skip to main content


Title: Circular Polarized Light Emission in Chiral Inorganic Nanomaterials
: Chiral inorganic nanostructures strongly interact with photons changing their polarization state. The resulting circularly polarized light emission (CPLE) has cross-disciplinary importance for a variety of chemical/biological processes and is essential for development of chiral photonics. However, the polarization effects are often complex and could be misinterpreted. CPLE in nanostructured media has multiple origins and several optical effects are typically convoluted into a single output. Analysing CPLE data obtained for nanoclusters, NPs, nanoassemblies, and nanocomposites from metals, chalcogenides, perovskite, and other nanostructures, we show that there are several distinct groups of nanomaterials for which CPLE is dominated either by circularly polarized luminescence (CPL) or circularly polarized scattering (CPS); there are also many nanomaterials for which they are comparable. We also show that (1) CPL and CPS contributions involve light-matter interactions at different structural levels; (2) contribution from CPS is especially strong for nanostructured microparticles, nanoassemblies and composites; and (3) engineering of materials with strongly polarized light emission requires synergistic implementation of CPL and CPS effects. These findings are expected to guide development of CPLE materials in a variety of technological fields, including 3D displays, information storage, biosensors, optical spintronics, and biological probes.  more » « less
Award ID(s):
1748529
NSF-PAR ID:
10397773
Author(s) / Creator(s):
;
Date Published:
Journal Name:
Advanced Materials
ISSN:
0935-9648
Page Range / eLocation ID:
2108431
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Abstract

    The transfer of structural mirror asymmetry from chiral molecules to the inorganic phase at solid‐liquid interfaces enabled rapid development of biomimetic chiral nanoparticles. They can be synthesized and assembled following a variety of chemical methods resulting in the broad family of chiral inorganic nanostructures (CNs). Their chemistry attracted large attention due to marked enhancement of circular dichroism and polarization rotation compared to organic molecules and particles, which opened application prospects in sensing, imaging, catalysis, nonlinear optics, electronics, and medicine. New physical, chemical and biological effects involving CNs such as giant optical activity, mechanical force‐assisted modulation of optical activity, photon‐to‐particle chirality transfer and suppression of amyloid toxicity have been observed. Marked strides toward enhancement of optical asymmetry (g‐factor), engineering dynamic chirality in nanostructures, and spectral range of optical activity of chiral inorganic nanostructures from the ultraviolet to terahertz regions have also been made. Here, we summarize these and other current trends in the research of chiral inorganic nanomaterials and offer our perspective how the fundamental and translational research in this area is likely to develop in the next two decades.

     
    more » « less
  2. Abstract

    Optical chirality is an effective means in screening molecules and their enantiomers in bioengineering, and recently has garnered attention as an implementation of qubits in quantum information processing. The conventional detection of circularly polarized light (CPL) is based on phase retardation and polarization separation using multiple optical components. An intrinsic solid‐state chirality detection device would be favorable for easier integration and implementation. Optical spin injection to the spin‐momentum‐locked topological surface states of topological insulators (TIs) by circularly polarized light leads to a directional DC photocurrent and hence possible circular polarization detection. However, this DC photocurrent is also accompanied by other photo‐responses. Here, a photodetection strategy using a TI transistor which senses CPL without the use of any additional components is demonstrated, it achieves a uniform response over the entire device with a sensitivity ≈5.6%. The Stokes parameters can also be extracted by arithmetic operation of photocurrents obtained with different bias and gate for a complete characterization of a polarized light beam. Therefore, this method enables chirality detection and Stokes parameter analysis using a single device. The proposed miniaturized intrinsic chirality detectors facilitate polarimetry sensing in applications from circular dichroism spectroscopy to biomedical diagnosis.

     
    more » « less
  3. Post-synthetic phase transfer ligand exchange has been established as a simple, reliable, and versatile method for the synthesis of chiral, optically active colloidal nanocrystals displaying circular dichroism (CD) and circularly polarized luminescence (CPL). Herein we present a water-free and purification-free cyclohexane → methanol ligand exchange system that led to the synthesis of stable, non-aggregating chiral and fluorescent cadmium sulfide quantum dots (CdS QDs). Absorption and emission studies revealed that the carboxylate capping ligands can tune the band gap by up to 65 meV as well as control the band gap and deep trap emission pathways. The CD data revealed that the addition of a 2nd stereogenic center did not automatically lead to an increase of the CD anisotropy of QDs, but rather match/mismatch cooperativity effects must be considered in the transfer of the chirality from the capping ligands to the achiral nanocrystals. Variation in position of the functional groups as well as the chemical identity of the functional groups impacted both the shape and anisotropy of the induced CD spectra and revealed the importance of the functional groups’ coordination and polarity on the binding geometry and induced chiroptical properties. Finally, we describe the first example where CD spectra of QDs capped with the same ligand and dissolved in the same solvent displayed very different spectral profiles. This work provides deeper insight into induced CD of QDs and paves the path to rational design of chiral nanomaterials. 
    more » « less
  4. Abstract

    Monolayer ternary tellurides based on alloying different transition metal dichalcogenides (TMDs) can result in new two‐dimensional (2D) materials ranging from semiconductors to metals and superconductors with tunable optical and electrical properties. Semiconducting WTe2xS2(1‐x)monolayer possesses two inequivalent valleys in the Brillouin zone, each valley coupling selectively with circularly polarized light (CPL). The degree of valley polarization (DVP) under the excitation of CPL represents the purity of valley polarized photoluminescence (PL), a critical parameter for opto‐valleytronic applications. Here, new strategies to efficiently tailor the valley‐polarized PL from semiconducting monolayer WTe2xS2(1‐x)at room temperature (RT) through alloying and back‐gating are presented. The DVP at RT is found to increase drastically from < 5% in WS2to 40% in WTe0.12S1.88by Te‐alloying to enhance the spin‐orbit coupling. Further enhancement and control of the DVP from 40% up to 75% is demonstrated by electrostatically doping the monolayer WTe0.12S1.88via metallic 1T′‐WTe2electrodes, where the use of 1T′‐WTe2substantially lowers the Schottky barrier height (SBH) and weakens the Fermi‐level pinning of the electrical contacts. The demonstration of drastically enhanced DVP and electrical tunability in the valley‐polarized emission from 1T′‐WTe2/WTe0.12S1.88heterostructures paves new pathways towards harnessing valley excitons in ultrathin valleytronic devices for RT applications.

     
    more » « less
  5. The interplay between dimensionality and anisotropicity leads to intriguing optoelectronic properties and exciton dynamics in low dimensional semiconductors. In this study we use nanostructured phosphorene as a prototypical example to unfold such complex physics and develop a general first-principles framework to study exciton dynamics in low dimensional systems. Specifically we derived the radiative lifetime and light emission intensity from 2D to 0D systems based on many body perturbation theory, and investigated the dimensionality and anisotropicity effects on radiative recombination lifetime both at 0 K and finite temperature, as well as polarization and angle dependence of emitted light. We show that the radiative lifetime at 0 K increases by an order of 103 with the lowering of one dimension (i.e. from 2D to 1D nanoribbons or from 1D to 0D quantum dots). We also show that obtaining the radiative lifetime at finite temperature requires accurate exciton dispersion beyond the effective mass approximation. Finally, we demonstrate that monolayer phosphorene and its nanostructures always emit linearly polarized light consistent with experimental observations, different from in-plane isotropic 2D materials like MoS2 and h-BN that can emit light with arbitrary polarization, which may have important implications for quantum information applications. 
    more » « less