1,915 research outputs found
Reactivity control of carboxylic acid-terminated self-assembled monolayers on gold: Acid fluoride versus interchain carboxylic anhydride
No full textReactions that occur at interfaces often show different behaviors from their solution analogues. In this paper, we demonstrated how proximity effect, one of the unique phenomena at interfaces, could control the product distributions of interfacial reactions. Self-assembled monolayers (SAMs) of 16-mercaptohexadecanoic acid on gold surfaces were treated with cyanuric fluoride and pyridine, which are generally used for forming acid fluorides from carboxylic acids in the solution-based reaction. After the treatment, two different products, acid fluorides (AFs) and interchain carboxylic anhydrides (ICAs), were controllably obtained at surfaces under different reaction conditions with keeping the reagents the same. Various factors, such as the concentrations of reagents, reaction time, and additives, affected the product distribution (or the reaction pathway) at surfaces. We found that one of the key factors in controlling the reaction pathway was a relative contribution from the proximity effect of adjacent carboxylic acid chains in the SAMs (kinetic control) and the equilibrium shift (thermodynamic control). The relative reactivity of AF- and ICA-presenting surfaces toward primary amines, such as undecylamine and [((6-aminohexyl)amino)carbonyl]ferrocene, was also investigated, in terms of the number and the ordering of the amines coupled onto the surfaces
Fluoro-N,N,N ,N -tetramethylformamidinium hexafluorophosphate: A reagent for formation of interchain carboxylic anhydrides on self-assembled monolayers
No full textIn this paper, we report the reactivity of fluoro-N, N, N', N'-tetramethylformamidinium hexafluorophosphate ( TFFH), a reagent for transformation of carboxylic acids into acid fluorides in solution, toward self-assembled monolayers ( SAMs) of 16-mercaptohexadecanoic acid on gold. Contrary to the solution-based reactions, we found that only interchain carboxylic anhydrides ( ICAs), not acid fluorides ( AFs), were obtained at surfaces by the facile interchain reaction under most reaction conditions studied. AFs were found to be formed only when tetrabutylammonium fluoride, a reagent inducing fast decomposition of ICAs, was added to the reaction mixture. The reactivity of TFFH toward carboxylic acid-terminated SAMs was different from that of cyanuric fluoride, which has been reported previously ( Langmuir 2005, 21, 11765-11772). This study provides more insight into the role of the proximity effect in SAM-based reactions as well as another approach to the formation of ICAs from carboxylic acid-terminated SAMs
Dip‐Pen Nanolithography Using the Amide‐Coupling Reaction with Interchain Carboxylic Anhydride‐ Terminated Self‐Assembled Monolayers
No full textHerein we report on a new type of dip-pen nanolithography (DPN), which utilizes an interfacial organic reaction-the amide-coupling reaction - between chemically activated surfaces and amine ink molecules transferred from an atomic force microscopy tip. As a representative of the chemically activated surfaces that could react with amine compounds, we formed a self-assembled monolayer terminating in interchain carboxylic anhydride (ICA) groups on gold, and generated chemically derived nanopatterns using alkylamines as ink molecules. Amine inks showed diffusive behavior similar to thiol inks on gold in conventional DPN, and the pattern sizes were controlled by changing the tip dwell times. In addition, nanopatterns of hydrolyzed ICAs were generated by taking advantage of the participation of the water meniscus in the DPN process and the chemical nature of the ICAs
Immobilization of Ti((OPr)-Pr-i)(4) onto silicon oxide surfaces and surface-initiated polymerization of epsilon-caprolactone
No full textReactivity of acetylenyl-terminated self-assembled monolayers on gold: Triazole formation
No full textWe report the reactivity of acetylenyl-terminated self-assembled monolayers (SAMs) on gold toward "click" chemistry, Huisgen 1,3-dipolar addition, leading to the formation of triazoles. After the formation of acetylenyl-terminated SAMs, the triazole formation was performed on the SAMs and the reaction was confirmed by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, ellipsometry, and contact angle goniometry. "Click" chemistry has offered a versatile strategy for the functionalization in solution chemistry with mild reaction conditions and a high compatibility in functional groups, and our result shows that the reaction could be applied to acetylenyl-terminated SAMs for the introduction of useful functional groups to the surfaces
Control of wettability by anion exchange on Si/SiO2 surfaces
No full textWater wettability Of Si/SiO2 surfaces was controlled by the formation of SAMs terminating in 1-alkyl-3-(3-silylpropyl)imidazolium ions and the anion exchange on the surfaces ("direct anion exchange"). The exchange was confirmed by X-ray photoelectron spectroscopy, and the water wettability was measured as a water contact angle by contact angle goniometry. We found that anions played a great role in determining water wettability Of Si/SiO2 surfaces. For example, water contact angles Of Si/SiO2 surfaces presenting 1-methyl-3-(3-silylpropyl)imidazolium ions changed from 28 to 42degrees when the counteranion Cl- was exchanged with PF6- In addition to the anions, the N-alkyl groups of imidazolium cations were also found to be important in determining water wettability: we did not observe any significant changes in the contact angles of Si/SiO2 surfaces presenting 1-butyl-3-(3-silylpropyl)imidazolium ions by the anion exchange. We also demonstrated that the reaction rate of the direct anion exchange was affected by a choice of solvents: the anion exchange from Cl- to PF6- was the fastest in an aqueous solution
Biosurface organic chemistry: Interfacial chemical reactions for applications to nanobiotechnology and biomedical sciences
No full textIn this review, the field of biosurface organic chemistry is defined and some examples are presented. The aim of biosurface organic chemistry, composed of surface organic chemistry, bioconjugation, and micro- and nanofabrication, is to control the interfaces between biological and non-biological systems at the molecular level. Biosurface organic chemistry has evolved into the stage, where the lateral and vertical control of chemical compositions is achievable with recent developments of nanoscience and nanotechnology. Some new findings in the field are discussed in consideration of their applicability to nanobiotechnology and biomedical sciences
Grafting nitrilotriacetic groups onto carboxylic acid-terminated self-assembled monolayers on gold surfaces for immobilization of histidine-tagged proteins
No full textIn this paper, we report a common intermediate method to present nitrilotriacetic acid (NTA) groups on gold surfaces for immobilizing His-tagged proteins onto the surfaces, and a full characterization of self-assembled monolayers (SAMs) terminating in carboxylic acids [HS(CH2)(15)COOH (C15-COOH), HS(CH2)(11)(OCH2CH2)(3)-OCH2COOH (EG3-COOH), and HS(CH2)(11)(OCH2CH2)(5)OCH2COOH (EG5-COOH)] and coupling reactions of an NTA-containing primary amine [(1S)-N-(5-amino-l-carboxypentyl)iminodiacetic acid; NTA-NH2] with the carboxylic acid on surfaces. The lateral packing densities of the COOH-terminated SAMs were calculated to be 4.32 (for C15-COOH), 3.49 (for EG3-COOH), and 2.65 (for EG5-COOH) molecules/nm(2). The packing densities were decreased by incorporating a relatively flexible ethylene glycol (EG) group into the backbone of alkanethiols and increasing the number of the EG groups in the backbone of alkanethiols. The NTA group was then attached by coupling NTA-NH2 with the COOH group on the surfaces, followed by a Ni(II) complexation. The coupling reaction was characterized by FT-IR spectroscopy, ellipsometry, and XPS, and the coupling efficiency ("yield") was estimated by comparing the experimentally determined N 1s to S 2p (N/S) ratio of XPS data with the N/S ratio calculated for the functionalization of the SAMs presenting NTANi(II): the coupling yields were 30% (for C15-COOH) and 25% (for EG3-COOH and EG5-COOH). Preliminary experiments on the binding of His-tagged proteins onto the surfaces were also performed
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