You-Nian Liu

Sensitive photoluminescent detection of Cu2+ in real samples using CdS quantum dots in combination with a Cu2+-reducing reaction

By reducing free and/or weakly complexed Cu(2+) with a Cu(2+)-reducing agent (ascorbic acid in the present study) and detecting the photoluminescence peak of Cu(2)S-covered CdS quantum dots (QDs) at 650 nm, Cu(2+) concentrations ranging from 1 nM to 1 μM can be readily determined. Unlike other related reports, the present method takes advantage of the more efficient chemical reduction of Cu(2+) to Cu(+) (with respect to the photochemical reduction inherent in CdS QDs) and the facile deposition of Cu(2)S. As a result, a detection limit of 0.5 nM was achieved, which is at least 2-3 orders of magnitude lower than QD-based detection methods. In contrast with other methods requiring sample pretreatment or Cu(2+)-specific ligands capping QDs, the selectivity of the method towards Cu(2+) is excellent. Among a number of metal ions examined, only Cu(2+) causes the red shift of the CdS photoluminescence. A process causing the shift of the CdS photoluminescence was investigated and described. The matrix effect on the photoluminescent behavior of CdS QDs and the amenability of this method for real samples were also studied. Analyses of Cu(2+) in a river water sample and Cu(2+) complexed by amino acids and proteins in cerebrospinal fluids were performed. The latter analysis reveals that our method can differentiate weakly complexed Cu(2+) ions from the more strongly bound ones. This simple method was also demonstrated to be highly sensitive, accurate and reproducible.

Hierarchical hybrid film of MnO2 nanoparticles/multi-walled fullerene nanotubes-graphene for highly selective sensing of hydrogen peroxide

Hierarchical hybrid films of MnO2 nanoparticles/multi-walled fullerene nanotubes-graphene (MNPs/MWFNTs-GS) have been prepared via a simple wet-chemical method. For this purpose, MWFNTs (~300nm in length) are fabricated from tailoring multi-walled carbon nanotubes (MWCNTs), and then inserted into GS to pile up into a hierarchical hybrid film with the in situ formative MNPs. Scanning electron microscope, transmission electron microscope and X-ray diffraction are used to confirm the morphology and structure of the as-obtained film. The electrochemical studies reveal that MNPs/MWFNTs-GS exhibit significantly enhanced electrocatalytic activity compared with MNPs/GS, and show a rapid response to H2O2 over a wide linear range of 2.0μM-8.44mM with a high sensitivity of 206.3μA mM(-1)cm(-2) and an excellent selectivity. These favorable electrochemical detection properties may be mainly attributed to the introduction of MWFNTs, which helps to promote the electron/ion transport between MNPs and GS and form the hierarchical film structure.

A reversible competition colorimetric assay for the detection of biothiols based on ruthenium-containing complex

A novel reversible colorimetric sensor, which based on a competitive ligation of Hg(2+) by thiols, cysteine (Cys) or glutathione (GSH), and thiocyanate (SCN) on the N3 dye (bis(4,4-dicarboxy-2,2-bipyridine) dithiocyanato ruthenium (II)), was developed for the detection of biothiols. First, Hg(2+) ions coordinate to the sulfur atom of the dyes SCN groups, and this interaction induces a change in color from red to yellow, owing to the formation of a complex of Hg(2+)-N3. Then, in the presence of biothiols, the red color of N3 is recovered concomitantly with the dissociation of the Hg(2+)-N3 complex, due to the extraction of Hg(2+) by biothiols. Thus the corresponding color variation in the process of the dissociation of the Hg(2+)-N3 complex can be employed for the quantitative detection of thiols using UV-vis spectroscopy. In particular, the transformation can be readily viewed with the naked eye. A good linear relationship between the change in absorbance (ΔAbs) of Hg(2+)-N3 at 461 nm and the thiol concentration was obtained in the range of 0.5-25 μM, and the detection limits are then calculated to be 57 and 52 nM for Cys and GSH, respectively. The proposed colorimetric assay displays a high selectivity for Cys over various other amino acids and GSSG (oxidized glutathione).

Kinetic studies of inhibition of the amyloid beta (1-42) aggregation using a ferrocene-tagged β-sheet breaker peptide.

The aggregation of amyloidogenic proteins/peptides has been closely linked to the neuropathology of several important neurological disorders. In Alzheimers disease, amyloid beta (Aβ) peptides and their aggregation are believed to be at least partially responsible for the etiology of Alzheimers disease. The aggregate-inflicted cellular toxicity can be inhibited by short peptides whose sequences are homologous to segments of the Aβ(1-42) peptide responsible for β-sheet stacking (referred to as the β-sheet breaker peptides). Here, a water-soluble ferrocene (Fc)-tagged β-sheet breaker peptide, Fc-KLVFFK(6), was used as an electrochemical probe for kinetic studies of the inhibition of the Aβ(1-42) fibrillation process and for determination of the optimal concentration of β-sheet breaker peptide for efficient inhibition. Our results demonstrate that Fc-KLVFFK(6) interacts with the Aβ aggregates instantaneously in solution, and a sub-stoichiometric amount of Fc-KLVFFK(6) is sufficient to inhibit the formation of the Aβ oligomers and fibrils and to reduce the toxicity of Aβ(1-42). The interaction between Fc-KLVFFK(6) and Aβ(1-42) follows a pseudo-first-order reaction, with a rate constant of 1.89 ± 0.05 × 10(-4) s(-1). Tagging β-sheet breaker peptides with a redox label facilitates design, screening, and rational use of peptidic inhibitors for impeding/altering Aβ aggregation.

A ratiometric fluorescent probe with excited-state intramolecular proton transfer for benzoyl peroxide

A novel ratiometric fluorescent probe A1, based on excited-state intramolecular proton transfer (ESIPT) mechanism, for the detection of benzoyl peroxide (BPO) was designed and synthesized. A1 was employed for determining BPO in food and pharmaceutical samples with good sensitivity and high selectivity.

Synthesis and highly efficient photocatalytic activity of mixed oxides derived from ZnNiAl layered double hydroxides

Abstract ZnO/NiO/ZnAl 2 O 4 mixed-metal oxides were successfully synthesized through a hydrotalcite-like precursor route, in which appropriate amounts of metal salts solutions were mixed to obtain a new series of ZnNiAl layered double hydroxides (LDHs) as precursors, followed by calcination under different temperatures. The as-obtained samples were characterized by SEM, HRTEM, TEM, XRD, BET, TG–DTA, and UV–Vis spectra techniques. The photocatalytic activities of the samples were evaluated by degradation of methyl orange (MO) under the simulated sunlight irradiation. The effects of Zn/Ni/Al mole ratio and calcination temperature on the composition, morphology and photocatalytic activity of the samples were investigated in detail. The results indicated that compared with ZnNiAl-LDHs, the mixed-metal oxide showed superior photocatalytic performance for the degradation of MO. A maximum of 97.3% photocatalytic decoloration rate within 60 min was achieved from the LDH with the Zn/Ni/Al mole ratio of 2:1:1 and the calcination temperature of 500 °C, which much exceeded that of Degussa P25 under the same conditions. The possible mechanism of photocatalytic degradation over ZnO/NiO/ZnAl 2 O 4 was discussed.

Green and large-scale one-pot synthesis of small-sized graphene-bridged manganese dioxide nanowire network as new electrode material for electrochemical sensing

The cross-linked MnO2 nanowire (MNWS) network bridged with small-sized graphene (SSGS) with a uniform size of ~200xa0nm is prepared by a one-pot green hydrothermal route from graphene oxide sol and KMnO4. The route causes KMnO4 to react and form MnOx through both self-decomposition and etching graphene, as a result that MnOx grow into nanowires and micrometer-scale graphene is cut into SSGS simultaneously. The as-prepared MNWS/SSGS is characterized by scanning electron microscope, transmission electron microscope and X-ray diffractometer. The electrocatalytic activity of MNWS/SSGS for H2O2 reduction is studied by means of cyclic voltammetry and chronoamperometry. The MNWS/SSGS modified glassy carbon electrode exhibits a sensitive and prompt amperometric response to H2O2, with a sensitivity of 56xa0μAxa0mM−1 and detection limit as low as 0.54xa0μM. These outstanding performances demonstrate that MNWS/SSGS is promising for fabrication of electrochemical sensors. Importantly, this study may offer a novel and insightful approach for the preparation and development of advanced materials based on the bridging architecture.Graphical Abstract

Grinding–sol–gel synthesis and electrochemical performance of mesoporous Li3V2(PO4)3 cathode materials

Abstract Li 3 V 2 (PO 4 ) 3 precursor was obtained with V 2 O 5 · n H 2 O, LiOH·H 2 O, NH 4 H 2 PO 4 and sucrose as starting materials by grinding-sol-gel method, and then the monoclinic-typed Li 3 V 2 (PO 4 ) 3 cathode material was prepared by sintering the amorphous Li 3 V 2 (PO 4 ) 3 . The as-sintered samples were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), N 2 adsorption-desorption and electrochemical measurement. It is found that Li 3 V 2 (PO 4 ) 3 sintered at 700 °C possesses good wormhole-like mesoporous structure with the largest specific surface area of 188 cm 2 /g, and the smallest pore size of 9.3 nm. Electrochemical test reveals that the initial discharge capacity of the 700 °C sintered sample is 155.9 mA·h/g at the rate of 0.2 C , and the capacity retains 154 mA·h/g after 50 cycles, exhibiting a stable discharge capacity at room temperature.

Sol-Gel Synthesis and Electrochemical Performance of Li 3 V 2-2x/3 Mn x (PO 4 ) 3 Cathode Material for Lithiumion Batteries: Sol-Gel Synthesis and Electrochemical Performance of Li 3 V 2-2x/3 Mn x (PO 4 ) 3 Cathode Material for Lithiumion Batteries

以CH 3 COOLi·2H 2 O、V 2 O 5 、Mn(CH 3 COO) 2 ·4H 2 O、(NH 4 ) 2 HPO 4 和蔗糖为原料, 采用溶胶–凝胶法合成了掺锰磷酸钒锂/碳(Li 3 V 2-2 x /3 Mn x (PO 4 ) 3 /C)复合正极材料, 用XRD、XPS、SEM、电化学性能对样品进行了表征. 测试结果表明, 少量锰的掺杂并未改变Li 3 V 2 (PO 4 ) 3 /C的单斜结构, Li 3 V 1.94 Mn 0.09 (PO 4 ) 3 中的Mn和V分别以+2和+3价存在, 其颗粒类似球形, 直径比较均匀且小于200 nm, 并表现出良好的电化学性能. 在0.1 C 倍率和3.0~4.8 V电压内, 该样品的首次充、放电容量分别为182.1和168.8 mAh/g, 放电效率高达92.69%, 而且100次循环后, 其放电比容量仍是首次放电容量的77.4%.以CH 3 COOLi·2H 2 O、V 2 O 5 、Mn(CH 3 COO) 2 ·4H 2 O、(NH 4 ) 2 HPO 4 和蔗糖为原料, 采用溶胶–凝胶法合成了掺锰磷酸钒锂/碳(Li 3 V 2-2 x /3 Mn x (PO 4 ) 3 /C)复合正极材料, 用XRD、XPS、SEM、电化学性能对样品进行了表征. 测试结果表明, 少量锰的掺杂并未改变Li 3 V 2 (PO 4 ) 3 /C的单斜结构, Li 3 V 1.94 Mn 0.09 (PO 4 ) 3 中的Mn和V分别以+2和+3价存在, 其颗粒类似球形, 直径比较均匀且小于200 nm, 并表现出良好的电化学性能. 在0.1 C 倍率和3.0~4.8 V电压内, 该样品的首次充、放电容量分别为182.1和168.8 mAh/g, 放电效率高达92.69%, 而且100次循环后, 其放电比容量仍是首次放电容量的77.4%.

Microspheric flower-like Co 4 S 3 @Co foam synthesized by in situ sulfidization for electrocatalytic hydrogen evolution reaction

Non-noble metal sulfide electrocatalysts have received increasing attentions for hydrogen evolution reaction (HER). In this work, a facile one-step in situ sulfidization strategy was developed for the first time to construct microspheric flower-like Co4S3@Co foam with excellent HER activity. In comparison with the bare Co foam, the in situ growth of microspheric flower-like Co4S3 on Co foam substrate substantially improves the HER performance, leading to a lower overpotential of 143xa0mV at a current density of 10xa0mAxa0cm−2, a smaller Tafel slope of 158xa0mVxa0dec−1, as well as good stability in alkaline medium. The enhanced HER performance could be mainly attributed to the synergistic effects of the well-dispersed catalytic microspheric flower-like Co4S3 and the three-dimensional (3D) porous Co foam substrate. The microspheric flower-like Co4S3 is beneficial for increasing the active surface area to expose more active sites, and the intimate contact between Co4S3 and Co foam facilitates the electron transport, thus enhancing the catalytic activity.