Due to complex structure and surface functionalities, photoluminescence mechanisms of Carbon Dots are unknown, and it is challenging to synthesize Carbon Dots to achieve the desired optical properties. Herein, Carbon Dots simultaneously exhibiting high-color-purity (FWHM~24 nm) long wavelength one-photon fluorescence emission at 620 nm and NIR induced two-photon fluorescence emission at 630 and 680 nm are prepared by edge amino protonation treatment. Systematic analysis reveals that the protonation of 2,3-diaminophenazine changes the molecular state of Carbon Dots, decreases the photon transition band gap, and triggers red fluorescence emission with the dramatically narrowed peak width. As the oxidation products of reactant o-phenylendiamine, the emergence of 2,3-diaminophenazine as a photoluminescence determiner suggests that fluorophore products of precursor conversion are viable determinants of the desired luminescence properties of Carbon Dots. This work shows a new way for predicting and controlling photoluminescence properties of Carbon Dots, and may guide the development of tunable Carbon Dots for a broad range of applications.

Background Osteoarthritis (OA) is a common joint disorder worldwide which causes great health and economic burden. However, there remains an unmet goal to develop an effective therapeutic method to prevent or delay OA. Chondrocytes, as the major cells involved in OA progression, may serve as a promising therapeutic target. Results A kind of carbon dots (CDs) with excellent biocompatibility was fabricated from folic acid via hydrothermal method and could effectively attenuate osteoarthritis. It was demonstrated that CDs treatment could rescue IL1β-induced proinflammatory responses, oxidative stress, cartilage degeneration and extracellular matrix degradation. Moreover, CDs reprogrammed lipopolysaccharide (LPS)-induced macrophage inflammation and polarization. Conditioned medium (CM) from CDs-treated macrophages could attenuate IL1β-induced chondrocyte injury. Also, CM from CDs-treated chondrocytes had immunoregulatory functions on macrophages. Mechanistically, CDs inhibited the activation of nuclear factor-κB (NF-κB) and mitogen-activated protein kinases (MAPK) signaling pathways in IL1β-stimulated chondrocytes. In vivo, anterior cruciate ligament transection (ACLT) mice model was adopted and it was indicated that intra-articular injection of CDs effectively delays OA pathogenesis. Conclusions Taken together, these findings indicated CDs could mediate OA via promoting cartilage repair and immunomodulating macrophages within local microenvironment, which may provide evidences for utilizing CDs as a novel nanomaterial for OA treatment.

Cover: Contact lenses were coated using a 15 kHz plasma polymerization equipment (background). On the upper left side one can see two lenses (one coated and one uncoated) with a sessile drop of water, illustrating the change in hydrophilicity induced by the plasma treatment. The bottom of the figure displays the accumulation of constituents on two lenses (one coated and one uncoated) after a wearing period, illustrating the improvement of wearing comfort of coated lenses.

Back Cover: Amorphous folic acid carbon nanoparticles (FA C‐NPs) are synthesized as FA solution at PH=7 (adjusted by NaHCO3) being processed by microplasma. The produced FA C‐NPs are of uniform size (around 47 nm diameter), exhibiting an excitation independent emission peak around 445 nm and an enhanced quantum yields (QYs) ranging from 7.1% to 13% depending on excitation wavelength. Cell experiment shows the produced FA C‐NPs can be absorbed by MCF‐7 cancer cells and mark the cells clearly with its fluorescence emission. Further details can be found in the article by Qingyang Wang et al. See article number http://doi.wiley.com/10.1002/ppap.201700088.

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