Modified Ag Nanoparticles Research Articles

Silver nanoparticle in biosensor and bioimaging: Clinical perspectives.

Recent developments in nanotechnology promoted the production of nanomaterials with various shapes and sizes by utilizing interdisciplinary researches of biology, chemistry, and material science toward the clinical perspectives. In particular, gold and silver (Ag) are noble metals that exhibit tunable and unique plasmonic properties for the downstream applications. Ag exhibits higher thermal and electrical conductivities, and more efficient in the electron transfer than gold with sharper extinction bands. In addition, modified Ag nanoparticle is more stable in water and air. With all these above features, Ag is an attractive tool in various fields, including diagnosis, drug delivery, environmental, electronics, and as antimicrobial agent. In particular, applications of Ag nanoparticle in the fields of biosensor and imaging are prominent in recent days. Enhancing the specific detection of clinical markers with Ag nanoparticle has been proved by several studies. This review discussed the constructive application of Ag nanoparticle in biosensor and bioimaging for the detection of small molecule to larger whole cell in the perspectives of diagnosing diseases.

Utilizing Ag–Au core-satellite structures for colorimetric and surface-enhanced Raman scattering dual-sensing of Cu (II)

This study develops a dual-channel colorimetric and surface-enhanced Raman scattering (SERS) strategy for detection of Cu2+ utilizing Ag-Au core-satellite nanostructures. 4-mercaptobenzoic acid (MBA) modified Ag nanoparticles (AgNPs@MBA) and 4-mercaptopyridine (Mpy) capped AuNPs (GNPs@Mpy) are first designed via metal-sulfur bonds, respectively. Benefiting from the Cu2+-triggered NPs self-aggregation, the dispersion of AgNPs-GNPs (AgNPs@MBA+GNPs@Mpy) is turned into AgNPs-Cu2+-GNPs core-satellite structures. Because of the presence of pyridyl nitrogen and carboxy group which have specific coordination ability towards Cu2+, induces a certain aggregation of NPs. As well it can be obviously discerned by the visual assay and easily captured by SERS analysis. The UV-Vis method exhibits good linearity in the ranging from 0.1μM-200 μM for Cu2+, while SERS method displays good linear response from 1 pM to 100μM. The detection limit of Cu2+ is 0.032μM by colorimetry and 0.6 pM by SERS method, which is significantly lower than the acceptable limit of Cu2+ in drinking water (20μM) set by the US EPA. Furthermore, colorimetric and SERS assay based on AgNPs-Cu2+-GNPs core-satellite structures is used to determine Cu2+ in various waters and soils, and the detection results are consistent with the traditional atomic analysis methods. This work offers a new method for detecting Cu2+ in environmental samples, and the plasmonic nanostructure provides new entry point for development of multiplexed sensing platform for in-field application.

Fabrication of ZnO Nanoparticles Modified by Uniformly Dispersed Ag Nanoparticles: Enhancement of Gas Sensing Performance.

Zinc oxide (ZnO) nanoparticles modified with uniformly dispersed silver (Ag) nanoparticles (Ag-ZnO) were prepared in one step by calcining precursor electrospun nanofibers. The molar ratios of Ag to Zn in the precursor solutions were 0, 1, 3, and 5%. The microstructure of the Ag-ZnO sensor was characterized by scanning electron microscopy and transmission electron microscopy. The existence of metallic Ag was confirmed by X-ray diffraction and X-ray photoelectron spectroscopy, and the gas sensing properties of Ag-ZnO were investigated. The results showed that the ZnO nanoparticles after Ag nanoparticles modification exhibited excellent gas sensing performance to ethanol and hydrogen sulfide (H2S). The optimal working temperature of the Ag-ZnO sensor significantly decreased for ethanol compared with pure ZnO. The 3% Ag-ZnO sensor exhibited the fastest response to ethanol with the response/recovery times of only 5 and 9 s, respectively. However, all the Ag-ZnO-based gas sensors showed a high response value to H2S, especially the 3% Ag-ZnO gas sensor exhibited a maximum response value of 298 at 10 ppm H2S. These results could be attributed to the spillover effect and electron sensitization effect of Ag nanoparticles, which led to more absorbed oxygen species and active sites, and thereby can further enhance the gas sensing performances of ZnO-based gas sensors.

Photocatalytic activity enhancement of Bi2WO6 nanoparticles by Ag doping and Ag nanoparticles modification

Bi2WO6 nanoparticles doped with Ag, and modified with Ag nanoparticles, were successfully prepared using a two-step microwave assisted and hydrothermal synthesis. With Ag doping, the Bi ions were substituted by the dopant Ag ions in the host lattice structure of Bi2WO6. With Ag nanoparticles modification, the Ag nanoparticles grew on the surface of the Bi2WO6 nanoparticles without changing the host lattice structure. The photocatalytic activities of the samples were studied by visible light irradiation of rhodamine B. Both the Ag doping and the Ag nanoparticles modification enhanced the photocatalytic activity of the Bi2WO6 nanoparticles. Moreover, Ag nanoparticles modification produced a more than two times higher enhancement of the photocatalytic activity than the Ag doping method. Furthermore, a mechanism of the significant photocatalytic activity enhancement by Ag nanoparticles modification is proposed.

Facet engineering of WO3 arrays toward highly efficient and stable photoelectrochemical hydrogen generation from natural seawater

Hydrogen generation via photoelectrochemical (PEC) technology is one of the most ideal strategies for providing sustainable fuel, in particular, from abundant natural resource (such as seawater). Herein, we demonstrate facet-controlled WO3 array decorated with reasonable distribution of dual-cocatalysts, which shows highly efficient and stable PEC H2 generation from natural seawater. The experimental and theoretical results illustrate that photo-generated electrons and holes accumulate directionally on different crystal facets of WO3 to achieve effective spatial separation, owing to the divergent energy levels of each crystal facet. Moreover, the charge utilization is further enhanced by selective modification of Ag nanoparticles and ZnFe-layered double hydroxide on different crystal facets reasonably, getting an average PEC H2 production of 38.18 μmol h−1 from natural seawater with excellent stability. This work opens up a new facet engineering pathway for the fabrication of novel photoelectrodes, which have potential applications in the fields of solar energy conversion and storage.

Control Assembly of Pillar[6]arene-Modified Ag Nanoparticles on Covalent Organic Framework Surface for Enhanced Sensing Performance toward Paraquat

In this study, a class of supramolecular host water-soluble pillar[6]arene (WP6)-modified Ag nanoparticle (WP6@Ag)-functionalized two-dimensional (2D) covalent organic framework (COF) composite is ...

Metal-enhanced fluorescence detection and degradation of tetracycline by silver nanoparticle-encapsulated halloysite nano-lumen

The ultrasensitive detection and efficient degradation of tetracycline (TC) residues are important for improving food safety and protecting human health. In this paper, a smart silver-enhanced fluorescence platform for the ultrasensitive detection of TC was constructed via a simple and selective modification of the interior and external tubes of natural halloysite nanotubes. The thick pipe wall of this platform provides a natural defense and promotes metal-enhanced fluorescence effects, which subsequently accelerates the detection of TC. Moreover, the nanoplatform of the modified Ag nanoparticles can induce the separation of electrons and holes, thereby enhancing photocatalytic activity in TC degradation. This platform provides new opportunities for studying natural halloysite nanotubes and for simultaneously detecting and photodegrading other deleterious substances.

Synthesis and infrared emissivity properties of novel polyurethane/Ag/ZnO array composite coatings

A kind of novel ternary polyurethane (PU)/silver (Ag)/zinc oxide (ZnO) array composite coatings was fabricated by the growth of ZnO arrays onto the stainless steel substrates, the modification of Ag nanoparticles and following PU spinning. The structure, morphologies, wettability and mechanical properties of the PU/Ag/ZnO array composite coatings were measured by SEM, TEM, XRD, UV-vis, surface contact angle (CA) and nano indentation technology. The infrared emissivity values of the composites (8–14 μm) were estimated. The results showed that hexagonal wurtzite ZnO arrays and face-centered cubic Ag nanoparticles were in the composite coatings with good dispersion. The content and the density of the Ag and ZnO arrays can be varied by controlling the deposition time of the Ag and the concentration of the ZnO crystal growth solution, which remarkably had effect on the surface roughness properties of the coatings. By comparison with PU, the mechanical properties of PU/Ag/ZnO array coatings were obviously improved. The PU/Ag/ZnO coatings exhibited improved infrared emissivity property than that of pure PU and PU/ZnO due to the introduction of component Ag with high reflectivity.

Surface morphology, electrochemical and electrical performances of ZnO thin films sensitized with Ag nanoparticles by UV irradiation

Pure zinc oxide and Ag/ZnO thin films were prepared via two step method. The crystal structure, topography, chemical composition and optical properties were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), ultraviolet–visible (UV–Vis) spectrophotometer and laser micro-Raman spectrometer. XRD, FE-SEM and XPS results indicated that Ag nanoparticles were successfully deposited on the zinc oxide nanorods. Ag nanoparticles on the zinc oxide nanorods would extend the photoabsorption region and reduce the electron transition from CB to VB. The photoelectrochemical performances of ZnO thin film could be effectively enhanced by moderate Ag nanoparticles modification. Under sunlight illumination, the photocurrent of the Ag-0.5/ZnO electrode was about three times as large as that of the zinc oxide electrode. The charge transfer process for the Ag/ZnO electrode under sunlight illumination has been discussed. With the increase of Ag content, the resistivity of the sample decreases sharply.

Glutathione modified Ag nanoparticles as efficient detector for pyrimethanil

This work reports on glutathione modified Ag nanoparticles (GSH-Ag NPs) as a chemosensor for detecting pyrimethanil in an aqueous medium. The GSH-Ag NPs were expediently obtained by reducing AgNO3 with NaBH4 and modified with glutathione based on the Ag–S bond. The rapid discrimination for pyrimethanil from other pesticides exhibited the high selectivity of GSH-Ag NPs, then the selectivity was proved by 1H NMR, FT-IR and computational simulation. Based on the good properties of localized surface plasmon resonance, the selective recognition was transformed to visible optical signal in colorimetric test. Additionally the quantitative detection was achieved with good sensitivity and could be applied to analyze practical samples. The experimental results have shown a good linear relationship with pyrimethanil concentration ranging from 10 μM to 1 mM and a low detection limit of 3.87 μM.

Multifunctional WS2&M-AgNPs superhydrophobic conductive sponges for application in various sensors

Superhydrophobic conductive sponge is prepared by an easy method based on WS2 nanosheets and modified Ag nanoparticles in this work, which is promising to apply in various sensors derived from superior liquid repellence, thermo stability, conductive property, mechanical and chemical durability.

Rapid and selective detection of trace Cu2+ by accumulation- reaction-based Raman spectroscopy

Developing detection method for trace copper ions (Cu2+) has attracted great attention since Cu2+ ions would threaten to human health, including cellular toxicity, liver damage, and neuro degenerative diseases. In this work, adding L-cysteine (L-Cys) into inositol hexaphosphate (IP6) modified Ag nanoparticles (designated as L-Cys/IP6@Ag) induces the certain aggregation of nanoparticles, resulting in increasng the surface enhanced Raman scattering (SERS) signal of rhodamine 6 G (R6 G). The presence of Cu2+ ions could be adsorbed by IP6 and the concentrated Cu2+ ions could further selectively oxide Cys molecules under certain pH value, which disperses the IP6@Ag again and decreases the SERS signal of R6 G. The linear range of determination of Cu2+ ions is from 10−5 to 10-1° M as well as a low detection concentration is of 10 pM. Furthermore, the L-Cys/IP6@Ag-R6 G-based SERS sensor has been successfully applied to detect trace Cu2+ in river water.

Hydrothermal preparation of Ag-TiO2-reduced graphene oxide ternary microspheres structure composite for enhancing photocatalytic activity

Photocatalysis technology is considered to be the most industrially feasible way to degrade industrial pollutants due to its low energy consumption and high efficiency. Graphene is considered to be the most potential carrier. Therefore, introducing it into TiO2 has great significance. In this study, We report Ag nanoparticles - modified TiO2 microspheres deposited on reduced graphene oxide (rGO) sheets material was prepared by two-step hydrothermal method. X-ray diffraction (XRD) analysis confirmed that the TiO2 microspheres are typical anatase phases and has the presence of Ag nanoparticles. The characterization of Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) indicated that the graphene oxide was well reduced to rGO, which binds well to Ag-TiO2 microspheres. The prepared 2% Ag-TiO2-rGO microspheres composite showed the best degradation efficiency when degrading Rhodamine B, which caused RhB to degrade 96% in 100 min. At the same time, The modification of Ag nanoparticles on TiO2 microspheres facilitates the separation of photogenerated electron-hole pairs of TiO2, and electrons are further transferred to rGO to participate in photocatalytic reactions. In addition, the composite of rGO also increases the specific surface area of the sample, which is more favorable for the adsorption of dye molecules, so that 2% Ag-TiO2-rGO microspheres composite showed the highest efficiency for photodegradation of RhB.

Apoptotic efficacy of multifaceted biosynthesized silver nanoparticles on human adenocarcinoma cells

Metallic nanoparticles (NPs) especially silver (Ag) NPs have shown immense potential in medical applications due to their distinctive physio-chemical and biological properties. This article reports the conjugation of Ag NPs with Rubus fairholmianus extract. The modification of Ag NPs was confirmed using various physico-chemical characterization techniques. The cytotoxic effect of Rubus-conjugated Ag NPs (RAgNPs) was studied by LDH assay and proliferation by ATP assay. The apoptotic inducing ability of the NPs were investigated by Annexin V/PI staining, caspase 3/7 analysis, cytochrome c release, intracellular ROS analysis, Hoechst staining and mitochondrial membrane potential analysis using flow cytometry. The expression of apoptotic proteins caspase 3, Bax and P53 were analyzed using ELISA and caspase 3, Bax using western blotting. Cells treated with 10 µg/mL RAgNPs showed an increased number of cell death by microscopic analysis compared to untreated control cells. The RAgNPs induced a statistically significant dose-dependent decrease in proliferation (p < 0.001 for 5 and 10 µg/mL) and increased cytotoxicity in MCF-7 cells. A 1.83 fold increase in cytotoxicity was observed in cells treated with 10 µg/mL (p < 0.05) compared to the untreated cells. Nuclear damage and intracellular ROS production were observed upon treatment with all tested concentrations of RAgNPs and the highest concentrations (5 and 10 µg/mL) showed significant (p < 0.05, p < 0.01) expression of caspase 3, Bax and P53 proteins. The data strongly suggest that RAgNPs induces cell death in MCF-7 cells through the mitochondrial-mediated intrinsic apoptosis pathway. The present investigation supports the potential of RAgNPs in anticancer drug development.

Preparation and properties of Ag modified Tb-doped ZrO2 nanotube arrays

Tb-doped ZrO2 nanotube arrays were first prepared by anodizing the Zr-Tb alloys, and then Ag modified Tb-doped ZrO2 nanotube arrays were obtained by loading Ag onto the Tb-doped ZrO2 nanotube arrays through a thermal decomposition and formaldehyde reduction method. The influences of modification of Ag nanoparticles and AgNO3 concentrations (0.0001, 0.001, 0.01 M) on the light absorption and photoluminescence (PL) properties were determined. Results show that Ag modified samples prepared by the thermal decomposition method exhibited a significant surface plasmon resonance(SPR) effect, and that the absorption and PL emission peaks were markedly enhanced. Compared to the Tb-doped ZrO2 nanotube arrays, the PL intensity of the sample prepared using the thermal decomposition method in 0.001 M AgNO3 solution was enhanced by 45.8%. The samples prepared by the formaldehyde reduction method displayed excessive deposition and oversizing of Ag particles, resulting in worsening of the properties of samples.

Hierarchical layered double hydroxides with Ag nanoparticle modification for ethanol sensing

Layered double hydroxides (LDHs) have recently been revealed to be promising in gas sensor applications due to their compositional flexibility and unique 2D-interlayer channel for gas diffusion and adsorption. This work demonstrates highly porous hierarchical LDHs containing Mg2+ and Al3+ (MgAl-LDHs) for ethanol sensing at room temperature. These MgAl-LDHs, with unique flower-like hierarchical structure and mesoporous interlayer, were synthesized hydrothermally using sodium dodecyl sulfate as soft template as well as intercalating agent. Further modification by discrete Ag nanoparticles (NPs) was achieved via an environmentally friendly glucose-reduction method to improve the gas-sensing response of the LDH-based sensor. It is found that the hierarchical MgAl-LDHs show potential in sensing ethanol gas with rapid dynamic characteristics at room temperature; their response magnitude towards ethanol can be enhanced significantly by Ag NP modification. The gas-response value of the Ag-modified MgAl-LDH sensor is about twice that of pristine MgAl-LDH sensors, towards 5–200 ppm ethanol at room temperature. Meanwhile, rapid response-recovery characteristics are achieved, with response and recovery times shorter than 10 and 50 s, respectively. The satisfactory sensing performance and remarkable response enhancement by Ag NP modification are demonstrated in terms of the unique microstructure of the hierarchical MgAl-LDHs and a constructed conductive effect model of Ag functionalized LDHs.

High‐performance dielectric poly(arylene ether nitrile)/Ag nanoparticles decorated halloysites nanotube composites through modified bio‐inspired method and synergistic effect

To obtain high‐performance dielectric materials with high dielectric constant and low dielectric loss, novel polymer composites based on poly(arylene ether nitrile) and Ag nanoparticles decorated halloysites nanotube(HNTs) were presented. For this purpose, halloysites nanotubes were modified by bio‐inspired polydopamine coating, which acted as both the template and reducing agent for decoration of HNTs by Ag nanoparticles. Moreover, a modified bio‐inspired method was developed to realize the surface modification of Ag nanoparticles decorated HNTs hybrid by introducing secondary functional monomer (KH550) to polydopamine system. Therefore, the synergistic effect and good interfacial adhesion contributed to the interesting properties of resulting PEN composites. With addition of 9 wt% Ag nanoparticles decorated HNTs hybrid, the dielectric constant of PEN composite was increased from 3.2 of pure PEN to 10.6 (100 Hz), and low dielectric loss of PEN composite was remained. Furthermore, the tensile strength of PEN composite with 3 wt% of Ag nanoparticles decorated HNTs hybrid increased from 81.07 MPa of pure PEN to 101.3 MPa (increased by 25%). In addition, the glass transition temperature (Tg) reached 171.9°C with addition of Ag nanoparticles decorated HNTs hybrid, which exhibited the significant enhancement in thermal stability. POLYM. ENG. SCI., 58:2227–2236, 2018. © 2018 Society of Plastics Engineers

Colorimetric detection of picric acid using silver nanoparticles modified with 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole

This article reports formulation of remarkably stable macromolecule capped silver nanoparticles for the instant naked eye assay of extremely hazardous environmental pollutant, picric acid. We have established a simple and sensitive colorimetric technique for the assay of picric acid using spherical FCC silver nanoparticles modified with 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole (AHMT). In this context, highly stable AHMT capped silver nanoparticles (Ag@AHMT) are developed and optimized via UV–vis, IR and zeta potential. The designed Ag@AHMT nanoparticles of 4–10 nm size range are symmetrically distributed, regularly arranged and utilized for the ultra-trace assay of picric acid. It is found that picric acid encourages the aggregation of modified Ag nanoparticles through charge transfer complex formation, leading to color varies from light yellow to brownish yellow. This variation can be visualized by naked eyes. Further it was examined through UV–vis spectra and the limit of detection was obtained as 0.13 nM with sensitivity 0.045 ng/mL. The new approach lightens scope for fabrication of naked eye sensing devices of environmental pollutants.

Fluorescence method for quickly detecting ochratoxin A in flour and beer using nitrogen doped carbon dots and silver nanoparticles

In this paper, a FRET (Forster resonance energy transfer) based fluorescence method was developed for the quickly detection of ochratoxin A (OTA) in agricultural products (e.g., flour and beer). A highly fluorescent nitrogen doped carbon dots (CD) were served as energy donor, the DNA and MCH (6-mercapto-1-hexanol) modified Ag nanoparticles were served as energy acceptor in the FRET system. OTA can be detected in a concentration range between 10 and 5000 nM, the limit of detection is 8.7 nM. This method has three advantages: (1) an enhanced fluorescent intensity can be acquired by utilizing the nitrogen doped CD synthesized by one-step approach without sophisticated modification of nanoparticles; (2) OTA detection was accomplished quickly (less than 30 min) by using MCH as assistant molecule; (3) an extended OTA detection linear range was acquired, which may facilitate the OTA detection in real agricultural samples, and is helpful for solving food safety problems.

Silver modified barium titanate as a highly efficient piezocatalyst

Surface modification of Ag nanoparticles on BaTiO3 can significantly enhance the piezocatalytic activity of the catalyst.