Fluorescent Au 25 nanoclusters recently have drawn considerable research interest due to their unique properties and potential applications. Despite significant advances in their synthesis methods and application development, the origin of the fluorescence and underlying mechanism still remain unclear. In this work we investigate the fluorescence dynamics in BSA-protected Au 25 nanoclusters by time-resolved photoluminescence and transient absorption techniques covering picosecond to microsecond time scales. We demonstrate here that the red fluorescence consists of both prompt fluorescence and thermally activated delayed fluorescence, and the latter is more dominant. A small energy gap of 30 meV between the triplet and the singlet states was determined from our temperature-dependent time-resolved fluorescence measurement. Moreover, we elucidate that the absorption band at 2.34 eV corresponds to the HOMO− LUMO transition in this system due to the interaction between Au 25 NCs and BSA. We also show that an effective relaxation pathway exists from the higher excited state to the LUMO.

The bone regeneration efficiency of bone marrow mesenchymal stem cells (BMSCs) and dental pulp mesenchymal stem cells (DPSCs) combined with xenografts in the craniofacial region remains unclear. Accordingly, this study commenced by comparing the cell morphology, cell proliferation, trilineage differentiation, mineral synthesis, and osteogenic gene expression of BMSCs and DPSCs in vitro. Four experimental groups (empty control, Bio-Oss only, Bio-Oss+BMSCs, and Bio-Oss+DPSCs) were then designed and implanted in rabbit calvarial defects. The BMSCs and DPSCs showed a similar morphology, proliferative ability, surface marker profile, and trilineage-differentiation potential in vitro. However, the BMSCs exhibited a higher mineral deposition and expression levels of osteogenic marker genes, including alkaline phosphatase (ALP), runt related transcription factor 2 (RUNX2), and osteocalcin (OCN). In the in vivo studies, the bone volume density in both MSC groups was significantly greater than that in the empty control or Bio-Oss only group. Moreover, the new bone formation and Collagen I / osteoprotegerin protein expressions of the scaffold+MSC groups were higher than those of the Bio-Oss only group. Finally, the Bio-Oss+BMSC and Bio-Oss+DPSC groups had a similar bone mineral density, new bone formation, and osteogenesis-related protein expression. Overall, the DPSCs seeded on Bio-Oss matched the bone regeneration efficacy of BMSCs in vivo and hence appear to be a promising strategy for craniofacial defect repair in future clinical applications.

Combining metal and semiconducting nanomaterials into one single nanocrystal, metal−semiconducting nanocomposites have been attracting considerable research interest due to the integrated and unprecedented properties that arise at the heterostructure interface. Herein, the dynamics of photoexcited charge carriers in CdSe/Au and CdSe/Pt nanorods is probed via ultrafast spectroscopy. Upon 400 nm photoexcitation, the results show both hot and cold electrons transfer from CdSe to the metal counterpart. The injection of photoinduced electrons into the Au tip is faster than that into the Pt nanoparticles, but only Pt can completely extract the excited electrons from the CdSe nanorod. Combined with temperature-dependent photoluminescence spectra, the electron migration can be ascribed to the band alignments and the charge storage/discharge behavior of the metallic tips. These findings not only support the distinct difference in photocatalytic efficiency between CdSe/Au and CdSe/Pt nanorods but also shed light on better designing novel nanocomposites in photoenergy-converting nanomaterials. SECTION: Energy Conversion and Storage; Energy and Charge Transport

Imipenem/cilastatin + relebactam (250 or 125 mg) was as effective as imipenem/cilastatin alone for treatment of cUTI. Both relebactam-containing regimens were well tolerated. (NCT01505634).

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