Colloidal Solution Of Nanoparticles Research Articles

Ultrathin and Isotropic Metal Sulfide Wrapping on Plasmonic Metal Nanoparticles for Surface Enhanced Ram Scattering-Based Detection of Trace Heavy-Metal Ions.

A facile and general strategy is presented for homogenous and ultrathin metal sulfide wrapping on plasmonic metal (PM) nanoparticles (NPs) based on a thiourea-induced isotropic shell growth. This strategy is typically implemented just via adding the thiourea into pre-formed PM colloidal solutions containing target metal ions. The validity of this strategy is demonstrated by taking the wrapped NPs with Au core and CuS shell or Au@CuS NPs as an example. They are successfully fabricated via adding the thiourea and Cu2+ solutions into pre-formed Au NP colloidal solution. The CuS shell layer is highly homogenous (<10% in relative standard deviation of shell thickness), regardless of the NPs' shape or curvature. The shell thickness can be controlled from tens down to 0.5 nm just by the addition of different amounts of shell precursors. The formation of the shell layer on the Au NPs can be attributed to the alternative deposition of Cu2+ and S2- ions on the thiourea-modified surface of Au NPs in the solution, which induces the isotropic shell growth. Further, this strategy is of good universality. Many other sulfide-wrapped PM NPs, such as Ag@CuS, Au@PtS2, Au@HgS, Ag@Ag2S NPs, and Ag@CuS nanorods, have been successfully obtained with homogeneous and ultrathin shells. Importantly, such ultrathin sulfide-wrapped PM NPs can be used for surface enhanced Raman scattering (SERS)-based detection of trace heavy-metal ions with strong anti-interference via the ion exchange process between the metal sulfide shell and heavy-metal ions. This study provides a simple and controllable route for wrapping the homogenous and ultrathin sulfide layers on the PM NPs, and such wrapped NPs have good practical applications in the SERS-based detection of trace heavy-metal ions.

Au nanoparticles coated with chitosan

This paper describes a method of coating metallic gold (Au) nanoparticles with chitosan (CS) shells in an aqueous solution. A colloidal solution of Au nanoparticles with a particle size of 16.5 ± 1.7 nm was prepared by reducing the Au ions (III) with sodium citrate in water at 80 °C. CS coating was achieved in an aqueous solution containing the Au nanoparticles by using CS as a shell source and sodium hydroxide as a pH adjuster at 25 °C. Ultraviolet-visible extinction spectroscopy and transmittance electron microscopy observation revealed that the Au nanoparticles were coated with CS shells. Additionally, the CS shell thickness could be varied in a range up to 2.2 nm by changing the CS concentration during the CS-coating process.

Functionalized silicon nanoparticles as fluorescent probe for detection of hypochlorite in water

In this work amine functionalized silicon nanoparticles colloid is utilized to prepare a fluorescent probe for detecting low concentration levels of hypochlorite in water. The sensor is prepared by adding organosilane in silicon nanoparticles colloidal solution which freshly synthesized by laser ablation of silicon target in distilled water. The amine-terminated surface of silicon nanoparticles is confirmed using Fourier transform infrared, UV–vis absorption spectroscopy and transmission electron microscopy methods. The photoluminescence measurements of the functionalized silicon nanoparticles colloid exhibit high photostability and good reproducibility making them ideal fluorescent probes for sensing applications. It shows high sensitivity, excellent selectivity and rapid response (˜6 min) toward hypochlorite. The room temperature fluorescent sensor detects hypochlorite of water in the linear concentration range from 1 to 5 μM with a 0.2 μM detection limit. The sensor properties including high sensitivity, fast response and facile synthesis of the amine-functionalized silicon nanoparticles are compared with other reports in literature for fluorescent detection of hypochlorite in water.

Stabilization of colloidal metallic nanoparticles using polymers and hexa-substituted compounds with 1,3,4-oxadiazole pendant groups

Stabilization of metallic nanoparticles in colloidal solutions has been realized by different capping agents. Heterocyclic compounds can interact with metallic surfaces, and some authors have reported the use of heterocyclic compounds for the stabilization of colloidal nanoparticles. In this work, we report stabilization of Au and Ag nanoparticles using polymers and hexa-substituted compounds with 1,3,4-oxadiazole pendant groups. Using a polyelectrolyte with 2-amino-1,3,4-oxadiazole groups was possible to reduce Au3+ and Ag+ ions and stabilize Au and Ag nanoparticles in colloidal solution. With polymers and hexa-substituted compounds containing 1,3,4-oxadiazoles substituted with methyl, phenyl, or acetyl groups, stabilize Au and Ag nanoparticles in a water-DMF medium was possible. Characterization by TEM revealed the obtaining of Au and Ag nanoparticles with control over the size and the shape. The lowest average size for Au and Ag nanoparticles was 4 and 10 nm, respectively, using the hexa-substituted compound with 2-acetamido-4-acetyl-1H-1,3,4-oxadiazole groups.

Laser ablation synthesis of silver nanoparticles in water and dependence on laser nature

Silver nanoparticles have been synthesized by a one step, easy, fast and green method. The nanoparticles were prepared in de-ionized water by laser ablation method using two lasers, a continuous wave (CW) diode laser and a pulsed Nd:YAG laser. The purpose of the experiment is to compare the role of nature of the laser for production of better NPs. The prepared silver nanoparticles were characterized for their, structural, physical and optical properties. The structural properties of the synthesized nanoparticles were characterized by X-ray Diffraction and the nanoparticles were found to be crystalline. The physical properties were analyzed by Atomic Force Microscopy which confirmed spherical and nanometer sized nanoparticles. The average size was 20 nm and 9 nm for continuous and pulsed laser respectively. The optical properties were analyzed by UV–Visible spectroscopy where band gap energy was investigated and increase in band gap energy as compared to bulk was observed. The green nature of laser ablation method, surface chemistry and chemical contamination of the surface of prepared nanoparticles were analyzed by Fourier Transform Infrared Spectroscopy. The thermal conductivity of the nanoparticles colloidal solutions (nanofluids) was calculated and an enhancement of 16% and 27% was observed for CW and pulsed laser prepared nanofluids respectively as compared to base liquid (de-ionized water).

Histological Comparative of Kidney of Neonatal Mice Exposed to Silver Nanoparticles During Fetal Development

This study aimed to compare the histological changes in the neonatal kidney after their mothers exposed to different doses of silver nanoparticles colloidal solution (AgNPs) during the three stages of pregnancy. Pregnant Swiss albino mice (n=60) were randomly divided into three treated groups. They were intraperitoneally injected with AgNPs for 7 days during each stage of the gestational period. The newborn mice were sacrificed immediately after the birth, and the kidneys were being collected for histopathological analysis. The results showed that the AgNPs caused histological changes in the neonatal kidneys; vacuolation of some renal vesicles and cortical tubules, cystic tubular dilation, glomerular tuft shrinkage, and focal tubular necrosis in the first week-dose exposed pregnant. Disintegrating of immature glomeruli, distention of Bowman’s space of mature glomeruli, tubular necrosis, loss of renal parenchyma, medullar tubules containing hyaline casts, and subcapsular haemorrhage in the second week-dose exposed pregnant. Massive hypercellularity in the deeper part of the renal cortex, cortical and medullary tubules dilation, atrophy of subcapsular immature tubules, cortical cyst formation, glomerular tuft necrosis, dilation of Bowman’s space with evidence of crescent formation, and medullar portion replaced by scant loose connective tissue containing few numbers of tubules the third week-dose exposed pregnant. The results showed that the AgNPs has more negative effects on the kidney development at the third week-high dose and comparing the histological changes in the neonatal kidney were appeared in a time-depended manner and in a dosedepended manner. More researches must be carried out to obtain better understanding of AgNPs toxicity on fetal development and its ability as a teratogenic agent to induce external and internal abnormalities in the fetus.

Comprehensive characterization of magnetite-based colloid for biomedical applications

An aqueous colloidal solution of dextran-coated magnetite nanoparticles was studied by nonlinear second-harmonic magnetic response (M2), transmission electron microscopy (TEM), dynamic light scattering (DLS) and electron magnetic resonance (EMR). Nanoparticles were found to aggregate. A set of magnetic parameters of the aggregates, such as the mean magnetic moment, the magnetization damping constant, the longitudinal relaxation time, the field and energy of magnetic anisotropy, and others were evaluated from M2 measurements with the data processing formalism based on the Gilbert–Landau–Lifshitz (GLL) equation for the stochastic dynamics of superparamagnetic (SP) particles. Combined with TEM and DLS, the M2 technique additionally enabled the differentiation between magnetic and nonmagnetic components of the colloid. To achieve full numerical consistency between the parameters obtained from the M2 and TEM data, magnetic correlations of nanoparticles inside the aggregates were taken into account and their correlation radius was evaluated. The observed crossover in the magnetic field dependence of the EMR signal occurring due to the break of the dipole–dipole (d–d) coupling between nanoparticles in the aggregates was described using the M2 and TEM data.

Colloidal synthesis of Au nanoparticles using polyelectrolytes with 1,3,4‐thiadiazole as reducing agents

ABSTRACTHeterocyclic compounds are well known for their biological activity and coordination properties. Some heterocyclic compounds have been employed in the stabilization against coalescence of metallic nanoparticles in colloidal solutions, for example, tetrazole, triazole, and pyrazole. The aim of this work is to design new polyelectrolytes with heterocyclic pendant groups useful as reducing agents of Au3+ and as stabilizing agents for the synthesis of colloidal Au nanoparticles. Thus, polyelectrolytes with thiosemicarbazone and 1,3,4‐thiadiazole pendant groups were used as reducing agents of Au3+ ions and stabilizing agents of Au nanoparticles. The voltammetry study of the polyelectrolytes showed that one with thiosemicarbazone pendant groups is the better reducing agent than polyelectrolytes with heterocyclic pendant groups. The polyelectrolytes can control the growth of the nanoparticles, obtaining structures with an average size of 9 nm. In this study, it was concluded that the nature of the heterocyclic group does not have an effect on the shape of nanoparticles and quasi‐spherical nanoparticles were obtained with all polyelectrolytes. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47790.

Unravelling the nature of the spongy dark material in aged Turkevich gold nanoparticles colloidal solutions by CytoViva® dark-field imaging and HRTEM analysis

Turkevich gold nanoparticles colloidal solutions undergo further changes after ageing for several weeks or months, and in most cases a spongy dark material can be observed suspended in the red solution. CytoViva® dark-field microscopy images and high resolution transmission electron micrographys (HRTEM) of the strange body played a central role and revealed a fibrous structure, consistent with cellulose, as commonly found in the cell-walls of many fungi. Surprisingly, the interior of the fibers are filled with gold nanoparticles, responsible for the high contrasting images obtained in this work. The fungi were replicated in the laboratory, characterized by Infrared Microscopy (FTIR) and revealed an ability to grow in gold-citrate media, even in dark and anaerobical conditions.

Integral Estimation of Effects of Aggregation of Nanoparticles in Solutions from Autocorrelation Functions of Intensity of Scattered Radiation

A method of investigation of processes that arise in aggregation of nanoparticles in colloidal solutions based on estimation of variations in the coefficients of rotational diffusion of nanoparticles is proposed. It is shown that rotational diffusion is more sensitive to variations in the dimensions of the particles than is translational diffusion. A comparative estimation of these types of variations is presented and the relative index of aggregation is calculated from the integral values of the autocorrelation function of depolarized dynamic light scattering. Results of numerical simulation of the proposed method and its experimental certification are compared.

Determining the Composite Structure of Au-Fe-Based Submicrometre Spherical Particles Fabricated by Pulsed-Laser Melting in Liquid.

Submicrometre spherical particles made of Au and Fe can be fabricated by pulsed-laser melting in liquid (PLML) using a mixture of Au and iron oxide nanoparticles as the raw particles dispersed in ethanol, although the detailed formation mechanism has not yet been clarified. Using a 355 nm pulsed laser to avoid extreme temperature difference between two different raw particles during laser irradiation and an Fe2O3 raw nanoparticle colloidal solution as an iron source to promote the aggregation of Au and Fe2O3 nanoparticles, we performed intensive characterization of the products and clarified the formation mechanism of Au-Fe composite submicrometre spherical particles. Because of the above two measures (Fe2O3 raw nanoparticle and 355 nm pulsed laser), the products—whether the particles are phase-separated or homogeneous alloys—basically follow the phase diagram. In Fe-rich range, the phase-separated Au-core/Fe-shell particles were formed, because quenching induces an earlier solidification of the Fe-rich component as a result of cooling from the surrounding ethanol. If the particle size is small, the quenching rate becomes very rapid and particles were less phase-separated. For high Au contents exceeding 70% in weight, crystalline Au-rich alloys were formed without phase separation. Thus, this aggregation control is required to selectively form homogeneous or phase-separated larger submicrometre-sized particles by PLML.

Preparation of Cu nanoparticle colloid from a Cu ion solution by using protein surfactant

ABSTRACTIn this paper, a colloidal solution of copper nanoparticles was prepared from a Cu ion aqueous solution with the protein casein surfactant by a liquid phase reduction method at low temperature below 373K. For the casein concentration ranging from 6g/L to 75g/L, the formation of copper nanoparticle colloid were observed. As a result, the peak was observed at the ranging of 450 to 650 nm corresponding to the copper nanoparticle colloid plasmon absorption. As the surfactant concentration increases, the absorption spectrum tends to blue-shift and the particle diameter decreases. Thus, it indicated that the optical property and particle diameter of copper nanoparticle colloidal solution will be controlled by the protein casein surfactant concentration.

A regioselective coating onto microarray channels of bamboo with chitosan-based silver nanoparticles

In this investigation, bamboo (Dendrocalamus giganteus Munro) timbers were coated selectively into vascular vessel bundles with a potential antimicrobial colloidal solution of silver nanoparticles (Ag-NPs). Electric charge and size of Ag-NPs, with different charged organic ligands (trisodium citrate and chitosan), affect their self-sorting in different anatomical structures of bamboo when submitted up to 20 impregnation cycles through a vacuum system. Physicochemical characterization of Ag-NPs was performed by spectroscopic techniques and electron microscopy. Confocal laser scanning microscopy and scanning electron microscopy were employed to characterize natural bamboo. Qualitative and quantitative determination of the metal coating in bamboo specimens was performed with X-ray microtomography (μCT), energy-dispersive X-ray spectroscopy, and X-ray diffraction. μCT revealed a gradient deposition of citrate-capped Ag-NPs into the parenchyma tissue with the higher concentration at the outer part of the bamboo. On the other hand, the chitosan-capped Ag-NPs were deposited mainly in the vessel bundles.

The Effect of Gold Nanoparticle Concentration and Laser Fluence on the Laser-Induced Water Decomposition

This Article covers the influence of the concentration of gold nanoparticles on laser-induced water decomposition. It was established that addition of gold nanoparticles intensifies laser-induced water decomposition by almost 2 orders of magnitude. The water decomposition rate was shown to be maximal at a nanoparticle concentration around 1010 NP/mL, whereas a decrease or increase of nanoparticle concentration leads to a decrease of water decomposition rate. It was demonstrated that, if the concentration of nanoparticles in water-based colloid was less than 1010 NP/mL, laser irradiation of the colloid caused formation of molecular hydrogen, hydrogen peroxide, and molecular oxygen. If the concentration of nanoparticles exceeded 1011 NP/mL, only two products, molecular hydrogen and hydrogen peroxide, were formed. Correlations between the water decomposition rate and the main optical and acoustic parameters of optical breakdown-generated plasma were investigated. Variants of laser-induced decomposition of colloidal solutions of nanoparticles based on organic solvents (ethanol, propanol-2, butanol-2, diethyl ether) were also analyzed.

Photosensitized TiO2 films on polymers – Titania-polymer interactions and visible light induced photoactivity

Photocatalytic coatings at polymers, showing a visible light induced photoactivity, can be synthesized using a low temperature oxygen plasma treatment of the polymer (PP) followed by deposition of TiO2 nanoparticles and their sensitization with organic ligands. The whole process consists of three major steps: surface activation involving its partial oxidation, immobilization of TiO2 nanoparticles and photosensitization of titania film by impregnation with the solution of organic ligands forming surface Ti(IV) charge transfer complexes. XPS and IR analysis revealed the formation of oxygen-containing groups at the polymer surface upon plasma treatment. These groups participate in the formation of TiOC bonds which ensure a very good adhesion of titania films to polymeric surface. The dip-coating process using an aqueous colloidal solution of TiO2 nanoparticles allows to synthesize a compact coating with a thickness of 100–300 nm. Coordination of catechol-like ligands to surface Ti(IV) centers results in formation of colored charge transfer complexes responsible for absorption of visible light and an effective photoinduced charge separation. Photogenerated electrons and holes can take part in surface redox reactions responsible for degradation of pollutants. Tests with various organic ligands (catechol, 2,3-naphthalenediol, pyrogallol and rutin) revealed, that the titanium dioxide coating modified with catechol was the most photoactive one when visible light irradiation was applied. Presented photocatalytic coatings can be effectively used as self-sterilizing surfaces activated by visible light.

A novel and comprehensive study on manufacturing and fabrication nanoparticles methods and techniques for processing cadmium oxide (CdO) nanoparticles colloidal solution

A novel and comprehensive study on manufacturing and fabrication nanoparticles methods and techniques for processing cadmium oxide (CdO) nanoparticles colloidal solution

Direct TEM observation of the "acanthite α-Ag2S-argentite β-Ag2S" phase transition in a silver sulfide nanoparticle.

For the first time, the α-Ag2S (acanthite)–β-Ag2S (argentite) phase transition in a single silver sulfide nanoparticle has been observed in situ using a high-resolution transmission electron microscopy method in real time. Colloid solutions of Ag2S nanoparticles and nanostructured powders of silver sulfide have been synthesized by one-stage chemical bath deposition from an aqueous solution of silver nitrate, sodium sulfide and sodium citrate. Ag2S nanoparticles were heated to different temperatures directly in an electronic microscope by regulating the energy of the electron beam. This allowed observation of the transition of acanthite into argentite and the reversible transition of argentite into acanthite in real time, and this phase transition to be filmed. Temperature dependence of the lattice constant aarg of argentite β-Ag2S in the temperature range 448–723 K is established by in situ high-temperature X-ray diffraction. The orientation relationships between the monoclinic acanthite α-Ag2S and the body-centered cubic argentite β-Ag2S are determined. It is shown that the possible distances between silver atoms in cubic argentite, in contrast to those in acanthite, are too small for the positions of the metal sublattice to be occupied by Ag atoms with a probability equal to 1.

Improved functional performances of traditional artistic pottery by sol-gel nanoparticles deposition

This work is focused on the realization of a new manufacturing process based on the introduction of TiO2 nanostructured coatings on the surface of red earthenware pottery for domestic use. The aim of the study is to improve the technical properties of the product made from lime and iron-rich clays used to produce traditional artistic Tuscan pottery (Italy). The identified strategy involves the application of nanoparticles onto the surface of ceramic substrates via a sol-gel based process; the initial porosity of the Earthenware promotes the insertion of inert nanoparticles in the outermost part of the ceramic material by simple immersion of bisqueware in the colloidal solutions of nanoparticles. Morphological investigation of the functionalized surfaces has been carried out by scanning electron microscope and atomic force microscopy, while the effectiveness of the treatment was checked by evaluating the water absorption capacity in compliance with the standard method AS-1012.21-1999. The obtained results show a reduction of surface porosity, which turns into a reduced water uptake respect to the traditional pottery, maintaining, at the same time, identical aesthetical characteristics.

Synthesis, characterization and antimicrobial activity of colloidal copper nanoparticles stabilized by cationic thiol polyurethane surfactants

Metal nanoparticles have attracted considerable interest particularly because of the size dependence of physical and chemical properties and its enormous technological potential. Among different metal nanoparticles, copper nanoparticles have attracted great attention because copper is one of the most key metals in new technology. Chemical methods are used to synthesize copper nanoparticles. Chemical reduction is the most frequently applied method for the preparation of stable, colloidal dispersions in organic solvents. In this paper, the new cationic thiol polyurethane surfactants with different alkyl chain length were synthesized (PQ10, PQ14 and PQ18). The chemical structure of the synthesized surfactants was confirmed using infra-red spectroscopy (IR) and proton nuclear magnetic resonance spectroscopy (1HNMR). Copper nanoparticles colloidal solution of 40–80 nm diameters was prepared using sodium borohydride in aqueous solution at room temperature as reducing agent. The synthesized surfactants decrease the aggreegation of copper nanoparticles. The nanostructure of the synthesized surfactant with copper nanoparticles with diameters ranging from 31.5 to 10.3 nm was prepared and characterized using ultra violet spectrophotometer (UV), infra-red spectroscopy (IR) and transmission electron microscope (TEM). The results declare formation and stabilization of copper nanoparticle using synthesized cationic surfactants. Antimicrobial activity of the synthesized cationic surfactants and their nanostructure with copper nanoparticles were evaluated against pathogenic bacteria and fungi.

Correction to: Influence of the Solvent on the Structure and Morphology of Nanoparticles Fabricated by Laser Ablation of Bulk Magnesium Targets

Ultrafine powders and colloid solutions of nanoparticles are fabricated by nanosecond pulsed laser ablation (a Nd:YAG laser, 1064 nm, 7 ns, 150 mJ, and 20 Hz) of metallic magnesium targets in water and organic solvents of different polarities (ethyl alcohol, ethyl acetate, and n-hexane). The morphology, dimensional characteristics, composition, and structure of the particles are studied by the methods of transmission electron microscopy, x-ray diffraction, and Fourier-transform infrared spectroscopy depending on the solvent used. For the first time it has been demonstrated that nanostructures of magnesium oxyhydroxide Mg5O(OH)8 are formed during the ablation in water. It is established that in organic solvents, formation of hexagonal and cubic magnesium oxides is possible. Nanoparticles fabricated by the ablation in less thermostable solvents – ethyl acetate and hexane – contain carbonates.