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Optical Chemical Sensor Using Intensity Ratiometric Fluorescence Signals for Fast and Reliable pH Determination
摘要： Optical pH sensors enable non-invasive monitoring of pH, yet in pure sensing terms, the potentiometric method of measuring pH is still vastly superior. Here, we report a full spectrometer-based optical pH sensor system consisting of sensor chemistry, hardware and software that for the first time is capable of challenging the performance of electrode-based pH meter in specific applications such as biopharmaceutical process monitoring and in single-use bioproduction. A highly photostable triangulenium fluorophore emitting at 590 nm was immobilized in an organically modified silicon matrix that allows for fast time-response by rapid diffusion of water in and out of the resulting composite polymer deposited on a polycarbonate substrate. Fluctuations from the fiber optical sensor hardware have been reduced by including a highly photostable terrylene-based reference dye emitting at 660 nm, thus enabling intensity-based ratiometric readouts. The dyes were excited by 505 nm light from a light emitting diode. The sensor was operational within a pH range of 4.6 and 7.6, and was characterized and demonstrated to have properties that are comparable to commercial pH electrodes considering time-response (t90 < 90 s), precision (0.03 pH-units) and drift.
关键词： ORMOSIL,optical pH sensors,pH optode,chemical sensors,ratiometric
更新于2025-09-23 15:23:52
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Time-resolved photoluminescence of pH-sensitive carbon dots
摘要： Time-resolved photoluminescence emission were performed to study the ? 100 ps time-scale photophysics of water soluble carbon dots (CDs) dispersed in different pH solutions. Excitation of the core and high-energy edge states at excitation wavelengths λex ￡ 350 nm produce hole-electron excitonic charge-carriers but do not yield any photoluminescence emission, implying efficient non-radiative recombination mechanisms for the charge-carriers. Using λex ~ 375 nm, surface fluorophores as well as low-lying edge-states are excited, producing emission over a broad range. However, the emission characteristics vary strongly depending on the pH condition and the choice of excitation wavelength. In particular, the edge state emission is abruptly extinguished at pH ≥ 5, which also marks the onset of deprotonation of surface-bound -COOH groups of the CDs, indicating that the -COO- anionic centers promote quenching of edge-state emission. Using λex ~ 450 nm, only the surface fluorophores are excited. The deprotonation of phenolic -OH group at pH>9 causes a sharp red-shift in the emission spectra at all excitation wavelengths. The pH-sensitive emission behavior of the CDs enable them to serve as optical pH sensors.
关键词： time-resolved spectroscopy,carbon dots,photoluminescence,pH-sensitive,optical pH sensors
更新于2025-09-04 15:30:14