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Here, we report an environmentally friendly fabrication strategy of bright yellow fluorescent carbon dots (y-CDs) and construct a rapid and accurate multifunctional sensing platform for the effective detection of temperature and Cu2+. The y-CDs were favorably obtained through a one-step hydrothermal treatment of natural Smilax China for the first time and exhibit long-wavelength emission at 542 nm under an excitation wavelength of 470 nm. Additionally, the obtained y-CDs exhibit superior biocompatibility and distinguished stability under different conditions, and display a respectable fluorescence quantum yield of up to 22.37%. Appealingly, the as-prepared y-CDs were implemented as temperature probes within ranges of 25 °C–40 °C and 45 °C–80 °C. Significantly, based on the static quenching effect, the as-prepared y-CDs were developed as an effective platform for fluorescence sensing of Cu2+, with linear ranges of 0.5 μM–10 μM, 75 μM–225 μM and 250 μM–350 μM, achieving a detection limit of 28 nM. Furthermore, confocal fluorescence imaging of PC12 cells was achieved successfully, which indicated that the as-synthesized y-CDs could visualize Cu2+ fluctuations in living cells.

A multifunctional sensing platform based on bright blue-fluorescent nitrogen-doped carbon dots (N-CDs) has been ingeniously designed for the sensitive determination of Hg2+ and pH. The N-CDs were facilely fabricated via a one-step hydrothermal treatment of citric acid and folic acid with admirable merits including exceptional stability, low toxicity and distinguished biocompatibility. Intriguingly, the obtained N-CDs can be utilized to detect Hg2+ on the basis of the dynamic quenching effect, showing a linear range of 0 μM-400 μM as well as a detection limit of 0.124 μM. In addition, the obtained N-CDs revealed a significant emission enhancement with increasing pH from 4.0 to 10.0 and acquired a good linearity in the pH range of 6.8-7.8. Taking advantage of efficient analysis of Hg2+ and pH in aqueous solution, the as-synthesized N-CDs have been extended to the visualization biosensing platform to timely track Hg2+ and pH in living cells.

Bright blue fluorescent N-doped carbon dots (N-CDs) with satisfactory yield (54%) were successfully fabricated by one-step hydrothermal treatment of astragalus. The obtained N-CDs possessed superior stability, solubility and high resistance to photo bleaching, and can be used as label-free nanosensors for the determination of Fe3+. The quantitative analysis of Fe3+ showed a linear range of 50 to 250 μM with the detection limit as low as 42 nM. Moreover, the as-prepared N-CDs have been used in cellular imaging owing to their distinct merits of simplicity, convenience, fast response and good selectivity towards Fe3+. Besides, the N-CDs could also be further used as fluorescent inks for drawing luminescent patterns.

A multifunctional sensing platform based on bright blue-fluorescent nitrogen-doped carbon dots (N-CDs) has been ingeniously designed for the sensitive determination of Hg2+ and pH. The N-CDs were facilely fabricated via a one-step hydrothermal treatment of citric acid and folic acid with admirable merits including exceptional stability, low toxicity and distinguished biocompatibility. Intriguingly, the obtained N-CDs can be utilized to detect Hg2+ on the basis of the dynamic quenching effect, showing a linear range of 0 μM-400 μM as well as a detection limit of 0.124 μM. In addition, the obtained N-CDs revealed a significant emission enhancement with increasing pH from 4.0 to 10.0 and acquired a good linearity in the pH range of 6.8-7.8. Taking advantage of efficient analysis of Hg2+ and pH in aqueous solution, the as-synthesized N-CDs have been extended to the visualization biosensing platform to timely track Hg2+ and pH in living cells.

Bright blue fluorescent N-doped carbon dots (N-CDs) with satisfactory yield (54%) were successfully fabricated by one-step hydrothermal treatment of astragalus. The obtained N-CDs possessed superior stability, solubility and high resistance to photo bleaching, and can be used as label-free nanosensors for the determination of Fe

Here, we report an environmentally friendly fabrication strategy of bright yellow fluorescent carbon dots (y-CDs) and construct a rapid and accurate multifunctional sensing platform for the effective detection of temperature and Cu2+. The y-CDs were favorably obtained through a one-step hydrothermal treatment of natural Smilax China for the first time and exhibit long-wavelength emission at 542 nm under an excitation wavelength of 470 nm. Additionally, the obtained y-CDs exhibit superior biocompatibility and distinguished stability under different conditions, and display a respectable fluorescence quantum yield of up to 22.37%. Appealingly, the as-prepared y-CDs were implemented as temperature probes within ranges of 25 °C-40 °C and 45 °C-80 °C. Significantly, based on the static quenching effect, the as-prepared y-CDs were developed as an effective platform for fluorescence sensing of Cu2+, with linear ranges of 0.5 μM-10 μM, 75 μM-225 μM and 250 μM-350 μM, achieving a detection limit of 28 nM. Furthermore, confocal fluorescence imaging of PC12 cells was achieved successfully, which indicated that the as-synthesized y-CDs could visualize Cu2+ fluctuations in living cells.

It is a common knowledge that detector fatigue causes a calibration curve to deviate from the preferred linear relationship at the higher concentration end. With the adaptation of an isotopically labeled analog of the analyte as the internal standard (IS), cross-contribution (CC) of the intensities monitored for the ions designating the analyte and the IS can also result in a non-linear relationship at both ends. A novel approach developed to assess 'the extent and the effect of [CC]… in quantitative GC-MS analysis' can be extended (a) to examine whether a specific set of CC values is accurate; and (b) to differentiate whether the observed non-linear calibration curve is caused by detector fatigue or the CC phenomenon. Data derived from the exemplar secobarbital (SB)/SB-d(5) system (as di-butyl-derivatives) are used to illustrate this novel approach. Comparing the non-linear nature of calibration data that are empirically observed to that derived from theoretical calculation (with the incorporation of adjustment resulting from the ion CC phenomenon), supports the conclusions that (a) both CC and detector fatigue contribute significantly to the observed non-linear nature of the calibration curve based on ion-pair m/z 207/212; and (b) detector fatigue is the dominating contributor when the calibration curve is based on ion-pair m/z 263/268.