# Self-assembled π-conjugated Cu(ii)–phenanthro[9,10-d]imidazole superstructures for VOC sensing and enhanced supercapacitor performance

## TL;DR

Researchers created copper-based self-assembled materials that can detect acetone and store energy, showing potential for sensors and supercapacitors.

## Contribution

The study introduces new π-conjugated Cu(ii) complexes that self-assemble into functional superstructures for VOC sensing and energy storage.

## Key findings

- (S1)2Cu shows superior acetone selectivity compared to (S2)2Cu in VOC sensing.
- (S1)2Cu achieves a specific capacitance of 230.0 F g−1 and retains 75% capacitance after 4000 cycles.
- The superstructures are governed by non-covalent interactions and metal–ligand coordination.

## Abstract

The development of self-assembled smart materials is a pivotal area of advanced research, particularly for sensing and electronic applications. π-Conjugated small organic molecules can self-assemble into well-ordered superstructures with remarkable optoelectronic, chemical, and structural properties, making them suitable for applications such as volatile organic compound (VOC) detection and energy storage in supercapacitors. However, the self-assembly behavior of Cu(ii) complexes derived from π-conjugated ligands, and their potential use in areas such as health, environmental monitoring, and energy storage, remain underexplored. In this study, we designed and synthesized two π-conjugated phenanthro[9,10-d]imidazole-based ligands (S1 and S2) and their corresponding Cu(ii) complexes, (S1)2Cu and (S2)2Cu. These complexes self-assemble into well-ordered superstructures with distinct morphologies and selectively detect acetone vapors via Scanning Kelvin Probe (SKP) measurements. Their properties are governed by multiple non-covalent interactions in combination with metal–ligand coordination, which control the shape and size of the assemblies. Surface photovoltage measurements under dark and UV conditions, in the presence of different VOC vapors, revealed that (S1)2Cu exhibits superior selectivity toward acetone compared to (S2)2Cu. The pseudo-capacitive performance of the self-assembled superstructures was also evaluated in 1.0 M KOH aqueous electrolyte, yielding specific capacitances of 230.0 F g−1 for (S1)2Cu and 195.0 F g−1 for (S2)2Cu. (S1)2Cu also demonstrated higher rate capability and better capacitance retention (75% after 4000 cycles). Overall, this work presents a promising strategy for designing self-assembled superstructures from metal-coordinated π-conjugated systems as advanced functional materials for VOC sensing and potential electrode materials for aqueous supercapacitor applications.

Cu(ii) complexes of S1 and S2, self-assembled into well-ordered superstructures present promising smart materials for acetone sensing, offering potential applications in designing VOC sensor devices and supercapacitor applications.