Colloidal diluted magnetic semiconductor (DMS) nanocrystals are model systems for studying spin effects in semiconductor nanostructures with relevance to future spin-based information processing technologies. The introduction of excess delocalized charge carriers into such nanocrystals turns on strong dopant-carrier magnetic exchange interactions, with important consequences for the physical properties of these materials. Here, we use pulsed electron paramagnetic resonance (pEPR) spectroscopy to probe the effects of excess conduction band electrons on the spin dynamics of colloidal Mn(2+)-doped ZnO nanocrystals. Mn(2+) spin-lattice relaxation is strongly accelerated by the addition of even one conduction band electron per Zn1-xMnxO nanocrystal, attributable to the introduction of a new exchange-based Mn(2+) spin relaxation pathway. A kinetic model is used to describe the enhanced relaxation rates, yielding new insights into the spin dynamics and electronic structures of these materials with potential ramifications for future applications of DMS nanostructures in spin-based technologies.

Metal-halide perovskites have rapidly emerged as one of the most promising materials of the 21st century, with many exciting properties and great potential for a broad range of applications, from photovoltaics to optoelectronics and photocatalysis. The ease with which metal-halide perovskites can be synthesized in the form of brightly luminescent colloidal nanocrystals, as well as their tunable and intriguing optical and electronic properties, has attracted researchers from different disciplines of science and technology. In the last few years, there has been a significant progress in the shape-controlled synthesis of perovskite nanocrystals and understanding of their properties and applications. In this comprehensive review, researchers having expertise in different fields (chemistry, physics, and device engineering) of metal-halide perovskite nanocrystals have joined together to provide a state of the art overview and future prospects of metal-halide perovskite nanocrystal research.