In this article, we report on the formation and mode-of-operation of an affinity biosensor, where alternate layers of biotin/streptavidin/biotinylated-CRP-antigen/anti-CRP antibody are grown on printed gold electrodes on disposable paper-substrates. We have successfully demonstrated and detected the formation of consecutive layers of supra-molecular protein assembly using an electrical (impedimetric) technique. The formation process is also supplemented and verified using conventional surface plasmon resonance (SPR) measurements and surface sensitive characterization techniques, such as X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The article provides a possible biosensor development scheme, where—(1) fabrication of paper substrate (2) synthesis of gold nanoparticle inks (3) inkjet printing of gold electrodes on paper (4) formation of the biorecognition layers on the gold electrodes and (5) electrical (impedimetric) analysis of growth—all are coupled together to form a test-structure for a recyclable and inexpensive point-of-care diagnostic platform.

The charge extraction (of injected carriers) by linearly increasing voltage in metal-insulator-semiconductor structures, or MIS-CELIV, is based on the theory of space-charge-limited currents. In this work, the validity of MIS-CELIV for mobility determination in organic thin-film devices has been critically examined and clarified by means of drift-diffusion simulations. It is found that depending on the applied transient voltage, the mobility might be overestimated by several orders of magnitude in the case of an ohmic injecting contact. The shortcomings of the MIS-CELIV theory can be traced back to the underlying assumption of a drift-dominated transport. However, the effect of diffusion can be taken into account by introducing a correction factor. In the case of non-ohmic injecting contacts, the extracted mobility becomes strongly dependent on device parameters, possibly leading to large deviations from the actual mobility.

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This paper presents the sub-ppm level electrical detection of H 2 S gas at room temperature using printed copper acetate-gold nanoparticle composite films. The excellent sensitivity of these films towards H 2 S can be attributed to the catalytic activity of gold nanoparticles in combination with the plasma oxidation of copper acetate films.Hydrogen sulde (H 2 S) is a toxic gas which poses a threat to human health. According to the National Institute of Occupational Safety and Health, the H 2 S concentration immediately dangerous to life is 100 ppm. 1 On the other hand, the recommended exposure limit is 10 ppm for a maximum duration of 10 min. 1 Contemporary H 2 S sensor devices can be divided into three major categories: semiconductor metal oxide sensors, electrochemical sensors, and optical sensors. 2 Current research aims for the development of robust and cost-effective H 2 S sensors with enhanced sensitivity and stability. In addition, sensors should be able to operate consistently in harsh environmental conditions. This can be accomplished through emerging materials science and modern processing technologies. Nano-materials are of particular interest in gas sensing applications because of their high surface to volume ratio. Furthermore, noble metals have been used as oxidation catalysts for enhancing the reaction on a gas sensor surface by means of a superior oxygen dissociation catalytic ability. 3 It has been reported in the literature that the sensitivity of the sensing layer towards the analyte gas can be improved by doping the sensing material with metals, such as Pt, Au, Pd and Ag. 4-6 Copper acetate (CuAc) has been recently introduced as an easily processable material which is sensitive to H 2 S gas. 7-9 CuAc lms have been shown to directly react with H 2 S gas to form copper sulde (CuS). 9 This resulted in a signicant and irreversible change in resistance of the lm at room temperature with relatively low (1-20 ppm) H 2 S concentrations. 7-9 The large change in resistance is attributed to a direct conversion of highly insulating CuAc (R > 1-100 GU) to a p-type semiconducting CuS (R $ 10-100 U). Chemiresistor-type sensors based on CuAc nanoparticles showing more than eight orders of magnitude change in resistance when exposed to H 2 S on ppm level have been previously demonstrated. 7-9 Furthermore it has been shown that robust CuAc-based H 2 S sensors can be fabricated on low-cost and exible substrates by using massmanufacturing technologies such as inkjet-printing. These inkjet-printed sensors have been successfully employed for quantitative detection of H 2 S (1 to 20 ppm). 7,8 In addition, good repeatability, long-term stability, negligible humidity effect (at RH < 80%) and selectivity of printed CuAc-based H 2 S sensors have been reported earlier. 7,8 However, the practical applicability of these sensors is still somewhat limited by rather slow response times and decient sensitivity (to sub-ppm level detection).This paper reports a CuAc-based chemiresistor-type sensor conguration printed on ...