Platinum nanoparticle-functionalized tin dioxide nanowires via radiolysis and their sensing capability
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Platinum (Pt) nanoparticles were synthesized on tin dioxide (SnO2) nanowires by applying c-ray radiolysis. The growth behavior of Pt nanoparticles was systematically investigated as a function of precursor concentration, illumination intensity and exposure time of the c-rays. We found that these processing parameters greatly influenced the growth behavior of Pt nanoparticles in terms of size and formation density. Vapor-phase-grown SnO2 nanowires were uniformly covered with Pt nanoparticles by the radiolysis process. The Pt nanoparticle-functionalized SnO2 nanowires were tested as sensors for detecting reductive gases including carbon monoxide, toluene, and benzene. The results indicate that the c-ray radiolysis is an efficient way of functionalizing the surface of oxide nanowires with catalytic Pt nanoparticles.
I. INTRODUCTION
In recent years, various shapes of nanomaterials have received increased attention due to their unique physical and chemical properties, which are significantly different from their bulk or thin film counterparts. In particular, noble metal nanoparticles are attracting considerable interests from researchers owing to their various potential surface-related catalytic applications. As of date, for synthesizing metal nanoparticles, various methods such as photochemistry,1 reverse micelles,2 arc discharge,3 radiolysis4 and sonochemistry5 have been attempted. According to the literature survey,6–8 some research groups have succeeded in synthesizing metal nanoparticles by the c-ray radiolysis process. Henglein reported the synthesis of ultrafine colloidal Au nanoparticles in aqueous solutions under a c-ray illumination of 1.8 106 rad/h for 4 min.6 Seino et al.8 successfully prepared Au/c-Fe2O3 composite nanoparticles via the radiolysis process. Metallic catalysts are known to functionalize the surface of nanomaterials. For instance, noble metals anchored on semiconducting oxides facilitate the dissociation of oxygen molecules into oxygen species, including atomic oxygen, thereby enhancing the oxygen sensitivity.9,10 Accordingly, some research groups have attempted to functionalize the surface of nanowires with nanosized noble metals using various methods.11–13 Platinum (Pt) nanoparticles were tested in the design of chemical sensors,14–16 on the premise that they can promote electron transfer and thus enhance mass transport
characteristics.14,17–20 For instance, Ikariyama et al.17 proved Pt nanoparticles as an excellent matrix for microenzyme sensors. Wang et al.18 reported ultrafine Pt particles-modified carbon fibers for detecting hydrazine (N2H4). In addition, Birkin et al.20 demonstrated that Pt nanoparticles could be used in combination with singlewall carbon nanotubes for constructing electrochemical sensors with a remarkably improved sensitivity to H2O2. Although the addition of noble metals to SnO2 nanowires is known to enhance gas sensitivity of SnO2, to the best of our knowledge, no work has been reported on Pt-functionalization via the c-rays radiolysis on SnO2 nanowires. In the present w
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