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1.
Template‐free fabrication of non‐spherical polymeric nanoparticles is desirable for various applications, but has had limited success owing to thermodynamic favorability of sphere formation. Herein we present a simple way to prepare cubic nanoparticles of block copolymers by self‐assembly from aqueous solutions at room temperature. Nanocubes with edges of 40–200 nm are formed spontaneously on different surfaces upon water evaporation from micellar solutions of triblock copolymers containing a central poly(ethylene oxide) block and terminal trimethylene carbonate/dithiolane blocks. These polymers self‐assemble into 28±5 nm micelles in water. Upon drying, micelle aggregation and a kinetically controlled crystallization of central blocks evidently induce solid cubic particle formation. An approach for preserving the structures of these cubes in water by thiol‐ or photo‐induced crosslinking was developed. The ability to solubilize a model hydrophobic drug, curcumin, was also explored.  相似文献   

2.
Integrins are important membrane receptors that form focal adhesions with the extracellular matrix and are transmembrane signaling proteins. We demonstrate that nanoparticles functionalized with c‐RGDfC ligands bind to intact cell membranes and selectively enhance the amino acid signals of the integrin receptor when coupled with tip‐enhanced Raman scattering (TERS) detection. Controlling the plasmonic interaction between the functionalized nanoparticle and the TERS tip provides a clear Raman signal from αVβ3 integrins in the cell membrane that matches the signal of the purified integrin receptor. Random aggregation of nanoparticles on the cell does not provide the same spectral information. Chemical characterization of membrane receptors in intact cellular membranes is important for understanding membrane signaling and drug targeting. These results provide a new method to investigate the chemical interactions associated with ligand binding to membrane receptors in cells.  相似文献   

3.
This work reports on an assembling–calcining method for preparing gold–metal oxide core–satellite nanostructures, which enable surface‐enhanced Raman spectroscopic detection of chemical reactions on metal oxide nanoparticles. By using the nanostructure, we study the photooxidation of Si?H catalyzed by CuO nanoparticles. As evidenced by the in situ spectroscopic results, oxygen vacancies of CuO are found to be very active sites for oxygen activation, and hydroxide radicals (*OH) adsorbed at the catalytic sites are likely to be the reactive intermediates that trigger the conversion from silanes into the corresponding silanols. According to our finding, oxygen vacancy‐rich CuO catalysts are confirmed to be of both high activity and selectivity in photooxidation of various silanes.  相似文献   

4.
The changes in the electronic and magnetic properties of graphene induced by interaction with semiconducting oxide nanoparticles such as ZnO and TiO2 and with magnetic nanoparticles such as Fe3O4, CoFe2O4, and Ni are investigated by using Raman spectroscopy, magnetic measurements, and first‐principles calculations. Significant electronic and magnetic interactions between the nanoparticles and graphene are found. The findings suggest that changes in magnetization as well as the Raman shifts are directly linked to charge transfer between the deposited nanoparticles and graphene. The study thus demonstrates significant effects in tailoring the electronic structure of graphene for applications in futuristic electronic devices.  相似文献   

5.
Overabundance of hydrogen peroxide originating from environmental stress and/or genetic mutation can lead to pathological conditions. Thus, the highly sensitive detection of H2O2 is important. Herein, supramolecular fluorescent nanoparticles self‐assembled from fluorescein isothiocyanate modified β‐cyclodextrin (FITC‐β‐CD)/rhodamine B modified ferrocene (Fc‐RB) amphiphile were prepared through host–guest interaction between FITC‐β‐CD host and Fc‐RB guest for H2O2 detection in cancer cells. The self‐assembled nanoparticles based on a combination of multiple non‐covalent interactions in aqueous medium showed high sensitivity to H2O2 while maintaining stability under physiological condition. Owing to the fluorescence resonance energy transfer (FRET) effect, addition of H2O2 led to obvious fluorescence change of nanoparticles from red (RB) to green (FITC) in fluorescent experiments. In vitro study showed the fluorescent nanoparticles could be efficiently internalized by cancer cells and then disrupted by endogenous H2O2, accompanying with FRET from “on” to “off”. These supramolecular fluorescent nanoparticles constructed via multiple non‐covalent interactions are expected to have potential applications in diagnosis and imaging of diseases caused by oxidative stresses.  相似文献   

6.
Hydrogel biomaterials are pervasive in biomedical use. Applications of these soft materials range from contact lenses to drug depots to scaffolds for transplanted cells. A subset of hydrogels is prepared from physical cross‐linking mediated by host–guest interactions. Host macrocycles, the most recognizable supramolecular motif, facilitate complex formation with an array of guests by inclusion in their portal. Commonly, an appended macrocycle forms a complex with appended guests on another polymer chain. The formation of poly(pseudo)rotaxanes is also demonstrated, wherein macrocycles are threaded by a polymer chain to give rise to physical cross‐linking by secondary non‐covalent interactions or polymer jamming. Host–guest supramolecular hydrogels lend themselves to a variety of applications resulting from their dynamic properties that arise from non‐covalent supramolecular interactions, as well as engineered responsiveness to external stimuli. These are thus an exciting new class of materials.  相似文献   

7.
The ability to engineer and re‐program the surfaces of cells would provide an enabling synthetic biological method for the design of cell‐ and tissue‐based therapies. A new cell surface‐engineering strategy is described that uses lipid‐chemically self‐assembled nanorings (lipid‐CSANs) that can be used for the stable and reversible modification of any cell surface with a molecular reporter or targeting ligand. In the presence of a non‐toxic FDA‐approved drug, the nanorings were quickly disassembled and the cell–cell interactions reversed. Similar to T‐cells genetically engineered to express chimeric antigen receptors (CARS), when activated peripheral blood mononuclear cells (PBMCs) were functionalized with the anti‐EpCAM‐lipid‐CSANs, they were shown to selectively kill antigen‐positive cancer cells. Taken together, these results demonstrate that lipid‐CSANs have the potential to be a rapid, stable, and general method for the reversible engineering of cell surfaces and cell–cell interactions.  相似文献   

8.
Alkynes can be metabolically incorporated into biomolecules including nucleic acids, proteins, lipids, and glycans. In addition to the clickable chemical reactivity, alkynes possess a unique Raman scattering within the Raman‐silent region of a cell. Coupling this spectroscopic signature with Raman microscopy yields a new imaging modality beyond fluorescence and label‐free microscopies. The bioorthogonal Raman imaging of various biomolecules tagged with an alkyne by a state‐of‐the‐art Raman imaging technique, stimulated Raman scattering (SRS) microscopy, is reported. This imaging method affords non‐invasiveness, high sensitivity, and molecular specificity and therefore should find broad applications in live‐cell imaging.  相似文献   

9.
Present work reports for the first time on successful synthesis of polyethylene glycol (PEG) coupled ZnO–chemically converted graphene (CCG) nanocomposites (ZGP) as well as pristine nano ZnO (ZO), ZnO–CCG (ZG) and ZnO–PEG (ZP) by adopting facile solvothermal method using zinc acetate dihydrate, graphene oxide and PEG as precursor materials. X‐ray diffraction measurement of samples showed nanocrystalline hexagonal ZnO. Agglomeration of ZnO nanoparticles formed microspheres in ZG, and the agglomeration was found to be decreased in ZGP as revealed from field emission scanning and transmission electron microscopes. Raman and FTIR spectral studies evidenced the presence of chemically interacted CCG and polyethylene glycol in the nanocomposites. Content of the organics in ZGP was determined by thermogravimetric analysis. A mechanism was proposed on the formation of ZGP nanocomposite. From the measurement of in vitro cytotoxicity, quantitative cell viability (CV) of human ovarian cancer cell line, OAW42, was obtained from control to a maximum of 200 µg/ml of sample concentrations. An excellent CV of the cancer cells was observed (nearly ~80% of viable cells at 50 µg/ml dose with respect to the control) for ZGP compared to ZO, ZG and ZP samples. The effective role of CCG and PEG in ZGP nanocomposite for enhancing the cell viability was explained. This simple strategy could be beneficial for synthesis of other metal oxide towards biomedical applications. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

10.
Nanoparticles covered with ligand shells comprising both positively and negatively charged ligands exhibit Gram‐selective antibacterial action controlled by a single experimental parameter, namely the proportion of [+] and [?] ligands tethered onto these particles. Gram selectivity is attributed to the interplay between polyvalent electrostatic and non‐covalent interactions that work in unison to disrupt the bacterial cell wall. The [+/?] nanoparticles are effective in low doses, are non‐toxic to mammalian cells, and are tolerated well in mice. These results constitute the first example of rational engineering of Gram selectivity at the (macro)molecular level.  相似文献   

11.
Based on the surface‐area‐difference model, the formation enthalpies and the formation Gibbs free energies of bimetallic nanoparticles are calculated by considering size and shape effects. Composition–critical size diagrams were graphed for bulk immiscible bimetallic nanoparticles with the developed model. The results reveal that both the formation enthalpy and formation Gibbs free energy decrease with the decrease of particle size. The effect of rising temperature is similar to the diminishing of particle size on reducing the formation Gibbs free energy. Contrary to the positive formation enthalpy of the bulk immiscible system, a negative formation enthalpy is obtained when the particles are smaller than a critical size. With the decrease of size, the alloying process first takes place in the dilute solute regions, then broadens to the dense solute regions and finally, particles with all compositions can be alloyed. The composition–critical size diagram is classified into three regions by the critical size curves with shape factors of 1 and 1.49, that is, the non‐alloying region, alloying region and possible alloying region. The model predictions correspond well with experimental evidences and computer simulation results for Cu–Ag, Au–Ni, Ag–Pt and Au–Pt systems.  相似文献   

12.
When a colloidal drop dries on a surface, most of the particles accumulate at the drop periphery, yielding a characteristic ring‐shaped pattern. This so‐called coffee‐ring effect (CRE) is observed in any pinned evaporating drop containing non‐volatile solutes. Here, the CRE is dynamically controlled for the first time by using light, and an unprecedented reconfigurability of the deposit profile is demonstrated. This is achieved through a new mechanism where particle stickiness is optically tuned on demand, thus offering reliable modulation of the deposition pattern. The system consists of anionic nanoparticles and photosensitive cationic surfactants dispersed in water. It is shown that light‐dependent modulation of surfactant–particle interactions dictates particle attraction and trapping at the liquid–gas interface, which allows us to direct particle deposition into a wide range of patterns from rings to homogeneous disks. Patterning from single drops is photoreversible upon changing the wavelength whereas spatial control in multiple drop arrays is achieved using a photomask.  相似文献   

13.
A three‐dimensional (3D) nitrogen‐doped reduced graphene oxide (rGO)–carbon nanotubes (CNTs) architecture supporting ultrafine Pd nanoparticles is prepared and used as a highly efficient electrocatalyst. Graphene oxide (GO) is first used as a surfactant to disperse pristine CNTs for electrochemical preparation of 3D rGO@CNTs, and subsequently one‐step electrodeposition of the stable colloidal GO–CNTs solution containing Na2PdCl4 affords rGO@CNTs‐supported Pd nanoparticles. Further thermal treatment of the Pd/rGO@CNTs hybrid with ammonia achieves not only in situ nitrogen‐doping of the rGO@CNTs support but also extraordinary size decrease of the Pd nanoparticles to below 2.0 nm. The resulting catalyst is characterized by scanning and transmission electron microscopy, X‐ray diffraction, Raman spectroscopy, and X‐ray photoelectron spectroscopy. Catalyst performance for the methanol oxidation reaction is tested through cyclic voltammetry and chronoamperometry techniques, which shows exceedingly high mass activity and superior durability.  相似文献   

14.
A new synthetic approach to prepare Ag nanoparticles protected side‐chain liquid crystalline (LC) azobenzene polymers was reported. It is based on the reduction of silver ions in presence of a LC polymer polymerized by RAFT. The formation of Ag colloidal nanoparticles was confirmed by TEM and UV analysis. At the same time, according to the results of DSC, XPS, and FTIR spectra, Ag nanoparticles were protected by the side‐chain LC azobenzene polymers through surface attachment interactions between thiol groups and Ag. The out‐plane orientation of side‐chain LC is confirmed by surface‐enhanced Raman spectra analysis and scanning near‐field optical microscope, resulting from the large electromagnetic field arising from the excitation of surface plasmon polariton of Ag nanoparticles. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5380–5386, 2007  相似文献   

15.
Most single‐stranded DNA oligonucleotides are random coils with a persistence length of below 1 nm. So far, no good methods are available to stretch oligonucleotides. Herein, it is shown that freezing can stretch DNA, as confirmed using fluorescence resonance energy transfer, thiazole‐orange staining, and surface‐enhanced Raman spectroscopy. Lateral inter‐strand interactions are critical, and the stretched DNA oligonucleotides are aligned. This work also provides a set of methods for studying frozen oligonucleotides. Upon freezing, DNA oligonucleotides are readily adsorbed onto various nanomaterials, including gold nanoparticles, graphene oxide, iron oxide, and WS2 via the most thermodynamically stable conformation, leading to more stable conjugates.  相似文献   

16.
In‐depth understanding of the biophysicochemical interactions at the nano–bio interface is important for basic cell biology and applications in nanomedicine and nanobiosensors. Here, the extracellular surface potential and topography changes of live cell membranes interacting with polymeric nanomaterials using a scanning ion conductance microscopy‐based potential imaging technique are investigated. Two structurally similar amphiphilic conjugated polymer nanoparticles (CPNs) containing different functional groups (i.e., primary amine versus guanidine) are used to study incubation time and functional group‐dependent extracellular surface potential and topographic changes. Transmembrane pores, which induce significant changes in potential, only appear transiently in the live cell membranes during the initial interactions. The cells are able to self‐repair the damaged membrane and become resilient to prolonged CPN exposure. This study provides an important observation on how the cells interact with and respond to extracellular polymeric nanomaterials at the early stage. This study also demonstrates that extracellular surface potential imaging can provide a new insight to help understand the complicated interactions at the nano–bio interface and the following cellular responses.  相似文献   

17.
We have designed and synthesis a new compound of zinc‐porphyrin bearing four pyrene groups (ZnP‐t‐P(py)4) and prepared a new hybrid materials of ZnP‐t‐P(py)4 with graphene oxide (GO) via non‐covalent interactions. The ZnP‐t‐P(py)4, along with four pendant pyrene entities ZnP‐t‐P(py)4, stacking on the (GO) surface due to π‐ π interactions, has been revealed by AFM measurements. FTIR, UV‐vis absorption confirm the non‐covalent functionalization of the GO. Raman spectral measurements revealed the electronic structure of the GO to be intact upon hybrid formation. In this donor‐acceptor nanohybrid, the fluorescence of photoexcited ZnP‐t‐P(py)4 is effectively quenched by a possible electron‐transfer process. The fluorescence and photoelectrical response measurements also showed that this hybrid may act as an efficient photoelectric conversion material for optoelectronic applications.  相似文献   

18.
We present a simple procedure for the synthesis of quasi‐spherical Au nanoparticles in a wide size range mediated by macrocyclic host molecules, ammonium pillar[5]arene (AP[5]A). The strategy is based on a seeded growth process in which the water‐soluble pillar[5]arene undergoes complexation of the Au salt through the ammonium groups, thereby avoiding Au nucleation, while acting as a stabilizer. The presence of the pillar[5]arene onto the Au nanoparticle particle surface is demonstrated by surface‐enhanced Raman scattering (SERS) spectroscopy, and the most probable conformation of the molecule when adsorbed on the Au nanoparticles surface is suggested on the basis of theoretical calculations. In addition, we analyze the host–guest interactions of the AP[5]A with 2‐naphthoic acid (2NA) by using 1H NMR spectroscopy and the results are compared with theoretical calculations. Finally, the promising synergetic effects of combining supramolecular chemistry and metal nanoparticles are demonstrated through SERS detection in water of 2NA and a polycyclic aromatic hydrocarbon, pyrene (PYR).  相似文献   

19.
The intrinsic features of (hetero‐arene)–metal interactions have been elusive mainly because the systematic structure analysis of non‐anchored hetero‐arene–metal complexes has been hampered by their labile nature. We report successful isolation and systematic structure analysis of a series of non‐anchored indole–palladium(II) complexes. It was revealed that there is a σ–π continuum for the indole–metal interaction, while it has been thought that the dominant coordination mode of indole to a metal center is the Wheland‐intermediate‐type σ‐mode in light of the seemingly strong electron‐donating ability of indole. Several factors which affect the σ‐ or π‐character of indole–metal interactions are discussed.  相似文献   

20.
Poly(diallyldimethylammonium chloride) (PDDA) has been employed as a modifying material for the development of new functional materials; then, the functionalized graphene was employed as a support for Pd nanoparticles through a facile method. The structures and morphologies of the as‐synthesized Pd/PDDA–graphene composites were extensively characterized by Raman spectroscopy, XRD, XPS, and TEM. Morphological observation showed that Pd NPs with average diameters of 4.4 nm were evenly deposited over the functionalized graphene sheets. Moreover, the electrochemical experiments indicated that the Pd/PDDA–graphene catalyst showed improved electrocatalytic activity toward alcohol‐oxidation reactions compared to the Pd/graphene and commercial Pd/C systems, as well as previously reported Pd‐based catalysts. This study demonstrates the great potential of PDDA‐functionalized graphene as a support for the development of metal–graphene nanocomposites for important applications in fuel cells.  相似文献   

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