Papers by Keyword: Photochemistry

Abstract: HAuCl₄ was reduced by glucose as reducing agent and dispersant under UV radiation and acetone as photo sensitizer. The experimental samples were characterized by the transmission electron microscopy and UV-visible spectrophotometer, and the results show that these gold nanoparticles’ size is uniform, monodisperse distribution of spherical particles of average diameter of 5.8 nm, and gold nanowires with two-dimensional network structure were successfully prepared. The influence of glucose concentration on reaction under this condition and the mechanism of nucleation and growth of the photochemical reduction were discussed.

Abstract: Humic acid plays an important role in regualting the physical, chemical and biological properties in aquatic systems. In this paper, photochemical degradation of humic acid and its effect on the copper binding coefficient were studied. Results showed that the copper binding coefficient decreased with increased irradiation time. The decrease of copper binding coefficient was significantly correlated with the humic acid structure parameters (SUVA270 and E2/E3) during the photodegradation. It suggested that photodegradation of humic acid may have effects on the bioaccumulation of copper and hence its toxicity to aquatic organisms.

Abstract: Photoreduction of Hg (II) is of great importance but remains not fully understood especially in the presence of SO₄^2-. In this study, laboratory experiments were conducted to investigate the reduction of Hg (Cl)₂ with various SO₄^2- concentrations under artificial solar radiation. The whole process was tracked by changing Hg (0) concentrations in argon; the rate constants were calculated by trial method and were compared with other experiment. The results show the reaction rate decreased with increasing SO₄^2- concentrations (0-20 mg L^-1) and the cause of inhibitory effect is assumed with two explanations. The concentration of Hg (0) in argon increased firstly and decreased later in each treatment, since the main reactions in rising and dropping period are different. The comparison indicates that reduction rate is influenced by combined factors such as the form of mercury, the quantity of DOM and TSSs, depth of water and quality of light source.

Abstract: The decolorization of Orange II in goethite/UV system was investigated. It was discovered that the optimum condition is: pH=3, [α-FeOOH]=0.5 g/L, [Orange II]=10 mg/L. Furthermore, the absorption of Orange II on goethite, and the effect of pH values, goethite dosage and carboxylate on the decolorization were investigated. The decolorization efficiency was 90% after 6h irradiation when the concentration of pyruvic acid was 1.0mmol/L, α-FeOOH concentration was 0.3 g/L, and Orange II concentration was 10 mg/L at pH 3.0. Besides, total organic carbon (TOC) and chemical oxygen demand (COD) were determined, and a possible reaction mechanism was prompted as well.

Abstract: A new unsymmetrical photochromic diarylethene, 1-[2, 4-dimethyl-5-thiazoly-2-[2-methyl-5-(3-methylphenyl)-3-thienyperfluorocyclopentene (1o) were synthesized, and its properties, such as photochromism in solution as well as in poly-methylmethacrylate (PMMA) amorphous films, and fluorescence properties were investigated in detail. The results showed the compound exhibited good photochromism in hexane solution and in PMMA amorphous film, the maxima absorption of its closed-ring isomer 1c are 492 nm and 498 nm respectively. The open-ring isomer of the diarylethene 1 exhibited relatively strong fluorescence at 465 nm in hexane solution (5 × 10^-5 mol/L) when excited at 289 nm. The fluorescence intensity decreased along with the photochromism upon irradiation with 297 nm light. The fluorescence intensity of diarylethene 1o also depended on the concentration. When the concentration of diarylethene 1o in hexane increase from 1 × 10^-6 mol/L to 2 × 10^-4 mol/L, the fluorescence intensity of the open-ring isomer become strong first, then become weak.

Abstract: Liquid crystalline polymer (LCP) and the copolymer of LCOand Pendant Polyhedral Oligomeric Silsequioxanes (LCP-POSS) showed the first-order photoisomerization reaction. As compared with LCP, the photoisomerization rate constant of LCP-POSS decreased a little. With a higher thermal stability and more stable LC behavior as well as a little decreased photoisomerization rate constant, the incorporation of POSS to azobenzene liquid crystalline polymers may have significant sense and will definitely play a key role in developing novel high-performance optic and photonic nanodevices.

Abstract: This paper reports on the in-situ synthesis of reactive polymeric monolith and its subsequent surface functionalization. Poly (N-acryloyloxysuccinimide-co-ethylene dimethacrylate) was prepared through free radical photopolymerization of the respective monomers. The grafting procedure is based on the preliminary grafting of alkyne units on the monolith surface and the further radical photoaddition of functional thiol molecules. Implementation of UV-driven polymerization and grafting methods enabled the locally controlled immobilization of generic monolith within the confines of the capillary channel, and the site-specific immobilization of ligands on the pore surface of the monolith. Our results suggest that such a synthesis methodology is promising for integrating multiple analytical modules within microstructures for on-line analysis.

Abstract: The Silver nanoparticles with chiroptical feature have been prepared via chiral transfer through supramolecular interaction during the photoirradiation of silver salt with the assistance of chiral environment provided by sodium deoxycholate at pH 9.7. The pH value plays a significant role for the formation of optically active silver nanoparticles, which may be due to the changes in distance and conformation caused by the addition of hydroxy anion. The as-synthesized silver nanoparticles exhibit the typical surface plasmon absorption, and most importantly, the positive circular dichroism signal in CD spectrum. This finding may be fundamentally important, on the one hand, in term of the fact that chiral photochemistry is extendable to the hot field of inorganic nanomaterials. On the other hand, the as-prepared chiral silver nanoparticles may find their application in chiral opto-electronic switches, the catalysts for asymmetric organic synthesis, or the host for chiral organic photochemistry.

Abstract: Hypocrellins, natural photosensitizers including hypocrellin A (HA) and hypocrellin B (HB), have been used as a traditional Chinese herbal medicine to cure various skin diseases. Hypocrellins have excellent antiviral activity, which can inhibit the growth of human immunodeficiency virus. They also exhibit significant light-induced antitumor property. In this article, the progress on of free radicals research and conformational research Hypocrollins is introduced.

Abstract: Photodegradation of dimethyl phthalate (DMP) in aqueous solutions by Fe(III)-pyruvate complex system was preliminarily investigated. The influences such as light sources, initial pH value, initial concentration of Fe(III), pyruvate and DMP on photodegradation efficiency of DMP were discussed in detail. The result indicates that DMP could be decomposed efficiently in Fe(III)-pyruvate system. The degradation efficiency of DMP are dependent on initial pH value, Fe (III) initial concentration and pyruvate initial concentration. The optimum pH for photodegration of DMP is 3.0. The degradation efficiency of DMP increases with increase of the initial concentrations of Fe(III) or pyruvate, whereas decreases with increase of the initial concentrations of DMP. Various light sources including metal halide lamps, daylight lamps, UV disinfection lamps and sunlight can be adopted in the system.