Fluorescence upconversion and transient absorption techniques are used to explain the source of the intense red/near-infrared emission of crystalline 4-dimethylamino-2'-hydroxychalcone. We found that the initially excited enol form undergoes tautomerization in 3 ps to form the keto tautomer. The latter is stable in the ground state as a consequence of J-type aggregation in the crystal packing and is manifested in an absorption peak at 550 nm that spectrally overlaps with the short-lived enol emission, leading to self-reabsorption and adding a factor to the complete depletion of the enol emission. Relaxation of the keto tautomer takes place in the form of intense fluorescence (600-750 nm) with 1.7 ns lifetime. The different spectroscopy in solution is due to vibrational cooling (300 fs), followed by solvation dynamics (5 ps in methanol) and twisting of the hydroxyphenyl ring (16 ps), before relaxation of the enol tautomer in the form of weak green fluorescence with 350 ps lifetime.

No abstract

Organic polymer electrolytes attracted a great deal of attention and research in the field of energy conversion and energy storage due to their benefits such as appreciable ionic conductivity and transference number, improved mechanical strength, thermal stability, and better interaction with the electrodes. In this study, a polymer electrolyte was synthesized from poly­(vinyl alcohol) (PVA) by electrospinning technique followed by soaking in a series of deep eutectic solvents (DESs) to enhance the electrical conductivity of the product. The result was a very thin, nonwoven membrane. The produced membranes showed appreciable improvement in electrical conductivity from 2.78 × 10–6 to 2.27 × 10–2 S/cm after soaking in DES2. The observed improvement in electrical properties opens the possibility for the PVA membranes to find their applications in batteries, storage cells, flexible thermoelectric devices, sensors, and solar cells.

Copper(ii) complexes exhibiting temperature-dependent mesomorphisms.

No abstract