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Direct growth of ultra-long platinum nanolawns on a semiconductor photocatalyst.

Shen YL, Chen SY, Song JM, Chin TK, Lin CH, Chen IG - Nanoscale Res Lett (2011)

Bottom Line: A template- and surfactant-free process, thermally assisted photoreduction, is developed to prepare vertically grown ultra-long Pt nanowires (NWs) (about 30-40 nm in diameter, 5-6 μm in length, and up to 80 NWs/100 μm2 in the wire density) on TiO2 coated substrates, including Si wafers and carbon fibers, with the assistance of the photocatalytic ability and semiconductor characteristics of TiO2.TEM analytical results suggest that the Pt NWs are single-crystalline with a preferred ⟨111⟩ growth direction.The interactions between the ions and the electrons in the Pt/TiO2 junction are discussed in this study.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Materials Science and Engineering, National Dong Hwa University, Hualien 974, Taiwan. samsong@mail.ndhu.edu.tw.

ABSTRACT
A template- and surfactant-free process, thermally assisted photoreduction, is developed to prepare vertically grown ultra-long Pt nanowires (NWs) (about 30-40 nm in diameter, 5-6 μm in length, and up to 80 NWs/100 μm2 in the wire density) on TiO2 coated substrates, including Si wafers and carbon fibers, with the assistance of the photocatalytic ability and semiconductor characteristics of TiO2. A remarkable aspect ratio of up to 200 can be achieved. TEM analytical results suggest that the Pt NWs are single-crystalline with a preferred 〈111〉 growth direction. The precursor adopted and the heat treatment conditions are crucial for the yield of NWs. The photoelectrons supplied by TiO2 gives rise to the formation of nano-sized Pt nuclei from salt melt or solution. The subsequent growth of NWs is supported by the thermal electrons which also generated from TiO2 during the post thermal treatment. The interactions between the ions and the electrons in the Pt/TiO2 junction are discussed in this study.

No MeSH data available.


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Proposed model for the growth of Pt NWs during the TAP process.
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Figure 8: Proposed model for the growth of Pt NWs during the TAP process.

Mentions: It has been demonstrated that metallic ions can be reduced to form nano-sized nuclei on the surface of photocatalytic TiO2 [22]. In our case, once the Pt4+ ions gained photoelectrons and the elemental Pt started to precipite on the surface of TiO2, a Schottky barrier formed since the work function of Pt (5.65 eV) [23] is larger than TiO2 (4.2 eV) [24], a n-type semiconductor according to the results of Hall measurement listed in Table 2. As sketched in Figure 8, in order to align Fermi levels for the metal (EFm) and semiconductor (EFs) at equilibrium, electrons move to the metal and then the positive charge due to ionized donor ions within W, the depletion region adjacent to the junction, matches the negative charge on the metal [25]. The equilibrium contact potential Vo (so-called built-in potential barrier, the difference in work functions between Pt and TiO2) prevents further net electron diffusion from the semiconductor conduction band into the metal. On the other side of the junction, ΦB is the potential barrier for backward electron flow from the metal to the semiconductor.


Direct growth of ultra-long platinum nanolawns on a semiconductor photocatalyst.

Shen YL, Chen SY, Song JM, Chin TK, Lin CH, Chen IG - Nanoscale Res Lett (2011)

Proposed model for the growth of Pt NWs during the TAP process.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211474&req=5

Figure 8: Proposed model for the growth of Pt NWs during the TAP process.
Mentions: It has been demonstrated that metallic ions can be reduced to form nano-sized nuclei on the surface of photocatalytic TiO2 [22]. In our case, once the Pt4+ ions gained photoelectrons and the elemental Pt started to precipite on the surface of TiO2, a Schottky barrier formed since the work function of Pt (5.65 eV) [23] is larger than TiO2 (4.2 eV) [24], a n-type semiconductor according to the results of Hall measurement listed in Table 2. As sketched in Figure 8, in order to align Fermi levels for the metal (EFm) and semiconductor (EFs) at equilibrium, electrons move to the metal and then the positive charge due to ionized donor ions within W, the depletion region adjacent to the junction, matches the negative charge on the metal [25]. The equilibrium contact potential Vo (so-called built-in potential barrier, the difference in work functions between Pt and TiO2) prevents further net electron diffusion from the semiconductor conduction band into the metal. On the other side of the junction, ΦB is the potential barrier for backward electron flow from the metal to the semiconductor.

Bottom Line: A template- and surfactant-free process, thermally assisted photoreduction, is developed to prepare vertically grown ultra-long Pt nanowires (NWs) (about 30-40 nm in diameter, 5-6 μm in length, and up to 80 NWs/100 μm2 in the wire density) on TiO2 coated substrates, including Si wafers and carbon fibers, with the assistance of the photocatalytic ability and semiconductor characteristics of TiO2.TEM analytical results suggest that the Pt NWs are single-crystalline with a preferred ⟨111⟩ growth direction.The interactions between the ions and the electrons in the Pt/TiO2 junction are discussed in this study.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Materials Science and Engineering, National Dong Hwa University, Hualien 974, Taiwan. samsong@mail.ndhu.edu.tw.

ABSTRACT
A template- and surfactant-free process, thermally assisted photoreduction, is developed to prepare vertically grown ultra-long Pt nanowires (NWs) (about 30-40 nm in diameter, 5-6 μm in length, and up to 80 NWs/100 μm2 in the wire density) on TiO2 coated substrates, including Si wafers and carbon fibers, with the assistance of the photocatalytic ability and semiconductor characteristics of TiO2. A remarkable aspect ratio of up to 200 can be achieved. TEM analytical results suggest that the Pt NWs are single-crystalline with a preferred 〈111〉 growth direction. The precursor adopted and the heat treatment conditions are crucial for the yield of NWs. The photoelectrons supplied by TiO2 gives rise to the formation of nano-sized Pt nuclei from salt melt or solution. The subsequent growth of NWs is supported by the thermal electrons which also generated from TiO2 during the post thermal treatment. The interactions between the ions and the electrons in the Pt/TiO2 junction are discussed in this study.

No MeSH data available.


Related in: MedlinePlus