No abstract

Carbon dots (CDs) with high quantum yield (QY), low toxicity and good biocompatibility are the major quests of biomedical research. In this paper, we develop a green, simple hydrothermal approach to synthesize water-soluble, nontoxic, highly photoluminescent carbon nanodots (CNDs) from Metronidazole, which possess selective antibacterial activity against obligate anaerobes for the first time. Metronidazole was used as a sole precursor to prepare CNDs at 250 °C (CNDs-250) for 8 h. After the CNDs-250 with an average size of 2.9 nm, consisting of a highly carbon crystalline core and various surface groups were obtained, the formation and fluorescence mechanisms of CNDs were further explored by adjusting the reaction time and reaction temperatures, respectively. Biological experimental data proved that CNDs-250 can only inhibit the growth of obligate anaerobes, such as Porphyromonas gingivalis (P. gingivalis) directly, instead of further functionalization. Besides, CNDs-250 with a QY around 28.1% exhibit an obvious excitation-dependent emission, which will be conducive to multicolor bioimaging. And it may not only develop a new approach for researchers to prepare multifunctional CDs, but also provide a valuable strategy for the theranostics of some diseases as well as other fields.

Two-dimensional (2D) materials are of great significance to the materials community for their high surface area and controllable surface properties. However, controlled preparation of 2D structures with biological functions and biodegradable features is considerably hard. In this work, we demonstrate that, by careful selection of building block structures and assembly conditions, the above obstacle can be overcome partially by crystallization-driven self-assembly (CDSA) from PLLA-based diblock glycopolymers. 1D glyco-cylinders and 2D diamond-shaped glyco-platelets with solid or hollow core were achieved, where the latter structures have not been reported in literatures so far. The glyco-platelets further demonstrated exciting macrophage activation efficiency with clear size effect compared to their 1D analogues, which indicated their possible potential in immunological applications.

Oleic acid-capped NaYF4:Yb(3+)/Er(3+) upconversion nanocrystals (UCNCs) with different sizes and crystalline phases were prepared, and their temperature-dependent upconversion luminescence (UCL) and dynamics were studied. It is interesting to observe that the temperature-dependent behavior of UCL for the β-phase (25 nm, 45 nm and bulk) and α-phase (<10 nm) UCNCs is quite different. The UCL intensity of Er(3+) ions of the β-phase NaYF4 demonstrates a maximum around 100 K, while the intensity of the α-phase quenches monotonously with elevated temperature (10-400 K). The intensity ratio of (2)H11/2-(4)I15/2 to (4)S3/2-(4)I15/2, RHS, increases solely with temperature for β-phase NaYF4, while for the α-phase sample, it demonstrates a complex and indeterminate variation as a function of temperature. In the β-phase samples, rising processes were observed in the dynamics of Er(3+) ions, while in the α-phase sample, no rising process was observed and the decay processes of Er(3+) ions were bi-exponential. The rationale for these different temperature-dependent UCL properties was explained carefully.