Electro-optical characterization of cyanine-based GUMBOS and nanoGUMBOS

Abstract

Over the last decade in materials science, molecular electronics has emerged as one of the most rapidly developing interdisciplinary research areas with the prospects of ultimate miniaturization and integration of functional organic species with traditional silicon based semiconductor technology. To this end, fundamental studies to investigate the electrical and optical properties of organic nanomaterials deserve special attention. In this work, conductive probe atomic force microscopy (CP-AFM) and Raman spectroscopy have been performed on a new class of ionic materials, referred to as group of uniform materials based on organic salts (GUMBOS) and nanoparticles derived from these GUMBOS, termed as nanoGUMBOS. The GUMBOS investigated in this study are 1,1′-Diethyl-2,2′-cyanine bis (trifluoromethanesulfonyl) imide ([PIC][NTf2]) and 1,1′-Diethyl-2,2′-cyanine bis (pentafluoromethanesulfonyl) imide ([PIC][BETI]), which have been synthesized by use of a facile, template free anion exchange reaction between their respective parent compounds, followed by an ultrasonication assisted, additive free re-precipitation reaction to obtain the nanoscale particles (nanoGUMBOS). The ([PIC][NTf2] nanoGUMBOS were found to self-assemble into distinct diamond-like, trapezoid structures whereas [PIC][BETI] exhibited rod-like structures. [PIC][NTf2] nanoGUMBOS induced ~25 and ~38 times enhancement in the Raman signal intensity as compared to the parent compound [PIC][I] and [PIC][BETI] nanoGUMBOS respectively. In conjunction with the results of Raman spectra, the current-voltage (I-V) data obtained by CP-AFM are also presented as first-time evidence of electrical performance exhibited by these unique class of materials. The results reported in this study are indicative of their potential incorporation into next generation organic thin film applications in optoelectronics, dye-sensitized solar cells, and chemical sensors.