Oxygen vacancy (VO) is a common native point defects that plays crucial roles in determining the physical and chemical properties of metal oxides such as ZnO. However, fundamental understanding of VO is still very sparse. Specifically, whether VO is mainly responsible for the n-type conductivity in ZnO has been still unsettled in the past fifty years. Here we report on a study of oxygen self-diffusion by conceiving and growing oxygen-isotope ZnO heterostructures with delicately-controlled chemical potential and Fermi level. The diffusion process is found to be predominantly mediated by VO. We further demonstrate that, in contrast to the general belief of their neutral attribute, the oxygen vacancies in ZnO are actually +2 charged and thus responsible for the unintentional n-type conductivity as well as the non-stoichiometry of ZnO. The methodology can be extended to study oxygen-related point defects and their energetics in other technologically important oxide materials.

Electrode material aging leads to a decrease in capacity and/or a rise in resistance of the whole cell and thus can dramatically affect the performance of lithium-ion batteries. Furthermore, the aging phenomena are extremely complicated to describe due to the coupling of various factors. In this review, we give an interpretation of capacity/power fading of electrode-oriented aging mechanisms under cycling and various storage conditions for metallic oxide-based cathodes and carbon-based anodes. For the cathode of lithium-ion batteries, the mechanical stress and strain resulting from the lithium ions insertion and extraction predominantly lead to structural disordering. Another important aging mechanism is the metal dissolution from the cathode and the subsequent deposition on the anode. For the anode, the main aging mechanisms are the loss of recyclable lithium ions caused by the formation and increasing growth of a solid electrolyte interphase (SEI) and the mechanical fatigue caused by the diffusion-induced stress on the carbon anode particles. Additionally, electrode aging largely depends on the electrochemical behaviour under cycling and storage conditions and results from both structural/morphological changes and side reactions aggravated by decomposition products and protic impurities in the electrolyte.

We studied characteristics of all, occasional, and frequent emergency department (ED) visits due to ambulatory care-sensitive conditions (ACSCs). We used a cross-sectional, split-sample design with multivariate logistic regressions using encounter-level, all-payer ED data from all Florida hospitals for the year of 2005. We evaluated associations of key patient characteristics, characteristics of ED utilization, and availability of primary care physicians in the area, with ED visits for ACSCs. We concluded that factors associated with ED use for ACSCs were similar for occasional and frequent ED users. Therefore, universal strategies for reduction of ED overutilization by increasing access to, timeliness, and quality of primary care for all patients likely to experience ACSCs should be used.

Polymer hydrogels and small-molecule-based (SMB) supramolecular hydrogels have been widely explored. But oligomeric hydrogels have remained a challenge because synthetic difficulties of the oligomers and control of their amphiphilicities. Reported herein is the rational design of two precursors Cys(SEt)-Lys-CBT (1) and (Cys-Lys-CBT)2 (2) (CBT=2-cyano-6-aminobenzothiazole) and the use of a biocompatible condensation to prepare oligomeric hydrogels. Glutathione reduction of 1 or 2 yields the same gelator Cys-Lys-CBT (3) which condenses with each other to yield amphiphilic cyclic oligomers. The oligomers instantly self-assemble into nanofibers and form oligomeric hydrogels with similar mechanic properties. Chemical analyses indicated that the major condensation product in both two hydrogels is a cyclic dimer. Considering its biocompatibility, optimal mechanical strength, and biodegradability, we believe that our oligomeric hydrogel might be useful for long-term drug delivery in the future.

Herein, we report a new "On-On" strategy based on the assembly and disassembly of fluorescein isothiocyanate nanoparticles (FITC-NPs) for sequential detections of glutathione (GSH) and caspase-3 (Casp3) with a multifunctional fluorescent probe 1. Theoretical investigations revealed the underlying mechanism that satisfactorily explained experimental results of such consecutive enhancements of fluorescence. Using this probe, we also successfully imaged the Casp3 activity in apoptotic cells.

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By employing fluorescence resonance energy transfer (FRET) quenching, we rationally designed two new FITC-quencher based nanoprobes for effectively sensing caspase 3 (Casp3) in vitro and in cells. Our nanoprobes hold promise for assessing the chemotherapeutic effect of cancer treatment.

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