The
novel optical response properties of MXene (Ti3C2Tx) have been applied in many cutting-edge areas, such as
solar utilization, laser therapy, and sensing. Understanding the interaction
between photons and MXene is critical to all these applications. However,
the ultrafast carrier pathway of this material under broad-wavelength-range
light excitation remains unknown. In this work, we conducted a comprehensive
ultrafast spectroscopy study of MXene under light excitation at various
wavelengths. With the combination of ultrabroadband transient spectra
(450–1100 nm) and dynamics, we provided schemes for the MXene–light
interaction. The transient spectra showed that light excitation in
the ultraviolet to near-infrared ranges could induce two transient
absorption regions in the visible and near-infrared ranges. An early
stage fast relaxation transient spectrum at 100–400 fs is attributed
to an electron–electron interaction process. The dynamics in
the early stage could be affected by the modulation of the excitation
wavelength, the fluence, and the probe wavelength. In addition, the
thermal diffusion dynamic process is sensitive to the surroundings
and is nearly independent of the excitation wavelength and the fluence,
whereas temporal signatures depend linearly on the excitation fluence
and the absorption efficiency. Our results could improve the fundamental
understanding of MXene–sunlight interaction and applications.
Carbon dots (CDs) with long-lived room-temperature phosphorescence (RTP) or long afterglow properties draw much attention. However, most room-temperature phosphorescent materials are metal containing, and the exploitation of long-lived color-tunable RTP materials faces great challenges. Here, we report metal-free borondoped CDs (B-CDs) for room-temperature phosphorescence with tunable color and an ultralong lifetime. B-CDs were obtained by simply calcining a mixture of boric acid and 1,3,5-benzenetricarboxylic acid in the atmosphere. The as-prepared B-CDs were characterized through UV−vis spectroscopy, photoluminescence spectroscopy, and so forth. Under the excitation of 310 nm UV light, B-CDs show RTP that appears as blue with a phosphorescence lifetime of 1042 ms, and after switching the excited wavelength to 365 nm, the RTP appears as green with a phosphorescence lifetime of 590 ms. Due to the unique RTP properties, B-CDs display promising applications in anticounterfeiting and information encryption.
Organic cathode materials are attractive for rechargeable lithium-ion batteries due to their advantages in sustainability and designability of molecular structure as well as the high upper limit of theoretical capacity....
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