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Zheng Y.,South China Normal University | Pang S.,South China Normal University | Zhou Z.,South China Normal University | Wang Q.,Key Laboratory of Theoretical Chemistry of Environment | And 3 more authors.
Journal of Cluster Science | Year: 2013

Two lanthanide complexes were encapsulated into silica matrix (aminopropyltriethoxysilane, APTS) via a mild sol-gel technique, resulting in two luminescent xerogels. Subsequently two novel luminescent polymeric hydrogels were successfully fabricated by incorporating these two lanthanide xerogels into the poly(acrylamide) matrix. The europium-ion-containing hydrogel can be sensitized by visible light (408 nm). More interestingly, the emissions of the Ln(III)-containing hydrogel can be switched "on-and-off" reversibly by a change of the pH value. The resulting color change can easily be observed by naked eyes. These luminescent hydrogels exhibited high stabilities in comparison with xerogels in aqueous media. © 2013 Springer Science+Business Media New York. Source

Liang S.,South China Normal University | Zhang L.,South China Normal University | Zhang L.,University of Aarhus | Jiang F.,South China Normal University | Jiang F.,Key Laboratory of Theoretical Chemistry of Environment
Water Research | Year: 2016

Nitrate dosing is commonly used to control hydrogen sulfide production in sewer systems. However, quick rebound of the sulfide concentration after nitrate depletion has been observed and results in more serious odor and corrosion problem. To investigate the mechanism of sulfide regeneration in the nitrate-free period, a laboratory-scale sewer reactor was run for 30 days to simulate sulfide production and oxidation with intermittent nitrate addition. The results show that nitrate addition substantially reduced the sulfide concentration, but the produced elemental sulfur was then quickly reduced back to sulfide in nitrate-free periods. This induced more and more sulfide production in the sewer reactor. Elemental sulfur and polysulfide reductions were found in the sewage in nitrate-free periods, showing their contributions to the sulfide regeneration. Through batch tests, polysulfide was confirmed as the key intermediate for accelerating sulfur reduction during the nitrate-free period in the sewer. Sulfide production rates significantly increased by 65% and 59% in the presences of tetrasulfide and sulfur with sulfide, respectively, at the beginning of the test. While polysulfide formation was prevented by the ferrous chloride addition, the sulfur reduction rate remarkably decreased from 12.8 mgS/L-h to 1.8 mgS/L-h. This indicates that direct sulfur reduction was significantly slower than the indirect sulfur reduction via polysulfide; the latter process could be the cause for the quick rebound of the sulfide concentration in the sewer with intermittent nitrate dosing. Thus, the pathways of sulfur transformations in a sewer, both in the presence and absence of nitrate, were proposed. Microbial community analysis results reveal that some common sulfate-reducing bacteria (SRB) genera in sewer sediment were possible sulfur reducers. According to this finding, the effect and strategy of nitrate dosing for hydrogen sulfide control in sewers should be re-evaluated and re-considered. © 2016 Elsevier Ltd. Source

Huang Y.,South China Normal University | Huang X.,South China Normal University | Xu X.,South China Normal University | Xu X.,Key Laboratory of Theoretical Chemistry of Environment | Xu X.,Guangdong Universities
Wuli Huaxue Xuebao/ Acta Physico - Chimica Sinica | Year: 2013

As potential molecular wire species, the geometrical and electronic structures of metal string complexes M3(dpa)4Cl2 (1: M=Co, 2: M=Rh, 3: M=Ir; dpa=dipyridylamide) were investigated theoretically using density functional theory with the PBE0 functional by considering the interaction of an external electric field along the M6+ 3 linear metal chain. The results show that the ground states of the complexes are all doublets. There is a 3-center-3-electron σ bond delocalized over the M6+ 3 chain for 1 and 2, while there is a 3-center-4-electron σ bond and a weak δ bond among the Ir6+ 3 chain in 3. Moving down the column of Co, Rh, and Ir elements in the periodic table, the complexes with the corresponding metals showed some regular trends, such as stronger M - M bonds, smaller LUMO-HOMO gaps, weaker anti-ferromagnetic spin coupling among the M6 + 3 chains, and stronger spin delocalization from M6+ 3 to ligands. In the external electric field along the Cl4→Cl5 direction, the M3 - Cl5 bonds at the low potential side tend to be shortened, while the M2-Cl4 distances at the high potential side increase. With the increase of electric field, the average M-M distances slightly decrease, which is beneficial for electron transport. When the electric field increases, the molecular energy decreases and the dipole moment linearly increases. Moreover, the negative charge moves from Cl5 at the low potential end towards Cl4 at the high potential end, and the spin electron moves from M3 at the low potential end to M1 and M2 at the high potential end, while the positive charges transfer in the opposite direction along the M6+ 3 chain of 3. However, there is no charge transfer between dpa- ligands and M6+ 3 chain or Cl- ligands. The LUMO-HOMO gaps decrease with increasing electric field, which is beneficial for electron transfer. The sensitivity of the frontier orbitals to the electric field is different, which leads to the orbital level crossing for LUMO or HOMO. Moving down the column of metal elements in the periodic table, the complexes with the corresponding metals showed weaker orbital level crossing for LUMO or HOMO and smaller deviation of average M-M distances due to the effect of the electric field. © Editorial office of Acta Physico-Chimica Sinica. Source

Li T.,South China Normal University | Li T.,Key Laboratory of Theoretical Chemistry of Environment | Yang J.,South China Normal University | Hong X.-J.,South China Normal University | And 4 more authors.
CrystEngComm | Year: 2014

A robust porous pillar-chained 3-D Cd-framework, {[Cd2(μ 3-OH)2(cpt)2]·(H2O)} n (1) (Hcpt = 4-(4-carboxyphenyl)-1,2,4-triazole), containing 1-D square nanotubular channels with impressive selective sorption for CO 2 over N2/H2 and interesting guest-driven tunable luminescence is reported. © the Partner Organisations 2014. Source

Lu X.,South China Normal University | Zhang Q.,South China Normal University | Zhang Q.,Key Laboratory of Theoretical Chemistry of Environment | Yang W.,South China Normal University | And 4 more authors.
RSC Advances | Year: 2015

Iron and nickel based bimetallic loaded activated carbon (Fe-Ni/AC) prepared by an impregnation method was employed as a heterogeneous catalyst for the ozonation of 2,4-dichlorophenoxyacetic acid (2,4-D) in aqueous solution. The Fe-Ni/AC was characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), N2 adsorption-desorption, and atomic absorption spectrometry (AAS). The results indicated that the degradation and mineralization efficiencies of 2,4-D were considerably improved in the presence of Fe-Ni/AC. During the ozonation (50 mg h-1 ozone flow rate) of 2,4-D aqueous solution (10 mg L-1, pH = 4.18) in the presence of Fe-Ni/AC, the TOC removal rate reached 72% at 60 min reaction time, while the rate was 60% with Fe/AC, 62% with Ni/AC, 50% with activated carbon (AC), and only 34% by ozonation alone. The 2,4-D removal process followed the pseudo first order reaction model well, its degradation rate constant with Fe-Ni/AC/O3 was 1.6 times higher than that with AC/O3, and 1.9 times than that by O3 alone. The Fe-Ni/AC showed much better catalytic activity and stability based on the seven times repetition of the ozonation of 2,4-D. In addition, the effects of 2,4-D initial concentration, pH value and reaction temperature on catalytic ozonation of 2,4-D over Fe-Ni/AC were also investigated. The addition of tert-butanol (TBA) strongly inhibited the catalytic degradation of 2,4-D, which suggests that the degradation reaction follows the mechanism of hydroxyl radical (HO•) oxidation. © The Royal Society of Chemistry 2015. Source

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