The rapid formation of functional monolayers on silicon under mild conditions

Abstract

We report on an exceedingly mild chemical functionalization of hydrogen-terminated Si(100) with unactivated and unprotected bifunctional α,ω-dialkynes. Monolayer formation occurs rapidly in the dark, and at room temperature, from dilute solutions of an aromatic-conjugated acetylene. The method addresses the poor reactivity of p-type substrates under mild conditions. We suggest the importance of several factors, including an optimal orientation for electron transfer between the adsorbate and the Si surface, conjugation of the acetylenic function with a π-system, as well as the choice of a solvent system that favors electron transfer and screens Coulombic interactions between surface holes and electrons. The passivated Si(100) electrode is amenable to further functionalization and shown to be a viable model system for redox studies at non-oxide semiconductor electrodes in aqueous solutions.

Quantitative Analysis of Cyclic Voltammetry of Redox Monolayers Adsorbed on Semiconductors: Isolating Electrode Kinetics, Lateral Interactions, and Diode Currents

“…The ket,ap value of 75 s −1 is in accordance with literature values reported for highly doped semiconductor electrodes. 22,23,24 The Laviron model underestimates the electron transfer constant, wrongly sensing a slower electron transfer than the actual one as a consequence of the potential drop across the semiconductor space charge layer. If the Laviron model is applied at the low- est light intensity the calculated electron transfer constant is 75 times lower (ket,ap = 1 s −1 ) than the one obtained applying the model we developed here.…”

A Mechanistic Study of the Oxidative Reaction of Hydrogen-Terminated Si(111) Surfaces with Liquid Methanol

“…Many nucleophiles react with H-Si(111) surfaces to yield unexpected products [50][51] compared to analogous reactions with molecular silanes. For example, the reaction of H-Si (111) surfaces with alcohols has no analogous molecular counterpart.…”

“…4 Moreover, hydrosilylation reactions of molecular silanes typically require ultraviolet illumination, whereas H-Si(111) surfaces react with unsaturated hydrocarbons under visible-light illumination 51 as well as under certain circumstances in the dark at room temperature. 50,78 The mechanisms for the reactions of Grignard reagents, alkenes, and alkynes at H-Si(111) surfaces involve electron transfer kinetics that closely parallel the reaction of CH 3 OH with HSi(111) surfaces. These reactions are known to be sensitive to the bulk electronic structure of the 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 34 which nucleophiles, including alcohols, alkenes, alkynes, and Grignards, can undergo reaction with H-Si(111) surfaces in the presence or absence of an oxidant and/or an illumination source.…”

Anti-Adhesion Behavior from Ring-Strain Amine Cyclic Monolayers Grafted on Silicon (111) Surfaces

“…In terms of the recipient substrate, silicon-based substrate remains an important material for anti-biofouling passivation in view of its diverse applications that may range from biosensing 11,12 to drug delivery 13 . Furthermore, these materials had often been the candidate of choice for examining interfacial behaviour of cells as the spectrum of surface chemistry can be easily fine-tuned by many surface grafting techniques such as silanization 4,14,15 or hydrosilylation [16][17][18][19][20][21] .…”