Influence of pyrazole on the photovoltaic performance of dye-sensitized solar cell with polyvinylidene fluoride polymer electrolytes

We investigate the influence of the pyrazole content on the polyvinylidene fluoride (PVDF)/KI/I₂ electrolytes for dye-sensitized solar cells (DSSCs). The solid polymer electrolyte films consisting of different weight percentage ratios (0 20, 30, 40, and 50 %) of pyrazole doped with PVDF/KI/I₂ have been prepared by solution casting technique using N,N-dimethyl formamide (DMF) as a solvent. The as-prepared polymer electrolyte films were characterized by various techniques such as Fourier transform infrared spectroscopy (FT-IR spectroscopy), differential scanning calorimetry (DSC), X-ray diffractometer (XRD), alternate current (AC)-impedance analysis, and scanning electron microscopy (SEM). The 40 wt% pyrazole-PVDF/KI/I₂ electrolyte exhibited the highest ionic conductivity value of 9.52?×?10^?5 Scm^?1 at room temperature. This may be due to the lower crystallinity of PVDF and higher ionic mobility of iodide ions in the electrolyte. The DSSC fabricated using this highest ion conducting electrolyte showed an enhanced power conversion efficiency of 3.30 % under an illumination of 60 mW/cm² than that of pure PVDF/KI/I₂ electrolyte (1.42 %).     

Selective Cosmetic Mercury Analysis Using a Silver Ink Screen‐Printed Electrode with Potassium Iodide Solution

A new method for selective determination of trace mercury has been demonstrated by linear scan voltammetry using silver ink screen printed electrode (AgSPE) in presence of potassium iodide (KI) dissolved 0.05 M H₂SO₄ solution. At AgSPE, iodide oxidation peak current signal found to be systematically decreased (inhibitory current anodic peak current signal, i ) with increase in the Hg concentrations, [Hg]. This observation is further utilized for construction of new Hg electroanalytical assays in this work. On the AgSPE, Hg inhibitory detection potential found at 0 V vs. Ag/AgCl, which is 720 mV lower than that of unmodified SPE system. Under optimal experimental conditions, i signals were linearly increased against [Hg] in the window of 500–4500 ppb (40 μM KI) with a correlation coefficient (r) of 0.9988. The limit of detection (LOD) and limit of quantification (LOQ) were 98 and 318 ppb, respectively. This approach was further utilized to analyze hidden Hg in the cosmetic samples. Real sample assays were consistent with that of result obtained from ICP‐OES, which confirm the applicability of the proposed method for practical applications.     

Existence of a new emitting singlet state of proflavine: femtosecond dynamics of the excited state processes and quantum chemical studies in different solvents

Proflavine (3,6-diaminoacridine) shows fluorescence emission with lifetime, 4.6 ± 0.2 ns, in all the solvents irrespective of the solvent polarity. To understand this unusual photophysical property, investigations were carried out using steady state and time-resolved fluorescence spectroscopy in the pico- and femtosecond time domain. Molecular geometries in the ground and low-lying excited states of proflavine were examined by complete structural optimization using ab initio quantum chemical computations at HF/6-311++G** and CIS/6-311++G** levels. Time dependent density functional theory (TDDFT) calculations were performed to study the excitation energies in the low-lying excited states. The steady state absorption and emission spectral details of proflavine are found to be influenced by solvents. The femtosecond fluorescence decay of the proflavine in all the solvents follows triexponential function with two ultrafast decay components (τ(1) and τ(2)) in addition to the nanosecond component. The ultrafast decay component, τ(1), is attributed to the solvation dynamics of the particular solvent used. The second ultrafast decay component, τ(2), is found to vary from 50 to 215 ps depending upon the solvent. The amplitudes of the ultrafast decay components vary with the wavelength and show time dependent spectral shift in the emission maximum. The observation is interpreted that the time dependent spectral shift is not only due to solvation dynamics but also due to the existence of more than one emitting state of proflavine in the solvent used. Time resolved area normalized emission spectral (TRANES) analysis shows an isoemissive point, indicating the presence of two emitting states in homogeneous solution. Detailed femtosecond fluorescence decay analysis allows us to isolate the two independent emitting components of the close lying singlet states. The CIS and TDDFT calculations also support the existence of the close lying emitting states. The near constant lifetime observed for proflavine in different solvents is suggested to be due to the similar dipole moments of the ground and the evolved emitting singlet state of the dye from the Franck-Condon excited state.     

Reactions of [η-carboxycyclopentadiene][η-tetraphenylcyclo butadiene] cobalt with alkyl and aryl tin oxides: Synthesis, structural studies and electrochemistry of novel monomeric and dimeric [η-carboxycyclopentadiene][η-tetraphenylcyclobutadiene]cobalt based stannoxanes

Reactions of [η⁵-carboxycyclopentadienyl][η⁴-tetraphenylcyclobutadiene] cobalt, Ph₄C₄CoC₅H₄COOH (1), with (Ph₃Sn)₂O, [(n-Bu)₂SnO]_n and (Ph₂SnO)_n in refluxing toluene resulted in the formation of the monomeric compound Ph₃SnOC(O)C₅H₄CoC₄Ph₄ (2) and dimeric compounds n-Bu₂Sn[OC(O)C₅H₄CoC₄Ph₄]₂ (3) and Ph₂Sn[OC(O)C₅H₄CoC₄Ph₄]₂ (4), respectively. Reactions carried out in the solid state by mechanical grinding also yielded same results. Crystal structure determination and cyclic voltammetric studies of compounds 1, 2, 3 and 4 have been carried out and compared with similar ferrocene carboxylic acid derivatives. The structures and electrochemistry of these compounds are compared with analogous organotin ferrocene carboxylates. The results obtained from the reaction of 1 with alkyl and aryl tin oxides suggest that the formation of stannoxanes assemblies having more than two carboxylate units are not favored indicating that 1 is a highly sterically hindered metallocene carboxylic acid.     

A highly stable and sensitive chemically modified screen-printed electrode for sulfide analysis

We report here a highly stable and sensitive chemically modified screen-printed carbon electrode (CMSPE) for sulfide analysis. The CMSPE was prepared by first ion-exchanging ferricyanide into a Tosflex anion-exchange polymer and then sealing with a tetraethyl orthosilicate sol-gel layer. The sol-gel overlayer coating was crucial to stabilize the electron mediator (i.e., Fe(CN)₆³⁻) from leaching. The strong interaction between the oxy-hydroxy functional group of sol-gel and the hydrophilic sites of Tosflex makes the composite highly rigid to trap the ferricyanide mediator. An obvious electrocatalytic sulfide oxidation current signal at ∼0.20 V versus Ag/AgCl in pH 7 phosphate buffer solution was observed at the CMSPE. A linear calibration plot over a wide range of 0.1 μM to 1 mM with a slope of 5.6 nA/μM was obtained by flow injection analysis. The detection limit (S/N = 3) was 8.9 nM (i.e., 25.6 ppt). Practical utility of the system was applied to the determination of sulfide trapped from cigarette smoke and sulfide content in hot spring water.     

Effect of Biochemical Stimulants on Biomass Productivity and Metabolite Content of the Microalga, Chlorella sorokiniana

The influence of 12 biochemical stimulants, namely 2-phenylacetic acid (PAA; 30 ppm), indole-3 butyric acid (IBA; 10 ppm), 1-naphthaleneacetic acid (NAA; 2.5, 5 and 10 ppm ), gibberellic acid (GA3, 10 ppm), zeatin (ZT; 0.002 ppm), thidiazuron (0.22 ppm), humic acid (20 ppm), kelp extract (250 ppm), methanol (500 ppm), ferric chloride (3.2 ppm ), putrescine (0.09 ppm), spermidine (1.5 ppm) were prescreened for their impact on growth and chlorophyll for the green alga—Chlorella sorokiniana. C. sorokiniana responded best to phytohormones in the auxin family, particularly NAA. Thereafter, two studies were conducted on combinations of phytohormones to compare blends from within the auxin family as well as against other families. These treatments were NAA_{5 ppm}+PAA_{30 ppm}, NAA_{2.5 ppm}+PAA_15 ppm, NAA_5 ppm+IBA_10 ppm, NAA_5 ppm+GA3_10 ppm, NAA_5 ppm+ZT_1 ppm, and NAA_5 ppm+GA3_10 ppm+ZT_1 ppm. Combinations of NAA with other auxins did not have synergistic or antagonistic effects on the growth. However, combinations of compounds from different phytohormone families, such as NAA_5 ppm+GA3_10 ppm+ZT_1 ppm, dramatically increased the biomass productivity by 170% over the control followed by the treatments: NAA _5 ppm+GA3_10 ppm (138%), NAA _5 ppm+ZT_1 ppm (136%), and NAA _5 ppm ( 133%). The effect of biochemical stimulants were also measured on metabolites such as chlorophyll, protein, and lipids in C. sorokiniana. Renewed interest in microalgae for biotechnology and biofuel applications may warrant the use of biochemical stimulants for cost reduction in large-scale cultivation through increased biomass productivity.     

Trilinearization and localized coherent structures and periodic solutions for the (2 + 1) dimensional K-dV and NNV equations

In this paper, using a novel approach involving the truncated Laurent expansion in the Painlevé analysis of the (2 + 1) dimensional K-dV equation, we have trilinearized the evolution equation and obtained rather general classes of solutions in terms of arbitrary functions. The highlight of this method is that it allows us to construct generalized periodic structures corresponding to different manifolds in terms of Jacobian elliptic functions, and the exponentially decaying dromions turn out to be special cases of these solutions. We have also constructed multi-elliptic function solutions and multi-dromions and analysed their interactions. The analysis is also extended to the case of generalized Nizhnik–Novikov–Veselov (NNV) equation, which is also trilinearized and general class of solutions obtained.