- pH Dependence of Interparticle Coupling for Gold Nanoparticle Assemblies Formation: Electrostatic Attraction and Hydrogen Bonding
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With the addition of ω-sulfanylalkanoic or ω -alkyldisulfanylalkanoic acids to sodium-contained aqueous Au colloidal solutions, close-packed self-assembly occurred UV-vis, TEM, solid-state 13C NMR, and FT-IR spectra were employed to study the resulting aggregation arrays. The resulting two-dimensional Au assemblies exhibited interparticle coupling via both hydrogen bonding and electrostatic interactions at pH 6. Either acidic (pH 3) or base (pH 11) generated significant three-dimensional close-packed aggregates. It is suggested that electrostatic interactions might lead to the aggregates during the dry-up process in the preparation of TEM samples of the Au nanoparticles capped with COO- terminals at pH 11. For the acidic solutions (pH 3), coagulation was governed by hydrogen-bonding forces.
- Su, Chia-Hao,Wu, Pei-Lin,Yeh, Chen-Sheng
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- Use of Self-Assembeld Monolayers of Alkyl Mercaptans To Investigate the Chemisorption and Photochemistry of p-Nitrobenzoic Acid on Silver Islands
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Surface-enhanced Raman spectra were obtained from p-nitrobenzoic acid (PNBA) adsorbed onto silver island films that had previously been coated with self-assembled monolayers of alkyl mercaptans.PNBA adsorbed onto silver as a p-nitrobenzoate ion, penetrating through the hydrocarbon layer.However, the alkyl coating hindered the chemisorption and revealed the existence and location of two types of adsorption sites.The photo-induced reduction of PNBA1,2 was not observable when the molecule was adsorbed on silver previously coated with hexadecyl mercaptan.In general, the reaction was much slower when silver was coated with hydrophobic layers than when it was bare or coated with hydrophilic layers.These results are discussed and interpreted in favor of a polymolecular mechanism for the photoinduced reaction.
- Bercegol, Herve,Boerio, F. James
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- Azurin immobilisation on thiol covered Au(111)
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Azurin is a blue single copper protein involved in the respiratory chain of denitrifying bacteria. The structural gene for azurin from Pseudomonas aeruginosa was cloned in an Escherichia coli recombinant strain. The protein overexpressed in the bacterial periplasmic space was subsequently purified. Two strategies were followed to anchor azurin to gold surfaces. First, the protein was immobilised on bare gold. Azurin adsorbs on gold via its disulfide group. Scanning tunnelling microscopy (STM) inspection of the azurin-Au(111) interface revealed the formation of a closely packed protein monolayer and allowed individual azurin molecules to be resolved. In order to uncouple the protein layer from the metal, the gold surfaces were then covered with self-assembled monolayers of 11-mercaptoundecanoic acid. The changes in the sample morphology due to the protein adsorption have been investigated by atomic force microscopy (AFM). A fairly uniform distribution of protein molecules covers the surface. Owing to the tip broadening effect, an average protein diameter of about 20 nm was measured. An upper limit of 1 nN for the non-disruptive imaging force in the contact mode was found.
- Cavalleri,Natale,Stroppolo,Relini,Cosulich,Thea,Novi,Gliozzi
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- Catalytic Hydrogenation of Thioesters, Thiocarbamates, and Thioamides
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Direct hydrogenation of thioesters with H2 provides a facile and waste-free method to access alcohols and thiols. However, no report of this reaction is documented, possibly because of the incompatibility of the generated thiol with typical hydrogenation catalysts. Here, we report an efficient and selective hydrogenation of thioesters. The reaction is catalyzed by an acridine-based ruthenium complex without additives. Various thioesters were fully hydrogenated to the corresponding alcohols and thiols with excellent tolerance for amide, ester, and carboxylic acid groups. Thiocarbamates and thioamides also undergo hydrogenation under similar conditions, substantially extending the application of hydrogenation of organosulfur compounds.
- Luo, Jie,Rauch, Michael,Avram, Liat,Ben-David, Yehoshoa,Milstein, David
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supporting information
p. 21628 - 21633
(2021/01/11)
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- Modular Bidentate Hybrid NHC-Thioether Ligands for the Stabilization of Palladium Nanoparticles in Various Solvents
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The synthesis of four different bidentate hybrid NHC-thioether ligands is presented. The corresponding palladium nanoparticles are stable in various solvents, depending on the ligand used, and show high chemoselectivity in the hydrogenation of olefins. The solubility of the nanoparticles can be switched multiple times depending on the pH value of the solvent. XPS analysis (which shows a subtle shift in the binding energy) was identified as a convenient tool to establish the binding mode of NHC ligands.
- Rühling, Andreas,Schaepe, Kira,Rakers, Lena,Vonh?ren, Benjamin,Tegeder, Patricia,Ravoo, Bart Jan,Glorius, Frank
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p. 5856 - 5860
(2016/05/09)
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- BORATE MOIETY-CONTAINED LINKER AND BIO-SENSING ELEMENT CONTAINING THE SAME
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A borate moiety-contained linker and a bio-sensing element containing the same are disclosed. The borate moiety-contained linker can be used to modify a sensing molecule and connect the sensing molecule to a substrate to form the bio-sensing element.
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Paragraph 0032
(2014/02/15)
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- Luminescent ruthenium(II) polypyridyl functionalized gold nanoparticles; Their DNA binding abilities and application as cellular imaging agents
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The synthesis and photophysical and biological investigation of Ru(II)-polypyridyl stabilized water-soluble, luminescent gold nanoparticles (AuNPs) are described. These structures bind to DNA and undergo rapid cellular uptake, being localized within the cell cytoplasm and nucleus within 4 h.
- Elmes, Robert B. P.,Orange, Kim N.,Cloonan, Suzanne M.,Williams, D. Clive,Gunnlaugsson, Thorfinnur
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p. 15862 - 15865
(2012/01/04)
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- Sodium borohydride-mediated transesterification
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In the presence of sodium borohydride, esters react with alcohols with formation of the corresponding esters. The reaction is sensitive to the solvent, structure of the ester, and is often concurrent with reduction. Thioesters containing an ester group can be selectively cleaved by the reagent. Both esters and thioesters attached to solid support are resistant toward sodium borohydride. The in situ prepared sodium tetraalkoxyborate is introduced as an efficient reagent and catalyst for transesterification.
- Sereda, Grigoriy,Pothula, Swetha,Dreessen, James
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experimental part
p. 1312 - 1321
(2010/07/05)
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- Synthesis of terminally perfluorinated long-chain alkanethiols, sulfides and disulfides from the corresponding halides
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Semifluorinated n-alkanethiols, symmetrical sulfides and disulfides bearing the chain(s) F(CF2)n(CH2)m with n=4, 6, 8, 10, and m=2, 11 have been prepared by various synthetic methods, starting from the corresponding iodides or bromides. Methods based on sodium hydrogen sulfide, commonly used to accomplish this conversion, treatment of the Bunte salt obtained from sodium thiosulfate, the basic hydrolysis of isothiouronium salts, the hydrolysis under mild conditions of thiophosphorates formed from sodium thiophosphate and the basic hydrolysis of thiol acetic acid derivatives, have been investigated and compared relatively to the selective synthesis of the title compounds. The thiolacetic route yields essentially the thiols with some amounts of disulfides. Results from thiourea appears similar. Sodium thiophosphate constitutes an excellent route for the synthesis of thioethers, particularly when starting from the bromides. The two classical methods based on sodium hydrogen sulfide and sodium thiosulfate exhibit poor selectivity. It has been possible to obtain all the sulfur compounds reported in the pure state.
- Naud,Calas,Blancou,Commeyras
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p. 173 - 183
(2007/10/03)
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- Multiple Electron Tunneling Paths across Self-Assembled Monolayers of Alkanethiols with Attached Ruthenium(II/III) Redox Centers
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Alkanethiol monolayers with pendant redox centers are deposited on gold electrodes by selfassembly.The monolayers are composed of both an electroactive thiol, HS(CH2)nC(O)NHCH2pyRu(NH3)5(2+/3+), with 10-15 methylene groups, and a diluent thiol, HS(CH2)mCOOH, also with 10-15 methylene groups.The monolayers are classified as "matched" (n = m), "exposed" ( n = 15, m = 10-14), and "buried" (n = 10, m = 11-15) according to the relative position of the redox center.Cyclic voltammograms in aqueous Na2SO4 indicate that the monolayers are close-packed with the redox centers residing in the aqueous phase in all but the most buried cases.Measurements of electron transfer kinetics by several methods (cyclic voltammetry, ac impedance spectroscopy, chronoamperometry) yield an internally consistent set of kinetic parameters, the standard rate constant ko, and the reorganization energy λ of the redox centers.The reorganization energies are in good agreement with the theoretically predicted value of 1.0 eV for the pyRu(NH3)5 redox centers.Plots of ln(ko) vs m are linear in all three cases.The slopes of the linear regression fit provide tunneling parameters (β, where ko ca. e-βm) of 0.97 +/- 0.03 (matched cases), 0,83 +/- 0.03 (exposed cases) and 0.16 +/- 0.02 (buried cases) per methylene.This pattern of β's is interpreted in terms of electronic coupling between the redox center and the electrode via both the redox thiol and the proximate diluent thiols, with the coupling via the diluent thiols dominating in the exposed cases.
- Finklea, Harry O.,Liu, Luna,Ravenscroft Melissa S.,Punturi, Sesto
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p. 18852 - 18858
(2007/10/03)
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- Derivatized virginiamycin M1
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Derivatized type A virginiamycins having a reactive functionalized side chain, and a process for making the virginiamycin derivatives. The side chain contains a thioether linkage and a reactive group, such as a carboxylate ester or free carboxylic acid group.
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- A NEW LB FILM FORMING MOLECULE CONTAINING BOTH AN ELECTRO- AND PHOTOACTIVE PART
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LB multilayers of the amphiphilic unsymmetrical disulphide S-(2-azobenzenethio)-11-mercapto-undecanoic acid (AMU) have been prepared and investigated by spectroscopic methods.A reversible photochromic switch can be observed upon film irradiation. - Keywords: photochromic, Langmuir-Blodgett film, ultrathin films, azobenzene, mercapto-alkanoic acids
- Burghard, M.,Schmelzer, M.,Roth, S.,Goepel, W.
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- The Effect of Two-dimensional Ordering on Photoreactions of Long-chain Unsaturated Carboxylic Acids
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Long chain alkanoic acids with terminal alkenyl and alkynyl groups are subjected to UV irradiation in ordered (Langmuir-Blodgett) and disordered films; polymerisation occurs in the LB films but only dissociation and desorption in the disordered films.
- Guo, Bo Zhang,Tripathi, Sadhana,Taylor, D. Martin,Stirling, Charles J. M.
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p. 479 - 481
(2007/10/02)
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- Sulfone peroxycarboxylic acids
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There are disclosed novel, highly stable sulfone peroxycarboxylic acids useful in detergent compositions or alone as bleaching agents which are represented by the formula STR1 wherein A and B are organic moieties bonded to the sulfur atom by a carbon atom and one of A and B contains from 1 to 4 STR2 groups bonded to carbon atoms.
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- Azole derivatives
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Azole derivatives of the formula SPC1 Wherein R1 is free or esterified carboxyl or other functionally modified carboxyl group, R2 and R3 each are aryl; A is Cn H2n in which n is an integer from 1 to 10, inclusive; and Z is O or S; and the physiologically acceptable salts thereof, possess, with good compatibility, excellent antiphlogistic activity and, in particular, influence favorably the chronic progressive diseases of the joints, e.g., arthritis. They can be prepared from compounds of the formula SPC2 Wherein X1 is a group convertible into the group --S--A--R1, and R2 and R3 have the values given above.
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