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Spatially controlling the Fermi level of topological insulators and keeping their electronic states stable are indispensable processes to put this material into practical use for semiconductor spintronics devices. So far, however, such a method has not been established yet. Here we show a novel method for doping a hole into n-type topological insulators Bi2X3 (X= Se, Te) that overcomes the shortcomings of the previous reported methods. The key of this doping is to adsorb H2O on Bi2X3 decorated with a small amount of carbon, and its trigger is the irradiation of a photon with sufficient energy to excite the core electrons of the outermost layer atoms. This method allows controlling the doping amount by the irradiation time and acts as photolithography. Such a tunable doping makes it possible to design the electronic states at the nanometer scale and, thus, paves a promising avenue toward the realization of novel spintronics devices based on topological insulators.

The reaction of cholesteryl acetate 1 with a Fe III (PA; picolinate) 3 /H 2 O 2 /MeCN system (reagent system A), a simple model system for mono-oxygenases, gave mainly the 7α-hydroxylation product 2a, along with 7-ketonization product 3 and the 5,6-epoxidation product 4. On the other hand, reaction of 1 using a Fe(PA) 3 /peracetic acid (AcOOH)/MeCN system (reagent system C) or a Fe III (ClO 4 ) 3 .9H 2 O-picolinic acid(PAH)-pyridine(Py)/AcOOH MeCN system (reagent system F), provided 4 predominantly without formation of 2a. The former reaction may proceed via the dimeric Fe III -Fe V manifold complex, (PAH)(PA) 2 Fe III -O-O-Fe V =O(PA)2 (VII) as a hypothetically active species and a nonradical pathway, and the latter may proceed through monomeric iron complexes, [(PAH)(PA) 2 Fe v =O] + (IX) and [(PAH)(PA) 2 Fe v (OH)(OOH)] (X).

The reaction of cholesteryl acetate 1 with a Fe III (PA; picolinate) 3 /H 2 O 2 /MeCN system (reagent system A), a simple model system for mono-oxygenases, gave mainly the 7α-hydroxylation product 2a, along with 7-ketonization product 3 and the 5,6-epoxidation product 4. On the other hand, reaction of 1 using a Fe(PA) 3 /peracetic acid (AcOOH)/MeCN system (reagent system C) or a Fe III (ClO 4 ) 3 .9H 2 O-picolinic acid(PAH)-pyridine(Py)/AcOOH MeCN system (reagent system F), provided 4 predominantly without formation of 2a. The former reaction may proceed via the dimeric Fe III -Fe V manifold complex, (PAH)(PA) 2 Fe III -O-O-Fe V =O(PA)2 (VII) as a hypothetically active species and a nonradical pathway, and the latter may proceed through monomeric iron complexes, [(PAH)(PA) 2 Fe v =O] + (IX) and [(PAH)(PA) 2 Fe v (OH)(OOH)] (X).