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1.
A new mesoporous organic–inorganic nanocomposite was formulated and then used as stabilizer and support for the preparation of palladium nanoparticles (Pd NPs). The properties and structure of Pd NPs immobilized on prepared 1,4‐diazabicyclo[2.2.2]octane (DABCO) chemically tagged on mesoporous γ‐Fe2O3@hydroxyapatite (ionic modified (IM)‐MHA) were investigated using various techniques. The synergistic effects of the combined properties of MHA, DABCO and Pd NPs, and catalytic activity of γ‐Fe2O3@hydroxyapatite‐DABCO‐Pd (IM‐MHA‐Pd) were investigated for the Heck cross‐coupling reaction in aqueous media. The appropriate surface area and pore size of mesoporous IM‐MHA nanocomposite can provide a favourable hard template for immobilization of Pd NPs. The loading level of Pd in the nanocatalyst was 0.51 mmol g?1. DABCO bonded to the MHA surface acts as a Pd NP stabilizer and can also lead to colloidal stability of the nanocomposite in aqueous solution. The results reveal that IM‐MHA‐Pd is highly efficient for coupling reactions of a wide range of aryl halides with olefins under green conditions. The superparamagnetic nature of the nanocomposite means that the catalyst to be easily separated from solution through magnetic decantation, and the catalytic activity of the recycled IM‐MHA‐Pd showed almost no appreciable loss even after six consecutive runs.  相似文献   

2.
Cast‐hybrid films composed of polyvinyl alcohol (PVA) and silver nitrate were treated according to three different ways, thermal annealing, UV‐irradiation, and chemical reduction by a borohydride solution, to obtain PVA/silver nanocomposite films. The nanostructuration process was studied as a function of the treatment conditions, and discussed as a function of the mobility state of the polymer chains in the nanocomposite matrix during treatment. A homogeneous dispersion of crystalline silver nanoparticles was obtained by thermal annealing above Tg and below Tm and UV‐lamp irradiation below Tg. For these two treatments, the major processing parameters were the annealing temperature and time and the UV‐exposure time, respectively. For low‐conversion rate in Ag(0), the films evolved upon ageing at room temperature. Totally different morphology and Ag(0) conversion were achieved by chemical reduction in a borohydride solution. All the silver ions were reduced into Ag(0), and crystalline silver nanoparticles layers parallel to the film surface were observed after the treatment. This morphology was related to the high‐swollen state of the polymer matrix during treatment. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2062–2071, 2008  相似文献   

3.
Green tea extract having many phenolic hydroxyl and carbonyl functional groups in its molecular framework can be used in the modification of Fe3O4 nanoparticles. Moreover, the feasibility of complexation of polyphenols with silver ions in aqueous solution can improve the surface properties and capacity of the Fe3O4@green tea extract nanoparticles (Fe3O4@GTE NPs) for sorption and reduction of silver ions. Therefore, the novel Fe3O4@GTE NPs nano‐sorbent has potential ability as both reducing and stabilizing agent for immobilization of silver nanoparticles to make a novel magnetic silver nanocatalyst (Fe3O4@GTE/Ag NPs). Inductively coupled plasma analysis, transmission and scanning electron microscopies, energy‐dispersive X‐ray and Fourier transform infrared spectroscopies, and vibrating sample magnetometry were used to characterize the catalyst. Fe3O4@GTE/Ag NPs shows high catalytic activity as a recyclable nanocatalyst for the reduction of 4‐nitrophenol at room temperature.  相似文献   

4.
Silver nanoparticles were formed in situ along with poly(2,5‐dimethoxyaniline) (PDMA) in an interconnected network matrix (reactor), comprising the electronic conductive polymer, PDMA, and a polyelectrolyte, poly(styrene sulfonic acid) (PSS), through the simultaneous reduction of Ag+ ions and polymerization of 2,5‐dimethoxyaniline. In situ ultraviolet‐visible spectroscopy showed that peaks corresponding to the plasmon resonance of silver nanoparticles at 411 nm and the polaronic transition of PDMA at 438 nm provided evidences for the simultaneous formation of silver nanoparticles and PDMA. Transmission electron microscopy and size distribution analysis revealed the presence of spherical silver nanoparticles with an average diameter of 12 nm in the composite. X‐ray photoelectron spectroscopy showed that the amine units in PDMA changed to imine units upon the formation of silver nanoparticles. A comprehensive mechanism for the formation of the PDMA‐PSS‐Ag nanocomposite is proposed. A 10‐fold increase in the conductivity was noticed for the PDMA–PSS–Ag nanocomposite (1 S/cm) in comparison with the PDMA–PSS composite (0.1 S/cm). © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3843–3852, 2006  相似文献   

5.
《先进技术聚合物》2018,29(3):1107-1116
Carbopol‐silver nanocomposites, CP‐Ag‐NCs, were prepared by a chemical reducing method by using formaldehyde as a reducing agent (nanocomposite F), and formaldehyde in the presence of an alkaline medium resulting from the addition of Na2CO3 (nanocomposite FC), or NaOH (nanocomposite FO) to enhance the rate of reduction of the silver ions. The UV‐visible spectra showed the appearance of bands centered around 275, 286, and 274 nm for the nanocomposites F, FC, and FO, respectively, attributed to small silver nanoparticles (Ag‐NPs) with an average size less than 10 nm. Other bands centered around 405 and 470 nm for the nanocomposites F and FC, respectively, were attributed to large Ag‐NPs with an average size greater than 50 nm. The absence of large Ag‐NPs in the nanocomposites FO makes them as the materials of choice for the preparation of selective ultrasmall Ag‐NPs with an average size less than 3 nm. Furthermore, photoluminescence was observed upon blue excitation of the ultrasmall colloidal Ag‐NPs. Scanning electron microscopy images showed a good dispersion of the metallic Ag‐NPs in the polymer matrix. Moreover, X‐ray diffraction patterns showed peaks corresponding to the face‐centered‐cubic of the Ag‐NPs. The nature of the interaction between carbopol and Ag‐NPs was further studied by attenuated total reflectance‐Fourier transform infrared spectroscopy, and the mechanism of reduction of the silver ions was proposed. The antimicrobial activities of the CP‐Ag‐NCs were examined against Escherichia coli and Candida albicans microorganisms. The results demonstrate that the CP‐Ag‐NCs can provide new applications of these nanocomposites as efficient sensors and antimicrobial materials.  相似文献   

6.
An advanced novel magnetic ionic liquid based on imidazolium tagged with ferrocene, a supported ionic liquid, is introduced as a recyclable heterogeneous catalyst. Catalytic activity of the novel nanocatalyst was investigated in one‐pot three‐component reactions of various aldehydes, malononitrile and 2‐naphthol for the facile synthesis of 2‐amino‐3‐cyano‐4H‐pyran derivatives under solvent‐free conditions without additional co‐catalyst or additive in air. For this purpose, we firstly synthesized and investigated 1‐(4‐ferrocenylbutyl)‐3‐methylimidazolium acetate, [FcBuMeIm][OAc], as a novel basic ferrocene‐tagged ionic liquid. This ferrocene‐tagged ionic liquid was then linked to silica‐coated nano‐Fe3O4 to afford a novel heterogeneous magnetic nanocatalyst, namely [Fe3O4@SiO2@Im‐Fc][OAc]. The synthesized novel catalyst was characterized using 1H NMR, 13C NMR, Fourier transform infrared and energy‐dispersive X‐ray spectroscopies, X‐ray diffraction, and transmission and field emission scanning electron microscopies. Combination of some unique characteristics of ferrocene and the supported ionic liquid developed the catalytic activity in a simple, efficient, green and eco‐friendly protocol. The catalyst could be reused several times without loss of activity.  相似文献   

7.
The heterostructured Ag nanoparticles decorated Fe3O4 Glutathione (Fe3O4‐Glu‐Ag) nanoparticles (NPs) were synthesized by sonicating glutathione (Glu) with magnetite and further surface immobilization of silver NPs on it. The ensuing magnetic nano catalyst is well characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), powder X‐ray diffraction (PXRD), thermogravimetric analysis (TGA). The prepared Fe3O4‐Glu‐Ag nanoparticles have proved to be an efficient and recyclable nanocatalyst with low catalyst loading for the reduction of nitroarenes and heteronitroarenes to respective amines in the presence of NaBH4 using water as a green solvent which could be easily separated at the end of a reaction using an external magnet and can be recycled up to 5 runs without any significant loss in catalytic activity. Gram scale study for the reduction of 4‐NP has also being carried out successfully and it has been observed that this method can serve as an efficient protocol for reduction of nitroarenes on industrial level.  相似文献   

8.
In this study, preparation and characterization of polyacrylamide/reduced graphene oxide-Ag (PAM/rGO-Ag) nanocomposites as a new nanocomposite film were investigated. First, PAM/GO nanocomposite was synthesized by in situ polymerization strategy. Afterward, highly stable and uniformly distributed silver nanoparticles (Ag NPs) have been obtained with PAM/GO nanocomposite as nanoreactors via in situ reduction of silver nitrate (AgNO3) using sodium borohydride (NaBH4) as reducing agent. In addition, the prepared PAM/rGO-Ag nanocomposite was thermally annealed in order to achieve high-performance nanocomposite film with antimicrobial activities. The prepared nanocomposite was characterized by XRD, FT-IR, SEM, TEM and TGA. The obtained results demonstrate that the silver nanoparticles were well decorated and dispersed on the graphene oxide nanosheets. In fact, the GO nanosheets and polyacrylamide chains act as a support and stabilize the Ag nanoparticles. Moreover, antimicrobial activities of the films were also examined, and the films containing well-dispersed and stabilized Ag nanoparticles showed outstanding antibacterial activity.  相似文献   

9.
This paper reports the green and in situ preparation of Fe3O4@SiO2‐Ag magnetic nanocatalyst synthesized using safflower (Carthamus tinctorius L.) flower extract without the addition of any stabilizers or surfactants. The catalytic performance of the resulting nanocatalyst was examined for the reduction of 4‐nitrophenol (4‐NP), methylene blue (MB) and methyl orange (MO) in an environment‐friendly medium at room temperature. The main factors such as pH, temperature and amount of catalyst influencing the nanocatalyst performance were studied. The apparent rate constants for 4‐NP, MO and MB reduction were calculated, being 0.756 min?1, 0.064 s?1 and 0.09 s?1, respectively. The catalyst was recovered using an external magnet and reused several times with negligible loss of catalytic activity. The as‐synthesized nanoparticles were characterized using powder X‐ray diffraction, transmission electron microscopy, UV–visible, Fourier transform infrared and inductively coupled plasma atomic emission spectroscopies, dynamic light scattering and vibrating sample magnetometry.  相似文献   

10.
In this study, the detailed characterisation of silver (Ag) nanoparticles/polymer nanocomposite chemical structure and morphology of grating has been carried out. Scanning electron microscopy measurements show spherical shape of Ag nanoparticles (40–80 nm in diameter) prepared in chloroform by reduction of silver nitrate. In the positive photoresist based on 2-diazo-2H-naphthalen-1-one (DNQ)–novolac, Ag nanoparticles were deposited from organic colloidal solution. The content of nanoparticles in the polymer matrix was varied by increasing the concentration of Ag colloidal solution. Grating was formed by contact lithography. The quantification of Ag nanoparticles and chemical analysis of Ag/DNQ-novolac-based nanocomposite was performed by means of energy dispersive X-ray analyzer and SEM/EDS. In order to study the effect of Ag nanoparticles on the DNQ-novolac-based nanocomposite structure, investigations with Fourier transform infrared spectroscopy were conducted. Ag nanoparticles cause changes associated with substituent-sensitive out-of-plane C–H bending vibrations of aromatic ring. Ag/DNQ-novolac-based nanocomposite film surface morphology and grating topography imaging were performed using atomic force microscopy. Added Ag nanoparticles change the geometrical parameters of the gratings. The split of corrugations was achieved in Ag/DNQ-novolac-patterned films. Their morphology can be tailored by altering the content of Ag nanoparticles.  相似文献   

11.
Visible‐light‐driven plasmonic photocatalyst Ag‐TiO2 nanocomposite hollow spheres are prepared by a template‐free chemically‐induced self‐transformation strategy under microwave‐hydrothermal conditions, followed by a photochemical reduction process under xenon lamp irradiation. The prepared samples are characterized by using scanning electron microscopy, transmission electron microscopy, X‐ray diffraction, N2 adsorption‐desorption isotherms, X‐ray photoelectron spectroscopy, UV/Vis and Raman spectroscopy. Production of ?OH radicals on the surface of visible‐light illuminated TiO2 was detected by using a photoluminescence method with terephthalic acid as the probe molecule. The photocatalytic activity of as‐prepared samples was evaluated by photocatalytic decolorization of Rhodamine B (RhB) aqueous solution at ambient temperature under visible‐light irradiation. The results show that the surface plasmon absorption band of the silver nanoparticles supported on the TiO2 hollow spheres was red shifted, and a strong surface enhanced Raman scattering effect for the Ag‐TiO2 nanocomposite sample was observed. The prepared nanocomposite hollow spheres exhibits a highly visible‐light photocatalytic activity for photocatalytic degradation of RhB in water, and their photocatalytic activity is higher than that of pure TiO2 and commercial Degussa P25 (P25) powders. Especially, the as‐prepared Ag‐TiO2 nanocomposite hollow spheres at the nominal atomic ratio of silver to titanium ( R ) of 2 showed the highest photocatalytic activity, which exceeds that of P25 by a factor of more than 2.  相似文献   

12.
Silver nanoparticles (narrowly dispersed in diameter) were electrodeposited on carbon ionic liquid electrode (CILE) surface using a two‐step potentiostatic method. Potentiostatic double pulse technique was used as a suitable and simple method for controlling the size and morphologies of silver nanoparticles electrodeposited on CILE. The obtained silver nanoparticles deposited on CILE surface showed excellent electrocatalytic activity (low overpotential of ?0.35 V vs. Ag/AgCl) towards reduction of hydrogen peroxide. A linear dynamic range of 2–200 μM with an experimental detection limit of 0.7 μM (S/N=3) and reproducibility of 4.1% (n=5) make the constructed sensor suitable for peroxide determination in aqueous solutions.  相似文献   

13.
A new magnetic metal–organic framework nanocomposite (CoFe2O4/TMU‐17‐NH2) was prepared via an embedding approach by synthesis of the metal–organic framework crystals in the presence of magnetic cobalt ferrite nanoparticles. We demonstrated that the resulting magnetic nanocomposite can serve as a recyclable nanocatalyst for one‐pot synthesis of bis‐3,4‐dihydropyrimidin‐2(1H)‐one and 3,4‐dihydropyrimidin‐2(1H)‐one derivatives via three‐component reaction of 1,3‐diketone, urea or thiourea and aromatic aldehyde under solvent‐free conditions. CoFe2O4/TMU‐17‐NH2 was characterized using various techniques. The recovery of the nanocomposite was achieved by a simple magnetic decantation and it was reused at least seven times without significant degradation in catalytic activity.  相似文献   

14.
Antibacterial coatings based on hydrogen-bonded multilayers containing in situ synthesized Ag nanoparticles were created on planar surfaces and on magnetic colloidal particles. We report the antibacterial properties of these coatings, determined using a disk-diffusion (Kirby-Bauer) test, as a function of the film thickness and the concentration of Ag nanoparticles in the hydrogen-bonded multilayers. The zone of inhibition (ZoI) determined by the disk-diffusion test increases as the thickness of the multilayer film is increased. Results obtained for the values of the ZoI as a function of film thickness can be described adequately with a simple diffusion model (i.e., the square of the zone of inhibition (ZoI) depended linearly on the logarithm of the thickness of the silver-loaded films). This observation suggests that, in order to incrementally increase the ZoI, an exponentially increasing amount of Ag is required within the multilayers. In general, there was no statistically significant correlation between the zone of inhibition and the number of Ag loading and reduction cycles. The duration of sustained release of antibacterial Ag ions from these coatings, however, could be prolonged by increasing the total supply of zerovalent silver in the films via multiple loading and reduction cycles. These results indicate that the release of silver is controlled by an oxidation mechanism at the surface of the nanoparticles and that repeated loading and reduction of silver leads preferentially to growth of the existing silver nanoparticles in the film as opposed to nucleation of new Ag nanoparticles. We also show that magnetic microspheres coated with silver nanoparticle loaded hydrogen-bonded multilayer thin films can be used to deliver antibacterial agents to specific locations. The minimum inhibitory concentration (MIC) of nanocomposite coated microspheres was determined by the agar dilution technique: antibacterial magnetic microspheres with higher concentrations of Ag nanoparticles exhibited lower MIC values.  相似文献   

15.
DABCO (1,4‐diazabicyclo[2.2.2]octane)‐modified magnetite with silica‐MCM‐41 shell (Fe3O4@silica‐MCM‐41@DABCO) as an effective, magnetic and novel heterogeneous reusable nanocatalyst was synthesized and analysed using various techniques. Evaluation of the catalytic activity of this nanocatalyst was performed in the clean synthesis of substituted 2‐aminodihydropyrano[3,2‐b]pyran‐3‐cyano in high yields via in situ reaction of azido kojic acid, malononitrile and various aldehydes.  相似文献   

16.
Microbial biofouling is one of the major obstacles for reaching the ultimate goal of realizing a high permeability over a prolonged period of nanofiltration operation. In this study, the hybrid nanocomposite membranes consisting of silver (Ag) nanoparticles with antibiofouling capability on microorganism and polyamide (PA) were prepared by in situ interfacial polymerization and characterized by X‐ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM). The hybrid membranes were shown to possess the dramatic antibiofouling effect on Pseudomonas. In addition, Ag nanocomposite membranes had little influence on the performances of the membrane such as on water flux and salt rejection. SEM analysis results showed that all Pseudomonas were dead on the PA/Ag nanocomposite membrane, indicating the effectiveness of silver nanoparticles. This investigation offers a strong potential for possible use as a new type of antibiofouling membrane. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

17.
Summary: Surface‐enhanced Raman scattering (SERS)‐active substrates with high enhancement were prepared by an in situ reduction method. Novel silver/poly(vinyl alcohol) (PVA) nanocomposite films were obtained, in which the silver nitrate, poly(γ‐glutamic acid) (PGA), and PVA acted as precursor, stabilizer, and polyol reducant, respectively. The UV‐visible spectra of the as‐fabricated films showed that the surface plasmon resonance (SPR) absorption band was narrow and of a stronger intensity, which indicates that the Ag nanoparticle size distribution on the substrate was highly uniform. This finding was further confirmed by X‐ray diffraction (XRD), transmission electron microscopy (TEM), and field‐emission scanning electron microscope (FE‐SEM) measurements. It was found that a PGA‐stabilized PVA nanocomposite film revealed the presence of well‐dispersed spherical silver nanoparticles with an average diameter of 90 nm. The new substrate presents high SERS enhancement and the enhanced factor is estimated to be 106 for the detection of benzoic acid.

The Raman scattering enhancement factor for the Raman spectra of benzoic acid on the various nanocomposite films.  相似文献   


18.
Novel nanocomposites consisting of genipin cross‐linked chitosan (GC), poly(ethylene glycol) (PEG), and silver nanoparticles were prepared for such biomedical applications as the wound‐healing materials. Various amounts of silver nanoparticles were dispersed in the GC/PEG hydrogel matrix without severe aggregation. The effects of composition and silver nanoparticles on the physico‐chemical properties of samples were evaluated by infrared analysis, contact angle measurements, and swelling tests. The GC/PEG/Ag nanocomposite showed a pH‐sensitive swelling behavior. The surface hydrophilicity of GC/PEG/Ag nanocomposites was improved with the increase of silver nanoparticle content. L929 cell attachment was improved in the presence of silver nanoparticles. The antimicrobial function was assessed for the GC/PEG/Ag nanocomposites containing the silver content over 100 ppm. The silver nanoparticles had the dual functions of reinforcing structural stability and enhancing antimicrobial activity of GC/PEG/Ag nanocomposites. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

19.
采用聚苯乙烯(PS)包裹Fe3O4磁性纳米粒子,制得Fe3O4@PS复合微球,以此作为磁性载体,通过微球表面的羧基将聚酰胺-胺类树形大分子(PAMAM)连接到磁性载体上,然后使Ag纳米粒子镶嵌在树形分子层中,制得可再生的金属复合催化粒子Fe3O4@PS@PAMAM-Ag.并采用红外光谱、扫描电镜、电感耦合等离子体质谱(ICP-MS)和X射线光电子能谱等方法对复合催化粒子进行了表征,结果表明,树形分子可以较好地分散和稳定金属Ag纳米粒子,所制复合催化粒子表面Ag含量为1.64%,具有较高的催化还原对硝基苯酚的活性.同时,利用外加磁场可以方便快捷地从反应体系中分离出来,继续用于下一次反应中,复合催化粒子循环使用6次后,仍保持完全的催化性能.  相似文献   

20.
Nanocomposites based on silver (Ag) and organically modified silicate (Ormosil) were prepared by an in situ reduction method, in which silver nitrate, tetraethoxysilane and N‐[3‐(trimethoxysilyl)propyl]diethylenetriamine (ATS) acted as precursor, linker, and colloidal suspension stabilizer, respectively. The objective of the study was to produce silver nanoparticles through AgNO3 chemical reduction in a continuous media, in which aminosilanes act as superficial modifiers of Ag nanoparticles, inhibiting their growth and preventing aggregation. The physical properties of the Ormosil/Ag composites were examined using NMR, electron spin resonance, scanning electron microscope, transmission electron microscope, and thermal gravimetric analysis spectroscopy, the results of which indicated that Ag was incorporated in the Ormosil matrix after impregnation. The Ag content and surface morphology of the Ormosil/Ag composites depended on the initial concentration of AgNO3. The antibacterial effects of the Ormosil/Ag composites were assessed by the zone of inhibition and plate‐counting methods, and an excellent antibacterial performance was discovered. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011  相似文献   

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