Metal ion implantation

Fujishima A, Honda K (1972) Electrochemical photolysis of water at a semiconductor electrode. Nature 238 37-38 Yamashita H, Harada M, Misaka J, Takeuchi M, Neppolian B, Anpo M (2003) Photocatalytic degradation of organic compounds diluted in water using visible light-responsive metal ion-implanted Ti02 catalysts Fe ion-implanted Ti02. Catal Today 84 191-196... 

Coloma F, Marquez F, Rochester CH, Anderson JA (2000) Determination of the nature and reactivity of copper sites in Cu-Ti02 catalysts. Phys Chem Chem Phys 2 5320-5327 Umebayashi T, Yamaki T, Itoh H, Asai K (2002) Analysis of electronic structures of 3d transition metal-doped Ti02 based on band calculations. J Phys Chem Solids 63 1909-1920 Yamashita H, Ichihashi Y, Takeuchi M, Kishiguchi S, Anpo M (1999) Characterization of metal ion-implanted titanium... 

This chapter deals with the design and development of such unique second-generation titanium oxide photocatalysts which absorb UV-visible light and operate effectively under visible and/or solar irradiation by applying an advanced metal ion-implantation method. 

Figure 3 Schematic diagram of an advanced metal ion-implantation method. High-energy implantation (bottom) was used in the present study.

The metal ion-implanted titanium oxide catalysts were calcined in O2 at around 725-823 K for 5 hr. Prior to various spectroscopic measurements such as UV-vis diffuse reflectance, SIMS, XRD, EXAFS, ESR, and ESCA, as well as investigations on the photocatalytic reactions, both the metal ion-implanted and unimplanted original pure titanium oxide photocatalysts were heated in O2 at 750 K and then degassed in cells at 725 K for 2 h, heated in O2 at the same temperature for 2 h, and, finally, outgassed at 473 K to 10 lorr [12-15]. 

Furthermore, as shown in Fig. 5, such red shifts in the absorption band of the metal ion-implanted titanium oxide photocatalysts can be observed for any... 

With unimplanted or chemically doped titanium oxide photocatalysts, the photocatalytic reaction does not proceed under visible-light irradiation (X > 450 nm). However, we have found that visible-light irradiation of metal ion-implanted... 

It is important to emphasize that the photocatalytic reactivity of the metal ion-implanted titanium oxides under UV light (X < 380 nm) retained the same photocatalytic efficiency as the unimplanted original pure titanium oxides under the same UV light irradiation conditions. When metal ions were chemically doped into the titanium oxide photocatalyst, the photocatalytic efficiency decreased dramatically under UV irradiation due to the effective recombination of the photo-formed electrons and holes through the impurity energy levels formed by the doped metal ions within the band gap of the photocatalyst (in the case of Fig. 6)... 

It was also found that increasing the number (or amounts) of metal ion implanted into the deep bulk of the titanium oxides caused the photocatalytic efficiency of these photocatalysts to increase under visible-light irradiation, passing through a maximum at around 6 X 10 ions/cm of the catalyst, then decreas-... 

Our results clearly show that modification of the electronic state of titanium oxide by metal ion implantation is closely associated with the strong and longdistance interaction which arises between the titanium oxide and the metal ions implanted, as shown in Fig. 13, and not by the formation of impurity energy levels within the band gap of the titanium oxides resulting from the formation of impurity oxide clusters which are often observed in the chemical doping of metal ions, as shown in Figs. 6 and 13. 

The advanced metal ion-implantation method has been successfully applied to modify the electronic properties of the titanium oxide photocatalysts, enabling... 

Thus, the advanced metal ion-implantation method has opened the way to many innovative possibilities, and the design and development of such unique titanium oxide photocatalysts can also be considered an important breakthrough in the utilization of solar light energy, which will advance research in sustainable green chemistry for a better environment [4,5,15,16,20-22]. 

Furthermore, as shown in Fig. 10.2, such red shifts in the absorption band of the metal ion-implanted titanium oxide photocatalysts can be observed for any kind of titanium oxide except amorphous types, the extent of the shift changing from sample to sample. It was also found that such shifts in the absorption band can be observed only after calcination of the metal ion-implanted titanium oxide samples in 02 at around 723-823 K. Therefore, calcination in 02 in combination with metal ion-implantation was found to be instrumental in the shift of the absoiption spectrum toward visible light regions. These results clearly show that shifts in the absorption band of the titanium oxides by metal ion-implantation is a general phenomenon and not a special feature of a certain kind of titanium oxide catalyst. 

It was also found that increasing the number (or amounts) of metal ion-implanted into the deep bulk of the titanium oxides caused the photocatalytic... 

Ti ion-implanted titanium oxides exhibited no shift, showing that such a shift is not caused by the high energy implantation process itself, but to some interaction of the transition metal ions with the titanium oxide catalyst. As can be seen in Fig. 10-1 ((b)—(d)), the absorption band of the Cr ion-implanted titanium oxide shifts smoothly to visible light regions, the extent of the red shift depending on the amount and type of metal ions implanted, with the absorption maximum and... 

Our results clearly show that modification of the electronic state of titanium oxide by metal ion-implantation is closely associated with the strong and long distance interaction which arises between the titanium oxide and the metal ions... 

Anpo M, Ichihashi Y, Takeuchi M, Yamashita H. Design and development of unique titanium oxide photocatalysts capable of operating under visible light irradiation by an advanced metal ion-implantation method. Stud Surf Sci Catal 1999 121 305-310. 

Yamashita H, Honda M, Harada M, et al. Preparation of titanium oxide photocatalysts anchored on porous silica glass by a metal ion-implantation method and their photo-catalytic reactivities for the degradation of 2-propanol diluted in water. J Phys Chem B 1998 102 10707-11. 

All electrodes react with their environment via the surfaces in ways which will determine their electrochemical performance. Properly selected surface modification can effectively enhance the electrode heterogeneous catalysis property, especially selectivity and activity. The bulk materials can be chosen to provide mechanical, chemical, electrical, and structural integrity. In this part, several surface modification methods will be introduced in terms of metal film deposition, metal ion implantation, electrochemical activation, organic surface coating, nanoparticle deposition, glucose oxidase (GOx) enzyme-modified electrode, and DNA-modified electrode. 

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