ABSTRACT
Multifunctional materials used for multimodal sensors are of great significance both for enriching variety of materials and overcoming the shortcomings of traditional single signal sensors. This work reports the ultrafast preparation of multifunctional coordination polymer (CP) spheres with metalloligand Ru (II)[4,4'-(COOH)2-bpy]3âªCl2 (L) and Gd3+ ions. Gd-L CPs were used for multi-modal detection of nitroaromatic explosives and trace water in organic solvents with their red fluorescence and magnetic resonance response. The red fluorescence was derived from the ligand, which is electron-rich because of the bipyridine rings. There were different emission behaviors when Gd-L CPs reacted with nitroaromatic explosives that have various electron-deficient properties through electron transfer donor-acceptor mechanism. The changes in the emission depended closely on the nitroaromatic explosives ability to withdraw electrons. Gd-L CPs also showed magnetic resonance response with r1 of 12.1 mM-1s-1 due to the integration of the paramagnetic property of Gd3+ ions. Smart sensing of trace water in organic solvents was achieved by magnetic signals. The fluorescence of Gd-L CPs was enhanced and there was a tiny blue-shift in protonic solvents with increased polarity. The fluorescence sensor used in detecting trace water had a consistent result like the MR response. Thus, Gd-L CPs enabled the use of fluorescence and magnetic resonance sensors simultaneously for the first time to overcome the shortcoming of single modal sensor and expand the application of magnetic resonance relaxation.
ABSTRACT
Counterfeiting is a global epidemic that is compelling the development of new anticounterfeiting strategy. Herein, we report a novel multiple anticounterfeiting encoding strategy of invisible fluorescent quick response (QR) codes with emission color as information storage unit. The strategy requires red, green, and blue (RGB) light-emitting materials for different emission colors as encrypting information, single excitation for all of the emission for practicability, and ultraviolet (UV) excitation for invisibility under daylight. Therefore, RGB light-emitting nanoscale metal-organic frameworks (NMOFs) are designed as inks to construct the colorful light-emitting boxes for information encrypting, while three black vertex boxes were used for positioning. Full-color emissions are obtained by mixing the trichromatic NMOFs inks through inkjet printer. The encrypting information capacity is easily adjusted by the number of light-emitting boxes with the infinite emission colors. The information is decoded with specific excitation light at 275 nm, making the QR codes invisible under daylight. The composition of inks, invisibility, inkjet printing, and the abundant encrypting information all contribute to multiple anticounterfeiting. The proposed QR codes pattern holds great potential for advanced anticounterfeiting.
ABSTRACT
Multitarget assay with single detection modality from individual stimulation mode has aroused great attention. Here, we realize multitarget detection with the color change as signal source from single white light-emitting metal-organic frameworks (MOFs) under single wavelength excitation for the first time. The white light-emitting MOFs are prepared by carefully tuning the ratio of Eu3+, Tb3+, and Dy3+ ions to obtain trimetal MOFs; 5-boronoisophthalic acid (5-bop) provides additional selectivity as ligand. Based on antenna effect, 5-bop is excited to produce its triplet-state, which sensitizes the Ln3+ ions for the white emission. Thus, all of the fluorescence emission is achieved under single wavelength excitation at 275 nm, while any factors affecting the procedure result in the modulation of emission for diverse wavelengths. The trimetal MOFs display distinctive emission colors after interacting with different targets, including metal ions, anions, small molecule, and even biomolecule as a Lab-on-MOFs system. This system shows higher integration degree and simpler preparation and sensing procedures than other multitarget detection strategies.
ABSTRACT
Here, we report that boric acid is used to tune the optical properties of lanthanide metal-organic frameworks (LMOFs) for dual-fluorescence emission and improves the selectivity of LMOFs for the determination of F- ions. The LMOFs are prepared with 5-boronoisophthalic acid (5-bop) and Eu3+ ions as the precursors. Emission mechanism study indicates that 5-bop is excited with UV photons to produce its triplet state, which then excites Eu3+ ions for their red emission. This is the general story of the antenna effect, but electron-deficient boric acid decreases the energy transfer efficiency from the triplet state of 5-bop to Eu3+ ions, so dual emission from both 5-bop and Eu3+ ions is efficiently excited at the single excitation of 275 nm. Moreover, boric acid is used to identify fluoride specifically as a free accessible site. The ratiometric fluorescent detection of F- ions is validated with the dual emission at single excitation. The LMOFs are very monodisperse, so the determination of aqueous F- ions is easily achieved with high selectivity and a low detection limit (2 µM). For the first time, we reveal that rational selection of functional ligands can improve the sensing efficiency of LMOFs through tuning their optical property and enhancing the selectivity toward targets.
ABSTRACT
A magnetic dispersion extraction method was developed based on a molecularly imprinted magnetic microsphere (MIMM) for the selective clean-up and enrichment of tetracycline antibiotics from milk samples. The MIMMs were prepared by inverse-emulsion suspension polymerization, using doxycycline, trimethylolpropane trimethacrylate, acrylamide, methacrylic acid, and surface-modified Fe3 O4 as a template molecule, crosslinker, functional monomer, and magnetic component, respectively. Synthesis and extraction conditions were optimized for obtaining excellent affinity and high selectivity. The magnetism, covering amount, and selectivity of the magnetic microspheres were characterized by a vibrating sample magnetometer, thermogravimetric analysis, and a competitive recognition experiment. The MIMMs were applied to separate tetracycline antibiotics from milk samples by magnetic dispersion extraction, and an enrichment factor of 9.28 and a good sample clean-up were obtained. The average recoveries of four tetracycline antibiotics were obtained in the range of 74.5-93.8% with a precision of 1.2-5.2%. The LODs and LOQs of the proposed method were in the range of 7.4-19.4 and 24.7-64.7 µg/kg, respectively. The results indicated that magnetic dispersion extraction using MIMMs is a powerful tool for food-sample pretreatment with high selectivity and a simplified procedure.
