首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 406 毫秒
1.
Polystyrene (PSt) seed latex was first prepared via soap‐free emulsion polymerization in the presence of a small amount of methacrylic acid using ammonium persulfate as initiator, and then seeded emulsion polymerization of sodium 4‐styrenesulfonate (NaSS) and St was carried out to synthesize P(St‐NaSS) core latex using 2,2′‐azobisisobutyronitrile as initiator. After that, P(St‐NaSS)/CaCO3 core‐shell nanoparticles were fabricated by sequentially introducing Ca(OH)2 aqueous solution and CO2 gas into the core latex. The morphology of the core and core‐shell nanoparticles was characterized by dynamic light scattering (DLS) and transmission electron microscopy (TEM), and the state of CaCO3 shell was confirmed with high‐resolution scanning transmission electron microscope (HR‐STEM) and selected area electron diffraction (SAED). Results showed that PNaSS chains were successfully grafted onto the PSt seed surface, and length of the PNaSS "hairs" could be modulated by adjusting NaSS amount. Sulfonic groups of the PNaSS hairs served as additives in the formation and stabilization of amorphous CaCO3(ACC) and prevented ACC from sequent transformation into crystalline states. The amount of the anchored CaCO3 increased with the growth of PNaSS hair length, and reached 51 wt% (by thermalgravimetric analysis) under the optimal encapsulating temperature of 45°C. Moreover, the forming mechanism of P(St‐NaSS)/CaCO3 core‐shell nanoparticles was proposed.  相似文献   

2.
《Electroanalysis》2017,29(11):2638-2645
A novel sensor architecture based on thin film of tapioca decorated within nitrogen‐doped titanium dioxide (N‐TiO2) nanoparticles is reported. The nanostructures were characterized by scanning electron microscope, transmission electron microscope, X‐rays diffraction and voltammetric techniques. The proposed electrode was used for detection of low concentrations of 17‐β estradiol in without purification step, which was investigated by using linear sweep adsorptive stripping voltammetry. Under optimal conditions, the analytical curve was linear over a 17β‐estradiol concentration range of 9.9×10−6 to 1.4×10−5 mol L−1, with a detection limit of 1.7×10−7 mol L−1. The tapioca and N‐TiO2 nanoparticles homogeneous film was applied for detection of 17‐β‐estradiol in tap water and synthetic urine samples, which presented satisfactory results.  相似文献   

3.
The catalytic activity of l ‐arginine‐coated nano‐Fe3O4 particles (Fe3O4@l ‐arginine) proves they are a novel magnetic catalyst without the use of heat and reflux for the synthesis of 1,3‐diaryl‐2‐N‐azaphenalene derivatives and n‐acyl‐1,3‐diaryl‐2‐N‐azaphenylene derivatives in a one‐pot pseudo‐five‐component condensation reaction of compounds of 2,7‐naphthalene diol, aldehydes, and ammonia derivatives (ammonium acetate or ammonium hydrogen phosphate) and solvent (water and alcohol) with high yield and short reaction times, economical, and simple workup. The structure and magnetic properties of the obtained nanoparticles were characterized via Fourier transform infrared spectroscopy (IR) and field emission scanning electron microscopy (FE‐SEM). The results demonstrated that the average size of the synthesized magnetite nanoparticles is about 21 nm. In addition, the heterogeneous catalyst can be easily recovered magnetically and can be reused for further runs without significant loss of its catalytic activity.  相似文献   

4.
Atom transfer radical emulsion polymerization of styrene using PEG‐Cl as macroinitiator under microwave irradiation was successfully conducted and monodispersed nanoparticles were prepared. The PEG‐Cl macroinitiator was synthesized, and confirmed by FTIR spectrum. The structure of the PEG‐b‐PSt diblock copolymer was characterized by 1H‐NMR and the number of styrene unit in the diblock copolymer was calculated. The morphology, size, and size distribution of the nanoparticles were characterized by transmission electron microscope (TEM) and photon correlation spectroscopy (PCS). The effects of the ratio of macroinitiator and monomer, the ratio of catalyst and macroinitiator on the size and size distribution of nanoparticles were investigated. It was found that the diameters of PEG‐b‐PSt nanoparticles prepared under microwave irradiation were smaller (<50 nm) and more monodispersed than those prepared with conventional heating. Moreover, with the increasing of the ratio of St/PEG‐Cl, the hydrodynamic diameters (Dh) of the nanoparticles increased and the poly index decreased, both Dh and poly index of the nanoparticles prepared under microwave irradiation were smaller then those prepared with conventional heating; as the concentration of catalyst increased, the Dh of the nanoparticles decreased and the poly index of the nanoparticles increased. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 481–488, 2008  相似文献   

5.
An emulsifier‐free core–shell polyacrylate emulsion, containing nano‐SiO2 nanoparticles in the core and diacetone acrylamide (DAAM) in the shell, has been successfully prepared by emulsifier‐free seeded emulsion polymerization. The effects of reaction temperature, dropping time, nano‐SiO2 and initiator contents, and variation of the composition of core monomers on the amount of coagulum, particle size, and monomer conversion have been investigated. The particle morphology and the distribution of emulsion particles have been measured by transmission electron microscopy (TEM) and dynamic light scattering. The keto‐carbonyl groups on the surface of the polyacrylate emulsion nanoparticles reacted with adipic dihydrazide (ADH) to form a film with a cross‐linked network structure at room temperature. Therefore, the emulsifier‐free core–shell emulsion could be used as a two‐component room temperature curable waterborne coating. It was also found that the properties of the coating were clearly superior after using the cross‐linker. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

6.
A highly enantioselective, chiral, Lewis acid calcium–bis(phosphate) complex, Ca[ 3 a ]n, which catalyzes the electrophilic amination of enamides with azodicarboxylate derivatives 2 to provide versatile chiral 1,2‐hydrazinoimines 4 is disclosed. The reaction gives an easy entry to optically active syn‐1,2‐disubstituted 1,2‐diamines 6 in high yields with excellent enantioselectivities, after a one‐pot reduction of the intermediate 1,2‐hydrazinoimines 4 . The geometry and nature of the N‐substituent of the enamide affect dramatically both the reactivity and the enantioselectivity. Although the calcium–bis(phosphate) complex was a uniquely effective catalyst, the exact nature of the active catalytic species remains unclear. NMR spectroscopy and MS analysis of the various calcium complexes Ca[ 3 ]n reveals that the catalysts exist in various oligomer forms. The present mechanistic study, which includes nonlinear effects and kinetic measurements, constitutes a first step in understanding these calcium–bis(phosphate) complex catalysts. DFT calculations were carried out to explore the mechanism and the origin of the enantioselectivity with the Ca[ 3 ]n catalysts.  相似文献   

7.
The magnetic core of manganese ferrite (MnFe2O4) nanoparticles has a significant stability in comparison with ferrite (Fe3O4) nanoparticles. The unique supramolecular properties of β‐cyclodextrin (β‐CD), such as hydrophobic cavity, hydrophilic exterior and ‐OH functional groups, make it a good candidate for functionalization and catalytic application. So, a surface‐modified magnetic solid support with the Cu (II)‐β‐CD complex was prepared. The structure of nanoparticles was characterized by Fourier transform‐infrared spectroscopy, X‐ray powder diffraction, thermogravimetric analysis, vibrating‐sample magnetometry, inductively coupled plasma‐optical emission spectrometry and scanning electron microscope analyses. The catalytic activity of these nanoparticles was investigated in the synthesis of spiropyrans and high yields of desired products obtained under green media. Some advantages of this novel catalyst for this reaction are high yields, short reaction times, green solvent and conditions, easy workup procedure, negligible copper leaching, reusability without a significant diminish in catalytic efficiency, and simple separation of nanocatalyst by using an external magnet alongside the environmental compatibility and sustainability.  相似文献   

8.
In this paper we present aluminum phosphate nanocrystals, prepared by a hydrothermal reaction, using amphiphilic triblock copolymer F127 [(EO)106(PO)70(EO)106] as a morphology‐directing template. By verifying the pH from 10 to 12, the morphology progression of AlPO4 nanocrystals from nanoparticles to nanoparticle‐aggregated nanowires, and finally to multi‐strand nano‐ropes, was successfully demonstrated. The most influential factors in the morphology process were the initial pH level, the participation of surfactant‐template F127, and the change in pH during the reaction. We proposed a pH‐dependent model to illustrate both the growth of AlPO4 nanocrystals inside F127 amphiphilic domains and the chemical driving force that aggregated the nanoparticles into chain‐shaped nanowires. The incorporation of water molecules as H‐bonding linkers, to combine single nanowires into multi‐strand nano‐ropes, is also discussed in this model. Powder X‐ray diffraction (XRD) patterns of the nanoparticle‐aggregated nanowires and multi‐strand nano‐ropes were consistent with a mixed phase of berlinite and cristobalite structures, corresponding to the low‐temperature form (a‐form), while the AlPO4 nanoparticles showed a pure berlinite phase only.  相似文献   

9.
A new electrochemical immunosensor for the detection of α‐1‐fetoprotien (AFP) was developed based on AFP antibody (anti‐AFP)‐functionalized organic/inorganic hybrid nanocomposite membrane. To fabricate such a hybrid composite membrane, 3,4,9,10‐perylenetetracarboxylic acid‐bound thionine molecules (PTCTH) were initially doped into titania colloids (TiO2), and then gold nanoparticles and anti‐AFP were immobilized onto the composite film in turn. Comparison with the electrode fabricated only with thionine not 3,4,9,10‐perylenetetracarboxylic acid, the immunosensor with PTCTH exhibited high sensitivity and fast electron transfer. The presence of gold nanoparticles provided a good microenvironment for the immobilization of biomolecules, enhanced the surface coverage of protein, and improved the sensitivity of the immunosensor. The modified process was characterized by scanning electron microscope (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The surface topography of the membrane was investigated by scanning electron microscopy (SEM). Under optimal conditions, the proposed immunosensor exhibited a wide linear range from 2.5 to 200.0 ng/mL towards AFP with a detection limit of 0.5 ng/mL (S/N=3). The stability, reproducibility and precision of the immunosensor were acceptable. Comparison with the conventional enzyme‐linked immunosorbent assay (ELISA), the present method did not require more labeled procedures and washing steps. Significantly, the detection methodology provides a promising approach for other proteins or biosecurities.  相似文献   

10.
In the present study, modification of nanoparticles (NPs) was investigated to mitigate aggregation of SiO2 nanoparticles and improve the polymeric membrane's performance. For this purpose, the surface of SiO2 nanoparticles was activated with amine groups, and polymethacrylic acid (PMAA) was grafted on the surface of NPs by atom transfer radical polymerization. Modified NPs were characterized by Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) tests. Polyethersulfone (PES) membranes were fabricated with both SiO2 and SiO2‐g‐PMAA NPs via nonsolvent‐induced phase separation method. The fabricated membranes were characterized regarding their permeability, hydrophilicity, and porosity properties, and their separation efficiency was tested using the synthetic oil‐in‐water emulsion. The surface and cross‐sectional morphologies of membranes were observed by field emission scanning electron microscopy (FESEM). The experimental trials showed that modified NPs dispersed more uniformly in the structure of membranes and hydroxyl groups on the surface of NPs acted more effectively. Modification of NPs enhance the membrane performance in terms of permeate flux, hydrophilicity, and porosity. NPs modification improved the permeate flux about 46%. Oil rejection for all tested membranes was more than 98%, and modification of NPs did not reduce the rejection of membranes. The optimum concentration was obtained as 1 wt.% and 1.5 wt.% for SiO2 and SiO2‐g‐PMAA, respectively. Aggregation effect dominated at concentrations beyond the optimum values that decreased the permeate flux, consequently.  相似文献   

11.
In the present work, the nanocrystalline particles of hydroxyapatite (HAp) using an easy alkoxide‐based sol–gel technique including triethyl phosphate [PO (OC2H5)3] and Ca (NO3)2·4H2O as P and Ca precursors have been synthesized. The sample characterization was performed by X‐ray diffraction, Fourier transform‐infrared analysis, scanning electron microscopy, thermal analysis (thermogravimetric analysis/differential thermal analysis), and elemental analysis of energy‐dispersive X‐ray analysis. It is interesting that single phase of HAp was obtained at a low firing temperature of 500 ° C. Modified Scherrer equation as the Williamson?Hall method was applied for the measurement of crystallite size distributions and micro‐strain of the sample. The determined crystallite size by complementary technique of transmission electron microscopy has good consistency with those obtained from the Scherrer formula. Moreover, we reported the one‐pot synthesis of 3,4‐disubstituted isoxazole‐5(4H)‐ones through the aqueous solution reaction of three components of ethyl acetoacetate, hydroxylamine hydrochloride and various aromatic aldehydes at room temperature. This protocol offers several advantages, including a simple work‐up procedure, very short reaction times (under 25 min), in accordance with the principles of green chemistry, recyclability, excellent yields (87–98%) and environmentally friendly.  相似文献   

12.
The drug delivery performances of pH‐responsive magnetic hydrogels (MHs) composed of tragacanth gum (TG), poly(acrylic acid) (PAA), and Fe3O4 nanoparticles (NPs) were investigated in terms of physicochemical as well as biological features. The fabricated drug delivery systems (DDSs) were analyzed using Fourier transform infrared spectroscopy, X‐ray diffraction, vibrating sample magnetometer, scanning electron microscopy, and transmission electron microscopy. The synthesized MHs were loaded with doxorubicin hydrochloride (Dox) as a universal model anti‐cancer drug. The MHs showed excellent Dox loading and encapsulation efficiencies, mainly due to strong hydrogen bonding and electrostatic interaction between the drug and polymeric matrix, as well as porous micro‐structures of the fabricated MHs. The drug‐loaded MHs showed negligible drug release values in physiological condition. In contrast, in cancerous condition (pH 5.0), both MHs exhibited highest drug release values that qualified them as “smart” DDSs. The cytocompatibilities of the MHs as well as the cytotoxicity of the Dox‐loaded MHs were investigated against human epidermoid‐like carcinoma (Hela) cells through MTT assay. In addition, hyperthermia therapy induced by Fe3O4 NPs was applied to locally raise temperature inside the Hela cells at 45 ± 3°C to promote cell death. As a result, the Dox‐loaded MHs can be considered as potential DDSs for chemo/hyperthermia therapy of solid tumors.  相似文献   

13.
Polypropylenimine dendrimer (DAB‐Am‐32, generation 4.0) was converted into a macroinitiator DAB‐Am‐32‐Cl via reaction with 2‐chloropropionyl chloride. Monodisperse nanoparticles containing poly(propylene imine)(NH2)32‐polystyrene were prepared by emulsion atom transfer radical polymerization (ATRP) of styrene (St), using the DAB‐Am‐32‐Cl/CuCl/bpy as initiating system. The structure of macroinitiator was characterized by FTIR spectrum, 1H NMR, and 13C NMR. The structure of poly(propylene imine)(NH2)32‐polystyrene was characterized by FT‐IR spectrum and 1H NMR; the molecular weight and molecular weight distribution of poly(propylene imine)(NH2)32‐polystyrene were characterized by gel permeation chromatograph (GPC). The morphology, size and size distribution of the nanoparticles were characterized by photon correlation spectroscopy (PCS), transmission electron microscopy (TEM), and atomic force microscopy (AFM). The effects of monomer/macroinitiator ratio and surfactant concentration on the size and size distribution of the nanoparticles were investigated. It was found that the diameters of the nanoparticles were smaller than 100 nm (30–80 nm) and monodisperse; moreover, the particle size could be controlled by monomer/macroinitiator ratios and surfactant concentration. With the increasing of the ratio of St/DAB‐Am‐32‐Cl, the number‐average diameter (Dn), weight‐average diameter (Dw) were both increased gradually. With enhancing the surfactant concentration, the measured Dh of the nanoparticles decreased, while the polydispersity increased. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2892–2904, 2009  相似文献   

14.
In recent years, the development of novel green chemistry routes for the synthesis of organic compounds has become very attractive to many research groups. Nanoparticles have been widely used because of their potential applications in catalysis, environmental remediation, electronic fields, biomedical, and industrial fields. In this article, a rapid, efficient, and simple approach was applied for the synthesis of 2,3‐diaminophenazine using a new photocatalytic system of CdFe2O4/TiO2 nanoparticles in water as a benign solvent. The structure of the synthesized CdFe2O4/TiO2 nanoparticle was confirmed using different methods such as transmission electron microscope (TEM), X‐ray diffraction (XRD), and magnetic measurements. It was found that the rate and yield of the photocatalytic synthesis of 2,3‐diaminophenazine were improved using CdFe2O4/TiO2 nanoparticles compared to other methods.  相似文献   

15.
The hyperbranched aliphatic polyester grafted calcium carbonate nanoparticles (HAPE‐CaCO3), was successfully prepared by the real one‐pot method. The AB2 monomer, 2,2‐bis(hydroxymethyl)propionic acid (bis‐MPA), was used as both the surface modifying agent and the monomer of the hyperbranched aliphatic polyester. It introduced the organic active group (hydroxyl group) onto the surfaces of the calcium carbonate nanoparticles (nano‐CaCO3) and its polycondensation took place subsequently, with the catalysis of p‐toluenesulfonic acid (p‐TSA). The HAPE‐CaCO3 had been characterized by elemental analysis (EA), Fourier transform infrared spectroscopy (FTIR), Thermogravimetric analysis (TGA), and transmission electron microscope (TEM).  相似文献   

16.
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   

17.
Three kinds of polyhedral α‐Fe2O3 nanoparticles enclosed by different facets including oblique parallel hexahedrons (op‐hexahedral NPs), cracked oblique parallel hexahedrons (cop‐hexahedral NPs), and octadecahedral nanoparticles (octadecahedral NPs), were successfully prepared by simply changing only one reaction parameter in the hydrothermal process. The structural and morphological of the products were systematically studied using various characterizations including X‐ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), revealing that the three kinds of α‐Fe2O3 nanoparticles were enclosed by {104}, {110}/{104}, and {102}/{012}/{104} crystal planes, respectively. The exposed facets and shape of the nanocrystals were found to be affected by the adding amount of ethylene glycol in the solvent. The gas‐sensing properties and mechanism of the α‐Fe2O3 samples were studied and analyzed, which indicated that the sensitivity of the three samples followed the order of octadecahedral NPs > cop‐hexahedral NPs > op‐hexahedral NPs due to the combined effects of specific surface area and oxygen defects in the nanocrystals.  相似文献   

18.
Summary: Biodegradable poly(1,5‐dioxepan‐2‐one) (PDXO) was grown directly from Si OH groups of a silica nanoparticle by surface‐initiated, ring‐opening polymerization (SI‐ROP) of 1,5‐dioxepan‐2‐one (DXO). The direct SI‐ROP of DXO was achieved by heating a mixture of Sn(Oct)2, DXO, and the silica nanoparticles (316 nm in diameter) in anhydrous toluene. The resulting silica/PDXO hybrid nanoparticles were characterized by means of 1H NMR spectroscopy, IR spectroscopy, thermogravimetric analysis, and field‐emission scanning electron microscopy.

The procedure for the surface‐initiated, ring‐opening polymerization of 1,5‐dioxepan‐2‐one on silica nanoparticles reported here.  相似文献   


19.
Carboxylic acid capped γ‐Fe2O3 nanoparticles were prepared by the standard decomposition of Fe(CO)5 in di‐n‐octyl ether and oleic acid. Two methods were employed to introduce surface functionality to the nanoparticles. First, a thermally stable, tert‐butyldiphenylsilyl‐protected hydroxyl group was incorporated into the carboxylic acid surfactant used during the synthesis. Subsequent deprotection and transformation installed a 2‐bromopropionyl ester group on the particle surface (the functional‐group‐interchange method). The resulting nanoparticles were 4.53 nm in average diameter and were characterized with IR spectroscopy, transmission electron microscopy (TEM), selected area electron diffraction, and elemental analysis. Second, a 2‐bromopropionyl ester group was installed on the particle surface after synthesis via the exchange of the surface oleic acid with a carboxylic acid containing the desired 2‐bromopropionyl ester unit (the ligand‐exchange method). The resulting nanoparticles were 4.30 nm in average diameter and were characterized with IR spectroscopy, TEM, and elemental analysis. Monitoring the percentage of bromine incorporated into the nanoparticle sample versus the ligand‐exchange reaction time indicated that the number of initiator‐containing carboxylic acids that could be exchanged onto the surface was limited, presumably by the steric size of the 2‐bromopropionyl ester group. Styrene was then polymerized directly off γ‐Fe2O3 nanoparticles, and this yielded hybrid core–shell structures. The measurements of the magnetic properties of the samples demonstrated that the magnetism of the core γ‐Fe2O3 nanoparticle did not change during the performance of the chemical transformations. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3675–3688, 2005  相似文献   

20.
A novel Cu (II) Schiff‐base complex immobilized on core‐shell magnetic Fe3O4 nanoparticles (Fe3O4@SPNC) was successfully designed and synthesized. The structural features of these nanoparticles were studied and confirmed by using various techniques including FT‐IR spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy‐dispersive X‐ray spectroscopy (EDS), vibrating sample magnetometer (VSM), X‐Ray diffraction (XRD), wavelength dispersive X‐ray spectroscopy (WDX), and inductively coupled plasma (ICP). These newly synthesized nanoparticles have been used as efficient heterogeneous catalytic system for one‐pot multicomponent synthesis of new pyrano[2,3‐b]pyridine‐3‐carboxamide derivatives. Notably, the catalyst could be easily separated from the reaction mixture by using an external magnet and reused for several successive reaction runs with no significant loss of activity or copper leaching. The present protocol benefits from a hitherto unreported MNPs‐immobilized Cu (II) Schiff‐base complex as an efficient nanocatalyst for the synthesis of newly reported derivatives of pyrano[2,3‐b]pyridine‐3‐carboxamide from one‐pot multicomponent reactions.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号