Quantum dot-based "turn-on" fluorescent probe for detection of zinc and cadmium ions in aqueous media

Health or environmental issue caused by abnormal level of metal ions like Zn²⁺ or Cd²⁺ is a worldwide concern. Developing an inexpensive and facile detection method for Zn²⁺ and Cd²⁺ is in urgent demand. Due to their super optical properties, fluorescent quantum dots (QDs) have been developed as a promising alternative for organic dyes in fluorescence analysis. In this study, a CdTe QDs-based sensitive and selective probe for Zn²⁺ and Cd²⁺ in aqueous media was reported. The proposed probe worked in fluorescence “turn-on” mode. The initial bright fluorescence of CdTe QDs was effectively quenched by sulfur anions (S²⁻). The presence of Zn²⁺ (or Cd²⁺) can “turn-on” the weak fluorescence of QDs quenched by S²⁻ due to the formation of ZnS (or CdS) passivation shell. Under optimal conditions, a good linear relationship between the fluorescence response and concentration of Zn²⁺ (or Cd²⁺) could be obtained in the range from 1.6 to 35 μM (1.3–25 μM for Cd²⁺). The limit of detection (LOD) for Zn²⁺ and Cd²⁺ were found to be 1.2 and 0.5 μM, respectively. Furthermore, the present probe exhibited a high selectivity for Zn²⁺ and Cd²⁺ over other metal ions and was successfully used in the detection of Zn²⁺ or Cd²⁺ in real water samples.     

Electrodeposition of cobalt oxide nanoparticles on carbon nanotubes, and their electrocatalytic properties for nitrite electrooxidation

We describe a modified glassy carbon electrode (GCE) for the sensitive determination of nitrite in waste water samples. The GCE was modified by electrodeposition of cobalt oxide nanoparticles on multi-walled carbon nanotubes (MWCNTs) deposited on a conventional GCE. Scanning electron microscopy and electrochemical techniques were used for the characterization of the composite material which is very uniform and forms a kind of nanoporous structure. Electrochemical experiments showed that the modified electrode exhibited excellent electrocatalytic properties for nitrite. Amperometry revealed a good linear relationship between peak current and nitrate concentration in the 0.5 to 250???M range with a detection limit of 0.3???M (S/N?=?3). The method has been applied to the amperometric detection of nitrite. The modified electrode displays good storage stability, reproducibility, and selectivity for a promising practical application.

Bi2S3 nanomaterials: morphology manipulation and related properties

The Bi(2)S(3) nanomaterials with various morphologies such as nanorods, nanowires, nanowire bundles, urchin-like microspheres and urchin-like microspheres with cavities have been successfully synthesized through a simple hydrothermal method. Experimental results indicate that sulfur sources play crucial roles in determining the morphologies of Bi(2)S(3) products. Moreover, formation mechanisms of different Bi(2)S(3) nanostructures are discussed based on understanding of the growth habit of Bi(2)S(3) crystal. Finally, we also studied the morphologies-dependent electrochemical and optical properties of the as-synthesized Bi(2)S(3) nanomaterials.     

质子化甜菜碱阳离子与双三氟甲磺酰亚胺阴离子相互作用的理论研究

利用密度泛函理论(DFT)方法, 在B3LYP/6-311＋G(d,p)水平下, 对质子化甜菜碱阳离子与双三氟甲磺酰亚胺阴离子形成的气态阴阳离子对([Hbet][Tf₂N])进行理论研究, 通过几何结构优化和频率分析得到势能面上的六个稳定构型. 计算结果表明[Hbet]^＋和[Tf₂N]^－之间能够形成较强的氢键相互作用, 氢键相互作用的稳定化能主要来源于[Tf₂N]^－中O, N原子的孤对电子和[Hbet]^＋中参与形成氢键的O-H, C-H反键轨道之间的相互作用. 自然布局分析(NPA)给出气态[Hbet][Tf₂N]离子对中阴阳离子间的电荷转移比传统离子液体中电荷转移的数值小. AIM (atoms in molecules)分析得到[Hbet]^＋和[Tf₂N]^－之间的氢键相互作用以静电作用为主. 通过实验和理论结果相比较, 初步探讨影响离子液体熔点及其对金属离子选择性溶解的结构因素.     

Inclusion Complexes of Coenzyme Q10 with Polyamine‐Modified β‐Cyclodextrins: Characterization,Solubilization, and Inclusion Mode

The inclusion‐complexation behavior of coenzyme Q10 (CoQ10) with the three polyamine‐modified β‐cyclodextrins (CDs) 1 – 3 was investigated in both solution and the solid state by means of NMR, XRD, and FT‐IR spectroscopy. The results showed that the apparent solubility of CoQ10 increased linearly upon addition of hosts 1 – 3 , giving A_L‐type phase‐solubility curves. These hosts 1 – 3 were able to solubilize CoQ10 to high levels, up to 1.35, 1.52, and 1.44 mg/ml (calculated as CoQ10), respectively. The host 2 with a moderate‐length chain is the most suitable for inclusion complexation of CoQ10. Accroding to the ROESY experiments, the MeO groups of CoQ10 and the tether of 2 can be co‐included into the cavity of β‐CD through the induced‐fit interaction between host and guest. The binding ability of modified β‐CDs 1 – 3 upon complexation with CoQ10 are discussed from the viewpoints of the size/shape‐matching relationship and the induced‐fit concept between host CDs and guest CoQ10 molecule.     

Screening of <Emphasis Type="Italic">Isochrysis</Emphasis> Strains and Utilization of a Two-Stage Outdoor Cultivation Strategy for Algal Biomass and Lipid Production

Isochrysis is a genus of marine algae without cell wall and capable of accumulating lipids. In this study, the lipid production potential of Isochrysis was assessed by comparing 15 Isochrysis strains with respect to their growth rate, lipid production, and fatty acid profiles. Three best strains were selected (lipid productivity, 103.0~121.7 mg L^?1 day^?1) and their lipid-producing capacities were further examined under different controlled parameters, e.g., growth phase, medium nutrient, and light intensity in laboratory cultures. Furthermore, the three Isochrysis strains were monitored in outdoor panel photobioreactors with various initial cell densities and optical paths, and the strain CS177 demonstrated the superior potential for outdoor cultivation. A two-stage semi-continuous strategy for CS177 was subsequently developed, where high productivities of biomass (1.1 g L^?1 day^?1) and lipid (0.35 g L^?1 day^?1) were achieved. This is a comprehensive study to evaluate the lipid-producing capability of Isochrysis strains under both indoor and outdoor conditions. Results of the present work lay a solid foundation for the physiological and biochemical responses of Isochrysis to various conditions, shedding light on the future utilization of this cell wall-lacking marine alga for biofuel production.     

Substituent effects on the redox potentials of dihydroxybenzenes: theoretical and experimental study

The redox reactions of p-hydroquinone and pyrocatechol undergo a two-proton-two-electron process in aqueous solution. We calculated their redox potentials at the B3LYP/6-311+G(d,p) level, and verified the values by employing cyclic voltammetry experiments. Then we selected seven substituent groups (–F, –Cl, –OH, –COOH, –CN, –NH₂, and –NO₂ groups) to systematically investigate the substituent effect, including the sort, position, and number of the substituent, on the redox potentials of p-hydroquinone and pyrocatechol. The calculated results show that –NH₂ and –OH groups can decrease the redox potentials, while –F, –Cl, –COOH, –CN, and –NO₂ groups increase the potential values of p-hydroquinone and pyrocatechol. The calculations can accurately predict the substituent effects on the redox potentials of pyrocatechol and p-hydroquinone. We would expect that the accurate calculation results for the model systems could be applied in the prediction of electrode potentials of other molecules.     

Defect passivation of CsPbI_2Br perovskites through Zn(Ⅱ) doping:toward efficient and stable solar cells

Defect passivation is an important strategy to achieve perovskite solar cells(PVSCs) with enhanced power conversion efficiencies(PCEs) and improved stability because the trap states induced by defects in the interfaces and grain boundaries of perovskites are harmful to both large open circuit voltage and high photocurrent of devices. Here, zinc cations(Zn~(2+)) were used as a dopant to passivate defects of the CsPbI_2Br perovskite leading to Zn~(2+)-doped CsPbI_2Br film with fewer trap states, improved charge transportation, and enhanced light-harvesting ability. Thus, the best-performance PVSC based on CsPbI2 Br with the optimal Zn~(2+)doping shows a higher PCE of 12.16% with a larger open-circuit voltage(V_(OC)) of 1.236 V, an improved shortcircuit current(J_(SC)) of 15.61 mA cm~(-2) in comparison with the control device based on the pure CsPbI_2Br which exhibits a PCE of 10.21% with a V_(OC)of 1.123 V, a J_(SC)of 13.27 mA cm~(-2). Time-resolved photoluminescence results show that the Zn~(2+)doping leads to perovskite film with extended photoluminescence lifetime which means a longer diffusion length and subsequently enhanced photocurrent and open circuit voltage. This work provides a simple strategy to boost the performance of PVSCs through Zn~(2+)doping.     

Effects of deposition of different contents of Ag nanoparticles on thickness and structural,morphological, compositional,optical, and photocatalytic properties of 1D TiO2 nanoarrays

Research on Chemical Intermediates - One-dimensional (1D) TiO2 nanoarrays (NAs) were synthesized by a hydrothermal process, and Ag nanoparticles (NPs) were deposited on the arrays using a...