New Findings for the Composition and Structure of Ni Nanoparticles Protected with Organomercaptan Molecules

CALDERÓN, MATIAS F.; ZELAYA, EUGENIA; SCHILARDI, PATRICIA L.; BENITEZ, GUILLERMO A.; RUBERT, ALDO A.; SALVAREZZA, ROBERTO C.; IBAÑEZ, FRANCISCO J.

LANGMUIR

AMER CHEMICAL SOC

Lugar: Washington; Año: 2013 p. 1 - 30

0743-7463

The reduction of NiCl2 with NaBH4 in the presence of dodecanethiol (C12SH) yields to a complex product difficult to be identified as illustrated in the figure of merit. We synthesized Ni(II) dodecanethiolate (C12S) (without the addition of NaBH4) for comparison and performed an exhaustive characterization with TEM, HR-TEM, AFM, MFM, XPS, XRD, UV-vis, magnetism, and FT-IR. It is found that the organic coating is not quite a well-organized self-assembled monolayer (SAM) surrounding the Ni cluster as previously reported. XPS and XRD data show slightly difference between both syntheses however; Ni(II) thiolate appears more stable than reduced Ni when exposed to ambient air indicating the propensity of metallic Ni to oxidize. It has been shown that irradiating with TEM electrons over various metal thiolates leads to nanoparticle formation. We irradiated over Ni(II) thiolate and observed no evidence of NPs formation whereas, irradiating on reduced Ni sample exhibited ~ 3.0 nm nanoparticle diameter. Magnetism studies showed difference between both samples indicating ferromagnetic character for reduced Ni sample. According to our results, the product of synthesis is comprised of ultrasmall metallic clusters embedded in some form of Ni(II) C12S. In this work we open the discussion about the chemical nature of the core and the shell in the synthesis of Ni NPs protected with organomercaptan molecules.