Über den Drehwert Einblicke in die Solvathülle gewinnen

The optical rotation of a chiral molecule is more than just a constant. Just like any other physical property, it depends on the exact environmental conditions under which it is measured. Introducing the example of propylene oxide, we show how this supposedly simple molecular property is significantly affected by the behavior and arrangement of the surrounding solvent environment.     

Silver Films with Hierarchical Chirality

Physical fabrication of chiral metallic films usually results in singular or large‐sized chirality, restricting the optical asymmetric responses to long electromagnetic wavelengths. The chiral molecule‐induced formation of silver films prepared chemically on a copper substrate through a redox reaction is presented. Three levels of chirality were identified: primary twisted nanoflakes with atomic crystal lattices, secondary helical stacking of these nanoflakes to form nanoplates, and tertiary micrometer‐sized circinates consisting of chiral arranged nanoplates. The chiral Ag films exhibited multiple plasmonic absorption‐ and scattering‐based optical activities at UV/Vis wavelengths based on their hierarchical chirality. The Ag films showed chiral selectivity for amino acids in catalytic electrochemical reactions, which originated from their primary atomic crystal lattices.     

Light‐Driven Self‐Healing of Nanoparticle‐Based Metamolecules

Metamolecules and crystals consisting of nanoscale building blocks offer rich models to study colloidal chemistry, materials science, and photonics. Herein we demonstrate the self‐assembly of colloidal Ag nanoparticles into quasi‐one‐dimensional metamolecules with an intriguing self‐healing ability in a linearly polarized optical field. By investigating the spatial stability of the metamolecules, we found that the origin of self‐healing is the inhomogeneous interparticle electrodynamic interactions enhanced by the formation of unusual nanoparticle dimers, which minimize the free energy of the whole structure. The equilibrium configuration and self‐healing behavior can be further tuned by modifying the electrical double layers surrounding the nanoparticles. Our results reveal a unique route to build self‐healing colloidal structures assembled from simple metal nanoparticles. This approach could potentially lead to reconfigurable plasmonic devices for photonic and sensing applications.     

Optical Multiplexed Bioassays for Improved Biomedical Diagnostics

Conventional analytical methods based on the detection of a single disease marker may not be sufficiently accurate because the progression of disease generally involves multiple chemicals and biomolecules. The drive for simultaneous analysis of multiple targets, which plays a key role in both basic biomedical research and clinical applications, demands the development of multiplexed bioassays with high‐throughput. In this minireview, we summarize the recent progress in optical multiplexed analytical techniques for improving biomedical diagnostics, in which fluorescence and surface enhanced Raman scattering (SERS) with distinctive optical features are chosen as the main readout signals. Focusing on multiplexed strategies in the biomedical field, a selection of recent contributions from biosensing of multiple analytes and multicolor cellular tracking to in vivo multiplexed bioimaging are highlighted. Finally, we frame the future challenges and opportunities for multiplexed bioanalysis.     

In Operando Visualization of the Electrochemical Formation of Liquid Polybromide Microdroplets

Zinc–bromine flow batteries are promising for stationary energy storage, and bromine‐complexing agents have been used to form phase‐separated liquid polybromide products. However, an understanding of the dynamics of polybromide nucleation is limited due to the beam sensitivity and complexity of polybromides. Here we report an in operando platform composed of dark‐field light microscopy and a transparent electrochemical cell to reveal the dynamics of polybromide formation in their native environment. Using our platform, we confirm and reveal the liquid nature, chemical composition, pinning effect (strong interaction with Pt), residual effect (residual charge products on the surface), self‐discharging, and over‐oxidation of the polybromide products. The results provide insights into the role of complexing agents and guide the future design of zinc–bromine flow batteries. Furthermore, our in operando platform can potentially be used to study sensitive species and phases in other electrochemical reactions.     

Optische Anisotropie in orientierten Polymeren

Zusammenfassung Der zur Bestimmung der Hauptdoppelbrechungen eines optisch anisotropen Mediums notwendige Zusammenhang zwischen Doppelbrechung und der Wellennormalenrichtung des eingestrahlten Lichtes wurde in anschaulich geometrischer Weise aus einer Schnittellipse des Indexellipsoids abgeleitet und die Beziehungen zur Ermittlung der Hauptbrechungsindexe bei Kenntnis eines Mittelwertes angegeben. Für die Messung der Doppelbrechung benutzten wir das Verfahren nach H. de Sénarmont, bei welchem die durch das doppelbrechende Medium hervorgerufene Elliptizität des Lichtes durch Zuschalten einer /4 Platte kompensiert wird.Im Rahmen einer Verfahrensanalyse wurde die Herstellung von Flachfolien aus Polypropylen im Zweistufenprozeß untersucht. Dem Einfluß des Längsstreckverhältnisses auf die Eigenschaften biaxial verstreckter Folien wurde dabei besondere Aufmerksamkeit geschenkt. Während die mechanischen Eigenschaften und der Schrumpf nur einen begrenzten Einblick in die Vorgänge beim Verstrecken erlaubten, konnte durch die Bestimmung der optischen Anisotropie ein Bild gewonnen werden, das sehr gut mit einfachen Vorstellungen über die Umorientierun übereinstimmt.Die Erhöhung des Längsstreckenverhältnisses führt bei sonst konstanten Verfahrensparametern zu einer Erhöhung des Flächenstreckenverhältnisses. Dadurch wird keine oder eine sehr geringe Verbesserung der planaren Orientierung erreicht. Die Orientierung in Maschinenrichtung hingegen nimmt zu, in Querrichtung ab. Diese Veränderungen sind aber so gering, daß sie den Einfluß der dominierenden zweiten Streckstufe in Querrichtung kaum beeinträchtigen.Die hier benutzte Methode zur Bestimmung der optischen Anisotropie erlaubt, bei gleichzeitigem Einsatz einer röntgenografischen Methode die Orientierung in biaxial verstreckten Polypropylenfolien vollständig, d. h. in den kristallinen wie auch den amorphen Bereichen zu bestimmen.Herrn Prof. Dr. Weissermel zum 60. Geburtstag gewidmet.     

Confining Excitation Energy in Er3+‐Sensitized Upconversion Nanocrystals through Tm3+‐Mediated Transient Energy Trapping

A new class of lanthanide‐doped upconversion nanoparticles are presented that are without Yb³⁺ or Nd³⁺ sensitizers in the host lattice. In erbium‐enriched core–shell NaErF₄:Tm (0.5 mol %)@NaYF₄ nanoparticles, a high degree of energy migration between Er³⁺ ions occurs to suppress the effect of concentration quenching upon surface coating. Unlike the conventional Yb³⁺‐Er³⁺ system, the Er³⁺ ion can serve as both the sensitizer and activator to enable an effective upconversion process. Importantly, an appropriate doping of Tm³⁺ has been demonstrated to further enhance upconversion luminescence through energy trapping. This endows the resultant nanoparticles with bright red (about 700‐fold enhancement) and near‐infrared luminescence that is achievable under multiple excitation wavelengths. This is a fundamental new pathway to mitigate the concentration quenching effect, thus offering a convenient method for red‐emitting upconversion nanoprobes for biological applications.     

Fluorescence Self-Reporting Precipitation Polymerization Based on Aggregation-Induced Emission for Constructing Optical Nanoagents

Precipitation polymerization is becoming increasingly popular in energy, environment and biomedicine. However, its proficient utilization highly relies on the mechanistic understanding of polymerization process. Now, a fluorescence self-reporting method based on aggregation-induced emission (AIE) is used to shed light on the mechanism of precipitation polymerization. The nucleation and growth processes during the copolymerization of a vinyl-modified AIEgen, styrene, and maleic anhydride can be sensitively monitored in real time. The phase-separation and dynamic hardening processes can be clearly discerned by tracking fluorescence changes. Moreover, polymeric fluorescent particles (PFPs) with uniform and tunable sizes can be obtained in a self-stabilized manner. These PFPs exhibit biolabeling and photosensitizing abilities and are used as superior optical nanoagents for photo-controllable immunotherapy, indicative of their great potential in biomedical applications.