排序方式: 共有134条查询结果,搜索用时 15 毫秒
61.
Guang Liu Melissa L. Kistler Tong Li Anish Bhatt Tianbo Liu 《Journal of Cluster Science》2006,17(2):427-443
This article reports the use of simple conductivity measurements to explore the state of small counter-ions (mostly NH 4 + and Na+) in $[\hbox{As}^{\rm III}_{12}\hbox{Ce}^{\rm III}_{16}(\hbox{H}_2\hbox{O})_{36}\hbox{W}_{148}\hbox{O}_{524}]^{76-} (\{\hbox{W}_{148}\})$ and $[\hbox{Mo}_{132}\hbox{O}_{372}(\hbox{CH}_{3}\hbox{COO})_{30} (\hbox{H}_{2}\hbox{O})_{72}]^{42-} (\{\hbox{Mo}_{132}\})$ macroanionic solutions. All the solutions are dialyzed to remove the extra electrolytes. Conductivity measurements on {(NH4)70Na6W148} and {(NH4)42Mo132} solutions at different concentrations both before and after dialysis indicate that the state of counter-ions has obvious concentration dependence. The “counter-ion association” phenomenon, that is, some small counter-ions closely associate with macroanions and move together, has been observed in both types of macroionic solutions above certain concentration. The association of counter-ions in hydrophilic macroionic solutions provides support on our previous speculation that the counter-ions might be responsible for the unique self-assembly of such macroanions into single-layer blackberry-type structures. 相似文献
62.
Campos R Guenthner AJ Meuler AJ Tuteja A Cohen RE McKinley GH Haddad TS Mabry JM 《Langmuir : the ACS journal of surfaces and colloids》2012,28(25):9834-9841
The liquid repellency and surface topography characteristics of coatings comprising a sprayed-on mixture of fluoroalkyl-functional precipitated silica and a fluoropolymer binder were examined using contact and sliding angle analysis, electron microscopy, and image analysis for determination of fractal dimensionality. The coatings proved to be an especially useful class of liquid repellent materials due to their combination of simple and scalable deposition process, low surface energy, and the roughness characteristics of the aggregates. These characteristics interact in a unique way to prevent the buildup of binder in interstitial regions, preserving re-entrant curvature across multiple length scales, thereby enabling a wide range of liquid repellency, including superoleophobicity. In addition, rather than accumulating in the interstices, the binder becomes widely distributed across the surface of the aggregates, enabling a mechanism in which a simple shortage or excess of binder controls the extent of coating roughness at very small length scales, thereby controlling the extent of liquid repellence. 相似文献
63.
Badu-Tawiah AK Cyriac J Cooks RG 《Journal of the American Society for Mass Spectrometry》2012,23(5):842-849
Solvent-free ion/surface chemistry is studied at atmospheric pressure, specifically pyrylium cations, are reacted at ambient
surfaces with organic amines to generate pyridinium ions. The dry reagent ions were generated by electrospraying a solution
of the organic salt and passing the resulting electrosprayed droplets pneumatically through a heated metal drying tube. The
dry ions were then passed through an electric field in air to separate the cations from anions and direct the cations onto
a gold substrate coated with an amine. This nontraditional way of manipulating polyatomic ions has provided new chemical insights,
for example, the surface reaction involving dry isolated 2,4,6-triphenylpyrylium cations and condensed solid-phase ethanolamine
was found to produce the expected N-substituted pyridinium product ion via a pseudobase intermediate in a regiospecific fashion.
In solution however, ethanolamine was observed to react through its N-centered and O-centered nucleophilic groups to generate
two isomeric products via 2H-pyran intermediates. The O-centered nucleophile reacted less rapidly to give the minor product.
The surface reaction product was characterized in situ by surface enhanced Raman spectroscopy, and ex situ using mass spectrometry
and H/D exchange, and found to be chemically the same as the major pyridinium solution-phase reaction product. 相似文献
64.
Cyriac A Jeon JY Varghese JK Park JH Choi SY Chung YK Lee BY 《Dalton transactions (Cambridge, England : 2003)》2012,41(5):1444-1447
Contrary to the stereotype, Jacobsen's catalyst, chiral (salcy)Co(III)OAc adopts an unusual binding mode. The tetradentate {ONNO} ligand does not form a square plane but wraps cobalt in a cis-β fashion while acetate is chelating. 相似文献
65.
Transition Metal Chemistry - This work describes a simple impregnation and soaking method for designing of stabilized nickel exchanged supported 12-tungstophosphoric acid, its characterization and... 相似文献
66.
We prove that a modified version of the Bak-Sneppen model obeys power law behaviour for avalanche duration and size. We do this through a coupling with a suitable branching process which is known to have power law behaviour at criticality. 相似文献
67.
A. Sreekumaran Nair Chandramouli Subramaniam M. J. Rosemary Renjis T. Tom V. R. Rajeev Kumar D. M. David Jeba Singh Jobin Cyriac Prashant Jain K. A. Kalesh Shreya Bhattacharya T. Pradeep 《Pramana》2005,65(4):631-640
In this paper, an overview of the synthesis, chemistry and applications of nanosystems carried out in our laboratory is presented.
The discussion is divided into four sections, namely (a) chemistry of nanoparticles, (b) development of new synthetic approaches,
(c) gas phase clusters and (d) device structures and applications. In ‘chemistry of nanoparticles’ we describe a novel reaction
between nanoparticles of Ag and Au with halocarbons. The reactions lead to the formation of various carbonaceous materials
and metal halides. In ‘development of new synthetic approaches’ our one-pot methodologies for the synthesis of core-shell
nanosystems of Au, Ag and Cu protected with TiO2 and ZrO2 as well as various polymers are discussed. Some results on the interaction of nanoparticles with biomolecules are also detailed
in this section. The third section covers the formation of gas phase aggregates/clusters of thiol-protected sub-nanoparticles.
Laser desorption of H2MoO4, H2WO4, MoS2, and WS2 giving novel clusters is discussed. The fourth section deals with the development of simple devices and technologies using
nanomaterials described above. 相似文献
68.
Divya Thomas Laina Lonappan Leena Rajith Soumya T. Cyriac Krishnapillai Girish Kumar 《Journal of fluorescence》2013,23(3):473-478
Fluorescent PET (Photoinduced Electron Transfer) has been of particular growth in recent times. A novel PET based fluorescent sensor using unmodified CdSe quantum dots (QDs) has been developed for the trace determination of Nimesulide (NIM). The sensor is based on the selective fluorescence quenching of quantum dots by NIM in presence of other NSAIDs and is found that intensity of quenching is linearly related to NIM concentration in the range 8.2?×?10?7 – 4.01?×?10?5?M. The mechanism of interaction is discussed. Finally, the potential application of the proposed method for the trace determination of NIM in pharmaceutical formulation is demonstrated. 相似文献
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