Because of the serious physiological toxicity of methanol, detection of methanol in ethanol medium is tremendously significant. Herein, excellent luminescent lanthanide-based supramolecular metallogels were prepared with the conventional low-molecular-weight-gelator 1,3,5-benzenetricarboxylic acid (BTC) and the lanthanide trivalent cations (Tb 3+ and Eu 3+ ), which exhibit distinctive characteristic photoluminescent emission of lanthanides. These metallogels were synthesized depending on the one-step method of a high-concentration reaction synergized with heat-assisted ultrasound. The mechanical characteristics of the supramolecular metallogels were investigated through a rheological study. The scanning electron microscopy study revealed the supramolecular interconnection structure of microcubic blocks formed through irregular self-assembly of nanoplates. The bi-metallogel (Eu/Tb-G) with an obvious brilliant yellow emission signal was favorably fabricated via utilizing the lanthanide co-doping strategy and manifests the characteristic emission bands of lanthanide trivalent ions (Eu 3+ and Tb 3+ ) simultaneously. The energy-transfer behavior between Tb 3+ and Eu 3+ was systematically studied. What is striking is that methanol facilitates the increase of Tb 3+ fluorescence intensity without affecting the characteristic emission of Eu 3+ , and this phenomenon induces a unique emission proportion between Tb 3+ and Eu 3+ ions. Inspired by this, a self-calibrated fluorescence sensor of methanol is acquired, which adopts the dynamic emission of Tb 3+ that can vary continuously and regularly as the target identification detection signal and utilizes the static emission of Eu 3+ as the internal reference system. The change of fluorescence lifetime and quantum yield confirmed that this obvious visual optical color signal varying phenomenon can be ascribed to the internal energy-transfer process conversion caused by the unique host−quest interaction between methanol and Eu/Tb-G. In addition, the prepared Eu/Tb-G paper-based sensor has good stimulation response and recyclability to methanol vapor. The above discussion can establish Eu/Tb-G as a ratiometric and colorimetric fluorescent sensor for the detection of methanol and its vapor.

Copper germanate (CuGeO 3 ) nanowires are used as the modified materials of glassy carbon electrode to investigate the electrochemical behavior of ascorbic acid. The results show that CuGeO 3 nanowire modified glassy carbon electrode exhibits good performance for the electrochemical detection of ascorbic acid in neutral solution. The intensities of two anodic peaks vary linearly with the concentration of ascorbic acid in the range of 0.01-5 mM and the detection limit is 24 μM and 8.6 μM, respectively at a signal-tonoise ratio of 3, which makes it possible to sensitive detection of ascorbic acid using the CuGeO 3 nanowire modified glassy carbon electrode. The CuGeO 3 nanowire modified electrode exhibits good reproducibility and stability. The good analytical performance makes that the CuGeO 3 nanowires can be used as the electrode modified materials for a wide range of potential application for detecting ascorbic acid.Ascorbic acid (AA, vitamin C) is a kind of important micronutrient and biomicromolecule with many physiological roles. 1, 2 Ascorbic acid is also a powerful antioxidant present in food, beverages and used as a marker chemical in evaluating product quality. 3 Furthermore, great interest has been devoted to ascorbic acid in the cosmetic industry for the production of antiaging treatments. It can protect skin against UVA-induced photoinsult and stimulate collagen and procollagen synthesis as well as human fibolast proliferation. 4, 5 As a result, developing convenient, rapid and facile method for detecting ascorbic acid has been the subject of considerable interest for food, chemistry industry, pharmaceutical quality and safety. [6][7][8][9][10][11][12] Electrochemical method has been used to detect ascorbic acid directly owing to the excellent sensitivity, rapid response, low cost and good convenience. The accurate determination of the concentration is of considerable importance, but the reliable sensing of the ascorbic acid using conventional carbon electrodes has been hindered by the large over-potentials required and electrode fouling by the oxidation products. 12 Direct amperometric detection of ascorbic acid at common electrodes, such as carbon and transition metals is difficult owing to the electrode fouling. 13,14 The amperometric determination of ascorbic acid is based on its electrochemical oxidation process. At bare platinum or glassy carbon electrodes, the reaction proceeds at the potential above +500 mV. However, at chemically modified electrodes (CMEs), the necessary overpotential is lowered substantially. 15 The noble metals, 10 C 60 film, 16 carbon nanotube composite films, 17-20 covalently modified polymers and transition metal compound-based cheap catalysts 21-23 have been employed for the detection of ascorbic acid in the presence of other interferents. Therefore, it is of great significance that a reliable electroanalytical technique might offer greater selectivity, time efficiency and reproducibility than existing methods, such as high-performance liquid chromatography, 24 capillary...

Epinephrine (EP) could exhibit an anodic peak at a bare gold electrode, but it was very insensitive. However, when the bare gold electrode was modified with 3-mercaptopropionic acid (3MPA) self-assembled monolayer (3MPA SAM), the peaks of EP became more reversible and sensitive due to the accumulation and mediate efficiency of 3MPA SAM. Conditions such as solution pH, concentration of supporting electrolyte and accumulation time were optimized. Under the selected conditions (i.e., 0.02 M pH 6.8 sodium phosphate buffer, accumulation time: 2 min under open-circuit.), the height of the anodic peak at about 0.18 V (vs. SCE) was linear to EP concentration in the range of 2 Â 10 À7 À 1 Â 10 À6 M and 1 Â 10 À6 À 5 Â 10 À4 M with correlation coefficient of 0.995 and 0.999, respectively. When the 3MPA/Au was further modified with cysteamine, the interference of H 2 O 2 and BrO 3 À was eliminated. But the resulting electrode still suffered from the interference of ascorbic acid. This method was used to determine the content of EP in adrenaline hydrochloride injections, and the recovery was in the range of 97.0% to 105.1%.

No abstract

No abstract