Application of X-ray based modern instrumental techniques to determine the heavy metals in soils, minerals and organic media.

To evaluate the environmental concerns associated with heavy metals (HMs) during their translocations in food chains, it is crucial to gather data on the types of HMs present in soils in order to ascertain their toxicity and potential to migrate. An overview of the findings from several physical techniques used to determine and identify the HMs, sediments, individual minerals, and organic components in contaminated agricultural and industrial soils, is provided in this review article. These studies cover a variety of X-ray-based analytical techniques, including most widely used ones like X-ray absorption near edge structure, extended X-ray absorption fine structure, X-ray diffraction, and less popular ones X-ray fluorescence, etc. When compared to techniques that rely on laboratory radiation sources, synchrotron radiation offers more precision and efficiency. These methods could pinpoint the primary mechanisms influencing the soil's ability to transport contaminants and track their subsequent migration up the food chain.

Advances in nanoparticle and organic formulations for prolonged controlled release of auxins.

Plant hormones have been well known since Charles Darwin as signaling molecules directing plant metabolism. Their action and transport pathways are at the top of scientific interest and were reviewed in many research articles. Modern agriculture applies phytohormones as supplements to achieve desired physiological plant response. Auxins are a class of plant hormones extensively used for crop management. Auxins stimulate the formation of lateral roots and shoots, seed germination, while extensively high concentrations of these chemicals act as herbicides. Natural auxins are unstable; light or enzyme action leads to their degradation. Moreover, the concentration dependant action of phytohormones denier one-shot injection of these chemicals and require constant slow additive of supplement. It obstructs the direct introduction of auxins. On the other hand, delivery systems can protect phytohormones from degradation and provide a slow release of loaded drugs. Moreover, this release can be managed by external stimuli like pH, enzymes, or temperature. The present review is focused on three auxins: indole-3-acetic, indole-3-butyric, and 1-naphthaleneacetic acids. We collected some examples of inorganic (oxides, Ag, layered double hydroxides) and organic (chitosan, organic formulations) delivery systems. The action of carriers can enhance auxin effects via protection and targeted delivery of loaded molecules. Moreover, nanoparticles can act as nano fertilizers, intensifying the phytohormone effect, providing slow controlled release. So delivery systems for auxins are extremely attractive for modern agriculture opening sustainable management of plant metabolism and morphogenesis.

Synthesis of ZnO Nanoparticles Doped with Cobalt Using Bimetallic ZIFs as Sacrificial Agents.

: We report here a simple two-stage synthesis of zinc-cobalt oxide nanoparticles. We used Zn/Co-zeolite imidazolate framework (ZIF)-8 materials as precursors for annealing and optional impregnation with a silicon source for the formation of a protective layer on the surface of oxide nanoparticles. Using bimetallic ZIFs allowed us to trace the phase transition of the obtained oxide nanoparticles from wurtzite ZnO to spinel Co3O4 structures. Using (X-Ray diffraction) XRD and (X-ray Absorption Near Edge Structure) XANES techniques, we confirmed the incorporation of cobalt ions into the ZnO structure up to 5 mol.% of Co. Simple annealing of Zn/Co-ZIF-8 materials in the air led to the formation of oxide nanoparticles of about 20-30 nm, while additional treatment of ZIFs with silicon source resulted in nanoparticles of about 5-10 nm covered with protective silica layer. We revealed the incorporation of oxygen vacancies in the obtained ZnO nanoparticles using FTIR analysis. All obtained samples were comprehensively characterized, including analysis with a synchrotron radiation source.

Modeling of the Temperature Effect on Oxygen Absorption by Iron-Based Oxygen Scavengers.

A new engineering-oriented model for prediction of the effect of temperature on the kinetics of oxygen absorption by iron-based oxygen scavengers (IOSs) was developed. The model is based on the physicochemical mechanism of the O2 scavenging process by the active component of the IOS (iron powder). The conclusions of this study are: (1) the iron deposits formed on the iron particles are composed of 2 different layers: an inner layer of Fe3 O4 and an outer layer of FeOOH that vanishes with the depletion of oxygen. (2) The model considers the chemical processes in the heterogeneous closed system "Fe-H2 O-NaCl-O2 " and describes the kinetics of oxygen absorption by the powder, depending on the characteristics of the system. (3) The nonlinear ordinary differential equation (ODE) of the O2 absorption kinetics was derived and a simple approximate solution to this ODE was obtained theoretically that is similar to the empirical exponential formula published in the relevant literature. (4) The temperature dependence of the oxygen absorption rate is more complicated than that described by the Arrhenius equation.

Modeling of the humidity effects on the oxygen absorption by iron-based scavengers.

UNLABELLED: It has been reported in the scientific literature that moisture is required for oxygen absorption by iron-based scavengers. The rate of oxygen absorption is crucial in oxygen-sensitive foods. However, no quantitative correlations between the relative humidity and the oxygen absorption by these scavengers have been found in the scientific literature. The humidity level, the O(2) concentration, and the gas composition inside the package are the major factors determining the isothermal O(2) absorption kinetics. In the present study, the effect of RH on the oxygen absorption of an iron powder taken from an oxygen scavenger was investigated. This process was modeled, and correlations have been developed and compared to experimental results. The developed models describe well the effect of humidity on the oxygen absorption by the iron powder. It was found that an increase in the rate of oxygen absorption results in a decrease in the porosity, an increase in the specific surface area of the iron powder's corrosion products, and a decrease in the O(2) diffusivity through the particles. The heat evolved during the exothermic reaction leads to a decrease in the amount of water adsorbed on the corrosion products. The results of the present study elucidate the effect of moisture on the O(2) absorption by iron-based oxygen scavengers and can be used for a proper design of packages intended for storage of foods and fruits and vegetables of intermediate and high water activity. PRACTICAL APPLICATION: Since humidity has an important role in determining the rate of oxygen absorption kinetics by iron-based oxygen scavengers, using the models derived and presented in the present publication can bring upon a better understanding of the oxygen absorption process and a more efficient way of using oxygen scavengers in the packaging and storing of different oxygen sensitive foods.

Pseudo-rotation mechanism for fast olefin exchange and substitution processes at orthometalated C,N-complexes of platinum(II).

Bridge splitting in chloroform of the orthometalated chloro-bridged complex [Pt(micro-Cl)(2-Me(2)NCH(2)C(6)H(4))](2)(1), with ethene, cyclooctene, allyl alcohol and phosphine according to 1+ 2L --> 2[PtCl(2-Me(2)NCH(2)C(6)H(4))(L)], where L = C(2)H(4)(3a), C(8)H(14), (3b), CH(2)CHCH(2)OH (3c), and PPh(3)(4a and 4b) gives monomeric species with L coordinated trans or cis to aryl. With olefins the thermodynamically stable isomer with L coordinated cis to aryl is formed directly without an observable intermediate. With phosphine and pyridine, the kinetically controlled trans-product isomerizes slowly to the more stable cis-isomer. Bridge splitting by olefins is slow and first-order in 1 and L, with largely negative DeltaS(++). Substitution of ethene cis to aryl by cyclooctene and allyl alcohol to form 3b and 3c, and substitution of cot from 3b by allyl alcohol to form 3c are first order in olefin and complex, ca. six orders of magnitude faster than bridge cleavage due to a large decrease in DeltaH(++), and with largely negative DeltaS(++). Cyclooctene exchange at 3b is first-order with respect to free cyclooctene and platinum complex. All experimental data for olefin substitution and exchange are compatible with a concerted substitution/isomerization process via a turnstile twist pseudo-rotation in a short-lived labile five-coordinated intermediate, involving initial attack on the labile coordination position trans to the sigma-bonded aryl. Bridge-cleavage reactions of the analogous bridged complexes occur similarly, but are much slower because of their ground-state stabilization and steric hindrance.

Structural and mechanistic look at the orthoplatination of aryl oximes by dichlorobis(sulfoxide or sulfide)platinum(II) complexes.

Structural and mechanistic aspects of orthoplatination of acetophenone and benzaldehyde oximes by the platinum(II) sulfoxide and sulfide complexes [PtCl(2)L(2)] (2, L = SOMe(2) (a), rac-SOMePh (b), R-SOMe(C(6)H(4)Me-4) (c), and SMe(2) (d)) to afford the corresponding platinacycles cis-(C,S)-[Pt(II)(C(6)H(3)-2-CR'=NOH-5-R)Cl(L)] (3, R, R' = H, Me) have been investigated. The reaction of acetophenone oxime with sulfoxide complex 2a in methanol solvent occurs noticeably faster than with sulfide complex 2d due to the fact that the sulfoxide is a much better platinum(II) leaving ligand than the sulfide. Evidence is presented that the orthoplatination is a multistep process. The formation of unreactive dichlorobis(N-oxime)platinum(II) cations accounts for the rate retardation by excess acetophenone oxime and suggests the importance of pseudocoordinatively unsaturated species for the C-H bond activation by Pt(II). A comparative X-ray structural study of dimethyl sulfoxide platinacycle 3b (R = R' = Me) and its sulfide analogue 3e (R = H, R' = Me), as well as of SOMePh complex 3c (R = H, R' = Me), indicated that they are structurally similar and a sulfur ligand is coordinated in the cis position with respect to the sigma-bound phenyl carbon. The differences concern the Pt-S bond distance, which is notably longer in the sulfide complex 3e (2.2677(11) A) as compared to that in sulfoxide complexes 3b (2.201(2)-2.215(2) A) and 3c (2.2196(12) A). Whereas the metal plane is practically a plane of symmetry in 3b due to the H-bonding between the sulfoxide oxygen and the proton at carbon ortho to the Pt-C bond, an S-bonded methyl of SOMePh and SMe(2) is basically in the platinum(II) plane in complexes 3c and 3e, respectively. There are intra- and intermolecular hydrogen bond networks in complex 3b. An interesting structural feature of complex 3c is that the two independent molecules in the asymmetric unit of the crystal reveal an extremely short Pt-Pt contact of 3.337 A.