Thermochemistry of NaRb[B4O5(OH)4]·4H2O

The enthalpies of solution of NaRb[B₄O₅(OH)₄]·4H₂O in approximately 1 mol dm⁻³ aqueous hydrochloric acid and of RbCl in aqueous (hydrochloric acid + boric acid + sodium chloride) were determined. From these results and the enthalpy of solution of H₃BO₃ in approximately 1 mol dm⁻³ HCl(aq) and of sodium chloride in aqueous (hydrochloric acid + boric acid), the standard molar enthalpy of formation of −(5128.02 ± 1.94) kJ mol⁻¹ for NaRb[B₄O₅(OH)₄]·4H₂O was obtained from the standard molar enthalpies of formation of NaCl(s), RbCl(s), H₃BO₃(s) and H₂O(l). The standard molar entropy of formation of NaRb[B₄O₅(OH)₄]·4H₂O was calculated from the Gibbs free energy of formation of NaRb[B₄O₅(OH)₄]·4H₂O computed from a group contribution method.     

Syntheses and crystal structures of two new hydrated borates, Zn8[(BO3)3O2(OH)3] and Pb[B5O8(OH)]·1.5H2O

Two new hydrated borates, Zn₈[(BO₃)₃O₂(OH)₃] and Pb[B₅O₈(OH)]·1.5H₂O, have been prepared by hydrothermal reactions at 170 °C. Single-crystal X-ray structural analyses showed that Zn₈[(BO₃)₃O₂(OH)₃] crystallizes in a non-centrosymmetric space group R32 with a=8.006(2) Å, c=17.751(2) Å, Z=3 and Pb[B₅O₈(OH)]·1.5H₂O in a triclinic space group P1¯ with a=6.656(2) Å, b=6.714(2) Å, c=10.701(2) Å, α=99.07(2)°, β=93.67(2)°, γ=118.87(1)°, Z=2. Zn₈[(BO₃)₃O₂(OH)₃] represents a new structure type in which Zn-centered tetrahedra are connected via common vertices leading to helical ribbons _∞¹[Zn₈O₁₅(OH)₃]¹⁷⁻ that pack side by side and are further condensed through sharing oxygen atoms to form a three-dimensional _∞³[Zn₈O₁₁(OH)₃]⁹⁻ framework. The boron atoms are incorporated into the channels in the framework to complete the final structure. Pb[B₅O₈(OH)]·1.5H₂O is a layered compound containing double ring [B₅O₈(OH)]²⁻ building units that share exocyclic oxygen atoms to form a two-dimensional layer. Symmetry-center-related layers are stacked along the c-axis and held together by interlayer Pb²⁺ ions and water molecules via electrostatic and hydrogen bonding interactions. The IR spectra further confirmed the existence of both triangular BO₃ and OH groups in Zn₈[(BO₃)₃O₂(OH)₃], and BO₃, BO₄, OH groups as well as guest water molecules in Pb[B₅O₈(OH)]·1.5H₂O.     

Synthesis and thermochemistry of SrB2O4·4H2O and SrB2O4

Two pure strontium borates SrB₂O₄·4H₂O and SrB₂O₄ have been synthesized and characterized by means of chemical analysis and XRD, FT-IR, DTA-TG techniques. The molar enthalpies of solution of SrB₂O₄·4H₂O and SrB₂O₄ in 1 mol dm⁻³ HCl(aq) were measured to be −(9.92 ± 0.20) kJ mol⁻¹ and −(81.27 ± 0.30) kJ mol⁻¹, respectively. The molar enthalpy of solution of Sr(OH)₂·8H₂O in (HCl + H₃BO₃)(aq) were determined to be −(51.69 ± 0.15) kJ mol⁻¹. With the use of the enthalpy of solution of H₃BO₃ in 1 mol dm⁻³ HCl(aq), and the standard molar enthalpies of formation for Sr(OH)₂·8H₂O(s), H₃BO₃(s), and H₂O(l), the standard molar enthalpies of formation of −(3253.1 ± 1.7) kJ mol⁻¹ for SrB₂O₄·4H₂O, and of −(2038.4 ± 1.7) kJ mol⁻¹ for SrB₂O₄ were obtained.     

Synthesis and thermochemistry of MgO·3B2O3·3.5H2O

A new magnesium borate MgO·3B₂O₃·3.5H₂O has been synthesized by the method of phase transformation of double salt and characterized by XRD, IR and Raman spectroscopy as well as by TG. The structural formula of this compound was Mg[B₆O₉(OH)₂]·2.5H₂O. The enthalpy of solution of MgO·3B₂O₃·3.5H₂O in approximately 1 mol dm⁻³ HCl was determined. With the incorporation of the standard molar enthalpies of formation of MgO(s), H₃BO₃(s), and H₂O(l), the standard molar enthalpy of formation of −(5595.02±4.85) kJ mol⁻¹ of MgO·3B₂O₃3.5H₂O was obtained. Thermodynamic properties of this compound was also calculated by group contribution method.     

Hydrothermal synthesis, characterization and thermochemistry of Ca2[B2O4(OH)2]·0.5H2O

A pure calcium borate Ca₂[B₂O₄(OH)₂]·0.5H₂O has been synthesized under hydrothermal condition and characterized by XRD, FT-IR and TG as well as by chemical analysis. The molar enthalpy of solution of Ca₂[B₂O₄(OH)₂]·0.5H₂O in HC1·54.582H₂O was determined. From a combination of this result with measured enthalpies of solution of H₃BO₃ in HC1·54.561H₂O and of CaO in (HCl + H₃BO₃) solution, together with the standard molar enthalpies of formation of CaO(s), H₃BO₃(s) and H₂O(l), the standard molar enthalpy of formation of −(3172.5 ± 2.5) kJ mol⁻¹ of Ca₂[B₂O₄(OH)₂]·0.5H₂O was obtained.     

Synthesis, characterization, and thermochemistry of a new form of 2MgO·3B2O3·17H2O

A new magnesium borate, β-2MgO·3B₂O₃·17H₂O, has been synthesized by the method of phase transformation of double salt and characterized by XRD, IR, and Raman spectroscopy as well as by TG. The structural formula of this compound was Mg[B₃O₃(OH)₅]·6H₂O. The enthalpy of solution of β-2MgO·3B₂O₃·17H₂O in approximately 1 mol dm⁻³ HCl was determined. With the incorporation of the standard molar enthalpies of formation of MgO(s), H₃BO₃(s), and H₂O(l), the standard molar enthalpy of formation of −(10256.39±4.93) kJ mol⁻¹ of β-2MgO·3B₂O₃·17H₂O was obtained. Thermodynamic properties of this compound was also calculated by group contribution method.     

Hydrothermal synthesis, crystal structure, and magnetic properties of a novel organo-templated iron(III) borophosphate: (C3H12N2)Fe 6(H2O)4[B4P8O32(OH)8]

The organo-templated iron(III) borophosphate (C₃H₁₂N₂)Fe^III ₆(H₂O)₄[B₄P₈O₃₂(OH)₈] was prepared under mild hydrothermal conditions (at 443 K) and the crystal structure was determined from single crystal X-ray data at 295 K (monoclinic, P2₁/c (No. 14), a=5.014(2) Å, b=9.309(2) Å, c=20.923(7) Å, β=110.29(2)°, V=915.9(5) Å³, Z=2, R1=0.049, wR2=0.107 for all data, 2234 observed reflections with I>2σ(I)). The title compound contains a complex inorganic framework of borophosphate trimers [BP₂O₈(OH)₂]⁵⁻ together with FeO₄(OH)(H₂O)- and FeO₄(OH)₂-octahedra forming channels with ten-membered ring apertures in which the diaminopropane cations are located. The magnetization measurements confirm the Fe(III)-state and show an antiferromagnetic ordering at T_N≈14.0(1) K.     

Thermochemistry of dicesium calcium tetraborate octahydrate

The enthalpies of solution of Cs₂Ca[B₄O₅(OH)₄]₂·8H₂O(s) in approximately 1 mol dm⁻³ aqueous hydrochloric acid and of CsCl(s) in aqueous (hydrochloric acid + boric acid + calcium oxide) were determined. From these results and the enthalpies of solution of H₃BO₃(s) in approximately 1 mol dm⁻³ HCl(aq) and of CaO(s) in aqueous (hydrochloric acid + boric acid), the standard molar enthalpy of formation of −(10328 ± 6) kJ mol⁻¹ for Cs₂Ca[B₄O₅(OH)₄]₂·8H₂O(s) was obtained from the standard molar enthalpy of formation of CaO(s), CsCl(s), H₃BO₃(s) and H₂O(l). The standard molar entropy of formation of Cs₂Ca[B₄O₅(OH)₄]₂·8H₂O(s) was calculated from the thermodynamic relation with the standard molar Gibbs free energy of formation of Cs₂Ca[B₄O₅(OH)₄]₂·8H₂O(s) computed from a group contribution method.     

Crystal structure and characterization of Rb2Ca[B4O5(OH)4]2·8H2O

Dirubidium calcium tetraborate octahydrate, Rb₂Ca[B₄O₅(OH)₄]₂·8H₂O, was prepared by reaction of Rb-borate aqueous solution with CaCl₂ and it's structure has been determined by single-crystal X-ray diffraction data. It crystallizes in the orthorhombic system, space group P2₁2₁2₁ with unit cell parameters, Z=4, The structure contains alternate layers of [B₄O₅(OH)₄]²⁻ polyanions separated by water molecules and Rb, Ca cations. The isolated [B₄O₅(OH)₄]²⁻ is constructed from two BO₃(OH) tetrahedron groups and two BO₂(OH) triangular groups joined at common oxygen atoms. The two BO₃(OH) tetrahedron groups are further linked by means of an oxygen bridge across the ring. The Ca²⁺ ion displays seven coordination, while the two non-equivalent Rb⁺ ions display nine and seven coordination, respectively. Infrared and Raman (4000-400 cm⁻¹) spectra of Rb₂Ca[B₄O₅(OH)₄]₂·8H₂O were recorded at room temperature and analyzed. Fundamental vibrational modes were identified and band assignments were made. The dehydration of this hydrated mixed borate occurs in one step and leads to an amorphous phase which undergoes a crystallization.     

Tetraphenylboroxinate(1-) salts of monoborate cations: Synthesis and single-crystal X-ray structures of [Ph2B{OCH2CH2N(Me)(CH2)n}2][Ph4B3O3] (n = 4, 5)

The salts, [Ph₂B{OCH₂CH₂N(Me)(CH₂)_n}₂][Ph₄B₃O₃] (n = 4, 5), were prepared in moderate yields in MeOH solution from reaction of Ph₂BOBPh₂ with [N(CH₂)_n(Me)(CH₂CH₂OH)][OH] and PhB(OH)₂ in a 1:2:4 ratio. The reactions also lead to Ph₃B₃O₃. Both salts were characterized by NMR (¹H, ¹³C, ¹¹B) IR, and single-crystal XRD studies. The salts are comprised of cationic monoborates (zwitterionic, 2N⁺ and 1B⁻) and tetraphenylboroxinate anions.     

Synthesis, crystal structure and NLO property of a nonmetal pentaborate [C6H13N2][B5O6(OH)4]

A nonmetal pentaborate [C₆H₁₃N₂][B₅O₆(OH)₄] (1) has been synthesized by 1,4-diazabicyclo[2.2.2] octane (DABCO) and boric acid, and characterized by single-crystal X-ray diffraction, FTIR, elemental analysis, and thermogravimetric analysis. Compound 1 crystallizes in the monoclinic system with space group Cc (no. 9), a=10.205(2) Å, b=14.143(3) Å, c=11.003(2) Å, β=113.97(3)°, V=1451.1(5) Å³, Z=4. The anionic units, [B₅O₆(OH)₄]⁻, are interlinked via hydrogen bonding to form a three-dimensional (3D) supramolecular network containing large channels, in which the protonated [C₆H₁₃N₂]⁺ cations are located. Second-harmonic generation (SHG) measurements on the powder samples reveal that 1 exhibits SHG efficiency approximately 0.9 times that of potassium dihydrogen phosphate (KDP).     

New high permittivity tetragonal tungsten bronze dielectrics Ba2LaMNb4O15: M=Mn, Fe

The new phases Ba₂LaMNb₄O₁₅: M=Mn, Fe were prepared by solid state reaction at 1100 °C. They have the tetragonal tungsten bronze structure, space group P4/mbm, at room temperature. The two octahedral sites show partial order of M and Nb with preferential occupancy of the smaller B(1) sites by M. Both phases have high permittivities 90±15 over the range 10-320 K. Ba₂LaFeNb₄O₁₅ is highly insulating with bulk conductivity ?10⁻⁸ ohm⁻¹ cm⁻¹ at 25 °C and tan δ?0.001 over the range 100-320 K and at 10⁵ Hz. Solid solutions between these new phases and the compositionally and structurally related relaxor ferroelectric Ba₂LaTi₂Nb₃O₁₅ show gradual loss of ferroelectric behaviour attributed to replacement of polarisable Ti⁴⁺ by a mixture of (Mn, Fe)³⁺ and Nb⁵⁺.     

The study of Bi3B5O12: synthesis, crystal structure and thermal expansion of oxoborate Bi3B5O12

The paper presents a new data on the crystal structure, thermal expansion and IR spectra of Bi₃B₅O₁₂. The Bi₃B₅O₁₂ single crystals were grown from the melt of the same stoichiometry by Czochralski technique. The crystal structure of Bi₃B₅O₁₂ was refined in anisotropic approximation using single-crystal X-ray diffraction data. It is orthorhombic, Pnma, a=6.530(4), b=7.726(5), c=18.578(5) Å, V=937.2(5) Å³, Z=4, R=3.45%. Bi³⁺ atoms have irregular coordination polyhedra, Bi(1)O₆ (d(B-O)=2.09-2.75 Å) and Bi(2)O₇ (d(B-O)=2.108-2.804 Å). Taking into account the shortest bonds only, these polyhedra are considered here as trigonal Bi(1)O₃ (2.09-2.20 Å) and tetragonal Bi(2)O₄ (2.108-2.331 Å) irregular pyramids with Bi atoms in the tops of both pyramids. The BiO₄ polyhedra form zigzag chains along b-axis. These chains alternate with isolated anions [B₂^IVB₃^IIIO₁₁]⁷⁻ through the common oxygen atoms to form thick layers extended in ab plane. A perfect cleavage of the compound corresponds to these layers and an imperfect one is parallel to the Bi-O chains. The Bi₃B₅O₁₂ thermal expansion is sharply anisotropic (α₁₁≈α₂₂=12, α₃₃=3×10⁻⁶ °C⁻¹) likely due to a straightening of the flexible zigzag chains along b-axis and decreasing of their zigzag along c-axis. Thus the properties like cleavage and thermal expansion correlate to these chains.     

The crystal structure of the monohydrate R2Mo6O21·H2O (R=Pr, Nd, Sm, and Eu): a layer structure containing disordered [Mo2O7] groups

Although R₂O₃:MoO₃=1:6 (R=rare earth) compounds are known in the R₂O₃-MoO₃ phase diagrams since a long time, no structural characterization has been achieved because a conventional solid-state reaction yields powder samples. We obtained single crystals of R₂Mo₆O₂₁·H₂O (R=Pr, Nd, Sm, and Eu) by thermal decomposition of [R₂(H₂O)₁₂Mo₈O₂₇]·nH₂O at around 685-715 °C for 2 h, and determined their crystal structures. The simulated XRD patterns of R₂Mo₆O₂₁·H₂O were consistent with those of previously reported R₂O₃:MoO₃=1:6 compounds. All R₂Mo₆O₂₁·H₂O compounds crystallize isostructurally in tetragonal, P4/ncc (No. 130), a=8.9962(5), 8.9689(6), 8.9207(4), and 8.875(2) Å; c=26.521(2), 26.519(2), 26.304(2), and 26.15(1) Å; Z=4; R₁=0.026, 0.024, 0.024, and 0.021, for R=Pr, Nd, Sm, and Eu, respectively. The crystal structure of R₂Mo₆O₂₁·H₂O consists of two [Mo₂O₇]²⁻-containing layers (A and B layers) and two interstitial R(1)³⁺ and R(2)³⁺ cations. Each [Mo₂O₇]²⁻ group is composed of two corner-sharing [MoO₄] tetrahedra. The [Mo₂O₇]²⁻ in the B layer exhibits a disorder to form a pseudo-[Mo₄O₉] group, in which four Mo and four O sites are half occupied. R(1)³⁺ achieves 8-fold coordination by O²⁻ to form a [R(1)O₈] square antiprism, while R(2)³⁺ achieves 9-fold coordination by O²⁻ and H₂O to form a [R(2)(H₂O)O₈] monocapped square antiprism. The disorder of the [Mo₂O₇]²⁻ group in the B layer induces a large displacement of the O atoms in another [Mo₂O₇]²⁻ group (in the A layer) and in the [R(1)O₈] and [R(2)(H₂O)O₈] polyhedra. A remarkable broadening of the photoluminescence spectrum of Eu₂Mo₆O₂₁·H₂O supported the large displacement of O ligands coordinating Eu(1) and Eu(2).     

[NH3CH2CHCH3NH3]][B8O11(OH)4]·H2O: Synthesis and characterization of the first 1D borate templated by 1,2-diaminopropane

A new hydrated borate compound, [NH₃CH₂CHCH₃NH₃]][B₈O₁₁(OH)₄]·H₂O 1, has been synthesized in the presence of 1,2-diaminopropane acting as a structure-directing agent under mild conditions. Its structure was determined by single crystal X-ray diffraction and further characterized FTIR, elemental analysis, powder X-ray diffraction and thermogravimetric analysis. Compound 1 crystallizes in the monoclinic system, space group P2₁/c (No. 14), a=10.0787(7) Å, b=8.8482(6) Å, c=19.3097(4) Å, β=91.352(6)°, V=1721.53(2) Å³, and Z=4. The structure consists of infinite open-branched borate chains constructed from [B₃O₆(OH)] units, onto which the [B₅O₇(OH)₃] groups are grafted. It represents the first example of one-dimensional borate templated by an organic amine. The adjacent borate chains are further linked together by extensive hydrogen bonds to form a 3D supramolecular network. The diprotonated organic amines and guest water molecules are filled in the free space of the hydrogen-bonded network and interact with the inorganic framework by extensive hydrogen bonds.     

Synthesis, crystal structure and thermal behavior of Sr3B2SiO8 borosilicate

Single crystals of Sr₃B₂SiO₈ were obtained by solid-state reaction of stoichiometric mixture at 1200 °C. The crystal structure of the compound has been solved by direct methods and refined to R1=0.064 (wR=0.133). It is orthorhombic, Pnma, a=12.361(4), b=3.927(1), c=5.419(1) Å, V=263.05(11) Å³. The structure contains zigzag pseudo-chains running along the b axis and built up from corner sharing (Si,B)−O polyhedra. Boron and silicon are statistically distributed over one site with their coordination strongly disordered. Sr atoms are located between the chains providing three-dimensional linkage of the structure.The formation of Sr₃B₂SiO₈ has been studied using annealing series in air at 900-1200 °C. According powder XRD, the probe contains pure Sr₃B₂SiO₈ over 1100 °C. The compound is not stable below 900 °C. In the pseudobinary Sr₂B₂O₅-Sr₃B₂SiO₈ system a new series of solid solutions Sr_3−xB₂Si_1−xO_8−3x (x=0-0.9) have been crystallized from melt. The thermal behavior of Sr₃B₂SiO₈ was investigated using powder high-temperature X-ray diffraction (HTXRD) in the temperature range 20-900 °C. The anisotropic character of thermal expansion has been observed: α_a= −1.3, α_b=23.5, α_c=13.9, and α_V=36.1×10⁻⁶ °C⁻¹ (25 °C); α_a= −1.3, α_b=23.2, α_c=5.2, and α_V=27.1×10⁻⁶ °C⁻¹ (650 °C). Maximal thermal expansion of the structure along of the chain direction [0 1 0] is caused by the partial straightening of chain zigzag. Hinge mechanism of thermal expansion is discussed.     

Synthesis, crystal structure, infrared and Raman spectra of Sr4Cu3(AsO4)2(AsO3OH)4·3H2O and Ba2Cu4(AsO4)2(AsO3OH)3

The two new compounds, Sr₄Cu₃(AsO₄)₂(AsO₃OH)₄·3H₂O (1) and Ba₂Cu₄(AsO₄)₂(AsO₃OH)₃(2), were synthesized under hydrothermal conditions. They represent previously unknown structure types and are the first compounds synthesized in the systems SrO/BaO-CuO-As₂O₅-H₂O. Their crystal structures were determined by single-crystal X-ray diffraction [space group C2/c, a=18.536(4) Å, b=5.179(1) Å, c=24.898(5) Å, β=93.67(3)°, V=2344.0(8) Å³, Z=4 for 1; space group P4₂/n, a=7.775(1) Å, c=13.698(3) Å, V=828.1(2) Å³, Z=2 for 2]. The crystal structure of 1 is related to a group of compounds formed by Cu²⁺-(XO₄)³⁻ layers (X=P⁵⁺, As⁵⁺) linked by M cations (M=alkali, alkaline earth, Pb²⁺, or Ag⁺) and partly by hydrogen bonds. In 1, worth mentioning is the very short hydrogen bond length, D···A=2.477(3) Å. It is one of the examples of extremely short hydrogen bonds, where the donor and acceptor are crystallographically different. Compound 2 represents a layered structure consisting of Cu₂O₈ centrosymmetric dimers crosslinked by As1φ₄ tetrahedra, where φ is O or OH, which are interconnected by Ba, As2 and hydrogen bonds to form a three-dimensional network. The layers are formed by Cu₂O₈ centrosymmetric dimers of CuO₅ edge-sharing polyhedra, crosslinked by As1O₄ tetrahedra. Vibrational spectra (FTIR and Raman) of both compounds are described. The spectroscopic manifestation of the very short hydrogen bond in 1, and ABC-like spectra in 2 were discussed.     

Synthesis, crystal structure and electrical characterization of two new potassium uranyl molybdates K2(UO2)2(MoO4)O2 and K8(UO2)8(MoO5)3O6

Two new potassium uranyl molybdates K₂(UO₂)₂(MoO₄)O₂ and K₈(UO₂)₈(MoO₅)₃O₆ have been obtained by solid state chemistry . The crystal structures were determined by single crystal X-ray diffraction data, collected with MoKα radiation and a charge coupled device (CCD) detector. Their structures were solved using direct methods and Fourier difference techniques and refined by a least square method on the basis of F² for all unique reflections, with R₁=0.046 for 136 parameters and 1412 reflections with I?2σ(I) for K₂(UO₂)₂(MoO₄)O₂ and R₁=0.055 for 257 parameters and 2585 reflections with I?2σ(I) for K₈(UO₂)₈(MoO₅)₃O₆. The first compound crystallizes in the monoclinic symmetry, space group P2₁/c with a=8.250(1) Å, b=15.337(2) Å, c=8.351(1) Å, β=104.75(1)°, ρ_mes=5.22(2) g/cm³, ρ_cal=5.27(2) g/cm³ and Z=4. The second material adopts a tetragonal unit cell with a=b=23.488(3) Å, c=6.7857(11) Å, ρ_mes=5.44(3) g/cm³, ρ_cal=5.49(2) g/cm³, Z=4 and space group P4/n.In both structures, the uranium atoms adopt a UO₇ pentagonal bipyramid environment, molybdenum atoms are in a MoO₄ tetrahedral environment for K₂(UO₂)₂(MoO₄)O₂ and MoO₅ square pyramid coordination in K₈(UO₂)₈(MoO₅)₃O₆. These compounds are characterized by layered structures. The association of uranyl ions (UO₇) and molybdate oxoanions MoO₄ or MoO₅, give infinite layers [(UO₂)₂(MoO₄)O₂]²⁻ and [(UO₂)₈(MoO₅)₃O₆]⁸⁻ in K₂(UO₂)₂(MoO₄)O₂ and K₈(UO₂)₈(MoO₅)₃O₆, respectively. Conductivity properties of alkali metal within the interlayer spaces have been measured and show an Arrhenius type evolution.     

Prussian Blue electrodeposited on MWNTs-PANI hybrid composites for H2O2 detection

A Prussian Blue (PB)/polyaniline (PANI)/multi-walled carbon nanotubes (MWNTs) composite film was fabricated by step-by-step electrodeposition on glassy carbon electrode (GCE). The electrode prepared exhibits enhanced electrocatalytic behavior and good stability for detection of H₂O₂ at an applied potential of 0.0 V. The effects of MWNTs thickness, electrodeposition time of PANI and rotating rate on the current response of the composite modified electrode toward H₂O₂ were optimized to obtain the maximal sensitivity. A linear range from 8 × 10⁻⁹ to 5 × 10⁻⁶ M for H₂O₂ detection has been observed at the PB/PANI/MWNTs modified GCE with a correlation coefficient of 0.997. The detection limit is 5 × 10⁻⁹ M on signal-to-noise ratio of 3. To the best of our knowledge, this is the lowest detection limit for H₂O₂ detection. The electrode also shows high sensitivity (526.43 μA μM⁻¹ cm⁻²) for H₂O₂ detection which is more than three orders of magnitude higher than the reported.     

Stabilisation of heterobimetallic networks by crown ethers and hydrogen-bonding in [Ni(H2O)6][Cu3Cl8(H2O)2] · (15-crown-5)2 · 2H2O: Structure and magnetism

[Ni(H₂O)₆][Cu₃Cl₈(H₂O)₂] · (15-crown-5)₂ · 2H₂O can be conveniently prepared by the interaction of NiCl₂ · 6H₂O, CuCl₂ · 2H₂O and 15-crown-5 in water. The X-ray crystal structure reveals an ionic complex involved in a hydrogen-bonded two dimensional network with the [Ni(H₂O)₆]²⁺ and [Cu₃Cl₈(H₂O)₂]²⁻ ions sandwiched between the 15-crown-5 macrocycles. The magnetic susceptibility data (4–300 K) and magnetisation isotherms (2–5.5 K; 0–5 T) are best interpreted in terms of intra-trimer ferromagnetic coupling within the [Cu₃Cl₈(H₂O)₂]²⁻ moieties, with J ∼ 6 cm⁻¹, and antiferromagnetic coupling between the trimers, the latter mediated by H-bonding pathways. Comparisons are made to other reported quaternary ammonium salts of [Cu₃Cl₈]²⁻ and [Cu₃Cl₁₂]⁶⁻, most of which display structures that involve close stacking of such Cu(II) trimers, rather than being of the present isolated, albeit H-bonded, types.