Search for: All records

Abstract Plasmon‐mediated synthesis enables isotropic metal nanocrystal growth with linearly polarized light. This limits the effect of the polarization of incident light during synthesis, and thus restricts the structural chirality of nanocrystals produced with circularly polarized light (CPL). This study here demonstrates that surface engineering of initial achiral silver nanorods (AgNRs) can enhance the structural chirality of the resulting nanostructures produced with CPL. Specifically, the surface ligand hexadecyltrimethylammonium bromide (CTAB) stabilizes the lateral (100) facet‐terminated sides of achiral AgNRs and inhibits lateral growth. This surface engineering with achiral ligands results in increased dissymmetry of the nanostructures during the early stages of photo‐growth and leads to the formation of “hook” structures, where silver preferentially deposits near the tips of the nanorods. Upon further CPL illumination, these “hook” structures exhibit a significantly larger dissymmetry in the local electric field enhancement distribution compared to the initial achiral AgNRs. This highly dissymmetric electric field enhancement profile influences subsequent growth, resulting in AgNRs with enhanced structural chirality. Notably, the optical dissymmetry of these chiral nanostructures withg‐factor≈0.05 is an order of magnitude greater than that reported in previous studies conducted under similar chemical conditions but without surface engineering. 

Si quantum dot (QD)-molecule hybrid systems have emerged as a popular architecture in many research fields due to the ability to select for the advantages conferred by the inorganic Si component and the organic sections. This perspective will focus on the optical properties of Si QDs, the parameters that affect Si QD photophysics or energy transfer in Si QD-molecule hybrid structures, and their resultant hybrid optoelectronic devices. Examples of recent applications that employ Si QD-molecule hybrid materials are presented. Finally, we discuss current issues involving basic structure–property relationships that need to be addressed for Si QDs and conclude with an outlook on the bright future of Si QD-molecule hybrid materials. 

Plasmonic nanoparticles with chiral resonances in the visible wavelengths complement optical dissymmetry in the ultraviolet and near-infrared wavelengths in natural products and metamaterials respectively. Here, we show that under oxidative conditions, hot holes photogenerated with circularly polarized light in gold nanoprisms can spatially direct the photodeposition of lead oxide (PbO2), resulting in chiral nanostructures tunable with the polarization and wavelength of light. We observe a g-factor of 3.6 × 10–3, which can be attributed to the enhanced optical dissymmetry with PbO2 deposition of the side of nanoprisms upon illumination with green 532 nm light. Our finite-difference time-domain calculations support the site-specific photodeposition of PbO2 onto nanoprisms. This work shows that plasmonic nanoparticles can have tunable chiral properties imbued as a function of the wavelength and polarization of light. 

Polyyne bridges have attracted extensive interest as molecular wires due to their shallow distance dependence during charge transfer. Here, we investigate whether triplet energy transfer from cadmium selenide (CdSe) quantum dots (QDs) to anthracene acceptors benefits from the high conductance associated with polyyne bridges, especially from the potential cumulene character in their excited states. Introducing π-electron rich oligoyne bridges between the surface-bound anthracene-based transmitter ligands, we explore the triplet energy transfer rate between the CdSe QDs and anthracene core. Our femtosecond transient absorption results reveal that a rate constant damping coefficient of β is 0.118 ± 0.011 Å−1, attributed to a through-bond coupling mechanism facilitated by conjugation among the anthracene core, the oligoyne bridges, and the COO⊖ anchoring group. In addition, oligoyne bridges lower the T1 energy level of the anthracene-based transmitters, enabling efficient triplet energy transfer from trapped excitons in CdSe QDs. Density-functional theory calculations suggest a slight cumulene character in these oligoyne bridges during triplet energy transfer, with diminished bond length alternation. This work demonstrates the potential of oligoyne bridges in mediating long-distance energy transfer. 

Photon upconversion is a process that combines low-energy photons to form useful high-energy photons. There are potential applications in photovoltaics, photocatalysis, biological imaging, etc. Semiconductor quantum dots (QDs) are promising for the absorption of these low-energy photons due to the high extinction coefficient of QDs, especially in the near infrared (NIR). This allows the intriguing use of diffuse light sources such as solar irradiation. In this review, we describe the development of this organic-QD upconversion platform based on triplet-triplet annihilation, focusing on the dark exciton in QDs with triplet character. Then we introduce the underlying energy transfer steps, starting from QD triplet photosensitization, triplet exciton transport, triplet-triplet annihilation, and ending with the upconverted emission. Design principles to improve the total upconversion efficiency are presented. We end with limitations in current reports and proposed future directions. This review provides a guide for designing efficient organic-QD upconversion platforms for future applications, including overcoming the Shockley-Queisser limit for more efficient solar energy conversion, NIR-based phototherapy, and diagnostics in vivo.