500-fold amplification of small molecule circularly polarised luminescence through circularly polarised FRET

Strongly dissymmetric circularly polarised (CP) luminescence from small organic molecules could transform a range of technologies, such as display devices. However, highly dissymmetric emission is usually not possible with small organic molecules, which typically give dissymmetric factors of photoluminescence (gPL) less than 10-2. Here we describe an almost 103-fold chiroptical amplification of a π-extended superhelicene when embedded in an achiral conjugated polymer matrix. This combination increases the |gPL| of the superhelicene from approximately 3 × 10-4 in solution to 0.15 in a blend film in the solid-state. We propose that the amplification arises not simply through a chiral environment effect, but instead due to electrodynamic coupling between the electric and magnetic transition dipoles of the polymer donor and superhelicene acceptor, and subsequent CP Förster resonance energy transfer. We show that this amplification effect holds across several achiral polymer hosts and thus represents a simple and versatile approach to enhance the g-factors of small organic molecules

Brain-muscle communication prevents muscle aging by maintaining daily physiology

Muñoz-Cánoves, Pur

Synthesis and Characterization of Hydroxyapatite Crystals

Pentacalcium hydroxide phosphate, or hydroxyapatite, is an important biological apatite found in tooth enamel and bone. Hydroxyapatite is used as a biomaterial to replace hard tissues, and as such, is useful synthetically. However, some synthetic hydroxyapatite crystals have too low of a fracture toughness to be viable for weight-bearing bone grafts. Acicular, or needle-like, hydroxyapatite crystals have been found to have higher fracture toughness than other crystal formations. For this reason, it is useful to focus on the synthesis of needle-like hydroxyapatite crystals. In this research, hydroxyapatite was synthesized with variable calcium to phosphorous ratios in order to investigate the effects of stoichiometry on crystal habit. It was found that the calcium to phosphorous ratio affected the crystal habit of synthetic hydroxyapatite crystals, which was then related to supersaturation values calculated with aqueous speciation software (OLI Systems). The crystals were identified to be hydroxyapatite through X-ray diffraction and characterized with optical microscopy. Future work will focus on synthesizing transition-metal complexed hydroxyapatite, and further characterization studies

Existence of a Size-Dependent Stokes Shift in CsPbBr₃ Perovskite Nanocrystals

The existence of a size-dependent Stokes shift is observed in CsPbBr₃ perovskite nanocrystals for the first time. Stokes shifts range from ∼100 to 30 meV for particles with edge lengths between ∼4 and 12 nm, respectively

Inquiry-Based Labs Using Paper Microfluidic Devices: The MICRO Project

The MICRO project has developed a series of active-learning labs that can be safely delivered to students either at home or in person using paper microfluidic technology. The skills covered in these labs are appropriate for sophomore-level analytical chemistry courses and general chemistry.<br /

Origin of the Size-Dependent Stokes Shift in CsPbBr₃ Perovskite Nanocrystals

The origin of the size-dependent Stokes shift in CsPbBr₃ nanocrystals (NCs) is explained for the first time. Stokes shifts range from 82 to 20 meV for NCs with effective edge lengths varying from ∼4 to 13 nm. We show that the Stokes shift is intrinsic to the NC electronic structure and does not arise from extrinsic effects such as residual ensemble size distributions, impurities, or solvent-related effects. The origin of the Stokes shift is elucidated via first-principles calculations. Corresponding theoretical modeling of the CsPbBr₃ NC density of states and band structure reveals the existence of an intrinsic confined hole state 260 to 70 meV above the valence band edge state for NCs with edge lengths from ∼2 to 5 nm. A size-dependent Stokes shift is therefore predicted and is in quantitative agreement with the experimental data. Comparison between bulk and NC calculations shows that the confined hole state is exclusive to NCs. At a broader level, the distinction between absorbing and emitting states in CsPbBr₃ is likely a general feature of other halide perovskite NCs and can be tuned via NC size to enhance applications involving these materials