Hollow Carbon Nanospheres with Tunable Hierarchical Pores for Drug,Gene, and Photothermal Synergistic Treatment

Design and synthesis of porous and hollow carbon spheres have attracted considerable interest in the past decade due to their superior physicochemical properties and widespread applications. However, it is still a big challenge to achieve controllable synthesis of hollow carbon nanospheres with center‐radial large mesopores in the shells and inner surface roughness. Herein, porous hollow carbon nanospheres (PHCNs) are successfully synthesized with tunable center‐radial mesopore channels in the shells and crater‐like inner surfaces by employing dendrimer‐like mesoporous silica nanospheres (DMSNs) as hard templates. Compared with conventional mesoporous nanospheres, DMSN templates not only result in the formation of center‐radial large mesopores in the shells, but also produce a crater‐like inner surface. PHCNs can be tuned from open center‐radial mesoporous shells to relatively closed microporous shells. After functionalization with polyethyleneimine (PEI) and poly(ethylene glycol) (PEG), PHCNs not only have negligible cytotoxicity, excellent photothermal property, and high coloading capacity of 482 µg of doxorubicin and 44 µg of siRNA per mg, but can also efficiently deliver these substances into cells, thus displaying enhanced cancer cell killing capacity by triple‐combination therapy.     

Fabrication of hollow polyelectrolyte nanospheres via surface-initiated atom transfer radical polymerization

Novel polyelectrolyte-grafted core-shell organic/inorganic hybrid nanospheres which possess hard backbone of silica nanoparticles and soft shell of cross-linked poly(ionic liquids) (PILs) have been synthesized via a surface-initiated atom transfer radical polymerization (SI-ATRP). After removal of the core templates of the core-shell nanospheres, nearly monodispersed hollow polyelectrolyte nanospheres were obtained. Various characterization techniques including FT-IR, XPS, and TEM were used to characterize the resulting core-shell and hollow polyelectrolyte nanospheres. The results showed that the hollow nanosphere has a hollow core of an average diameter of ca. 200 nm with a shell thickness of ca. 25 nm. The obtained hollow polyelectrolyte nanospheres could be applied in release-control systems.     

Facile fabrication of wurtzite ZnS hollow nanospheres using polystyrene spheres as templates

Wurtzite ZnS hollow nanospheres were fabricated using PS nanospheres as templates by a facile method at relative low temperature. The prepared hollow nanospheres are uniform, monodispersed with homogeneous size of around 480 nm, and spherical shape. The shell thickness of these hollow nanospheres is about 60 nm, and composed of many wurtzite ZnS nanocrystals with the size of 8 nm. The definite shape, thick and denser shell with higher specific surface area reveals that these hollow nanospheres will find a great deal of potential applications in environment protection, photocatalysis and so on.     

Macroscale Colloidal Noble Metal Nanocrystal Arrays and Their Refractive Index‐Based Sensing Characteristics

Colloidal noble metal nanocrystals are promising for a large number of optical and biotechnological applications. Many practical applications require the formation of large‐area, high‐density, and uniformly distributed metal nanocrystal arrays on various substrates, to overcome the limitations brought by the instability of colloidal metal nanocrystal solutions and the high cost of single‐particle spectroscopy characterizations. A method is developed for directly depositing colloidal metal nanocrystals, including Au nanospheres, Au nanorods, Au nanobipyramids, and (Au core)/(Ag shell) nanorods, from their solutions onto different substrates. The resultant nanocrystal arrays are relatively uniform and dense, with the peak extinction value of a single layer reaching 0.3. Their areas are up to 10 cm by 10 cm and can be further increased if larger‐size containers are utilized. The refractive index sensitivities are studied for Au nanorod arrays supported on glass slides, mesoporous silica and titania films, and capped with different molecules. Au nanorods deposited on mesoporous titania films are found to exhibit the highest index sensitivities, comparable to those of the same nanorod sample in solutions. It is expected that this approach will greatly facilitate plasmonic applications that require large‐area arrays of noble metal nanocrystals.     

中空二氧化硅纳米球的制备与应用研究进展

中空二氧化硅纳米球是一种具有单个空腔或多个空腔,直径在纳米级的新型结构材料。目前已开发出多种中空二氧化硅纳米球的制备方法,不同制备方法各具差异性。中空二氧化硅纳米球在医学、保温隔热和光学等多领域中有广泛应用。对模板法、喷雾干燥法、选择性刻蚀法等多种中空二氧化硅纳米球的制备方法及其特点进行了梳理和分析,评价了其优缺点,并探讨了中空二氧化硅纳米球的应用进展。     

ZnS包覆 SiO2核壳和空腔结构纳米球制备研究

ZnS包覆SiO2三维核壳结构或空腔结构纳米球可用于光子晶体的组装.本实验采用层层自组装法,利用二氧化硅模板表面的静电作用吸附纳米晶粒子,生成纳米晶包覆层,制备核壳结构的SiO2@ZnS和SiO2@ZnS：Mn^2＋纳米球.控制氢氟酸对二氧化硅的蚀刻程度,制备了空腔型硫化锌纳米球.采用XRD、UV、PL、TEM、SEM、AFM等测试手段对核壳结构和空腔型硫化锌纳米球进行了表征.结果表明ZnS纳米晶包覆SiO2后,在其表面形成了包裹紧密、形貌规整、粒径均一的ZnS壳层;经5%氢氟酸蚀刻得到的空腔纳米球结构完好、厚度均匀.     

BiOCl nano/microstructures on substrates: Synthesis and photocatalytic properties

Bismuth oxycholoride (BiOCl) nano/microstructures, including flake and nanowire arrays, were successfully synthesized on Anodic Aluminum Oxide (AAO) templates via sol-gel combined with the vacuum air-extraction method. The flakes are almost vertically aligned on the surface, but nanowires at a lower sol concentration are aligned along the channels. A possible formation mechanism is proposed. Furthermore, the photocatalytic activity of the BiOCl nano/microstructures is investigated by photocatalytic decomposition of Rhodamine B (Rh B) dye under UV-Visible light irradiation. Compared with the BiOCl flake-like film on the glass substrate, where the flakes are horizontally oriented on the surface, the vertically aligned flake and nanowire arrays on AAO templates, have higher photocatalytic efficiency.     

A controlled formation of cage-like nanoporous hollow silica microspheres

Cage-like hollow silica microspheres composed of mesoporous silica nanoparticles and macroporous interparticle voids were fabricated via the latex-surfactant dual templates route, simply by controlling the surfactant additions below its critical micelle concentration. The surface area, pore volume increase, and both the mesopore and macropore sizes decrease with the increase in surfactant amount. The surfactant cations preferentially assemble with negatively charged silica species generated by the hydrolysis and condensation of tetraethyl orthosilicate to form composite silica-surfactant nanoparticles. The electrostatic repulsion between the silica-surfactant composite nanoparticles and negatively charged polystyrene (PS) beads is smaller than that between surfactant-free silica and PS, favoring the deposition of composite nanoparticles on the surface of PS template. In the meantime, the deposited nanoparticles also have reduced repulsion from their neighbors, favoring their bridging to form silica shells. The more the surfactant is used, the less the repulsion exists among the composite particles and the smaller the interparticle macroporous voids are.     

Vertically aligned single crystal TiO2 nanowire arrays grown directly on transparent conducting oxide coated glass: synthesis details and applications

Single-crystal one-dimensional (1D) semiconductor architectures are important in materials-based applications requiring a large surface area, morphological control, and superior charge transport. Titania has widespread utility in applications including photocatalysis, photochromism, photovoltaics, and gas sensors. While considerable efforts have focused on the preparation of 1D TiO2, no methods have been available to grow crystalline nanowire arrays directly onto transparent conducting oxide (TCO) substrates, greatly limiting the performance of TiO2 photoelectrochemical devices. Herein, we present a straightforward low temperature method to prepare single crystal rutile TiO2 nanowire arrays up to 5 microm long on TCO glass via a non-polar solvent/hydrophilic substrate interfacial reaction under mild hydrothermal conditions. The as-prepared densely packed nanowires grow vertically oriented from the TCO glass substrate along the (110) crystal plane with a preferred (001) orientation. In a dye sensitized solar cell, N719 dye, using TiO2 nanowire arrays 2-3 microm long we achieve an AM 1.5 photoconversion efficiency of 5.02%.     

Mn掺杂ZnO囊泡结构的制备

通过两步或三步法分别制备两层或三层结构的碳球模板,在溶液中的Zn离子和Mn离子在模板上吸附后再进行煅烧.TEM及SEM显示,煅烧后得到完全复制碳膜板结构的多层Mn掺杂ZnO囊泡.EDS显示Mn在ZnO中的掺杂含量约为1％.样品具有室温铁磁性,饱和磁化率(Ms)及矫顽磁场(Hc)分别为0.032A·m²/kg及0.781kA/m.这种Mn掺杂ZnO纳米囊泡结构使新奇的囊泡结构和ZnO的磁性性能得到了完美的结合.     

TiO2 array films with controllable morphology

Titanium dioxide films with large-area 2D ordered pore structure were prepared on glass substrate via a sol dip-coating latex template method. By simply controlling the concentration of the precursor sol, TiO2 array films with different morphologies, such as hollow sphere shell, bowl, pot, and ring arrays were obtained. Such films have large-scale periodic feature and large specific areas, which is promising to be useful in the optical, gas-sensing, catalysis applications.     

Large-area pattern transfer of metallic nanostructures on glass substrates via interference lithography

In this paper, we report a simple and effective nanofabrication method for the pattern transfer of metallic nanostructures over a large surface area on a glass substrate. Photoresist (PR) nano-patterns, defined by laser interference lithography, are used as template structures where a metal film of controlled thickness is directly deposited and then transferred onto a glass substrate by the sacrificial etching of the PR inter-layer. The laser interference lithography, capable of creating periodic nano-patterns with good control of their dimensions and shapes over a relatively large area, allows the wafer-scale pattern transfer of metallic nanostructures in a very convenient way. By using the approach, we have successfully fabricated on a glass substrate uniform arrays of hole, grating, and pillar patterns of Ti, Al, and Au in varying pattern periodicities (200 nm-1 μm) over a surface area of up to several cm(2) with little mechanical crack and delamination. Such robust metallic nanostructures defined well on a transparent glass substrate with large pattern coverage will lead to advanced scientific and engineering applications such as microfluidics and nanophotonics.     

通过粒子辅助水滴模板法制备超疏水材料

利用水滴模板法成功制备出孔径可控的具有结构规则的聚合物多孔膜,并以所制备多孔膜为模板利用反向复刻法复制孔洞阵列结构,得到具有微米级突起阵列结构的聚二甲基硅氧烷(PDMS)膜片,然后将事先排布好的二氧化硅微球阵列通过热压印法转移到具有微米级突起结构的PDMS膜片上,然后成功制备出具有微纳米复合突起结构的膜片。通过对具有不同突起结构组合的PDMS膜片进行接触角测试发现,膜片的接触角随着其表面粗糙程度的增大而增大,即具有微纳复合结构膜片接触角((150.7±3.2)°)最大,达到了超疏水的效果;无突起结构膜片的接触角((108.9±3.1)°)最小;而仅具有微米级结构膜片的接触角((134.6±1.0)°)居中,这符合目前已知的物质表面浸润性与其表面粗糙度的关系。另外,经测试,具有微纳复合结构的膜片接触角最大达到155°,同时具有非常大的滚动角,使得这种膜片材料具备了粘性超疏水的性能,而这种特殊浸润表面性质可以在液体无损传输、生化分离等领域拥有巨大的应用前景。     

Solution‐Processable Photonic Inks of Mie‐Resonant Hollow Carbon–Silica Nanospheres

Hollow carbon–silica nanospheres that exhibit angle‐independent structural color with high saturation and minimal absorption are made. Through scattering calculations, it is shown that the structural color arises from Mie resonances that are tuned precisely by varying the thickness of the shells. Since the color does not depend on the spatial arrangement of the particles, the coloration is angle independent and vibrant in powders and liquid suspensions. These properties make hollow carbon–silica nanospheres ideal for applications, and their potential in making flexible, angle‐independent films and 3D printed films is explored.     

Preparation and characterization of acrylated-SiO2@TiO2 hollow hybrid nanospheres

Novel inorganic-organic hybrid hollow nanospheres, acrylated SiO2 and SiO2@TiO2, were synthesized via a sol-gel polymerization, using crown-appended sugar gelator 1 as an organic template for the unique nanospherical structures in demand for a fast expanding area in nanomaterial research. In this work, hollow SiO2 nanospheres were obtained by a simple sol-gel method followed by calcination and rather rough TiO2 nanolayers were coated onto the highly dispersed surface of SiO2 nanospheres and further copolymerization of MPA on the surface of SiO2 and SiO2@TiO2 nanosphseres was successfully conducted. The morphological properties of those hollow nanospheres were characterized by TEM, SEM and powder-XRD. Furthermore, the physical and chemical properties of the synthesized nanocomposites were characterized by the analysis of EDX, FT-IR, TGA and ESCA.     

Surface-enhanced Raman spectroscopy studies of orderly arranged silica nanospheres-synthesis,characterization and dye detection

Silica nanospheres have been explored much for drug delivery, photocatalysis, sensors and energy storage applications. It also acts as a template for Surface-Enhanced Raman Spectroscopy (SERS) substrates. Uniform nanostructures at low cost with high reproducibility are the major challenges in SERS substrate fabrication. In the present work, silica nanospheres were synthesized using stober method and deposited on to glass slides using Vertical deposition techniques. Different size/thickness of Silver (Ag) nanoparticles were deposited onto silica thin films using sputter deposition technique. The monodispersity of silica nanospheres and size of silver nanoparticles (10 nm, 20 nm and 30 nm) were confirmed by FESEM analysis. The structural properties were confirmed through XRD. UV–Vis analysis revealed that the plasmonic properties of Ag@SiO₂ give high surface plasmons for 30 nm thickness of silver. The binding energy of Ag@SiO₂ confirmed through XPS spectrum. The fabricated SERS substrates were used to detect Rhodamine 6G (R6G), Methylene blue (MB), Methylene violet (MV) and Methyl orange dyes as an analyte molecule with a limit of detection at about 10^?11 mol/L. The addition of SiO₂ nanospheres decreases the Ag oxidation rate and increases their stability. The maximum enhancement factor (1.5?×?10⁷) achieved for 30nm thickness of Ag@SiO₂. The results and technique establish the potential applications and reproducible SERS substrate.

     

Fabrication of hollow silica spheres and their application in polyacrylate film forming agent

Polystyrene (PS)/silica core/shell spheres were fabricated using mono-dispersed PS as templates by hydrolysis and condensation of two different silica precursors. The PS cores of PS/silica core/shell spheres were dissolved subsequently in the tetrahydrofuran medium to form mono-dispersed hollow silica spheres. The structures and morphologies of hollow silica spheres were characterized by scanning electron microscopy and transmission electron microscopy. Then, polyacrylate/hollow silica composite film forming agents were prepared via physical blending of polyacrylate and two different hollow silica spheres, and the water vapor permeability of their films were compared. The results showed that the structure of hollow silica spheres were very typical and obvious. The silica shell was continuous and uniform using tetraethylorthosilicate as precursor, which was accumulated by many silica seeds with size of 10–20 nm, and the thickness of silica shell was about 16.7 nm. However, the hollow silica spheres using tetraethylorthosilicate and vinyl triethoxysilane as precursors had mesoporous structure in the shell. The introduction of hollow silica spheres could significantly improve the water vapor permeability of polyacrylate film. At last, a possible mechanism for the formation of hollow silica spheres was proposed and the process of water vapor through polyacrylate/hollow silica composite films was modeled.     

Synthesis of hollow silica microparticles from bacterial templates

Hollow inorganic particles have attracted great interest because of their unique physicochemical properties. In this study, hollow silica microparticles were prepared using a rod-shaped gram-negative bacterium, Escherichia coli (KP7600), as a biological template. Silica nanoparticles were generated in addition to coated biological templates when the reaction rate was increased, so control of reaction rate is important for coating silica smoothly onto the bacterial surface. Silica coating was also carried out using the fixed cells (with and without internal water) using glutaraldehyde as templates. When the fixed cells without internal water were used as templates, no rod-shaped particles were observed after calcination of the synthesized particles. By contrast, silica hollow particles were formed using the fixed cells with internal water as templates. This means that the internal water inside biological cells acts as an initiator for hydrolysis of tetraethyl orthosilicate (TEOS) and results in the formation of smooth silica shell surface and indicates that the use of dry cultured bacteria templates is not required. Thus, there is a significant benefit in using gram-negative bacteria as templates for producing hollow silica microparticles, compared with the method using dried gram-positive bacteria templates.     

Development of a simple method for the preparation of novel egg-shell type Pt catalysts using hollow silica nanostructures as supporting precursors

A simple method for the preparation of novel egg-shell type platinum catalysts was developed and achieved by utilizing unique hollow silica nanostructures, i.e., hollow silica nanospheres and nanotubes, as supports. The observation by transmission electron microscopy indicated that the well-dispersed hollow silica supported Pt catalysts with a Pt particle diameter of 8-14 nm can be successfully prepared by wet impregnation process and heat treatment. The Pt-loaded hollow silica nanostructures were also characterized by inductively coupled plasma, X-ray diffraction, specific surface area, Fourier transformation infrared spectroscopy, X-ray photoelectron spectroscopy and energy dispersive spectroscopy. It was thus demonstrated that a higher Pt loading amount (0.392%) could be obtained under the same conditions except the addition of ammonia, which was found to be more effective than that (0.061%) with the addition of HCl in the immobilization of Pt. In addition, the effect of soaking time, Pt precursor concentration and calcination temperature on the loading of Pt in hollow silica nanostructures were investigated as well.     

Fast synthesis and formation mechanism of γ-MnO2 hollow nanospheres for aerobic oxidation of alcohols

γ-MnO₂ hollow nanospheres of about 300-800 nm in size have been synthesized by a fast 1-h 2-step process in the presence of an excess amount of Mn²⁺ in aqueous solution without using any templates, hydrothermal processes and catalytic routes. The evolution of morphologies evidenced that the fast formation mechanism of the γ-MnO₂ hollow nanospheres in the presence of the excess amount of Mn²⁺ in solution followed the “Ostward ripening” process. The as-synthesized γ-MnO₂ hollow nanospheres showed high catalytic activity and selectivity in aerobic oxidation of various alcohols which was attributed to their hollow nature and larger BET specific surface area.