Rheoreversible metallosupramolecular soft-nanostructure of Cd(ii) for fabricating a thin-film-based semiconducting device

Abstract

A self-assembly-based supramolecular soft network of Cd(II)-metallogel (i.e., Cd–PDCA) of Cd(II)–acetate salt and 2,6-pyridinedicarboxylic acid (PDCA) is successfully achieved through an instant mixing protocol under ordinary conditions. 2,6-Pyridinedicarboxylic acid is used as a low molecular weight gelator (LMWG), and DMF is utilized as a gel-immobilized polar aprotic solvent for the preparation of mechanically stable Cd–PDCA. A specific stoichiometry of Cd(II) and PDCA (i.e., 1 : 1, having [Cd(II)-salt] = 0.3 mM and [PDCA] = 0.3 mM) was maintained by experimentally obtained minimum critical gelation (MCG) concentration values. The mechanical properties of the synthesized Cd–PDCA metallogel are explored through rheological measurements (involving frequency sweep, strain sweep, and thixotropic measurements). The strain sweep-based rheological study demonstrates that the experimentally determined value of the critical shear strain for the Cd–PDCA metallogel is 1.56%. The material shows excellent thixotropic features with multiple cycles, as observed in the time-sweep-based experimental observation. Morphological features of the xerogel sample of the metallogel are observed by collecting FESEM images depicting the nano-structural patterns of the metallogel-forming network. EDAX elemental detection is also performed to determine the involvement of all chemical components playing a crucial role in the construction of the metallogel soft scaffold. The critical effect of pyridylamine-mediated chemo-responsiveness of the Cd–PDCA metallogel is also tested through visual observation and FESEM morphological imaging. Moreover, the stimuli-responsiveness of the metallogel is evaluated by applying various external stimuli, such as ultrasonication, mechanical agitation through a vortex, followed by subsequent rest, heating effect, UV-light exposure, and repercussion by diverse chemicals like ammonia and acetic acid. FT-IR and ESI-mass spectrometric analyses are performed to establish the metallogel-fabricating mechanistic technique. Schottky barrier diode aptitudes of Cd–PDCA metallogel are also examined by means of Al/Cd–PDCA metallogel/ITO sandwich-type device-fabrication strategy. The metallogel-based device effectively shows excellent I–V features with a conductivity of 1.002 × 10⁻⁵ S m⁻¹ and a high ON/OFF ratio of 27.78 under dark condition. The fabricated device shows a remarkable ideality factor of 2.30. Charge transport parameter, like the carrier mobility (μ_eff) of the device, is found to be 3.86 × 10⁻⁶ m² V⁻¹ s⁻¹.