Visualizing Motion Trail via Phosphorescence Carbon Nanodots-Based Delay Display Array.

A scene that contains both old and instant events with a clear motion trail is visually intriguing and dynamic, which can convey a sense of change, transition, or evolution. Developing an eco-friendly delay display system offers a powerful tool for fusing old and instant events, which can be used for visualizing motion trails. Herein, we brighten triplet excitons of carbon nanodots (CNDs) and increase their emission yield by a multidimensional confinement strategy, and the CND-based delay display array is demonstrated. The intense confinement effects via multidimensional confinement strategy suppress nonradiative transitions, and 240% enhancement in the phosphorescence efficiency and 260% enhancement in the lifetime of the CNDs are thus realized. Considering their distinctive phosphorescence performances, a delay display array containing a 4 × 4 CND-based delay lighting device is demonstrated, which can provide ultralong phosphorescence over 7 s, and the motion that occurred in different timelines is recorded clearly. This finding will motivate the investigation of phosphorescent CNDs in motion trail recognition.

Thermally Enhanced Phosphorescent Carbon Nanodots for Monitoring Cold-Chain Logistics.

Room-temperature phosphorescent materials, renowned for their long luminescence lifetimes, have garnered significant attention in the field of optical materials. However, the challenges posed by thermally induced quenching have significantly hindered the advancement of luminescence efficiency and stability. In this study, thermally enhanced phosphorescent carbon nanodots (CND) are developed by incorporating them into fiber matrices. Remarkably, the phosphorescence lifetime of the thermally enhanced CND exhibits a twofold enhancement, increasing from 326 to 753 ms, while the phosphorescence intensity experienced a tenfold enhancement, increasing from 25 to 245 as the temperature increased to 373 K. Rigid fiber matrices can effectively suppress the non-radiative transition rate of triplet excitons, while high temperatures can desorb oxygen adsorbed on the surface of the CND, disrupting the interaction between the CND and oxygen. Consequently, a thermally enhanced phosphorescence is obtained. In addition, benefiting from the thermally enhanced phosphorescence property of CND, a warning indicator with an anti-counterfeiting function for monitoring cold-chain logistics is demonstrated based on CND.

Enhanced Phosphorescence of Carbon Nanodots via Double Confinement for 3D Artworks with Long Emission Lifetimes.

Phosphorescent materials as block elements to build artwork incorporating the time and emission, enable them with spectacular lighting effects. In this work, enhanced phosphorescence of carbon nanodots (CNDs) is demonstrated via double confinement strategy, which silica and epoxy resin are used as the first and the second order confinement layer. The multi-confined CNDs show an enhanced phosphorescence quantum yield up to 16.4%, with enduring emission lifetime up to 1.44 s. Delicately, the plasticity of the epoxy resin enables them easily to be designed for 3D artworks with long emission lifetimes in different shapes. The efficient and eco-friendly phosphorescent CNDs may arouse intense interest both in the academic community and markets.

Paper-Fiber-Activated Triplet Excitons of Carbon Nanodots for Time-Resolved Anti-counterfeiting Signature with Artificial Intelligence Authentication.

The easy-to-imitate character of a personal signature may cause significant economy loss due to the lack of speed and strength information. In this work, we report a time-resolved anti-counterfeiting signature strategy with artificial intelligence (AI) authentication based on the designed luminescent carbon nanodot (CND) ink, whose triplet excitons can be activated by the bonding between the paper fibers and the CNDs. Paper fibers can bond with the CNDs through multiple hydrogen bonds, and the activated triplet excitons release photons for about 13 s; thus, the speed and strength of the signature are recorded through recording the changes in luminescence intensity over time. The background noise from commercial paper fluorescence is completely suppressed, benefiting from the long phosphorescence lifetime of the CNDs. In addition, a reliable AI authentication method with quick response based on a convolutional neural network is developed, and 100% identification accuracy of the signature based on the CND ink is achieved, which is higher than that of the signature with commercial ink (78%). This strategy can also be expanded for painting, calligraphy identification.

Ultraviolet phosphorescent carbon nanodots.

Phosphorescent carbon nanodots (CNDs) have generated enormous interest recently, and the CND phosphorescence is usually located in the visible region, while ultraviolet (UV) phosphorescent CNDs have not been reported thus far. Herein, the UV phosphorescence of CNDs was achieved by decreasing conjugation size and in-situ spatial confinement in a NaCNO crystal. The electron transition from the px to the sp2 orbit of the N atoms within the CNDs can generate one-unit orbital angular momentum, providing a driving force for the triplet excitons population of the CNDs. The confinement caused by the NaCNO crystal reduces the energy dissipation paths of the generated triplet excitons. By further tailoring the size of the CNDs, the phosphorescence wavelength can be tuned to 348 nm, and the room temperature lifetime of the CNDs can reach 15.8 ms. As a demonstration, the UV phosphorescent CNDs were used for inactivating gram-negative and gram-positive bacteria through the emission of their high-energy photons over a long duration, and the resulting antibacterial efficiency reached over 99.9%. This work provides a rational design strategy for UV phosphorescent CNDs and demonstrates their novel antibacterial applications.

Brighten Triplet Excitons of Carbon Nanodots for Multicolor Phosphorescence Films.

Triplet excitons usually do not emit light under ambient conditions due to the spin-forbidden transition rule, thus they are called dark excitons. Herein, triplet excitons in carbon nanodots (CNDs) are brightened by embedding the CNDs into poly(vinyl alcohol) (PVA) films; flexible multicolor phosphorescence films are thus demonstrated. PVA chains can isolate the CNDs, and excited state electron or energy transfer induced triplet exciton quenching is thus reduced; while the formed hydrogen bonds between the CNDs and PVA can restrict vibration/rotation of the CNDs, thus further protecting the triplet excitons from nonradiative recombination. The lifetimes of the flexible multicolor phosphorescence films can reach 567, 1387, 726, and 311 ms, and the longest-lasting phosphorescence film can be observed by naked eyes for nearly 15 s even after bending 5000 times. The phosphorescence films can be processed into various patterns, and a dynamic optical signature concept has been proposed and demonstrated based on the phosphorescence films.

Phosphorescent Carbon-Nanodots-Assisted Förster Resonant Energy Transfer for Achieving Red Afterglow in an Aqueous Solution.

Water-soluble red afterglow imaging agents based on ecofriendly nanomaterials have potential application in time-gated afterglow bioimaging due to their larger penetration depth and nondurable excitation. Herein, red afterglow imaging agents consisted of Rhodamine B (RhB) and carbon nanodots (CNDs) have been designed and demonstrated. In these agents, CNDs act as energy donors, and RhB acts as an energy acceptor. Both of them are confined into a hydrophilic silica shell to form a CNDs-RhB@silica nanocomposite. The phosphorescence emission spectrum of the CNDs and the absorption spectrum of the RhB match well, and efficient energy transfer from the CNDs to the RhB via Förster resonant energy transfer process can be achieved, with a transfer efficiency can reach 99.2%. Thus, the as-prepared nanocomposite can emit a red afterglow in aqueous solution, and the afterglow spectrum of CNDs-RhB@silica nanocomposite can extend to the first near-infrared window (NIR-I). The luminescence lifetime and afterglow quantum yield (QY) of the CNDs-RhB@silica can reach 0.91 s and 3.56%, respectively, which are the best results in red afterglow region. Time-gated in vivo afterglow imaging has been demonstrated by using the CNDs-RhB@silica as afterglow agents.

Ratiometric fluorescence sensor based on europium-grafted ZnO quantum dots for visual and colorimetric detection of tetracycline.

An europium functionalized ZnO quantum dots (QDs) ratiometric fluorescent nanoprobe is designed to establish a real time, on-site visual, and highly sensitive probe method for tetracycline (TC). The yellow-emitting ZnO QDs serves as the internal reference, while the Eu3+ chelated on the surface of ZnO QDs is used as the signal reporting unit. This nanoprobe exhibits rapid response, excellent selectivity, and high sensitivity with a detection limit of 4 nM in detecting the levels of TC. In addition, fluorescence of the nanoprobe can change from yellow to red as the concentration of TC increases. Thus, naked eye detection of TC was realized using the test paper processed by nanoprobe, followed by RGB value analysis function on the mobile phone APP.

Lifetime-Engineered Carbon Nanodots for Time Division Duplexing.

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.

Water-induced MAPbBr3@PbBr(OH) with enhanced luminescence and stability.

Poor stability has long been one of the key issues that hinder the practical applications of lead-based halide perovskites. In this paper, the photoluminescence (PL) quantum yield (QY) of bromide-based perovskites can be increased from 2.5% to 71.54% by introducing water, and the PL QY of a sample in aqueous solution decreases minimally over 1 year. The enhanced stability and PL QY can be attributed to the water-induced methylamino lead bromide perovskite (MAPbBr3)@PbBr(OH). We note that this strategy is universal to MAPbBr3, formamidine lead bromide perovskite (FAPbBr3), inorganic lead bromide perovskite (CsPbBr3), etc. Light-emitting devices (LEDs) are fabricated by using the as-prepared perovskite as phosphors on a 365 nm UV chip. The luminance intensity of the LED is 9549 cd/m2 when the driven current is 200 mA, and blemishes on the surface of glass are clearly observed under the illumination of the LEDs. This work provides a new strategy for highly stable and efficient perovskites.

Ultrasensitive Mechano-Stimuli Luminescence Enhancement in ZnO Nanoparticles.

Ultrasensitive mechano-stimuli photoluminescence enhancement was observed in pyramid-like zinc oxide nanoparticles (ZnO NPs), which are fabricated by a facile hydrothermal route. The response of the ZnO NPs to mechanical stimuli is so sensitive that even an ant walking and acoustic vibration can trigger the luminescence enhancement. The mechanism for this unusual behavior was attributed to the electron injection process between crystal boundaries. Thus, this work opens up the possibility of detecting slight mechanical stimuli wirelessly, rapidly, and sensitively. Importantly, the sensitive response of the NPs to sound waves can find potential application in devices for hearing-impaired people.

A self-calibrated luminescent thermometer based on nanodiamond-Eu/Tb hybrid materials.

Luminescent hybrid materials based on nanodiamonds (NDs) and rare earth ions have been successfully synthesized by covalently modifying NDs with pyromellitic acid (PMA) which is capable of coordinating to Eu3+ and Tb3+ ions. With NDs acting as a host matrix, the PMA and rare earth ions serve as an organic sensitizer and activator, respectively, yielding a highly bright hybrid composite. Interestingly, for the co-doped hybrid composites ND-PMA-Eu/Tb, the intensity ratio of the two emissions, 5D4→7F5 transition (Tb3+) to 5D0→7F2 transition (Eu3+), is linearly related to temperature in the range from 77 K to 277 K. Therefore, the hybrid could be developed as a self-calibrated ratiometric luminescent thermometer due to its temperature-dependent luminescence performance.

Multi-zinc oxide-cores@uni-barium sulfate-shell with improved photo-, thermal-, and ambient-stability: Non-equilibrium sorption fabrication and light-emitting diodes application.

ZnO as an eco-friendly material shows bright luminescence under UV illumination when it is tailored into nanoscale size, which makes it a promising luminescent nanomaterial. However, the poor stability of ZnO hinders its applications drastically. In this work, multi-ZnO-cores@uni-BaSO4-shell (mZnO@uBaSO4) nanocomposite has been prepared through a non-equilibrium sorption process employing ZnO QDs as the "seeds" and BaSO4 as the "valve". The mZnO@uBaSO4 nanocomposite shows improved photo-, thermal- and ambient-stability compare with bare ZnO QDs. The fluorescence efficiency of the mZnO@uBaSO4 nanocomposite decreases little even after 60 h of UV irradiation compare with ZnO QDs. The mZnO@uBaSO4 nanocomposite shows bright luminescence with little decrease even the ambient temperature up to 160 °C and the nanocomposite shows strong resistance to harsh environment. By coating the mZnO@uBaSO4 nanocomposite and commercial phosphors onto UV-chip, light-emitting diode (LED) with correlated color temperature, Commission Internationale de L'Eclairage coordinate, color rendering index and luminous efficiency of 6109 K, (0.32, 0.33), 85 and 47.33 lm/W have been realized, and this will make a great step towards eco-friendly UV-pumped LEDs.

Carbon-ZnO alternating quantum dot chains: electrostatic adsorption assembly and white light-emitting device application.

Aggregation-induced quenching (ACQ) in carbon nanodots (CNDs) impede their applications in solid devices. Herein, the concept of alternating quantum dot (QD) chains was proposed to overcome the common issue of fluorescence quenching in CNDs; in this study, CNDs and ZnO QDs were interlinked to form carbon-ZnO alternating quantum dot chains (CZA-QDCs), which overcame the ACQ of CNDs and hence ensured efficient full-spectrum fluorescence for white light-emitting devices (WLEDs) without excessive blue emission. Under the excitation of 365 nm lines, white emission resulting from the combination of blue emission from the CNDs and yellow emission from the ZnO QDs has been achieved from these powders. The quantum efficiency of the CZA-QDC powders can reach 49% and remain stable for two months. By coating the powders onto an ultraviolet chip as phosphors, WLEDs with a luminous efficiency of 20.1 lm W-1, color coordinate of (0.30, 0.35), correlated color temperature of 5205 K, and a color rendering index of 84 have been fabricated. Due to the relatively high abundance and eco-friendly characteristics of both carbon and ZnO, the results reported herein may provide a promising alternative to fluorescent phosphors that are widely used in WLEDs.

Branched-chain amino acids and arginine improve performance in two consecutive days of simulated handball games in male and female athletes: a randomized trial.

UNLABELLED: The central nervous system plays a crucial role in the development of physical fatigue. The purpose of this study is to investigate the effect of combined supplementation of branched-chain amino acids (BCAA) and arginine on intermittent sprint performance in simulated handball games on 2 consecutive days. METHODS: Fifteen male and seven female handball players consumed 0.17 g/kg BCAA and 0.04 g/kg arginine together (AA trial), or placebo (PB trial) before exercise. Each trial contained two 60-min simulated handball games on consecutive days. The game was consisted of 30 identical 2-min blocks and a 20 m all-out sprint was performed at the end of each block. The performance, measured by percentage changes of sprint time between day 1 and 2, was significantly better in the AA trial (first half: AA trial: -1.34 ± 0.60%, PB trial: -0.21 ± 0.69%; second half: AA trial: -1.68 ± 0.58%, PB trial: 0.49 ± 0.42%). The average ratings of perceive exertion throughout the 2-day trial was significantly lower in the AA trial (14.2 ± 0.3) than the PB trial (15.1 ± 0.4). Concurrently, post-exercise tryptophan/BCAA ratio on both days in the AA trial was significantly lower than the baseline. This study showed that BCAA and arginine supplementation could improve performance in intermittent sprints on the second consecutive day of simulated handball games in well-trained athletes by potentially alleviating central fatigue.