Temperature‐Independent Hole Mobility of a Smectic Liquid‐Crystalline Semiconductor based on Band‐Like Conduction

A liquid‐crystalline (LC) phenylterthiophene derivative, which exhibited an ordered smectic phase at room temperature, was purified by vacuum sublimation under a flow of nitrogen. During the sublimation process, thin plates with sizes of 1 mm grew on the surface of the vacuum tube. The crystals exhibited the same X‐ray diffraction patterns as the ordered smectic phase of the LC state that was formed through a conventional recrystallization process by using organic solvents. Because of the removal of chemical impurities, the hole mobility in the ordered smectic phase of the vacuum‐grown thin plates increased to 1.2×10^?1 cm² V^?1 s^?1 at room temperature, whereas that of the LC precipitates was 7×10^?2 cm² V^?1 s^?1. The hole mobility in the ordered smectic phase of the vacuum‐sublimated sample was temperature‐independent between 400 and 220 K. The electric‐field dependence of the hole mobility was also very small within this temperature range. The temperature dependence of hole mobility was well‐described by the Hoesterey–Letson model. The hole‐transport characteristics indicate that band‐like conduction affected by the localized states, rather than a charge‐carrier‐hopping mechanism, is a valid mechanism for hole transport in an ordered smectic phase.     

Board‐like Fused‐Thiophene Liquid Crystals and their Benzene Analogs: Facile Synthesis,Self‐Assembly,p‐Type Semiconductivity,and Photoluminescence

Fused‐thiophene discotic liquid crystals were designed and easily synthesized by Suzuki coupling and FeCl₃ oxidized tandem cyclodehydrogenation reactions, including homo‐ and cross‐coupling reactions. The resulting hexagonal and rectangular columnar mesomorphic supramolecular structures formed were characterized by polarizing optical microscopy, differential scanning calorimetry, and small‐angle X‐ray scattering. The charge carrier transport properties in the mesophases of two of the synthesized fused‐thiophene discogens were measured by transient photocurrent time‐of‐flight (TOF) technique, revealing fast hole transport values in the range of 10^?3 to 10^?2 cm² V^?1 s^?1, thus demonstrating potential applications in electronic devices. The luminescent sanidic mesogens, with different extended π‐conjugated systems, also emit blue, green, or red light, with absolute photoluminescent quantum yields as high as 18 %.     

Toward Ultralow‐Bandgap Liquid Crystalline Semiconductors: Use of Triply Fused Metalloporphyrin Trimer–Pentamer as Extra‐large π‐Extended Mesogenic Motifs

In contrast with their dimeric homologue, triply fused zinc porphyrin trimer–pentamer, as extra‐large π‐extended mesogens, assemble into columnar liquid crystals (LCs) when combined with 3,4,5‐tri(dodecyloxy)phenyl side groups ( 3 P_Zn – 5 P_Zn , Figure 1 ). Their LC mesophases develop over a wide temperature range, namely, 41–280 °C (on heating) for 5 P_Zn , and all adopt an oblique columnar geometry, typically seen in columnar LC materials involving strong mesogenic interactions. These LC materials are characterized by their wide light‐absorption windows from the entire visible region up to a near infrared (NIR) region. Such ultralow‐bandgap LC materials are chemically stable and serve as hole transporters, in which 5 P_Zn gives the largest charge carrier mobility (2.4×10^?2 cm V^?1 s^?1) among the series. Despite a big dimensional difference, they coassemble without phase separation, in which the resultant LC materials display essentially no deterioration of the intrinsic conducting properties.     

Structural elucidation of rat biliary metabolites of corynoxeine and their quantification using LC‐MSn

Corynoxeine (COR) is one of 4 bioactive oxindole alkaloids in Uncaria species. In this work two phase I metabolites, namely 11‐hydroxycorynoxeine (M1) and 10‐hydroxycorynoxeine (M2), and two phase II metabolites, namely 11‐hydroxycorynoxeine 11‐O‐β‐d ‐glucuronide (M3) and 10‐hydroxycorynoxeine 10‐O‐β‐d ‐glucuronide (M4), were detected in rat bile after oral dose of COR (0.105 mmol/kg), by optimized high‐performance liquid chromatography–tandem mass spectrometry (LC‐MSⁿ) with electrospray ionization in positive ion mode. Structures of M1–4 were determined by LC‐MSⁿ, nuclear magnetic resonance, circular dichroism and high‐resolution MS spectra. COR and its metabolites in rat bile were quantified by LC‐MSⁿ. The LC‐MSⁿ quantification methods for COR and its metabolites yielded a linearity with coefficient of determination ≥0.995 from 5.0 × 10^?10 to 5.0 × 10^?7 m . The recoveries of stability tests varied from 96.80 to 103.10%. Accuracy ranged from 91.00 to 105.20%. Relative standard deviation for intra‐day and inter‐day assay was <5.0%. After the oral dose 0.14% of COR was detected in rat bile from 0 to 8 h, in which in total 97.8% COR biotransformed into M1–4. M1 and M2 yielded 48.1 and 49.7%, which successively glucuronidated to M3 and M4 at 47.2 and 43.8%, respectively. Copyright © 2014 John Wiley & Sons, Ltd.     

Simultaneous Determination of Dopamine and Ascorbic Acid Using the Nano‐Gold Self‐Assembled Glassy Carbon Electrode

Electrochemical behavior of dopamine (DA) was investigated at the gold nanoparticles self‐assembled glassy carbon electrode (GNP/LC/GCE), which was fabricated by self‐assembling gold nanoparticles on the surface of L ‐cysteine (LC) modified glassy carbon electrode (GCE) via successive cyclic voltammetry (CV). A pair of well‐defined redox peaks of DA on the GNP/LC/GCE was obtained at E_pa=0.197 V and E_pc=0.146 V, respectively. And the peak separation between DA and AA is about 0.2 V, which is enough for simultaneous determination of DA and AA. The peak currents of DA and AA were proportional with their concentrations in the range of 6.0×10^?8–8.5×10^?5 mol L^?1 and 1.0×10^?6–2.5×10^?3 mol L^?1, with the detection limit of 2.0×10^?8 mol L^?1 and 3.0×10^?7 mol L^?1 (S/N=3), respectively. The modified electrode exhibits an excellent reproducibility, sensibility and stability for simultaneous determination of DA and AA in human serum with satisfactory result.     

Simultaneous determination of fifteen multiclass organic pollutants in human saliva and serum by liquid chromatography–tandem ultraviolet/fluorescence detection: A validated method

A quick and inexpensive validated method, based on sample treatment by liquid–liquid microextraction followed by liquid chromatography (LC) coupled with ultraviolet tandem fluorescence detection is proposed for the determination of 15 multiclass pollutants both in serum and in saliva, as a simple and easy to draw matrix. The method was set up and validated according to European guidelines. The compounds of interest include some endocrine‐disrupting chemicals (i.e. bisphenol A, bisphenol B, bisphenol E, bisphenol F, bisphenol AF, bisphenol A diglycidyl ether, bisphenol M, diethylhexyl phthalate, monoethylhexyl phthalate, triclosan and 4‐nonylphenol), as well as other pollutants belonging to the class of volatile organic compounds (2‐chlorophenol, 1,2 dichlorobenzene, 1,2,4,5‐tetrachlorobenzene). The limits of quantifications ranged from 2.28 × 10^?3 μg mL^?1 (bisphenol A diglycidyl ether) to 6.29 μg mL^?1 (diethylhexyl phthalate), while those of detection ranged from 0.068 × 10^?3 μg mL^?1 (bisphenol A diglycidyl ether) to 1.031 μg mL^?1 (diethylhexyl phthalate). To test method suitability, it was applied to real saliva and serum samples of healthy human volunteers and was found to meet the demands of the laboratories handling simple and relatively inexpensive equipment for screening oriented at rapid and reliable contamination assessment of a population.     

Electron Transport of Photoconductive n‐Type Liquid Crystals Based on a Redox‐Active Tetraazanaphthacene Framework

The preparation of two liquid crystals composed of a redox‐active tetraazanaphthacene (TANC) framework is reported. The materials form smectic A (SmA) thin‐film liquid‐crystalline (LC) phases over a wide temperature range. Cyclic voltammetry analysis revealed that LC TANCs behave as organic electron acceptors. The electron mobilities of the thin films were determined by time‐ of‐flight (TOF) measurements, which are the order of 10^?4 cm² V^?1 s^?1 in the SmA LC phase. This value is two orders of magnitude larger than those of amorphous organic semiconductors. To the best of our knowledge, very few reports exist on the electron‐transporting behaviors of LC N‐heteroacene semiconductors.     

Effect of Fullerene Volume Fraction on Two‐Dimensional Crystal‐Constructed Supramolecular Liquid Crystals

The volume fraction plays an important role in phase segregated soft matters. We demonstrate here that at high fullerene volume fraction in soft chain‐tethered‐fullerene dyads, different two‐dimensional (2D) crystal‐constructed smectic‐like lamella liquid crystalline (LC) phases can be formed with triple‐layer (S_T phase) or quadruple‐layer (S_Q phase) stacking of fullerenes in 2D crystals. The combination of 2D crystal and LC properties in one system affords these fullerene dyads controlled electron mobility in the range of 10^?5–10^?3 cm² V^?1 s^?1 at room temperature (S_T phase), by regulating the insulated soft layer thickness between 2D crystals via the manipulation of fullerene volume fraction.     

Novel polymer electrolytes prepared by copolymerization of ionic liquid monomers

Ionic liquid monomer couples were prepared by the neutralization of 1‐vinylimidazole with vinylsulfonic acid or 3‐sulfopropyl acrylate. These ionic liquid monomer couples were viscous liquid at room temperature and showed low glass transition temperature (Tg) at ?83 °C and ?73 °C, respectively. These monomer couples were copolymerized to prepare ion conductive polymer matrix. Thus prepared ionic liquid copolymers had no carrier ions, and they showed very low ionic conductivity of below 10^?9 S cm^?1. Equimolar amount of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) to imidazolium salt unit was then added to generate carrier ions in the ionic liquid copolymers. Poly(vinylimidazolium‐co‐vinylsulfonate) containing equimolar LiTFSI showed the ionic conductivity of 4 × 10^?8 S cm^?1 at 30 °C. Advanced copolymer, poly(vinylimidazolium‐co‐3‐sulfopropyl acrylate) which has flexible spacer between the anionic charge and polymer main chain, showed the ionic conductivity of about 10^?6 S cm^?1 at 30 °C, which is 100 times higher than that of copolymer without spacer. Even an excess amount of LiTFSI was added, the ionic conductivity of the copolymer kept this conductivity. This tendency is completely different from the typical polyether systems. Copyright © 2002 John Wiley & Sons, Ltd.     

Bulk heterojunction solar cells made from carbazole copolymer and fullerene derivative with an inserted layer of discotic material with improved efficiency

Bulk heterojunction photovoltaic cells based on composites of copolymer poly [N-90-hepta-decanyl-2,7-carbazole-alt-5,5-(40,70-di-2-thienyl-20,10,30-benzothiadiazole)] and the fullerene derivative [6,6]-phenyl C71-butyric acid methyl ester with an inserted layer of discotic liquid crystalline material (2, 3, 6, 7, 10, 11-hexabutyloxytriphenylene) between the interface of active layer and hole transporting layer has been reported. Different hole transporting layers deposited on indium tin oxide substrates such as poly (3,4-ethylenedioxythiophene)-poly (styrenesulphonate) or molybdenum trioxide has been used in these devices. All the devices with inserted discotic liquid crystal layer showed better performance than the reference cells. Power conversion efficiency of 5.14% was achieved for these photovoltaic solar cells containing self-organised discotic liquid crystal layer of 30 nm thickness under one sun condition which is substantial jump as compared to earlier reports. The mobility of holes in the discotic liquid crystal inserted devices was found to be of the order of 10^–6 cm² V^–1 s^–1 due to which high values of current density was achieved. The influence of varying the thickness of liquid crystal layer and annealing on the photovoltaic parameters of these devices was also studied.     

Ionic conductivity probed in main chain liquid crystalline azobenzene polyesters

Three main chain thermotropic liquid crystalline (LC) azobenzene polymers were synthesized using the azobenzene twin molecule (P4P) having the structure Phenylazobenzene‐tetraethyleneglycol‐Phenylazobenzene as the AA monomer and diols like diethylene glycol, tetraethylene glycol (TEG), and hexaethylene glycol as the BB comonomer. Terminal ? C(O)OMe units on P4P facilitated transesterification with diols to form polyesters. All polymers exhibited stable smectic mesophases. One of the polymers, Poly(P4PTEG) was chosen to prepare composite polymer electrolytes with LiCF₃SO₃ and ionic conductivity was measured by ac impedance spectroscopy. The polymer/0.3 Li salt complex exhibited a maximum ionic conductivity in the range of 10^?5 S cm^?1 at room temperature (25 °C), which increased to 10^?4 S cm^?1 above 65 °C. The temperature dependence of ionic conductivity was compared with the phase transitions occurring in the sample and it was observed that the glass transition had a higher influence on the ionic conductivity compared to the ordered LC phase. Reversible ionic conductivity switching was observed upon irradiation of the polymer/0.3 Li salt complex with alternate UV and visible irradiation. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 629–641     

Electroanalysis of Benazepril Hydrochloride Antihypertensive Drug Using an Ionic Liquid Crystal Modified Carbon Paste Electrode

Electroanalysis of benazepril HCl was successful using a carbon paste electrode modified with an ionic liquid crystal ( 1‐butyl‐1‐methylpiperidinium hexafluorophosphate) in presence of sodium dodecyl sulfate. The electrode performance was compared to ionic liquids (1‐n‐hexyl‐3‐methyl imidazolium tetrafluoroborate and 1‐butyl‐4‐methyl pyridinium tetrafluoroborate). Electrochemical determination of benazepril HCl was in the linear dynamic range of 8.89×10^?7 to 1.77×10^?5 mol L^?1 (correlation coefficient 0.999) and LOD 7.17×10^?9 mol L^?1. benazepril HCl was determined using this sensor in presence of urine metabolites such as uric acid, ascorbic acid. Binary mixtures of dopamine/benazepril and amlodipine/benazepril were also determined successfully.     

Stepwise optimization approach for improving LC‐MS/MS analysis of zwitterionic antiepileptic drugs with implementation of experimental design

In this article, a step‐by‐step optimization procedure for improving analyte response with implementation of experimental design is described. Zwitterionic antiepileptics, namely vigabatrin, pregabalin and gabapentin, were chosen as model compounds to undergo chloroformate‐mediated derivatization followed by liquid chromatography coupled with tandem mass spectrometry (LC‐MS/MS) analysis. Application of a planned stepwise optimization procedure allowed responses of analytes, expressed as areas and signal‐to‐noise ratios, to be improved, enabling achievement of lower limit of detection values. Results from the current study demonstrate that optimization of parameters such as scan time, geometry of ion source, sheath and auxiliary gas pressure, capillary temperature, collision pressure and mobile phase composition can have a positive impact on sensitivity of LC‐MS/MS methods. Optimization of LC and MS parameters led to a total increment of 53.9%, 83.3% and 95.7% in areas of derivatized vigabatrin, pregabalin and gabapentin, respectively, while for signal‐to‐noise values, an improvement of 140.0%, 93.6% and 124.0% was achieved, compared to autotune settings. After defining the final optimal conditions, a time‐segmented method was validated for the determination of mentioned drugs in plasma. The method proved to be accurate and precise with excellent linearity for the tested concentration range (40.0 ng ml^?1–10.0 × 10³ ng ml^?1). Copyright © 2013 John Wiley & Sons, Ltd.     

Design,synthesis, and self‐assembly manipulating of polymerized ionic liquids contained imidazolium based on “Jacketing” effect

A series of novel polymerized ionic liquids (PILs) contained imidazolium, poly (2,5‐bis{[6‐(1‐butyl‐3′‐imidazolium)hexyl] oxy carbonyl}styrene salts) (denoted as P1? X^?, X^??Br^?, BF₄^?, PF₆^? and TFSI^?) were successfully synthesized via radical polymerization. The chemical structures of the monomers and their corresponding PILs were confirmed by ¹H NMR, ¹³C NMR, and Fourier transform infrared spectroscopy. Thermogravimetric analysis results showed that these PILs had excellent thermal stability. The phase transitions and liquid‐crystalline (LC) behaviors of these polymers were investigated by differential scanning calorimetry, polarized light microscopy (PLM), and wide‐angle X‐ray diffraction. The combined experimental results showed that all the PILs could form hexagonal columnar (?H) LC ordered structures because of the strong interaction between the anions and cations in the side groups except for P1? TFSI^?. The conductivities of monomers and PILs were sketchily investigated, and monomers had higher conductivities than those of conprespoding PILs. For comparison, we have synthesized a polymer without counter‐anion, but similar to the chemical structure of P1? X^?, poly (2, 5‐bis{[6‐(4‐butoxy‐4′‐oxy phenyl) hexyl] oxycarbonyl} styrene) (denoted as P2). In this case, phenyl took place of imidazolium of side chain, and LC ordered structure did not form. The comparison between P1? X^? and P2 suggested that ion played an important role in the constructing of LC ordered structure. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Bulk heterojunction solar cells based on self-assembling disc-shaped liquid crystalline material

In this article, effect of addition of disc-shaped liquid crystalline material, namely 2, 3, 6, 7, 10, 11-hexabutyloxytriphenylene, in poly (3-hexylthiophene): [6, 6]-phenyl-C61-butyric acid methyl ester containing bulk heterojunction (BHJ) solar cells has been investigated. These disc-shaped molecules organise into ordered columnar hexagonal structures through intermolecular π ? π interactions as monitored by polarised light optical microscopy. Current–voltage characteristics of the device prepared with liquid crystal layer exhibited a short-circuit current of 10.5 mA cm^?2 and a fill factor of 35%. The resultant power conversion efficiency (PCE) was 1.54%. The influence of varying the thickness of liquid crystal layer and annealing on these solar cells was also studied. The short circuit current and PCE of 12.9 mA cm^?2 and 2.3% was achieved for these BHJ solar cells containing self-organised discotic liquid crystals in the active layer under one sun condition after annealing.     

Incorporation of liquid crystalline triphenylene derivative in bulk heterojunction solar cell with molybdenum oxide as buffer layer for improved efficiency

We report efficient bulk heterojunction solar cells fabricated by inserting a discotic triphenylene derivative into poly (3-hexylthiophene): [6, 6]- phenyl-C61-butyric acid methyl ester. A layer of molybdenum oxide was inserted between anode and active layer. Power conversion efficiency of 2.0% was achieved for these photovoltaic solar cells containing self-organised discotic liquid crystals in the active layer under one sun condition. The influence of varying the thickness of liquid crystal layer and annealing on these solar cells was also studied. Post annealing the bulk heterojunction devices with discotic liquid crystal layer of thickness 20 nm in them yielded an open circuit voltage of 0.41 V, short circuit current density of 17.0 mA cm^?2, a Fill factor of 0.35 and power conversion efficiency of 2.5%.     

On‐line solid‐phase extraction coupled with liquid chromatography/electrospray ionization mass spectrometry for the determination of trace tributyltin and triphenyltin in water samples

On‐line solid‐phase extraction (SPE) for pre‐concentration and sample cleanup is one strategy to reduce matrix effects and to simultaneously improve detection sensitivity in liquid chromatography/mass spectrometry (LC/MS). This paper describes an on‐line SPE‐LC/MS method for the determination of tributyltin (TBT) and triphenyltin (TPhT) at trace levels in water samples. The direct coupling of an on‐line C₁₈ pre‐column to LC/MS was used to pre‐concentrate TBT and TPhT at trace levels from waters and to remove interfering matrix effects. Pre‐concentration was followed by separation of TBT and TPhT on a C₁₈ column using a mobile phase containing 0.1% (v/v) HCOOH/5 mM HCOONH₄ and methanol. While both electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) can be interfaced with MS for the detection of TBT and TPhT, ESI‐MS was preferred for this application. The calibration curve for the targets was linear in the concentration range 0.1–30 µg L^?1. The detection limit (signal‐to‐noise (S/N) ratio = 3) was 0.02 µg L^?1 when 3.0 mL of sample was enriched on the C₁₈ pre‐column. The recoveries of TBT and TPhT in spiked waters were from 81.0 to 101.9%. The reproducibilities for the analysis of the standard mixture (10 µg L^?1) for TBT and TPhT were 13.1 and 5.0%, respectively. The developed method was an easy and fast way to analyze TBT and TPhT in water samples. Copyright © 2009 John Wiley & Sons, Ltd.     

Determination of polychlorinated biphenyls by liquid chromatography–atmospheric pressure photoionization–mass spectrometry

This study presents the atmospheric pressure photoionization (APPI) of high‐chlorinated (five or more chlorine atoms) polychlorinated biphenyls (PCBs) using toluene as dopant, after liquid chromatographic separation. Mass spectra of PCB 101, 118, 138, 153, 180, 199, 206 and 209 were recorded by using liquid chromatography‐APPI‐tandem mass spectrometry (LC‐APPI‐MS/MS) in negative ion full scan mode. Intense peaks appeared at m/z that correspond to [M ? Cl + O]^? ions, where M is the analyte molecule. Furthermore, a detailed strategy, which includes designs of experiments, for the development and optimization of LC‐APPI‐MS/MS methods is described. Following this strategy, a sensitive and accurate method with low instrumental limits of detection, ranging from 0.29 pg for PCB 209 to 8.3 pg for PCB 101 on column, was developed. For the separation of the analytes, a Waters XSELECT HSS T3 (100 mm × 2.1 mm, 2.5 µm) column was used with methanol/water as elution system. This method was applied for the determination of the above PCBs in water samples (surface water, tap water and treated wastewater). For the extraction of PCBs from water samples, a simple liquid–liquid extraction with dichloromethane was used. Method limits of quantification, ranged from 4.8 ng l^?1, for PCB 199, to 9.4 ng l^?1, for PCB 180, and the recoveries ranged from 73%, for PCB 101, to 96%, for PCB 199. The estimated analytical figures were appropriate for trace analysis of high‐chlorinated PCBs in real samples. Copyright © 2014 John Wiley & Sons, Ltd.     

Speciation and detection of organotins from PVC pipe by micro‐liquid chromatography–electrospray–ion trap mass spectrometry

This paper describes the application of a micro‐liquid chromatography–electrospray–ion trap mass spectrometry (µ‐LC–ES–ITMS) method for separation and detection of organotin compounds leached from potable‐water polyvinyl chloride (PVC) pipe. Dibutyltin (DBT) is added as a heat stabilizer to PVC. DBT was determined in 1 l water samples that had remained static in PVC pipes over several days (totaling 96 h). Other organotin compounds in the leachate were screened for, by using µ‐LC–ES–ITMS. An initial level of approximately 1 µgl^?1 of DBT resulted within 24 h, with a subsequent drop and then a rise in DBT levels over the next 96 h to 0.8 µgl^?1. Published in 2001 by John Wiley & Sons, Ltd.     

Determination of Nitrofuran Residues in Tilapia Tissue by Enzyme‐Linked Immunosorbent Assay and Confirmation by Liquid Chromatography Tandem Mass Spectrometric Detection

Furazolidone is a broad‐spectrum antibiotic that is frequently used in aquaculture on account of its excellent antibacterial properties. In this study, both the enzyme‐linked immunosorbent assay (ELISA) and high‐performance liquid chromatography‐tandem mass spectrometry (LC‐MS/MS) methods were used to analyze the content of residual 3‐amino‐2‐oxazolidinone (AOZ), a metabolite of furazolidone in Tilapia tissue. Homogenized fish samples were spiked with various amounts of AOZ, and following combined acid‐hydrolysis and derivatization of the homogenized tissue with 2‐NBA (2‐nitrobenzaldehyde), sample clean‐up was performed and the derived 2‐nitrophenylmethylene‐3‐amino‐2‐oxazolidinone (NPAOZ) was analyzed. Using the LC‐MS/MS method, a linear correlation between measured concentration Y and spiked concentration × was observed: Y = 0.4518X ? 0.0166, R² = 0.9972. The linear equation for the ELISA method was Y = 0.9322X + 0.5168, R² = 0.9066. These results demonstrated that the ELISA method might overestimate the residual AOZ content at low concentrations. The detection limit and recovery of the known addition were 0.05 μg kg^?1a and 108% for the LC‐MS/MS method and 0.31 μg kg^?1 and 305% for the ELISA method, respectively.