Graphene Nanobuds: A New Second-Generation Phosgene Sensor with Ultralow Detection Limit in Aqueous Solution

Abstract

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.

Surface and morphology analyses, and voltammetry studies for electrochemical determination of cerium(iii) using a graphene nanobud-modified-carbon felt electrode in acidic buffer solution (pH 4.0 ± 0.05)

“…SI11 †). 25 From the abovementioned electron microscopy results, we largely concluded that DAN-GQD in nanobud morphology can be propitious for the electrochemical determination of Ce 3+ ions without changing its morphology even in acidic conditions.…”

“…11a and b). Aer the electrochemical studies, the X-ray diffraction (XRD) prole of the GNB-modied-CF electrode was centered at 24.95 (002), which indicates that there was no change in the graphitic structure of GNB aer the adsorption of Ce 3+ ion onto the electrode surface 25 (Fig. 11c).…”

“…36,37 The well-designed and structurally modied materials on the electrodes can promote the enhancement of trace analytes to attain an ultra-low concentration detection. 18 The electrode material, 1,8-diaminonaphthalene (DAN)-GQD, in nanobud morphology was synthesized without using any surfactant in an aqueous medium and was systematically characterized by standard physiochemical techniques, 25 which is shown in the ESI (Fig. SI1).…”

“…24 Furthermore, the COO À and OH À present at their edges enable the GQDs to be remarkably water soluble, and thus appropriate for consecutive functionalization with various organic, inorganic, polymeric, or biological components. 23,25,26 However, there have been few reports available describing the functionalization of GQDs with organic molecules or polymers for sensing applications, and none of them have demonstrated Ce 3+ detection. 24,[27][28][29][30][31] Based on the above exploration and continuation of our study on multifunctional sensors, 23,25,32-34 herein, we report the detection of Ce 3+ using a graphene nanobud (GNB)-modiedcarbon felt (CF) electrode as a working electrode in acetate buffer solution (ABS) at a pH of 4.0 AE 0.05 using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques.…”

Do amino acid functionalization stratagems on carbonaceous quantum dots imply multiple applications? A comprehensive review

“…The wide-ranging properties of CQDs and GQDs allow their exploration in almost all the fields including biological sciences, 3,4 electronics, 5 energy devices, 6 sensors, 7 agricultural, 8 cosmetics, 9 pharmaceuticals, 10 and medical devices. 11 Both the QDs possess characteristic properties such as low toxicity, great solubility in a variety of solvents, good optoelectronic behavior, strong inertness toward chemicals, high surface area, and surface edges for functionalization.…”