Size Of Ag Nanoparticles Research Articles

Third-order nonlinear optical effects of silver nanoparticles and third harmonic generation from their plasma plumes

We investigated the third-order nonlinear optical (NLO) properties of the silver (Ag) nanoparticles (NPs) of various sizes, which were produced by disintegration of commercially available 20 and 100 nm NPs in different solvents. It is observed that NPs with the sizes less or greater than 30 nm possess saturable absorption or reverse saturable absorption (or two-photon absorption), respectively. The NPs suspensions show a self-focusing effect. In addition, the third harmonic generation from the plasma plumes produced by nanosecond laser ablation of bulk Ag and Ag NPs of 100 nm and 20 nm sizes is reported. The third harmonic efficiency from the plasmas containing NPs was higher compared with the plasmas produced on the bulk silver. Finally, the ionization probabilities of Ag atom and Ag+ were calculated.

Ag-coated cotton fabric as ultrasensitive and flexible SERS substrate

Surface enhanced Raman scattering (SERS) has proven to be increasingly valuable as an analytical tool since this phenomenon was first observed in 1973. However, challenges still exist to ensure their ability to access targeted analytes and adequate levels of sensitivity to them on irregular surfaces. Herein, silver (Ag) nanoparticles are deposited onto cotton fabric through magnetron sputtering to develop a flexible and ultrasensitive SERS-active substrate. To obtain a better enhancement effect, Ag nanoparticles of different sizes are produced by controlling the argon flow rate and the sputtering time. The finite-difference time-domain (FDTD) method and Raman mapping are used to explain the process behind Raman signal enhancement. The cotton fabric sample with Ag nanoparticles deposited at an argon flow rate of 200 sccm (labelled as AC-200) shows a high enhancement factor (EF) of 104 with a Methylene blue (MB) solution of 10−3 M, stability with a related standard deviation (RSD) of 1.03%, excellent reproducibility with an RSD of 1.92% and high sensitivity with 10−9 M of MB solution. Therefore, AC-200 demonstrates exceptional SERS signal reproducibility and stability for different types of chemical analytes and has the potential to be used in future practical applications.

Control of localized surface plasmon resonance of Ag nanoparticles by changing its size and morphology

Ag thin-films with thicknesses of 5, 10, 15, 20, and 25 nm are deposited by thermal vacuum evaporation, and the obtained films are subsequently annealed at 400 °C for 1 h to form the Ag nanoparticles (NPs). The averaged diameters of the resultant Ag NPs are increased from 50 to 300 nm as increasing the initial Ag deposition thickness, according to the morphological observation using scanning electron microscopy (SEM). The significant red-shift of the extinction peak depending on the particle size of the Ag NPs, which can be assigned to the localized surface plasmon resonance of the Ag NPs. The organic emitter, tris(8-hydroxyquinolinato)aluminum (Alq3) film is overcoated on the Ag NPs. About 4-fold enhancement of the photoluminescence of Alq3 was observed in combination with the larger size Ag NPs fabricated from the 15–25 nm thick Ag films, which can be applied for the improvement of the light-extraction efficiency of the organic light-emitting devices.

Ag-doped Cobweb-like structure of TiO2 nanotubes for antibacterial activity against Methicillin-resistant Staphylococcus aureus (MRSA)

Hydrothermal reaction and photodeposition were used to transform TiO2 nanoparticles to TiO2 nanotubes (TNTs) loaded with Ag. The structure and morphology of TNTs and Ag/TNTs were characterized, and the antibacterial activity of all catalysts against Methicillin-resistant S. aureus was tested using agar well diffusion and total viable plate count methods in the absence and presence of UV light. The cobweb-like structure of TNTs was noticed, and the network could increase the surface area to 184–216 m2/g, an up to fourfold increase compared to TiO2 P25. The XRD, EDS, HRTEM and UV-DR results revealed Ag nanoparticle deposition on the TNTs surface. The HRTEM result also showed no change in the shape or morphology of TNTs. The Ag nanoparticle size on the TNTs surface ranged from 8.928 ± 1.487 to 14.654 ± 2.901 nm. The light absorption capacity of TiO2, TNTs, and Ag/TNTs displayed antibacterial activity in the presence of UV light. In contrast, only Ag/TNTs could reduce the bacteria growth in the dark condition, which decreased the restriction of TNTs and TiO2. The maximum antibacterial activity was obtained at 1.5%Ag/TNT, at which the cell viability was 77.86% of the initial number concentration. Based on the result of this research work, it could be confirmed that Ag/TNTs can potentially be used as a disinfection material in both presence as well as absence of UV light.

Genomic Damage Induced in Nicotiana tabacum L. Plants by Colloidal Solution with Silver and Gold Nanoparticles.

Tobacco seedlings (Nicotiana tabacum L cv. Wisconsin 38) were treated for 24 h with colloidal solution of silver and gold nanoparticles (AgNPs and AuNPs) of different size or cultivated for 8 weeks on soil polluted with these NPs. DNA damage in leaf and roots nuclei was evaluated by the comet assay. AgNPs of the size 22–25 nm at concentrations higher than 50 mg·L−1 significantly increased the tail moments (TM) values in leaf nuclei compared to the negative control. Ag nanoparticles of smaller size 12–15 nm caused a slight increase in tail moment without significant difference from the negative control. The opposite effect of AgNPs was observed on roots. The increasing tail moment was registered for smaller NPs. Similar results were observed for AuNPs at a concentration of 100 mg·L−1. DNA damaging effects after growing tobacco plants for 8 weeks in soil polluted with AgNPs and AuNPs of different size and concentrations were observed. While lower concentrations of both types of particles had no effect on the integrity of DNA, concentration of 30 mg·kg−1 of AgNPs caused significant DNA damage in leaves of tobacco plants. AuNPs had no effect even at the highest concentration. The content of Ag was determined by ICP–MS in above-ground part of plants (leaves) after 8 weeks of growth in soil with 30 mg·kg−1. AgNPs and was 2.720 ± 0.408 µg·g−1. Long term effect is much less harmful probably due to the plant restoration capability.

Synthesis of porous silicon based nanoparticles for applications in surface enhanced Raman spectroscopy

In this work porous Si (PSi) nanoparticles (NPs) were prepared by magnesiothermic reduction of the synthesized SiO2 spheres, and Ag NPs were deposited on the PSi with formaldehyde or HF. In addition, silver NPs were deposited on the porous Si obtained by milling and etching the Si wafer. Silver NPs on SiO2 spheres and particles with Ag core and mesoporous SiO2 shell were also synthesized. SEM analysis showed the Ag NPs size distributions between 30.1 and 64.3 nm. The synthesized samples were quite stable in aqueous media and had zeta potential between −11.5 and −44.3 mV. The samples exhibited reversible physisorption isotherms of type II except for the sample with Ag core and SiO2 (Ag–S) coating, which exhibited a type IVa isotherm accompanied by the hysteresis characteristic of mesoporous adsorbents. The BET surface areas of the samples ranged from 9 to 56 m2g-1, with the mesoporous Ag–S sample having the largest surface area of 378 m2g-1. The surface enhanced Raman spectroscopy (SERS) performance of the synthesized samples was studied by analysing the detection limit of 4-mercaptophenylboronic acid (4-MPBA) as a probe molecule at 532 nm laser excitation. The lowest limit of detection of 1 × 10−5 mol dm−3 was obtained with the sample in which silver NPs were deposited on silica spheres (S–Ag).

Influence of Co contents on the microstructure and SERS performance of self-formed Ag nanoparticles/Ag-Co alloy films on flexible substrates

Self-formed Ag nanoparticles/Ag-Co alloy films with various Co contents were fabricated by sputtering Ag-Co composite target. Effects of Co contents in Ag-Co films on the microstructure and SERS performance of nanoparticles/alloy films were thoroughly investigated through SEM, TEM and Raman spectrometer. Amorphous Co in Ag-Co films restricted the growth of Ag grains in the films and promoted the formation and growth of Ag nanoparticles on the film’s surface. The size and number of Ag nanoparticles grown on the surface were closely related to Co contents in Ag-Co films, Ag-Co film thicknesses and annealing temperatures. Ag nanoparticles/Ag-Co films covered with Ag layers performed ultra-sensitive Raman signals due to forming abundant active hot spots. This flexible SERS substrate could detect 10−12 mol/L Rhodamine 6G (R6G), which indicated that this novel type of Ag nanoparticles/Ag-Co alloy films could be used and applied as high-efficient SERS substrates.

Pulsed laser-induced dewetting and thermal dewetting of Ag thin films for the fabrication of Ag nanoparticles

Two different dewetting methods, namely pulsed laser-induced dewetting (PLiD)—a liquid-state dewetting process and thermal dewetting (TD)—a solid-state dewetting process, have been systematically explored for Ag thin films (1.9–19.8 nm) on Si substrates for the fabrication of Ag nanoparticles (NPs) and the understanding of dewetting mechanisms. The effect of laser fluence and irradiation time in PLiD and temperature and duration in TD were investigated. A comparison of the produced Ag NP size distributions using the two methods of PLiD and TD has shown that both produce Ag NPs of similar size with better size uniformity for thinner films (<6 nm), whereas TD produced bigger Ag NPs for thicker films (≥8–10 nm) as compared to PLiD. As the film thickness increases, the Ag NP size distributions from both PLiD and TD show a deviation from the unimodal distributions, leading to a bimodal distribution. The PLiD process is governed by the mechanism of nucleation and growth of holes due to the formation of many nano-islands from the Volmer−Weber growth of thin films during the sputtering process. The investigation of thickness-dependent NP size in TD leads to the understanding of void initiation due to pore nucleation at the film-substrate interface. Furthermore, the linear dependence of NP size on thickness in TD provides direct evidence of fingering instability, which leads to the branched growth of voids.

Insights into effects of O-incorporated Ag nanoparticles as wetting seeds toward improving Ag wetting on oxides

Ag wetting on oxides is essential for implementing exceptional layered Ag superstructures with simultaneous ultralow losses in electrical conductance and optical transmittance. This goal is difficult to achieve by conventional synthetic techniques involving the incorporation of heterogeneous transition metals or metalloids into Ag as wetting inducers as they cause detrimental optoelectrical changes. This study provides novel insights into the use of homogeneous Ag wetting seeds to improve the wetting of Ag on oxides. We investigated the effect of atomic O incorporation on the improvement of Ag wetting by monitoring its participation in and contribution to the Ag clustering and layering processes. Minimal incorporation of dissolved atomic O as a surfactant into the Ag nanoparticles transposed the nanoparticle evolution path from a complete to incomplete coalescence mode at significantly reduced thicknesses, which was attributed to a reduction in the nanoparticle free energy. The size and shape of the O-incorporated Ag nanoparticles were precisely controlled to accelerate the wetting transition of Ag on ZnO substrates by circumventing the transmutation effect of O. These results demonstrate a notable strategy for accomplishing a rapid Ag wetting transition toward a completely continuous layer with ultralow optoelectrical losses.

Ag Nanoparticle-Incorporated Natural Rubber for Mechanical Energy Harvesting Application.

The energy conversion performance of the triboelectric nanogenerator (TENG) is a function of triboelectric charges which depend on the intrinsic properties of materials to hold charges or the dielectric properties of triboelectric materials. In this work, Ag nanoparticles were synthesized and used to incorporate into natural rubber (NR) in order to enhance the dielectric constant for enhancing the electrical output of TENG. It was found that the size of Ag nanoparticles was reduced with the increasing CTAB concentration. Furthermore, the CTAB surfactant helped the dispersion of metallic Ag nanoparticles in the NR-insulating matrix, which promoted interfacial polarization that affected the dielectric properties of the NR composite. Ag nanoparticle-incorporated NR films exhibited an improved dielectric constant of up to almost 40% and an enhanced TENG performance that generated the highest power density of 262.4 mW/m2.

Silver nanoparticles enhanced photoluminescence and the spectroscopic performances of Nd3+ ions in sodium lanthanum borate glass host: Effect of heat treatment

Silver nanoparticles (NPs) impact on the emission attributes of Nd3+ activated Na2O–La2O3–B2O3 vitreous host matrix has been studied and discussed in detail. The effect of nucleation and growth of Ag NPs occurred due to the different heat–treatment durations at the temperature of 450 °C has been discussed. Transmission electron microscopy measurement revealed the formation of spherically shaped Ag NPs in the studied samples. The median Ag NPs size was increased from 2 to 9 nm with heat–treatment durations. Utilizing the absorption spectra of Nd3+ ions, the phenomenological Judd–Ofelt (J–O) parameters (Ωλ= 2, 4, 6) were estimated. The optimized luminescence intensity at 1056 and 875 nm have realized for 10 h of annealing at 450 °C, with an enhancement factor of 160%. Moreover, the quantum efficiency for 1056 nm increased steadily with the heat–treatment duration. The stimulated emission cross–section and gain bandwidth for 1056 nm laser transition has shown to be 2.92 × 10−20 cm2 and 9.19 × 10−26 cm3 for the Ag NPs embedded glass–composite. The results exemplifies the suitability of Ag NPs embedded glass–composites for the fabrication of compact solid–state infrared lasers.

Thermal annealing and laser-induced mechanisms in controlling the size and size-distribution of silver nanoparticles in Ag+-Na+ ion-exchanged silicate glasses

Controlled precipitation of metal nanostructures into glassy matrices have demonstrated to be a valid way to synthesize materials suitable for photonics, optoelectronics and telecom purposes. However, the development of strategies for driving nanostructure formation, and then for tailoring the optical response of the metal doped systems, is still a challenge. Aiming at this, the present study focuses on silver state modification including nucleation/growth of Ag nanoparticles (NPs), manipulation of Ag NPs size and size-distribution in Ag+-Na+ ion exchanged silicate glasses undergone post-exchange treatments, such as thermal annealing and laser irradiation with different irradiation parameters. Raman and optical absorption spectroscopy analyses allow to follow the evolution of the Ag NPs precipitation process starting from the early stages of the overall mechanism, where the glassy matrix is permeated by a dense distribution of Ag0, Ag+ and small aggregates, which are the seeds for the formation of the larger particles upon energetic treatments. In these regards, it is observed that a proper choice of laser irradiation conditions, in terms of wavelength and pulse energy, has a direct impact on the occurrence of the overall clustering process, by specifically promoting Ag ion reduction as well as cluster nucleation, growth and fragmentation. This definitely paves the way to efficient strategies for the realization of optical materials based on controlled distribution of metal clusters with finely tuned structural and optical properties.

Plasmon-enhanced lateral photovoltaic effect observed in Ag-ZnO core–shell nanoparticles

The lateral photovoltaic effect (LPE) is widely used in sensitive position detectors. Discovering comprehensive mechanisms and continuously improving their sensitivity are the ongoing goals in this field. However, the limited absorption and rapid recombination are two major challenges in the traditional LPE. Here, surface plasmon-based approaches have been used to boost the energy conversion efficiency, and the Ag-ZnO core–shell nanoparticles (NPs) with enhanced LPE are prepared on the Si substrate through atomic layer deposition. Owing to the enhanced light absorption, prolonged hot electron generation, and plasmon-induced charge separation, this system exhibits good LPE performance with a maximum sensitivity of 122.1 mV/mm at 980 nm, which is about seven times larger than that observed in conventional Ag/Si (5.03 mV/mm) and ZnO/Si (76.13 mV/mm). Besides, its sensitivity can increase up to 114.7% by using rapid thermal annealing to change the shape and size of active plasmon Ag NPs. Furthermore, the surface-enhanced Raman scattering spectra and finite-difference time-domain electric field simulation prove the occurrence of localized surfaced plasmon resonance excitation. This infrared sensitive shell-isolated structure has great potential for applications in high sensitivity and stability photoelectric devices.

The high active SERs substrate prepared by self assembling Ag nanoparticles on PPy@PEDOT:PSS film to detect the sodium formaldehyde sulfoxylate molecules

Abstract The Ag/PPy@PEDOT:PSS film was used as a Surface-enhanced Raman scattering (SERs) substrate to directly detect the low concentration of sodium formaldehyde sulfoxylate (SFDS) molecules in solution. We prepared the PPy@PEDOT:PSS film by electrochemical potentiostatic (ECP) method and then directly grew Ag nanoparticles on its surface to prepare the SERs substrate of Ag/PPy@PEDOT:PSS film. The results showed that with the increase of depositional time of Ag nanoparticles, accordingly, the size and density of Ag nanoparticles could be increased on the film surface, and their SERs effect was also enhanced gradually; this SERs substrate could sensitively detect the SFDS molecules in aqueous solution. Moreover, the minimum detection limit was up to 1 ng/mL. This preparing and detecting method of SERs substrates provides a new way for the preparation of high sensitivity SERs substrate and for direct and rapid detection of low concentration of SFDS molecules in food and drug.

Interplaying Role of Particle Size and Polymer Layer Thickness on the Large Tunable Optical Response of Polymer-coated Silver Nanostructures

The interplaying role of particle size and polymer layer thickness on the tunable optical response of polymer-coated Ag nanoparticles (NPs) has been studied experimentally and theoretically. A large redshift ( $$\sim$$ 38 nm) of surface plasmon resonance (SPR) peak position has been observed experimentally for Ag NPs of sizes in the range of 8−18 nm synthesized by polyol process with the varying concentration of metal precursor (AgNO $$_{3}$$ ) and using a surfactant (PVP) as a stabilizer. The observed large redshift of the SPR peak position of Ag NPs coated with PVP has been argued due to mainly change of NP size as well as change of local dielectric environment in the vicinity of the Ag NPs. The experimentally observed SPR peak shift has been explained by considering the system as a metal-core polymer-shell nanostructure. The change of local dielectric environment of the surrounding of the NPs is due to the change in the PVP layer on the NPs. Such observation has been confirmed through the theoretical studies considering the changes of NP size as well as the effective thickness of the PVP layers on the NPs. The SPR peak of the system with core-shell nanostructure has been found to vary linearly with the increase in radius of core and thickness of shell together. However, it changes exponentially with particle size alone. It has been found from a detailed study that the change in the ratio of radius of core and thickness of the shell is responsible for the observed redshift. Thus, the redshift of SPR peak position of Ag NPs cannot be justified by only considering the increase in particle size. Rather shell thickness has been found to play a prominent role in the SPR peak shift. This study can be used to understand the optical response of noble metal NPs coated with organic polymers.

Insecticidal and fungicidal performance of bio-fabricated silver and gold nanoparticles

The current article focuses on the synthesis of silver and gold nanoparticles by different parts (bark, leaf, and flower) of Moringa oleifera, and their insecticidal activities against larvae of culex quinquefasciatus and Aedes aegypti mosquitoes and fungicidal activity against Aspergillus sp. Both the nanoparticles were characterized by several analytical instruments such as UV–Visible spectroscopy, transmission electron microscopy (TEM), field emission scanning electron microscope (FESEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and atomic force microscopy (AFM). A clear signature of surface plasmon resonance of both Ag and Au nanoparticles was recorded at 415 nm and 545 nm with respective salt solution and bark extract of Moringa oleifera, respectively. The non-uniform spherical size of both Ag and Au nanoparticles was confirmed from TEM, XRD, and EDX-FESEM studies. Similarly, the existence of significant functional groups was also identified by FTIR analysis. The larvicidal activity of both the nanoparticles exhibited nonsignificant difference (for both LC50 and LC90) at 24 and 48 h of incubation for both the mosquito species. However, antifungal activity of Ag and Au nanoparticles against Aspergillus sp. at higher concentration (200 mg/L) was exhibited with the inhibition zone 0.502 and 0.125 cm2, respectively. The toxicological study also revealed that both nanoparticles had no adverse effect on the nontarget species, Chironomus sp. Therefore, it could be concluded that both the synthesized nanoparticles have enough potentiality in respect of larvicidal and fungicidal activities.

Structure characterization and antibacterial properties of Ag-DLC films fabricated by dual-targets HiPIMS

Abstract Silver doped diamond-like carbon (DLC) films were prepared on Si (111) substrates by dual-targets high power impulse magnetron sputtering (HiPIMS), and the chemical composition, microstructure, mechanical properties and antibacterial properties of the as-deposited films were obtained. When the sputtering voltage of the Ag target was varied from 450 to 580 V, X-ray photoelectron spectroscopy results revealed that the concentration of Ag in the as-deposited films was increased from 19.1 to 32.0 at. %. High resolution transmission electron microscopy images depicted that the as-deposited films were composed of Ag nanoparticles (AgNPs) embedded in DLC matrix. Along the cross-section of the film, the size of silver nanocrystals was varied from 5–12 (in the middle) to 2–5 nm (in the top surface). When the sputtering voltage was increased, the density of AgNPs was raised also. In addition, when the bias was increased from −50 to −100 V, the size of AgNPs in the top surface was reduced from 5–12 to 2–5 nm. AgNPs with a small size benefited the release of silver ions and improved the antibacterial ability, and the samples fabricated with the sputtering voltage (Ag target) of 500–560 V and a larger bias (-100 V) obtained an excellent antibacterial efficiency (> 99.5%) against Escherichia coli and Staphylococcus aureus.

Supported Silver Nanoparticles as Catalysts for Liquid-Phase Betulin Oxidation.

Herein, it has been shown that betulin can be transformed into its biologically active oxo-derivatives (betulone, betulinic and betulonic aldehydes) by liquid-phase oxidation over supported silver catalysts under mild conditions. In order to identify the main factors determining the catalytic behavior of nanosilver catalysts in betulin oxidation, silver was deposited on various alumina supports (γ-alumina and boehmite) using deposition–precipitation with NaOH and incipient wetness impregnation methods, followed by treatment in H2 or O2. Silver catalysts and the corresponding supports were characterized by X-ray diffraction, nitrogen physisorption, inductively coupled plasma optical emission spectroscopy, photoelectron spectroscopy and transmission electron microscopy. It was found that the support nature, preparation and treatment methods predetermine not only the average Ag nanoparticles size and their distribution, but also the selectivity of betulin oxidation, and thereby, the catalytic behavior of Ag catalysts. In fact, the support nature had the most considerable effect. Betulin conversion, depending on the support, increased in the following order: Ag/boehmite < Ag/boehmite (calcined) < Ag/γ-alumina. However, in the same order, the share of side reactions catalyzed by strong Lewis acid centers of the support also increased. Poisoning of the latter by NaOH during catalysts preparation can reduce side reactions. Additionally, it was revealed that the betulin oxidation catalyzed by nanosilver catalysts is a structure-sensitive reaction.

Plasmonic composites WO3/Bi12O17Cl2 decorated with uniform Ag nanoparticles in tiny size: Synthesis, analyses, and visible-light photocatalytic performance

Various novel ternary composites Ag/WO3/Bi12O17Cl2 were successfully constructed through a rapid and facile microwave-assisted approach to decorate Ag nanoparticles onto WO3/Bi12O17Cl2 surface. Through analyses, three expected components were coexisted and formed n–p heterojunctions with Ag nanoparticles of uniform morphology and size below 20 nm. These plasmonic composites with favorable physiochemical properties showed greatly reinforced photocatalytic performance over degradation of Rhodamine B (RhB), methyl orange (MO), and tetracycline hydrochloride (TC) upon visible light irradiation. Moreover, these samples exhibited satisfactory structural stability and reusability in both aqueous and saline solution. Eventually, a plausible photocatalysis mechanism was speculated upon analytical and experimental results. Such investigation might provide a series of ternary composites with small size of Ag nanoparticles for sake of contaminants control and environmental preservation.

Flexible Ag SERS substrate for non-destructive and rapid detection of toxic materials on irregular surface

In this study, silver (Ag) is deposited onto polyester fabric through a magnetron sputtering system. The argon flow rate and sputtering time are both controlled to produce Ag nanoparticles of different sizes on the polyester substrate with different gap distances. The scanning electron microscope images, X-ray diffraction spectra, and Raman intensity are used to evaluate the produced substrates. With an average grain size of ~ 46 nm, Ag particles deposited at an argon flow rate of 200 sccm on polyester fabric (AP-200) provides the best SERS performance of 33,625.34 counts towards a 10−3 M MB solution. The results show that the AP-200 SERS substrate is highly sensitive, reproducible and stable, and it also demonstrates good reusability. Image of “hotspots” that forms between two Ag nanoparticles based on electric field distribution is simulated by the finite-difference time-domain (FDTD) method which is used to explain the phenomenon of signal enhancement. In addition, AP-200 is used to directly collect R6G from an irregular surface, and shows high sensitivity with a limit of detection of 1 ppm.