Employing Silver Nanoparticles Research Articles

Eco-friendly fabrication of silver nanoparticle-decorated electrodes for aqueous bisphenol A sensing

This work fabricated an electrochemical sensor for detecting bisphenol A (BPA) by employing silver nanoparticles (AgNPs) synthesized through an eco-friendly approach. The AgNPs were produced using parsley leaf extract, which acted as a reducing and stabilizing agent in the synthesis process. The AgNPs synthesized using the green approach exhibited an average size of 15.2 ± 2.1 nm. The AgNP-modified screen-printed electrode (SPE) exhibited excellent electrocatalytic activity towards BPA oxidation, with an enhanced peak current of 28.6 μA compared to 5.2 μA for the bare SPE. The optimized sensor exhibited impressive analytical performance, boasting a broad linear range spanning 0.05–5 μM for BPA detection. Remarkably, it achieved a low limit of detection of 0.02 μM, coupled with high sensitivity. Furthermore, the sensor demonstrated commendable reproducibility, with a RSD of 3.6%, and exceptional repeatability, evidenced by an RSD of 2.4%. Upon evaluating the sensor's performance in analyzing real water specimens, the recoveries oscillated between 95.8% and 103.5%, accompanied by RSDs not exceeding 4.2%, thereby demonstrating its successful application for BPA detection. The eco-friendly synthesis approach and superior analytical performance make the AgNP-modified SPE a promising tool for on-site environmental monitoring and drinking water analysis.

Silver nanoparticles/graphene oxide arranged on polytetrafluoroethylene substrate hydrophilic modified with TiO2 to construct efficient air purification material

Recently, the harsh air environment caused by disasters and human activities poses a great challenge to the development of efficient and antibacterial air purification systems to protect human health. In this work, a new type of high-efficiency polytetrafluoroethylene (PTFE) air filter was successfully prepared by employing silver nanoparticles decorated with graphene oxide (Ag NPs/GO) functional materials that deposited in PTFE substrate membranes hydrophilic modified with TiO2 for the improvement of the enclosed space air quality. The results revealed that the introduction of TiO2 can improve the interfacial adhesion between PTFE membrane and functional materials, improving the feasibility of long-term application of composite membrane. The composite membrane possessed the crisscross network structure interconnected by fibrils, which gives the membrane high-efficiency particulate matters (PMs) removal rate (99.25% for PM2.5) without sacrificing the pressure drop (90.52 Pa). Moreover, the prepared composite membrane also has more excellent antibacterial performance (98.7% for Escherichia coli (E. coli)), which can reduce the secondary pollution caused by improper post-treatment of the polluted filter in practical applications. After simple cleaning and regeneration, the composite membrane can still maintain an ultra-high particle removal rate (over 95%) after 5 cycles. The prepared efficiency air filtration composite membranes have positive potential applications in air purification.

Antiproliferiative Activity of Biogenic Silver Nanoparticles Synthesized from Leonotis nepetifolia (L) on Human Cancer Cell lines

Currently, nanobiotechnology is the growing science in the field of medicine employing silver nanoparticles to deliver drugs to target cancer cells and proved to be potential anticancer agents. In this study, silver nanoparticles were synthesized using leaf extract of Leonotis nepetifolia (L). Gas chromatography-mass spectrometry data showed a total of 13 phytochemical constituents identified from ethanolic leaf extract of Leonotis nepetifolia (L). The effect of physicochemical factors such as the reaction time, temperature, concentration of Silver nitrate, concentration of leaf extract and pH in the synthesis of silver nanoparticles. For biosynthesis, the optimal conditions were 1 mM silver nitrate, 0.1 ml of leaf extract at 80° for 90 min. Ultra violet-visible spectroscopy, field emission scanning electron microscopy; high-resolution transmission electron microscopy and various techniques characterized the synthesized AgNPs. The silver nanoparticles obtained had absorbance maxima at 398 nm, were spherical in shape, had an average particle size of 11.32 nm, polydispersity index 0.44, the zeta potential of -23.75.69 mv and were crystalline. A cytotoxicity study was conducted on two human cancer cell lines, pancreatic and ovarian, using sulforhodamine B assay. We had compared the cytotoxicity of biogenic silver nanoparticles with that of synthetic silver nanoparticles. Treatment of pancreatic and ovarian with different concentrations of silver nanoparticles inhibited the cell viability with half maximal inhibitory concentration values of 25.4 μg/ml and 23.9 μg/ml. In contrast, silver nanoparticles inhibited cell viability with half maximal inhibitory concentration values of 48.2 μg/ ml and 42 μg/ml, which were statistically significant (p<0.001), when compared with that of doxorubicin and Camptothecin. Leonotis nepetifolia mediated silver nanoparticles effectively reduced the proliferation of pancreatic and ovarian cancer cell lines than that of synthetic nanoparticles.

A review: Effect of silver nanoparticles on human health following various routes of administration

Individuals are employing silver nanoparticles in a wide range of medications, scientific studies and medical devices, which necessitates more study in order to understand the long-term implications of exposure. It is not always possible to avoid exposure to silver nanoparticles if they are spread across a large area, such as an industrial site. Silver nanoparticles can be inhaled, ingested, or interact with the skin. People's health is impacted by several aspects, including how much exposure (how much), how long they have had it (how long it is been), what form of exposure they have used, what other chemicals present in the environment (such pesticides), and how healthy they are at the time of exposure. Toxicology following exposure to silver in a variety of ways necessitates additional investigation, even though several studies have already been published (AgNPs).

Tapered depressed-cladding waveguide lasers modulated by Ag nanoparticles embedded in SiO2

We report on fabrication of tapered circular depressed-cladding waveguides in Nd:YAG crystal by femtosecond laser direct writing (FsLDW). Based on the fabricated waveguides, for the first time to the best of our knowledge, efficient Q-switched mode-locked (QML) lasers are realized by employing silver nanoparticles (NPs) embedded in fused silica as saturable absorber (SA) element. Laser pulses as short as 25 ps with a repetition rate of 7.7 GHz are generated at a wavelength of 1064 nm. We systematically explore the influence of incident-output facet and the reduction factors on guiding properties and laser performance by conducting a comparative study of different tapers, and it has been found that the waveguides with tapered structures can suppress multi-mode guiding while ensure fundamental-mode output for waveguide lasers. Our work paves a new way toward developing three-dimensional (3D) waveguide for applications in on-chip ultrafast laser sources.

Fully stretchable self-charging power unit with micro-supercapacitor and triboelectric nanogenerator based on oxidized single-walled carbon nanotube/polymer electrodes

A key requirement for wearable electronics is an adequate and sustainable power source. Accordingly, a self-powering unit that replaces rechargeable secondary batteries is a promising solution. However, to realize permanent, maintenance-free, and highly durable wearable electronics, stretchable self-powering units that can harvest and store energy should be developed. In this study, we developed a fully stretchable self-charging power unit that integrates a micro-supercapacitor and triboelectric nanogenerator using oxidized single-walled carbon nanotube/polymer electrodes. The fully stretchable micro-supercapacitor with oxidized single-walled carbon nanotube/polyvinylalcohol electrodes exhibited a double layer capacitance of 20 mF cm −2 at 0.1 mA cm −2 and improved mechanical flexibility and stretchability over 10,000 cycles of stretching tests. A stretchable, polydimethylsiloxane-based current collector employing silver nanoparticles embedded with oxidized single-walled carbon nanotubes enabled the fully stretchable, freestanding-triboelectric-layer based nanogenerators to produce a maximum instantaneous power density of 84.4 mW m −2 under periodic and round-trip sliding of a Nylon fabric while stretching up to 40% without significant performance degradation. Furthermore, a micro-supercapacitor of fully stretchable self-charging power unit could be successfully charged by the nanogenerator from 0 to 2.2 V in 1200 s and powered commercial digital clock for approximately 10 s. These results demonstrate that stretchable polymer composites with oxidized single-walled carbon nanotubes are suitable electrodes and active materials for fully stretchable and self-powered wearable electronics. • Ag NPs embedded with Ox-SWCNTs for current collectors of fully stretchable FTENG and MSC. • Intrinsically stretchable Ox-SWCNT/PVA/H 3 PO 4 electrode for fully stretchable MSCs. • Highly durable, fully stretchable self-charging power unit that integrates MSC and FTENG. • Simultaneous energy harvesting and storage functions of the FS-SCPU from repetitive human motion.

"Trojan Horse" Salmonella Enabling Tumor Homing of Silver Nanoparticles via Neutrophil Infiltration for Synergistic Tumor Therapy and Enhanced Biosafety.

Salmonella selectively colonizes into the hypoxic tumor region and exerts antitumor effects via multiple mechanisms, while the tumor colonized Salmonella recruits host neutrophils into the tumor, presenting a key immunological restraint to compromise the Salmonella efficacy. Here, we develop a combinatorial strategy by employing silver nanoparticles (AgNPs) to improve the efficacy and biosafety of Salmonella. The AgNPs were decorated with sialic acid (SA) to allow selective recognition of L-selectin on neutrophil surfaces, based on which the tumor-homing of AgNPs was achieved by neutrophil infiltration in the Salmonella colonized tumor. The tumor-targeting AgNPs exert the functions of (1) local depletion of neutrophils in tumors to boost the efficacy of Salmonella, (2) direct killing tumor cells via L-selectin-mediated intracellular delivery, and (3) clearing the residual Salmonella after complete tumor eradication to minimize the side effects. With a single tail vein injection of such combination treatment, the tumor was eliminated with high biosafety, resulting in a superior therapeutic outcome.

Silver nanoparticles: synthesis, characterisation and biomedical applications.

Nanotechnology is a rapidly growing field due to its unique functionality and a wide range of applications. Nanomedicine explores the possibilities of applying the knowledge and tools of nanotechnology for the prevention, treatment, diagnosis and control of disease. In this regard, silver nanoparticles with diameters ranging from 1 to 100 nm are considered most important due to their unique properties, ability to form diverse nanostructures, their extraordinary range of bactericidal and anticancer properties, wound healing and other therapeutic abilities and their cost-effectiveness in production. The current paper reviews various types of physical, chemical and biological methods used in the production of silver nanoparticles. It also describes approaches employing silver nanoparticles as antimicrobial and antibiofilm agents, as antitumour agents, in dentistry and dental implants, as promoters of bone healing, in cardiovascular implants and as promoters of wound healing. The paper also explores the mechanism of action, synthesis methods and morphological characterisation of silver nanoparticles to examine their role in medical treatments and disease management.

SERS-based trace-level quantification of sulindac: Spectroscopic and molecular modeling evaluation

Sulindac is a common non-steroidal anti-inflammatory drug used for the treatment of various types of cancer. However, its overdose or long-term exposure may increase the risk of heart attack and intestinal bleedings. In the present study, a reliable spectroscopic approach for the trace-level identification and quantification of sulindac using the surface-enhanced Raman scattering (SERS) technique and employing silver nanoparticles (AgNPs) substrates was developed. An unprecedented sensitivity with a wide dynamic range (1 × 10−2 M to 1 × 10−9 M) and a low detection limit (1 × 10−10 M) was achieved. Molecular modeling results for the interaction of sulindac molecules with silver nanoparticles were correlated with the experimental findings. Significant enhancements, due to charge transfer processes, in the Raman bands at 1111, 1653, 1607 and 1340 cm−1 corresponding to the -S=O stretching, -C=O stretching, -C=C- stretching and ring stretching vibrations were observed. The approach developed in this work has the potential for sensitive quantification of sulindac and could be extended to structurally relevant drugs.

Highly enantioselective photo-polymerization enhanced by chiral nanoparticles and in situ photopatterning of chirality

Chiral noble metal nanoparticles has recently gained great interest due to their potential applications including ultrasensitive chiral recognition and asymmetric synthesis. We anticipate that they could be utilized to induce asymmetric photo-polymerization reactions with high enantioselectivity and reactivity. Here, we report such a system. By employing silver nanoparticles modified with cysteine as the chiral inducer, polydiacetylene (PDA) with high chiral asymmetry was obtained from achiral diacetylene monomers triggered with unpolarized UV light. Furthermore, the helical sense of chirality can be controlled by varying the wavelength of UV irradiation. This enables a feasible and economical method to fabricate programmable 2D patterns of chiral PDA with tailored chirality distributions, such as smooth gradients in chirality and micropatterns with tailorable circularly polarized luminescence. Our finding not only opens a pathway for producing programmable chiroptical micropatterns, but also is highly valuable for deeper understanding of symmetry breaking in enantioselective photochemical reactions.

Red, green and blue phosphorescent organic light-emitting diodes with ITO-free anode material

The non-productive hole-current from blue, green and red phosphorescent OLEDs was reduced by employing silver nanoparticles embedded glass:Ni-Ag-codoped ZnO (SNSZO) anode and enhanced the efficiencies. The blue device using SNSZO: Ir(fdbdi)3 exhibit maximum luminance (L) of 42683 cd/m2, current efficiency (ηc) of 43.6 cd/A and power efficiency (ηp) of 45.3 lm W-1 with external quantum efficiency (ηex) of 20.2 % than ITO: Ir(fdbdi)3 based device [L- 35126 cd/m2; ηc - 38.4 cd/A; ηp - 37.3 lm w-1; ηex -15.1 %]. The green device with SNSZO: Ir(mnmpdi)2(acac) show intensified emission at 520 nm and exhibit higher efficiency; L - 47238 cd/m2, ηc -50.9 cd/A, ηp - 49.3 lm w-1 and ηex - 18.9 % [ITO: Ir(mnmpdi)2(acac): L- 39326 cd/m2; ηc-46.0 cd/A; ηp -39.3 lm w-1; ηex -13.8 %]. The red device (620 nm) with SNSZO: Ir(mnpbi)2(acac) show L - 9058 cd/m2, ηc - 8.3 cd/A, ηp -6.4 lm w-1 and ηex - 12.2 % [ITO: Ir(mnpbi)2(acac): L- 7632 cd/m2; ηc -4.1 cd/A; ηp -6.40 lm w-1; ηex -6.0 %]. The proposed OLEDs with SNSZO anode shows excellent efficiencies than ITO and providing alternate for high-performance OLEDs and other optoelectronic devices.

Control of Resistive Switching Voltage by Nanoparticle‐Decorated Wrinkle Interface

AbstractControl of resistive switching voltage in nonvolatile memory devices plays a critical role in building commercial ultra‐low power data storage technology. Here, an effective strategy to control the resistive switching voltage in polymer memory devices by interfacial engineering is presented. By creating a wrinkled surface in reduced graphene oxide (rGO) film as the conductive electrode, an electrical bistable phenomenon is observed in polymer diode with this rGO electrode, with the feature of a write‐once‐read‐many‐times nonvolatile memory effect. By further employing silver nanoparticles and controlling their density at the wrinkled rGO electrode/polymer interface, the optimized device exhibits a high performance nonvolatile memory effect with an ultra‐low switching voltage of 0.9 V, high ON/OFF ratio of 1000, and desirable long retention time over 104 s. To the best knowledge, the value of switching voltage is much lower than that of previous related polymer memory devices. This study paves a new way toward ultra‐low power manufacturing of nonvolatile polymer memory devices.

SERS Enhancement on the Basis of Temperature-Dependent Chemisorption: Microcalorimetric Evidence.

The mechanism of surface-enhanced Raman spectroscopy (SERS) is not very clear in view of the magnitude of the contribution of electromagnetic factor as well as the chemical mechanism. This report presents the extent of adsorption at different temperatures in terms of signal enhancements in SERS employing silver nanoparticles (AgNPs) of various shapes as substrate and dye molecules, crystal violet or Rhodamine 6G, as model Raman probes. Initially, the SERS signal increases with increasing temperature until a maximum intensity is reached, before it gradually decreases with increasing temperature. This trend is independent of the shape of the Raman substrates and probes. However, the temperature at which maximum intensity is obtained may depend upon the nature of the Raman probe. The energetics involved in the chemisorption process between dye molecules and AgNPs were determined through isothermal titration calorimetry and their implications for the observed SERS signals were assessed. The maximum heat change occurred at the temperature at which the maximum signal enhancement in SERS was obtained and the enhanced interaction at optimum temperature was confirmed by absorption spectroscopy.

Efficient Green Organic Light-Emitting Diodes by Plasmonic Silver Nanoparticles

The resonance effect between the localized surface plasmon mode and the excited excitons in organic materials can enhance the optical and electrical performances of organic light-emitting diodes (OLEDs). Here, we show an enhancement in the luminescence efficiency of a green OLED by employing silver nanoparticles without an optical microcavity effect. The enhanced photoluminescence and exciton decay rate support the idea that the improved luminescence efficiency is due to the increased spontaneous emission rate of the emitter. Our results indicate that the plasmonic near-field interaction of the light-matter can be a strong engineering tool for high-efficiency organic optoelectronic devices in the display industry.

Chiral recognition of tyrosine enantiomers based on decreased resonance scattering signals with silver nanoparticles as optical sensor.

A novel chiral sensing platform, employing silver nanoparticles capped with N-acetyl-L-cysteine (NALC-Ag NPs), was utilized for the discrimination of L-tyrosine and D-tyrosine. This nanosensor, which could be used as an optical sensing unit and chiral probe, was characterized by transmission electron microscopy (TEM) and resonance Rayleigh scattering (RRS) spectroscopy. After the proposed sensing platform interacted with L-tyrosine and D-tyrosine, a decreased resonance scattering signal was only obtained from L-tyrosine. This phenomenon offered a useful assay for the selectivity and determination of L-tyrosine with the RRS method. The linear range and detection limit of L-tyrosine were 0.2838-20.0 µg⋅mL(-1) and 0.0860 µg⋅mL(-1) , respectively. In addition, experimental factors such as acidity, interaction time, and the concentration of enantiomers were investigated with regard to the effect on enantioselective interaction.

Ultrasensitive detection and co-stability of mercury(ii) ions based on amalgam formation with Tween 20-stabilized silver nanoparticles

A rapid and sensitive colorimetric sensing strategy employing silver nanoparticles (AgNPs) to detect trace Hg2+ in aqueous solutions is described. The citrate-capped AgNPs were functionalized to form a Tween 20-stabilized AgNPs (Tween 20-AgNPs) probe, which was stable in a high ionic strength environment. When Hg2+ was present in the aqueous solution, citrate reduced Hg2+ to Hg0 and formed a Ag/Hg amalgam with the AgNPs, followed by the removal of Tween 20 from the surface of the AgNPs. The AgNPs were unstable in high ionic strength solutions, resulting in AgNPs aggregation and co-stabilization with Hg2+, observed by a decrease in the UV-vis absorption. This decrease in the UV-vis absorption was proportional to the concentration of Hg2+. Under optimized conditions, the sensing system exhibited a linear range of 5.0 × 10−10 to 1.2 × 10−7 M for Hg2+, with a detection limit of 0.31 nM in buffer. The co-stabilization assays showed no Hg2+ was detected to be remaining in solution using our proposed method. The AgNPs removal percentage was correlated well with the concentration of Hg2+ with a correlation coefficient of 0.99862. When the concentration of Hg2+ was in excess, the AgNPs removal percentage correlated with the concentration of AgNPs with a correlation coefficient 0.994 as well. Moreover, this probe was successfully used to detect and co-stabilize Hg2+ in tap water, spring water, and surface water samples.

A RESONANCE TUNABLE AND DURABLE LSPR NANO-PARTICLE SENSOR: AL&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; CAPPED SILVER NANO-DISKS

Localized surface plasmon resonance (LSPR) biosensors are employed to detect target biomolecules which have particular resonance wavelengths. Accordingly, tunability of the LSPR wavelength is essential in designing LSPR devices. LSPR devices employing silver nano-particles present better efficiencies than those using other noble metals such as gold; however, silver nano-particles are easily oxidized when they come in contact with liquids, which is inevitable in biosensing applications. To attain both durability and tunabilty in a LSPR biosensor, this paper proposes alumina (AL2O3) capped silver nano-disks. It is shown that through controlling the thickness of the cap, the LSPR resonance frequency can be finely tuned over a wide range; and moreover, the cap protects silver nano-particles from oxidation and high temperature.

Inherently Colored Antimicrobial Fibers Employing Silver Nanoparticles

Here we are reporting a novel method of producing inherently colored antimicrobial fibers employing silver nanoparticles. Without using undesirable dyes and chemical finishes, colors as well as antimicrobial properties have been imparted in textile grade acrylic fibers through silver nanoparticles, in such a way that these properties become inherent part of the fibers. The motivation behind silver nanoparticles is their unique optical properties as well as biomedical applications. A composite solution of polyacrylonitrile copolymer containing silver nanoparticles, synthesized in-situ, was converted into fibers using solution spinning technique. The fibers, so formed, have in-built silver nanoparticles in size ranging from 20-120 nm. Colors ranging from red to blue could be prepared by varying the silver concentration, aggregate size and process. The antibacterial efficacy of the fiber was as high as 94.3% against Escherichia coli.

Surface modification on silver nanoparticles for enhancing vapor selectivity of localized surface plasmon resonance sensors

Abstract This study focuses on localized surface plasmon resonance (LSPR) sensors employing silver nanoparticles that were surface functionalized with various thiolate self-assembled monolayers (SAM) to provide chemical selectivity for detection of volatile organic compounds (VOCs). Changes in the LSPR spectrum of silver nanoparticles were measured as the response signal. One unmodified and three surface-modified nanoparticle LSPR sensors generated distinguishable patterns for tested organic vapors with different functional groups. The sensor responses were rapid and reversible for all tested vapors. The detection limits of the LSPR sensor were as low as 18–30 ppm for heptanone, depending on the surface modification of Ag nanoparticles. SAM modification not only altered chemical affinity of the surface, but also moderately improved the detection limit without lengthening the response time. Surface modification using thiolates with refractive indices higher than condensed VOC neither reduced nor reversed the sensor response. Mechanisms for this phenomenon are also discussed.

Probing Silver Nanoparticles During Catalytic H2 Evolution

Employing silver nanoparticles from a recently developed synthesis [Evanoff, D. D.; Chumanov, G. J. Phys. Chem. B 2004, 108, 13948] and a well-studied probe molecule, p-aminothiophenol, we follow changes at the surface of the particles during the conditioning and eventually the catalytic production of hydrogen from water using strongly reducing radicals. Injection of electrons into the particles causes pronounced variations in the intensity of the surface enhanced Raman scattering (SERS) spectrum of the probe molecule. These spectral changes are caused by changes in the Fermi-level energy that are in turn caused by changes in the silver ion concentrations or in the pH, or by changes in electron density in the particle. This correlation highlights the effect of the chemical potential on the SERS enhancement at the end of the particles synthesis. The intensity of the SERS spectra increases in the presence of the silver ions when excitation at 514 nm is utilized. When the Ag(+) ions in the colloidal suspension are completely reduced by the radicals and the particles operate in the catalytic mode, the SERS spectrum is too weak to record, but it can reversibly be recovered upon the addition of Ag(+). The effect of pH on the SERS intensity is similar in nature to that of the silver ions but is complicated by the pKa of the aminothiol and the point of zero charge (pzc) of the particles. It is hypothesized that as the particles cross the pzc (around neutral pH) the electrostatic interaction between the protonated amine headgroup of the probe and the positively charged surface increases the density of probe molecules in the perpendicular orientation at the expense of a competing species. This conversion results in enhanced SERS signals and is observable during the preconditioning stage of the particles. Indeed, adsorption isotherms of the probe indicate the presence of two species. In analogous previous observations these two species have been attributed to perpendicular and flat adsorption orientations of the deprotonated probe molecule relative to the particle surface. However, preliminary density functional calculations on relevant prototypes raise the possibility that the two species may be the probe molecule and a cationic form produced by charge transfer in the ground state from the chemisorbed probe to the metal. These two forms of the probe have differing electronic structures and vibrational frequencies, with perhaps differing orientations relative to the surface. Whichever is the correct interpretation, a neutral molecule in a flat orientation or a radical cation, this species is easier to replace than the other in competitive adsorption by ethanethiol.