Solution Reaction Time Research Articles

Optimization ZnO Properties for Electron Transport Layer (ETL) of Hybrid Solar-cell Prepared with Sol-gel Method Combined with Reflux Treatment

Electron-hole pair (exciton) generation and extraction from solar-cell photoactive layer is the main parameters determined solar-cell performance. Generally solar-cell consists of a photoactive layer sandwiched between electron transport layer (ETL) and hole transport layer (HTL). Exciton separation and extraction from photoactive layer depend on several properties: energy level match of photoactive layer and charge transport layer, surface contact area of photoactive layer and charge transport layer, and charge transport properties of charge transport layer. ETL and HTL should meet several characteristic e.g.: high transparency in UV-visible light region, high degree of crystallization to minimize charge lose and high electron or hole mobility. In this study we try to fabricate ZnO as an ETL of hybrid solar-cell with sol-gel method combined with reflux treatment. The quality of ZnO ETL highly effected by precursor solution properties; solution homogeneity, viscosity and stability. These precursor solution properties depend on chemical composition and reaction condition, reflux treatment designed to enhance precursor solution reaction time and increase solution stability. Previous study shown low solution stability of ZnO precursor prepared with sol-gel without reflux treatment which resulting on low ETL quality. Visible observation of the resulting precursor solution showed that reflux treatment enhances solution stability, while solution prepared without reflux treatment easily formed precipitation phase. Furthermore, ZnO powder prepared with reflux treatment exhibit preferable crystallization and small ZnO crystallite size. Low-temperature crystallization of ZnO prepared with sol-gel method combined with reflux treatment, make it is possible to fabricate thin film with small particle size therefore able to enhance surface contact area of photoactive layer and ETL.

Enhanced enzymatic transformation of 1-naphthol in the presence of catechol by peroxidase

Effect of catechol on 1-naphthol transformation by horse radish peroxidase (HRP) was examined. The impact of catechol to 1-naphthol ratio, enzyme activity, pH, and reaction time in solution were studied. The results obtained indicated that, in the presence of catechol, 1-naphthol transformation by peroxidase shows enhancement greater than that in an equivalent catechol free system. Only 27% of 1-naphthol (0.3 mM) was able to transform when catechol was absent in solution, but reached 79% in its presence (3.0 mM) in 0.1M sodium phosphate buffer (pH 7.0), and 0.3 mM H2O2 by peroxidase (0.5 unit/mL) after 3 h. The 1-naphthol transformation rate was accelerated by increase of pH or HRP concentration. High-performance liquid chromatography analysis was performed to characterize transformation products based on their relative polarities, and molecular weights of products were identified by mass spectrometry. The transformation products were found to be (hydroxy) naphthoquinones, 1-naphthol: hydroxy-naphthoquinone, and 1-naphthol oligomers (dimer, trimer, tetramer) with the molecular weights (m/z) ranging 100–600. Liquid chromatography-tandem mass spectrometry technique, to the best of our knowledge, was used for the first time to elucidate the product structure at m/z 191. The study shows that 1-naphthol is transformed rapidly by peroxidase when catechol is present, which could be useful information for improving the efficiencies of decontamination techniques.

Fabrication of Hollow and Yolk–Shell Structured η-Fe2O3 Nanoparticles with Versatile Configurations

A solution-based approach has been developed for the synthesis of hollow or yolk–shell structured η-Fe2O3 nanoparticles with versatile configurations via the Ostwald ripening process. By simply controlling the amount of PVP and reaction time in solution, hollow or yolk–shell structured η-Fe2O3 nanoparticles with spherical, egg-like, olivary, elliptical, and shuttle-like configurations can be easily fabricated. The interior structures and morphologies of the particles are found to be effective ways to affect both the specific saturation magnetization and coercivity of the η-Fe2O3 nanoparticles.

Structure of surface films of malonate mono- and dinitroxyl methanofullerenes

An effect of aqueous subphases composition on the character of change of the bilayer structure of malonate mono- and dinitroxyl methanofullerenes surface films has been established. Their transformation to monolayers takes place in the presence of hydroxy-containing compounds (quercetin, dihydroquercetin, 4-methylphenol, ascorbic acid, as well as in a buffer mixture with pH 10). A loosening of mixed films on the basis of nitroxyl methanofullerenes in the presence of compounds affecting radical processes (2,4,6-tri(tert-butyl)phenol, 2-methyl-3-nitrosopropane, and TEMPO) has been demonstrated. The character of compression isotherms π = f(A 0) (π is a surface pressure, A 0 is an effective molecular area of methanofullerene) of the mixed films on water depends on the nature of component incorporated and the reaction time in solution: in all the cases, A 0 increased almost 2-fold, to 1.05 nm2 molecule−1, whereas a compressibility parameter β decreased 2–3-fold, to (1–2)·1017 N m−3. Visualization of the thin film surfaces (atomic force spectroscopy) showed that a decrease of parameter β in the Langmuir layers corresponds to the particle aggregation and structurization of the films.

Structural Analysis of Oligomeric Molecules Formed from the Reaction Products of Oleic Acid Ozonolysis

The products arising from the ozonolysis of oleic acid (cis-9-octadecenoic acid) in solution have been studied using negative ion mode electrospray ionization ion trap mass spectrometry. Oleic acid is an important component of atmospheric organic aerosol and is a key model species in predicting aerosol physical and chemical characteristics. The four predicted reaction products, 1-nonanal, nonanoic acid, 9-oxononanoic acid, and azelaic acid, were all observed in roughly equal yields. In addition to these products a large number of higher molecular weight compounds were detected with m/z ratios of up to 1000 Daltons. Tandem mass spectrometry of these larger ions revealed thatthey represented a complex mixture of linear alpha-acyloxyalkyl hydroperoxides, secondary ozonides, and cyclic diperoxides, formed by reactions between ozonolysis products and Criegee intermediates. These comprise the first directly elucidated structures of large oligomeric species from oleic acid ozonolysis. The degree of oligomerization and hence molecular weight distribution was observed to increase with reaction time in solution.

Characterization of Titanium and Zirconium Valerate Sol-Gel Films

FTIR and XPS have been used to characterize titanium and zirconium valerate thin films prepared using sol-gel techniques. Films were prepared by hydrolysis of titanium(IV) isopropoxide or zirconium(IV) n-propoxide in excess valeric acid at room temperature. Film solution chemistry, from precursors to cast films, was followed with FTIR. The structure and chemical composition of films spin cast from fresh and day-old solutions were determined. Results of these studies suggest that all films consist of a metal-oxygen polymer backbone coordinated with bidentate valerate ligands. No evidence for the presence of alkoxide ligands has been found. A small amount of water is present in all cast films. While solution aging experiments indicate that the zirconium film structure does not change with solution reaction time, carboxylate ligand concentrations are higher in titanium films made from aged solutions. Titanium films made from aged solutions contain slightly less than 1.5 valerate ligands/titanium atom. Zirconium films are more highly carboxylated with almost two valerate groups per metal center. 57 refs., 6 figs., 1 tab.

An optical sensor for the detection of heavy metal ions

An optic-chemical sensor (optrode) for the detection of heavy metal ions has been developed. The sensitive layer consists of 5,10,15,20-tetra( p-sulfonatophenyl)porphyrin covalently immobilized onto a polymeric matrix. Complexation of ions, such as Cd(II), Pb(II) or Hg(II), results in different absorbance spectra and thus changes the reflection behaviour of the sensor. The effect of immobilization on the complexation characteristics of the dye has been studied in the case of Cd(II). Depending on the length of the spacer molecule, the response time of the sensor is about 40 min, which is of the order of the reaction time in solution. The sensor is reversible and its detection limit is 3 × 10 −6 mol/l for Cd(II). The immobilized dye shows different absorbance spectra for Cd(II), Pb(II) and Hg(II), which enables these ions to be detected simultaneously.

X-ray photoelectron spectroscopic studies of carbon-fibre surfaces. Part 4.—The effect of electrochemical treatment in nitric acid

Carbon fibres, electrochemically treated using nitric acid, have been analysed using X.p.s., F.t.i.r. and s.e.m. Substantial quantities of surface oxide (mainly carbonyl-type oxides) could be produced leading to large topographical changes on the fibre surfaces. The nature of the surface oxide depended upon the potential, the reaction time in solution and the electrolyte concentration. No nitrogen-containing species were found on the surface.