New Insights into Single-Molecule Junctions Using a Robust, Unsupervised Approach to Data Collection and Analysis

We have applied a new, robust and unsupervised approach to data collection, sorting and analysis that provides fresh insights into the nature of single-molecule junctions. Automation of tunneling current-distance (<i>I</i>(<i>s</i>)) spectroscopy facilitates the collection of very large data sets (up to 100 000 traces for a single experiment), enabling comprehensive statistical interrogations with respect to underlying tunneling characteristics, noise and junction formation probability (JFP). We frequently observe unusual low-to-high through-molecule conductance features with increasing electrode separation, in addition to numerous other “plateau” shapes, which may be related to changes in interfacial or molecular bridge structure. Furthermore, for the first time we use the JFP to characterize the homogeneity of functionalized surfaces at the nanoscale

Effective Ligand Passivation of Cu₂O Nanoparticles through Solid-State Treatment with Mercaptopropionic Acid

In colloidal nanoparticle (NPs) devices, trap state densities at their surface exert a profound impact on the rate of charge carrier recombination and, consequently, on the deterioration of the device performance. Here, we report on the successful application of a ligand exchange strategy to effectively passivate the surface of cuprite (Cu₂O) NPs. Cu₂O NPs were prepared by means of a novel synthetic route based on flame spray pyrolysis. FTIR, XRD, XPS, and HRTEM measurements corroborate the formation of cubic cuprite Cu₂O nanocrystals, excluding the possible presence of undesired CuO or Cu phases. Most importantly, steady-state emission and transient absorption assays document that surface passivation results in substantial changes in the intensity of emissive excitonic statescentered at copper and oxygen vacanciesand in the lifetime of excitons near the band edge. To shed light onto ultrafast processes in Cu₂O nanocrystals additional pump probe experiments on the femtosecond and nanosecond time scales were carried out. Two discernible species were observed: on one hand, an ultrafast component (∼ps) that relates to the excitons; on the other hand, a long-lived component (∼μs) that originates from the defects/trap states