Self-assembled thin films of thiocyanate and selenocyanate bithiophenes
Kelly, Kaitlyn T.
SubjectThiolate thin film
Development of thiocyanate precursors
Surface analysis techniques
Atomic force microscopy (AFM)
Scanning electron microscopy and energy dispersive microscopy (SEM/EDX)
X-ray photoelectron spectroscopy (XPS)
Time-of-flight secondary ion mass spectrometry (ToF-SIMS)
MetadataShow full item record
Presented herein is the organic synthesis and thin film (TF) assembly of six alkyl-substituted thiocyante and selenocyante bithiophene molecules: NCSe-T2-Hx, NCS-T2-Hx, NCS-Hx-T2-Hx, NCSe- Hx-T2-Hx, NCS-Hx-T2-Hx-SCN and NCSe-Hx-T2-Hx-SeCN. TFs assembled from these thio and selenocyanates were characterized by six different techniques: electrochemical capacitance (Cp) measurements, scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDX), atomic force microscopy (AFM), x-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). Cp experiments were used to confirm the development of TFs on an amorphous Au surface using ethanol or hexanes as a reaction solvent. A sputtered Au surface was observed by SEM/EDX to be an inappropriate surface for TF assembly. TFs assembled onto epitaxially grown Au were characterized by multiple techniques. Large crystallites were observed on TFs assembled from NCSe-T2-Hx and NCSe-Hx-T2-Hx-SeCN. Chemical maps of these crystallites were obtained through SEM/EDX. The presence of a covalent Au-S or Au-Se bond on the surface was confirmed by XPS signals from the S 2p3/2 and Se 3d5/2/3d3/2 regions respectively. XPS signals of ~ 399 eV in the N 1s region were observed in all assemblies characterized by this technique, indicating the presence of residual gold-bound cyanide (Au(CN)ads) on the surface. ToF-SIMs chemical intensity maps confirmed the presence of expected TF fragments on the surface of all TFs characterized by this technique. ToF-SIMS results suggested that TFs connected to the Au surface through an aromatically bound S or Se atom produced TFs with higher surface coverage.