The photoluminescence (PL) emission states of heteroatom-doped graphene quantum dots (GQDs) remain unknown, particularly the assignment of the low-energy excitation band (more than 330 nm). To address these issues, this work synthesized three different types of GQDs: undoped GQDs (UGQDs), nitrogen-doped GQDs (NGQDs), and boron-doped GQDs (BGQDs), with similar sizes, chemical compositions (types and compositions of surface functional groups), and defects using a constant potential electrolysis method. The PL emissive states in these GQDs and the effects of the dopant heteroatom on the PL were revealed based on the combination of spectroscopic methods and theoretical calculations. The results indicated that the GQDs exhibit multiemissive centers for the PL emission mechanism. An excitation-independent PL emission band (band I) results from a highenergy transition originating from the quantum confinement of the carbon core (carbon π−π* transitions in sp 2 domain), and an excitation-dependent PL emission band (band II) originates from a low-energy edge band transition, which is attributed to radiative recombination associated with both the n−π* transition of N/O/B-containing groups and the π−π* charge transfer between the carbon core and the edge of the GQDs. Moreover, the PL emission maxima (both bands I and II) for NGQDs and BGQDs show a blue shift and a red shift, respectively, relative to UGQDs because of the doping that led to the alteration in the electronic structure and the distribution of molecular orbitals in the GQDs. These results clarify previous inconsistencies regarding the PL emission mechanism and the electronic properties of GQDs and can thus provide a foundation for the application of doped GQDs in electronics, photonics, and biology.

Stimuli-responsive molecular junctions, where the conductance can be altered by an external perturbation, are an important class of nanoelectronic devices. These have recently attracted interest as large effects can be introduced through exploitation of quantum phenomena. We show here that significant changes in conductance can be attained as a molecule is repeatedly compressed and relaxed, resulting in molecular folding along a flexible fragment and cycling between an anti and a syn conformation. Power spectral density analysis and DFT transport calculations show that through-space tunneling between two phenyl fragments is responsible for the conductance increase as the molecule is mechanically folded to the syn conformation. This phenomenon represents a novel class of mechanoresistive molecular devices, where the functional moiety is embedded in the conductive backbone and exploits intramolecular nonbonding interactions, in contrast to most studies where mechanoresistivity arises from changes in the molecule−electrode interface.

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Polyoxometalates have been proposed in the literature as nanoelectronic components, where they could offer key advantages with their structural versatility and rich electrochemistry. Apart from a few studies on their ensemble behaviour (as monolayers or thin films), this potential remains largely unexplored. We synthesised a pyridyl‐capped Anderson–Evans polyoxometalate and used it to fabricate single‐molecule junctions, using the organic termini to chemically “solder” a single cluster to two nanoelectrodes. Operating the device in an electrochemical environment allowed us to probe charge transport through different oxidation states of the polyoxometalate, and we report here an efficient three‐state transistor behaviour. Conductance data fits a quantum tunnelling mechanism with different charge‐transport probabilities through different charge states. Our results show the promise of polyoxometalates in nanoelectronics and give an insight on their single‐entity electrochemical behaviour.