Nonaqueous route for the synthesis of copper organosol from copper stearate: An effective catalyst for the synthesis of octylphenyl ether

Good quality highly stable copper organosol has been synthesized in a nonhydrolytic approach from the single phase reduction of the precursor Cu(II) stearate by sodium borohydride in toluene under nitrogen gas atmosphere. Surface modification of the synthesized copper organosol with an amino acid, L-cysteine and an alkanethiol (1-dodecanethiol, DDT) is accomplished by the thiolate bond formation between the ligands and the nanoparticle surface. Cysteine molecule binds the copper surface via a thiolate bond and amine linkage but not by the electrostatic interaction with the carboxylate group due to solvent polarity and dielectric medium of the solvent. The synthesized copper particles have been characterized by the optical spectroscopy (UV-vis), electron microscopy (transmission electron microscopy), X-ray photoelectron spectroscopy, and X-ray diffraction. Fourier transform infrared analysis was performed to confirm the surface functionalization of the copper particles either by the amino acid, L-cysteine, or DDT. The synthesized particles are stable for a couple of months without alteration of the spectral profile. After that, the copper particles lead to aggregation via hydrogen bond formation between the amino acid molecules located on the neighboring copper particles. It was found that only DDT (without the need of any reducing agent) could reduce copper stearate to Cu(0) but the synthesized particles remain stable for a week only. It was also observed that the chain length of the alkanethiols does not affect the particle morphology remarkably but has a bearing on the stability of the evolved particles. Furthermore, the synthesized copper particles have been found to serve as an effective catalyst for the synthesis of octlyphenyl ether under nitrogen gas atmosphere.