Papers by Keyword: Hg²⁺

Abstract: In this study, the advantages and disadvantages of different immobilization approaches, proposed for a luminescent Hg²⁺chemosensor based in a spirocyclic phenyl-thiosemicarbazide Rhodamine 6G derivative (FC1), are analysed, and a comparative study of the different immobilization protocols is performed. The results demonstrated that the chemosensor is able to detect Hg²⁺ at ng mL^-1 trace levels, with a remarkable selectivity, allowing its determination in biological, toxicological and environmental samples. Methyl methacrylate (MMA) and hydroxyethylmethacrylate (HEMA) polymeric film, electrospinning generated polymeric microfibres, nylon membranes and Au nanoparticles were tested as immobilization materials. The utilization of gold nanoparticles (AuNPs) is the method with the lowest limit of detection (LOD = 0.15 ng mL^-1), but the response time is too high for practical use (7 hours). Nylon membranes give a very low detection limit (0.4 ng mL^-1) and a practical response time (4 min), being the method of choice for practical applications to determine Hg²⁺ in aquatic, biological and toxicological samples, at a sampling rate of about 15 samples per hour.

Abstract: This article presents a simple method for fabrication of Au-CdS composite thin films onto indium-tin-oxide (ITO) coated glass substrates. The method starts with electrodeposition of CdS thin films onto ITO substrates and followed by spontaneous growth of Au nanoparticles onto the CdS surface in solutions containing AuCl₄^- ions. X-ray diffraction (XRD) and UV-vis spectroscopy were used to investigate the Au-CdS thin films. The photoelectrochemical property and sensing for Hg²⁺ ions of the Au-CdS/ITO were studied. The electrode exhibits a low limit of detection of 2.5 μM and a high selectivity for Hg²⁺ ions, even in the presence of a large excess (1000-fold) of other metal (Na⁺, K⁺, Ca²⁺, Mg²⁺, Cd²⁺, Pb²⁺, and Zn²⁺) ions.

Abstract: Alginate-diatomite immobilized microspheres were prepared through immobilized biosorption of diatomite and Mucor sp. by sodium alginate, which were employed to adsorb acephate and Hg²⁺ in wastewater. Several major factors were investigated. Results showed that initial concentration of acephate and Hg²⁺ were both 300ug/l, percent of adding immobilized microspheres full of Mucor sp.was 6%(m:m), rotating speed 160~200r/min. Keywords: Adsorption; Acephate; Hg²⁺; Mucor sp.

Abstract: Chlorophyll fluorescence is a quick, precise, non-invasive technique which has been widely used in studies of photosynthesis in micro algae, particularly for investigations of stress physiology of micro algae. The toxicity of heavy metal Hg²⁺ on alga M. aeruginosa was studied by the change in fluorescence intensity of M. aeruginosa at 435 nm/680 nm which treaded with different Hg²⁺ concentrations for 25 min. The results showed that high concentrations of Hg²⁺ inhibited the photosynthesis of M. aeruginosa, while a low concentration (0.0005 mg/L) of Hg²⁺ promoted photosynthesis. When Hg²⁺ level range from 0.001 mg/L to 0.500 mg/L, it had significant inhibition effects on photosynthesis of M. aeruginosa. The chlorophyll fluorescence intensity increased with the concentration of Hg²⁺ (0.001~0.400 mg/L), even the concentration of Hg²⁺ and algal photosynthetic signal had a significant positive correlation, r=0.983 3.

Abstract: Herring sperm DNA (hsDNA) was used to modify 5 nm nanosilver to obtain a hsDNA-nanosilver probe (Ag-hsDNA) for Hg²⁺. In the presence of Hg²⁺, it combined with hsDNA to produce Hg²⁺-hsDNA complexes and to release nanosilver particles, based on formation of stable T-Hg²⁺-T mismatches. Nanosilver particles aggregated to form larger nanosilver clusters and led the absorption at 412 nm decreased in the pH 6.5 Na₂HPO^4-NaH₂PO₄ buffer solution and 0.05 mol/L NaCl medium. The decreased absorption (ΔA₄₁₂ nm) is linear to Hg²⁺ concentration in the range of 1.36-10.86μg/L Hg²⁺, with regress equation of ΔA=0.0987CHg²⁺ +0.0624, correlation coefficient of 0.9890, and detection limit of 0.30μg/L Hg²⁺. The assay was applied to the analysis of Hg²⁺ in wastewater with satisfactory results.

Abstract: A novel near-infrared absorbing colorimetric sensor with multifunctional groups, bis-dibenzo-18-crown-6 squaraine (BCSQ), has been identified and applied for accurate Hg²⁺ analysis based on the decrement of its UV absorbance (A) in the aqueous medium. The proposed method was successfully applied to analyse synthetic Hg²⁺ samples and natural Hg²⁺ samples. The results show that the linear range of Hg²⁺ detection in aqueous medium is 7.5~150×10⁸ mol·L¹ with a correlation coefficient (R) of 0.9983 and a limit of detection (3σ, n=20) of 5.6 ×10⁹ mol·L¹. The relative standard deviation (R.S.D.) for Hg²⁺ detection was lower than 2.4% (n=5). The proposed method possesses the advantages of simplicity, rapidity, high selectivity and sensitivity.

Abstract: The Au/MnO2 nanoalloy in diameter of 10 nm were prepared, using sodium citrate as the stabilizing agent and NaHB4 as the reductant. An aptamer Au/MnO2 nanoprobe (Apt-Au/MnO2) for Hg2+ was prepared using the aptamer modified. In the pH 7.0 Na2HPO4-NaH2PO4 and NaCl, The nanoprobe reacted with Hg2+ to form double-stranded T-Hg2+-T mismatches, and the released Au/MnO2 nanoparticles aggregated to big particles, which induced an increase in the resonance scattering (RS) signal at 570 nm. The RS signal was linear to the concentration of Hg2+ in the range of 0.1-7.5 nmol/L, with detection limit of 0.06 nmol/L Hg2+. This aptamer modified nanoalloy RS method was applied to detect Hg2+ in water samples, with satisfactory results.

Abstract: Using PEG-10000 and sodium citrate as stabilizer, and NaBH4 as reducer, a stable nanosilvers (AgNPs) sol was prepared. In pH 6.6 phosphate buffer solution containing NaCl, the AgNPs were aggregated to large particles, which lead to resonance Rayleigh scattering (RRS) peak at 350 nm enhancement. Upon addition of cysteine, the peak decreased. The decreased value ΔI is linear to cysteine concentration in the range of 5-60×10^-8 mol/L. Thus, a new RRS method was proposed for detection of cysteine.

Abstract: The extraction behavior of metal ions (Hg²⁺ and Cd²⁺, M²⁺) was investigated in ionic liquid (IL) extraction system using 1-butyl-3-methyl- imidazolium hexafluorophosphate ionic liquid ([Bmim]PF₆) as extraction solvent and 8-hydroxyl-quinoline (HQ) as extractant. The extraction percentage of M²⁺ using [Bmim]PF₆ was less than 5% without HQ. When sufficient HQ was included in IL phase, the extraction percentage of M²⁺ could be higher than 98%. The extracted species in the M²⁺-[Bmim]PF6-HQ system was neutral MQ₂ and the recovery of M²⁺ extracted into [Bmim]PF₆ can be achieved using 0.25 mol•L^-1 HNO₃ as stripping agent. [Bmim]PF₆ can be recycled in the experiment.

Abstract: The effects of Hg²⁺ on microbial community structures of aerobic activated sludge were investigated by nested PCR-DGGE techniques. The results showed that the microbial community of each group might have obvious change compared with the group without Hg²⁺ in the inflow, especially when the Hg²⁺ concentration was 46.87mg/L in the inflow, and the microbial community changed obviously with the extend of operation time. The variance of microbial species become obvious in each activated sludge group with the extend of operation time. Compared with the group without Hg²⁺ in the inflow, the dominant microbial species of each activated sludge group changed, and the dominant microbial species of the group whose concentration of Hg²⁺ increased gradually in the inflow had the biggest changes after 60 days. Hg²⁺ in the inflow may stimulate the growth of Actinomycetes after an operation period of 30 days.