Polymer microspheres stabilized by titania nanoparticles

Polymer microspheres stabilized by titania nanoparticles were synthesized using a two-step Pickering emulsion polymerization process, in which nanosized titania nanoparticles were used as solid emulsifiers and building blocks. It gives a simple but novel route for the fabrication of functional inorganic/polymer hybrid materials with controlled microstructures. The final Pickering emulsion can be applied to various substrates forming continuous films with highly ordered nanosized to microsized TiO₂ protuberances across the films. Those films will have potential applications for photo-catalyst, water and air purification.     

光谱学研究银纳米颗粒在玻璃中的生成规律

通过离子交换法将银离子引入白硅酸盐玻璃和绿硅酸盐玻璃,利用光致发光(photoluminescence-PL)和光吸收(optical absorption-OA)谱研究银离子的团簇化、成核和生长.由于白硅酸盐玻璃不含二价铁离子,因此,银纳米颗粒形成困难,颗粒体积分数非常低,以致样品中银纳米颗粒的共振吸收峰不明显.在这种条件下,样品中存在大量银离子和银的小原子团簇.在绿玻璃中,氧化铁含量较高,引入到玻璃中的银离子大部分被二价铁离子还原成中性银原子,通过热处理,银离子在玻璃中成核和生长.在相近的热处理条件下,绿玻璃有利于银纳米颗粒的生成.银纳米颗粒在形成过程中,消耗大量银离子,造成样品的发光强度逐渐降低.     

聚苯乙烯/银核壳结构纳米微球的制备与表征

采用两步法的简单路线制备出银纳米粒子包覆的聚苯乙烯(PS)微球,首先通过乳液聚合法合成出聚苯乙烯微球;然后对苯乙烯进行敏化和活化,搅拌下加入银的还原液,从而制备出Ag-PS核壳结构的纳米微球.同时借助于TEM、UV-vis、 FE-SEM进行表征,分析其微观结构.结果表明,所得的聚苯乙烯微球粒径约为40nm;聚苯乙烯/银核壳结构纳米微球粒径为45～350nm,银层厚度可随意调控.     

Preparation and characterization of poly(acrylonitrile-co-acrylic acid) nanofibrous composites with Fe3O4 magnetic nanoparticles

Nanofibrous composites are a new class of polymer materials with controlled and tailored properties. Novel Fe₃O₄/poly(acrylonitrile-co-acrylic acid) nanofibrous composites with magnetic behavior have been prepared by a simple electrospinning process. The nanofibrous composites were characterized by X-ray diffraction, field emission scanning electron microscopy and vibrating sample magnetometer. The distribution of Fe₃O₄ nanoparticles inside the nanofibrous composites was investigated by field emission scanning electron microscopy. X-ray diffraction revealed the presence of Fe₃O₄ nanoparticles in the nanofibrous composites. The maximum saturation magnetization for the composites, measured at 300 K, was 30.51 emu/g.     

Magnetoresponsive on-demand release of hybrid liposomes formed from Fe3 O4 nanoparticles and thermosensitive block copolymers

A new approach to control the release of encapsulated materials from liposomes by using thermosensitive block copolymers and magnetic nanoparticles is reported. Hydrophobized Fe(3) O(4) nanoparticles are synthesized via the hydrothermal process, and can be incorporated into liposomal membranes by hydrophobic interactions. Thermosensitive block copolymers of (2-ethoxy)ethoxyethyl vinyl ether (EOEOVE) and octadecyl vinyl ether (ODVE) are synthesized by living cationic polymerization. The poly(EOEOVE) block acts as a temperature-sensitive moiety, and the poly(ODVE) block acts as an anchor unit. Hybrid liposomes encapsulating pyranine, a water-soluble fluorescent dye, are prepared from mixtures of phospholipids, the hydrophobized Fe(3) O(4) nanoparticles, and the copolymer. While the hybrid liposomes released negligible amounts of pyranine under static conditions, the release of pyranine is drastically enhanced by alternating magnetic field irradiation. The magnetically induced release is attributed to the transition of the thermosensitive segment of the copolymer, which is caused by the release of localized heat from the Fe(3) O(4) nanoparticles under magnetic stimuli, rather than the rupture of the capsules. The release rate of the hybrid capsules is controlled by varying the amount of Fe(3) O(4) nanoparticles embedded into the liposomes.     

Localized surface plasmon resonance-based hybrid Au–Ag nanoparticles for detection of Staphylococcus aureus enterotoxin B

A triangular hybrid Au–Ag nanoparticles array was proposed for the purpose of biosensing in this paper. Constructing the hybrid nanoparticles, an Au thin film is capped on the Ag nanoparticles which are attached on glass substrate. The hybrid nanoparticles array was designed by means of finite-difference and time-domain (FDTD) algorithm-based computational numerical calculation and optimization. Sensitivity of refractive index of the hybrid nanoparticles array was obtained by the computational calculation and experimental detection. Moreover, the hybrid nanoparticles array can prevent oxidation of the pure Ag nanoparticles from atmosphere environment because the Au protective layer was deposited on top of the Ag nanoparticles so as to isolate the Ag particles from the atmosphere. We presented a novel surface covalent link method between the localized surface plasmon resonance (LSPR) effect-based biosensors with hybrid nanoparticles array and the detected target molecules. The generated surface plasmon wave from the array carries the biological interaction message into the corresponding spectra. Staphylococcus aureus enterotoxin B (SEB), a small protein toxin was directly detected at nanogramme per milliliter level using the triangular hybrid Au–Ag nanoparticles. Hence one more option for the SEB detection is provided by this way.     

Simple method for preparation of cubic Ag nanoparticles and their self-assembled films

Thiol-derivatised cubic Ag nanoparticles were prepared by adding an AgNO₃ solution containing a trace amount of alkanethiol into a solution of NaBH₄ and sodium oleate. Their preparation and character were compared with randomly shaped Ag nanoparticles. The thiol was used purposely as orientation agent instead of protective agent. Transfer of cubic Ag nanoparticles from aqueous phase into organic phase or to the interface of aqueous/organic phase has resulted in self-assembled films on the surface of microscope slides and of many other substrates. Transmission electron microscope and UV–vis spectra were used to characterize the cubic Ag nanoparticles. The nanoparticle films were also observed using conventional optical and scanning electron microscope. The mechanisms of the nanoparticles phase-transfer and the formation of the self-assembled nanoparticle films are discussed.     

Preparation of Ag nanoparticles coated tetrapod-like ZnO whisker photocatalysts using photoreduction

Ag/tetrapod-like ZnO whisker (T-ZnOw) photocatalysts with different Ag loadings were synthesized by photoreduction of Ag⁺ on the surface of T-ZnOw. The chemical composition, morphology and photocatalytic properties of Ag/T-ZnOw photocatalysts were characterized and studied in detail. It is found that metal Ag can exist either as nanoparticles or as agglomerates through varying the Ag/ZnO molar ratio (MR). In photodegradation of methyl orange, enhanced degradation rates are achieved by all Ag/T-ZnOw photocatalysts due to increased separation efficiency of photogenerated electron and hole pairs. Specifically, the photocatalytic activities of Ag/T-ZnOw photocatalysts increase with increasing Ag/ZnO MR from 2.4 to 12%. However, further increasing the Ag/ZnO MR to 14.4% induces the formation of more agglomerates, which can act as recombination centers of photogenerated electron and hole pairs, leading to decreased photocatalytic activity of the photocatalyst.     

Ag纳米粒子磁控溅射制备及其热稳定性研究

利用磁控溅射在玻璃衬底上制备Ag纳米粒子及其氧化物（AgOx）薄膜，通过高温退火实验，研究银及AgOx薄膜的热稳定特性。采用x射线衍射分析薄膜的晶相结构，采用UV-Vis分光光度计测定薄膜的吸收光谱。结果表明：Ag纳米薄膜在450nm附近出现特征吸收峰，200℃退火后，峰位蓝移，400℃退火后，吸收峰显著减弱，表明Ag纳米粒子在退火过程中发生了蒸发；AgOx薄膜在200℃下退火后，出现Ag纳米粒子特征吸收峰，表明AgOx的热分解，400℃退火同样导致Ag纳米粒子的蒸发。     

Ag nanoparticles enhanced near-IR emission from Er3+ ions doped glasses

Vitreous materials containing rare-earth (RE) ions and metallic nanoparticles (NPs) attract considerable interest because the presence of the NPs may lead to an intensification of luminescence. In this work, the characteristics of 1.54 μm luminescence for the Er³⁺ ions doped bismuthate glasses containing Ag NPs were studied under 980 nm excitation. The surface plasmon resonance (SPR) band of Ag NPs appears from 500 to 1500 nm. Transmission electron microscopic (TEM) image reveals that the Ag NPs are dispersed homogeneously with the size from 2 to 7 nm. The strength parameters Ω_t(t = 2, 4, 6), spontaneous emission probability (A), radiative lifetime (τ) and stimulated emission section (σ_em) of Er³⁺ ions were calculated by the Judd–Ofelt theory. When the glass contains 0.2 wt% AgCl, the 1.54 μm fluorescence intensity of Er³⁺ reaches a maximum value, which is 7.2 times higher than that of glass without Ag NPs. The Ag NPs embedded glasses show significantly fluorescence enhancement of Er³⁺ ions by local field enhancement from SPR.     

Synthesis of silver nano particles and fabrication of aqueous Ag inks for inkjet printing

The main problem in preparing stable and printable inks containing nanoparticles for inkjet printing is to overcome the strong agglomeration of the particles in dispersion medium. In this study, the silver particles with diameter around 50 nm were produced by a simple wet chemistry method. Stable aqueous printable inks were formulated by using the combination of a triblock copolymer and high intensity focused ultrasound (HIFU). Various factors that affect the ink stability, such as, copolymer content and time of HIFU treatment, were investigated. The ink containing 5 wt% silver has a viscosity of about 2 mPa s and surface tension 30 mN m⁻¹ at 25 °C, which meet inkjet printer requirements. Such inks have been successfully printed on Al₂O₃ ceramics and low-temperature co-fired ceramics (LTCC) and the printed films show low resistivity.     

装甲铝合金显微硬度及微动磨损对其影响的研究

利用MH-6型显微硬度仪和MGW-01高频往复式微动磨损试验机进行7A52装甲铝合金的显微硬度测试和微动磨损试验,分析不同取向表面显微硬度及微动磨损试验对显微硬度的影响。结果表明不同取向表面显微硬度基本相同,试验范围内微动磨损表面显微硬度比基体表面显微硬度增加。     

Preparation of surface-silvered graphene-CNTs/polyimide hybrid films: Processing,morphology and properties

Silver nanoparticles modified graphene-carbon nanotubes/polyimide (Gr-CNTs/PI) films have been prepared by electrochemical reduction of silver nitrate on potassium hydroxide hydroxylated of Gr-CNTs/PI films surface. The as-prepared nanocomposites were characterized by transmission electron microscopy, scanning electron microscopy, X-ray diffraction analyzer and semiconductor characterization system. The lower content of Gr-CNTs (≤10 wt. %) doping in PI matrix can improve the conductivity of PI films more clearly than pure CNTs. The conductivity can be regulated by controlling Gr-CNTs content in PI matrix. These silver nanoparticles into Gr-CNTs/PI films presented here can act as deposition seeds which can initiate subsequent electroless silver or copper or electrodeposition other metal.     

离子交换法在磷酸盐玻璃中合成CdS/Ag复合微粒的研究

采用离子交换法在磷酸盐玻璃中制备了CdS/Ag复合微粒,研究了不同工艺条件下样品的吸收光谱和光致发光光谱.吸收光谱研究发现离子交换后在380～420nm附近有一个大的吸收,光照后吸收带变窄,可以认为是银粒子的表面等离子体共振而导致的吸收所致.在波长为325nm的光激发下,玻璃中不同化学状态的银分别在420、530nm附近发光.研究了银离子在玻璃表面的扩散、还原过程,结果表明控制离子交换时间可以控制交换层的厚度,而控制盐浴浓度则可以有效控制银离子在玻璃表面层的浓度分布及总扩散量.     

Formation of aligned silver nanoparticles by ion implantation

Synthesis of metal nanoparticles by ion implantation has a number of advantages. Nevertheless, certain remaining difficulties must be overcome in order to optimize the characteristics of ion-implanted nanocomposites. The principle among these are the lack of control over the size distribution and position of the precipitates within the implanted layer. Two-dimensionally ordered arrangements of Ag nanoparticles are formed in Ag-implanted silica glass by post-implanted Cu ions. The spherical Ag nanoparticles are formed to align at the same deep depth in the silica. Cross-sectional transmission electron microscopy revealed that the Ag nanoparticles are a size of 35-48 nm in diameter. The evolution of nanoparticles is characterized by transmission electron microscopy.     

Direct control of the spatial arrangement of gold nanoparticles in organic-inorganic hybrid superstructures

The directed assembly of gold nanoparticles is essential for their use in many kinds of applications, such as electronic devices, biological labels, and sensors. Herein an atomic alteration in the molecular structure of ligand-stabilized gold nanoparticles that can shift the interparticle distance up to 1 nm upon covalent coupling to organic-inorganic superstructures is presented. Gold nanoparticles are stabilized by two octadentate thioether ligands and have a mean diameter of 1.1 nm. The ligands contain a central rigid rod varying in length and terminally functionalized with a protected acetylene. The two peripheral functional groups on each particle enable the directed assembly of nanoparticles to dimers, trimers, and tetramers by oxidative acetylene coupling. This is a wet chemical protocol resulting in covalently bound nanoparticles. These organic-inorganic hybrid superstructures are analyzed by transmission electron microscopy, small angle X-ray scattering, and UV/vis spectroscopy. The focus of the comparison here is the subunit, which is anchoring the bridgehead, either a pyridine or benzene moiety. The pyridine-based ligands reflect the calculated length of the rigid-rod spacer in their interparticle distances in the obtained hybrid structures. This suggests a perpendicular arrangement that results from the coordination of the pyridine's lone pair to the gold surface. An atomic variation in the ligand's center leads to smaller interparticle distances in the case of hybrid structures obtained from benzene ligands. This large difference in the spatial arrangement suggests a tangential arrangement of the interparticle bridging structure in the latter case. Consequently a rather flat arrangement parallel to the particle surface must be assumed for the central benzene unit of the benzene-based ligand.     

Improved thermal stability of poly(vinyl chloride) by nanoscale layered double hydroxide particles grafted with toluene-2,4-di-isocyanate

A novel interlamellar surface modification of layered double hydroxides (LDHs) via covalent bonding by toluene-2,4-di-isocyanate (TDI) has been successfully obtained, and poly(vinyl chloride) (PVC)/TDI-modified LDH nanocomposites have been prepared via solution intercalation process. After the interlamellar modification, TDI was grafted to the surface hydroxyl groups of LDHs with nitrate, dodecyl sulfate or stearate anion as counterion anion. The structures of the TDI-modified LDHs and the nanocomposites were characterized by powder X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectra, and transmission electron microscopy (TEM) techniques. The enhanced thermal stability of PVC/TDI-modified LDH nanocomposites was confirmed by means of conventional Congo Red test and dynamic thermogravimetric analysis (TGA). In addition, the thermal degradation mechanism was briefly discussed on the basis of the above experimental results.     

A facile synthetic route to aqueous dispersions of silver nanoparticles

Stable aqueous dispersions of silver nanoparticles have been synthesized from an organometallic precursor dissolved in an organic phase. Hydrogen gas is used to reduce the precursor to form silver nanoparticles which spontaneously transfer into an immiscible aqueous phase where they are stabilized. This route provides a simple pathway for the preparation of aqueous nanoparticle solutions and avoids production of the inorganic ions that are usually associated with aqueous methods. The effectiveness of a variety of aqueous stabilizing agents is evaluated. All products show plasmon absorption bands characteristic of silver nanoparticles and transmission electron microscopy reveals most particles to be below 40 nm in diameter.     

Combination of MoS2 nanopetals with Ag nanoparticles decorated graphene oxide for boosting photocatalytic abatement of recalcitrant pollutants under visible light irradiation

Herein, various weight ratios (1:1, 1:3, and 3:1) of MoS₂/GO composites decorated with Ag nanoparticles (named as MAG) have been prepared by microwave-assisted route. XRD and XPS investigations indicated the catalyst crystallinity and elemental oxidation states. Morphological analysis revealed presence of small MoS₂ nanopetals scattered on GO sheets with Ag NPs dispersed on surface whereas BET-analysis disclosed its excellent surface area (～88 m²/g). Optical properties of MAG catalysts revealed that they were highly visible-light active, with a bandgap of 2.15 eV and a lower charge recombination rate. Excellent efficiency was observed for TC (90.7%; 0.0186 min^?1) and FIP-degradation (85.2%; 0.0177 min^?1) with 4 mg MAG (3:1) catalyst at neutral pH under visible-light irradiation owing to high synergistic interaction (～2.21) in the composite. Effects of catalyst amount, pH, and effective area of illumination on degradation were investigated. High reusable nature of the catalyst (65% (TC) and 58% (FIP) efficiency after 5 cycles) was supported by post-photocatalytic characterization studies. Photodegradation products of TC were determined via LC-MS studies. Holes and hydroxyl radicals were majorly involved in degradation process revealed by trapping studies. High COD (70.4%) and TOC (55.1%) removal rates confirm high photo-mineralization of real-wastewater without any pre-treatment. The current investigation, combined with comparative literature, illustrates real-world potential of MAG catalysts for eradication of resistant pollutants.     

Thermoelectric characteristics of nanocomposites made of HgSe and Ag nanoparticles for flexible thermoelectric devices

We synthesized thermoelectric nanocomposites by mixing HgSe nanoparticles (NPs) and Ag NPs in a solution and investigated the thermoelectric properties of the nanocomposite thin films on flexible plastic substrates.The X-ray diffraction patterns and the X-ray photoelectron spectra of the nanocomposites demonstrate that cation-exchange reactions occurred spontaneously in the mixed solution of HgSe and Ag NPs and that the HgSe NPs were completely converted to Ag2Se when the Ag NP content was 20 vol.％.The maximum power factor and the thermoelectric figure of merit were obtained as 75 FμW/mK2 and 0.043 at 300 K,respectively,when the Ag NP content was 10 vol.％,which is 100 times higher than that of HgSe NP thin films.In addition,the mechanical stability of the thermoelectric nanocomposite film was confirmed through repeated bending tests.