Robust Carboxylic Acid-Terminated Organic Thin Films and Nanoparticle Protectants Generated from Bidentate Alkanethiols

Lee, Han Ju; Jamison, Andrew C.; Yuan, Yuehua; Li, Chien-Hung; Rittikulsittichai, Supachai; Rusakova, Irene; Lee, T. Randall

doi:10.1021/la4017118

Cited by 29 publications

(86 citation statements)

References 57 publications

(91 reference statements)

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“…31 Table 1 provides useful insight into the influence of the tailgroup on film formation. The ellipsometric thicknesses of SAMs generated from ammonium-terminated alkanethiols (AHT, AHPMT, AHPDT) in both ethanol and THF were greater than expected when compared to the thickness values of films generated from the reference carboxylic acid-terminated adsorbates.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Boc-Protected ω-Amino Alkanedithiols Provide Chemically and Thermally Stable Amine-Terminated Monolayers on Gold

2015

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Four custom-designed bidentate adsorbates having either ammonium or Boc-protected amino termini and either methanethiol or ethanethioate headgroups were prepared for the purpose of generating amine-terminated self-assembled monolayers (SAMs) on evaporated gold surfaces. These adsorbates utilize a phenyl-based framework to connect the headgroups to a single hexadecyloxy chain, extending the amino functionality away from the surface of gold, providing two regions within the adsorbate structure where intermolecular interactions contribute to the stability of the fully formed thin film. The structural features of the resulting SAMs were characterized by ellipsometry, X-ray photoelectron spectroscopy, and polarization modulation infrared reflection-absorption spectroscopy. The collected data were compared to those of eight additional SAMs formed from analogous monodentate alkanethiols and alkanethioacetates having either a similar aromatic framework or a simple alkyl chain connecting the headgroup to the tailgroup. The analysis of the data obtained for the full set of SAMs revealed that both the tailgroup and headgroup influenced the formation of a well-packed monolayer, with the Boc-protected amine-terminated alkanethiols producing films with superior surface bonding and adsorbate packing as compared to those formed with ammonium tailgroups or alkanethioacetate headgroups. A comparison of the structural differences before and after deprotection of the Boc-protected amine-terminated thiolate SAMs revealed that the bidentate adsorbate was the most resistant to desorption during the Boc-deprotection procedure. Furthermore, solution-phase thermal desorption tests performed to evaluate the thermal stability of the Boc-deprotected amine-terminated alkanethiolate films provided further evidence of the enhanced stability associated with SAMs formed from these bidentate adsorbates.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Boc-Protected ω-Amino Alkanedithiols Provide Chemically and Thermally Stable Amine-Terminated Monolayers on Gold

2015

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“…In addition, the calculated relative packing densities of the azidoalkanethiolate SAMs reveal that the bidentate adsorbates have reduced packing densities as compared to the monodentate adsorbate (see Table S2 in the Supporting Information), which is in line with reported values in the literature for other bidentate adsorbates. 23,31 The presence of the azide functional group is apparent in the XPS data. As shown in Figure 2d, peaks at 404 eV and 401 eV appear in a ratio of 1:2 and represent two distinctly different nitrogen species in the azide group.…”

Section: Analysis By Xps Xps Provides Important Information Regardinmentioning

confidence: 99%

“…The second step involved a thiol-Michael addition of the cysteine-terminated poly-L-lysine to the maleimide and was conducted under ambient conditions; 19 this latter reaction has been used in a wide variety of materials/biomaterials applications. 2,15,20 The use of a short-chained dithiol platform for producing a polypeptide interface offers at least three advantages when compared to related approaches involving the physisorption of peptides: 5,21 (1) a reliable site for covalent attachment of peptide molecules, (2) a highly stable monolayer on the surface, 22,23 and (3) circumvention of problems that are encountered when using adsorbates having long alkyl chains (e.g., disarray in the resulting peptide films). Further, the minor differences in structure between the two dithiol adsorbates provide an opportunity to assess the value of the added conformational mobility afforded by a limited increase in the length of the alkyl spacer extending from the rigid aromatic ring.…”

Section: Introductionmentioning

confidence: 99%

Poly(l-lysine) Interfaces via Dual Click Reactions on Surface-Bound Custom-Designed Dithiol Adsorbates

2015

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Surfaces modified with poly(L-lysine) can be used to immobilize selected biomolecules electrostatically. This report describes the preparation of a set of self-assembled monolayers (SAMs) from three different azide-terminated adsorbates as platforms for performing controlled surface attachments and as a means of determining the parameters that afford stable poly(L-lysine)-modified SAM surfaces having controlled packing densities. A maleimide-terminated alkyne linker was "clicked" to the azide-terminated surfaces via a copper-catalyzed cycloaddition reaction to produce the attachment sites for the polypeptides. A thiol-Michael addition was then used to immobilize cysteine-terminated poly(L-lysine) moieties on the gold surface, avoiding adsorbate self-reactions with this two-step procedure. Each step in this process was analyzed by ellipsometry, X-ray photoelectron spectroscopy, polarization modulation infrared reflection-absorption spectroscopy, and contact angle goniometry to determine which adsorbate structure most effectively produced the targeted polypeptide interface. Additionally, a series of mixed SAMs using an azidoalkanethiol in combination with a normal alkanethiol having an equivalent alkyl chain were prepared to provide data to determine how dilution of the azide reactive site on the SAM surface influences the initial click reaction. Overall, the collected data demonstrate the advantages of an appropriately designed bidentate absorbate and its potential to form effective platforms for biomolecule surface attachment via click reactions.

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“…[2b] Furthermore,w e observed the binding energy of the alkyl/aromatic carbon at about 285 eV,carboxylate carbon at about 290 eV,and also p to p*a ta bout 291.5 eV from the C1ss pectrum (Supporting Information, Figure S11). [11] Thee xtent of surface functionalization was estimated by TGA analysis.F or the larger NHC-Aun anoparticles (NP 2 -7h)w ith am oderate SPR band, the Au :NHC ratio was determined to be 90:10, whereas smaller nanoparticles (NP 1 -5h and NP 2/3 -5h)h ad ar atio of 85:15, both of which correlated well with the respective core sizes based on TEM (Table 1; Supporting Information, Figure S9). Remarkably, Figure 2.…”

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Water‐Soluble N‐Heterocyclic Carbene‐Protected Gold Nanoparticles: Size‐Controlled Synthesis, Stability, and Optical Properties

et al. 2017

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NHC-Au complexes were used to prepare stable, water-soluble, NHC-protected gold nanoparticles. The water-soluble, charged nature of the nanoparticles permitted analysis by polyacrylamide gel electrophoresis (PAGE), which showed that the nanoparticles were highly monodisperse, with tunable core diameters between 2.0 and 3.3 nm depending on the synthesis conditions. Temporal, thermal, and chemical stability of the nanoparticles were determined to be high. Treatment with thiols caused etching of the particles after 24 h; however larger plasmonic particles showed greater resistance to thiol treatment. These water-soluble, bio-compatible nanoparticles are promising candidates for use in photoacoustic imaging, with even the smallest nanoparticles giving reliable photoacoustic signals.

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Robust Carboxylic Acid-Terminated Organic Thin Films and Nanoparticle Protectants Generated from Bidentate Alkanethiols

Cited by 29 publications

References 57 publications

Boc-Protected ω-Amino Alkanedithiols Provide Chemically and Thermally Stable Amine-Terminated Monolayers on Gold

Boc-Protected ω-Amino Alkanedithiols Provide Chemically and Thermally Stable Amine-Terminated Monolayers on Gold

Poly(l-lysine) Interfaces via Dual Click Reactions on Surface-Bound Custom-Designed Dithiol Adsorbates

Water‐Soluble N‐Heterocyclic Carbene‐Protected Gold Nanoparticles: Size‐Controlled Synthesis, Stability, and Optical Properties

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