Comparison study of conductometric, optical and SAW gas sensors based on porous sol–gel silica films doped with NiO and Au nanocrystals

Abstract

Conductometric, optical and surface acoustic wave gas sensors based on sol-gel silica porous films doped with NiO and Au nanoparticles are studied. The nanocomposite films are characterized by optical absorption in the visible and near-infrared region, spectroscopic ellipsometry, X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray (EDX) analysis and X-ray photoemission spectroscopy (XPS). They show poor conductometric gas sensing response toward CO and H 2 . However, both optical and surface acoustic wave (SAW) responses are reversible and stable to H 2 . Moreover, exploiting the wavelength dependence of the optical sensor response it is possible to selective recognition of H 2 . Choosing the appropriate wavelength, almost no variation in absorption is observed when introducing different gases into the testing chamber.

Unusual magnetic properties of NiO nanoparticles embedded in a silica matrix

“…The preparation of magnetic nanoparticles embedded in a non-magnetic matrix has been very interesting for fundamental studies and applications. Among different matrixes silica is advanced because of its non-toxic nature, high biocompatibility, prevention of agglomeration, temperature resistance, chemical inertness and adjustable pore diameter [26,29,30,[49][50][51][52][53][54][55][56]. Sol-gel method has been very useful for preparation of the nanoparticles in amorphous silica [49][50][51].…”

Porous Ceramic Sensors: Hydrocarbon Gas Leaks Detection

“…when a gaseous hydrocarbon leaks takes place and it migrates to the environment; this would require an immediate detection procedure of hydrocarbon vapors in order to take the respectively actions to control any catastrophic accident. This section extensively reviews the recent development of porous ceramic gas sensor materials for hydrocarbon gas leaks including LPG [64,65], CH 4 [66][67][68], H 2 [69][70][71], ethanol [29,[84][85][86][87][88], methanol [89][90][91][92], and associated gases such as NO 2 [41,[73][74][75][76][77], H 2 S [78][79][80][81][82][83], and CO [72]. Basically, the discussion will be focused on the specific overlapped section between three interesting areas such as (1) porous ceramic materials, (2) hydrocarbon gas leaks detection, and (3) sensor materials giving the opportunity to explore the interesting niche area for sensing hydrocarbons and their associated gases leaks by porous ceramic materials.…”

“…; and (3) the porous zinc oxide (ZnO) that has been used to sensing ethanol, acetone, NO 2 , H 2 S, etc. On the other hand, the catalyst elements mostly used as doping materials in order to improve the sensing properties of the porous ceramics are palladium (Pd) [65,66,85], gold (Au) [77], tungsten (W) [76,95], vanadium (V) [71], cerium (Ce) [90], platinum (Pt) [69], and/or combinations thereof [70,76,91]. The Pd could be used to explain the principle of operation of these doping elements which is based on the fact that Pd is a catalytic metal that dissociates the ambient gas to ions.…”

“…In addition, other compounds such as Sb 2 O 5 [41], NiO [70], and graphene [88] have been also evaluated as doping or as secondary materials in advanced composite sensors.…”

Potentiometric Zinc Ion Sensor Based on Honeycomb-Like NiO Nanostructures

“…Nickel oxide nanostructures are of great interest for the development of electrochemical energy-storage tools due to their large specific surface area, rapid redox reactions and lowered diffusion path in the solid form. Nickel oxide is also used as magnetic storage material [40], optical active counter-electrode [41], in dye-sensitized solar cells [42], electrochromic films [43] and gas sensors [44,45]. Many methods have been reported for the synthesis of NiO nanostructures such as thermal evaporation [46], RF magnetron sputtering [47], and spray pyrolysis [48].…”