Investigation on compositional effect of PEG:BaTiO<Subscript>3</Subscript> in plasticized PVC–LiBETi polymer composite electrolytes

The blend-based polymer electrolyte comprising poly(vinyl chloride) (PVC) and poly(ethylene glycol) (PEG) as host polymer and lithium bis(perfluoroethanesulfonyl)imide as complexing salt have been prepared. Ethylene carbonate and dimethyl carbonate (50:50 v/v) are used as plasticizer for the system. The barium titanate is used as a filler, and the ratio of (PEG:BaTiO₃) is varied to study its effect on the conductivity behavior of the electrolyte. XRD and ac impedance studies are carried out on the prepared samples. The ac impedance measurements show that the conductivity of the prepared samples depends on the (PEG:BaTiO₃) ratio, and its value is higher for (15:5) wt.% of (PEG:BaTiO₃)-incorporated film. The temperature dependence of the conductivity of the polymer films obeys VTF relation. The role of ferroelectric filler in enhancing the conductivity is studied. The thermal stability of the film is ascertained from TG/DTA studies. The phase morphological study reveals that the porous nature of the polymer electrolyte membranes depends on the (PEG:BaTiO₃) ratio.     

Direct electrochemistry of glucose oxidase and sensing glucose using a screen-printed carbon electrode modified with graphite nanosheets and zinc oxide nanoparticles

We have studied the direct electrochemistry of glucose oxidase (GOx) immobilized on electrochemically fabricated graphite nanosheets (GNs) and zinc oxide nanoparticles (ZnO) that were deposited on a screen printed carbon electrode (SPCE). The GNs/ZnO composite was characterized by using scanning electron microscopy and elemental analysis. The GOx immobilized on the modified electrode shows a well-defined redox couple at a formal potential of ?0.4 V. The enhanced direct electrochemistry of GOx (compared to electrodes without ZnO or without GNs) indicates a fast electron transfer at this kind of electrode, with a heterogeneous electron transfer rate constant (K_s) of 3.75 s^?1. The fast electron transfer is attributed to the high conductivity and large edge plane defects of GNs and good conductivity of ZnO-NPs. The modified electrode displays a linear response to glucose in concentrations from 0.3 to 4.5 mM, and the sensitivity is 30.07 μA mM^?1 cm^?2. The sensor exhibits a high selectivity, good repeatability and reproducibility, and long term stability. Figure

Graphical representation for the fabrication of GNs/ZnO composite modified SPCE and the immobilization of GOx     

Optical phase-conjugation in erioglaucine dye-doped thin film

Optical phase-conjugation (OPC) has been demonstrated in erioglaucine (acid blue 9) dye-doped gelatin films via continuous-wave degenerate four-wave mixing (DFWM) using a low-power He-Ne laser at 633 nm. DFWM and holographic processes are found to contribute to the observed phase-conjugate signal. A maximum phase-conjugate beam reflectivity of about 0.24% has been observed in these dye-doped gelatin films.     

Enhanced photovoltaic characterization and charge transport of TIO2 nanoparticles/nanotubes composite photoanode based on indigo carmine dye-sensitized solar cells

Dye-sensitized solar cells (DSSCs) have established themselves as an alternative to conventional solar cells owing to their remarkably high power conversion efficiency, longtime stability and low-cost production. DSSCs composed of a dyed oxide semiconductor photoanode, a redox electrolyte and a counter electrode. In these devices, conversion efficiency is achieved by ultra-fast injection of an electron from a photo excited dye into the conduction band of metal oxide followed by subsequent dye regeneration and holes transportation to the counter electrode. The energy conversion efficiency of DSSC is to be dependent on the morphology and structure of the dye adsorbed metal oxide photoanode. Worldwide considerable efforts of DSSCs have been invested in morphology control of photoanode film, synthesis of stable optical sensitizers and improved ionic conductivity electrolytes. In the present investigation, a new composite nano structured photoanodes were prepared using TiO₂ nano tubes (TNTs) with TiO₂ nano particles (TNPs). TNPs were synthesized by sol–gel method and TNTs were prepared through an alkali hydrothermal transformation. Working photoanodes were prepared using five pastes of TNTs concentrations of 0, 10, 50, 90, and 100 % with TNPs. The DSSCs were fabricated using Indigo carmine dye as photo sensitizer and PMII (1-propyl-3-methylimmidazolium iodide) ionic liquid as electrolyte. The counter electrode was prepared using Copper sulfide. The structure and morphology of TNPs and TNTs were characterized by X-ray diffraction and electron microscopes (TEM and SEM). The photocurrent efficiency is measured using a solar simulator (100 mW/cm²). The prepared composite TNTs/TNPs photoanode could significantly improve the efficiency of dye-sensitized solar cells owing to its synergic effects, i.e. effective dye adsorption mainly originated from TiO₂ nanoparticles and rapid electron transport in one-dimensional TiO₂ nanotubes. The results of the present investigation suggested that the DSSC based on 10 % TNTs/TNPs showed better photovoltaic performance than cell made pure TiO₂ nanoparticles. The highest energy-conversion efficiency of 2.80 % is achieved by composite TNTs (10 %)/TNPs film, which is 68 % higher than that pure TNPs film and far larger than that formed by bare TNTs film (94 %). The charge transport and charge recombination behaviors of DSSCs were investigated by electrochemical impedance spectra and the results showed that composite TNTs/TNPs film-based cell possessed the lowest transfer resistances and the longest electron lifetime. Hence, it could be concluded that the composite TNTs/TNPs photoanodes facilitate the charge transport and enhancing the efficiencies of DSSCs.     

基于双金属高核钛氧簇基电极的高性能超级电容器的制备

制备了一系列专为超级电容器设计的新型钛氧簇(TOCs,包括Zn-Ti₁₁和Cd-Ti₁₁),扩大了TOCs材料的潜在应用范围。此类材料具有的优异赝电容性能充分展示了钛基材料的优点。所制备的TOCs基超级电容器的最大功率密度为9.5 W·kg^-1,能量密度为463 Wh·kg^-1。     

Green biosynthesis of silver nanoparticles and nanomolar detection of p-nitrophenol

Green biosynthesis of nanoparticles and their applications in sensor field is of great interest to the researchers. We report herein a simple green approach for the synthesis of silver nanoparticles (Ag-NPs) using Acacia nilotica Willd twig bark and its application for the detection of 4-nitro phenol (4-NP). The synthesized Ag-NPs were characterized by Transmission electron microscopy, X-ray diffraction and elemental analysis. The size of synthesized Ag-NPs was in the range of 10–50 nm. The Ag-NPs modified electrode shows a high sensitivity and selectivity towards the sensing of 4-NP. The fabricated modified electrode shows a low detection limit of 15 nM on the wider linear response range from 100 nM to 350 μM with the sensitivity of 2.58?±?0.05 μAμM^?1 cm^?2. In addition, the fabricated sensor shows good repeatability and reproducibility.

Efficient oxidation of hydrazine using amine-functionalized cobalt and nickel porphyrin-modified electrodes

The meso-tetra(para-aminophenyl) porphyrinatocobalt(II) (Co(II)MTpAP) and meso-tetra(para-aminophenyl)porphyrinatonickel(II) (Ni(II)MTpAP) were self-assembled on a glassy carbon electrode (GCE) and were utilized for the oxidation of hydrazine. The oxidation of hydrazine at the self-assembled monolayers (SAMs) of Co(II)MTpAP and Ni(II)MTpAP occurred at ?0.20 and 0.42 V, respectively. When compared to the SAM of Ni(II)MTpAP, Co(II)MTpAP SAM not only decreased the overpotential of hydrazine oxidation but also enormously increased its current. The oxidation of hydrazine was influenced by pH. While increasing the pH, the oxidation potential of hydrazine was shifted towards a less positive potential. Further, an inverted shape cyclic voltammogram (CV) was observed for the oxidation of hydrazine at Co(II)MTpAP-modified GCE, whereas a normal CV curve was observed at Ni(II)MTpAP-modified GCE. The appearance of the inverted shape peak for hydrazine oxidation at the SAM of Co(II)MTpAP is due to the oxidation of axially ligated hydrazine molecules during the reverse potential scan. The hydrazine oxidation was also performed at amine-functionalized cobalt and nickel phthalocyanine-modified electrodes in order to study the influence of a macrocyclic ring. Irrespective of the macrocyclic ring, an inverted shape CV was observed at cobalt phthalocyanine-modified electrode.     

Interaction of rac-[Ru(5,6-dmp)3]2+ with DNA: enantiospecific DNA binding and ligand-promoted exciton coupling

The X-ray crystal structure of the complex rac-[Ru(5,6-dmp)(3)]Cl(2) (5,6-dmp = 5,6-dimethyl-1,10-phenanthroline) reveals a distorted octahedral coordination geometry with the Ru-N bond distances shorter than in its phen analogue. Absorption spectral titrations with CT DNA reveal that rac-[Ru(5,6-dmp)(3)](2+) interacts (K(b), (8.0 +/- 0.2) x 10(4) M(-1)) much more strongly than its phen analogue. The emission intensity of the 5,6-dmp complex is dramatically enhanced on binding to DNA, which is higher than that of the phen analogue. Also, interestingly, time-resolved emission measurements on the DNA-bound complex shows biexponential decay of the excited states with the lifetimes of short- and long-lived components being higher than those for the phen analogue. The CD spectral studies of rac-[Ru(5,6-dmp)(3)](2+) bound to CT DNA provide a definite and elegant evidence for the enantiospecific interaction of the complex with B-form DNA. Competitive DNA binding studies using rac-[Ru(phen)(3)](2+) provide support for the strong binding of the complex with DNA. The Delta-enantiomer of rac-[Ru(5,6-dmp)(3)](2+) binds specifically to the right-handed B-form of poly d(GC)(12) at lower ionic strength (0.05 M NaCl), and the Lambda-enantiomer binds specifically to the left-handed Z-form of poly d(GC)(12) generated by treating the B-form with 5 M NaCl. The strong electronic coupling of the DNA-bound complex with the unbound complex facilitates the change in its enantiospecificity upon changing the conformation of DNA. The (1)H NMR spectra of rac-[Ru(5,6-dmp)(3)](2+) bound to poly d(GC)(12) reveal that the complex closely interacts most possibly in the major grooves of DNA. Electrochemical studies using ITO electrode show that the 5,6-dmp complex stabilizes CT DNA from electrocatalytic oxidation of its guanine base more than the phen analogue does.     

Lithium ion transport in PVC/PEG 2000 blend polymer electrolytes complexed with LiX (X=ClO 4? , BF 4? , and CF3SO 3? )

This paper describes preparation and characterization of polyvinyl chloride and polyethylene glycol 2000 blend polymer electrolytes with LiX (X=ClO₄⁻, BF₄⁻, and CF₃SO₃⁻) salt by solution casting technique. Ethylene carbonate and propylene carbonate mixture was used as the plasticizers. LiClO₄-based electrolytes exhibited better ionic conduction behavior than other salts. The thermal profiles ascertain the stability of the membranes up to 120°C by differential scanning calorimetry. Complexation and crystallinity were studied through X-ray diffraction measurements. Phase morphological study reveals the porous nature of the polymer electrolyte membranes.