中空碳球负载TiO2纳米颗粒用于增强光催化抗菌性能

以聚吡咯包覆聚苯乙烯核壳结构衍生的中空碳球(hollow carbon spheres,HCS)为载体,乙酰丙酮钛(TOAC)为钛源,通过湿化学法和可控热解法制备了HCS负载纳米二氧化钛(HCS@TiO₂)复合材料。通过粉末X射线衍射、紫外可见光谱、X射线光电子能谱、热重分析、扫描电子显微镜、透射电子显微镜、光致发光光谱和Mott-Schottky曲线对HCS@TiO₂的晶态结构、微观形貌、光学性能等进行表征,并通过调控TiO₂的负载量和热解温度对HCS@TiO₂复合材料进行了结构优化。在模拟太阳光照射条件下,以大肠杆菌(E. coli)和金黄色葡萄球菌(S. aureus)为实验对象,研究了不同TiO₂负载量的HCS@TiO₂复合材料及TiO₂和HCS对照样品的光催化抗菌性能,以及光照时间对抗菌性能的影响。结果表明,当TOAC与HCS质量比为15∶1、热解温度为650℃时,最优化的HCS@TiO₂-15复合材料...     

C60 trianion-mediated electrocatalysis and amperometric sensing of hydrogen peroxide

Heterogeneous electrocatalytic reduction of hydrogen peroxide (H₂O₂) by C₆₀ is reported for the first time. C₆₀ is embedded in tetraoctylammonium bromide (TOAB) film and is characterized by scanning electron microscopy and cyclic voltammetry. Electrocatalytic studies show that the trianion of C₆₀ mediates the electrocatalytic reduction of H₂O₂ in aqueous solution containing 0.1 M KCl. Application of such film modified electrode as an amperometric sensor for H₂O₂ determination is also examined. The sensor shows a fast response within 1 s and a linear response is obtained (R = 0.9986) in the concentration range from 3.33 × 10⁻⁵ to 2.05 × 10⁻³ mol L⁻¹ for H₂O₂, with the detection limit of 2 × 10⁻⁵ mol L⁻¹ and the sensitivity of 1.65 μA mM⁻¹. A good repeatability and stability is shown for the sensor during the experiment.     

Ordered hierarchical mesoporous anatase TiO2 from yeast biotemplates

A novel approach is proposed to prepare ordered hierarchical mesoporous TiO₂ by using yeast cells as the template via biomimetic mineralization. The structure and the mophology were characterized by atomic force microscopy (AFM), X-ray diffraction (XRD), energy-dispersive X-ray analysis (EDX), Raman spectra, high-resolution transmission electron microscopy (HRTEM), and N₂ adsorption–desorption isotherms (NADI). The bio-templated TiO₂ has a hierarchical pore structure mainly distributed at 4.7 nm and 11.3 nm. An air electrode fabricated using this hierarchical mesoporous TiO₂ exhibited remarkable electrocatalytic activity for oxygen reduction reaction (ORR). Compared to the electrolytic manganese dioxide (EMD) air electrode employed commercially, a 90% higher catalytic reduction current was achieved for this mesoporous TiO₂ electrode. It is supposed that the hierarchically mesoporous structure and ordered pore distribution play important roles in significantly reducing electrochemical polarization and improving mass transport of the air diffusion electrode. This simple and efficient approach could spread as a general way to prepare advanced mesoporous materials in mild condition.     

Preparation and characterization of SiO2/TiO2 composite microspheres with microporous SiO2 core/mesoporous TiO2 shell

SiO₂/TiO₂ composite microspheres with microporous SiO₂ core/mesoporous TiO₂ shell structures were prepared by hydrolysis of titanium tetrabutylorthotitanate (TTBT) in the presence of microporous silica microspheres using hydroxypropyl cellulose (HPC) as a surface esterification agent and porous template, and then dried and calcined at different temperatures. The as-prepared products were characterized with differential thermal analysis and thermogravimetric (DTA/TG), scanning electron microscopy (SEM), X-ray diffraction (XRD), nitrogen adsorption. The results showed that composite particles were about 1.8 μm in diameter, and had a spherical morphology and a narrow size distribution. Uniform mesoporous titania coatings on the surfaces of microporous silica microspheres could be obtained by adjusting the HPC concentration to an optimal concentration of about 3.2 mmol L⁻¹. The anatase and rutile phase in the SiO₂/TiO₂ composite microspheres began to form at 700 and 900 °C, respectively. At 700 °C, the specific surface area and pore volume of the SiO₂/TiO₂ composite microspheres were 552 and 0.652 mL g⁻¹, respectively. However, at 900 °C, the specific surface area and pore volume significantly decreased due to the phase transformation from anatase to rutile.     

A sensitive amperometric sensor for hydrazine and hydrogen peroxide based on palladium nanoparticles/onion-like mesoporous carbon vesicle

Onion-like mesoporous carbon vesicle (MCV) with multilayer lamellar structure was synthesized by a simply aqueous emulsion co-assembly approach. Palladium (Pd) nanoparticles were deposited on the MCV matrix (Pd/MCV) by chemical reduction of H₂PdCl₄ with NaBH₄ in aqueous media. Pd(X)/MCV (X wt.% indicates the Pd loading amount) nanocomposites with different Pd loading amount were obtained by adjusting the ratio of precursors. The particular structure of the MCV results in efficient mass transport and the onion-like layers of MCV allows for the obtainment of highly dispersed Pd nanoparticles. The introduction of Pd nanoparticles on the MCV matrix facilitates hydrazine oxidation at more negative potential and delivers higher oxidation current in comparison with MCV. A linear range from 2.0 × 10⁻⁸ to 7.1 × 10⁻⁵ M and a low detection limit of 14.9 nM for hydrazine are obtained at Pd(25)/MCV nanocomposite modified glassy carbon (GC) electrode. A nonenzymatic amperometric sensor for hydrogen peroxide based on the Pd(25)/MCV nanocomposite modified GC electrode is also developed. Compared with MCV modified GC electrode, the Pd(25)/MCV nanocomposite modified GC electrode displays enhanced amperometric responses towards hydrogen peroxide and gives a linear range from 1.0 × 10⁻⁷ to 6.1 × 10⁻³ M. The Pd(25)/MCV nanocomposite modified GC electrode achieves 95% of the steady-current for hydrogen peroxide within 1 s. The combination of the unique properties of Pd nanoparticles and the porous mesostructure of MCV matrix guarantees the improved analytical performance for hydrazine and hydrogen peroxide.     

Photocatalytic hydrogen evolution over mesoporous TiO2/metal nanocomposites

Na⁺ complex with the dibenzo-18-crown-6 ester was used as a template to synthesize mesoporous titanium dioxide with the specific surface area 130–140 m²/g, pore diameter 5–9 nm and anatase content 70–90%. The mesoporous TiO₂ samples prepared were found to have photocatalytic activity in Cu^II, Ni^II and Ag^I reduction by aliphatic alcohols. The resulting metal–semiconductor nanostructures have remarkable photocatalytic activity in hydrogen evolution from water–alcohol mixtures, their efficiency being 50–60% greater than that of the metal-containing nano-composites based on TiO₂ Degussa P25.The effects of the thermal treatment of mesoporous TiO₂ upon its photocatalytic activity in hydrogen production were studied. The anatase content and pore size were found to be the basic parameters determining the photoreaction rate. The growth of the quantum yield of hydrogen evolution from TiO₂/Ag⁰ to TiO₂/Ni⁰ to TiO₂/Cu⁰ was interpreted in terms of differences in the electronic interaction between metal nanoparticles and the semiconductor surface. It was found that there is an optimal metal concentration range where the quantum yield of hydrogen production is maximal. A decrease in the photoreaction rate at further increment in the metal content was supposed to be connected with the enlargement of metal nanoparticles and deterioration of the intimate electron interaction between the components of the metal–semiconductor nanocomposites.     

Al2O3 @ TiO2—A simple sol-gel strategy to the synthesis of low temperature sintered alumina-aluminium titanate composites through a core-shell approach

A simple sol-gel based core-shell approach for the synthesis of alumina-aluminium titanate composite is reported. Alumina is the core and titania is the shell. The coating of titania has been performed in aqueous medium on alumina particle by means of heterocoagulation of titanyl chloride. Further heat treatment results in low temperature formation of aluminium titanate as well as low temperature sintering of alumina-aluminium titanate composites. The lowering of the reaction temperature can be attributed to the maximisation of the contact surface between the reactants due to the core-shell approach involving nanoparticles. The mechanism of formation of aluminium titanate and the observations on densification features in the present process are compared with that of mixture of oxides under identical conditions. The sintered alumina-aluminium titanate composite has an average grain size of 2 μm.     

Mesoporous TiO2 nanoparticles for highly sensitive solid-phase microextraction of organochlorine pesticides

Mesoporous TiO₂ nanoparticles were synthesized with the hydrothermal method and characterized by powder X-ray diffraction (PXRD) and transmission electron microscope (TEM). Then a superior solid-phase microextraction (SPME) fiber was fabricated by sequentially coating the stainless steel fiber with silicone sealant film and mesoporous TiO₂ powder. The developed fiber possessed a homogeneous surface and a long life-span up to 100 times at direct immersing (DI) extraction mode. Under the optimized conditions, the extraction efficiencies of the self-made 17 μm TiO₂ fiber for six organochlorine pesticides (OCPs) were higher than those of the two commercial fibers (65 μm PDMS/DVB and 85 μm PA fibers) which were much thicker than the former. As for analytical performance, low detection limits (0.08–0.60 ng L⁻¹) and wide linearity (5–5000 ng L⁻¹) were achieved under the optimal conditions. The repeatabilities (n = 5) for single fiber were between 2.8 and 12.3%, while the reproducibilities (n = 3) of fiber-to-fiber were in the range of 3.7–15.7%. The proposed fiber was successfully applied to the sensitive analysis of OCPs in real water samples and four of the six analytes were detected from the rainwater and the lake water samples.     

Electrochemical hydrogen evolution efficiently boosted by interfacial charge redistribution in Ru/MoSe2 embedded mesoporous hollow carbon spheres

The strong metal-support interaction inducing combined effect plays a crucial role in the catalysis reaction. Herein, we revealed that the combined advantages of MoSe₂, Ru, and hollow carbon spheres in the form of Ru nanoparticles(NPs) anchored on a two-dimensionally ordered MoSe₂ nanosheet-embedded mesoporous hollow carbon spheres surface(Ru/MoSe₂@MHCS) for the largely boosted hydrogen evolution reaction(HER) performance. The combined advantages from the conduct...     

A facile one-pot interfacial synthesis of Pt nanoparticles/polypyrrole composites and their application for non-enzymatic sensing hydrogen peroxide

Pt nanoparticles (PtNPs)/polypyrole (PPy) composites were successfully prepared through a facile one-pot interfacial polymerization of pyrrole by using H₂PtCl₆ as the oxidant for the first time. The as-prepared PPy was granular particles with particle size within a few hundred nanometers, on which PtNPs (1.7–3.5) nm were homogeneously dispersed. The PtNPs/PPy composites displayed excellent electrocatalytic activity toward redox of H₂O₂. The non-enzyme sensor constructed with PtNPs/PPy composites displayed good sensing ability toward H₂O₂ at ?0.1 V with a significantly high sensitivity of 6056 μAmM^?1cm^?2 and a low detection limit of 1.8 μM (S/N = 3).     

Fabrication of synthetic opals composed of mesoporous SnO2 spheres with an anodization-assisted double template process

Synthetic opals composed of mesoporous SnO₂ spheres were successfully fabricated from anodization of Sn opals, double templated from polystyrene opals. The mesoporous SnO₂ spheres were 440 nm in diameter containing mesopores of 20–40 nm. The resultant mesoporous SnO₂ opals possessed a high specific surface area of 196 m²/g and a grain size of 12 nm as estimated from XRD patterns. Such a hierarchical structure of SnO₂ is a promising candidate for applications in gas sensors, catalysts, and electrode materials since the regularity of the sub-micron opal structure eases transfers of relevant chemical species within the structure while the mesoporosity of the constituent SnO₂ spheres offers sufficient functioning surfaces for targeted applications.     

晶相组成可调的高活性可见光应答型二氧化钛纳米复合光催化材料的制备

采用新的化学溶液法,通过不同体积的钛酸四异丙酯的2-乙二醇单乙醚溶液与一定浓度的H₂O₂水溶液直接反应并对生成的钛过氧化配合物进行焙烧,制备了一系列TiO₂光催化剂. 表征发现,所得TiO₂样品为金红石和锐钛矿的纳米复合晶体,改变2-乙二醇单乙醚的体积可实现金红石相比例在0~96%广范围的调变.与商业二氧化钛P-25相比,所得的TiO₂紫外-可见光吸收谱出现明显红移,间隙能降低, 在可见光照射下,该样品对亚甲基蓝有良好的降解活性. 当2-乙二醇单乙醚的添加量为5 ml时,所得样品体相中金红石相比例接近50%,其光催化活性和吸附性能最好,可分别是P-25的3倍和5倍. 拉曼光谱结合X射线衍射等表征结果表明,该样品的表面仅含少量的金红石相. TiO₂纳米复合晶表面晶相的组成和分布对其光催化降解亚甲基蓝的活性及其吸附能力有直接的影响. 另外,TiO₂纳米复合晶的缺陷浓度也是增强其光吸收能力,提高其可见光光催化活性的原因之一.     

Characterization and photocatalytic properties of silver and silver chloride doped TiO2 hollow nanoparticles

Using polystyrene（PSt） particles as template,PSt/TiO₂ composite particles with AgCl incorporation were prepared through hydrolysis of tetrabutyl titanate in the presence of AgNO₃ and NaCl.AgCl doped TiO₂ hollow particles were successfully prepared with the PSt/TiO₂ composite microspheres pretreated at 180℃followed by calcination.The morphology of PSt/TiO₂ particles and the crystal structures of the AgCl doped TiO₂ hollow particles were characterized.The photocatalytic activity of the doped TiO₂ hollow particles in degradation of Rhodamine B was tested under UV and visible lights and compared to that with Ag doped TiO₂ particles.The results showed that TiO₂ hollow particles,either doped with Ag or AgCl,demonstrated higher photocatalytic activity than the pure TiO₂ particles.This enhancement in photocatalytic activity was more significant with AgCl doped TiO₂ than that with Ag doped,and more distinct when the degradation was done under visible light than that under LTV light.     

Synthesis and visible light photocatalysis of Fe-doped TiO2 mesoporous layers deposited on hollow glass microbeads

Nano-composite of Fe-doped anatase TiO₂ nanocrystals loaded on the hollow glass microbeads was prepared by co-thermal hydrolysis deposition and calcining treatment. The adherence of TiO₂ mesoporous layers to the surfaces of hollow glass microbeads prevented the aggregation of TiO₂ nanoparticles and benefited to their catalytic activity. The doping of Fe ions makes the absorption edge of the TiO₂ based nano-composite red-shifted into the visible region. An effective photodegradation of the methyl orange aqueous solution was achieved under visible light (λ>420 nm) irradiation, revealing the potential applicability of such nano-composite in some industry fields, such as air and water purifications.     

Micro- and nano-scale hollow TiO2 fibers by coaxial electrospinning: Preparation and gas sensing

We report the preparation of micro- and nano-scale hollow TiO₂ fibers using a coaxial electrospinning technique and their gas sensing properties in terms of CO. The diameter of hollow TiO₂ fibers can be controlled from 200 nm to several micrometers by changing the viscosity of electrospinning solutions. Lower viscosities produce slim hollow nanofibers. In contrast, fat hollow microfibers are obtained in the case of higher viscosities. A simple mathematical expression is presented to predict the change in diameter of hollow TiO₂ fibers as a function of viscosity. The successful control over the diameter of hollow TiO₂ fibers is expected to bring extensive applications. To test a potential use of hollow TiO₂ fibers in chemical gas sensors, their sensing properties to CO are investigated at room temperature.     

Catalytic properties of TiO2 in wood delignification by acetic acid - hydrogen peroxide mixture

Catalytic properties of solid TiO₂ suspended in a mixture of acetic acid with hydrogen peroxide were studied in the delignification of aspen, birch and abies woods at varying the pulping conditions.     

Preparation and characterization of mesoporous TiO2-CeO2 nanopowders respond to visible wavelength

Mesoporous TiO₂-CeO₂ nanopowders responding to visible wavelength were synthesized by using a surfactant assisted sol-gel technique. They were obtained using metal alkoxide precursors modified with acetylacetone (ACA) and laurylamine hydrochloride (LAHC) as surfactant. The samples were characterized by XRD, nitrogen adsorption isotherm, SEM, TEM, and selected area electron diffraction (SAED), respectively. The 95 mol% TiO₂-5 mol% CeO₂ system yielded single anatase phase, however, further addition of the CeO₂ formed cubic CeO₂ structure while anatase TiO₂ decreased. Additions of 5 and 10 mol% CeO₂ increased the surface area, but those of 25, 50, and 75 mol% CeO₂ did not affect it very much. By using this mixed metal oxides system, TiO₂ can be modified to respond to the visible wavelength. The mixed metal oxides had catalytic activity (evaluating the formation rate of I₃⁻) about 2-3 times higher than pure CeO₂, while nanosize anatase type TiO₂ materials had no catalytic activity under visible light. The catalytic activity was almost proportional to the specific surface area. The formation rate of I₃⁻ was much improved by changing the calcination temperature and calcination period. Highest catalytic activity in this study was obtained for the 50 mol% TiO₂-50 mol% CeO₂ nanopowders calcined at 250 °C for 24 h.     

In situ radical polymerization of methyl methacrylate in a solution of surface modified TiO2 and nanoparticles

Surface modified TiO₂ nanoparticles dissolved in toluene were encapsulated in PMMA by in situ radical polymerization of methyl methacrylate initiated by 2,2′-azobisisobutyronitrile. The surface modification of the TiO₂ nanoparticles (average diameter of 4.5 nm) was achieved by the formation of a charge transfer complex between TiO₂ nanoparticles and 6-palmitate ascorbic acid. The surface modified TiO₂/nanoparticles were characterized using UV−Vis and FTIR spectroscopy, while the obtained polymer nanocomposites were characterized using reflection and ¹H NMR spectroscopy, as well as gel permeation chromatography. The influence of the TiO₂ nanoparticles on the thermal properties of the PMMA matrix was investigated using thermo-gravimetric analysis and differential scanning calorimetry. The glass transition temperature of the polymer was not influenced by the presence of the nanoparticles while the thermal stability was significantly improved.     

Graphene enhanced electrochemiluminescence of CdS nanocrystal for H2O2 sensing

Graphene-CdS (G-CdS) nanocomposites were successfully prepared by CdS nanocrystals (CdS NCs) formed in situ on the surface of graphene sheets, using graphene oxide (GO) sheets with rich negatively charged carboxylic acid groups as starting materials. Compared with pure CdS NCs, the presence of the graphene doped in G-CdS nanocomposites could facilitate the electrochemical redox process of CdS NCs; further, the as-prepared G-CdS nanocomposite can react with H₂O₂ to generate strong and stable electrochemiluminescent (ECL) emission, which not only enhances its ECL intensity by about 4.3-fold but also decreases its onset potential for about 320 mV. The as-prepared solid-state ECL H₂O₂ sensor shows acceptable linear response from 5 μM up to 1 mM with a detection limit of 1.7 μM (S/N = 3). The ECL H₂O₂ sensor exhibits excellent reproducibility and long-term stability. Such a property would promote the potential application of the graphene as enhanced materials in fabricating sensors for chemical and biochemical analysis.     

A one-pot method to prepare the carbene complex [TpRhCl2(CHNiPr2)] from [TpRh(CO)2], CHCl3, and NHiPr2

The complex [Tp^Me₂,ClRh(CO)₂] reacts with chloroform to give quantitatively the rhodium(III) complex [Tp^Me₂,ClRhCl(CHCl₂)(CO)] resulting from the oxidative addition of a C-Cl bond. Further reaction with diisopropylamine gives the aminocarbene complex [Tp^Me₂,ClRhCl₂(CHNiPr₂)], whose X-ray crystal structure has been solved. Addition of an excess of diisopropylamine to [Tp^Me₂,ClRh(CO)₂] in chloroform provides directly [Tp^Me₂,ClRhCl₂(CHNiPr₂)].