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Herein, for the first time, research on water-in-oil (water/oil) emulsion droplets by electrochemical analysis has been reported. When the water/1,2-dichloroethane emulsion droplets collided with an ultramicroelectrode (UME), the blocking property of the droplets resulted in a “staircase” current decrease. Each “staircase” current decrease is associated with the collision of an emulsion droplet with the UME surface. The experimental collision frequency was proportional to the concentration of the emulsion droplet. In addition, the size of each water droplet was estimated from the magnitude of the “staircase” current decrease and the simulation data. Results obtained from the collision signals provide information about the size of each single droplet (nano- to micro-) and the pM level concentrations of the water droplets in the organic continuous phase. [ABSTRACT FROM AUTHOR]

In previous studies, PSCs based on polymers with an inward alkyl positioned DTBT unit showed poor power conversion efficiency mainly due to the greatly distorted polymer backbone structure caused by severe steric hindrance between the alkyl groups on the flanking thiophene of DTBT and the BT unit. In this study, PSCs based on polymers with an inward alkyl positioned DTBT unit are markedly improved by controlling the molecular weight and alkyl chain length. Two BDT-DTBTs and one BDT-BT polymers were synthesized by engineering alkylthienyl chains on BDT and by installing these with a short alkyl chain on the inward alkyl positioned DTBT. Extraordinary bathochromic shifts in the absorption maxima at 146 nm for PA and 165 nm for PB were observed going from solution to a solid film state, suggesting great differences in the polymer structures of the two states. Optical and electrochemical measurements were taken, and the HOMO levels of PA , PB , and PC were determined to be −5.76, −5.66, and −5.71 eV, respectively, indicating very low-lying HOMO energy levels. The optimized PSCs based on PA , PB , and PC exhibit power conversion efficiencies (PCEs) of 3.75%, 2.42%, and 2.30%, respectively, with V oc (0.77–0.86 V), J sc (6.9–8.7 mA/cm 2 ), and FF (38–52%). We believe that the highest PCE for the PSCs based on PA may be attributed to the high molecular weight and improved processability relative to those of PB and PC . A theoretical study suggests that the polymer backbones of PA and PB are highly distorted between the donor unit and the acceptor unit, by as much as 49°, possibly by the steric hindrance between BT and the inward positioned methyl group on the flanking thiophene. Therefore, the conjugations for the HOMO p-orbitals of PA and PB are highly localized throughout the backbone while the conjugations for the HOMO p-orbitals of PC are well delocalized. The AFM study revealed that DIO additive greatly changed the morphology of the polymer blend from an amorphous state into distinct nanoscale phase separated states, leading to a great improvement in PCEs. The XRD study revealed that all polymers are amorphous. [ABSTRACT FROM AUTHOR]

Four BDT-TPD polymers ( PA – PD ) were synthesized by modifying the alkylthienyl chains on BDT, placing spacer group between BDT and TPD, and installing extended conjugated side chains on the BDT of the polymer to investigate the correlation between structure and photovoltaic performance for these polymers. The molecular weight of PA – PD polymers ranged from the highest ( Mn = 80 kDa for PA ) to the lowest ( Mn = 7.9 kDa for PD ), and their decomposition temperatures at 5% weight loss were in the range 401–435 °C. PA, PB , and PC showed similar UV–vis absorption spectra; however, PD showed much broader absorption spectrum in the entire UV–vis region, because of the extended conjugated side chains. The HOMO levels of the polymers were −5.72, −5.63, −5.48, and −5.61 eV for PA , PB , PC , and PD , respectively, indicating very low-lying HOMO energy levels. The bandgaps of these polymers were calculated and found to be in the range 1.85–1.88 eV. The theoretical calculations clearly show that the torsional angles between the alkylthienyl group and BDT unit of the simplified dimer correlated to the π-orbital delocalization, suggesting that the HOMO π-electrons of vertically aligned conjugated side chains do not delocalize well in the polymers such as PA , PB , and PC bearing high torsional angles. The optimized weight ratios of the polymer to PC 61 BM were determined to be 1:1, 1:1.5, and 1:1 for PA , PC , and PD , respectively, and the average PCEs of the devices were 5.36%, 4.62%, and 2.74% for PA , PC , and PD, respectively, after optimization with 1,8-diiodooctane (DIO). A relatively small amount of DIO as an additive was necessary to reach the optimal PCEs of the devices, and the device incorporating PC needed only 0.5% DIO to obtain the best PCE. The AFM study reveals that the blend films after adding DIO showed much smooth morphologies, and the blend film of PA exhibited more crystalline property, as shown by the XRD analysis. [ABSTRACT FROM AUTHOR]

Abstract: In this work an electrochemical protein detection based on enzymatic silver deposition has been proposed and applied to the detection of thrombin. The target protein, thrombin, was first captured by thrombin binding thiolated aptamer self-assembled monolayers (SAMs) on the gold electrode surface, and then sandwiched with another biotinylated thrombin binding aptamer for the association of alkaline phosphatase (Av-ALP). The attached Av-ALP enzymatically converts the nonelectroactive substrate p-aminophenyl phosphate (p-APP) to p-aminophenol (p-AP) which can reduce silver ions in solution leading to deposition of the metal onto the electrode surface. Finally, linear sweep voltammetry (LSV) is used to detect the amount of deposited silver. The peak current during the anodic scan was found to reflect the amount of the target protein captured into the sandwich configuration. The proposed approach has been successfully implemented for the detection of thrombin in the range of 0.1nM to 1μM. Therefore, the current work has demonstrated enzymatic silver deposition for detection at aptamer-modified electrode. [Copyright &y& Elsevier]

We report the electrochemical detection of single water droplets in an electrolyte-free organic solvent by collision events using a platinum ultramicroelectrode (Pt-UME). Water droplet emulsions were prepared by the ultrasonication of an organic solvent (e.g., dichloroethane) and an aqueous solution containing hydroquinone (H 2 Q) as the redox species and MgSO 4 as an emulsion stabilizer as well as the supporting electrolyte. Under the appropriate potentials, we could observe single water droplet collision phenomena at the Pt-UME by amperometric current-time (I-t) measurements. Water droplets that established contact with the Pt-UME led to amperometric current spikes due to the instantaneous electrolysis of the constituent redox species. The concentration of H 2 Q in the emulsion was adjusted to confirm that the amperometric spike resulted from the electrochemical reaction in the water droplet. As the concentration of H 2 Q increased, the oxidation peak current increased. The size and contact area of the water droplets were also estimated. Based on these single droplet collision results, we could successfully establish a facile water droplet detection system in an organic solvent without the addition of a hydrophobic organic electrolyte. Image 1 [ABSTRACT FROM AUTHOR]