Ruthenium(II) polypyridyl complexes (RPCs) that emit from metal-to-ligand charge transfer (MLCT) states have been developed as DNA probes and are being examined as potential anticancer agents. Here, we report that MLCT-emissive RPCs that bind DNA undergo Förster resonance energy transfer (FRET) with Cy5.5-labeled DNA, forming mega-Stokes shift FRET pairs. Based on this discovery, we developed a simple and rapid FRET binding assay to examine DNA-binding interactions of RPCs with diverse photophysical properties, including non-"light switch" complexes [Ru(dppz)₂(5,5'dmb)]²⁺ and [Ru(PIP)₂(5,5'dmb)]²⁺ (dppz = dipyridophenazine, 5,5'dmb = 5,5'-dimethyl-2,2'-bipyridine, PIP = 2-phenyl-imidazo[4,5-f][1,10]phenanthroline). Binding affinities toward duplex, G-quadruplex, three-way junction, and mismatch DNA were determined, and derived FRET donor-acceptor proximities provide information on potential binding sites. Molecules characterized by this method demonstrate encouraging anticancer properties, including synergy with the PARP inhibitor Olaparib, and mechanistic studies indicate that [Ru(PIP)₂(5,5'dmb)]²⁺ acts to block DNA replication fork progression.

A “toolbox” of processes is highlighted to recycle metals from energy storage and renewable energy devices.

The increase of digitization, alongside the growth in consumer electronics and shortened life cycles, has led to a significant global increase in the volume of electronic waste (e-waste). Printed circuit boards (PCBs) are the most valuable components within e-waste due to the higher content of valuable (critical) metals compared to ores. Although some of these metals can be recycled by traditional methodologies, e.g., pyro- and hydrometallurgy, the utilisation of deep eutectic solvents (DESs) offers the opportunity to recover metals from e-waste with higher selectivity and lower toxicity. Yet, DESs are often characterised by very high viscosity, which slows dissolution kinetics. This study investigates the effect of ultrasound on the catalytic dissolution of metals, in the deep eutectic solvent formed from calcium chloride hexahydrated and ethylene glycol. Copper(II) chloride was considered as an oxidising agent, which has high solubility and reversibility in this solvent. High ultrasonic power prevented passivation leading to an enhancement of copper dissolution at a rate 10 000-times faster than without ultrasound. Thus, leaching rates determined with an optical profiler showed that metals can be extracted from a PCB much faster (7 μm min⁻¹) with high power ultrasound rather than in silent conditions (0.6 μm min⁻¹), and this is discussed in terms of chemical oxidation, passivation and cavitation activity.

Deep eutectic solvents (DESs) are an emerging class of ionic liquids that offer a solution to reclaiming technology critical metals (TCMs) from electronic waste, with potential for improved life cycle analysis. The high viscosities typical of DESs, however, impose mass transport limitations such that passive TCM removal generally requires immersion over extended durations, in some cases in the order of hours. It is postulated that, through the targeted application of power ultrasound, delamination of key structures in electronic components immersed in DESs can be significantly accelerated, thereby enabling rapid recovery of TCMs. In this paper, we fully characterise cavitation in a Choline Chloride-Ethylene Glycol DES as a function of sonotrode input power, by the acoustic detection of the bubble collapse shockwave content generated during sonications at more than 20 input powers over the available range. This justifies the selection of two powers for a detailed study of ultrasonically enhanced TCM-delamination from printed circuit boards (PCBs). Dual-perspective high-speed imaging is employed, which facilitates simultaneous observation of TCM removal, and the cavitation evolution and interaction with the PCB surface. Bubble jetting is identified as a key contributor to initial pitting of the TCM layers, exposing the larger underlying copper layer, with the contributions of additional inertial cavitation-mediated phenomena such as bubble-collapse shockwaves also demonstrated as important for delamination. Optimal cavitation activity throughout the sonication then promotes etching of the copper base layer of the PCB structure targeted by the DES, liberating the overlaying TCMs in sections as large as 0.79 mm². We report a thirtyfold improvement in processing time compared to passive delamination, with sonications at the lower power outperforming those at the higher power. The results demonstrate the potential for industrially scalable recovery of TCMs from the growing quantities of global e-waste, using combined power ultrasonics and DESs.