Single Excited Dual Band Luminescent Hybrid Carbon Dots-Terbium Chelate Nanothermometer

Easy Synthesis and Characterization of Novel Carbon Dots Using the One-Pot Green Method for Cancer Therapy

In this study, hyaluronic acid (HA) and carboxymethyl chitosan (CMCS) were used for the synthesis of novel targeted nanocarrier carbon dots (CDC-H) with photo-luminescence using a one-step hydrothermal method. Doxorubicin (DOX), a common chemotherapeutic agent, was loaded with the CDC-H through electrostatic interactions to form DOX-CDC-H complexes as a targeted antitumor drug delivery system. The synthesized CDC-H show a particle size of approximately 6 nm and a high fluorescence quantum yield of 11.64%. The physical and chemical character properties of CDC-H and DOX-CDC-H complexes were investigated using various techniques. The results show that CDC-H have stable luminescent properties and exhibit excellent water solubility. The in vitro release study showed that DOX-CDC-H exhibited pH-dependent release for 24 h. Confocal laser scanning microscopy was applied to investigate the potential of CDC-H for cell imaging and the cellular uptake of DOX-CDC-H in different cells (NIH-3T3 and 4T1 cells), and the results confirmed the target cell imaging and cellular uptake of DOX-CDC-H by specifically binding the CD44 receptors on the surface of tumor cells. The r MTT results suggest that the DOX-CDC-H complex may induce apoptosis in 4T1 cells, reducing the cytotoxicity of free DOX-induced apoptosis. In vivo antitumor experiments of DOX-CDC-H exhibited enhanced tumor cancer therapy. CDC-H have potential applications in bioimaging and antitumor drug delivery.

High-Efficiency Utilization of Waste Tobacco Stems to Synthesize Novel Biomass-Based Carbon Dots for Precise Detection of Tetracycline Antibiotic Residues

Recycling waste biomass into valuable products (e.g., nanomaterials) is of considerable theoretical and practical significance to achieve future sustainable development. Here, we propose a one-pot hydrothermal synthesis route to convert waste tobacco stems into biomass-based N, S-codoped carbon dots (C-dots) with the assistance of carbon black. Unlike most of the previously reported luminescent C-dots, these biomass-based C-dots showed a satisfactory stability, as well as an excitation-independent fluorescence emission at ~520 nm. Furthermore, they demonstrated a pH-dependent fluorescence emission ability, offering a scaffold to design pH-responsive assays. Moreover, these as-synthesized biomass-based C-dots exhibited a fluorescence response ability toward tetracycline antibiotics (TCs, e.g., TC, CTC, and OTC) through the inner filter effect (IFE), thereby allowing for the establishment a smart analytical platform to sensitively and selectively monitor residual TCs in real environmental water samples. In this study, we explored the conversion of waste tobacco stems into sustainable biomass-based C-dots to develop simple, efficient, label-free, reliable, low-cost, and eco-friendly analytical platforms for environmental pollution traceability analysis, which might provide a novel insight to resolve the ecological and environmental issues derived from waste tobacco stems.

Passivator-Free Microwave–Hydrothermal Synthesis of High Quantum Yield Carbon Dots for All-Carbon Fluorescent Nanocomposite Films

Based on the self-passivation function of chitosan, an efficient, and green synthesis strategy was applied to prepare chitosan carbon dots (CDs). The quantum yield of carbon dots reached 35% under the conditions of hydrothermal temperature of 200 °C, hydrothermal time of 5 h, and chitosan concentration of 2%. Moreover, the obtained carbon dots had high selectivity and sensitivity to Fe3+. Based on the Schiff base reaction between the aldehyde groups of dialdehyde cellulose nanofibrils (DNF) and the amino groups of CDs, a chemically cross-linked, novel, fluorescent composite film, with high transparency and high strength, was created using one-pot processing. Knowing that the fluorescence effect of the composite film on Fe3+ had a linear relationship in the concentration range of 0–100 μM, a fluorescent probe can be developed for quantitative analysis and detection of Fe3+. Owing to their excellent fluorescent and mechanical properties, the fluorescent nanocomposite films have potential applications in the fields of Fe3+ detection, fluorescent labeling, and biosensing.

A Review on Carbon Dots: Synthesis, Characterization and Its Application in Optical Sensor for Environmental Monitoring

The development of carbon dots (CDs), either using green or chemical precursors, has inevitably led to their wide range application, from bioimaging to optoelectronic devices. The reported precursors and properties of these CDs have opened new opportunities for the future development of high-quality CDs and applications. Green precursors were classified into fruits, vegetables, flowers, leaves, seeds, stem, crop residues, fungi/bacteria species, and waste products, while the chemical precursors were classified into acid reagents and non-acid reagents. This paper quickly reviews ten years of the synthesis of CDs using green and chemical precursors. The application of CDs as sensing materials in optical sensor techniques for environmental monitoring, including the detection of heavy metal ions, phenol, pesticides, and nitroaromatic explosives, was also discussed in this review. This profound review will offer knowledge for the upcoming community of researchers interested in synthesizing high-quality CDs for various applications.

Role of PSS-based assemblies in stabilization of Eu and Sm luminescent complexes and their thermoresponsive luminescence

The present work introduces self-assembled polystyrenesulfonate (PSS) molecules as soft nanocapsules for incorporation of Eu³⁺-Sm³⁺ complexes by the solvent exchange procedure. The high levels of Eu³⁺- and Sm³⁺-luminescence of the complexes derives from the ligand-to-metal energy transfer, in turn, resulted from the complex formation of Eu³⁺and Sm³⁺ ions with the three recently synthesized cyclophanic 1,3-diketones. The structural features of the ligands are optimized for the high thermal sensitivity of Eu³⁺- luminescence in DMF solutions. The PSS-nanocapsules (∼100 nm) provide both colloid and chemical stabilization of the ultrasmall (3-5 nm) nanoprecipitates of the complexes, although their luminescence spectra patterns and excited state lifetimes differ from the values measured for the complexes in DMF solutions. The specific concentration ratio of the Eu³⁺-Sm³⁺ complexes in the DMF solutions allows to tune the intensity ratio of the luminescence bands at 612 and 650 nm in the heterometallic Eu³⁺-Sm³⁺ colloids. The thermal sensitivity of the Eu³⁺- and Sm³⁺-luminescence of the complexes derives from the static quenching both in PSS-colloids and in DMF solutions, while the thermo-induced dynamic quenching of the luminescence is significant only in DMF solutions. The reversibility of thermo-induced luminescence changes of the Eu³⁺-Sm³⁺ colloids is demonstrated by six heating-cooling cycles. The DLS measurements before and after the six cycles reveal the invariance of the PSS-based capsule as the prerequisite for the recyclability of the temperature monitoring through the ratio of Eu³⁺-to- Sm³⁺ luminescence.

Graphene Quantum Dots and Phthalocyanines Turn-OFF-ON Photoluminescence Nanosensor for ds-DNA

Supramolecular hybrids of graphene quantum dots (GQDs) and phthalocyanine (Pc) dyes were studied as turn-OFF-ON photoluminescence nanosensors for detection of ds-DNA. Pcs with four (Pc4) and eight (Pc8) positive charges were selected to interact with negatively charged GQDs. The photoluminescence of the GQDs was quenched upon interaction with the Pcs, due to the formation of non-emissive complexes. In the presence of ds-DNA, the Pcs interacted preferentially with the negatively charged ds-DNA, lifting the quenching effect over the photoluminescence of the GQDs and restoring their emission intensity. The best performance as a sensor of ds-DNA was registered for the GQD-Pc8, with a limit of detection (LOD) in the picomolar range. The LOD for GQD-Pc8 was more than one order of magnitude lower and its sensitivity was about a factor of three higher than that of the analogue GQD-Pc4 nanosensor. The sensitivity and selectivity of this simple GQD-Pc8 nanosensor is comparable to those of the more sophisticated carbon-based nanosensors for DNA reported previously.

Facile and Green Synthesis of Highly Fluorescent Carbon Quantum Dots from Water Hyacinth for the Detection of Ferric Iron and Cellular Imaging

Natural biomass is used for facile synthesis of carbon quantum dots (CQDs) with high fluorescence, owing to its abundance, low cost, and eco-friendliness. In this study, a bottom-up hydrothermal method was used to prepare CQDs from water hyacinth (wh) at a constant temperature of 180 °C for 12 h. The synthesized wh-CQDs had uniform size, amorphous graphite structure, high water solubility (containing multiple hydroxyl and carboxyl groups on the surface), excitation light-dependent characteristics, and high photostability. The results showed that the aqueous solution of CQDs could detect Fe³⁺ rapidly, sensitively, and highly selectively with a detection limit of 0.084 μM in the linear range of 0–330 μM, which is much lower than the detection limit of 0.77 μM specified by the World Health Organization. More importantly, because the wh-CQDs were synthesized without any additives, they exhibited low toxicity to Klebsiella sp. cells even at high concentrations. Moreover, wh-CQDs emitted bright blue fluorescence in Klebsiella sp. cells, indicating its strong penetrating ability. Correspondingly, the fluorescent cell sorting results also revealed that the proportion of cell internalization reached 41.78%. In this study, wh-CQDs derived from natural biomass were used as high-performance fluorescent probes for Fe³⁺ detection and Klebsiella sp. imaging. This study is expected to have great significance for the application of biomass carbon spots in the field of cellular imaging and biology.

The Role of N and S Doping on Photoluminescent Characteristics of Carbon Dots from Palm Bunches for Fluorimetric Sensing of Fe3+ Ion

This work aims to enhance the value of palm empty fruit bunches (EFBs), an abundant residue from the palm oil industry, as a precursor for the synthesis of luminescent carbon dots (CDs). The mechanism of fIuorimetric sensing using carbon dots for either enhancing or quenching photoluminescence properties when binding with analytes is useful for the detection of ultra-low amounts of analytes. This study revealed that EFB-derived CDs via hydrothermal synthesis exceptionally exhibited luminescence properties. In addition, surface modification for specific binding to a target molecule substantially augmented their PL characteristics. Among the different nitrogen and sulfur (N and S) doping agents used, including urea (U), sulfate (S), p-phenylenediamine (P), and sodium thiosulfate (TS), the results showed that PTS-CDs from the co-doping of p-phenylenediamine and sodium thiosulfate exhibited the highest PL properties. From this study on the fluorimetric sensing of several metal ions, PTS-CDs could effectively detect Fe3+ with the highest selectivity by fluorescence quenching to 79.1% at a limit of detection (LOD) of 0.1 µmol L−1. The PL quenching of PTS-CDs was linearly correlated with the wide range of Fe3+ concentration, ranging from 5 to 400 µmol L−1 (R2 = 0.9933).

Rapid Preparation of Fluorescent Carbon Dots from Pine Needles for Chemical Analysis

Fluorescent carbon dots with blue, green, and red emissions were rapidly prepared from modified pine needles through microwave irradiation in a one-pot reaction. The fluorescence intensity and emission versatility for a carbon source were experimentally optimized. The reaction times were under 10 min and the reaction temperatures were lower than 220 °C. Potential applications of magnetic fluorescence-linked immunoassays of carcinoembryonic antigen (CEA) and tumor necrosis factor-alpha (TNF-α) were presented. The detection limits for CEA and TNF-α (3.1 and 2.8 pg mL^-1, respectively) are lower than those presented in other reports, whereas the linear ranges for CEA and TNF-α (9 pg mL^-1 to 18 ng mL^-1 and 8.5 pg mL^-1 to 17 ng mL^-1, respectively) are wider than those presented in other reports. Magnetic immunoassays with fluorescent CD_s prepared from pine needles can enable rapid, sensitive, and selective detections for biochemical analysis.