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991.
Kyung Min Do Haldorai Yuvaraj Min Hee Woo Hyun Gyu Kim Euh Duck Jeong Keith P. Johnston Kwon Taek Lim 《Colloid and polymer science》2008,286(11):1343-1348
A novel synthetic route to prepare polystyrene/SiO2 composite microparticles in supercritical carbon dioxide (scCO2) is presented. Silica particles with the size of 130 nm which were surface-modified with 3-(trimethoxysilyl) propyl methacrylate
were used as seeds in the dispersion polymerization of styrene in the presence of a polymeric stabilizer, poly(1,1-dihydroheptafluorobutyl
methacrylate-co-diisopropylaminoethyl methacrylate) to produce dry composite particles. The transmission electron microscopy analysis revealed
that the composite microspheres contained several silica particles. 相似文献
992.
Soyoung Kwon Kyoungwon Lee Hwayong Kim Youn-Woo Lee Won Bae 《Colloid and polymer science》2008,286(10):1181-1191
The free radical copolymerization of N-vinyl-2-pyrrolidone and 2-methylene-1,3-dioxepane was carried out in supercritical carbon dioxide (scCO2) using three kinds of dispersants and 2,2′-azobisisobutyronitrile as the initiator. Polymerization was performed with fluorinated
polymeric dispersants synthesized in scCO2 using the solution polymerization method and commercially available siloxane-based surfactant. Spherical biocompatible and
biodegradable polymeric particles were prepared within the sub-micron size range. The effect of various ratios of the comonomer,
reaction temperature, and concentration of initiator, in addition to the types and concentrations of the dispersants, on the
particle size and morphology was investigated. The particle size and particle size distribution of copolymer particles were
controlled using the above mentioned experimental parameters. Glass transition temperatures of copolymers were varied according
to the comonomer ratios used. 相似文献
993.
Yeong-Soon Gal Sung-Ho Jin Won-Chul Lee Jong-Wook Park Kwon Taek Lim Won Seok Lyoo Sang Youl Kim 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2008,82(9):1447-1450
The electrooptical and electrochemical properties of a self-dopable ionic conjugated polyacetylene, poly(2-ethynylpyridinium-N-benzoylsulfonate)
(PEPBS), were studied. The photoluminescence spectra of the polymer showed that the photoluminescence peak was located at
545 nm corresponding to the photon energy of 2.27 eV. The cyclic voltammograms of the polymer exhibited reversible electrochemical
behaviors between the doped and undoped peaks. It was found from the dependence of the oxidation current density of the polymer
on scan rate that the kinetics of the redox process was diffusion-controlled. The electrical conductivity (σ) of undoped PEPBS
was 5.7 × 10−9 S/cm.
The text was submitted by the authors in English. 相似文献
994.
Choi SH Na HB Park YI An K Kwon SG Jang Y Park MH Moon J Son JS Song IC Moon WK Hyeon T 《Journal of the American Chemical Society》2008,130(46):15573-15580
Heterostructured nanoparticles composed of metals and Fe3O4 or MnO were synthesized by thermal decomposition of mixtures of metal-oleate complexes (for the oxide component) and metal-oleylamine complexes (for the metal component). The products included flowerlike-shaped nanoparticles of Pt-Fe3O4 and Ni-Fe3O4 and snowmanlike-shaped nanoparticles of Ag-MnO and Au-MnO. Powder X-ray diffraction patterns showed that these nanoparticles were composed of face-centered cubic (fcc)-structured Fe3O4 or MnO and fcc-structured metals. The relaxivity values of the Au-MnO and Au-Fe3O4 nanoparticles were similar to those of the MnO and Fe3O4 nanoparticles, respectively. Au-Fe3O4 heterostructured nanoparticles conjugated with two kinds of 12-base oligonucleotide sequences were able to sense a complementary 24-mer sequence, causing nanoparticle aggregation. This hybridization-mediated aggregation was detected by the overall size increase indicated by dynamic light scattering data, the red shift of the surface plasmon band of the Au component, and the enhancement of the signal intensity of the Fe3O4 component in T2-weighted magnetic resonance imaging. 相似文献
995.
Pawin G Wong KL Kwon KY Frisbee RJ Rahman TS Bartels L 《Journal of the American Chemical Society》2008,130(46):15244-15245
9,10-Dithioanthracene adsorbed on Cu(111) diffuses exclusively along the high-symmetry axis of the molecule-substrate system. Further reduction of the symmetry of the system by asymmetric methylation does not reduce the symmetry of the motion although it has a substantial effect on the diffusion rate (100-fold reduction) and renders the diffusion barrier asymmetric. This is in contrast to the behavior expected of a classical particle, and it provides a direct single-molecule-scale vista on the validity of The Principle of Microscopic Reversibility first formulated by Tolman in 1924, which despite its fundamental role has attracted little visualization. 相似文献
996.
Lee TW Park JJ Kwon Y Hayakawa T Choi TL Park JH Das RR Kakimoto MA 《Langmuir : the ACS journal of surfaces and colloids》2008,24(21):12704-12709
We introduced a spin-assembled nanolayer of hyperbranched poly(ether sulfone) with sulfonic acid terminal on top of an indium-tin oxide anode in organic light-emitting diodes. This results in great improvement in luminous efficiency, better than that of devices using a commercially available conducting polymer composition as a hole-injection layer. The effect of the nanolayer was investigated by impedance spectroscopy, photovoltaic measurement for built-in-potential, and transient electroluminescence. We concluded that the high luminous efficiency resulted from the efficient electron-blocking by the nanolayer and hole-injection assisted by the accumulation of electrons at the interface. This result implies that, for an efficient hole-injection layer, the electron-blocking capability should be incorporated in addition to the hole-injection and -transport capability. 相似文献
997.
Yang J Eom K Lim EK Park J Kang Y Yoon DS Na S Koh EK Suh JS Huh YM Kwon TY Haam S 《Langmuir : the ACS journal of surfaces and colloids》2008,24(21):12112-12115
We fabricate the high-performance probes based on Au nanoparticles (AuNP) for detection of live cancer cell. AuNP were synthesized with narrow sized distribution (ca. 10 nm) by Au salt reduction method and deposited onto the aminated substrate as a cross-linker and hot spot. Herein, AuNP has enabled the easy and efficient immobilization of the antibody (Cetuximab), which can selectively interact with epidermal growth factor receptor (EGFR) on the surface of epidermal cancer, as detecting moiety onto the AuNP-deposited substrate without nanolithography process. After conjugation of Cetuximab with AuNP-deposited substrate, Cetuximab-conjugated probe as a live cancer cell detector (LCCD) could detect EGFR-highexpressed A431 cells related to epithelial cancer with 54-times larger specificity and sensitivity in comparison with EGFR-deficient MCF7 cells. This implies that AuNP-based probes demonstrate abundant potentials for detection and separation of small biomolecules, cells and other chemicals. 相似文献
998.
Minimalism in fabrication of self-organized nanogels holding both anti-cancer drug and targeting moiety 总被引:1,自引:0,他引:1
Kim S Park KM Ko JY Kwon IC Cho HG Kang D Yu IT Kim K Na K 《Colloids and surfaces. B, Biointerfaces》2008,63(1):55-63
Recent researches to develop nano-carrier systems in anti-cancer drug delivery have focused on more complicated design to improve therapeutic efficacy and to reduce side effects. Although such efforts have great impact to biomedical science and engineering, the complexity has been a huddle because of clinical and economic problems. In order to overcome the problems, a simplest strategy to fabricate nano-carriers to deliver doxorubicin (DOX) was proposed in the present study. Two significant subjects (i) formation of nanoparticles loading and releasing DOX and (ii) binding specificity of them to cells, were examined. Folic acid (FA) was directly coupled with pullulan (Pul) backbone by ester linkage (FA/Pul conjugate) and the degree of substitution (DS) was varied, which were confirmed by 1H NMR and UV spectrophotometry. Light scattering results revealed that the nanogels possessed two major size distributions around 70 and 270 nm in an aqueous solution. Their critical aggregation concentrations (CACs) were less than 10 microg/mL, which are lower than general critical micelle concentrations (CMCs) of low-molecular-weight surfactants. Transmission electron microscopy (TEM) images showed well-dispersed nanogel morphology in a dried state. Depending on the DS, the nanogels showed different DOX-loading and releasing profiles. The DOX release rate from FA8/Pul (with the highest DS) for 24h was slower than that from FA4/or FA6/Pul, indicating that the FA worked as a hydrophobic moiety for drug holding. Cellular uptake of the nanogels (KB cells) was also monitored by confocal microscopy. All nanogels were internalized regardless of the DS of FA. Based on the results, the objectives of this study, to suggest a new method overcoming the complications in the drug carrier design, were successfully verified. 相似文献
999.
Park SJ Kwon OH Lee KS Yamaguchi K Jang DJ Hong JI 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(17):5353-5359
The acid-assisted and guest-induced formation of superstructures was achieved by the addition of haloacetic acids to a toluene solution of the resorcin[4]arene derivatives 1 and [60]fullerenes. The formation of dimeric superstructures that encapsulated a nanosized guest molecule was observed when appropriate acids, such as haloacetic acids, and suitable guest molecules, such as [60]fullerenes, were co-added to a toluene solution of cavitand 1 that has four pyridine units, whereas a complicated equilibrium between several species was detected without [60]fullerenes, and the formation of discrete superstructures was not monitored in the absence of haloacetic acids. The spectroscopic data indicate that the formed [60]fullerene-encapsulated complexes have the structure of 2. These complexes are self-assembled through pyridinium-anion-pyridinium interactions and by pi-pi and van der Waals interactions. The rate of decomplexation of 2 is estimated to be 3.1 s(-1) from a 2D exchange NMR spectrum. The [60]fullerene encapsulation process can be controlled by modifying the amounts of acids used, changing the temperature of the system, altering the ratio of acid/base, and even through varying the solvent polarity. Moreover, the fluorescence spectra show band-narrowing spectral changes and a retardation of the relaxation characteristics of isolated and isotropic [60]fullerenes, which indicates that the environmental change around [60]fullerene is induced upon its encapsulation. 相似文献
1000.
An ensemble sensor system that exhibited selective luminescence enhancement upon binding to thymidine 5'-triphosphate (TTP) in HEPES buffer over other nucleotides was developed. The ensemble system consisted of an energy acceptor (FIrpic-bis(Zn2+-dipicolylamine conjugate, FIrpic=bis[(4,6-difluorophenyl)-pyridinato-N,C2+]picolinate) derivative) and an energy donor (mCP-Zn2+-cyclen, mCP=N,N'-dicarbazolyl-3,5-benzene). Among the nucleotides, the selective recognition and luminescence enhancement for TTP was achieved by the strong binding of the thymine unit to Zn2+-cyclen (cyclen=1,4,7,10-tetraazacyclododecane) and intermolecular energy transfer between the mCP and FIrpic moieties. 相似文献