Structures and properties of functional metal iodates

Metal iodates with a lone-pair containing I(V) that is in an asymmetric coordination geometry can form a diversity of unusual structures and many of them are promising new second homonic generation (SHG) materials. They exhibit wide transparency wavelength regions, large SHG coefficients and high optical-damage thresholds as well as moderately high thermal stability. In this paper, the structures and properties of the metal iodates are reviewed. The combination of d0 transition-metal cations with the iodate groups afforded a large number of metal iodates, with cations covering alkali metal, alkaline earth and lanthanide elements. Many of them are noncentrosymmetric (NCS) and display excellent SHG properties due to the additive effects of polarizations from both types of the asymmetric units. Some lanthanide iodates are able to emit strong luminescence in the visible or near-IR regions. The use of transition metal ions with dn (n ≠ 0) electronic configuration into iodate systems can also induce the formation of NCS compounds when the lone pairs of the iodate groups are properly aligned. The dn transition metal cations are normally octahedrally coordinated or in a square-planar coordination geometry. Furthermore, the combination of two different types of lone-pair-containing cations is also an effective strategy to design new SHG materials.

Discovery of <i>β</i>-HIO₃: A Metastable Polymorph of HIO₃

The β-HIO3 polymorph, previously difficult to detect and whose existence was questioned, has been structurally characterized. The crystal structure of β-HIO3 was solved in the same space group as α-HIO3 (P212121);however, it was found that the unit cell axes were all different by about 1 &#197;. Similar to that of α and γ phases, the unit cell contains only a single HIO3 molecule in the asymmetric unit with I-O bond lengths ranging from 1.786(5) to 1.903(7) &#197;. The I(V) atom is further coordinated by three oxygen atoms of neighboring acid molecules forming a distorted octahedral with a range of I-O distances (2.498(6) - 2.795(7) &#197;). The one structural difference that separates the β phase from the α and γ phases is that the hydroxyl group is bridging between two I(V) atoms, resulting in a smaller hydrogen bonding distance (O-O distance: 2.559 &#197;(β), 2.665 &#197;(γ) and 2.696 &#197;(α)) and presumably a different crystalline energy. Similar to γ-HIO3, β-HIO3 is metastable and slowly converts to α-HIO3. It is hypothesized that β-HIO3 is a transition step in the formation of α-HIO3 and β-HIO3 is a result of trapped water inside particles during crystallization.

Surface-Renewable AgNPs/CNT/rGO Nanocomposites as Bifunctional Impedimetric Sensors

In this study, glassy carbon electrode modified by silver nanoparticles/carbon nanotube/reduced graphene oxide(AgNPs/CNT/rGO) composite has been utilized as a platform to immobilize cis-dioxomolybdenum(VI)–salicylaldehydehistidine(MoO_2/Sal-His). The modified electrode shows two reversible redox couples for MoO_2/Sal-His. Electrocatalytic oxidation of cysteine(CySH) and electrocatalytic reduction of iodate on the surface of the modified electrode were investigated with cyclic voltammetry and electrochemical impedance spectroscopy methods. The presence of MoO_2/SalHis on AgNPs/CNT/rGO shifted the catalytic current of iodate reduction to a more positive potential and the catalytic current of cysteine oxidation to a more negative potential. The change of interfacial charge transfer resistance(R_(ct))recorded by the modified electrode was monitored for sensitive quantitative detection of CySH and iodate. Moreover, the sensor has a good stability, and it can be renewed easily and repeatedly through a mechanical or electrochemical process.

Primary Organicamine Templated Indium Iodate (H_2en)KIn(IO_3)_6·2(H_2O) with Hydrogen-bonded Helices

The first primary organicamine templated indium iodate with the formula （H2en）KIn（IO3）6-2（H2O） was hydrothermally synthesized via reaction at 100 ℃ for 7 d and characterized by single-crystal X-ray diffraction and thermal analysis. The compound crystallized in a triclinic system with space group P1, a=0.69803（14） nm, b=0.70863（14） nm, c=1.2091（2） nm, a=76.417（4）°,β=79.953（4）°, γ=72.206（3）°, V=0.55012（19） nm3. Structure determination indicates that it is made up of zero-dimensional units each of which consists of [In（IO3）6]3 anion, potassium, water and ethylenediamine cation. The most striking feature of the compound is that it possesses helical hydrogen bonds formed by organic amine template, water molecules and inorganic network.

AgCu(IO3)3：Synthesis,Crystal Structure and Magnetic Property

A new mixed metal iodate, namely Ag Cu（IO3）3, has been prepared using hydrothermal method. Ag Cu（IO3）3 crystallizes in the triclinic group P1 with a = 7.3063（6）, b = 7.8050（6）, c = 8.2447（6） A, α = 67.212（7）, β = 74.978（7）, γ = 80.972（7）°, V = 417.80（6） A^3 and Z = 2. The structure features one-dimensional [Cu（IO3）3]n^n- anionic chains that are separated by Ag~＋ cations. Such [Cu（IO3）3]n^n- chain is composed of [Cu2O（11）]n chain decorated by unidentate hanging and bidentate bridging iodate groups. Thermal study implies that Ag Cu（IO3）3 is thermally stable up to 460 oC and the optical measurement determined the optical band gap of 3.11 eV with a broad absorption band centered at 765 nm. Magnetic investigations show that Ag Cu（IO3）3 is a soft ferromagnet.

Liquid waveguide capillary cell for the spectrophotometric determination of nanomolar iodate concentrations in marine waters

A new spectrophotometric method based on a liquid waveguide capillary cell for an enhanced detection was developed to measure nanomolar iodate concentrations.This method has a detection limit and precision of 1-2 nmol/L,which is equivalent to 10%that of conventional methods,a recovery of 97.7%-104.0%,and a working range of 10-120 nmol/L.Water samples were collected from three estuaries and one coastal ocean for testing,and the proposed technique detected as low as 11 nmol/L and 18 nmol/L iodate in these samples.This newly developed method is helpful in understanding the biogeochemical cycle of iodine in nature.

Investigation of Discoloration of Packaged Fortified Salt under Conditions Relevant to Product Packaging and Storage

Double fortified salt containing both potassium iodate and ferrous fumarate microcapsules was produced at an Indian commercial facility. The packaged product became discolored, turning yellow, to a degree that would impact consumer acceptance. Therefore, there was a need for an investigation into the cause and possible remedy for this discoloration. The components of the fortified salt product, storage conditions, and processing characteristics were taken into consideration. Canadian and Indian salt samples were prepared unfortified as well as with iodine and/or iron microcapsules;stored at 25°C and 45°C in glass, polyethylene, or commercial polymer film. Some samples were heat treated prior to storage. Salt samples containing iodine that were heated before storage in packaging material turned yellow in color. From this study, it was found that due to heat and the presence of a sacrificial antioxidant component in the packaging film, potassium iodate was reduced to elemental iodine (I2) turning packaged salt samples to a yellow/orange color. Hence it is recommended that in the manufacture of foods containing potassium iodate, the packaging material selected should be free from readily accessible antioxidants.

Iodine Fortification Study of Some Common African Vegetables

Iodine Deficiency Diseases (IDDs) occupy important positions in the health problems of developing countries. Salt Iodisation has been the common approach to solving these problems. However, apart from the problems of lack of compliance by salt manufacturers, and inculturation of the consumers, health conditions aggravated by high salt intake by humans have become increasingly relevant. These problems can be eliminated if the commonly produced and consumed plants are fortified with Iodine. The prospects are in the inclusion of Iodine-containing compounds in the inorganic fertilizers used by farmers. In this study, Potassium Iodide and Potassium Iodate were used as inoculants. Five different concentrations—0.1 M, 0.2 M, 0.3 M, 0.4 M, and 0.5 M of Potassium Iodide and Potassium Iodate solutions were used to inoculate the soils on which the following edible African plants were planted: Murraya koenigii;Ocimum gratissimum;Cucurbita pepo;Solanum nigrum;Amaranthus hybridus and Abelmoschus esclentus, Corchorous olitoruis, Solanum lycopersicum, Zingiber officinale, Telfairia occidentalis, Talinium triangulare, Solanum melongena. Controls were also planted. After 14 days, alkaline dry ash method was used to determine the Iodine concentrations in the plants. The results showed that Murraya koenigii showed the highest absorption of Iodine 6.90 mg/kg at 0.3 M using KI, followed by Amaranthus hybridus 6.40 mg/kg at 0.1 M. Solanum nigrum, Ocimum gratissimum and Zingiber officinale also showed good absorption. Other plants except Murraya koenigii, Ocimum gratissimum, Solanum nigrum and Zingiber officinale showed very low tolerance to KI absorption. The result also showed that Telfairia occidentalis showed the highest absorption of iodine 8.20 mg/kg at 0.2 M of KIO3 followed by Cucurbita pepo 6.40 mg/kg at also 0.2 M of KIO3. Murraya koenigii, Ocimum gratissimum, Solanum nigrum, Zingiber officinale also showed good absorption of KIO3. Some of the plants were not able to tolerate the absorption at higher concentration for both KI and KIO3. All the plants were poisoned at concentration of 0.5 M for both Ki and KIO3. Murraya koenigii, Ocimum gratissimum, Solanum nigrum, Zingiber officinale can be used in iodine biofortification using KI and KIO3 at concentration < 0.5 M. The overall result may be very significant, when it is considered that Iodine is a micronutrient, with a daily intake requirement of 100 - 150 μg/kg. It can be seen that there is hope in achieving this kind of biofortification.

Iodine Concentration of Iodized Salts Consumed in Harper

This study determined concentrations of iodine, consistent with WHO iodine fortification standards, in commercial edible salts mostly consumed in Harper. The following hypothesis was put forward in the research study;H1: the iodine content of the two brands of iodized salts is different from the WHO iodine fortification levels;H0: the iodine content of the two brands of iodized salts is not different from the WHO iodine fortification levels. The hypothesis was tested in MS Excel 2010 and 2016 via the T-Test function giving p-value = 0.1476 and p-value = 0.0395 indicative of no significant difference in the iodine concentration of the salts compared with the lower limit of WHO standard 20 mg·Kg-1 and huge contrast in the iodine concentration of the salts compared with the upper limit of WHO standard 40 mg·Kg-1 respectively. The UV spectrophotometric method was used to analyze and measure the iodine concentration in the twelve (12) samples of two different brands bought from grocery stores in Harper city. Results indicated that all samples of the two (2) brands of iodized salts contained iodine of no significant difference relative to the lower limit of WHO standard but far below the upper limit of the WHO standard. The study therefore recommends monitoring of commercial iodized salts by appropriate authorities in Harper to ascertain the WHO iodization fortification standards before reaching consumers.

Toward better understanding vacuum ultraviolet-iodide induced photolysis via hydrogen peroxide formation,iodine species change,and difluoroacetic acid degradation

Recently,a photochemical process induced by ultraviolet(UV),vacuum UV(VUV),and iodide(I–)has gained attention for its robust potential for contaminant degradation.However,the mechanisms behind this process remain unclear because both oxidizing and reducing reactants are likely generated.To better understand this process,this study examined the evolutions of hydrogen peroxide(H_(2)O_(2))and iodine species(i.e.,iodide,iodate,and triiodide)during the UV/VUV/I–process under varying pH and dissolved oxygen(DO)conditions.Results show that increasing DO in water enhanced H2O2 and iodate production,suggesting that high DO favors the formation of oxidizing species.In contrast,increasing pH(from 6.0 to 11.0)resulted in lower H_(2)O_(2) and iodate formation,indicating that there was a decrease of oxidative capacity for the UV/VUV/I–process.In addition,difluoroacetic acid(DFAA)was used as an exemplar contaminant to verify above observations.Although its degradation kinetics did not follow a constant trend as pH increases,the relative importance of mineralization appeared declining,suggesting that there was a redox transition from an oxidizing environment to a reducing environment as pH rises.The treatability of the UV/VUV/I–process was stronger than UV/VUV under pH of 11.0,while UV/VUV process presented a better performance at pH lower than 11.0.

Sol-Gel Derived Carbon Ceramic Electrode Bulk-Modified with Tris(1,10-phenanthroline-5,6-dione)iron(II) Hexafluorophos-phate and Its Use as an Amperometric Iodate Sensor

A surface-renewable tris(1, 10-phenanthroline-5,6-dione)iron (Ⅱ)hexafluorophosphate (FePD) modified carbon ceramic electrode was constructed by dispersing FePD andgraphite powder in methyltrimethoxysilane (MTMOS) based gels. The FePD-modified electrode presentedpH-dependent voltammetric behavior, and its peak currents were diffusion-controlled in 0.1 mol/LNa_2SO_4 + H_2SO_4 solution (pH = 0.4). In the presence of iodate, clear electrocatalytic reductionwaves were observed and thus the chemically modified electrode was used as an amperometric sensorfor iodate in common salt. The linear range, sensitivity, detection limit and response time of theiodate sensor were 5 x 10^(-6)―1 x 10~2 mol/L, 7.448 μA·L/mmol, 1.2 x 10^(-6) mol/L and 5 s,respectively. A distinct advantage of this sensor is its good reproducibility of surface-renewal bysimple mechanical polishing.

Kinetics and mechanism of the reaction between thiourea and iodate in unbuffered medium

The reaction between iodate and thiourea has been studied in an unbuffered acidic medium. In excess iodate the reaction shows not only oligooscillations in pH, Pt potential and the concentration of iodide ion, [I?], but also an initial induction period which has the linear relation with initial pH. At the end of the induction period, [I?] decreases sharply and a yellow coloration (due to iodine) appears transiently. While in excess thiourea iodine is produced and finally con- sumed, leaving milky deposits (due to sulfur) at the end of the reaction. The induction period from the start of the reaction to the maximum of [I2] is also directly proportional to initial pH. A 14-step mechanism, including a H+-mediated preequalibrium, Dusman reaction, iodine-sulfur reactions and sulfur-sulfur reactions, is proposed. Computer simulations using this mechanism give good agreement with experiments.

Lanthanide Inorganic Solids Based on Main Group Borates and Oxyanions of Lone Pair Cations

Lanthanide borates containing post transition metal main group elements, including Ga（Ⅲ）, Ge（Ⅳ）, Sb（Ⅴ） and Te（Ⅵ）, as well as lanthanide salts of the oxyanions of lone pair cations, such as I（Ⅴ）, Se（Ⅳ） and Te（Ⅳ）, were reviewed. The post transition metal main group elements in lanthanide borates adopt octahedral or tetrahedral geometry only. In the structure of lanthanide galloborates, only octahedral GaO6 was found while both octahedral GeO6 and tetrahedral GeO4 appeared in borogermanates. The fifth period elements Sb（Ⅴ） and Te（VI） prefer octahedral coordination geometry in lanthanide borates system. The second groups introduced to lanthanide oxyanions of lone pairs are mainly focused on do TM units, such as WO4 tetrahedron, VO5 square pyramid or MoO6 octahedron, and rigid tetrahedral groups like sulfate SO4, silica SiO4 or selenate SeO4 units. Divalent cations like Pb（Ⅱ） and magnetic ions of Cu（Ⅱ） or Mn（Ⅱ） were also included. The structure chemistry of lanthanide ions in these systems is rich. Coordination numbers from six to ten are discovered, yielding a wide range of coordination geometries including the pentagonal bipyramid, square antiprism, metabidiminished icosahedron, tricapped trigonal prism, capped triangular cupola, etc. The connectivity modes between the Ln polyhedra are miscellaneous, from 3D network, to 2D layer, 1D chain, tetramer, trimer, dimer and finally monomer. A number of compounds display NCS structures and strong SHG response, and many lanthanide compounds exhibit good luminescent properties in visible and IR region.

Highly Sensitive and Selective Amperometric Sensor for Iodate Based on 9,10-Phenanthrenequinone Derived Graphene

We reported on a new amperometric sensor for the sensitive and selective determination of iodate in table salt. The iodate sensor was constructed by the integration of a novel nanocomposite which was made from 9,10-phenanthrenequinone（PQ） and graphene（GP） with a glassy carbon electrode（GCE）. The synthesized graphene and the nanocomposite were well characterized by X-ray diffraction（XRD）, transmission electron microscopy（TEM）, Fourier transform infrared（FTIR） spectroscopy and Raman spectroscopy. We fully studied the electrochemical beha- vior and kinetic characteristics of the PQ/GP nanocomposite at GCE. The PQ/GP electrode shows a good electrochemical catalytic activity towards the reduction of iodate, which makes itself a sensitive and selective electrochemical sensor for iodate. The iodate sensor displays a high sensitivity（1.04 p.A.tamol.L-1）, a low detection limit（1.0X 10-8 mol/L）, a rapid response（less than 2 s）, and a broad linear range（from 5.0X 10-8 mol/L to 6.0X 10-3 mol/L ）. In addition, the sensor is interference free. The practical application of the proposed sensor was tested by the detection of iodate in table salt.

Determination of Ge in Au alloys using sodium hypophosphite and potassium iodate potentiometric titration method

This paper presents a new method of determining Ge in AuGe alloys by potassium iodate(KIO3)potentiometric titration when Ge(Ⅱ)and Au(0)are simultaneously reduced from Ge(Ⅳ)and Au(Ⅲ)by sodium hypophosphite rather than by distillation separation.The influences of such conditions as the reduction acidity,the dosage of sodium hypophosphite and the reduction time on the determination of Ge were studied.Ge in AuGe alloys such as AuGe_(12),AuGeNi_(12-2),AuAgGe_(18.8-12.5),and AuAgGeNi_(43.8-6-0.2)was measured with the relative standard deviation(RSD)of 0.10%-0.31%and the recoveries of added standard Ge in sample of 99.40%-100.40%under the conditions of 0.40-0.80 mol·L^(-1)HCl,3.3 mol·L^(-1)H^(3)PO^(4),15 g sodium hypophosphite,and reduction time of40 min.The new method presented is of high accuracy in results,good stability and sensibility in end-point,and easy operation and strong selectivity of determination.

Quasi-3-D Gadolinium Iodate Constructed from Infinite Polyiodate: Structure, Green-emission and UV Light-driven Degradation on Organic Dye

A new gadolinium iodate has been synthesized via hydrothermal method,and its structure was determined as[Gd(H2O)(IO3)2(IO3H2O)]n(1)by X-ray single-crystal diffraction.The 2-D layer is built from the linkage of Gd2O16I4 dimer viaμ2/μ3-bridged iodates,and the quasi-3-D network is generated via weak I···O bonds and hydrogen bonds.FTIR,powder X-ray diffraction(PXRD)and UV-Vis spectra were conducted to characterize the as-synthesized sample.Interestingly,1 exhibits green emission,which might be assigned to electronic transfer within iodate groups.The UV adsorption of 1 hints its UV light-driven photocatalytic property,and as expected,it exhibits photocatalytic activity for the degradation of rhodamine B.Theoretical calculation was conducted to give structure/property correlation.

[Y(IO3)3(H2O)2]n: a New Rare Earth Iodate Featuring the Circle-shaped I4O12 Polyiodate Anion and Three-order Nonlinear Optical Property

A new layered yttrium iodate[Y(IO3)3(H2O)2]n(1)has been prepared from the hydrothermal reaction of Y(NO3)3?6H2O with I2O5 at 170℃,and its structure was determined by X-ray single-crystal diffraction method.It belongs to the triclinic system,space group P1 with a=7.355(5),b=7.515(5),c=9.413(7)?,α=79.65(2)o,β=85.18(3)o,γ=71.870(19)o,Z=2,V=486.2(6)?3.1 was further characterized by FTIR,powder X-ray diffraction(PXRD)and UV-Vis spectra.In 1,the Y centers in a monocapped trigonal prism environment are bound by IO-3 anion and unique circle-shaped I4O12 polyiodate anion to generate a wave-like 2-D layer.The adjacent layers are further linked with each other by hydrogen bonds to form a quasi-3-D supramolecular network.1 exhibits a reverse saturation absorption and a self-defocusing effect with the nonlinear absorption coefficientβbeing–0.66×10-5 mW-1,which stems mainly from the electron transition from O-2p to I-5p orbital within iodates upon theoretical calculation.