Here, we report ultraspeed preparation of highly emissive nitrogen‐doped carbon dots (NCDs) using threonine and guanidine hydrochloride by the microwave irradiation method. Experimental conditions such as microwave power, irradiation time, and reactant ratio were varied to achieve high‐quality NCDs. NCDs were thoroughly characterized using transmission electron microscopy, X‐ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, UV–visible spectroscopy, and fluorescence spectroscopy. NCDs presented high aqueous solubility, bright emission with a quantum yield of 30%, and excitation‐dependent emission. Investigation of optical properties unveiled their admirable characters of tolerance to photobleaching, high salinity, pH, and long shelf life. Evaluation of their metal ion detection ability unveiled their selective fluorescence quenching response to Mn (VII), and further explorations revealed the application of NCDs as a label‐free probe for Mn (VII) detection. The probe presented a good linear response (R2 = 0.992) in the concentration range of 5–35 μM with a detection limit of 0.66 μM. Mechanistic studies disclosed that the inner filter effect was responsible for fluorescence quenching. The probe presented no significant interference and was successfully applied for the quantification of Mn (VII) in spiked real‐water samples.

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A Pd/C and TFA-promoted effective one-pot synthesis of oxepines starting from iodoheteroaryl/aryl ethers and terminal alkyne has been developed under mild conditions. This transformation involves intermolecular CÀ C bond formation between the aryl iodide and terminal alkynes followed by intramolecular hydroarylation of alkyne, affording the desired oxepines in good yields. A possible mechanism was proposed.

Using UV Spectrophotometric methods, a simple, precise and accurate approach is devised and verified for the simultaneous assessment of Dextromethorphan (DEX) and Cetrizine (CET) in combined dosage form. The approach 1 is the Dual wavelength method, which was developed, evaluates the difference in the absorbance of mixtures at wavelengths where single drugs have the same absorbance and vice versa. Approach 2 is a mean-centered ratio method that relies on the production of calibration by dividing the spectra of one substance by the spectra of the other. Approach 3 is a derivative spectrum method that relies on the derivative spectrum's zero crossing points to create calibration for two medications in the presence of the second. Simultaneous estimation of DEX and CET using the Q-absorption method and the simultaneous equation method has already been published. The two techniques Simultaneous equation method (Approach 4) and Q-Absorption method (Approach 5) are repeated to preserve the same circumstances throughout the experiment. To assess the accuracy and precision of all five approaches, six replication tests and recovery investigations utilizing recognized synthetic blends are used. The calibrations are used to analyze two pharmaceuticals contained in the tablet. The procedures have been validated in accordance with ICH recommendations.

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