Miaomiao Ye

Magnetically Recoverable Core–Shell Nanocomposites with Enhanced Photocatalytic Activity

Core-shell structured Fe(3)O(4)/SiO(2)/TiO(2) nanocomposites with enhanced photocatalytic activity that are capable of fast magnetic separation have been successfully synthesized by combining two steps of a sol-gel process with calcination. The as-obtained core-shell structure is composed of a central magnetite core with a strong response to external fields, an interlayer of SiO(2), and an outer layer of TiO(2) nanocrystals with a tunable average size. The convenient control over the size and crystallinity of the TiO(2) nanocatalysts makes it possible to achieve higher photocatalytic efficiency than that of commercial photocatalyst Degussa P25. The photocatalytic activity increases as the thickness of the TiO(2) nanocrystal shell decreases. The presence of SiO(2) interlayer helps to enhance the photocatalytic efficiency of the TiO(2) nanocrystal shell as well as the chemical and thermal stability of Fe(3)O(4) core. In addition, the TiO(2) nanocrystals strongly adhere to the magnetic supports through covalent bonds. We demonstrate that this photocatalyst can be easily recycled by applying an external magnetic field while maintaining their photocatalytic activity during at least eighteen cycles of use.

Electron-beam-assisted superplastic shaping of nanoscale amorphous silica

At room temperature, glasses are known to be brittle and fracture upon deformation. Zheng et al. show that, by exposing amorphous silica nanostructures to a low-intensity electron beam, it is possible to achieve dramatic shape changes, including a superplastic elongation of 200% for nanowires.

Self-assembled TiO2 nanocrystal clusters for selective enrichment of intact phosphorylated proteins.

Mesoporous oxides have been used for selective separation and adsorption of biomolecules. Inorganic oxide materials such as silica can be synthesized into highly ordered mesoporous structures featuring high in-pore surface areas, narrow pore size distributions, adjustable pore sizes, and modifiable surface properties. 12–15] Such unique properties favor the selective enrichment of proteins or peptides based on the size-exclusion mechanism. Classic mesoporous silica structures with narrow pore size distributions, such as MCM41 and SBA-15, have been used to selectively enrich peptides from human plasma and exclude other proteins according to an accurate molecular weight (MW) cutoff. However, this type of enrichment method is limited mainly to silica and alumina because currently it is still difficult to extend broadly the surfactant-templating method to the synthesis of mesoporous structures of many other oxides in a convenient, controllable, and scalable manner (although the literature does contain some relevant procedures). The limited choice of materials makes it difficult to further enhance the selectivity by taking advantage of both the size-exclusion effect and the specific binding between many oxides and proteins or peptides. Herein, we propose a general strategy for the fabrication of novel porous nanostructured materials for the efficient separation of biomolecules such as proteins, peptides, and DNA. Briefly, nanoparticles of various nanostructured materials with uniform sizes and shapes are firstly synthesized and then self-assembled into three-dimensional submicrometer clusters containing uniform mesoscale pores. Thanks to rapid progress in colloidal nanostructure synthesis, a great number of materials can now be routinely produced in the form of nanoparticles with excellent control over size, shape, and surface properties, making it possible to utilize specific material–protein/peptide interactions to enhance the selectivity in protein/peptide enrichment. 24] Additionally, size exclusion can also be achieved by controlling the dimensions of the pores produced by the packing of constituent nanoparticles, allowing selective enrichment of biomolecules based on their sizes. The outer surface of each cluster can be made highly hydrophilic, so that nonspecific binding of many hydrophobic proteins/peptides can be avoided. The selfassembly process also brings the convenience of incorporation of multiple components into the clusters to further facilitate separation and detection. For example, the incorporation of fluorescent nanocrystals, such as quantum dots, during the assembly process may produce multifunctional microspheres that are able not only to selectively enrich but also to easily identify the targeted biomolecules. Also, adding superparamagnetic iron oxide nanocrystals to the clusters allows their efficient removal from the analyte solution after selective adsorption by using an external magnetic field. As an example, we report herein the fabrication of mesoporous TiO2 nanocrystal clusters and demonstrate their use for selective enrichment of intact phosphorylated proteins from complex biological samples by taking advantage of both the specific affinity offered by the metal oxide and the sizeexclusion mechanism enabled by the mesoporous structure. The efficient separation and accurate analysis of phosphorylated proteins are highly demanded in biomedical applications because phosphorylation of proteins is a key event in most cellular processes, including signal transduction, gene expression, cell cycle, cytoskeletal regulation, and apoptosis. 28] The combination of peptide mapping by matrixassisted laser desorption/ionization time-of-flight mass spectrometry (MALDI–TOF MS) with the methods of phosphopeptide enrichment represents an efficient tool for the characterization of the phosphorylated proteins after digestion. The most widely used approaches for specific enrichment of phosphopeptides are immobilized metal affinity chromatography (IMAC) and metal oxide affinity chromatography (MOAC). 29–32] In IMAC, phosphopeptides can be selectively retained because of the affinity of metal ions for the phosphate groups, whereas in MOAC, the specific adsorption results from bridging bidentate bindings formed between the phosphate anions and the surface of a metal oxide, such as TiO2, ZrO2, Fe2O3, and Al2O3. [33] However, these techniques can provide information about the original phosphorylated proteins only indirectly, and direct enrichment of phosphorylated proteins by IMAC or MOAC is rarely reported because of the low adsorption efficiency and significant losses of phosphorylated proteins during the washing steps. 35] Therefore, despite the intense interest in studying phosphorylation events, the direct enrichment of intact phosphorylated proteins remains a technical challenge. In this Communication, we describe the selective enrichment of phosphorylated proteins from protein mixtures by using mesoporous colloids of TiO2 fabricated through self-assembly [*] Z. Lu, M. Ye, N. Li, Prof. W. Zhong, Prof. Y. Yin Department of Chemistry, University of California Riverside, CA 92521 (USA) Fax: (+ 1)951-827-4713 E-mail: yadong.yin@ucr.edu Homepage: http://faculty.ucr.edu/~ yadongy/

Self-assembly of superparamagnetic magnetite particles into peapod-like structures and their application in optical modulation

Superparamagnetic Fe3O4/SiO2/TiO2 peapod-like nanostructures have been successfully synthesized by using Fe3O4/SiO2 core/shell particles as building blocks and TiO2 as the adhesive without the need of any hard or soft templates. The fabrication process involves chaining the Fe3O4/SiO2 cores during magnetic stirring and subsequent fixing of the chain structure during TiO2 coating. The number of Fe3O4/SiO2 cores arranged linearly in the chains could be effectively controlled by tuning the amount of titanium precursor or the magnetic stirring rate. The double layer coating of SiO2 and TiO2 enhances thermal and chemical stability of the nanopeapods, and the one-dimensional chain structure produces interesting properties that enable applications not possible with conventional magnetite materials. As a demonstration, we show here the use of these superparamagnetic peapod-like nanostructures for low-frequency optical modulation.

Nanocrystalline TiO2-Catalyzed Photoreversible Color Switching

We report a novel photoreversible color switching system based on the photocatalytic activity of TiO2 nanocrystals and the redox-driven color switching property of methylene blue (MB). This system rapidly changes from blue to colorless under UV irradiation and recovers its original blue color under visible light irradiation. We have identified four major competing reactions that contribute to the photoreversible switching, among which two are dominant: the decoloration process is mainly driven by the reduction of MB to leuco MB by photogenerated electrons from TiO2 nanocrystals under UV irradiation, and the recoloration process operates by the TiO2-induced self-catalyzed oxidation of LMB under visible irradiation. Compared with the conventional color switching systems based on photoisomerization of chromophores, our system has not only low toxicity but also significantly improved switching rate and cycling performance. It is envisioned that this photoreversible system may promise unique opportunities for many light-driven actuating or color switching applications.

Fabrication of a cross-linked supramolecular polymer on the basis of cucurbit[8]uril-based host–guest recognition with tunable AIE behaviors

A photoresponsive ternary host–guest molecular recognition motif between cucurbit[8]uril (CB[8]), the 1,1-dimethyl-4,4-bipyridinium dication (DMV2+) and an azobenzene derivative (trans-2) in water was applied in this paper to construct a cross-linked supramolecular polymer. Various characterization methods were adopted to prove the formation of the polymer, such as 1H NMR, DOSY, specific viscosity measurements, and fluorescence spectroscopy. Additionally, the tetraphenylethylene moiety was incorporated into this system and the aggregation induced emission (AIE) properties of the supramolecular polymer were also investigated.

Magnetically recyclable self-assembled thin films for highly efficient water evaporation by interfacial solar heating

Magnetic microspheres including Fe3O4, MnFe2O4, ZnFe2O4, and CoFe2O4 have been synthesized via a simple solvothermal method followed by surface hydrophobization with 1H,1H,2H,2H-perfluorooctyltrichlorosilane. The hydrophobic magnetic microspheres can self-assemble into a thin film under simulated solar light irradiation and float on the surface of water. The formed film was used as photothermal material for water evaporation based on a new concept of interfacial solar heating. The water evaporation efficiency was significantly enhanced by the Fe3O4 thin film, and is about 1.4, 1.7 and 2.2 times higher than that without the formation of a Fe3O4 thin film, Fe3O4 uniformly dispersed in water, and water evaporation itself, respectively. The temperature gradient distributions from the surface to the bottom of the water directly demonstrated the advantage of interfacial solar heating for water evaporation. We believe that the water evaporation efficiency with the magnetic thin film is mainly due to the high light absorption, rapid heat transfer and good solid–liquid adhesion performance. In addition, the hydrophobic magnetic microspheres also have advantages over other reported photothermal materials due to their easy recycling, non-toxicity, low dose, and low cost.

Mesoporous titanate-based cation exchanger for efficient removal of metal cations

A mesoporous titanate-based Na+-exchanger with high surface area and tunable pore size has been successfully synthesized by using NaOH-etched silica mesoporous microspheres as templates. Templating against porous silica microspheres followed by etching the templates with base produces amorphous sodium titanate spheres with controllable porosity. The resultant Na+ exchangers have BET surface areas as high as 386.47 m2 g−1 and average pore sizes tunable from ∼5 nm to 30 nm. Adsorption experiments indicate that the as-obtained Na+-exchangers possess excellent adsorption capacity (up to 2.90 mmol g−1) for ten metal cations in low concentration ranges without any selectivity due to fast ion exchange between Na+ and the target cations, while at high concentrations, the selectivity sequence follows the order of Hg2+ < Co2+ < Cd2+ < Cu2+ < Ni2+ < Mn2+ < Zn2+ < Sn4+ < Cr3+ < Fe3+.

Adsorption behavior and mechanism of ibuprofen onto BiOCl microspheres with exposed {001} facets.

BiOCl microspheres with exposed {001} facets have been synthesized through a simple solvothermal method. The adsorption and photocatalytic activities of BiOCl microspheres were evaluated by removal of ibuprofen (IBP) as the model reaction. Parameters including IBP concentration, BiOCl dosage, and inorganic ions were investigated to reveal the role of adsorption in BiOCl-based photocatalysis. We found that the high IBP removal rate by BiOCl is not due to photocatalytic oxidation but to surface adsorption. The combination of ICP/MS, IC, XPS, and FT-IR results directly proved that anion exchange between dissociated IBP and Cl accompanied by the formation of surface complex (O–Bi–OOC–C12H17) onto the BiOCl surface is the main adsorption mechanism. In addition, we also demonstrated that organic compounds with carboxyl group (–COOH) such as diclofenac, benzoic acid, and p-phthalic acid can be adsorbed by BiOCl while organic compounds without carboxyl group such as carbamazepine, nitrobenzene, and p-chloronitrobenzene cannot be adsorbed. We believe that the BiOCl adsorption behavior and mechanism should be considered when discussing its photocatalytic mechanism.

The consistency of product design and brand image

Through the analysis of consumers, products and brand image, this paper intercept product design and brand image, analysis brand image by understanding consumer motivation, product design processes and brand development, summarize design methods suitable for brand products, so as to provide some inspiration and ideas for product design study.