Tunable Photoelectrochemical Properties of Chalcopyrite AgInS₂ Nanoparticles Size-Controlled with a Photoetching Technique

Abstract

Size-selective photoetching enabled precise size control of chalcopyrite AgInS 2 nanoparticles in a basic aqueous solution containing ammonia by selecting the wavelength of monochromatic irradiation light in the range between 650 and 520 nm. The energy gap of the photoetched particles was enlarged from 1.8 to 2.4 eV with a decrease in particle size from 5.1 to 2.7 nm due to the quantum size effect, while the crystal structure and chemical composition of the particles were unchanged after the photoetching processes. AgInS 2 nanoparticle-immobilized electrodes exhibited an anodic photocurrent similar to that of n-type semiconductors, the onset potential of which was negatively shifted with a decrease in particle size. Potentials of the conduction band edge (E CB ) and the valence band edge (E VB ) of AgInS 2 nanoparticles were estimated from their photoelectrochemical measurements, and they exhibited remarkable size dependence: with a decrease in particle size from 5.1 to 2.7 nm, E CB was shifted negatively from −0.6 to −1.0 V vs Ag/AgCl, accompanied by a positive shift of E VB from 1.3 to 1.7 V vs Ag/AgCl.

Fabrication of AgInS2 nanoparticles sensitized TiO2 nanotube arrays and their photoelectrochemical properties

“…Ternary AgInS 2 has a distinctive absorption in the visible and near-infrared regions because of its large absorption coefficient and its band gap energy between 1.87 and 2.03 eV, and it is considered one of the potential candidates for promising applications in photovoltaic and photocatalytic fields [16,17]. Various preparation methods for the preparation of AgInS 2 have been reported, such as thermal decomposition [18,19], hot-injection method [20] and hydrothermal method [21]. Coupling of AgInS 2 and TiO 2 NTs would be a perfect strategy to improve the visible light photoelectrochemical property of TiO 2 NTs.…”

Photoelectrochemical etching and energy gap control of silver clusters

“…On the other hand, disappearance was not significant when the TiO 2 substrate with Ag 32 was left for 30 min in the dark. 40,41 Since the absorption edge of those QDs also depends on the particle size, it can be controlled by self-oxidation of QDs at an appropriate irradiation wavelength. The injected electrons may be accepted by ambient oxygen or released Ag + to give small Ag particles as is the case for the photooxidation of plasmonic Ag nanoparticles.…”

Nanostructure Engineering of Size-Quantized Semiconductor Particles for Photoelectrochemical Applications

“…Figure 1 summarizes the size-dependent E g reported for several kinds of semiconductor particles with a spherical shape. [16][17][18][19][20][21][22] In each case, E g was remarkably enlarged with a decrease in particle size due to the quantum size effect when the particle size became smaller than twice the effective exciton Bohr radius of the corresponding bulk semiconductor. Considering the strong size dependence of E g , it is concluded that narrowing the size dispersibility is required for precisely controlling the photoelectrochemical properties of semiconductor nanoparticles as a function of their size.…”

“…The sizeselective photoetching technique has been widely used to control the size of quantized nanoparticles such as ZnO, 29 ZnS, 30 CdS, 26,27,31 CdSe, 32 CdTe, 33 InP, 34 InGaN, 35 and AgInS 2 nanoparticles. 21 However, being different from the case of photoetching CdS particles, an additional complexing agent such as NH 3 was necessary to successfully complete size-selective photoetching of AgInS 2 nanoparticles, because Ag + ions released along with the photoetching formed an insoluble Ag 2 O passivation layer on the particle surface to prevent further photoetching of AgInS 2 . The photoetched AgInS 2 particles had the same crystal structure and the same chemical composition (Ag/In ratio) as those of the original particles.…”

“…The photoetched AgInS 2 particles had the same crystal structure and the same chemical composition (Ag/In ratio) as those of the original particles. 21 The potentials of E CB and E VB for bulk semiconductors are exclusively determined by their chemical composition. In contrast, size-quantized nanoparticles have tunable energy levels depending on the particle size.…”