Mesoporous single-crystal CoSn(OH)6 hollow structures with multilevel interiors.
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ABSTRACT:
SUBMITTER: Wang Z
PROVIDER: S-EPMC3589726 | biostudies-literature | 2013
REPOSITORIES: biostudies-literature
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Project description:A solid-to-hollow evolution in macroscopic structures is challenging in synthetic materials. A fundamentally new strategy is reported for guiding macroscopic, unidirectional shape evolution of materials without compromising the material's integrity. This strategy is based on the creation of a field with a "swelling pole" and a "shrinking pole" to drive polymers to disassemble, migrate, and resettle in the targeted region. This concept is demonstrated using dynamic hydrogels containing anchored acrylic ligands and hydrophobic long alkyl chains. Adding water molecules and ferric ions (Fe3+ ) to induce a swelling-shrinking field transforms the hydrogels from solid to hollow. The strategy is versatile in the generation of various closed hollow objects (for example, spheres, helix tubes, and cubes with different diameters) for different applications.
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Project description:Remarkable recent demonstrations of ultra-low-loss inhibited-coupling (IC) hollow-core photonic-crystal fibres (HCPCFs) established them as serious candidates for next-generation long-haul fibre optics systems. A hindrance to this prospect and also to short-haul applications such as micromachining, where stable and high-quality beam delivery is needed, is the difficulty in designing and fabricating an IC-guiding fibre that combines ultra-low loss, truly robust single-modeness, and polarisation-maintaining operation. The design solutions proposed to date require a trade-off between low loss and truly single-modeness. Here, we propose a novel IC-HCPCF for achieving low-loss and effective single-mode operation. The fibre is endowed with a hybrid cladding composed of a Kagome-tubular lattice (HKT). This new concept of a microstructured cladding allows us to significantly reduce the confinement loss and, at the same time, preserve truly robust single-mode operation. Experimental results show an HKT-IC-HCPCF with a minimum loss of 1.6 dB/km at 1050 nm and a higher-order mode extinction ratio as high as 47.0 dB for a 10 m long fibre. The robustness of the fibre single-modeness is tested by moving the fibre and varying the coupling conditions. The design proposed herein opens a new route for the development of HCPCFs that combine robust ultra-low-loss transmission and single-mode beam delivery and provides new insight into IC guidance.
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Project description:Both deprotonated and neutral achiral title dipeptides assume similar structures of two conformations, which are related by a unit-cell inversion centre. Two mol-ecules of both conformations of the metal-free neutral dipeptide are linked by two hydrogen bonds, while two mol-ecules of both conformations of the ionized form coordinate a calcium ion in calcium(II) bis-[2-(2-{[(benz-yl-oxy)carbon-yl]amino}-acetamido)-2-methyl-propano-ate] monohydrate, 0.5Ca2+·C14H17N2O5-·0.5H2O, which lies on an inversion centre and forms a distorted octa-hedral complex with the metal ion. These CaII complexes are connected in the crystal via hydrogen bonds in the b- and c-axis directions, whereas in the a-axis direction, they stack via apolar contacts. In the metal-free crystal, namely 2-(2-{[(benz-yloxy)carbon-yl]amino}-acetamido)-2-methyl-propanoic acid, C14H18N2O5, mol-ecules are hydrogen bonded in the a- and c-axis directions, and stack in the b-axis direction via apolar contacts.
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Project description:A facile and general method for the controllable synthesis of N-doped hollow mesoporous carbon nanocapsules (NHCNCs) with four different geometries has been developed. The spheres (NHCNC-1), low-concaves (NHCNC-2), semi-concaves (NHCNC-3) and wrinkles (NHCNC-4) shaped samples were prepared and systematically investigated to understand the structural effects of hollow particles on their supercapacitor performances. Compared with the other three different shaped samples (NHCNC-1, NHCNC-2, and NHCNC-4), the as-synthesized semi-concave structured NHCNC-3 demonstrated excellent performance with high gravimetric capacitance of 326?F?g-1 (419?F?cm-3) and ultra-stable cycling stability (96.6% after 5000 cycles). The outstanding performances achieved are attributed to the unique semi-concave structure, high specific surface area (1400 m2 g-1), hierarchical porosity, high packing density (1.41?g?cm-3) and high nitrogen (N) content (up to 3.73%) of the new materials. These carbon nanocapsules with tailorable structures and properties enable them as outstanding carriers and platforms for various emerging applications, such as nanoscale chemical reactors, catalysis, batteries, solar energy harvest, gas storage and so on. In addition, these novel carbons have negligible cytotoxicity and high biocompatibility for human cells, promising a wide range of bio applications, such as biomaterials, drug delivery, biomedicine, biotherapy and bioelectronic devices.
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Project description:Mesoporous silica materials have attracted great research interest for various applications ranging from (bio)catalysis and sensing to drug delivery. It remains challenging to prepare hollow mesoporous silica nanoparticles (HMSN) with large center-radial mesopores that could provide a more efficient transport channel through the cell for guest molecules. Here, we propose a novel strategy for the preparation of HMSN with large dendritic mesopores to achieve higher enzyme loading capacity and more efficient bioreactors. The materials were prepared by combining barium sulfate nanoparticles (BaSO4 NP) as a hard template and the in situ-formed 3-aminophenol/formaldehyde resin as a porogen for directing the dendritic mesopores' formation. HMSNs with different particle sizes, shell thicknesses, and pore structures have been prepared by choosing BaSO4 NP of various sizes and adjusting the amount of tetraethyl orthosilicate added in synthesis. The obtained HMSN-1.1 possesses a high pore volume (1.07 cm3 g-1), a large average pore size (10.9 nm), and dendritic mesopores that penetrated through the shell. The advantages of HMSNs are also demonstrated for enzyme (catalase) immobilization and subsequent use of catalase-loaded HMSNs as bioreactors for catalyzing the H2O2 degradation reaction. The hollow and dendritic mesoporous shell features of HMSNs provide abundant tunnels for molecular transport and more accessible surfaces for molecular adsorption, showing great promise in developing efficient nanoreactors and drug delivery vehicles.
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Project description:Tunable glutathione (GSH)-sensitive hollow mesoporous silica nanoparticles (HMSiO2 NPs) were developed using a structural difference-based selective etching strategy. These organosilica hollow nanoparticles contained disulfide linkages (S-S) in the outer shell which were degraded by GSH. The particles were compared with their nonGSH-sensitive tetraethyl orthosilicate (TEOS) HMSiO2 counterparts in terms of their synthesis method, characterization, doxorubicin (DOX) release profile, and in vitro cytotoxicity in MCF-7 breast cancer cells. Transmission electron microscopy (TEM) of the particles indicated that the fabricated HMSiO2 NPs had an average diameter of 130?±?5?nm. Thermogravimetric analysis (TGA) revealed that GSH-sensitive particles had approximately 5.3% more weight loss than TEOS HMSiO2 NPs. Zeta potential of these redox-responsive particles was -23?±?1?mV at pH?6 in deionized (DI) water. Nitrogen adsorption-desorption isotherm revealed that the surface area of the hollow mesoporous nanoreservoirs was roughly 446?±?6?m2?g-1 and the average diameter of the pores was 2.3?±?0.5?nm. TEM images suggest that the nanoparticles started to lose mass integrity from Day 1. The particles showed a high loading capacity for DOX (8.9?±?0.5%) as a model drug, due to the large voids existing in the hollow structures. Approximately 58% of the incorporated DOX released within 14?days in phosphate buffered saline (PBS) at pH?6 and in the presence of 10?mM of GSH, mimicking intracellular tumor microenvironment while release from TEOS HMSiO2 NPs was only c.a. 18%. The uptake of these hollow nanospheres by MCF-7 cells and RAW 264.7 macrophages was evaluated using TEM and confocal microscopy. The nanospheres were shown to accumulate in the endolysosomal compartments after incubation for 24?h with the maximum uptake of c.a. 2.1?±?0.3% and 5.2?±?0.4%, respectively. Cytotoxicity of the nanospheres was investigated using CCK-8 assay. Results indicate that intact hollow particles (both GSH-sensitive and TEOS HMSiO2 NPs) were nontoxic to MCF-7 cells after incubation for 24?h within the concentration range of 0-1000??g?ml-1. DOX-loaded GSH-sensitive nanospheres containing 6??g?ml-1 of DOX killed c.a. 51% of MCF-7 cells after 24?h while TEOS HMSiO2 NPs killed c.a. 20% with the difference being statistically significant. Finally, cytotoxicity data in RAW 264.7 macrophages and NIH 3?T3 fibroblasts shows that intact GSH-sensitive HMSiO2 NPs did not show any toxic effects on these cells with the concentrations equal or <125??g?ml-1.
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Project description:BackgroundStimulus-responsive degradable mesoporous organosilica nanoparticles (MONs) have shown great promise as drug carriers via enhancing the efficiency of drug delivery and accelerating the degradation of nanocarriers. However, it remains a great challenge to develop novel light-enabled spatial and temporal degradable MONs with both superior responsiveness for efficient anti-cancer drug delivery and safe exocytosis.ResultsWe report a novel photo-responsive degradable hollow mesoporous organosilica nanoplatform (HMONs@GOQD). The platform is based on organosilica nanoparticles (HMONs) containing singlet oxygen (1O2)-responsive bridged organoalkoxysilanes and wrapped graphene oxide quantum dots (GOQDs). The unique hollow mesoporous structure of the HMONs guarantees an excellent drug loading and release profile. During light irradiation, 1O2 produced by the GOQDs leads to the degradation of the organosilica nanoparticles, resulting in enhanced local drug release.ConclusionsWe carried out in vitro and in vivo experiments using DOX as a model drug; DOX-HMONs@GOQDs exhibited high biocompatibility, accelerated degradation, and superior therapeutic efficacy during light irradiation, indicating a promising platform for clinical cancer therapy.
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Project description:The reaction of Fe(NO3)3?9 H2O with KOH under hydroflux conditions at about 200?°C produces red crystals of K2-x Fe4O7-x (OH) x in a quantitative yield. In the crystal structure, edge-sharing [FeO6] octahedra form ?2[ Fe2O6] honeycomb nets. Pillars consisting of pairs of vertex-sharing [FeO4] tetrahedra link the honeycomb layers and form columnar halls in which the potassium ions are located. The trigonal (P 3? 1m) and the hexagonal (P63/mcm) polytypes of K2-x Fe4O7-x (OH) x show oriented intergrowth. The sub-stoichiometric potassium content (x?0.3) is compensated by hydroxide ions. K2-x Fe4O7-x (OH) x is an antiferromagnet above 2?K and its magnetic structure was determined by neutron powder diffraction. Under ambient conditions, K2-x Fe4O7-x (OH) x hydrolyzes and K2CO3???H2O forms gradually on the surface of the K2-x Fe4O7-x (OH) x crystals. Upon annealing at air at about 500?°C, the potassium atoms in the columnar halls start to order into a superstructure. The thermal decomposition of K2-x Fe4O7-x (OH) x proceeds via a topotactic transformation into K1+x' Fe11O17, adopting the rhombohedral ?'' or the hexagonal ?-aluminate-type structure, before ?-Fe2O3 is formed above 950?°C, which then converts into thermodynamically stable ?-Fe2O3.
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