Ultrasound-Assisted Hydrothermal Synthesis of Highly Fluorescent Sulfur Quantum Dots for Fe3+ Ion and Ascorbic Acid Detection in Real Samples.

In this work, the ultrasound-assisted hydrothermal synthesis method offers a facile method to synthesize highly efficient photoluminescence sulfur quantum dots (SQDs). Impressively, a switchable fluorescent "on-off-on" sensor was developed using the acquired SQDs, which are capable of sequentially detecting iron ions (Fe3+) and ascorbic acid (AA) with exceptional sensitivity and selectivity. Meanwhile, SQDs and Fe3+ formed complexes through coordination, causing the fluorescence quenching of SQDs because of the static quenching effect. Upon the addition of AA into the SQDs/Fe3+ system, a redox-reaction-mediated mechanism leads to the recovery of fluorescence. The fluorescence intensity of SQDs exhibits a linear relationship with the concentrations of Fe3+ and AA in the ranges 5-30 and 20-100 µM, respectively. Notably, the detection limits achieved are 14.31 nM for Fe3+ and 0.64 µM for AA. Moreover, the chemosensor was successfully employed for monitoring Fe3+ in real water samples and AA in fruits. These results demonstrate the excellent analysis and detection capabilities of SQDs in the complex environment.

A New Cd(II)-Based Coordination Polymer for Efficient Photocatalytic Removal of Organic Dyes.

Coordination polymers (CPs) are a diverse class of multi-dimensional compounds that show promise as photocatalysts for degrading dyes in polluted water. Herein, a new 1D Cd(II)-based coordination polymer with the formula [Cd(bpyp)(nba)2] (1) (bpyp = 2,5-bis(pyrid-4-yl)pyridine and Hnba = 4-nitrobenzoic acid) is synthesized and characterized. In 1, the two carboxyl groups of two different nba- ligands show µ2-η1:η1 and µ1-η1:η1 coordination modes to connect the CdII centers and sit on either side of the chain along the b direction. The produced CP 1 was utilized as the photocatalyst in the process of the photodegradation of methyl blue (MB), methyl orange (MO), rhodamine B (RhB), and methyl violet (MV) dyes when exposed to UV light. The photocatalytic degradation activities of CP 1 were analyzed, and the results suggest that it exhibits an extraordinary efficiency in the degradation of MB, MV, MO, and RhB. RhB has a 95.52% efficiency of degradation, whereas MV has a 58.92% efficiency, MO has 35.44%, and MB has 29.24%. The photodecomposition of dyes is catalyzed mostly by •O2- and •OH-, as shown by research involving the trapping of radicals.

Removal of ammonia nitrogen and phenol by pulsed discharge plasma combined with modified zeolite catalyst.

In this work, the removal of ammonia nitrogen and phenol by pulsed discharge plasma (PDP) and modified zeolite was investigated. The Fe-zeolite and Mn-zeolite catalysts were prepared by the impregnation method. Catalysts' morphology, specific surface area, and chemical bond structure were characterized. Based on the pollutants removal experiments, Fe-zeolite (0.01) in the PDP system had better catalytic oxidation of phenol and adsorption effect of ammonia nitrogen. The removal efficiency of the pollutants increased with the increase of discharge voltage and solution conductivity, but decreased with the increase of discharge distance. During the plasma discharge process, the pH value in the solution decreased, and the solution conductivity gradually increased. After PDP/Fe-zeolite system treatment, the toxicity of the wastewater was significantly reduced. This study provided a new treatment method for inorganic and organic pollutants treated by PDP.

An off-on electrochemiluminescence detection for microRNAs based on TiO2 nanotubes sensitized with gold nanoparticles as enhanced emitters.

A sensitive electrochemiluminescence (ECL) assay for microRNAs (miRNAs) based on a semiconductor nanomaterial sensitized with noble-metal Au nanoparticles (NPs) is successfully developed. TiO2 nanotubes (NTs) were equipped with Au NPs to obtain an enhanced ECL emitter. Then, an ECL assay for miRNA-21 was fabricated, which was based on the use of probe 2 DNA-functionalized Pt/PAMAM nanocomposites (NCs) assembled on the surface of Au/TiO2 NT conjugate via DNA hybridization between probe 1 DNA and capture DNA. The Pt/PAMAM NCs act as an ECL quencher of Au/TiO2 NTs via resonance energy transfer. After the binding of target miRNA-21 and the capture DNA, the Pt/PAMAM NCs were released and the ECL signal was recovered. An "off-on" ECL assay was achieved with a linear response from 0.01 to 10,000 pM. Finally, this method has been validated to be sensitive and specific for miRNAs in human serum samples. The ECL enhancement strategy opens a new way for fabricating various sensitive biosensors. Graphical abstract A sensitive "off-on" electrochemiluminescence analysis method was developed, which combined Au NP-enhanced ECL emission of TiO2 nanotubes and an efficient energy-transfer system between Au/TiO2 nanotubes and Pt/PAMAM nanocomposites.

TiO2 nanotubes loaded with CdS nanocrystals as enhanced emitters of electrochemiluminescence: application to an assay for prostate-specific antigen.

An enhanced cathodic electrochemiluminescence (ECL) assay for prostate-specific antigen (PSA) is developed based on the in situ activation of a semiconductor nanomaterial. An excellent ECL emitter (CdS/TiO2 nanotubes) was fabricated by the combination of TiO2 nanotubes (NTs) and thioglycolic acid-capped CdS nanocrystals (NCs). After the activation of the hydrogen peroxide-citric acid solution, the ECL signal was enhanced 265 times compared with that of the original TiO2 NT with H2O2 as co-reactant. For the ECL assay, activated CdS/TiO2 NTs were assembled with complementary DNA, PSA aptamer and probe DNA-functionalized SiO2@Pt nanoparticles (NPs) via DNA hybridization to form the detection platform. The SiO2@Pt NPs acted as ECL quencher of CdS/TiO2 NTs. In the presence of PSA, ECL increased after the release of pDNA-SiO2@Pt NPs because of the binding of PSA to the aptamer. An "off-on" ECL phenomenon appeared. The enhanced ECL signals were used for sensitive determination of PSA. The dynamic range was 0.001 to 50 ng mL-1 with a detection limit of 0.4 pg mL-1 (S/N = 3). This new approach conceivably paves the way for fabricating various other enhanced ECL emitter systems, with good application prospects in clinical practice. Graphical abstract The activated CdS/TiO2 nanotubes and SiO2@Pt nanoparticles were synthesized and used to develop an energy-transfer electrochemiluminescence analysis method with high sensitivity and anti-interference performance.

Unique Topology Analysis by ToposPro for a Metal-Organic Framework with Multiple Coordination Centers.

The reactions of 2-(4-pyridyl) thiazole-4-carboxylic acid (Hptca) and CuCl2·6H2O have led to a novel 3D mixed-valence, four-copper-center, metal-organic framework (MOF) [Cu8Cl2(ptca)10·17H2O] n (1). The topology analysis using ToposPro software package for 1 resulted in three chain-based topology types of sra (42, 63, 8), pcu (412, 63), and dia (66) via choosing corresponding connection atoms as central atoms. The study indicates that connection atoms associated directly with multiple coordination centers are applicable to act as central atoms. This unique topology analysis approach is conceptually different from the current analytical methods which use node atoms as central atoms. In addition, complex 1 exhibits significant selective adsorption of CO2 over N2. This study provides a great example of the topological analysis of MOFs with multiple coordination centers.

Two Isostructural Metal-Organic Frameworks Directed by the Different Center Metal Ions, Exhibiting the Ferrimagnetic Behavior and Slow Magnetic Relaxation.

Two 3D isostructural metal-organic frameworks with 1D ferrimagnetic chains, formulated as [M3(L)(µ3-OH)2(H2O)4] [H4L = (1,1':4',1″-terphenyl)-2',3,3″,5'-tetracarboxylic acid, where M = Mn for 1 and Co for 2], have been successfully synthesized by employing different center metal ions and a multicarboxylate ligand under identical reaction conditions in this work. The single-crystal X-ray diffraction data of 1 and 2 reveal that the complexes are two 3D isostructural frameworks based on 1D [M3(OH)2]n chains composed of triangular subunits as rod-shaped secondary building units, which are classified as binodal 4,6-connected fry nets with the point symbol (5(10)·6(3)·7(8))(5(4)·6(2)). The magnetic properties revealed that complexes 1 and 2 exhibit ferrimagnetic behavior. Also, the alternating-current susceptibility of 2 displays slow magnetic relaxation, showing interesting magnetic behavior of a single-chain magnet with an effective energy barrier of 32 K.

MOF-templated synthesis of photoluminescent MoS2 QDs.

Fabricating MoS2 QDs using porous metal-organic frameworks (MOFs) as templates remains a great challenge, because the MOF structure is prone to collapse during solvothermal reactions, resulting in a loss of the function of the template. In the present work, the production of homogeneous photoluminescent MoS2 QDs was achieved by using the structurally stable MOF MIL-101 as limited nanoreactors. The process developed opens up a new route for fabricating other photoluminescent QDs and their derived nanomaterials.

Properties, Preparation and Applications of Low Dimensional Transition Metal Dichalcogenides.

Low-dimensional layered transition metal dichalcogenides (TMDs) have recently emerged as an important fundamental research material because of their unique structural, physical and chemical properties. These novel properties make these TMDs a suitable candidate in numerous potential applications. In this review, we briefly summarize the properties of low-dimensional TMDs, and then focus on the various methods used in their preparation. The use of TMDs in electronic devices, optoelectronic devices, electrocatalysts, biosystems, and hydrogen storage is also explored. The cutting-edge future development probabilities of these materials and numerous research challenges are also outlined in this review.

A microporous anionic metal-organic framework for a highly selective and sensitive electrochemical sensor of Cu(2+) ions.

We first reported an anionic metal-organic framework for electrode material for the electrochemical detection of Cu(2+). The modified electrode shows an excellent selectivity, high stability and sensitivity, wide linear range and lower detection limit. This strategy for generating new electrode materials will be useful for preparing new sensors and reporters for biological systems.

Two porous luminescent metal-organic frameworks: quantifiable evaluation of dynamic and static luminescent sensing mechanisms towards Fe(3.).

Two novel porous luminescent metal-organic frameworks (MOFs, 1 and 2) have been constructed using 3,4-di(3,5-dicarboxyphenyl)phthalic acid using a hydrothermal method. Both MOFs can work as highly sensitive sensors to Fe(3+) by luminescent quenching. Analyses of the structures indicate a higher quenching efficiency of 2 because of the existence of active -COOH groups. Based on this consideration, the quenching mechanisms are studied and the processes are controlled by multiple mechanisms in which dynamic and static mechanisms of MOFs are discussed. Besides, the corresponding dynamic and static quenching constants are calculated, achieving the quantification evaluation of the quenching process. As expected, experimental data show that compound 2 possesses an overall quenching efficiency 6.9 times that of compound 1. Additionally, time-dependent intensity measurements, the shifts of the excitation spectrum and the appearance of a new emission peak all give visual proofs of the distinct mechanisms between the two MOFs.

Syntheses and crystal structures of a series of coordination polymers constructed from C2-symmetric ligand 1,3-adamantanedicarboxylic acid.

This article systematically investigates the influence of the properties of inhomogeneous N-auxiliary ligands and pH value on the helical structures of complexes based on C(2)-symmetric ligand 1,3-adamantanedicarboxylic acid (H(2)ADC). Five kinds of neutral ligands (phen=1,10-phenanthroline, bipy=4,4'-bipyridine, bpa=1,2-bis(4-pyridyl)ethane, bpe=1,2-bis(4-pyridyl)ethane, and bpp=1,3-bis(4-pyridyl)propane) were selected, and a series of new Zn(II)/Co(II) dicarboxylates have been synthesized by slow diffusion, namely, [Zn(phen)(ADC)(H(2)O)](2).CH(3)OH (1), {[Zn(ADC)(bpe)].H(2)O}(n) (2), {[Zn(ADC)(bipy)].2H(2)O}(n) (3), {[Zn(ADC)(bpa)](2).5H(2)O}(n) (4), {[Zn(ADC)(bpp)](2).CH(3)OH}(n) (5), {[Zn(ADC)(bpp)]}(n) (6), {[Co(ADC)(bpp)(CH(3)OH)(H(2)O)].CH(3)OH2 H(2)O}(n) (7), and {[Co(ADC)(bpp)]}(n) (8). Single-crystal X-ray structural analysis shows that complex 1 forms a 0D dinuclear with closed-loop unit. The complex 2 is a 2D layer framework. Compounds 3 and 4 are isomorphous with a small discrepancy and present one-dimensional chainlike structures. It is interesting that the 2D organic-inorganic hybrid frameworks containing meso-helical chains have been observed. Compound 5 is a 2D interpenetrated network with (4,4) topology, in which homochiral left-handed helical chains are arranged in an ABAB sequence parallel to the plane defined by (a,c), and right-handed helical chains running along the a axis are also observed in the solid state, resulting in a meso-helical structure. Compounds 6, 7, and 8 crystallize in a chiral space group P212121. Highly dimensional 6 and 8 are essentially isostructural and present a threefold interpenetrated 3D diamondoid network containing three helical chains, whereas 7 exhibits a 2D grid layer with a left-handed helical chain. Furthermore, thermal stability, X-ray powder diffraction, and the luminescent properties of 1-6 are also discussed.

Interplay of coordinative and supramolecular interactions in formation of a series of metal-organic complexes bearing diverse dimensionalities.

A series of new metal-organic coordination complexes, {[Ni(IP)(H(2)O)(4)].(2H(2)O)(SO(4))} (1), [M(IP)(mu(2)-SO(4))(H(2)O)(2)] (M = Zn 2 , and M = Mn 3 ), {[M(2)(IP)(2)(mu(2)-SO(4))(2)(H(2)O)(4)].2H(2)O} (M = Zn 4 , and M = Co 5 ), {[Mn(2)(IP)(mu(2)-SO(4))(H(2)O)(2)].(6.5H(2)O)(sdba)} (6), {[Mn(IP)(2)(H(2)O)(2)][Mn(pydc)(2)(H(2)O)(2)].(4H(2)O)} (7), {[Mn(IP)(fum)(H(2)O)].H(2)O} (8), {[M(3)(IP)(3)(fum)(3)].(8H(2)O)} (M = Cd 9, and M = Zn 10 ), {[Cd(2)(IP)(2)(bptc)(H(2)O)(2)].(7.3H(2)O)} (11), {[Zn(2)(IP)(2)(bptc)(H(2)O)(2)].(3H(2)O)} (12), {Cd(1,4-BDC)(IP)(H(2)O)].(0.5H(2)O)} (13), {[Mn(1,4-BDC)(IP)(H(2)O)].H(2)O} (14), {[Zn(2)(1,4-BDC)(2)(IP)].2.5H(2)O} (15) (IP = 1H-imidazo[4,5-f][1,10]-phenanthroline, H(2)sdba = 4,4'-sulfonyldibenzoic acid, H(2)pydc = pyridine-2,6-dicarboxylic acid, H(2)fum = fumaric acid, H(4)bptc = 3,3',4,4'-benzophenonetetracarboxylic acid and 1,4-H(2)BDC = 1,4-benzendicarboxylic acid) were prepared via self-assembly of pharmaceutical agent IP with different metal sulfates in the absence/presence of the carboxylate under mild conditions. All these compounds were structurally determined by single-crystal X-ray diffraction. Compounds 2-6 crystallize with N-donor chelating ligands and sulfate anion linkers. Complexes 2-6 possess sulfate anions with mu(2)-bridging modes, the roles of sulfate anions result in 1D chains (2 and 3) and dinuclear units (4, 5and 6). For complex 7 , two different Mn units are chelated by two IP and pydc ligands, respectively. Compound 8 is a 1D chain connected by fum ligands. Polymers 9-12 exhibit 2D network structures composed of tetrametallic and hexametallic clusters. The Cd(ii)/Zn(ii) layers are interdigitated in pairs for complexes 11 and 12 by stacking forces, which exhibit unusual 2D-->3D interdigitated architectures. In 13 and 14, they show 1D undulating and linear chains due to the different coordinate modes of 1,4-BDC. IP firstly acts in a tridentate mode via the two N atoms of pyridyl rings and the third N atom of imidazole ring, and the two carboxylate groups of 1,4-BDC ligand taking three types of coordinative modes connect Zn atoms into a complicated 3D network in 15 . The structural differences among complexes 1-15 indicate the backbone of such dicarboxylate ligands, nature of metal resources and the ratio of metal to ligand play important roles in modulating the formation of the coordination polymers. Thermal stabilities of these crystalline materials, fluorescent properties of these complexes and TD-DFT calculation of spectra of IP were also investigated.

New types of di-, tetra-, hexa- and octanuclear Ag(I) complexes containing 1,3-adamantanedicarboxylic acid.

This article represents a systematical investigation on the structures of silver(I) dicarboxylate incorporating secondary ligands, revealing that the secondary interactions could play an important role in interlinking low-dimensional entities to high-dimensional supramolecular frameworks. A new 2D silver(I) crystalline dicarboxylate, {[Ag(6)(ADC)(3)(H(2)O)(1.5)](2).5.18H(2)O}(n) (1) (H(2)ADC = 1,3-adamantanedicarboxylic acid), has been obtained by slow diffusion of corresponding precursors. To investigate the influence of the properties of pyridylic neutral ligands on the complex structures based on compound 1, five kinds of neutral ligands (bipy = 4,4'-bipyridine; bpa = 1,2-bis(4-pyridyl)ethane; bpe = 1,2-bis(4-pyridyl)ethene; bpp = 1,3-bis(4-pyridyl)propane; bpdap = N,N'-bis(3-pyridyl)-2,6-diaminopyridine) were selected, and a series of new silver(I) dicarboxylate have been synthesized: {[Ag(bpa)(HADC)]}(n) (2), {[Ag(bpp)(HADC)].CH(3)OH}(n) (3), {[Ag(4)(bpe)(3)(ADC)(2)].2H(2)O}(n) (4), {[Ag(bipy)(HADC)].H(2)O}(n) (5), {[Ag(2)(bipy)(2)(ADC)].6H(2)O}(n) (6), and [Ag(8)(bpdap)(4)(ADC)(4)].2C(2)H(5)OH.6H(2)O (7). Single-crystal X-ray structural analysis shows that complexes 1 and 4 are formed by hexanuclear and tetranuclear Ag(I) clusters with weak Ag-Ag interactions. Complexes 2 and 3 are dinuclear structures, 5 and 6 exhibit an infinite 1D chain structure, whereas 7 is a discrete octanuclear Ag(I) unit. The structures of 1-7 span from dinuclear, tetranuclear, hexanuclear, to octanuclear Ag(I) complexes, which indicates that secondary ligands do play important roles in the formation of such coordination architectures. Thermal stability, X-ray powder diffraction and luminescent properties of the compounds are also discussed.