SMS2, a Novel Allele of OsINV3, Regulates Grain Size in Rice.

Grain size has an important effect on rice yield. Although several key genes that regulate seed size have been reported in rice, their molecular mechanisms remain unclear. In this study, a rice small grain size 2 (sms2) mutant was identified, and MutMap resequencing analysis results showed that a 2 bp insertion in the second exon of the LOC_Os02g01590 gene resulted in a grain length and width lower than those of the wild-type Teqing (TQ). We found that SMS2 encoded vacuolar acid invertase, a novel allele of OsINV3, which regulates grain size. GO and KEGG enrichment analyses showed that SMS2 was involved in endoplasmic reticulum protein synthesis, cysteine and methionine metabolism, and propionic acid metabolism, thereby regulating grain size. An analysis of sugar content in young panicles showed that SMS2 reduced sucrose, fructose, and starch contents, thus regulating grain size. A haplotype analysis showed that Hap2 of SMS2 had a longer grain and was widely present in indica rice varieties. Our results provide a new theoretical basis for the molecular and physiological mechanisms by which SMS2 regulates grain size.

Genome-Wide Identification and Expression Analysis of the DA1 Gene Family in Sweet Potato and Its Two Diploid Relatives.

The DA1-like gene family plays a crucial role in regulating seed and organ size in plants. The DA1 gene family has been identified in several species but has not yet been reported in sweet potatoes. In this study, nine, eleven, and seven DA1s were identified in cultivated sweet potato (Ipomoea batatas, 2n = 6x = 90) and its two diploid wild relatives, I. trifida (2n = 2x = 30) and I. triloba (2n = 2x = 30), respectively. The DA1 genes were classified into three subgroups based on their phylogenetic relationships with Arabidopsis thaliana and Oryza sativa (rice). Their protein physiological properties, chromosomal localization, phylogenetic relationships, gene structure, promoter cis-elements, and expression patterns were systematically analyzed. The qRT-PCR results showed that the expression levels of four genes, IbDA1-1, IbDA1-3, IbDA1-6, and IbDA1-7, were higher in the sweet potato leaves than in the roots, fiber roots, and stems. In our study, we provide a comprehensive comparison and further the knowledge of DA1-like genes in sweet potatoes, and provide a theoretical basis for functional studies.

Patterns of Spatial Variation in Rumen Microbiology, Histomorphology, and Fermentation Parameters in Tarim wapiti (Cervus elaphus yarkandensis).

The rumen is divided into multiple rumen sacs based on anatomical structure, and each has its unique physiological environment. Tarim wapiti preserved roughage tolerance after domestication, and adaptation to the desertified environment led to the development of a unique rumen shape and intraruminal environment. In this work, six Tarim wapiti were chosen and tested for fermentation parameters, microbes, and histomorphology in four rumen areas (Dorsal sac, DS; Ventral sac, VS; Caudodorsal blind sac, CDBS; Caudoventral blind sac, CVBS). Tarim wapiti's rumen blind sac had better developed rumen histomorphology, the ventral sac was richer in VFAs, and the dominant bacteria varied most notably in the phylum Firmicutes, which was enriched in the caudoventral blind sac. The ventral sac biomarkers focused on carbohydrate fermentation-associated bacteria, the dorsal sac focused on N recycling, and the caudoventral blind sac identified the only phylum-level bacterium, Firmicutes; we were surprised to find a probiotic bacterium, Bacillus clausii, identified as a biomarker in the ventral sac. This research provides a better understanding of rumen fermentation parameters, microorganisms, and histomorphology in the Tarim wapiti rumen within a unique ecological habitat, laying the groundwork for future regulation targeting the rumen microbiota and subsequent animal production improvement.

Asymmetric vortex beam emission from a metasurface-integrated microring with broken conjugate symmetry.

Vortex beams that carry orbital angular moment (OAM) have recently attracted a great amount of research interest, and metasurfaces and planar microcavities have emerged as two prominent, but mostly separated, methods for Si chip-based vortex beam emission. In this work, we demonstrate in numerical simulation for the first time the hybridization of these two existing methods in a Si chip-based passive emitter (i.e., a light coupler). A unique feature of this device is its broken conjugate symmetry, which originates from introducing a metasurface phase gradient along a microring. The broken conjugate symmetry creates a new phenomenon that we refer to as asymmetric vortex beam emission. It allows two opposite input directions to generate two independent sets of OAM values, a capability that has never been reported before in Si chip-based passive emitters. In addition, we have also developed here a new analytical method to extract the OAM spectrum from a vector vortex beam. This analytical method will prove to be useful for vector vortex beam analysis, as mode purity analysis has rarely been reported in literature due to the complexity of the full-vector nature of such beams. This study provides new approaches for both the design and the analysis of integrated vortex beam emission, which could be utilized in many applications such as free-space optical communications and microfluidic particle manipulation.

Catalase associated with antagonistic changes of abscisic acid and gibberellin response, biosynthesis and catabolism is involved in eugenol-inhibited seed germination in rice.

KEY MESSAGE: The inhibitory effect of eugenol on rice germination is mediated by a two-step modulatory process: Eugenol first regulates the antagonism of GA and ABA, followed by activation of catalase activity. The natural monoterpene eugenol has been reported to inhibit preharvest sprouting in rice. However, the inhibitory mechanism remains obscure. In this study, simultaneous monitoring of GA and ABA responses by the in vivo GA and ABA-responsive dual-luciferase reporter system showed that eugenol strongly inhibited the GA response after 6 h of imbibition, whereas eugenol significantly enhanced the ABA response after 12 h of imbibition. Gene expression analysis revealed that eugenol significantly induced the ABA biosynthetic genes OsNCED2, OsNCED3, and OsNCED5, but notably suppressed the ABA catabolic genes OsABA8ox1 and OsABA8ox2. Conversely, eugenol inhibited the GA biosynthetic genes OsGA3ox2 and OsGA20ox4 but significantly induced the GA catabolic genes OsGA2ox1 and OsGA2ox3 during imbibition. OsABI4, the key signaling regulator of ABA and GA antagonism, was notably induced before 12 h and suppressed after 24 h by eugenol. Moreover, eugenol markedly reduced the accumulation of H2O2 in seeds after 36 h of imbibition. Further analysis showed that eugenol strongly induced catalase activity, protein accumulation, and the expression of three catalase genes. Most importantly, mitigation of eugenol-inhibited seed germination was found in the catc mutant. These findings indicate that catalase associated with antagonistic changes of ABA and GA is involved in the sequential regulation of eugenol-inhibited seed germination in rice.

On-Chip Monolithically Integrated Ultraviolet Low-Threshold Plasmonic Metal-Semiconductor Heterojunction Nanolasers.

The metal-semiconductor heterojunction is imperative for the realization of electrically driven nanolasers for chip-level platforms. Progress in developing such nanolasers has hitherto rarely been realized, however, because of their complexity in heterojunction fabrication and the need to use noble metals that are incompatible with microelectronic manufacturing. Most plasmonic nanolasers lase either above a high threshold (101 -103 MW cm-2 ) or at a cryogenic temperature, and lasing is possible only after they are removed from the substrate to avoid the large ohmic loss and the low modal reflectivity, making monolithic fabrication impossible. Here, for the first time, record-low-threshold, room-temperature ultraviolet (UV) lasing of plasmon-coupled core-shell nanowires that are directly grown on silicon is demonstrated. The naturally formed core-shell metal-semiconductor heterostructure of the nanowires leads to a 100-fold improvement in growth density over previous results. This unprecedentedly high nanowire density creates intense plasmonic resonance, which is outcoupled to the resonant Fabry-Pérot microcavity. By boosting the emission strength by a factor of 100, the hybrid photonic-plasmonic system successfully facilitates a record-low laser threshold of 12 kW cm-2 with a spontaneous emission coupling factor as high as ≈0.32 in the 340-360 nm range. Such architecture is simple and cost-competitive for future UV sources in silicon integration.

Metasurfaces integrated with a single-mode waveguide array for off-chip wavefront shaping.

Integration of metasurfaces and SOI (silicon-on-insulator) chips can leverage the advantages of both metamaterials and silicon photonics, enabling novel light shaping functionalities in planar, compact devices that are compatible with CMOS (complementary metal-oxide-semiconductor) production. To facilitate light extraction from a two-dimensional metasurface vertically into free space, the established approach is to use a wide waveguide. However, the multi-modal feature of such wide waveguides can render the device vulnerable to mode distortion. Here, we propose a different approach, where an array of narrow, single-mode waveguides is used instead of a wide, multi-mode waveguide. This approach tolerates nano-scatterers with a relatively high scattering efficiency, for example Si nanopillars that are in direct contact with the waveguides. Two example devices are designed and numerically studied as demonstrations: the first being a beam deflector that deflects light into the same direction regardless of the direction of input light, and the second being a light-focusing metalens. This work shows a straightforward approach of metasurface-SOI chip integration, which could be useful for emerging applications such as metalens arrays and neural probes that require off-chip light shaping from relatively small metasurfaces.

Toxic effects of cadmium on the physiological and biochemical attributes of plants, and phytoremediation strategies: A review.

Anthropogenic activities pose a more significant threat to the environment than natural phenomena by contaminating the environment with heavy metals. Cadmium (Cd), a highly poisonous heavy metal, has a protracted biological half-life and threatens food safety. Plant roots absorb Cd due to its high bioavailability through apoplastic and symplastic pathways and translocate it to shoots through the xylem with the help of transporters and then to the edible parts via the phloem. The uptake and accumulation of Cd in plants pose deleterious effects on plant physiological and biochemical processes, which alter the morphology of vegetative and reproductive parts. In vegetative parts, Cd stunts root and shoot growth, photosynthetic activities, stomatal conductance, and overall plant biomass. Plants' male reproductive parts are more prone to Cd toxicity than female reproductive parts, ultimately affecting their grain/fruit production and survival. To alleviate/avoid/tolerate Cd toxicity, plants activate several defense mechanisms, including enzymatic and non-enzymatic antioxidants, Cd-tolerant gene up-regulations, and phytohormonal secretion. Additionally, plants tolerate Cd through chelating and sequestering as part of the intracellular defensive mechanism with the help of phytochelatins and metallothionein proteins, which help mitigate the harmful effects of Cd. The knowledge on the impact of Cd on plant vegetative and reproductive parts and the plants' physiological and biochemical responses can help selection of the most effective Cd-mitigating/avoiding/tolerating strategy to manage Cd toxicity in plants.

3D carbonized wood-based integrated electrochemical immunosensor for ultrasensitive detection of procalcitonin antigen.

This work presents a novel 3D carbonized wood-based integrated electrochemical immunosensor for ultrasensitive detection of procalcitonin (PCT) antigen at picogram level, achieving a wide linear detection range for PCT concentrations range from 0.05 to 90 pg mL-1 with a low detection limit of 0.014 pg mL-1 (S/N = 3), outperforming the previous reports. 3D carbonized wood as a new immunosensor matrix is used for electrochemical PCT biosensing, improving the stability of electrode and overcoming the disadvantages of traditional glassy carbon electrode (GCE). It obtained an excellent detection result, due to it has abundant mutual crisscross microchannels that promote the reactants and electrons transfer, greatly amplify the current signal. This novel sandwich-type electrochemical immunosensor is composed of 3D carbonized wood, carboxylic multi-walled carbon nanotube (cMWCNT), Au@Co3O4 core-shell nanosphere and Au/single layer nitrogen-doped graphene (Au/SL-NG), when it is applied for PCT detection in real clinical samples, it exhibits high accuracy same as enzyme-linked immunosorbent assay (ELISA) method.

The Influence of Helium Dielectric Barrier Discharge Jet (DBDjet) Plasma Treatment on Bathocuproine (BCP) in p-i-n-Structure Perovskite Solar Cells.

A bathocuproine (BCP) layer is typically used as the hole-blocking layer in p-i-n-structure perovskite solar cells (PSCs) between PC61BM and Ag electrodes. Before evaporating the Ag, we used a low-temperature (<40 °C) atmospheric-pressure dielectric barrier discharge jet (DBDjet) to treat the BCP with different scan rates. The main purpose of this was to change the contact resistance between the BCP layer and the Ag electrodes through surface modification using a DBDjet. The best power conversion efficiency (PCE) of 13.11% was achieved at a DBDjet scan rate of 2 cm/s. The He DBDjet treatment introduced nitrogen to form C-N bonds and create pits on the BCP layer. This deteriorated the interface between the BCP and the follow-up deposited-Ag top electrode. Compared to the device without the plasma treatment on the BCP layer, the He DBDjet treatment on the BCP layer reduced photocurrent hysteresis but deteriorated the fill factor and the efficiency of the PSCs.

Fe(II) Redox Chemistry in the Environment.

Iron (Fe) is the fourth most abundant element in the earth's crust and plays important roles in both biological and chemical processes. The redox reactivity of various Fe(II) forms has gained increasing attention over recent decades in the areas of (bio) geochemistry, environmental chemistry and engineering, and material sciences. The goal of this paper is to review these recent advances and the current state of knowledge of Fe(II) redox chemistry in the environment. Specifically, this comprehensive review focuses on the redox reactivity of four types of Fe(II) species including aqueous Fe(II), Fe(II) complexed with ligands, minerals bearing structural Fe(II), and sorbed Fe(II) on mineral oxide surfaces. The formation pathways, factors governing the reactivity, insights into potential mechanisms, reactivity comparison, and characterization techniques are discussed with reference to the most recent breakthroughs in this field where possible. We also cover the roles of these Fe(II) species in environmental applications of zerovalent iron, microbial processes, biogeochemical cycling of carbon and nutrients, and their abiotic oxidation related processes in natural and engineered systems.

A ferrocene-linked metal-covalent organic polymer as a peroxidase-enzyme mimic for dual channel detection of hydrogen peroxide.

A novel ferrocene-linked metal-covalent organic polymer (MCOP-NFC) was synthesized through the Claisen-Schmidt condensation reaction of 1,1'-diacetyl ferrocene and tris(4-formylphenyl)amine. MCOP-NFC acts as a highly efficient artificial enzyme for mimicking peroxidase, and shows good stability in harsh chemical environments including strong bases and acids, and boiling water. Based on the peroxidase-like activity of MCOP-NFC, a highly sensitive dual channel detection method for hydrogen peroxide was developed. For the colorimetric detection strategy, the limit of detection (LOD) reached 2.1 µM, while the limit of detection was found to be as low as 0.08 µM based on the electrochemical detection channel. This study offers a new strategy for the development of an enzyme mimetic on the basis of the covalent assembly of nanostructures, and the proposed electrochemical-colorimetric sensor for H2O2 detection has great potential for applications in biology and biomedicine.

Preparation of Gas-Responsive Imprinting Hydrogel and Their Gas-Driven Switchable Affinity for Target Protein Recognition.

Novel gas-responsive imprinting hydrogels were fabricated by combining N,N'-dimethylaminoethyl methacrylate gas-sensitive monomers, N,N'-methylenebis(acrylamide) cross-linkers, and human serum albumin (HSA) template proteins via a free radical polymerization. The hydrogel exhibited a reversible gas-responsive property upon N2/CO2 exchange. This result was supported by the evidences from hydrogen nuclear magnetic resonance spectroscopy and scanning electron microscopy. By applying this property to sensing application, a CO2-responsive imprinted biosensor was originally designed on the surface of a glassy carbon electrode. The biosensor exhibited unique self-clean and self-recognition properties toward HSA proteins based on reversible conformational changes driven by N2/CO2 stimuli. Moreover, the proposed imprinted biosensor favored HSA proteins by showing satisfactory sensitivity and selectivity and a wider detection range with a low detection limit. As a rare example in imprint sensing, the biosensor was successfully applied to the HSA extraction from complex serum samples. With gas stimuli, the whole process was efficient, controllable, and harmless to the proteins. Thus, the developed biosensor may provide a new prospect in molecularly imprinted sensing applications.

Surveying Manganese Oxides as Electrode Materials for Harnessing Salinity Gradient Energy.

The potential energy contained in the controlled mixing of waters with different salt concentrations (i.e., salinity gradient energy) can theoretically provide a substantial fraction of the global electrical demand. One method for generating electricity from salinity gradients is to use electrode-based reactions in electrochemical cells. Here, we examined the relationship between the electrical power densities generated from synthetic NaCl solutions and the crystal structures and morphologies of manganese oxides, which undergo redox reactions coupled to sodium ion uptake and release. Our aim was to make progress toward developing rational frameworks for selecting electrode materials used to harvest salinity gradient energy. We synthesized 12 manganese oxides having different crystal structures and particle sizes and measured the power densities they produced in a concentration flow cell fed with 0.02 and 0.5 M NaCl solutions. Power production varied considerably among the oxides, ranging from no power produced (ß-MnO2) to 1.18 ± 0.01 W/m2 (sodium manganese oxide). Power production correlated with the materials' specific capacities, suggesting that cyclic voltammetry may be a simple method to screen possible materials. The highest power densities were achieved with manganese oxides capable of intercalating sodium ions when their potentials were prepoised prior to power production.

Fast and selective detection of mercury ions in environmental water by paper-based fluorescent sensor using boronic acid functionalized MoS2 quantum dots.

In this study, the B-MoS2 QDs, boronic acid functionalized MoS2 quantum dots, are synthesized by a simple aminoacylation reaction between MoS2 QDs and 3-aminobenzeneboronic acid (APBA). It not only exhibits excellent thermo-stability, photo-stability and good salt tolerance, but shows excellent fluorescence stability even under industrial wastewater with high concentration. These good characters can be used to construct a new fluorescence sensor for sensitive and selective detection of mercury ions (Hg2+). The fluorescence intensity of B-MoS2 QDs linearly decreases with the increase of Hg2+ concentration ranging from 0.005 to 41 µmol L-1, and the limit of detection as low as 1.8 nmol L-1. Due to the mercury ion-promoted transmetalation reaction of aryl boronic acid, this proposed method exhibits fast response, ultra-sensitivity and high selectivity for analysis of Hg2+ in different environmental water, and which also uses to online monitoring of Hg2+. The B-MoS2 QDs-based test paper can be used to detect the trace amounts of Hg2+ under UV lamp by naked eyes, suggesting that the proposed method has potential application in on-site monitoring of environmental Hg2+.

Near-Infrared Emission Induced by Shortened Pt-Pt Contact: Diplatinum(II) Complexes with Pyridyl Pyrimidinato Cyclometalates.

Four diplatinum(II) complexes with the formula [Pt(pypm)(µ-Fn)]2 (2, 3a-c) bearing both a pyridine-pyrimidinate chelate and formamidinate bridge, where (pypm)H and FnH stand for 5-(pyridin-2-yl)-2-(trifluoromethyl)pyrimidine and functional formamidines with various substituents of iPr (n = 1), Ph (n = 2), C6H4tBu (n = 3), and C6H4CF3 (n = 4), were synthesized en route from a mononuclear intermediate represented by [Pt(pypm)Cl(F1H)] (1). Single-crystal X-ray diffraction studies confirmed the structure of 1 and 3a comprised of an individual "Pt(pypm)" unit and two "Pt(pypm)" units with a Pt···Pt distance of 2.8845(2) Å, respectively. Therefore, in contrast to the structured emission of mononuclear 1 with the first vibronic peak wavelength at 475 nm, all other diplatinum complexes with shortened Pt···Pt separation exhibited greatly red shifted and structureless metal-metal to ligand charge transfer (MMLCT) emission that extended into the near-infrared region in solid states. Their photophysical characteristics were measured under three distinctive morphological states (i.e., crystals, sublimed powders, and vacuum-deposited thin films) by steady-state UV-vis spectroscopy, while retention of Pt···Pt interactions in deposited thin films of 2 and 3a-c was confirmed using Raman spectroscopy, demonstrating lowered Pt···Pt stretching at 80-200 cm-1. Most importantly, complexes 3a-c exhibited a gradual red shift with the trends crystals < sublimed powders < vacuum-deposited thin films, a result of increased intermolecular π-π stacking interactions and Pt···Pt interactions, while crystalline samples exhibited the highest luminescence among all three morphological states due to the fewest defects in comparison to other morphologies. Finally, 3b was selected as a nondoped emitter for the fabrication of NIR-emitting OLEDs, giving an electroluminescence peak at 767 nm and a maximum external quantum efficiency of 0.14% with negligible roll-off.

Mn-based catalysts for sulfate radical-based advanced oxidation processes: A review.

Sulfate radical-based advanced oxidation processes (AOPs) have drawn increasing attention during the past two decades, and Mn-based materials have been proven to be effective catalysts for activating peroxymonosulfate (PMS) and peroxydisulfate (PDS) to degrade many contaminants. This article presents a comprehensive review of various Mn-based materials to activate PMS and PDS. The activation mechanisms of different Mn-based catalysts (i.e., Mn oxides MnOx, MnOx hybrids, and MnOx­carbonaceous material composites) were first summarized and discussed in detail. Besides the commonly reported free radicals (SO4-• and •OH), non-radical mechanisms such as singlet oxygen and direct electron transfer have also been discovered for selected materials. The effects of pH, inorganic ions, natural organic matter (NOM), dissolved oxygen content, temperature, and the crystallinity of the materials on the catalytic reactivity were also discussed. Then, important instrumentations and technologies employed to characterize Mn-based materials and to understand the reaction mechanisms were concisely summarized. Three common overlooks in the experimental designs for examining the PMS/PDS-MnOx systems were also discussed. Finally, future research directions were suggested to further improve the technology and to provide a guidance to develop cost-effective Mn-based materials to activate PMS/PDS.

H2O2-Based Method for Rapid Detection of Transgene-Free Rice Plants from Segregating CRISPR/Cas9 Genome-Edited Progenies.

Genome-editing techniques such as CRISPR/Cas9 have been widely used in crop functional genomics and improvement. To efficiently deliver the guide RNA and Cas9, most studies still rely on Agrobacterium-mediated transformation, which involves a selection marker gene. However, several limiting factors may impede the efficiency of screening transgene-free genome-edited plants, including the time needed to produce each life cycle, the response to selection reagents, and the labor costs of PCR-based genotyping. To overcome these disadvantages, we developed a simple and high-throughput method based on visual detection of antibiotics-derived H2O2 to verify transgene-free genome-edited plants. In transgenic rice containing hygromycin phosphotransferase (HPT), H2O2 content did not change in the presence of hygromycin B (HyB). In contrast, in transgenic-free rice plants with 10-h HyB treatment, levels of H2O2 and malondialdehyde, indicators of oxidative stress, were elevated. Detection of H2O2 by 3,3'-diaminobenzidine (DAB) staining suggested that H2O2 could be a marker to efficiently distinguish transgenic and non-transgenic plants. Analysis of 24 segregating progenies of an HPT-containing rice plant by RT-PCR and DAB staining verified that DAB staining is a feasible method for detecting transformants and non-transformants. Transgene-free genome-edited plants were faithfully validated by both PCR and the H2O2-based method. Moreover, HyB induced overproduction of H2O2 in leaves of Arabidopsis, maize, tobacco, and tomato, which suggests the potential application of the DAB method for detecting transgenic events containing HPT in a wide range of plant species. Thus, visual detection of DAB provides a simple, cheap, and reliable way to efficiently identify transgene-free genome-edited and HPT-containing transgenic rice.

Effects of light intensity and plant growth regulators on callus proliferation and shoot regeneration in the ornamental succulent Haworthia.

BACKGROUND: Haworthia are desert succulents belonging to the Asphodelaceae family. Haworthia species are cultivated commercially as ornamentals and some rare species are quite valuable at retail market but growth slowly and difficult to propagation. However, an efficient micropropagation protocol was remained insufficient. RESULTS: The organogenic cultures obtained from inflorescence explants were cultured on Murashige and Skoog (MS) medium supplemented with various combinations of 6-benzylaminopurine (BA) and α-naphthalene acetic acid (NAA) under a light intensity of 10 µmol m-2 s-1 or 45 µmol m-2 s-1. The highest callus proliferation index (93.15%) with 1.0 mg L-1 BA + 0.1 mg L-1 NAA under a light intensity of 10 µmol m-2 s-1. The best shoot proliferation rates were on media with either 1 mg L-1 BA + 0-0.4 mg L-1 NAA (65.57-81.01%) under a light intensity of 45 µmol m-2 s-1. The highest root length (15.57 mm) and the highest rooting frequency (17 roots per shoot) were obtained when adventitious shoots were inoculated on MS medium with 0.4 mg L-1 NAA + 0.4 mg L-1 IBA. The survival rate of the transplanted plantlets was about 100%. The efficient micropropagation protocol proliferated Haworthia regenerate plants from inflorescence within 11 weeks. CONCLUSIONS: The present study determined the best combination of light intensity and plant growth regulators (PGRs) for improved organogenesis of Haworthia during propagation by tissue culture. This optimized protocol showed light intensity is an important factor for efficient callus or shoot regeneration. These results indicate that it will be useful to optimize the light conditions for future commercial cultivation, germplasm conservation, genetic engineering and molecular biology research of this ornamental plant.

Interactions and Reductive Reactivity in Ternary Mixtures of Fe(II), Goethite, and Phthalic Acid Based on a Combined Experimental and Modeling Approach.

The interactions between organic ligands, Fe(II), and iron oxides are important in biogeochemical redox processes. The effect of phthalic acid (PHA) on the reductive reactivity of Fe(II) associated with goethite was examined using batch adsorption and kinetic studies, attenuated total reflectance?Fourier transform infrared spectroscopy (ATR?FTIR), and surface complexation modeling (SCM). PHA significantly inhibited the reductive reactivity of Fe(II)/goethite, as quantified by the pseudo-first-order reduction rate constants ( k) of p-cyanonitrobenzene. The k value decreased from 1.68 ? 0.03 to 0.338 ? 0.14 h?1 at pH 6.0 as the PHA concentration increased from 0 to 1000 ?M. The effects of the co-adsorption of Fe(II) and PHA onto goethite were then investigated to study the inhibition mechanism. The adsorption experiments showed that Fe(II) slightly enhanced PHA adsorption, whereas PHA did not affect Fe(II) adsorption, suggesting that the inhibition was not due to different amounts of Fe(II) adsorbed. The ATR?FTIR spectra of the adsorbed PHA in the ternary mixtures demonstrated that the major surface species was outer-sphere species, with minor inner-sphere complexes formed. SCM results showed that the presence of PHA (L) led to the formation of a type A ternary species ((?FeOFe+)2???L2?) on the goethite surface, decreasing the abundance of the reactive species (?FeOFeOH). Moreover, the adsorption of PHA on the surface of goethite might block the reactive sites and inhibit the electron transfer between Fe(II) and goethite, thus decreasing the reactivity. Overall, these findings provided new insights into the reaction mechanisms of surface-adsorbed Fe(II), which will facilitate the development of new technologies for site remediation and more accurate risk assessment.