The Metal Type Governs Photocatalytic Reactive Oxygen Species Formation by Semiconductor‐Metal Hybrid Nanoparticles

Abstract

Semiconductor‐metal hybrid nanoparticles (HNPs) are promising photocatalysts for redox reactions, including water reduction for hydrogen generation and reactive oxygen species (ROS) formation. Herein we study the effect of the metal co‐catalyst type on the light‐induced ROS formation using a combination of spectrophotometric and fluorescence assays, as well as electron paramagnetic resonance spectroscopy. We find that although Pt tips are more efficient for H2 generation, hydrogen peroxide and hydroxyl radicals are formed more effectively by Au tipped HNPs. These variations are attributed to the different surface reactivity and selectivity related to the metal tip composition. The obtained understanding contributes to the optimal design of these hybrid nanosystems as photocatalysts in various ROS‐driven applications such as photopolymerization, and environmental and biomedical scenarios.

One‐Step Formation of Hybrid Nanocrystal Gels: Deposition of Metal Domains on CdSe/CdS Nanorod and Nanoplatelet Networks

“…The Fermi level of the domain material alters the extent of fluorescence quenching, and consequently, the efficiency of the electronhole separation. Based on the relative alignment of the Fermi levels in the prepared hybrid nanostructures, [32,40,63] Pt and Au accumulate electrons more efficiently than in situ generated Co and Ni. This is in agreement with the measured QYs as well as average exciton lifetimes.…”

“…As a result, CdTe quantum dots (QDs), CdSe QDs, CdSe nanorods (NRs), CdS NRs and CdSe/CdS dot-in-rod NCs can be efficiently decorated with Ag, [18] Au, [19][20][21][22][23] Pt, [24][25][26] AuPd, [27] Ni, [28,29] Co [30][31][32][33] , Ni(OH) 2 , [34][35][36] or Co(OH) 2 [37] domains; furthermore, we also published a method for the site-selective growth of noble metals on CdSe/CdS core/crown NPLs. [38] The electronic structure of these hybrid NCs (i.e., band alignment, Fermi level) allows the enhancement of the light-induced charge carrier separation endowing them with high potential in photocatalytic applications such as water splitting [16,29,33,35,[37][38][39][40] or H 2 O 2 production. [40,41] Except solely few examples, the abovementioned synthetic procedures take place in organic solvents and require external trigger to initiate the reduction of the metal precursors.…”

“…[38] The electronic structure of these hybrid NCs (i.e., band alignment, Fermi level) allows the enhancement of the light-induced charge carrier separation endowing them with high potential in photocatalytic applications such as water splitting [16,29,33,35,[37][38][39][40] or H 2 O 2 production. [40,41] Except solely few examples, the abovementioned synthetic procedures take place in organic solvents and require external trigger to initiate the reduction of the metal precursors. This stimulus can be heat, light or the presence of reducing agents.…”

Metal/semiconductor interfaces in nanoscale objects: synthesis, emerging properties and applications of hybrid nanostructures

“…16a). 348 They have synthesized single-tipped CdS NRs (48 AE 5 nm  3.3 AE 0.5 nm) with either gold (2.5 AE 0.6 nm) or platinum (1.9 AE 0.5 nm) tips. Surprisingly they have found that though Pt is considered the 'better' H 2 (g) production catalyst, Au-tips have higher photocatalytic efficiencies towards H 2 O 2 and cOH generation.…”

“…357 Many additional variations to the cadmium chalcogenide NR/M system were attempted to improve the stability and increase catalytic efficiencies-including variation of the NR's dimensions, CdSe@CdS seeded NRs, variation of tip size, number of metal catalysts, composition of the tip (core-shell, multi-domain, alloy bimetallic tips) and so forth. 100,348,351,[358][359][360] It is important to note that since the reaction conditions and measurement protocols are not standardized, it is hard to compare between different reports, especially since the illumination intensity and wavelength can change the number of photoexcited charge carriers per HNS and inuence the charge transfer mechanism. As pointed out by Ben-Shahar et al, this is especially important in photocatalytic reactions involving multielectron reactions such as water splitting.…”