Experimental and theoretical studies of 1-alkanethiols SAMs of various chain-lengths on gold nanoparticles and their effect on SERS, stability and surface properties

Shumbula, Ndivhuwo P.; Ndala, Zakhele B.; Nkabinde, Siyabonga S.; Kolokoto, Tshwarela; Shumbula, Poslet; Mdluli, Phumlane Selby; Hlatshwayo, Thulani Thokozani; Mlambo, Mbuso; Moloto, Nosipho

doi:10.1016/j.molstruc.2020.128801

Cited by 4 publications

(4 citation statements)

References 29 publications

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“…The negligible effect of octanethiol coating on iron particle settling can be attributed to the fact that the octanethiol chain length is not long enough to create particle–particle repulsion between the iron particles. This is similar to the results observed by Shumbula et al who showed that short-chain 1-alkanethiols provided less steric hindrance, leading to agglomeration of gold nanoparticles relative to longer chain alkanethiols …”

Section: Resultssupporting

confidence: 91%

“…Improved sedimentation stability for hexadecanethiol was seen only for adsorbed iron particles prepared in MeOH (0.09%), EtOH (0.13%), and chloroform (0.13%) after 7 days, indicating that sedimentation behavior is a strong function of adsorption solvent. Packing of SAMs has already been shown to be a function of adsorption solvent in addition to alkanethiol chain length and substrate properties. ,,,,,− Hence, it can be hypothesized that the difference in SAM packed structures due to the adsorption solvent is the reason for enhanced MRF sedimentation stability in the presence of MeOH, EtOH, and chloroform of hexadecanethiol adsorbed iron.…”

Section: Resultsmentioning

confidence: 99%

“…This is similar to the results observed by Shumbula et al who showed that short-chain 1-alkanethiols provided less steric hindrance, leading to agglomeration of gold nanoparticles relative to longer chain alkanethiols. 120 Figures 7 and 8 (middle row) demonstrate that the dodecanethiol adsorbed iron enhanced iron particle settling. The decrease in voltage of neat iron-based MRFs was 0.14%, while a decrease of 0.17% (MeOH), 0.18% (EtOH), 0.18% (IPA), 0.18% (chloroform), 0.17% (toluene), and 0.17% (hexane) was observed for dodecanethiol adsorbed iron-based MRFs after 7 days, indicating a lower iron concentration at a given time.…”

Section: Rheological Measurements Of Alkanethiol Adsorbed Ironmentioning

confidence: 90%

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Study ofn-Alkanethiol Self-Assembly Behavior on Iron Particles: Effect of Alkyl Chain Length and Adsorption Solvent on Resulting Iron-Based Magnetorheological Fluids

et al. 2022

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Self-assembled monolayers (SAMs) of organic molecules on metal surfaces are a type of inexpensive surface coating often used to improve metal substrate properties for sensors, electrochemistry, and nanofabrication applications. Iron, specifically, is one of the most commonly used metals, both as a pure metal and as an alloy due to its high conductivity, strong ferromagnetism, and low cost. However, magnetorheological fluids, which have shown impressive energy dampening in fields from civil infrastructure to biomedical devices utilizing iron dispersions, have suffered from low reliability and efficiency due to iron particle oxidation, corrosion, and settling. To understand the effect of self-assembled monolayers on iron and both the adsorbed particle's resistance against aggregation and performance impact, this work performs an in-depth study on alkanethiol-based self-assembled monolayers on iron particles. Adsorption of alkanethiols and the generation of SAMs on micronsized iron particles were evaluated as a function of adsorption solvent polarity and alkanethiol chain length. Maximum alkanethiol loading, determined from appropriate isotherms, was found to strongly be a function of both parameters. Alkanethiol adsorption increased with increasing alkyl chain length and increasing solvent log P values in polar solvents. With respect to magnetorheologically relevant parameters, alkanethiol adsorption did not show any significant effect on both the magnetic properties of iron (as particles) and fluid on-state yield stress. The colloidal stability of n-alkanethiol adsorbed iron-based magnetorheological fluids (MRFs) was a function of both n-alkanethiol chain length and the iron particle adsorption solvent. MRFs composed of hexadecanethiol adsorbed iron prepared in polar solvents like methanol and ethanol showed excellent sedimentation stability compared to all other MRFs prepared in this study.

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Section: Resultssupporting

confidence: 91%

Section: Resultsmentioning

confidence: 99%

Section: Rheological Measurements Of Alkanethiol Adsorbed Ironmentioning

confidence: 90%

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Study ofn-Alkanethiol Self-Assembly Behavior on Iron Particles: Effect of Alkyl Chain Length and Adsorption Solvent on Resulting Iron-Based Magnetorheological Fluids

et al. 2022

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“…Similar modifications are required for in vitro biosensing as a limited stability of the AuNPs strongly affects the sensing performance and decoration with targeting ligands is mandatory to provide specificity for a given analyte. , The PEGylation of AuNPs, that consists in covering the metallic gold core with hydrophilic and uncharged polyethylene glycol (PEG) chains, is often used to afford steric stabilization of the AuNPs as it limits their stability dependence on pH and ionic strength and confers them biocompatibility via stealth properties. Indeed, PEGylated AuNPs exhibit less protein nonspecific adsorption, a reduced uptake by the reticular endothelial system, and thus an increased in-blood circulation time. , PEGs are commonly grafted on AuNPs via thiol groups as it is a very convenient grafting strategy based on the formation of Au–S bonds. − However, thiol chemistry possesses two severe drawbacks limiting their use for in vivo applications: (i) a limited chemical robustness of the organic layer due to the lability of the Au–S bond , and (ii) the difficulty to control the grafting density of different thiolated molecules on the AuNP surface . An alternative strategy for the modification of surfaces consists in using aryl diazonium salts and in particular calix[4]arene-tetradiazonium salts .…”

Section: Introductionmentioning

confidence: 99%

Ultrastable PEGylated Calixarene-Coated Gold Nanoparticles with a Tunable Bioconjugation Density for Biosensing Applications

et al. 2021

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Many in vivo and in vitro applications using gold nanoparticles (AuNPs) require (i) their PEGylation, as it increases their stability and prevents nonspecific protein adsorption, and (ii) their conjugation to biomolecules, that provides them with specific recognition properties. Currently, the functionalization of AuNPs is based on thiol chemistry that suffers from two major drawbacks: (i) the Au–S bond is labile and confers limited chemical robustness to the organic layer, and (ii) control over the bioconjugation density is highly challenging. We report here a novel functionalization strategy based on calix[4]arene-tetradiazonium platforms for the coating of AuNPs with a robust PEG layer and their controlled bioconjugation. AuNPs were first modified with a functional calix[4]arene-diazonium salt bearing three PEG chains ended by a methoxy group and one by a carboxyl group. The resulting particles showed excellent chemical and colloidal stabilities, compared to similar systems obtained via a classical thiol chemistry, and could even be dispersed in human serum without degrading or aggregating. In addition to that, the carboxyl groups protruding from the PEG layer allowed their conjugation via amide bond formation with amine-containing biomolecules such as peptides. The control of the bioconjugation was obtained by grafting mixed layers of functional and nonfunctional PEGylated calix[4]arenes, that allowed varying the number of functional groups carried by the AuNPs and subsequently their bioconjugation capacity while preserving their dense protective PEG shell. Finally, we used these nanomaterials, modified with peptide aptamers, for the in vitro biosensing of a cancer biomarker, Mdm2.

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Dopamine capped silver/copper bimetallic elongated nanoparticles and their potential application in wound healing

Shumbula,

Ndala,

Nkabinde

et al. 2024

Next Nanotechnology

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Experimental and theoretical studies of 1-alkanethiols SAMs of various chain-lengths on gold nanoparticles and their effect on SERS, stability and surface properties

Cited by 4 publications

References 29 publications

Study ofn-Alkanethiol Self-Assembly Behavior on Iron Particles: Effect of Alkyl Chain Length and Adsorption Solvent on Resulting Iron-Based Magnetorheological Fluids

Study ofn-Alkanethiol Self-Assembly Behavior on Iron Particles: Effect of Alkyl Chain Length and Adsorption Solvent on Resulting Iron-Based Magnetorheological Fluids

Ultrastable PEGylated Calixarene-Coated Gold Nanoparticles with a Tunable Bioconjugation Density for Biosensing Applications

Dopamine capped silver/copper bimetallic elongated nanoparticles and their potential application in wound healing

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