Spin and valley degrees of freedom in materials without inversion symmetry promise previously unknown device functionalities, such as spin-valleytronics. Control of material symmetry with electric fields (ferroelectricity), while breaking additional symmetries, including mirror symmetry, could yield phenomena where chirality, spin, valley, and crystal potential are strongly coupled. Here we report the synthesis of a halide perovskite semiconductor that is simultaneously photoferroelectricity switchable and chiral. Spectroscopic and structural analysis, and first-principles calculations, determine the material to be a previously unknown low-dimensional hybrid perovskite (R)-(−)-1-cyclohexylethylammonium/(S)-(+)-1 cyclohexylethylammonium) PbI3. Optical and electrical measurements characterize its semiconducting, ferroelectric, switchable pyroelectricity and switchable photoferroelectric properties. Temperature dependent structural, dielectric and transport measurements reveal a ferroelectric-paraelectric phase transition. Circular dichroism spectroscopy confirms its chirality. The development of a material with such a combination of these properties will facilitate the exploration of phenomena such as electric field and chiral enantiomer–dependent Rashba-Dresselhaus splitting and circular photogalvanic effects.
Herein, by directly using Watson-Crick base pairing, a highly ordered and field-free three-dimensional (3D) DNA nanostructure is self-assembled by azobenzene (azo)-functionalized DNA nippers in a few minutes, which was applied as a 3D DNA nanomachine with an improved movement efficiency compared to traditional Au-based 3D nanomachines due to the organized and high local concentration of nippers on homogeneous DNA nanostructure. Once microRNA (miRNA) interacts with the 3D nanomachine, the nippers "open" to hybridize with the miRNA. Impressively, photoisomerization of the azo group induces dehybridization/hybridization of the nippers and miRNA under irradiation at different wavelengths, which easily solves one main technical challenge of DNA nanotechnology and biosensing: reversible locomotion in one step within 10 min. As a proof of concept, the described 3D machine is successfully applied in the rapid single-step detection of a biomarker, which gives impetus to the design of new generations of mechanical devices beyond the traditional ones with ultimate applications in sensing analysis and diagnostic technologies.
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