Monitoring hydrogen sulfide (Hsub.2S) in living organisms is very important because Hsub.2S acts as a regulator in many physiological and pathological processes. Upregulation of endogenous Hsub.2S ...concentration has been shown to be closely related to the occurrence and development of tumors, atherosclerosis, neurodegenerative diseases and diabetes. Herin, a novel fluorescent probe HND with aggregation-induced emission was designed. Impressively, HND exhibited a high selectivity, fast response (1 min) and low detection limit (0.61 μM) for Hsub.2S in PBS buffer (10 mM, pH = 7.42). Moreover, the reaction mechanism between HND and Hsub.2S was conducted by Job’s plot, HR-MS, and DFT. In particular, HND was successfully employed to detect Hsub.2S in HeLa cells.
The work represents a rare example of an aza-crown-based macrocyclic chemosensor, H
(H
= 1,16-dihydroxy-tetraaza-30-crown-8) for the selective detection of both Zn
and Cu
in HEPES buffer medium (pH ...7.4). H
exhibits a fluorescence response for both Zn
and Cu
ions. The reversibility of the chemosensor in its binding with Zn
and Cu
ions is also examined using a Na
EDTA solution. H
exhibits a chelation-enhanced fluorescence (CHEF) effect in the presence of Zn
ions and a quenching effect (CHEQ) in the presence of paramagnetic Cu
ions. Furthermore, the geometry and spectral properties of H
and the chemosensor bound to Zn
have been studied by DFT and TDDFT calculations. The limit of detection (LOD) values are 0.11 × 10
and 0.27 × 10
M for Cu
and Zn
, respectively. The formation constants for the Zn
and Cu
complexes have been measured by pH-potentiometry in 0.15 M NaCl in 70:30 (v:v) water:ethanol at 298.1 K. UV-vis absorption and fluorometric spectral data and pH-potentiometric titrations indicate 1:1 and 2:1 metal:chemosensor species. In the solid state H
is able to accommodate up to four metal ions, as proved by the crystal structures of the complexes Zn
(
)(OH)
(NO
)
(
) and {Cu
(
(OCH
)
(NO
)
·H
O}
(
). H
can be used as a potential chemosensor for monitoring Zn
and Cu
ions in biological and environmental media with outstanding accuracy and precision. The propensity of H
to detect intracellular Cu
and Zn
ions in the triple negative human breast cancer cell line MDA-MB-468 and in HeLa cells has been determined by fluorescence cell imaging.
BFsub.2-azadipyrromethenes are highly versatile fluorophores used for cellular and in vivo imaging in the near-infrared and far-red regions of the spectrum. As of yet, their use in conjunction with ...super-resolution imaging methodologies has not been explored. In this report, a series of structurally related BFsub.2-azadipyrromethenes has been examined for their suitability for use with stimulated emission depletion (STED) nanoscopy. The potential for STED imaging was initially evaluated using aqueous solutions of fluorophores as an effective predictor of fluorophore suitability. For live cell STED imaging in both 2D and 3D, several far-red emitting BFsub.2-azadipyrromethenes were successfully employed. Image resolution below the diffraction limit of a confocal microscope was demonstrated through measurement of distinct intracellular features including the nuclear membrane, nuclear lamina invaginations, the endoplasmic reticulum, and vacuoles. As the STED ability of BFsub.2-azadipyrromethene fluorophores has now been established, their use with this super-resolution method may be expected to increase in the future.
Keywords: frequency-upconverted stimulated emission; MPA cross-section; multiphoton absorption (MPA); oligo(p-phenylene)s; spiro-fused molecules Frequency-upconverted fluorescence and stimulated ...emission induced by multiphoton absorption (MPA) have attracted much interest. As compared with low-order MPA processes, the construction of high-order MPA processes is highly desirable and rather attractive, yet remains a formidable challenge due to its inherent low transition probability. We report the observation of the first experimental frequency-upconverted fluorescence and stimulated emission by simultaneous six-photon excitation in an organic molecular system. The well-designed organic conjugated system based on cross-shaped spiro-fused ladder-type oligo(p-phenylene)s (SpL-z, z=1-3) manifests reasonably high MPA cross-sections and brilliant luminescence emission simultaneously. The six-photon absorption cross-section of SpL-3 with an extended I-conjugation was evaluated as 8.67x10.sup.-169 cm.sup.12s.sup.5photon.sup.-5. Exceptionally efficient 2- to 6-photon excited stimulated emission was achieved under near-infrared laser excitation. Article Note: These authors contributed equally to this work. Supporting information: Additional Supporting Information may be found in the online version of this article As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. CAPTION(S): Supplementary Byline: ,, Kun Gao, He Lin, Hoi Lam Tam, Yuan-Yuan Liu, Yu Shu, Ka-Leung Wong, Wen-Yong Lai, Kok Wai Cheah, Wei Huang
High-crystalline, hollow-mesh-like Tm.sup.3+/Yb.sup.3+-co-doped La.sub.2Ti.sub.2O.sub.7 (LTO) submicron fibers are prepared by electrospinning technique and identified as monoclinic structure. The ...LTO matrix fibers and the Tm.sup.3+/Yb.sup.3+-co-doped fibers exhibit different frequency upconversion luminescence. The fluorescence of the matrix at the 487 and 542 nm is ascribed to the two-photon absorption and the cross-relaxation processes caused by the defect center at 977 nm excitation, respectively. The upconversion luminescence intensity enhances when the rare-earth ions are incorporated into LTO fibers. The emissions of Tm.sup.3+ in co-doped LTO membranes at 479 and 789 nm under the excitation of 977 nm indicate the effectiveness of the three- and two-photon absorption processes, respectively. The pristine LTO fibers have the potential to be employed for water purification as a laser-excited photocatalytic material because the LTO materials are conducive to absorbing the highly penetrating NIR laser. Furthermore, the Tm.sup.3+/Yb.sup.3+ ions play a positive role in further promoting the laser-absorption capacity, and the hybrid excitation mechanism in the Tm.sup.3+/Yb.sup.3+-co-doped LTO composite fibers provides a new perspective for the development of anti-laser inorganic materials.
A novel strategy is proposed based on the efficient energy transfer from Tb.sup.3+ to Pr.sup.3+ for the sensitive and selective discrimination of praseodymium ions due to the matched energy levels of ....sup.5D.sub.4 (Tb.sup.3+) and .sup.3P.sub.0 (Pr.sup.3+). The electron of Tb.sup.3+ transfers from the ground state to the excited state under the excitation of ultraviolet light and relaxes to the .sup.5D.sub.4 level. In the presence of Pr.sup.3+ the electron has no time to return to the ground state, thus it transfers to the .sup.3P.sub.0 level of Pr.sup.3+ resulting in the quenching of Tb.sup.3+ luminescence. In the case of GdPO.sub.4: Tb.sup.3+ nanowire, its fluorescence intensity at 545 nm linearly decreased when Pr.sup.3+ concentration ranged from 1 x 10.sup.-7 to 1 x 10.sup.-5 M, and the detection limit was 75 nM. To further investigate the sensing mechanism, CePO.sub.4: Tb.sup.3+, YPO.sub.4: Tb.sup.3+, and YBO.sub.3: Tb.sup.3+ nanoparticles were also synthesized for Pr.sup.3+ ion detection. For all materials, similar fluorescence quenching by Pr.sup.3+ ions occurred, which confirmed the efficient energy transfer from Tb.sup.3+ to Pr.sup.3+ ions. Graphical abstract
A dual-channel "naked-eye" colorimetric and ratio fluorescent probe has been developed based on titanium carbide quantum dots for the detection of curcumin and hypochlorite (ClO.sup.-). The ...fluorescence emission of Ti.sub.3C.sub.2 MXene quantum dots (Ti.sub.3C.sub.2 MQDs) is in the range 350-600 nm, and the maximum emission peak is at 430 nm that overlaps with the UV absorption of curcumin at 430 nm to a large extent. This facilitates the fluorescence resonance energy transfer (FRET) between Ti.sub.3C.sub.2 MQDs and curcumin. When ClO.sup.- is added, the phenolic and methoxy groups of curcumin are oxidized to quinones, resulting in the restoration of the fluorescence of Ti.sub.3C.sub.2 MQD. In addition, the probe designed makes it easier to distinguish colors with the naked eye to detect curcumin and ClO.sup.-. The linear detection range of curcumin was 0.05-10 muM, and the detection limit was 20 nM. The linear detection ranges of ClO.sup.- are 25-150 muM and 150-275 muM, and the detection limit is 5 muM. This study is the first report on the determination of curcumin and ClO.sup.- based on Ti.sub.3C.sub.2 MQDs by dual-channel "naked-eye" colorimetric and ratio fluorescence method.
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