Influence of the grafting process on the orientation and the reactivity of azide-terminated monolayers onto silica surface

Abstract

Click chemistry is widely used in materials and surface science for its high efficiency, ease of use and high yields. Azide-terminated SAMs have been prepared successfully by using three different deposition methods (postfunctionalization and direct grafting by immersion as well as spin coating). Strikingly, our study shows that the reactivity of the azido group on the surface with the alkyne in solution is not trivial and seems to be closely related to the orientation of the azide. Indeed, more the azide is vertically oriented more it is accessible and reactive. The orientation of azido dipoles at the surface depends strongly on the method used to prepare the monolayer. The post-functionalization method allows to have a homogeneous population of the azide groups on the surface with a better vertical orientation than that obtained using direct grafting by immersion or spin coating processes. Whatever the type of azide-terminated SAMs, the reactivity of the accessible vertical azido groups is complete. This study clearly demonstrates that it is possible to control the amount of reactive azides and, consequently, the amount of molecules immobilized on the surface after the click reaction by choosing the deposition method.

Click chemistry: An efficient tool to control the functionalization of metallic surfaces with alkyl chains possessing two reactive end groups

“…The success of the click reaction and the subsequent formation of a triazole ring were also evidenced with the N1s XPS spectra (see Figure 14b and 15b) by the presence of two peaks of binding energies 400.7 eV and 402.1 eV. [25,40,46] These two peaks at 400.7 eV and 402.1 eV are related to N-C and N-N bonds, respectively. [47,49,50] Moreover, presence of iron and therefore of ferrocene on the metal surface is evidenced with Fe2p XPS spectra (see Figure 14c and 15c), where a broad peak is detected at 707.5 eV containing both the Fe2p 3/2 and the Fe2p 1/2 peaks.…”

“…A large number of techniques can be used to investigate and characterize SAMs, among which polarization modulation infrared reflection-absorption spectroscopy (PM-IRRAS) was selected as a method of choice to characterize the different monolayers. [37][38][39][40] Additionally, this technique is a very simple and non-destructive way to detect the different functional groups that are present in the SAMs deposited onto metallic substrates and to acquire molecular information on these bi-dimensional systems. PM-IRRAS was performed on gold substrates modified with SAM 1, SAM 2, SAM 3 and SAM 4 and the spectra are shown in Figure 13 (a to d, respectively) in which characteristic bands could be identified.…”

Stack‐and‐Draw Applied to the Engineering of Multi‐Material Fibers with Non‐Cylindrical Profiles

“…Grafting of the Fluorescent Dye Cy5 on Fiber Surface: The azideterminated SAM was prepared according to the literature. [31] The optical fibers were rinsed with Milli-Q water (18 MΩ.cm), sonicated for 15 min in CHCl 3 , and activated by a 30 min exposure to UV/O 3 . The optical fibers were immersed in a silanization flask under an inert atmosphere (N 2 ) and exposed for 16 h to a solution containing 11-bromoundecyltrimethoxysilane (5 × 10 −5 mol) synthesized according to literature and trichloroacetic acid (TCA, 5 × 10 −6 mol) in 200 mL of anhydrous toluene at 20 °C.…”

“…Then, this SAM-Br undergoes a modification of the terminal bromine substituted by an azide. [30,31] The resulted azide-terminated SAM constitutes a universal reactive molecular platform to Table 1. Physical properties of the materials involved in the present work: Refractive index measured at 589 nm (n@ 589nm ), glass transition temperature (T g ), drawing temperature range (T Draw ), melting temperature (T m ), density (d), and electric resistivity (ρ).…”

“…Then, this SAM‐Br undergoes a modification of the terminal bromine substituted by an azide. [ 30, 31 ] The resulted azide‐terminated SAM constitutes a universal reactive molecular platform to immobilize covalently (bio)molecular probe by an azide–alkyne click chemistry [ 32,33 ] (See “Experimental” section for the full description of the fiber surface preparation mechanism).…”