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This paper describes the development of simple, sustainable, and low-cost strategies for signal enhancement on paper-based carbon platforms through gold nanoparticles electrogenerated from small volumes of tetrachloroauric (III) acid solutions. Carbon ink is deposited on a hydrophilic working area of the paper delimited with hydrophobic wax. This maskless procedure is fast and cuts down ink waste. The connection of this working electrode to the potentiostat is ensured with the use of screen-printed electrodes (SPEs). Close contact of the whole area of both carbon electrodes improves the precision of the nanostructuration. Resulting gold-modified paper-based carbon working electrodes (AuNPs-PCWEs) were characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), and electron dispersion X-ray spectrometry (SEM/EDX). This methodology was applied for the first time to the inorganic arsenic determination in commercial white wines by chronoamperometric stripping of the electrodeposited As(0). In an optimized system, As(III) was reduced and deposited as As(0) on the nanostructured surface by applying a potential of -0.3 V during 180 s. Then, anodic stripping chronoamperometry was performed at +0.4 V. The analytical signal was the current recorded at 30 s. On the other hand, As(V) was chemically reduced to As(III) with 0.2 M KI, and total determination of arsenic could be carried out. As(V) was determined as the difference between total As and As(III). Then, this fast, simple and low-cost method can be employed for speciation purposes. Limits of detection for As(III) and total arsenic (in the presence of KI) are 2.2 µg L-1 and 2.4 µg L-1, respectively, and indicate that this method is suitable for regulated quality control. [ABSTRACT FROM AUTHOR]

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]

Abstract: SERS of C60/C70 adsorbed on gold nanoparticles coated on filter paper or filter film was studied. As a new SERS substrate, dried gold-coated filter paper or filter film has a high SERS activity, whose enhancement factor can be up to about 105, because it avoided the influence of solvents in C60/C70 solution and water in gold hydrosols. The influence of the gold thickness coated on filter paper or filter film to SERS of C60/C70 adsorbed on gold nanoparticles was mainly discussed. It is indicated that the SERS effect of C60/C70 was very sensitive to the distribution and aggregated characteristics of gold nanoparticles, and the SERS intensity of each mode increased at its own proportion, but it integrally tended to saturation when the thickness of colloidal gold coatings increased. [Copyright &y& Elsevier]

An optical shutter based on charged particles is presented. The output light intensity of the proposed device has an intrinsic dependence on the interparticle spacing between charged particles, which can be controlled by varying voltages applied to the control electrodes. The interparticle spacing between charged particles can be varied continuously and this opens up the possibility of particle based displays with continuous grayscale. [ABSTRACT FROM AUTHOR]

This paper reviews the development of research on one-dimensional self-assembly of gold nano-particles. The experimental strategies to realize 1D self-assembly of gold nanoparticles are first introduced; the applications of gold self-assembled 1D nanomaterials in colorimetric sensing, Raman enhancement, electronic devices and biomedicine are then summarized; remarks on future directions of this research topic are presented. [ABSTRACT FROM AUTHOR]

N‐Heterocyclic carbenes (NHCs) have drawn considerable interest in the field of nanomaterials chemistry as highly stabilizing ligands enabling the formation of strong and covalent carbon–metal bonds. Applied to gold nanoparticles synthesis, the most common strategy consists of the reduction of a preformed NHC‐AuI complex with a large excess of a reducing agent that makes the particle size difficult to control. In this paper, we report the straightforward synthesis of NHC‐coated gold nanoparticles (NHC‐AuNPs) by treating a commercially available gold(I) precursor with an easy‐to‐synthesize NHC‐BH3 reagent. The latter acts as both the reducing agent and the source of surface ligands operating under mild conditions. Mechanistic studies including NMR spectroscopy and mass spectrometry demonstrate that the reduction of gold(I) generates NHC‐BH2Cl as a by‐product. This strategy gives efficient control over the nucleation and growth of gold particles by varying the NHC‐borane/gold(I) ratio, allowing unparalleled particle size variation over the range of 4.9±0.9 to 10.0±2.7 nm. Our strategy also allows an unprecedented precise and controlled seeded growth of gold nanoparticles. In addition, the as‐prepared NHC‐AuNPs exhibit narrow size distributions without the need for extensive purification or size‐selectivity techniques, and are stable over months. [ABSTRACT FROM AUTHOR]

An analyzed substance's signal intensity and detection sensitivity in surface-enhanced Raman spectroscopy (SERS) significantly depend on the size and agglomeration degree of nanoparticles (NPs) forming the enhancing structure. Structures were manufactured by aerosol dry printing (ADP), where NPs' agglomeration depends on printing conditions and additional particle modification techniques. The influence of agglomeration degree on SERS signal enhancement was studied in three types of printed structures using the methylene blue model molecule as an analyte. We demonstrated that the ratio between individual NPs and agglomerates in a studied structure strongly affects SERS signal amplification, and structures formed mainly from non-agglomerated NPs enhance the signal better. In this sense, aerosol NPs modified by pulsed laser radiation provide better results than thermally modified NPs, since in laser modification a larger number of individual NPs is observed due to the absence of secondary agglomeration effects in the gas stream. However, increasing gas flow may minimize the secondary agglomeration, since the time allotted for the agglomeration processes is reduced. In this paper, we show how different NPs' agglomeration tendencies influence SERS enhancement to demonstrate the process of using ADP to form inexpensive and highly efficient SERS substrates with huge application potential. [ABSTRACT FROM AUTHOR]

Fluorescence, and more in general, photoluminescence (PL), presents important advantages for imaging with respect to other diagnostic techniques. In particular, detection methodologies exploiting fluorescence imaging are fast and versatile; make use of low-cost and simple instrumentations; and are taking advantage of newly developed powerful, low-cost, light-based electronic devices, such as light sources and cameras, used in huge market applications, such as civil illumination, computers, and cellular phones. Besides the aforementioned simplicity, fluorescence imaging offers a spatial and temporal resolution that can hardly be achieved with alternative methods. However, the two main limitations of fluorescence imaging for bio-application are still (i) the biological tissue transparency and autofluorescence and (ii) the biocompatibility of the contrast agents. Luminescent gold nanoclusters (AuNCs), if properly designed, combine high biocompatibility with PL in the near-infrared region (NIR), where the biological tissues exhibit higher transparency and negligible autofluorescence. However, the stabilization of these AuNCs requires the use of specific ligands that also affect their PL properties. The nature of the ligand plays a fundamental role in the development and sequential application of PL AuNCs as probes for bioimaging. Considering the importance of this, in this review, the most relevant and recent papers on AuNCs-based bioimaging are presented and discussed highlighting the different functionalities achieved by increasing the complexity of the ligand structure. [ABSTRACT FROM AUTHOR]

This paper reports the synthesis and characterization of a graphene oxide–gold nanohybrid (GO-Au) and evaluates its suitability as a test material, e.g., in nano(eco)toxicological studies. In this study, we synthesised graphene oxide (GO) and used it as a substrate for the growth of nano-Au decorations, via the chemical reduction of gold (III) using sodium citrate. The GO-Au nanohybrid synthesis was successful, producing AuNPs (~17.09 ± 4.6 nm) that were homogenously distributed on the GO sheets. They exhibited reproducible characteristics when characterised using UV-Vis, TGA, TEM, FTIR, AFM, XPS and Raman spectroscopy. The nanohybrid also showed good stability in different environmental media and its physicochemical characteristics did not deteriorate over a period of months. The amount of Au in each of the GO-Au nanohybrid samples was highly comparable, suggesting a potential for use as chemical label. The outcome of this research represents a crucial step forward in the development of a standard protocol for the synthesis of GO-Au nanohybrids. It also paves the way towards a better understanding of the nanotoxicity of GO-Au nanohybrid in biological and environmental systems. [ABSTRACT FROM AUTHOR]

Simple Summary: Pancreatic cancer is one of the leading causes of cancer deaths worldwide. The use of nanoparticles as radiosensitizers and drug delivery vehicles could open the door to solving many of the obstacles in current cancer treatments. Gold nanoparticles (GNPs) and docetaxel (DTX) have shown very promising synergetic radiosensitization effects, despite DTX toxicity to normal tissues. In this paper, we explored the effect of a DTX prodrug encapsulated in lipid nanoparticles (LNPDTX-P) on GNP uptake in pancreatic cancer models in vitro and in vivo. The results show that LNPDTX-P-treated tumour samples have twice the amount of GNP uptake in both in vitro and in vivo models. These very promising results establish that LNPDTX-P have very similar outcomes to free DTX on tumour tissues. These results demonstrate the potential of incorporating GNPs and LNPDTX-P as radiosensitization tools to current radiotherapy protocols for improved tumour targeting. Current chemoradiation therapy suffers from normal tissue toxicity. Thus, we are proposing incorporating gold nanoparticles (GNPs) and docetaxel (DTX), as they have shown very promising synergetic radiosensitization effects. Here, we explored the effect of a DTX prodrug encapsulated in lipid nanoparticles (LNPDTX-P) on GNP uptake in pancreatic cancer models in vitro and in vivo. For the in vitro experiment, a pancreatic cancer cell line, MIA PaCa-2, was cultured and dosed with 1 nM GNPs and 45 nM free DTX or an equivalent dose of LNPDTX-P. For the in vivo experiment, MIA PaCa-2 cells were implanted subcutaneously in NRG mice, and the mice were dosed with 2 mg/kg of GNPs and 6 mg/kg of DTX or an equivalent dose of LNPDTX-P. The results show that LNPDTX-P-treated tumour samples had double the amount GNPs compared to control samples, both in vitro and in vivo. The results are very promising, as LNPDTX-P have superior targeting of tumour tissues compared to free DTX due to their nanosize and their ability to be functionalized. Because of their minimal toxicity to normal tissues, both GNPs and LNPDTX-P could be ideal radiosensitization candidates in radiotherapy and would produce very promising synergistic therapeutic outcomes. [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]

Simple Summary: Many cancer therapeutics do not account for the complexity of the tumor microenvironment (TME), which may result in failure when applied clinically. In this paper we utilized a simple tumor model made of two types of pancreatic cancer cells that contribute to the tumor environment, i.e., cancer cells and cancer associated fibroblasts. Herein, radiotherapy along with radiosensitizing gold nanoparticles were used to test the efficacy of a co-culture vs. monoculture model. The results show that the co-culture model exhibited heightened resistance to radiation. Furthermore, we found that the combination of gold radiosensitizers with radiotherapy reduced the radioresistance of the co-culture model compared to radiotherapy alone. This study demonstrates the potential of using nanotherapeutics in targeting the complex tumor microenvironment. Many cancer therapeutics are tested in vitro using only tumour cells. However, the tumour promoting effect of cancer associated fibroblasts (CAFs) within the tumour microenvironment (TME) is thought to reduce cancer therapeutics' efficacy. We have chosen pancreatic ductal adenocarcinoma (PDAC) as our tumor model. Our goal is to create a co-culture of CAFs and tumour cells to model the interaction between cancer and stromal cells in the TME and allow for better testing of therapeutic combinations. To test the proposed co-culture model, a gold nanoparticle (GNP) mediated-radiation response was used. Cells were grown in co-culture with different ratios of CAFs to cancer cells. MIA PaCa-2 was used as our PDAC cancer cell line. Co-cultured cells were treated with 2 Gy of radiation following GNP incubation. DNA damage and cell proliferation were examined to assess the combined effect of radiation and GNPs. Cancer cells in co-culture exhibited up to a 23% decrease in DNA double strand breaks (DSB) and up to a 35% increase in proliferation compared to monocultures. GNP/Radiotherapy (RT) induced up to a 25% increase in DNA DSBs and up to a 15% decrease in proliferation compared to RT alone in both monocultured and co-cultured cells. The observed resistance in the co-culture system may be attributed to the role of CAFs in supporting cancer cells. Moreover, we were able to reduce the activity of CAFs using GNPs during radiation treatment. Indeed, CAFs internalize a significantly higher number of GNPs, which may have led to the reduction in their activity. One reason experimental therapeutics fail in clinical trials relates to limitations in the pre-clinical models that lack a true representation of the TME. We have demonstrated a co-culture platform to test GNP/RT in a clinically relevant environment. [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]

In this paper, the run of the decorating process of the active support, like CeO2, by the gold nanoparticles via deposition‐precipitation method has been studied. Two types of the Au/CeO2 systems with different mean particle size (but the same morphology) of the support have been investigated. It was noted that the decoration process proceeds easily only for large crystals with average size about 67 nm. Three hypotheses were tested in order to explain unsuccessful initial Au nanoparticles decoration of the cube‐like CeO2 crystals with average size about 14 nm as a support. The tests have shown that the ratio of the molar content of the chloroauric acid to the total surface area of the support (MAu/SCeO2) has a significant impact on the decorating process of CeO2 by nano‐Au. If the above ratio is too small, the thin layer of gold instead of the Au nanoparticles is formed on the support surface. In this paper, the calculations of the real surface area (from TEM/HRTEM data) were used to adjust the optimum the MAu/SCeO2 to obtain the Au/CeO2 system with the desired properties. [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]

Surface enhanced Raman spectra (SERS) of C70 adsorbed on the gold nanoparticles coated on the filter paper were obtained by employing pyridine molecule as medium. As a new SERS substrate, dried gold coated filter paper has a high SERS activity, of which enhancement factor can be up to 8.2×106. When the C70 molecule is adsorbed on the gold nanoparticle surface, its symmetry is reduced. Different orientations on the surface of gold nanoparticles will lead to different symmetry lowering. Generally, symmetry lowering may lead to the splitting of the Raman bands due to the degenerate modes. It was demonstrated that the C70 molecule was adsorbed on its pentagonal face with its long axis perpendicular to the gold nanoparticles surface. Its surface enhanced Raman spectral behavior is consistent with the analysis based on the group theory. [ABSTRACT FROM AUTHOR]

In this paper, the scattering-to-absorption ratio that is a measurable factor and defined as the ratio of the scattering cross section to the absorption cross section in plasmonic core-shell nanoparticles with different shapes is investigated. The effect of various plasmonic materials on the scattering-to-absorption ratio is presented that can tune the plasmon resonance and play a key role in plasmonic solar cell efficiency improvement. In addition to using plasmonic materials as silver and gold, we use poor metals as bismuth because these types of metals are good materials for UV plasmonics. We also use semiconductor copper chloride (CuCl) in our calculations, because this material exhibits a strong exciton resonance, while the interaction between the plasmon resonance in metals and the exciton resonance in CuCl leads to new plexcitonic modes. [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]

• Diverse applications of GNPs in microelectronics and biomedicine are explored. • GNPs' role in cancer therapy, drug delivery, and imaging. • Discussion on optimization methods for gold nanorods (GNRs) in nanophotonics. Gold nanoparticles (AuNPs) possess unique size-dependent optical, electronic, and chemical properties, making them auspicious and tunable nanoscale building blocks for microelectronics applications. This paper reviews recent advances in integrating AuNPs into miniaturized electronic components and devices to enhance performance and enable new functionalities. The tunable plasmonic behavior, electrical conductivity, and biocompatibility of AuNPs facilitate their integration into electronic circuits, printed electronics, optoelectronics, plasmonic, and biosensing devices. Functionalizing AuNPs with specific ligands permits selective biochemical interactions for biosensing. Controlled synthesis and assembly techniques allow AuNPs to be tailored and positioned precisely within microelectronic architectures. AuNPs synthesized with well-defined size and shape distributions and deposited on substrates using lithography, self-assembly, and layer-by-layer techniques act as versatile nanoscale components for fabricating miniaturized transistors, memory devices, photodetectors, plasmonic devices, and sensors. Ongoing review addresses reproducibility, stability, and scalability challenges to fully exploit their potential in microelectronics. Overall, this review highlights recent progress in harnessing the exceptional functional properties of AuNPs for innovating the next generation of microelectronic devices and biomedical applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Natural Au-bearing nanoparticles in five species of plants in the Yangshan gold deposit were analyzed. • Plants differ in terms of their absorption and tolerance of Au-bearing nanoparticles. • Anemone vitifolia was the Au-bearing-nanoparticle-enriched plants in Yangshan gold mine area. • Advances a new technology for gold deposit exploration using Au-bearing nanoparticles for the enrichment of plants. This study analyzes Au-bearing nanoparticles in five plant species (Anemone vitifolia, Taraxacum mongolicum, Artemisia argyi, Larix gmelinii, and Equisetum arvense) from the Yangshan gold deposit. Numerous Au-bearing nanoparticles were discovered in the five predominant plants within the ore deposit. It was found that plants differ in terms of their absorption and tolerance of Au-bearing nanoparticles. Among the five dominant plant species, Anemone vitifolia exhibits the highest absorption and accumulation capacity for Au-bearing nanoparticles, making it an Au-bearing-nanoparticle-enriched plants. The Au-bearing-nanoparticle-enriched plants which can super enrich Au-bearing nanoparticles store more abundant and intuitive information about deeply concealed gold ore bodies. Nanoparticles with similar composition and morphology were found in both the root and stem specimens of the Anemone vitifolia. It is shown that the Au-bearing nanoparticles in the stem cells were probably transported from the root. Furthermore, we discuss the relationship between Au-bearing nanoparticles in plants and deep concealed gold deposits and the process whereby Au-bearing nanoparticles migrate from gold orebodies to plants. The Au-bearing nanoparticles can carry information from the concealed gold ore body to the surface medium, and then be absorbed by the roots of Au-bearing-nanoparticle-enriched plants, gaining access to the aboveground parts of the plants. Therefore, this paper advances a new technology for gold deposit exploration using Au-bearing nanoparticles for the enrichment of plants. [ABSTRACT FROM AUTHOR]

Gold clusters are considered as widely used catalyst for chemical industry, but the efficiency of catalyst has been limited by the aggregation of the gold atoms, since the active sites are only located on the surface of the catalyst particles. In this paper the surface distribution of gold clusters influenced by spontaneous polarization and temperature is discussed. The morphology of the gold particle on different ferroelectric surface was simulated by the dissipative particle dynamics method, and the results are examined by pulsed laser deposition and Atomic Force Microscopy. The negatively poled surface with temperature adjustment could grow more dispersed gold clusters and offer a new progress to select the ferroelectric materials as the substrates for metal catalyst. [ABSTRACT FROM AUTHOR]

This paper reports x-ray photoemission spectroscopy results regarding the nucleation and growing process of gold nanoparticles (AuNPs) in CaO-SiO2-P2O5 bioactive glasses heat treated at different temperatures. The analysis of the valence band (VB) spectra is discussed in terms of the AuNPs' shape, size, and distribution at the sample surface at different temperatures. Moreover, the theoretical VB photoemission spectra of the investigated samples are presented, and their agreement with experimentally obtained spectra is discussed in detail. [ABSTRACT FROM AUTHOR]

In this paper, we show that when nanoparticles of Fe3O4 are coated with gold there is a distinct enhancement of magnetization by a factor of six. This increase of magnetization has been attributed to large orbital magnetic moment formation at the magnetic particle/Au (core/shell) interface. Our theoretical analysis indicates that the enhanced magnetism observed in Fe3O4-Au (core-shell) nanoparticles is an interfacial effect. The origin of magnetism in Au as an interfacial phenomenon is supported by the observation of positive magnetization in citrate coated gold nanoparticles. In citrate coated gold nanoparticles, we observe a crossover from positive magnetization value to negative magnetization value upon increasing magnetic field indicating cancellation of interfacial magnetization by the diamagnetic contribution from the bulk. We propose a theoretical formalism which semi-quantitatively explains our experimental results and supports the origin of magnetization in Au as an interfacial effect. [ABSTRACT FROM AUTHOR]

Irradiation with swift heavy ions of spherical Au nanoparticles confined within a silica matrix shapes them into prolate nanorods and nanowires whose principal axes are aligned along the beam direction. In the present paper, we investigate the role that is played by the initial nanoparticle size and concentration in this so-called ion-shaping mechanism. We have produced silica films wherein Au nanoparticles with average diameters of 15, 30, and 45 nm were embedded within a single plane and have irradiated these films at 300 K at normal incidence with 18, 25, and 54 MeV Ag ions. We demonstrate the existence of both threshold and saturation fluences for the elongation effects mentioned. The values of these critical fluences depend both on the ion energy and the initial nanoparticle size. Moreover, we show that 45 nm Au particles are not deformed when irradiated with 18 MeV Ag ions, such that this value corresponds to an energy threshold for the deformation process. As far as the influence of the nanoparticle concentration on the shaping characteristics is concerned, we have found that above the critical irradiation fluence, the deformation effect becomes very sensitive to the initial concentration of the nanoparticles. [ABSTRACT FROM AUTHOR]

This paper reports a method for the efficient formation of surface relief grating (SRG) on azopolymer films in which gold nanoparticles are dispersed. The height and shape of the SRG, which were formed by a two-beam interference technique, were found to be dependent on the content of gold nanoparticles. The optimum concentration of gold nanoparticles for the efficient formation of SRG was confirmed by atomic force microscopy (AFM), and the height of SRG at the content of 0.06 wt % was about 2.2 times higher than that of pure azopolymer film without gold nanoparticles. This is due to the field enhancement effect derived from the localized plasmon excitations of gold nanoparticles dispersed in the azopolymer film. [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]

Background: Biosensor-based detection provides a rapid and low-cost alternative to conventional analytical methods for revealing the presence of the contaminants in water as well as solid matrices. Although important to be detected, small analytes (few hundreds of Daltons) are an issue in biosensing since the signal they induce in the transducer, and specifically in a Quartz-Crystal Microbalance, is undetectable. A pesticide like parathion (M = 292 Da) is a typical example of contaminant for which a signal amplification procedure is desirable. Methods/Findings: The ballasting of the analyte by gold nanoparticles has been already applied to heavy target as proteins or bacteria to improve the limit of detection. In this paper, we extend the application of such a method to small analytes by showing that once the working surface of a Quartz-Crystal Microbalance (QCM) has been properly functionalized, a limit of detection lower than 1 ppb is reached for parathion. The effective surface functionalization is achieved by immobilizing antibodies upright oriented on the QCM gold surface by a simple photochemical technique (Photonic Immobilization Technique, PIT) based on the UV irradiation of the antibodies, whereas a simple protocol provided by the manufacturer is applied to functionalize the gold nanoparticles. Thus, in a non-competitive approach, the small analyte is made detectable by weighing it down through a “sandwich protocol” with a second antibody tethered to heavy gold nanoparticles. The immunosensor has been proved to be effective against the parathion while showing no cross reaction when a mixture of compounds very similar to parathion is analyzed. Conclusion/Significance: The immunosensor described in this paper can be easily applied to any small molecule for which polyclonal antibodies are available since both the functionalization procedure of the QCM probe surface and gold nanoparticle can be applied to any IgG, thereby making our device of general application in terms of target analyte. [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]

In this paper, a general method for making nanoscale Au–Fe3O4 clusters in an oil-in-water emulsion is reported, which involves thermolytic decomposition of Fe(acac)3 and reduction of AuCl3 in a hot oleyl amine–oleic acid mixture. A detailed investigation by transmission electron microscopy (TEM), X-ray diffraction, UV-vis, and vibrating-sample magnetometry was done in order to study the morphology and properties of the hybrid nanoparticulate clusters (NPCs). The NPCs are all spherical and their building blocks are individual Au and Fe3O4 nanoparticles (NPs) with an average diameter of 9.6 and 7.1 nm, respectively. TEM images show that these clusters have a flower-like morphology with controllable size. It is found that the cetyltrimethylammonium bromide concentration, the time, and the temperature of reaction are three important parameters that significantly affect the shape, size, and magnetic properties of these clusters. Magnetic measurements reveal the superparamagnetic behavior of individual NPs of Fe3O4 with a blocking $T_{\mathrm {B}}= 80.2$ K. The blocking temperature is significantly shifted to higher temperatures in the case of the clusters. The Au–Fe3O4 NPCs show a plasmonic peak at 530 nm and have a much higher magnetization than the individual NPs, making them better suited for biomedical applications. [ABSTRACT FROM AUTHOR]

In this paper, we propose a novel technique to overcome the conductance limitation in metal contacted single-walled carbon nanotubes (SWNTs)-based devices using metal nanoparticles (MNPs). Schottky barrier (SB) height at metal-SWNTs contact is believed to be the major contributor for this conductance limitation. Metal contacts with SWNTs are fabricated on a thermally grown SiO2/Si substrate using a conventional lithography process. The SWNTs are aligned between the metal electrodes using dielectrophoresis method. MNPs are introduced in the device using a small drop of MNP suspension to decorate the SWNTs. It is observed that the introduction of MNPs in the device reduces the SB height significantly. We found 0.34 eV reduction in SB height with silver (Ag) nanoparticles (NPs) and 0.15 eV with gold (Au) NPs. The proposed technique has improved the conductance in decorated SWNTs four times for Ag and Au NPs as compared to the bare SWNTs. Improvement in the conductance behavior of the SWNTs using MNPs enhances the sensitivity and switching speed of the devices, therefore, make it a promising alternative to silicon-based devices. [ABSTRACT FROM AUTHOR]

Three-dimensional large scale integration (3D-LSI) packaging is crucial toward obtaining increased circuit density within a small footprint. In a 3D-LSI package, chip-to-chip interconnection is typically obtained using through-silicon vias and microbumps. In particular, microbumps realized by nanoparticle deposition (NPD) are promising to obtain high-density interconnections. However, the effect of temperature on the mechanical properties (i.e., hardness) of NPD bumps is little understood. This paper seeks to investigate the influence of temperature on the hardness of NPD bumps, with reference to NPD films. The results obtained suggest a significant reduction in the NPD bump hardness from room temperature to 200 °C. In particular, the hardness was observed to be mainly dependent on temperature rather than grain size, as the grain microstructures obtained at room temperature and 200 °C are similar. Overall, these results suggest a simple approach to control the NPD bump compression during flip-chip bonding, where the hardness-temperature data for the NPD bumps suffices to estimate for the bump compression during flip-chip bonding. [ABSTRACT FROM AUTHOR]

Microelectrode Arrays are established platforms for biosensing applications; however, limitations in electrode impedance and cell-electrode coupling still exist. In this paper, the SNR of $25~\mu \text{m}$ diameter gold (Au) microelectrodes was improved by decreasing the impedance with precision electrodeposition. SEM determined that N-P Pt. microelectrodes had nano-porous structures that filled the insulation cylinders. EIS, CV, and RMS noise measurements concluded that the optimized electrodeposition of N-P Pt. led to a lowered impedance of $18.36~\text {k}\Omega \pm 2.6~\text {k}\Omega $ at 1 kHz, a larger double layer capacitance of 73 nF, and lowered RMS noise of $2.08 \pm 0.16~\mu \text{V}$ as compared to the values for Au of $159~\text {k}\Omega \pm 28~\text {k}\Omega $ at 1 kHz, 17nF, and $3.14 \pm 0.42~\mu \text{V}$ , respectively. Human motoneurons and human cardiomyocytes were cultured on N-P Pt. devices to assess their biocompatibility and signal quality. In order to improve the cell-electrode coupling, a precision plating technique was used. Both cell types were electrically active on devices for up to 10 weeks, demonstrated improved SNR, and expected responses to precision chemical and electrical stimulation. The modification of Au microelectrodes with nanomaterials in combination with precision culturing of human cell types provides cost effective, highly sensitive, well coupled and relevant biosensing platforms for medical and pharmaceutical research. [2018-0187] [ABSTRACT FROM AUTHOR]

Recently, uniform metal-assisted chemical etching (UMaCE) has been demonstrated as an effective wet etch method for fabrication of deep trenches and holes on silicon (Si). However, attempts to achieve higher aspect ratio by UMaCE was not successful because etching in random directions was observed. In this paper, the etching uniformity in UMaCE is systematically studied at different etching solution composition and catalyst configuration. The surface chemistry evolution of Si during etching is characterized by X-ray photoelectron spectroscopy, water contact angle, and electrical impedance spectroscopy. Based on the data, the reaction kinetics is analyzed, which shows that an electropolishing-type charge transport and a higher amount of oxide species on Si surface help mitigate the random etching behavior and effectively promote the aspect ratio of the etching with uniformity. Under the rationalized condition, uniform trenches with width of $2~\mu \text{m}$ and aspect ratio of 120:1 is successfully fabricated by UMaCE. [2018-0212] [ABSTRACT FROM AUTHOR]

Biomass constitutes a renewable source for new chemical platforms. Among other processes the catalytic ones represent a green alternative when active and selective catalysts can be developed. In this paper, applications of gold and gold‐based catalysts have been reviewed in the field of the selective oxidations. Indeed, from the discovery of the peculiarity of gold as catalytic material, the liquid phase oxidations have been differently viewed. Three important biomass‐derived molecules, namely glucose, hydroxymethyl furfural (HMF) and glycerol have been considered as precursors for products of industrial interest where gold catalysts have played an important role. This review starts from the research on monometallic gold catalysts which have been explored initially and then look at gold as modifier of other metal catalyst. This latter field is still in evolution and probably needs to be look at in the future. Golden path: Applications of gold and gold‐based catalysts for selective liquid‐phase oxidation of biomass‐derived products have been reviewed. Three important molecules, namely glucose, hydroxymethyl furfural (HMF) and glycerol have been considered as precursors for products of industrial interest. [ABSTRACT FROM AUTHOR]

Nanoparticles are very fascinating area of science not only due to their unique properties but also possibility of producing new more complex materials, which may find an application in modern chemistry, engineering and medicine. In process of nanoparticles formation very important aspect is a rate of individual stage i.e. reduction, nucleation and autocatalytic growth, because this knowledge allows for proper materials design, morphology manipulation, stability. The last one aspect can be realized using proper electrostatic, steric and electrosteric stabilization. However until now nobody reports and measures kinetic rates of all stages during process of particles formation in the presence of steric stabilizers. Thus, the main contribution of this paper is determination of individual rate constants for nanoparticles formation in the presence of steric stabilizers and their comparison to the system without stabilizer. For this purpose, an aqueous solution of Au(III) and Pt(IV) ions were mixed with steric stabilizers like PVA and PVP, and reduced using L-ascorbic acid as a mild and sodium borohydride as a strong reductant. As a results stable nanoparticles were formed and process of their formation was registered spectrophotometrically. From obtained kinetic curves the values of observed rate constants for reduction metal ions, slow nucleation and fast autocatalytic growth were determined using Watzky-Finke model. It was found that the addition of polymer affects the rate of the individual stages. The addition of steric stabilizers to gold ions reduced with L-ascorbic acid causes that the process of nucleation and autocatalytic growth slows down and the value of observed rate constants for nucleation changes from 3.79·10-3 (without polymer) to 7.15·10-5s-1 (with PVA) and for growth changes from 1.15·103 (without polymer) to 0.48·10²s-1M-1 (with PVA). However, the rate of the reduction reaction of Au(III) ions is practically unchanged. In case of using strong reductant the addition of polymer effects on the shape of kinetic curve for reduction of Au(III) and it suggests that mechanism is changed. In case of Pt(IV) ions reduction with L-ascorbic acid, the process speeds up a little when PVA was added. Determined values of observed rate constants for nucleation and growth platinum nanoparticles decrease twice comparing to the system without polymer. The reduction of Pt(IV) ions with sodium borohydride accelerates when PVP was added and slows down when PVA was used. Moreover, the size of obtained colloidal gold and platinum was also analysed using DLS method. Obtained results (rate constants) may be useful in the process of nanomaterials synthesis, in particular in microflow. [ABSTRACT FROM AUTHOR]

In this paper, we aimed at investigating the effect of the presence of small TiO2 crystallites over the transfer of hot electrons from Au nanoparticles (NPs) mediated by the surface plasmon resonance (SPR) excitation and its subsequent photocatalytic activities. To this end, we employed TiO2 colloidal spheres composed of TiO2 crystallites of 8.5 nm in size decorated with Au NPs (TiO2–Au) of 17 nm in size over the TiO2 surface as model materials. Moreover, the photocatalytic degradation of methylene blue (MB) under visible light excitation was employed as a target plasmonic transformation. We found that the plasmonic photocatalytic activity was significantly higher for the TiO2–Au hybrid relative to its individual Au NPs or TiO2 counterparts under excitation at 633 nm. These results could be explained based on the transfer of hot electrons generated upon the SPR excitation from Au NPs to the TiO2 conduction band in the TiO2–Au material, which will be recombined on the surface of TiO2 crystallites or at the interface between TiO2 crystallites, decreasing electrons density in Au NPs that lead to the formation of hydroxyl radicals that contribute and improve the photocatalytic degradation of MB. This mechanism was supported by the fact that the presence of TiO2 leads to a decrease in the p‐aminothiophenol to p,p′‐dimercaptoazobenzene SPR‐mediated oxidation in the TiO2–Au relative to Au NPs. We believe that the results reported herein suggest that TiO2–Au materials may represent attractive systems for designing plasmonic photocatalysts with improved performances towards a variety of transformations using solar/visible light as the energy input. TiO2–Au material presented improved plasmonic photocatalytic activity under visible light. TiO2 formed by small crystallites enhances plasmonic photocatalytic performance. This mechanism involving the transfer of SPR‐excited hot electrons from Au to TiO2 was further supported by probing the SPR‐mediated catalytic oxidation of p‐aminothiophenol (PATP) to p,p′‐dimercaptoazobenzene (DMAB). [ABSTRACT FROM AUTHOR]

The influence of the size and oxidation state of Au nanoparticles (AuNPs) as electrocatalysts for the electro-oxidation of cellulose was studied. Carbon paper electrodes modified with AuNPs were used as the electrocatalysts for the electro-oxidation of cellulose dissolved in 1.3 m NaOH. The size and oxidation state of the AuNPs were determined by using SEM, TEM, and X-ray photoelectron spectroscopy. Both the size and the oxidation state of the AuNPs were found to influence the electrocatalytic properties of the electrode, as studied by using cyclic voltammetry, square wave voltammetry, and electrochemical impedance spectroscopy. The carbon paper electrodes decorated with AuNPs (less than 25 nm) that consist of metallic Au gave rise to a significantly higher electrocatalytic activity than a bare polycrystalline Au electrode. [ABSTRACT FROM AUTHOR]

The preparation and stabilization of gold nanoparticles with a precise control of size and dispersion is highly attractive for a variety of applications, and a key aspect is thermal stability of the nanoparticles. This paper focuses on understanding the effect of TiO 2 -based nanodomains, dispersed on mesoporous silicas, and how they control gold nanoparticle stability. The anatase domains have been incorporated through two different strategies: co-hydrolysis of Si and Ti reagents that directly form the mesoporous material through self-assembling with surfactant micelles, or the post-impregnation of the mesosporous silica with Ti(acac) 2 . Both strategies lead to different incorporation of the anatase domains: partially embedded inside the silica walls, or occupying the mesopores. We have observed that the inclusion in the pores favors the stability of the final material due to a more favorable gold-support interaction and also due to a stabilizing effect associated with a scaffold effect of the anatase crystals, which hinders the collapse of the mesostructure. [ABSTRACT FROM AUTHOR]

Abstract: Mg(OH)2‐ and Mg(OH)2‐containing materials can provide excellent performance as supports for AuPd nanoparticles for the oxidation of glycerol in the absence of base, which is considered to be a result of additional basic sites on the surface of the support. However, its influence on the reaction solution is not generally discussed. In this paper, we examine the relationship between the basic Mg(OH)2 support and AuPd nanoparticles in detail using four types of catalyst. For these reactions, the physical interaction between Mg(OH)2 and AuPd was adjusted. It was found that the activity of the AuPd nanoparticles increased with the amount of Mg(OH)2 added under base‐free conditions, regardless of its interaction with the noble metals. In order to investigate how Mg(OH)2 affected the glycerol oxidation, detailed information about the performance of AuPd/Mg(OH)2, physically mixed (AuPd/C+Mg(OH)2) and (AuPd/C+NaHCO3) was obtained and compared. Furthermore, NaOH and Mg(OH)2 were added during the reaction using AuPd/C. All these results indicate that the distinctive and outstanding performance of Mg(OH)2 supported catalysts in base‐free condition is in fact directly related to its ability to affect the pH during the reaction and as such, assists with the initial activation of the primary alcohol, which is considered to be the rate determining step in the reaction. [ABSTRACT FROM AUTHOR]

A nanoparticle has been reported as a promising lubricant to increase the durability of microelectromechanical systems (MEMS) switches, but there remains much room for development and scientific observations. In this paper, we present the fabrication and research platform for a nanoparticle lubricated MEMS switch; we measured its characteristics and investigated the mechanisms behind it. In the measurements, gold nanoparticle lubrication demonstrated an increased average adhesion force from 16.38 to 23.68 \mu \textN by 44.51% and a decreased average electrical contact resistance from 211.20 to 49.85 \textm\Omega by 76.40%. In a hot switching mode lifetime test, the gold nanoparticle lubricated MEMS switch exhibited extension of reliability from 5.13\times 10^4 to 4.75\times 10^5 cycles, which corresponds to 9.26-fold increase. We attribute this remarkable enhancement to a mechanical stress release via lateral deformation of the nanoparticle and refreshment of the contact spots owing to movement of nanoparticles. [2017-0127] [ABSTRACT FROM PUBLISHER]

In this paper we report synthesis of aqueous based gold coated iron oxide nanoparticles to integrate the localized surface plasma resonance (SPR) properties of gold and magnetic properties of iron oxide in a single system. Iron oxide-gold core shell nanoparticles were stabilized by attachment of thiolated sodium alginate to the surface of nanoparticles. Transmission electron microscope (TEM) micrograph presents an average elementary particle size of 8.1 ± 2.1 nm. High resolution TEM (HR-TEM) and X-ray photon spectroscopy further confirms the presence of gold shell around iron oxide core. Gold coating is responsible for reducing saturation magnetization (M s ) value from ~ 41 emu/g to ~ 24 emu/g – in thiolated sodium alginate stabilized gold coated iron oxide core-shell nanoparticles. The drug (curcumin) loading efficiency for the prepared nanocomposites was estimated to be around 7.2 wt% (72 μg drug/mg nanoparticles) with encapsulation efficiency of 72.8%. Gold-coated iron oxide core-shell nanoparticles could be of immense importance in the field of targeted drug delivery along with capability to be used as contrast agent for MRI & CT. [ABSTRACT FROM AUTHOR]

The immobilization of nanoparticles (NPs) is of great interest to many technological applications and scientific fields. Methods to immobilize NPs either lack the uniformity, robustness and controllability or require complex and impractical preparation techniques. This paper aims in closing this gap by presenting practical routes in preparation of poly(2-vinyl pyridine) (P2VP) brush grafted silicon oxide terminated substrates for immobilization of NPs. Here, we demonstrate that hydroxyl-terminated P2VP can be deposited using different coating techniques and grafted in air at processing times as short as a few minutes. The grafted P2VP brushes can immobilize spherical Au nanoparticles that are 20 nm in diameter, on the surface of substrates with densities as high as ∼600 particles/μm 2 . The density of the immobilized NPs can be further tuned with the grafting conditions and duration of the particle treatment. More than 80% of the grafted brushes and Au NPs remain on the substrate following abrasion tests proving mechanical robustness of the coatings. The immobilized Au NPs can impart surface enhanced Raman scattering effects in sensing of molecules, illustrating a representative use of the presented platform. [ABSTRACT FROM AUTHOR]

Titania-supported gold nanoparticles exhibit excellent low-temperature carbon monoxide (CO) oxidation activity, which is sensitive to the structure of the TiO2 support and the preparation method. In this paper, gold catalysts were prepared on TiO2 with different anatase-to-rutile ratios by the deposition–precipitation method (Au/TiO2-C) and plasma-assisted deposition–precipitation method (Au/TiO2-PC). The highest performance for CO oxidation was obtained over Au/TiO2 for an anatase-to-rutile ratio of 4:6, which may be ascribed to the phase transformation mechanism of TiO2 and the preferential deposition of Au nanoparticles on rutile TiO2 in the deposition–precipitation process. Therefore, enlarged contact surface between the Au nanoparticles and the TiO2 support was obtained, and more oxygen vacancies may be formed, which are beneficial to CO oxidation. Interestingly, compared with Au/TiO2-C, Au/TiO2-PC exhibited enhanced CO oxidation activity. For example, the reaction rate ( $\xi )$ at 30 °C for CO oxidation over Au/TiO2-PC was about 5.8 times greater than that over Au/TiO2-C for an anatase-to-rutile ratio of about 4:6, which was primarily caused by the more active gold species on the surface of TiO2 support in Au/TiO2-PC due to the Coulomb interaction during plasma preparation. [ABSTRACT FROM AUTHOR]

Traditional Feigl's spot tests can be greatly improved with the aid of gold nanoparticles and Raman probes, by monitoring the changes in the surface enhanced Raman scattering (SERS) of the analytes directly applied on a filter paper previously impregnated with the selective organic reagent. As a proof of concept, diphenyithiocarbazone (dithizone) was treated with citrate stabilized gold nanoparticles and employed in paper spot tests for a variety of transition and heavy metal ions. Below 10-5 mol L-1, only mercury(II) ions were able to displace the dithizone molecules from the "coordination shell" of the gold nanoparticles, leading to a systematic decay of the Raman signals. Because of the huge enhancement of the dithizone vibrational peaks, the SERS spot tests allowed the detection of picograms of Hg2+ ions. [ABSTRACT FROM AUTHOR]

Many papers have been written on the synthesis of gold nanoparticles but very few included pictures of the process, and none of them used video to show the whole process of synthesis. This paper records the process of synthesis of gold nanoparticles using video clips. Every process from cleaning of glassware, an important step in the synthesis of metallic nanoparticles, to the dialysis process is shown. It also includes the preparation of aqua regia and the actual synthesis of gold nanoparticles. In some papers, the dialysis process was omitted, but in this paper, it is included to complete the whole process as it is being used for purification. [ABSTRACT FROM AUTHOR]

Functional nanomaterials have recently attracted strong interest from the biology community, not only as potential drug delivery vehicles or diagnostic tools, but also as optical nanomaterials. This is illustrated by the explosion of publications in the field with more than 2,000 publications in the last 2 years (4,000 papers since 2000; from ISI Web of Knowledge, 'nanoparticle and cell' hit). Such a publication boom in this novel interdisciplinary field has resulted in papers of unequal standard, partly because it is challenging to assemble the required expertise in chemistry, physics, and biology in a single team. As an extreme example, several papers published in physical chemistry journals claim intracellular delivery of nanoparticles, but show pictures of cells that are, to the expert biologist, evidently dead (and therefore permeable). To attain proper cellular applications using nanomaterials, it is critical not only to achieve efficient delivery in healthy cells, but also to control the intracellular availability and the fate of the nanomaterial. This is still an open challenge that will only be met by innovative delivery methods combined with rigorous and quantitative characterization of the uptake and the fate of the nanoparticles. This review mainly focuses on gold nanoparticles and discusses the various approaches to nanoparticle delivery, including surface chemical modifications and several methods used to facilitate cellular uptake and endosomal escape. We will also review the main detection methods and how their optimum use can inform about intracellular localization, efficiency of delivery, and integrity of the surface capping. [ABSTRACT FROM AUTHOR]

This paper reports a method for assembling midnanosized Au nanoparticles (25 < d< 100 nm) into close-packed 2D arrays with a high degree of local order. An in situ coating of Au nanoparticles with an alkanethiol surfactant can induce close-packed particle arrays when the nanoparticles are trapped at the interface. The film morphology was determined to be either monoparticulate or multiparticulate depending on the 1-dodecanethiol concentration. This paper reports on the optimum conditions for the formation of a close-packed 2D array by suggesting a phase diagram obtained from a plot of the 1-dodecanethiol concentration versus the nanoparticle diameter. When the diameter of Au nanoparticles was larger than ca. 40 nm, the full coverage of 1-dodecanethiols on the surface of nanoparticles was not enough to form close-packed nanoparticle arrays. The larger nanoparticles required the more 1-dodecanethiols to form a close-packed 2D array. This method also allows the nanoparticle surface to be coated asymmetrically with 1-dodecanethiols, which was confirmed qualitatively from contact angle measurements. [ABSTRACT FROM AUTHOR]

This paper reports our novel approach in an attempt to grow high-density gold nanoparticles on an indium tin oxide (ITO) surface using an improved “touch” seeding technique, instead of the “normal” seeding approach, in a seed-mediated growth procedure as we reported previously [Kambayashi et al., Cryst. Growth Des. 2005, 5, 81−84]. The present approach provides a simple and useful strategy to promote the growth of gold nanoparticles on ITO surfaces by simply touching the surface that has already been covered with a drop of gold nanoparticle seed solution with a tissue paper. The FE-SEM characterization of the growth of gold nanoparticles on two different surface structures, i.e., rough and smooth structures, has confirmed that this approach is very effective and prospective in fostering the growth of high-density gold nanoparticles with a relatively small size (ca. 10−30 nm) of spherical-like structure. An optical properties study confirmed that the modified ITO system could be used as a functionalized optically transparent electrode for spectro- and photoelectrochemical applications. [ABSTRACT FROM AUTHOR]

Abstract: The recent interest in gold catalysis provides the focus for this perspectives paper. Until recently gold has been overlooked as a key component of both homogeneous and heterogeneous catalysts. Two observations in the 1980s showed that gold could be a catalyst of choice, but it is only relatively recently that gold has been shown to be a very versatile redox catalyst. In this paper aspects of both the background to this interest and some of the recent work on gold will be discussed. [Copyright &y& Elsevier]