Hydrazine sensor

M. Mehregany and S. D. Senturia, Anisotropic etching of silicon in hydrazine. Sensors Actuators 13, 375, 1988. 

To optimize the OLED-based hydrazine sensor performance, the OLED pulse width and voltage were varied. The optimal values were found to be 20 ps and 30 V, respectively. The corresponding results of the change in the PL of the hydrazine/ADA solution are shown in Fig. 3.16. They clearly show that the LOD of hydrazine by this system is 60 ppb in 1 min, i.e., roughly equivalent to 1 ppb in 1 h. That is, the sensitivity of this system exceeds the OSH A requirements by a factor of 80. Methods to develop ADA-based solid state sensors are currently being explored. 

The PL-based hydrazine sensor is based on the reaction between N2H4 and anthracene 2,3-dicarboxaldehyde (ADA). While the reactants are not emissive, the reaction product can be excited at 476nm by a blue 4,4 -bis(2,2 -diphenylvinyl)-l,l -biphenyl (DPVBi)-based OLED to emit at 549 nm the signal is proportional to the N2H4 level. The OLEDs used were operated in a dc or pulsed mode with a forward bias of 9-20 V or up to 35 V, respectively. The PD was a PMT. The LOD of hydrazine was -60ppb in 1 min, i.e., roughly equivalent to 1 ppb in 1 h. That is, the LOD using this system exceeds the OSHA requirements by a factor of -80. 

Quintino MSM, Araki K, Toma HE, Angnes L (2008) New hydrazine sensors based on electropolymerized meso-tetra(4-sulphonatephenyl)porphyrinate manganese(III)/silver nanomaterial. Talanta 74(4) 730-735... 

Gil ED, Kubota LT (2000) Electrochemical behavior of rhodium acetamidate immobilized on a carbon paste electrode a hydrazine sensor. J Braz Chem Soc 11 304—310... 

D.R. Shankaran and S.S. Narayanan, Amperometric sensor for hydrazine determination based on mechanically immobilized nickel hexacyanoferrate modified electrode. Russian J. Electrochem. 37, 1149-1153 (2001). 

A thin film of manganese oxides deposited over a glassy earbon electrode dramatically lowers the overpotential for oxidation of various hydrazines ad hydrogen peroxide, thereby facilitating their amperometric detection in flow systems. Sensors based on this principle are highly sensitive and provide... 

About the size of a package of cigarettes, individual sensors are available for H2S, phosgene, N02, HCN, and CO. In the near future, the series will be expanded to include CI2 and hydrazine. When used with the Chronotox microprocessor, the Monitox serves as a personal monitor as well as a gas detection alarm system. 

Sensor devices -for hydrazine detection [HYDRAZINE AND ITS DERIVATIVES] (Vol 13) -pressure [OXYGEN-GENERATION SYSTEMS] (Vol 17) -inclusion compounds [INCLUSION COMPOUNDS] (Vol 14)... 

A sensor for organic chloride-containing compounds was constructed by immobilization of luminol or tris (2,2 bipyridyl) ruthenium (III) between a PMT and a poly (tetrafluoro) ethylene (PTFE) membrane [15], through which a stream of air was sampled by diffusion. A heated Pt filament incorporated in the gas line leading to the CL cell was used to oxidize the analytes prior to diffusion across the PTFE membrane. Detection limits for CC14, CHC13, and CH2C12 were 1.2-4 ppm. A similar device could also be used for the determination of hydrazine and its monomethyl and dimethyl derivatives or NH3 vapor. The detection limit for hydrazine was only 0.42 ppb [16]. 

CO sensor allows detection of CO in the presence of hydrocarbons and other adsorbable contaminants. The membrane Is usually chosen for Its ability to protect the sensing electrode. However, If It has low permeability to air, the sensor will have a slower response time. The electrolyte and counter electrode have also been reported as Influencing selectivity and device performance In the determination of hydrazines (5) and NO2 (9), respectively. Finally, materials of construction are typically Teflon and high-density plastics like polypropylene because such materials must be compatible with reactive gases and corrosive electrolytes. 

In this manner, a nearly universal and very nonselective detector is created that is a compromise between widespread response and high selectivity. For example, the photoionization detector (PID) can detect part-per-billion levels of benzene but cannot detect methane. Conversely, the flame ionization detector (FID) can detect part-per-billion levels of methane but does not detect chlorinated compounds like CCl very effectively. By combining the filament and electrochemical sensor, all of these chemicals can be detected but only at part-per-million levels and above. Because most chemical vapors have toxic exposure limits above 1 ppm (a few such as hydrazines have limits below 1 ppm), this sensitivity is adequate for the initial applications. Several cases of electrochemical sensors being used at the sub-part-per-million level have been reported (3, 16). The filament and electrochemical sensor form the basic gas sensor required for detecting a wide variety of chemicals in air, but with little or no selectivity. The next step is to use an array of such sensors in a variety of ways (modes) to obtain the information required to perform the qualitative analysis of an unknown airborne chemical. 

Amperometric gas sensors are - electrochemical cells that produce a - current signal directly related to the concentration of the - analyte by - Faraday s law and the laws of - mass transport. The schematic structure of an amperometric gas sensor is shown in Fig. 1. The earliest example of this kind of sensor is the - Clark sensor for oxygen. Since that time, many different geometries, membranes, and electrodes have been proposed for the quantification of a broad range of analytes, such as CO, nitrogen oxides, H2S, O2, hydrazine, and other vapors. 

The response and recovery time of the sensor are < 30 s. Mixed films containing BDN and stearyl alcohol are electrically conducting and derived chemiresistor sensors were fabricated by depositing layers of this material onto interdigital electrodes. When exposed to NH3 or ppb levels of hydrazine,... 

Fig. 23 Sensor response to chemical vapor of hydrazine (H4N2)...

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