Facile synthesis of N,B-co-doped carbon dots with the gram-scale yield for detection of iron (III) and E. coli.

A simple method was developed to prepare fluorescent nitrogen/boron-doped carbon dots (N,B-CDs) in the gram scale. The results showed that the CDs exhibited blue photoluminescence (PL) under 365 nm ultraviolet radiation and excitation-dependent emission. Heteroatoms entered the CDs to enhance the photochemical properties, and their positive properties can be attributed to the presence of guanidino group and functionalized with boronic acid for realizing their utilization in certain applications. These materials could be applied to monitor Fe3+ via static PL quenching, yielding a limit of detection (LOD) of 0.74 µM. Furthermore, the charged and boronic acid groups on the prepared N,B-CDs enabled their use as recognition elements to bind with the bacteria through electrostatic interaction and allowed covalent interactions to form the corresponding boronate ester with E. coli (E. coli) bacterial membrane. This method could satisfy a linear range of 102-107 with LOD of 165 cfu ml-1 for E. coli. This method was applied for the determination of E. coli in tap water and orange juice samples, and satisfactory results were obtained.

Luminescence investigation of red-emitting Sr2MgMoO6:Eu3+ phosphor for visualization of latent fingerprint.

Fingerprints are widely studied due to their unique shape and lifelong properties. The latent fingerprint (LFP) visualization is critical in identifying crime scenes and personal information. At present, the powder dusting method for LFP detection is favored due to its environmental friendliness and nontoxicity. However, this method has low resolution, low sensitivity, and large background interference. To address these shortcomings, the red-emitting Sr2MgMoO6:xEu3+ (x = 0-0.50) phosphors were synthesized using the solid-state reaction process. The products were systematically studied through the structural phase, luminescent property, decay curve, and color purity. Sr2MgMoO6:xEu3+ phosphors were monitored at 596 nm and exhibited a commendable broad excitation band between 250 and 475 nm. This result indicated that the disadvantage of the poor absorption of commercial red phosphors (Y2O2S:Eu3+) in the near-ultraviolet region was overcome. Under excitation at 393 nm, the synthesized Sr2MgMoO6:Eu3+ phosphor exhibited intense red light at 596 and 616 nm, due to the 5D0 â†’ 7F1 and 5D0 â†’ 7F2 transitions of Eu3+ ions. The optimal concentration for the Sr2MgMoO6:xEu3+ phosphor was x = 20 mol%, and the concentration quenching effect was ascribed to the dipole-dipole interaction. The Commission International del'Eclairage (CIE) chromaticity coordinates of Sr2MgMoO6:Eu3+ were (0.643, 0.356), and the color purity was 99.8%. Furthermore, the fluorescent LFP images developed by Sr2MgMoO6:0.20Eu3+ phosphors were well visualized, and level 1-3 details were well identified with high resolution, contrast, sensitivity, and selectivity. The obtained results suggested that the Sr2MgMoO6:Eu3+ phosphor can be applied for LFP detection.