共查询到20条相似文献,搜索用时 7 毫秒
1.
Jigar Patel Gregory Wilson R. Michael L. McKay Robert Vincent Zhaohui Xu 《Applied biochemistry and biotechnology》2010,162(4):1160-1173
Microbial biofilms can be valuable in many biotechnological applications, including bioremediation. We have previously constructed a recombinant strain of Caulobacter crescentus JS4022/p723-6H by inserting a hexahistidine peptide to a permissive site of the host surface layer (S-layer) protein RsaA. This engineered strain is highly effective in removal of cadmium from water as free cells. In this communication, we examined the biofilms formed by self-immobilized JS4022/p723-6H and evaluated their ability to retrieve cadmium from contaminated water samples. According to light and electron microscopic observations, JS4022/p723-6H cells developed a uniform monolayer biofilm on borosilicate surfaces through their intrinsic appendage, a stalk with an adhesive holdfast. The density of the biofilms reached a maximum after 48 h of incubation and was not affected by exposure to at least 1 ppm cadmium. When 0.4 ppm Cd(II) was added to the growth medium, immobilized JS4022/p723-6H removed 76.9% of the total metal, whereas the control strain only removed 13.5%. When a water sample collected from Lake Erie was spiked with various amounts of CdCl2, immobilized JS4022/p723-6H was able to sequester 44~51% of the total metal, compared to 37~42% accumulated by the control strain. By combining two powerful techniques, cell surface display and self-immobilization, we achieved complete separation of dissolved heavy metals from contaminated water in a single step. This study laid down the foundation to cost-effectively construct large-scale bioreactors with high efficiency and specificity to retrieve environmental contaminants from water. 相似文献
2.
M. Teresa Barros João Martins Rui M. Pinto Mónica S. Santos Helena M. V. M. Soares 《Journal of solution chemistry》2009,38(12):1504-1519
As part of a search for environmentally friendly metal chelating ligands, the stability constants of N, N′-ethylenedi-L-cysteine
(EC) complexes with Ca(II), Cu(II), Mg(II) and Mn(II) were determined by potentiometry with a glass electrode in aqueous solutions
containing 0.1 mol⋅L−1 KCl at 25 °C. Final models are proposed. For the Ca(II)–EC system, the overall stability constants are log 10
β
CaHL=14.53±0.03, log 10
β
CaL=4.79±0.01 and log 10
β
CaL2=8.38±0.04. For the M(II)–EC systems, where M=Cu(II) or Mg(II), the overall stability constants are log10
β
CuHL=31.19±0.02 and log 10
β
CuL=27.02±0.06 for Cu(II), and are log 10
β
MgHL=14.84±0.02 and log 10
β
MgL=6.164±0.008 for Mg(II). For the Mn(II)–EC system, the overall stability constant is log 10
β
MnL=10.12±0.01.
Metal–chelate speciations simulations showed that EC is an efficient chelating agent for Cd(II), Co(II), Cu(II), Ni(II), Pb(II)
and Zn(II) for pH≥7. 相似文献
3.
Keiichi Satoh Toshio Suzuki Kiyoshi Sawada 《Monatshefte für Chemie / Chemical Monthly》2001,132(10):1145-1155
Summary. The molecular structures of bis-(pyridine base) complexes of cadmium(II) chloride and bromide, where the pyridine base is pyridine ( py), 3-methylpyridine (3-Me-py), 4-methylpyridine (4-Me-py), and 4-ethylpyridine (4-Et-py), were investigated by means of single-crystal X-ray diffraction and Raman spectroscopy. The crystal structures of CdCl2 py
2 (1), CdCl2(3-Me-py)2 (2), and CdCl2(4-Me-py)2 (3) were determined. All crystals are monoclinic; 1: a = 17.784(2), b = 8.666(1), c = 3.8252(7) ?, β = 91.54(1)°, space group: P21/n; 2: a = 11.89(1), b = 14.41(1), c = 3.874(6) ?, β = 92.3(1)°, space group: P21/a; 3: a = 21.091(2), b = 3.8884(5), c = 18.2317(3) ?, β = 113.64(1)°, space group: C2/c. The structures were refined to R/R
w
values (%) of 3.2/5.5, 3.0/5.0, and 3.4/5.1 for 1–3. All cadmium atoms are octahedrally coordinated with the chloride ions forming infinite di-μ-chloro polymeric linear chains
and the nitrogen atoms of the pyridine base in trans configuration. The Cd chains are oriented along the c-axis in 1 and 2 and along the b-axis in 3. The crystal structures indicate the absence of a peculiar interaction between the polymeric chains. The Raman spectra of eight complexes were measured in the range of 550–50 cm−1, and the Raman peaks originating from cadmium-halogen vibrations were assigned. The Raman spectra of 1 and 2 are quite alike in the lattice mode vibration region. The resemblance of the cadmium-halogen vibration peaks indicates the
same halogenide ion bridged octahedral structure for all complexes.
Received March 27, 2001. Accepted (revised) June 19, 2001 相似文献
4.
The electrochemical solid phase micro-extraction of salicylic acid (SA) at graphite-epoxy-composed solid electrode surface
was studied by cyclic voltammetry. SA was oxidized electrochemically in pH 12.0 aqueous solution at 0.70 V (vs. saturated
calomel electrode) for 7 s. The oxidized product shows two surface-controlled reversible redox couples with two proton transferred
in the pH range of 1.0∼6.0 and one proton transferred in the pH range of 10.0∼13.0 and is extracted on the electrode surface
with a kinetic Boltzman function of i
p = 3.473–4.499/[1 + e(t − 7.332)/6.123] (χ
2 = 0.00285 μA). The anodic peak current of the extracted specie in differential pulse voltammograms is proportional to the
concentration of SA with regression equation of i
p = −5.913 + 0.4843 c (R = 0.995, SD = 1.6 μA) in the range of 5.00∼200 μM. The detection limit is 5.00 μM with RSD of 1.59% at 60 μM. The method
is sensitive and convenient and was applied to the detection of SA in mouse blood samples with satisfactory results. 相似文献
5.
Zhirong Mo Faqiong Zhao Fei Xiao Baizhao Zeng 《Journal of Solid State Electrochemistry》2010,14(9):1615-1620
Gold–platinum (AuPt) alloy particles were fabricated directly on multi-walled carbon nanotubes (MWNT)–ionic liquid (i.e.,
trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imide, [P6,6,6,14][NTf2]) composite coated glassy carbon electrode (GCE) by electrodeposition method. Scanning electron microscope image showed that
they were well-dispersed nanocluster consisting of smaller nanoparticles, and their size was about 70 nm. X-ray diffraction
experiment showed that they were single-phase alloy nanomaterial, and the calculated composition was consisting with that
obtained by energy dispersive X-ray spectroscopy. The resulting modified electrode (i.e., AuPt–MWNT–[P6,6,6,14][NTf2]/GCE) presented high catalytic activity for the electrochemical oxidation of cysteine. The peak potential of cysteine shifted
to 0.42 V (versus saturated calomel electrode) in 0.1 M H2SO4 and the peak current increased greatly in comparison with that on the corresponding Pt (or Au)–MWNT–[P6,6,6,14][NTf2]/GCE. Under the optimized conditions, the oxidation current of cysteine at 0.45 V was linear to its concentration in the
range of 5.0 × 10−7 ∼ 4.0 × 10−5 M with a sensitivity of 43.8 mA M−1. 相似文献
6.
Adsorption of iodide ions at the Bi(111) and Cd(0001) electrodes from the aqueous solutions with constant ionic strength 0.1x M KI + 0.1(1−x) M KF and 0.1x M KI + 0.033(1−x) M K2SO4 has been studied by impedance spectroscopy. It was found that, to a first approximation, the classical Frumkin–Melik–Gaikazyan
equivalent circuit with the slow diffusion-like and adsorption steps can be applied for fitting the experimental impedance
data for iodide ions adsorption on Bi(111) and Cd(0001) from aqueous solutions with constant ionic strength. The modified
Grafov–Damaskin circuit can be used in the region of electrode potentials, where parallel faradic processes (electroreduction
of protons, oxygen traces) are probable. The more complicated Ershler equivalent circuit, taking into account the slow diffusion-like,
adsorption and charge transfer steps, is not applicable for characterization of the adsorption process of I− at Bi(111) and Cd(0001) electrodes. 相似文献
7.
Arvydas Survila Jolanta Pileckien? Stas? Kanapeckait? Putinas Kalinauskas Giedrius Stalnionis 《Journal of Solid State Electrochemistry》2012,16(2):521-527
In accordance with thermodynamic analysis, cuprous oxide layers are formed spontaneously in the Cu|Cu(II), gluconic acid system
at pH > 3.7 under open-circuit conditions. A current peak of Cu2O reduction is observed on cathodic voltammograms at ca −0.7 V, its height being dependent on the exposure time. The analysis
of the charge transferred in this region yields the rate of Cu2O formation equal to 1.25 × 10−10 mol cm−2 s−1. The light perturbation of Cu electrode under open-circuit conditions results in the generation of a negative photopotential,
which is indicative of n-type conductivity. The threshold wavelength is equal to ∼590 nm and is consistent with a band gap of ∼2.1 eV. Anodic photocurrents,
which are observed near the open-circuit potential, decrease with cathodic polarization and change their sign at ∼0.05 V.
Analysis of impedance data was performed, invoking the equivalent circuit that accounts for the two-step charge transfer.
In the presence of Cu2O, some retardation of Cu(II) reduction was found to occur with a slight increase in the admittance of the double layer. The
suggestion has been made that oxide layers formed in Cu(II) gluconate solutions cannot be compact and uniformly distributed
over the entire electrode surface. Relevant investigations of surface morphology support this conclusion. 相似文献
8.
An “off–on” rhodamine-based fluorescence probe for the selective signaling of Cr(III) has been designed by exploiting the
guest-induced structure transform mechanism. This system shows a sharp Cr(III)-selective fluorescence enhancement response
in 100% aqueous system under physiological pH value and possesses high selectivity against the background of environmentally
and biologically relevant metal ions including Cr(VI), Al(III), Fe(III), Cd(II), Co(II), Cu(II), Ni(II), Zn(II), Mg(II), Ba(II),
Pb(II), Na(I), and K(I). Under optimum conditions, the fluorescence intensity enhancement of this system is linearly proportional
to Cr(III) concentration from 5.0 × 10−8 to 7.0 × 10−6 mol L−1 with a detection limit of 1.6 × 10−8 mol L−1. 相似文献
9.
Atanu Jana Chinmoy Bhattacharya Subrata Sinha Jayati Datta 《Journal of Solid State Electrochemistry》2009,13(9):1339-1350
Bismuth sulfide (Bi2S3) thin films were electrodeposited from non-aqueous dimethyl sulfoxide medium containing Bi(NO3)3 and thiourea as the precursor salts, triethanol amine as the complexing agent, and TritonX-100 as the surface active agent.
The prepared films were subjected to rigorous experimentation in order to validate their potential candidature for solar cells.
The films exhibited band gap energy of ∼1.3 eV and resistivity of the order of 2 × 106 Ω cm at room temperature as was obtained from UV–Vis spectroscopy and four-probe measurements, respectively. Scanning electron
microscopy, transmission electron microscopy, X-ray diffraction, and energy dispersive analysis of X-ray were employed to
reveal the morphology, structure, and chemical composition of the film matrix. The Bi2S3 films were found to be non-decomposable up to the temperature of 1,000 °C with the help of thermogravimetry–differential
thermal analysis. The Nyquist and Mott–Schottky plots derived from electrochemical impedance spectroscopy measurements provided
important information regarding electrical and semiconducting properties of the films. The n-type film with a donor density of the order of ∼1023 m−3 displayed reasonable photoactivity under illumination and is recommended as a promising candidate for potential photoelectrochemical
applications. 相似文献
10.
Jianping Li Xiongzhi Wu Yong Yu Shangwang Le 《Journal of Solid State Electrochemistry》2009,13(12):1811-1818
Gold electrode with self-assembled D,L-cysteine grafted β-cyclodextrin sulfonic acid (Cys-β-CD∼SO3) layer was fabricated and used to investigate the electrochemical behavior of dopamine. The experimental results indicated
that the self-assembled Cys-β-CD∼SO3 layer modified gold electrode has selective electrochemical response to dopamine with high sensitivity and excellent tolerance
of ascorbic acid, which is the most common accompanying component in biological samples. Dopamine could be accurately determined
in the concentration range of 1–200 μM in the presence of ascorbic acid of 5 mM. The relative standard deviation of 1.9% (n = 5) was achieved at a dopamine concentration of 5 × 10−5 M. The proposed sensor was successfully applied to the determination of dopamine in human blood serum samples. 相似文献
11.
Jun-Ying Ge Sai-Feng Xue Qian-Jiang Zhu Zhu Tao Jian-Xin Zhang 《Journal of inclusion phenomena and macrocyclic chemistry》2007,58(1-2):63-69
The structures and optical properties of host–guest complexes produced from cucurbit[n = 6–8]urils and some benzimidazole derivatives have been investigated by 1H NMR spectroscopy, electronic absorption spectroscopy and fluorescence spectroscopy. The experimental results reveal that
calculations of A∼NQ[n]/Nguest and If∼NQ[n]/Nguest for the same association complex both support a good fit to an identical binding model. In particular, the A∼NQ[n]/Nguest, If∼NQ[n]/Nguest calculations and the 1H NMR determinations for three Q[6]–ge(1∼3) complexes and three Q[8]–ge(1∼3) complexes all support a binding model of 1:1
and 1:2 respectively. 相似文献
12.
Jahan Bakhsh Raoof Reza Ojani Maryam Ramine 《Journal of Solid State Electrochemistry》2009,13(9):1311-1319
A p-duroquinone (tetramethyl-p-benzoquinone) modified carbon paste electrode (DMCPE) was employed to study the electrocatalytic reduction of nitrite in
aqueous solutions using cyclic voltammetry (CV), double potential-step chronoamperometry, and differential pulse voltammetry
(DPV). It has found that under an optimum condition (pH 1.00), the reduction of nitrite at the surface of DMCPE occurs at
a potential of about 660 mV less negative than that of an unmodified carbon paste electrode (CPE). The catalytic rate constant,
k′h, based on Andrieux and Saveant theoretical model was calculated as for scan rate 10 mV s-1. Also, the apparent diffusion coefficient, D
app, was found as 2.5 × 10–10 and 3.61 × 10–5 cm2 s-1
for p-duroquinone in carbon paste matrix and nitrite in aqueous buffered solution, respectively. The values for αnα were estimated to be −0.65 and −0.19 for the reduction of nitrite at the surface of DMCPE and CPE, respectively. The electrocatalytic
reduction peak currents showed a linear dependence on the nitrite concentration, and a linear analytical curve was obtained
in the ranges of 5.0 × 10–5 M to 8.0 × 10–3 M and 6.0 × 10–6 M to 8.0 × 10–4 M of nitrite concentration with CV and DPV methods, respectively. The detection limits (2σ) were determined as 2.5 × 10–5 M and 4.3 × 10–6 M by CV and DPV methods. This method was also applied as a simple, selective and precise method for determination of nitrite
in real samples (the weak liquor from the wood and paper factory of Mazandaran province in Iran) by using a standard addition
method. 相似文献
13.
A new method for the separation and determination of trace amounts of cadmium and zinc in water as their thenoyltrifluoroacetone
(TTA) complexes with dibenzo-18-crown-6 (DB18C6) in o-dichlorobenzene has been established by means of synergistic extraction
and back-extraction combined with atomic absorption spectrometry. The effect of various factors (synergism with TTA and DB18C6,
shaking time, composition of the extracted species, and mutual separation etc.) on the extraction and back-extraction of cadmium
and zinc has been in- vestigated. When the mixtures were extracted for 4 min at pH 4.9, only zinc was extracted quantitatively,
whereas cadmium remained in the aqueous phase. After the phases were separated, cadmium was again extracted quantitatively
at pH 7.5. Then, the two phases were each shaken with 0.05–0.1 mol/l HCl in order to back-extract cadmium and zinc from the
organic phases; the ions were determined individually by atomic absorption spectrometry. In the process cadmium and zinc TTA
chelates in o-dichlorobenzene form stable adducts with DB18C6 (Cd(TTA)2 ⋅ nDB18C6 and Zn(TTA)2 ⋅ nDB18C6, n=0∼2). The stability constants (βn) of the adducts determined by means of the curve fitting method were log β1=4.62 and log β2=6.74 for cadmium, and log β1=3.48 and log β2=5.18 for zinc.
Received: 8 September 1995/Revised: 22 January 1996/Accepted: 24 January 1996 相似文献
14.
Pandey G. P. Agrawal R. C. Hashmi S. A. 《Journal of Solid State Electrochemistry》2011,15(10):2253-2264
Effect of fumed silica dispersion on poly(vinylidene fluoride-co-hexafluoropropylene)-based magnesium ion-conducting gel polymer
electrolyte has been studied using various physical and electrochemical techniques. The composite gel electrolytes are free-standing
and flexible films with enough mechanical strength. The optimized composition with 3 wt.% filler offers a maximum ionic conductivity
of ∼1.1 × 10−2 S cm−1 at ∼25 °C with good thermal and electrochemical stabilities. The Mg2+ ion conduction in the gel nanocomposite film is confirmed from the cyclic voltammetry, impedance spectroscopy, and transport
number measurements. The space-charge layers formed between filler particles and gel electrolyte are responsible for the enhancement
in ionic conductivity. The applicability of the gel nanocomposite to a rechargeable battery is examined by fabricating a prototype
cell consisting of Mg [or Mg-multiwalled carbon nanotube (MWCNT) composite] and MoO3 as negative and positive electrodes, respectively. The discharge capacity and the rechargeability of the cell have been improved
when Mg metal is substituted by Mg-MWCNT composite. The discharge capacity of the optimized cell has found to be ∼175 mAh g−1 of MoO3 for an initial ten charge–discharge cycles. 相似文献
15.
Bing-Joe Hwang Yu-Chuan Liu Wen-Cheng Hsu 《Journal of Solid State Electrochemistry》1998,2(6):378-385
The influences of the reductant concentration of NaBH4 and the quantity of Pt loading on the active surface area and the sensitivity of the Pt/Nafion electrodes prepared by an
impregnation-reduction method in detecting oxygen were investigated in this study. The Pt/Nafion electrodes with a Pt loading
of 4.99 mg/cm2, obtained at 0.0107 M Pt(NH3)4Cl2 and 0.06 M NaBH4, show maximum sensitivities of 0.0528 A/ppm and 0.0538 A/ppm obtained in O2 concentration regions of 0–5000 and 5000–50 000 ppm, respectively. A sensing model was also proposed to illustrate the sensing
phenomenon.
Received: 21 January 1998 / Accepted: 10 March 1998 相似文献
16.
K. M. Ibrahim I. M. Gabr G. M. Abu El-Reash R. R. Zaky 《Monatshefte für Chemie / Chemical Monthly》2009,100(1):625-632
Abstract
Acetone [N-(3-hydroxy-2-naphthoyl)] hydrazone (H2AHNH) has been prepared and its structure confirmed by elemental analysis and 1H NMR spectroscopy. It has been used to produce diverse complexes with Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and U(VI)O2 ions. The complexes obtained have been investigated by thermal analysis, spectral studies (1H NMR, IR, UV–visible, ESR), and magnetic measurements. IR spectra suggest that H2AHNH acts as a bidentate ligand. The electronic spectra of the complexes and their magnetic moments provide information about geometries. The ESR spectra give evidence for the proposed structure and the bonding for some Cu(II) complexes. Thermal decomposition of the Ni(II) and Cu(II) complexes afforded metal oxides as final products. Kinetic data were obtained for each stage of thermal degradation of some of the complexes using the Coats–Redfern method. The formation of complexes in solution was studied pH-metrically and the order of their stability constants (log K) was found to be U(VI)O2 > Cu(II) > Zn(II) > Ni(II) > Cd(II) > Co(II). Antimicrobial and eukaryotic DNA studies were carried out. 相似文献17.
S. Agnello R. Boscaino F. La Mattina S. Grandi A. Magistris 《Journal of Sol-Gel Science and Technology》2006,37(1):63-68
We have studied the generation mechanisms of H(II) paramagnetic centers in Ge-doped silica by investigating up to 104 mol ppm sol-gel Ge-doped silica materials. We have considered materials with the same concentrations of Ge but that are produced
by two different densification routes that give rise to different concentrations of Ge-related oxygen deficient centers (GeODC(II)).
These centers are characterized by an optical absorption band at ∼5.2 eV (B2β band) and two related emissions at ∼3.2 eV and ∼4.3 eV. The GeODC(II) content was estimated by absorption and emission measurements.
The H(II) centers were induced by room temperature γ-ray irradiation and their concentration was determined by electron paramagnetic
resonance measurements.
The comparison between the two kinds of materials, obtained by different preparations, shows that the GeODC(II) concentration
increases with the Ge content and is enhanced by vacuum densification. The comparison of irradiated samples shows that beyond
the already known process of conversion of preexisting GeODC(II) into H(II) centers, another generation process of H(II) centers
is effective that involves irradiation induced GeODC(II). 相似文献
18.
5,10,15,20-tetrakis(phenoxy acetic acid) porphyrin (PAAP) was covalently linked to Merrifield chloromethylated resin. Characterization
of PAAP and the modified polymeric matrix were performed by 1H NMR, FTIR and elemental analysis. The sorbent was used for the separation and enrichment of the d-electron metals (Mn(II), Co(II), Ni(II), Cu(II) and Zn(II)) at pH 6–8 and of the f-electron metals U(VI) and Th(IV) at pH 4–5. The metals ions were preconcentrated with a concentration factor range of 115–215
and then determined by flame atomic absorption spectrometry or visible spectrophotometry using Arsenazo(III). The retained
metals were eluted with 2.0 mol L−1 HNO3 in the case of the d-electron metals and 0.1/0.25 mol L−1 HCl in the case of the f-electron metals. The procedure was validated by analyzing the NIST standard reference material 2709 (San Joaquin Soil).
Correspondence: Melek Merdivan, Chemistry Department, Faculty of Arts and Sciences, Dokuz Eylul University, 35160 Buca, Izmir,
Turkey 相似文献
19.
A new H2O2 biosensor was fabricated on the basis of nanocomposite films of hemoglobin (Hb), silver nanoparticles (AgNPs), and multiwalled
carbon nanotubes (MWNTs)–chitosan (Chit) dispersed solution immobilized on glassy carbon electrode (GCE). The immobilized
Hb displayed a pair of well-defined and reversible redox peaks with a formal potential (E
θ′) of −22.5 mV in 0.1 M pH 7.0 phosphate buffer solution. The apparent heterogeneous electron transfer rate constants (k
s) in the Chit–MWNTs film was evaluated as 2.58 s−1 according to Laviron’s equation. The surface concentration (Γ*) of the electroactive Hb in the Chit–MWNTs film was estimated to be (2.48 ± 0.25) × 10−9 mol cm−2. Meanwhile, the Chit–MWNTs/Hb/AgNPs/GCE demonstrated excellently electrocatalytical ability to H2O2. Its apparent Michaelis–Menten constant (K
Mapp) for H2O2 was 0.0032 mM, showing a good affinity. Under optimal conditions, the biosensors could be used for the determination of H2O2 ranging from 6.25 × 10−6 to 9.30 × 10−5 mol L−1 with a detection limit of 3.47 × 10−7 mol L−1 (S/N = 3). Furthermore, the biosensor possessed rapid response to H2O2 and good stability, selectivity, and reproducibility. 相似文献
20.
Reza Ansari Ali Fallah Delavar Alireza Aliakbar Ali Mohammad-khah 《Journal of Solid State Electrochemistry》2012,16(3):869-875
A pencil graphite electrode coated by copper (II)–carmoisine dye complex in polyaniline (emeraldine base form) matrix (termed
as PGE/PA/Cu-Car) was prepared and used as copper ion-selective electrode. The introduced electrode was found to have high
selectivity toward copper ion (II) and exhibited wide working concentration range, low response time, and good shelf life.
The sensor electrode showed a linear Nernstian response over the range of 5.0 × 10−6 to 1.0 × 10−1 M with a slope of 29.7 ± 1 mV per decade change in concentration. A detection limit of 2.0 × 10−6 M was obtained. The optimum pH working range of the electrode was found to be 4.0–7.0. 相似文献