An easy approach for large‐scale and low‐cost synthesis of photoluminescent (PL) graphene quantum dots (GQDs) based on the carbonization of commercially available polycyclic aromatic hydrocarbon (PAH) precursors with strong acid and followed by hydrothermal reduction with hydrazine hydrate is reported. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) characterizations indicate that the size and height of GQDs are in the range of 5–10 nm and 0.5–2.5 nm, respectively. PAH, which has more benzene rings, generally forms GQDs with relatively larger size. The GQDs show high water solubility, tunable photoluminescence, low cytotoxicity, and good optical stability, which makes them promising fluorescent probes for cellular imaging. In addition, the fluorescence of GQDs shows a sensitive and selective quenching effect to Fe 3+ with a detection limit of 5 × 10 −9 m . By combination with the Fe 2+ /Fe 3+ redox couple, the PL GQDs are able to detect oxidant, using H 2 O 2 as an example. This study opens up new opportunities to make full use of GQDs because of their facile availability, cost‐effective productivity, and robust functionality.
Here we present new results for the Born cross section and the effective form factor of the neutron at the center-of-mass energies ${\bf \sqrt{s}}$ between 2.0 and 3.08 GeV, using 18 data sets corresponding to an integrated luminosity of 647.9 pb${\bf ^{-1}}$ from e${\bf ^+}$e${\bf ^-}$ annihilation reactions collected at the BESIII experiment. The process $e^{+}e^{-}\to n\bar{n}$ is analyzed with three individual categories to improve the efficiency of $n\bar{n}$ reconstruction. The cross section of $e^{+}e^{-}\to n\bar{n}$ is measured at 18 c.m. energies where the best precision is 8.1\% at $\sqrt{s}=2.396$ GeV. The corresponding effective form factors are extracted under the assumption $|G_{E}|=|G_{M}|$. Our results improve the statistical precision on the neutron form factor by more than a factor of 60 over previous measurements from the FENICE and DM2 experiments and usher in a new era where neutron form factor data from annihilation in the time-like regime is on par with that from electron scattering experiments. In addition, an oscillatory behavior of the effective form factor observed for the proton is discussed for the neutron.
Abstract Inverse vulcanization of cheap elemental sulfur (S) to prepare polymers that simultaneously possess high sulfur content and good solubility is still in its infancy. In this paper, the authors report the synthesis of a novel S‐rosin (Ro) copolymer (S x ‐Ro) based on the inverse vulcanization of S with natural Ro. The sulfur content of S x ‐Ro can be regulated in a wide range, while S x ‐Ro still presents excellent solubility in low boiling point solvents at high sulfur content. Even if the sulfur content in S x ‐Ro is as high as 50%, its solubility in tetrahydrofuran (THF) can still reach 26 mg mL −1 . Moreover, the S x ‐Ro exhibits excellent ultraviolet (UV) absorption capability in the entire UV region (200–400 nm) and can be utilized as an effective anti‐UV agent to enhance the UV‐blocking performance of other polymers (e.g., polymethyl methacrylate [PMMA] and polystyrene [PS]) without compromise of transparency and thermal stability. Considering the fine solubility and superior UV‐blocking properties of S x ‐Ro, this work not only provides a versatile and effective anti‐UV material but also opens new opportunities for value‐added utilization of abundant S and Ro resources.
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