Correction to Ion-Selective Nanosensor for Photoacoustic and Fluorescence Imaging of Potassium

Anal. Chem. 2017, 89, 7943–7949. DOI:10.1021/acs.analchem.7b00930

There were some typos regarding subscripts in the experimental section (page 7945 of the original manuscript) and in the Y-axis legend of Figure 5.

Figure 5.

Optical and sensing properties of NIR-K+ NS. (a) Schematic of NIR-K⁺ NS preparation. (b) Absorption spectra of NIR K⁺ NS at different K⁺ concentrations (10 μM to 1 M). (c) Calibration curve of K⁺ NS with protonation degree vs log potassium concentration, by using the peak intensity ratios of the sensing 660 nm absorbance and the reference 800 nm absorbance of the NIR-K⁺ NS, in a pH 7.4 Tris buffer.³ (d) Fluorescence emission spectra (540 nm excitation/660 nm emission) of NIR K⁺ NS at different K⁺ concentrations (10 μM to 1 M). The spectra were normalized by potassium independent NIR fluorescence (760 nm excitation/820 nm emission, data not shown). (e) Calibration curve of K⁺ NS with deprotonation degree vs log potassium concentration, by using the potassium-dependent sensing emission (620–700 nm emission) and potassium-independent reference emission (800–840 nm emission) of the NIR-K⁺ NS, in a pH 7.4 Tris-buffer.³

The degree of protonation for NIR-K⁺ NS (eq 2) was mistakenly defined as $\pi =1-\alpha =\frac{R-R_{max}}{R_{max}-R_{min}}$. The calibration curves (Figure 5c,e) were actually correctly generated with $\pi =1-\alpha =\frac{R-R_{min}}{R_{max}-R_{min}}$, where we defined R as the ratio of the sensing signal over the reference signal, R_min as ratio of the minimum sensing signal and reference signal, and R_max as ratio of the maximum sensing signal and reference signal.

For the absorption based calibrations of NIR-K⁺ NS in the experimental section (page 7945 of the original manuscript), R_max was incorrectly defined as A_{660 nm at 1 M KCl}/A_{800 nm at 1 M KCl}, and R_min as A_{660 nm at 10 μM KCl}/A_{800 nm at 10 μM KCl}. The calibration curve (Figure 5c) was actually generated using R_max as A_{660 nm at 10 μM KCl}/A_{800 nm at 10 μM KCl}, and R_min as A_{660 nm at 1 M KCl}/A_{800 nm at 1 M KCl} because the 660 nm absorption of the sensor is at its maximum at the lowest potassium concentration (10 μM) and at its minimum at the highest potassium concentration (1 M).

We also note that for the fluorescence based calibrations, our chosen sensing peak is the 540 nm excitation (following an opposite trend to absorption at 660 nm), which is related to the chromoionophore’s deprotonation signal (in comparison to the chromoionophore’s protonation signal, the 660 nm absorption). The y-axis label of Figure 5e has to be corrected to “Deprotonation Degree (660 nm:820 nm)” instead of “Protonation Degree (660 nm:820 nm)”. Thus, Figure 5c,e are complementary rather than identical. The slightly corrected figure (inserting Deprotonation) is presented here.