The application of 7H-indolo[1,2-a]quinolinium merocyanine as a new water sensor in organic solvents

Enhancing the optical path inside a capillary without sacrificing light intensity: application to a compact and highly sensitive photometer

In order to increase the optical path and related sensitivity of photometers, multiple axial-reflection of parallel light-beam inside a capillary cavity is one of the most effective ways. However, there is a non-optimum trade-off between optical path and light intensity, e.g., smaller aperture on cavity mirror can increase multiple axial-reflection times (i.e., longer optical path) due to the lower cavity-loss, but it would also reduce coupling efficiency, light intensity, and related signal-to-noise ratio. Herein, an optical beam shaper, which is composed of two optical lenses with an apertured mirror, was proposed to focus the light beam (i.e., increasing coupling efficiency) without deteriorating beam parallelism and related multiple axial-reflection. Thus, by combining the optical beam shaper with a capillary cavity, large optical path enhancement (10-fold of capillary length) and high coupling efficiency (>65%) can be realized simultaneously, where the coupling efficiency was improved 50-fold. An optical beam shaper photometer (with a 7 cm long capillary) was fabricated and applied to detect water in ethanol with a detection limit of 12.5 ppm, which is 800-fold and 32∼80 fold lower than that of the commercial spectrometer (1 cm cuvette) and previous reports, respectively.

Synthesis, Solvatochromic Performance, pH Sensing, Dyeing Ability, and Antimicrobial Activity of Novel Hydrazone Dyestuffs

New tricyanofuran intramolecular charge transfer dyes comprising the hydrazone group were prepared and fully characterized in order to study their possible solvatochromism, dyeing ability, and antimicrobial activity. The preparation of the hydrazone dyes was achieved in relatively good yields starting from different aromatic amines. The hydrazone functional group was presented via the azo-coupling reaction of the tricyanofuran compound by the properly substituted diazonium chloride. Chemical structures of the prepared hydrazones were confirmed via nuclear magnetic resonance spectroscopy (1H- and 13C-NMR), Fourier-transform infrared spectroscopy (FT-IR), and elemental analysis (C, H, and N). The UV-visible absorption spectra of the produced sensor colorants displayed interesting solvatochromism in solvents with a different polarity, which was found to be affected by the substituents bonded to the aromatic hydrazone moiety. The pH molecular switching was investigated through tuning the intramolecular charge transfer stimulated by the reversible deprotonation/protonation process in acetonitrile solution showing color change from yellow to purple. The produced disperse dyestuffs were employed for dyeing polyester fibers to introduce acceptable color strength and colorfastness properties. Moreover, the dyes verified a weak to moderate antimicrobial activity against some selected pathogens, including S. aureus, E. coli, and Candida albicans.