Deposition Of Ag Nanoparticles Research Articles

Spontaneous and Selective Nanowelding of Silver Nanowires by Electrochemical Ostwald Ripening and High Electrostatic Potential at the Junctions for High-Performance Stretchable Transparent Electrodes.

Metal nanowires have been gaining increasing attention as the most promising stretchable transparent electrodes for emerging field of stretchable optoelectronic devices. Nanowelding technology is a major challenge in the fabrication of metal nanowire networks because the optoelectronic performances of metal nanowire networks are mostly limited by the high junction resistance between nanowires. We demonstrate the spontaneous and selective welding of Ag nanowires (AgNWs) by Ag solders via an electrochemical Ostwald ripening process and high electrostatic potential at the junctions of AgNWs. The AgNWs were welded by depositing Ag nanoparticles (AgNPs) on the conducting substrate and then exposing them to water at room temperature. The AgNPs were spontaneously dissolved in water to form Ag+ ions, which were then reduced to single-crystal Ag solders selectively at the junctions of the AgNWs. Hence, the welded AgNWs showed higher optoelectronic and stretchable performance compared to that of as-formed AgNWs. These results indicate that electrochemical Ostwald ripening-based welding can be used as a promising method for high-performance metal nanowire electrodes in various next-generation devices such as stretchable solar cells, stretchable displays, organic light-emitting diodes, and skin sensors.

Parameter optimization for Ag-coated TiO2 nanotube arrays as recyclable SERS substrates

The Ag-coated titanium dioxide nanotube arrays (Ag-coated TNTs) are obtained via the deposition of Ag nanoparticles on the two-step anodized TNTs. The wall thickness of TNTs is modulated via finite difference time domain simulation to get the favorable electromagnetic field for surface enhanced Raman scattering (SERS). Ag-coated TNTs with optimal wall thickness of 20 nm were employed as the SERS substrates to detect 2-mercaptobenzoxazole, which show superior detection sensitivity and uniformity. In addition, due to the photocatalysis of TNTs, the SERS substrates could clean themselves and be repeatedly used by photo-degradation of target molecules under the ultra-violet irradiation. The Ag-coated TNTs are a kind of bifunctional SERS substrates which can produce high-quality SERS signals and reuse to reduce the cost.

AgBr/diatomite for the efficient visible-light-driven photocatalytic degradation of Rhodamine B

The treatment of organic pollution via photocatalysis has been investigated for a few decades. However, earth-abundant, cheap, stable, and efficient substrates are still to be developed. Here, we prepare an efficient visible-light-driven photocatalyst via the deposition of Ag nanoparticles (< 60 nm) on diatomite and the conversion of Ag to AgBr nanoparticles (< 600 nm). Experimental results show that 95% of Rhodamine B could be removed within 20 min, and the degradation rate constant (κ) is 0.11 min−1 under 100 mW/cm2 light intensity. For comparison, AgBr/SiO2 (κ = 0.04 min−1) and commercial AgBr nanoparticles (κ = 0.05 min−1) were measured as well. The experimental results reveal that diatomite acted more than a substrate benefiting the dispersion of AgBr nanoparticles, as well as a cooperator to help harvest visible light and adsorb dye molecules, leading to the efficient visible-light-driven photocatalytic performance of AgBr/diatomite. Considering the low cost ($10 per ton) and large-scale availability of diatomite, our study provides the possibility to prepare other types of diatomite-based efficient photocatalytic composites with low-cost but excellent photocatalytic performance.

Facile fabrication of superhydrophobic hybrid nanotip and nanopore arrays as surface-enhanced Raman spectroscopy substrates

We demonstrate the fabrication of superhydrophobic hybrid nanotip and nanopore arrays (NTNPAs) that can act as sensitive surface-enhanced Raman spectroscopy (SERS) substrates. The large-area substrates were fabricated by following a facile, low-cost process consisting of the one-step voltage-variation anodization of Al foil, followed by Ag nanoparticle deposition and fluorosilane (FS) modification. Uniformly distributed, large-area (5 × 5 cm2) NTNPAs can be obtained rapidly by anodizing Al foil for 1560 s followed by Ag deposition for 400 s, which showed good SERS reproducibility as using1 μM Rhodamine 6G (R6G) as analyte. SERS performances of superhydrophobic NTNPAs with different FS modification and Ag nanoparticle deposition orders were also studied. The nanosamples with FS modification followed by Ag nanoparticle deposition (FS-Ag) showed better SERS sensitivity than the nanosamples with Ag nanoparticle deposition followed by FS modification (Ag-FS). The detection limit of a directly dried R6G droplet can reach 10−8 M on the FS-Ag nanosamples. The results can help create practical high sensitive SERS substrates, which can be used in developing advanced bio- and chemical sensors.

Facile photochemical synthesis of hierarchical cake-like ZnO/Ag composites with enhanced visible-light photocatalytic activities

ZnO/Ag composites were synthesized by photochemical deposition of Ag nanoparticles onto pre-synthesized three dimensional hierarchical cake-like ZnO microstructures, which were fabricated by DMF (N,N-dimethylformamide)-mediated solvothermal method. The crystal phase and microstructures of the as-obtained ZnO and ZnO/Ag were characterized by XRD, DRS, SEM, EDS, TEM and PL. The SEM and TEM results indicated that Ag nanodisks with diameters of 120 nm are uniformly deposited on the surface of hierarchical cake-like ZnO. Furthermore, the visible-light photocatalytic activity of the ZnO/Ag composites was evaluated by the degradation of Rhodamine B (RhB) under Xe lamp irradiation. Such ZnO/Ag composites showed an enhanced visible-light photocatalytic activity, the rate of degradation was nearly five times faster than that of bare hierarchical cake-like ZnO under visible-light irradiation due to the increase of electron-transfer rate of ZnO after hybridized with Ag nanoparticles.

Enhanced photocatalytic activity of ternary Ag/g-C3N4/NaTaO3 photocatalysts under wide spectrum light radiation: The high potential band protection mechanism

Constructing heterojunction photocatalyst is an effective method to enhance the separation of photogenerated electron and hole and benefit the wide-bandgap photocatalyst with significant visible light response ability. In this study, a novel and highly efficient ternary photocatalyst was prepared by depositing Ag nanoparticles on the surface of graphitic carbon nitride nanosheets (g-C3N4)/NaTaO3 nanohybrid. It showed an enhanced photocatalytic degradation of tetracycline (TC), rhodamine B (RhB) and phenol under wide-spectrum light irradiation. Compared to pure NaTaO3, g-C3N4 and binary g-C3N4/NaTaO3, Ag/g-C3N4/NaTaO3 displayed enhanced photodegradation efficiency with 95.47% removal of TC (20 mg/L) in 60 min under visible light irradiation. From the free radical quenching experiment and ESR characterization results, the charge transfer process can be identified as a Z-scheme transfer mechanism, which can significantly enhance the charge separation rate and protect the high potential valence band (VB) of NaTaO3 and conduction band (CB) of g-C3N4. This work provides a new promising approach for designing novel Z-scheme photocatalysts.

Ag and CoFe2O4 co-sensitized TiO2 nanowire for photocathodic protection of 304 SS under visible light

Ag and CoFe2O4 co-sensitized TiO2 nanowire (NW) structures were fabricated by photoreduction deposition and hydrothermal methods. The morphology, chemical composition and optical absorption capabilities of the nanocomposites were systematically investigated by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and UV-visible absorption spectra methods. The photo-induced open circuit potential (OCP) and photocurrent density were measured under visible light to evaluate the photocathodic protection effects of the nanocomposites for 304 SS in the presence and absence of illumination. The results indicated that the deposition of Ag and CoFe2O4 nanoparticles (NPs) shifted the light absorption of TiO2 to the visible light region and enhanced the separation efficiency of the photogenerated charges. The nanocomposite exhibited more efficient photocathodic protection for 304 SS compared with pure TiO2 under visible light.

Plasmonic Photocatalyst Design: Metal—Semiconductor Junction Affecting Photocatalytic Efficiency

Silver-zinc oxide nanorods (Ag-ZnO NRs) and gold-zinc oxide nanorods (Au-ZnO NRs) plasmonic photocatalysts were fabricated by the deposition of Ag and Au nanoparticles on ZnO NRs. The photocatalysts were studied with electron microscopy, energy dispersive spectroscopy (EDS), UVvis optical absorption and photoluminescence spectroscopy. The effect of type of metals on the ZnO surface on its photocatalytic activity under ultra violet (UV) as well as visible light excitation are investigated and their contribution towards enhanced photo-generated charge separation in terms of the type of junction (Ohmic or Schottky) the metal forms with the semiconductor are explained.

Fluorescence turn-off Ag/fluorinated graphene composites with high NIR absorption for effective killing of cancer cells and bacteria.

The unique structure and special chemical surface make fluorinated graphene-silver (FG-Ag) hold great promise in many biological fields. However, the synthesis of this nano-composite has not yet been achieved mostly due to the strong hydrophobicity and inertness of C-F bonds. Herein, we demonstrate an interesting concept of multifunctional FG-Ag and integrate it as a highly effective targeted drug carrier, photothermal therapy (PTT) and antibacterial agent. To achieve this, the F-sacrificing method is first employed to enrich FG with oxygen groups (FGO), which then serve as necessary and active reaction sites for controlled deposition of Ag nanoparticles (AgNPs) and modification of cancer targeting molecules. Interestingly, AgNPs well quench FGO's fluorescence, and FGO-Ag then acts as another effective quencher for the anticancer drug doxorubicin, all of which guarantee it as a novel sensor to visually monitor drug loading by "turn-off" fluorescence. More importantly, this nano-composite also possesses special targeting toward cancer cells; it exhibits high near-infrared absorption for PTT and shows effective antibacterial activity. This study establishes FGO-Ag as a novel nanocarrier with good targeting efficiency, high NIR absorption and drug loading and demonstrates its first application in antibacterial and cancer chemo-photothermal treatments.

TiO2 surfaces self-doped with Ag nanoparticles exhibit efficient CO2 photoreduction under visible light.

Doping with intrinsic defects to enhance the photocatalytic performance of TiO2 has recently attracted attention from many researchers. In this report, we developed an original approach to realise stabilized surface doping using intrinsic defects with the loading of Ag nanoparticles (AgNPs) on the surface. Herein, atmospheric pressure dielectric barrier discharge (DBD) cold plasma was used to help load the AgNPs, and ethanol treatment was used to introduce intrinsic defects (oxygen vacancies and Ti3+) on the surface of materials. This method avoids environmentally hazardous reducing regents and is undertaken under atmospheric pressure, thus reducing energy-consuming and complex operation. We combine the advantages of noble metal nanoparticles and surface doping to enhance the photocatalytic performance under the visible light. The characterization of the materials indicates that the loading of AgNPs and introduction of intrinsic defects can change the electronic structure of the composite material and improve its efficiency. The samples show significant enhancement in CO2 photoreduction to obtain CO and CH4, with yields reaching 141 μmol m−2 and 11.7 μmol m−2, respectively. The formation mechanism of the method for TiO2 modification and CO2 reduction is also discussed.

Fabrication of charge reversible graphene oxide-based nanocomposite with multiple antibacterial modes and magnetic recyclability

In this work, N-alkylated poly (4-vinylpyridine) (NPVP), a cationic polymer, was firstly applied for the surface modification of Fe3O4 nanoparticles. Then the modified Fe3O4 nanoparticles (Fe3O4@NPVP NPs) combined with graphene oxide (GO) through simple electrostatic binding. Subsequently, deposited Ag nanoparticles (Ag NPs) procedure was carried out to form the multiple antibacterial nanocomposites (GO-Fe3O4@NPVP-Ag). The synthesized nanostructures were well characterized by Transmission Electron Microscope (TEM), X-ray powder diffraction (XRD), Fourier-transform infrared (FT-IR) and Raman spectroscopy. The zeta potentialmeasurement showed that the novel antibacterial nanocomposites exhibited a capacity of reversing its surface charge from negative (physiological pH) to positive (acidic condition). Furthermore, the incorporation of magnetic Fe3O4 NPs into the nanosystems facilitates the cyclic utilization of GO-Fe3O4@NPVP-Ag by magnetic separation. The antibacterial properties of GO-Fe3O4@NPVP-Ag nanocomposites were evaluated with Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus. Moreover, the cytotoxicity of GO-Fe3O4@NPVP-Ag nanocomposites was studied using NIH-3T3 cells. The results showed that the GO-Fe3O4@NPVP-Ag nanocomposites exhibited excellent antibacterial properties and low cytotoxicity, thus confirming its application as a promising rapid bactericide in various antibacterial fields.

Highly efficient visible-light photocatalytic performance of Ag/AgIn5S8 for degradation of tetracycline hydrochloride and treatment of real pharmaceutical industry wastewater

The deposition of Ag nanoparticles (NPs) on semiconductors has been demonstrated to be an efficient route to improve the separation of photogenerated electrons and holes due to plasma resonance effect, but the photocatalytic efficiency of the available Ag-based photocatalysts is still low and far from practical application. In this study, a novel photocatalyst with Ag NPs deposited on the surface of AgIn5S8 (Ag/AgIn5S8) was fabricated via solvothermal method and further photo-reduction approach. The amount of deposited Ag nanoparticles has an obvious effect on the charge separation and visible-light photocatalytic activity of Ag/AgIn5S8, and 2.5% Ag/AgIn5S8 nanocomposites exhibit the highest visible-light photocatalytic activity with 95.3% degradation efficiency of tetracycline hydrochloride (TCHCl) compared with that of the other samples due to the surface plasmon resonance of Ag NPs, proper bandgap of AgIn5S8 and the synergistic effect between them. The main reactive species in TCHCl degradation are OH and O2−. The possible degradation pathway of TCHCl and photocatalytic mechanism of Ag/AgIn5S8 were proposed according to high performance liquid chromatography-tandem mass spectrometry (HPLC-MS) analysis, main reactive species, and conduction band and valence band of AgIn5S8. Moreover, Ag/AgIn5S8 nanohybrids were applied to treat real pharmaceutical industry wastewater, and it was found that the mineralization efficiency and COD removal of real pharmaceutical industry wastewater can reach 56.3% and 77.6%, respectively. The above results indicate Ag/AgIn5S8 photocatalysts have a promising prospect in the treatment of real pharmaceutical industry wastewater.

High-performance visible light-driven Ni-ZnO/rGO/nylon-6 & Ni-ZnO/rGO/nylon-6/Ag nanofiber webs for degrading dye pollutant and study their antibacterial properties

A composite of Ni-ZnO/rGO/nylon-6 electrospun nanofiber decorated by Ag nanoparticles was successfully introduced as a novel hybrid material with good visible light-driven photocatalytic and antibacterial properties having potential for repeated use. The Fourier transform infrared (FT-IR) spectroscopy, X-ray powder diffraction (XRD), scanning electron microscopy (SEM), UV–vis diffuse reflectance spectroscopy (DRS) and thermogravimetric analysis (TGA) measurements were employed to characterize the phase structure, morphology, optical properties, and thermal stability of the as-synthesized composite. The results confirmed the successful incorporation of Ni-ZnO/rGO nanocomposite into the electrospun nylon-6 fibers as well as deposition of Ag nanoparticles on the surface of fibers. The effective photodegradation of methyl orange (MO) dye under visible light was demonstrated under the visible-light irradiation. Owing to the rational design and special structure of Ni-ZnO/rGO/nylon-6/Ag nanofibers, this new hybrid provides an efficient electron-hole separation to further react with adsorbed dye molecules and degrade them into non-toxic products. Furthermore, the antibacterial properties of the nanofibers were investigated against Escherichia coli (Gram-negative) and Bacillus Subtilis (Gram-positive) bacteria and excellent antibacterial activities against both studied bacteria were found. This work offers a new class of inorganic/organic nanocomposites with promising efficiency as good economically and environmentally friendly candidates for visible light-driven photocatalysis and water filter media.

Magnetic separable chitosan microcapsules decorated with silver nanoparticles for catalytic reduction of 4-nitrophenol

In the work, we have synthesized silver (Ag) nanoparticles deposited chitosan (CS) microcapsules with magnetic multiple Fe3O4 cores (denoted as Fe3O4/CS-Ag) as efficient catalysts for the reduction of 4-nitrophenol. The Fe3O4/CS-Ag catalysts are prepared by coating hydrophobic Fe3O4 nanoparticles with chitosan via a multiple emulsion-chemical crosslinking method and following in situ deposition of Ag nanoparticles onto the surfaces. The morphology and composition of the Fe3O4/CS-Ag microcapsules are characterized by Fourier transform infrared (FT-IR) spectra, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy. Moreover, the catalytic activity of the Fe3O4/CS-Ag catalyst was investigated, which shows a conversion efficiency as high as 98% within 15min for the reduction of p-nitrophenol to p-aminophenol. At the same time, the recovered Fe3O4/CS-Ag catalyst with an external magnet can retain good activity after 10 cycles. These results indicate that the multiple emulsion-chemical crosslinking method is an efficient and simple way for the preparation of magnetic separable chitosan microcapsules, and the fabricated Fe3O4/CS-Ag is a promising catalytic material with excellent catalytic activity and convenient recovery ability.

Enhanced photocatalytic degradation of sulfamethoxazole by deposition of Au, Ag and Cu metallic nanoparticles on TiO2

ABSTRACTMono- (Au, Ag and Cu) and bi-metallic (Au–Ag and Au–Cu) nanoparticles were deposited on TiO2 and tested for the photocatalytic degradation of sulfamethoxazole using either UV-C or simulated sunlight. The optimal loading of metallic nanoparticles was determined as 1.5 wt% for Au and Ag, and 1.0 wt% for Cu. In the case of bi-metallic nanoparticles, only the ratio 1:0.5 wt% for both Au–Ag and Au–Cu was tested. In experiments using UV-C light, the highest degradation performance was found for Ag/TiO2, while bi-metallic nanoparticles supported on TiO2 also showed increased photocatalytic activity compared with unmodified TiO2. In simulated sunlight irradiation tests, Au/TiO2 showed to be the most efficient material. Complete mineralization of sulfamethoxazole was achieved when surface-modified materials were tested in both UV-C and simulated sunlight experiments. Photolysis was efficient to fully degrade sulfamethoxazole, although mineralization was lower than 10% for both luminic sources. The main by-products of sulfamethoxazole were determined in photolysis and photocatalysis tests using UV-C light, and degradation paths were proposed. By-products showed non-toxicity and low antibiotic activity. Reuse of the catalysts upon three reaction cycles did not result in the loss of activity.

Tailoring heterostructures of Ag/Cu2O hybrids for enhanced photocatalytic degradationdegradation

Abstracts A facile solution deposition method using the etched Cu2O truncated octahedrons as the substrates has been successfully demonstrated for tailoring Ag/Cu2O heterostructures with excellent reproducibility, and Ag nanoparticles have been deposited on the surface of different Cu2O particles including freshly prepared Cu2O truncated octahedrons, the etched Cu2O truncated octahedrons, Cu2O cube assemblies and Cu2O octahedron assemblies. The obtained tailoring Ag/Cu2O heterostructures prepared by the etched Cu2O truncated octahedrons exhibits enhanced photocatalytic activity for the degradation of MB solution under visible-light irradiation, and the photocatalytic activity of tailoring Ag/Cu2O heterostructures was 3.1 and 5.7 times higher than those of the etched Cu2O truncated octahedrons and bare Cu2O truncated octahedrons. The enhanced photocatalytic activity of tailoring Ag/Cu2O heterostructures can be attributed to tailoring surface of Cu2O truncated octahedrons, the enhancement of UV–vis absorbance spectra and electron sink effect due to Ag nanoparticle deposition. The facilely prepared tailoring Ag/Cu2O heterostructure products are promising materials in fields such as photocatalytic and optoelectronic applications.

Surface‐enhanced Raman spectroscopy of dye molecules on Ag‐modified silicon nanowire substrates: influence of photoinduced probe degradation on enhancement factors

Photobleaching effect is an immense problem in optical spectroscopy, especially when fluorophores are adsorbed on metal nanoparticles (NPs). Nevertheless, little effort has been assigned to the study of fluorophore photostability under this condition. In this paper, the effect of photobleaching on the Raman signal enhancement factor (RS‐EF) of dye molecules on Ag‐modified silicon nanowire (SiNW) substrates is investigated. For this purpose, SiNWs are fabricated by using the vapor–liquid–solid growth mechanism and decorated with Ag NPs by means of electroless deposition method. This process provides the possibility of forming uniformly and tightly packed Ag NPs on SiNWs. The effect of photostability of the crystal violet as analyte molecules on surface‐enhanced Raman spectroscopy is investigated as a function of time evolution and laser power. The influence of Ag NP deposition time on Raman signal enhancement is explored. Our work shows how we can optimize the excitation power for achievement of higher RS‐EF and, consequently, lower detectable concentration. Time evolution of surface‐enhanced Raman spectroscopy signal shows an exponential decay behavior, which indicates an almost uniform distribution of EFs. Capability of our nanostructure is assessed for different concentration, and subsequently, limit of detection of 10 pm with RS‐EF of 2.4×109 is obtained. Copyright © 2017 John Wiley &amp; Sons, Ltd.

Ultrasound assisted synthesis of Ag-decorated TiO2 active in visible light

Titanium dioxide is the most popular photocatalyst to degrade organic pollutants in air, as well as in water. The principal drawback preventing its commercial application lies in its limited absorption of the visible light (400–700nm), while it is active under UV irradiation (≤387nm). Supporting noble metals in the form of nanoparticles on TiO2 increases its activity in the visible range. However, both the synthesis of noble metal nanoparticles and their deposition on TiO2 are multi-step processes that often require organic solvents. Here, we deposit Ag nanoparticles from AgNO3 on the surface of micrometric TiO2 with H2O as a solvent and under ultrasound irradiation at 30Wcm−2. Ultrasound increases the surface amount of Ag on TiO2 with heterogeneous size distribution of Ag nanoparticles, which are bigger and overlaid (1–20nm vs. 0.5–3nm) compared to the sample obtained in traditional conditions (TEM images). While this change in morphology had no effect on acetone photodegradation under UV light, the 5%, 10%, and 20% Ag-TiO2 degraded 17%, 20% and 24% acetone under visible light, respectively. The 10% by weight Ag-TiO2 sample obtained in absence of ultrasound only degraded 14% acetone in 6h, while the bare TiO2 was not active.

Deposition of Ag/a-C:H nanocomposite films with Ag surface enrichment

The nanocomposite films Ag/a-C:H were prepared by vacuum-based method which combines deposition of Ag nanoparticles by means of gas aggregation source (GAS) and PECVD deposition of a-C:H matrix. The matrix was deposited in a mixture of Ar and n-hexane on the substrates placed on the powered RF electrode facing the beam of Ag NPs from the GAS. Anisotropic plasma etching was used to increase Ag concentration on the surface of the coating. The influence of three types of plasma on the chemical composition of the coatings and on the size of Ag nanoparticles is described. It is shown that the best etching selectivity and thus the highest Ag surface concentration was reached in case of etching of grounded samples in low pressure oxygen plasma. This treatment enhances the short term antibacterial efficiency of produced coatings.

Ag nanoparticles modified large area monolayer MoS2 phototransistors with high responsivity.

Monolayer MoS2 is considered to be one of the best candidates for next generation electronics because of its ultra-thin body and direct band gap. However, MoS2 based transistors have relatively low photoresponsivity, field effect mobility and narrow response spectrum range, which hinder the application of MoS2 in optoelectronic devices. Here, based on the enhancement of localized surface plasmon resonance (LSPR), a simple method of depositing Ag nanoparticles on the MoS2 surface is used. By adjusting the size of Ag nanoparticles, the response spectral range of phototransistor is broadened from red to near ultra-violet. The photoresponsivity gains an increase of 470% up to 2.97 × 104 A W-1 at 610 nm, and the response time also shows a decrease to some extent. The enhanced responsivity is comparable to those of devices encapsulated with high-quality dielectrics, and superior over other reported monolayer MoS2 in ambient conditions. The high responsivity and working current enables a wide range of device applications. This work provides a viable route towards performance enhancement of two-dimensional phototransistors.