Pyrene containing Schiff base molecule, namely 4-[(pyren-1-ylmethylene)amino]phenol (KB-1), was successfully synthesized and well characterized by using (1)H, (13)C NMR, FT-IR, and EI-MS spectrometry. UV-visible absorption, steady-state fluorescence, time-resolved fluorescence, and transient absorption spectroscopic techniques have been employed to elucidate the photophysical processes of KB-1. It has been demonstrated that the absorption characteristics of KB-1 have been bathochromatically tuned to the visible region by extending the π-conjugation. The extended π-conjugation is evidently confirmed by DFT calculations and reveals that π→π* transition is the major factor responsible for electronic absorption of KB-1. The photophysical property of KB-1 was carefully examined in different organic solvents at different concentrations and the results show that the fluorescence of this molecule is completely quenched due to photoinduced electron transfer. Intriguingly, the fluorescence intensity of KB-1 increases enormously by the gradual addition of water up to 90% with concomitant increase in fluorescence lifetime. This clearly signifies that this molecule has aggregation-induced emission (AIE) property. The mechanism of AIE of this molecule is suppression of photoinduced electron transfer (PET) due to hydrogen bonding interaction of imine donor with water. A direct evidence of PET process has been presented by using nanosecond transient absorption measurements. Further, KB-1 was successfully used for antimicrobial and bioimaging studies. The antimicrobial studies were carried out through disc diffusion method. KB-1 is used against both Gram-positive (Rhodococcus rhodochrous and Staphylococcus aureus) and Gram-negative (Escherichia coli and Pseudomonas aeruginosa) bacterial species and also fungal species (Candida albicans). The result shows KB-1 can act as an excellent antimicrobial agent and as a photolabeling agent. S. aureus, P. aeruginosa, and C. albicans were found to be the most susceptible microorganisms at 1 mM concentration among the bacteria used in the present investigation.

Photocatalysis provides excellent potentials for the complete removal of organic pollutants in environmentally friendly ways and sustainable means of technology. It has been noted that under UV-visible light irradiation, nanostructured semiconductor metal oxides photocatalysts can degrade different organic pollutants. Taking into consideration of the photocatalytic activity, the present study deals with the synthesis of cuprous oxide (Cu 2 O) nanoparticles (NPs) by the sonochemical method and characterized for their physicochemical, optical, and photocatalytic properties. The powdered X-ray diffraction (XRD) analysis confirmed for the cubic phase crystalline structure while the Field emission scanning electron microscopy (SEM) supported for the icosahedron morphology. The bandgap of the synthesized Cu 2 O NPs was found to be 2.26 eV, which is the suitable bandgap energy so as to achieve the enhanced photocatalytic degradation efficiency. On testing for the degradation of Malachite green (MG) as a model pollutant, the synthesized Cu 2 O NPs demonstrated a high degradation efficiency under visible light irradiation. The observed results suggest that the synthesized Cu 2 O NPs are attractive photocatalysts for the degradation of toxic organic wastes in the water under visible light. Further investigation confirmed for the photocatalytic reduction of 4-nitrophenol (4-NP) into 4-aminophenol (4-AP) under aqueous conditions with visible light.

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The main aim is to develop a simple, rugged, and sensitive method for determining the Montelukast Sodium-related impurities in a tablet dosage form using reverse-phase high-performance liquid chromatography (RP-HPLC) method. Chromatographic separation on the Agilent Eclipse XDB C18 (octadecylsilane) column of the dimension (100 mm × 4.6 mm, 5 µm) was carried out in the gradient mode with triethylamine and acetonitrile in various combinations and adjusted to a pH of 6.60 using phosphoric acid. The mobile phase was pumped at a flow rate of 1.0 mL min −1 and the analyte was monitored with a UV detector at a wavelength of 220 nm. The method was developed and validated under the stress conditions such as acidic, basic, peroxide, thermal, photolytic, and humidity degradation, respectively. Under the above conditions, oxidative degradation was performed which served as the system suitability solution providing a resolution of 2.5 between the Impurity 3 (retention time = 13.8 min) and Montelukast Sodium (retention time = 24.2 min). The method was validated with respect to specificity, linearity, precision, accuracy, limit of detection, and limit of quantification provided by the ICH guidelines. Results of linear regression analysis of the calibration plot revealed a good linear relationship between response and concentration with a correlation coefficient value of r 2 = 0.9999. The accuracy of known impurities was obtained in the range of 94-108%. From the analysis, their LOD and LOQ values for impurities were measured and found to be 0.007 and 0.025 μg g −1 , respectively. Chromatographic interference was not found during the degradation and excipients were detected from the tablet. The proposed method was successfully used to estimate the Montelukast Sodium-related impurities in a tablet dosage form.