Gold Nanoparticles In Solution Research Articles

Silicon Nanowire Biosensors for Diabetes Mellitus Monitoring

The main goal of this research is the development of a label-free biosensor for the detection of diabetes mellitus (DM) using the target molecule retinol-binding protein 4 (RBP4). The enzyme-linked immunosorbent assay (ELISA) approach, currently used to detect DM, is time-consuming and difficult. As a result, label-free biosensors are being considered as an alternative. In this research, silicon nanowires (SiNWs) were selected as the transducer for this biosensor due to their low cost, real-time analysis capability, high sensitivity, and low detection limit. The SiNWs were created using conventional lithography, reactive ion etching (RIE), and physical vapor deposition (PVD), and then dripped with a gold nanoparticle solution to create gold-decorated SiNWs. The surface of the gold-decorated SiNWs was functionalized using 3-aminothiophenol and glutaraldehyde solutions before being immobilized with DM RBP4 antibodies and targets. The electrical characterization of the gold nanoparticle decorated SiNWs biosensor revealed good performance in DM detection. The pH tests confirmed that the SiNWs acted as a transducer, with current proportional to the DM RBP4 concentration. The estimated limit of detection (LOD) and sensitivity for detecting DM RBP4 binding were 0.076 fg/mL and 8.92 nA(g/mL)-1, respectively. This gold nanoparticle decorated SiNWs biosensor performed better than other methods and enabled efficient, accurate, and direct detection of DM. The SiNWs could be used as a distinctive electrical protein biosensor for biological diagnostic purposes. In conclusion, gold nanoparticle deposition offers effective label-free, direct, and high-accuracy DM detection, outperforming previous approaches. Thus, these SiNWs serve as novel electrical protein biosensors for future biological diagnostic applications.

Complex Formation of Gold Nanoparticles with Collagen in Aqueous Media Studied by X-ray Scattering and Absorption Spectroscopy.

Small-angle X-ray scattering and UV-vis absorption measurements were performed on mixed solutions of gold nanoparticles (AuNPs) and atelocollagen (AC), triple-helical collagen without telopeptide, in acetate buffer at pH 4 under different temperature conditions, i.e., preparation temperature Tprep and measurement temperature Tmeas. Due to the significantly higher electron density of gold than that of AC, the structure factor S(q) of AuNPs is readily estimated from the scattering intensities of AuNP-only and mixed solutions. The resulting S(q) profile for the mixed solution indicated significant attractive interactions, especially for the smaller AuNPs. Therefore, the sticky sphere model was applied to analyze S(q) to determine the interaction parameters at different Tprep and Tmeas. The attractive interactions between AuNPs were higher at higher Tprep, suggesting that single-chain AC tends to make the interactions between AuNPs more attractive than those for triple-helical AC. Complex formation was also detected by the aggregation-induced surface plasmon absorption shift. More densely packed AuNPs were detected from the absorption spectra for higher AuNP content at which the ζ potential disappeared, while a split absorption band was also found, indicating that not all AuNPs can form a complex with AC at ζ = 0.

Unraveling the Dominant Size Effect in Polydisperse Solutions and Maximal Electric Field Enhancement of Gold Nanoparticles

Unraveling the Dominant Size Effect in Polydisperse Solutions and Maximal Electric Field Enhancement of Gold Nanoparticles

Development of Gold Inks for Inkjet Printing of Gas Sensors Electrodes on Plastic Support

Among the conventional inks used for inkjet printing, metals, oxides, or polymers have been deposited in order to form functional coatings. Gold is one of the most used metals for electrode fabrication in the gas sensor field due to its inert behavior when exposed to reactive gases and conductive properties. However, only a few commercial gold inks are commercially available, and the combination of excessive price, a high minimum purchase quantity, and an unknown composition renders the actual products unappealing. To meet these shortcomings, gold inks were formulated with different solvents in order to reach sufficient properties for the inkjet printing process, such as surface tension and viscosity. On the one hand, gold ink was developed using a gold nanoparticle (AuNP) solution as the metal. This ink was optimized from nanoparticle synthesis, with the ink formulation obtaining a 32 mN·m−1 surface tension and 11.2 mPa·s viscosity in order to be inkjet-printed onto polyimide foil. On the other hand, a particle-free ink, called a precursor based of ink, was also developed. In this case, ink was made by solubilizing gold salt in aqueous medium in order to reach jettable properties. Surface tension was measured at 32 mN·m−1 while viscosity was 14.0 mPa·s. Then, printing and deposition parameters were optimized in order to obtain a highly conductive gold coating. The measured resistivity was 2 × 10−7 Ω·m which is close to the bulk gold conductive value. These coatings could be used for the fabrication of various devices in different working fields.

Photometric evaluations of reverse micellar solutions of gold and silver nanoparticles and their adsorption activity upon the contact with MF-4SK film

Photometric evaluations of reverse micellar solutions of gold and silver nanoparticles and their adsorption activity upon the contact with MF-4SK film

Nanoparticles Enhanced Laser-Induced Breakdown Spectroscopy for Characterisation and Discrimination of Gemstones

Laser-induced breakdown spectroscopy (LIBS) is an excellent technique for rapid on-site investigations that attracts interest from diverse research areas. Gemmology is no exception. The application of LIBS for gemstone characterisation is limited due to ineffective ablation and crack formation, even more so with cost-effective, non-gated LIBS systems. Nanoparticle-enhanced LIBS (NELIBS) has proven to improve the effectiveness of LIBS by minimizing sample damage and enhancing the spectral features. Therefore, this study is dedicated to exploring the advantages of NELIBS, for characterising Sapphire and Opal and discrimination based on spectral differences. Our objective is to explore enhancing spectral features and performing discriminant analysis using the PLS-DA algorithm. Nanoparticles (NPs) were deposited in two layers by sequentially drying two drops (2µL) of a colloidal solution of 20nm gold nanoparticles (AuNPs) on the sample surface. Targeted areas were shot with 3 pulses of Nd:YAG laser (~350mJ, 10ns, 1064nm, 1Hz) for collecting NELIBS spectra with the OceanOptics HR4000 spectrometer. The procedure was repeated without NPs for comparative analysis with conventional LIBS (CLIBS). Results have shown a significant enhancement in spectral features, i.e., the emergence of several new spectral lines of major gemstone elements in the UV-Vis regions of the NELIBS spectra, while the CLIBS spectra were devoid of any meaningful spectral information. The PLS-DA model was trained and validated using a 4fold cross-validation approach. The model discriminated gemstones with 99.48% accuracy at the 4th fold and exhibited a mean cross-validation accuracy of 98.97%. This preliminary investigation demonstrates the effectiveness of NELIBS for characterization and the potential for onsite identification of gemstones.

A novel dye-sensitised solar cell based portable sensor for chemical detection

In recent years, chemical sensors have shown the potential to provide rapid, accurate, and on-site quantitative detection of analytes, but current methods often require specialised equipment. In this study, a novel dye-sensitised solar cell (DSSC) based sensor is reported for convenient detection of tert-butylhydroquinone (TBHQ) in drinking water. The sensor consists of a gold nanoparticle (AuNP) solution based unit that responds to the concentration of TBHQ and produces an electrical signal change via an integrated DSSC based transducer component. Through analysing the current signal generated by the DSSC sensor, the quantity of TBHQ in an unknown sample can be achieved. Finite difference time domain (FDTD) simulation has been used to explain the relationship between the particle morphologies and optical properties of AuNPs. This work offers a novel strategy of developing portable sensors without needing any scientific instrument.

Effect of Aspect Ratio of a Gold-Nanorod-Modified Screen-Printed Carbon Electrode for Carbaryl Detection in Three Different Samples of Vegetables.

In this study, three different sizes of gold nanorods (AuNRs) were synthesized using the seed-growth method by adding various volumes of AgNO3 as 400, 600, and 800 μL into the growth solution of gold nanoparticles. Three different sizes of AuNRs were then characterized using UV-vis spectroscopy, high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED) patterns, and atomic force microscopy (AFM) to investigate the surface morphology, topography, and aspect ratios of each synthesized AuNR. The aspect ratios from the histogram of size distributions of three AuNRs as 2.21, 2.53, and 2.85 can be calculated corresponding to the addition of AgNO3 volumes of 400, 600, and 800 μL. Moreover, each AuNR in three different aspect ratios was drop-cast onto the surface of a commercial screen-printed carbon electrode (SPCE) to obtain three different SPCE-modified AuNRs (SPCE-A400, SPCE-A600, and SPCE-A800, respectively). All SPCE-modified AuNRs were then evaluated for their electrochemical behavior using cyclic voltammetry and electrochemical impedance spectroscopy (EIS) techniques and the highest electrochemical performance was shown as the order of magnitude of SPCE-A400 > SPCE-A600/SPCE-A800. The reason for the highest electrocatalytic activity of SPCE-A400 might be due to the smallest particle size and uniform distribution of AuNRs ∼ 2.2, which enhanced the charge transfer, thus providing the highest electroactive surface area (0.6685 cm2) compared to other electrodes. These results also confirm that the sensing mechanism for all SPCE-modified AuNRs is controlled by diffusion phenomena. In addition, the optimum pH was obtained as 4 for carbaryl detection for all SPCE-modified AuNRs with the highest current shown by SPCE-A400. Furthermore, SPCE-A400 has the highest fundamental parameters (surface coverage, catalytic rate constant, electron transfer rate constant, and adsorption capacity) for carbaryl detection, which were investigated using cyclic voltammetry and chronoamperometric techniques. The electroanalytical performances of all SPCE-modified AuNRs for carbaryl detection were also investigated with SPCE-A400 displaying the best performance among other electrodes in terms of its linearity (0.2-100 μM), limit of detection (LOD) ∼ 0.07 μM, and limit of quantification (LOQ) ∼ 0.2 μM. All SPCE-modified AuNRs were also subsequently evaluated for their stability, reproducibility, and selectivity in the presence of interfering species such as NaNO2, NH4NO3, Zn(CH3CO2)2, FeSO4, diazinon, and glucose and show reliable results as depicted from %RSD values less than 3%. At last, all SPCE-modified AuNRs have been employed for carbaryl detection using a standard addition technique in three different samples of vegetables (cabbage, cucumber, and Chinese cabbage) with its results (%recovery ≈ 100%) within the acceptable analytical range. In conclusion, this work demonstrates the great potential of a disposable device based on an AuNR-modified SPCE for rapid detection and high sensitivity in monitoring the concentration of carbaryl as a residual pesticide in vegetable samples.

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.

Multivariate Analysis of Protein-Nanoparticle Binding Data Reveals a Selective Effect of Nanoparticle Material on the Formation of Soft Corona.

When nanoparticles are introduced into the bloodstream, plasma proteins accumulate at their surface, forming a protein corona. This corona affects the properties of intravenously administered nanomedicines. The firmly bound layer of plasma proteins in direct contact with the nanomaterial is called the "hard corona". There is also a "soft corona" of loosely associated proteins. While the hard corona has been extensively studied, the soft corona is less understood due to its inaccessibility to analytical techniques. Our study used dynamic light scattering to determine the dissociation constant and thickness of the protein corona formed in solutions of silica or gold nanoparticles mixed with serum albumin, transferrin or prothrombin. Multivariate analysis showed that the nanoparticle material had a greater impact on binding properties than the protein type. Serum albumin had a distinct binding pattern compared to the other proteins tested. This pilot study provides a blueprint for future investigations into the complexity of the soft protein corona, which is key to developing nanomedicines.

Experimental and Theoretical Study of Biosurfactants Functionalized Gold Nanoparticles for Mixture Detection and Chiral Recognition of Tryptophan by UV-VIS Spectroscopy

Background: Tryptophan (Trp) is an essential amino acid and plays important roles in biological processes. The detection of Trp is very important for its biological and chemical study. Moreover, Trp is a chiral compound; due to its importance in biological processes, researchers have been long committed to the chiral recognition and sensing of Trp enantiomers. Methods: Two biosurfactants, sodium cholate and sodium deoxycholate, were used for the preparation of functionalized gold nanoparticles (AuNPs) which were characterized by transmission electron microscope and potentiometer. UV-Vis spectra of functionalized gold nanoparticle solutions with different concentrations of Trp, tyrosine, phenylalanine, D-Trp, and L-Trp were analyzed. Then, the discrimination mechanism was further investigated, and the promotion mechanism of biosurfactants was studied by density functional theory (DFT). Results: Trp could induce the aggregation of unmodified AuNPs in 2 h, while phenylalanine and tyrosine could not. Adding biosurfactants promoted the aggregation process, and D- Trp rather than LTrp was found to be responsible for the aggregation. Therefore, there were interaction differences not only between Trp, phenylalanine, and tyrosine but also between Trp enantiomers. Conclusions: UV-vis spectroscopy could be applied for the direct detection of Trp in mixtures as well as the chiral recognition of Trp enantiomers. DFT calculations proved that the interactions of D-Trp with biosurfactants were the strongest, which contributes to the promotion of aggregation.

Theoretical investigation on the effect of volume fraction in the optical trapping of gold nanoparticles

Stable optical trapping of gold nanoparticles is essential and desirable because of its wide applications in nanotechnology. While several factors have been proposed to affect optical trapping stability, the sample’s volume fraction during optical trapping has often been neglected. To address this, by utilizing the effective medium theory, we analyze the stability of optical trapping of a gold nanoparticle in human serum albumin solutions, HIV-1,virus solutions, and gold nanoparticle solutions in this article. Our comparative analysis of the optical force and potential on a single gold nanoparticle in solutions of varying volume fractions reveals that both parameters decrease with increasing volume fraction. This finding can aid in more effective control of gold nanoparticles in various applications.

Headspace single-drop microextraction combined with nanodrop spectrophotometry for ultra-trace detection of ethanethiol using a suspended drop of AuNPs as a plasmonic sensor

It is challenging to achieve ethanethiol extraction, enrichment in a single-drop microextraction system, and an assay with good sensitivity and selectivity for analyzing food analytes in complex matrices. In this study, we combined headspace single-drop microextraction (HS-SDME) with nanodrop array spectrophotometry applied for ultra-trace determination of ethanethiol. A suspended drop of gold nanoparticles (AuNPs) solution was utilized for sensing ethanethiol as an acceptor phase. The thiol portion of ethanethiol molecules binds to the negatively charged AuNPs. Thus, the aim of target enrichment was attained, while matrix effects interference was also minimized. The approach can be used for the direct detection of ethanethiol in food without any sample pretreatment. The obtained range of linearity was 1–1000 µM and 100–1000 nM. The detection limits were 66.62 nM, comparable with those of previously reported methods. The method successfully determined ethanethiol in food (beverage, non-alcoholic beer, and cheese).

Hydrophobicity and FTIR absorbance spectroscopy of Polydimethylsiloxane (PDMS) films treated with aqueous gold nanoparticles (AuNP) solution

Polydimethylsiloxane (PDMS) thin films were treated with aqueous solutions of gold nanoparticles. Samples treated for 24, 48, and 72 h, including untreated PDMS film, were subjected to hydrophobicity test and FTIR absorbance spectroscopy. Hydrophobicity test involved measuring the contact angle of water droplets placed on top of the sample films. Contact angles were measured using Image J software. Treated samples showed significant hydrophobicity changes shown by the increasing value of measured contact angle from 71.3° for the untreated sample to 104.0° for the sample treated for 72 h. FTIR absorbance spectra of the treated sample showed peaks at 3374 cm−1, 3295 cm−1, 2096 cm−1 and 2031 cm−1 with the peak intensity values increasing with corresponding samples of increasing hours of treatment. With the presence of gold nanoparticles on the PDMS film confirmed, the gold nanoparticles may now be functionalized for biosensing and biotesting applications of liquid samples.

Wavelength-dependence of the photothermal efficiency of gold nanoparticles in solution by Z-scan photothermal lens spectroscopy

Using continuous-wave (cw) single-beam Z-scan technique, the absorption and scattering efficiencies of spherical gold nanoparticles (NPs) of varying diameter are determined experimentally through the thermal lens (TL) effect for three different wavelengths in the blue, the green and the red. The main characteristics of the measurement method are detailed, extending the usual experimental procedure for weak absorption with Gaussian beams to higher absorption with top-hat beams. To confirm the validity of our approach, the experimental TL data were compared to the theoretical values from Mie theory and found to be in good agreement within the experimental errors. As expected, the photothermal efficiency of spherical gold NPs increases with lower diameters and towards shorter wavelengths.

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.

Spectroscopic properties of gold nanoparticles by laser irradiation

In this work a gold nanoparticles solutions has been irradiated by laser beam.The gold nanoparticles are prepared by using potassium bitarate as a reducing agent and Polyethylene glycol as a dispersion factor. The particles size of prepared solutions between 50-100 nanometers. Colloidal gold nanoparticles are irradiate with laser diode at period 5 and 10 minutes then the comparisons between two solutions with and without irradiation was done. The results are obtained by measuring the absorbance and using a spectrophotometer for the both solutions before and after irradiation. The result shows the differences between the spectrum of nanoparticles at ordinary state and spectrum of nanoparticles irradiated with laser beam. It's clear that the resolution is increase when the time of radiation is increasing. When spectrophotometers testing are done, we can note that there are broadening in the beginning of the spectrum of nanoparticles and increasing when time of exposure of laser beam is increasing.

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.

User-friendly and ultra-stable all-inclusive gold tablets for cysteamine detection.

To date, a range of nanozymes has been reported for their enzyme-mimicking catalytic activity such as solution-based sensors. However, in remote areas, the need for portable, cost-effective, and one-pot prepared sensors is obvious. In this study, we report the development of a highly stable and sensitive gold tablet-based sensor for cysteamine quantification in human serum samples. The sensor is produced in two steps: synthesis of a pullulan-stabilized gold nanoparticle solution (pAuNP-Solution) using a pullulan polymer as a reducing, stabilizing, and encapsulating agent and then, casting the pAuNP-Solution into a pullulan gold nanoparticle tablet (pAuNP-Tablet) by a pipetting method. The tablet was characterized by UV-vis, DLS, FTIR, TEM, and AFM analyses. The pAuNP-tablet exhibited a high peroxidase-mimetic activity via a TMB-H2O2 system. The presence of cysteamine in the system introduced two types of inhibition which were dependent on the cysteamine concentration. By determining Michaelis-Menten's kinetic parameters, we gained mechanistic insights into the catalytic inhibition process. Based on the catalytic inhibition capability of cysteamine, the limit of detection (LoD) was calculated to be 69.04 and 82.9 μM in buffer and human serum samples, respectively. Finally, real human serum samples were tested, demonstrating the applicability of the pAuNP-Tablet for real-world applications. The % R values in human serum samples were in the range of 91-105% with % RSD less than 2% for all replicas. The stability tests over 16 months revealed the ultra-stable properties of the pAuNP-Tablet. Overall, with a simple fabrication method and a novel employed technique, this study contributes to the advancement of tablet-based sensors and helps in cysteamine detection in clinical settings.

A Dihydropyridine Derivative as a Highly Selective Fluorometric Probe for Quantification of Au3+ Residue in Gold Nanoparticle Solution.

Novel dihydroquinoline derivatives (DHP and DHP-OH) were synthesized in one pot via a tandem trimerization-cyclization of methylpropiolate. DHP and DHP-OH possess strong blue fluorescence with high quantum efficiencies over 0.70 in aqueous media. DHP-OH displays a remarkable fluorescence quenching selectively to the presence of Au3+ through the oxidation of dihydropyridine to pyridinium ion as confirmed by NMR and HRMS. DHP-OH was used to demonstrate the quantitative analysis of Au3+ in water samples with the limit of detection of 33 ppb and excellent recovery (>95%). This fluorescent probe was also applied for the determination of Au3+ residue in the gold nanoparticle solution and a paper-based sensing strip for the on-site detection of Au3+.