Gold Nanoparticles In Water Research Articles

A simple optical sensor for the simultaneous determination of trace amounts of silver and gold nanoparticles in water by cloud point microextraction

Nowadays, metal nanoparticles are widely used in many fields due to their excellent properties. This has led to an increasing presence of these species in water, which, although in very low concentrations, can cause damage to ecosystems. These nanomaterials are currently considered as emerging pollutants in water, so there is a need to know their concentrations. In particular, gold and silver nanoparticles are among the most widely used. Therefore, the development of simple methods that allow their determination even at trace concentrations is of interest. In this work, a method has been developed for the simultaneous determination of low concentrations of silver and gold nanoparticles (AgNPs and AuNPs, respectively) in water by cloud point microextraction using Triton X-114 as extractant and UV–Vis molecular spectrophotometry. It is a simple, environmentally friendly method with an easy-to-use portable instrument that requires only a microdrop of the extracted phase for the analysis of both species. Detection limits reached were 17 and 15 µg L−1 for AgNPs and AuNPs, respectively. The enrichment factors were 160 for AgNPs and 165 for AuNPs.

Physical Regimes and Mechanisms of Picosecond Laser Fragmentation of Gold Nanoparticles in Water from X-ray Probing and Atomistic Simulations.

Laser fragmentation in liquids has emerged as a promising green chemistry technique for changing the size, shape, structure, and phase composition of colloidal nanoparticles, thus tuning their properties to the needs of practical applications. The advancement of this technique requires a solid understanding of the mechanisms of laser-nanoparticle interactions that lead to the fragmentation. While theoretical studies have made impressive practical and mechanistic predictions, their experimental validation is required. Hence, using the picosecond laser fragmentation of Au nanoparticles in water as a model system, the transient melting and fragmentation processes are investigated with a combination of time-resolved X-ray probing and atomistic simulations. The direct comparison of the diffraction profiles predicted in the simulations and measured in experiments has revealed a sequence of several nonequilibrium processes triggered by the laser irradiation. At low laser fluences, in the regime of nanoparticle melting and resolidification, the results provide evidence of a transient superheating of crystalline nanoparticles above the melting temperature. At fluences about three times the melting threshold, the fragmentation starts with evaporation of Au atoms and their condensation into small satellite nanoparticles. As fluence increases above five times the melting threshold, a transition to a rapid (explosive) phase decomposition of superheated nanoparticles into small liquid droplets and vapor phase atoms is observed. The transition to the phase explosion fragmentation regime is signified by prominent changes in the small-angle X-ray scattering profiles measured in experiments and calculated in simulations. The good match between the experimental and computational diffraction profiles gives credence to the physical picture of the cascade of thermal fragmentation regimes revealed in the simulations and demonstrates the high promise of the joint tightly integrated computational and experimental efforts.

Multiplexable and Scalable Aqueous Synthesis Platform for Oleate-Based, Bilayer-Coated Gold Nanoparticles.

Despite gold-based nanomaterials having a unique role in nanomedicine, among other fields, synthesis limitations relating to reaction scale-up and control result in prohibitively high gold nanoparticle costs. In this work, a new preparation procedure for lipid bilayer-coated gold nanoparticles in water is presented, using sodium oleate as reductant and capping agent. The seed-free synthesis not only allows for size precision (8-30nm) but also remarkable particle concentration (10mm Au). These reaction efficiencies allow for multiplexing and reaction standardization in 96-well plates using conventional thermocyclers, in addition to simple particle purification via microcentrifugation. Such a multiplexing approach also enables detailed spectroscopic investigation of the nonlinear growth process and dynamic sodium oleate/oleic acid self-assembly. In addition to scalability (at gram-level), resulting gold nanoparticles are stable at physiological pH, in common cell culture media, and are autoclavable. To demonstrate the versatility and applicability of the reported method, a robust ligand exchange with thiolated polyethylene glycol analogues is also presented.

Forensic Analysis of Salivary Nicotine by Calix[4]Arene Customized Gold Nanoparticles in Water and Soil

Nicotine, a potent stimulant found in tobacco products, has significant effects on oral health and overall well-being. Saliva samples showing the presence of nicotine can be very helpful as evidence in a variety of situations. Salivary nicotine levels can reveal smoking habits. It offers proof of whether a person has recently used tobacco goods. Saliva testing can be used, for instance, to support or contradict smoking behaviours in court cases involving custody disputes, child endangerment, or employment regulations. Saliva nicotine testing can be used in criminal investigations to determine a suspect's smoking history. If saliva includes nicotine traces, it can be used to identify the person to a place or occasion, particularly at the crime scene which may reveal discarded cigarette butts or other tobacco-related evidence. Also, exposure to nicotine impacts general health. Saliva tests can reveal whether or not a person uses tobacco, which is important information for determining health risks. For example, nicotine testing can be used by medical practitioners to assess a patient's willingness to stop smoking or to track their progress while participating in smoking cessation programmes. Moreover, some insurance providers take nicotine usage into account when setting insurance premiums or providing coverage. Saliva test results can impact judgments about disability claims, health insurance, and life insurance. However, it's crucial to properly interpret the findings of nicotine tests. Due to the variety of benefits associated with the identification of salivary nicotine, this article aims to develop an affordable technique that can facilitate the in-situ, real-time detection of nicotine in saliva samples.

A Dissipative Reaction Network Drives Transient Solid–Liquid and Liquid–Liquid Phase Cycling of Nanoparticles

AbstractTransient states maintained by energy dissipation are an essential feature of dynamic systems where structures and functions are regulated by fluxes of energy and matter through chemical reaction networks. Perfected in biology, chemically fueled dissipative networks incorporating nanoscale components allow the unique properties of nanomaterials to be bestowed with spatiotemporal adaptability and chemical responsiveness. We report the transient dispersion of gold nanoparticles in water, powered by dissipation of a chemical fuel. A dispersed state that is generated under non‐equilibrium conditions permits fully reversible solid–liquid or liquid–liquid phase transfer. The molecular basis of the out‐of‐equilibrium process is reversible covalent modification of nanoparticle‐bound ligands by a simple inorganic activator. Activator consumption by a coupled dissipative reaction network leads to autonomous cycling between phases. The out‐of‐equilibrium lifetime is tunable by adjusting the pH value, and reversible phase cycling is reproducible over several cycles.

A Dissipative Reaction Network Drives Transient Solid-Liquid and Liquid-Liquid Phase Cycling of Nanoparticles.

Transient states maintained by energy dissipation are an essential feature of dynamic systems where structures and functions are regulated by fluxes of energy and matter through chemical reaction networks. Perfected in biology, chemically fueled dissipative networks incorporating nanoscale components allow the unique properties of nanomaterials to be bestowed with spatiotemporal adaptability and chemical responsiveness. We report the transient dispersion of gold nanoparticles in water, powered by dissipation of a chemical fuel. A dispersed state that is generated under non-equilibrium conditions permits fully reversible solid-liquid or liquid-liquid phase transfer. The molecular basis of the out-of-equilibrium process is reversible covalent modification of nanoparticle-bound ligands by a simple inorganic activator. Activator consumption by a coupled dissipative reaction network leads to autonomous cycling between phases. The out-of-equilibrium lifetime is tunable by adjusting the pH value, and reversible phase cycling is reproducible over several cycles.

Investigations on the damping of acoustic vibrations of single gold nanoparticles in water by continuum and atomistic simulations

Investigations on the damping of acoustic vibrations of single gold nanoparticles in water by continuum and atomistic simulations

Automated calculations for computing the sample-limited spatial resolution in (scanning) transmission electron microscopy

MATLAB scripts were designed to compute the sample-limited spatial resolution in transmission electron microscopy (TEM) and scanning TEM (STEM) as a function of different microscopy parameters including the electron dose eD, sample geometry, and materials parameters. The scripts can be used to select the optimum microscopy modality and optimize the experimental conditions to achieve the best possible resolution considering the limitations set by both the electron optics and the examined sample. The resolution can be computed as function of the objective opening semi-angle α for TEM and detector opening semi-angle β for STEM. Optional code for computing a range over the sample thickness t or eD are provided as well, whereby the opening angle is optimized for each data point. The spatial resolution depends on the type of material of the nanoscale object (for example, gold or carbon nanoparticles), the type of matrix holding the objects (for example, water or ice), the depth of the nanoscale object inside the matrix, and eD. The optimization is consistent with the typical situation that carbon nanoparticles are best examined with TEM embedded in a thin matrix (t = 0.1 µm), while STEM is better suited for high atomic number objects such as gold nanoparticles in water, irrespective of t. The script also calculates the reduction of beam broadening in thick samples (t > 1 µm) using bright field STEM.

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.

The Fragmentation Mechanism of Gold Nanoparticles in Water under Femtosecond Laser Irradiation

The Fragmentation Mechanism of Gold Nanoparticles in Water under Femtosecond Laser Irradiation

Measurement of Navier Slip on Individual Nanoparticles in Liquid.

The Navier slip condition describes the motion of a liquid relative to a neighboring solid surface, with its characteristic Navier slip length being a constitutive property of the solid-liquid interface. Measurement of this slip length is complicated by its small magnitude, expected to be in the nanometer range based on molecular simulations. Here, we report an experimental technique that interrogates the Navier slip length on individual nanoparticles immersed in liquid with subnanometer precision. Proof-of-principle experiments on individual, citrate-stabilized, gold nanoparticles in water give a constant slip length of 2.7 ± 0.6 nm (95% C.I.), independent of particle size. Achieving this feature of size independence is central to any measurement of this constitutive property, which is facilitated through the use of individual particles of varying radii. This demonstration motivates studies that can now validate the wealth of existing molecular simulation data on slip.

The fragmentation mechanism of gold nanoparticles in water under femtosecond laser irradiation.

Plasmonic nanoparticles in aqueous solution have long been known to fragment under irradiation with intense ultrafast laser pulses, creating progeny particles with diameters of a few nanometers. However, the mechanism of this process is still intensely debated, despite numerous experimental and theoretical studies. Here, we use in situ electron microscopy to directly observe the femtosecond laser-induced fragmentation of gold nanoparticles in water, revealing that the process occurs through ejection of individual progeny particles. Our observations suggest that the fragmentation mechanism involves Coulomb fission, which occurs as the femtosecond laser pulses ionize and melt the gold nanoparticle, causing it to eject a highly charged progeny droplet. Subsequent Coulomb fission events, accompanied by solution-mediated etching and growth processes, create complex fragmentation patterns that rapidly fluctuate under prolonged irradiation. Our study highlights the complexity of the interaction of plasmonic nanoparticles with ultrafast laser pulses and underlines the need for in situ observations to unravel the mechanisms of related phenomena.

Time-Resolved Shadowgraph Photography of Laser-Heated Plasmonic Gold Nanoparticles in Water

Fragmentation and the subsequent heat transfer from solvated gold nanoparticles with sizes 50, 100, 150, and 250 nm to water are studied by time-resolved shadowgraph photography. The measured fragm...

One-Pot Synthesis of Small and Uniform Gold Nanoparticles in Water by Flash Nanoprecipitation

One pot synthesis of gold nanoparticles in aqueous phase is of special interests. We herein report a facile strategy, namely flash nanoprecipitation (FNP) based on a multi-inlet vortex mixer (MIVM)...

Thermodynamics of the formation of water dispersions of graphene and water solutions of the nanostructures based on graphene and gold nanoparticles

The thermodynamics of the formation of water dispersions of graphene and water solutions of the nanostructures based on graphene and gold nanoparticles was studied by the method of differential scanning calorimetry. It is found that the initial process of ultradispergation of nanofillers in water leads to disordering of the thermodynamic systems, which is accompanied by decrease in the specific heat capacity and an increase in the free energy in the both systems. It was first established that process of formation of nanocomposites by evaporation of water leads to a decrease in the entropy and free energy, that is, to the ordering in both thermodynamic systems as a result of the self-aggregation of nanofillers in a dilute water solution. In the water solutions of the nanostructures based on graphene and gold nanoparticles an additional effect of sedimentation of gold nanoparticles in water discovered, which accompanied by a more intense decrease in excess enthalpy, excess entropy and excess free energy compared to water dispersions of the graphene.

Dithiosulfindene Adsorption and Reaction on Gold Nanoparticles in Water

Dithiosulfindene (DTS) is a model molecule for dithiolethiones, a class of biomedically important sulfur-rich compounds with a general formula R1-S-S-C(=S)-R2. Reported herein is a combined experimental and computational study of DTS interactions with plasmonic gold nanoparticles (AuNPs) in water. DTS adsorptions and reactions on AuNPs were investigated using a combination of UV-vis, Raman, and surface enhanced Raman spectroscopic (SERS) methods. The saturation packing density of DTS on AuNPs is 596 pmol/cm2, and its structure and conformation on AuNP surfaces depends critically on its packing density. NaOH reacts with DTS both in water and on AuNPs, converting DTS into thiosalicyclic acid (TSA). TSA produced by NaOH reaction with DTS preadsorbed onto AuNPs partitions between remaining on AuNP surfaces and being released to the supernatant of the reaction solution. UV-vis measurements revealed that NaOH reaction with DTS in solution and on AuNPs both follow first order kinetics with a rate constant of 0.7...

Selective oxidation of aldehyde over hydroxymethyl group catalyzed by gold nanoparticles in aqueous phase

A protocol for selectively oxidizing aldehyde over hydroxymethyl group is developed, using biomass starch protected gold nanoparticles (NPs) as catalyst. The Au NPs show high selectivity that aldehyde is oxidized into carboxylic acid while alcoholic hydroxyl group stays intact in selective oxidation of 4-(hydroxymethyl)-benzaldehyde. The heterogeneous catalysis system is composed of soluble catalysts and insoluble substrate. The gold catalyst is prepared, preserved and applied for catalytic oxidation all in water. After reaction conditions are optimized, H2O2 is found to be the best oxidizing agent with complete conversion. Besides, the gold catalyst displays good versitility for aldehyde derivatives. After reaction completes, organic components are extracted by organic solvent and gold NPs in water are separated and recycled.

Brownian Motion and Large Electric Polarizabilities Facilitate Dielectrophoretic Capture of Sub-200 nm Gold Nanoparticles in Water.

Dielectrophoresis can move small particles using the force resulting from their polarization in a divergent electric field. In liquids, it has most often been applied to micrometric objects such as biological cells or latex microspheres. For smaller particles, the dielectrophoretic force becomes very small and the phenomenon is furthermore perturbed by Brownian motion. Whereas dielectrophoresis has been used for assembly of superstructures of nanoparticles and for the detection of proteins and nucleic acids, the mechanisms underlying DEP of such small objects require further study. This work presents measurements of the alternating-current (AC) dielectrophoretic response of gold nanoparticles of less than 200 nm diameter in water. An original dark-field digital video-microscopic method was developed and used in combination with a microfluidic device containing transparent thin-film electrodes. It was found that the dielectrophoretic force is only effective in a small zone very close to the tip of the electrodes, and that Brownian motion actually facilitates transport of particles towards this zone. Moreover, the fact that particles as small as 80 nm are still efficiently captured in our device is not only due to Brownian transport but also to an effective polarizability that is larger than what would be expected on basis of current theory for a sphere in a dielectric medium.

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

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

Hexaniobate Cluster Anion Monolayers on Gold Nanoparticles: A New Structural Role for Alkali Metal Countercations.

Monolayer shells of polyoxotungstate cluster anions on gold nanoparticles in water were electrostatically stabilized by structurally integrated countercations, with formation constants, K, increasing in the order: Li+ < Na+ < K+ < TMA+ < Cs+ (TMA+ = tetramethylammonium). We now report that for hexaniobate cluster anions, K values increase in the same order, with the notable exception of TMA+, which is effectively unable to induce monolayer formation. These findings point to a new structural model in which hexaniobate anions form a spherical coordination polymer at the gold surface with alkali metal countercations serving as single-atom structural building units between hexaniobate linkers.