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141.
利用荧光猝灭法,研究了不同温度、酸度下,Cu2+和 Fe3+与明胶的相互作用.计算了猝灭常数和结合常数.紫外光谱和显微红外光谱的测定结果表明,Cu2+、Fe3+与明胶分子中的酰胺键发生了作用.探讨了猝灭机理.计算出的热力学函数表明,在Cu2+、Fe3+与明胶的相互作用过程中熵变起主要的作用. 相似文献
142.
A novel and sensitive electrochemical method for determination of mercury (II) ions (Hg2+) based on the formation of thymine–Hg2+–thymine complexes and gold nanoparticle-mediated signal amplification is reported. Two 5′ end thiolated complementary oligonucleotides containing six strategically placed thymine–thymine mistakes were introduced in this work. One of the two oligonucleotides was immobilized on a gold electrode and the other one on gold nanoparticles (AuNPs). Due to six thymine–thymine mistakes the two oligonucleotides were not able to be hybridized, so AuNPs could not be immobilized onto the electrode surface after the electrode was immersed in the DNA–AuNPs solution. However, if Hg2+ existed, T–Hg2+–T complexes could be formed and AuNPs could be immobilized onto the electrode surface. Meanwhile, large numbers of [Ru(NH3)6]3+ molecules as electrochemical species could be localized onto the electrode surface. The Hg2+ detection limit of this assay could be as low as 10 nM, which is the US Environmental Protection Agency (EPA) limit of Hg2+ for drinkable water. This method is proven to be simple, convenient, high sensitive and selective. 相似文献
143.
144.
Sudipta Das Mischa Bonn Ellen H. G. Backus 《Angewandte Chemie (International ed. in English)》2019,58(44):15636-15639
The behavior of hydroxide and hydrated protons, the auto‐ionization products of water, at surfaces is important for a wide range of applications and disciplines. However, it is unknown at which bulk concentration these ions start to become surface active at the water–air interface. Here, we report changes in the D2O–air interface in the presence of excess D+hyd/OD?hyd determined using surface‐sensitive vibrational sum‐frequency generation (SFG) spectroscopy. The onset of the perturbation of the D2O surface occurs at a bulk concentration as low as 2.7±0.2 mm D+hyd. In contrast, a concentration of several hundred mm OD?hyd is required to change the D2O surface. The hydrated proton is thus orders of magnitude more surface‐active than hydroxide at the water–air interface. 相似文献
145.
Health or environmental issue caused by abnormal level of metal ions like Zn2+ or Cd2+ is a worldwide concern. Developing an inexpensive and facile detection method for Zn2+ and Cd2+ is in urgent demand. Due to their super optical properties, fluorescent quantum dots (QDs) have been developed as a promising alternative for organic dyes in fluorescence analysis. In this study, a CdTe QDs-based sensitive and selective probe for Zn2+ and Cd2+ in aqueous media was reported. The proposed probe worked in fluorescence “turn-on” mode. The initial bright fluorescence of CdTe QDs was effectively quenched by sulfur anions (S2−). The presence of Zn2+ (or Cd2+) can “turn-on” the weak fluorescence of QDs quenched by S2− due to the formation of ZnS (or CdS) passivation shell. Under optimal conditions, a good linear relationship between the fluorescence response and concentration of Zn2+ (or Cd2+) could be obtained in the range from 1.6 to 35 μM (1.3–25 μM for Cd2+). The limit of detection (LOD) for Zn2+ and Cd2+ were found to be 1.2 and 0.5 μM, respectively. Furthermore, the present probe exhibited a high selectivity for Zn2+ and Cd2+ over other metal ions and was successfully used in the detection of Zn2+ or Cd2+ in real water samples. 相似文献
146.
Conductance measurements of 12 quaternary ammonium salts in propylene carbonate (PC) have been made at 25°C. The cations were either tetramethylammonium, tetraethylammonium, or tetra-n-butylammonium, and the concentrations of salt varied from about 2×10–4 to 5×10–3
M. The data were analyzed by the equation of Pitts. The results showed that the benzoate, nitrobenzoate, and pentachlorophenolate salts are completely dissociated. The nitrophenolate, chlorophenolate, methylsulfonate, and nitrate salts are only slightly associated (K
A
from 2.5 to 6.5), while the acetate, phenylacetate, and nitrophenolate salts display somewhat more extensive association, with ionpair association constants from 17 to 45. Limiting molar conductances for the anions were derived. The factors affecting ionic mobilities in this dipolar aprotic solvent are discussed.On leave 1973–1975 from the University of Gdask, Poland. 相似文献
147.
J. -L. Fortier P. -A. Leduc P. Picker J. E. Desnoyers 《Journal of solution chemistry》1973,2(5):467-475
The enthalpies of dilution of NaCl, Me4NBr, andn-Bu4NBr were measured in water at 25°C with a new flow microcalorimeter. The data were analyzed with a polynomial equation, and the derived relative apparent molal enthalpies L are in good agreement with literature values. Provided care is taken that mixing is complete, flow calorimeters are as reliable and much less time-consuming than cell-type instruments for enthalpies of dilution measurements. 相似文献
148.
149.
The consecutive stepwise formation constants of 1:1 and 1:2 chelate species formed by the interaction of DC-2-CPHD and DC-3-CPHD anions with tripositive lanthanon and divalent copper, nickel, cobalt, zinc, manganese, and cadmium cations were determined potentiometrically at ionic strengh of 0.1 (KNO3) and 30°C. The results indicate that two different coordination modes, one tridentate (DC-2-CPHD), and one bidentate (DC-3-CPHD), are in evidence. 相似文献
150.
From conductance and viscosities measurements on Pr4NCl, Et4NBr, and AgNO3 in acetonitrile and Et3NBr in nitrobenzene, the Walden products of the anion at infinite dilution were determined in presence of various concentrations of substituted benzoic acids. From these data it was possible to compute the values of the Walden products of the once complexed anions and to estimate the order of magnitude of the Walden products of twice complexed anions. Stokes' law is not obeyed, and the Walden products are not proportional to the third root of the molar volume of the complexed ions, as a consequence of their lack of sphericity. The assumption that the drag force which acts on the ions is proportional to the volume of the substituents results in a linear expression between the reciprocals of the Walden products and the molar volume of the ligands. The experimental results fit this expression within the limits of the experimental errors, and the slopes of the lines are nearly the same for all the anions and for the two solvents studied here, namely, 2.5×10–4 ohm-cm–5 mole-cP–1. 相似文献