Regioregular poly(3-dodecylthiophene) films self-organized on highly oriented pyrolytic graphite have been investigated by scanning tunneling microscopy and two-dimensional scanning tunneling spectroscopy (STS). Simulated spectra in very good agreement with the experimental data have been obtained by a method combining ab initio and semiempirical approaches, which allows a careful discussion of the polymer electronic states. From the experimental data, with the support of modeling, it is shown that the STS spectra give a direct access to the polymer semiconducting band gap without noticeable charge-transfer effects from the substrate. Spectroscopic images are achieved at the single chain scale, which allows scrutinizing the electronic consequences of chain folds and π-stacking effects through spectroscopic contrasts. While chain folds do not locally increase the polymer band gap more than a few tens of millielectonvolt, a striking widening of the STS conductance gap is observed in the case of electronic tunneling through two interacting polymer layers. Scenarios based on nonplanar configuration of thiophene cycles within the second layer or variations of the charge screening effects are proposed to explain this phenomenon.

37The analysis of the potential risks of engineered nanomaterials (ENM) has so far been almost 38 exclusively focused on the pristine, as-produced particles. However, when considering a life-39 cycle perspective, it is clear that ENM released from genuine products during manufacturing, 40 use, and disposal is far more relevant. Research on release of materials from nano-products 41 is growing and the next necessary step is to investigate the behavior and effects of these 42 released materials in the environment and on humans. Therefore, sufficient amounts of 43 released materials need to be available for further testing. In addition, ENM-free reference 44 materials are needed since many processes not only release ENM but also nano-sized 45 fragments from the ENM-containing matrix that may interfere with further tests. The SUN 46 consortium (Project on "Sustainable Nanotechnologies", EU 7 th Framework funding) uses 47 methods to characterize and quantify nanomaterials released from composite samples that 48 are exposed to environmental stressors. Here we describe an approach to provide materials 49 in hundreds of gram quantities mimicking actual released materials from coatings and 50 polymer nanocomposites by producing what is called "Fragmented Products" (FP). These FP 51can further be exposed to environmental conditions (e.g. humidity, light) to produce 52 "Weathered Fragmented Products" (WFP) or can be subjected to a further size fractionation 53 to isolate "Sieved Fragmented Products" (SFP) that are representative for inhalation studies. 54In this perspective we describe the approach, and the used methods to obtain released 55 materials in amounts large enough to be suitable for further fate and (eco)toxicity testing. 56We present a case study (nanoparticulate organic pigment in polypropylene) to show 57 exemplarily the procedures used to produce the FP. We present some characterization data 58 of the FP and discuss critically the further potential and the usefulness of the approach we 59 developed. 60 61 62 This is a post-prinnt version of Nowack et al.