Size Distribution Of Gold Nanoparticles Research Articles

Tuning the plasmon resonance of Au-Ag core-shell nanoparticles: The influence on the visible light emission for inorganic fluorophores application

In this study, the gold and gold-silver (Au-Ag) core-shell nanoparticles were synthesized via chemical reduction method at different types and quantities of precursor materials. Initially, the gold nanoparticles were prepared with different reducing agents (i.e., sodium borohydride, sodium citrate, and ascorbic acid) and their composites. The optical absorbance, morphology, and size distribution of gold nanoparticles were analyzed to observe the best deposition conditions, used for the Au-Ag core-shell synthesis. Then, the Au-Ag core-shell nanoparticles were grown at four different quantities (i.e., 175 µL, 200 µL, 225 µL, and 250 µL) of silver nitrate precursor to study their effects on the fluorescence property. Optical absorbance, transmission electron microscopy, and laser scanning confocal microscopy were used to characterize the as-synthesized Au-Ag core-shell nanoparticles. From the results of optical absorbance, a single peak is seen for gold nanoparticles while two peaks (major and minor peaks) are observed for Au-Ag core-shell nanoparticles. The sizes of gold and core-shell particles observed from TEM measurement are less than 10 nm, which is typically used in fluorescence applications. The CoSh-2 sample showed a better fluorescence property compared to other core-shell samples. With a rise in exposure time in a laser with a specific wavelength of 405 nm, the intensity of fluorescence declined more for the filter having shorter wavelengths than larger wavelengths. Analyzing these results can be useful to understand the perspective applications of Au-Ag core-shell nanoparticles like synthetic fluorophores application.

Biogenic proficient synthesis of (Au-NPs) via aqueous extract of Red Dragon Pulp and seed oil: Characterization, antioxidant, cytotoxic properties, anti-diabetic anti-inflammatory, anti-Alzheimer and their anti-proliferative potential against cancer cell lines

Gold nanoparticles with tiny sizes and biostability are particularly essential and are employed in a variety of biomedical applications. Using a reducing agent and a stabilising agent to make gold nanoparticles has been reported in a number of studies. Gold nanoparticles with a particle size of 25.31 nm were synthesized in this study utilising Hylocereus polyrhizus (Red Pitaya) extract, which functions as a reducing and stabilising agent. The extract of Red Pitaya is said to be a powerful antioxidant and anti-cancer agent. Because of its substantial blood biocompatibility and physiological stability, green production of gold nanoparticles with H. polyrhizus fruit extract is an alternative to chemical synthesis and useful for biological and medical applications. The formation and size distribution of gold nanoparticles were confirmed by HPLC, UV-Vis spectrophotometer, X-ray diffraction (XRD), Dynamic light scattering (DLS), Zeta potential, Transmission electron microscopy (TEM), Fourier transformed infrared spectroscopy (FTIR), Energy dispersive X-ray (EDX) and X-ray photoelectron spectroscopy (XPS). The well-analysed NPs were used in various biological assays, including anti-diabetic, anti-inflammatory, anti-Alzheimer, and antioxidant (DPPH), and cytotoxic investigations. The NPs also showed a dose-dependent cytotoxic activity against HCT-116, HepG2 and MCF-7 cell lines, with IC50 of 100 µg/mL for HCT-116 cells, 155 µg/mL for HepG2, and for MCF-7 cells the value was 165 µg/mL respectively. Finally, the outstanding biocompatibility of Au-NPs has led to the conclusion that they are a promising choice for various biological applications.

The electrodeposition of gold nanoparticles from aqueous nanodroplets.

Nanodroplet-mediated electrodeposition is a reliable method for electrodepositing nanoparticles by confining a small amount of metal-salt precursor in water nanodroplets (radius ∼400 nm) suspended in an oil continuous phase. This technique provides a great advantage in terms of nanoparticle size, morphology, and porosity. For an electrochemical reaction to proceed in the aqueous nanodroplet, the electroneutrality condition must be maintained. Classically, [NB4][ClO4] or a comparable salt is added to the oil continuous phase to maintain charge balance. Unfortunately, the presence of this salt in the oil phase causes some metal salts, such as HAuCl4, to phase transfer, disallowing the formation of gold nanoparticles. Here, we demonstrate the partitioning of HAuCl4 is orders of magnitude lower using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) when LiClO4 is added to the nanodroplet phase and [NBu4][ClO4] is not added to the continuous phase. This simple change allows for the electrodeposition of gold nanoparticles. Scanning electron microscopy shows the morphology and size distribution of gold nanoparticles obtained at different concentrations of LiClO4. Transmission electron microscopy in selected diffraction mode was used and it determined the gold nanoparticles obtained are polycrystalline with miller indices of (222) and (200). This work widens the variety of nanoparticles that can be electrodeposited from nanodroplets for applications in energy storage and conversion, photoelectrochemistry, and biosensing.

Size Distributions of Gold Nanoparticles in Solution Measured by Single-Particle Mass Photometry.

Specialized applications of nanoparticles often call for particular, well-characterized particle size distributions in solution, but this property can prove difficult to measure. High-throughput methods, such as dynamic light scattering, detect nanoparticles in solution with an efficiency that scales with diameter to the sixth power. This diminishes the accuracy of any determination that must span a range of particle sizes. The accurate classification of broadly distributed systems thus requires very large numbers of measurements. Mass-filtered particle-sensing techniques offer a better dynamic range but are labor-intensive and so have low throughput. Progress in many areas of nanotechnology requires a faster, lower-cost, and more accurate measure of particle size distributions, particularly for diameters smaller than 20 nm. Here, we present a tailored interferometric microscope system, combined with a high-speed image-processing strategy, optimized for real-time particle tracking that determines accurate size distributions in nominal 5, 10, and 15 nm colloidal gold nanoparticle systems by automatically sensing and classifying thousands of single particles sampled from solution at rates as high as 4000 particles per minute. We demonstrate this method by sensing the irreversible binding of gold nanoparticles to poly-d-lysine functionalized coverslips. Variations in the single-particle signal as a function of time and mass, calibrated by TEM, show clear evidence for the presence of diffusion-limited transport that most affects larger particles in solution.

Study on particle size and size distribution of gold nanoparticles by TEM and SAXS

Particle size and size distribution are two of the most vital parameters of nanomaterials since their physical properties as well as applications are highly dependent on these key factors. The objective of this work is to study the particle size and size distribution of gold nanoparticles (AuNPs), which were synthesized by a simple green synthesis in HAuCl4 and water-soluble chitosan solution (WSCS). Transmission electron microscope (TEM) and small-angle X-ray scattering (SAXS) techniques were carried out to determine the particle size, size distribution and polydispersity of AuNPs. The evidences from TEM and SAXS indicated that AuNPs can be formed in spherical shape with the size in the range of 10–30 nm. From TEM, the particle sizes of the AuNPs prepared in WSC, S at the concentration of 0.02 and 0.05 mg/mL containing 0.1 mM HAuCl4 were 20.5 ± 2.1 and 21.2 ± 1.8 nm, respectively. By increasing the concentration of HAuCl4 precursor up to 0.5 mM, AuNPs exhibited a slightly larger particle size (24.4 ± 2.2 nm). The particle size, size distribution and polydispersity of AuNPs observed by TEM and SAXS were in agreement. However, AuNPs sizes from SAXS were smaller than those from TEM because only the Au core of the AuNPs was detected by X-ray scattering. In addition, the chemical structure and specific surface plasmon resonance (SPR) absorption of AuNPs were well characterized by FTIR and UV-vis spectrophotometer. The FTIR results of AuNPs implied that the stabilization of AuNPs in the WSCS was due to electrostatic interaction and steric hindrance of C=O, C–O–C, –OH, –NH2 groups. By using WSCS at concentration 0.02 and 0.05 mg/mL, the SPR absorption bands were observed at 545 and 535 nm, respectively. The TEM and SAXS results of AuNPs in this study will provide an essential basis for synthesis of metallic nanoparticles for various applications in the future.

New concept of radiolytic synthesis of gold nanoparticles in continuous flow

Radiolytic synthesis has been used to produce a plethora of unsupported and supported metallic nanoparticles in batch. As proof of a new concept, we evaluated the formation of gold nanoparticles by radiolytic synthesis in continuous flow using a millifluidic reactor. A mixture of gold ions solution, branched polyethyleneimine, and ethylene glycol yielded gold nanoparticles with a mean size of 3.4 ± 1.0 nm after irradiation with an X-ray irradiator (127 Gy/min) at an absorbed dose of 5.1 kGy. The morphology and size distribution of gold nanoparticles was influenced by AgNO3, where its absence resulted in a mean size of 20.9 ± 15.8 nm. The radiolytic synthesis of gold nanoparticles in continuous flow was achieved in short reaction times (<60 min), at room temperature, and with low concentrations of both stabilizing and reducing agents. These results demonstrate the potential of radiolytic synthesis in continuous flow for high-throughput formation of metallic nanoparticles with controlled specifications in size and distribution.

Evolution of the Size Distribution of Gold Nanoparticles under Laser Irradiation

Evolution of the Size Distribution of Gold Nanoparticles under Laser Irradiation

Poly (Vinyl Alcohol) Assisted Synthesis and Anti-Solvent Precipitation of Gold Nanoparticles.

Gold nanoparticles (GNPs) are commonly synthesized using the Turkevich method, but there are limitations on the maximum concentration of gold nanoparticles that can be achieved using this method (often < 1 mM (=0.34 mg/mL) gold precursor loading). Here, we report an inverse Turkevich method which significantly increases the concentration of gold nanoparticles (up to 5-fold) in the aqueous phase by introducing poly (vinyl alcohol) (PVA) to the synthesis system for stabilization. The aim of this study is to understand the effect of PVA and other synthesis parameters, such as trisodium citrate and tetrachloroauric acid concentration, with the goal of maximizing concentration while maintaining gold nanoparticle morphology, stability, and narrow size distribution. The size distribution of GNPs is investigated for a range of parameters by dynamic light scattering and electron microscopy, and ultraviolet-visible (UV–vis) spectroscopy is also utilized to explore the localized surface plasmon resonance (LSPR). Further, the interaction between GNPs and PVA is investigated by Fourier-transform infrared spectroscopy. In addition to increasing the gold loading by varying synthesis parameters, we also develop a novel anti-solvent precipitation method for the PVA-coated GNPs, which enables continuous condensation and purification of GNPs by forming a gold/PVA nanocomposite.

Functionalized Gold Nanoparticles Decorated Reduced Graphene Oxide Sheets for Efficient Detection of Mercury

Functionalized gold nanoparticles decorated reduced graphene oxide (RGO) sheets were used as an electrical sensing platform for highly selective and sensitive Hg2+ detection. RGO sheets were synthesized by reduction of graphene oxide (GO) produced by well-known Hummer’s method. RGO sheets were further decorated with thioglycolic acid (TGA) functionalized gold nanoparticles (GNPs) by simple chemical approach. Field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and Ultraviolet-visible (UV-Vis) absorbance analysis were done to confirm the presence of gold nanoparticles being attached to the RGO sheets. Transmission electron microscopy (TEM) was performed to analyze the shape and size distribution of gold nanoparticles on RGO sheets. TGA functionalization of GNPs was confirmed by Fourier transform infrared (FTIR) spectroscopic analysis. The RGO sheets as fabricated were observed to impart n-type nature to the sensing characteristics which was supported by Hall measurements. The sensor performance towards Hg2+ was investigated electrically in presence of other competitive contaminants. The sensor was found to be highly selective towards Hg2+ in presence of Pb2+, Cd2+ and As5+. The interaction of Hg2+ with the sensing layer was also studied using UV-Vis spectrophotometer. Our work suggests that RGO-GNP-TGA (RGT) hybrid structures are promising for low-cost, portable and real-time room temperature heavy metal ion detectors.

Gold nanoparticles size distribution by pulsed laser varying the wavelength

In this work the influence of the wavelength variation of a pulsed laser on the size distribution of gold nanoparticles, synthesized by laser ablation in liquid medium, was determined, since this technique is the most used due to its simplicity as it is not developed under strict conditions of temperature, pressure, agitation, etc. Three different wavelengths were used: (i) 532 nm, (ii) 355 nm and (iii) 266 nm, due to equipment restrictions. The distributions and sizes of nanoparticles were studied by dynamic light scattering, scanning electron microscopy and atomic force microscopy. In addition, it is shown that the spectra of the gold region determine the chemical state of the nanoparticle. The results showed that the smallest particle size was obtained with the wavelength of 266 nm with a size of 9.6 nm, while for the other wavelengths; sizes of 55.4 nm and 77.3 nm were obtained respectively. Thus, smallest average diameter of gold nanoparticles was obtained with smallest wavelength.

Synthesis And Characterization Of Gold Nanoparticles Using Beluntas Leaf Extract Plucheaindica

Gold nanoparticles have been successfully synthesized using beluntas leaf extract as reducing agents. This is indicated by the change of the color from yellow gold to purple solution after the addition of the beluntas leaf extract. The gold nanoparticles formed were observed for 92 hours using uv-vis and obtained stability after 72 hours with a wavelength about 545.50-546.00 nm. The size distribution of gold nanoparticles was determined using Particle Size Analyzer (PSA) with an average distribution of 101.6 nm. Based on the characterization using XRD, the diffraction pattern obtained at 2θ is 38.1077; 44,2935; 64,5155; 77,4862 which show the presence of gold nanoparticles. Furthermore, it was characterized using SEM EDX showed that the average shape of gold nanoparticles was spherical with a composition ofAu 48%, C 43.33%, and several other elements around 8.67%.

Validation of Single Particle ICP-MS for Routine Measurements of Nanoparticle Size and Number Size Distribution.

Singleparticle inductively coupled plasma-mass spectrometry (spICP-MS) is an emerging technique capable of simultaneously measuring nanoparticle size and number concentration of metal-containing nanoparticles (NPs) at environmental levels. single particle ICP-MS will become an established measurement method once the metrological quality of the measurement results it produces have been proven incontrovertibly. This Article presents the first validation of spICP-MS capabilities for measuring mean NP size and number size distribution of gold nanoparticles (AuNPs). The validation is achieved by (i) calibration based on the consensus value for particle size derived from six different sizing techniques applied to National Institute of Standards and Technology (NIST) Reference Material (RM) 8013; (ii) comparison with high-resolution scanning electron microscopy (HR-SEM) used as a reference method, which is linked to the International System of Units (SI) through a calibration standard characterized by the NIST metrological atomic force microscope; and (iii) evaluation of the uncertainty associated with the measurement of the mean particle size to enable comparison of the spICP-MS and HR-SEM methods. After establishing HR-SEM and spICP-MS measurement protocols, both methods were used to characterize commercial AuNP suspensions of three different sizes (30, 60, and 100 nm) with four different coatings and surface charge at pH 7. Single particle ICP-MS measurements (corroborated by HR-SEM) revealed the existence of two distinct subpopulations of particles in the number size distributions for four of the 60 nm commercial suspensions, a fact that was not apparent in the measurement results supplied by the vendor using transmission electron microscopy. This finding illustrates the utility of spICP-MS for routine characterization of commercial AuNP suspensions regardless of size or coating.

A novel and simple microemulsion method for synthesis of biocompatible functionalized gold nanoparticles

Synthesize of functionalized gold nanoparticles has attracted a great deal of interest due to their favorable optical properties and broad range of biomedical applications. One challenge for biomedical application is to find a simple method in the manufacturing of biocompatible and stable water soluble gold particles with a well-controlled shape and size. In the current study, a novel methodology based on microemulsion system has been introduced to prepare biocompatible gold nanoparticles protected by a monohydroxy thioalkylated PEG ligand. The morphology and size distribution of gold nanoparticles was determined by different methods including dynamic light scattering (DLS), UV–visible spectrophotometry, Energy-dispersive X-ray analysis (EDX) and transmission electron microscopy (TEM). It is verified that the prepared water-based functionalized gold colloidal system has particles size in the range of 7–9 nm with no cytotoxicity effect to HeLa cells.

Nanoparticles-shape influenced high-efficient degradation of dyes: Comparative evaluation of nano-cubes vs nano-rods vs nano-spheres

Implementation of engineered nanoparticles as efficient catalysts for the degradation of hazardous dyes is being explored drastically. However, with predominant focus on correlating the catalytic activity with nanoparticle size and one particular shape (spheres), but other factors such as shape or morphology that can likely have a significant role in determining the catalytic reactivity remains elusive. In the present study we for the first time comparatively evaluate the influence of nearly uniform size-distributions of gold nanoparticles but with different crystallographic shapes; nano-cubes vs nano-rods vs nano-spheres, imparting overall diverse packing, density, electronic state, surface area and surface chemistry that can essentially determine the catalytic performances, on the catalysis of commonly used organic dyes; Methylene Blue and Safranin O as models. Our results highlighted that shape-influenced surface nano-chemistry had a drastic influence on the dye-degradation efficiencies. Relatively, at constant experimental parameters; nano-cubes possessing multi-flat-faceted surfaces were found to be highly efficient with instant degradation, followed by nano-rods with bilateral flat surface, that took up to 10min for Methylene Blue and 16min for Safranin O, whereas non-flat structured nano-spheres were least catalytic and took up to 90min for Methylene Blue, and showed only partial degradation against Safranin O, even after several hours. Nanoparticles shape assessments, quantitative and qualitative analysis of the dye-degradation, along with kinetic parameters were evaluated based on visual confirmation, capturing images using a digital camera, and advanced physical characterization techniques including UV-Vis Spectroscopy, Fourier Transform Infrared Spectroscopy and Transmission Electron Microscopy measurements.

A Novel Synthesis of Gold Nanoparticles Supported on Hybrid Polymer/Metal Oxide as Catalysts for p-Chloronitrobenzene Hydrogenation

This contribution reports a novel preparation of gold nanoparticles on polymer/metal oxide hybrid materials (Au/P[VBTACl]-M metal: Al, Ti or Zr) and their use as heterogeneous catalysts in liquid phase hydrogenation of p-chloronitrobenzene. The support was prepared by in situ radical polymerization/sol gel process of (4-vinyl-benzyl)trimethylammonium chloride and 3-(trimethoxysilyl)propyl methacrylate in conjunction with metal-alkoxides as metal oxide precursors. The supported catalyst was prepared by an ion exchange process using chloroauric acid (HAuCl4) as gold precursor. The support provided the appropriate environment to induce the spontaneous reduction and deposition of gold nanoparticles. The hybrid material was characterized. TEM and DRUV-vis results indicated that the gold forms spherical metallic nanoparticles and that their mean diameter increases in the sequence, Au/P[VBTACl]-Zr &gt; Au/P[VBTACl]-Al &gt; Au/P[VBTACl]-Ti. The reactivity of the Au catalysts toward the p-CNB hydrogenation reaction is attributed to the different particle size distributions of gold nanoparticles in the hybrid supports. The kinetic pseudo-first-order constant values for the catalysts in the hydrogenation reaction increases in the order, Au/P[VBTACl]-Al &gt; Au/P[VBTACl]-Zr &gt; Au/P[VBTACl]-Ti. The selectivity for all the catalytic systems was greater than 99% toward the chloroaniline target product. Finally the catalyst supported on the hybrid with Al as metal oxide could be reused at least four times without loss in activity or selectivity for the hydrogenation of p-CNB in ethanol as solvent.

Preparation and Characterization of Ganciclovir Loaded Glutathione Modified Gold Nanoparticles

In this research, ganciclovir-loaded gold nanoparticles were developed via glutathione surface modification. First citrate reduced gold nanoparticles were prepared from chloroauric acid. Further the surface of gold nanoparticles was also modified with glutathione. Then ganciclovir was loaded onto glutathione modified gold nanoparticles through the reaction between carboxyl group of glutathione and amino group of ganciclovir. Gold nanoparticles were characterized by photon correlation spectroscopy, transmission electron microscopy and infrared spectroscopy. The drug loading of 87.27±2.52% was observed for ganciclovir loaded gold nanoparticles. The particle size distribution of gold nanoparticles was ranged from 26.3 to 31 nm. Thus ganciclovir loaded gold nanoparticles were successfully prepared which may further improve the oral bioavailability of ganciclovir.

An improved methodology of asymmetric flow field flow fractionation hyphenated with inductively coupled mass spectrometry for the determination of size distribution of gold nanoparticles in dietary supplements

Engineered nanoparticles are available in large numbers of commercial products claiming various health benefits. Nanoparticle absorption, distribution, metabolism, excretion, and toxicity in a biological system are dependent on particle size, thus the determination of size and size distribution is essential for full characterization. Number based average size and size distribution is a major parameter for full characterization of the nanoparticle. In the case of polydispersed samples, large numbers of particles are needed to obtain accurate size distribution data. Herein, we report a rapid methodology, demonstrating improved nanoparticle recovery and excellent size resolution, for the characterization of gold nanoparticles in dietary supplements using asymmetric flow field flow fractionation coupled with visible absorption spectrometry and inductively coupled plasma mass spectrometry. A linear relationship between gold nanoparticle size and retention times was observed, and used for characterization of unknown samples. The particle size results from unknown samples were compared to results from traditional size analysis by transmission electron microscopy, and found to have less than a 5% deviation in size for unknown product over the size range from 7 to 30nm.

PH-dependent size distribution of gold nanoparticles investigated by in situ pH-monitoring throughout the synthetic reaction

The pH, one of the critical factors in determining the size distribution of gold nanoparticles (AuNPs), is not maintained at a constant value during the synthetic reaction. In this work, AuNPs were synthesized in the pH range of 5.5–10.5 and the pH was monitored in situ throughout the whole synthetic process. It was found that the citrate-based AuNP synthesis could be divided into two stages according to phases of pH change: a pH-decreasing early stage and a pH-increasing final stage. The narrowest size distribution at pH 7.5 can be well understood with these two phases of pH change.

A biocompatible synthesis of gold nanoparticles by Tris(hydroxymethyl)aminomethane.

Gold nanoparticles' novel properties are widely realized in catalysis, plasmonics, electronics, and biomedical applications. For biomedical application, one challenge is to find a non-toxic chemical and/or physical method of functionalizing gold nanoparticles with biomolecular compounds that can promote efficient binding, clearance, and biocompatibility and to assess their safety to other biological systems and their long-term effects on human health and reproduction. In the present study, we describe a new method by using Tris(hydroxymethyl)aminomethane (Tris), a widely used buffer solvent of nucleic acid and proteins, as the reducing agent for synthesizing gold nanoparticles by one step. It is found that Tris carries out the reduction reactions in relatively mild conditions for biomacromolecules. Particularly, it can be used to modify the DNA during the process of preparation of gold nanoparticles. The morphology and size distribution of gold nanoparticles are consistent and were confirmed by many different approaches including dynamic light scattering (DLS), UV-visible (UV-vis) spectrophotometry, atomic force microscopy (AFM), and transmission electron microscopy (TEM).

Growth and size distribution of Au nanoparticles in annealed Au/TiO2 thin films

Nanocomposites consisting of noble metal nanoparticles (NPs) embedded in TiO2 thin films are of great interest for applications in optoelectronics, photocatalysis and solar-cells for which the plasmonic properties of the metal NPs play a major role. This work investigates the first stages of the formation of gold NPs by thermal annealing of Au-doped TiO2 thin films grown by magnetron sputtering. A low concentration of gold in the films is considered (5at.%) in order to study the first stages of the formation of the NPs. Raman spectroscopy is used to follow the crystallization of TiO2 when increasing the annealing temperature. In addition, low-frequency Raman scattering (LFRS) is used to investigate the formation of gold NPs and to determine their size. Resonant LFRS measurements obtained by using a laser wavelength matching the surface plasmon resonance of the metallic NPs significantly enhances the Raman peak intensity enabling to focus on the first stages of the NPs formation. A double size distribution is observed at Ta=800°C calling for additional investigations by transmission electron microscopy (TEM). TEM observations reveal an inhomogeneous in-depth size distribution of gold NPs. The annealed films are structured in two sublayers with bigger NPs at the bottom and smaller NPs at the top. At Ta=800°C, a double size distribution is confirmed near the surface. A mechanism is proposed to explain the formation of the sublayers. The modification of the diffusion of gold atoms by stresses in the film near the substrate is assumed to be responsible for the observed two layers structure.