Self-assembly Of Silver Nanoparticles Research Articles

Multifunctional nanocoating for enhanced titanium implant osseointegration

Preventing bacterial infection and promoting osseointegration are essential for the long-term success of titanium (Ti) implants. In this study, we developed a multifunctional nanocoating on Ti mini-implants to simultaneously address these challenges. The nanocoating consists of self-assembled antimicrobial peptides GL13K and silver nanoparticles, referred to as Ag-GL. Our results showed that the Ag-GL coating did not alter the surface morphology of the mini-implants. Ag-GL coated mini-implants demonstrated a two orders of magnitude reduction in colony-forming unit (CFU) values compared to the noncoated eTi group, resulting in minimal inflammation and no apparent bone destruction in a bacterial infection in vivo model. When evaluating osseointegration properties, micro-CT analysis, histomorphometric analysis, and pull-out tests revealed that the Ag-GL coating significantly enhanced osseointegration and promoted new bone formation in vivo.

Silver nanoparticle-induced enhancement of light extraction in two-dimensional light-emitting diodes.

Monolayer transition metal dichalcogenides (TMDCs) with direct bandgaps are considered promising candidates for building light-emitting diodes (LEDs). One crucial indicator of their performance is the brightness of electroluminescence (EL). In this study, we fabricate WS2-based LEDs that make full use of the assistance of effective transient-mode charge injection. By introducing self-assembled silver nanoparticles (NPs) on top of the LED, the extraction efficiency is significantly improved, with a 2.9-fold EL enhancement observed in the experiment. Full-wave simulations further confirm that the improvement comes from the scattering capability of silver NPs, with results qualitatively fitting the experiment. This approach, with its compatibility with van der Waals heterostructures, can be further promoted to enhance the brightness of 2D monolayer TMDC-based LEDs.

Fabrication of submicron linewidth silver grid/ionogel hybrid films for highly stable flexible transparent electrodes via asymmetric wettability template-assisted self-assembly

High-performance flexible transparent electrodes are the basis for the continuous upgrading of optoelectronic devices. Silver grids are attractive for replacing traditional indium tin oxide (ITO) as the premier transparent electrode materials, due to their high transmittance, excellent conductivity, and low cost. However, large linewidth and oxidation of silver grids are limiting the practical application of the resulting optoelectronic devices. Here, we report an effective and scalable solution-based method to prepare highly stable flexible transparent silver grid electrodes with submicron linewidth by the asymmetric wettability template-assisted self-assembly of silver nanoparticles (AgNPs), which is then encapsulated by a thin transparent conductive ionogel as protective layer. It is demonstrated that the linewidth of silver grids can be precisely controlled by the concentration of the AgNP dispersion. Wrapping with the ionogel nanolayer have no deterioration for conductivity and transmittance of the grid electrodes. The optimized hybrid grid electrodes exhibit low sheet resistance of 24.6 Ω sq−1 and high transparency of 99%. More importantly, the introduction of the iongel nanolayer endows the hybrid grid electrodes with excellent mechanical flexibility and thermal, electrical, and chemical stability. As a proof of concept demonstration, the submicron linewidth silver grid/ionogel hybrid films are successfully used to fabricate flexible smart windows and transparent touch panel. We envision that this work will shed new light on the development of next-generation optoelectronic applications which need ultrahigh resolution displays.

Controllable Patterning of Metallic Photonic Crystals for Waveguide-Plasmon Interaction.

Waveguide-plasmon polaritons sustained in metallic photonic crystal slabs show fascinating properties, such as narrow bandwidth and ultrafast dynamics crucial for biosensing, light emitting, and ultrafast switching. However, the patterning of metallic photonic crystals using electron beam lithography is challenging in terms of high efficiency, large area coverage, and cost control. This paper describes a controllable patterning technique for the fabrication of an Ag grating structure on an indium-tin oxide (ITO) slab that enables strong photon-plasmon interaction to obtain waveguide-plasmon polaritons. The Ag grating consisting of self-assembled silver nanoparticles (NPs) exhibits polarization-independent properties for the excitation of the hybrid waveguide-plasmon mode. The Ag NP grating can also be annealed at high temperature to form a continuous nanoline grating that supports the hybrid waveguide-plasmon mode only under transverse magnetic (TM) polarization. We tuned the morphology and the periodicity of the Ag grating through the concentration of silver salt and the photoresist template, respectively, to manipulate the strong coupling between the plasmon and the waveguide modes of different orders.

Multifunctionalization of self-assembled silver nanoparticle coated poly(ethyleneimine)/poly(diallyldimethylammonium chloride) modified silk fabric

Multifunctionalization of self-assembled silk fabrics with antibacterial ability, UV protection and catalytic degradation activity was successfully prepared by surface modification with poly(diallyldimethylammonium chloride) (PDDA) and poly(ethylenimine) (PEI) successively. The silver nanoparticle-coated silk fabrics modified with PEI/PDDA were characterized by scanning electron microscope, Fourier transform infrared spectroscopy, X-ray diffraction, energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. The results indicate that a uniform distribution of silver nanoparticles is observed on the silk fabric modified with PEI/PDDA. Color feature, ultraviolet (UV) protection and antibacterial ability of the silver nanoparticle-coated silk fabrics were evaluated. Silk fabric modified with PEI/PDDA exhibits catalytic degradation activity for methyl blue (MB) with rate constants of 0.31999 min−1, and the degradation rate of 100% for the first time, which possesses a potential application in multifactional textile.

Surface-Enhanced Raman Scattering Sensor Based on Self-Assembled Silver Nanoparticles for Detecting Rotten Eggs

Surface-Enhanced Raman Scattering Sensor Based on Self-Assembled Silver Nanoparticles for Detecting Rotten Eggs

Self-assembled monolayer silver nanoparticles: Fano resonance and SERS application

Plasmonic response of noble metal nanoparticle are of fundamental interest in nanophotonic applications, such as photocatalysis, information storage, sensing, optical switches, and nonlinear optics. We comprehensively investigate the Fano resonance and SERS (surface–enhanced Raman scattering) application of self–assembled monolayer silver nanoparticles using commercial FDTD (finite difference time domain) solver, cartesian multipole decompositions method, two coupled oscillators model and experiments. We found that the higher–energy antibonding mode is not only from the antibonding dipole–dipole mode (ADD), but also from the antibonding quadrupole–quadrupole mode (AQQ) and the hybridized magnetic mode when the particle size is relatively large in homodimer, as for the heterodimer, the case will change even more. The effects of dimer gap and size are discussed in details. A two coupled oscillators model is used to illustrate the mechanism of the Fano resonance, and the energy storage as a function of radiation loss and intrinsic loss in the plasmonic system is qualitatively evaluated, which is directly related to the near–field enhancement. Finally, SERS (surface–enhanced Raman scattering) experiments are carried out to meet the numerical results, and the SERS performance is also investigated and given.

Synthesis of vanadium carbide MXene with improved inter-layer spacing for SERS-based quantification of anti-cancer drugs

The development of rapid and efficient spectroanalytical protocols to detect bioactive drugs in aqueous samples is linked with the evolution of new generations of nanostructured materials. The 2D vanadium carbide (V2CTx) family of MXenes has been proved to be a promising material owing to its excellent plasmonic effects, short-range charge transfer (CT), and covers a wide variety of applications, especially in the fields of sensing and optics. For several years, research is focused on the stability and inter-layers spacing of a few-layered V2CTx in colloidal states. In this work, the synthesis and characterization of vanadium carbide sheets using a soft condition approach were reported. The delamination with the triethylamine (TEA) intercalant resulted in deceased interlayer spacing of 8.13 Å and enhanced the shelf life by up to six weeks. The synthesized highly stable MXene was treated with self-assembled silver nanoparticles (AgNPs) to fabricate a hybrid material as a potential surface-enhanced Raman scattering (SERS) substrate for the detection of ultra-trace quantities of anti-cancer drug gemcitabine (GMC). The developed approach showed an unprecedented limit of detection of 10-12 M with a wide dynamic range of 10-4-10-12 M. The MXene-based SERS sensor has achieved a Raman signal amplification corresponding to an enhancement factor of 109, with high sensitivity and reproducibility.

(Digital Presentation) Highly Sensitive Detection of Cell Endogenous Hydrogen Sulfide Based on in-Situ Dynamic Reaction of Ag NPs

The performance of nanoscale sensors can often provide insights into the extremely subtle differences between biomolecules. Meanwhile, several innovative signal transduction pathways of biosensing systems have attracted a lot of attention, but most of these are always driven by a single mechanism[1]. Herein, we demonstrate a biosensor for in situ quantification of active sulfide in the cell that utilizes the electrochemical solid-state phase transformation mechanism of the self-assembled silver nanoparticles[2], which is immobilized on the surface of the gold microelectrode through Raman signal molecules (4-aminothiophenol, 4-ATP). Taking the detection of cell endogenous hydrogen sulfide (H2S) as an example, Ag NPs could first slowly react with local H2S. Under the occurrence of the electrochemical oxidation reaction, a large number of silver ions (Ag+) are released to quickly react with H2S. Subsequently, the execution of the reduction reaction brings the complex complexes to the electrode surface. The electrochemical solid-phase transfer mechanism has a fast reaction rate, and the shift of the redox peak of Ag NPs and the strength of the Raman spectrum of 4-ATP can quickly and accurately quantitatively analyze the cell endogenous H2S with two channels, and the detection limit can reach nanomolar level. Going beyond conventional biosensing, the elaborate dynamic coupling of multiple mechanisms in a micro/nanoscale interface may open a new approach for future highly sensitive biosensing.

200 MeV Ag ion irradiation mediated green synthesis and self assembly of silver nanoparticles into dendrites for enhanced SERS applications

In this paper, we report green and controlled synthesis of silver nanoparticles in water with spherical, hetrogeneously shaped and extended chain like networks using pristine Bergenia ciliata root extracts and the extracts irradiated with Ag15+ swift heavy ion irradiation. The ion fluence on the thin layer of extract modifies the phytomolecules responsible for the reduction and capping of the silver ion and thus changing the morphologies and sizes of the resultant nanoparticles. In addition, the irradiation assists the nanoparticles to agglomerate via surface oxidation providing a core for the growth of dendritic assemblies. Optical, crystallographic and morphological studies reveal surface oxidation of silver nanoparticles is enhanced upon the irradiation of the phytomolecules due to which the surface chemistry of the nanoparticles changes. In addition, these silver nanoparticles and their dendritic assembly exhibit high SERS enhancement factors for methylene blue analyte. The effects of irradiation promote the dendritic assemblies, roughened surfaces over the nanoparticle clusters and hence offer higher enhancement factors as compared to those which have been synthesized using pristine plant extracts.

Functionalized silver nanoparticles for SERS amplification with enhanced reproducibility and for ultrasensitive optical fiber sensing in environmental and biochemical assays.

Plasmonic sensors have broad application potential in many fields and are promising to replace most bulky sensors in the future. There are various method-based chemical reduction processes for silver nanoparticle production with flexible structural shapes due to their simplicity and rapidity in nanoparticle fabrication. In this study, self-assembled silver nanoparticles (Ag NPs) with a plasmon peak at 424 nm were successfully coated onto -NH2-functionalized glass and optical fiber sensors. These coatings were rapidly produced via two denaturation reactions in plasma oxygen, respectively, and an APTES ((3-aminopropyl)triethoxysilane) solution was shown to have high strength and uniformity. With the use of Ag NPs for surface-enhanced Raman scattering (SERS), excellent results and good stability with the detection limit up to 10-10 M for rhodamine B and 10-8 M for methylene blue, and a signal degradation of only ∼20% after storing for 30 days were achieved. In addition, the optical fiber sensor with Ag NP coatings exhibited a higher sensitivity value of 250 times than without coatings to the glycerol solution. Therefore, significant enhancement of these ultrasensitive sensors demonstrates promising alternatives to cumbersome tests of dye chemicals and biomolecules without any complicated process.

Self-Assembled Silver Nanoparticles Decorated on Exfoliated Graphitic Carbon Nitride/Carbon Sphere Nanocomposites as a Novel Catalyst for Catalytic Reduction of Cr(VI) to Cr(III) from Wastewater and Reuse for Photocatalytic Applications.

Silver nanoparticles decorated on an exfoliated graphitic carbon nitride/carbon sphere (AgNP/Eg-C3N4/CS) nanocomposites were synthesized by an adsorption method with a self-assembled process. These nanoparticles were characterized by different techniques like UV–visible (UV–vis) spectroscopy, photoluminescence (PL) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), thermal gravimetric analysis (TGA), Raman spectroscopy, scanning electron spectroscopy (SEM), transmission electron spectroscopy (TEM), electrochemical impedance spectroscopy (EIS), and ζ potential. AgNP/Eg-C3N4/CS nanocomposites showed a higher catalytic reduction activity for the conversion of Cr(VI) into Cr(III) with formic acid (FA) at 45 °C when compared to bulk graphitic carbon nitride (Bg-C3N4, Eg-C3N4, CS, and Eg-C3N4/CS). The kinetic rate constants were determined as a function of catalyst dosage, concentration of Cr(VI), pH, and temperature for the AgNP/Eg-C3N4/CS nanocomposite. This material showed higher reduction efficiency (98.5%, k = 0.0621 min–1) with turnover frequency (0.0158 min–1) for the reduction of Cr(VI) to Cr(III). It also showed great selectivity and high stability after six repeated cycles (98.5%). Further, the reusability of the Cr(III)-AgNP/Eg-C3N4/CS nanocomposite was also investigated for the photocatalytic degradation of methylene blue (MB) under visible light irradiation with various time intervals and it showed good degradation efficiency (α = 97.95%). From these results, the AgNP/Eg-C3N4/CS nanocomposite demonstrated higher catalytic activity, improved environmental friendliness, lower cost for the conversion of toxic Cr(VI) to Cr(III) in solutions, and also good reusability.

Enhanced degradation capability of white-rot fungi after short-term pre-exposure to silver ion: Performance and selectively antimicrobial mechanisms

Azo dyes in wastewater have great threats to environment and human health. White-rot fungi (WRF) have broad-spectrum potential for such refractory organics bioremediation; however, their applications are largely restrained by the poor viability owning to microbial invasion under non-sterile conditions. In this study, short-term pre-exposure to silver ion (Ag+) was demonstrated to be a practical, economic, and green method to enhance the perdurability of azo dyes decoloration by WRF Phanerochaete chrysosporium under non-sterile conditions. In control (without Ag+ pre-exposure), decoloration deactivated since cycle 7 (<10%), whereas in Ag+ pre-exposure groups, the decoloration ratios remained 91.5%–94.7% after 7 cycles. Variations in decoloration-related extracellular lignin enzyme activities were consistent with the decoloration effectiveness. The enhanced decoloration capability in Ag+ pre-exposure groups under non-sterile conditions could be ascribed to the selectively antimicrobial action by Ag+. The released Ag+ from the self-assembled silver nanoparticles (AgNPs) could selectively “stimulate” the proliferation and viability of P. chrysosporium, and simultaneously inhibit the growths of invasive microorganisms. The pyrosequencing results indicated that genus Sphingomonas (24.1%–31.3%) was the main invasive bacteria in Ag+ pre-exposure groups after long-term operation owing to the AgNPs passivation. As control, the invasive fungi (Asterotremella humicola) and bacteria (Burkholderia spp.) occurred in control after short-term operation, and genus Burkholderia (74.9%) dominated after long-term operation, leading to decoloration deactivation. Overall, these findings offer a new insight into the bio-nano interactions between WRF and invasive microorganisms in response to Ag+ or biogenic AgNPs, and could extend WRF application perspective under non-sterile conditions in future.

Surface-enhanced Raman spectroscopic chemical imaging reveals distribution of pectin and its co-localization with xyloglucan inside onion epidermal cell wall.

The primary plant cell wall is a complex matrix composed of interconnected polysaccharides including cellulose, hemicellulose, and pectin. Changes of this dynamic polysaccharide system play a critical role during plant cell development and differentiation. A better understanding of cell wall architectures can provide insight into the plant cell development. In this study, a Raman spectroscopic imaging approach was developed to visualize the distribution of plant cell wall polysaccharides. In this approach, Surface-enhanced Raman scattering (SERS through self-assembled silver nanoparticles) was combined with Raman labels (4-Aminothiophenol. 4ATP) and targeted enzymatic hydrolysis to improve the sensitivity, specificity, and throughput of the Raman imaging technique, and to reveal the distribution of pectin and its co-localization with xyloglucan inside onion epidermal cell (OEC) wall. This technique significantly decreased the required spectral acquisition time. The resulted Raman spectra showed a high Raman signal. The resulted Raman images successfully revealed and characterized the pectin distribution and its co-localization pattern with xyloglucan in OEC wall.

Self-assembly of silver nanoparticles on chitosan/polyvinylpyrrolidone modified micro-needle electrode for amperometric detection of nitrate in seawater

In this work, silver nanoparticles (AgNPs) were self-assembled on the micro-needle electrode (MNE) with the help of chitosan (CTS) and polyvinylpyrrolidone (PVP) and used for the amperometric (i-t) determination of nitrate (NO3–) in seawater samples. CTS/PVP was electrodeposited on the MNE surface to improve the conductivity and specific surface area of the MNE, and to provide reduction conditions needed for Ag+ reduction and strong binding affinity for combination of AgNPs which had excellent catalytic activity for NO3–. AgNPs were self-assembled uniformly on the surface of MNE with the diameter of about 150–400 nm. Thanks to the unique aciform structure of MNE, the outstanding adhesion ability of CTS/PVP, and the excellent electrocatalytic ability of AgNPs, the so-prepared AgNPs/CTS/PVP/MNE showed significantly improved performance and stability for the amperometric determination of NO3–. Under the optimal conditions, the AgNPs/CTS/PVP/MNE was found to have a wide linear range (5–2000 μM) and a low limit of detection (1.2 μM). Furthermore, the AgNPs/CTS/PVP/MNE was successfully used for the direct determination of NO3– in coastal seawater samples with satisfactory results.

Comparison of hot carrier generation between self-assembled gold and silver nanoparticle arrays tailored to the same hybrid plasmon resonance

We evaluated the properties of hot carrier generation on Au and Ag nanoparticle (NP) 2D arrays by monitoring chemical transformation. The arrays were fabricated by assembling the Au and AgNPs, respectively, with a diameter of ∼30 nm. The plasmon resonance peaks of both the arrays were tuned to around 671 nm, where the intraband transition was the dominant pathway for the surface plasmon excitation since the incident photon energy is below the interband transition threshold for both Au and Ag. Time-resolved surface-enhanced Raman scattering (SERS) spectroscopy was utilized to monitor the changes in the molecular structure sensitively. We selected para-aminothiophenol as the molecule, which was well known to transform to 4,4′-dimercaptoazobenzene (DMAB) by hot carriers generated from the plasmonic excited surface. It was observed that the peak intensity of DMAB increased as the total exposure increased due to the increase in the number of DMAB molecules for both metals, similar to our previous reports. The analysis of the SERS spectra showed that larger laser intensity progressed the transformation more rapidly. The analysis also clarified that the chemical transformation occurs more efficiently on the AgNP array compared to the AuNP array. The superiority in the efficiency for Ag may be derived from contribution of more hot carriers generated in the material with the smaller plasmon damping constant.

Photo-Induced Self-Assembly of Silver Nanoparticles for Rapid Generation of First and Second Surface Mirrors

Interesting mirror-like, highly reflective, and conductive silver films have been successfully generated directly on a glass slide using a simple and fast photoinduced approach. A water-based photo...

Characterization of self-assembled silver nanoparticle ink based on nanoemulsion method.

A well-dispersed self-assembled silver nanoparticles (AgNPs) ink with high purity was synthesized via AgNO3 emulsion prepared by blending an AgNO3 aqueous solution and a liquid paraffin solution of both polyoxyethylene (20) sorbitan monooleate (Tween 80) and sorbitan monooleate (Span 80). The ink remained as an emulsion at low temperatures; however, it produced AgNPs after sintering at about 60°C and showed a high stability at nanoscale sizes (with diameters ranging 8.6–13.4 nm) and a high conductivity. During the whole procedure, Tween 80 acted as a surfactant, reductant and stabilizer. Presumably, Tween 80 underwent an autoxidation process, where a free radical of an α-carbon of ether oxygen was formed by hydrogen abstraction. The mean diameter of emulsion droplets could be reduced by decreasing water content and increasing the ratio of surfactant and concentration of AgNO3 aqueous solution. Consequently, the thermogravimetric analysis and X-ray diffraction result clarified the purity of the produced Ag0. Dynamic light scattering and ultraviolet-visible spectroscopy clarified that an increased concentration of AgNO3 decreased the particle size.

Self-assembly of silver nanoparticles through functionalization with coumarin-thiazole fused-ring thiol

Self-assembly of nanoscale building blocks plays a critical role for the edifice of functional nanomaterials. In this work coumarin based fused-ring heterocyclic thiol functionalized silver nanoparticle exhibiting large self-assembly is reported. The particles spontaneously self-organise towards the formation of larger superstructures, yet still retaining their individual particle morphology (~10nm). The π-stacking behaviour of coumarin based fused ring aromatic skeleton seems to play the key role for the induction of dense assembly in this hybrid nanoparticles. In the present work the anchoring group (thiol) is directly attached to the aromatic framework of the Coumarin-thiazole fused-ring, for easier electron flow between the metal and the aromatic ligand. The synthesized materials have been characterized by UV-Vis, Fluorescence, XRD, TEM, SAED, IR, 1H and 13C NMR. The synthesis of the ligand and process of functionalization is simple and easily reproducible.

Surface Enhanced Raman Scattering of Crystal Violet with Low Concentrations Using Self-Assembled Silver and Gold-Silver Core-Shell Nanoparticles

Surface Enhanced Raman Scattering of Crystal Violet with Low Concentrations Using Self-Assembled Silver and Gold-Silver Core-Shell Nanoparticles