This PDF file contains the front matter associated with SPIE Proceedings Volume 8118, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

Organic photodiodes open new possibilities concerning the integration into micro-optical systems. The ease of processing, based on layer-by-layer vacuum deposition, and the possibility to deposit these devices basically on any substrate as well as the possibility to tune the spectral response make organic photodiodes attractive for integrated systems, especially allowing facile integration with planar chip-based systems. For the application of these devices as integrated detectors two examples will be presented. The first example presents the monolithic integration of OPDs with optical waveguides. A further example presents the utilization of OPDs for the direct electric detection of surface plasmon polaritons. Plasmon diodes could be beneficial for a wide range of plasmonic applications, from sensors to nanooptical circuitry.

We present an integrated optical sensor platform suitable for the parallel detection of multiple parameters in an array format. This sensor technology combines fluorescent sensor layers with ring-shaped thin-film organic photodiodes (OPDs), serving as integrated fluorescence detectors. The sensing layers are deposited by screen-printing on the upper side of a PET substrate, which is exposed to an analyte, whereas the ring-shaped photodiodes are monolithically integrated, by vapour phase deposition, on the backside of the transparent substrate, in correct alignment to the sensing layers. The monolithic integration of sensor layers and detectors on one common substrate as well as the special ring shaped form of the photodiodes guarantees that a maximum of the fluorescent light emitted from the sensor layers is collected. A key advantage of the above described sensor geometry is the straightforward potential to realise sensor arrays for the parallel detection of multiple parameters: different sensor spots are illuminated by commercial LEDs or alternatively with one large area OLED, and are read-out by individual integrated organic photodiodes, surrounding the respective sensor layers. Three different sensing principles including absorption, fluorescence and surface plasmon resonance can be applied in the same basic sensor platform. The functionality of the concept is demonstrated by an integrated oxygen sensor. Sensor schemes for the analytical parameters carbon dioxide, temperature and ammonia, are proposed. Efficient front end electronics enabling intensity and time domain detection of sensor signals for the testing and characterisation of the integrated sensor devices have been developed.

Sensing films specific to nitric oxide and zinc were fabricated by embedding respectively indicator 1,2-diaminoanthraquinone (DAQ) and 11,16-Bis(phenyl)-6,6,21,21-tetramethyl-m-benzi-6,21-porphodimethene (BPDM-H) in hydrogel host poly(2-hydroxyethyl methacrylate). The sensing film contains DAQ, which responses to nitric oxide, shows stability in acid environment. The sensing film contains BPDM-H responses to zinc. The electrospinning technique was also utilized to fabricate the fibrous film.

For high-performance low-cost applications based on organic field-effect transistors (OFETs) and corresponding sensors essential properties of the applied semiconducting materials include solution-processability, high field-effect mobility, compatibility with adjacent layers and stability with respect to ambient conditions. In this combined study regioregular poly(3-hexylthiophene)- and pentacene-based bottom-gate bottom-contact OFETs with various channel lengths are thoroughly investigated with respect to short-channel effects and the implications of dielectric surface modification with hexamethyldisilazane (HMDS) on device performance. In addition, the influences of oxygen, moisture and HMDStreatment on the ambient stability of the devices are evaluated in detail. While OFETs without surface modification exhibited the expected degradation behavior upon air exposure mainly due to oxygen/moisture-induced doping or charge-carrier trapping, the stability of the investigated semiconductors was found to be distinctly increased when the substrate surface was hydrophobized. The presented results thoroughly summarize important issues which have to be considered when selecting semiconducting materials for high-performance OFETs and OFET-based sensors.

Nowadays, wearable sensors such as heart rate monitors and pedometers are in common use. The use of wearable systems such as these for personalized exercise regimes for health and rehabilitation is particularly interesting. In particular, the true potential of wearable chemical sensors, which for the real-time ambulatory monitoring of bodily fluids such as tears, sweat, urine and blood has not been realized. Here we present a brief introduction into the fields of ionogels and organic electrochemical transistors, and in particular, the concept of an OECT transistor incorporated into a sticking-plaster, along with a printable "ionogel" to provide a wearable biosensor platform.

Explosive sensing is a promising, emerging application for conjugated polymers. One exciting potential area of application is to clear landmines left after military actions. In this work, we demonstrate three ways to detect 10 partsper- billion of the model explosive, 1,4-dinitrobenzene (DNB): by monitoring fluorescence intensity, by measuring fluorescence lifetime, and by distributed-feedback (DFB) laser emission. A quenching of the fluorescence is observed upon DNB exposure. The reversibility of the quenching process has been demonstrated by purging with nitrogen.

The absorption and fluorescence of free base, tetraphenyl-substituted porphyrins are shown to be sensitive to exposure to NO₂. The Soret band absorption red-shifts and fluorescence is quenched by an order of magnitude. The fluorescence spectrum of a gassed sample is also red-shifted and broadened following exposure. Several solid state embodiments of a fluorescent sensor based upon free base porphyrins are proposed.

Pentacene based organic thin-film transistors were used to study the effects of polar analytes on charge transport behavior during vapor sensing. Four analytes were tested with various dipole moments and polarization properties. The analytes include, ethyl acetate, ethanol, cyclohexane, and styrene. While the ethanol and ethyl acetate molecules, with the larger dipole moment, have a more significant effect on the sensing behavior, a non-polar molecule such as styrene, which is polarizable, also has the ability to produce a response. The non-polar molecule, cyclohexane produced no significant response. This study helps provide a physical basis and insight into the analyte/organic semiconductor interactions for the organic transistor based sensor response.

Herein we report our recent efforts in employing natural materials and synthetic derivatives of natural molecules for organic field effect transistors (OFETs) and organic photovoltaics (OPVs). We evaluated dyes from the following chemical families: acridones, anthraquinones, carotenoids, and indigoids. These materials have proven effective in organic field effect transistors, with mobilities in the 4 × 10^-4 - 0.2 cm²/V-s range, with indigoids showing promising ambipolar behavior. We fabricated complementary-like voltage inverters with high gains using indigoids. The photovoltaic properties of these materials were characterized in metal-insulator-metal (MIM) diodes, as well as in donoracceptor bilayer devices. Additionally, we have found that indigoids and Quinacridone, show long-range crystalline order due to hydrogen binding, and have considerably higher relative permittivities (ε) compared to typical organic semiconductors. Higher permittivities result in lower exciton binding energies and thus may lead to high photocurrents in photovoltaic devices.

Over the past decade conducting polymer electrodes have played an important role in bio-sensing and actuation. Recent developments in the field of organic electronics have made available a variety of devices that bring unique capabilities at the interface with biology. One example is organic electrochemical transistors (OECTs) that are being developed for a variety of bio-sensing applications, including the detection of ions, and metabolites, such as glucose and lactate. Room temperature ionic liquids (RTILs) are organic salts, which are liquid at ambient temperature. Their nonvolatile character and thermal stability makes them an attractive alternative to conventional organic solvents. Here we report an enzymatic sensor based on an organic electro-chemical transistor with RTIL's as an integral part of its structure and as an immobilization medium for the enzyme and the mediator. Further investigation shows that these platforms can be incorporated into flexible materials such as carbon cloth and can be utilized for bio-sensing. The aim is to incorporate the overall platform in a wearable sensor to improve athlete performance with regards to training. In this manuscript an introduction to ionic liquids (ILs), IL - enzyme mixtures and a combination of these novel materials being used on OECTs are presented.

Residual levels of O₂ in OLEDs and their relation to device performance were evaluated by measuring (i) the photoluminescence (PL) decay time (following pulsed UV LED excitation) of the O₂ sensing dye Pd octaethylporphyrin (PdOEP) doped in the active OLED layer poly(N-vinyl carbazole) (PVK) and (ii) the electroluminescence (EL) decay time (following a bias pulse) of glass/ITO/PEDOT:PSS/6 wt.% PdOEP:PVK/CsF/Al OLEDs. The active layer was prepared under various conditions of exposure to controlled O2 levels and relative humidity. PdOEP was used successfully for monitoring exposure of PdOEP:PVK to low levels of oxygen and shortened device PL decay times often indicated device deterioration. The PL decay time at various applied voltages and the EL decay time at various current densities were monitored to evaluate degradation processes related to oxygen and other bimolecular quenching phenomena.