Dimensional Layered Structure Research Articles

Liquid Phase Exfoliation of Two Dimensional Transition Metal Oxides for Electrochemical Applications

Transition metal oxides (TMOs) represent an attractive family of materials for their electrochemical charge storage properties. The theory is mainly based on the two dimensional layered structure of these materials providing increased surface area for charge storage alongside decreased diffusion paths for lithium and other intercalation ions. Much work is done into the exfoliation of two dimensional materials such as V2O5 and anatase TiO2, however many methods require multistep chemical processes which can be lengthy and introduce the possibility of unwanted by-products. Liquid phase exfoliation by sonolysis provide a simple cost effective method to exfoliate these two dimensional TMOs to produce relatively thin nanoflakes with impressive charge storage capacities, cycle lifetime and efficiency. This work aims to show the charge storage capabilities of V2O5 and anatase TiO2 which both exceed their theoretical capacities without the use of polymer binders or conductive additives. Sonication of bulk material in common solvents for a relatively short time scale produces desirable nanoflakes while ultrasonic spraying produces uniform electrodes which are tested electrochemically vs. Li/Li+. In conclusion, this project, using simple methodology, produces electrochemically impressive two dimensional materials. Figure 1

Layered MoS2 based Electrochemical Biosensor

Recently two dimensional layered structures, such as graphene and Molybdenum disulfide (MoS2), have got attention because of their unique physical and chemical properties. It has been reported that the integration of carbon-based materials and metal oxide nanoparticle shows synergistic effects in electrochemical application. Graphene sheets are explored due to their large active surface area, which can be embedded by intercalation methods and high mobility, on/off ratio. However, graphene doesn’t have band-gap which adds a large leakage current and reduces dynamic range of sensor hence it is difficult to use in sensing applications. In contrast, MoS2 has a direct band gap whereas all other features are similar to graphene. Typically, MoS2 is composed of three atomic layers which are composed by a Mo layer between Surfer layers. These layers are stacked and held each other by weak van der Waals force so molecule can be embedded. These properties lead to fabrication of MoS2 nanosheet-based field effect biosensor for potential use in the bio-sensing applications.It is well known that for biosensor, selective, accurate and rapid detection methods are necessary. As an example significant work has been carried out for the detection of H2O2 using fluorescence, chemiluminescence, titrimetry, cell imaging, spectrophotometry and electrochemical methods. Among them, electrochemical method has great advantages including high sensitivity, selectivity, low cost and simple instrumentation. Until now, horseradish peroxidase (HRP), a heme enzyme, has been commonly used to contrast an efficient H2O2 biosensor. However, the preparation of H2O2 biosensor with high performance has proven challenging. For achieving it, MoS2 has been utilized to modify the surface of electrode and immobilize HRP because of high surface reaction activity and good catalytic efficiency.In the present work, the electrocatalytic activity of layered MoS2 toward the reduction of H2O2 with the help of HRP is demonstrated. The chemical vapor deposition (CVD) synthesized MoS2 thin films are transferred on gold (Au) electrode and was characterized by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and high-resolution transmission microscopy (HR-TEM). IgG-HRP was then immobilized on MoS2 thin film layers. Here MoS2 work as an electrocatalyst between Au electrode and active centers of HRP. Cyclic voltammetry (CV) results demonstrated the fast electron transfer process between HRP and the Au electrode. Figure 1 show the CV plots of IgG-HRP modified MoS2 towards H2O2 for 10 to 100 mVs-1 scan rates. It is observed that no reduction peak for 10 mM PBS (curve a). However, reduction peak were observed (curve b, c, and d) as the scan rate increases from 10 to 100 mVs-1. This phenomenon can be attributed to electrochemical reaction of immobilized IgG-HRP on MoS2 Au electrode and H2O2.In conclusion, in the present work we successfully demonstrated MoS2 based electrochemical biosensor platform for the detection of H2O2. Further H2O2 concentration dependent evolution is in process. We believe that this work will be helpful for the research community to develop MoS2 based electrochemical biosensors.

Chemical Solution Based MoS2 Thin Film Deposition Based on Dimensional Reduction

ABSTRACTAs a promising transition metal dichalcogenide (TMDC), molybdenum disulfide (MoS2) has recently attracted a lot of attention due to its graphene-liked two dimensional layer structure, which leads to potential applications in electronic and optoelectronic devices. However, the fabrication of mono- or few-layer MoS2 is limited to ether liquid exfoliation or CVD, and the chemical solution deposition is limited to ammonium thiomolybdate-based precursor. In this paper, hydrazine-based dimensional reduction technique is applied in the chemical solution deposition of MoS2 thin-film, and a larger area uniform thin-film is obtained from bulk powder MoS2. This solution-based process could be applied with a variety coating techniques and lead to wafer level MoS2 thin film production.

Cation Intercalation and High Volumetric Capacitance of Two-Dimensional Titanium Carbide

The intercalation of ions into layered compounds has long been exploited in energy storage devices such as batteries and electrochemical capacitors. However, few host materials are known for ions much larger than lithium. We demonstrate the spontaneous intercalation of cations from aqueous salt solutions between two-dimensional (2D) Ti3C2 MXene layers. MXenes combine 2D conductive carbide layers with a hydrophilic, primarily hydroxyl-terminated surface. A variety of cations, including Na(+), K(+), NH4(+), Mg(2+), and Al(3+), can also be intercalated electrochemically, offering capacitance in excess of 300 farads per cubic centimeter (much higher than that of porous carbons). This study provides a basis for exploring a large family of 2D carbides and carbonitrides in electrochemical energy storage applications using single- and multivalent ions.

Designed synthesis of copper(II) and nickel(II) complexes with a tridentate N2O donor Schiff base: Modulation of crystalline architectures through C[sbnd]H⋯π and anion⋯π interactions

Two copper(II) complexes, Cu(L1)Cl (1), Cu(L1)NCS (3) and two nickel(II) complexes Ni(L1)Cl (2), Ni(L1)NCS (4), where HL1=1-[(2-diethylamino-ethylimino)-methyl]-naphthalen-2-ol act as tridentate N2O donor ligand, have been prepared and characterized by elemental analysis, IR and UV–Vis spectroscopy and single crystal X-ray diffraction studies. The geometry of the central metal ion in each of the four complexes is square planar. The existence of CH⋯π interactions in 2 gives rise to one dimensional chain structure. Complex 3 shows two CH⋯π interactions and one anion⋯π interactions which leads to a two dimensional layer structure. Each mononuclear unit of 4 has two CH⋯π interactions along b axis to form a double strand one dimensional array of the molecules in crystal packing.

Syntheses, crystal structures of two coordination polymers constructed from imidazole-based dicarboxylate ligands containing alkyl group

Two new coordination polymers, |DMF|[Zn 2 (C 7 N 2 O 4 H 6 ) 2 (C 10 N 2 H 8 )] ( 1 ) and |(H 2 O) 3 |[Co(C 8 N 2 O 4 H 9 ) 2 (H 2 O) 2 ] ( 2 ) have been synthesized based on 2-ethyl-1H-imidazole-4,5-dicarboxylic acid (H 3 EtImDC) and 2-propyl-1H-imidazole-4,5-dicarboxylic acid (H 3 PrImDC) as organic ligands, respectively. Single-crystal X-ray diffraction analysis reveals that compound 1 is a two dimensional layered structure constructed from two types of six-membered metallocycle, and the layers are stacked in an –ABCABC– sequence. For 2 , the mononuclear [Co(C 8 N 2 O 4 H 9 ) 2 (H 2 O) 2 ] molecules are connected with each other through hydrogen bonds forming a three dimensional supermolecular structure. Further characterizations including elemental analyses, IR spectra, and thermogravimetric analyses have been studied. Compound 1 shows a 2D layered structure, which is generated from two types of six-membered metallocycle, and the layers are stacked in an -ABCABC- sequence. For 2 , the mononuclear [Co(C 8 N 2 O 4 H 9 ) 2 (H 2 O) 2 ] molecules are connected with each other through hydrogen bonds forming a 3D supermolecular structure. ► Both the two compounds constructed from H 3 ImDC derivatives with alkyl group ► Compound 1 shows a 2D structure formed by two types of six-membered metallocycle. ► Compound 2 presents a 3D supermolecular structure.

Coordination assemblies of the CdII–BDC/bpt mixed-ligand system: positional isomeric effect, structural diversification and luminescent properties

To further systematically investigate the influence of the positional isomeric ligands on the structures and properties of transition metal complexes, we synthesized six Cd(II) complexes with three positional isomeric dipyridyl ligands (4,4′-bpt, 3,4′-bpt and 3,3′-bpt) and three positional isomeric phenyl dicarboxylate anions (p-BDC, m-BDC and o-BDC), namely, [Cd3(p-BDC)3(4,4′-bpt)2(H2O)5]·H2O (1), [Cd(p-HBDC)(p-BDC)0.5(3,4′-bpt)] (2), [Cd4(p-BDC)4(3,3′-bpt)4]·9H2O (3), [Cd(m-BDC)(3,3′-bpt)(H2O)]·2H2O (4), [Cd(o-BDC)(3,3′-bpt)(H2O)]·(3,3′-bpt)·4H2O (5), [Cd(o-BDC)(3,4′-bpt)(H2O)]·H2O (6). Structural analysis reveals that 1 is composed of a three dimensional (3D) 4-connected net giving an interesting 3-fold interpenetrating architecture. 2 and 3 possess a similar two dimensional (2D) layer structures. 4 presents an infinite one dimensional (1D) tubular-like chain. 5 displays a 2D honeycomb structure consisting of a 1D metal–organic helical chain. 6 exhibits a 2D wave-like layer structure with a (44)-sql network. Structural diversities indicate that the nature of isomeric benzene–dicarboxylates and bpt ligands plays crucial roles in modulating structures of these complexes. Intermolecular forces have important effects on the formation and strengthening of the supra-molecular architecture in these complexes. Moreover, the luminescent properties of them have been briefly investigated.

Supramolecular structure of bis(N,N′,N″-triisopropylguanidinium) phthalate

In the structure of the N,N′,N″-triisopropylguanidinium salt of phthalate (I), 2(IPGH)+·(C8H4O4)2−, the asymmetric unit contains two symmetry-independent cations and one anion having different inter-species hydrogen-bonding environments, which includes cyclic R22(8) and R44(16) associations. These interactions give a two dimensional layered structure.

Two Cadmium-Cluster-Based Metal–Organic Frameworks with Mixed Ligands of 1,2,3-Benzenetriazole (HBTA) and 1,4-Benzenedicarboxylic acid (H2BDC)

Two cadmium(II) metal–organic frameworks based on two mixed ligands of HBTA and H2BDC, [Cd5(BTA)6(BDC)2(DMF)4(H2O)2]n·n(2DMF·H2O) (1) and [Cd7(BTA)2(BDC)6(DMF)8]n·2nDMF (2) (HBTA = 1,2,3-benzenetriazole; H2BDC = 1,4-benzenedicarboxylic acid), have been prepared through methods of liquid to liquid diffusion and solvothermal reaction, respectively. The results of single-crystal X-ray diffraction analyses indicate that both MOFs are constructed from cadmium clusters. In 1, six BTA– anions connect five Cd(II) ions to generate a tetrahedral Cd5 cluster, which further links with four equivalent Cd5 clusters through four BDC2– bridges, forming a (4,4)-connected two–dimensional (2D) layer structure. In 2, each BTA– anion connects three Cd(II) ions to generate a triangular Cd3 cluster, which further links with four Cd3 clusters and two 3-connected BDC2– anions, forming a (3,6)-connected three-dimensional (3D) framework. The results of photoluminescent measurements illustrate that in the solid state, both 1 and 2 can emit fluorescence at 465 and 450 nm, respectively.

The Structure of Two-Dimensional Layered Cu (ΙΙ) Complex Material

A Cu (II) complex has been obtained by one-pot reaction of copper nitrate with 4-aminobenzene sulfonic acid, 2-acetylpyridine and sodium hydroxide. Unfortunately, the complex does not contain 2-acetylpyridine molecules, and 4-aminobenzene sulfonic acid coordinate to Cu (II) ion. The structure of Cu (II) complex was characterized by single-crystal X-ray diffraction. The results show that the complex crystallizes in monoclinic, space group P2(1)/n with a = 0.7437(3) nm, b = 1.7408(6) nm, c = 0.7644(3) nm, V = 0.8846(5) nm3, Z = 2, F (000) = 494, Rint = 0.0697, and the complex formed two dimensional layered structure through intramolecule and intermolecule hydrogen bonds and π-π stacking interaction.

A novel two dimensional samarium(III) coordination framework with N-(2-Hydroxyethyl)iminodiacetic acid and oxalate ligands: Synthesis, crystal structure and magnetic property

Under hydrothermal conditions, Sm(NO(3))(3)center dot 6H(2)O reacts with N-(2-Hydroxyethyl)iminodiacetic acid (H(3)heidi), oxalic acid (H(2)Ox), in the presence of NiCl(2)center dot 6H(2)O and NaOH, producing a novel two dimensional coordination polymer with the empirical formula of Na[Sm(Hheidi)(Ox)]center dot 2H(2)O (1). X-ray diffraction analyses show that 1 crystallizes in the orthorhombic system, Pna21 space group, a=25.9008(19) angstrom, b=6.2593(5) angstrom, c=8.7624(6) angstrom, in which the network of SmNO(8) and oxalate units forms an extended two dimensional layered structure. To the best of our knowledge, 1 represents the first structurally characterized lanthanide complex containing H(3)heidi ligand. The variable-temperature magnetic property of 1 has been investigated and the results of magnetic determination suggest the existence of a weak antiferromagnetic coupling between the samarium ions. (C) 2011 Elsevier B.V. All rights reserved.

Cobalt and cadmium complexes with N-heterocyclic dicarboxylic acid ligands: Syntheses, structures, magnetic and fluorescent properties

Two new complexes, [Co(Himdc)2(H2O)2] (1) and {[Cd(pzdc)(H2O)]·H2O}n (2) (H2imdc=imidazole-4, 5-dicarboxylic acid, H2pzdc=pyrazine-2, 3-dicarboxylic acid), have been synthesized and structurally characterized. Compound 1 is a new triclinic mononuclear complex formed by two Himdc− ligands trans coordinated to the CoII center in bidentate chelate mode and two water ligands. Compound 2 shows a two dimensional layer structure in which pzdc2− dianion ligand adopts unique doubly bridging bis-bidentate μ4 coordination mode. Temperature-dependent magnetic susceptibilities and thermal stability for 1 and solid-state fluorescent properties for 2 have been discussed in detail.

Copper(ii) metal–organic networks derived from bis(pyridylformyl)piperazineligands and aromatic polycarboxylates: 2D layered structures and a novel 3,5-connected binodal 3D topology

Three novel coordination polymers [Cu2(3-bpfp)(BDC)2(H2O)2]·4H2O (1), [Cu(3-bpfp)(HBTC)]·0.5H2O (2) and [Cu(4-bpfp)0.5(HBTC)(H2O)] (3) have been hydrothermally synthesized by self-assembly of aromatic polycarboxylate ligands H2BDC (H2BDC = 1,3-benzenedicarboxylate acid) or H3BTC (H3BTC = 1,3,5-benzenetricarboxylate acid), bridging ligands 3-bpfp/or 4-bpfp [3-bpfp = bis(3-pyridylformyl)piperazine, 4-bpfp = bis(4-pyridylformyl)piperazine], and copper chloride. X-Ray diffraction analysis reveals that each CuII ion is connected by BDC/or HBTC and 3-bpfp/or 4-bpfp ligands to form two dimensional (2D) layer structures in compounds 1 and 3. Ligands 3-bpfp and 4-bpfp both display μ4-bridging coordination mode in 1 and 3 (via ligation of pyridyl nitrogen and carbonyl oxygen atoms). In compound 2, each CuII ion is connected by HBTC to construct 2D polymeric layers, which are further linked into a novel 3,5-connected 3D coordination polymeric framework with (4·62)(4·66·83) topology by 3-bpfp ligand in μ2-bridging mode (via ligation of pyridyl nitrogen atoms). Compound 2 is the first 3D example of coordination polymer constructed from 3-bpfp and aromatic polycarboxylate ligands. Moreover, the electrochemical properties of the three copper compounds bulk modified carbon paste electrodes have been studied.

Hydrogen-bonding self-assembly of two dimensional (2D) layer structures generating metal–organic nanotubes

Two metal–organic nanotubular architectures are built from 2D layer structures with big windows through hydrogen-bonding self-assembly of a thiourea group, representing a strategy for the preparation of metal–organic nanotubes generated from 2D layer structures.

Two new ferrimagnetic MnII-carboxylate coordination polymers constructed from 5-tert-butyl isophthalic acid with (5/2, 15/2) and (5/2, 10/2) spin topologies

Two new MnII coordination polymers, {[Mn4(TBIP)4(CH3OH)2]·(H2O)2}n (1) and {[Mn3(TBIP)2(HTBIP)2((CH3)2CHOH)2]}n (2) (H2TBIP = 5-tert-butyl isophthalic acid), have been synthesized by a solvothermal reaction and characterized magnetically. Single-crystal X-ray diffraction studies reveal that 1 is a three-dimensional framework, which is based on a helical chain with a new periodic –J1J1J2J2– sequence. Compound 2 has a two dimensional layer structure constructed by trinuclear Mn(II) subunits that are extended into a 3D architecture by hydrogen bonds. Magnetic measurements indicate that both of the compounds show ferrimagnetic behaviour with different spin topologies. Compound 1 is a rare even-spin centre homometallic ferrimagnetic compound, in which the ferrimagnetism arises from the nature of carboxylate bridging modes. It is also the first example of a 3D homometallic ferrimagnetic compound, featuring a ferrimagnetic helical chain with a (5/2, 15/2) spin topology and a 1/2 magnetization plateau. Compound 2 is a three-spin centre homometallic ferrimagnetic complex with a (5/2, 10/2) spin topology and a 1/3 magnetization plateau.

From (Cd2Se2)(pa) (pa = propylamine) hybrid precursors to various CdSe nanostructures: structural evolution and optical properties

Nanostructural evolution of II-VI semiconductors emerges as a hot research field because it offers a novel route for the synthesis of functional semiconductor nanomaterials. Here, we report a "top-down" process of structural evolution from two dimensional Cd(2)Se(2)(pa) hybrid structures to zero- or one- dimensional CdSe nanostructures. We firstly synthesized the Cd(2)Se(2)(pa) hybrid by a facile solvothermal reaction and determined the hybrid crystal structure through the Rietveld refinement based on the PXRD data. The (Cd(2)Se(2))(pa) hybrid consists of [Cd(2)Se(2)] slabs sandwiched by coordinated n-propylamine layers. Then, we used this hybrid as a precursor to explore the "top-down" fabrication process of structural evolution from two dimensional layered structures to zero- or one- dimensional nanocrystals. It has been shown that various CdSe nanostructures including lamellar structures, nanoparticles, nanowires, and nanorods can be obtained through the pyrolysis of (Cd(2)Se(2))(pa) hybrid precursor under different conditions. It is worth mentioning that the oriented attachment of nanoparticles has been observed during the pyrolysis process. Additionally, the variation of optical properties with structural evolution has been investigated in detail.

A two dimensional heterospin layer coordination polymer of {[LCuIIGdIII(NO3)CuI2(CN)4]·MeOH}n with short CuI⋯CuI bonds

Reaction of [LCuIIGdIII(NO3)3] (L = N,N′-ethylenebis(salicylideneimine)) and [LiTCNE] (TCNE = tetracyanoethylene) in MeOH–CH3CN affords an unexpected cyano-bridged coordination polymer {[LCuIIGdIII(NO3)CuI2(CN)4]·MeOH}n (1) featuring unexpectedly short CuI⋯CuI bonds (2.470(2) Å). X-ray crystallographic analysis reveals that 1 possesses a two dimensional heterospin layer structure comprised of a chain of five-membered rings. The magnetic analysis of 1 reveals a ferromagnetic interaction between the GdIII and CuII ions.

Chiral layered molecular spaces with amino acids

Novel chiral layered molecular space L-(+)-leucine amidepropylamidephenylsilica (L-(+)-Leu-APAPhS) and D-(−)-alanine amidepropylamidephenylsilica (D-(−)-Ala-APAPhS) were synthesized through grafting L-leucine tert-butyl ester (L-Leu-OtBu) and D-alanine tert-butyl ester (D-Ala-OtBu), in layered carboxylpropylamidephenylsilica (CPAPhS), which was developed in our previous research, with regular carboxyl groups, and the tert-butyl ester as protective groups of carboxyls in amino acids was cleaved with dilute trifluoroacetic acid (TFA). The improved XRD response indicated that the two dimensional layered structure had been retained in L-Leu-APAPhS and D-Ala-APAPhS. The chiral behaviors of layered molecular spaces CPAPhS, L-(+)-Leu-APAPhS and D-(−)-Ala-APAPhS were investigated. DL-Alanine tert-butyl ester (DL-Ala-OtBu) was grafted in the achiral layered molecular space CPAPhS as enantiomer pair, even if 70% L-Ala-OtBu and 30% D-Ala-OtBu existed in the reaction solution. L-(+)-Leu-APAPhS and D-(−)-Ala-APAPhS represented better chiral selectivity for amino acids both in chiral selective reactions and chiral column chromatography experiments, and exhibited the potential of chiral layered molecular space with an amino acid structure for chiral molecular recognition and selection processes. The formation of L-Leu-APAPhS-L-Ala-OMe also exhibited potential for that multi-amino acid (peptide) can be grafted in CPAPhS to form layered molecular spaces with peptides.

Investigation on Liquid Crystalline Systems

The results of experiments carried out by us on two samples exhibiting a macroscopic helical structure.While one of them shows a direct transition from chiral orientationally ordered fluid(referred to an N* phase) to a phase with one dimensional layer structure,the second sample exhibits a liquid crystal analog of the Abrikosov flux lattice of super conductors,between the N* and layered phase.The chapter compares and contrasts the differences in the behavior of the two compounds.

Double stranded chains and interwoven structures: the role of conformational isomerism in coordination polymers

The 1:3 and 1:1.5 coordination complexes of 1,3–bis(4–pyridyl)propane, 1, [Ni( 1) 2(H 2O) 2][NO 3] 2⋅( 1)⋅(H 2O), 2 and [Cd 4(1) 6(NO 3) 8], 3 form a double stranded chain and four-fold interwoven structures, respectively. Complex 2 is an unusual coordination complex where the ligand not only coordinates with the metal salt but also cocrystallizes with the coordination complex. The double stranded linear chains in 2 have 24 membered rings with a Ni···Ni intra-chain distance of 11.53 Å and close-pack to form a two dimensional layered structure. The anions, non-coordinating ligands, and the solvated water molecules sandwich between the layers in a bilayer fashion. Complex 3 forms an open network owing to its T-shaped geometry but the conformational flexibility of the ligand blurs the difference between the expected brick wall pattern and the distorted hexagonal network. The internal dimensions between opposite Cd metal centers in the distorted non-planar network are ca 18.3×23.2×28.5 Å. These open networks readily undergo four-fold parallel interpenetration and result in a carpet like structure.