order to produce antimicrobial materials without using harmful agents for possible applications in biologic systems. In this way, the nanocomposites could be able to apply in biomedicine area avoiding going through exhaustive processes of purification. Biocompatible hydrogel based on N-isopropylacrylamide (NIPAM) copolymerized with different proportions of methacrylic acid (MAA) and 2-acrylamido-2-methylpropanesulfonic acid (AMPS), were proposed as matrixes of Ag-nanocomposites. A comprehensive study of the physicochemical behavior, reducing and stabilizing character of the matrixes were carried out at pH 2 and 7. Hydrogel nanopores were used as photoreducing of Ag+ ions and stabilizing of Ag nanoparticles (Ag-NPs) at the same time. Most of the matrixes showed high reducing character at pH 7 while at pH 2 it was significantly reduced. Photoreducer character at pH 7 increased with MAA co-monomer concentration and Ag-NPs sizes of 4–5 nm were obtained. In addition, it was demonstrated that acidic co-monomers favor the stabilization of Ag-NPs avoiding agglomerations. It was possible to conclude that the photoreduction reaction takes mainly place at pH 7 when non bonding electron pairs from carboxylic and amide groups of the matrix are available. Therefore, biocompatible and antimicrobial nanocomposites can be easily synthesized without using damaging additives (reducer, solvent) and be applied in biomedicine.

Efficient inner filter effect sensors based on CdTeS quantum dots and Ag nanoparticles for sensitive detection of l-cysteine

In the design of new fluorescence sensors, exploration of new sensors with excellent performances and smart designs for the detection of ions and biomolecules is of continuing interest. Therefore, we designed an inner filter effect (IFE) based sensor by effectively combining between CdTeS quantum dots (QDs) and Ag nanoparticles (NPs). Ternary alloyed CdTeS QDs were synthesized by two steps and using 3-mercaptopropionic acid (MPA) as stabilizer, polyvinylpyrrolidone (PVP) stabilized Ag NPs were prepared by crystal-seed. The emission peak of CdTeS QDs and the absorption peak of Ag NPs could availably overlap by changing the Te/S molar ratios and l-ascorbic acid (AA) concentrations. The CdTeS QDs/Ag NPs (QNs) with an obviously emission at 580 nm were used as IFE-based sensors for l-cysteine (L-Cys). The QNs fluorescence was increasing with addition of l-Cysteine (L-Cys), the fluorescence (PL) intensity (F/F0) was linearly proportional to the L-Cys concentrations ranging from 20 μM to 400 μM with the correlation coefficient (R2) of 0.9942 and the detection limit was calculated to be 0.025 μM (S/N = 3), where F and F0 were the PL intensity in the presence and absence of L-Cys at 580 nm, respectively. Moreover, there was no interference to some potential interfering substances, which showed high sensitivity and selectivity for L-Cys.

Green solid-state based curcumin mediated rhamnolipids stabilized silver nanoparticles: Interaction of silver nanoparticles with cystine and albumins towards fluorescence sensing.

Curcumin mediated rhamnolipids stabilized Ag Nanoparticles (NPs) have been successfully synthesized in a green solid-state procedure and in a solvent free environment. Depending on growth time, the synthesis process offers Ag NPs of different sizes and spherical shapes as reflected in the scanning electron microscope (SEM) images. The absorbance of rhamnolipids stabilized Ag NPs consistently increases with increase in growth time in rhamnolipids medium reconfirming growth in size of the particles. Even after 7 days of growth time in the rhamnolipids medium, the size slightly increases but the shapes remain spherical unlike the case observed in ethanolic environment. During reduction process, curcumin is conjugated at the surfaces of Ag NPs making Ag NPs fluorescent active. The fluorescence/RRS spectral measurements show an enhancement in fluorescence/SFS intensity without changing the spectral position suggesting more curcumin molecules are bound in larger particles. The fluorescence of rhamnolipids stabilized Ag NPs increases while interacting with cystine and albumins. Fluorescence of Ag NPs can estimate cystine and albumins in the 1 μM-100 μM concentration ranges. While binding with cystine is 1:1 with curcumin molecules, for Human Serum Albumin (HSA) and Bovine Serum Albumin (BSA) it is more. The association constant of cystine with rhamnolipids stabilized Ag NPs is high whereas for HSA it is moderate and for BSA is weak, thus, these Ag NPs have better selectivity for cystine sensing.