Aqueous Solution Enhanced Room Temperature Phosphorescence through Coordination-Induced Structural Rigidity.

Achieving aqueous solution enhanced room temperature phosphorescence (RTP) is critical for the applications of RTP materials in solution phase, but which faces a great challenge. Herein, for the first time, a strategy of coordination-induced structural rigidity is proposed to achieve enhanced quantum efficiency of aluminum/scandium-doped phosphorescent microcubes (Al/Sc-PMCs) in aqueous solution. The Al/Sc-PMCs in a dry state exhibit a nearly invisible blue RTP. However, they emit a strong RTP emission in aqueous solution with a RTP intensity increase of up to 22.16-times, which is opposite to common solution-quenched RTP. The RTP enhancement mechanism is attributed to the abundant metal sites (Al3+ and Sc3+ ions) on the Al/Sc-PMCs surface that can tightly combine with water molecules through the strong coordination. Subsequently, these coordinated water molecules as the bridging agent can bind with surface groups by hydrogen bonding interaction, thereby rigidifying chemical groups and inhibiting their motions, resulting in the transition from the nonradiative decay to the radiative decay, which greatly enhances the RTP efficiency of the Al/Sc-PMCs. This work not only develops a coordination rigidity strategy to enhance RTP intensity in aqueous solution, but also constructs a phosphorescent probe to achieve reliable and accurate determination of analyte in complex biological matrices.

Inorganic salt recrystallization strategy for achieving ultralong room temperature phosphorescence through structural confinement and aluminized reconstruction.

Achieving highly efficient and stable room temperature phosphorescence (RTP) with ultralong lifetime is critical for the multi-purpose applications of phosphorescent materials. In this work, we propose an inorganic salt heating recrystallization strategy to simultaneously improve the lifetime, quantum efficiency, and stability of phosphorescent scandium/leucine microspheres (Sc/Leu-MSs). Inorganic salt-treated Sc/Leu-MSs are obtained by simply heating and drying inorganic salt solution containing Sc/Leu-MSs, which can achieve a maximum lifetime increase of 4.42-times from 208.37 ms (Sc/Leu-MSs) to 920.08 ms (Al2(SO4)3-treated Sc/Leu-MSs), accompanied by a RTP intensity increase up to 24.08-times. The enhancement mechanism of RTP efficiency is attributed to the stabilization of triplet excitons caused by inorganic salt coating that suppresses molecular motion and isolates oxygen on the one hand, and the efficient intersystem crossing promoted by aluminized reconstruction-caused duplex heavy atom effects on the other hand. This study provides new design principle and a facile strategy to construct RTP materials with ultralong lifetime, high phosphorescent quantum efficiency, and high stability for promising applications such as anti-counterfeiting and light emitting diodes.

Environmentally relevant concentrations of F-53B induce eye development disorders-mediated locomotor behavior in zebrafish larvae.

The perfluorooctane sulfonate alternative, F-53B, induces multiple physiological defects but whether it can disrupt eye development is unknown. We exposed zebrafish to F-53B at four different concentrations (0, 0.15, 1.5, and 15 µg/L) for 120 h post-fertilization (hpf). Locomotor behavior, neurotransmitters content, histopathological alterations, morphological changes, cell apoptosis, and retinoic acid signaling were studied. Histology and morphological analyses showed that F-53B induced pathological changes in lens and retina of larvae and eye size were significantly reduced as compared to control. Acridine orange (AO) staining revealed a dose-dependent increase in early apoptosis, accompanied by upregulation of p53, casp-9 and casp-3 genes. Genes related to retinoic acid signaling (aldh1a2), lens developmental (cryaa, crybb, crygn, and mipa) and retinal development (pax6, rx1, gant1, rho, opn1sw and opn1lw) were significantly downregulated. In addition, behavioral responses (swimming speed) were significantly increased, while no significant changes in the neurotransmitters (dopamine and acetylcholine) level were observed. Therefore, in this study we observed that exposure to F-53B inflicted histological and morphological changes in zebrafish larvae eye, induced visual motor dysfunctions, perturbed retinoid signaling and retinal development and ultimately triggering apoptosis.

Increased production of succinic acid in Escherichia coli by overexpression of malate dehydrogenase.

Escherichia coli NZN111 is a double mutant with inactivated lactate dehydrogenase and pyruvate formate-lyase. It cannot utilize glucose anaerobically because of its unusually high intracellular NADH/NAD(+) ratio. We have now constructed a recombinant strain, E. coli NZN111/pTrc99a-mdh, which, during anaerobic fermentation, produced 4.3 g succinic acid l(-1) from 13.5 g glucose l(-1). The NADH/NAD(+) ratio decreased from 0.64 to 0.26. Furthermore, dual-phase fermentation (aerobic growth followed by anaerobic phase) resulted in enhanced succinic acid production and reduced byproduct formation. The yield of succinic acid from glucose during the anaerobic phase was 0.72 g g(-1), and the productivity was 1.01 g l(-1) h(-1).