Chiral Plasmonic Nanocrystals for Generation of Hot Electrons: Toward Polarization-Sensitive Photochemistry

Abstract

The use of biomaterials -with techniques such as DNA-directed assembly or biodirected synthesis -can surpass top-down fabrication techniques in creating plasmonic superstructures, in terms of spatial resolution, range of functionality and fabrication speed.Particularly, by enabling a very precise placement of nanoparticles in a bio-assembled complex or a controlled bio-directed shaping of single nanoparticles, plasmonic nanocrystals can show remarkably strong circular dichroism (CD) signals. Here we show that chiral bio-plasmonic assemblies can enable polarization-sensitive photochemistry based on the generation of energetic (hot) electrons. It is now established that hot plasmonic electrons can induce surface photochemistry or even reshape plasmonic nanocrystals. Here we show that merging chiral plasmonic nanocrystal systems and the hot-election generation effect offers unique possibilities in photochemistry -such as polarization-sensitive photochemistry promoting nonchiral molecular reactions, chiral photo-induced growth of a colloid at the atomic level and chiral photochemical destruction of chiral nanocrystals. In contrast, for chiral molecular systems the equivalent of the described effects is challenging to be observed because molecular species exhibit typically very small CD signals. Moreover, we compare our findings with traditional chiral photochemistry at the molecular level, identifying new, different regimes for chiral photochemistry with possibilities that are unique for plasmonic colloidal systems. In this study, we bring together the concept of hot-electron generation and the field of chiral colloidal plasmonics. Using chiral plasmonic nanorod complexes as a model system, we demonstrate remarkably strong CD in both optical extinction and generation rates of hot electrons. Studying the regime of steady-state excitation, we discuss the influence of geometrical and material parameters on the chiral effects involved in the generation of hot electrons. Optical chirality and the chiral hot-electron response in the nanorod dimers result from complex inter-particle interactions, which can appear in the weak coupling 3 regime or in the form of Rabi splitting. Regarding practical applications, our study suggests interesting opportunities in polarization-sensitive photochemistry, chiral recognition or separation, and in promoting chiral crystal growth at the nanoscale.

Chiral Surface and Geometry of Metal Nanocrystals

“…Polarization-selective amplitude and phase change of light in engineered chiral building blocks have been a core technology for nanometer-thin flat metalens, [26,27] chiral photodetector, [28] and 3D holographic display. [29,30] Further, chiral nanomaterials have extended the limit of light-matter interaction to an extreme regime, such as ultrasensitive detection of biomolecular structures, [31][32][33][34] negative refractive index material, [35,36] chiral optical forces, [37,38] chiral photochemical reactions, [39,40] quantum information processing, and cryptography. [41][42][43][44] The hybrid of chiral nanomaterials with the intriguing spin-associated systems such as valleytronics, [45] topological materials, [46] and magnetic skyrmion [47] can be the possible applications.…”

Electromagnetic chirality: from fundamentals to nontraditional chiroptical phenomena

“…Not only absorptive and scattering phenomena but also optomechanical effects can be explained using this theoretical framework. Other chiroptical effects, such as the photothermal effect 167,168 , magnetic circular dichroism 169 , and nonlinear chirality 170,171 , could also be interpreted based on these same outlines. We expect this review to provide a clear understanding of the underlying theory of chiroptical systems and help guide research on and applications of chiroptical phenomena in a theoretically robust manner.…”

Chiral 432 Helicoid II Nanoparticle Synthesized with Glutathione and Poly(T)20 Nucleotide

“…Chirality, a structural property prevalent in nature, refers to a geometrical orientation being non‐superimposable to each other. Especially in the field of plasmonics, strong chiral light‐matter interaction has been one of the fundamental needs with its wide potential application in chiral recognition sensing, optical metamaterials, enantioselective catalysis, and opto‐tele communication technologies . In this sense, relentless efforts have been dedicated to the construction of chiral plasmonic nanostructures using E‐beam lithography, direct laser writing, and macromolecular assembly .…”

“…Especially in the field of plasmonics, strong chiral lightmatter interaction has been one of the fundamental needs with its wide potential application in chiral recognition sensing, optical metamaterials, enantioselective catalysis, and opto-tele communication technologies. [1][2][3][4][5][6][7][8][9] In this sense, relentless efforts have been dedicated to the construction of chiral plasmonic nanostructures using E-beam lithography, [10][11][12] direct laser writing, [13,14] and macromolecular assembly. [15][16][17][18][19][20] Despite sophisticated control of chiral nanostructures, state of the art technologies require complicated synthetic processes and have limitations on constructible morphologies.…”