​Chiral Perovskites
Chiral semiconductor perovskites are class of materials that offer a flexible approach to inclusion of chiral symmetry. Our group is developing different strategies for synthesizing chiral perovskite nanomaterials and determining the factors which govern their chiroptical response. We have shown that the placement of chiral organic ligands on the surface of CsPbBr3 nanocubes imprints chiro-optical properties on its electronic transitions and the strength of the imprinting, assessed via their circular dichroism response changes strongly with the nanoparticle size (magnitude of the exciton’s quantum confinement). The plot on the bottom left shows this effect for four different sized nanoparticles: 2.2 nm (red), 4.1 nm (blue), 5.2 nm (purple), and 6 nm (green). In related work, we have shown how electronic effects of para substituted phenethylamine ligands, used to passivate CsPbBr3 nanoparticles, can affect the chiroptical properties of the nanoparticles; ligands with greater electron donating groups (EDG) show larger Cotton effects. Collectively, these data suggest that the mechanism for chiral imprinting in perovskite NPs is dominated by electronic interactions at small sizes.
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Recent publications on Chiral Perovskites:
6. Tabassum, N.; Bloom, B. P.; Debnath, G. H.; Waldeck, D. H. Factors influencing the chiral imprinting in perovskite nanoparticles Nanoscale 2024, 16, 22120.

5. Dunlap‑Shohl, W. A.; Tabassum, N.; Zhang, P.; Shiby, E.; Beratan, D. N.; Waldeck, D. H. Electron-Donating Functional Groups Strengthen Ligand-Induced Chiral Imprinting on CsPbBr3 Quantum Dots. Sci. Rep.2024, 14, 336.

4. Tabassum, N.; Georgieva, Z. N.; Debnath, G. H.; Waldeck, D. H. Size Dependent Chiro-Optical Properties of CsPbBr3 Nanoparticles, Nanoscale 2023, 15, 2143.

3. Georgieva, Z. N.; Zhang, Z.; Zhang, P.; Bloom, B. P.; Beratan, D. N.; Waldeck, D. H. Ligand Coverage and Exciton Delocalization Control of Chiral Imprinting in Perovskite Nanoplatelets. J. Phys. Chem. C 2022, 126, 15986.

2. Debnath, G. H.; Georgieva, Z. N.; Bloom, B. P.; Tan, S.; Waldeck, D. H.; Using Post-Synthetic Ligand Exchange to Imprint Chirality onto the Electronic States of Cesium Lead Bromide (CsPbBr3) Perovskite Nanoparticles. Nanoscale 2021, 13, 15248.

1. Huang, Z.; Bloom, B. P.; Ni, X.; Georgieva, Z. N.; Merciesky, M.; Vetter, E.; Liu, F.; Waldeck, D. H.; Sun, D. Magneto-Optical Detection of Photoinduced Magnetism via Chirality-Induced Spin Selectivity in 2D Chiral Hybrid Organic-Inorganic Perovskites, ACS Nano, 2020, 14, 10370.
Chiral Metal Oxides
In addition to chiral perovskites, we are developing techniques to synthesize chiral metal oxide thin films and nanoparticles. These exciting materials are providing insights into the fundamental properties of the CISS effect (See here), as well as providing novel materials for spin polarized catalysis (See here). The Figure on the left shows spin polarization measurements using Mott polarimetry (top) on CuO thin films. Here, the asymmetry in spin population of photoelectrons \(\frac{I_{up} - I_{down}}{I_{up} + I_{down}} \times 100 \%\), where \(I_{up}\) and \(I_{down}\) correspond to the number of spin up and down electrons respectively, is directly quantified as a function of CuO thickness (bottom). The Figure on the right shows spin polarization measurements using mc-AFM (top) on L-CoOx and Mn-doped L-CoOx thin films. Here, an asymmetric i-V response is observed and quantified as a spin polarization \( \frac{I_{up} - I_{down}}{I_{up} + I_{down}} \times 100 \%\) , where \(I_{up}\) and \(I_{down}\) correspond to the current when the AFM tip is magnetized North and South respectively. Our data suggest metal doping as a strategy to increase spin polarization in metal oxides.

Recent publications on Chiral Metal Oxides:
4. Sun, R.; Wang, Z.; Bloom, B. P.; Comstock, A. H.; Yang, C.; McConnell, A.; Clever, C.; Molitoris, M.; Lamont, D.; Cheng, Z.-H.; Yuan, Z.; Zhang, W.; Hoffmann, A.; Liu, J.; Waldeck, D. H.; Sun, D. Colossal Anisotropic Absorption of Spin Currents Induced by Chirality. Sci. Adv. 2024, 10, eadn3240.

3. Vadakkayil, A.; Clever, C.; Kunzler, K. N.; Tan, S.; Bloom, B. P.; Waldeck, D. H. Chiral Electrocatalysts Eclipse Water Splitting Metrics through Spin Control. Nat. Commun. 2023, 14, 1067.

2. Möllers, P. V.; Wei, J.; Salamon, S.; Bartsch, M.; Wende, H.; Waldeck, D. H.; Zacharias H. Spin-Polarized Photoemission from Chiral CuO Catalyst Thin Films. ACS Nano 2022, 16, 12145.

1. Ghosh, S.; Bloom, B. P.; Lu, Y.; Lamont, D.; Waldeck, D. H. Increasing the Efficiency of Water Splitting through Spin Polarization using Cobalt Oxide Thin Film Catalysts. J. Phys. Chem. C 2020, 124, 22610.