Sensing effect

Mologni L., Lecoutre P., Nielsen P.E., Gambacorti-Passerini G. Additive anti-sense effects of different PNAs on the in vitro translation of the PML/RAR-alpha gene. Nucleic Acids Res. 1998 26 1934-1938. 

The waveguide is split into two arms one arm (the reference arm) is shielded and not affected by the environment. At the interface of the other arm, the evanescent field will be influenced by any sensing effect. Thus, the two partial beams will propagate in a different way within the two arms, in dependence on the difference in the refractive indices adjacent to the two arms. 

Two types of cell have been described. In Fig. 1 a cell with a rotating disk electrode is shown. Connections to a pH-stat and to the interface are indicated simultaneously with recording CMT measurements, the metal and reference electrode and a counter electrode (not shown in Fig. 1) can be connected to a potentiostat, so that electrochemical measurements can be recorded intermittently. The volume of solution in the cell is ca. 400 ml. What matters for safe and reliable conditions of measurement is that the disk electrode rotating at a speed of no less than 1000 rpm ensures efficient stirring, so that the effect of alkali formed at the corroding metal (or sometimes at the counter electrode located ca. 1 cm below and parallel to the metal electrode) is immediately sensed effectively by the glass electrode and also the effect of acid supplied from the autoburet is quickly detected. 

A = 430, 440 nm) with HS04. Electrochemical studies displayed cathodic shifts in the [Cp2Co]/[Cp2Co] redox couple of 35-75 mV on addition of Gl or HS04, and 225 mV for H2P04. Smaller shifts were seen in the porphyrin oxidation wave. It should be noted that these anion-sensing effects are specific to the m-a,a,a,a-atropisomer. 

A systematic study of a large number of oxides showed that sensitivity of conductivity to the presence of traces of reactive gases is a phenomenon common to oxides. If the conductivity is high, then the gas sensing effect is not expected. Similarly, if the conductivity is very low as an insulator, then the effect will be difficult to measure as evidenced from the previous studies. However, if an oxide sample has a resistivity between 10" and 10 Q cm at 300°C-400°C and moderate conductivity, then it will function as a gas sensor. Mgln204 is one such material having... 

Almost every sohd state gas sensor exhibits a sensing effect for humidity. Figure 14.21 shows the humidity dependence of a frequency shift of a polymer-type SAW sensor for different sensing fihns. As shown in this hg-ure, the SAW sensor shows comparatively high sensitivity to humidity. Thus, there needs to be an improvement in this regard in order to ameliorate this drawback before SAW sensors can be used in practical applications. - ... 

Flexible picene thin film field-effect transistors have been fabricated using a gate dielectric from poly(tetra-lluoro-/7-xylylene) on a poly(ethylene terephthalate) substrate [39]. These field-effect transistors show /I-channel output/transfer characteristics. A sensing effect for oxygen is observed. The hysteresis in the transfer curves is negligible. The parylene gate can eliminate a reduction in the drain current. 

The explanations of observed gas-sensing effects in CNT-based devices are usually based on the analysis of adsorption/desorption phenomena taking place on the surface of CNTs (Peng and Cho 2000 Zhao et al. 2001, 2002 Bauschlicher and Ricca 2004). According to this approach, the resistance of CNT-based gas sensors is conditioned by the change of the CNT resistance caused by interaction with analyte. In particular, in many papers the interaction of NO with the nanotube was interpreted as strictly connected to a bulk doping effect. Actually, NO can be bound to a semiconducting nanotube... 

Fig. 3.11 Diagrams illustrating difference in gas-sensing effects in (a) polycrystaUme material and (b) individual nanowires. One can see that any intergrain necks or boundaries are absent in ID-based gas sensors. Moreover, and fields are always orthogonal and independent (Reprinted with permission from Hemandez-Ramirez et al. (2009), Copyright 2009 Royal Society of Chemistry)...

Fig. 15.4 Principle of the optical gas-sensing effect, (a) Schematic iiiustration of goid nanoparticles embedded in the volume and on the surface of a semiconducting metal oxide layer with refractive index n. (b) Shift of the absorption peak of a single gold nanocluster (75 nm in diameter) by a variation of the refractive index of the surrounding medium at exposure to a reducing or oxidizing gas (Reprinted with permission from Schleunitz et ai. 2007, Copyright 2007...

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