Suspensions Of Gold Nanoparticles Research Articles

Potential-Modulated Surface-Enhanced Raman Spectroscopy of Tolmetin at Gold Nanoparticle Film Functionalized Polarizable Liquid-Liquid Interfaces.

An aqueous colloidal suspension of gold nanoparticles (AuNPs) may be condensed into a thin fractal film at the polarizable liquid-liquid interface formed between two immiscible electrolyte solutions upon injection of millimolar concentrations of sodium chloride to the aqueous phase. By adjusting the interfacial polarization conditions (negative, intermediate, and positive open-circuit potentials), the morphology of the film is modified, resulting in unique surface plasmon properties of the film, which enable in situ surface-enhanced Raman spectroscopy (SERS). Intense SERS signals are observed at the polarizable liquid-liquid interface when micromolar concentrations of tolmetin, a nonsteroidal anti-inflammatory drug, are entrapped in the AuNP fractal film. The change in the signal intensity, averaged over multiple spectra, with respect to the concentration of tolmetin, depends on the polarization conditions and suggests the presence of chemical-induced damping effects on the surface plasmons of the gold film.

Reply to “Comment on Comparison of direct and indirect measures of transport efficiency in single particle inductively coupled plasma mass spectrometry” by H. Goenaga-Infante

This paper provides a rebuttal to the comments on our original research article entitled “Comparison of Direct and Indirect Measures of Transport Efficiency in Single Particle ICP-MS” recently published by Goenaga-Infante in Spectrochimica Acta Part B: Atomic Spectroscopy.The intent of our study is not to condemn the dynamic mass flow (DMF) method but rather to explore the use parameters under which it can and cannot be applied. As explained in the original paper, the goal of this study is to evaluate the ranges of use conditions under which measures of transport efficiency (TE) yield accurate and reproducible results for spICP-MS measurements of particle number concentration (PNC) and particle size (diameter, PS) of various gold nanoparticle (AuNP) suspensions. The evaluation was performed through a systematic comparison of three methods for the measurement of TE: the particle frequency (TEF), particle size (TES), and DMF methods using three types of spray chambers operated at cooled and ambient temperature conditions and employing different ICP-MS platforms. While we appreciate thorough critical and constructive comments on our paper, we strongly disagree that the conclusions and highlights are not supported by the content and findings about the features and benefits of the DMF method.The discussion of three additional independent studies in this field by other spICP-MS expert groups that have been published after the submission of our manuscript is included in this paper. While the DMF approach has been used in two interlaboratory comparisons for TE determination in spICP-MS measurements of PNC, only one laboratory, namely the laboratory led by Goenaga-Infante, provided results using the DMF method in both projects. A method cannot be considered validated if successful results have only been demonstrated within one laboratory.The paper by Goenaga-Infante claims that the main use of DMF, the assignment of a SI traceable PNC value to new commercial nanomaterials (NMs), has not been highlighted explicitly in our original paper. The advantages and disadvantages of the DMF, TES, and TEF methods to measure TE were presented throughout the manuscript and are clearly summarized in the conclusion. The assignment of PNC that is metrologically traceable to the SI implies that all known or suspected uncertainty components including bias are taken into account. Our research shows that under some use conditions, the biases inherent to the DMF method are not yet fully understood and cannot be accounted for. While Cuello-Nuñez et al. Journal of Analytical Atomic Spectrometry, 2020, DOI: https://doi.org/10.1039/c9ja00415g state that cooled conditions (2 °C) were used in their work, they do not define the level of bias that can be expected if different spray chamber temperatures are used, and they do not provide recommendations on the optimal use conditions that define the field of applicability of the DMF method. Furthermore, besides the use of a Scott-type spray chamber cooled to 2 °C, neither the composition material of the spray chamber nor the volume of the Scott-type spray chamber were specified. It is important to note that in our original research, fifteen of the nineteen experiments were conducted using a cooled spray chamber. Also, the four different ICP-MS platforms were used in the standard configuration and with additional spray chamber options encountered in common ICP-MS usage. The value of our work is that it extends the study of Cuello-Nuñez et al. to a wide variety of use conditions routinely encountered in spICP-MS analysis.

Sensing of gene expression in live cells using electrical impedance spectroscopy and DNA-functionalized gold nanoparticles

A novel electrical impedance spectroscopy-based method for non-destructive sensing of gene expression in living cells is presented. The approach used takes advantage of the robustness and responsiveness of electrical impedance spectroscopy and the highly specific and selective nature of DNA hybridization. The technique uses electrical impedance spectroscopy and gold nanoparticles functionalized with single-stranded DNA complementary to an mRNA of interest to provide reliable, real-time, and quantifiable data on gene expression in live cells. The system was validated by demonstrating specific detection of the uidA mRNA, which codes for the β-glucuronidase (GUS) enzyme, in Solanum lycopersicum MsK8 cells. Gold nanoparticles were functionalized with single-stranded DNA oligonucleotides consisting of either a sequence complementary to uidA mRNA or an arbitrary sequence. The DNA-functionalized gold nanoparticles were mixed with cell suspensions, allowing the gold nanoparticles to penetrate into the cells. The impedance spectra of suspensions of cells with gold nanoparticles inserted within them were then studied. In suspensions of uidA-expressing cells and gold nanoparticles functionalized with the complementary single-stranded DNA oligonucleotide, the impedance magnitude in the frequency range of interest was significantly higher (146 %) in comparison to all other controls. Due to its highly selective nature, the methodology has the potential to be used as a precision agricultural sensing system for accurate and real-time detection of markers of stress, viral infection, disease, and normal physiological activities.

Evaluating the therapeutic importance of gold nanoparticles formed by the biogenic synthesis route of Madhuca longifolia reduction

Herbal plants have been used, in light of their responsiveness and wide availability, for the construction of a pioneering nanomaterial. In this study, a colloidal suspension of gold nanoparticles (GNPs) was synthesized from an extract of Madhuca longifolia (ML) using chloroauric acid. For biomedical applications, Madhuca longifolia (ML) was used as a bioreductant as well as a capping agent The formed ML-GNPs were analyzed using different analytical techniques, antioxidant assays, and thiazolyl blue formazan assay against A549 cell lines to evaluate clinical relevance. They were further evaluated for their influence on antimicrobial activity using a disc diffusion test against two different microorganisms, Proteus vulgaris and Micrococcus luteus. The ML-GNPs produced had good antioxidant, antibacterial, and anticancer activities. The conformation of the XRD spectra with prominent characteristic planes was indexed to the face-centered cubic (fcc)-structured GNPs. Surface morphology analysis was used to determine the particle size of the GNPs. Fourier transform infrared spectra of the samples were used to determine the analogs for strong H bonding. The MIC values of biogenic GNPs against both strains of Proteus vulgaris and Micrococcus luteus was calculated as 0.29 and 0.96 g/mL, respectively, and triclosan was considered as 0.4 and 2 g/mL, respectively. The findings of this study will be beneficial for future studies of the therapeutic potential of ML-GNPs. Actively, ML-GNPs can be a capable material for formulating nanomedicines after subsequent clinical experiments.

Plasmonic Magnesium Nanoparticles Are Efficient Nanoheaters.

Understanding and guiding light at the nanoscale can significantly impact society, for instance, by facilitating the development of efficient, sustainable, and/or cost-effective technologies. One emergent branch of nanotechnology exploits the conversion of light into heat, where heat is subsequently harnessed for various applications including therapeutics, heat-driven chemistries, and solar heating. Gold nanoparticles are overwhelmingly the most common material for plasmon-assisted photothermal applications; yet magnesium nanoparticles present a compelling alternative due to their low cost and superior biocompatibility. Herein, we measured the heat generated and quantified the photothermal efficiency of the gold and magnesium nanoparticle suspensions. Photothermal transduction experiments and optical and thermal simulations of different sizes and shapes of gold and magnesium nanoparticles showed that magnesium is more efficient at converting light into heat compared to gold at near-infrared wavelengths, thus demonstrating that magnesium nanoparticles are a promising new class of inexpensive, biodegradable photothermal platforms.

Zn2+/GNPs nanocomposite for highly selective colorimetric detection of creatinine in urine samples of CKD patients

This research reports the fabrication of Zn2+/gold nanoparticles (GNPs) nanocomposite for colorimetric detection of creatinine (CR) in diverse media (e.g., water, artificial urine, and urine samples) between healthy subjects and chronic kidney disease (CKD) patients. The color of GNPs in suspension changed from characteristic wine-red (λabsorption = 545 ± 5 nm) to colorless or black upon the formation of nanocomposite with Zn2+ ions. However, upon addition of CR to Zn2+/GNPs nanocomposite suspension, the characteristic wine-red color of GNPs was restored. Our experimental analysis evidently validated the hypothesis on Zn2+ induced agglomeration of GNPs and their subsequent anti-agglomeration upon the addition of CR to the Zn2+/GNPs. Overall, our approach offered highly sensitive recognition of CR with a limit of detection of 2 µg·mL−1 (R2 = 0.95) along with excellent stability (>three months), selectivity (in the presence of interfering biochemicals (e.g., urea,ascorbic acid, and glucose, glutathione, Na+, K+, Ca2+, Mg2+, PO43−, and SO4 2−)), and reproducibility (relative standard deviation ∼ 9 %). Finally, the great potential of our method for CR recognition was also confirmed by good agreement (R2 = 0.95) with the gold standard ‘Jaffe’ method along with the Bland-Altman analysis for urine samples between health subjects (n = 15) and CKD patients (n = 11). In near future, a quantitative lateral flow biosensor is expected to be developed for non-invasive detection of CR through the integration of the proposed approach with the machine learning tools.

Irreversibility treatment and colloidal suspension of gold and silver nanoparticles in a microchannel

The silver and gold nanoparticles show noteworthy outcomes on anticancer therapies and antimicrobials. The silver was the noticeable anti-swelling and gold nanoparticles efficiently helped to convert these photons by heat into demolished cancer cells. So, the purpose of this work is devoted to studying the effect of linear radiation on the hybrid nanoparticles (gold and silver with hemoglobin) in a microchannel. This dimensionless numerical expression was determined mathematically into the finite element method. The second law study was required to predict these sources by irreversibility approximate into that thermal system. Although the comprehensive parametric analysis was well-known in the production of entropy may be enhanced into viscous dissipation and radiation form. That was established in the hybrid nanoparticles shows the greater Bejan number related to both hemoglobin and nanofluid.

Inferring the Interfacial Reactivity of Gold Nanoparticles by Surface Plasmon Resonance Measurements.

Gold nanoparticles (GNPs) require a functionalization step in most cases to be suitable for applications. Optimizing this step in order to maintain both the stability and the plasmonic properties of the GNPs is a demanding process. Indeed, multiple analyses are required to get sufficient information on the grafting rate and the stability of the obtained suspension, leading to material and time waste. In this study, we propose to investigate ligand reactivity on a gold surface with surface plasmon resonance (SPR) measurements as a way to simulate the reactivity in GNP suspensions. We consider two thiolated ligands in this work: thioglycolic acid (TA) and 6-mercaptohexanoic acid (MHA). These thiols are grafted using different conditions on GNPs (monitored by optical absorption) and on a gold surface (monitored by SPR) and the grafting efficiency and stability are compared. The same conclusions are reached in both cases regarding the best protocol to implement, namely, the thiol molecules should be introduced in a water solution at a low concentration. This demonstrates the suitability of SPR to predict the reactivity on a GNP surface.

Modified Darcy’s law and couple stress effects on electro-osmotic flow of non-Newtonian nanofluid with peristalsis

In this study, we focused on the heat transfer through a uniformly inclined rectangular duct caused by the electro-osmotic peristaltic flow of an unsteady non-Newtonian nanofluid. With couple stress, the fluid obeys the Papanastasiou model. The flow is through a porous medium that follows Darcy’s law in a modified form. In addition, Dufour and Soret effects, mixed convection, the impacts of a chemical reaction, and the effects of viscous couple stress dissipation are all considered. The governing equations that explain the velocity, temperature, and concentration of nanoparticles are simplified when wave transformation is used. The homotopy perturbation method was used to solve these equations analytically. Additionally, a collection of figures is used to discuss and visually illustrate the consequences of the physical characteristics. In fact, the modified Darcy’s law makes the velocity gradient appear in the momentum equation, which increases the contribution of the velocity gradient to the velocity profile. In addition, the electro-osmotic parameter and Helmholtz-Smoluchowski velocity have a significant impact on the velocity gradient’s direction, as well as the velocity gradient’s ability to be either positive or negative, depending on their values. In addition, in the case of forced convection, the values of the Nusselt number and the Sherwood number are highly affected by the value of Helmholtz–Smoluchowski velocity. The current findings have applications in biology and medicine, particularly in cancer therapy, which involves peristaltic blood pumps(arteries) and suspended gold nanoparticles (nanofluid). According to our knowledge, no prior studies have merged the couple stress Papanastasiou model and the modified Darcy’s law.

Electrothermoplasmonic flow in gold nanoparticles suspensions: Nonlinear dependence of flow velocity on aggregate concentration

Efficient mixing and pumping of liquids at the microscale is a technology that is still to be optimized. The combination of an AC electric field with a small temperature gradient leads to a strong electrothermal flow that can be used for multiple purposes. Combining simulations and experiments, an analysis of the performance of electrothermal flow is provided when the temperature gradient is generated by illuminating plasmonic nanoparticles in suspension with a near-resonance laser. Fluid flow is measured by tracking the velocity of fluorescent tracer microparticles in suspension as a function of the electric field, laser power, and concentration of plasmonic particles. Among other results, a non-linear relationship is found between the velocity of the fluid and particle concentration, which is justified in terms of multiple scattering-absorption events, involving aggregates of nanoparticles, that lead to enhanced absorption when the concentration is raised. Simulations provide a description of the phenomenon that is compatible with experiments and constitute a way to understand and estimate the absorption and scattering cross-sections of both dispersed particles and/or aggregates. A comparison of experiments and simulations suggests that there is some aggregation of the gold nanoparticles by forming clusters of about 2–7 particles, but no information about their structure can be obtained without further theoretical and experimental developments. This nonlinear behavior could be useful to get very high ETP velocities by inducing some controlled aggregation of the particles.

Nano‐Impact Single‐Entity Electrochemistry Enables Plasmon‐Enhanced Electrocatalysis**

AbstractPlasmon‐enhanced electrocatalysis (PEEC), based on a combination of localized surface plasmon resonance excitation and an electrochemical bias applied to a plasmonic material, can result in improved electrical‐to‐chemical energy conversion compared to conventional electrocatalysis. Here, we demonstrate the advantages of nano‐impact single‐entity electrochemistry (SEE) for investigating the intrinsic activity of plasmonic catalysts at the single‐particle level using glucose electrooxidation and oxygen reduction on gold nanoparticles as model reactions. We show that in conventional ensemble measurements, plasmonic effects have minimal impact on photocurrents. We suggest that this is due to the continuous equilibration of the Fermi level (EF) of the deposited gold nanoparticles with the EF of the working electrode, leading to fast neutralization of hot carriers by the measuring circuit. The photocurrents detected in the ensemble measurements are primarily caused by photo‐induced heating of the supporting electrode material. In SEE, the EF of suspended gold nanoparticles is unaffected by the working electrode potential. As a result, plasmonic effects are the dominant source of photocurrents under SEE experimental conditions.

Nano-Impact Single-Entity Electrochemistry Enables Plasmon-Enhanced Electrocatalysis.

Plasmon-enhanced electrocatalysis (PEEC), based on a combination of localized surface plasmon resonance excitation and electrochemical bias applied to a plasmonic material, can result in improved electrical-to-chemical energy conversion compared to conventional electrocatalysis. Here, we demonstrate the advantages of nano-impact single-entity electrochemistry (SEE) for investigating the intrinsic activity of plasmonic catalysts at the single-particle level using glucose electrooxidation and oxygen reduction on gold nanoparticles as model reactions. We show that in conventional ensemble measurements, plasmonic effects have minimal impact on photocurrents. We suggest that this is due to the continuous equilibration of the Fermi level (EF) of the deposited gold nanoparticles with the EF of the working electrode, leading to fast neutralization of hot carriers by the measuring circuit. The photocurrents detected in the ensemble measurements are caused by photo-induced heating of the supporting electrode material. In SEE, the EF of suspended gold nanoparticles is unaffected by the working electrode potential. As a result, plasmonic effects are the dominant source of photocurrents under SEE experimental conditions.

Fluorescent Gold Nanoparticles in Suspension as an Efficient Theranostic Agent for Highly Radio-Resistant Cancer Cells

Gold nanoparticles are a promising candidate for developing new strategies of therapy against cancer. Due to their high atomic number and relative biocompatibility, they are commonly investigated as radiosensitizers to locally increase the dose of radiotherapy. In order to optimize this radiosensitizing effect, it is necessary to control the positioning of the nanoparticles in the cells. The purpose of this study is to investigate, by means of fluorescent gold nanoparticles in suspension, the dose enhancement on highly radio-resistant cancer cells. These nanoparticles were successfully produced using modern click-chemistry methods, first by attaching a chelating agent Diethylenetriamine pentaacetate benzylamine to L-cysteine, bonding the resulting ligand to a gold core, grafting propargylamine and then utilizing copper-catalyzed azide-alkyne cycloaddition (CuAAC) to fuse AlexaFluor 647 to the ligands. The results of this study prove the success of the reactions to produce a minimally cytotoxic and highly stable nanoparticle suspension that increases the radiosensitivity of gliosarcoma 9L tumor cells, with a 35% increase in cell death using 5 Gy kilovoltage radiation. Their fluorescent functionalization allowed for their simple localization within living cells and detection in vivo post-mortem.

Quantification of nanoparticles' concentration inside polymer films using lock-in thermography.

Thin nanocomposite polymer films embedding various types of nanoparticles have been the target of abundant research to use them as sensors, smart coatings, or artificial skin. Their characterization is challenging and requires novel methods that can provide qualitative as well as quantitative information about their composition and the spatial distribution of nanoparticles. In this work, we show how lock-in thermography (LIT) can be used to quantify the concentration of gold nanoparticles embedded in polyvinyl alcohol (PVA) films. LIT is an emerging and non-destructive technique that measures the thermal signature produced by an absorbing sample illuminated by modulated light with a defined frequency. Films with various concentrations of gold nanoparticles of two different sizes have been prepared by evaporation from homogeneous aqueous PVA gold nanoparticle suspensions. When the thin films were illuminated with monochromatic light at a wavelength close to the plasmonic resonance signature of the nanoparticles, the amplitude of the thermal signature emitted by the nanoparticles was recorded. The measurements have been repeated for multiple modulation frequencies of the incident radiation. We have developed a mathematical method to quantitatively relate the concentration of nanoparticles to the measured amplitude. A discussion about the conditions under which the sample thickness can be determined is provided. Furthermore, our results show how LIT measurements can easily detect the presence of concentration gradients in samples and how the model allows the measured signal to be related to the respective concentrations. This work demonstrates the successful use of LIT as a reliable and non-destructive method to quantify nanoparticle concentrations.

Electrophoretic deposited gold nanoparticle thin film on silver substrate

AbstractEffects of the deposition time and voltage on the characteristics of gold nanoparticles (NPs) thin films, prepared by the electrophoretic deposition (EPD) method on the silver substrate, were investigated experimentally. Au NPs were synthesised using the pulsed laser ablation method in distilled water. The suspended solution of the gold NPs was used as the electrolyte of EPD. An irradiation was carried out by the fundamental wavelength of a Q‐switched NdYAG laser at 1064 nm and 7 ns pulse width. The electrophoretic deposition apparatus consisted of two 2 × 2 cm pieces of silver plates as the electrodes. They were immersed in parallel with a 7 mm gap in the gold NP suspension. Five samples of gold NP thin films were prepared at different deposition times and applied voltages. Results show that the roughness, thickness and surface quality of EPD prepared thin films can be strongly controlled by the deposition time and applied voltage. The thickness of deposited films was dependent on the voltage of deposition in which their roughness was increased with increasing the deposition time. Furthermore, the reflection of deposited films was affected by the surface roughness.

Electro-magnetohydrodynamics hybrid nanofluid flow with gold and magnesium oxide nanoparticles through vertical parallel plates

The hybrid nanofluid flow under suspension of Gold and Magnesium oxide nanoparticles (Au/MgO-NPs) propagating between vertical parallel plates is investigated. Sodium alginate third-grade non-Newtonian fluid is used as the base fluid. The effect of electro-magnetohydrodynamics is also taken into account. The energy equation also includes the effect of Joule heating and viscous dissipation. Due to the nonlinear nature of the formulated differential equations, perturbation strategy is utilized to acquire the analytical solutions. Discussion and plotting are presented with respect to most significant parameters. It is analyzed that the rate of heat transfer is dramatically increased, and this is owing to an increase in the thermal conductivity of the fluid due to hybrid nanofluid. With increment in buoyancy convection parameter and electric field parameter, the flow is accelerated. It is also noted that the temperature is boosted with increasing nanoparticle volume fraction of both magnesium oxide and gold nanoparticles. A comparison with previously studied results is also included. The applications of the work include novel thermal duct processing technologies in biomedical, nuclear and process engineering.

Antioxidant and Anti-Melanogenesis Effects of Colloidal Gold Camellia sinensis L. Extracts.

Green tea extract derived from the leaves of Camellia sinensis L. (CS), is a representative beverage with antioxidant, anti-cancer, and anti-viral properties. CS extract is also used in cosmetics. Colloidal gold is generally a sol or colloidal suspension of gold nanoparticles in water. Colloidal gold green tea (CGCS), cultivated as a fertilizer using this colloidal gold solution, contains gold minerals and possesses anti-inflammatory, analgesic, and anti-tumor properties. However, the skin bioactivity of CGCS has not yet been investigated. In this study, we investigated the effect of the CGCS extract on skin whitening. CGCS extract contained high levels of phenols and flavonoids and displayed 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity in a concentration-dependent manner. CGCS extract inhibited melanin synthesis and tyrosinase activity in B16F10 cells more effectively than the CS extract. Moreover, the CGCS extract decreased the expression levels of the melanogenesis-related proteins, tyrosinase, tyrosinase-related proteins (TRPs), and microphthalmia-associated transcription factor (MITF). In conclusion, our study showed that the CGCS extract inhibits the expression of tyrosinase, TRP-1, and TRP-2 via the downregulation of MITF, thereby inhibiting melanin synthesis. Therefore, CGCS can potentially be used as a skin-whitening ingredient in the cosmetic industry.

Study the Effect of Polymers Type on Preparation and Characterization of Etoposide-loaded Gold Nanoparticles

In the last few years, the discoveries in pharmaceutical nanotechnology have triggered a revolution in the field of therapeutic, delivering an abundance of novel applications and actual approaches of metallic nanoformulations for the treatment and diagnosis of tenacious diseases. From this point of view, gold nanoparticles (GN) have been awarded an attractive platform for the development of efficient multifunctional therapeutic, controlled release systems, targeted delivery and diagnostic. The objective of this research was to prepare etoposide-loaded gold nanoparticles (E-GN) by incorporating of etoposide in to the functionalized GN by using different biocompatible polymers. In the present study, GN suspension was prepared by inverse citrate reduction method. Polymeric suspensions 19 (PGN 1-19) were prepared and characterized by atomic force microscopy measurement (AFM). The obtained results indicated that PGN10, PGN13, PGN17 and PGN19 with the preferable polymers and their concentration of (1-mg/mL HPMC-E5, 1-mg/mL PVA, 1.5 mg/mL gelatin and 0.5: 0.5 mg/mL of HPMC-E5: PVA combination) respectively, showed the better morphology, particles size (PS), and particles size distribution (PSD). Subsequently, eight formulas were prepared and optimized through the study of various variables as PS, PSD, etoposide loading efficiency (LE) and in-vitro dissolution profile. F7 revealed a greater LE of 99.39% with higher loading capacity (1 mg/mL) and in-vitro dissolution with controlled mode also, AFM results showed smooth surface nanoparticles, average PS (24.43 nm) with uniform PSD (9.84%). In addition, the result of transmission electron microscopy (TEM) revealed a spherical uniform shape with zeta potential of -34.13. In conclusion, polymeric functionalization of GN improved the etoposide loading efficiency and capacity and controlled the in-vitro dissolution profile and enhanced their colloidal stability.

Enhanced heat transfer in Maxwell bio-nanofluid flow in a blood arterial: a modified thermal flux model

Nowadays, gold (Au) nanoparticles are widely used in nanomedicine due to their physicochemical features. Maxwell model is the most relevant non-Newtonian model to characterize the blood-based nanofluids due to their viscoelastic nature. Because of this, a mathematical model was established to investigate the enhanced heat transfer in Maxwell bio-nanofluid (blood-Au) flow across a stenosed artery. A modified thermal flux is used to enhance the blood heat transfer, which is helpful in anticancer therapy. The gold nanoparticles are made with fresh moringa oleifera leaves using biosynthesis. The thermic heat, particle shape, magnetic field, and dissipative effects are incorporated to make the problem more realistic. The impact of physical features on flow and thermal areas is examined numerically. It is significant to mention that the suspension of gold nanoparticles in blood in the existence of modified Fourier thermal flux effectively enhances the heat transfer in blood. Also, the blood-Au (lamina) combination heat transfer rate is higher than the blood-Au (spherical) combination. This is very useful in nano drug delivery.

Formula omitted]-Carrageenan-capped core–shell gold@silver nanoparticles: Optical device for hydrogen peroxide detection

Metallic nanoparticles have outstanding properties that can be used to design optical detection devices, such as their high surface area and localized surface plasmon resonance (LSPR) effect. Despite these properties, metallic nanoparticles have low stabilities against aggregation and silver nanoparticles are quickly oxidized even in aqueous suspensions. To overcome these disadvantages, this study reports a new κ-carrageenan-stabilized core–shell gold@silver nanoparticles (κ-CAR-Au@AgNPs) composite. The κ-carrageenan (κ-CAR) was used as a reducing and stabilizing agent toward Au(III)/Ag(I) and Au0/Ag0, respectively. A pre-synthesized κ-CAR-capped gold nanoparticle (κ-CAR-AuNPs) suspension was mixed with Ag(I) ions and ascorbic acid to produce the κ-CAR-Au@AgNPs composite. The as-synthetized composite had an average hydrodynamic radius of 122 nm and a Zeta potential of −24 mV. The composite suspension had an LSPR band with high intensity after 15 days of storage. The κ-CAR stabilized the nanoparticles against aggregation and environmental oxidation. The physiochemical properties of κ-CAR-Au@AgNPs were compared to the properties of κ-CAR-capped silver nanoparticles (κ-CAR-AgNPs). The core–shell nanoparticle LSPR intensity was higher (10-fold) than that of the monometallic sample. Therefore, its optical response is improved for sensing applications. Thus, core–shell nanoparticles were used to detect hydrogen peroxide (H2O2). The H2O2 can almost completely oxidize the Ag shell of the Au@AgNPs after 4 h, altering the optical absorption intensity of the nanoparticles. Therefore, the κ-CAR-Au@AgNPs LSPR intensity can be used as an optical signal to assess H2O2 concentration in aqueous solutions.