In this study, magnetic polypyrrole nanowires (mPPYs) were fabricated via a simple co-mixing method based on an "aggregation-wrap" mechanism. The polypyrrole (PPy) nanowires were synthesized by in situ chemical oxidative polymerization using cetyltrimethylammonium bromide as the "soft template" and the magnetic nanoparticles (MNPs) prepared using solvothermal methods. Typically, when these two nanomaterials were vortically mixed in a solvent, the MNPs were wrapped into the PPy nanowire networks that formed during the aggregation process, leading to the formation of mPPYs which can be separated from the solvent rapidly and conveniently by a magnet. Due to the better permeability, good adsorption ability, and magnetic separability of the resultant material, mPPYs were applied for the enrichment of 11 pesticides including organophosphorus, organochlorine, and pyrethroid using magnetic solid phase extraction (MSPE) to test their feasibility in sample preparation. Several parameters affecting the extraction efficiency were investigated, and under the optimized conditions, a simple and effective method for the determination of pesticide residues was established by coupling with gas chromatography/mass spectrometry (GC/MS) analysis. The whole pretreatment process was rapid and can be accomplished within 15 min. The linearity range of the proposed method was 0.2-10 μg/L, with correlation coefficients (R) of 0.995-0.999; the limits of quantification for the target compounds were in the range of 0.09-0.29 μg/L. In addition, an acceptable reproducibility was achieved by evaluating the intra- and inter-day precisions with relative standard deviations of less than 14 and 16 %, respectively. Finally, the established MSPE-GC/MS method was successfully applied for the determination of pesticide residues in beverage teas, juices, and environmental water samples.

A rationally designed graphene-hollow polypyrrole (PPy) nanoarchitecture in which hollow PPy spheres were inserted between graphene layers was constructed by mixing graphene oxide and polystyrene (PS)@PPy core-shell sphere, followed by reduction of graphene oxide and etching of PS. The as-prepared graphene-hollow PPy nanoarchitecture was explored as electrode material for supercapacitor applications. The specific capacitance may gradually rise to as high as 500 F g(-1) with a charging/discharging current density of 5 A g(-1), and remains stable even after 10,000 cycles. Analysis indicates that the tailored nanoarchitecture enhances specific area of the electrode and promotes synergetic effect between RGO and PPy, thus leading to a significantly enhanced electrochemical performance.

The performance of many stretchable electronics, such as energy storage devices and strain sensors, is highly limited by the structural breakdown arising from the stretch imposed. In this article, we focus on a detailed study on materials matching between functional materials and their conductive substrate, as well as enhancement of the tolerance to stretch-induced performance degradation of stretchable supercapacitors, which are essential for the design of a stretchable device. It is revealed that, being widely utilized as the electrode material of the stretchable supercapacitor, metal oxides such as MnO2 nanosheets have serious strain-induced performance degradation due to their rigid structure. In comparison, with conducting polymers like a polypyrrole (PPy) film as the electrochemically active material, the performance of stretchable supercapacitors can be well preserved under strain. Therefore, a smart design is to combine PPy with MnO2 nanosheets to achieve enhanced tolerance to strain-induced performance degradation of MnO2-based supercapacitors, which is realized by fabricating an electrode of PPy-penetrated MnO2 nanosheets. The composite electrodes exhibit a remarkable enhanced tolerance to strain-induced performance degradation with well-preserved performance over 93% under strain. The detailed morphology and electrochemical impedance variations are investigated for the mechanism analyses. Our work presents a systematic investigation on the selection and matching of electrode materials for stretchable supercapacitors to achieve high performance and great tolerance to strain, which may guide the selection of functional materials and their substrate materials for the next-generation of stretchable electronics.

The development of wearable electronics that can monitor human physiological information demands specially structured materials with excellent stretchability and electrical conductivity. In this study, a new stretchable conductive polypyrrole/polyurethane (PPy/PU) elastomer was designed and prepared by surface diffusion and in situ polymerization of PPy inside and on porous PU substrates. The structures allowed the formation of netlike microcracks under stretching. The netlike microcrack structures make possible the reversible changes in the electrical resistance of PPy/PU elastomers under stretching and releasing cycles. The variations in morphology and chemical structures, stretchability, and conductivity as well as the sensitivity of resistance change under stretching cycles were investigated. The mechanism of reversible conductivity of the PPy/PU elastomer was proposed. This property was then used to construct a waistband-like human breath detector. The results demonstrated its potential as a strain sensor for human health care applications by showing reversible resistance changes in the repeated stretching and contracting motion when human breathes in and out.

An ammonia sensor is described in this work. The sensing membrane is a thin layer of oxidized polypyrrole (PPy) on a platinum substrate. This sensor is used as the working electrode in a conventional three-electrode system for amperometric measurement of ammonia in aqueous solutions in the potential range of + 0.2 to + 0.4 V (vs. Ag/AgCl). Contact with ammonia causes a current to flow through the electrode. This current is proportional to the concentration of free ammonia in the solution and ammonium ions do not contribute to the measured signal. The signal is due to reduction of PPy by ammonia with subsequent oxidation of PPy by the external voltage source. The sensor is able to detect ammonia reproducibly at the muM level. The main interference is the doping effect of small anions such as Cl(-) and NO(3)(-), also giving a response on PPy at the mM level. This anionic response can, to a certain degree, be reduced by covering the polymer surface with dodecyl sulfate. The sensor gradually loses its activity when exposed to ammonia concentrations greater than 1 mM. The sensor has been tested by the flow injection analysis technique.

Electronic structure and photophysical properties have been investigated for a new series of fluorinated iridium complexes with the parent [Ir(ppy)2(deeb)](PF6) (deeb is 4,4'-diethylester-2,2'-bipyridine). Time resolved infrared spectroscopy (TRIR) has been used to observe the long-lived triplet excited state of each complex confirming its mixed charge transfer character. Supplementary evidence of charge transfer in the triplet state is provided via emission spectroscopy, transient absorption spectroscopy, and density functional theory (DFT) calculations. Both computational and spectroscopic assignments reveal consistency in the first excitation throughout the series of complexes. Electrochemical measurements meanwhile show that increasing fluorination still induces expected shifting of frontier orbitals. Excited states beyond the lowest lying triplet are probed for the complexes via UV-vis spectroscopy which reveals three distinct features. These features are assigned via time-dependent DFT (TD-DFT) to build a broader understanding of electronic structure.

A fully diarylmethylene-bridged triphenylamine derivative is efficiently synthesized. It has an almost planar triphenylamine (TPA) skeleton and exhibits excellent thermal and morphological stability. Devices with the novel TPA derivative as host material and Ir(ppy)(3) as triplet emitter show a maximum current efficiency of 83.5 cd/A and a maximum power efficiency of 71.4 lm/W for green electrophosphorescence.

BACKGROUND

Although left ventricular assist device (LVAD) management strategies are undertaken to reduce the development of aortic insufficiency (AI), the effect of AI on patient morbidity and mortality is not known.

METHODS

Patients undergoing HeartMate II (Thoratec, Pleasanton, CA) implant were prospectively monitored with serial echocardiograms. Kaplan-Meier methods and log-rank testing were used to estimate and compare mortality and freedom from moderate or worser right ventricular hypokinesis (RVHK), moderate or worse mitral regurgitation (MR), and hemolysis according to AI severity. Mixed modelling was used to examine for correlates of AI development in the pre-operative and post-operative setting and to investigate the effect of AI on post-operative MR and RVHK.

RESULTS

There were 930 echocardiograms completed in 166 patients. During 291 person-years of follow-up, mild-moderate or worse AI developed in 70 (0.38 persons per year [PPY]), moderate or worse AI in 36 (0.17 PPY), moderate-severe AI in 11 (0.039 PPY), and severe AI in 2 (0.0069 PPY). Overall 2-year survival and 2-year survival after onset of moderate or worse AI was 87% ± 6.2% and 65% ± 11%, respectively, compared with 76% ± 5.1% and 76% ± 5.1%, respectively, in those with less AI (p = 0.57). Patients with moderate AI were not more likely to develop MR, hemolysis events, or worsening RVHK, but patients with pre-existing RVHK appeared to be less tolerant of AI. Three of 35 deaths were directly attributed to AI. No reoperations were performed solely for AI.

CONCLUSIONS

AI is common after LVAD implant but did not affect survival in this cohort. Except in those with significant RV dysfunction, this calls into question need for echocardiogram-guided device settings to ensure aortic valve opening.

Five N-methyl-D-aspartate receptor subunit genes and six metabotropic glutamate receptor subtype genes have been assigned to particular rat chromosomes by using a rat x mouse somatic cell hybrid clone panel. N-Methyl-D-aspartate receptor subunit genes (gene symbol, GRIN) GRIN1, GRIN2A, GRIN2B, GRIN2C, and GRIN2D have been assigned to chromosomes (Chr) 3, 10, 4, 10, and 1, respectively. Metabotropic glutamate receptor subtype genes (gene symbol, GRM) GRM1, GRM2, GRM3, GRM4, GRM5, and GRM6 have been assigned to Chr 1, 8, 4, 20, 1, and 10, respectively. In addition, GRIN2A and GRM6 loci were successfully localized on Chr 10 linkage maps by linkage analyses. The genetic distances between loci in cM (+/- SD) are as follows: GRIN2A-28.6(+/- 7.0)-RR24-23.3(+/- 6.4)-MYHSE, from a linkage analysis using the (SHR x WTC)F1 x WTC cross, and RR24-4.2(+/- 2.9)-GRM6-4.2(+/- 2.9)-MMYHSE-2.1(+/- 2.1)-ASGR, SHBG-27.1(+/- 6.4)-PPY, from a linkage analysis using the (ZI x TM)F1 x ZI cross.

BACKGROUND

The Initiation of Insulin to reach A1C Target (INITIATEplus) trial studied the effect of self-titrating biphasic insulin aspart 70/30 (BiAsp 30) twice daily during 24 weeks in insulin-naïve patients with type 2 diabetes who were poorly controlled by oral medication, and originally randomized according to frequency of dietary counseling interventions.

OBJECTIVE

The purpose of this study was to compare the efficacy and tolerability of biphasic insulin aspart 70/30 (BIAsp 30, NovoLog Mix 70/30) in INITIATEplus patients ≤65 versus >65 years old, irrespective of dietary counseling frequency, and to test the hypothesis that self-titrating BIAsp 30 in patients >65 years old could be well-tolerated and effective in this age group.

METHODS

An exploratory post hoc subanalysis, using standard statistical methods, was performed on patients stratified according to age. Data collected from 3492 patients in the intent-to-treat population who were ≤65 years old and 716 patients who were >65 years old compared glycosylated hemoglobin (HbA(1c)) and plasma glucose changes from baseline. Hypoglycemia rates and adverse event (AE) incidence were compared for the tolerability population of 4007 patients ≤65 years old and 805 patients >65 years old.

RESULTS

Baseline-adjusted HbA(1c) changes for patients ≤65 versus >65 years old were -2.38% versus -2.73% (P < 0.0001), with final HbA(1c) achieving 7.55% and 7.06%, respectively. Thirty-nine percent of patients ≤65 years old achieved HbA(1c) ≤7% compared with 51% of patients >65 years old. Baseline-adjusted fasting plasma glucose decreases were greater for the >65 year old population (85.2 vs 91.2 mg/dL; P = 0.004; ≤65 vs >65 years old, respectively). Minor hypoglycemia was reported in 9.7% and 7.7% of patients ≤65 versus >65 years old, respectively (0.52 vs 0.41 episodes per patient per year [ppy]; P = 0.01). Major hypoglycemia occurred in 1.5% and 3.1% of patients (0.05 vs 0.14 episodes ppy, ≤65 vs >65 years old, respectively; P < 0.0001). Nocturnal major hypoglycemia was reported for 0.4% and 0.6% of patients (P = 0.0028), whereas nocturnal minor hypoglycemia was reported for 3.8% and 2.6% (P = 0.007) of patients ≤65 and >65 years old, respectively. AEs were reported for 24% and 28% of patients ≤65 and >65 years old, respectively, serious AEs were reported for 4% and 9% of patients, respectively, and AE-related withdrawals were reported for 1.3% and 2% of patients, respectively.

CONCLUSIONS

Self-titrated biphasic insulin aspart 70/30 was found to be well-tolerated and effective in type 2 diabetes patients >65 years old, as well as in patients ≤65 years old. HbA(1c) and fasting plasma glucose decreases were significantly (P < 0.05) higher for patients >65 years old versus patients ≤65 years old. Tolerability was indicated by major and minor hypoglycemia rates at or below <0.5 episodes ppy in both age groups. Overall rates of AE and serious AEs were higher among patients>> 65 years; withdrawals related to AEs were 2% compared with 1.3% in the younger age group.

Accurate diagnosis of tumor is promising to guide photothermal therapy (PTT) for efficacious tumor ablation with minimal damage to healthy tissues. Here, we report an activatable dual-modal imaging agent, which is based on PEGylated-gadolinium metallofullerene-polypyrrole nanoparticle (PEG-GMF-PPy NP) for imaging-guided PTT. A contrast agent (gadolinium metallofullerene, GMF) with excellent magnetic resonance imaging (MRI) performance and an ultra-pH-responsive polymer (PEG-PC7A) are successively modified to the surface of photothermal agent (PPy NP). The prepared PEG-GMF-PPy NPs show strong absorption in the near-infrared (NIR) region, so they can be utilized for photoacoustic imaging. Furthermore, in a tumor extracellular environment, the PEG-GMF-PPy NPs can achieve pH-enhanced MRI because of the hydrophobic-to-hydrophilic conversion of the PC7A. Upon accurate diagnosis-guided NIR laser irradiation, excellent tumor ablation effect is achieved. The results suggest that the PEG-GMF-PPy NPs are promising agents for activatable imaging-guided PTT.

A lightweight, flexible, and highly efficient energy management strategy is highly desirable for flexible electronic devices to meet a rapidly growing demand. Herein, Ni-Co-S nanosheet array is successfully deposited on graphene foam (Ni-Co-S/GF) by a one-step electrochemical method. The Ni-Co-S/GF composed of Ni-Co-S nanosheet array which is vertically aligned to GF and provides a large interfacial area for redox reactions with optimum interstitials facilitates the ions diffusion. The Ni-Co-S/GF electrodes have high specific capacitance values of 2918 and 2364 F g-1 at current densities of 1 and 20 A g-1, respectively. Using such hierarchical Ni-Co-S/GF as the cathode, a flexible asymmetric supercapacitor (ASC) is further fabricated with polypyrrple(PPy)/GF as the anode. The flexible asymmetric supercapacitors have maximum operation potential window of 1.65 V, and energy densities of 79.3 and 37.7 Wh kg-1 when the power densities are 825.0 and 16100 W kg-1, respectively. It's worth nothing that the ASC cells have robust flexibility with performance well maintained when the devices were bent to different angles from 180° to 15° at a duration of 5 min. The efficient electrochemical deposition method of Ni-Co-S with a preferred orientation of nanosheet arrays is applicable for the flexible energy storage devices.

We report phosphorescent sensitized fluorescent near-infrared (NIR) light-emitting electrochemical cells (LECs) utilizing a phosphorescent cationic transition metal complex [Ir(ppy)(2)(dasb)](+)(PF(6)(-)) (where ppy is 2-phenylpyridine and dasb is 4,5-diaza-9,9'-spirobifluorene) as the host and two fluorescent ionic NIR emitting dyes 3,3'-diethyl-2,2'-oxathiacarbocyanine iodide (DOTCI) and 3,3'-diethylthiatricarbocyanine iodide (DTTCI) as the guests. Photoluminescence measurements show that the host-guest films containing low guest concentrations effectively quench host emission due to efficient host-guest energy transfer. Electroluminescence (EL) measurements reveal that the EL spectra of the NIR LECs doped with DOTCI and DTTCI center at ca. 730 and 810 nm, respectively. Moreover, the DOTCI and DTTCI doped NIR LECs achieve peak EQE (power efficiency) up to 0.80% (5.65 mW W(-1)) and 1.24% (7.84 mW W(-1)), respectively. The device efficiencies achieved are among the highest reported for NIR LECs and thus confirm that phosphorescent sensitized fluorescence is useful for achieving efficient NIR LECs.

Vapour phase polymerisation (VPP) is a well established technique in which the monomer is introduced to an oxidant-coated substrate in vapour form. Polymerisation then takes place at the oxidant vapour interface. VPP is a technique that could be used to immobilise materials to the modified electrode surface. This review article concentrates on the VPP of conducting polymers such as Polypyrrole (PPy) polythiophen (PT) and polyaniline (PANi). VPP of conducting polymers and other non-conducting polymers have extensively been investigated. This review article is divided into three main parts as given in Table of contents related to the VPP process of some important conducting polymers such as PPy, PT, PANi and Poly(3,4-ethylenedioxythiophene). A total of 181 references are cited in this review article and it attempts to look into VPP from inception of the method till present day.

The relatively unexplored luminophore architecture [Ir(N^N^N)(C^N)L](+) (N^N^N = tridentate polypyridyl ligand, C^N = 2-phenylpyridine derivative, and L = monodentate anionic ligand) offers the stability of tridentate polypyridyl coordination along with the tunability of three independently variable ligands. Here, a new family of these luminophores has been prepared based on the previously reported compound [Ir(tpy)(ppy)Cl](+) (tpy = 2,2':6',2″-terpyridine and ppy = 2-phenylpyridine). Complexes are obtained as single stereoisomers, and ligand geometry is unambiguously assigned via X-ray crystallography. Electrochemical analysis of the materials reveals facile HOMO modulation through ppy functionalization and alteration of the monodentate ligand's field strength. Emission reflects similar modulation shifting from orange to greenish-blue upon replacement of chloride with cyanide. Many of the new compounds exhibit impressive room temperature phosphorescence with lifetimes near 3 μs and quantum yields reaching 28.6%. Application of the new luminophores as photosensitizers for photocatalytic hydrogen generation reveals that their photostability in coordinating solvent is enhanced as compared to popular [Ir(ppy)2(bpy)](+) (bpy = 2,2'-bipyridine) photosensitizers. Yet, the binding of their monodentate ligand emerges as a source of instability during the redox processes of cyclic voltammetry and mass spectrometry. DFT modeling of electronic structure is provided for all compounds to elucidate experimental properties.

This work presents a novel bienzymatic biosensor for the simultaneous determination of nitrite (NO2(-)) and nitrate (NO3(-)) ions using copper, zinc superoxide dismutase (SOD1) and nitrate reductase (NaR) coimmobilized on carbon nanotubes (CNT)-polypyrrole (PPy) nanocomposite modified platinum electrode. Morphological changes of the PPy and CNT modified electrodes were investigated using scanning electron microscopy. The electrochemical behavior of the bienzymatic electrode (NaR-SOD1-CNT-PPy-Pt) was characterized by cyclic voltammetry exhibiting quasi-reversible redox peak at +0.06 V and reversible redox peaks at -0.76 and -0.62V vs. Ag/AgCl, for the immobilized SOD1 and NaR respectively. The electrocatalytic activity of SOD1 towards NO2(-) oxidation observed at +0.8 V was linear from 100 nM to 1mM with a detection limit of 50 nM and sensitivity of 98.5 ± 1.7 nA µM(-1)cm(-2). Similarly, the coimmobilized NaR showed its electrocatalytic activity towards NO3(-) reduction at -0.76 V exhibiting linear response from 500 nM to 10mM NO3(-) with a detection limit of 200 nM and sensitivity of 84.5 ± 1.56 nA µM(-1)cm(-2). Further, the present bienzymatic biosensor coated with cellulose acetate membrane for the removal of non-specific proteins was used for the sensitive and selective determinations of NO2(-) and NO3(-) present in human plasma, whole blood and saliva samples.

In this work, an organic-inorganic hybrid optical upconverter that can convert irradiated 980 nm IR light to 510 nm green phosphorescence sensitively was fabricated and studied. fac-Tris(2-phenylpyridine) iridium (Ir(ppy)3) doped 4,4'-bis(N-carbazolyl)-1,1'-biphenyl (CBP) was used as emitting layer in the phosphorescent organic light-emitting diode (OLED) unit. The upconverter using a phosphorescent OLED as display unit can achieve a higher upconversion efficiency and a low power consumption when compared with the one using fluorescent. An upconversion efficiency of 4.8% can be achieved for phosphorescent device at 15 V, much higher than that of fluorescent one (2.0%). The upconverter's transient optical and electric response to IR pulse were also investigated for the first time. The response time was found to be influenced by IR intensity and applied voltage. It has a response time as short as 60 μs. The rapid response property of the upconverter makes it feasible to be applied to high-speed IR imaging systems.

Three iridium(III) polypyridyl complexes [Ir(ppy)₂(PYTA)](PF₆) (1) (ppy = 2-phenylpyridine), [Ir(bzq)₂(PYTA)](PF₆) (2) (bzq = benzo[h]quinolone) and [Ir(piq)₂(PYTA)](PF₆) (3) (piq = 1-phenylisoquinoline, PYTA = 2,4-diamino-6-(2'-pyridyl)-1,3,5-triazine) were synthesized and characterized by elemental analysis, IR, ¹H NMR and ¹³C NMR. The cytotoxic activity of the complexes toward cancer SGC-7901, Eca-109, A549, HeLa, HepG2, BEL-7402 and normal LO2 cell lines was investigated by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method. Complex 3 shows the most effective on inhibiting the above cell growth among these complexes. The complexes locate at the lysosomes and mitochondria. AO/EB, Annex V and PI and comet assays indicate that the complexes can induce apoptosis in SGC-7901 cells. Intracellular ROS and mitochondrial membrane potential were examined under fluorescence microscopy. The results demonstrate that the complexes increase the intracellular ROS levels and induce a decrease in the mitochondrial membrane potential. The complexes can enhance intracellular Ca²⁺ concentration and cause a release of cytochrome c. The autophagy was studied using MDC staining and western blot. Complexes 1-3 can effectively inhibit the cell invasion with a concentration-dependent manner. Additionally, the complexes target tubules and inhibit the polymerization of tubules. The antimicrobial activity of the complexes against S. aureus, E. coli, Salmonella and L. monocytogenes was explored. The mechanism shows that the complexes induce apoptosis in SGC-7901 cells through ROS-mediated lysosomal-mitochondrial, targeting tubules and damage DNA pathways. Three iridium(III) complexes [Ir(N-C)₂(PYTA)](PF₆) (N-C = ppy, 1; bzq, 2; piq, 3) were synthesized and characterized. The anticancer activity of the complexes against SGC-7901 cells was studied by apoptosis, comet assay, autophagy, ROS, mitochondrial membrane potential, intracellular Ca²⁺ levels, release of cytochrome c, tubules and western blot analysis. The antibacterial activity in vitro was also assayed.

A variety of cell types respond to electrical stimuli; accordingly, many conducting polymers (CPs) have been used as tissue engineering (TE) scaffolds, and one such CP is polypyrrole (PPy). PPy is a well-studied biomaterial with potential TE applications because of its electrical conductivity and many other beneficial properties. Combining its characteristics with an elastomeric material, such as polyurethane (PU), may yield a hybrid scaffold with electrical activity and significant mechanical resilience. Pyrrole was in situ polymerized within a PU emulsion mixture in weight ratios of 1:100, 1:20, 1:10, and 1:5, respectively. Morphology, electrical conductivity, mechanical properties, and cytocompatibility with C2C12 myoblast cells were characterized. The polymerization resulted in a composite with a principle base of PU interspersed with an electrically percolating network of PPy nanoparticles. As the mass ratio of PPy to PU increased so did electrical conductivity of the composites. In addition, as the mass ratio of PPy to PU increased, stiffness of the composite increased while maximum elongation length decreased. Ultimate tensile strength was reduced by ~47% across all samples with the addition of PPy to the PU base. Cytocompatibility assay data indicated no significant cytotoxic effect from the composites. Static cellular seeding of C2C12 cells and subsequent differentiation showed myotube formation on the composite materials.

Zinc oxide nanoparticles (ZnO-NPs) were synthesized from zinc nitrate by simple and efficient method in aqueous media at 55°C without any requirement of calcinations step. A mixture of ZnO-NPs and pyrrole was eletropolymerized on Pt electrode to form a ZnO-NPs-polypyrrole (PPy) composite film. Xanthine oxidase (XOD) was immobilized onto this nanocomposite film through physiosorption. The ZnO-NPs/polypyrrole/Pt electrode was characterized by Fourier transform infrared (FTIR), cyclic voltammetry (CV), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electrochemical impedance spectroscopy (EIS) before and after immobilization of XOD. The XOD/ZnO-NPs-PPy/Pt electrode as working electrode, Ag/AgCl as reference electrode and Pt wire as auxiliary electrode were connected through a potentiostat to construct a xanthine biosensor. The biosensor exhibited optimum response within 5s at pH 7.0, 35°C and linearity from 0.8 μM to 40 μM for xanthine with a detection limit 0.8 μM (S/E=3). Michaelis Menten constant (K(m)) for xanthine oxidase was 13.51 μM and I(max) 0.071 μA. The biosensor measured xanthine in fish meat and lost 40% of its initial activity after its 200 uses over 100 days, when stored at 4°C.

Reaction of the precursor complex Ir2(ppy)4Cl2 (ppy = 2-phenylpyridine) with the bridging ligand 3,8-dipyridyl-4,7-phenanthroline (L) affords, in 94% yield, the cyclometalated iridium dinuclear complex [(ppy)2Ir(mu-L)Ir(ppy)2]2+ (12+) as a mixture of three stereoisomers. This mixture consists of a meso form Delta,Lambda and a racemic form (enantiomeric pair Delta,Delta and Lambda,Lambda) in the ratio 1:1.5. Single-crystal X-ray characterization of the perchlorate salt of the meso form reveals (i) the distortion of the bridging ligand from the planarity and (ii) the location of the two iridium subunits above and below the medium plane of the bridging ligand. Ion-pair chromatography with Delta-TRISPHAT anion (TRISPHAT = tris(tetrachlorobenzenediolato)phosphate(V)) as resolving anion permits the separation of the three stereoisomers. The 1H NMR spectroscopic analysis of each fraction indicates high diastereomeric purity. Electronic circular dichroism properties and comparison with literature data establish their absolute configuration. The absorption and emission properties of the three stereoisomers show only very small variations. The anisotropic properties can be interpreted as distinct interactions of the isomers with the chiral resolving Delta-TRISPHAT anion.

In conjugated polymer devices that switch from one oxidation level to another, such as artificial muscles, it is important to understand memory effects that stem from conformational relaxation movements of the polymer chains. Chronoamperometry during electrochemical switching of polypyrrole doped with dodecylbenzenesulfonate, PPy(DBS), is used to gain insight into the conformational relaxation processes in cation-transporting materials. During oxidation, the current decays exponentially with a time constant that decreases with the anodic voltage. During reduction, there is again an exponentially decaying current with a time constant that decreases with the cathodic voltage, but superimposed on that is a small current peak that increases in size with the voltage. This peak accounts for a maximum of approximately 20% of the total reduction charge, which is approximately the same amount of charge that is in the most cathodic pair of peaks in the cyclic voltammogram. The position of this peak depends logarithmically on the applied cathodic potential (shifting to shorter times with larger Eca) as well as on the anodic potential that was applied just prior to the reduction step (shifting to longer times with Ean). Furthermore, the shoulder position depends logarithmically on the time that the prior anodic voltage was held (shifting to longer times with twait). These results are consistent with the electrochemically stimulated conformational relaxation (ESCR) model.

An iridium(III)-containing phosphorescent chemosensor Ir(ppy)(2)(L)(PF(6)) (1, ppy = 2-phenylpyridine) containing a 2,2'-bipyridyl ligand (L) functionalized with an alpha,beta-unsaturated ketone for selective detection of thiol was synthesized and characterized by spectroscopic and photophysical measurements. The structure of complex 1 was determined by X-ray crystallography. In order to get an insight into 1,4-addition reactions of thiol to complex 1, the adduct 2 from reaction of 1 with benzenethiol was successfully prepared and characterized. Complex 1 shows a lowest energy absorption at ca. 450 nm, primarily ascribable to an intraligand charge transfer (ILCT) transition from the HOMO (pi) resident on the fragment -C(O)C(6)H(4)N(C(2)H(5))(2) to the LUMO (pi*) localized on the 2,2'-bipyridyl moiety in the functionalized 2,2'-bipyridyl ligand as suggested from DFT computational studies. Complex 1 is weakly emissive at ca. 587 nm at ambient temperature, arising likely from the (3)ILCT excited state. Upon addition of thiol to a semi-aqueous solution of complex 1, the lowest energy absorption is obviously blue-shifted and the emission is remarkably enhanced due probably to a conversion from the primary ILCT state to the predominant [pi(ppy)->>pi*(L)] LLCT and the [5d(Ir)->>pi*(L)] MLCT state caused by the formation of the 1-thiol adduct. The sensing properties of 1 to thiol were also investigated by ESI-MS spectrometry and (1)H NMR spectroscopy.