Strong Metal–Adsorbate Interactions Increase the Reactivity and Decrease the Orientational Order of OH-Functionalized N-Heterocyclic Carbene Monolayers

Dery, Shahar; Berg, Iris; Kim, Suhong; Cossaro, Albano; Verdini, Alberto; Toste, F. Dean; Gross, Elad

doi:10.1021/acs.langmuir.9b02401

Cited by 30 publications

(30 citation statements)

References 54 publications

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“…Thus, the lack of a symmetric N-O vibration can indicate that the -NO 2 groups in EC-deposited NO 2 -NHCs were not oriented in a standing position, as identified in DFT calculations ( Supplementary Fig. 3) and in other addressable NHC monolayers 17,48 .…”

Section: Resultsmentioning

confidence: 86%

Electrochemical deposition of N-heterocyclic carbene monolayers on metal surfaces

Amit

Dery

et al. 2020

Nat Commun

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N-heterocyclic carbenes (NHCs) have been widely utilized for the formation of self-assembled monolayers (SAMs) on various surfaces. The main methodologies for preparation of NHCs-based SAMs either requires inert atmosphere and strong base for deprotonation of imidazolium precursors or the use of specifically-synthesized precursors such as NHC(H)[HCO3] salts or NHC–CO2 adducts. Herein, we demonstrate an electrochemical approach for surface-anchoring of NHCs which overcomes the need for dry environment, addition of exogenous strong base or restricting synthetic steps. In the electrochemical deposition, water reduction reaction is used to generate high concentration of hydroxide ions in proximity to a metal electrode. Imidazolium cations were deprotonated by hydroxide ions, leading to carbenes formation that self-assembled on the electrode’s surface. SAMs of NO2-functionalized NHCs and dimethyl-benzimidazole were electrochemically deposited on Au films. SAMs of NHCs were also electrochemically deposited on Pt, Pd and Ag films, demonstrating the wide metal scope of this deposition technique.

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Section: Resultsmentioning

confidence: 86%

Electrochemical deposition of N-heterocyclic carbene monolayers on metal surfaces

Amit

Dery

et al. 2020

Nat Commun

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“…2b-c). [21][22][23] The shift in the peak position following deprotonation was correlated to neutralization of the positive charge in stilbene-imidazolium and was identified as well in other NHC-based monolayers. 17 Surface-anchoring of stilbene-NHC on Au and Pt films changed their WF values by -0.36 eV and -0.25 eV, respectively.…”

Section: Resultsmentioning

confidence: 70%

“…27 The higher change in the surface potential of Au, in comparison to Pt, can be associated with the higher order of stilbene-NHC on Au. 21 The photoswitchability of surface-anchored stilbene-NHC and its impact on surface properties was examined by WF measurements under irradiation. Each cycle consisted of one-hour irradiation (365 nm) followed by relaxation without illumination.…”

Section: Resultsmentioning

confidence: 99%

“…17 Since NHCs are anchored to the surface through the carbene of the imidazole ring, N-substitution of the imidazole allows the positioning of a responsive group in high proximity to the metal. 19,[21][22][23][24][25][26] The ability to position chemically-reactive groups in proximity to the metal support enabled to utilize metal-adsorbate interactions for tuning the chemical reactivity of the addressable group [21][22][23]25,26 and the metal properties, i.e. surface potential.…”

Section: Introductionmentioning

confidence: 99%

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Using Photoactive N-Heterocyclic Carbenes Monolayers to Identify the Influence of Surface Proximity on Photoswitching Activity

Dery¹,

Alshanski²,

Mervinetsky³

et al. 2020

Preprint

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Self-assembly of photoresponsive molecules is a robust technology for reversibly tuning the chemical and electronic properties of functional materials. In most systems the photoactive group is separated from the surface by a spacer and thus the photo-responsiveness does not benefit from interactions with the metal. Herein, the impact of metal photoactive-group interactions on photoswitchability and surface potential were probed by self-assembly of N-heterocyclic carbene molecules (NHCs) that were functionalized with stilbene group directly on their imidazole ring. Stilbene-NHCs that were adsorbed on weakly interacting Au surface accumulated a vertical orientation, as identified by FTIR measurements. This positioning enabled structural flexibility and high photoisomerization efficiency that induced reversible changes in surface potential. Stilbene-NHCs that were anchored on Pt film accumulated flat-lying adsorption geometry due to strong metal-adsorbate interactions. These interactions limited the structural flexibility of the stilbene groups and induced deteriorated photoswitchability that led to lower photoinduced changes in surface potential. While stronger metal-adsorbate interactions hindered the photo-induced isomerization yield of stilbene, these interactions prompted the cis-to-trans thermal-induced isomerization rate, which was an order of magnitude higher on Pt than on Au.

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“…However, using metal substrate has several disadvantages in detecting molecules. For example, the metal catalytic effect would affect the analyte molecule [12], the strong interaction between the metal and the molecule deforms the molecule structure easily [13,14], and the metal surface is prone to produce carbonization effects causing additional strong background signals generated during analysis [15]. In recent years, many studies have demonstrated that 2D materials, such as graphene, boron nitride, and molybdenum disulfide (MoS 2 ), Nanomaterials 2021, 11, 733 2 of 9 could be utilized as SERS substrates for biomedical detections [16,17].…”

Section: Introductionmentioning

confidence: 99%

Using Si/MoS2 Core-Shell Nanopillar Arrays Enhances SERS Signal

Liu

Shieh

et al. 2021

Nanomaterials

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Two-dimensional layered material Molybdenum disulfide (MoS2) exhibits a flat surface without dangling bonds and is expected to be a suitable surface-enhanced Raman scattering (SERS) substrate for the detection of organic molecules. However, further fabrication of nanostructures for enhancement of SERS is necessary because of the low detection efficiency of MoS2. In this paper, period-distribution Si/MoS2 core/shell nanopillar (NP) arrays were fabricated for SERS. The MoS2 thin films were formed on the surface of Si NPs by sulfurizing the MoO3 thin films coated on the Si NP arrays. Scanning electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy were performed to characterize Si/MoS2 core-shell nanostructure. In comparison with a bare Si substrate and MoS2 thin film, the use of Si/MoS2 core-shell NP arrays as SERS substrates enhances the intensity of each SERS signal peak for Rhodamine 6G (R6G) molecules, and especially exhibits about 75-fold and 7-fold enhancements in the 1361 cm−1 peak signal, respectively. We suggest that the Si/MoS2 core-shell NP arrays with larger area could absorb more R6G molecules and provide larger interfaces between MoS2 and R6G molecules, leading to higher opportunity of charge transfer process and exciton transitions. Therefore, the Si/MoS2 core/shell NP arrays could effectively enhance SERS signal and serve as excellent SERS substrates in biomedical detection.

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Strong Metal–Adsorbate Interactions Increase the Reactivity and Decrease the Orientational Order of OH-Functionalized N-Heterocyclic Carbene Monolayers

Cited by 30 publications

References 54 publications

Electrochemical deposition of N-heterocyclic carbene monolayers on metal surfaces

Electrochemical deposition of N-heterocyclic carbene monolayers on metal surfaces

Using Photoactive N-Heterocyclic Carbenes Monolayers to Identify the Influence of Surface Proximity on Photoswitching Activity

Using Si/MoS2 Core-Shell Nanopillar Arrays Enhances SERS Signal

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