ABSTRACT
First synthesis of the macrocycle cyclohexa(1,3-pyrenylene) is achieved in six steps starting with pyrene, leading to a non-aggregating highly twisted blue-light-emitting material. The cyclodehydrogenation of the macrocycle offers a promising synthesis route to holey-nanographene.
ABSTRACT
In this work, we subject bi- and terpyrenyls to selective fusion for formation of extended polycyclic aromatic hydrocarbons (PAHs). Connecting the pyrene units at 4-4'- or 1-4'-positions led to smooth formation of extended PAHs, achieved via cyclodehydrogenation. This is far more difficult if pyrene is coupled in the 1,1'-position.
ABSTRACT
Free-standing nanomembranes with molecular or atomic thickness are currently explored for separation technologies, electronics, and sensing. Their engineering with well-defined structural and functional properties is a challenge for materials research. Here we present a broadly applicable scheme to create mechanically stable carbon nanomembranes (CNMs) with a thickness of ~0.5 to ~3 nm. Monolayers of polyaromatic molecules (oligophenyls, hexaphenylbenzene, and polycyclic aromatic hydrocarbons) were assembled and exposed to electrons that cross-link them into CNMs; subsequent pyrolysis converts the CNMs into graphene sheets. In this transformation the thickness, porosity, and surface functionality of the nanomembranes are determined by the monolayers, and structural and functional features are passed on from the molecules through their monolayers to the CNMs and finally on to the graphene. Our procedure is scalable to large areas and allows the engineering of ultrathin nanomembranes by controlling the composition and structure of precursor molecules and their monolayers.
Subject(s)
Carbon/chemistry , Nanoparticles/chemistry , Nanotechnology/methods , Nanotubes, Carbon/chemistry , Biomimetics , Biosensing Techniques , Electrons , Graphite/chemistry , Helium/chemistry , Ions , Materials Testing , Membranes, Artificial , Microscopy, Scanning Tunneling/methods , Models, Chemical , Nanostructures/chemistry , Particle Size , Surface PropertiesABSTRACT
Thorough analyses of the photo- and devicephysics of poly-7-tert-butyl-1,3-pyrenylene (PPyr) by the means of absorption and photoluminescence emission, time resolved photoluminescence and photoinduced absorption spectroscopy as well as organic light emitting devices (OLEDs) are presented in this contribution. Thereby we find that this novel class of polymers shows deep blue light emission as required for OLEDs and does not exhibit excimer or aggregate emission when processed from solvents with low polarity. Moreover the decay dynamics of the compound is found to be comparable to that of well blue emitting conjugated polymers such as polyfluorene. OLEDs built in an improved device assembly show stable bright blue emission for the PPyr homopolymer and further a considerable efficiency enhancement can be demonstrated using a triphenylamine(TPA)/pyrene copolymer.
