Silver/dendrimer nanocomposites as biomarkers: fabrication, characterization, in vitro toxicity, and intracellular detection

We have synthesized water-soluble, biocompatible, fluorescent, and stable silver/dendrimer nanocomposites that exhibit a potential for in vitro cell labeling. Amino-, hydroxyl-, and carboxyl-terminated ethylenediamine core generation 5 poly(amidoamine) dendrimers were utilized to prepare aqueous silver(I)-dendrimer complexes (with the molar ratio of 25 Ag+ per dendrimer) at the biologic pH of 7.4. Conversion of silver(I)-dendrimer complexes into dendrimer nanocomposites was achieved by irradiating the solutions with UV light to reduce the bound Ag+ cations to zerovalent Ag0 atoms, which were simultaneously trapped in the dendrimer network, resulting in the formation of {(Ag0)25-PAMAM_E5.NH2}, {(Ag0)25-PAMAM_E5.NGly}, and {(Ag0)25-PAMAM_E5.NSAH} dendrimer nanocomposites (DNC), respectively. The silver-DNCs were characterized by means of UV-vis, fluorescence spectroscopy, dynamic light-scattering, zeta potential measurements, high-resolution transmission electron microscopy, X-ray energy dispersive spectroscopy, and selected area electron diffraction. The cytotoxicity of dendrimers and related silver nanocomposites was evaluated using an XTT colorimetric assay of cellular viability. The cellular uptake of nanoparticles was examined by transmission electron and confocal microscopy. Results indicate that {(Ag0)25-PAMAM_E5.NH2}, {(Ag0-)25-PAMAM_E5.NGly}, and {(Ag0)25-PAMAM_E5.NSAH} form primarily single particles with diameters between 3 and 7 nm. The dendrimer nanocomposites are fluorescent, and their surface charge, cellular internalization, toxicity, and cell labeling capabilities are determined by the surface functionalities of dendrimer templates. The {(Ag0)25-PAMAM_E5.NH2} and {(Ag0)25-PAMAM_E5.NSAH} nanocomposites exhibit potential application as cell biomarkers.     

Dendrimer templated synthesis of one nanometer Rh and Pt particles supported on mesoporous silica: catalytic activity for ethylene and pyrrole hydrogenation

Monodisperse rhodium (Rh) and platinum (Pt) nanoparticles as small as approximately 1 nm were synthesized within a fourth generation polyaminoamide (PAMAM) dendrimer, a hyperbranched polymer, in aqueous solution and immobilized by depositing onto a high-surface-area SBA-15 mesoporous support. X-ray photoelectron spectroscopy indicated that the as-synthesized Rh and Pt nanoparticles were mostly oxidized. Catalytic activity of the SBA-15 supported Rh and Pt nanoparticles was studied with ethylene hydrogenation at 273 and 293 K in 10 torr of ethylene and 100 torr of H 2 after reduction (76 torr of H 2 mixed with 690 torr of He) at different temperatures. Catalysts were active without removing the dendrimer capping but reached their highest activity after hydrogen reduction at a moderate temperature (423 K). When treated at a higher temperature (473, 573, and 673 K) in hydrogen, catalytic activity decreased. By using the same treatment that led to maximum ethylene hydrogenation activity, catalytic activity was also evaluated for pyrrole hydrogenation.     

Catalytic properties of silica/silver nanocomposites

The catalytic properties of silver nanoparticles supported on silica and the relation between catalytic activity of silver particles and the support (silica) size are investigated in the present article. The silver nanoparticles with 4 nm diameters were synthesized and were attached to silica spheres with sizes of 40, 78, 105 nm, respectively. The reduction of Rhodamine 6G (R6G) by NaBH4 was designed by using the SiO2/Ag core-shell nanocomposites as catalysts. The experimental results demonstrated that the catalytic activity of silica/silver nanoparticles depends on not only the concentration of catalysts (silver) but also the support silica size. Silver particles supported on small SiO2 spheres (approximately 40 nm) show high catalytic activity. Moreover, by making a comparison between the UV-vis spectra of the catalyst before and after the catalytic reaction, we found that the position of surface plasma resonance (SPR) peak of Ag nanoparticles changes little. The above results suggested that the size and morphology of silver particles were probably kept unchanged after the reduction of R6G and also implied that the catalytic activity of silver particles was hardly lost during the catalytic reaction.     

纳米态电极催化材料Au-Pt/半胱氨酸/Au电极的制备及性能研究

利用自组装技术制备了纳米态Au-Pt/半胱氨酸/Au电极,TEM、ED、XPS等研究表明双金属纳米粒子为Au合金,粒子的平均粒径＜10nm;通过组装时间可以控制双金属纳米颗粒组装的数量.对组装电极的电化学性能进行了测试,通过SEM对其表面结构进行了表征.结果表明,利用自组装方法可以制备纳米态Au-Pt/半胱氨酸/Au电极,该电极具有良好的电催化性能.     

Au-Pt纳米颗粒/石墨烯-纤维素微纤维复合电极的制备与电化学性能

石墨烯和金属纳米是优异的导电纳米材料,为构建具有高效活性表面积的电化学传感界面,以玻碳电极作为导电基底,采用滴涂法结合一步电沉积成功制备了Au-Pt纳米颗粒/还原氧化石墨烯-纤维素微纤维(Au-Pt NPs/RGO-CMF)复合材料。SEM、原子力显微镜(AFM)、EDS和拉曼光谱分析表明,Au-Pt纳米颗粒均匀分布在RGO-CMF的薄层上,同时实现了氧化石墨烯(GO)还原为RGO。以铁氰化钾作为氧化还原探针对界面的电化学性质进行研究,在优化的实验条件下(循环伏安法电沉积:电位为?1.2~0 V,周期为20,电解质pH值为6,滴涂GO-CMF体积为8 μL),得到Au-Pt NPs/RGO-CMF复合材料的高效活性表面积(3.54 cm2)远远优于裸玻碳电极(1.52 cm2)。表明构建界面具有高的电催化活性,为传感器的进一步应用提供理论支持。      

Characterization of silver nanoparticles synthesized on titanium dioxide fine particles

Silver nanoparticles with a narrow size distribution were synthesized over the surface of two different commercial TiO(2) particles using a simple aqueous reduction method. The reducing agent used was NaBH(4); different molar ratios TiO(2):Ag were also used. The nanocomposites thus prepared were characterized using transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), x-ray photoelectron spectroscopy (XPS), x-ray diffraction (XRD), dynamic light scattering (DLS) and UV-visible (UV-vis) absorption spectroscopy; the antibacterial activity was assessed using the standard microdilution method, determining the minimum inhibitory concentration (MIC) according to the National Committee for Clinical Laboratory Standards. From the microscopy studies (TEM and STEM) we observed that the silver nanoparticles are homogeneously distributed over the surface of TiO(2) particles and that the TiO(2):Ag molar ratio plays an important role. We used three different TiO(2)Ag molar ratios and the size of the silver nanoparticles is 10, 20 and 80?nm, respectively. It was found that the antibacterial activity of the nanocomposites increases considerably comparing with separated silver nanoparticles and TiO(2) particles.     

Novel rigid poly(vinyl chloride) ternary nanocomposites containing ultrafine full-vulcanized powdered rubber and untreated nano-sized calcium carbonate

Novel rigid poly(vinyl chloride)/ultrafine full-vulcanized powdered rubber (UFPR)/untreated nano-sized calcium carbonate (UNCC) ternary nanocomposites were fabricated. TEM observation revealed that good dispersion of UNCC particles (about 40 nm) in the PVC matrix was achieved with the help of UFPR (about 150 nm). Interestingly, the PVC ternary nanocomposites excel corresponding PVC binary ones, as well as neat rigid PVC, in both heat resistance and toughness due to the synergistic effect of UNCC and NBR-UFPR.     

Radiation induced synthesis of Au-Pd nanoparticles of random alloy structure supported on carbon particles using the high energy electron beam

Au-Pd bimetallic nanoparticles supported on carbon particles were synthesized by reduction of precursor ions in an aqueous solution irradiated with a high energy electron beam. The composition of the samples was analyzed by the inductively coupled plasma atomic emission spectrometry (ICP-AES), and the morphology of the samples was observed by the transmission electron microscope (TEM). TEM micrographs indicated that Au-Pd particles of ca. 5-nm were well dispersed on the surface of carbon particles of ca. 30-nm without any serious agglomeration. Addition of citric acid to the initial solution and high pH were found to be effective for formation of random alloy structure in the resultant bimetallic nanoparticles. The change in the bimetallic structure from core-shell to random alloy was identified by techniques of the X-ray diffraction (XRD) and the extended X-ray absorption fine structure (EXAFS).     

Structural analysis of graphene oxide/silver nanocomposites: optical properties,electrochemical sensing and photocatalytic activity

In the present study, graphene oxide/silver (GO/Ag) nanocomposites were synthesized via a facile simple one pot chemical reduction method using ethylene glycol/sodium borohydrate (EG/NaBH₄) as solvent and reducing agent. GO was selected as a substrate and stabilizer to prepare GO/Ag nanocomposites. The synthesized GO/Ag nanocomposites were characterized by a series of techniques. Highly monodispersed stable crystalline silver nanoparticles having a face-centered cubic (fcc) phase were confirmed by X-ray powder diffraction (XRD) on GO signature. Scanning electron microscopy images showed that Ag nanoparticles are deposited on the GO sheet with a narrow size distribution. Transmission electron microscopy observations revealed that large numbers of Ag nanoparticles were uniformly distributed on GO sheet and well separated with an average size of 18 nm. Ultraviolet–visible (UV–Vis) spectroscopic results showed the peak of GO and surface plasmon resonance (SPR) of Ag nanoparticles. The SPR property of GO/Ag nanocomposites showed that there was an interaction between Ag nanoparticles and GO sheet. The intensities of the Raman signal of GO/Ag nanocomposites are gradually increased with attachment of Ag nanoparticles i.e. there is surface-enhanced Raman scattering activity. Electrochemical investigations indicated that the nanocomposites possessed an excellent performance for detecting towards 4-nitrophenol. An application of the obtained GO/Ag nanocomposites as a catalyst in the reduction of 4-nitrophenol to 4-aminophenol by NaBH₄ was demonstrated. The GO/Ag nanocomposites exhibited high activity and stability for the catalytic reduction of 4-nitrophenol. The prepared GO/Ag nanocomposites act as photo-catalysts.     

以酯端基PAMAM树形分子为模板在N，M-二甲基甲酰胺溶剂中制备金纳米粒子

用UV-vis、FT-IR光谱研究了HAuCl4和酯端基聚酰胺胺(PAMAM)树形分子在N，N-二甲基甲酰胺(DMF)溶剂中的相互作用，提出HAuCl4与树形分子之间的络合机理：[AuCl4]^-离子与质子化叔胺基团形成离子对，Au^3 离子与PAMAM树形分子上的酯基和酰胺基团形成配位作用。在DMF溶剂中酯端基PAMAM树形分子与HAuCl4配位后用柠檬酸钠还原形成金纳米粒子，UV-vis光谱和TEM图像分析表明了随树形分子代数的增加，金纳米粒子的直径减小，并提出了树形分子-金纳米复合物的结构模型：(1)较低代数的树形分子环绕在金粒子的外围；(2)在较高代数的树形分子空腔内部封装金纳米粒子。     

Reduced graphene oxide/CoSe2 nanocomposites: hydrothermal synthesis and their enhanced electrocatalytic activity

Reduced graphene oxide (RGO)/CoSe₂ nanocomposites were synthesized by self-assembly of CoSe₂/DETA (DETA: diethylenetriamine) onto the surface of graphene oxide (GO), followed by subsequent chemical reduction of GO during a hydrothermal process. The as-synthesized products were characterized by powder X-ray diffraction, energy dispersive X-ray spectroscopy, Raman spectra, scanning electron microscopy, and transmission electron microscopy. The morphology of the CoSe₂ on the RGO nanosheets can be well controlled by adjusting the reaction time during the hydrothermal process. The catalytic activities of the RGO/CoSe₂ nanocomposites were investigated for oxygen evolution reaction (OER) in alkaline conditions. It was found that the as-formed RGO/CoSe₂ nanocomposites show higher catalytic activity compared with the unsupported CoSe₂. In addition, the loading amounts and morphologies of CoSe₂ on RGO sheets have a great influence on the catalytic performance of RGO/CoSe₂. Our studies raise promising possibilities for designing effective OER electrocatalysts for energy conversion.     

Design and synthesis of polymetallic nanoparticles and their catalytic applications

High-temperature hydrogen reduction reactions enable the synthesis and processing of binary metal oxide composite nanoparticles starting from titanium, ruthenium, and silicon, while the use of a surface modifier and an organic surfactant enables the synthesis of catalytic thin films from binary semiconductor oxides. Surface characterization by XRD, SEM, TEM, AFM, Raman spectroscopy, and BET measurements indicate that the incorporation of binary oxide particles into the semiconductor materials altered the surface properties and morphology of the nanoparticles while the surface modifier and organic surfactant loading can be experimentally adjusted to obtain thin films of varying morphological characteristics.     

Preparation and characterization of PtRu nanoparticles supported on nitrogen-doped porous carbon for electrooxidation of methanol

N-doped porous carbon nanospheres (PCNs) were prepared by chemical activation of nonporous carbon nanospheres (CNs), which were obtained via carbonization of polypyrrole nanospheres (PNs). The catalysts, PtRu and Pt nanoparticles supported on PCNs and Vulcan XC-72 carbon black, were prepared by ethylene glycol chemical reduction. Transmission electron microscopy, X-ray diffraction, and energy-dispersive X-ray spectroscopy were employed to characterize samples. It was found that PCNs containing N function groups possess a large number of micropores. Uniform and well-dispersed Pt and PtRu particles with narrow particle size distribution were observed. The electrooxidation of liquid methanol on these catalysts was investigated at room temperature by cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy (EIS). The results showed that alloy catalyst (Pt(1)Ru(1)/PCN) possessed the highest catalytic activity and better CO tolerance than the other PtRu and Pt-only catalysts; PtRu nanoparticles supported on PCN showed a higher catalytic activity and more stable sustained current than on carbon black XC-72. Compared to commercial Alfa Aesar PtRu catalyst, Pt(1)Ru(1)/PCN reveals an enhanced and durable catalytic activity in methanol oxidation because of the high dispersion of small PtRu nanoparticles and the presence of N species of support PCNs.     

Maghemite/ZnO nanocomposites: A highly efficient,reusable and non-noble metal catalyst for reduction of 4-nitrophenol

Maghemite/ZnO nanocomposites synthesized by a two step process were used for catalytic reduction of p-nitrophenol. Maghemite nanoparticles were synthesized by hydrothermal technique followed by deposition of ZnO on it via co-precipitation process. X-ray diffraction analysis suggested formation of Maghemite and ZnO with tetragonal and hexagonal close packed structure respectively whereas electron microscopy images indicated the formation of near spherical nanocomposites with a size range of 30–50 nm. Maghemite/ZnO calcined at 300 °C is investigated as heterogeneous catalyst for reduction of p-nitrophenol and its catalytic activity is compared with that of Maghemite and ZnO nanoparticles. The parameters responsible for reduction of p-nitrophenol over Maghemite/ZnO were scrutinized using Response Surface Methodologyand the predicted values of reduction efficiency were found to be in a good agreement with the experimental findings (R² > 0.9). The highest achievable percentage of reduction of target molecular species was noted to be of 98.6%. Optimization study showed that maximum reduction efficiency was observed at optimum conditions: p-NP concentration = 0.2 mM, Maghemite/ZnO loading = 200 ppm, reaction time = 6 min. Maghemite/ZnO has shown noticeably higher catalytic activity than pure oxides which remained almost unaltered for five consecutive cycling suggesting possible commercial potential of the developed material.     

Nickel oxide/polypyrrole/silver nanocomposites with core/shell/shell structure: Synthesis,characterization and their electrochemical behaviour with antimicrobial activities

Magnetic and conducting Nickel oxide–polypyrrole (NiO/PPy) nanoparticles with core–shell structure were prepared in the presence of Nickel oxide (NiO) in aqueous solution containing sodium dodecyl benzenesulfonate (SDBS) as a surfactant as well as dopant. A stable dispersion of silver (Ag) nanoparticles was synthesized by chemical (citrate reduction) method. NiO/PPy nanocomposites were added to the Ag colloid under stirring. Ag nanoparticles could be electrostatically attracted on the surface of NiO/PPy nanocomposites, leading to formation of NiO/PPy/Ag nanocomposites with core/shell/shell structure. The morphology, structure, particle size and composition of the products were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, cyclic voltammetry (CV) and current–voltage (I–V) analysis. The resultant nanocomposites have the good conductivity and excellent electrochemical and catalytic properties of PPy and Ag nanoparticles. Furthermore, the nanocomposites showed excellent antibacterial behaviour due to the presence of Ag nanoparticles in the composite. The thermal stability of NiO–PPy as well as NiO/PPy/Ag nanocomposites was higher than that of pristine PPy. Studies of IR spectra suggest that the increased thermal stability may be due to interactions between NiO and Ag nanoparticles with the PPy backbone.     

乙二醇法制备负载型钴基-堇青石催化剂及其催化燃烧甲苯的活性

用乙二醇法和浸渍法制备两种负载在堇青石上的钴基负载催化剂,并用XRD、XPS、TPR和TPD对制备的催化剂进行表征,比较两种催化剂催化氧化(燃烧)甲苯的活性。研究结果表明,与浸渍法制备的Co/cord催化剂相比,乙二醇法制备的催化剂Co/cord-EG对甲苯催化燃烧活性明显提高。应用乙二醇法制备Co/cord-EG负载型催化剂,Co元素主要以Co2+存在于载体表面;而传统浸渍法制备的Co/cord催化剂,Co元素是以Co2+与Co3+的两种化学状态存在于载体表面。应用乙二醇法制备Co/cord-EG负载型催化剂,有助于在载体表面形成比较均匀的吸附活性位。应用乙二醇法制备的Co/cord-EG催化剂,催化活性组分能在载体表面上以更小颗粒而且更高的分散度存在,从而能明显提高其催化活性。     

Copper oxide coated polyester fabrics with enhanced catalytic properties towards the reduction of 4-nitrophenol

A novel functional polyester fabric (PF) was successfully prepared by a facile method. PF were coated by copper oxide (CuO) followed by chemical grafting of 3-chloropropyltriethoxysilane (ClPTES) and diethanolamine (DEA). The morphology and structure of the resulting material PF@CuO–Si–N(OH)₂ was characterized by X-ray diffraction, scanning electron and optical microscopy, thermogravimetry and Fourier-transformed infrared spectroscopy. The results revealed that the CuO particles were densely surrounded PF, and the covalent surface-grafting of ClPTES and DEA within PF was confirmed. It was also demonstrated that CuO/ClPTES/DEA addition generated new functional sites at the PF surface, improving the catalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). The prepared PF@CuO–Si–N(OH)₂ exhibited high catalytic activity with appreciable cycling stability for the reduction of 4-NP to 4-AP, even after six successive cycles with nearly 90% conversion. Hence, it may be conclude that the catalytic activity and stability of this catalyst allows envisaging great prospect for large scale reduction of 4-NP.     

Fabrication of nanocomposites based on carbon nanotubes containing Pt nanoparticles and TiO<Subscript>2</Subscript>

Using conical multiwalled carbon nanotubes (CNTs), we have prepared Pt/CNT and Pt/TiO₂/CNT nanocomposites with an average platinum particle size of 3–5 nm, Pt/Ti molar ratio on the surface in the range 3.5–4, and C/Pt = 21–22. Titania was deposited onto the CNTs through titanium tetrachloride (TiCl₄) hydrolysis. Platinum particles were produced by reducing chloroplatinic acid (H₂PtCl₆) with sodium borohydride (NaBH₄) in the presence of CNTs. The composition and structure of the composites have been studied using X-ray photoelectron spectroscopy, electron microscopy, X-ray diffraction, and thermogravimetry. The materials have been tested as catalysts for hydrogen oxidation and oxygen reduction. The results demonstrate that the modification of Pt/CNT with titania enhances the catalytic activity of the material.     

Cobalt and nickel supported on HY zeolite: Synthesis,characterization and catalytic properties

Bifunctional catalysts consisting of cobalt and nickel supported on HY zeolite were synthesized by solvent excess impregnation and characterized by X-ray diffraction, Fourier-transformed infrared spectroscopy, scanning electron microscopy, atomic absorption spectroscopy, thermogravimetric analysis and nitrogen adsorption. The profiles of metal reduction on zeolite were obtained by temperature-programmed reduction. The catalytic properties of the bifunctional catalysts were verified by n-hexane hydroconversion. X-ray diffraction and microstructural analyses showed the presence of crystalline phases in HY zeolite and in samples after impregnation. A decrease in the micropore surface area was observed by nitrogen adsorption experiments and attributed to a reduction in the accessibility to micropores. The catalysts showed catalytic activity in the hydroconversion of n-hexane with selectivity to branched hydrocarbons. Such catalytic activity was related to the acid and metallic properties of the bifunctional catalysts used.     

Synthesis and characterization of nano-gold composite using Cylindrocladium floridanum and its heterogeneous catalysis in the degradation of 4-nitrophenol

Greener synthesis of nanogold-biocomposite by fungus, Cylindrocladium floridanum was reported in this study. Results revealed that when cultured in static condition for a period of 7d, the fungus accumulated gold nanoparticles on the surface of the mycelia. Bionanocomposites with Au nanocrystals were characterized by UV-Vis spectroscopy, XRD, SEM, EDX and high-resolution TEM. The SPR band of UV-Vis spectrum at 540 nm confirmed the presence of gold nanoparticles on the surface of the fungal mycelia. The fcc (111)-oriented crystalline nature of particles was identified by XRD pattern. The synthesized particles are spherical in shape as evidenced by TEM image. The biocomposites with Au nanoparticles function as an efficient heterogeneous catalyst in the degradation of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP), in the presence of reducing agent, sodium borohydride which was reflected by UV-Vis spectra of the catalytic reaction kinetics. The reduction of 4-nitrophenol follows pseudo-first-order kinetic model with the reaction rate constant of 2.67 × 10(-2)min(-1) with 5.07 × 10(-6)mol/dm(3) of gold at ca. 25 nm. The rate of the reaction was increased by increasing the concentration of gold nanoparticles from 2.54 × 10(-6) to 12.67 × 10(-6)mol/dm(3) (～ 25 nm) and with reduced size from 53.2 to 18.9 nm respectively. This is the first report on fungal-matrixed gold(0) nanocomposites heterogeneously catalyzing the reduction of the toxic organic pollutant, 4-nitrophenol that enable the recovery and recycling of AuNPs catalysts.