Selective and sensitive detection of highly toxic chemicals by a suitable, fast, inexpensive, and trustworthy method is vital due to its serious health threats to humankind and breach of public security caused by unexpected terrorist attacks and industrial accidents. Phosgene or carbonyl dichloride is widely employed in many chemical industries and pharmaceuticals, and in pesticide production, which is extremely toxic by severe (short-term) inhalation exposure. Because of the non-existence of a phosgene sensor in aqueous solution and the immense emphasis gained by nanomaterials, especially carbonaceous materials, augmented attention has been given to the development of a fluorophore-functionalized carbon-based method to detect this noxious substance. In this study, surfactant free 1,8-diaminonaphthalene (DAN)-functionalized graphene quantum dots (DAN-GQDs) were prepared to detect phosgene in aqueous solution. The FESEM (field emission scanning electron microscopy) and HRTEM (high-resolution transmission electron microscopy) analyses confirm the as-prepared DAN-GQD morphology as nanobuds (NBs) with an average diameter of ca. 35–40 nm. The crystalline nature, elemental composition, and chemical state of DAN-GQDs were analyzed by standard physiochemical techniques. The edge-termination at the carboxyl functional group of GQDs with DAN was examined by XPS, Raman, FT-IR, and 1H NMR spectroscopy analyses. The aqueous solution of DAN-GQDs (4.89 × 10–9 M) exhibits a strong emission peak at 423 nm upon excitation at 328 nm. The addition of the phosgene molecule (0 → 88 μL) quenches the initial fluorescence intensity of DAN-GQDs (ΦF 53.6 → 34.6%) through the formation of a stable six-membered cyclized product. The DAN-GQDs displayed excellent selectivity and sensitivity for phosgene (K a = 3.84 × 102 M–1 and LoD (limit of detection) = 2.26 ppb) over other competing toxic pollutants in water. The time-resolved fluorescence analysis confirms that the quenching of DAN-GQDs follows nonradiative relaxation of excited electrons. Furthermore, bioimaging experiments of phosgene in living human breast cancer (HeLa) cells and cell viability test successfully demonstrated the practicability of DAN-GQDs.

Background Herbal plants are potent in curing various ailments of ancient times as they have comparatively lesser side effects. The demands for natural drugs, mostly from plant sources, are increasing over the past few decades. Because of their potent antioxidant activity, Acacia species are used to treat a variety of diseases. One of the species Acacia ferruginea, an endangered medicinal plant, is widely used in the traditional medicine system, and it is considered that standardization would be beneficial. The present study investigates the physicochemical parameters, preliminary phytochemical screening, trace metals by SEM–EDS, and fluorescence properties of various extracts (non-polar to polar) of leaf and bark parts. Standard spectrophotometric methods (UV–Vis, FT-IR, fluorescence spectroscopy) are employed to analyze the functional groups, and the DPPH and total antioxidant methods are used to assess antioxidant potential. Results The ethyl acetate extract of leaves and ethanol extract of the bark are found to be the highest in yield, 16.32% and 2.54%. Results reveal that the total ash percentage and moisture content are of bark and the water-soluble ash of leaves is higher (10.3 ± 0.85, 7.6 ± 0.34, 3.22 ± 0.24%). The bark polar extract contained more macro-elements such as Na, K, Mg, Ca, S, and Cl. Phytochemical analysis reveals the polar extracts of leaves and bark show saponins, flavonoids, steroids, phenolic compounds, and non-polar extracts show mild positive. The total alkaloids, phenolics, and terpenoids (1.58 ± 0.08%; 0.56 ± 0.11; 0.75 ± 0.15) are found to be higher in A. ferruginea leaves. The FT-IR result shows the presence of alkanes, alkenes, aromatic compounds, aldehydes, phenolics and does not contain any toxic substances since there is no peak observed in the region between 2220 and 2260 cm−1. The in vitro antioxidant activity of the species demonstrated that both the leaf and bark parts have prominent antioxidant properties. Conclusions The results obtained from the preliminary standardization of A. ferruginea are very helpful in the determination of the quality and purity of the crude drug. The refurbished findings of A. ferruginea are promising, and further research is important to identify the bioactive compounds, thereby developing nutritional supplements and medications through therapeutic compound isolation. Graphical Abstract

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Creatinine (Crn) is an important excretory product of the human body. Medical laboratory technology has improved over years and brought many advancements in clinical diagnostics equipment, and testing techniques and made the tests more efficient. Yet, the quantitative analysis of Crn is still carried out by the classical Jaffe’s reaction (using Picric acid (PA) with NaOH) method. Since PA is hazardous to human health, alternative solutions such as; nanoparticles and surface-modified nanoparticles can be used. Exploring the optoelectronic properties of carbon-based quantum dots for biomolecule sensing is of current interest among researchers. Nitrogen functionalized graphene quantum dots (Alk-NGQDs) measured featured Crn easier and reduced the time taken for the test carried out in laboratories. The synthesized Alk-NGQDs optical, structural, morphological properties, surface and compositions are studied through XPS, HRTEM, XRD, FTIR, and spectroscopic techniques. Alk-NGQDs at alkaline conditions (pH 9.5) form a stable complex with Crn through intermolecular charge transfer (ICT). The fluorescence titration method is used to sense Crn in commercial Crn samples and human blood serum. To understand the efficacy of sensing creatinine using Alk-NGQDs, working concentration, fluorescence quantum yield, the limit of detection, and quenching constant are calculated using the Stern-Volmer plot. The emission property of Alk-NGQDs is aimed to bring an alternative to the traditional colorimetric Jaffe’s reaction.