Suci Meng

Two-Dimensional CaIn2S4/g-C3N4 Heterojunction Nanocomposite with Enhanced Visible-Light Photocatalytic Activities: Interfacial Engineering and Mechanism Insight

Design and exploitation of efficient visible light photocatalytic systems for water splitting and degradation of organic dyes are of huge interest in the fields of energy conversion and environmental protection. Herein, two-dimensional CaIn2S4/g-C3N4 heterojunction nanocomposites with intimate interfacial contact have been synthesized by a facile two-step method. Compared with pristine g-C3N4 and CaIn2S4, the CaIn2S4/g-C3N4 heterojunction nanocomposites exhibited significantly enhanced H2 evolution and photocatalytic degradation of methyl orange (MO) activities under visible light irradiation. The optimal CaIn2S4/g-C3N4 nanocomposite shows a H2 evolution rate of 102 μmol g(-1) h(-1), which is more than 3 times that of pristine CaIn2S4. The mechanisms for improving the photocatalytic performance of the CaIn2S4/g-C3N4 nanocomposites were proposed by using the photoluminescence measurement and electrochemical analyses. It was demonstrated that the enhanced photocatalytic performance of CaIn2S4/g-C3N4 heterojunction nanocomposites mainly stems from the enhanced charge separation efficiency. In addition, a plausible mechanism for the degradation of MO dye over CaIn2S4/g-C3N4 nanocomposites is also elucidated using active species scavengers studies.

A coumarin-based fluorescent probe for biological thiols and its application for living cell imaging

In this work, compound 1 has been rationally designed and synthesized as a new fluorescent probe for biological thiols. Notably, probe 1 has almost no background fluorescence (Φf < 0.0001) in aqueous solutions; however, it exhibited fluorescence turn-on response to thiols with high sensitivity (a 246-fold fluorescence enhancement and a low detection limit of 0.22 μM for Cys). Moreover, probe 1 showed excellent thiol specificity over other biologically relevant species. The kinetic studies indicated that the probe responded to thiols rapidly, and the pseudo-first-order rate constants of probe 1 reaction with Cys, Hcy, and GSH were determined to be 1.85842, 0.67656, and 0.51519 min(-1), respectively. A possible detection mechanism was proposed to involve the Michael addition of the thiol to the α,β-unsaturated ketone, followed by a cleavage of the hemiketal group, thereby leading to the formation of a fluorescent 7-hydroxyl coumarin derivative. Furthermore, the optical responses of probe 1 to thiols were studied by TD-DFT calculations. Finally, probe 1 has been successfully applied to the detection of biological thiols in human blood serum. And the intracellular imaging applications established that probe 1 can be used to detect different concentrations of intracellular thiols in living cells.

A ratiometric fluorescent probe for iron(III) and its application for detection of iron(III) in human blood serum

A simple and versatile ratiometric fluorescent Fe(3+) detecting system, probe 1, was rationally developed based on the Fe(3+)-mediated deprotection of acetal reaction. Notably, this reaction was firstly employed to design fluorescent Fe(3+) probe. Upon treatment with Fe(3+), probe 1 showed ratiometric response, with the fluorescence spectra displaying significant red shift (up to 132 nm) and the emission ratio value (I522/I390) exhibiting approximately 2362-fold enhancement. In addition, the probe is highly sensitive (with the detection limit of 0.12 μM) and highly selective to Fe(3+) over other biologically relevant metal ions. The sensing reaction product of the probe with Fe(3+) was confirmed by NMR spectra and mass spectrometry. TD-DFT calculation has demonstrated that the ratiometric response of probe 1 to Fe(3+) is due to the regulation of intramolecular charge transfer (ICT) efficiency. Moreover, the practical utility in fluorescence detection of Fe(3+) in human blood serum was also conducted, and probe 1 represents the first ratiometric fluorescent probe that can be used to monitor Fe(3+) level in human blood serum. Finally, probe 1 was further employed in living cell imaging with pancreatic cancer cells, in which it displayed low cytotoxicity, satisfactory cell permeability, and selective ratiometric response to Fe(3+).

Dodecanuclear‐Ellipse and Decanuclear‐Wheel Nickel(II) Thiolato Clusters with Efficient Femtosecond Nonlinear Absorption

Thiolate ligands have been of longstanding interest for a variety of reasons: 1) their diverse binding modes give rise to an array of bonding motifs that are of fundamental importance in coordination chemistry, 2) metal–thiolate interactions are key elements of numerous metalloproteins and play a crucial role in the broader field of bioinorganic chemistry, and 3) thiolate-mediated magnetic coupling is an essential component in novel molecular magnets. Amongst the range of metal thiolate-derived structures, the synthesis, structure, and magnetic properties of toroidal (or tiara-like) architectures have raised considerable interest. However, most of the known tiara-like [M(m-SR)]n (M = Ni, Pd) clusters to date have been constructed by single thiolate ligands and possess geometrically similar ring systems, which has restricted, to some extent, the abundance of examples and structural diversity of the tiara family. The development of high-performance molecular materials with optimized nonlinear optical (NLO) properties has also been the focus of much current research. 7] Previous studies have demonstrated that the presence of large pelectron delocalization and a symmetrical planar structure play crucial roles in determining the properties of nonlinear chromophores. 8] Curiously, though, despite the quasiaromatic nature of the bonding that has been proposed in nickel toroidal species, their optical properties are little explored; in particular, no study of the NLO properties is extant. We present here the synthesis of the largest tiara-like nickel(II)–thiolate cluster thus far by a novel route that employs two different thiolate bridges, structural studies that reveal an unprecedented elliptical structure for [Ni(m-StBu)(m-etet)]12 (etet = 2-ethylthioethanethiolate) and two new decanuclear-wheel nickel(II)–thiolato clusters [Ni(m-StBu)(m-pyet)]10 (pyet = 2-(2-mercaptoethyl)pyridine) and [Ni(mStBu)(m-atet)]10 (atet = 2-aminoethanethiol), and the first NLO studies of examples from this important class of molecules, together with time-dependent DFT studies that shed light on the optical behavior. The reaction of NiCl2·6 H2O with 1 equivalent K(etet) gave, after work-up, separable [(CH3C6H5) {Ni(m-StBu)(metet)}10] (1a) and [Ni(m-StBu)(m-etet)]12·(CH3C6H5)2 (1 b), whereas similar reactions with K(pyet) or K(atet), instead of K(etet), afforded [(CH3C6H5) {Ni(m-StBu)(m-pyet)}10]·(CH3C6H5)4 (2) and [(0.5CH3C6H5) {Ni(m-StBu)(m-atet)}10]·(CH3C6H5)2 (3), respectively. The atomic arrangements and stoichiometries of 1 a, 1b, 2, and 3 were unequivocally established from low-temperature CCD area-detector X-ray diffraction studies. The single-crystal X-ray analysis of 1b reveals a heretofore unknown dodecagonal-ellipse Ni12S24 framework, as displayed in Figure 1. The top view (Figure 1 a) of the cyclic Ni12S24 architecture shows that edge-fusion of the 12 localized planar [NiS4] subunits along opposite nonbonding S–S edges gives rise to a triple-layer elliptical geometry that approximately conforms to pseudo-D2 symmetry. The transannular Ni···Ni distances of 1 b are in the range of 11.343(6)–13.528(7) , while the dihedral angles between adjoining [NiS2] planes vary from 140.32 to 157.848 because of the unsymmetrical elliptical geometry of this unique 12membered Ni ring. The side view (Figure 1b) of the toroid 1b [*] Prof. Dr. C. Zhang, Dr. S. C. Meng, Dr. J. F. Zhang Molecular Materials Research Center, Scientific Research Academy, School of Chemistry and Chemical Engineering, Jiangsu University Zhenjiang 212013 (P.R. China) Fax: (+ 86)511-8879-7815 E-mail: chizhang@ujs.edu.cn

Amino-coumarin based fluorescence ratiometric sensors for acidic pH and their application for living cells imaging

Two novel ratiometric sensors, 1a and 1b, for acidic pH have been rationally developed with 7-diethylamino-coumarin as the fluorophore and pyridine as the receptor. Both of the sensors exhibited a fluorescence ratiometric response to acidic pH. For sensor 1a, upon decreasing the pH from 8.35 to 2.36, the fluorescence emission spectra exhibited a large red shift from 529 to 616 nm, the emission ratio (I529 : I616) changed dramatically from 8.58 to 0.09, and the pKa value was calculated to be 5.36. The emission ratio also displayed a good linearity with the pH in the range of 4.0 to 6.5, which is valuable for quantitative determination of pH in this acidic pH window. Similar behaviour was observed for sensor 1b. In addition, NMR experiments and theoretical calculations demonstrated that the ratiometric response of the sensors to acidic pH was due to H+ binding with the N of pyridine and the induced enhancement of the intramolecular charger transfer (ICT) process. The sensors have been successfully applied to quantitatively detect pH in biological fluids. The intracellular pH imaging experiments also proved that the sensors are suitable for detecting acidic pH fluctuations in living cells.

Cooperative enhancement of optical nonlinearities in a porphyrin derivative bearing a pyrimidine chromophore at the periphery

A novel porphyrin derivative bearing one D-π-A-π-D pyrimidine chromophore at the periphery was designed, prepared, and studied using the Z-scan technique, the results showing that this compound exhibits enhanced nonlinear optical (NLO) absorption, refraction and optical limiting responses. The significant NLO properties can be ascribed to an effective combination of distinct nonlinear mechanisms.

Syntheses and NLO properties of 1D heterothiometallic anionic W/S/Ag clusters possessing solvento-ytterbium cation-directed isomeric skeletons

The sequential addition to [WS4]2− of different solvent-coordinated ytterbium cations as templates and silver iodide as Ag+ source afforded the heterothiometallic clusters {[Yb(DMSO)7][Yb(DMSO)8][W6S24Ag6]}n1 (DMSO = dimethyl sulfoxide), {[Yb(DMF)8][W3S12Ag3]}n2 (DMF = N,N′-dimethylformamide) and {[Yb(HMP)4(NO3)2][WS4Ag]}n3 (HMP = hexamethylphosphoramide) with isomeric anionic skeletons and in high yields. 1–3 have been fully characterized by elemental analysis, IR and UV-vis spectroscopies, and single-crystal X-ray crystallographic studies. 1 possesses a 1D anionic helical chain with unusual hexavalent repeat units, a structure directed by the combination of seven- and eight-coordinated ytterbium cations, 2 exhibits an unusual 1D anionic zigzag chain, while 3 contains a 1D anionic linear chain. Z-scan studies (532 nm, 8 ns pulses) reveal that 1 and 2 possess strong third-order nonlinear optical properties. Density functional theory and time-dependent density functional theory calculations at the B3LYP/LanL2DZf+6-31G* level were performed on 1–3 to rationalize their experimental absorption spectra.

Construction of novel WO3/SnNb2O6 hybrid nanosheet heterojunctions as efficient Z-scheme photocatalysts for pollutant degradation

The artificially Z-scheme heterojunctions between WO3 nanosheet and SnNb2O6 nanosheet with strongly coupled heterointerfaces were successfully constructed via a simple hydrothermal coassembly method. Transmission electron microscopy (TEM) and high-resolution TEM proved that an intimate contact interface was formed. The synthesized heterojunctions exhibites enhanced photodegradation efficiency for Rhodamine B under irradiation of visible light, and the highest reaction rate over 30%-WO3/SnNb2O6 nanosheet heterojunctions is about 4.7-fold and 2-fold higher than that of pristine WO3 and SnNb2O6, respectively. Such a considerable improvement could be mainly attributed to the rapid migration of the photo-induced e-/h+ pairs through the nanosheets-coupled heterojunction interfaces. A possible directly Z-scheme charge transfer mechanism was proposed for the elimination of organic contaminants under irradiation of visible light. This work may furnish new insights into development of novel 2D/2D nanosheet heterojunctions with the enhanced photocatalytic activity.

A highly selective and sensitive fluorescence ratiometric probe for cyanide and its application for the detection of cyanide in natural water and biological samples

A fluorescent ratiometric probe, compound 1, for cyanide has been rationally constructed based on an intramolecular charge transfer (ICT) mechanism. Upon treatment with cyanide, probe 1 exhibited a fluorescence ratiometric response, with the emission wavelength displaying a very large shift (up to 160 nm). When 2 equivalents of cyanide were added, the emission ratios (I458/I618) of probe 1 changed dramatically from 0.027 to 28.306. In addition, the emission ratios (I458/I618) showed good linearity with the cyanide concentration in the range of 0–6.0 μM, and the detection limit measured to be 0.126 μM. The NMR experiments and theoretical calculations confirmed that the ratiometric response of probe 1 to cyanide is due to the nucleophilic addition reaction of the cyanide with the vinyl malononitrile group of probe 1, which results in the inhibition of the ICT process in the probe. Importantly, probe 1 has been applied to detection of cyanide in a natural water sample with satisfactory recovery. Furthermore, the quantitative determination of endogenous cyanide in cassava root demonstrated that the probe can be employed to detect endogenous cyanide in real biological samples.

Nickel core–palladium shell nanoparticles grown on nitrogen-doped graphene with enhanced electrocatalytic performance for ethanol oxidation

Herein, we report a facile two-step strategy for green synthesis of nickel core–palladium shell nanoclusters on nitrogen-doped graphene (Ni@Pd/NG) without any surfactant and additional reducing agent. During the synthesis, nitrogen-doped graphene acted as both the active substance and support by taking advantage of its moderate reducing and highly dispersing capacities. Characterization indicated that a uniform dispersion of Ni@Pd nanoparticles on nitrogen-doped reduced graphene oxide had a 2.8 nm average particle size. Unexpectedly, the as-prepared Ni@Pd/NG hybrid exhibited much greater activity and stability than that of Pd/graphene and commercial Pd/C electrocatalyst at the same Pd loadings. Possible mechanisms for the enhanced electrocatalytic performance of nitrogen-doped reduced graphene oxide after combining with Ni@Pd are proposed. The present study provides an efficient strategy to synthesize highly efficient electrocatalysts.