In this study, well-crystallized black phosphorus nanosheets are obtained via shock-induced phase transformation. Red phosphorus powder is filled in a sample container and subjected to high shock pressure and temperature using a shock-driven flyer. Moreover, flyer impact velocity is adjusted to investigate the influence of shock pressure and temperature on the phase transformation of red phosphorus. The recovered black samples are characterized via multiple techniques, such as X-ray diffraction, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy and atomic force microscopy. The characteristic results demonstrate the presence of black phosphorus nanosheets with a lateral size of 0.5–20 μm and a thickness of 1.5–50 nm. Moreover, the results also confirm the critical influence of the shock pressure on the micromorphology of the recovered samples. The increase of shock pressure thickens the formed black phosphorus nanosheets and decreases their lateral size. In addition, the formation mechanism of black phosphorus nanosheets by shock-induced phase transformation of red phosphorus is carefully analyzed. This research provides a new method to prepare gram-scale black phosphorous nanosheets through shock treatment for the first time.
Multicolor afterglow carbon dots (CDs) have significant application potential in information encryption, anti-counterfeiting, and optoelectronics. However, achieving afterglow CDs with a high quantum yield (QY) across the visible spectrum using a one-step, solvent-free route on a large scale remains a formidable challenge. In this work, a series of CDs-based composites with tunable full-color afterglow (454–602 nm), high QY (30.4–20.6 %), long lifetime (169–416 ms) and high production yield (64–78 %) were successfully synthesized on a gram scale by thermally heating a solid mixture of boric acid (BA), salicylic acid, acrylamide, and rhodamine B (RhB). Comprehensive characterizations revealed that the blue-to-green afterglow originates from room-temperature phosphorescence (RTP) activated by the B 2 O 3 matrix and that emission tunability is attributed to the quantum size effect. Furthermore, the yellow-to-red tunable afterglow, belonging to delayed fluorescence (DF), results from in situ Förster resonance energy transfer (FRET) between the phosphorescent CDs and the increasing content of rhodamine B moieties anchored on the CD surfaces. This work demonstrates an efficient and environmentally friendly synthesis strategy for producing full-color afterglow CDs on the gram scale and highlights their promising applications in anti-counterfeiting, information encryption, and organic optoelectronic devices.
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