As representative two-dimensional (2D) materials, layered double hydroxides (LDHs) have received increasing attention in electrochemical energy storage and conversion because of the facile tunability between their composition and morphology. The high dispersion of active species in layered arrays, the simple exfoliation into monolayer nanosheets and chemical modification offer the LDHs an opportunity as active electrode materials in electrochemical capacitors (ECs). LDHs are favourable in providing large specific surface areas, good transport features as well as attractive physicochemical properties. In this review, our purpose is to provide a detailed summary of recent developments in the synthesis and electrochemical performance of the LDHs. Their composites with carbon (carbon quantum dots, carbon black, carbon nanotubes/nanofibers, graphene/graphene oxides), metals (nickel, platinum, silver), metal oxides (TiO2, Co3O4, CuO, MnO2, Fe3O4), metal sulfides/phosphides (CoS, NiCo2S4, NiP), MOFs (MOF derivatives) and polymers (PEDOT:PSS, PPy (polypyrrole), P(NIPAM-co-SPMA) and PET) are also discussed in this review. The relationship between structures and electrochemical properties as well as the associated charge-storage mechanisms is discussed. Moreover, challenges and prospects of the LDHs for high-performance ECs are presented. This review sheds light on the sustainable development of ECs with LDH based electrode materials.

Nitrite (NO2-) supplementation limits hypoxia-induced oxidative stress and activates the alternate NO pathway which may partially account for the nitrite-mediated cardioprotection. So, sensitive and selective biosensors with point-of-care devices need to be explored to detect the physiological nitrite level due to its important role in human pathophysiology. In this work, cytochrome c reductase (CcR) biofunctionalized self assembled monolayer (SAM) functionalized on gold nanoparticles (GNPs) in polypyrrole (PPy) nanocomposite onto the screen printed carbon electrode (SPCE) was investigated as a biosensor for the detection of nitrite based on its electrochemical and catalytic properties. CcR was covalently coupled with SAM layers on GNPs by using EDC and NHS. Direct electrochemical response of CcR biofunctionalized electrodes showed a couple of well-defined and nearly reversible cyclic voltammetric peaks at -0.34 and -0.45 vs. Ag/AgCl. Under optimal conditions, the biosensor could be used for the determination of NO2- with a linear range from 0.1-1600µm and a detection limit of 60nM with a sensitivity of 0.172µAµM-1cm-2. Further, we have designed and developed a novel and cost effective portable electrochemical analyzer for the measurement of NO2- in hypoxia induced H9c2 cardiac cells using ARM microcontroller. The results obtained here using the developed portable electrochemical nitrite analyzer were also compared with the standard cyclic voltammetry instrument and found in agreement with each other.

A novel polypyrrole (PPy) and graphene quantum dots (GQDs) @ Prussian Blue (PB) nanocomposite has been grafted on a graphite felt (GF) substrate (PPy/GQDs@PB/GF), and has been proven to be an efficient electrochemical sensor for the determination of l-cysteine (l-cys). GQDs, which were fabricated by carbonization of citric acid and adsorbed on GF surface ultrasonically, played an important role for promoting the synthesis process of PB via a spontaneous redox reaction between Fe(3+) and [Fe(CN)6](3-). The PPy film has been electro-polymerized to improve the electrochemical stability of the PPy/GQDs@PB/GF electrode. The as-prepared electrode was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), infrared spectroscopy (IR), X-ray diffraction (XRD) and electrochemical methods. It exhibited an excellent activity for the electrocatalytic oxidation of l-cys, with a detection sensitivity equal to 0.41 Amol(-1) L for a concentration range of 0.2-50 μmolL(-1), and equal to 0.15 Amol(-1) L for a concentration range of 50-1000 μmolL(-1). A low detection limit of 0.15 μmolL(-1), as well as a remarkable long-time stability and a negligible sensitivity to interfering analytes, were also ascertained.

We synthesized cysteine-functionalized graphene oxide (sGO) using carbonyldiimidazole as a cross-linker via amide and carbamate linkages. The sGO/polypyrrole (PPy) nanocomposite film was grown on the working electrode surface of a screen-printed electrode (SPE) via controlled one-step electrochemical deposition. The sGO/PPy-SPE was used to detect lead ions (Pb(2+)) in water by first depositing Pb(2+) on the working electrode surface for 10 min at -1.2 V, and then anodic stripping by differential pulse voltammetry (DPV). The DPV signals were linear in the ranges of 1.4-28 ppb (R(2) = 0.994), 28-280 ppb (R(2) = 0.997), and 280-14 000 ppb (R(2) = 0.990) Pb(2+). The measurable detection limit of the sensor is 0.07 ppb (S/N = 3), which is more than 2 orders of magnitude below the 10 ppb threshold for drinking water set by the World Health Organization. The average removal efficiency of Pb(2+) deposited on the electrode was 99.2% (S/N = 3), with relative standard deviation (RSD) of 3.8%. Our results indicate good affinity of sGO/PPy nanocomposite to Pb(2+), which can be used to effectively adsorb and remove Pb(2+) in water samples. Therefore, sGO/PPy nanocomposite we synthesized is useful for highly sensitive on-site and real-time monitoring of heavy metal ions and water treatment.

A new sensor has been developed by a simple electrodeposition of multi-walled carbon nanotubes (MWCNT), polypyrrole (PPy) and colloidal silver nanoparticles on the platinum (Pt) electrode surface. The Pt/MWCNT/PPy/AgNPs electrode was applied to the detection of serotonin in plasmatic serum samples using differential pulse voltammetry (DPV). The synergistic effect of MWCNT/PPy/AgNPs nanohybrid formed yielded a LOD of 0.15 μmol L(-1) (26.4 μg L(-1)). Reproducibility and repeatability values of 2.2% and 1.7%, respectively, were obtained compared to the conventional procedure. The proposed electrode can be an effective material to be used in biological analysis.

We report the functionalization of polypyrrole (PPy) with a "sticky" biomolecule dopamine (DA), which mimics the essential component of mussel adhesive protein. PPy is one of the most promising electrically conductive polymers with good biocompatibility. The research findings reveal that the DA functionalization enhances the dispersibility and stability of PPy in water and its film adhesion to substrate surface significantly. The electrical conductivity of PPy increases to a maximum value and then decreases with the increasing DA concentration. An optimal DA to pyrrole (Py) mole ratio is found to be between 0.1 and 0.2, at which both conductivity and adhesion of DA-functionalized PPy has been improved.

A manganese oxide (MnO(2)) nanosheet film, hybridized with a conducting polymer polypyrrole (PPy), was prepared through the direct reaction of a carbon cloth with potassium permanganate (KMnO(4)) and through the subsequent chemical polymerization; this type of prepared nanosheet has been used as an electrode for symmetric supercapacitors. The influence of the reaction time in the KMnO(4) solution on the capacitive property of the MnO(2) film was systematically investigated. Further experimentation revealed that the PPy with the high electrical conductivity had promoted the charge transfer in the MnO(2) nanofilm and had played an important role in enhancing the electrode performance (∼45.6 mF cm(-2)). An areal capacitance of 25.9 mF cm(-2) and an excellent rate performance (∼50.08% of the initial capacitance when the scan rate increases 100 times from 2.5 to 250 mV s(-1)) can be achieved for an aqueous symmetric supercapacitor that is assembled from the MnO(2)-PPy nanofilm. In particular, an operating voltage of 1.2 V can be delivered by choosing an appropriate electrolyte; this voltage level is much larger than that of traditional aqueous symmetric supercapacitors (≤1.0 V) and contributes to a high energy density (∼3.5 μWh cm(-2)). Under such a high output voltage, the device can still maintain ∼86.21% of the initial capacitance, even after 2000 cycles.

Polypyrrole (PPy) is a biocompatible, electrically conductive polymer that has great potential for battery, sensor, and neural implant applications. Its amorphous structure and insolubility, however, limit the experimental techniques available to study its structure and properties at the atomic level. Previous theoretical studies of PPy in bulk are also scarce. Using ab initio calculations, we have constructed a molecular mechanics force field of chloride-doped PPy (PPyCl) and undoped PPy. This model has been designed to integrate into the OPLS force field, and parameters are available for the Gromacs and TINKER software packages. Molecular dynamics (MD) simulations of bulk PPy and PPyCl have been performed using this force field, and the effects of chain packing and electrostatic scaling on the bulk polymer density have been investigated. The density of flotation of PPyCl films has been measured experimentally. Amorphous X-ray diffraction of PPyCl was obtained and correlated with atomic structures sampled from MD simulations. The force field reported here is foundational for bridging the gap between experimental measurements and theoretical calculations for PPy based materials.

Polypurine/polypyrimidine (pPu/pPy) tracts, which exist in the promoter regions of many growth-related genes, have been proposed to be very dynamic in their conformation. In this chapter, we describe a detailed protocol for DNase I and S1 nuclease footprinting experiments with supercoiled plasmid DNA containing the promoter regions to probe whether there are conformational transitions to B-type DNA, melted DNA, and G-quadruplex structures within this tract. This is demonstrated with the proximal promoter region of the human vascular endothelial growth factor (VEGF) gene, which also contains multiple binding sites for Sp1 and Egr-1 transcription factors.

The crown ether-linked iridium(III) complex [Ir(ppy)2 (di-aza-phen)]+ (1) {ppy = 2-phenylpyridine and di-aza-phen = 4,7-di(1,4-dioxa-7,13-dithia-10-azacyclopenta-dec-10-yl)-1,10-phenanthroline (7)} has been prepared. Compound 1 exhibits a notable luminescence enhancement in the presence of Ag+ in aqueous media. The analogous ruthenium(II) complex [Ru(phen)2(di-aza-phen)]2+ (4) {phen = 1,10-phenanthroline}, although equally exhibiting a luminescence enhancement in the presence of Ag+, is a far inferior sensor for Ag+ than 1. The 10 times higher luminescence enhancement (I - I0)/I0 of 1 was attributed to a dominance of the emission involving the di-aza-phen ligand that is responsible for binding to the metal ion. In contrast, the 3MLCT emission of 4 does not involve the di-aza-phen ligand but does involve the phen ligand, thus only allowing for a remote effect upon addition of Ag+ ions. While 1 is a highly selective chemosensor for Ag+ in the presence of many metal ions, there is a strong interference of Hg2+ that may restrict its practical use.

The electrochemical incorporation of a sulfonated cobalt phthalocyanine (sCoPc) in conducting polypyrrole (PPy) was done, in the presence or absence of LiClO4, in order to use the resulting hybrid material for the sensing of ammonia. After electrochemical deposition, the morphological features and structural properties of polypyrrole/phthalocyanine hybrid films were investigated and compared to those of polypyrrole films. A gas sensor consisting in platinum microelectrodes arrays was fabricated using silicon microtechnologies, and the polypyrrole and polypyrrole/phthalocyanine films were electrochemically deposited on the platinum microelectrodes arrays of this gas sensor. When exposed to ammonia, polymer-based gas sensors exhibited a decrease in conductance due to the electron exchange between ammonia and sensitive polymer-based layer. The characteristics of the gas sensors (response time, response amplitude, reversibility) were studied for ammonia concentrations varying from 1 ppm to 100 ppm. Polypyrrole/phthalocyanine films exhibited a high sensitivity and low detection limit to ammonia as well as a fast and reproducible response at room temperature. The response to ammonia exposition of polypyrrole films was found to be strongly enhanced thanks to the incorporation of the phthalocyanine in the polypyrrole matrix.

In recent years, magnetic hyperthermia nanoparticles have drawn great attention for cancer therapy because they have no limitation of tissue penetration during the therapy process. In this study, cubic nanoporous Fe2O3 nanoparticles derived from cubic Prussian blue nanoparticles were used as magnetic cores to generate heat by alternating the current magnetic field (AMF) for killing cancer cells. In addition, polypyrrole (PPy) was coated on the surfaces of the cubic Fe2O3 nanoparticles to load doxorubicin hydrochloride (DOX). The PEG component was then physically adsorbed onto the surfaces of the nanoparticles, resulting in a Fe2O3@PPy-DOX-PEG nanocomposite. The nanocomposite was triggered by acid stimulus and AMF to release DOX, resulting in a remarkable combination therapeutic effect via chemotherapy and magnetic hyperthermia. Furthermore, the nanocomposite could realize magnetic resonance imaging (MRI) due to the magnetic core structure. The study provides an alternative for the development of new nanocomposites for combination cancer therapy with MR imaging in vivo.

Novel phosphorescent hydrogels have been explored by immobilizing an Ir(III) metal complex into the matrices of hydrogels. FTIR spectra demonstrate that the Ir(III) -PNaAMPS hydrogel is achieved by irreversible incorporation of positively charged [Ir(ppy)(2)(dmbpy)]Cl (ppy = 2-phenylpyrine, dmbpy = 4,4'-dimethyl-2,2'-bipyridine) into negatively charged poly(2-acrylamido-2-methylpropane sulfonic acid sodium) (PNaAMPS) hydrogel via electrostatic interaction. The photoluminescent spectra indicate that the Ir(III)-PNaAMPS hydrogel exhibits stable phosphorescence. In vitro cultivation of human retinal pigment epithelial cells demonstrates the cytocompatibility of the Ir(III)-PNaAMPS hydrogel. This work herein represents a facile pathway for fabrication of phosphorescent hydrogels.

Hollow polypyrrole (PPy) nanospheres with high sodium storage capacity as cathode materials for Na-ion batteries were reported. PPy hollow nanospheres demonstrated high current rate capacity and good cyclability. It was revealed by electrochemical testing and DFT calculation that the as-prepared PPy hollow nanospheres participate in reversible doping/de-doping reactions.

A novel catalyst, Co-PPy-TsOH/C, for oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs) was prepared by pyrolyzing cobalt salt and p-toluenesulfonic acid (TsOH)-doped polypyrrole-modified carbon support in an inert atmosphere. The characteristics and electrocatalytic activities of Co-PPy-TsOH/C were analyzed with various techniques, including Raman spectroscopy, elemental analysis, rotating ring disk electrode analysis, and a single H(2)-O(2) PEMFC, and compared with those of undoped catalyst Co-PPy/C. The results showed that doping TsOH introduces larger N and S contents in Co-PPy-TsOH/C, leading to much better electrocatalytic performance for ORR than Co-PPy/C, and that Co-PPy-TsOH/C is more likely to follow a four-electron-transfer reaction to reduce oxygen directly to H(2)O. The performance of PEMFCs with Co-PPy-TsOH/C as cathode catalyst is better than that with Co-PPy/C, and the resulting maximum output power density of 203 mW cm(-2) is a substantial improvement over the best values reported in the literature with Co-PPy/C-based cathode catalyst. This implies that doping TsOH is a valuable method to improve the catalytic activity of Co-PPy/C and that Co-PPy-TsOH/C is a promising cathode catalyst for PEMFCs. The function and mechanism of doping have also been analyzed and the configurations of PPy-TsOH/C and Co-PPy-TsOH/C proposed.

A simple and sensitive method for the determination of polar pesticides in water and wine samples was developed by coupling automated in-tube solid-phase microextraction (SPME) to high-performance liquid chromatography-electrospray ionization mass spectrometry (HPLC-ESI-MS). To achieve optimum performance, the conditions for both the in-tube SPME and the ESI-MS detection were investigated. In-tube SPME conditions were optimized by selecting the appropriate extraction parameters, especially the stationary phases used for SPME. For the compounds studied, a custom-made polypyrrole (PPY)-coated capillary showed superior extraction efficiency as compared to several commercial capillaries tested, and therefore, it was selected for in-tube SPME. The influence of the ethanol content on the performance of in-tube SPME was also investigated. It was found that the amount of pesticides extracted decreased with the increase of ethanol content in the solutions. The ESI-MS detection conditions were optimized as follows: nebulizer gas, N2 (30 p.s.i.; 1 p.s.i.=6894.76 Pa); drying gas, N2 (10 l/min, 350 degrees C); capillary voltage, 4500 V; ionization mode, positive; mass scan range, 50-350 amu; fragmentor voltage, variable depending on the ions selected. Due to the high extraction efficiency of the PPY coating and the high sensitive mass detection, the detection limits (S/N = 3) of this method for the compounds studied are in the range of 0.01 to 1.2 ng/ml, which are more than one order of magnitude lower than those of the previous in-tube SPME-HPLC-UV method. A linear relationship was obtained for each analyte in the concentration range of 0.5 to 200 ng/ml with MS detection. This method was applied to the analysis of phenylurea and carbamate pesticides in spiked water and wine samples.

Recent research has speculated that the risk of developing atherosclerosis is due to the accumulation of the effects of daily diet choices. The purpose of this study was to examine which of our previously identified preclinical disease risk biomarkers were further elevated when consuming a high-fat (644±50 kcal; 100% recommended dietary allowance for fat), high-calorie (1118±100 kcal; 70% daily caloric needs) breakfast on consecutive days. Young, normal weight females (N=7) participated in this study.

Blood samples were taken premeal and hourly for 5-h postprandial. Serum biomarkers (C-peptide, eotaxin, gastric inhibitory polypeptide, granulocyte colony-stimulating factor (G-CSF), granulocyte-monocyte colony-stimulating factor (GM-CSF), insulin, leptin, monocyte chemoattractant protein 1, pancreatic polypeptide (PPY) and tumor necrosis factor-α), monocyte concentration, and adhesion molecule expression (CD11a, CD18 and CD54) were measured. Area under the curve was calculated for each outcome variable as a function of day and data were analyzed for significance.

We found significant (P<0.05) increases on Day 2 for: GM-CSF (+47%; P=0.041), G-CSF (+31%; P=0.012), PPY (+51%; P=0.049), total monocyte (+110%; P=0.043), pro-inflammatory (PI) monocyte (+60%; P=0.012), PI monocyte CD18 (+960%; P=0.003), PI monocyte CD11a (+230%; P=0.006), and PI monocyte CD54 (+208%; P=0.015).

To our knowledge, the present study is the first to report changes in selected biomarkers and monocytes following eating a high-fat, high-calorie breakfast on consecutive days in humans. More research is needed to determine how transient the observed changes are and what the long-term implications for disease risk are.

We present a methodology for production and application of electrospun hybrid materials containing commercial polyester (poly (butylene adipate-co-terephthalate; PBAT), and a conductive polymer (polypyrrole; PPy) as scaffold for neuronal growth and differentiation. The physical-chemical properties of the scaffolds and optimization of the electrospinning parameters are presented. The electrospun scaffolds are biocompatible and allow proper adhesion and spread of mesenchymal stem cells (MSCs). Fibers produced with PBAT with or without PPy were used as scaffold for Neuro2a mouse neuroblastoma cells adhesion and differentiation. Neuro2a adhered to PBAT and PBAT/PPyPPyPPy can support neuronal differentiation.

A fiber optic salivary cortisol sensor using a contemporary approach of lossy mode resonance and molecular imprinting of nanocomposites of zinc oxide (ZnO) and polypyrrole (PPY) is structured and depicted for the concentration range of 0-10-6g/ml of cortisol prepared in artificial saliva. Components of polymer preparation and the nanocomposite of polymer with ZnO are optimized for realizing the molecular imprinted layer of the sensor. Nanocomposite having 20% of ZnO in PPY is found to give highest sensitivity of the sensor. The sensor reports the best limit of detection ever reported with better stability, repeatability and response time. Lossy mode resonance based salivary cortisol sensor using nanocomposite molecular imprinted layer reported first time boosts the specificity of the sensor. The implementation of sensor over optical fiber adds up other advantages such as real time and online monitoring along with remote sensing abilities which makes the sensor usable for nonintrusive clinical applications.

Nanoscale metal-organic layers (nMOLs) are an emerging class of 2D crystalline materials formed by reducing the dimensionality of nanoscale metal-organic frameworks (nMOFs). nMOLs hold significant potential in biomedical applications by combining the structural and compositional tunability of nMOFs and anisotropic properties of 2D nanomaterials. Here we report two novel nMOLs, Hf12-Ir and Hf6-Ir, based on Hf12 and Hf6 secondary building units (SBUs) and photosensitizing Ir(bpy)[dF(CF3)ppy]2+ derived ligands [bpy = 2,2'-bipyridine; dF(CF3)ppy = 2-(2,4-difluorophenyl)-5-(trifluoromethyl)pyridine] for radiotherapy (RT) and radiodynamic therapy (RDT). Upon X-ray irradiation, the Hf12 or Hf6 SBUs in the nMOLs efficiently absorb X-rays to enhance RT by producing hydroxyl radicals and to elicit RDT through the excitation of Ir(bpy)[dF(CF3)ppy]2+ derived ligands to generate singlet oxygen and superoxide anions. Hf12-Ir and Hf6-Ir promoted effective cell instant death through RDT and cell reproductive death through RT to elicit superb anticancer efficacy, resulting in >99% tumor regression at low X-ray doses of 0.5 × 5 Gy.

Conducting (or π-conjugated) polymers are promising materials for preparing supramolecular nano-structures and nanocomposites. We report controlled nanostructure syntheses of polypyrrole (PPy) and poylaniline (PANi) via electropolymerization (i.e., in-situ electrochemical anodic oxidation). The density, shape, caliber and thickness of self-assembled PPy micro-containers are regulated by electrochemical potential window for H2 bubbles and number of cyclic voltammetric (potentiodynamic) scans. Likewise, we employed amperometry, chronopotentiometry and potentiodynamic modes using hydrochloric acid as oxidizing agent to prepare PANi nanoparticles and nanotubules. We present our findings from the viewpoint of molecular electrochemistry with growth kinetic aspects yielding mechanistic details (initially forming dimers and oligomers as nucleating agents followed by polymer growth). Also targeted is forming nanocomposites with functionalized single- and multi-walled carbon nanotubes (FSWCNTs and FMWCNTs) as reinforced agent to optimize structural and functional properties. All of these novel nanomaterials are characterized using a range of complementary techniques to establish microscopic structure-property-function relationship.

A nonenzymatic electrochemical sensor is described for the prostate cancer biomarker sarcosine (Sar). Riboflavin was employed to mimic the active center of the enzyme sarcosine oxidase for constructing the biomimetic sensor. The use of riboflavon (Rf) avoids the disadvantages of an enzymatic sensor, such as high cost and poor stability. A glassy carbon electrode (GCE) was modified with a graphene-chitosan (GR) composite and further modified with gold-platinum bimetallic nanoparticles in a polypyrrole (PPy) matrix in order to enhance the catalytic activity of the enzyme mimic. Finally, Rf was electrodeposited on the surface of the AuPt-PPy/GR-modified GCE. Under optimized conditions, the GCE provided high sensitivity and selectivity for Sar at around 0.61 V. Response covers the 2.5-600 μM concentration range, and the detection limit is 0.68 μM. The method was successfully applied to the determination of Sar in spiked urine with 98.0%-103.2% recovery. Graphical abstract Schematic presentation of the fabrication of the Rf/AuPt-PPy/GR/GCE surface and the measurement principle by differential pulse voltammetry (DPV).

Irradiation of a mixture of enamines and α-bromo ketones, with a catalytic amount of Ir(ppy)3 by visible light (λ = 450 nm), enables the production of various 2,5-diaryl-substituted pyrroles in good to excellent yields. The key intermediates in this reaction have been identified as alkyl radicals, generated from single-electron transfer from the photoexcited Ir(ppy)3* to α-bromo ketones, which subsequently react with a broad range of enamines to undergo the Hantzsch reaction rapidly at ambient conditions.

Herein, polypyrrole-based porous carbon (PPC) was prepared by ZnCl₂ activation for toluene adsorption from paraffin liquid. The structure properties were adjusted by a dosage of activating agents and carbonization temperature. The result with a 3:1 mass ratio of ZnCl₂/PPy at 600 °C showed the highest micropore area and percentage of micropore volume of 1105 m²/g and 86.26%, respectively. In addition, the PPC surface was rich in functional groups and obtained a high N-doped content from 7.00 to 8.82%. The toluene adsorption behavior onto the PPC was comprehensively investigated including isotherms, kinetics, and thermodynamics. The adsorption isotherm accorded with the Freundlich model well, and the kinetic model was fitted more closely to the pseudo-second-order chemisorption. The thermodynamic research uncovered that the adsorption was spontaneous and an endothermic process in essence. The ZnCl₂ activation mechanism is discussed based on TG/TGA curves and pore structure analysis at last. The devised way of synthesized microporous carbon is green and simple, which is suited to mass production for the adsorption of toluene from paraffin liquid and reducing environmental pollution.