A single-crystalline
Bi2S3 nanowire array
(Bi2S3NWA) is synthesized by an in situ hydrothermal
reaction on the surface of a Bi2MoO6 film. As
no additional source of Bi3+ is provided during the process,
the Bi2MoO6 layer acts as the Bi3+ source for the synthesis of Bi2S3 nanowires.
The fabricated Bi2MoO6/Bi2S3NWA electrode exhibited an increased photoelectrochemical (PEC) sulfite
oxidation activity, which is attributed mainly to the effective interface
obtained by the in situ hydrothermal growth, compared to other Bi2S3 electrodes. The generated electron from the
Bi2S3 conduction band rapidly transfers to that
of Bi2MoO6, yielding an enhanced electron separation
of Bi2S3. Furthermore, the single-crystalline
Bi2S3 nanowire can provide a fast electron pathway
to Bi2MoO6 through its single domain, which
also contributes to the improved PEC activity.
We describe a general approach for the synthesis of allylated and benzylated pyrazoles. An electron-withdrawing substituent, such as nitro, chloro, and ester groups, at C4 renders the Lewis basic nitrogen atom to be less basic and the C-H bond more acidic than the ones of the parent ring, enabling Pd-catalyzed C-H allylation and benzylation reactions of pyrazoles. The new method expanding the scope of the C-H functionalization of pyrazoles beyond arylation reactions provides a rapid access to complex pyrazole compounds.
A palladium-catalyzed C-H arylation reaction of nitroimidazoles and nitropyrazoles was developed using aryl bromides as arene donors. The electron-withdrawing effect of the nitro group allows for direct C-H arylation reactions of the nitro diazoles with high regioselectivity under mild conditions. The new C-H arylation approach is thus complementary to nucleophilic substitution reactions, enabling the preparation of complex nitroazole compounds.
In this study, the
reaction mechanisms of metal–semiconductor
composites used as photocatalysts were demonstrated by first preparing
bismuth vanadate (BiVO4) and then performing photodeposition
of metal nanoparticles. The photocatalytic activity of metal–BiVO4 (M–BiVO4, where M = Pt, Au, Ag) composites
were evaluated through dye decomposition under UV–vis irradiation.
The photocatalytic efficiency was significantly enhanced after Pt
deposition as compared to other M–BiVO4 composites.
The size or shape of BiVO4 was not the main factor for
the efficiency of Pt–BiVO4. However, a deposited
Pt co-catalyst was essential for the photocatalytic decomposition
of dye on the BiVO4 surface. Radical scavengers were employed
to elucidate the reaction mechanism during the photocatalytic reaction
with the Pt–BiVO4 composite. This study provides
details on the reaction mechanism of the photocatalytic reaction on
Pt at the BiVO4 surface under solar irradiation.
A BiVO4/Bi2S3 composite comprising Bi2S3 nanowires on top of a BiVO4 film was prepared
via hydrothermal reaction. Because additional Bi3+ ions
were not delivered during the reaction, BiVO4 served as
the Bi3+ ion source for the development of Bi2S3. A detailed growth mechanism of the nanowire was elucidated
by an analysis of the concentration gradient of Bi3+ and
S2– ions during the reaction. The in situ growth was followed by the etching of BiVO4 to Bi3+ and VO4
3– ions and regrowth
to Bi2S3, which resulted in the rapid evolution
of nanowires on the BiVO4 substrate. The fabricated BiVO4/Bi2S3NW composite exhibited an improved
photoelectrochemical activity compared to other Bi2S3 samples. The improved efficiency was mainly attributed to
both improved charge separation and effective adhesion obtained by
the in situ growth.
The simple and fast ultrasonic-assisted synthesis of high-performance, low-interfacial-resistance Bi2O3/Bi2S3 composite semiconductors is demonstrated.
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