Abstract Ag Nanoparticles Research Articles

Microstructural and Surface Plasmon Resonance Properties of Green-Synthesized Ag Nanoparticles Using <i>Moringa oleifera</i> Extract

Ag nanoparticles (NPs) have been successfully synthesized by the green synthesis method using Moringaoleifera (MO) extract with various incubation times (24 and 48 hours) as an active material for surface plasmon resonance (SPR) biosensor. Transmission electron microscopy analysis indicated the formation of spherical particles with an average crystal size of 29 nm. Selected area electron diffraction confirmed that Ag NPs is face-centered cubic (FCC) crystal structure. Fourier-transform infrared measurements show the band at 3330 cm-1, 2067 cm-1, 1634 cm-1 for an incubation time of 24 hours and 3328 cm-1, 2063 cm-1, 1633 cm-1 for an incubation time of 48 hours. The results prove the proteins and phenolics compound present in the MO extract responsible as reducing agents. The maximum absorption of the green-synthesized Ag NPs in the UV-Vis spectra shows the SPR band at 326 nm and 328 nm for an incubation time of 24 and 48 hours, respectively, and absorption intensity decrease with the increase of incubation time. The result shows the SPR angle shifted to the larger angle of incident light by using green-synthesized Ag NPs. However, the increased incubation time affects the angle shift to the lower angle of the SPR shift. The addition of the green-synthesized Ag NPs leads to enhance the sensitivity of the SPR biosensor.

Emulsion Confinement Self-Assembly Induced Localization of Ag NPs in Janus Polymeric Superparticles

Ag nanoparticles (Ag NPs) showing excellent optical, antistatic and antibiotic properties have been widely applied in antibacterial materials and wearable device, the improvement of oxidative stability of Ag NPs as well as their interfacial interaction with surrounding matrix are the pre-requests for these applications. Emulsion confinement self-assembly of block copolymer and Ag NPs has been considered as one of the most effective strategy to prepare hybrid functional superparticles. Herein, different structured polyarylene ether nitrile (PEN) was employeed as surface capping agent to synthesis Ag NPs and then encapsulated in amphiphilic block copolymer of PEN (amPEN) via emulsion self-assembly. Homo-SHQ shows strongest interaction with Ag+ and the average size of synthesized Ag NPs is about 25 nm. Interestingly, we found that the obtained Ag NPs modified amPEN super-particles showed Janus structure, which is attributed to the controlled localization of Ag NPs in amPEN microparticles enabled by the preferred interfacial interaction. Given the diverse characteristics of Ag NPs, the present work will open the way for self-assembly of Ag NPs to obtain functional devices.

Controlling size and distribution of Ag nanoparticles in near surface of SiO2 glass by low-energy ion implantation

Ag nanoparticles were embedded in the near surface of SiO2 substrate and fabricated by low-energy ion implantation method in this study. The optical and structural properties of Ag implanted samples were investigated using optical spectroscopy, transmission electron microscope (TEM) and atomic force microscopy (AFM). The grain size and distribution of nanoparticles embedded in the substrate were characterized by TEM and AFM characterization. Results showed that the grain size and depth of distribution of nanoparticles were controlled by changing the ion implantation energy and dose. Furthermore, the Ag nanoparticles embedded near surface of substrate prepared by this low-energy ion implantation method had strong local surface plasmon resonance (LSPR) characteristics. Our work demonstrates a practical means for fabrication of metal nanoparticles with controllable size and distribution using ion implantation technology, which is helpful to the application of local plasmon resonance effect of metal nanoparticles.

Enhanced Photocatalytic Activity of GO-Ag@CoCN Composite for RhB Degradation under Visible Light Irradiation

Ag nanoparticles and GO co-modified Co-g-C3N4 composites were prepared successfully. The visible-light adsorption of the optimized GO-Ag@Co-g-C3N4 was improved significantly by the SPR effect of Ag nanoparticles, and the separation efficiency of photo-induced electron-hole pairs of g-C3N4 was accelerated to a large extent by the heterojunction structure of the composite and the superior conductivity of GO. The optimized GO-Ag@CoCN showed promising degradation efficiency for RhB (10 mg/L) under visible light illumination (λ>420 nm) for 160 min, which was 130% and 16.5% higher than the performance using bare g-C3N4 and optimized Ag@Co-g-C3N4, respectively. This work provided a novel way for improving the optical property and photocatalytic activity of g-C3N4.

Optical detection of CO gas by the surface-plasmon resonance of Ag nanoparticles and nanoclusters synthesized on a hydrogenated amorphous carbon (a-C:H) film

Ag nanoparticles were deposited on a hydrogenate amorphous carbon (a-C:H) thin film as a host by radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) for various deposition times. We observed that as the sputtering time increases, the particle shape of the deposited nanostructures changes to a cluster shape. AFM images show that the accumulation of the nanoparticles on each other leads to the vertical growth of the nanoclusters. According to X-ray diffraction patterns, the crystalline structure is formed for the nanocluster shape. The Fourier-transform infrared (FTIR) spectroscopy showed that bonds are formed between Ag ions and free hands of carbons on the surface of the a-C:H film. The peak related to carbide structures is seen around 2100cm^-1. UV-Vis spectroscopy demonstrates that the formation of Ag nanoclusters leads to the appearance of a sharp plasmonic peak, shifted towards longer wavelengths. The plasmonic peak of Ag was used for detecting CO gas in the ambient air. The adhesion of CO molecules to the Ag particles makes a significant change in the plasmonic peak. In the presence of CO gas flow, the localized surface plasmon resonance (LSPR) of Ag nanoclusters moves to a longer wavelength (red-shift) and the LSPR intensity increases. The sample with a nanocluster structure is a better adsorber for CO molecules due to its larger specific surface area.

Surface plasmon-enhanced luminescence of NaYFPO4:Dy3+ phosphor by Ag nanoparticles

Ag nanoparticles (Ag-NPs) were adsorbed onto the surface of phosphor NaYFPO4:Dy3+ through an in situ reduction. The structure, morphology, composition, and optical properties were confirmed by X-ray diffraction, high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, and photoluminescence spectroscopy, respectively. The excitation peaks slightly shifted to long waves in the presence of Ag-NPs. Emission intensity increased by 115% owing to the enhancement of the local electromagnetic field near Ag-NPs because of the localized surface plasmon resonance. All these results indicated that the sample was a promising candidate for white LED devices.

Structural and electrical properties of HCl–polyaniline–Ag composites synthesized by polymerization using Ag-coated (NH4)2S2O8 powder

Ag nanoparticles were sputter-deposited on ammonium persulfate ((NH4)2S2O8) powder to obtain (NH4)2S2O8−Ag powder, which was used to synthesize the HCl-doped polyaniline−Ag (HCl−PANI−Ag) composite via a polymerization procedure. The Ag nanoparticles were dispersed in the HCl−PANI matrix, and their sizes mainly ranged from 3 to 6 nm. The Ag nanoparticles did not affect the structure of emeraldine salt in the composite, and they increased the ordered crystalline regions in the HCl−PANI matrix. The HCl−PANI−Ag composite had a conductivity of (6.8 ± 0.1) S/cm, which is about four times larger than that of the HCl−PANI. The charge transport mechanism in the composite is explained by the three-dimensional Mott variable-range hopping (3D-Mott-VRH).

Studies on the Optical and Electrical Properties of Transparent, Conductive Gallium-Doped Zinc Oxide with Ag Nanoparticles

Ag nanoparticles were deposited on top of a gallium-doped zinc oxide (GZO) layer utilizing a pulsed current electrodeposition method. Scanning electron microscopy images confirmed that the formation of Ag nanoparticles spanning several tens of nanometers in diameter occurred, which were able to reduce the sheet resistance of GZO film by approximately 28% compared with the bare GZO film. The reduced sheet resistance of the GZO film was mainly attributed to the increase in the electron concentration on the GZO surface. Absorption and photoluminescence (PL) data showed that both the increased absorption and the PL intensity of the GZO films with Ag nanoparticles were due to the surface plasmon resonance phenomenon of the Ag nanoparticles' conduction electrons.

Microwave-assisted synthesis of Ag/rGO composites and their cytotoxicity for HT22 Neuronal cell

Ag nanoparticles/ reduced graphene oxide (Ag/rGO) composites were rapidly synthesised by one-step microwave irradiation. Ag/rGO composites were characterised via several analytical techniques namely XRD, Raman Spectroscopy, UV–Vis spectroscopy, FTIR spectroscopy, SEM and TEM. It indicated that Ag nanoparticles with average size approximately 10 nm are homogeneously anchored on the reduced graphene oxide sheets, and their cytotoxicity for HT22 Neuronal cell was also investigated. The results show that degree of cell disintegration, nuclear fragmentation and dissolution became more obvious at 12 h and the antibacterial effects of graphene oxide (GO), reduced graphene oxide (rGO) and Ag/rGO were time dependent and dose related. Moreover, Ag/rGO composites performed with good cytocompatibility on account of their surface plasmon resonance effects and near-infrared thermal effects, which had a bright future in biomedical applications.

Synthesis and characterization of Ag@polycarbazole nanoparticles using different oxidants and their dispersion behavior

AbstractAg nanoparticles (NPs) encapsulated by polycarbazole (PCz) have been synthesized using ion adsorption method. The PCz synthesis around Ag NPs has been performed by adsorbing Ag+1and Fe+3oxidants onto Ag NPs, which initiated surface polymerization and thus, Ag NPs@PCz nanocomposite has been synthesized. The morphology of pure NPs and composite NPs was characterized by TEM which also elucidated the effect of oxidant on the core NPs, beside their morphologies and phase contrasts of metal NPs and polymer. The polymer around the surface of core NPs was characterized by FT-IR which proved that PCz was the organic phase of the composite NPs. UV-Vis spectroscopy has been employed to study surface plasmon resonance (SPR) of pure NPs and composite of NP which demonstrated that SPR of core NPs remained preserved after coating with the polymer. Furthermore, Zeta Sizer Nano series has been applied to analyze the dispersion behavior of pure NPs and composite NPs which displayed the greatly improved dispersion behavior of the composite NPs as compared to pure Ag NPs. Therefore, our study proved helpful to analyze the suitability of metal oxidants for PCz based nanocomposite synthesis and determination of their optical and dispersion behavior.

Investigation of Size Effect of Ag Nanoparticles on Oxygen Reduction Reaction Using Ag/Co/C Catalysts Prepared by Galvanic Deposition Method

Ag nanoparticles (AgNPs) were prepared by a galvanic reaction between Ag+ ions and Co metal particles supported on carbon. Variation of the preparation conditions provided a series of AgNPs with various sizes (ca. 2–12 nm). By using the various AgNPs, the size effect on the oxygen reduction reaction activity was investigated. The mass activity of AgNPs increased with a decrease of the size. On the other hand, the Ag-surface-area-specific activity decreased with a decrease of the size.

Rapid synthesis of Ag nanoparticles and Ag@SiO2 core–shells

Abstract Ag nanoparticles were synthesized using microwave irradiation. Oleylamine was used as a stabilizer and capping agent, dimethylformamide as a reducing agent, and deionized water as a solvent. The subsequent use of functionalized Ag nanoparticles for microwave irradiation obtained Ag@SiO2 core–shell nanoparticles. UV–Vis spectroscopy shows a characteristic plasmon peak at 407 nm and 430 nm for Ag nanoparticles and Ag@SiO2 core–shells. Transmission electron microscope images show that Ag nanoparticles have an average size of 15 nm. It is also shown that the core–shell structure was formed with an average size of 100 nm for Ag core and 25 nm SiO2 shell thickness.

Ag Nanoparticles: An Efficient and Versatile Reagent for Synthesis of Bis(indolyl)methanes

Ag nanoparticles are found to be an efficient catalyst for the electrophilic substitution reaction of indole with aldehydes to afford the corresponding bis(indolyl)methanes in good yields. The remarkable features of this new procedure are high conversions, shorter reaction times, cleaner reaction profiles, and simple experimental and work-up procedures.

Enhancing electrical conductivity and electron field emission property of free standing diamond films by employing embedded Ag nanoparticles

Abstract Ag nanoparticles (NPs) were introduced into free-standing diamond (FSD) film by ion implantation to improve its electrical conductivity and electron field emission (EFE) property. Ag-implanted FSD film exhibits improved conductivity with the carrier mobility of 16.2 cm 2 V −1 s −1 , owing to the conductive paths provided by Ag NPs. The EFE behavior of Ag -implanted FSD film can be turned on at E 0 =18 V/μm, attaining a current density of 89.6 μA/cm 2 at an applied field of 30 V/μm. The origin of improving the EFE was discussed based on F-N equation. The present study shows the interest of using embedded conductive NPs to improve the EFE of diamond.

Antimicrobial activity of Ag surfaces sputtered by magnetron sputtering

Ag nanoparticles were deposited on polyamide textiles by direct current magnetron sputtering with an Ag target. This kind of composite material is effective in bacterial inactivation due to the presence of silver. It has been observed that the morphology of composite materials was affected by many factors, such as sputtering power, working pressure, sputtering time, etc. In this study, these parameters were 20 W and 0·5 Pa respectively with different sputtering times. Through antibacterial test on Escherichia coli, it has been found that the shortest sputtering time leading to inactivation was 160 s. The results of X-ray diffraction implied the crystalline and uncrystalline kinds of Ag, which showed that the thickness of the Ag surface must be above a certain value to form crystals. X-ray photoelectron spectroscopy was used to analyse the surface atomic concentration and state. The result indicated that there were different kinds of sliver spaces on the polyamide textiles. According to this, the antibacterial mechanism of the composite materials was discussed.

Distinct spatial profiles and antibacterial effects of 20-nm Ag nanoparticles dripped on ZnO nanorods grown on a polished Ti substrate

Abstract Ag nanoparticles (NPs) were spread by dropping them on hexagonal-shaped ZnO nanorods (NRs) to obtain nanocomposites. ZnO NRs were grown on a polished Ti substrate. The Ag-ZnO nanocomposites were characterized using field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, Fourier-transform infrared spectroscopy and optical imaging. The experimental results indicated that Ag NPs tend to aggregate at the tip of ZnO NR surfaces. Furthermore, antibacterial tests confirmed that adding Ag NPs enhances antibacterial effects. The findings regarding the distinct behaviors of Ag NPs may facilitate the development of future biomedical devices.

Gel-assisted synthesis of Ag nanoparticles: a novel hydrogen peroxide sensor based on Ag nanoparticles-carbon nanotube composite film

Ag nanoparticles (AgNPs) catalyst has been synthesized by a simple and low-cost method using gelatin as organic precursor. Techniques of X-ray diffraction (XRD), transmission electron microscope (TEM) and energy dispersive X-ray (EDAX) were used to characterize the structure and properties of the Ag nanoparticles. Gelatin plays an important role in formation of the Ag nanoparticles. Moreover, glassy carbon electrode modified with Ag nanoparticles and multi wall carbon nanotube (AgNPs-MWNT/GCE) was prepared by casting of the AgNPs-MWNT solution on GCE. The sensor responded linearly to hydrogen peroxide (H2O2) in the concentration of 6 to 900 μM with detection limit of 4.2 μM at 3σ using amperometry. Also, AgNPs-MWNT/GCE was used for H2O2 detection in real sample. The studied sensor exhibited good reproducibility and long-term stability. The produced nanosilver is stable and shows potential applications in the field of sensors, catalysis, fuel cells and nanodevices.

Synthesis, Characterization, and Photocatalytic Properties of Ag/TiO2 Composite Nanofibers Prepared by Electrospinning

Ag nanoparticles (Ag NPs) embedded titanium dioxide (TiO2) nanofibers were fabricated by colloidal sol process, electrospinning, and calcination technique. Calcination of the electrospun nanofibers were heat treated at 600°C for 180 minutes in air atmosphere. X-ray diffraction patterns exhibited that the anatase phase and silver coexisted in the resulted Ag NPs/TiO2 nanofibers; transmission electron microscopy demonstrated Ag NPs well spread in the porous microstructure of composite fibers. The prepared nanofibers were utilized as photocatalyst for degradation of methyl orange. The degradation rate of methyl orange dye solution containing Ag/TiO2 composite nanofibers is 99% only after irradiation for 3 hours. It is proposed that these new Ag NPs/TiO2 composite nanofibers will have potential application in water pollution treatment.

PREPARATION AND CHARACTERIZATION OF SILVER NANOPARTICLES/CARBON NANOFIBERS VIA ELECTROSPINNING WITH RESEARCH ON THEIR CATALYTIC PROPERTIES

Ag nanoparticles ( Ag NPs) embedded carbon nanofibers (CNFs) were prepared by a new route which included chemical reaction process, electrospinning and calcination technique. The morphology and structure of the composite nanofibers were investigated by scanning electron microscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy and X-ray diffraction. It indicated that Ag NPs were uniformly distributed in the CNFs. This effective synthesis method can be used to prepare other composite nanofibers with functionality. The Ag NPs/CNFs that served as supported catalysts were used in the styrene epoxidation by TBHP. The Ag NPs/CNFs catalyst showed its highly catalytic activity for the epoxidation of styrene (conversion: 40.6%, SO selectivity: 35.9%). This kind of composite nanofiber membrane was proved effectively catalytic activity and recycled easily in the styrene epoxidation.

AG NANOPARTICLES-MODIFIED ANATASE TiO2 SINGLE CRYSTALS CUBES FOR IMPROVING PHOTOELECTRIC CONVERSION

Ag nanoparticles were deposited by polyol process onto the as-synthesized anatase TiO 2 cubes with single crystals by hydrothermal method. The materials were characterized by SEM, XRD, TEM, XPS and UV-vis spectroscopy and their photoconversion efficiencies were also evaluated. The photocurrent measurements revealed that the modification of the anatase TiO 2 cubes with Ag nanoparticles improved the photoelectrochemical properties of electrodes.