A novel bifunctional protein supramolecule for construction of carbon nanotube-titanium hybrid material

Carbon nanotube-TiO(2) hybrid materials with many nano-scale cavities were realized using a bifunctional protein supramolecule possessing carbonaceous material-binding peptides and Ti-binding peptides. The obtained structure was confirmed to consist of a central nanotube, surrounding proteins, and a swathing titanium-layer. All processes were carried out at room temperature, using an environmentally friendly method.     

Formation of N-heterocyclic, donor-stabilized borenium ions

Cationic and zwitterionic boryl bromide species and a borenium-boryl bromide cation have been synthesised which represent new N-donor stabilised cationic boron compounds with β-diketiminate ligands. The unexpected borenium-boryl bromide results from a head-to-tail dimerisation of the corresponding zwitterionic boryl bromide accompanied by proton migration. The electronic nature of these new species was studied by DFT calculations.     

Simultaneous determination of ionic and neutral preservatives by inline dialysis-ion chromatography coupled with a hydrophobic-ion exchange mixed mode column

A quantitative analysis was developed for eight acidic and neutral preservatives in foods and daily necessities using the inline dialysis-IC combined with hydrophobic anion-exchange separation. The eight preservatives were dialyzed by inline dialysis and separated on a hydrophobic anion exchange column. Under the optimized separation conditions, the detection limits (S/N = 3) for the eight preservatives were from 0.08 to 0.66 mg L(-1), moreover, a good linearity (R(2) > 0.998) for each preservative was obtained in the range to 100 mg L(-1). Although the dialysis rate of the neutral preservatives was not so high, a good repeatability (RSD, n = 8) of less than 1.5% for the eight preservatives was obtained. The inline dialysis-IC method was applied to the determination of the preservatives in foods and daily necessities. The preservatives were quantified without any interference. The proposed method will be useful for the determination of the preservatives in foods and daily necessities containing high concentration matrices.     

Counter-ionic effect on the separation of water-soluble compounds applying a hydrophilic stationary phase bonded with a zwitter-ionic polymer

A novel hydrophilic stationary phase bonded with a zwitter-ionic polymer for HPLC was synthesized. The stationary phase, in combination with a mobile phase containing various salts, was evaluated for its ability to separate water-soluble compounds, such as nucleobases, nucleosides and glycosides. The retention of a large majority of the solutes, except for cytosine, was increased by adding anti-chaotropic ions to the mobile phase. These results suggested that the retention of solutes depended on the thickness of the hydration layer on the stationary phase. In the zwitter-ionic polymer adsorbent, the formation of the hydration layer and the ionicity of the zwitter-ionic group on the stationary phase will be controlled by the properties of the ions added to the mobile phase.     

UV irradiation enhances the bonding strength between citric acid-crosslinked gelatin and stainless steel

The effect of ultraviolet ray (UV) irradiation on the bonding strength between low carbon stainless steel 316 (SUS316L) and trisuccinimidyl citrate (TSC)-crosslinked alkali-treated gelatin (AlGelatin-TSC) was investigated. The UV irradiation effectively generated hydroxyl groups on the surface of SUS316L. The bonding strength between AlGelatin-TSC and SUS316L before UV irradiation was 0.345±0.007 MPa, and upon UV irradiation it increased to 0.750±0.069 MPa. In order to explain this enhanced bonding strength, the surface of SUS316L was examined using its water contact angle and X-ray photoelectron spectroscopy. Furthermore, the N 1s peaks derived from the TSC succinimidyl group were assigned to the surface of SUS316L after the immobilization of the TSC. This indicates that ester bond formation between the TSC active esters and the SUS316L hydroxyl groups contributed to the enhanced bonding strength. Therefore, UV irradiation and subsequent TSC immobilization is a simple way to functionalize biometal surfaces with various structures. This has practical applications for medical devices such as drug-eluting stents, dental implants, and metallic artificial bone.     

Host–guest complexation of antioxidative caffeic and ferulic acid amides with a functionalized cyclophane

Host?guest complexation has been studied by ¹H NMR on the benzyl and phenethyl amides of ferulic and caffeic acids as the guests in chloroform and acetonitrile; the counter host is a cyclophane which integrates four phenylene rings, amino and amide groups in the macrocyclic framework and bears four pendant methyl acetate ester arms. CAPE, one of the best known natural antioxidants, also has been studied for comparison. Among the guests studied, ferulic acid benzyl amide shows NMR shifts due to the formation of a host?guest complex in chloroform. The complexation occurs in two steps with the formation constants K ₁?=?[HG]/[H][G]?=?6?M^?1 and β ₂?=?[HG₂]/[H][G]²?=?87?M^?2. Two guest molecules are bound on the surface of the macrocyclic framework of a host molecule by two hydrogen bonds, NH(host amide)···O=C(guest amide) and C=O(host ester)···HO(guest phenol). The latter hydrogen bond may protect the bioactive site, i.e., phenol OH, of guest molecules captured in the complex against undesirable oxidation. This feature is observed only for ferulic acid benzyl amide in chloroform; the cyclophane ester interacts with this amide, distinctively from the other hydroxycinnamic acid derivatives.     

Hydrophilicity Control of Visible‐Light Hydrogen Evolution and Dynamics of the Charge‐Separated State in Dye/TiO2/Pt Hybrid Systems

Visible‐light‐driven H₂ evolution based on Dye/TiO₂/Pt hybrid photocatalysts was investigated for a series of (E)‐3‐(5′‐{4‐[bis(4‐R¹‐phenyl)amino]phenyl}‐4,4′‐(R²)₂‐2,2′‐bithiophen‐5‐yl)‐2‐cyanoacrylic acid dyes. Efficiencies of hydrogen evolution from aqueous suspensions in the presence of ethylenediaminetetraacetic acid as electron donor under illumination at λ>420 nm were found to considerably depend on the hydrophilic character of R¹, varying in the order MOD (R¹=CH₃OCH₂, R²=H)≈ MO4D (R¹=R²=CH₃OCH₂)> HD (R¹=R²=H)> PD (R¹=C₃H₇, R²=H). In the case of MOD /TiO₂/Pt, the apparent quantum yield for photocatalyzed H₂ generation at 436 nm was 0.27±0.03. Transient absorption measurements for MOD ‐ or PD ‐grafted transparent films of TiO₂ nanoparticles dipped into water at pH 3 commonly revealed ultrafast formation (<100 fs) of the dye radical cation (Dye^.+) followed by multicomponent decays, which involve minor fast decays (<5 ps) almost independent of R¹ and major slower decays with significant differences between the two samples: 1) the early decay of the major components for MOD is about 2.5 times slower than that for PD and 2) a redshift of the spectrum occurred for MOD with a time constant of 17 ps, but not for PD . The substituent effects on H₂ generation as well as on transient behavior have been discussed in terms substituent‐dependent charge recombination (CR) of Dye^.+ with electrons in bulk, inner‐trap, and/or interstitial‐trap states, arising from different solvent reorganization.     

Facile Access to Silicon‐Functionalized Bis‐Silylene Titanium(II) Complexes

A series of unprecedented bis‐silylene titanium(II) complexes of the type [(η⁵‐C₅H₅)₂Ti(LSiX)₂] (L=PhC(NtBu)₂; X=Cl, CH_3, H) has been prepared using a phosphane elimination strategy. Treatment of the [(η⁵‐C₅H₅)₂Ti(PMe₃)₂] precursor ( 1 ) with two molar equivalents of the N‐heterocyclic chlorosilylene LSiCl ( 2 ), results in [(η⁵‐C₅H₅)₂Ti(LSiCl)₂] ( 3 ) with concomitant PMe₃ elimination. The presence of a Si? Cl bond in 3 enabled further functionalization at the silicon(II) center. Accordingly, a salt metathesis reaction of 3 with two equivalents of MeLi results in [(η⁵‐C₅H₅)₂Ti(LSiMe)₂] ( 4 ). Similarly, the reaction of 3 with two equivalents of LiBHEt₃ results in [(η⁵‐C₅H₅)₂Ti(LSiH)₂] ( 5 ), which represents the first example of a bis‐(hydridosilylene) metal complex. All complexes were fully characterized and the structures of 3 and 4 elucidated by single‐crystal X‐ray diffraction analysis. DFT calculations of complexes 3 – 5 were also carried out to assess the nature of the titanium–silicon bonds. Two σ and one π‐type molecular orbital, delocalized over the Si‐Ti‐Si framework, are observed.     

Selective recovery of gold(III) using cotton cellulose treated with concentrated sulfuric acid

Novel utilization of cotton cellulose was developed by chemically modifying with concentrated sulfuric acid to prepare a novel kind of adsorption gel for gold. The adsorption behaviors of the gel were investigated for various metals from acidic chloride media. The gel was found to be highly selective for Au(III) over other precious and base metals tested over the whole concentration range of hydrochloric acid. The maximum adsorption capacity for Au(III) was evaluated as 6.21 mmol/g at 303 K. The amount of adsorbed Au(III) was increased with increasing temperature. A kinetic study for the adsorption of Au(III) at various temperatures confirmed the endothermic adsorption process following pseudo-first order kinetics. The activation energy was evaluated as 78.8 kJ/mol. Interestingly, it was found that the adsorbed Au(III) was reduced to elemental form which was evidenced by the clearly visible elemental gold particles which was further confirmed by means of the X-ray diffraction spectrum and optical microscope image of the gel after the adsorption of Au(III). The mechanism of Au(III) adsorption on the cotton gel and its reduction to elemental gold was proved from the results of IR-spectra. The main mechanism could be explained in terms of the coordination of Au(III) to oxygen atom of C–O–C linkage of cross linked cotton gel and to the oxygen atoms of the hydroxyl groups at C₂ and C₃ atoms of pyranose ring of cotton cellulose followed by the reduction to metallic gold. The adsorbed gold in the cotton gel can easily be recovered by incineration.