Effects of Alkyl Chain Length on the Adsorption ofn-Alkyl Isocyanides (RN⋮C) on Gold Powder

Abstract

The chemisorption of the alkyl isocyanides n-butyl (C4H9NC), n-hexyl (C6H13NC), n-octyl (C8H17NC), n-dodecyl (C12H25NC), and n-octadecyl isocyanide (C18H37NC) on Au powder from 1,2-dichloroethane (DCE) was examined using both solution (FTIR) and surface (diffuse reflectance infrared fourier transform or DRIFT) spectroscopic techniques. For the isocyanides with fewer than 12 carbon units in their alkyl tails, equilibrium binding constants (K 1), surface coverages (n 1s and n a mol/gAu), and qualitative rates of solution−surface equilibria in DCE solvent are the same. Competition studies between 13C-labeled C18H37NC and nonlabeled C4H9NC show that the ratio of adsorbed isocyanides at equilibrium, C18H37N13C/C4H9NC, is 4.1. Adsorption studies show that isocyanides are bound strongly to the surface at low coverages (less than 70% of saturation coverage), but binding affinity is significantly lower at higher coverages. Studies of C18H37NC and C4H9NC in n-decane, DCE, and nitromethane (MeNO2) solvents show that solvent polarity affects the rate of monolayer formation, surface coverage, and equilibrium binding constants.

Surface-Enhanced Raman Scattering: A Powerful Tool for Chemical Identification

“…This is caused by the donation of antibonding lone-pair electrons of the pendent isocyanide group to the Au nanoparticles. [43][44][45] Another advantage of organic isocyanide as a SERS probe is that the peak position of the NC stretching band is very sensitive to the applied potential under electrochemical conditions. This would suggest that the peak position of the NC stretching band could be used as an indicator of the surface potential of metal nanostructures.…”

Organometallic chemistry and catalysis on gold metal surfaces

“…This gold powder was re-used many times for both the adsorption and catalysis studies. Typically, the gold powder was cleaned before each use by treatment with ''piranha" solution (concentrated H 2 SO 4 /30% aqueous H 2 O 2 ) [20,21], which restored the powder to its original catalytic reactivity. If the gold powder were only washed with a solvent, e.g., MeOH, between catalytic runs, its activity would be slightly decreased ($10%).…”

Adsorption of 4,4′‐biphenyl diisocyanide on gold nanoparticle surfaces investigated by surface‐enhanced Raman scattering

“…The adsorptions of mono-, bi-and tridentate alkyl isocyanides on an Au powder surface have been investigated. 7,8 Lin and McCarley 9 reported that 1,6-diisocyanohexane could form a robust layer on Pt and Au surfaces. 4,4 0 -Biphenyl diisocyanide (BPDNC) was found to adsorb on Au with its one pendant NC group in reflection-absorption infrared spectroscopic, ellipsometric, and contact-angle measurement studies.…”