We present noncontact atomic force microscopy and Kelvin probe force microscopy studies of nanophase segregated photovoltaic blends based on an oligothiophene-fluorenone oligomer and [6,6]-phenyl C70 butyric acid methyl ester. We carried out a complete analysis of the influence of the tip-surface interaction regime on the topographic, in-dark contact potential and surface photovoltage contrasts. It is demonstrated that an optimal lateral resolution is achieved for all channels below the onset of a contrast in the damping images. With the support of electrostatic simulations, it is shown that in-dark contact potential difference contrasts above subsurface acceptor clusters are consistent with an uneven distribution of permanent charges at the donor-acceptor interfaces. A remarkable dependence of the surface photovoltage magnitude with respect to the tip-surface distance is evidenced and attributed to a local enhancement of the electromagnetic field at the tip apex.

We report the coexistence of charge puddles and topographic ripples in graphene decoupled from the Ir(111) substrate it was grown on. We show the topographic and the charge disorder to be locally correlated as a result of the intercalation of molecular species. From the analysis of quasiparticle scattering interferences, we find a linear dispersion relation, demonstrating that graphene on a metal can recover its intrinsic electronic properties. The measured Fermi velocity v(F) = 0.9 +/- 0.04x10(6) m/s is lower than in graphene on dielectric substrates, pointing to a strong screening of electron-electron interactions in graphene by the nearby metallic substrate.

By means of STM and nc-AFM the self-assembly of a new donor-acceptor (DA) dyad molecule on highly oriented pyrolytic graphite is identified and compared to molecular simulations. Kelvin probe force microscopy (KPFM) measurements clearly show the photovoltaic activity of this model system under illumination. The optoelectronic properties and the local morphology of the DA dyad assembly are simultaneously probed by KPFM down to the level of one molecular monolayers.

Diagnostic sensing device using exhaled breath of human have critical advantages due to the noninvasive diagnosis and high potential for portable device with simple analysis process. Here, we report ultrafast as well as highly sensitive bumpy WO3 hemitube nanostructure assisted by O2 plasma surface modification with functionalization of graphene-based material for the detection of acetone (CH3COCH3) and hydrogen sulfide (H2S) which are biomarkers for the diagnosis of diabetes and halitosis, respectively. 0.1 wt % graphene oxide (GO)- and 0.1 wt % thin layered graphite (GR)- WO3 hemitube composites showed response times of 11.5 ± 2.5 s and 13.5 ± 3.4 s to 1 ppm acetone as well as 12.5 ± 1.9 s and 10.0 ± 1.6 s to 1 ppm of H2S, respectively. In addition, low limits of detection (LOD) of 100 ppb (Rair/Rgas = 1.7 for acetone and Rair/Rgas = 3.3 for H2S at 300 °C) were achieved. The superior sensing properties were ascribed to the electronic sensitization of graphene based materials by modulating space charged layers at the interfaces between n-type WO3 hemitubes and p-type graphene based materials, as identified by Kelvin Probe Force Microscopy (KPFM). Rapid response and superior sensitivity of the proposed sensing materials following cyclic thermal aging demonstrates good potential for real-time exhaled breath diagnosis of diseases.

High band gap copolymers containing were synthesized and compared for application in bulkheterojunction solar cells.

For correct height measurements by noncontact atomic force microscopy a precise knowledge of the interacting tip-surface forces is required. Preceding studies have shown the necessity to compensate the electrostatic forces between tip and surface with Kelvin probe force microscopy to obtain realistic topographic height values for samples out of multiple components. In the present study we demonstrate, however, that a simple Kelvin compensation can be insufficient using the example of poly(3-dodecylthiophene) on highly oriented pyrolytic graphite (HOPG). The measured polymer height on HOPG can be strongly falsified due to the uncompensated long-range (LR) van der Waals (vdW) forces. We conclude that in order to minimize the perturbing influence of these LR-vdW forces on the height measurement, imaging should be performed in the regime where the fast-decaying short-range forces are dominant.