The nature of the transient species leading to emission from the spin/orbital-forbidden Mn d−d transition in doped semiconductor quantum dots has intrigued scientists for a long time. This understanding is important in the quest for energy efficiency as the energy from the conduction band is transferred efficiently to Mn in the femtosecond time scale overcoming other nonradiative recombination pathways. In this work, we have shown the presence of the transient species using materials with band gaps in resonance with the energy of the Mn emission to understand the nature of the absorbing, transient, and emitting species. Detailed studies lead to the emergence of a transient Mn 3+ state that is further corroborated with spin-dependent density functional theory calculations. This opens up a unique opportunity to realize a reversible photochemical reaction and high radiative efficiency in a semiconductor nanostructure by controlling the spin state of the magnetic ion by external illumination.

In the quest for new functional materials, transition metal doping in semiconductors has attracted significant attention, wherein introduction of dopant atoms alters a range of physical properties of the host such as its optical, magnetic, and electronic properties. Hence, the choice of appropriate dopants to meet the current challenges makes semiconductor doping a highly versatile field. In the past, Mn doping in II-VI semiconductors has been extensively studied. The interest in these systems arises from a prominent orange emission from an optically forbidden state. An extended debate in the literature spanning the last three decades has so far shed light on various anomalous properties of Mn emission, specifically in quantum-confined systems leading to more questions. In this perspective, we review the literature with specific emphasis on the mechanism of Mn emission and an understanding of the electron–hole pathway during the excitation and de-excitation process in doped quantum dots. We explore various phenomena of energy and charge transfer mechanisms along with experiments in support of these phenomena which can eventually lead to a better understanding of spin driven optoelectronics.

An unusually large exciton coupling and spontaneous self-localization safeguards the long-lived excitons of H-aggregated perylene bisimide against a notoriously universal excimeric trapping process, and rekindles its potential as a light-harvesting material.

Optoelectronic devices based on all-inorganic perovskite systems are an energy-efficient source of lighting due to their high photoluminescence quantum yield (QY). However, dominant surface trapping continues to plague the field, despite their high defect tolerance, as evidenced by the several-fold improvements in the external quantum efficiency of perovskite nanocrystals (NCs) upon appropriate surface passivation or physical confinement between high-band-gap materials. Here, we introduce the concept of drip-feeding of photoexcited electrons from an impurity-induced spin-forbidden state to address this major shortcoming. An increased and delayed (about several milliseconds) excitonic QY, Raman spectroscopy demonstrating specific vibrational modes of the PbX6 octahedra, and density functional theory establish the electron back-transfer, signifying an efficient recombination. We term this electron back-transfer from Mn2+ to the host conduction band in this prototypical example of Mn-doped CsPbX3 (X = Cl, Br) NCs through vibrational coupling as vibrationally assisted delayed fluorescence (VADF).

As olvent responsive dynamic nanoscale metalorganic framework (NMOF) [Zn(1a)(H 2 O) 2 ]h as been devised based on the self-assembly of Zn II and asymmetric bola-amphiphilic oligo-(p-phenyleneethynylene) (OPE) dicarboxylate linker 1a having dodecyl and triethyleneglycolmonomethylether (TEG,p olar) side chains.I nT HF solvent, NMOF showed nanovesicular morphology (NMOF-1)w ith surface decorated dodecyl chains.I nw ater and methanol, NMOF exhibited inverse-nanovesicle (NMOF-2)a nd nanoscroll (NMOF-3)m orphology,r espectively,w ith surface projected TEG chains.The pre-formed NMOFs also unveiled reversible solvent responsive transformation of different morphologies.T he flexible NMOF showed cyan emission and no cytotoxicity,a llowing live cell imaging.C isplatin (14.4 wt %) and doxorubicin (4.1 wt %) were encapsulated in NMOF-1 by non-covalent interactions and, in vitro and in vivo drug release was studied. The drug loaded NMOFs exhibited micromolar cytotoxicity.