Abstract
Quinoxaline-based novel acid-responsive probe Q1 was designed on the basis of a conjugated donor-acceptor (D-A) subunit. Q1 shows colorimetric and fluorometric changes through protonation and deprotonation in dichloromethane. With the addition of the trifluoroacetic acid (TFA), UV-vis absorption spectral changes in peak intensity of Q1 was observed. Moreover, the appearance of a new peaks at 284 nm 434 nm in absorption spectra with the addition of TFA indicating protonation of quinoxaline nitrogen and form Q1.H+ and Q1.2H+. The emission spectra display appearance of new emission peak at 515 nm. The optical property variations were supported by time resolved fluorescence studies. The energy band gap was calculated by employing cyclic voltammetry and density functional calculations. Upon addition of triethylamine (TEA) the fluorescence emission spectral changes of Q1 are found to be reversible. Q1 shows color changes from blue to green in basic and acidic medium, respectively. The paper strip test was developed for making Q1 a colorimetric and fluorometric indicator.
Highlights
In live cells the intracellular and extracellular pH are changed by variations in physiological processes
We report the synthesis and sensing properties of quinoxaline chromophore Q1
Are not separated, suggesting electronic transitions notbe pure charge but may we have investigated protonated form of the quinoxaline receptor to investigate the be treated as π-π transitions
Summary
In live cells the intracellular and extracellular pH are changed by variations in physiological processes. PH is measured by using large number of analytical tools such as glass electrodes and photometric methods and are many are commercialized Though these methods are well established, they have several disadvantages such as the need for frequent calibration of pH electrodes, corrosion caused by alkaline solutions or fluoride ions and the electrodes’ susceptibility towards interference leading to limited usefulness [14]. To overcome these disadvantages scientists have directed their efforts towards the development of Sensors 2018, 18, 3433; doi:10.3390/s18103433 www.mdpi.com/journal/sensors
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