Gold Nanoparticles In Solution Research Articles

Gold nanoparticle-based colorimetric methods to determine protein contents in artificial urine using membrane micro-concentrators and mobile phone camera

In this paper, we use an ion-exchange membrane disk to develop miniaturized concentration device, which employs gold nanoparticle (GNP) colorimetric assay to determine human serum albumin content in artificial urine samples.When an external field is applied across cation exchange substrate, the ion depletion appears on the anodic side when the ions are enriched on the cathodic side to fulfill mass conservation and electrical neutrality constrains. In particular when the ion exchange substrates are of round shape, the field lines passing through the membrane disk are focused at the exit pole to further enhance concentration polarization to result in a superconcentraiton spot.GNP colorimetric assays to determine albumin are carried out using the miniaturized concentration chip containing a Nafion® cation-exchange membrane disk. Under alkaline condition when GNP solution is spiked with albumins to concentrate using the membrane disk, anionic albumins can prevent the concentrated GNP’s from aggregation and the concentrated GNP’s remain in red color even in highly salty solutions. On the other hand without efficient protections by absorbed albumins, GNP’s aggregate and change color to blue. Using smart phone camera to acquire the concentration images of non-aggregated nanoparticles, one linear correlation is found between the red color intensity and the logarithm values of albumin concentration to quantify albumin amounts. This colorimetric assay is validated to determine the samples of the main urine protein, human serum albumin at the range of clinical significance (0.1–20μM) in artificial urine matrix containing creatinine and urine. These results prove the feasibility of using the membrane-based micro-concentration device with mobile phone camera.

Development of enhancing agglutination reaction using gold nanoparticle for pre-transfusion testing.

To explore an alternative way for antibody detection testing, the examination of gold nanoparticle solution for enhancing unexpected antibodies for pre-transfusion testing was investigated. Exposure of foreign antigens on red blood cells from transfusion can trigger the immune system to produce unexpected antibodies. This immunological response may cause the complication to future transfusion. For detection of unexpected antibodies, the antibody screening test is performed approximately 30-60 min. To reduce turnaround time, enhancing reagent, low-ionic strength solution (LISS), is widely used. However, cost of enhancing reagent is an issue which has concerned in resource limited countries. Gold nanoparticle solution can increase red blood cells agglutination reaction. To solve this issue, study of gold nanoparticle solution was investigated. Samples were performed comparing between LISS and gold nanoparticle solution at antiglobulin phase. After reading the agglutination reaction, supernatants were collected and measured at the optical density at 760 nm by spectrophotometer. The optical density in the tube of gold nanoparticle solution was higher than in the tube of 2-5% cell suspension and monoclonal antibody. It has been observed that gold nanoparticle solution enhanced the reaction of agglutination 98% while LISS enhanced the agglutination only 60·8%. Employing a commercially available enhancing reagent, parallel samples confirmed results providing validation of the assay. It approximately costs $1 US dollars compared to $30 for a commercially available reagent. The low cost and yet effective time-consuming test for antibody screening is a practical and viable solution alternative way for performing in antibody screening test in resource limited countries.

Side Effect of Good's Buffers on Optical Properties of Gold Nanoparticle Solutions

AbstractIn search of fluorescent nanoclusters (NCs) for bioimaging, several methods of synthesis have been attempted. Particularly, formation of gold NCs (AuNCs) during synthesis of gold nanoparticles (AuNPs) using Good's buffers has been reported based on the optical properties of the reaction mixtures. Here we chose Good's buffers 2‐(N‐morpholino)ethanesulfonic acid (MES), 3‐(N‐morpholino)propanesulfonic acid (MOPS) and 4‐(N‐morpholino)butanesulfonic acid (MOBS) as [AuCl4]−‐reducing agents. Resulting AuNP solutions were subjected to electrochemical investigations along with UV/Vis and fluorescence spectroscopy. Distinct absorption features at approximately 290 and 360 nm and fluorescence emission in the 408–484 nm range in filtered AuNP‐free solutions were observed. Electrochemical oxidation of these buffers generates similar optical properties, suggesting that the degradation products of the buffers contribute to the optical properties of AuNP solutions. This work indicates that a deeper evaluation of fluorescence signals based on metal NPs or NCs is needed.

Plasmonic Metamaterial Absorbers from Dense Gold Nanoparticle Stacks

Gold nanoparticle solutions were used to make highly absorbing, dense nanoparticle stacks (DNpS) using a simple and inexpensive solution cast method. UV-Vis spectroscopy and reflection measurements were used to characterize absorption. The critical nanoparticle number necessary to obtain maximal absorption was determined for each sample. DNpS metamaterials made from 18- and 44-nm-diameter particles exhibited broadband absorbances above 80 %, with the highest absorption of 95 % at 532 nm. The experimental absorption results agree well with finite-difference time-domain (FDTD) modeling.

Role of Au(III) coordination by polymer in ⿿green⿿ synthesis of gold nanoparticles using chitosan derivatives

Here we report ⿿green⿿ synthesis of gold nanoparticles in solutions of heterocyclic chitosan derivatives (N-(4-imidazolyl)methylchitosan (IMC), N-2-(2-pyridyl)ethylchitosan (2-PEC), and N-2-(4-pyridyl)ethylchitosan (4-PEC)) and show how efficiency of Au(III) binding to polymer influences the Au(III) reduction rate and the size of the gold nanoparticles formed using only the reducing power of these chitosan derivatives. Rheology measurements and 1H NMR spectroscopy data have confirmed that cleavage of glycosidic bond is a common mechanism of reducing species generation in solutions of chitosan and its N-heterocyclic derivatives. However, the emerging additional reducing species in 2-PEC and 4-PEC solutions due to vinylpyridine elimination promotes Au(III) reduction and gold nanoparticles growth despite lower efficiency of glycosidic bond cleavage in pyridyl derivatives. The decrease of the average size of gold nanoparticles in the row chitosan>2-PEC>IMC supported assumption that the increase of ligand nucleophilicity and stability of Au(III)-polymer complex results in formation of smaller nanoparticles.

On-Demand Surface- and Tip-Enhanced Raman Spectroscopy Using Dielectrophoretic Trapping and Nanopore Sensing

Surface-enhanced Raman spectroscopy (SERS) and tip-enhanced Raman spectroscopy (TERS) have shown great promise in the detection and analysis of trace analytes throughout numerous fields of study. Both SERS and TERS utilize nanoscale plasmonic surface features to increase the intensity of observed Raman signals by many orders of magnitude (>108). One of the major factors limiting the wider and more routine implementation of the enhanced Raman phenomena is in the difficulty of forming consistent and reliable plasmonic substrates with well-defined “hot-spots”. We address this limitation by designing a platform that can be used for both SERS and TERS. The presented technique allows for rapid, controlled, “on-demand”, and reversible formation of a SERS substrate using dielectrophoresis at the end of a nanoscale pipet. This drives gold nanoparticles in solution to concentrate and self-assemble at the tip of the pipet, where analytes can be detected effectively using SERS. An additional benefit of the platform i...

Electrodeposition of Gold Nanoparticles in Dimethylformamide Solutions of H[AuCl4

We study the electrochemical deposition of gold nanoparticles in solutions of 0.002–0.008 M H[AuCl4] + 0.05 M Bu4NClO4 in dimethylformamide on the surfaces of glassy carbon, titanium, and ITO-glass (Indium-Tin Oxide glass). It is shown that the electric reduction of the metal begins at a cathode potential E = – 0.1 V and continues up to – 1.2 V. As a result, we observe the formation of discrete particles from tens to hundreds nanometers in size. It is shown that the main factors affecting the morphology of deposits are the cathode potential, the duration of electrodeposition, and the concentration of H[AuCl4] in the solution.

Synthesis and stabilization of gold nanoparticles by inverse reduction method using sodium citrate and sodium boro hydride as reducing agent

In recent decades, observed focus largely on the preparation of nano metallic elements, including the gold because of its unique properties and many applications. In most of these researches, the Turkevich' method has been adopted. This method is based on the reduction of gold ion Au3+ to the nano gold Au0 by the addition of a reducing agent to the gold salt H[AuCl4].3H2O. In this research, a novel simple and cost-effective technique is enhanced via the addition of the gold ion (Au3+) to the decreasing agent in opposite to the previous method. This is the cause to call it "The inverse method". In this inverse method one can control the amount of gold salt solution that add and stop this addition by observing the formation of the red color, which indicates the formation of gold nanoparticles(GNPs).Many reactions were conducted to prepare stable gold nanoparticles by usingchemical reducing agents such as (sodium tri-citrate, sodium borohydride),The reactions to prepare GNPs using these reducing agents were done at temperature of 60 – 80 °C.The resulted GNPs were characterized by UV- Vis spectra, zeta potential, atomic force microscope(AFM), scanning electron microscope(SEM), and transmission electron microscope(TEM).The absorption spectrum of the red GNPs solution appeared at the range of 520-540 nm. The gold nanoparticles which formed from various reactions have different shapes but the most prominent form is the spherical, and the sizes have also been different and appeared at the range of 14.5- 44 nm, which are consistent with published researches.

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.

Synthesis of Gold Nanoparticles and Association of DNA-Gold Nanoparticles

<p>This study examined the synthesis of gold nanoparticles using a non-ionic surfactant, polysorbate 80, and KAuCl<sub>4 </sub>in water. The gold nanoparticles, which were well dispersed in water, were analyzed by UV-vis spectroscopy and transmission electron microscopy (TEM). In addition, the SRY(sex-determining region Y) gene of the Bos taurus specific primer was designed, and this primer solution was mixed with the aqueous gold nanoparticles solution. The binding ability of DNA and gold nanoparticles was identified by polyacryllamide gel electrophoresis. The products of DNA linked with gold nanoparticles were also characterized by UV-vis spectroscopy and TEM.</p>

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.

Modeling the atomistic growth behavior of gold nanoparticles in solution.

The properties of gold nanoparticles strongly depend on their three-dimensional atomic structure, leading to an increased emphasis on controlling and predicting nanoparticle structural evolution during the synthesis process. In order to provide this atomistic-level insight and establish a link to the experimentally-observed growth behavior, a kinetic Monte Carlo simulation (KMC) approach is developed for capturing Au nanoparticle growth characteristics. The advantage of this approach is that, compared to traditional molecular dynamics simulations, the atomistic nanoparticle structural evolution can be tracked on time scales that approach the actual experiments. This has enabled several different comparisons against experimental benchmarks, and it has helped transition the KMC simulations from a hypothetical toy model into a more experimentally-relevant test-bed. The model is initially parameterized by performing a series of automated comparisons of Au nanoparticle growth curves versus the experimental observations, and then the refined model allows for detailed structural analysis of the nanoparticle growth behavior. Although the Au nanoparticles are roughly spherical, the maximum/minimum dimensions deviate from the average by approximately 12.5%, which is consistent with the corresponding experiments. Also, a surface texture analysis highlights the changes in the surface structure as a function of time. While the nanoparticles show similar surface structures throughout the growth process, there can be some significant differences during the initial growth at different synthesis conditions.

Impedance Analysis of Colloidal Gold Nanoparticles in Chromatography Paper for Quantitation of an Immunochromatographic Assay.

A detection method of gold nanoparticles in chromatography paper has been developed for a simple, cost-effective and reliable quantitation of immunochromatographic strip test. The time courses of the solution resistance in chromatography paper with the gold nanoparticles solution are electrochemically measured by chrono-impedimetry. The dependence of the solution resistance on the concentration of gold nanoparticles has been successfully observed. The main factor to increase the solution resistance may be obstruction of the ion transport due to the presence of gold nanoparticles. The existence of gold nanoparticles with 1.92 × 10(9) particles/mL in an indistinctly-colored chromatography paper is also identified by a solution resistance measurement. This indicates that the solution resistance assay has the potential to lower the detection limit of the conventional qualitative assay.

Pegylated Curcumin with Gold Nanoparticles: Antimicrobial Agent Evaluation

Extended Abstract Curcumin is a polyphenol derived from the Curcuma Longa plant. Curcumin exhibits a variety of therapeutic properties, including antioxidant, analgesic, anti-inflammatory, anticancer and antiseptic activities [1]. Curcumin acts as photosensitizer in photodynamic therapy (PDT), which is an alternative way to kill pathogenic microorganisms [2]. The use of gold nanoparticles (AuNPs) as the vehicle for curcumin delivery increases photodynamic ability [3]. Therefore, the present study aim is to investigate the effect of the photodynamic action of LED-activated curcumin gold nanoparticles, on cell viability of Staphylococcus aureus, Staphylococcus aureus (Sa), Staphylococcus epidermidis (Se), Pseudomonas aeruginosa (Pa), Escherichia coli (Ec), Citrobacter freundii (Cf) and Klebsiella pneumoniae (Kp). To prepare Curcumin gold nanoparticles (Curc:AuNps) solutions, 3.2 mg of HAuCl4 was mixed with 1.5 mg Curcumin and Polyethylene glycol (PEG) in Mili-Q water. This solution was exposed to light from a mercury metal halide lamp. The resulting solutions were characterized by UV-Vis and transmission electron microscopy (TEM). The in vitro antibacterial activity of Curc:AuNps was evaluated against Sa, Se, Pa, Ec, Cf and Kp using the minimum inhibitory concentration (MIC) test. The effects of exposure to yellow LED light with ~38 J/cm fluence and variations in the Curc:AuNPs concentrations (50, 75 and 100% dilutions) were studied. The presence of a surface plasmon resonance band at ~520 nm indicated the formation of spherical gold nanoparticles. In the presence of PEG, the solution color changed some minutes after the mixing of reagents, and solution size homogeneity was improved with the mercury metal halide lamp illumination. TEM analyses showed ~17±2 nm nanoparticles. The results indicate that PDT with curcumin gold nanoparticles strongly inhibits the development of Gram positive and Gram negative bacteria. This study revealed antibacterial probability of inhibition >80% with 32 mM of Curc:AuNPs and light against Sa, Se, Cf and Kp strains after 18 hours of incubation. NOVA/Tukey's tests were conducted to compare groups curcumin/Curc:AuNPs, with and without photodynamic excitation. This work was supported by the “Fundacao de Amparo a Pesquisa do Estado de Sao Paulo” (FAPESP), Grant number 2014/06960-9.

Gold Nanoparticle Treated Textile-Based Materials for Potential use as Wearable Sensors

Wearable sensors for monitoring and clinical applications for non-hospital-based healthcare has the potential to significantly reduce healthcare costs and permit individuals to maintain an independent lifestyle free of the constraints imposed by hospital-based care. Wearable, small chemical sensors have the potential to deliver a wide range of reliable on body monitoring systems for personal monitoring and detecting chemicals in the environment. The present work investigates the potential of using widely available commercial fabric materials as chemical sensors. Various fabrics including natural, synthetics and blends of both natural and synthetic were treated with gold nanoparticle solutions to determine the treatments effectiveness in changing a materials electrical resistance. The studies found treating the fabrics reduced the materials resistive characteristics. The study also found that treated natural silk fabrics could also be used to detect ethanol vapour. Thus, making treated silk fabrics a potential chemical sensor.

Preparation of high-concentration colloidal solution of silica-coated gold nanoparticles and their application to X-ray imaging

This study proposes a method for preparing high-concentration silica-coated Au (Au/SiO2) nanoparticles in colloidal solution from 1.5 × 10−3 M hydrogen tetrachloroaurate (III) trihydrate as the Au source and 1.0 × 10−2 M sodium citrate as the reducing reagent. The colloidal solution is applied to X-ray computed tomography (CT) imaging of mouse tissue. The Au nanoparticles in the colloidal solution had a diameter of 18.9 nm, and the Au concentration reached 1.5 × 10−3 M. The Au nanoparticles were silica-coated by modifying their surfaces with (3-aminopropyl)trimethoxysilane (APMS), then depositing silica nuclei generated by a sol–gel reaction of tetraethyl orthosilicate (TEOS) in water/ethanol initiated with sodium hydroxide (NaOH) on the surface modified with APMS. A colloidal solution of Au/SiO2 core–shell particles (silica shell thickness = 19.7 nm) was formed in a final as-prepared solution of 2.7 × 10−4 M Au, 2.0 × 10−5 M APMS, 24 M H2O, 1.9 × 10−3 M NaOH, and 4.1 × 10−3 M TEOS. The Au in the as-prepared colloidal solution was further concentrated to 0.27 M by salting-out and centrifugation. The CT value of the concentrated Au/SiO2 colloidal solution was 2.52 × 103 Hounsfield units, double that of a commercial X-ray contrast agent with the same I concentration as the Au concentration. When injected into mouse tissue, the Au/SiO2 colloidal solution demonstrated good imaging capability.

Biosynthesis of Gold Nanoparticles with <i>Serratia marcescens </i>Bacteria

This paper presents the biosynthesis of gold nanoparticles from the bacteria, Serratia marcescens.The intra-and extra-cellular synthesis of gold nanoparticles is shown to occur over a range of pH and incubation times in cell-free exracts and biomass ofserratia marcescensthat were reacted with 2.5mM Tetrachloroauric acid (HAuCl4). The formation of gold nanoparticles was identified initially via color changes from yellow auro-chloride to shades of red or purple in gold nanoparticle solutions. UV-Visible spectroscopy (UV-Vis), Transmission Electron Microscopy (TEM) and Energy Dispersive X-ray spectroscopy (EDS), Helium Ion Microscopy (HIM) and Dynamic Light Scattering (DLS) were also used to characterize gold nanoparticles produced within a range of pH conditions. The results show clearly that the production of gold nanoparticles from cell-free extracts require shorter times than the production of gold nanoparticles from the biomass.

Polarization and spectral characteristics of the two-photon luminescence from colloidal gold nanoparticles excited by tunable laser radiation

We have experimentally studied two-photon luminescence from a colloidal solution of spherical gold nanoparticles by tuning the wavelength of the exciting radiation. The measured polarization and spectral characteristics of the two-photon luminescence signal show that the observed nonlinear optical response is determined by the dimers present in the solution with a concentration of a few percent of total nanoparticle number.

Transport equation in the problem of the distribution function of nanoparticles in a colloidal solution exposed to laser pulses

The behaviour of a colloidal solution of gold nanoparticles irradiated by a repetitively pulsed laser with a pulse duration of a few nanoseconds is investigated theoretically and experimentally. A mathematical model is constructed, which allows the behaviour of the nanoparticle distribution function to be described. The model is based on the transport equation in the ‘space’ of particle sizes. The proposed model allows for a relatively simple study and makes it possible to establish some common patterns in the behaviour of an ensemble of nanoparticles under various conditions. The results obtained are in satisfactory agreement with the available experimental data.

Highly sensitive gold nanoparticles-based optical sensing of DNA hybridization using bis(8-hydroxyquinoline-5-solphonate)cerium(III) chloride as a novel fluorescence probe

A simple and sensitive method for the detection of DNA hybridization in a homogeneous format was developed, using bis(8-hydroxyquinoline-5-solphonate)cerium(III) chloride (Ce(QS)2Cl) as a novel fluorescent probe. The method is based on fluorescence quenching by gold nanoparticles used as both nanoscafolds for the immobilization of the probe DNA sequence, which is related to Alicyclobacillus acidophilus strain TA-67 16S ribosomal RNA, and nanoquenchers of the Ce(QS)2Cl probe. The probe DNA-functionalized GNPs were synthesized by derivatizing the colloidal gold nanoparticles solution with 3-thiolated 16-base oligonucleotides. Addition of sequence-specific target DNAs (16 bases) into the mixture containing probe DNA-functionalized GNPs and fluorescent probe lead to the quenching of Ce(QS)2Cl fluorescence at 360nm (λex=270nm), due to DNA hybridization, the resulting quenched intensity being proportional to the concentration of target DNA. Under optimal conditions of pH 7.4 and Ce(QS)2Cl concentration of 1.0×10−7M, the linear dynamic range found to be 1.0×10−10−3.0×10−8M DNA, with a limit of detection of 7.0×10−11M. The interaction mechanism for the binding of Ce(QS)2Cl to DNA was studied in detail, and results proved that the interaction mode between Ce(QS)2Cl and DNA is groove binding, with a binding constant of 1.0×105M−1.