Molecular selective photocatalysis by TiO2/nanoporous silica core/shell particulates

The coating of TiO(2) particles (P25) by a nanoporous silica layer was conducted to impart molecular recognitive photocatalytic ability. TiO(2)/nanoporous silica core/shell particles with varied pore diameters of the shell were synthesized by the reaction of P25 with an aqueous mixture of tetraethoxysilane and alkyltrimethylammonium chloride with varied alkyl chain lengths, followed by calcination. The TEM and nitrogen adsorption/desorption isotherms of the products showed that a nanoporous silica shell with a thickness of ca. 2nm and controlled pore diameter (1.2, 1.6, and 2.7 nm) was deposited on the titania particle when surfactants with different alkyl chain lengths (C12, C16 and C22) were used. The water vapor adsorption/desorption isotherms of the core/shell particles revealed that a larger amount of water adsorbed on the core/shell particles when the pore diameter is larger. The (29)Si MAS NMR spectra of the core/shell particles showed that the amount of surface silanol groups was independent of the water vapor adsorption capacity of the products. The possible molecular recognitive photocatalysis on the products was investigated under UV irradiation using two kinds of aqueous mixtures containing different organic compounds with varied sizes and functional groups: a 4-butylphenol, 4-hexylphenol, and 4-nonylphenol mixture and a 2-nitrophenol, 2-nitro-4-phenylphenol, and 4-nitro-2,6-diphenylphenol mixture. It was found that the core/shell particles exhibited selective adsorption-driven molecular recognitive photocatalytic decomposition of 4-nonylphenol and 2-nitrophenol in the two mixtures.     

Synthesis of monodispersed Fe3O4@C core/shell nanoparticles

We report a facile method to synthesize dispersed Fe₃O₄@C nanoparticles（NPs）. Fe₃O₄ NPs were firstly prepared via the high temperature diol thermal decomposition method. Fe₃O₄@C NPs were fabricated using glucose as a carbon source by hydrothermal process. The obtained products were characterized by X-ray diffraction（XRD）, transmission electron microscopy（TEM）, vibrating sample magnetometer（VSM） and Raman spectra. The results indicate that the original shapes and magnetic property of Fe₃O₄ NPs can be well preserved. The magnetic particles are well dispersed in the carbon matrix. This strategy would provide an efficient approach for existing applications in Li-ion batteries and drug delivery. Meanwhile, it offers the raw materials to assemble future functional nanometer and micrometer superstructures.     

氮掺杂碳包覆纳米钴颗粒用于硝基芳烃室温选择性加氢（英文）

通过硝基芳烃选择性加氢能高效地制备芳香胺和环胺,其中芳香胺作为重要的化工中间体应用于多个领域(精细化工、商业产品和聚合物).在加氢反应过程中,硝基的还原伴随着生成一些副产物(如亚硝基和偶氮化合物).同时对于含还原性基团的取代硝基苯,硝基的选择还原也面临着很大的挑战.金属钴是常用的硝基加氢催化剂活性成分,但是由于对反应底物的过度吸附,导致其选择性不高.早期研究发现,氮掺杂碳催化剂能有效吸附硝基基团,从而在硝基苯加氢中表现出一定活性,但对分子氢的活化不足.因此,氮掺杂碳作为吸附材料与钴构建复合催化剂,能够发挥吸附和活化氢的协同作用,从而高效催化硝基苯加氢.基于此,本课题组发展了一种制备方法,可将钴颗粒尺寸限制在10 nm左右,且包覆在氮掺杂碳中,并应用于对硝基苯酚的室温选择性加氢反应中,发现相较于碳负载钴和氮掺杂碳催化剂,所制催化剂在室温下表现出了很好的活性和选择性.在此基础上,本文采用元素分析、X射线光电子能谱(XPS)和拉曼光谱(Raman)等手段对催化剂形貌和结构进行了研究.表征结果表明,保持钴前驱体的量不变,随着氮化碳加入量的增加,催化剂中氮掺杂浓度提高;当氮化碳/钴1时,氮掺杂浓度不变.红外结果表明,与普通碳载体相比,氮掺杂碳对硝基苯有很强的吸附作用,而氮掺杂碳包覆的钴催化剂也表现出同样的结果.通过调节氮的掺杂浓度,一方面可以修饰碳载体的电子结构,增加表面缺陷的浓度,提高与反应底物的相互作用;另一方面可以促进电子由钴颗粒转移至与之相连的氮原子上,因此进一步促进钴颗粒对分子氢的活化作用.该复合结构的催化剂实现了底物吸附和氢活化的协同作用,氮掺杂碳将反应底物吸附在表面,钴颗粒活化氢,随后解离的氢原子与表面吸附物反应,从而实现硝基苯的高效加氢.其中Co@NC-1催化活性最高,并在循环套用10次后,仍维持较高的催化活性,同时对含其它取代基的硝基苯均表现很高的活性和选择性.     

氟功能化蛋黄型氧化硅材料负载Pd纳米粒子用于水相烯烃加氢

先将Pd纳米粒子负载于SiO₂球表面上,再经包裹、刻蚀、硅烷化修饰,得到氟丙基功能化“蛋黄”型结构催化剂.并采用X射线衍射、透射电镜、N₂吸附-脱附和热重等对催化剂进行了表征.结果表明,该催化剂在水相烯烃加氢反应中表现出较高的活性,明显高于未经氟丙基修饰的同类催化剂.该催化剂通过离心便可实现回收,多次循环使用后仍保持较高的活性.     

Fabrication and characterization of mesoporous Co3O4 core/mesoporous silica shell nanocomposites

A mesoporous Co(3)O(4) core/mesoporous silica shell composite with a variable shell thickness of 10-35 nm was fabricated by depositing silica on Co(3)O(4) superlatticed particles. The Brunauer-Emmett-Teller (BET) surface area of the composite with a shell thickness of ca. 2.0 nm was 238.6 m(2)/g, which varied with the shell thickness, and the most frequent pore size of the shell was ca. 2.0 nm. After the shell was eroded with hydrofluoric acid, mesoporous Co(3)O(4) particles with a pore size of ca. 8.7 nm could be obtained, whose BET surface area was 86.4 m(2)/g. It is proposed that in the formation of the composite the electropositive cetyltrimethylammonium bromide (CTAB) micelles were first adsorbed on the electronegative Co(3)O(4) particle surface, which directed the formation of the mesoporous silica on the Co(3)O(4) particle surface. Electrochemical measurements showed that the core/shell composites exhibited a higher discharge capacity compared with that of the bare Co(3)O(4) particles.     

Atom transfer radical polymerization synthesis and magnetic characterization of MnFe2O4/polystyrene core/shell nanoparticles

An atom transfer radical polymerization route is developed for the coating of MnFe2O4 nanoparticles with polystyrene yielding the core-shell nanoparticles with size <15 nm. Magnetic studies show a decrease in coercivity after the formation of polystyrene shell, which is considered due to the reduction of magnetic surface anisotropy upon polymer coating. The MnFe2O4 nanoparticles as the magnetic core were separately prepared by a reverse micelle microemulsion method. Polymerization initiators are chemically attached onto the surface of nanoparticles. The modified nanoparticles are then used as macro-initiators in the subsequent polymerization reaction. This approach provides great flexibility in the selection of magnetic core. Consequently, magnetic tunability is able to be introduced into these core/shell nanoparticulate systems to achieve the desired superparamagnetic response.     

Magnetic loading of tyrosinase-Fe3O4/mesoporous silica core/shell microspheres for high sensitive electrochemical biosensing

A new protocol is proposed for magnetic loading and sensitive electrochemical detection of phenol via the tyrosinase cross-linked mesoporous magnetic core/shell microspheres. The mesoporous magnetic microspheres, characterized by transmission electron microscopy, N(2) adsorption/desorption isotherms, and magnetic curve displays high capacity for enzyme immobilization and strong magnetism to adhere to the magnetic electrode surface without any additional adhesive reagent. The biosensor exhibits a wide linear response to phenol ranging from 1.0×10(-9) to 1.0×10(-5) M, a high sensitivity of 78 μA mM(-1), a low detection limit of 1 nM, and a fast response rate (less than 5s). The proposed method is simple, rapid, inexpensive and convenient in electrode renewal, which is recommended as a promising experimental platform for wider applications in biosensing.     

Ni/NiO core/shell nanoparticles for selective binding and magnetic separation of histidine-tagged proteins

Ni/NiO core/shell nanoparticles having high affinity with polyhistidine were synthesized by decomposition of a Ni surfactant complex followed by air oxidation. Ni/NiO nanoparticles showed selective and efficient binding to histidine-tagged proteins and easy separation by using a magnet. These provided a more convenient way to efficient purification of histidine-tagged proteins compared with the conventional Ni-NTA complex-bound resins and microbeads.     

Synthesis of orientedly bioconjugated core/shell Fe3O4@Au magnetic nanoparticles for cell separation

Orientedly bioconjugated core/shell Fe₃O₄@Au magnetic nanoparticles were synthesized for cell separation. The Fe₃O₄@Au magnetic nanoparticles were synthesized by reducing HAuCl₄ on the surfaces of Fe₃O₄ nanoparticles, which were further characterized in detail by TEM, XRD and UV-vis spectra. Anti-CD3 monoclonal antibody was orientedly bioconjugated to the surface of Fe₃O₄@Au nanoparticles through affinity binding between the Fc portion of the antibody and protein A that covalently immobilized on the nanoparticles. The oriented immobilization method was performed to compare its efficiency for cell separation with the non-oriented one, in which the antibody was directly immobilized onto the carboxylated nanoparticle surface. Results showed that the orientedly bioconjugated Fe₃O₄@Au MNPs successfully pulled down CD3⁺ T cells from the whole splenocytes with high efficiency of up to 98.4%, showing a more effective cell-capture nanostructure than that obtained by non-oriented strategy. This developed strategy for the synthesis and oriented bioconjugation of Fe₃O₄@Au MNPs provides an efficient tool for cell separation, and may be further applied to various fields of bioanalytical chemistry for diagnosis, affinity extraction and biosensor.     

Preparation of surface plasmon resonance biosensor based on magnetic core/shell Fe3O4/SiO2 and Fe3O4/Ag/SiO2 nanoparticles

In this paper, surface plasmon resonance biosensors based on magnetic core/shell Fe(3)O(4)/SiO(2) and Fe(3)O(4)/Ag/SiO(2) nanoparticles were developed for immunoassay. With Fe(3)O(4) and Fe(3)O(4)/Ag nanoparticles being used as seeding materials, Fe(3)O(4)/SiO(2) and Fe(3)O(4)/Ag/SiO(2) nanoparticles were formed by hydrolysis of tetraethyl orthosilicate. The aldehyde group functionalized magnetic nanoparticles provide organic functionality for bioconjugation. The products were characterized by scanning electronic microscopy (SEM), transmission electronic microscopy (TEM), FTIR and UV-vis absorption spectrometry. The magnetic nanoparticles possess the unique superparamagnetism property, exceptional optical properties and good compatibilities, and could be used as immobilization matrix for goat anti-rabbit IgG. The magnetic nanoparticles can be easily immobilized on the surface of SPR biosensor chip by a magnetic pillar. The effects of Fe(3)O(4)/SiO(2) and Fe(3)O(4)/Ag/SiO(2) nanoparticles on the sensitivity of SPR biosensors were also investigated. As a result, the SPR biosensors based on Fe(3)O(4)/SiO(2) nanoparticles and Fe(3)O(4)/Ag/SiO(2) nanoparticles exhibit a response for rabbit IgG in the concentration range of 1.25-20.00 μg ml(-1) and 0.30-20.00 μg ml(-1), respectively.     

Encapsulation of superparamagnetic Fe3O4@SiO2 core/shell nanoparticles in MnO2 microflowers with high surface areas

Microflowers made of interconnected MnO₂ nanosheets have been successfully synthesized in a microwave reactor through a hydrothermal reduction of KMnO₄ with aqueous HCI at elevated temperatures in the presence of superparamagnetic Fe₃O₄SiO₂ core-shell nanoparticles.Due to the chemical compatibility between SiO₂ and MnO₂,the heterogeneous reaction leads to the spontaneous encapsulation of the Fe₃O₄@SiO₂ core-shell nanoparticles in the MnO₂ microflowers.The resulting hybrid particles exhibit multiple properties including high surface area associated with the MnO₂nanosheets and superparamagnetism originated from the Fe₃O₄@SiO₂ core-shell nanoparticles.which are beneficial for applications requiring both high surface area and magnetic separation.     

Tuning the shape of nanoparticles to control their catalytic properties: selective hydrogenation of 1,3-butadiene on Pd/Al2O3

Shape-controlled Pd nanoparticles supported on powder alumina are more efficient for selective butadiene hydrogenation to butene when they exhibit high fractions of (111) facets.     

Anchored Ni-dimethylglyoxime complex on Fe3O4@SiO2 core/shell nanoparticles for the clean catalytical synthesis of dicoumarols

Ni-Dimethylglyoxime complex immobilized on functionalized Fe₃O₄ was synthesized by a post-grafting way and utilized as a novel, thermally stable, recoverable, and efficient for green synthesis of dicoumarols through reaction of 4-hydroxycoumarin with various aldehydes in excellent yields and higher rate. Fe₃O₄@SiO₂-silylcyclopropyl-dimethylglyoxime-Ni superparamagnetic nanoparticles (MNP_s) were investigated by Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, vibrating sample magnetometer, and Brunauer–Emmett–Teller technique. This nanocatalyst could be conveniently recovered via the use of an external magnetic field and reused for subsequent reactions for at least 7 times without any remarkable change and decrease in catalytic activity.     

Synthesis and characterization of multifunctional Fe3O4/poly(fluorescein O-methacrylate) core/shell nanoparticles

Multifunctional fluorescent and superparamagnetic Fe(3)O(4)/poly(fluorescein O-methacrylate) [Fe(3)O(4)/poly(FMA)] nanoparticles with core/shell structure were synthesized via surface-initiated polymerization. First, polymerizable double bonds were introduced onto the surface of Fe(3)O(4) nanoparticles via ligand exchange and a condensation reaction. A fluorescent monomer, FMA, was then polymerized to the double bonds at the surface via free-radical polymerization, leading to form a fluorescent polymer shell around the superparamagnetic Fe(3)O(4) core. The resultant Fe(3)O(4)/poly(FMA) nanoparticles were characterized by Fourier transform infrared, nuclear magnetic resonance, and X-ray diffraction spectroscopy to confirm the reactions. Transmission electron microscopy images showed that the Fe(3)O(4)/poly(FMA) nanoparticles have a spherical and monodisperse core/shell morphology. Photoluminescence spectroscopy and superconducting quantum interference device magnetometer analyses confirmed that the Fe(3)O(4)/poly(FMA) nanoparticles exhibited fluorescent and superparamagnetic properties, respectively. In addition, we demonstrated the potential bioimaging application of the Fe(3)O(4)/poly(FMA) nanoparticles by visualizing the cellular uptake of the nanoparticles into A549 lung cancer cells.