title: Design of efficient zeolite sensor materials for n-hexane.
abstract: The effectiveness of several zeolite catalysts was investigated using the cataluminescence (CTL) gas sensor system. Trace amounts of n-hexane in air samples were detected by this method. This research establishes that the specific pore size of the zeolite offers designable environment for selective CTL reaction, and "Lewis-type" basic sites appear to contribute to the catalytic nature of the zeolite surface. By incorporating either Cs+ or K+, the velocity and luminescence intensity of these catalytic reactions increase while going from Na to Cs, according to the basic nature of this group of cations in the following order: Cs > K > Na. The proposed sensor shows high sensitivity and selectivity to n-hexane at a mild reaction temperature of 225 degrees C. Quantitative analysis was performed at a selected wavelength of 460 nm. The linear range of CTL intensity versus concentration of n-hexane was 0.776-23.28 microg/mL (R = 0.997, n = 7) on CsNaY, and 0.776-23.28 microg/mL (R = 0.998, n = 7) on CsNaX, with a detection limit of 0.155 microg/mL (signal-to-noise ratio 3). Interferences from foreign substances such as methanol, ethanol, 2-propanol, acetone, acetonitrile, chloroform, or dichlormethane and other alkanes, aromatics, and alkyl aromatics such as methane, n-pentane, 3-methylpentane, 3,3-dimethylpentane, methylbenzene, ethylbenzene, and sec-butylbenzene were very low or not detectable. Results of a series of GC and GC/MS experiments suggest that the possible mechanism of the reaction is the formation of an unstable transition structure with a four-member ring, and this ring most probably consists of an oxygen atom and a carbonium ion localized on the zeolite suface.
authors.affiliation: School of Pharmacy, Fudan University, 138 Yixueyuan Road, Shanghai 200032, China.
authors.forename: Ping
authors.initials: P
authors.lastname: Yang
authors.forename: Xingnan
authors.initials: X
authors.lastname: Ye
authors.forename: Choiwan
authors.initials: C
authors.lastname: Lau
authors.forename: Zengxi
authors.initials: Z
authors.lastname: Li
authors.forename: Xia
authors.initials: X
authors.lastname: Liu
authors.forename: Jianzhong
authors.initials: J
authors.lastname: Lu
mesh_terms: D002384:Catalysis; D004867:Equipment Design; D019544:Equipment Failure Analysis; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods; D005740:Gases / Q000737:chemistry; D006586:Hexanes / Q000032:analysis*; D008163:Luminescent Measurements / Q000295:instrumentation* / Q000379:methods*; D008958:Models, Molecular; D053758:Nanoparticles / Q000737:chemistry*; D010316:Particle Size; D016062:Porosity; D012680:Sensitivity and Specificity; D013499:Surface Properties; D013696:Temperature; D013997:Time Factors; D017641:Zeolites / Q000737:chemistry*; D015040:Zirconium / Q000737:chemistry*
chemical_list: D005740:Gases; D006586:Hexanes; D017641:Zeolites; C026385:n-hexane; D015040:Zirconium; C028541:zirconium oxide