Covalent
organic framework (COF) as a kind of crystalline porous
material possesses intriguing advantages, including low density, large
surface area, permanent porosity, and excellent chemical stability.
This novel material has shown great potential in the development of
chromatographic stationary-phase materials. In this work, a room-temperature
solvothermal method was utilized to yield a uniformly spherical COF-modified
silica named Sil-COF. Then, the thiol-ene click chemistry was further
used to modify thiolated β-cyclodextrin on the spherical Sil-COF
composite for chiral separation called Sil-COF-CD. A series of characterization
methods were performed to identify the successful construction of
COF-modified stationary-phase materials. Then, three types of nonpolar
substances realized baseline separation on the Sil-COF column. In
addition, 2-phenylpropionic acid and 1-phenyl-1-propanol were selected
as model enantiomers to identify the chiral recognition capability
of the Sil-COF-CD column. Sil-COF and commercial β-CD columns
were compared to further confirm the superiority of the prepared chiral
column. In addition, both COF-modified columns possessed good repeatability.
The results open a new avenue to apply spherical chiral COF for the
preparation of the HPLC stationary phase.
MXene quantum dots (MQDs) have excellent photoelectrochemical properties and are attracting considerable attention in the academic field. In this study, we synthesized amino-rich MQDs on the surface by modifying the Ti 3 C 2 nanosheets with 3-aminopropyltriethoxysilane (APTES) and then cutting the functional nanosheets into quantum dots by hydrothermal reaction. The N-MQDs were characterized by UV−vis spectrophotometry, Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The prepared N-MQDs had an average particle size of 8.63 nm. The N-MQDs exhibited excellent linearity and sensitivity for the detection of Fe 3+ and Cu 2+ ions over a concentration range of 0.5−500 μM. The limits of detection (LODs) for the Fe 3+ and Cu 2+ ions were calculated to be 0.17 and 0.15 μM, respectively. Compared with previous N-doped Ti 3 C 2 MQDs, our prepared N-MQDs possessed lower LOD for the detection of Cu 2+ ions. The quantum dot showed a potential to detect Cu 2+ ions in water samples with sodium hexametaphosphate (SHPP) as a Fe 3+ ions masking agent. N-doped MQDs can enhance the fluorescence quantum yield and detection sensitivity for metal ions over that of MQDs without amination. N-MQDs prepared by the method with active amino groups and high stability than previous works, which can expand the application of MQDs in other fields. This study also opens an avenue for the covalent modification of MXene QDs materials and surface engineering fields.
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