Spin selection in atomic-level chiral metal oxide for photocatalysis

Abstract

The spin degree of freedom is an important and intrinsic parameter in boosting carrier dynamics and surface reaction kinetics of photocatalysis. Here we show that chiral structure in ZnO can induce spin selectivity effect to promote photocatalytic performance. The ZnO crystals synthesized using chiral methionine molecules as symmetry-breaking agents show hierarchical chirality. Magnetic circular dichroism spectroscopic and magnetic conductive-probe atomic force microscopic measurements demonstrate that chiral structure acts as spin filters and induces spin polarization in photoinduced carriers. The polarized carriers not only possess the prolonged carrier lifetime, but also increase the triplet species instead of singlet byproducts during reaction. Accordingly, the left- and right-hand chiral ZnO exhibit 2.0- and 1.9-times higher activity in photocatalytic O2 production and 2.5- and 2.0-times higher activities in contaminant photodegradation, respectively, compared with achiral ZnO. This work provides a feasible strategy to manipulate the spin properties in metal oxides for electron spin-related redox catalysis.

Near-Infrared Chiroptical Activity Titanium Dioxide Supraparticles with Circularly Polarized Light Induced Antibacterial Activity

“…The reason that CPL irradiating chiral TiO 2 SPs efficiently generated ROSs lay in the spin polarization during the carrier separation process induced by CPL. In cases where spin angular momentum was conserved, the recombination of polarized electrons and holes can be suppressed, thereby generating a large amount of ROS and enhanced catalytic activity …”

“…This discrepancy arose due to the weak polarization of simulated In cases where spin angular momentum was conserved, the recombination of polarized electrons and holes can be suppressed, thereby generating a large amount of ROS and enhanced catalytic activity. 45 In addition, ESR spectroscopy was used to determine the specific types of ROS generated by chiral TiO 2 when exposed to light, predominantly hydroxyl radicals and singlet oxygen (Figure 4E,F). The mechanism by which the hydroxyl radical was produced was thoroughly investigated and aligned with previously reported findings, as presented below: 20…”

Unraveling Rigidified Superexchange Couplings in Organic Donor–Acceptor Polymers for Boosting the Photocatalytic Reduction of Nitrate

“…AFM images reveal that the uniform thickness of D-PDI is about 3–7 nm (Figure c). On the other hand, a clear lattice fringe of about 0.32 nm can be observed in Figure d, confirming the intermolecular H-type π–π stacking interaction, demonstrating that the face-to-face overlap of the geometrical configuration provides a delocalized electron cloud for promoting the carrier migration between layers. − In addition, the elemental distribution in D-PDI exhibits a homogeneous dispersion of C, N, and O elements (Figure e,h). Moreover, the Brunauer–Emmett–Teller (BET)-specific surface area of D-PDI is 65.8 m 2 g –1 , which is much larger than those of other PDI polymers (Figure S4), indicating that the special structure of D-PDI makes more active sites exposed …”

Chiral Induced Spin Selectivity

“…In subsequent studies with helically aggregated dye molecules additional features of spin polarization on the characteristics of water splitting became apparent; not only was spin polarization responsible for decreasing the reaction overpotential for the OER, it was shown to inhibit the formation of hydrogen peroxide, as well as other super oxides . These effects have since been shown for other chiral catalysts, − including chiral metal oxides ,,,− and metal sulfides. , As an aside, we note that CISS may account, in part, for the high activity of photosystem II …”