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1.
Precise synthesis of nanobuilding blocks with accurately positioned functional groups presents a daunting challenge. Herein, a practical synthesis and thorough characterization of a series of T8‐polyhedral oligomeric silsesquioxane (POSS) di‐ and triadducts is reported. Upon addition of triflic acid across the double bonds in octavinylPOSS (V8T8) followed by hydrolysis, the cubic symmetry of the T8‐POSS cage (Oh) is broken into C2v (ortho‐), C2v (meta‐), and D3d (para‐) for diadducts and further to Cs (oom‐), Cs (omp‐), and C3v (mmm‐) for triadducts in a stochastic fashion. Their structures and regioconfigurations have been unambiguously demonstrated by 1H, 13C, and 29Si NMR spectroscopy, as well as MALDI‐TOF mass spectrometry. The assignment of the diadducts was further corroborated by converting each individual diadduct into triadduct(s), the structure of which is controlled by the symmetry of the precursor. Except for the C3v triadduct, they can all be prepared in synthetically useful quantities. The presence of two types of highly reactive and mutually orthogonal functional groups facilitates further modification into complex nanostructures and composite materials. These unique regioisomers provide a versatile platform for constructing giant molecules and Janus silsesquioxanes.  相似文献   

2.
Clusters with diverse structures and functions have been used to create novel cluster‐assembled materials (CAMs). Understanding their self‐assembly process is a prerequisite to optimize their structure and function. Herein, two kinds of unlike organo‐functionalized inorganic clusters are covalently linked by a short organic tether to form a dumbbell‐shaped Janus co‐cluster. In a mixed solvent of acetonitrile and water, it self‐assembles into a crystal with a honeycomb superstructure constructed by hexagonal close‐packed cylinders of the smaller cluster and an orderly arranged framework of the larger cluster. Reconstruction of these structural features via coarse‐grained molecular simulations demonstrates that the cluster crystallization and the nanoscale phase separation between the two incompatible clusters synergistically result in the unique nano‐architecture. Overall, this work opens up new opportunities for generating novel CAMs for advanced future applications.  相似文献   

3.
Solvent‐free single crystals of 1,3,5,7,9,11,13,15‐octaphenylpentacyclo[9.5.1.13,9.15,15.17,13]octasiloxane (abbreviated as octaphenyl‐POSS), C48H40O12Si8, were obtained by dehydration/condensation of the tetrol Si4O4(Ph)4(OH)4. The powder pattern generated from the single‐crystal data matches well with the experimentally measured powder pattern of commercial octaphenyl‐POSS. The geometry of the centrosymmetric molecule in the crystal was compared with that in the gas phase, and had shorter Si—O bond lengths and a broader range of Si—O—Si bond angles. The average Si—O bond length [1.621 (3) Å], and Si—O—Si and O—Si—O bond angles [149 (5) and 109 (1)°, respectively] were within the same range measured previously for octaphenyl‐POSS solvates.  相似文献   

4.
Noble metal nanoparticles are promising catalysts in electrochemical reactions, while understanding the relationship between the structure and reactivity of the particles is important to achieve higher efficiency of electrocatalysis, and promote the development of single‐molecule electrochemistry. Electrogenerated chemiluminescence (ECL) was employed to image the catalytic oxidation of luminophore at single Au, Pt, and Au‐Pt Janus nanoparticles. Compared to the monometal nanoparticles, the Janus particle structure exhibited enhanced ECL intensity and stability, indicating better catalytic efficiency. On the basis of the experimental results and digital simulation, it was concluded that a concentration difference arose at the asymmetric bimetallic interface according to different heterogeneous electron‐transfer rate constants at Au and Pt. The fluid slip around the Janus particle enhanced local redox reactions and protected the particle surface from passivation.  相似文献   

5.
《Electrophoresis》2018,39(19):2417-2424
A theoretical framework is provided for determining the self‐thermophoretic velocity of a light irradiated spheroidal Janus nanoparticle consisting of symmetric dielectric and perfectly conducting semi‐spheroids. The analysis is based on solving the linearized Joule heating problem due to uniform laser irradiance and on explicitly determining the temperature fields inside and outside the particle. We employ the thermoelectric (Peltier‐ Seebeck) methodology to find the surface self ‐ induced temperature gradient and the related slip velocity which determines the autonomous phoretic (self ‐ propulsion) mobility of the Janus particle. Simplified explicit expressions for the self ‐ thermophoretic velocities of spheroidal (prolate and oblate) Janus particles in terms of their aspect ratios are found and few practical limiting cases (i.e., sphere, disk and needle) are also discussed.  相似文献   

6.
A new phosphorus‐containing aromatic diamine, 1,4‐bis(4‐aminophenoxy)‐2‐(6‐oxido‐6H‐dibenz[c,e] [1,2]oxaphosphorin‐6‐yl) phenylene ( 3 ) was synthesized by the nucleophilic aromatic substitution of 2‐(6‐oxido‐6H‐dibenz[c,e] [1,2]oxaphosphorin‐6‐yl)‐1,4‐dihydroxy phenylene ( 1 ) with 4‐fluoronitrobenzene, followed by catalytic hydrogenation. Light color, flexible, and creasable polyimides with high molecular weight, high glass transition, high thermal stability, improved organosolubility, and good oxygen plasma resistance were synthesized from the condensation of ( 3 ) with various aromatic dianhydrides in N,N‐dimethylacetamide, followed by thermal imidization. The number‐average molecular weights of polyimides are in the range of 7.0–8.3 × 104 g/mol, and the weight‐average molecular weights are in the range of 12.5–16.5 × 104 g/mol. The Tgs of these polyimides range from 230 to 304 °C by differential scanning calorimetry and from 228 to 305 °C by DMA. These polyimides are tough and flexible, with tensile strength at around 100 MPa. The degradation temperatures (Td 5%) and char yields at 800 °C in nitrogen range from 544 to 597 °C and 59–65 wt %, respectively. Polyimides 5c and 5e , derived from OPDA and 6FDA, respectively, with the cutoff wavelength of 347 and 342 μm, respectively, show very light color. These polyimides also exhibit good oxygen plasma resistance. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2897–2912, 2007  相似文献   

7.
We report on the formation of shape‐ and surface‐anisotropic Janus nanocups (JNCs) by evaporation‐induced confinement assembly (EICA) of ABC triblock terpolymers. During microphase separation in spherical confinement, the triblock terpolymer spontaneously adopted a hemispherical shape with an inner concentric lamella–lamella (ll) morphology. Cross‐linking and disassembly of the microparticles resulted in well‐defined JNCs with different chemistry on the inside and outside. By synthesizing polymers with increasing length of the cross‐linkable block, we tuned the mechanical stability of the nanocups, which is relevant to control opening and closing of the cup cavity. We utilize the Janus properties for selective uptake of cargo exemplified by the filling of JNCs with polymer or gold nanoparticles. The directional properties of JNCs suggest applications in locomotion, oil‐spill recovery, storage and release, templating, and as nanoreactors with attoliter volume.  相似文献   

8.
Anthracyclines belong to the anticancer drugs that are widely used in chemotherapy. However, due to their systemic toxicity they also exert dangerous side effects associated mainly with cardiovascular risks. The pathway that is currently often developed is their chemical and physical modification via formation of conjugated or complexed prodrug systems with a variety of nanocarriers that can selectively release the active species in cancer cells. In this study, six new nanoconjugates were synthesized with the use of polyhedral oligosilsesquioxanes [POSS(OH)32] as nanocarriers of the anticancer drugs anthracyclines—doxorubicin (DOX) and daunorubicin (DAU). These prodrug conjugates are also equipped with poly(ethylene glycol) (PEG) moieties of different structure and molecular weight. Water-soluble POSS, succinic anhydride modified (SAMDOX and SAMDAU) with carboxylic function, and PEGs (PEG1, PEG2 and PEGB3) were used for the synthesis. New nanoconjugates were formed via ester bonds and their structure was confirmed by NMR spectroscopy (1H-NMR, 13C-NMR, 1H-13C HSQC, DOSY and 1H-1H COSY), FTIR and DLS. Drug release rate was evaluated using UV-Vis spectroscopy at pH of 5.5. Release profiles of anthracyclines from conjugates 4–9 point to a range of 10 to 75% (after 42 h). Additionally, model NMR tests as well as diffusion ordered spectroscopy (DOSY) confirmed formation of the relevant prodrugs. The POSS-anthracycline conjugates exhibited prolonged active drug release time that can lead to the possibility of lowering administered doses and thus giving them high potential in chemotherapy. Drug release from conjugate 7 after 42 h was approx. 10%, 33% for conjugate 4, 47% for conjugate 5, 6, 8 and 75% for conjugate 9.  相似文献   

9.
We report the successful fabrication of photoresponsive Janus particles (JPs) composed of an epoxy‐based azo polymer and poly(methyl methacrylate) (PMMA). Two representative azo polymers, of which one polymer (BP‐AZ‐CN) has cyano groups as electron‐withdrawing substituents on the azobenzene moieties and the other polymer (BP‐AZ‐CA) has carboxyl groups as the electron‐withdrawing substituents, were adopted for the investigation. The nanoscaled JPs, with a narrow size distribution and different azo polymer/PMMA ratios, were fabricated through self‐assembly in solution and as dispersions. Upon irradiation with linearly polarized light (λ=488 nm), two types of photoresponsive behavior were observed for JPs in the solid state. For JPs composed of BP‐AZ‐CN and PMMA, the light irradiation caused the azo‐polymer component to be stretched along the light polarization direction. Conversely, for JPs composed of BP‐AZ‐CA and PMMA, the azo‐polymer component became separated from PMMA component under the same irradiation conditions. These observations are valuable for a deeper understanding of the nature of self‐assembly and photoinduced mass‐transport at the nanometer scale.  相似文献   

10.
A facile, reproducible, and scalable method was explored to construct uniform Au@poly(acrylic acid) (PAA) Janus nanoparticles (JNPs). The as‐prepared JNPs were used as templates to preferentially grow a mesoporous silica (mSiO2) shell and Au branches separately modified with methoxy‐poly(ethylene glycol)‐thiol (PEG) to improve their stability, and lactobionic acid (LA) for tumor‐specific targeting. The obtained octopus‐type PEG‐Au‐PAA/mSiO2‐LA Janus NPs (PEG‐OJNP‐LA) possess pH and NIR dual‐responsive release properties. Moreover, DOX‐loaded PEG‐OJNP‐LA, upon 808 nm NIR light irradiation, exhibit obviously higher toxicity at the cellular and animal levels compared with chemotherapy or photothermal therapy alone, indicating the PEG‐OJNP‐LA could be utilized as a multifunctional nanoplatform for in vitro and in vivo actively‐targeted and chemo‐photothermal cancer therapy.  相似文献   

11.
Synthesis, Crystal Structures, and Vibrational Spectra of [Pt(N3)6]2– and [Pt(N3)Cl5]2–, 195Pt and 15N NMR Spectra of [Pt(N3)nCl6–n]2– and [Pt(15NN2)n(N215N)6–n]2–, n = 0–6 By ligand exchange of [PtCl6]2– with sodium azide mixed complexes of the series [Pt(N3)nCl6–n]2– and with 15N‐labelled sodium azide (Na15NN2) mixtures of the isotopomeres [Pt(15NN2)n(N215N)6–n]2–, n = 0–6 and the pair [Pt(15NN2)Cl5]2–/[Pt(N215N)Cl5]2– are formed. X‐ray structure determinations on single crystals of (Ph4P)2[Pt(N3)6] ( 1 ) (triclinic, space group P1, a = 10.175(1), b = 10.516(1), c = 12.380(2) Å, α = 87.822(9), β = 73.822(9), γ = 67.987(8)°, Z = 1) and (Ph4As)2[Pt(N3)Cl5] · HCON(CH3)2 ( 2 ) (triclinic, space group P1, a = 10.068(2), b = 11.001(2), c = 23.658(5) Å, α = 101.196(14), β = 93.977(15), γ = 101.484(13)°, Z = 2) have been performed. The bond lengths are Pt–N = 2.088 ( 1 ), 2.105 ( 2 ) and Pt–Cl = 2.318 Å ( 2 ). The approximate linear azido ligands with Nα–Nβ–Nγ‐angles = 173.5–174.6° are bonded with Pt–Nα–Nβ‐angles = 116.4–121.0°. In the vibrational spectra the PtCl stretching vibrations of (n‐Bu4N)2[Pt(N3)Cl5] are observed at 318–345, the PtN stretching modes of (n‐Bu4N)2[Pt(N3)6] at 401–428 and of (n‐Bu4N)2[Pt(N3)Cl5] at 408–413 cm–1. The mixtures (n‐Bu4N)2[Pt(15NN2)n(N215N)6–n], n = 0–6 and (n‐Bu4N)2[Pt(15NN2)Cl5]/(n‐Bu4N)2[Pt(N215N)Cl5] exhibit 15N‐isotopic shifts up to 20 cm–1. Based on the molecular parameters of the X‐ray determinations the vibrational spectra are assigned by normal coordinate analysis. The average valence force constants are fd(PtCl) = 1.93, fd(PtNα) = 2.38 and fd(NαNβ, NβNγ) = 12.39 mdyn/Å. In the 195Pt NMR spectrum of [Pt(N3)nCl6–n]2–, n = 0–6 downfield shifts with the increasing number of azido ligands are observed in the range 4766–5067 ppm. The 15N NMR spectrum of (n‐Bu4N)2[Pt(15NN2)n(N215N)6–n], n = 0–6 exhibits by 15N–195Pt coupling a pseudotriplett at –307.5 ppm. Due to the isotopomeres n = 0–5 for terminal 15N six well‐resolved signals with distances of 0.03 ppm are observed in the low field region at –201 to –199 ppm.  相似文献   

12.
The development of highly sensitive and selective methods for the detection of lead ion (Pb2+) is of great scientific importance. In this work, we develop a new surface‐enhanced Raman scattering (SERS)‐based sensor for the selective trace measurement of Pb2+. The SERS‐based sensor is assembled from gold nanoparticles (AuNPs) and graphene using cucurbit[7]uril (CB[7]) as a precise molecular glue and a local SERS reporter. Upon the addition of Pb2+, CB[7] forms stronger complexes with Pb2+ and desorbs from AuNPs, resulting in a sensitive “turn‐off” of SERS signals. This SERS‐based assay shows a limit of detection (LOD) of 0.3 nm and a linear detection range from 1 nm to 0.3 μm for Pb2+. The feasibility of the assay is further demonstrated by probing Pb2+ in real water samples. This SERS‐based analytical method is highly sensitive and selective, and therefore holds promising applications in environmental analysis.  相似文献   

13.
The potassium salt of the [1‐H2N‐2‐F‐closo‐1‐CB11H10] anion ( 1 ) was obtained from an insertion reaction of Li3[7‐H2N‐nido‐7‐CB10H10] with BF3 · OEt2. Anion 1 was protonated to the neutral species 1‐H3N‐2‐F‐closo‐1‐CB11H10 (H 1 ) and it was iodinated with ICl to the [1‐H2N‐2‐F‐closo‐1‐CB11I10] anion ( 2 ). All species were characterized by multinuclear NMR, IR, and Raman spectroscopy as well as by elemental analysis. The structure of H 1· (CH3)2CO was studied by single‐crystal X‐ray diffraction and the experimentally determined bond lengths are compared to values derived from density functional calculations.  相似文献   

14.
Magneto‐plasmonic Janus vesicles (JVs) integrated with gold nanoparticles (AuNPs) and magnetic NPs (MNPs) were prepared asymmetrically in the membrane for in vivo cancer imaging. The hybrid JVs were produced by coassembling a mixture of hydrophobic MNPs, free amphiphilic block copolymers (BCPs), and AuNPs tethered with amphiphilic BCPs. Depending on the size and content of NPs, the JVs acquired spherical or hemispherical shapes. Among them, hemispherical JVs containing 50 nm AuNPs and 15 nm MNPs showed a strong absorption in the near‐infrared (NIR) window and enhanced the transverse relaxation (T2) contrast effect, as a result of the ordering and dense packing of AuNPs and MNPs in the membrane. The magneto‐plasmonic JVs were used as drug delivery vehicles, from which the release of a payload can be triggered by NIR light and the release rate can be modulated by a magnetic field. Moreover, the JVs were applied as imaging agents for in vivo bimodal photoacoustic (PA) and magnetic resonance (MR) imaging of tumors by intravenous injection. With an external magnetic field, the accumulation of the JVs in tumors was significantly increased, leading to a signal enhancement of approximately 2–3 times in the PA and MR imaging, compared with control groups without a magnetic field.  相似文献   

15.
In chemical functionalization of colloidal particles, the functional moieties are generally distributed rather homogeneously on the particle surface. Recently, a variety of synthetic protocols have been developed in which particle functionalization may be carried out in a spatially controlled fashion, leading to the production of structurally asymmetrical particles. Janus particles represent the first example in which the two hemispheres exhibit distinctly different chemical and physical properties, which is analogous to the dual‐faced Roman god, Janus. Whereas a variety of methods have been reported for the preparation of (sub)micron‐sized polymeric Janus particles, it has remained challenging for the synthesis and (unambiguous) structural characterization of much smaller nanometer‐sized Janus particles. Herein, several leading methods for the preparation of nanometer‐sized Janus particles are discussed and the important properties and applications of these Janus nanoparticles in electrochemistry, sensing, and catalysis are highlighted. Some perspectives on research into functional patchy nanoparticles are also given.  相似文献   

16.
Rechargeable sodium batteries are a promising technology for low‐cost energy storage. However, the undesirable drawbacks originating from the use of glass fiber membrane separators have long been overlooked. A versatile grafting–filtering strategy was developed to controllably tune commercial polyolefin separators for sodium batteries. The as‐developed Janus separators contain a single–ion‐conducting polymer‐grafted side and a functional low‐dimensional material coated side. When employed in room‐temperature sodium–sulfur batteries, the poly(1‐[3‐(methacryloyloxy)propylsulfonyl]‐1‐(trifluoromethanesulfonyl)imide sodium)‐grafted side effectively enhances the electrolyte wettability, and inhibits polysulfide diffusion and sodium dendrite growth. Moreover, a titanium‐deficient nitrogen‐containing MXene‐coated side electrocatalytically improved the polysulfide conversion kinetics. The as‐developed batteries demonstrate high capacity and extended cycling life with lean electrolyte loading.  相似文献   

17.
The new indide hydride Ba9[In]4[H] was synthesized from the elements in stoichiometric proportions using the inherent hydrogen content of commercial elemental barium as hydrogen source. Its structure, constituting a new type, was determined using single‐crystal X‐ray data (tetragonal, space group I4/m, a = 1397.3(2), c = 591.8(1) pm, Z = 2) in sufficient quality (R1 = 0.0261) to allow identification and location of the hydride ion as well as the refinement of its thermal parameter. The crystal structure of Ba9[In]4[H] exhibits isolated indium atoms, which are coordinated by 10 barium cations in a cubicosahedral arrangement. The hydride anions are octahedrally surrounded by six Ba2+ cations. According to [HBa4Ba2/2] these octahedra are connected by opposite corners to form chains running along the c axis. The presence of the hydride ion was determined by solid state NMR spectroscopy, where the chemical shift of the 1H‐MAS‐NMR signal of–9.0 ppm nicely corresponds to the values in BaH2 and other metallid hydrides. Like in other binary alkaline‐earth indides, the band structure calculated in the frame of the FP‐LAPW methods shows a pseudo band gap slightly above the Fermi level, associated with the electron precise valence electron count after Zintl (isolated In5–). The title compound was compared to other hydrides and indides both according to the structural as well as the bonding features.  相似文献   

18.
19.
Nitrogen‐containing polycyclic aromatic hydrocarbons are very attractive compounds for organic electronics applications. Their low‐lying LUMO energies points towards a potential use as n‐type semiconductors. Furthermore, they are expected to be more stable under ambient conditions, which is very important for the formation of semiconducting films, where materials with high purity are needed. In this study, the syntheses of naphtho[2,3‐g]quinoxalines and pyrazino[2,3‐b]phenazines is presented by using reaction conditions, that provide the desired products in high yields, high purity and without time‐consuming purification steps. The HOMO and LUMO energies of the compounds are investigated by cyclic voltammetry and UV/Vis spectroscopy and their dependency on the nitrogen content and the terminal substituents are examined. The photostability and the degradation pathways of the naphtho[2,3‐g]quinoxalines and pyrazino[2,3‐b]phenazines are explored by NMR spectroscopy of irradiated samples affirming the large influence of the nitrogen atoms in the acene core on the degradation process during the irradiation. Finally, by identifying the degradations products of 2,3‐dimethylnaphtho[2,3‐g]quinoxaline it is possible to track down the most reactive position in the compound and, by blocking this position with nitrogen, to strongly increase the photostability.  相似文献   

20.
Sonodynamic therapy (SDT) has the advantages of high penetration, non‐invasiveness, and controllability, and it is suitable for deep‐seated tumors. However, there is still a lack of effective sonosensitizers with high sensitivity, safety, and penetration. Now, ultrasound (US) and glutathione (GSH) dual responsive vesicles of Janus Au‐MnO nanoparticles (JNPs) were coated with PEG and a ROS‐sensitive polymer. Upon US irradiation, the vesicles were disassembled into small Janus Au‐MnO nanoparticles (NPs) with promoted penetration ability. Subsequently, GSH‐triggered MnO degradation simultaneously released smaller Au NPs as numerous cavitation nucleation sites and Mn2+ for chemodynamic therapy (CDT), resulting in enhanced reactive oxygen species (ROS) generation. This also allowed dual‐modality photoacoustic imaging in the second near‐infrared (NIR) window and T1‐MR imaging due to the released Mn2+, and inhibited orthotopic liver tumor growth via synergistic SDT/CDT.  相似文献   

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