Development of a sensitive and selective Riboflavin sensor based on carbon ionic liquid electrode

The electrochemical properties of Riboflavin adsorbed on carbon ionic liquid electrode (CILE) were studied by cyclic voltammetry. A film with a surface coverage of up to 3.3 × 10⁻⁹ mol cm⁻² was formed after 10 min exposure time. Electron transfer coefficient and rate constant of electron transfer across the modified electrode were found to be 0.43 and 3.03 s⁻¹, respectively. Differential pulse voltammetry was used for the determination of Riboflavin. Two linear working ranges of 0.8-110 nM and 0.11-1.0 μM were obtained with correlation coefficients of 0.998 and 0.996, respectively. The experimental detection limit was obtained as 0.1 nM. The relative standard deviation for five replicate analyses was 4.7%. Other soluble vitamins had no significant interferences and the electrode was used for the determination of Riboflavin in pharmaceutical products, nutrition and beverages.     

Salicylate-selective electrode based on lipophilic tin(IV)phthalocyanine

A new PVC membrane electrode based on lipophilic (2,9,16,23-tetra-tert-butylphthalocyanine)tin(IV) dichloride which demonstrates excellent selectivity and fast response toward the salicylate ion is described. The membrane electrode displayed a linear response for salicylate in the concentration range 10(-5)-0.1 M and exhibited an antiHofmeister pattern, with high selectivity for salicylate compared with lipophilic inorganic and biologically important organic anions. The electrode was successfully applied to the determination of salicylate in pharmaceutical preparations and biological samples.     

基于原位聚合离子液体凝胶的固态电致变色器件的制备及性能研究

本文通过在离子液体BmimPF6中原位热聚合甲基丙烯酸甲酯得到了透明的离子液体凝胶。通过交流阻抗测定,当BmimPF6与甲基丙烯酸甲酯的质量比为5∶1时,离子液体凝胶的导电率为1.33×10-3Scm-1。将通过电化学沉积制得的三氧化钨(WO3)和普鲁士蓝(PB)修饰FTO电极,与上述离子液体凝胶一起组装得到了全固态的电致变色器件。原位吸收光谱数据显示所制得的电致变色器件,在±2V的工作电压下,具有稳定的电致变色响应,其着色和褪色时间分别为4.5s和4.0s,着色效率达190cm2C-1(λ=660nm)。     

基于室温离子液体的电导型气体传感器

本文利用室温离子液体对水或有机蒸气吸收后其离子导电性的改变,研制了以离子液体BmimPF6为敏感材料的电导型气体传感器.考查了BmimPF6用量对传感器响应的影响,测定了传感器对不同浓度的水蒸汽及乙醇、二氯甲烷等饱和有机蒸气的响应.实验结果显示,该传感器具有制作方便、结构简单、稳定性高及线性范围宽等优点,可被用于不同浓度的水或有机蒸气/氮气混合气氛中,水蒸汽或有机蒸气浓度的测定.此外,还针对该传感器对乙醇等不同饱和有机蒸气响应信号与这些有机溶剂的理化性质参数间的定量关系,采用化学计量学方法进行了建模分析.     

Quasi solid-state electrolytes based on ionic liquid (IL) and ordered mesoporous matrix MCM-41 for supercapacitor application

Journal of Solid State Electrochemistry - Quasi solid-state electrolytes (QS-SEs) based on an ionic liquid ([EMIM][FSI]) immobilized in ordered mesoporous silica MCM-41 using physical imbibition...     

Highly selective colorimetric sensor for cysteine and homocysteine based on azo derivatives

A simple colorimetric method for the determination of cysteine and homocysteine has been developed. The reaction of the azo dyes containing an aldehyde group with cysteine or homocysteine afforded very stable derivatives thiazolidines or thiazinanes under neutral pH conditions. The method is selective and sensitive for cysteine and homocysteine detection without the interference of other amino acids. Importantly, the recognition of Cys and Hcy could be observed by naked eyes.     

A selective electrolytic sensor for nitrite based on a modified platinum electrode

The electrolytic sensor described is based on the oxidation of nitrite at a platinum electrode modified with chemisorbed iodine and coated with a thin layer of quaternized poly(4-vinylpyridine), qPVP. The sealed sensor uses an anion-exchange membrane to separate Donnan transport of nitrite across the membrane and controlled potential electrolysis at the Pt/qPVP indicator electrode. The sensor has a linear response to nitrate concentration in aqueous samples over the range 4 × 10^?6?2 × 10^?3 M nitrite. The detection limit is 2 × 10^?6 M nitrite. The sensor is free of interference by nitrate, dissolved oxygen, cations, and many neutral species. Anions that are electroactive at 0.7 V vs. Ag/ AgCl would interfere, but they are uncommon in most samples. Initial tests with lake water samples suggest that this sensor is unaffected by this matrix. The system was also evaluated for monitoring nitrite levels in spiked meat extracts.     

Fabrication of an iodide-selective electrode based on phthalocyaninatotitanium(IV) oxide and the selective determination of iodide in actual samples

This work describes the development and fabrication of a selective polymeric membrane electrode for iodide ion based on a metallophthalocyanin complex with a titanium(IV) atom at the center (as an oxo-titanium, Ti=O, group), phthalocyaninatotitanium(IV) oxide (PcTiO), as a sensing carrier. The potential response characteristics of the electrode were investigated by changing the type of plasticizer as well as the amounts of the carrier and different lipophilic ionic site additives in the sensing membrane. It is shown that the membrane electrode incorporated with 2-nitrophenyl octyl ether as the plasticizer and hexadecyl trimethylammonium bromide as the appropriate cationic additive exhibits enhanced potential response toward iodide over other anions tested. Over the period of this study, the resulting electrode based on PcTiO displayed a stable near-Nernstian slope approaching -58.9 mV decade(-1) with a linear response spanning at least 5 orders of magnitude in concentration from 1.0 x 10(-1) to 9.2 x 10(-7) mol L(-1) and a detection limit of 8.5-10(-7) mol L(-1). The preferential potential response to iodide may be attributed to the unique recognition of carrier PcTiO in the organic membrane phase for iodide in solution. Under laboratory conditions, the present electrode also works well in partially nonaqueous media. The excellent analytical features of the proposed electrode could lead to its successful application in determining the end point in electrometric titration of iodide with Ag(+) and the direct potential determination of iodide concentration in wastewater and drug preparations.     

Importance of platinum(II)-assisted platinum(IV) substitution for the oxidation of guanosine derivatives by platinum(IV) complexes

Guanosine derivatives with a nucleophilic group at the 5' position (G-5') are oxidized by the Pt (IV) complex Pt( d, l)(1,2-(NH 2) 2C 6H 10)Cl 4 ([Pt (IV)(dach)Cl 4]). The overall redox reaction is autocatalytic, consisting of the Pt (II)-catalyzed Pt (IV) substitution and two-electron transfer between Pt (IV) and the bound G-5'. In this paper, we extend the study to improve understanding of the redox reaction, particularly the substitution step. The [Pt (II)(NH 3) 2(CBDCA-O,O')] (CBDCA = cyclobutane-1,1-dicarboxylate) complex effectively accelerates the reactions of [Pt (IV)(dach)Cl 4] with 5'-dGMP and with cGMP, indicating that the Pt (II) complex does not need to be a Pt (IV) analogue to accelerate the substitution. Liquid chromatography/mass spectroscopy (LC/MS) analysis showed that the [Pt (IV)(dach)Cl 4]/[Pt (II)(NH 3) 2(CBDCA-O,O')]/cGMP reaction mixture contained two Pt (IV)cGMP adducts, [Pt (IV)(NH 3) 2(cGMP)(Cl)(CBDCA-O,O')] and [Pt (IV)(dach)(cGMP)Cl 3]. The LC/MS studies also indicated that the trans, cis-[Pt (IV)(dach)( (37)Cl) 2( (35)Cl) 2]/[Pt (II)(en)( (35)Cl) 2]/9-EtG mixture contained two Pt (IV)-9-EtG adducts, [Pt (IV)(en)(9-EtG)( (37)Cl)( (35)Cl) 2] and [Pt (IV)(dach)(9-EtG)( (37)Cl)( (35)Cl) 2]. These Pt (IV)G products are predicted by the Basolo-Pearson (BP) Pt (II)-catalyzed Pt (IV)-substitution scheme. The substitution can be envisioned as an oxidative addition reaction of the planar Pt (II) complex where the entering ligand G and the chloro ligand from the axial position of the Pt (IV) complex are added to Pt (II) in the axial positions. From the point of view of reactant Pt (IV), an axial chloro ligand is thought to be substituted by the entering ligand G. The Pt (IV) complexes without halo axial ligands such as trans, cis-[Pt(en)(OH) 2Cl 2], trans, cis-[Pt(en)(OCOCF 3) 2Cl 2], and cis, trans, cis-[Pt(NH 3)(C 6H 11NH 2)(OCOCH 3) 2Cl 2] ([Pt (IV)(a,cha)(OCOCH 3) 2Cl 2], satraplatin) did not react with 5'-dGMP. The bromo complex, [Pt (IV)(en)Br 4], showed a significantly faster substitution rate than the chloro complexes, [Pt (IV)(en)Cl 4] and [Pt (IV)(dach)Cl 4]. The results indicate that the axial halo ligands are essential for substitution and the Pt (IV) complexes with larger axial halo ligands have faster rates. When the Pt (IV) complexes with different carrier ligands were compared, the substitution rates increased in the order [Pt (IV)(dach)Cl 4] < [Pt (IV)(en)Cl 4] < [Pt (IV)(NH 3) 2Cl 4], which is in reverse order to the carrier ligand size. These axial and carrier ligand effects on the substitution rates are consistent with the BP mechanism. Larger axial halo ligands can form a better bridging ligand, which facilitates the electron-transfer process from the Pt (II) to Pt (IV) center. Smaller carrier ligands exert less steric hindrance for the bridge formation.     

Nonenzymatic sensor for hydrogen peroxide based on the electrodeposition of silver nanoparticles on poly(ionic liquid)-stabilized graphene sheets

We have developed a nonenzymatic sensor for hydrogen peroxide (HP) that is based on a new kind of nanocomposite consisting of silver nanoparticles (AgNPs) electrodeposited on a basic film of a poly(ionic liquid) containing graphene. The nanocomposite was characterized by scanning electron microscopy, energy dispersive X-ray studies, cyclic voltammetry, and chronoamperometry. The AgNPs on the basic composite film provide the electrode with enhanced sensitivity in that the signal obtained for HP is 10-fold improved in the best case. The sensor exhibits good linear response in the 0.1 μM to 2.2 mM HP concentration range, and the detection limit is 0.05 μM (at S/N?=?3).      

Potentiometric membrane sensors based on zirconyl(IV) phthalocyanine for detection of sulfosalicylic acid

A metallophthalocyanine complex with zirconium(IV) ion in the center (as an oxo-zirconium, Zr=O, group) was used in poly vinyl chloride (PVC) membranes for the selective detection of 5-sulfosalicylic acid (SSA). The resulting electrodes demonstrate Nernstian responses over a wide range of sulfosalicylic acid concentration (10⁻⁶ to 10⁻¹ mol dm⁻³) with a slope of about −29 mV per decade. The influence of lipophilic ion-exchanger sites on the response properties of the electrodes was investigated. The optimal potentiometric response was observed for the electrode in the presence of about 150 mol% of cationic additive (relative to ionophore) in the phase membrane. The electrodes have a fast response time, micromolar detection limit and good long-term stability (more than 2 months). The feasibility of the application of these sensors for the potentiometric titration of iron in solutions that were prepared from magnetite samples was investigated.     

Preparation and application of a new glucose sensor based on iodide ion selective electrode

An electrode for glucose has been prepared by using an iodide selective electrode with the glucose oxidase enzyme. The iodide selective electrode used was prepared from 10% TDMAI and PVC according our previous study. The enzyme was immobilized on the iodide electrode by holding it at pH 7 phosphate buffer for 10 min at room temperature. The H₂O₂ formed from the reaction of glucose was determined from the decrease of iodide concentration that was present in the reaction cell. The iodide concentration was followed from the change of potential of iodide selective electrode. The potential change was linear in the 4×10⁻⁴ to 4×10⁻³ M glucose concentration (75-650 mg glucose/100ml blood) range. The slope of the linear portion was about 79 mV per decade change in glucose concentration. Glucose contents of some blood samples were determined with the new electrode and consistency was obtained with a colorimetric method. The effects of pH, iodide concentration, the amount of enzyme immobilized and the operating temperature were studied. No interference of ascorbic acid, uric acid, iron(III) and Cu(II) was observed. Since the iodide electrode used was not an AgI-Ag₂S electrode, there was no interference of common ions such as chloride present in biological fluids. The slope of the electrode did not change for about 65 days when used 3 times a day.     

Highly selective piezoelectric sensor for lead(II) based on the lead-catalyzed release of gold nanoparticles from a self-assembled nanosurface

A novel quartz crystal microbalance (QCM) sensor has been developed for highly selective and sensitive detection of Pb²⁺ by exploiting the catalytic effect of Pb²⁺ ions on the leaching of gold nanoparticles from the surface of a QCM sensor. The use of self-assembled gold nanoparticles (AuNPs) strongly enlarges the size of the interface and thus amplifies the analytical response resulting from the loss of mass. This results in a very low detection limit for Pb²⁺ (30 nM). The high selectivity is demonstrated by studying the effect of potentially interfering ions both in the absence and presence of Pb²⁺ ions. This simple and well reproducible sensor was applied to the determination of lead in the spiked drinking water. This work provides a novel strategy for fabricating QCM sensors towards Pb²⁺ in real samples. Figure

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Transparent,flexible and solid-state supercapacitors based on room temperature ionic liquid gel

This paper describes a novel strategy to make fully transparent, solid-state and flexible supercapacitors based on room temperature ionic liquid (RTIL) gel and ITO electrodes coated on transparent polymer substrate without a separator, which enables the roll-to-roll technique for fabrication of such supercapacitors as printable devices. This is the first type of transparent electrochemical double layer capacitor (EDLC) based on ionic liquid gel.     

Highly selective and sensitive monohydrogen phosphate membrane sensor based on molybdenum acetylacetonate

In this work, a highly selective and sensitive monohydrogen phosphate membrane sensor based on a molybdenum bis(2-hydroxyanil) acetylacetonate complex (MAA) is reported. The sensor shows a linear dynamic range between 1.0 × 10⁻¹ and 1.0 × 10⁻⁷ M, with a nice Nernstian behavior (−29.5 ± 0.3 mV decade⁻¹) in pH of 8.2. The detection limit of the electrode is 6.0 × 10⁻⁸ M (∼6 ppb). The best performance was obtained with a membrane composition of 32% poly(vinyl chloride), 58% benzyl acetate, 2% hexadecyltrimethylammonium bromide and 8% MAA. The sensor possesses the advantages of short response time, low detection limit and especially, very good selectivity towards a large number of organic and inorganic anions including salicylate, citrate, tartarate, acetate, oxalate, fluoride, chloride, bromide, iodide, sulfite, sulfate, nitrate, nitrite, cyanide, thiocyanate, perchlorate, metavanadate, and bicarbonate ions. The electrode can be used for at least 10 weeks without any considerable divergence in its slope and detection limit. It was used as an indicator electrode in potentiometric titration of monohydrogenphosphate ion with barium chloride. The proposed sensor was successfully applied to direct determination of monohydrogenphosphate in two fertilizer samples (NPK).     

Highly selective iodide electrode based on the copper(II)-N,N'-bis(salicylidene)-1,2-bis(p-aminophenoxy)ethane tetradentate complex.

In this paper, a new PVC-based liquid-membrane anion-selective electrode based on a copper(II) of N,N'-bis(salicylidene)-1,2-bis(p-aminophenoxy)ethane tetradentate complex (Cu(II)BBAP) is described, which displays a preferential potentiometric response to iodide ion at pH 2.0 and an anti-Hofmeister selectivity sequence: I->SCN->ClO4->NO2->H2PO4->NO3->SO4(2-)>Br->Cl-. The electrode exhibits a near-Nernstian potential linear range of 8.2x10(-7)-1.0x10(-1) M with a detection limit of 5.3x10(-7) M and a slope of -58.8 mV per decade. The A.C. impedance technique and the UV/Vis spectroscopy technique were used to analyze the response mechanism. The electrode could be applied to determine iodide in medicine analysis, and the obtained results were fairly satisfactory.     

Highly sensitive composite electrode based on electrospun carbon nanofibers and ionic liquid

A novel composite electrode has been developed using electrospun carbon nanofibers (CNF) and the ionic liquid 1-butyl-4-methylpyridinium hexaflurophosphate (PFP). The highly pure CNF without any pretreatment exhibited very low background noise and high voltammetric responses. When applied to sensing of biomolecules under physiological conditions, the CNF/PFP electrode provided attractive electrochemical performances, such as high sensitivity and good selectivity for simultaneous detection of dopamine, ascorbic acid and uric acid, guanine and adenine, as well as high signal-to-noise ratio and good stability for amperometric detection of NADH.