Controlling the Bonding Site of Photosynthetic Reaction Centers on Au Electrode by Different Bifunctional Agents

The orientation of the immobilized protein is the key factor to effect the surface electrochemistry of the redox couples therein. The photosynthetic reaction centers (RCs) composite film was fabricated by self-assembled monolayers (SAMs) on Au electrode. The bifunctional reagents e.g. 4-aminothiophenol (ATP), 2-mercaptoehtylamine (MEA), 2-mercaptoethanol (ME), 2-mercaptoacetic acid (MAA), and Poly(dimethyldiallylammonium) chloride(PDDA) were found to bond RCs at different sites. The square wave voltammetry (SWV), bulk electrolysis were employed for characterizing the composite film. The electrochemically-driven electron transfer (ET) behavior in films was found driven by SWV or bulk electrolysis. In case the electrode was modified directly by amino compound reagent, the greater force was needed. If the film was activated by SWV with frequency of 15 Hz, the SWV amplitude of about lOOmV for MAA-PDDA-RC and 250 mV or more for MA-RC film was needed respectively. When the ME-PDDA-RC composite film was stimulated by SWV, the peak for the bacteriochlorophyll dimmer (P) and secondary quinone (Q_B) appeared at first, then the peak of primary quinone (Q_A) came into being. Further more,if the simulated signal of SWV was continually applied, all of the peak current increased. On the other hand, the opposite process was observed while the potential of -0.4 V was applied by bulk electrolysis. For all the composite films,the redox potential for P⁺/P declined with frequency increasing from 30 to 150 Hz.As reported before, the redox potential of species in RC were:0.45-0.60 V (vs.NHE)for P⁺/p, +0.05~-0.15 V for Q_A and -0.20~-0.35 V for Q_B.     

Surfactant Effects on the Permeability of Photosynthetic Membrane from Rhodobacter sphaeroides 2.4.1 Probed by Electrochromic Shift of Endogenous Carotenoids

Four surfactants, sodium cholate(SC), n-dodecyl-β-D-maltopyranoside(DDM), lauryldimethylamine oxide(LDAO) and Triton X-100(TX), which are generally used in photosynthetic pigment-protein complexes preparation, were studied on their interaction with photosynthetic membrane from Rhodobacter sphaeroides 2.4.1 by electrochromic absorption band-shift of endogenous carotenoids and by vesicle size measurements as well. The surfactant critical micelle concentration(cmc) was found to be negatively correlated with the capability of enhancing the permeability of photosynthetic membranes to proton, and more elaborated model of surfactants interacting with membranes was obtained. The electrochromic absorption band-shift measurement might develop into a useful tool to evaluate the effects of surfactants on various membranes.     

Copper-Silica Sol-Gel Catalysts: Structural Changes of Cu Species upon Thermal Treatment

In this work the encapsulation of copper species in sol-gel silica catalysts thermally treated up to 1100°C was studied. XRD, TPR, BET data showed the occurrence of a vitrification/densification process upon treatment at temperatures higher than 900°C leading to the partial or complete encapsulation of the copper species by the silica matrix. As result of this process the copper catalyst particles become unavailable for the reaction with gas phase molecules and are not active for reactions such as carbon monoxide oxidation.     

Wide Band Gap Transparent Polymer-Inorganic Composite Thin Films by Dip-Coating Method: Preparation and Characterizations

Wide band gap transparent polymer-inorganic (PVA-ZnO) composite thin films were prepared by the dip-coating method. Functional groups and metal oxide vibrations were found from Fourier transform-infrared spectroscopy. The elements Zn and O were confirmed from energy dispersive X-ray spectroscopy. The X-ray diffraction patterns revealed that the sharp diffraction peaks correspond to the hexagonal wurtzite structure of ZnO in the PVA matrix. Scanning electron microscopy images showed that the ZnO nanoparticles are randomly distributed throughout the entire film surface. The optical study reveals that the transmittance was more than 85% with very low absorption and wide band gap energy (4.03 to 3.95 eV). The obtained results indicate that the high transmittance, very low absorption, and wide band gap energy of the prepared dip-coated composite thin films make them suitable for use in transparent optoelectronic device applications in the near future.     

Effects of Ultraviolet Radiation (UVA+UVB) on Young Gametophytes of Gelidium floridanum: Growth Rate,Photosynthetic Pigments,Carotenoids, Photosynthetic Performance,and Ultrastructure

This study investigated the effects of radiation (PAR+UVA+UVB) on the development and growth rates (GRs) of young gametophytes of Gelidium floridanum. In addition, photosynthetic pigments were quantified, carotenoids identified, and photosynthetic performance assessed. Over a period of 3 days, young gametophytes were cultivated under laboratory conditions and exposed to photosynthetically active radiation (PAR) at 80 μmol photons m^?2 s^?1 and PAR+UVA (0.70 W m^?2)+UVB (0.35 W m^?2) for 3 h per day. The samples were processed for light and electron microscopy to analyze the ultrastructure features, as well as carry out metabolic studies of GRs, quantify the content of photosynthetic pigments, identify carotenoids and assess photosynthetic performance. PAR+UVA+UVB promoted increase in cell wall thickness, accumulation of floridean starch grains in the cytoplasm and disruption of chloroplast internal organization. Algae exposed to PAR+UVA+UVB also showed a reduction in GR of 97%. Photosynthetic pigments, in particular, phycoerythrin and allophycocyanin contents, decreased significantly from UV radiation exposure. This result agrees with the decrease in photosynthetic performance observed after exposure to ultraviolet radiation, as measured by a decrease in the electron transport rate (ETR), where values of ETRmax declined approximately 44.71%. It can be concluded that radiation is a factor that affects the young gametophytes of G. floridanum at this stage of development.     

Highly Oxidized Platinum Nanoparticles Prepared through Radio‐Frequency Sputtering: Thermal Stability and Reaction Probability towards CO

Platinum‐oxide nanoparticles were prepared through the radio‐frequency (RF) discharge sputtering of a Pt electrode in an oxygen atmosphere. The structure, particles size, electronic properties, and surface composition of the RF‐sputtered particles were studied by using transmission electron microscopy and X‐ray photoelectron spectroscopy. The application of the RF discharge method resulted in the formation of highly oxidized Pt⁴⁺ species that were stable under ultrahigh vacuum conditions up to 100 °C, indicating the capability of Pt⁴⁺–O species to play an important role in the oxidation catalysis under real conditions. The thermal stability and reaction probability of Pt⁴⁺ oxide species were analyzed and compared with those of Pt²⁺ species. The reaction probability of PtO₂ nanoparticles at 90 °C was found to be about ten times higher than that of PtO‐like structures.     

Mononuclear to Polynuclear UIV Structural Units: Effects of Reaction Conditions on U-Furoate Phase Formation

Uranium(IV) complexation by 2-furoic acid (2-FA) was examined to better understand the effects of ligand identity and reaction conditions on species formation and stability. Five compounds were isolated: [UCl₂(2-FA)₂(H₂O)₂]_n ( 1 ), [U₄Cl₁₀O₂(THF)₆(2-FA)₂] ⋅ 2 THF ( 2 ), [U₆O₄(OH)₄(H₂O)₃(2-FA)₁₂] ⋅ 7 THF ⋅ H₂O ( 3 ), [U₆O₄(OH)₄(H₂O)₂(2-FA)₁₂] ⋅ 8.76 H₂O ( 4 ), and [U₃₈Cl₄₂O₅₄(OH)₂(H₂O)₂₀] ⋅ m H₂O ⋅ n THF ( 5 ). The structures were determined by single-crystal X-ray diffraction and further characterized by Raman, IR, and optical absorption spectroscopy. The thermal stability and magnetic behavior of the compounds were also examined. Variations in the synthetic conditions led to notable differences in the structural units observed in the solid state. At low H₂O/THF ratios, a tetranuclear oxo-bridged [U₄O₂] core was isolated. Aging of this solution resulted in the formation a U₃₈ oxo cluster capped by chloro and water ligands. However, at increasing water concentrations only hexanuclear units were observed. In all cases, at temperatures of 100–120 °C, UO₂ nanoparticles formed.     

Triplet Energy Transfer between the Primary Donor and Carotenoids in Rhodobacter sphaeroides R-26.1 Reaction Centers Incorporated with Spheroidene Analogs Having Different Extents of π-Electron Conjugation

Abstract— Three carotenoids, spheroidene, 3,4-dihydrospheroidene and 3,4,5,6-tetrahydrospheroidene, having 8, 9 and 10 conjugated carbon-carbon double bonds, respectively, were incorporated into Rhodobacter (Rb.) sphaeroides R-26.1 reaction centers. The extents of binding were found to be 95±5% for spheroidene, 65±5% for 3,4-dihydrospheroidene and 60±10% for 3,4,5,6-tetrahydrospheroidene. The dynamics of the triplet states of the primary donor and carotenoid were measured at room temperature by flash absorption spectroscopy. The carotenoid, spheroidene, was observed to quench the primary donor triplet state. The triplet state of spheroidene that was formed subsequently decayed to the ground state with a lifetime of 7.0±0.5 μs. The primary donor triplet lifetime in the Rb. sphaeroides R-26.1 reaction centers lacking carotenoids was 60±5 μs. Quenching of the primary donor triplet state by the carotenoid was not observed in the Rb. sphaeroides R-26.1 reaction centers containing 3,4-dihydrospheroidene nor in the R-26.1 reaction centers containing 3,4,5,6-tetrahydrospheroidene. Triplet-state electron paramagnetic resonance was also carried out on the samples. The experiments revealed carotenoid triple-state signals in the Rb. sphaeroides R-26.1 reaction centers incorporated with spheroidene, indicating that the primary donor triplet is quenched by the carotenoid. No carotenoid signals were observed from Rb. sphaeroides R-26.1 reaction centers incorporating 3,4-dihydrospheroidene nor in reaction centers incorporating 3,4,5,6-tetrahydrospheroidene. Circular dichroism, steady-state absorbance band shifts accompanying the primary photochemistry in the reaction center and singlet energy transfer from the carotenoid to the primary donor confirm that the carotenoids are bound in the reaction centers and interacting with the primary donor. These studies provide a systematic approach to exploring the effects of carotenoid structure and excited state energy on triplet transfer between the primary donor and carotenoids in reaction centers from photosynthetic bacteria.     

Structural Changes Induced by Quinones: High-Resolution Microwave Study of 1,4-Naphthoquinone

1,4-Naphthoquinone (1,4-NQ) is an important product of naphthalene oxidation, and it appears as a motif in many biologically active compounds. We have investigated the structure of 1,4-NQ using chirped-pulse Fourier transform microwave spectroscopy and quantum chemistry calculations. The rotational spectra of the parent species, and its ¹³C and ¹⁸O isotopologues were observed in natural abundance, and their spectroscopic parameters were obtained. This allowed the determination of the substitution r_s, mass-weighted r_m and semi-experimental r_e^SE structures of 1,4-NQ. The obtained structural parameters show that the quinone moiety mainly changes the structure of the benzene ring where it is inserted, modifying the C−C bonds to having predominantly single or double bond character. Furthermore, the molecular electrostatic surface potential reveals that the quinone ring becomes electron deficient while the benzene ring remains a nucleophile. The most electrophilic areas are the hydrogens attached to the double bond in the quinone ring. Knowledge of the nucleophilic and electrophilic areas in 1,4-NQ will help understanding its behaviour interacting with other molecules and guide modifications to tune its properties.     

Anionic Aliovalent Substitution from Structure Models of ZnS: Novel Defect Diamond-like Halopnictide Infrared Nonlinear Optical Materials with Wide Band Gaps and Large SHG Effects

To design pnictide nonlinear optical materials with wide band gap and large second-harmonic generation, the heavy halogen I was introduced into pnictides through anionic aliovalent substitution with diamond-like ZnS as templates. Thus, four excellent halopnictide-based infrared nonlinear optical crystals, M^II₃PnI₃ (M^II=Zn, Cd; Pn=P, As), were obtained. They all exhibited defect diamond-like structures with highly parallel-oriented [M^IIPnI₃] mixed-anionic tetrahedral groups, leading to excellent physical properties including wide band gaps (2.38–2.85 eV), large second harmonic generation responses (2.7–5.1×AgGaS₂), high laser-induced damage thresholds (5.5–10.7×AgGaS₂), and good IR transparency. In particular, Cd₃PI₃ and Cd₃AsI₃ achieved phase-matching (Δn=0.035 and 0.031) that their template β-ZnS could not do. Anionic aliovalent substitution provides a feasible strategy to design novel promising halopnictide IR NLO materials.     

Thermal Conversion of Heavy Oil Systems and Analysis of Structural Changes of their High Components with PMR Method

Heavy oil systems are thermolyzed with different ratios of amount of resins and asphaltenes: 3.4, 3.8, 5.3, and 12.4. The change in yield and composition of gaseous, liquid and solid products of thermolysis is shown depending on the ratio of the resin: asphaltenes. In the liquid products of thermolysis, resins content decreases and s the amount of asphaltenes and oils increases. According to PMR spectroscopy, the distribution of protons is compared in the secondary resin and asphaltene molecules of the initial samples and the thermolysis products. It is shown that the relative content of hydrogen aromatic rings in the molecules of asphaltenes is higher, and for β- and γ- positions relative to the aromatic rings and heterofunction, it is lower than in the resin molecules.     

Uranium Oxide Nanocrystals by Microwave‐Assisted Thermal Decomposition: Electronic and Structural Properties

Uranium oxides have attracted much attention not only in the context of nuclear energy generation but also for their application as pristine catalysts or as supports for other (transition metal) oxides and (precious) metals. Their propensity to adopt high coordination numbers and manifest multiple oxidation states (from +II to +VI) makes them attractive candidates for catalyzed transformation reactions. Herein, we report a new synthesis route to phase‐pure, crystalline UO₂ nanoparticles via microwave‐assisted decomposition of a molecular uranium(IV) precursor. The electronic structure and optical absorption properties of these nanocrystals were investigated using spectroscopic methods to evaluate their suitability for photo(electro)catalytic applications.     

不同铝源合成的β沸石结构表征与热分解行为的研究

考察了以固体硅胶为硅源、 NaAlO2及α Al2O3· H2O两种铝源、以及不同晶化混合液的 SiO2/Al2O3比（ 15～ 50）对β沸石合成的影响。通过 XRD、 DSC/TGA、 29Si NMR及 ICP研究表明,以 NaAlO2为铝源合成的β沸石更易形成 Si(0Al)、 Si(1Al)、 Si(O－ )配位,且化学 SiO2/Al2O3比与晶化混合液 SiO2/Al2O3比基本一致,以α Al2O3· H2O为铝源合成的β沸石更易形成 Si(0Al)、 Si(O－ )、 Si(2Al)配位,且化学 SiO2/Al2O3比低于晶化混合液的 SiO2/Al2O3比; TGA失重量随β沸石 SiO2/Al2O3比增加而增加, DSC吸热量随β沸石 SiO2/Al2O3增加而减少。     

Solvent and Structural Effects on the Activation Parameters of the Reaction of Carboxylic Acids with Diazodiphenylmethane

The kinetics of the reaction of benzoic, 2‐methylbenzoic, phenylacetic, cyclohex‐1‐enecarboxylic, 2‐methylcyclohex‐1‐enecarboxylic, and cyclohex‐1‐eneacetic acids with diazodiphenylmethane was studied at 30, 33, 37, 40, and 45°C in a set of 12 protic and aprotic solvents. The reactions were found to follow the second‐order kinetics. The activation energy as well as the activation parameters, such as the standard entropy, the standard enthalpy, and the standard Gibbs energy of the activation, was calculated from the second‐order rate constants. The solvent and structural effects on the activation energy and the standard Gibbs energy of activation, for each examined compound, were analyzed. The results of Kamlet–Taft multiple correlation analysis show that the specific solvent–solute interactions play a dominant role in the governing of the reaction. The signs of the equation coefficients support the proposed reaction mechanism.     

Giant Single-Crystal Shape Transformation with Wide Thermal Hysteresis Actuated by Synergistic Motions of Molecular Cations and Anions

Manipulating the collective molecular movements to implement macroscopic mechanical response of bulk material is attractive and challenging. Here, an organic-inorganic hybrid single crystal is synthesized, which exhibits a giant macroscopic shape transformation with a remarkable thermal hysteretic feature. The colossal anisotropic shape change, which manifests as an abrupt elongation of ca. 9 % along the crystallographic c-axis and a concomitant contraction of ca. 9 % in a perpendicular direction, is induced by a significant reorientation of imidazolium, accompanied with a substantial configurational variation in CuBr₄²⁻ complex anions. The synergistic motions of both the molecular cations and anions engender a remarkable large thermal hysteresis (>30 K) in the shape transformation of the single crystal, implying that this material may play a role in alternating memory media. Furthermore, due to the stable crystal lattice, a single crystal that demonstrates naked-eye detectable large shape transformation was used as a thermal actuator to spontaneously control an electric circuit by temperature variation.     

Ion Mobility Measurements of Multianionic Metalloporphyrin Dimers: Structural Changes Induced by Countercation Exchange

We present gas-phase structures of dimers of Mn^III and Fe^III meso-tetra(4-sulfonatophenyl)porphyrin multianions with various amounts of sodium and hydrogen counterions. The structural assignments are achieved by combining mass spectrometry, ion mobility measurements, quantum chemical calculations, and trajectory method collision cross section calculations. For a common charge state, we observe significant topological variations in the dimer structures of [(MTPPS)₂+nX]^(6-n)- (M=Mn^III, Fe^III; X=H, Na; n?=?1–3) induced by replacing hydrogen counterions by sodium. For sodium, the dimer structures are much more compact, a finding that can be rationalized by the stronger interactions of the sodium cations with the anionic sulfonic acid groups of the porphyrins as compared to hydrogen.

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Structural Study of Micro and Nanotubes Synthesized by Rapid Thermal Chemical Vapor Deposition

The structures of micro and nanotubes obtained by pyrolysis of hydrocarbons, hold onto silicon (Si) substrates, are reported in this work. The tubes fabrication experiments were carried out by Rapid Thermal Chemical Vapor Deposition (RTCVD) using propane (C₃H₈) as carbon (C) precursor. Selection of parameters such as temperature of deposition, vacuum conditions or surface cleaning leads to the creation of tubular structures. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), selected area electron diffraction (SAED) and energy dispersive X-ray measurements (EDX) are the microbeam techniques that allow to characterize the tubes found in the studied specimens. Different tube configurations such as isolated nanorods, Y-type junctions or fiber-like layers are evidenced. Metallic catalysis seems to be the mechanism involved in the wires formation since Fe particles are present inside the CNT tubes. Other poly-crystalline inclusions are also evidenced by SAED. The composition of the nanotubes changes from tip to tail in an amorphous matrix. The growth mechanisms leading to tube formation are described.