Colloidal Solution Of Gold Nanoparticles Research Articles

High-Precision Optical Excited Heaters Based on Au Nanoparticles and Water-Soluble Porphyrin

Gold nanoparticles are widely used as local heaters under optical excitation. Hybrid molecular-plasmon nanostructures based on gold nanoparticles and water-soluble porphyrin have been developed. A colloidal solution of gold nanoparticles was obtained by laser ablation of metallic gold in water, ensuring its highest chemical purity. The hybrid nanostructures formation was performed due to the Coulomb interaction of cationic porphyrin and gold nanoparticles. The revealed functional properties of hybrid nanostructures make them promising for controllable nano-heater applications (for example, photothermal therapy). Gold nanoparticles act as heaters, whereas porphyrin serves as a fluorescent thermometer with a single optical excitation.

Вплив наночастинок золота на морфофункціональний стан гіпоталамуса та кори надниркових залоз щурів при ожирінні

The aim of our study was to compare the effects of a gold salt (sodium tetrachloroaurate) and gold nanoparticles colloidal solution on the morphofunctional state of the hypothalamus and adrenal glands of 6-month-old male rats with obesity, which was induced using a diet-induced model of metabolic disorders. The rats, modeled for obesity, were divided into three groups that received a NaCl solution, gold salt solution and colloidal solution of gold nanoparticles for 10 days. Rats of the control group received a standard diet. After the end of the experiment, the hypothalamic nuclei and adrenal glands, prepared according to the appropriate histological methods, were collected from the animals. In the paraventricular nucleus of the hypothalamus, a small-cell area of neurons was examined. In the adrenal glands, cells of three zones of the cortex were examined: glomerular, fascicular, and reticular. The results of the study showed that obesity led to the increase of functional activity in the nuclei of neurons in the small-cell region of the paraventricular nucleus of the rat hypothalamus. Functional activity increased maximally in the cells of the glomerular zone of the adrenal cortex, moderately increased in the fascicular zone, and no significant changes were recorded in the reticular zone. It was shown that the gold salt caused a decrease in the functional activity of neurons of the paraventricular nucleus of the hypothalamus in obese rats. In the glomerular zone of the adrenal cortex, the functional activity of cells significantly decreased; in the fascicular zone, the parameters of cell nuclei decreased to a greater extent; in the reticular zone, there were almost no changes. The introduction of gold nanoparticles colloidal solution caused the intensification of functional activity of the paraventricular hypothalamic nucleus cells in obese rats. In the glomerular zone of the adrenal cortex, cell parameters decreased; in the fascicular zone, cytoplasmic parameters decreased, but nuclear parameters did not change; in the reticular zone, measured values of nuclei increased and cytoplasmic parameters remained unchanged. In general, the administration of gold nanoparticles colloidal solution produced more pronounced effects than gold salt solution on cells of the paraventricular nucleus of the hypothalamus and the adrenal cortex in obese rats.

Improvement of Proton Irradiation Effectiveness of Human Lung Carcinoma Cells A 549 in the Presence of Gold Nanoparticles

Purpose: To study was to study the effect of GNP nanoparticles on tumor cells of human lung carcinoma A 549 when irradiated with protons.
 Materials and methods:
 Cell culture: Human lung carcinoma cells A 549.
 Gold nanoparticles Au/PEG 6000/W 200/30 nm: A colloidal solution of gold nanoparticles purchased from the firm M 9 Nanomaterials & Technologies was used in the work.
 Proton irradiation: The irradiation of cells was carried out on a therapeutic proton beam in the Medical and Technical Complex of the Laboratory of Nuclear Problems Joint Institute for Nuclear Research.
 Determination of radiosensitivity of cells: By determining the clonogenic survival of cells.
 Determination of the genotoxic activity of nanoparticles under the action of proton irradiation: investigated using a micronucleus test with blocking cytokinesis. The genotoxicity of gold nanoparticles was estimated by the number of micronuclei per 1000 binuclear cells. Micronucleus were counted only in binuclear cells. At least 1000 binuclear cells were calculated for each dose, experiments were carried out in three repeats.
 Results: The frequency of micronucleus formation indicates an increase in the genotoxic effect of nanoparticles when irradiated with protons at a dose of 2 Gy. Proton irradiation caused an increase in the frequency of micronucleus formation depending on the concentration of nanoparticles. When irradiated with protons at a dose of 2 Gy in the presence and absence of nanoparticles, the difference in the frequency of micronucleus formation for the concentration of nanoparticles was 2.5 mg/ml – 1.1; for 5 mg/ml and 10 mg/ml – 1.2; for 15 mg/ml – 1.3 and for 30 mg/ml –1.5. Cell survival curves reflect a decrease in their survival rate when metal nanoparticles with high Z are added, which reflects the occurrence of radiosensitization effects. The gain for 10 % and 50 % survival rates is 1.4 and 2.5, respectively.
 Conclusions: Under the influence of proton irradiation, the genotoxic activity of gold nanoparticles in human lung carcinoma cells A 549 increases, depending on their concentration. The survival rate of human lung carcinoma A 549 cells irradiated with protons in the presence of gold nanoparticles decreases.

P-type Inversion at the Surface of β-Ga2O3 Epitaxial Layer Modified with Au Nanoparticles.

The electric properties and chemical and thermal stability of gallium oxide β-Ga2O3 make it a promising material for a wide variety of electronic devices, including chemiresistive gas sensors. However, p-type doping of β-Ga2O3 still remains a challenge. A β-Ga2O3 epitaxial layer with a highly developed surface was synthesized on gold electrodes on a Al2O3 substrate via a Halide Vapor Phase Epitaxy (HVPE) method. The epitaxial layer was impregnated with an aqueous colloidal solution of gold nanoparticles with an average diameter of Au nanoparticle less than 5 nm. Electrical impedance of the layer was measured before and after modification with the Au nanoparticles in an ambient atmosphere, in dry nitrogen, and in air containing dimethyl sulfide C2H6S (DMS). After the impregnation of the β-Ga2O3 epitaxial layer with Au nanoparticles, its conductance increased, and its electric response to air containing DMS had been inversed. The introduction of Au nanoparticles at the surface of the metal oxide was responsible for the formation of an internal depleted region and p-type conductivity at the surface.

Fabrication of hierarchical hybrid ZnO/Au micro-/nanostructures for efficient dye degradation: role of gold nanostructures in photophysical process

In this work, colloidal solutions of gold nanoparticles (AuNPs) with an average diameter of 16 nm and gold nanorods (AuNRs) with an average aspect ratio of 6.8 were synthesized. These gold nanostructures were decorated on nanosheets assembled 3D ZnO microflower (ZnO-MF) synthesized via facile and cost-effective co-precipitation method. Plasmonic gold nanostructures act as optical concentrators and a reservoir of electrons under LSPR excitation. They extend the light harvesting capability of ZnO from UV–VIS–NIR region, promotes interfacial charge transfer process and helps in electron-hole pair separation. We report the occurrence of FRET (Fluorescence Resonance Energy Transfer) between defect rich ZnO-MF and gold nanostructures under UV light excitation as evident from micro-PL spectra. This triggers surface plasmon resonance in gold nanostructures which causes direct transfer of hot electrons to ZnO-MF. Time-resolved Photoluminescence of the hybrid samples monitored at near band edge of ZnO shows elongated decay kinetics as compared to bare samples which could be attributed to direct transfer of hot electrons from gold to conduction band of ZnO-MF after LSPR excitation. Thereafter, the photocatalytic activity of the hybrids is evaluated by degradation of four different dyes under sunlight. ZnO-MF/AuNPs exhibited superior photocatalytic activity compared to ZnO-MF/AuNRs. This could be attributed to numerous reasons like better energy transfer efficiency, effective near-field enhancement, small size of AuNPs and enhanced electron-hole pair separation which makes ZnO-MF/AuNPs a promising photocatalyst.

PH activated colloidal Nanospheres: A viable sensing platform for the Therapeutic Drug Monitoring of the anticancer Drug 6-Mercaptopurine

A SERS colloidal solution of gold nanoparticles is proposed as a sensing platform potentially suitable for the Therapeutic Drug Monitoring of the anticancer drug 6-mercaptopurine. The as-synthesized nanospheres were fully characterized in terms of morphological features, plasmonic properties and SERS activity. Modifying the pH of the colloidal solution toward acidic values allowed us to improve considerably the platform sensitivity. A kinetic analysis performed at different analyte concentrations revealed the occurrence of adsorption/aggregation processes which induced a time-dependent SERS response. This dependence, causing unreliable quantitative analysis, was accounted for by a normalizing procedure based on the enhanced elastic scattering signal. After normalization for hot-spot concentration, a 1 – 15 μM linearity range was identified, within which the quantitative analysis is accurate and reproducible. The working range of the present assaying platform is suitable for clinical applications.

Application of gold and silver nanoparticles for selective assay of spermine in mixture with spermidine.

To assess the applicability of the novel technique based on the detection of spermine in solutions by spectrocolorimetric method using gold and silver colloidal nanoparticles. Colloidal solution of gold nanoparticles were synthesized by chemical reduction of tetrachlorauric acid with trisodium citrate. Colloidal solution of silver nanoparticles was obtained by chemical reduction of silver nitrate with tryptophan. The absorption spectra of gold/silver metal colloids and their mixtures with polyamines were recorded. The increase of spermine concentration in solution caused the change in the intensity of the band of localized surface plasmon resonance that was not affected by the excess of spermidine. The color shift in colloidal gold due to its aggregation with spermine was registered spectrophotometrically. The principal possibility of selective quantification of spermine in the presence of spermidine in extremely high concentration using colloidal gold has been shown. This method can be used to assay selectively spermine in biological fluids.

Femto-nanosecond laser ablation of gold target in liquid

Colloidal solutions of gold nanoparticles were generated in deionized water from bulk target at different energies of nanosecond and femtosecond lasers. The obtained colloidal nanoparticles were characterized by scanning electron microscopy, optical transmission spectroscopy and dynamic light scattering.

Synthesis of gold nanostar using chitosan as reductive agent by the seedless reduction method

The gold nanostars (AuNS) were prepared through seedless reductive method by using the natural biodegradable polymer chitosan acting both as the stabilizing and shape-directing agent, ascorbic acid as a reducting agent. This reaction synthesis was carried out at room temperature and facile conditions. In an effort to control the size and shape of AuNS, many experimental parameters were investigated for the thorough understanding the role of chitosan in the formation of gold nanostar. In this novel method, the pH condition and appropriate stabilizer concentration were crucial factors to prepare the well-defined AuNS. The obtained AuNS were characterized by many physical-chemistry analysis method such as transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), UV-Vis spectroscopy, dynamic light scattering (DLS), and X-Ray diffraction (XRD). The AuNS have an average size of about 55 nm and narrow size distribution when characterized by TEM images. UV-Vis spectroscopy of the gold nanoparticles colloidal solution showed the characteristic peaks at 587-700 nm, corresponding to the surface plasmon resonance of star-shaped nanostructure. The specific interactions between the functional groups of chitosan chain and the as-prepared gold nanostars are analyzed by the FT-IR spectroscopy technique. These results provided insight into the role of biopolymer as both a protecting agent and structure-directing agent. This novel method can overcome previous limitations in controlled synthesis of star-shaped gold nanoparticles such as surfactant use and complex implementation. Besides, the gold nanostars stabilized by chitosan could be a potential material in many applications in the field of biomedical medicine.

Spectral features of colloidal solutions of elongated gold nanoparticles produced by laser ablation in aqueous solutions

The extinction spectra of colloidal solutions of gold nanoparticles produced by laser ablation in water and aqueous solutions of salts using two near-IR lasers with pulse durations of 200 ns and 1 ps are experimentally investigated. The extinction spectrum of the particles formed by ablation in aqueous solutions is characterised by enhanced optical density in the red and IR regions. This feature is due to the formation of elongated gold nanoparticles, as confirmed by transmission electron microscopy. The surface images of a gold target subjected to multipulse laser ablation exhibit micron and submicron structures.

Tuning of localized plasmon resonance in colloidal gold nano-particles by ultrafast interband photoinjection of free carriers: Superplasmonic states?

Colloidal solutions of gold nanoparticles in water were pumped by filamentary 800-nm, 100-fs laser pulses at variable supercritical peak powers and probed by the accompanying ultrashort white-light supercontinuum pulses. Their broadband (UV-near-IR) spectra revealed the localized plasmon resonance blue-shifting, broadening, and intensity reduction vs the incident peak laser power as a result of the increasing concentration of s-band free carriers additionally photoinjected from high-density d-bands.

Coating identification in spherical and anisotropic gold nanomaterials by SERS technique

AbstractRecently the use of nanomaterials for the diagnosis and detection of malignant diseases has increased due to the versatility and properties of these nanostructures. For this work 60 nm commercial gold nanoparticles (TED PELLA inc.) and Nanostars manufactured by chemical synthesis (precursor reagent: HAuCl4, cationic surfactant: CTAB) of 117 nm were used for coating. Malachite green Isotyocianate (MGITC), mPEG-SH and ortho-pyridyldisulfide-polyethylene glycol-N-succinimidyl propionate (OPSS-PEG-NHS) was used. A SERS active nanoparticle complex was obtained by addition of a solution of MGITC to the gold nanoparticles colloidal solution in a 1:6 ratio. Later, an mPEG-SH solution was added to the mix. The nanoparticle-MGITC-mPEG-SH complex stability was revised using a UV-Vis spectrophotometer and a JEOL JEM 1000 transmission electron microscope. The SERS spectra were registered with a Raman Thermoscientific DXR microscopy system. Amplified bands associated with OPSS-PEG-NHS were identified in 389, 622, 859, 929, 1080, 1283, 1360, 1443, 1490 and 1450 cm-1. The results indicate that through this methodology it is possible to identify gold nanomaterials coated with polymer through the Raman technique. In addition, greater amplification is observed with the use of nanostars compared to gold spheres. Finally, these nanomaterials are available for the marking of specific membrane for the study of different types of cancer by the SERS technique.

Temporal and Spectral Characterization of Breakdown Plasma Induced by Laser Radiation in Colloidal Solutions of Gold Nanoparticles

Temporal and spectral characteristics of laser-induced breakdown plasma in colloidal solutions of gold nanoparticles were experimentally studied. Near-infrared laser sources of nanosecond pulses were used. It was shown that under certain experimental conditions nanosized plasma around nanoparticles might change to laser-induced breakdown plasma in liquid. The dependencies of the plasma temporal and spectral characteristics on laser pulse duration as well as resulting nanoparticles properties were studied. Laser-induced breakdown plasma lifetime was shown to be comparable with laser pulse duration. The efficiency of gold nanoparticles fragmentation was shown to depend on laser pulse duration. Similar experiments were carried out under reduced external pressure. It turned out to affect the properties of both plasma plume and nanoparticles. Transmission electron microscopy and disc measuring centrifuge were used for nanoparticle morphology and size analysis. Extinction spectra of colloidal solutions and emission spectra of plasma were studied by means of optical spectroscopy.

In situ analysis of the formation steps of gold nanoparticles by oleylamine reduction

A colloidal solution of gold nanoparticles is synthesized with the use of sodium tetrachloroaurate(III) as a precursor, oleylamine as a reducer and surfactant, and 1-octadecene as a solvent. Reaction stages are analyzed in situ by optical (UV-vis) absorption spectroscopy with a simultaneous analysis of particle sizes by dynamic light scattering and X-ray absorption near edge spectroscopy for the analysis of the gold oxidation state. After the synthesis the size of obtained nanoparticles is determined by transmission electron microscopy. The analysis of the obtained experimental data reveals the presence of three main steps in the reduction reaction mechanism, corresponding to Au3+, Au+, Au0, which enables the construction of the reaction model. The reaction mechanism involves the formation of gold(I) complexes with oleylamine, followed by polymerization and the formation of gold nanoclusters coated with oleylamine.

Qualitative analysis of the nephrotoxicity of gold nanoparticles in case of enteral administration

The experiments on animals show the different effects of gold nanoparticles. Gold particles of various sizes may have a variety of toxic effects on the tissues, and more damage is often produced by small nanoparticles. In this work histological and ultrastructural changes of renal parenchyma caused by enteric administration of gold nanoparticles of small sizes (2 nm) were studied used different concentrations of colloidal solutions of gold nanoparticles: 10 µg/ml; 50 μg/ml; 100 µg/ml in drinking water within 7, 14 and 28 days. There were 9 groups of animals (non-linear mice weighing 20-25 g) on different dates of the experiment, as well as 3 control groups of mice, respectively, each term of experiment. Histological and ultrastructural changes were detected in the material of all groups of experimental animals compared with control. In general all small focal alterations relate to a small number of vessels, individual profiles of tubules and single cells. Light microscopy analysis of the overall picture of integrity of renal parenchyma showed that the most pronounced changes are observed in the cortex of the organ. Medulla is less affected. It identifies, first of all, microvascular disorders, then the renal tubular epithelium changes and finally, a minor involvement of interstitial elements in the response. Tubules of nephrons compared with the renal corpuscles undergo more changes at all dose levels of exposure and in all periods under study. Signs of dystrophy and necrobiosis often relate to the cell cytoplasm and less of their nuclei. Evidence of microvessel disorders detected in the renal cortex is not dependent on the dose of administered nanoparticles already in the early stages of the experiment. Histological findings as a whole are confirmed by the presence of ultrastructure alterations, that points to the primacy of cell damage.

Thin‐layer chromatography–surface‐enhanced Raman spectroscopy and chemometric tools applied to Pilsner beer fingerprint analysis

This work proposes a novel use of thin‐layer chromatography with detection by surface enhancement Raman spectroscopy (SERS) to generate chromatographic and spectral fingerprints of complex samples, aiming toward samples classification. Ten commercial beer brands were analyzed in order to verify clusters related to each brand and the brewery location. The samples were eluted in thin‐layer chromatography plates and sprayed by gold nanoparticles colloidal solution using a simple and cheap lab‐made apparatus. The plates were analyzed by SERS, so, at the end of the measurement, one SERS‐chromatogram matrix was acquired for each sample. The high sensitivity of the SERS analysis allows the detection of compounds in low concentrations, unseen via common thin‐layer chromatography detection procedures, increasing the information for fingerprint analyses. Because of the high complexity of the sample, coelution problems and slight shifts in chromatographic peaks might appear in this kind of analysis; it was necessary to use chemometric tools for data analysis. Two chemometric methods of data deconvolution were compared, multivariate curve resolution–alternating least squares and independent component analysis. From the chromatographic peaks recovered by both methods, it was possible to perform a fingerprint analysis using principal component analysis, which allowed identifying patterns among the samples according to the brands and brewery location of Pilsner beers produced in Brazil. Copyright © 2017 John Wiley & Sons, Ltd.

Headspace single-drop microextraction coupled to microchip-photothermal lens microscopy for highly sensitive determination of captopril in human serum and pharmaceuticals

The authors describe the combination of headspace single drop microextraction with microchip-photothermal lens microscopy (HS-SDME/MC-PTLM) as a new method for highly sensitive determination of the angiotensin-converting enzyme inhibitor captopril. A single drop of a colloidal solution of gold nanoparticles is applied to the headspace. This then acts as both acceptor phase and labeling agent for the thiol groups of captopril. Following extraction of captopril, the drop is injected into a glass microchip and detected by PTLM using a 50-mW diode solid-state laser with an emission line of 532 nm. The interaction of captopril and GNPs reduces the surface plasmon resonance of GNPs and as a consequence the PTLM signal of GNPs decreases. At the optimum condition, the PTLM signal increases linearly in the 0.5–70.0 nM captopril concentration range, and the detection limit (at an S/N ratio of 3) is 0.31 nM. This is much better than those of previously reported methods. The method was successfully applied to the determination of captopril in (spiked) human serum and in pharmaceutical samples.

Effect of nanoparticle sizes on the extinction spectrum of colloidal solutions produced by laser ablation of gold in water

We have measured the extinction spectra of colloidal solutions of gold nanoparticles synthesised by nanosecond laser ablation in water for the conditions of a bimodal particle size distribution. The extinction spectra are analysed by using the Mie theory and the contribution of particles of different sizes to the radiation attenuation is established. A method is proposed for determining the concentrations of individual populations of particles in a solution on the basis of the spectral dependence of the extinction coefficient. Mechanisms of the nanoparticle formation during laser ablation of metals in liquids are discussed.

Study of Cu-Zn and Au/TiO2 Catalysts on Anodized Aluminum Monoliths for Hydrogen Generation and Purification

Abstract This work reports the preparation of Cu-Zn and Au/TiO2 catalysts on anodized aluminum monoliths (AAM). The structured catalysts were studied for the generation of H2 by methanol steam reforming (MSR) and its purification by preferential oxidation of CO (CO-PrOx). Initially, it was possible to generate a surface with whiskers and larger surface area by hydrothermal treatment of the AAM. Subsequently, the structured catalysts were synthesized by incipient wetness impregnation (IWI) and hydrothermal synthesis (HS). IWI synthesis allowed for the deposition of a larger amount of catalytic material than HS, with very good adhesion. The TiO2-IWI structured catalyst presented a homogeneous catalytic coating, with the presence of agglomerated particles. On the other hand, Cu-Zn-IWI showed good dispersion of the deposited particles with a homogeneous surface coating. EDX analysis corroborated the presence of Ti, Cu and Zn in all the catalytic surfaces. The incorporation of Au over TiO2-IWI structured catalysts was successfully performed by IWI using a colloidal solution of gold nanoparticles. MSR was studied over the developed metallic monoliths functionalized with Cu-Zn by the IWI method. The samples showed promising results in terms of activity, selectivity, and stability. Both diluted and concentrated methanol + water feeds were assayed. Complete methanol conversion was achieved for the diluted feed. Maximum methanol conversions of 55 % with 60 % H2 yield were measured when the concentrated feed was selected. Promising results were also achieved for the Au-based structured catalysts in the CO-PrOx in an H2-rich atmosphere. Although CO conversions of approximately 60 % were achieved, operating with higher catalyst loadings would be recommended to reach the high CO conversions required for PrOx catalysts.

SYNTHESIZE OF GOLD NANOPARTICLES WITH 532 NM AND 1064 NM PULSE LASER ABLATION

The effect of laser wavelength on gold nanoparticle fabrication is reported. Colloidal solutions of gold nanoparticles were prepared by pulsed laser ablation technique in deionized water. A Q-switched Nd:YAG laser with constant energy of 65mJ and operation at fundamental wavelength and second harmonic generation was utilized as a source of energy. Fabricated particles were characterized by using Smart Nanoparticles Measurements (SNM) system. The average diameters of gold nanoparticles achieved as19 nm and 12 nm corresponding to 1064 nm and 532 nm respectively. The fragmentation of colloidal particles by self-absorption of laser pulses is the responsible mechanism to cause for reduction.