We demonstrate tuning of hole injection barriers in bottom contact triisopropylsilylethynyl pentacene ͑TIPS-pentacene͒ organic thin film transistors ͑OTFTs͒ by forming the self-assembled monolayers ͑SAMs͒ of thiophenol, 4-fluorothiophenol, or pentafluorothiophenol on the pristine Ag electrode. The work functions of SAM-treated Ag electrodes are measured by Kelvin probe method. The TIPS-pentacene OTFT devices were fabricated by a drop-cast method with a micropipette like an inkjet printing. The OTFTs with pentafluorothiophenol-Ag electrodes as source and drain exhibit carrier mobility of 0.17 cm 2 / V s and on/off current ratio of 10 5 because of almost no hole injection barrier to TIPS pentacenes. The SAM-treated Ag electrodes are robust over repeated electrical scans of 100 cycles.

We developed highly luminescent and cost-effective quantum dot (QD)-neutravidin (NTV) bioconjugates to detect the tyrosine kinase B (TrkB) receptors distributed in the cultured hippocampus neurons. Hippocampal neurons were incubated with biotinylated anti-TrkB antibody, followed by further incubation with QD-NTV bioconjugates. QD-NTV biomarkers on the extracellular domain of TrkB receptors were imaged by the combined atomic force microscope and confocal laser scanning microscope (AFM-CLSM) providing resolved (nanometer-scale) structural and fluorescent images. We found that TrkB receptors were distributed over the neuronal cell bodies (soma) and neurites. TrkB receptors in the somata looked more concentrated, but those in the neurites appeared punctate. Thus, our QD-based immunocytochemistry technique combined with an AFM-CLSM can be used for three-dimensional morphology of neurons on nanometer-scale structural resolution and their fluorescence images with QDs. Furthermore, this technique can be applied for real-time fluorescence imaging or long-term study of live neurons.

The structural and functional plasticity of Aplysia mechanosensory presynaptic neurons has been studied in relation with the mechanism underlying learning and memory. Long-term facilitation (LTF), which is a well-known cellular model for long-term memory in Aplysia, is accompanied by new synaptic structural growth or change. We developed a combined atomic force microscope and confocal laser scanning microscope (AFM-CLSM) system integrated with a MATLAB routine for image processing to concurrently obtain high-resolution 3-dimensional (3D) outer-surface morphological images and 3D interior fluorescence images. With our combined AFM-CLSM system, volumetric changes in the presynaptic structures (varicosities) of Aplysia live sensory-motor neuron cocultures were observed. The spatial distribution of synaptic vesicle molecules in the preexisting varicosities was monitored together with a volumetric change in the varicosities. Our combined AFM-CLSM system is successfully adapted for measuring learning-related structural changes and the movement of synaptic molecules in the single live neuron through interaction force and fluorescence imaging.