Spherical Shaped Gold Nanoparticles Research Articles

Efficient nitrite determination by electrochemical approach in liquid phase with ultrasonically prepared gold-nanoparticle-conjugated conducting polymer nanocomposites.

An electrochemical nitrite sensor probe is introduced herein using a modified flat glassy carbon electrode (GCE) and SrTiO3 material doped with spherical-shaped gold nanoparticles (Au-NPs) and polypyrrole carbon (PPyC) at a pH of 7.0 in a phosphate buffer solution. The nanocomposites (NCs) containing Au-NPs, PPyC, and SrTiO3 were synthesized by ultrasonication, and their properties were thoroughly characterized through structural, elemental, optical, and morphological analyses with various conventional spectroscopic methods, such as field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, high-resolution transmission electron microscopy, powder X-ray diffraction, X-ray photoelectron spectroscopy, and Brunauer-Emmett-Teller method. The peak currents due to nitrite oxidation were characterized in detail and analyzed using conventional cyclic voltammetry (CV) as well as differential pulse voltammetry (DPV) under ambient conditions. The sensor response increased significantly from 0.15 to 1.5mM of nitrite ions, and the sensor was fabricated by coating a conducting agent (PEDOT:PSS) on the GCE to obtain the Au-NPs/PPyC/SrTiO3 NCs/PEDOT:PSS/GCE probe. The sensor's sensitivity was determined as 0.5μA/μM∙cm2 from the ratio of the slope of the linear detection range by considering the active surface area (0.0316cm2) of the flat GCE. In addition, the limit of detection was determined as 20.00 ± 1.00 µM, which was found to be satisfactory. The sensor's stability, pH optimization, and reliability were also evaluated in these analyses. Overall, the sensor results were found to be satisfactory. Real environmental samples were then analyzed to evaluate the sensor's reliability through DPV, and the results showed that the proposed novel electrochemical sensor holds great promise for mitigating water contamination in the real samples with the lab-made Au-NPs/PPyC/SrTiO3 NC. Thus, this study provides valuable insights for improving sensors for broad environmental monitoring applications using the electrochemical approach.

Green decorated of gold nanoparticles over kaolin mediated by plant extract and investigation of its anti-bile duct cancer properties in the in vitro condition

In the current research, kaolin-decorated Au nanoparticles were produced by a green medication method by using Strawberry root’s extract as a natural coating and reducing component for capping and stabilizing Au NPs over the kaolin. The Au NPs/kaolin material was thoroughly characterized using XRD, FE-SEM, EDX-elemental mapping, TEM, and ICP. Characterization data confirmed the well-supporting of Au NPs over the kaolin. TEM images displayed the spherical shaped gold nanoparticles averaging 20–40 nm in size over the kaolin surface. The cytotoxicity and anti-bile duct cancer properties of Au NPs/kaolin were investigated through the utilization of MTT assay on three bile duct cancer cell lines, namely OCUCHLM1, EGI1, and GBCSD. Au nanoparticles (Au NPs) combined with kaolin exhibited dose-dependent anti-bile duct cancer properties and significantly reduced cell viability in OCUCHLM1, EGI1, and GBCSD cell lines. Importantly, these effects were observed without causing any cytotoxicity in the normal cell line (HUVECs). The OCUCHLM1 cell line exhibited the most significant anti-bile duct cancer effects when treated with Au NPs/kaolin, surpassing the results observed in other cell lines. Upon the successful validation of the aforementioned findings in the clinical trial investigations, Au NPs/kaolin could potentially serve as an effective chemotherapeutic agent in combating bile duct cancer.

Optimization and evaluation of anticancer, antifungal, catalytic, and antibacterial activities: Biosynthesis of spherical-shaped gold nanoparticles using Pistacia vera hull extract (AuNPs@PV)

In the past years, use of plant sources for the biosynthesis of nanoparticles has become very important. Gold nanoparticles with unique biological properties are one of these materials which are being investigated extensively. In the present study, the aqueous extract of Pistacia vera hull was utilized to fabrication of gold nanoparticles (AuNPs@PV) in a facile, environmentally friendly, and affordable way. Then the anticancer, antifungal, antibacterial, and photocatalytic potentials of AuNPs@PV were also investigated. The results of various techniques applied, including XRD, UV–vis, TEM, FT-IR, EDS, and FESEM showed the biological reduction of Au3+ ions to Au0. Antibacterial studies were performed on a wide range of bacteria including seven strains of ATCC and seven strains of drug-resistant pathogens. According to the findings of this research, it seems that biosynthesized gold nanoparticles had good antibacterial activity against ATCC and drug-resistant strains of bacteria. The MIC values of E. coli, S. aureus, P. mirabilis, P. aeruginosa, E. faecalis, K. pneumonia, A. baumannii were 34.37, 4.2, 8.59, 4.29, 0.5, 34.37, and 8.59 μg/mL, respectively. The result of the antifungal investigation showed that two pathogenic fungi, Candida albicans (IFRC1873) and Candida albicans (IFRC1874) were susceptible to AuNPs@PV with MIC values of 550 and 137 μg/mL, respectively. Furthermore, AuNPs@PV revealed noteworthy anticancer efficacy against AGS-3 and MCF-7 cell lines with IC50 values of 58.31 and 148.1 μg/mL, respectively. The results of the cytotoxicity effect of AuNPs@PV on BEAS-2B as a normal cell line indicated the selectivity of AuNPs@PV on cancerous cells. Furthermore, the fabricated AuNPs@PV under UV irradiation exhibited significant potential in the decolorization of methylene orange (MO) with a percent decolorization of 91.5 % after 20 min. Therefore, it can be concluded that biosynthesized gold nanoparticles as a photocatalyst, anti-bacterial, antifungal, and anti-cancer agents have potential applications in the fields of environment and biology.

Fast responsive optically functionalized mesoporous gold nanostructures for pH sensing

Two different routes turkivish and sol-gel methods are used to synthesize sodium citrate and polyethylene glycol functionalized gold nanostructures. Field emission scanning electronmicroscope (FESEM) analysis confirms spherical-shaped gold nanoparticles (AuNPs) and self-assembled Au nanodendritic (AuNDs) structures. High-resolution transmission electron microscopy (HRTEM) confirmed the spherical and dendritic morphology with particle sizes 9 nm of AuNPs and 3 nm of AuNDs, respectively. An atomic force microscope (AFM) shows average surface roughness (Ra) ∼2.5 nm of AuNPs which is reduced to 1.5 nm in AuNDs. The AuNPs and AuNDs show heterogeneous chemical bonding and thermal stability at high temperatures. Brunauer-Emmett-Teller-based surface area is calculated at around 18 m2/g for AuNPs and 54 m2/g for AuNDs. The creosol red immobilized AuNPs (CR-AuNPs) and AuNDs (CR-AuNDs) sol demonstrate pka around 8.9 and 9.2 at 575 nm, respectively. The CR-AuNDs sol exhibit a time reaction 0.5 s which is relatively high than CR-AuNPs ∼0.6 s. Both Au-structures show non-leachable behavior.

Fabrication of a Low Cost Triboelectric Nanogenerator (TENG) for Wearable Devices

During the last few years, considerable research has been conducted for the design and development of the self-powered devices to supply sustained power to various electronic devices by converting waste mechanical energy into useful electrical energy. Out of many energy sources available in nature, mechanical energy has attracted the researchers due to its availability in abundance. Various methods such as an electromagnetic [1], electrostatic [2] and piezoelectric [3] are being used for converting this waste mechanical energy into useful electrical energy. A novel, eco-friendly and highly reliable triboelectric nanogenerator (TENG) with low cost of fabrication has been considered for fabrication of proposed device [4]. Contact electrification process has been used at the interface of two different materials (metal and a polymer) to generate the electrical energy in the proposed TENG. In order to enhance the surface charge density of the contact electrification process, it is required that the surface area of contact should be increased by surface engineering using micro and nanostructures [5]. Many studies have shown the polymer surface engineering by various processes like template based moldings and plasma treatment [6], surface engineering on the metals like gold nanoparticles (AuNP’s) of different shapes and sizes on the other hand have shown various applications where gold have been used such as in sensors as it is highly robust against the oxygen present in the air and thus it may not get corroded or oxidized unlike other metals. With the deposition of gold nanoparticles on the surface of the metal, an improvement in the output parameters will be observed as compared with the metal without any surface engineering. Another advantage of using gold nanoparticles is that no special protection packaging is required in order to protect the TENG device because of the gold’s robustness against oxygen. The surface stability of gold nanoparticles makes them suitable in various TENG applications.In this paper, we present a very simple technique to fabricate a triboelectric nanogenerator consisting of aluminum and PDMS (Polydimethylsiloxane) layers to harvest mechanical energy present in our surroundings. The proposed TENG device is capable of generating electricity by the process of contact-separation based triboelectrification between the anodic layer of aluminum (metal) and a cathodic layer of PDMS (polymer). To improve the performance of fabricated TENG, spherical shaped gold nanoparticles were synthesized and sprayed on the metallic layer to increase its contact area by increasing the surface roughness. In order to characterize the samples, various characterization techniques has been used like FESEM (Field Emission Scanning Electron Microscopy) and EDS (Energy Dispersive X-ray Spectroscopy). With the application of static weights/ force by hand on the fabricated TENG device, an open circuit voltage of 169 mV, short circuit current of 120.4 µA and maximum output power of 6.006µW has been achieved for an applied load resistance of 68 kΩ. Further the voltage, current and power output performance of the fabricated device has been measured and studied for different load resistances. The fabricated TENG demonstrates its application in the self-powered systems and wearable devices. The deposition of gold nanoparticles (AuNP’s) on the surface of the aluminum metal results in increasing the surface charge density with an increase in the surface area of contact between the metal and the PDMS based polymer layer. The device is sandwiched and force is applied either by fingers or by the use of static weights. With the variations in the force applied, there is a variation in various parameters like open circuit voltage, short circuit current and power. From the results it has been observed that the AuNP’s based TENG generates good results in spite of the fact that the gold has inferior triboelectric coefficient as compared with other metals. The AuNP’s based TENG so fabricated shows high robustness even in very hot and humid environment. References Bin, et al. Electromagnetic Energy Harvesting from Vibrations of Multiple Frequencies. J. Micromechanics Microengineering 19, 035001 (2009).Suzuki, , Miki, D., Edamoto, M. &Honzumi, M.A MEMS Electrets Generator with Electrostatic Levitation for Vibration-Driven Energy-Harvesting Applications. J. Micromechanics Micro engineering 20, 104002 (2010).Seol, M. L. et al. Design Strategy for a Piezoelectric Nanogenerator with a Well Ordered Nano shell ACS Nano 7, 10773–10779 (2013).Li, , Sun, J. & Chen, M. Triboelectric Nanogenerator Using Nano AgInk as Electrode Material. Nano Energy 3, 95–101 (2014).Fan, -R. et al. Transparent Triboelectric Nanogenerators and Self-Powered Pressure Sensors Based on Micro patterned Plastic Films. Nano Lett. 12, 3109–3114(2012).Bai, et al .Integrated Multilayered Triboelectric Nanogenerator for Harvesting Biomechanical Energy from Human Motions. ACS Nano 7, 3713–3719 (2013). Figure 1

Optimizing and Quantifying Gold Nanospheres Based on LSPR Label-Free Biosensor for Dengue Diagnosis

The localized surface plasmon resonance (LSPR) due to light–particle interaction and its dependence on the surrounding medium have been widely manipulated for sensing applications. The sensing efficiency is governed by the refractive index-based sensitivity () and the full width half maximum (FWHM) of the LSPR spectra. Thereby, a sensor with high precision must possess both requisites: an effective and a narrow FWHM of plasmon spectrum. Moreover, complex nanostructures are used for molecular sensing applications due to their good values but without considering the wide-band nature of the LSPR spectrum, which decreases the detection limit of the plasmonic sensor. In this article, a novel, facile and label-free solution-based LSPR immunosensor was elaborated based upon LSPR features such as extinction spectrum and localized field enhancement. We used a 3D full-wave field analysis to evaluate the optical properties and to optimize the appropriate size of spherical-shaped gold nanoparticles (Au NPs). We found a change in Au NPs’ radius from 5 nm to 50 nm, and an increase in spectral resonance peak depicted as a red-shift from 520 nm to 552 nm. Using this fact, important parameters that can be attributed to the LSPR sensor performance, namely the molecular sensitivity, FWHM, , and figure of merit (FoM), were evaluated. Moreover, computational simulations were used to assess the optimized size (radius = 30 nm) of Au NPs with high FoM (2.3) and sharp FWHM (44 nm). On the evaluation of the platform as a label-free molecular sensor, Campbell’s model was performed, indicating an effective peak shift in the adsorption of the dielectric layer around the Au NP surface. For practical realization, we present an LSPR sensor platform for the identification of dengue NS1 antigens. The results present the system’s ability to identify dengue NS1 antigen concentrations with the limit of quantification measured to be 0.07 μg/mL (1.50 nM), evidence that the optimization approach used for the solution-based LSPR sensor provides a new paradigm for engineering immunosensor platforms.

Photo-Driven Synthesis of Anisotropic Gold Nanoparticles Using Silk Fibroin—Cell Viability Activities in Lymphocyte and Jurkat Cancer Cells

A simple, environmentally benign and low-cost method for the synthesis of different-shaped gold nanoparticles using silk fibroin (SF) under ultraviolet (UV-B) radiation has been reported in this work. No additives such as organic solvents, surfactants, external reducing, stabilizing agents or high temperature were used for the synthesis of the particles. SF acts as a reducing and subsequently, stabilizing agent. The UV-Visible (UV-Vis) absorption spectra support the formation of different-shaped gold nanoparticles by displaying transverse and longitudinal surface plasmon bands at different wavelengths. The size and shape evolution of the nanoparticles was studied using the transmission electron microscope (TEM) to confirm the formation of different-shaped particles. Nano-crystalline structure and FCC crystal family of gold were confirmed by X-ray diffraction (XRD) measurement study. Furthermore, the proliferative activities of the synthesized colloidal gold nanoparticles were tested against lymphocyte and Jurkat cancer cell lines. The obtained results proved that the biogenic different-shaped AuNPs showed better activity in comparison with the spherical-shaped gold nanoparticles.

Mechanism of visible-light-driven photocatalytic degradation of endosulfan pesticide by gold nanoparticles

Spherical shaped gold nanoparticles (GNPs) of size around ∼9 nm were successfully used for photocatalytic degradation of hazardous endosulfan (ES) pesticide. GNPs absorb sunlight at ambient condition in aqueous medium to enhance localized surface plasmon resonance (LSPR) which initiate hydrolysis, oxidation and reduction chemical reactions for the mineralization of ES molecules. Infrared transmittance spectra of GNPs treated ES solutions revealed formation of amorphous carbon and hydrocarbon as final reaction products indicating the nearly complete mineralization of ES as evidenced from their TEM images also. The disappearance of chloro carbon and sulphite functional groups peaks of ES in IR transmittance spectra confirmed their degradation. TEM images also support the optical absorption spectra consisting of inter-band and LSPR bands pertaining to individual and clustered GNPs ensembles. The redshift in LSPR absorption peak positions along minor and major axis of clustered GNPs ensembles is attributed to the change in GNPs polarizability on interaction with the electric component of visible light. The chemical reaction pathway for ES molecule degradation by the photocatalytic GNPs has been proposed in the light of inferences drawn from TEM images, IR transmittance and optical absorption spectra.

Quats stabilized gold nanospheres for efficient ligand exchange procedure

In present work, fine spherical shaped gold nanoparticles are prepared by using a new type of quaternary ammonium cationic surfactant (quats) i.e. didecyldimethylammonium chloride (DDAC) following one step room temperature method. Optical characterization and crystal symmetry has been observed through UV–Vis spectroscopy and XRD analysis, respectively. DDAC coated gold nanospheres (GNSs) are also analysed by using FTIR technique in order to observe binding of the ligand onto the surface of gold. Ligand weight loss has been determined by using TGA technique. Particle size has been examined by using TEM and DLS techniques both. Stability of DDAC coated gold nanoparticles are also examined by using Zeta-potential. A comparison of stabilities of different quats stabilized gold nanoparticles (GNPs) has also been discussed in the present work. Unlike usual CTAB and CTAC ligands, the low binding affinity of DDAC to the gold surface may be more efficient for ligand-exchange procedure. A sharp and fine peak of PL spectrum at around 600 ​nm has been noticed for these GNSs. These luminescent, monodispersed and fine spherical shaped GNPs of size less than 40 ​nm can be valuable in plasmonics and single molecular tracking for further characterizations.

A simulation study of gold nanoparticles localisation effects on radiation enhancement at the mitochondrion scale

This paper presents a Monte-Carlo study focusing on the effects of gold nanoparticles on the energy deposition patterns produced by incident photons in the close vicinity of the mitochondrial network modeled as a tube. Spherical shaped gold nanoparticles of 30 nm diameter were placed in a micrometric (10 × 10 × 10 μm3) water phantom containing a tube of 300 nm diameter and 5 μm length. The tube represented a mitochondrial fragment and nanoparticles were distributed in the water phantom outside the tube. Photons of 120 keV were simulated using the Geant4 Livermore processes and the Geant4-DNA electron processes to account for secondary electrons collisions. The Livermore processes took into account the Auger cascade inside the gold material. A data mining algorithm was then used to analyze the energy deposition clusters inside the water phantom and the tube. A comparison was made between the results obtained for a uniform distribution of nanoparticles and a vesicle distribution model. The results including energy deposition clusters are also compared to dose enhancement ratios.

A clean approach for the reduction of hazardous 4-nitrophenol using gold nanoparticles decorated multiwalled carbon nanotubes

Abstract 4-Nitrophenol (4-NP) has become anthropogenic pollutant and poses a threat to the environment and human health. The fast detection and reduction of 4-NP can reduced their environmental and health issues. In this study, we have prepared the spherical shaped gold nanoparticles (AuNPs) decorated multi-walled carbon nanotubes (MWCNTs) in the hydrogel matrix. The prepared nanocomposite (Au@MWCNTs) was characterized successfully by several analytical techniques such as FTIR, Ramman, UV–visible spectra, XRD, XPS, and TEM. The surface of MWCNTs was decorated with AuNPs with the diameters range between 10 and 35 nm, the HRTEM results show 2.36 A interlayer spacing corresponding to (111) crystal planes. The prepared nanocomposite was used as an electrochemical detector in the detection of 4-nitrophenol (4-NP). A large reduction peak was observed at −0.56 V corresponding to the reduction of 4-NP toward p-hydroxyaminophenol using 4 e− processes, additionally two peaks were observed at 0.13 V and 0.19 V corresponding to the redox behavior p-hydroxyaminophenol and p-nitrosophenol. It was clearly observed, that the Au@MWCNts electrode detects at low concentration range with high sensitivity. Moreover, Au@MWCNTs was also used as a catalyst for the reduction 4-NP to 4-AP (4-aminophenol) using NaBH4 via pseudo-first-order and the rate constant was found to be 4.9 × 10−3 s−1 supporting the promising reduction of 4-NP.

Green synthesis of stabilized spherical shaped gold nanoparticles using novel aqueous Elaeis guineensis (oil palm) leaves extract

In the last decade, development of bioinspired protocols to synthesize gold nanoparticles (AuNPs) using plants and their extracts have been dealt by researchers due to their low cost, renewability and non-toxic features. A simple, cheap and ecofriendly method is reported to synthesize stabilized AuNPs of size 35–75 nm at room temperature using aqueous Elaeis guineensis (oil palm) leaves extract without addition of any external agent. Oil palm leaves mediated AuNPs were characterized using FTIR, UV–vis spectrophotometer, EDAX, XPS, FESEM, TEM, DLS and TGA. FTIR spectra results revealed contribution of phenolic, carboxylic, amines and amides in reduction of trivalent gold ions and stabilization of formed gold atoms. Reaction solution color change and UV–vis spectra confirmed reduction of gold ions to generate gold atoms. Reaction mechanism explained the role of phenolic compounds in reduction reaction using FTIR and UV–vis spectra results. EDAX and XPS results further validated the formation of metallic gold particles through bioreduction of gold ions. Crystal structure of metallic gold particles was confirmed through XRD peaks indexing to (111), (200), (220) and (311) planes. TEM and FESEM particles size measurements exhibited the formation of nanostructured AuNPs. Synthesis of well scattered and spherical shaped AuNPs was revealed through FESEM and TEM images. The excellent stability of AuNPs was shown through high negative zeta potential value (−14.7 ± 4.68 mV) and uniform dispersion in aqueous media. Our results disclosed the excellent potential of Elaeis guineensis (oil palm) leaves as reducing and stabilizing agents in green synthesis of well scattered spherical shaped AuNPs, which can be employed as strong candidates in medical drug delivery and industrial applications.

Biosynthesis of gold nanoparticles (AuNPs) from C. orchioides and study their antimicrobial efficacy

In this study, silver nanoparticles were synthesized using the C. orchioides plant extract as a reducing agent. The bioactive phytochemicals/ secondary metabolites present in the plant and were responsible for the quick reduction of silver ion (Au + ) to metallic silver nanoparticles (Au 0 ). The reduced silver nanoparticles were characterized by UVvis spectroscopy, Scanning electron microscopy (SEM), Fourier Transform-Infra Red Spectroscopy (FT-IR), Dynamic light scattering (DLS) and Zeta potential analysis. The UV-VIS spectroscopic studies revealed the presence of beard peaks at around 540 nm. SEM studies showed spherical-shaped gold nanoparticles at 90 nm in higher densities. The microbial derived gold nanoparticles were also showing more inhibition activity in both bacterial and fungus strains. In bacteria, gram negative strains are highly affected by the test samples than gram positive. In fungal strains, the highest effect was noticed in Aspergillus niger while less effect was observed in Candida albicans . The plant materials mediated synthesis of silver nanoparticles have comparatively rapid and less expensive and wide application to antibacterial therapy in modern medicine.

Phytosynthesis of gold nanoparticles using Mappia foetida leaves extract and their conjugation with folic acid for delivery of doxorubicin to cancer cells

Mappia foetida leaves extract is used as bioreductant for the synthesis of gold nanoparticles and their application in the efficient delivery of doxorubicin to human cancer cells is reported here. The formation of gold nanoparticles is evident from their characteristic optical absorption at ~560nm. X-ray diffraction pattern of gold nanoparticles confirmed their fcc structure. Fourier transform infrared spectroscopy shows the bioactive molecules from plant extract capped on the surface of gold nanoparticles and conjugation of doxorubicin along with activated folic acid as navigational molecules for targeted drug delivery. Such a conjugation of gold nanoparticles is characterized by their weight loss, ~35-40%, due to thermal degradation of plant biomass and conjugated drug along with receptor, as observed in thermogravimetric analysis. The spherical shaped gold nanoparticles (Φ 10-20nm) are observed by field emission scanning electron microscopy and transmission electron microscopy images and the expected elemental composition by energy dispersive X-ray spectroscopy. Gold nanoparticles conjugated with activated folic acid and doxorubicin complex is found to be toxic for human cancer cells viz., MDA-MB-231, HeLa, SiHa and Hep-G2. Furthermore, the amount of drug released was maximum at pH 5.3 (an ambient condition for intravenous cancer drugs) followed by pH 7.2 and pH 6.8.

Green Synthesis Of Gold Nanoparticles From The Leaf Extract Of Nepenthes Khasiana And Antimicrobial Assay

Synthesis of nanoparticles from various biological systems has been reported, but among all, biosynthesis of nanoparticles from plants is considered as the most suitable method. The use of plant material not only makes the process eco-friendly but also the abundance makes it more economical. The aim of this study was to investigate the ability of this plant to synthesis gold nanoparticles and study the properties of the nanoparticles thus produced. Antimicrobial activity and medicinal values of Nepenthes khasiana fascinated us to utilize it for biosynthesis of gold nanoparticles. The synthesized gold nanoparticles were characterized by UV-vis spectrophotometry, Scanning Electron Microscopy, X-ray Diffraction, Fourier Transform Infra-red Spectroscopy and Transmission Electron Microscopy. Different time intervals for the reaction with aqueous chloroauric acid solution increase in the absorbance with time and became constant giving a maximum absorbance at 599.78 nm at three hours of incubation. The results from XRD, TEM and SEM supports the biosynthesis of triangular and spherical shaped Gold nanoparticles between 50nm to 80 nm. In this study, the antimicrobial property of the AuNPS was exploited against human pathogenic micro-organisms. The results of TEM, SEM, FT-IR, UV-VIS and XRD confirm that the leaves extract of N. Khasiana can be used to produce Gold nanoparticles with significant amount of antimicrobial activity. Copyright © 2015 VBRI Press.

Biosynthesis of gold nanoparticles using a kind of flavonol: Dihydromyricetin

The present paper investigated the biosynthesis of gold nanoparticles (AuNPs) using dihydromyricetin (DMY) without adding external surfactant, capping agent or template. The synthesized nanoparticles were characterized by using UV–vis spectroscopy, transmission electron microscopy (TEM), Fourier transform infrared (FTIR) and particle size analyzer. TEM images showed that anisotropic growth of AuNPs happened at pH=4.5 and 5.5 and relatively uniform small spherical shaped gold nanoparticles were obtained at pH=6.5 and 8.5. Furthermore, both the ratios of nHAuCl4/nDMY and process temperatures were discussed, respectively. DMY or DMY oxidation products which made AuNPs solution stable were directly adsorbed on the surface of AuNPs at the ratio of nHAuCl4/nDMY being 1:3 and 1:1 in the reduction process. Besides, the monodisperse and uniform AuNPs were easily obtained at higher temperatures (90°C). Based on the FTIR analysis, hydroxyl groups of DMY played an important reduction role during synthesis process. The experimental approach is simple, rapid, cost-effective and reproducible at room temperature.

Langmuir–Schaefer films of a polyaniline–gold nanoparticle composite material for applications in organic memristive devices

Langmuir–Shaefer films of a polyaniline–gold nanoparticle composite were fabricated and characterized. The thickness of each deposited monolayer, determined with AFM, was found to be about 0.8 nm. The film morphology was studied by SEM, revealing the presence of embedded spherical-shaped gold nanoparticles of about 5–10 nm in diameter. The fabricated films were used as the active channel of the organic memristor. Its electric characterisation has revealed new phenomena, such as an increased working voltage range and sigmoidal voltage current characteristics that were connected to the charge trapping.

Ultrasonic Intercalation of Gold Nanoparticles into Clay Matrix in the Presence of Surface-Active Materials. Part I: Neutral Polyethylene Glycol

The combined application of polyethylene glycol and ultrasonic irradiation has been investigated as a possible method to synthesize intercalated Au/clay nanocomposites. Twenty minutes of ultrasonic irradiation on the Na+−montmorillonite clay matrix in the presence of polyethylene glycol suffices to introduce polymer molecules into the lamellar space of the clay, increasing the basal distance between clay layers. Additional ultrasonic treatment allowed the successful replacement of the intercalated polyethylene glycol by gold nanoparticles within the interlamellar space. The incorporation of gold nanoparticles in the clay matrix under ultrasound is twice as efficient with PEG as without it. Eventually, spherical-shaped gold nanoparticles of 6−8 nm diameter spread homogeneously within the nanocomposites. The structures of the produced nanocomposites have been studied by small and wide-angle X-ray scattering, transmission electron microscopy, scanning electron microscopy, BET, Fourier transform infrared measurements, and thermogravimetric analysis.

Sonochemical Intercalation of Preformed Gold Nanoparticles into Multilayered Clays

Multilayered Na (+)-montmorillonite clays intercalated with Au nanoparticles were synthesized by direct ultrasonic impregnation of preformed gold colloid into the clay matrix. The sonicated composite product then consists of Au nanoparticles homogeneously dispersed in the clay. The resulting clay/nano-Au composite was calcined at 800 degrees C and characterized by BET surface area analysis, transmission electron microscopy, scanning electron microscopy, X-ray diffraction, and Fourier transform infrared measurements. Nearly spherical-shaped gold nanoparticles, with a size of 6 +/- 0.5 nm, are located in the pores of clay calcined at 800 degrees C. Their nanocomposites are thermally stable as was shown by thermogravimetric analysis. No aggregation of the gold nanoparticles was observed during calcination. The proposed ultrasonic intercalation approach is an universal one and can be employed for synthesis of catalytically active metal-clay nanocomposites stable at high temperatures with high dispersability of the metal nanoparticles in the clay matrix.

Particle size-dependent organ distribution of gold nanoparticles after intravenous administration

A kinetic study was performed to determine the influence of particle size on the in vivo tissue distribution of spherical-shaped gold nanoparticles in the rat. Gold nanoparticles were chosen as model substances as they are used in several medical applications. In addition, the detection of the presence of gold is feasible with no background levels in the body in the normal situation. Rats were intravenously injected in the tail vein with gold nanoparticles with a diameter of 10, 50, 100 and 250 nm, respectively. After 24 h, the rats were sacrificed and blood and various organs were collected for gold determination. The presence of gold was measured quantitatively with inductively coupled plasma mass spectrometry (ICP-MS). For all gold nanoparticle sizes the majority of the gold was demonstrated to be present in liver and spleen. A clear difference was observed between the distribution of the 10 nm particles and the larger particles. The 10 nm particles were present in various organ systems including blood, liver, spleen, kidney, testis, thymus, heart, lung and brain, whereas the larger particles were only detected in blood, liver and spleen. The results demonstrate that tissue distribution of gold nanoparticles is size-dependent with the smallest 10 nm nanoparticles showing the most widespread organ distribution.