Kees Hummelen: a creative, inspirational and unorthodox scientist from Groningen

To mark the occasion of the official retirement of Prof. J. C. (Kees) Hummelen, the Journal of Materials Chemistry C has dedicated a special issue to honour his achievements in the field of materials chemistry. This personal essay, written by his study mate, close colleague and long-standing friend, highlights the pioneering contributions that Kees Hummelen has made in various fields of organic and materials chemistry during his 45 year long career. His research in chemistry began with asymmetric synthesis and chemiluminescence and culminated in his most notable results in the field of fullerene chemistry and the development of organic photovoltaic technology. More recently, he has also been active in the field of materials for molecular field-effect transistors, biosensors and the development of single molecule electronics based on internal π logic. He was also a dedicated teacher and was deeply involved in societal challenges. Because of my personal relationship with Kees during all of those 45 years, I have written this essay in a somewhat unorthodox way; a way that is so characteristic of Kees.

π-Conjugated organosilanes at the nexus of single-molecule electronics and imaging

This article explores the fundamental σ-π orbital interactions that underlie the physical properties of conjugated organosilane molecular materials in single-molecule electronics and single-molecule imaging.

Single molecule electronic devices with carbon-based materials: status and opportunity

The field of single molecule electronics has progressed remarkably in the past decades by allowing for more versatile molecular functions and improving device fabrication techniques.

Understanding resonant charge transport through weakly coupled single-molecule junctions

Off-resonant charge transport through molecular junctions has been extensively studied since the advent of single-molecule electronics and is now well understood within the framework of the non-interacting Landauer approach. Conversely, gaining a qualitative and quantitative understanding of the resonant transport regime has proven more elusive. Here, we study resonant charge transport through graphene-based zinc-porphyrin junctions. We experimentally demonstrate an inadequacy of non-interacting Landauer theory as well as the conventional single-mode Franck–Condon model. Instead, we model overall charge transport as a sequence of non-adiabatic electron transfers, with rates depending on both outer and inner-sphere vibrational interactions. We show that the transport properties of our molecular junctions are determined by a combination of electron–electron and electron-vibrational coupling, and are sensitive to interactions with the wider local environment. Furthermore, we assess the importance of nuclear tunnelling and examine the suitability of semi-classical Marcus theory as a description of charge transport in molecular devices.