Embedded Silver Nanoparticles Research Articles

Resistive switching kinetics and second-order effects in parylene-based memristors

Parylene is a widely used polymer possessing advantages such as simple and cheap production, possibility of fabrication on flexible substrates, transparency, and safety for the human body. Moreover, parylene can be used as an active layer of memristors—circuit design elements that are promising for the implementation of hardware neuromorphic systems. Recent studies show that memristors are not merely memory but also highly dynamical systems that can encode timing information. Here, a study of the switching kinetics and the timing second-order effects in memristors based on pristine and nanocomposite (with embedded silver nanoparticles) parylene is presented. The strong decrease in the resistive switching time and increase in the amplitude of the resistive state change after preliminary heating pulses are revealed. These effects are explained by the local heating of the parylene matrix by electric pulses, and the given explanation is supported by the numerical electrothermal model. Spike-timing-dependent plasticity with symmetrical nonoverlapping spikes is demonstrated. The obtained results indicate a possibility of the utilization of second-order effects in the development of the neuromorphic systems.

Wound dressing of chitosan-based-crosslinked gelatin/ polyvinyl pyrrolidone embedded silver nanoparticles, for targeting multidrug resistance microbes

Wound dressing composed of chitosan, based crosslinked gelatin/ polyvinyl pyrrolidone, embedded silver nanoparticles were fabricated using solution casting method. The membrane was characterized by FTIR, SEM and TGA. Glutaraldehyde (0.5 %) was used for the crosslinking of membrane components and associated with 7-folds boosted mechanical performance, 28 % more hydrolytic stability, 3-folds thickness reduction and morphological roughness. Silver nanoparticles were characterized by UV–vis, XRD and TEM for an average size of 9.9 nm. The membrane with higher concentration of silver nanoparticles showed maximum antibacterial activity against human pathogenic bacteria; and the measured inhibition zones ranged from 1.5 to 3 cm. The activity of the particles ranged from severe to complete reduction in Penicillin, Erythromycin and Macrolide family’s resistance genes expression such as β-Lactamase, mecA and erm. This developed membrane can serve as promising and cost-effective system against severe diabetic and burn wound infections.

Attenuation of hepatic and breast cancer cells by Polygonatum verticillatum embedded silver nanoparticles

Abstract The aim of the current research was to investigate the anti-hepatic and anti-breast cancer activity of Polygonatum verticillatum rhizome extract embedded silver nanoparticles (Pv-AgNPs). The addition of AgNO3 (1 mM) in the process of synthesis, showed change in color of the rhizome extract from brown to dark brown, suggested the formation of silver nanoparticles. Further, FTIR spectra of Pv-AgNPs showed polyphenolic vibrational peaks of hydroxyl groups (3734 - 3367 cm−1 range) that are responsible for the stabilization of nanoformulation. SEM, TEM, EDX, and XRD analysis showed that nanoparticles contain spherical shape, irregular size and well dispersed throughout the plane. Whereas, the elemental analysis results confirmed that 93.28% of Ag ions were present in the formulation. In-vitro anticancer evaluation showed that Pv-AgNPs (86.58 ± 0.84–46.17 ± 1.27% cell viability) have dose-dependent inhibition potency against HepG-2 and MCF-7 cancer cells lines. The comparison study also suggested that Pv-AgNPs consist higher anticancer efficacy than rhizome extract. Computational ADMET and topoisomerase activity prognosis showed optimal drug like properties of major phyto-compounds, which were adsorbed on the surface of silver during the synthesis of nanoformulation. Docking and molecular dynamics simulation study confirmed that the selected phyto-compounds anthraquinones, diosgenin, 5-hydroxymethyl-2-furaldehyde, and santonin have strong tendency to interact with the topoisomerase enzyme. The overall computational studies illustrated that phyto-compounds have mild tendency to act as anticancer agents but the experimental assay showed that in a combination such as whole extract of rhizome and Pv-AgNPs possessed significant potency against the breast and hepatic cancer.

Intrinsic optical properties of Ag-doped poly-(vinyl alcohol) nanocomposites: an analysis of the film thickness effect on the plasmonic resonance parameters

The optical properties of silver nanoparticles originating from the collective oscillations of their conduction electrons (LSPR) play a major role in the development of nanotechnology-based optical devices, from optical sensors to bactericide materials via non-linear optical devices. In this study, nanocomposites polymer films embedding silver nanoparticles were prepared by thermal annealing of poly-(vinyl alcohol) films doped by silver nitrate using a “one-pot synthesis” method. In this upscalable solution-based process, the nanoparticles are directly grown in the polymer matrix, yielding a plasmonic nanocomposite with a high density of nano-objects. Low (2.5% w:w) and high (25% w:w) doping concentration of silver were considered as well as their effect on the optical properties of thin (30 nm) and thick (300 nm and more) films. The topography and the optical properties (refractive index n and extinction coefficient k) of such films were studied by atomic force microscopy and spectroscopic ellipsometry. Unexpectedly, for a given doping level, the parameters of the surface plasmon resonance (amplitude, position and width) were shown to be thickness-dependent. A multivariate statistical analysis technique was used to identify the differences in the optical behavior of thick and thin films.

Madhuca longifolia Embedded Silver Nanoparticles Attenuate Diethylnitrosamine (DEN)-Induced Renal Cancer via Regulating Oxidative Stress.

Madhuca longifolia has been used for the treatment of renal cancer. Therefore, the current study describes the protective effects of biofabricated silver nanoparticles (MLAg- NPs) using Madhuca longifolia aqueous leaves extract against diethylnitrosamine (DEN) induced Renal Cell Carcinoma (RCC) in rats. Animals were categorized into five groups and treated with doses of silver nanoparticles for 16 weeks. Antineoplastic effect in renal cancer was dose dependent to control the macroscopical variations when compared to DEN induced group. Significant changes were observed in biochemical parameters and dose graded improvement in the level of antioxidants parameters were accountable for its protective nature. Silver nanoparticles in dose dependent manner was effective to modify the raised levels of pro-inflammatory cytokines and inflammatory mediators during renal cancer. Alteration in renal histopathology were also detected in the silver nanoparticles treated group, which show its safety concern. Biofabricated silver nanoparticles (MLAgNPs) using Madhuca longifolia can convey significant chemo-protective effect against renal cancer by suppressing the IL-6, TNF-α and IL-1β by nuclear factor-kappa B (NF-κB) pathway. Our outcomes implicates that biofabricated MLAgNPs exhibited a chemoprotective potential in the prevention and intervention of RCC.

Superhydrophilic carbonaceous-silver nanofibrous membrane for complex oil/water separation and removal of heavy metal ions, organic dyes and bacteria

Fouling has been the stubbornest challenge for the development of oil/water separation membranes. The commensal surfactants, heavy metals, organic foulants as well as microorganisms usually aggravate the membrane fouling. In this study, a superhydrophilic and underwater superoleophobic nanofibrous membrane with hydrogel-like surface was fabricated to tackle with the complex oil/water emulsion. Carbonaceous microspheres were covalently attached to the nanofiber surface and then trapped silver nanoparticles via in situ reduction to form carbonaceous-silver nanofibrous membrane. The fabricated membrane showed a permeability of 45612 ± 430 Lm-2h-1bar-1 for toluene-in-water emulsion with separation efficiency of higher than 99%. Moreover, it can remove above 90% Pb2+ through the adsorption of covalently attached carbonaceous microspheres and nearly 100% methylene blue through the Fenton-like oxidation of embedded silver nanoparticles. The gas bubbles generated from catalytic reaction promoted the floatation demulsification. In addition, the incorporated silver nanoparticles endowed the membrane with excellent antibacterial property towards to E. coil. The rational design of nanofibrous membrane aiming to fouling alleviation give more opportunities for the practical remediation of complex oil/water emulsions.

Plasmon-induced photoluminescence and Raman enhancement in Pr:CaF2 crystal by embedded silver nanoparticles

Photoluminescence (PL) enhancement of rare earth ions is in high demand due to their crucial applications in optoelectronics devices and biomedical frequency up-convertors for endoscopy, which could be realized by a plasmonic field enhancement effect of metallic nanoparticles (NPs). In this work, both the PL emission and Raman scattering enhancement of Pr3+ ions in CaF2 crystal host have been observed for the first time by embedding silver NPs. By Ag+ ion implantation, Ag NPs (around 5 nm) have been encapsulated into the Pr:CaF2 matrix. Analysis of the difference between linear optical absorption and PL excitation spectra within the plasmon band, the mechanism of observed PL enhancement has been attributed to the local field enhancement induced by the plasmonic NPs. The classical energy transfer process nanoparticle-emitter was not present. The detailed analysis of the PL enhancement induced by unannealed and annealed Ag NPs is compared under the measurement of PL decay, showing the dominant mechanism of the increased absorption and radiative decay rate, respectively. This work shows an efficient method to enhance PL emission of rare earth ions in the crystal based on the embedded metallic NPs, which could be used to optimize the photonic sensors and light emitting devices.

Fabrication of multifunctional Guar gum-silver nanocomposite hydrogels for biomedical and environmental applications

Poly(acrylamide-co-acrylamidoglycolic acid)/guar gum@ Ag-nanocomposite (AgNC@PAAG) hydrogels has been fabricated by a green protocol utilizing rhubarb stem-extract as bioreductant. The prepared nanocomposites (NCs) are formulated by varying guar gum (GG) polymer and cross-linker content, and used remarkably to study the release of an anticancer drug, 5-fluorouracil (FU). The AgNC@PAAG has demonstrated its potential in bacterial inactivation and p-nitrophenol (PNP) reduction. The AgNC@PAAG hydrogels showed extended FU release time, which was up to 23 h in pH 7.4. The higher zone of inhibition was documented for AgNC@PAAG against B. subtilis and E. coli. It was noticed that, the inhibition activity of AgNC@PAAG, was directly proportional to cross-linker content than the GG polymer. The efficiency of AgNC@PAAG as a nanocatalyst was evaluated for a model reduction reaction of p-nitrophenol (PNP) reduction by aqueous sodium borohydride (NaBH4), with an apparent rate constant of 121.8 × 10−3 min−1 at ambient temperature. The proposed nanocatalysts are reliable and recyclable, demonstrated its catalytic recycle efficacy of 85% after the third successive run. These NCs robust its biological and catalytic activity after embedding silver nanoparticles (AgNPs) by the bioreduction process; these optimized nanocatalysts can be remarkably used in biomedical healthcare sectors and industrial catalysis.

Microfluidic platform for encapsulation of plant extract in chitosan microcarriers embedding silver nanoparticles for breast cancer cells

In this study, the controlled synthesis of microcarriers and CpE loading were aimed to achieve by microfluidic system. The effect of temperature on chitosan in the stabilization of silver nanoparticles, microcarrier size and the encapsulation efficiency was measured. Encapsulation was achieved by the controlled rapid mixing in polymethyl-methacrylate (PMMA) microfluidic chip. The CpE was found to contain primary and secondary phenols in the phytochemical screening. The capping property of chitosan was achieved by heating reaction mixture in polytetrafluoroethylene (PTFE) tube to get the stabilized silver nanoparticles which were found to be embedded in chitosan microspheres of size 23.7 µm on average. Fourier-transform infrared (FTIR) and ultraviolet–visible (UV–Vis) spectroscopy results indicated the successful encapsulation of CpE in microcarriers. The average percentage encapsulation efficiency (% EE) of CsAg was found to be 77.125 ± 6.9%. The CpE-loaded microcarriers had shown significant anti-oxidant activity (p < 0.01). CpE-loaded microcarriers were evaluated to have robust cytotoxicity against 4T1 breast cancer cells at very low dose (IC50 = 42.53 µg/mL), which inhibited 95% of cancer cells viability. These results confer that microfluidic system plays an important role in the formation of CpE-loaded CsAg microcarriers that could effectively (p < 0.0001) kill the breast cancer cells.

Silver-decorated gel-shell nanobeads: physicochemical characterization and evaluation of antibacterial properties.

We report on the synthesis of composite nanobeads with antibacterial properties. The particles consist of polystyrene cores that are surrounded by sulfonic gel shells with embedded silver nanoparticles. The nanocomposite beads are prepared by sulfonation of polystyrene particles followed by accumulation of silver ions in the shell layer and subsequent reduction with sodium borohydride. The resulting material has been characterized by electron microscopy, vibrational and X-ray photoelectron spectroscopy and several other experimental techniques. It was shown that sodium borohydride reduces silver ions embedded in the gel layer producing silver nanoparticles but also transforms a fraction of sulfonic groups in the polymer to moieties with sulfur in a lower oxidation state, likely thiols. It is hypothesized that the generated thiol groups are anchoring the nanoparticles in the gel shell of the nanobeads stabilizing the whole structure. The silver-decorated nanobeads appear to be a promising material with considerable antimicrobial activity and were tested against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Staphylococcus epidermidis. The determined minimum inhibitory (MIC) and minimum biofilm inhibitory (MBIC) concentrations are comparable to those of non-incorporated silver nanoparticles.

Wound healing of nanofiber comprising Polygalacturonic/Hyaluronic acid embedded silver nanoparticles: In-vitro and in-vivo studies

The current study is pertaining to develop a novel wound dressing, comprising natural biologically absorbable materials for wound healing In-vivo. Wound dressing is composed of Polygalacturonic acid, Hyaluronic acid embedded silver nanoparticles, which is further fabricated to form nanofibrous mat, using electrospinning. Silver nanoparticles was prepared using PGA. AgNPs in this formula will serve as an antioxidant and anti-inflammatory that protect cells from destructive effect of elevated ROS and accelerate wound healing. The physical performance and water contact angle for nanofiber was evaluated. The produced nanofiber was characterized by Fourier-transform infrared (FTIR), scanning electron microscopy and thermal analysis. Also, the embedded AgNPs was also characterized by UV–vis spectroscopy and TEM. The nanofiber mates embedded AgNPs was applied to the wounded site of albino rats in-vivo. Histopathological assessment for the wound was fully performed. Also, the antimicrobial activity for the fabricated wound dressing was evaluated against gram+ve and gram −ve bacteria.

An innovative Azadirachta indica gum‐mediated synthesis of cocoon‐shaped nano‐AgHAp from Lamellidens marginalis shells

AbstractIn this work, the evaluations of noble nanoparticles for the structural and morphological characteristics are focused. The control of desired particles size and morphology for hydroxyapatite (HAp) and Ag‐substituted hydroxyapatite (AgHAp) derived from Lamellidens marginalis shells using Azadirachta Indica (AI) gum as a potential surfactant for the synthesis of stable nanoparticles are reported. The morphological change with respect to the concentration of AI gum is analyzed. The functional group (FTIR) and crystallographic (XRD) characterization of the HAp and AgHAp nanoparticles confirm the presence of HAp with desired apatite functional peaks. The morphological evaluation (FE‐SEM) exhibited the formation of cocoon‐shaped nanoparticles for the AI gum‐medicated synthesis. Higher AI gum concentration reduces the particle size along with the formation of unique surface morphology. The average diameter of the synthesized AgHAp nanoparticles was found to be ≤30 nm which is revealed from HR‐TEM. The bacterial investigation against bacterial strains substantiates the higher resistance of bacterial growth for Staphylococcus aureus was observed than Escherichia coli for the AgHAp particles. Hence, embedding silver nanoparticles in the HAp is an efficient approach to enhance the long‐term antibacterial effect of the orthopedic and dental applications.

Solution-processed upconversion photodetectors based on quantum dots

Upconversion photodetectors convert photons from the infrared to the visible light spectrum and are of use in applications such as infrared detection and imaging. High-performance upconversion devices are, however, typically based on vacuum-deposited materials, which are expensive and require high operating voltages, which limits their implementation in flexible systems. Here we report solution-processed optical upconversion photodetectors with a high photon-to-photon conversion efficiency of 6.5% and a low turn-on voltage of 2.5 V. Our devices consist of a colloidal lead sulfide quantum dot layer for harvesting infrared light that is monolithically coupled to a cadmium selenide/zinc selenide quantum dot layer for visible-light emission. We optimized the charge-extraction layers in these devices by incorporating silver nanoparticles into the electron transport layers to enable carrier tunnelling. Our photodetectors exhibit a low dark current, high detectivity (6.4 × 1012 Jones) and millisecond response time, and are compatible with flexible substrates. We also show that the devices can be used for in vitro bioimaging. By embedding silver nanoparticles in the electron transport layer, solution-processed quantum-dot-based photodetectors with a high photon-to-electron conversion efficiency of 6.5% and a low turn-on voltage of 2.5 V can be created for use in infrared imaging applications.

Utilization of High throughput microcrystalline cellulose decorated silver nanoparticles as an eco-nematicide on root-knot nematodes

The present study aimed to evaluate the influence of high throughput microcrystalline cellulose embedded silver nanoparticles (Ag-NPs), as an alternative eco-nematicide on Root-knot nematode (Meliodogyne incognita), which deem the main reason toward the loss of more than 20% in crops worldwide. In this work, Ag-NPs was prepared in very high concentration. Ag-NPs prepared using such technique has many advantages such as: absence of organic or solvents, scaling up thru using high concentration of silver precursor and utilization of environmentally benign polymer; Microcrystalline Cellulose (MCC). At the beginning, the bulk Ag-NPs colloidal solution is diluted to 5, 10, 15, 20, 25, 30, 40, 50, 60, 75, 80 and 100 ppm. Then, heavily galled roots of annual seed-propagated weed, Solanum nigrum L. family Solanaceae were selected to identify the Meloidogyne species and followed by treatment with the previously Ag-NPs concentrations. Results obtained after 24 h incubation, showed the highest mortality (M%) (40.36 ± 1.15%) which was achieved by means of 20 ppm of Ag-NPs compared with the highest concentration of Ag-NPs; 100 ppm (42.85 ± 3.51%). It was obviously noticed that, by increasing the concentration of Ag-NPs, M % decreased. On the other hand, after 48 h, 30 ppm Ag-NPs showed the highest M%; (52.82 ± 0.57%), while, after 72 h of treatments, the M% reached 95.53 ± 0.57% using 40 ppm Ag-NPs, then decreased to 66.67 ± 2.00% using 100 ppm Ag-NPs. All previous finding affirms the effectiveness of lower concentrations of Ag-NPs compared with the highest one, after 72 h. In conclusion, Ag-NPs could be successfully used as eco-nematicide for Root-knot nematodes; Meloidogyne incognita with a recommended dose of 20−40 ppm that is acquired higher M% and caused many aberrations during the different growth stages.

Memristors Based on Poly(p-xylylene) with Embedded Silver Nanoparticles

The properties of memristors based on poly(p-xylylene) with embedded silver nanoparticles have been studied, including current–voltage characteristics, resistive switching phenomenon, stability with respect to multiple switching cycles, and ability to store the resistive state in time. It is established that the incorporation of silver nanoparticles into polymer matrix significantly improves the main characteristics of memristors. The obtained results can be used for the creation of large memristor arrays with homogeneous characteristics capable of emulating synapses in neuromorphic computing systems.

Polystyrene Embedded Silver Nanoparticles as Potential Zinc Heavy Metals Removal in Wastewater Remediation Application

Polystyrene Embedded Silver Nanoparticles as Potential Zinc Heavy Metals Removal in Wastewater Remediation Application

Мемристоры на основе поли-n-ксилилена с внедренными наночастицами серебра

The properties of parylene based memristors with embedded silver nanoparticles were studied: current–voltage characteristics and resistive switching effect, endurance and retention time. It was found that introduction of nanoparticles leads to a significant improvement of the main memristive characteristics. Obtained results could be used to create large memristor arrays with homogeneous characteristics that emulate synapses in neuromorphic computing systems.

Multiple Scattering from Electrospun Nanofibers with Embedded Silver Nanoparticles of Tunable Shape for Random Lasers and White-Light-Emitting Diodes.

Random lasers (RLs) are convenient, tunable, and widely applicable. However, the influence of fluorescence lifetime on the scattering and nanofiber distribution of nanofibers with various shapes of silver nanoparticles (Ag NPs) embedded within is unclear. We prepared poly(vinyl alcohol) (PVA) nanofibers with Ag NPs through electrospinning (ES) and pyrromethene 597 dye doping. We determined the influences of the particles on scattering enhancement and localized surface plasmon resonance (LSPR) in RLs. The distinct scattering rates and LSPR can be used to control optical properties for sensing devices and other applications. Compared with traditional films, the threshold of the nanofibers with Ag NPs is 35% lower. In addition to improved matching between the LSPR and emission spectra, enhanced coupling of the electric field with nonradiative energy amplifies the radiative emission. Furthermore, the luminescence lifetime shortened by increasing the scattering rate. An excessive scattering rate may accelerate radiative recombination and convert some recombination into nonradiative recombination to produce a more sensitive device. Finally, we applied the prepared nanofibers to a backlight display and fabricated a white-light-emitting diode (LED) with a distinct thickness of nanofibers. The fabricated device is suitable for application in other LEDs and RL devices.

Femtosecond laser fabrication of silver nanostructures on glass for surface enhanced Raman spectroscopy

We report on an optimized fabrication protocol for obtaining silver nanoparticles on fused silica substrates via laser photoreduction of a silver salt solution. We find that multiple scans of the laser over the surface leads to a more uniform coverage of densely packed silver nanoparticles of approximately 50 nm diameter on the fused silica surface. Our substrates yield Raman enhancement factors of the order of 1011 of the signal detected from crystal violet. We use a theoretical model based on scanning electron microscope (SEM) images of our substrates to explain our experimental results. We also demonstrate how our technique can be extended to embedding silver nanoparticles in buried microfluidic channels in glass. The in situ laser inscription of silver nanoparticles on a laser machined, sub-surface, microfluidic channel wall within bulk glass paves the way for developing 3D, monolithic, fused silica surface enhance Raman spectroscopy (SERS) microfluidic sensing devices.

Tailoring of Silver Nanoparticle Size Distributions in Hydrogenated Amorphous Diamond‐Like Carbon Nanocomposite Thin Films by Direct Femtosecond Laser Interference Patterning

Patterning of nanocomposites by conventional lithography processes is problematic due to the different physical properties of matrix and filler. Direct laser interference patterning (DLIP) promises rapid micromachining of virtually any material with subwavelength resolution. A control of intense laser light modifies the filler particle size distribution in nanocomposite films. Herein, DLIP of periodic patterns with half‐pitch &lt;1 μm in reactive magnetron‐sputtered hydrogenated amorphous diamond‐like carbon nanocomposite thin films with embedded silver nanoparticles (DLC:Ag) is demonstrated. Periodic patterns of regularly repeating areas with modified size distributions of silver nanoparticles are obtained by a variation of fluences and number of pulses of 515 nm wavelength femtosecond laser. Depending on the silver content in nanocomposite films, nanoparticle size distributions are either bimodal (for 14.1 at% Ag containing films) or unimodal (7.9 at%) with effective average diameters shifting from 13 to 69 nm, depending on the laser processing parameters. The importance of localized surface plasmon absorption and localized field enhancement at the DLC–Ag interface for lowering the ablation threshold of DLC:Ag nanocomposites below 6 mJ cm−2 at 1000 pulses is demonstrated. This is at least four times lower than the threshold for pure DLC obtained using the same DLIP setup.