Time Division Colorful Multiplexing Based on Carbon Nanodots with Modifiable Colors and Lifetimes.

Optical multiplexing technology plays a crucial role in various fields such as data storage, anti-counterfeiting, and time-resolved biological imaging. Nevertheless, employing single-wavelength phosphorescence for multiplexing often results in spectral overlap among the emission peaks of various channels, which can precipitate crosstalk and misinterpretation in the information-decoding process, thereby compromising the integrity and precision of the encrypted data. This paper proposes a time-divided colorful multiplexing technology based on phosphorescent carbon nanodots with different colors and lifetimes. Using different luminescence colors to symbolize varying information levels helps achieve multitiered information encryption and storage. By modulation of the lifetime and the emission wavelength, intricate information can be encoded, thereby enhancing the intricacy and security of the encryption mechanism. By assigning different data bits to each color, more information can be encoded in the same physical space. This method enables higher-density information storage and fortifies encryption, ensuring the compactness and security of information.

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.

Hydrophobic Mn-Doped Solid-State Red-Emitting Carbon Nanodots with AIE Effect and Their Hydrogel Composites for Color-Changing Anticounterfeiting.

The aggregation-caused quenching has always limited the high concentration and solid-state applications of carbon nanodots. While the aggregation-induced emission effect, dominated by intramolecular motion, may be an effective means to solve this problem. Here, hydrophobic solid-state red-light carbon nanodots (M-CDs) with 95% yield are synthesized by a one-step hydrothermal method using 2,2'-dithiodibenzoic acid as the carbon source and manganese acetate as the dopant source. The disulfide bond of 2,2'-dithiodibenzoic acid serves as the symmetry center of molecular rotation and Mn catalyzes the synthesis of M-CDs, which promotes the formation of the central graphitic carbon structure. The M-CDs/agar hydrogel composites can achieve fluorescence transition behavior because of the special fluorescence transition properties of M-CDs. When this composite hydrogel is placed in water, water molecules contact with M-CDs through the network structure of the hydrogels, making the aggregated hydrogels of M-CDs fluorescence orange-red under 365 nm excitation. While in dimethyl sulfoxide, water molecules in the hydrogels network are replaced and the M-CDs fluoresce blue when dispersed, providing a potential application in information encryption. In addition, high-performance monochromatic light-emitting diode (LED) devices are prepared by compounding M-CDs with epoxy resin and coating them on 365 nm LED chips.

L-Arginine Doped Carbon Nanodots from Cinnamon Bark for Improved Fluorescent Yeast Cell Imaging.

In this study, we present an economical and efficient synthesis method for carbon nanodots (CNDs) derived from cinnamon bark wood powder, with the incorporation of L-arginine as a dopant at varying ratios (Cinnamon : L-Arginine - 1:0.25, 1:0.5) via a hydrothermal reaction. Extensive structural and optical characterization was conducted through techniques such as FTIR, XRD, HR-TEM, DLS, UV-Vis, and PL spectra, providing a comprehensive understanding of the properties of CNDs and doped-CNDs. Quantum yields (QY) were quantified for synthesized materials, contributing to the assessment of their fluorescence efficiency. The synthesized CNDs were successfully applied for bioimaging of yeast cells, employing fluorescence microscopy to visualize their interaction. Remarkably, L-arginine-doped CNDs exhibited enhanced fluorescence, showcasing the influence of the dopant. The nature of these CNDs was rigorously investigated, confirming their biocompatibility. Notably, this work presents a novel approach to synthesizing CNDs from a renewable and sustainable source, cinnamon bark wood powder, while exploring the effects of L-arginine doping on their optical and biological properties. This work not only contributes to the synthesis and characterization of CNDs but also highlights their potential for diverse applications, emphasizing their structural, optical, and biological attributes. The findings underscore the versatility of CNDs derived from cinnamon bark wood powder and their potential for advancing biotechnological and imaging applications.

Sleep deprivation boosts O2·- levels in the brains of mice as visualized by a Golgi apparatus-targeted ratiometric fluorescence nanosensor.

Sleep deprivation (SD) is highly prevalent in the modern technological world. Emerging evidence shows that sleep deprivation is associated with oxidative stress. At the organelle level, the Golgi apparatus actively participates in the stress response. In this study, to determine whether SD and Golgi apparatus stress are correlated, we rationally designed and fabricated a novel Golgi apparatus-targeted ratiometric nanoprobe called Golgi dots for O2·- detection. This probe exhibits high sensitivity and selectivity in cells and brain slices of sleep-deprived mice. Golgi dots can be readily synthesized by coprecipitation of Golgi-F127, an amphiphilic polymer F127 modified with a Golgi apparatus targeting moiety, caffeic acid (CA), the responsive unit for O2·-, and red emissive carbon nanodots (CDs), which act as the reference signal. The fluorescence emission spectrum of the developed nanoprobe showed an intense peak at 674 nm, accompanied by a shoulder peak at 485 nm. As O2·- was gradually added, the fluorescence at 485 nm continuously increased; in contrast, the emission intensity at 674 nm assigned to the CDs remained constant, resulting in the ratiometric sensing of O2·-. The present ratiometric nanoprobe showed high selectivity for O2·- monitoring due to the specific recognition of O2·- by CA. Moreover, the Golgi dots exhibited good linearity with respect to the O2·- concentration within 5 to 40 µM, and the limit of detection (LOD) was ~ 0.13 µM. Additionally, the Golgi dots showed low cytotoxicity and an ability to target the Golgi apparatus. Inspired by these excellent properties, we then applied the Golgi dots to successfully monitor exogenous and endogenous O2·- levels within the Golgi apparatus. Importantly, with the help of Golgi dots, we determined that SD substantially elevated O2·- levels in the brain.

Highly Antibacterial and Antioxidative Carbon Nanodots/Silk Fibroin Films for Fruit Preservation.

The issues of fruit waste and safety resulting from rot have spurred a demand for improved packaging systems. Herein, we present highly antibacterial and antioxidative carbon nanodot/silk fibroin (CD/SF) films for fruit preservation. The films are composed of CDs and SF together with a small amount of glycerol via hydrogen bonding, exhibiting outstanding biosafety, transparency, and stretchability. The films effectively integrate key functionalities (atmosphere control, resistance to food-borne pathogens, and antioxidation properties) and can be manufactured in large sizes (about 20 × 30 cm), boasting a transmission rate of 13 183 cm3/m2·day for oxygen and 2860 g/m2·day for water vapor, favoring the preservation of fresh fruits. A convenient dip-coating method enables in situ fabrication of films with a thickness of approximately 14 µm directly on the fruits' surface providing comprehensive protection. Importantly, the films are washable and biodegradable. This work presents a promising technology to produce multifunctional and eco-friendly antibacterial packaging systems.

Supramolecular Aggregation of Carbon Nanodots.

Supramolecular aggregation has provided the archetype concept to understand the variants in an emerging systems property. Herein, we have achieved the supramolecular assembly of carbon nanodots (CDs) for the first time and employ supramolecular aggregation to understand their alteration in photophysical properties. In detail, we have employed the CDs as a block to construct the supramolecular assembly of aggregates in the CDs' antisolvent of ethanol. The CD-based aggregates exhibit complex and organized morphologies with another long-wavelength excitation-dependent emission band. The experimental results and density functional theoretical calculations reveal that the supramolecular assembly of CDs can decrease the energy gap between the ground and excited states, contributing to the new long-wavelength excitation-dependent emission. The supramolecular aggregation can be employed as one universal strategy to manipulate and understand the luminescence of CDs. These findings cast new light to build the emerging systems and understand the light emission of CDs through supramolecular chemistry.

Synthetic Strategies for the Selective Functionalization of Carbon Nanodots Allow Optically Communicating Suprastructures.

The surface of Carbon Nanodots (CNDs) stands as a rich chemical platform, able to regulate the interactions between particles and external species. Performing selective functionalization of these nanoscale entities is of practical importance, however, it still represents a considerable challenge. In this work, we exploited the organic chemistry toolbox to install target functionalities on the CND surface, while monitoring the chemical changes on the material's outer shell through nuclear magnetic resonance spectroscopy. Following this, we investigated the use of click chemistry to covalently connect CNDs of different nature en-route towards covalent suprastructures with unprecedent molecular control. The different photophysical properties of the connected particles allowed their optical communication in the excited state. This work paves the way for the development of selective and addressable CND building blocks which can act as modular nanoscale synthons that mirror the long-established reactivity of molecular organic synthesis.

A facile approach for sulphur and nitrogen co-doped carbon nanodots to improve photothermal eradication of drug-resistant bacteria.

In this study, we produced S, N co-doped CNDs (SN@CNDs) by using dimethyl sulfoxide (DMSO) and formamide (FA) as single sources of S and N, respectively. We varied the S/N ratios by adjusting the volume ratios of DMSO and FA and investigated their effect on the red-shift of the CNDs' absorption peak. Our findings demonstrate that SN@CNDs synthesized using a volume ratio of 5:6 between DMSO and FA exhibit the most significant absorption peak redshift and enhanced near-infrared absorption performance. Based on comparative analysis of the particle size, surface charge, and fluorescence spectrum of the S@CNDs, N@CNDs, and SN@CNDs, we propose a possible mechanism to explain the change of optical properties of CNDs due to S, N doping. Co-doping creates a more uniform and smaller band gap, resulting in a shift of the Fermi level and a change in energy dissipation from radioactive to non-radiative decay. Importantly, the as-prepared SN@CNDs exhibited a photothermal conversion efficiency of 51.36% at 808 nm and demonstrated exceptional photokilling effects against drug-resistant bacteria in both in vitro and in vivo experiments. Our facile method for synthesizing S and N co-doped CNDs can be extended to the preparation of other S and N co-doped nanomaterials, potentially improving their performance.

The Importance of the Purification Step and the Characterization of the Products in the Synthesis of Carbon Nanodots.

In the synthesis of carbon nanodots (CNDs), the critical step of the purification from the starting materials and unwanted side products is faced. In the exciting race toward new and interesting CNDs, this problem is often underestimated, leading to false properties and erroneous reports. In fact, on many occasions, the properties described for novel CNDs derive from impurities not completely eliminated during the purification process. Dialysis, for instance, is not always helpful, especially if the side products are not soluble in water. In this Perspective, the importance of the purification and characterization steps, in order to obtain solid reports and reliable procedures, is emphasized.

Luminescent Carbon Nanodots Doped with Gadolinium (III): Purification Criteria, Chemical and Biological Characterization of a New Dual Fluorescence/MR Imaging Agent.

Carbon Dots (CDs) are luminescent quasi-spherical nanoparticles, possessing water solubility, high biocompatibility, and tunable chemical and physical properties for a wide range of applications, including nanomedicine and theranostics. The evaluation of new purification criteria, useful to achieve more reliable CDs, free from the interference of artifacts, is currently an object of debate in the field. Here, new CDs doped with gadolinium (Gd (III)), named Gd@CNDs, are presented as multifunctional probes for Magnetic Resonance Imaging (MRI). This new system is a case of study, to evaluate and/or combine different purification strategies, as a crucial approach to generate CDs with a better performance. Indeed, these new amorphous Gd@CNDs display good homogeneity, and they are free from emissive side products. Gd@CNDs (7-10 nm) contain 7% of Gd (III) w/w, display suitable and stable longitudinal relaxivity (r1 ) and with emissive behavior, therefore potentially useful for both MR and fluorescence imaging. They show good biocompatibility in both cellular and in vivo studies, cell permeability, and the ability to generate contrast in cellular pellets. Finally, MRI recording T1 -weighted images on mice after intravenous injection of Gd@CNDs, show signal enhancement in the liver, spleen, and kidney 30 min postinjection.

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.

Understanding the Visible Absorption of Electron Accepting and Donating CNDs.

Carbon nanodots (CNDs) synthesized from citric acid and formyl derivatives, that is, formamide, urea, or N-methylformamide, stand out through their broad-range visible-light absorbance and extraordinary photostability. Despite their potential, their use has thus far been limited to imaging research. This work has now investigated the link between CNDs' photochemical properties and their chemical structure. Electron-rich, yellow carbon nanodots (yCNDs) are obtained with in situ addition of NaOH during the synthesis, whereas otherwise electron-poor, red carbon nanodots (rCNDs) are obtained. These properties originate from the reduced and oxidized dimer of citrazinic acid within the matrix of yCNDs and rCNDs, respectively. Remarkably, yCNDs deposited on TiO2 give a 30% higher photocurrent density of 0.7 mA cm-2 at +0.3 V versus Ag/AgCl under Xe-lamp irradiation (450 nm long-pass filter, 100 mW cm-2 ) than rCNDs. The difference in overall photoelectric performance is due to fundamentally different charge-transfer mechanisms. These depend on either the electron-accepting or the electron-donating nature of the CNDs, as is evident from photoelectrochemical tests with TiO2 and NiO and time-resolved spectroscopic measurements.

See the Unseen: Red-Emissive Carbon Dots for Visualizing the Nucleolar Structures in Two Model Animals and In Vivo Drug Toxicity.

Nucleolus, which participates in many crucial cellular activities, is an ideal target for evaluating the state of a cell or an organism. Here, bright red-emissive carbon dots (termed CPCDs) with excitation-independent/polarity-dependent fluorescence emission are synthesized by a one-step hydrothermal reaction between congo red and p-phenylenediamine. The CPCDs can achieve wash-free, real-time, long-term, and high-quality nucleolus imaging in live cells, as well as in vivo imaging of two common model animals-zebrafish and Caenorhabditis elegans (C. elegans). Strikingly, CPCDs realize the nucleolus imaging of organs/flowing blood cells in zebrafish at a cellular level for the first time, and the superb nucleolus imaging of C. elegans suggests that the germ cells in the spermatheca probably have no intact nuclei. These previously unachieved imaging results of the cells/tissues/organs may guide the zebrafish-related studies and benefit the research of C. elegans development. More importantly, a novel strategy based on CPCDs for in vivo toxicity evaluation of materials/drugs (e.g., Ag+ ), which can visualize the otherwise unseen injuries in zebrafish, is developed. In conclusion, the CPCDs represent a robust tool for visualizing the structures and dynamic behaviors of live zebrafish and C. elegans, and may find important applications in cell biology and toxicology.

Gram-Scale Room-Temperature Synthesis of Solid-State Fluorescent Carbon Nanodots for Bright Electroluminescent Light Emitting Diodes.

The reaction conditions of high temperature and high pressure will introduce structural defects, high energy consumption, and security risks, severely hindering the industrial application of organic carbon nanodots (CDs). Moreover, the aggregation caused quenching effect also fundamentally limits the CDs based electroluminescent light emitting diodes (LEDs). Herein, for the first time, a rapid one-step room temperature synthetic strategy is introduced to prepare highly emissive solid-state-fluorescent CDs (RT-CDs). A strong oxidizing agent, potassium periodate (KIO4 ), is adopted as a catalyst to facilitate the cyclization of o-phenylenediamine and 4-dimethylamino phenol in aqueous solution at room temperature for only 5 min. The resultant organic molecule, 2-(dimethylamino) phenazine, will self-assemble kinetically to generate supramolecular-structure CDs during crystallization. The elaborately arranged supramolecular structure (J aggregates) endows CDs with intense solid-state-fluorescence. Density functional theory (DFT) calculation shows that the excited state of RT-CDs exhibits charge transfer characteristic owing to the unique donor-Π-acceptor structure. A high-performance monochrome RT-CDs based electroluminescent LEDs (2967 cd m-2 and 1.38 cd A-1 ) were fabricated via systematic optimizations of device engineering. This work provides a concrete and feasible avenue for the rapid and massive preparation of CDs, advancing the commercialization of CDs based optoelectronic devices.

Fluorescent and Biocompatible Nitrogen and Sulfur Co-Doped Carbon Nanodot as an Ocular Fundus Angiography Imaging Agent.

The florescence characteristics and the toxicities of carbon nanodots (CDs) are directly related to their elemental compositions. Fluorescent and non-toxic agent for imaging of biological systems was aimed. Sulfur and nitrogen co-doped CDs (S/N-CDs) was hydrothermally produced in an average size of 8 nm. S/N-CDs showed blue fluorescence under UV-light with an excitation wavelength of 365 nm. After 24 h, S/N-CDs was non-cytotoxic in HUVEC and L929 cells. S/N-CDs have a great potential to act as an alternative material for commercial fluorescent materials with its 85.5% of quantum yield. S/N-CDs was approved in vitro as an imaging agent for an ocular fundus angiography of rats.

A Fluorescence Turn On-off-on Method for Sensitive Detection of Sn2+ and Glycine Using Waste Eggshell Membrane Derived Carbon Nanodots as Probe.

Changes in Sn2+ and glycine levels are relevant to many important physiological procedures in human health. However, investigation of their physiological functions is limited because few versatile methods towards Sn2+ and glycine detection have been developed. In this work, a fluorescence turn on-off-on strategy was firstly constructed for rapid and sensitive detection of Sn2+ and glycine through the specific binding between Sn2+ and glycine. Carbon nanodots (CDs) with a quantum yield of 19.5% were synthesized by utilizing inner film of waste eggshell as carbon source and employed as fluorescent probe. In the presence of Sn2+, the fluorescence of CDs was quenched by Sn2+ via the primary inner filter effect (IFE). However, the binding between Sn2+ and glycine prevented the IFE between Sn2+ and CDs, resulting in fluorescence recovery of CDs. Under optimized conditions, the fluorescent response of CDs displayed good linear relationships with the concentrations of Sn2+ in the range of 10-200 µM and 200-5000 µM, and the limit of detection (LOD) was 2.4 µM. For glycine detection, a good linear relationship was obtained in the concentration range of 5-1000 µM with a low LOD down to 0.76 µM. Moreover, the practicability of the assay was also demonstrated by measuring glycine content in human serum samples. This work provides an economical, green and fast method for biological analysis of Sn2+ and glycine.

Luminous Insights: Harnessing Carbon Nanodots from Black Seed Powder via Pyrolysis for Bioimaging and Antifungal Investigations.

This study delves into the fabrication of carbon nanodots (CNDs) through a bottom-up approach, utilizing black seed powder as the precursor material and employing the pyrolysis method. CNDs were synthesized across four distinct temperature settings. The investigation encompasses an extensive characterization of the CNDs, including optical and structural attributes. UV-visible and fluorescence spectroscopy were utilized to assess their optical properties, while FT-IR and XRD analyses confirmed their structural integrity. To elucidate size, shape, and nature, HR-TEM imaging was employed. Furthermore, the functional applications of the synthesized CNDs were explored. The material's antifungal potential was evaluated, and its viability for bioimaging was demonstrated by successfully labeling yeast cells with CNDs. This study underscores the multifaceted nature of CNDs, serving as a bridge between synthesis, comprehensive characterization, and practical applications. In summary, the investigation provides insights into the versatile applications of CNDs derived from black seed powder through pyrolysis. The study contributes to the understanding of their fundamental properties and establishes their potential for both antifungal treatments and cellular bioimaging.

Carbon nanodots constructed by ginsenosides and their high inhibitory effect on neuroblastoma.

BACKGROUND: Neuroblastoma is one of the common extracranial tumors in children (infants to 2 years), accounting for 8 ~ 10% of all malignant tumors. Few special drugs have been used for clinical treatment currently. RESULTS: In this work, herbal extract ginsenosides were used to synthesize fluorescent ginsenosides carbon nanodots via a one-step hydrothermal method. At a low cocultured concentration (50 µg·mL- 1) of ginsenosides carbon nanodots, the inhibition rate and apoptosis rate of SH-SY5Y cells reached ~ 45.00% and ~ 59.66%. The in vivo experiments showed tumor volume and weight of mice in ginsenosides carbon nanodots group were ~ 49.81% and ~ 34.14% to mice in model group. Since ginsenosides were used as sole reactant, ginsenosides carbon nanodots showed low toxicity and good animal response. CONCLUSION: Low-cost ginsenosides carbon nanodots as a new type of nanomedicine with good curative effect and little toxicity show application prospects for clinical treatment of neuroblastoma. It is proposed a new design for nanomedicine based on bioactive carbon nanodots, which used natural bioactive molecules as sole source.

Carbon nanodots with a controlled N structure by a solvothermal method for generation of reactive oxygen species under visible light.

Carbon nanodots can function as photosensitizers that have the ability to generate reactive oxygen species such as singlet oxygen, hydroxy (OH) radicals, and superoxide ions. However, most of these can only be generated upon ultraviolet light excitation. Additionally, the mechanism of reactive oxygen species generation by carbon nanodots remains unclear. The development of carbon nanodots that can photosensitize under visible light irradiation is desirable for applications such as photodynamic therapy and pollutant decomposition under visible light. Here, we report novel carbon nanodot-based photosensitizers that generate reactive oxygen species under visible light; they were synthesized using a solvothermal method with two solvents (formamide and water) and amidol as the carbon source. Carbon nanodots from the solvothermal synthesis in formamide showed blue fluorescence, while those obtained in water showed green fluorescence. The photo-excited blue-fluorescent carbon nanodots produced OH radicals, superoxide ions, and singlet oxygen, and therefore could function as both type I and type II photosensitizers. In addition, photo-excited green-fluorescent carbon nanodots generated only singlet oxygen, therefore functioning as type II photosensitizers. It is proposed that the two photosensitizers have different origins of reactive oxygen species generation: the enrichment of graphitic N for blue-fluorescent carbon nanodots and molecular fluorophores for green-fluorescent carbon nanodots.