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Reaching emissive nanomaterials at short wavelengths with a high quantum efficiency (QE) is an attractive task for researchers. This is more demanding in carbon dots (CDs) with diverse applications that usually emit photons at wavelengths around 450â€"620 nm. In this study, deep blue-emissive doped-CDs (d-CDs) with high photoluminescence (PL) QE up to 62% and excitation-independent properties were prepared via a short-time microwave irradiation method. The prepared CDs showed simultaneous amorphous and crystalline features, with average sizes of 4.75 nm and bright emission color located at 422 nm. It was found that the presence of sulfur-related dopant levels plays a key role in emission properties in such a way that the PL signal drops significantly in the absence of N-acetyl-l-cysteine (NAC) as a dopant source. On the other hand, the trisodium citrate dihydrate (TSC) was selected as a carbon source to form the main carbon skeleton without it no emission was recorded. Monoexponential-fitted recombination trend with an average lifetime of about 10 ns also confirmed excellent PL emission properties with uniform energy levels and minimized defect-contributing recombinations. The practical use of the as-prepared N, S-doped CDs was assessed in fingerprint detection indicating a bright and clear scheme for both core and termination regions of the fingerprint. Simplicity, cost-effectiveness, high-product yield, low toxicity, along with high/stable PL quantum efficiency in deep-blue wavelengths, and demonstrated ability for fingerprint purposes, support the prospective application of these dual doped-CDs for sensing and bioimaging applications. [ABSTRACT FROM AUTHOR]

The emergence of phosphorescence in diamonds has aroused great interest in their photoelectric information applications. Nevertheless, the existing phosphorescence in diamonds have a short lifetime, which severely restrains their application prospects. Moreover, the phosphorescence mechanism in diamonds is incomplete, which needs to be explored further. Herein, the synthetic diamonds with ultralong phosphorescence lifetime have been investigated. The phosphorescence emission bands centered at 470 nm and 580 nm have a long lifetime of 31 s and 93 s, respectively, outperforming other reported diamond materials. Detailed spectroscopy characterizations and density functional theory calculations reveal that the phosphorescence with ultralong lifetime involves a three-level system including donor, acceptor, and electron trap energy levels. The excited electrons can be captured by electron trap levels and transferred to the donor centers under thermal activation, then radiatively recombine with the holes from the acceptor level for persistent light emission. Based on the phosphorescence emission and photophysicochemical stability of the diamonds, a diamond-based data storage device has been demonstrated with outstanding repeatability (200 times with no attenuation) and durability (more than 3600 s). These results may prospect the application of phosphorescent diamonds in optical data storage. [Display omitted] • Phosphorescence emission is derived from three-level system in diamonds due to negative thermal quenching behavior. • Ultralong phosphorescence lifetime over 90 s has been achieved, outperforming previously reported diamond materials. • Diamonds with thermally-activated afterglow are used in optical data storage with good repeatability and durability. [ABSTRACT FROM AUTHOR]

Optical multiplexing attracts considerable attention in the field of information encryption, optical probe, and time‐resolved bioimaging. However, the optical multiplexing based on rare‐earth nanoparticles suffers from heavy metal elements and relatively short lifetimes; sophisticated facilities are thus needed. Herein, time division duplexing based on eco‐friendly carbon nanodots (CNDs) with manipulative luminescence lifetimes is demonstrated. In a single green color emission channel, the luminescence lifetimes of the CNDs can be manipulated from nanosecond level to second level by introducing water, while the lifetime of the CNDs confined by a silica shell stays. Time division duplexing based on the CNDs and CNDs@silica with distinct lifetimes is realized and spatio‐temporal overlapping information is thus resolved. High‐level information encryption using the time division duplexing technology is realized. This work may promise the potential applications of CNDs in multi‐lifetime channels biological imaging, high‐density information storage, and anti‐counterfeiting. [ABSTRACT FROM AUTHOR]

Herein, ultralong and efficient phosphorescence has been achieved from silica confined carbon nanodots (CNDs) in acqueous solution, and the lifetime and phosphorescence quantum yield of the CNDs are 1.86 s and 11.6 %, both of which are the best values ever reported for water-soluble phosphorescent nanoparticles. In terms of the efficient phosphorescence, in vivo/vitro afterglow imaging has also been demonstrated, which addresses demonstration of CNDs in afterglow bioimaging. • Water-soluble phosphorescent CNDs with world-record lifetime and quantum yield of 1.86 s and 11.6% have been achieved. • The silica layer increases the stability of the triplet excitons in CNDs. • In vivo / vitro afterglow imaging has been demonstrated with our proposed CNDs. Water-soluble phosphorescent nanoparticles are highly desirable for biomedical applications. However, the phosphorescence of nanoparticles is usually quenched in aqueous solutions due to the nonradiative deactivation of triplet excitons by the oxygen in water, thus it is a huge challenge to realize water-soluble phosphorescent nanoparticles. Herein, ultralong and efficient phosphorescence has been achieved from water-soluble carbon nanodots (CNDs) by confine CNDs in a nanospace. Silica capsulation layer is used to ensure the solublity of the CNDs, isolate the CNDs from the surrounding oxygen in the aqueous solution. Furthermore, the motion and vibration of covalent bonds in the CNDs are limited. In this way, the nonradiative deactivation rates of triplet excitons has been decreased, and efficient phosphorescence is achieved from water-soluble CNDs. The lifetime and phosphorescence quantum yield of the CNDs are 1.86 s and 11.6 %, both of which are the best values ever reported for water-soluble phosphorescent nanoparticles. In terms of the efficient phosphorescence of the CNDs in aqueous solution, in vivo/vitro afterglow imaging is also been demonstrated. [ABSTRACT FROM AUTHOR]

Synthetic diamonds have inspired much interest for their unique photophysical properties and versatile potential applications, but their phosphorescent phenomenon and mechanism have been paid much less attention. Here, phosphorescent diamonds with a lifetime of 5.4 s were synthesized by high-pressure and high-temperature method, and the diamonds exhibit an emission band at around 468 nm under the excitation wavelength of 230 nm. The quantum yield of the phosphorescent diamonds is about 4.7% at ambient temperature and atmosphere, which is the first report on the quantum yield of diamonds. The unique phosphorescence emission can be attributed to the radiative recombination from iron related donors and boron related acceptors. [ABSTRACT FROM AUTHOR]

Quadruple-mode emitting carbon nanodots (QM-CDs) have been designed via an ionic crystal confining strategy. The results reveal that the high-density ionic bonds can inactivate the nonradiative defect centers, stabilize triplet excitons, increase the cross-sectional absorption and boost the chemiluminescence resonance energy transfer of the QM-CDs, endowing their efficient fluorescence, upconversion photoluminescence, phosphorescence, and chemiluminescence simultaneously. And the confining aggregation of CDs in the NaOH matrix contribute to the tunable light emission wavelength. With the QM-CDs, one kind of all-photonic multiple-inputs logic gates with programmable emitting modes have been established to achieve information processing and security. [Display omitted] • The QM-CDs with tunable multiple-mode light emitting are prepared. • The high-density ionic bonds endow the multiple-mode light emitting of QM-CDs. • The confining aggregation endow the tunable light emission wavelengths of QM-CDs. • The programmable multiple-inputs logic gates are established with the QM-CDs. Multiple-mode light emitting in one material system is tremendous desirable for various applications. Herein, we have developed an ionic crystal confining strategy to prepare the carbon nanodots (CDs) with quadruple-mode light emitting and demonstrated their promising application in information anti-counterfeiting via optical logic gates. In detail, the quadruple-mode light emitting of CDs (QM-CDs) are prepared with the citric acid and urea with NaOH matrix via microwave-assisted polymerization. Mechanically, the high-density ionic bonds stemmed from the NaOH ionic-crystal can effectively inactivate nonradiative defect centers, stabilize triplet excitons, increase absorption cross-section and boost resonance energy transfer, evoking the outstanding solid-state fluorescence, upconversion photoluminescence (UCPL), phosphorescence, and chemiluminescence simultaneously. Meanwhile, the isolated NaOH matrix can promote the confining aggregation of CDs, leading to the redshifted emission wavelength and endowing the light emitting with tunable wavelength. With the excitability of logic functions between the light emitting and controlled excitation, the programmable multiple-inputs logic gates are established with the QM-CDs, enabling the application in high-throughput logical operations and information anti-counterfeiting. This research provides a new insight into the synthesize of multiple-mode luminescent CDs, and thus promote the applications of nanomaterials in intelligent encryption and anti-counterfeiting. [ABSTRACT FROM AUTHOR]

Room temperature phosphorescence (RTP) materials are highly attractive in many fields, but it is still a great challenge to obtain RTP materials with color tunability. Herein, we report a new type of multicolor phosphorescence carbon dots (CDs) through confining CDs into rigid crystal network through the introduction of ionic bonds. The RTP color can rationally vary from green (553 nm) to orange-red (640 nm) under different excitation wavelengths. More importantly, the obtained CDs can also maintain their RTP emission in ethanol solution. The excitation-dependent property was owing to the existence of polychromatic emission centers on the surface of CDs, and the generation of RTP can be attributed to the ionic bond in CDs system to suppress non-radiative transition of triplet states. Based on this unique multicolor RTP phenomenon, the CDs were successfully applied in anticounterfeiting and light-emitting diodes. This finding not only provides a new strategy for the preparation of multicolor RTP materials but also reveals a great potential of CDs in developing novel optical materials. [Display omitted] • We report a new type of color-tunable phosphorescence carbon dots (CDs) under ambient conditions. • The RTP color can rationally vary from 553 to 640 nm. • The CDs ethanol solution also maintained a bright RTP (625 nm). • Based on this unique color-tunability RTP phenomenon, the CDs were successfully applied in anticounterfeiting and light-emitting diodes (LEDs). [ABSTRACT FROM AUTHOR]