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Highly pH-responsive sensor based on amplified spontaneous emission coupled to colorimetry

View Article: PubMed Central - PubMed

ABSTRACT

We demonstrated a simple, directly-readable approach for high resolution pH sensing. The method was based on sharp changes in Amplified Spontaneous Emission (ASE) of a Stilbene 420 (ST) laser dye triggered by the pH-dependent absorption of Bromocresol Green (BG). The ASE threshold of BG:ST solution mixtures exhibited a strong dependence on BG absorption, which was drastically changed by the variations of the pH of BG solution. As a result, ASE on-off or off-on was observed with different pH levels achieved by ammonia doping. By changing the concentration of the BG solution and the BG:ST blend ratio, this approach allowed to detect pH changes with a sensitivity down to 0.05 in the 10–11 pH range.

No MeSH data available.


ASE spectra of pristine ST (top), undoped BG:ST solution (middle) and doped BG:ST solution (bottom) for different BG:ST contents: (a) 1:10 under 0.94 kW/pulse pumped, (b) 1:5 under 2.38 kW/pulse pumped, (c) 1:1 under 9.48 kW/pulse pumped.
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f2: ASE spectra of pristine ST (top), undoped BG:ST solution (middle) and doped BG:ST solution (bottom) for different BG:ST contents: (a) 1:10 under 0.94 kW/pulse pumped, (b) 1:5 under 2.38 kW/pulse pumped, (c) 1:1 under 9.48 kW/pulse pumped.

Mentions: The sensor sensitivity is addressed in Fig. 2. Figure 2(a) shows the emission spectra of ST (upper), the undoped mixture with BG:ST = 1:10 ratio (middle) and the same mixture doped with pH = 10.43 ammonia dispersion (down) upon excitation with 0.94 kW/pulse. As observed, ST solutions exhibit sharp ASE peak at wavelength of 420 nm when pumped at energy of 0.94 kW/pulse. In contrast, BG:ST blend solutions exhibit a wide PL spectrum under the same pump energy, i.e., the ASE of ST experience “on” to “off” upon adding BG. Note that the absorbance at 355 nm of BG in mixtures is well below that of ST, suggesting that most of the pumped light is absorbed by ST. Therefore ASE changes are more likely related to re-absorption of ST emitted photons rather than absorption changes at the pumping wavelength. Interestingly, the ASE is recovered upon doping with ammonia (pH = 10.43), i.e, from “off” to “on” keeping constant the pump power, due to the BG absorption maximum shifting away from the ST ASE peak at 420 nm. This means, for a fixed BG:ST content, an off-on ASE response will be triggered upon a certain pH value, without need to increase the excitation power.


Highly pH-responsive sensor based on amplified spontaneous emission coupled to colorimetry
ASE spectra of pristine ST (top), undoped BG:ST solution (middle) and doped BG:ST solution (bottom) for different BG:ST contents: (a) 1:10 under 0.94 kW/pulse pumped, (b) 1:5 under 2.38 kW/pulse pumped, (c) 1:1 under 9.48 kW/pulse pumped.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5384246&req=5

f2: ASE spectra of pristine ST (top), undoped BG:ST solution (middle) and doped BG:ST solution (bottom) for different BG:ST contents: (a) 1:10 under 0.94 kW/pulse pumped, (b) 1:5 under 2.38 kW/pulse pumped, (c) 1:1 under 9.48 kW/pulse pumped.
Mentions: The sensor sensitivity is addressed in Fig. 2. Figure 2(a) shows the emission spectra of ST (upper), the undoped mixture with BG:ST = 1:10 ratio (middle) and the same mixture doped with pH = 10.43 ammonia dispersion (down) upon excitation with 0.94 kW/pulse. As observed, ST solutions exhibit sharp ASE peak at wavelength of 420 nm when pumped at energy of 0.94 kW/pulse. In contrast, BG:ST blend solutions exhibit a wide PL spectrum under the same pump energy, i.e., the ASE of ST experience “on” to “off” upon adding BG. Note that the absorbance at 355 nm of BG in mixtures is well below that of ST, suggesting that most of the pumped light is absorbed by ST. Therefore ASE changes are more likely related to re-absorption of ST emitted photons rather than absorption changes at the pumping wavelength. Interestingly, the ASE is recovered upon doping with ammonia (pH = 10.43), i.e, from “off” to “on” keeping constant the pump power, due to the BG absorption maximum shifting away from the ST ASE peak at 420 nm. This means, for a fixed BG:ST content, an off-on ASE response will be triggered upon a certain pH value, without need to increase the excitation power.

View Article: PubMed Central - PubMed

ABSTRACT

We demonstrated a simple, directly-readable approach for high resolution pH sensing. The method was based on sharp changes in Amplified Spontaneous Emission (ASE) of a Stilbene 420 (ST) laser dye triggered by the pH-dependent absorption of Bromocresol Green (BG). The ASE threshold of BG:ST solution mixtures exhibited a strong dependence on BG absorption, which was drastically changed by the variations of the pH of BG solution. As a result, ASE on-off or off-on was observed with different pH levels achieved by ammonia doping. By changing the concentration of the BG solution and the BG:ST blend ratio, this approach allowed to detect pH changes with a sensitivity down to 0.05 in the 10–11 pH range.

No MeSH data available.