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[Display omitted] • Multifunctional CDs were prepared hydrothermally from eco-friendly Coccinia Grandis. • EC-Dots exhibited uniform globular shape with an average size of 4 nm (QY of 17 %). • EC-Dots emit bright fluorescence that is dependent on the excitation wavelength. • The current research provided a new platform in the field of bioimaging. • Also, the EC-Dots are a versatile component in various types of fluorescent ink. This study adopted an eco-friendly approach for the one-step hydrothermal conversion of sustainable Coccinia grandis into well-dispersed, uniform-sized carbon dots. The resulting eco-friendly carbon dots (EC-Dots) were harnessed for bioimaging and fluorescent ink applications. EC-Dots exhibited an average size of 4 nm. Further, cytotoxicity assessments on live nematodes revealed cell viability > 95 %. In-vivo studies showed excellent uptake and their ability to emit light in multiple colors, including blue, green, and red, achieved by adjusting the excitation wavelength. Additionally, the EC-Dots exhibited robust fluorescence in aqueous solutions and exceptional resistance to photobleaching, rendering them highly effective for generating fluorescent ink for drawing and writing. Thus, this research showcases an environmentally sustainable, cost-effective, and straightforward hydrothermal method for creating biocompatible EC-Dots with diverse hydrophilic properties. These synthesized EC-Dots stand as a promising platform for applications in fluorescent ink and in vivo bioimaging, offering a high level of safety with minimal cytotoxicity. [ABSTRACT FROM AUTHOR]

A hydrothermal synthetic approach is developed for the preparation of graphitic carbon nitride quantum dots (g-C 3 N 4 QDs) from human urine. The reported synthetic method is green, simple, low-cost, less time-consuming, and can be used for the large-scale production of the g-C 3 N 4 QDs. The as-prepared g-C 3 N 4 QDs possess a high quantum yield of 15.7% by using quinine sulfate as a reference, and display excitation-wavelength dependent fluorescent emission. In addition, the g-C 3 N 4 QDs exhibit high photostability, low cytotoxicity. and are successfully used as fluorescent probes for cell multicolor imaging. It is believed that the valuable nanomaterials, g-C 3 N 4 QDs, which are transformed from the human bodily wastes, are promising in diverse chemical applications. [ABSTRACT FROM AUTHOR]

Diethylenetriamine-β-cyclodextrin (3N-β-CD)-modified carbon quantum dots were synthesized for the first time via a one-step hydrothermal method using citric acid as the carbon source and diethylenetriamine-β-cyclodextrin as the nitrogen source. The synthesized carbon quantum dots were used as fluorescent probes for the selective detection of Hg2+ and Fe3+ in an aqueous solution and live cell imaging application on Hela cancer cell line. [Display omitted] • 3 N -CQDs were synthesized readily using citric acid as the carbon source by hydrothermal method. • The 3 N -CQDs showed a favorable fluorescence performance towards Hg2+ and Fe3+ detection. • Cytotoxicity assay indicated that the 3 N -CQDs had extremely low cytotoxicity. • The 3 N -CQDs showed good biocompatibility and bioimaging property in the cell imaging. Diethylenetriamine-β-cyclodextrin-modified carbon quantum dots (3 N -CQDs) were synthesized via a one-step hydrothermal method using citric acid as the carbon source and diethylenetriamine-β-cyclodextrin (3 N-β-CD) as the nitrogen source. The successful preparation of 3 N -CQDs were revealed by infrared absorption spectroscopy, ultraviolet (UV)-visible absorption spectroscopy, fluorescence spectroscopy, XRD, XPS, TEM, and TG. Further spectroscopic studies showed that the synthesized carbon quantum dots offered good anti-interference capability. The relative fluorescence quantum yield was 67.2 %. The limits of detection for Hg2+ and Fe3+ were 0.25 µM and 0.57 μM, respectively. Cytotoxicity and imaging studies showed that the prepared carbon quantum dots had low cytotoxicity, good biocompatibility, and good cellular imaging capability for HeLa cells. They offered fluorescent sensing of Hg2+ and Fe3+ in live cells. Therefore, 3 N -CQDs were ideal fluorescent probes for the detection of Hg2+ and Fe3+ in water. [ABSTRACT FROM AUTHOR]

[Display omitted] • Switchable two-color graphene quantum dot was designed and synthesized by via one-step pyrolysis. • Synergy of histidine, serine, pentaethylenehexamine and boron realizes unique optical behavior. • Two-color fluorescence emissions can be sensitively switched by varying excitation wavelength. • The optical probe was successfully applied in pH detection and bioimaging with high sensitivity. • The study provides approach for design and synthesis of various functional graphene quantum dots. Graphene quantum dots have been widely applied in biosensing, fluorescence imaging, biomedicine, energy storage and conversion and catalysis, but design and synthesis of polychromatic graphene quantum dot with high luminous efficiency still faces great challenges. The study reports synthesis of histidine, serine and pentaethylenehexamine-functionalized and boron-doped graphene quantum dot (HSPB-GQD) via one-step pyrolysis. The resulting HSPB-GQD consists of graphene sheets of 2–5 nm with carboxyl, hydroxyl, amino, imino and imidazole. Synergy of histidine, serine, pentaethylenehexamine and boron atoms improves the luminescence behavior. This realizes unique switchable two-color luminescence. UV excitation of 370 nm produces one strong blue fluorescence with the maximum emission wavelength of 455 nm and quantum yield of 72.34%. Vis. excitation of 480 nm produces one strong yellow fluorescence with the maximum emission wavelength of 560 nm and quantum yield of 72.59%. The multiple proton dissociation system constructed by nitrogen-containing and oxygen-containing groups makes yellow fluorescence sensitive to environmental pH value. The intensity linearly increases with increasing pH in the range of 4.5–10.0. Organic molecules and inorganic ions do not interfere pH detection. HSPB-GQD as a promising fluorescence probe with negligible effect on cell viability was successfully applied to pH detection in biological and environmental water samples and cell imaging. [ABSTRACT FROM AUTHOR]

[Display omitted] • The N-CQDs were synthesized by a simple and economical one-pot hydrothermal method. • The prepared N-CQDs possess an ultra-high quantum yield (92.1%). • N-CQDs shows promising applications in sensing, bioimaging and anti-counterfeiting. The exploration of carbon quantum dots (CQDs) with ultra-high quantum yield, simple synthesis path, and satisfying output to facilitate their wide applications in numerous fields are always the research focus. In this work, nitrogen-doped carbon quantum dots (N-CQDs) with strong blue fluorescence were synthesized with a simple one-step hydrothermal method using citric acid and o-phenylenediamine as raw materials, and the absolute quantum yield was as high as 92.1%. The detailed research results demonstrate that the N-CQDs have outstanding fluorescence stability, high selectivity, and anti-interference in Hg2+ detection. The obtained N-CQDs also possess excellent biocompatibility, which can also be successfully applied in cell imaging and intracellular Hg2+ detection. Most importantly, due to their high quantum yield and excellent dispersibility, the N-CQDs solution can be used as a quick-drying fluorescent ink for ink-jet printing. Therefore, the as-prepared N-CQDs have great potential in fluorescence sensing, biomedical diagnosis, data encryption, and anti-counterfeiting. [ABSTRACT FROM AUTHOR]

• His-GQDs synthesized via pyrolysis green-synthesis route. • His-GQDs were used for cellular imaging of ACHN cell lines as a novel bright green fluorescence probe. • This is the first reported of label-free, selective and non-toxic fluorescence probe for cellular imaging of ACHN cell lines. • Cellular imaging was achieved successfully show that His-GQDs can be easily penetrated into cytoplasm. In this study, bright green-luminescent probe (His-GQDs) were synthesized using a new one-pot "bottom-up" pyrolysis green-synthesis route, without consuming any water and chemical reagent. Citric acid as carbon source and Histidine as amino-functionalized agent, with optimized ratios, were used for fabricating His-GQDs as a novel, label-free, and selective probe. His-GQDs can be then used for cellular imaging of human ACHN cell lines that are composed of graphene sheets with the average size of 2.0 nm. Obtained His-GQDs probe has ultra-small size, low toxicity, chemical stability, biocompatibility, anti-photo bleaching and excellent optical properties with a rather high quantum yield of 62.8%. The detailed structural studies were confirmed by FT-IR, HR-TEM and powdered X-ray diffraction analysis respectively. In this project, the His-GQDs were utilized for cellular imaging of human ACHN cell lines for the first time. This probe indicated the presence desired biocompatibility of His-GQDs in human ACHN cell lines even at high their concentration (1800 µg mL−1) at 24 h post-treatment and their distribution in ACHN cell lines cytoplasm. [ABSTRACT FROM AUTHOR]

The carbon quantum dot (CQD), a fluorescent carbon nanoparticle, has attracted considerable interest due to its photoluminescent property and promising applications in cell imaging and bioimaging. In this work, biocompatible, photostable, and sustainably sourced CQDs were synthesized from byproducts derived from a biorefinery process using one-pot hydrothermal treatment. The main components of byproducts were the degradation products (autohydrolyzate) of biomass pretreated by autohydrolysis. The as-synthesized CQDs had a size distribution from 2.0–6.0 nm and had high percentage of sp2 and sp3 carbon groups. The CQDs showed blue-green fluorescence with a quantum yield of ~13%, and the fluorescence behaviors were found to be stable with strong resistance to photobleaching and temperature change. In addition, it is found that the as-synthesized CQDs could be used for imaging of cells and tumors, which show potential applications in bioimaging and related fields such as phototherapy and imaging. [ABSTRACT FROM AUTHOR]