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In this paper, a highly connected chain-like Au/Ag nanoconfiguration which is synthesized by pulsed laser ablation pathway was investigated as an efficient SERS nanophotonics sensor. Very low SERS detection limit LOD for Thiram is about 10−8 M (0.024 ppm) that is lower than the allowed limit in the world of about 240 times. The results showed that the sensor performance (sensitivity) provides an excellent linear relationship between the Thiram concentrations and the SERS intestines, so the lower Thiram residence can efficiently monitor. The main reason behind this efficient performance is significantly related to the high specific surface area and the high density of the Au/Ag nanoconfiguration over the apple's surface. [ABSTRACT FROM AUTHOR]

This paper provides an efficient approach for making effectual and active substrates utilized for the detection of the Pyrromethene 580 (PM 580) molecule through the improvement of surface-enhanced Raman scattering (SERS). Those substrates have been fabricated with the use of the Au/Ag nanoparticles-coated porous silicon (PS). Au/Ag NPs have been prepared through laser ablation technique. This investigation is comparing Au/Ag NPs characteristics that have been generated by nanosecond laser ablation in PolyVinyl Alcohol (PVA) at 532 nm and 1064 nm laser wave-lengths. Then, Au/AgNPs were ablated in PVA colloidal solution to form (AuNPs:AgNPs)/PS plasmonic nano-structures. These plasmonic nanostructures on the SERS activities were studied utilizing PM 580 dye as examination molecule. Results have shown that the roughness and spots on nanostructures surfaces have resulted in causing increased absorbance spectra intensities and SERS signals. After effectual substrates have been excited by (λex. = 532 nm) laser source, the enhancement factor (EF) of SERS signals of PM 580 (0.01 M) attained 13.7 × 107 and 5.6 × 107 of the characteristic peaks at wavenumber 1657 cm−1 for the Au:AgNPs-532 nm/PS and Au:AgNPs-1064 nm/PS effectual substrates, respectively. The present research had shown that the nanostructure-coated PS substrates have repeatable and high signal frequency, inexpensive technique, stability in storage, and simplicity of use. [ABSTRACT FROM AUTHOR]

Because of their small size and large specific surface area, nanoparticles (NPs) have special properties that are different from bulk materials. In particular, Au/Ag NPs have been intensively studied for a long time, especially for biomedical applications. Thereafter, they played a significant role in the fields of biology, medical testing, optical imaging, energy and catalysis, MRI contrast agents, tumor diagnosis and treatment, environmental protection, and so on. When synthesizing Au/Ag NPs, the laser ablation and biosynthesis methods are very promising green processes. Therefore, this review focuses on the progress in the laser ablation and biological synthesis processes for Au/Ag NP generation, especially in their fabrication fundamentals and potential applications. First, the fundamentals of the laser ablation method are critically reviewed, including the laser ablation mechanism for Au/Ag NPs and the controlling of their size and shape during fabrication using laser ablation. Second, the fundamentals of the biological method are comprehensively discussed, involving the synthesis principle and the process of controlling the size and shape and preparing Au/Ag NPs using biological methods. Third, the applications in biology, tumor diagnosis and treatment, and other fields are reviewed to demonstrate the potential value of Au/Ag NPs. Finally, a discussion surrounding three aspects (similarity, individuality, and complementarity) of the two green synthesis processes is presented, and the necessary outlook, including the current limitations and challenges, is suggested, which provides a reference for the low-cost and sustainable production of Au/Ag NPs in the future. [ABSTRACT FROM AUTHOR]

Chitosan is embedded by different ratios of Au/Ag NPs. Au/Ag NPs have been synthesised by laser ablation. The electrical conductivity and antibacterial behaviour of the synthesized films were obtained. In x-ray diffraction (XRD), a new pattern appeared at 2θ = 38.3° and 44.0° which correspond to face-centered cubic Ag, and a new pattern appeared at 38.5°, 45.0°, and 66.1° which corresponds to face-centered cubic Au. Fourier transform infrared (FTIR) data confirmed the interaction and miscibility between chitosan chains and Ag/Au NPs. Chitosan embedded with a 2/3 ratio of Au/Ag NPs reacted properly. Ultraviolet-visible (UV-Vis) spectroscopy results show a peak at 410 nm, corresponding to Ag NPs, and a very weak peak at 528 nm, corresponding to Au NPs, which shows evidence of the complexation between chitosan and Au/Ag NPs. The values of the ε' and loss ε̎ were increased after being embedded by pure Ag NPs until they reached a high value for sample S3 (2/3) (Au/Ag), then began to decrease by increasing the content of Au NPs and decreasing the ratio of Ag NPs. By decreasing the concentration of Ag NPs from S1 (0/5) to S6 (5/0) in the ration of Au/Ag NPs, there are decreases in the inhibition zone for both of the gram-negative bacterial strains tested, and the two gram-positive strains, using the zone of inhibition. The obtained results suggest that chitosan embedded with 2/3 Au/Ag possesses possible antibacterial action against the given bacteria. The given results suggest that the 2/3 Au/Ag-doped chitosan is the proper ratio used for both electrical and biomedical applications. [ABSTRACT FROM AUTHOR]

Proanthocyanidins-functionalized Au/Ag bimetallic nanoparticles were synthesized by a hydrothermal method. The obtained Au/Ag nanoparticles have been characterized by UV-Vis absorption spectra (UV), Fourier transform infrared spectroscopy (FTIR), Transmission electron microscopy (TEM) and X-ray diffraction (XRD). The UV and FTIR measurement indicated that the as-synthesized colloids have the spherical shapes and the presence of the polymerized proanthocyanidins around metal nanoparticles. TEM and XRD results revealed that the nanoparticles have uniform core-shell structures and the metal core possessed a highly crystalline structure. Furthermore, it was found that the proanthocyanidins-functionalized Au/Ag bimetallic nanoparticles have high removal efficiency for some organic dyes.

Because of their small size and large specific surface area, nanoparticles (NPs) have special properties that are different from bulk materials. In particular, Au/Ag NPs have been intensively studied for a long time, especially for biomedical applications. Thereafter, they played a significant role in the fields of biology, medical testing, optical imaging, energy and catalysis, MRI contrast agents, tumor diagnosis and treatment, environmental protection, and so on. When synthesizing Au/Ag NPs, the laser ablation and biosynthesis methods are very promising green processes. Therefore, this review focuses on the progress in the laser ablation and biological synthesis processes for Au/Ag NP generation, especially in their fabrication fundamentals and potential applications. First, the fundamentals of the laser ablation method are critically reviewed, including the laser ablation mechanism for Au/Ag NPs and the controlling of their size and shape during fabrication using laser ablation. Second, the fundamentals of the biological method are comprehensively discussed, involving the synthesis principle and the process of controlling the size and shape and preparing Au/Ag NPs using biological methods. Third, the applications in biology, tumor diagnosis and treatment, and other fields are reviewed to demonstrate the potential value of Au/Ag NPs. Finally, a discussion surrounding three aspects (similarity, individuality, and complementarity) of the two green synthesis processes is presented, and the necessary outlook, including the current limitations and challenges, is suggested, which provides a reference for the low-cost and sustainable production of Au/Ag NPs in the future.

Proanthocyanidins-functionalized Au/Ag bimetallic nanoparticles were synthesized by a hydrothermal method. The obtained Au/Ag nanoparticles have been characterized by UV-Vis absorption spectra (UV), Fourier transform infrared spectroscopy (FTIR), Transmission electron microscopy (TEM) and X-ray diffraction (XRD). The UV and FTIR measurement indicated that the as-synthesized colloids have the spherical shapes and the presence of the polymerized proanthocyanidins around metal nanoparticles. TEM and XRD results revealed that the nanoparticles have uniform core-shell structures and the metal core possessed a highly crystalline structure. Furthermore, it was found that the proanthocyanidins-functionalized Au/Ag bimetallic nanoparticles have high removal efficiency for some organic dyes. [ABSTRACT FROM AUTHOR]

[Display omitted] • AgNTs@AuNHs with Ag nano-triangle core and Au nano-hexagonal shell was firstly synthesized. • AgNTs@AuNHs has strong surface plasmon resonance. • AgNTs@AuNHs can be etched by Pb2+ and Cu2+ in the presence of Na 2 S 2 O 3. • AgNTs@AuNHs is applied for simultaneous detection of Pb2+ and Cu2+. A colorimetric gold nanohexagonals coated silver nanotriangles (AgNTs@AuNHs) nanoprobe has been constructed for the ultrasensitive detection of trace Pb2+ and Cu2+, based on the fact that Pb2+ and Cu2+ as the catalyzer can selectively enhance the etching rate of AgNTs@AuNHs by S 2 O 3 2−. In the presence of Pb2+, the inner AgNTs within the AgNTs@AuNHs undergo complete etching to form the hollow AuNHs, leading to the marked decrease in both absorbance and chrominance at 585 nm. In contrast, Cu2+ initiates an etching reaction on the AgNTs, subsequently extending to the AuNHs. These transformations give rise to the formation of hollow gold nanotriangles, accompanied by pronounced red-shifts in the absorption peaks of the detection system. The distinct optical responses induced by Pb2+ and Cu2+ in the AgNTs@AuNHs nanoprobe enable the sensitive and selective detection and quantification of these heavy metal ions. Furthermore, we successfully extracted RGB data from the color changes of AgNTs@AuNHs nanoprobe, enabling a straightforward visual readout for detection of Pb2+ and Cu2+. This method yields satisfactory recoveries when applied to the analysis of Pb2+ and Cu2+ in river water, rice, and onion samples, with detection results closely matching those obtained using ICP-MS. These results collectively underscore the practical applicability of the AgNTs@AuNHs nanoprobe. [ABSTRACT FROM AUTHOR]

[Display omitted] • Based on the synergistic effect between Au and Ag elements, Au/Ag bimetallic nanoparticles usually possess unique localized surface plasmon resonance absorption from visible to near-infrared spectral regions, which lead to a superior photocatalytic activity for the degradation of many organic pollutants. • The ultrafast synthesis of multi-branched Au/Ag bimetallic nanoparticles is at room temperature using tannic acid as both reducing and capping agent. • The catalytic rate constant and TOF value are 0.13 s−1 and 1.33 s−1, respectively, when Au/Ag bimetallic nanoparticles are used as a catalyst to catalyst the reduction of p-nitrophenol under 808 nm laser irradiation. • The catalytic activity of Au/Ag bimetallic nanoparticles is higher than that of most previously reported Au, Ag or Au/Ag based catalysts. We report the ultrafast synthesis of multi-branched Au/Ag bimetallic nanoparticles (BMNPs) at room temperature using tannic acid (TA) as both reducing and capping agent. Based on the UV–Vis, TEM, HR-TEM, XRD and SAED analyses, the structure and absorption properties of Au/Ag BMNPs were realized. The prepared Au/Ag BMNPs exhibited excellent catalytic activity and good cycling stability toward 4-nitrophenol (4-NP) reduction according to the synergistic effect between Au and Ag elements. In addition, the catalytic activity was further enhanced under NIR laser irradiation because of their high Surface Plasmon Resonance (SPR) efficiency. The kinetic rate constant (k) and TOF value could reach 0.13 s−1 and 1.33 s−1, respectively, under NIR light (808 nm, 1.0 W/cm2) irradiation at room temperature. We envision that the development of promising routes for high quality of BMNPs could have broad applications in catalysis and environmental governance. [ABSTRACT FROM AUTHOR]

We present a convenient method to immobilize Au/Ag nanoparticles (NPs) within electrospun polyvinyl alcohol (PVA)/polyethylenimine (PEI) nanofibers by in-situ reduction for catalytic applications. Water-stable electrospun PVA/PEI nanofibers were initially fabricated by crosslinking with glutaraldehyde (GA) vapor. Then, the nanofibers were used as a nanoreactor to bind Au salt via electrostatic interaction with the free PEI amines, followed by NaBH 4 reduction to form Au NPs. The formed Au NP-containing nanofibers were then used to bind Ag + ions via chelation with the free PEI amines, followed by reduction with ascorbic acid to form the Au/Ag NP-loaded PVA/PEI nanofibers. The small size (4.9 ± 1.8 nm) and narrow size distribution of the immobilized Au/Ag NPs reveal that the nanofibrous structure is able to efficiently prevent the aggregation of the NPs. We then evaluated the catalytic activity and reusability of Au/Ag NP-immobilized PVA/PEI nanofiers by catalytic transformation of 4-nitrophenol to 4-aminophenol in aqueous solution. The material exhibited excellent catalytic efficiency and reusability. The developed approach could be applied to create other bimetallic NP-incorporated nanofibers for catalysis, tissue engineering, and environmental remediation applications. [ABSTRACT FROM AUTHOR]

Porous nanocomposites of Au/Ag-TiO 2 aerogels benefit from unique morphological characteristics of aerogels, intrinsic physical, chemical and also photocatalytic required properties of TiO 2 and strong plasmonic effects of metal nanoparticles, i.e., Au and Ag. Therefore, they are able to be applied as an ideal photocatalyst overcoming the intrinsic weak points of conventional TiO 2 . In this research, several composites of TiO 2 aerogel modified with Au, Ag and mixture of Au-Ag nanoparticles were prepared by applying two different methods of synthesis. The photocatalytic efficiency of the samples was established by using salicylic acid (SA) as a standard pollutant molecule. The photodegradation rate of SA under irradiation was investigated by the decrease in its concentration in time, and found to depend on specific surface area and type of metal nanoparticles trapped into the TiO 2 network. The larger surface area and the presence of the two metal nanoparticles lead to the best results. Furthermore, the morphological characterizations and physical properties of the nanocomposites were investigated through BET results, FESEM and TEM images. [ABSTRACT FROM AUTHOR]

Two novel Fourier transform-surface plasmon resonance immunosensors were fabricated for the determination of the subgroup J avian leukosis virus. The immunosensors were based on a functionalized gold substrate and immobilized gold–silver nanoparticles. For the first immunosensor, the gold substrate was functionalized with a dense self-assembled monolayer of 3-mercaptopropionic acid through gold–sulfur bonds, and then protein A which can combine subgroup J avian leucosis virus antibody on the antigen nonbinding site was modified on the sensor chip surface via covalent bonds formed between the amino groups and the activated carboxyl groups of 3-mercaptopropionic acid. After inactivation by ethanolamine, the sensor chip immobilized the antibody by the combination with protein A to produce a sensor. For the second immunosensor, 1,6- hexanedithiol formed a self-assembled monolayer on the sensor chip surface through gold–sulfur bonds. Then gold–silver nanoparticles were immobilized on the sensor chip by gold–sulfur and silver–sulfur bonds. The modification by various reagents and determination of the subgroup J avian leukosis virus antigen were the same as in the first immunosensor. The immunosensors determined the subgroup J avian leukosis virus antigen to analyte concentrations of 659 TCID50·mL− 1and 1054 TCID50·mL− 1, respectively. The result suggested that introducing gold–silver nanoparticles to the Fourier transform-surface plasmon resonance immunosensor is beneficial to effectively improving the sensitivity of the immunosensor. Moreover, the contrast experiment presented that the immunosensors showed high specificity for the subgroup J avian leucosis virus detection. [ABSTRACT FROM AUTHOR]