Insertion of Carbon Monoxide into the Terminal Co–O Bond in a Methoxocobalt(III) Complex via a Tuneable Mechanism

The insertion of CO into the terminal Co–OMe bond in (Salophent‑Bu)­(MeOH)­Co­(III)­(OMe), which led to the formation of (Salophent‑Bu)­(MeOH)­Co­(III)­(COOMe), was investigated without and with the addition of free MeO–. The free MeO– concentration in the reaction system showed a nonlinear influence on the carbonylation rate, and the fastest rate was observed upon the addition of 1.8 equiv of MeO–, referred to as the methoxocobalt complex. Two classical migratory insertion-based pathways and a direct CO insertion-based pathway were envisioned to occur in the reaction system and be responsible for the production of (Salophent‑Bu)­(MeOH)­Co­(III)­(COOMe). Two of these three reaction pathways could be promoted by the addition of MeO–, thus yielding an overall mechanism that could be tuned based on the concentration of free MeO– in the reaction system. Furthermore, the anionic [(Salophent‑Bu)­Co­(III)­(OMe)2]−, a key intermediate in the direct CO insertion-based pathway, was independently synthesized and characterized. The reactivity of (Salophent‑Bu)­(MeOH)­Co­(III)­(COOMe) as a potential methoxy carbonyl radical-yielding reagent under light irradiation was also examined

Insertion of Carbon Monoxide into the Terminal Co–O Bond in a Methoxocobalt(III) Complex via a Tuneable Mechanism

The insertion of CO into the terminal Co–OMe bond in (Salophent‑Bu)­(MeOH)­Co­(III)­(OMe), which led to the formation of (Salophent‑Bu)­(MeOH)­Co­(III)­(COOMe), was investigated without and with the addition of free MeO–. The free MeO– concentration in the reaction system showed a nonlinear influence on the carbonylation rate, and the fastest rate was observed upon the addition of 1.8 equiv of MeO–, referred to as the methoxocobalt complex. Two classical migratory insertion-based pathways and a direct CO insertion-based pathway were envisioned to occur in the reaction system and be responsible for the production of (Salophent‑Bu)­(MeOH)­Co­(III)­(COOMe). Two of these three reaction pathways could be promoted by the addition of MeO–, thus yielding an overall mechanism that could be tuned based on the concentration of free MeO– in the reaction system. Furthermore, the anionic [(Salophent‑Bu)­Co­(III)­(OMe)2]−, a key intermediate in the direct CO insertion-based pathway, was independently synthesized and characterized. The reactivity of (Salophent‑Bu)­(MeOH)­Co­(III)­(COOMe) as a potential methoxy carbonyl radical-yielding reagent under light irradiation was also examined

Revealing Charge Transfer Dynamics in Methylammonium Lead Bromide Perovskites via Transient Photoluminescence Characterization

It is an important but difficult issue to identify charge and energy transfer processes in materials where multiple band gaps coexist. Conventional methods using transient absorption and optoelectrical characterization based on devices could not provide a clear picture of transfer dynamics. According to the bimolecular and monomolecular nature of each process, the carrier dynamics is supposed to solve this issue. In this work, we established a novel, convenient and universal strategy based on the calculation of carrier dynamics to distinguish energy/charge transfer and reveal their transfer dynamics in methylammonium lead bromide (MAPbBr3) films with mixing wide-band gap small grains and narrow-band gap large grains. A highly efficient charge transfer process is confirmed with a high negative nonradiative bimolecular recombination coefficient of −2.12 × 10–7 cm–3 s–1, indicating that free carriers within small grains are efficiently transferred from small grains to large grains. As a result, emission from large grains becomes dominant when increasing the photoexcitation intensity. In addition, current-density-dependent electroluminescence results in emission only from large grains, further verifying the charge transfer process. Moreover, it is interesting to find that when decreasing the size of small grains, the charge transfer process is facilitated, leading to an increased nonradiative bimolecular recombination coefficient from −2.12 × 10–7 to −4.01 × 10–7 cm–3 s–1 in large grains. Our work provides a convenient strategy to identify and quantify energy and charge transfer in metal halide perovskites, which can be used to enrich our understanding of perovskite photophysics

Biotin–Avidin Based Universal Cell–Matrix Interaction for Promoting Three-Dimensional Cell Adhesion

To promote cell adhesion in three-dimensional (3D) extracellular matrix (ECM) is crucial for avoiding cell anoikis, which is one of the most important issues for fundamental cell biology. Herein, a biotin–avidin based universal cell–matrix interaction for different types of cells is developed in order to achieve the promoted adhesion in 3D ECM. For the purpose, biotinylated nanofibrous hydrogels are constructed by coassembling 1,4-benzyldicarboxamide (C₂) based non-biotinylated and biotinylated supramolecular gelators. The used cells are modified by avidin (AV-cells) through biotinylating cells and then interacting with avidin. After in situ encapsulating AV-cells in the hydrogels, the adhered amount can be increased by tens of percent even with adding several percentages of the biotinylated C₂ gelators in the coassembly due to the specific biotin–avidin interaction. Reverse transcription polymerase chain reaction (RT-PCR) confirms that AV-cells can proliferate without varying gene expression and denaturation. Compared with the interaction between RGD and cells, this avidin–biotin interaction should be much more universal and it is feasible to be employed to promote cell adhesion for most types of cells in 3D matrix

Investigation on Upconversion Luminescence and Optical Temperature Sensing Behavior for Ba₂Gd₂Si₄O₁₃:Yb³⁺-Er³⁺/Ho³⁺/Tm³⁺ Phosphors

To explore new phosphors for temperature sensing with high detection sensitivity, the Yb³⁺-Er³⁺/Ho³⁺/Tm³⁺ doped Ba₂Gd₂Si₄O₁₃ (BGS) was designed. Different strategies were introduced based on the upconversion (UC) luminescence. For BGS:0.2Yb³⁺,0.02Er³⁺, the fluorescence intensity ratio (FIR) of two green emissions of Er³⁺ shows a gradual enhancement with increasing temperature due to the thermally coupled levels. The piecewise expression of sensitivity was proposed in the temperature range of 293–553 K based on the Boltzmann distribution. For BGS:0.2Yb³⁺,0.01Ho³⁺, the FIR of the red to green emissions of Ho³⁺ changes with temperature, showing a linear relationship from 293 to 453 K. The absolute sensitivity was gained to be 0.0452 K^–1. For BGS:0.2Yb³⁺,0.02Tm³⁺, the high absolute and relative sensitivities were both achieved by employing the thermally coupled (³F₂,³F₃) and ³H₄ levels of Tm³⁺. The above study could have special reference to the development of new luminescent materials with high sensitivity

Gross motor movement characteristics of left-behind children aged 3 to 6 years.

Gross motor movement characteristics of left-behind children aged 3 to 6 years.</p

Analysis of the correlation between gross motor movement and screen time among left-behind children aged 3 to 6 years.

Analysis of the correlation between gross motor movement and screen time among left-behind children aged 3 to 6 years.</p

Biodegradable Polyurethane Pressure-Sensitive Adhesives Using Biobased Polyols with Distinct Intrinsic Properties

Polyurethane pressure-sensitive adhesives (PSAs) were synthesized by reacting isophorone diisocyanate (IPDI) with mixtures of different biobased polyols, where polylactide diol (PLA 1000) acted as a hard polyol and cashew nut shell liquid (CNSL)-derived diol and castor oil (CO) acted as soft segments. Besides, CO played another role in the synthesis of the polyurethanes as a cross-linker to enhance the cohesion of the prepared PSAs. The effects of different ratios of polyols and NCO/OH on microphase separation, thermal, rheological, and adhesive properties of the polyurethane were comprehensively studied. A balanced PSA with excellent tack and sufficient peel strength was prepared by adjusting the ratio of different polyols at PLA1000/CNSL diol/CO = 4:4:2 and a suitable NCO/OH value of 0.70. Eventually, the biodegradability of PSA 442-0.70 was investigated, and the biodegradation rate reached 64.47% within 8 weeks, making it a promising environmentally friendly adhesive tape for packaging applications

Multiple regression analysis of screen time and gross motor movement among left-behind children aged 3 to 6 years.

Multiple regression analysis of screen time and gross motor movement among left-behind children aged 3 to 6 years.</p

Average daily video screen time for 1 week for left-behind children aged 3 to 6 years.

Average daily video screen time for 1 week for left-behind children aged 3 to 6 years.</p