Carbon dots: synthesis, formation mechanism, fluorescence origin and sensing applications

The rapid evolution of consumer electronics means that out-of-date devices quickly end up in the scrap heap. Here, the authors fabricate electrical components using biodegradable and flexible cellulose nanofibril paper—a natural sustainable resource derived from wood.

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High-performance green flexible electronics based on biodegradable cellulose nanofibril paper

From waste plastics to industrial raw materials: A life cycle assessment of mechanical plastic recycling practice based on a real-world case study.

In recent years, nano carbon quantum dots (CQDs) have received increasing attention due to their properties such as small size, fluorescence emission, chemical stability, water solubility, easy synthesis, and the possibility of functionalization. CQDs are fluorescent 0D carbon nanostructures with sizes below 10 nm. The fluorescence in CQDs originates from two sources, the fluorescence emission from bandgap transitions of conjugated π-domains and fluorescence from surface defects. The CQDs can emit fluorescence in the near-infrared (NIR) spectral region which makes them appropriate for biomedical applications. The fluorescence in these structures can be tuned with respect to the excitation wavelength. The CQDs have found applications in different areas such as biomedicine, photocatalysis, photosensors, solar energy conversion, light emitting diodes (LEDs), etc. The biomedical applications of CQDs include bioimaging, drug delivery, gene delivery, and cancer therapy. The fluorescent CQDs have low toxicity and other exceptional physicochemical properties in comparison to heavy metals semiconductor quantum dots (QDs) which make them superior candidates for biomedical applications. In this review, the synthesis routes and optical properties of the CQDs are clarified and recent advances in CQDs biomedical applications in bioimaging (in vivo and in vitro), drug delivery, cancer therapy, their potential to pass blood–brain barrier (BBB), and gene delivery are discussed.

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Carbon quantum dots and their biomedical and therapeutic applications: a review

Insight into the design of defect electrocatalysts: From electronic structure to adsorption energy

Carbon quantum dots (CQDs) have emerged as potential alternatives to classical metal-based semiconductor quantum dots (QDs) due to the abundance of their precursors, their ease of synthesis, high biocompatibility, low cost, and particularly their strong photoresponsiveness, tunability, and stability. Light is a versatile, tunable stimulus that can provide spatiotemporal control. Its interaction with CQDs elicits interesting responses such as wavelength-dependent optical emissions, charge/electron transfer, and heat generation, processes that are suitable for a range of photomediated bioapplications. The carbogenic core and surface characteristics of CQDs can be tuned through versatile engineering strategies to endow specific optical and physicochemical properties, while conjugation with specific moieties can enable the design of targeted probes. Fundamental approaches to tune the responses of CQDs to photo-interactions and the design of bionanoprobes are presented, which enable biomedical applications involving diagnostics and therapeutics. These strategies represent comprehensive platforms for engineering multifunctional probes for nanomedicine, and the design of QD probes with a range of metal-free and emerging 2D materials.

Engineering carbon quantum dots for photomediated theranostics

Mechanical and thermal properties of date palm leaf fiber reinforced recycled poly (ethylene terephthalate) composites

Collagen derived carbon quantum dots for cell imaging in 3D scaffolds via two-photon spectroscopy

Two-photon excitation triggers combined chemo-photothermal therapy via doped carbon nanohybrid dots for effective breast cancer treatment

Ferric ions play significant roles in human bodily functions, since both overload and deficiency can cause major physiological dysfunctions. Hence, engineering of sensitive, selective sensors to detect such ions merits attention. We found that certain CDs derived from a nitrogen-containing precursor (phthalocyanine) in suitable media could provide significant advantages. Excitation-independent carbon dots (CDs) were prepared through facile one-pot hydrothermal (W-CDs) and solvothermal (E-CDs) methods. Compared to W-CDs, ethanol-mediated E-CDs provide narrower particle size distribution, higher pyrrolic and pyridinic N-content, higher quantum yield ( Q Y E - C D s / Q Y W - C D s = 2.58), strong green luminescence, excellent biocompatibility and efficient two-photon absorption. The E-CDs enabled superior NIR excitable two-photon bioimaging of breast cancer cells at variable depths and fluorescence quenching (81% extinction) for 10–600 μM Fe3+ ions. The mechanism of sensing was elucidated based on the fluorescence lifetime and the Stern-Volmer formalism. Intracellular Fe3+ ion sensing was first confirmed with E-CDs for lysed MCF-7 cells and quenching was detected in direct proportion to Fe3+ concentration (0–80 μM test range) with an LOD of 10.8 nM. Next, MCF-7 cells supplemented with variable concentrations of Fe3+ were incubated with E-CDs for sensing intracellular Fe3+ in live cells. The E-CDs showed high sensitivity for sensing endogenous Fe3+ ions in a stress-induced cell-based model.

Alireza Dehghani

Papers

Engineering carbon quantum dots for photomediated theranostics

Mechanical and thermal properties of date palm leaf fiber reinforced recycled poly (ethylene terephthalate) composites

Collagen derived carbon quantum dots for cell imaging in 3D scaffolds via two-photon spectroscopy

Two-photon excitation triggers combined chemo-photothermal therapy via doped carbon nanohybrid dots for effective breast cancer treatment

Excitation-independent carbon dot probes for exogenous and endogenous Fe3+ sensing in living cells: Fluorescence lifetime and sensing mechanism