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Abstract: Nanomaterials with unique electronic, optical and catalytic properties have recently been at the forefront of research due to their tremendous range of applications. Taking gold, silver and titania nanoparticles as examples, we have reviewed the current research works on paper functionalized by these nanoparticles. The functionalization of paper with only a very small concentration of nanoparticles is able to produce devices with excellent photocatalytic, antibacterial, anti-counterfeiting, Surface Enhanced Raman Scattering (SERS) and Surface Plasmon Resonance (SPR) performances. This review presents a brief overview of the properties of gold, silver and titania nanoparticles which contribute to the major applications of nanoparticles-functionalized paper. Different preparation methods of the nanoparticles-functionalized paper are reviewed, focusing on their ability to control the morphology and structure of paper as well as the spatial location and adsorption state of nanoparticles which are critical in achieving their optimum applications. In addition, main applications of the nanoparticles-functionalized papers are highlighted and their critical challenges are discussed, followed by perspectives on the future direction in this research field. Whilst a few studies to date have characterized the distribution of nanoparticles on paper substrates, none have yet optimized paper as a nanoparticles'' substrate. There remains a strong need to improve understanding on the optimum adsorption state of nanoparticles on paper and the heterogeneity effects of paper on the properties of these nanoparticles. [Copyright &y& Elsevier]

The problem of aflatoxin contamination emerged gradually in the field of food safety. Surface-enhanced Raman spectroscopy (SERS) is an ultra-sensitive and non-destructive spectroscopy technology with extensive application prospects in the detection field. In this paper, with the detection of AFB1 as the target, Au@Ag NPs substrate with uniform morphology and strong SERS effect was prepared. Furthermore, the intermediates formed by hydrogen bonding between AFB1 and melamine facilitate the binding of toxin molecules to the substrate. Moreover, the AFB1- melamine-Au@Ag NPs detection system was established by optimizing the melamine dosage, and the limit of detection can reach 10-8 mol/L (M). In this method, AFB1 (concentration range of 10-4 M -10-7 M) in tea oil, the Raman signal intensity of AFB1 shows an excellent linear, logarithmic relationship, and the correlation coefficient is 0.9685. Therefore, this work has achieved simple, sensitive, and stable AFB1 detection and has broad application potential in food safety detection. [ABSTRACT FROM AUTHOR]

The problem of aflatoxin contamination emerged gradually in the field of food safety. Surface-enhanced Raman spectroscopy (SERS) is an ultra-sensitive and non-destructive spectroscopy technology with extensive application prospects in the detection field. In this paper, with the detection of AFB1 as the target, Au@Ag NPs substrate with uniform morphology and strong SERS effect was prepared. Furthermore, the intermediates formed by hydrogen bonding between AFB1 and melamine facilitate the binding of toxin molecules to the substrate. Moreover, the AFB1-melamine-Au@Ag NPs detection system was established by optimizing the melamine dosage, and the limit of detection can reach 10-8 mol/L (M). In this method, AFB1 (concentration range of 10-4 M -10-7 M) in tea oil, the Raman signal intensity of AFB1 shows an excellent linear, logarithmic relationship, and the correlation coefficient is 0.9685. Therefore, this work has achieved simple, sensitive, and stable AFB1 detection and has broad application potential in food safety detection. [ABSTRACT FROM AUTHOR]

Light scattering of noble metal nanoparticles was widely used in solar cells, sensing and spectroscopy, so the research on the light scattering itself will be beneficial for their increasing applications. In this paper, gold and silver nanoparticles with different sizes and shapes were synthesized and their elastic scattering was investigated. The results demonstrate that the elastic scattering of metal nanoparticles is influenced by their size and shape, and the scattering behavior has a specific correlation with the surface plasmon resonance. The elastic scattering spectra of gold and silver nanospheres basically cover the extinction spectra, indicating plasmon resonance enhanced scattering of spherical nanoparticles. The elastic scattering spectra of nonspherical gold nanorods and silver nanoprisms only overlap the extinction peaks at short wavelengths. The elastic scattering is considered to be enhanced by the transverse resonance bands at short wavelengths for nonspherical gold or silver nanoparticles, but it cannot be contributed by the longitudinal resonance bands at the corresponding long wavelengths. This result will be helpful in selecting size and shape in the scattering application of plasmonic metal nanoparticles. [Display omitted] • Elastic scattering spectra of spherical Au and Ag nanoparticles basically cover their extinction peak. • Elastic scattering of spherical metal nanoparticles is enhanced by the surface plasmon resonance. • Elastic scattering spectra of Au nanorods and Ag nanoprisms overlap the extinction at short wavelengths. • Transverse resonance of nonspherical nanoparticles at short wavelengths enhances the elastic scattering. • Longitudinal resonance of nonspherical nanoparticles at long wavelengths cannot enhance the elastic scattering. [ABSTRACT FROM AUTHOR]

Many important discoveries have been made in the field of nanotechnology in the last 40 years. Since then, nanoparticles became nearly ubiquitous. With their spreading use, safety concerns have warranted extensive research of nanotoxicity. This paper offers information about the occurrence, transport, and behaviour of metallic nanoparticles in the aquatic environment. It further summarizes details about parameters that dictate the toxicity of nanoparticles and discusses the general/common mechanisms of their toxicity. This review also focuses on fish exposure to nanoparticles, including the possibility of trophic transport through the food chain. Information on some of the most frequently used metallic nanoparticles, such as silver, gold, and titanium dioxide, is further elaborated on. [ABSTRACT FROM AUTHOR]

In understanding of the hot spot phenomenon in single-molecule surface enhanced Raman scattering (SM-SERS), the electromagnetic field within the gaps of dimers (i.e., two particle systems) has attracted much interest as it provides significant field amplification over single isolated nanoparticles. In addition to the existing understanding of the dimer systems, we show in this paper that field enhancement within the gaps of a particle chain could maximize at a particle number N>2, due to the near-field coupled plasmon resonance of the chain. This particle number effect was theoretically observed for the gold (Au) nanoparticles chain but not for the silver (Ag) chain. We attribute the reason to the different behaviors of the dissipative damping of gold and silver in the visible wavelength range. The reported effect can be utilized to design effective gold substrate for SM-SERS applications. [ABSTRACT FROM AUTHOR]

In this paper, we report on the simple polyol synthesis of copper-doped hybrid Agx–Auy@ZnO photocatalysts. The obtained samples have been characterized by X-ray diffraction, UV–Vis diffuse reflectance spectroscopy, transmission electron microscopy and an N2 adsorption study. The experiment results show that Ag, Au and Ag–Au alloy nanoparticles (NPs) successfully load onto the surface of the assembled Cu-doped ZnO. The photocatalytic performances of Cu-doped Agx–Auy@ZnO nanomaterials have been tested using diuron herbicide as a model contaminant under simulated solar light irradiation. The addition of Ag and/or Au nanoparticles to doped ZnO was strongly beneficial to the rate constant displaying a volcano-like pattern as a function of the Ag and Au content. A maximum pseudo-first-order rate constant of 18.55 × 10−3 min−1, 22.70 × 10−3 min−1 and 24.74 × 10−3 min−1 was achieved on Cu-doped Ag0.3@ZnO, Au0.5@ZnO and Ag0.5–Au0.3@ZnO respectively. The Cu-doped Ag0.5–Au0.3@ZnO bimetallic nanoparticles show the highest photocatalytic activity due to the synergistic effect by effective electron transfer. [ABSTRACT FROM AUTHOR]

Abstract: Non-invasive assay for the early stage diagnosis of methicillin resistant Staphylococcus aureus ( MRSA ) related pneumonia is of great clinical importance and still a great challenge. In this paper, we reported a novel kind of Au@Ag core–shell theranostic nanoparticles (NPs) conjugated with MRSA specific antibody on their surface. Compared with the raw Au@Ag NPs, these antibody modified NPs (AAMA NPs) showed 10.66 fold enhancement targeting to the MRSA in vitro. In vivo target efficacy was measured with rats bearing pneumonia induced by different pathogens. Computed tomography (CT) results revealed that these AAMA NPs had higher CT contrast enhancement (498 HU), than those of raw Au@Ag and Omnipaque (oth <100 HU). In addition, lesions labeled by AAMA NPs could be distinguished from lung parenchyma by taking advantage of spectra CT. Bio-distribution analysis confirmed that these AAMA NPs accumulated in the MRSA rich site. Both BAL and Elisa assays indicated that these AAMA NPs greatly alleviated the inflammation reaction by reducing bacterial proliferation and cytokine production. Pathological study showed that these NPs exerted negligible long term cytotoxicity in vivo. [Copyright &y& Elsevier]

Purpose: Noble metal nanoparticles have found several medical applications in the areas of radiation detection; x-ray contrast agents and cancer radiation therapy. Based on computational methods, many papers have reported the nanoparticle effect on the dose deposition in the surrounding medium. Here the authors report experimental results on how silver and gold nanoparticles affect the dose deposition in alanine dosimeters containing several concentrations of silver and gold nanoparticles, for five different beam energies, using electron spin resonance spectroscopy (ESR). Methods: The authors produced alanine dosimeters containing several mass percentage of silver and gold nanoparticles. Nanoparticle sizes were measured by dynamic light scattering and by transmission electron microscopy. The authors determined the dose enhancement factor (DEF) theoretically, using a widely accepted method, and experimentally, using ESR spectroscopy. Results: The DEF is governed by nanoparticle concentration, size, and position in the alanine matrix. Samples containing gold nanoparticles afford a DEF higher than 1.0, because gold nanoparticle size is homogeneous for all gold concentrations utilized. For samples containing silver particles, the silver mass percentage governs the nanoparticles size, which, in turns, modifies nanoparticle position in the alanine dosimeters. In this sense, DEF decreases for dosimeters containing large and segregated particles. The influence of nanoparticle size-position is more noticeable for dosimeters irradiated with higher beam energies, and dosimeters containing large and segregated particles become less sensitive than pure alanine (DEF < 1). Conclusions: ESR dosimetry gives the DEF in a medium containing metal nanoparticles, although particle concentration, size, and position are closely related in the system. Because this is also the case as in many real systems of materials containing inorganic nanoparticles, ESR is a valuable tool for investigating DEF. Moreover, these results alert to the importance of controlling the sizeposition of nanoparticles to enhance DEF. [ABSTRACT FROM AUTHOR]

Abstract: In this paper we investigate the applicability of T-matrix light scattering calculations to determine the spectral behaviour of metallic nanoparticles during a sintering process. We are especially interested in spectral changes and plasmonic effects during the process of approaching and sintering as this might help to establish a measurement method for the degree of sintering. For this, we consider two separate spherical nanoparticles which get closer and closer until they touch; then the sintering process starts, resulting in a single particle. This resulting shape of the single particle is described by a Cassini-oval. As materials we choose silver (Ag), gold (Au), titanium nitride (TiN) and indium tin oxide (ITO). The calculations are done using the Nullfield Method with Discrete Sources. [Copyright &y& Elsevier]

This paper describes a surface-enhanced Raman scattering (SERS) systematic investigation regarding the functionalization of gold (Au) and silver (Ag) nanoparticles with diphenyl dichalcogenides, i.e. diphenyl disulfide, diphenyl diselenide, and diphenyl ditelluride. Our results showed that, in all cases, functionalization took place with the cleavage of the chalcogen-chalcogen bond on the surface of the metal. According to our density functional theory calculations, the molecules assumed a tilted orientation with respect to the metal surface for both Au and Ag, in which the angle of the phenyl ring relative to the metallic surface decreased as the mass of the chalcogen atom increased. The detected differences in the ordinary Raman and SERS spectra were assigned to the distinct stretching frequencies of the carbon-chalcogen bond and its relative contribution to the ring vibrational modes. In addition, the SERS spectra showed that there was no significant interaction between the phenyl ring and the surface, in agreement with the tilted orientation observed from our density functional theory calculations. The results described herein indicate that diphenyl dichalcogenides can be successfully employed as starting materials for the functionalization of Au nanoparticles with organosulfur, organoselenium, and organotellurium compounds. On the other hand, diphenyl disulfide and diphenyl diselenide could be employed for the functionalization of Ag nanoparticles, while the partial oxidation of the organotellurium unit could be detected on the Ag surface. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In this work, we show theoretical results of the behaviour of the extinction cross section as a function of the incident wavelength for metallic nanotubes (Nts) with a 2D core-shell structure. To calculate the optical response of the gold, silver and cooper system, an exact integral formalism is implemented. The method is based on Green's integral theorem, and it allows us to compute the electromagnetic field at any point in space. For a correct description of the constitutive parameters of the metallic shell, we introduce a corrective model for the dielectric function in terms of the shell thickness in the range 1 to 10 nm. In particular, we investigate the features of surface plasmons in metallic Nts, and in the cases of Au and Cu, the mechanisms of the interband transitions play a relevant role. In this paper, we show that a quasi-static approach is not sufficient to account the plasmon-plasmon interaction in Ag Nts. The aim of these studies is to characterize core size and shell thicknesses of the Nts by means of the surface plasmon resonance observed in the far field. [ABSTRACT FROM AUTHOR]

The use of nanoparticles in electroanalysis is an area of research which is continually expanding. A wealth of research is available discussing the synthesis, characterization and application of nanoparticles. The unique properties of nanoparticulate materials (e.g. enhanced mass transport, high surface area, improved signal-to-noise ratio) can often be advantageous in electroanalytical techniques. The aim of this paper is to provide an updated overview of the work in this field. In this review we have concentrated on the advances with regards to silver, gold, platinum, palladium, ruthenium, copper and nickel. The synthesis, characterization and practical application of these materials are discussed. We have also identified the conditions under which each metal is likely to be stable, which is likely to be a useful tool for those practising in the field. Furthermore, we have provided a theoretical overview of advances in the theoretical modelling and simulation of nanoparticle behaviour. [ABSTRACT FROM AUTHOR]

Abstract: Recently, gram quantities of monodisperse gold or silver nanoparticles were reported to be produced through a digestive ripening process, in which colloidal particles of size from 2 to 40nm are transformed to nearly monodisperse particles of 4–5nm diameter. Digestive ripening, an example for inverse Ostwald ripening, is a puzzling phenomenon since it appears to avoid the usual capillary consequence, i.e., reduction of interfacial free energy. This paper presents a theoretical model which accounts for the self-assembled monodisperse state of such nanoparticles by considering the effect of charges, and therefore electrostatic energy, in the coarsening behavior of the particles. An appropriate Gibbs–Thomson equation is first derived, and then particle growth rates are calculated. The results show that success of a monodisperse state depends on, among other things, the initial particle distribution, and the size distribution at equilibrium follows some of the thermodynamic principles observed in binary phase diagrams of alloy systems. [Copyright &y& Elsevier]

Abstract: In this paper, we demonstrate a simple and reproducible method for the synthesis of triangular Au core–Ag shell nanoparticles. The triangular gold core is obtained by the reduction of gold ions by lemongrass extract. Utilizing the negative charge on the gold nanotriangles, silver ions are bound to their surface and thereafter reduced by ascorbic acid under alkaline conditions. The thickness of the silver shell may be modulated by varying the pH of the reaction medium. The formation of the Au core–Ag shell triangular nanostructures has been followed by UV–vis–NIR Spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy (TEM) and atomic force microscopy (AFM) measurements. The sharp vertices of the triangles coupled with the core–shell structure is expected to have potential for application in surface enhanced Raman spectroscopy and in the sensitive detection of biomolecules. [Copyright &y& Elsevier]

The surface of a nanofiber that is formed from a self-assembling pseudopeptide has been decorated by gold and silver nanoparticles that are stabilized by a dipeptide. Transmission electron microscopic images make the decoration visible. In this paper, a new strategy of mineralizing a pseudopeptide based nanofiber by gold and silver nanoparticles with use of a two-component nanografting method is described. [ABSTRACT FROM AUTHOR]

In the study described in this paper we deposited gold, silver and copper on γ-Al2O3 as nanoparticles ( <4 nm) and investigated the behavior of these nanoparticles in the preferential oxidation of CO in presence of H2. In addition, the effect of addition of CeO x and/or Li2O was investigated. All the three metals show preferential oxidation of CO at low temperatures. The oxides added to Au/γ-Al2O3, Ag/γ-Al2O3 and Cu/γ-Al2O3 improve the catalytic performance of the gold, silver and copper. Interesting and synergistic effects were observed when both the CeO x and Li2O were added. Possible mechanisms are proposed. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we report the reduction of silver and gold salts by methanolic solution of sodium borohydride in tetrazolium based ionic liquid as a solvent at 30°C leads to pure phase of silver and gold nanoparticles. Silver and gold nanoparticles so-prepared were well characterized by powder X-ray diffraction measurements (XRD), transmission electron microscopy (TEM) and QELS. XRD analysis revealed all relevant Bragg''s reflection for crystal structure of silver and gold metal. XRD spectra also revealed no oxidation of silver nanoparticles to silver oxide. TEM showed nearly uniform distribution of the particles in methanol and it was confirmed by QELS. Silver and gold nanoparticles in ionic liquid can be easily synthesized and are quite stable too. [Copyright &y& Elsevier]

Currently, metal nanoparticles have varied uses for different medical, pharmaceutical, and agricultural applications. Nanobiotechnology, combined with green chemistry, has great potential for the development of novel and necessary products that benefit human health, environment, and industries. Green chemistry has an important role due to its contribution to unconventional synthesis methods of gold and silver nanoparticles from plant extracts, which have exhibited antimicrobial potential, among other outstanding properties. Biodiversity-rich countries need to collect and convert knowledge from biological resources into processes, compounds, methods, and tools, which need to be achieved along with sustainable use and exploitation of biological diversity. Therefore, this paper describes the relevant reported green synthesis of gold and silver nanoparticles from plant extracts and their capacity as antimicrobial agents within the agricultural field for fighting against bacterial and fungal pathogens that can cause plant, waterborne, and foodborne diseases. Moreover, this work makes a brief review of nanoparticles' contribution to water treatment and the development of "environmentally-friendly" nanofertilizers, nanopesticides, and nanoherbicides, as well as presenting the harmful effects of nanoparticles accumulation in plants and soils. [ABSTRACT FROM AUTHOR]

The present work summarizes our experimental data on Surface-enhanced Raman scattering (SERS) of inorganic pigments. The effect of pigment type on Raman scattering enhancement was studied. The paper also describes the features of the SERS-active substrates used as well as the methods of sample preparation for SERS analysis of the pigments. The results of successful application of SERS and micro-SERS for art pigments identification in the canvas paintings and icons have been demonstrated. The techniques allowed us to clearly identify the composition of blue and green paint layers as well as grounds in the nine artworks. This lead to determination of the lower time limit of work creation, to dating of the restoration interventions, to distinguish red ochers from two different deposit sources of raw mineral. The enhancement of Raman scattering intensities allows to reduce significantly the amount of the sample being taken from artwork (up to 1 μg). Unlabelled Image • The analysis of 18 inorganic microcrystalline pigments was carried out by SERS. • The comparison of SERS experimental data with the traditional Raman spectra was reported. • Successful application of SERS for art pigments identification in the 9 easel paintings and icons have been demonstrated. [ABSTRACT FROM AUTHOR]

The cover picture shows the growth mechanism of Cu2O/noble‐metal nanocomposites and the application of these nanocomposites as surface‐enhanced Raman scattering (SERS) substrates, as reported by Z. Wang and co‐workers in their Full Paper on page 684 ff. They aim to synthesize SERS substrates with high sensitivity and good reproducibility for the detection of food contaminants. [ABSTRACT FROM AUTHOR]