聚丙烯胺稳定铜纳米粒子的制备及其SERS活性研究

报道了聚丙烯胺稳定的球形和棒状铜纳米粒子的制备方法。在水溶液中空气条件下,通过水合肼还原二价铜离子到铜纳米粒子。聚丙烯胺的作用除稳定粒子防止聚集外,也可使粒子分散在水溶液中。该法的优点是在室温下,无需惰性气体保护,即可制备水溶液中分散的铜纳米粒子。紫外光谱和透射电镜监测了铜纳米粒子的生长过程。发现氢氧化钠的用量,聚丙烯胺浓度,反应时间等因素都影响到铜纳米粒子的组成,尺寸,形貌和聚集程度。氢氧化钠用量决定了制备粒子的组成成分是铜或氧化亚铜。所制备的球形铜纳米粒子表现出优良的表面增强拉曼散射活性。     

Microwave-assisted polyol synthesis of Cu nanoparticles

Microwave heating was applied to synthesize copper colloidal nanoparticles by a polyol method that exploits the chelating and reducing power of a polidentate alcohol (diethylenglycol). The synthesis was carried out in the presence of eco-friendly additives such as ascorbic acid (reducing agent) and polyvinylpirrolidone (chelating polymer) to improve the reduction kinetics and sols stability. Prepared suspensions, obtained with very high reaction yield, were stable for months in spite of the high metal concentration. In order to optimize suspensions, synthesis parameters were modified and the effects on particle size, optical properties, and reaction yield were investigated. XRD analysis, scanning transmission electron microscopy (STEM), and DLS measurements confirmed that prepared sols consist of crystalline metallic copper with a diameter ranging from 45 to 130 nm. Surface plasmon resonance (SPR) of Cu nanoparticles was monitored by UV–Vis spectroscopy and showed both a red shift and a band weakening due to nanoparticle diameter increase. Microwave use provides rapid, uniform heating of reagents and solvent, while accelerating the reduction of metal precursors and the nucleation of metal clusters, resulting in monodispersed nanostructures. The proposed microwave-assisted synthesis, also usable in large-scale continuous production, makes process intensification possible.     

Synthesis and characterization of monodisperse copper nanoparticles using gum acacia

A simple method was put forward in this paper for preparing colloidal copper nanoparticles in aqueous solutions using copper sulfate, gum acacia and hydrazine hydrate as copper precursor, capping agents and reducing agents, respectively, without any inert gas. The formation of nanosized copper was confirmed by its characteristic surface plasmon absorption peak at 604 nm in UV–vis spectra. The transmission electron microscopic (TEM) and scanning electron microscope (SEM) images show that the as-synthesized copper fine spherical particles are distributed uniformly with a narrow distribution from 3 nm to 9 nm. The X-ray diffraction (XRD) and high resolution transmission electron microscopic (HRTEM) demonstrated that the obtained metallic nanoparticles are single crystalline copper nanoparticles. Fourier transform infra-red (FT-IR) spectroscopic data suggested that the copper nanoparticles are coated with gum acacia. The effects of the quantity of gum acacia on the particle size were investigated by the UV–vis spectra and TEM images. The growth process of the nanoparticles was monitored by the UV–vis spectra. The mechanism of the formation copper nanoparticles was discussed. The process raised in this study can be served as an excellent candidate for the preparation of copper nanoparticles in a large scale production.     

A Simple Strategy to Prepare Colloidal Cu‐Doped ZnSe(S) Green Emitter Nanocrystals in Aqueous Media

A novel and simple method is described for preparing colloidal Cu‐doped ZnSe(S) quantum dots (QDs) in aqueous media by introducing copper ions using the same method as to prepare colloidal ZnSe(S). More specifically, the Cu‐doped ZnSe(S) are prepared through the nucleation‐doping method in the presence of 3‐mercaptopropionic acid as stabilizers using zinc perchlorate, copper sulphate, and NaHSe as precursors. Confirmation of the preparation of Cu‐doped ZnSe(S) nanocrystals (NCs) is done with absorption and emission spectroscopies (UV–vis and PL) as the QDs show intensive green emissions. The reduction of ions Cu²⁺ to Cu⁺ is confirmed by using electron paramagnetic resonance (EPR), in which Cu⁺ ions are silent. The size determination is performed by using transmission electron microscopy (TEM) and dynamic light scattering (DLS), resulting in Cu‐doped ZnSe(S) particles with a mean diameter of 4.6 ± 3.5 nm. The excellent stability observed for the nanoparticles overcomes the intrinsic instability of traditional aqueous Cu‐doped ZnSe(S) NCs.     

Physicochemical properties and toxicological assessment of modified CdS nanoparticles

The synthesis procedure represents a key aspect in designing the physical and chemical properties of gold nanoparticles. The current study proposes a simple approach for gold nanoparticles synthesis using non-thermal plasma. The novelty of the setup consists in producing an in-liquid plasma discharge in argon bubbles that are externally generated in the solution exposed to treatment. Because plasma is the source of active species which are directly involved in gold reduction, no additional reducing agent was necessary. Collagen protein was used as capping agent. A plasma treatment of 10 min is sufficient for obtaining stable colloidal solutions with UV-Vis absorption maximum at 530 nm. Transmission electron microscopy images revealed preponderant spherical nanoparticles with dimensions in the range of 6–20 nm. The method of synthesis distinguishes by its good reproducibility, facility, efficiency, and ability to generate stable colloidal nanoparticles after several minutes of plasma exposure.     

A novel method for synthesis of colloidal silver nanoparticles by arc discharge in liquid

This paper presents a novel, inexpensive and one-step approach for synthesis of silver nanoparticles (Ag NPs) using arc discharge between titanium electrodes in AgNO₃ solution. The resulting nanoparticles were characterized using UV–Vis spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Silver nanoparticles of 18 nm diameter were formed during reduction of AgNO₃ in plasma discharge zone. Optical absorption spectroscopy of as prepared samples at 15 A arc current in AgNO₃ solution shows a surface plasmon resonance around 410 nm. It was found that sodium citrate acts as a stabilizer and surface capping agent of the colloidal nanoparticles. SEM images exhibit the increase of reduced nanoparticles in 6 min arc duration compared with 1 min arc duration. TEM image of the sample prepared at 6 min arc duration shows narrow size distribution with 18 nm mean particle size. Antibacterial activities of silver nanoparticles were investigated at the presence of Escherichia coli (E-coli) bacteria.     

Photochemical synthesis of copper nanoparticles incorporated in poly(vinyl pyrrolidone)

The effect of the presence of poly(vinyl pyrrolidone) (PVP) on the copper nanoparticle formation, obtained by UV irradiation of ethanol solution of Cu(acac)₂ (acac = 2,4-pentanedionato), was investigated. At 254 nm, in conditions of light completely absorbed by complex, the PVP exhibited protective and stabilizing effects, as shown by the formation of a colloidal copper solution and by a block of the heterogeneous process, which leads to thin film formation on the quartz walls. The colloidal solution was tested for several months by plasmon position and it was found that it remained unaltered in inert atmosphere, but returned to the starting complex on contact with air. The PVP ability to control the particle size was investigated by carrying out photoreduction sensitized by Hacac at 254 and 300 nm, in the presence of PVP concentration varying from 0 to 0.2 M. In this range it was possible to obtain copper nanoparticles of dimensions decreasing from 30 to 4 nm. Besides this, the PVP (0.005–0.05 M) role as sensitizer was investigated by irradiating solutions of Cu(acac)₂ at 300 nm which is an inactive wavelength for copper reduction by direct light absorption. It was found that the PVP was an efficient sensitizer of the copper photoreduction. The nanoparticles were characterized by plasmon band, Trasmission Electron Microscope (TEM) as well as Dynamic Light Scattering (DSL) analysis. The overall results evidence the advantages of the PVP use in the nanoparticle copper formation through the photochemical technique such as the exclusive formation of colloidal copper, their size control, stable colloidal solution and complete return to the starting complex.     

Study of tryptophan assisted synthesis of gold nanoparticles by combining UV–Vis, fluorescence, and SERS spectroscopy

We developed a rapid and non-toxic method for the preparation of colloidal gold nanoparticles (GNPs) by using tryptophan (Trp) as reducing/stabilizing agent. We show that the temperature has a major influence on the kinetics of gold ion reduction and the crystal growth, higher temperatures favoring the synthesis of anisotropic nanoparticles (triangles and hexagons). The as-synthesized nanostructures were characterized by UV–Vis absorption spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), fluorescence, and surface-enhanced Raman scattering (SERS) spectroscopy. The UV–Vis measurements confirmed that temperature is a critical factor in the synthesis process, having a major effect on the shape of the synthesized GNPs. Moreover, fluorescence spectroscopy was able to monitor the quenching of the Trp fluorescence during the in situ synthesis of GNPs. Using Trp as molecular analyte to evaluate the SERS efficiency of as-prepared GNPs at different temperatures, we demonstrated that the Raman enhancement of the synthesized gold nanoplates is higher than that of the gold spherical nanoparticles.     

Size,composition and optical properties of copper nanoparticles prepared by laser ablation in liquids

Colloidal copper nanoparticles were prepared by pulsed Nd:YAG laser ablation in water and acetone. Size and optical properties of the nanoparticles were characterized by transmission electron microscopy and UV–visible spectrophotometry, respectively. The copper particles were rather spherical and their mean diameter in water was 30 nm, whereas in acetone much smaller particles were produced with an average diameter of 3 nm. Optical extinction immediately after the ablation showed surface plasmon resonance peaks at 626 and 575 nm for the colloidal copper in water and acetone, respectively. Time evaluation showed a blue shift of the optical extinction maximum, which is related to the change of the particle size distribution. Copper nanoparticles in acetone are yellowish and stable even after 10 months. In water, the color of the blue-green solution was changed to brown-black and the nanoparticles precipitated completely after two weeks, which is assigned to oxidation of copper nanoparticles into copper oxide (II) as was confirmed by the electron diffraction pattern and optical absorption measurements. We conclude that the ablation of bulk copper in water and acetone is a physical and flexible method for synthesis of stable colloidal copper and oxidized copper nanoparticles. PACS 42.62.-b; 81.07.-b; 61.46.+w     

Copper-assisted shape control in colloidal synthesis of indium oxide nanoparticles

Indium oxide is an important n-type transparent semiconductor, finding application in solar cells, sensors, and optoelectronic devices. We present here a novel non-injection synthesis route for the preparation of colloidal indium oxide nanocrystals by using oleylamine (OLA) as ligand and as solvent. Indium oxide with cubic crystallographic structure is formed in a reaction between indium acetate and OLA, the latter is converted to oleylamide during the synthesis. The shape of the nanocrystals can be influenced by the addition of copper ions. When only indium (III) acetate is used as precursor flower-shaped indium oxide nanoparticles are obtained. Addition of copper salts such as copper (I) acetate, copper (II) acetate, copper (II) acetylacetonate, or copper (I) chloride, under otherwise identical reaction conditions changes the shape of nanoparticles to quasi-spherical or elongated. The anions, except for chloride, do not influence the shape of the resulting nanocrystals. This finding suggests that adsorption of copper ions on the In₂O₃ surface during the nanoparticles growth is responsible for shape control, whereas changes in the reactivity of the In cations caused by the presence of different anions play a secondary role. X-ray diffraction, transmission electron microscopy, nuclear magnetic resonance, energy dispersive X-ray analysis, and UV–Vis-absorption spectroscopy are used to characterize the samples.     

Synthesis of Linoleic Acid Capped Copper Nanoparticles and Their Fluorescence Study

Copper nanoparticles have been prepared through the reduction of cupric ions by ethanol with linoleic acid as a capping agent. The morphology and structure of these nanoparticles have been investigated using transmission electron microscopy. The X-diffraction study shows that the nanoparticles are crystalline and mainly composed of face-centered cubic (fcc) copper with a narrow size distribution having an average size of 5 nm. Fluorescence spectra of these copper nanoparticles have been analysed which show two emission peak at 450 nm and 625 nm corresponding to the large energy band and small energy band respectively, when illuminated at 250 nm of an optical source.     

Vermiculite decorated with copper nanoparticles: Novel antibacterial hybrid material

Vermiculite decorated with copper nanoparticles is a new antibacterial material that was prepared in this study through ion-exchange process and hydrogen reduction. The replacement of magnesium ions in interlayer structure was carried out using concentrated copper sulfate solutions at elevated temperature. Copper ions were reduced to elemental copper at 400-600 °C using hydrogen as the reducing agent. During the reduction process copper diffused primarily to vermiculite surface regions and formed copper nanoparticles with a broad range of sizes, from ∼1 to 400 nm. Strong adhesion of copper nanoparticles to the vermiculite carrier makes this hybrid very stable and durable. The new vermiculite-metallic copper hybrid material shows strong antibacterial activity against Staphylococcus aureus at 37 °C. Vermiculite is an inexpensive mineral that is very stable under a wide range of industrial and environmental conditions, and extensively used as filler in fireproof materials, plastics, paints and lightweight concrete, so the addition of copper as an antibacterial agent opens new avenues for the application of vermiculite in consumer products and other areas.     

Interphase synthesis and some characteristics of aqueous nickel dispersions

The facilities of one-step preparation method of nickel nanoparticles by the interphase reduction of nickel oleate using sodium borohydride at room temperature without soluble polymer as a protective agent were studied. Nickel obtained by such technique was concentrated in aqueous phase as a black dispersion. The composition and morphology of the colloid's dispersive phase were investigated by transmission electron microscopy, XRD and IR-spectroscopy. The dispersive phase of the prepared colloidal solution represents crystalline spherical nickel nanoparticles with some admixture of nickel boride. Their average size varies between 2 and 6 nm. In accordance with the IR-spectroscopy results the stability of the nickel colloidal dispersions was provided by the surfactant produced through the interphase reaction.     

Surface coating of Al nanoparticles by using a wet ball milling method: A facile synthesis and characterization of colloidal stability

A facile surface coating of aluminum (Al) nanoparticles with various dispersants by using a wet ball milling method is reported. Various mixtures of Al nanoparticles (d = 30–130 nm) and dispersants in solvent were ball milled. The excellent surface coating was observed with coating thickness ranging from 10 to 13 nm. The resulting good colloidal stability confirmed by both visual inspection of colloidal precipitation and Turbiscan backscattering was attributed to a stable dispersant organic layer formed on Al nanoparticle surfaces after ball milling as observed in HRTEM images. This method can be extended to the synthesis of a variety of any other metallic nano-colloidal solutions.     

Continuous production of inorganic magnetic nanocomposites for biomedical applications by laser pyrolysis

Magnetic composites of Fe-based nanoparticles encapsulated in carbon/silica (C/SiO₂@Fe) or carbon (C@Fe) matrices were prepared by laser-induced pyrolysis of aerosols. The powders were dispersed in aqueous solutions at pH 7 resulting in biocompatible colloidal dispersions with a high resistance to biodegradation. Structural and magnetic properties and the suitability of aqueous dispersions as contrast agent for MRI were analyzed. The results of these characterizations and the NMR relaxivity data are very encouraging for application of laser pyrolysis products in the field of living tissues.     

Controlled Self‐Assembly of Mesoporous CuO Networks Guided by Organic Interlinking

The controlled aggregation of copper oxide nanoparticles (CuO NPs) induced by a multitopic carboxylic acid allows the formation of mesoporous structures with high surface area, in the order of 100 m² g^?1, as demonstrated herein. The main novelty in the designed process is the use, as a previous step, of a sacrificeable monotopic carboxylate ligand for capping the CuO NPs. This step avoids the often observed unwanted behavior of uncontrolled aggregation and material densification. The monotopic 3,6,9‐trioxadecanoate (HTODA) is used as the capping agent to prepare TODA@CuO, a starting material that forms colloidal dispersions in ethanol. For NPs self‐assembly, the bulky tricarboxylic acid 4,4′,4′′,‐benzene‐1,3,5‐triyl‐tris(benzoic acid) (H₃BTB) is chosen as an efficient interlinker in the controlled aggregation. The obtained mesoporous network shows a considerable thermal stability, retaining ≈70% of its specific surface area after annealing at 300 °C under vacuum. Thermal treatment involves TODA capping agent elimination, but not BTB linker. The simultaneous reduction of the CuO NPs to a Cu₂O/Cu mixture is observed.     

Magnetoabsorption of Dirac Fermions in InAs/GaSb/InAs “Three-Layer” Gapless Quantum Wells

Subablative exposure of tightly focused visible-range femtosecond laser pulses on a thin translucent nanocrystalline copper(I) oxide on a silica glass substrate results not only in its annealing (resolidification), but apparently also in reduction of copper ions to the metallic state via single-photon absorption and the following thermal decomposition (disproportioning). Partial or complete ablation of the film within the laser focal spot and also its subablative optically contrast modification through formation of colloidal nanoparticles or annealing (resolidification) make it possible to consider this material in the thin-film form as a novel optical platform for direct laser writing of vis-IR metasurfaces and thin-film sensing plasmonic and all-dielectric nanostructures.     

The Study of Aggregation Processes in Colloidal Solutions of Magnetite–Silica Nanoparticles by NMR Relaxometry,AFM, and UV–Vis-Spectroscopy

Colloidal solutions of magnetic nanoparticles were studied as a promising magnetic resonance imaging (MRI) contrast agent. The problem of aggregative stability of solutions is considered. Sol-gel synthesis of magnetite colloidal solutions stabilized by silica is described. Transmittance spectra were measured to analyze sedimentation of nanoparticles in magnetite–silica solutions of different compositions and concentrations. It is shown that the synthesized nanoparticles can be used as MRI contrast agents. The surface morphology and particle size of Fe₃O₄/SiO₂ layers were estimated by atomic force mictroscopy (AFM) technique. The mechanism of magnetic-field-induced aggregation of Fe₃O₄/SiO₂ nanoparticles into chain-like and fractal structures is described.     

Nucleation and growth of silver nanoshells through copper vapor laser irradiation

Silica core–silver shell, silver nanoshells (NSs), have been synthesized by an innovative laser-based approach. The NSs’ nucleation and growth progressed upon the pulse strikes of a copper vapor laser on a colloidal solution containing silver and silica nanoparticles (NPs). The silver NPs were separately synthesized by ablation of a silver target in deionized water by a 1064 nm Q-switched Nd:YAG laser. The dependence of silver NSs’ growth on the laser exposure time has been systematically studied by UV–VIS absorption spectroscopy technique. Transmission electron microscopy was exploited as well to visually confirm the NSs’ evolution through the process.     

Potential to raise the efficiency of neutron and neutron–photon therapy using metal nonradioactive nanoparticles

The use of metal nonradioactive nanoparticles (specifically, gold ones) in neutron and neutron–photon cancer therapy is proposed. The minimum therapeutically effective average density of gold within a tumor subjected to neutron irradiation is estimated as a value on the order of 10^-5-10^-4 g/cm³. Potential benefits of the use of data obtained when using Peteosthor (a drug containing ²²⁴Ra and colloidal platinum) and Thorotrast (a radiopaque contrast agent containing thorium oxide nanoparticles) and its analogues in the analysis of safety and efficiency of application of nonradioactive nanoparticles in radiation therapy and diagnostics are discussed.