Electrografting and Langmuir-Blodgett: Covalently Bound Nanometer-Thick Ordered Films on Graphite.

We present two different molecular organizations obtained from octadecylamine (ODA) molecules on a highly oriented pyrolytic graphite (HOPG) surface: (i) self-organized physisorbed ODA molecules lying flat on the surface and (ii) a strongly electrografted compact crystalline monolayer of ODA molecules standing up on the surface. This new structure is obtained by combining the Langmuir-Blodgett transfer of an ODA Langmuir film onto HOPG with oxidative electrografting. The presence of an organic film on HOPG is characterized by attenuated total reflectance-infrared spectroscopy and Raman spectroscopy, while atomic force microscopy and scanning tunneling microscopy allow the observation of the two molecular organizations with adsorbed molecules lying flat on HOPG or strongly grafted in an upright position on the HOPG surface.

Simultaneous Photografting of Two Organic Groups on a Gold Surface by using Arylazo Sulfones as Single Precursors.

Arylazo sulfones have been exploited as photoactivatable substrates for the simultaneous photografting of both aryl and methanesulfonyl groups on a gold surface. The obtained samples have been characterized by different spectroscopic techniques including ellipsometry and electrochemistry, infrared reflection absorption, surface-enhanced Raman spectroscopy, XPS, and AFM. Grafting occurs through a simple N-S cleavage and not, as usually observed with aromatic precursors, by electron transfer.

From Langmuir-Blodgett to Grafted Films.

A locally organized monolayer film strongly attached to a gold surface is obtained by transfer of a Langmuir-Blodgett (LB) film of octadecylamine (ODA) or alcohol (ODOH) onto a Au surface and simultaneous oxidative electrografting of this film still in contact with the aqueous subphase. As opposed to LB films, these films resist ultrasonication; and unlike electrografted films, they are organized monolayers by construction. They are characterized by AFM (atomic force microscopy), water contact angle, ellipsometry, XPS (X-ray photoelectron spectroscopy), IRRAS (infrared reflection absorption spectroscopy), and GIXD (grazing incidence X-ray diffraction).

Grafting of Diazonium Salts on Surfaces: Application to Biosensors.

This review is divided into two parts; the first one summarizes the main features of surface modification by diazonium salts with a focus on most recent advances, while the second part deals with diazonium-based biosensors including small molecules of biological interest, proteins, and nucleic acids.

Alkyl-Modified Gold Surfaces: Characterization of the Au-C Bond.

The surface of gold can be modified with alkyl groups through a radical crossover reaction involving alkyliodides or bromides in the presence of a sterically hindered diazonium salt. In this paper, we characterize the Au-C(alkyl) bond by surface-enhanced Raman spectroscopy (SERS); the corresponding peak appears at 387 cm close to the value obtained by theoretical modeling. The Au-C(alkyl) bond energy is also calculated, it reaches -36.

Surface functionalisation of polymers.

Many applications of polymers require the functionalisation of their surface for use in sensors, composite materials, membranes, microfluidic and biomedical devices and many others. Such surface modifications endow the surface with new properties independent of those of the bulk polymer. This tutorial review describes the different methods, based on very diverse principles, that are available to perform this surface functionalisation, including plasma and UV irradiation, atomic layer deposition, electrochemistry, oxidation, reduction, hydrolysis, the use of radicals and grafting "on" or "from" polymers.

Some Theoretical and Experimental Insights on the Mechanistic Routes Leading to the Spontaneous Grafting of Gold Surfaces by Diazonium Salts.

The spontaneous grafting of diazonium salts on gold may involve the carbocation obtained by heterolytic dediazonation and not necessarily the radical, as usually observed on reducing surfaces. The mechanism is addressed on the basis of DFT calculations and experiments carried out under conditions where the carbocation and the radical are produced selectively. The calculations indicate that the driving force of the reaction leading from a gold cluster, used as a gold model surface, and the carbocation to the modified cluster is higher than that of the analogous reaction starting from the radical.

Reversible Trapping of Functional Molecules at Interfaces Using Diazonium Salts Chemistry.

Developing thin polymeric films for trapping, releasing, delivering, and sensing molecules is important for many applications in chemistry, biotechnology, and environment. Hence, a facile and scalable technique for loading specific molecules on surfaces would rapidly translate into applications. This work presents a novel method for the trapping of functional molecules at interfaces by exploiting diazonium salt chemistry.

Surface Modification of Polymers by Reaction of Alkyl Radicals.

The surfaces of poly(methyl methacrylate) and polyethylene are modified either (i) by a two-step process including the thermal reaction of alkyl radicals derived from bromohexanoic acid in a mixture of 2,6-dimethylbenzene diazonium salt and neat isopentyl nitrite at 60 °C, followed by reaction with p-nitroaniline, anthraquinone, neutral red, and polyethylene glycol moieties, or (ii) by reaction of a previously anthraquinone-modified bromohexanoic acid. The modified surfaces are characterized by IR, XPS, UV, and water contact angles. A mechanism is proposed to rationalize the results.

Powerful Surface Chemistry Approach for the Grafting of Alkyl Multilayers on Aluminum Nanoparticles.

The synthesis of aluminum nanoparticles (Alnp) has raised promising perspectives these past few years for applications in energetic materials. However, because of their high reactivity, it is crucial to functionalize them before their use. In this work, we propose an original and simple chemical approach to graft spontaneously alkyl layers derived from alkyl halides at the surface of Alnp, by relying on the highly reductive character of these nanoparticles, when they are in the unoxidized form.

One-step formation of bifunctionnal aryl/alkyl grafted films on conducting surfaces by the reduction of diazonium salts in the presence of alkyl iodides.

The formation of partial perfluoroalkyl or alkyl radicals from partial perfluoroalkyl or alkyl iodides (ICH2CH2C6F13 and IC6H13) and their reaction with surfaces takes place at low driving force (∼-0.5 V/SCE) when the electrochemical reaction is performed in acetonitrile in the presence of diazonium salts (ArN2(+)), at a potential where the latter is reduced. By comparison to the direct grafting of ICH2CH2C6F13, this corresponds to a gain of ∼2.

Electrografting of alkyl films at low driving force by diverting the reactivity of aryl radicals derived from diazonium salts.

Alkyl and partial perfluoroalkyl groups are strongly attached to carbon surfaces through (i) the abstraction of the iodine atom from an iodoalkane by the sterically hindered 2,6-dimethylphenyl radical and (ii) the reaction of the ensuing alkyl radical with the carbon surface. Since the 2,6-dimethylphenyl radical is obtained at -0.25 V/Ag/AgCl by reducing the corresponding diazonium salt, the electrografting reaction is facilitated by ∼1.