Basheer Aazaad

The use of one-step products and their applications in sensory applications has gained much importance. Herein, Schiff’s base fluorescent turn-on sensor, namely FBTS, was synthesised via a condensation reaction between 6-fluorobenzo[d]thiazol-2-amine and 2-hydroxybenzaldehyde. The probe FBTS exhibits an intense “turn-on” blue fluorescence upon binding to Al³⁺ ions in a dimethyl sulfoxide–water (DMSO–H₂O (8:2, v/v)) medium. From photoluminescence (PL) titrations, the detection limit (LOD) for Al³⁺ is estimated to be 0.14 microM, and the Benesi–Hildebrand plot-based association constant (K_a) of 5.4 × 10⁴ M⁻¹ confirm a strong association between FBTS and Al³⁺. Negligible interference is observed in the presence of other metal ions. From the pH effect studies, the optimal pH range for Al³⁺ detection is 7–9. The recyclable reversibility of FBTS + Al³⁺ complex has been demonstrated via the sodium salt of ethylenediaminetetraacetic acid (Na₂-EDTA) chelation. A Job’s plot and interrogations, such as high-resolution mass spectrometry (HR-MS), ¹H-nuclear magnetic resonance (NMR) titration, and density functional theory (DFT), verified the 1:1 stoichiometry of binding between FBTS and Al³⁺. Based on multiple analyses, the binding mode and mechanism have been detailed. In addition, the practical application of FBTS for detecting Al³⁺ is demonstrated using the strip paper method, fish analysis, spiked real sample analysis, and cellular imaging.

A one-pot-synthesized anthracene derivative with potential anticancer activity has been reported as a probe for CN ⁻ detection via a 1,4 addition reaction.

The photocatalytic CO ₂ reduction reaction (CO ₂ RR) has attracted considerable attention as a promising strategy for sustainable fuel production.

Context. Despite the identification of the smallest sugar molecule, glycolaldehyde (GA), in the interstellar medium (ISM), its mechanism of formation in the ISM is still not fully understood. A more profound understanding of the interstellar chemistry of GA and related molecules could provide insights into whether larger sugar molecules can also form and survive under such conditions. Aims. The primary objectives of this research are to delve into the sugar formation mechanism in the ISM, especially in dark molecular clouds; unravel intricate details of H-atom-mediated reactions involving glyoxal (GO), GA, and ethylene glycol (EG); and identify intermediates playing potential roles in the formation of larger sugars or serving as intermediates in the destruction reaction paths of sugar molecules. Methods. The study utilizes the para-H₂ matrix isolation method with infrared (IR) spectroscopic detection and quantum chemical computations to investigate H-atom reactions of GO, GA, and EG at a low temperature. Results. Several radical products were spectroscopically identified that might be key active species in the interstellar formation of larger sugar molecules.

Dicarboxylic acids (DCAs) are major players in the formation of secondary organic aerosols (SOAs) and climate change. DCAs have potential impact on human health and environmental issues ranging from local scale to global scale participate mainly in the cloud condensation. In this context, oxalic acid (OA) and malonic acid (MA) are the most dominant DCAs in the atmosphere. A full atmospheric degradation mechanism of OA and MA with the most reactive tropospheric oxidants, namely, OH, Cl and NO₃ radicals, were studied using M06‐2X, ωB97XD/cc‐pVTZ and 6‐311++G(2df,2p) level of theories. To evaluate the atmospheric influence, this study enables us to deep investigation of fate of OA and MA with respect to the mentioned radicals and their subsequent secondary reactions. The latter result in the formation of carbon dioxide (CO₂), formic acid (HCOOH), which contributes to the formation of SOA and climate change. The reaction mechanism in this study was initiated through H‐abstraction reaction, followed by dehydrogenation and decarboxylation reaction of both DCAs. The rate coefficients of OA, MA with OH, Cl and NO₃ radicals are determined theoretically using variational transition state theory (VTST) with Eckart tunnelling method in the temperature range of 278–1000 K. At 298 K, the rate coefficient of OA with OH, Cl and NO₃ are 2.48 × 10⁻¹⁵, 2.37 × 10⁻²⁰, 6.16 × 10⁻²³ in cm³ molecule⁻¹ s⁻¹, whereas MA with OH, Cl and NO₃ are 9.76 × 10⁻¹⁴, 1.01 × 10⁻¹² and 5.89 × 10⁻¹⁸ in cm³ molecule⁻¹ s⁻¹, respectively. Our present results shed light on the atmospheric implications of two DCAs and provide the significant insight for the atmospheric pathways.

Menthol is a naturally occurring compound belonging to the cyclic monoterpene family and is one of the main constituents of peppermint oil, recognized worldwide as a cooling agent. This study is the first report on the reaction mechanism of menthol with OH radical by exploring the hydrogen abstraction mechanism using theoretical methods like M06-2X and wB97X-D/6-311+G(d,p) level of theory. Menthol has three chiral centres with cyclohexane, isopropyl and methyl groups; all the reactive sites have been studied to identify the dominant route. The H atom abstracted from the isopropyl group of menthol is found to be more energetically favourable than the entire reactive site. The results acquired are compared with high level G3B3 for the most prominent pathway. Further, the rate coefficients of all initial reactions are calculated using canonical variational transition state theory (CVT) with Wigner tunnelling correction. The most favourable pathway shows the rate coefficient of 9.83 × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹ (298 K) at the M06-2X level of theory and the results are consistent with the experimental value (1.48 ± 0.31 × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹). The formation of a peroxy radical and its reaction with atmospheric species is analyzed theoretically. The stable product 2-(1-hydroperoxy-1-methyl-ethyl)-5-methyl-cyclohexanol is formed via reaction of the peroxy radical with HO₂. The thermochemistry of the entire reaction channel shows both exothermic and exergonic nature. The atmospheric life time of menthol in the presence of OH radical is found to be 1.13 hours indicates the inevitable contribution of the present study at local scale.

Novel anthracene-based Schiff base derivative (4-(anthracen-9-ylmethylene) amino)-5-phenyl-4H-1,2,4-triazole-3-thiol; AT2) is synthesized and utilized as an aggregation-induced emission-enhancement (AIEE) active probe to detect Zn²⁺ and Tyrosine. Ultraviolet-visible absorption/photoluminescence (UV-vis/PL) spectroscopy studies on the AIEE property of AT2 (in ethanol) with increasing water fractions (f_w: 0–97.5%) confirm the J-type aggregation. Excellent sensor selectivity of AT2 to Zn²⁺ and its reversibility with Tyrosine are demonstrated with PL interrogations. 2:1 and 1:1 stoichiometry and binding sites of AT2-Zn²⁺ and Tyrosine-Zn²⁺ complexes are elucidated from Job plots, HR-mass, and ¹H-NMR results. Nanomolar-level detection limits (LODs) of Zn²⁺ (179 nM) and Tyrosine (667 nM) and association constants (K_as) of 2.28 × 10⁻⁶ M⁻² (for AT2-Zn²⁺) and 1.39 × 10⁻⁷ M⁻¹ (for Tyrosine-Zn²⁺) are determined from standard deviation and linear fittings. Nanofiber formation in AIEE and aggregated/dispersed nanoparticles in the presence of the Zn²⁺/Tyrosine are supported by scanning-electron microscope (SEM), transmission-electron microscope (TEM), atomic-force microscope (AFM), and dynamic-light scattering (DLS) investigations. Density-functional theory (DFT) studies confirm an “On-Off” twisted intramolecular charge transfer/photo-induced electron transfer (TICT/PET) and “On-Off-On” PET mechanisms for AIEE and sensors, respectively. B16-F10 cellular and zebrafish imaging are conducted to support the applications of AIEE and sensors.

We investigated the kinetics, mechanism and secondary organic aerosols formation of the ozonolysis of trans-2-pentenal (T2P) using four different reactors with Fourier Transform InfraRed (FTIR) spectroscopy and Gas Chromatography (GC) techniques at T = 298 ± 2 K and 760 Torr in dry conditions. The rate coefficients and branching ratios were also evaluated using the canonical variational transition (CVT) state theory coupled with small curvature tunneling (CVT/SCT) in the range 278–350 K. The experimental rate coefficient at 298 K was (1.46 ± 0.17) × 10⁻¹⁸ cm³ molecule⁻¹ s⁻¹, in good agreement with the theoretical rate. The two primary carbonyls formation yields, glyoxal and propanal, were 57 ± 10% and 42 ± 12%, respectively, with OH scavenger compared to 38 ± 8% for glyoxal and 26 ± 5% for propanal without OH scavenger. Acetaldehyde and 2-hydroxypropanal were also identified and quantified with yields of 9 ± 3% and 5 ± 2%, respectively, in the presence of OH scavenger. For the OH production, an upper limit of 24% was estimated using mesitylene as OH tracer. Combining experimental and theoretical findings enabled the establishment of a chemical mechanism. Finally, the SOA formation was observed with mass yields of about 1.5%. This work provides additional information on the effect of the aldehyde functional group on the fragmentation of the primary ozonide.