Molecular Ordering at the Interface Between Liquid Water and Rutile TiO2(110)

The pivotal importance of TiO₂ as a technological material involves most applications in an aqueous environment, but the single‐crystal TiO₂/bulk‐water interfaces are almost completely unexplored, since up to date solid/liquid interfaces are more difficult to access than surfaces in ultrahigh vacuum (UHV). Only a few techniques (as scanning probe microscopy) offer the opportunity to explore these systems under realistic conditions. The rutile TiO₂(110) surface immersed in high‐purity water is studied by in situ scanning tunneling microscopy. The large‐scale surface morphology as obtained after preparation under UHV conditions remains unchanged upon prolonged exposure to bulk water. Moreover, in contrast to UHV, atomically resolved images show a twofold periodicity along the [001] direction, indicative of an ordered structure resulting from the hydration layer. This is consistent with density‐functional theory based molecular dynamics simulations where neighboring interfacial molecules of the first water layer in contact with the bulk liquid form dimers. By contrast, this dimerization is not observed for a single adsorbed water monolayer, i.e., in the absence of bulk water.     

(Bi, C and N) codoped TiO2 nanoparticles

Bi, C and N codoped TiO2 photocatalysts were prepared by doping TiO2 with BiCl3 and KSCN in a sol-gel process (denoted as (Bi,SCN)-TiO2). The catalyst samples were then characterized by XRD, TEM, diffuse reflectance spectra (DRS), XPS, FT-IR and N2 sorption. Bi, C and N elements were detected both by XPS and elemental analysis, while S element was not found, suggesting that SCN- group may have decomposed during the sol-gel process. The effects of the doping on the properties and photocatalytic activity of the TiO2 were investigated. It was found that the cation and the anion affected the properties of TiO2 differently. The optical absorption onset of TiO2 red shifted in the presence of Bi3+, while long tail occurred in the presence of SCN-. The order of photoreactivity for TiO2 samples was as follow: (Bi,SCN)-TiO2>Bi-TiO2>undoped TiO2>p25 TiO2, whatever under UV or visible light illumination. The high photoreactivity of the doped TiO2 was also discussed.     

Studies of electron-transfer and charge-transfer coupling processes at a liquid/liquid interface by double-barrel micropipet technique

Investigation of a heterogeneous electron-transfer (ET) reaction at the water/1,2-dichloroethane interface employing a double-barrel micropipet technique is reported. The chosen system was the reaction between Fe(CN)63- in the aqueous phase (W) and ferrocene in 1,2-dichloroethane (DCE). According to the generation and the collection currents as well as collection efficiency, the ET-ion-transfer (IT) coupling process at such an interface and competing reactions with the organic supporting electrolyte in the organic phase can be studied. In addition, this technique has been found to be an efficient method to distinguish and measure the charge-transfer coupling reaction between two ions (IT-IT) processes occurring simultaneously at a liquid/liquid interface. On this basis, the formal Gibbs energies of transfer of some ions across the W/DCE interface, such as NO3-, NO2-, Cl-, COO-, TBA+, TPAs+, Cs+, Rb+, K+, Na+, and Li+, for which their direct transfers are usually difficult to obtain because of the IT-IT coupling processes, were quantitatively evaluated.     

Multi-modal mesoporous TiO(2)-ZrO(2) composites with high photocatalytic activity and hydrophilicity

Utilizing the amphiphilic triblock copolymer Pluronic P123 as the surfactant, and Ti(O(n)Bu)(4) and ZrOCl(2)·8H(2)O as the inorganic sources, a series of multi-modal mesoporous TiO(2)-ZrO(2) composites have been successfully synthesized through a one-step method. The resultant materials were characterized in detail by x-ray diffraction, atomic force microscopy, high resolution scanning electron microscopy, transmission electron microscopy, N(2) adsorption and water contact angle measurements. The effect of calcination temperatures on the physical parameters, hydrophilicity and photocatalytic activity of the obtained mesoporous TiO(2)-ZrO(2) composites was also investigated in this paper.     

Facial synthesis of polyaniline/AgCl nanocomposites at the interface of water and ionic liquid

Uniformly polyaniline/AgCl nanocomposites were prepared at the interface of water and ionic liquid. The morphology and structure of the nanocomposites have been studied by transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction and thermogravimetric analysis. The experimental results indicated that highly dispersed polyaniline/AgCl nanocomposites with their size of around 50-100 nm were obtained by the polymerization of aniline and the formation of AgCl at the interface simultaneously. The electroactivity of polyaniline/AgCl nanocomposites was further characterized.     

In situ measurements of aggregation and disaggregation of Cu(II) complex at liquid/liquid interface

Aggregation of Cu(II)-5-(octadecyloxy)-2-(2-thiazolylazo)phenol (TARC18) complex at the heptane/water interface was measured directly by a centrifugal liquid membrane spectrometry and a two-phase microflow API-MS method. When the pH of an aqueous phase was increased from 4 to 6, the 1:1 complex of Cu(II)-TARC18, which was formed as a positively charged complex at the interface, formed further an aggregate, accompanied by the change of spectra suggesting its aggregation. The MS spectra of the interfacial species indicated the formation of 2:3 complex for Cu(II) and TARC18 under the conditions that the aggregate was formed. This observation allowed us to analyze the interfacial aggregation stoichiometrically: the aggregate of the 2:3 complex was formed from a 1:1 complex at the interface. The addition of purine base of adenine or guanine into the system resulted in the disruption of the aggregate by the formation of a new three-element complex of 1:1:1 for Cu(II), TARC18, and the base, showing a bathochromic shift in the spectra. Thus, the disaggregation experiment showed an interfacial molecular recognition ability of the Cu(II)-TARC18 aggregate for hydrophobic bases.     

Free-standing graphene oxide-poly(vinyl alcohol) membranes self-assembled at liquid/air interface

Graphene-based composites are appealing as a new class of materials that hold great promise for many applications. In this paper, highly ordered, homogeneous graphene oxide-poly(vinyl alcohol) (GO-PVA) with different content of PVA membranes and reduced graphene oxide-poly(vinyl alcohol) (RGO-PVA) membrane at 75% loading of PVA in the presence of hydrazine hydrate solution are prepared by the self-assemble process at liquid/air interface. The as-prepared membranes were investigated by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermal gravimetric analysis (TGA), transmission electron microscopy (TEM), Ultraviolet-visible (UV-vis) spectroscopy and four-probe resistance measurements. It was shown that the free-standing GO-PVA and RGO-PVA membranes are thickness controlled and area adjustable. The GO-PVA membranes have excellent transparent. The electrical conductivity of RGO-PVA membranes was up to 0.6 S/m by the chemical reduction of hydrazine hydrate. The membranes would be promising for practical applications in future nanotechnology.     

Synthesis, characterization, and photocatalytic activity of TiO(2-x)N(x) nanocatalyst

Nitrogen-doped titanium dioxide powders were prepared by wet method, that is, the hydrolysis of acidic tetra-butyl titanate using aqueous ammonia solution, followed by calcination at temperatures about 350 degrees C. The catalysts exhibited photocatalytic activity in the visible light region owing to N-doping. The light absorption onset of TiO(2-x)N(x) was shifted to the visible region at 459 nm compared to 330 nm of pure TiO(2). An obvious decrease in the band gap was observed by the optical absorption spectroscopy, which resulted from N2p localized states above the valence band of TiO(2-x)N(x) (compared to TiO(2)). The TiO(2-x)N(x) catalyst was characterized to be anatase with oxygen-deficient stoichiometry by X-ray diffraction (XRD), surface photovoltage spectroscopy (SPS) and X-ray photoelectron spectroscopy (XPS). The binding energy of N1s measured by XPS characterization was 396.6 eV (TiN bonds, beta-N) and 400.9 eV (NN bonds, gamma-N(2)), respectively. The photocatalytic activity of TiO(2-x)N(x) under visible light was induced by the formation of beta-N in the structure. Photocatalytic decomposition of benzoic acid solutions was carried out in the ultraviolet and visible (UV-vis) light region, and the TiO(2-x)N(x) catalyst showed higher activity than pure TiO(2).     

Coordination assisted molecular assemblies of perylene-3,4,9,10-tetracarboxylic acid with copper (II) ion at the air/water interface

Perylene-3,4,9,10-tetracarboxylic acid (PTCA) was found to form stable Langmuir films at the air/water interface through the coordination with Cu(II) ion in the subphase although the compound itself could not form monolayer on a plain water surface. The Langmuir films can be transferred onto solid substrates by a Langmuir–Schaefer (LS) method. Surface pressure–area isotherm and measurement of the UV–Vis and FT-IR spectra of the transferred LS films confirmed the coordination between the carboxylic group and Cu(II) ion in the Langmuir films. Atomic force microscopy (AFM) measurements indicated that the Langmuir film was composed of small nanoparticles with a diameter of several tens of nanometers. X-ray diffraction (XRD) measurement on the transferred LS films revealed that the film formed a clear layer structure with a distance of 3.9 nm, which was in agreement with the height measurement from the AFM.     

Facial synthesis of polypyrrole/silver nanocomposites at the water/ionic liquid interface and their electrochemical properties

Polpyrrole (PPy)/silver nanocomposites with their size of around 80-120 nm were successfully synthesized at the interface of water and ionic liquid. High dispersed PPy/silver nanocomposites were obtained in the presence of polyvinylpyrrolidone (PVP) by controlling the reacting conditions. The morphology and structure of the resulting nanocomposites were characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy. It was also found that the electrical conductivity of PPy/silver nanocomposites was much higher than that of pure PPy. Cyclic voltammetric experiments further indicated that the nanocomposite had excellent redox ability: polypyrrole; silver; ionic liquid; interface synthesis; and nanocomposites.     

Macroporous/mesoporous bioglasses doped with Ag/TiO(2) for dual drug action property and bone repair

A series of macroporous-mesoporous bioglasses (MMBGs) doped with Ag, TiO(2) and Ag/TiO(2) have been successfully prepared using the nature plants as the macroporous templates and P123 as the mesoporous one. The dual drug action (antifungus and anti-inflammatory) and bone regeneration systems have been obtained by Ibuprofen (Ibu) loaded. Meanwhile, the antifungus as well as drug control release profiles of these materials have been investigated. Compared with pure MMBGs, MMBGs-Ag, MMBGs-TiO(2) and MMBGs-Ag/TiO(2) showed much higher antimicrobial efficiency, faster hydroxyapatite-forming ability and better drug sustained release performance. The multifunctional hierarchical porous bioglasses materials may have potential applications in bone tissue engineering.     

Poly(methyl methacrylate) monolayers at the air–water interface

Several poly(methyl methacrylate) (PMMA) molecules with various chain numbers has been synthesised using Emulsifier-free emulsion polymerisation method. Langmuir–Blodgett thin film technique is an excellent method to investigate the surface behaviours of organic monolayers at the air–water interface. In this study, PMMA molecules have been studied at the air–water interface using Langmuir–Blodgett thin film method. Area per molecule for several PMMA molecules is found to be between 0.29 ± 0.01 and 0.98 ± 0.01 nm². The surface pressure–area graphs were taken in two stages i.e. during the first compression of the monolayer and also during the second compression of the same monolayer before the collapsed stage of the monolayer. It is also found that first surface pressure–area graph for the first compressing of the monolayer at the water surface is different than the surface pressure–area graph obtained after a decompression of the monolayer. Isotherm graphs show that long alkyl chain groups of these molecules may cause aggregation behaviours on water surface and a model for the behaviour of PMMA molecules on the air–water interface due to surface interactions has been proposed.     

Degradation of 1,4-dioxane in water using TiO2 based photocatalytic and H2O2/UV processes

1,4-dioxane is a synthetic compound found in industrial effluent and subsequently contaminates water bodies due to its high solubility and high volatility. It is of concern due to its toxic and hazardous nature and has been listed as a class 2B carcinogen. This study involved optimisation of the photocatalytic and H(2)O(2)/UVC processes for 1,4-dioxane removal. Different photocatalysts and loadings were investigated for the degradation of low concentrations of 1,4-dioxane in water including a commercial P25, a synthesised magnetic photocatalyst and an immobilised sol-gel system. A commercial catalyst (Degussa P25) was the most efficient. A lifetime study of the sol-gel reactor showed that the coating was stable over the time period studied. The optimum H(2)O(2) concentration in the H(2)O(2)/UVC process was found to be 30ppm. The addition of H(2)O(2) to the photocatalytic process for 1,4-dioxane removal caused a decrease in rate for the commercial P25 photocatalyst and an increase in rate for the lab-made magnetic photocatalyst.     

TiO2/UV/O3-BAC processes for removing refractory and hazardous pollutants in raw water

TiO2/UV/O3-BAC (biological activated carbon) process was employed to treat raw water and compared to UV/O3-BAC process in its optimum parameters (3 mg/L ozone dosage with 15 min oxidation time and 15 min empty bed contact time in BAC). The results showed that the presence of TiO2 improved ozone utilization and biodegradability of the effluent. For the dissolved organic carbon (DOC) removal, TiO2/UV/O3-BAC was more efficient than UV/O3-BAC and its synergetic effect is more than that in UV/O(3)-BAC process. It was showed that small molecules with MW<3000 Da predominated in the raw water accounting for more than 56% DOC, they were increased after oxidation, accounting for more than 64% DOC. GC/MS analysis showed that TiO2/UV/O3-BAC process was effective in removing phthalate esters (PAEs) and persistent organic pollutants (POPs). PAEs' removal ratio reached more than 94% and reduced with the increase of the length of the alkyl side chains and the alkyl branch chains. TiO2/UV/O3-BAC process was also very effective in removing POPs. Polybromobiphenyls' removal rate reached more than 89% and decreased with the increase of substitutional bromines except for 2,2',5,5'-tetrabromobiphenyl, which can be completely removed.     

Photocatalytic degradation of mixed pollutants in aqueous wastewater using mesoporous 2D/2D TiO2(B)-BiOBr heterojunction

There are multiple contaminants in practical wastewater;and the photodegradation of mixed pollutants is a challenge in the field of photocatalysis.Herein,we design a mesoporous 2D/2D TiO2(B)-BiOBr hetero-junction photocatalyst for the photodegradation of mixed pollutants.Such a coupling structure results in an enhancement in the disconnection of photoexcited carriers,and the increase of absorption and reaction sites.The 2D/2D TiO2(B)-BiOBr demonstrates outstanding photocatalytic activity for photode-grading rhodamine B(RhB),methyl orange(MO),tetracycline hydrochloride(TCH),and bisphenol A(BPA)simultaneously under visible light,which is 4.7.1.4,23 and 16.4 times as high as that of original BiOBr,respectively.Our work represents a possible solution to devise promising and efficient photocatalysts for the treatment of practical wastewater in the near future.     

Surface charge and adsorption of sodium ions at the controlled porosity glasses/electrolyte interface

Controlled porosity glasses (CPGs) are used as adsorbents, supports or catalysts. Their properties depend on the amount of surface boron and sodium concentration. The surface boron and sodium concentration can be changed by proper thermal treatment. The presented paper deals with the change of charge surface density and pH of point zero charge of the thermally treated CPG. The surface reaction constants according to the site binding theory of the electric double layer were calculated on the basis of the surface charge data. The results of Na⁺ adsorption on the CPGs are presented.