RESUMO
Carbon dots are emerging fluorescent nanomaterials with unique physical and chemical properties and a wide range of applications. Herein, we have designed and successfully synthesized thermally stable green emissive nitrogen-doped carbon dots (NCDs) with a photoluminescent quantum yield of 11.32% through facile solvent-free carbonization. NCDs demonstrated zero thermal quenching upon various temperatures modulating from 20 to 80 °C. The green emissive NCDs perform very stably even after heating them at 80 °C for 1 h. The thermal stability mechanism demonstrates that CâO and CâN functional groups control the particle aggregation and protect the fluorescent hub from photo-oxidation and thermal oxidation. Highly biocompatible CDs exhibit bright, stable, and multicolor emissions in T-ca cells under hot circumstances (25-45 °C). Additionally, NCDs offer long-term stability in the biosystem, as evidenced by the fact that the cell retains its brightness about 70% after prolonging the incubation time to 8 days. Furthermore, the fluorescent NCDs are utilized as in vivo imaging agents in the hot environment as they display bright and thermally stable imaging (27-45 °C) under 488 nm excitation. The results confirmed that the produced thermally stable NCDs could be used in biology and related medical fields that require hot environment imaging.
RESUMO
High stability and water solubility of fluorescent nanomaterials are considered key factors to evaluate their feasibility for fundamental applications. Herein, water-soluble and thermally stable, green-emitting carbon nanodots (CNDs) have been synthesized via a facile hydrothermal method with an average size of 1.9 nm. CNDs showed green emission centered at 544 nm with the photo-luminescence quantum yield (PLQY) of up to 10.1% under the excitation of 400 nm. The obtained CNDs demonstrated high resistance towards photo-bleaching and an ionic (KCl) environment. Moreover, the aqueous solution of CNDs exhibited excellent stability under harsh thermal conditions from 10 °C to 80 °C. The as-prepared CNDs showed stable performance at high temperatures, even after keeping them at 80 °C for 30 min. Furthermore, the green emissive CNDs were incubated in T-ca cancer cells for bio-imaging applications. The results indicated that CNDs can served as an effective thermally-stable bio-imaging agent in T-ca cells at the physiological temperature range of 25 °C-45 °C. Green emission and excellent thermal stability make these CNDs promising fluorescent materials for potential applications in the medical field, which requires long-wavelength fluorescence and high-temperature imaging.
Assuntos
Carbono , Nanoestruturas , Corantes , Microscopia de Fluorescência , ÁguaRESUMO
Fluorescent sensing of temperature in nanoscale regions has many advantages and applications in the biological field. Herein, blue emitting carbon dots (CDs) are designed and successfully developed using a one step hydrothermal method. As synthesized CDs exhibit temperature dependent photoluminescent (PL) intensity and PL decay lifetime over the physiological temperature ranging from room temperature (RT) to 70 °C. The PL intensity and PL decay lifetime of the obtained CDs correlate linearly to temperature (RT-70 °C) with correlation coefficient of 0.997 and 0.996, respectively. Additionally, dual mode thermal sensing (PL intensity/lifetime) make these CDs a promising optical nanothermometer over alternative semiconductors quantum dots and CD-based quantum dots. Moreover, the resultant aqueous CDs demonstrate excitation-independent blue emission, and the PL quantum yield (QY) is reached at 44.5%. The obtained CDs illustrate stable performance to high ionic environments and photobleaching even after keeping them for 2 h under continues UV irradiation. Furthermore, blue emitting CDs have low cytotoxicity for T-ca. cells and illuminate deep blue fluorescence under the excitation of 406 nm. As a result, high thermal sensitivity of these fluorescent CDs has potential to detect temperature in living cells in the range of 25-40 °C.
