Plasmon‐Enhanced Polymer Photovoltaic Device Performance Using Different Patterned Ag/PVP Electrospun Nanofibers

Significant enhancement of P3HT (poly(3‐hexylthiophene)):PC₆₁BM ([6,6]‐phenyl C61‐butyric acid methyl ester) photovoltaic devices using different patterns of electrospun Ag/PVP composite nanofibers, including nonwoven, aligned, and crossed patterns, is reported. The composite electrospun nanofibers are prepared using in situ reduction of silver (Ag) nanoparticles in Ag/poly(vinyl pyrrolidone) (PVP) via a two‐fluid coaxial electrospinning technique. The composition, crystalline orientation, and particle size of Ag are manipulated by controlling the core/shell solution concentration. The smallest diameter of the composite nanofibers leads to the highest orientation of the Ag nanoparticles and results in the largest conductivity due to geometric confinement. Such composite nanofibers exhibit the surface plasmon resonance (SPR) effect, which provides near field enhancement of electromagnetic field around active layer. Additionally, composite nanofibers with the crossed or nonwoven patterns further enhance high carrier mobility, compared to that of the aligned pattern. It leads to the 18.7% enhancement of the power conversion efficiency of photovoltaic cell compared to the parent device. The results indicate that the high conductivity and SPR effect of the Ag/PVP electrospun nanofibers can significantly improve the photocurrent and PCE, leading to promising organic solar cell applications.     

π-Bonded alkene and arene complexes of silver(I): an electrospray mass spectrometric study

Electrospray mass spectra have been observed for a number of alkene and arene complexes of Ag(I) formed by the interaction of AgNO₃ and the organometallic ligand in water/methanol solution. The ES mass spectra show that almost all the alkene and arene ligands in stoichiometric excess form labile 1:2 cationic complexes with Ag(I) which are easily decomposed by collisional activation to the 1:1 species. However, with a deficiency of organic ligand polymeric species are observed. The cation [Ag(cod)₂]⁺ (cod=1,5-cyclooctadiene) was reacted with a variety of other potential ligands, such as PPh₃, AsPh₃, PhSCH₂SPh etc. In most cases, mixed complexes [Ag(cod)(ligand)]⁺ were observed, and excess ligand usually produced [Ag(ligand)₂]⁺.     

An amperometric immunosensor for osteoproteogerin based on gold nanoparticles deposited conducting polymer

An amperometric immunosensor was fabricated for the detection of osteoproteogerin (OPG) by covalently immobilizing a monoclonal OPG antibody (anti-OPG) onto the gold nanoparticles (AuNPs) deposited functionalized conducting polymer (5,2′:5′,2″-terthiophene-3′-carboxylic acid). AuNPs were electrochemically deposited onto the conducting polymer using cyclic voltammetry. The particle size of deposited AuNPs was controlled by varying the scan rate and was characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The immobilization of anti-OPG was also confirmed using XPS. The principle of immunosensor was based on a competitive immunoassay between free-OPG and labeled-OPG for the active sites of anti-OPG. HRP was used as a label that electrochemically catalyzes the H₂O₂ reduction. The catalytic reduction was monitored amperometrically at −0.4 V vs. Ag/AgCl. The immunosensor showed a linear range between 2.5 and 25 pg/ml and the detection limit was determined to be 2 pg/ml. The proposed immunosensor was successfully applied for real human samples to detect OPG.     

The role of ultraviolet radiation, photosensitizers, reactive oxygen species and ester groups in mechanisms of methane formation from pectin

Ultraviolet (UV) radiation has recently been demonstrated to drive an aerobic production of methane (CH₄) from plant tissues and pectins, as do agents that generate reactive oxygen species (ROS) in vivo independently of UV. As the major building-blocks of pectin do not absorb solar UV found at the earth's surface (i.e. >280 nm), we explored the hypothesis that UV radiation affects pectin indirectly via generation of ROS which themselves release CH₄ from pectin. Decreasing the UV absorbance of commercial pectin by ethanol washing diminished UV-dependent CH₄ production, and this was restored by the addition of the UV photosensitizer tryptophan. Certain ROS scavengers [mannitol, a hydroxyl radical (^•OH) scavenger; 1,4-diazabicyclo[2.2.2] octane; and iodide] strongly inhibited UV-induced CH₄ production from dry pectin. Furthermore, pectin solutions emitted CH₄ in darkness upon the addition of ^•OH, but not superoxide or H₂O₂. Model carbohydrates reacted similarly if they possessed —CH₃ groups [e.g. methyl esters or (more weakly) acetyl esters but not rhamnose]. We conclude that UV evokes CH₄ production from pectic methyl groups by interacting with UV photosensitizers to generate ^•OH. We suggest that diverse processes generating ^•OH could contribute to CH₄ emissions independently of UV irradiation, and that environmental stresses and constitutive physiological processes generating ROS require careful evaluation in studies of CH₄ formation from foliage.     

AgNO3逆转的黄芩组培玻璃化苗的活性成分含量及其生物活性研究

研究AgNO3对黄芩组培玻璃化苗的逆转作用,并在此基础上对逆转的黄芩组培玻璃化苗的活性成分含量及活性进行分析。结果表明,AgNO3对黄芩的玻璃化苗具有明显的逆转作用,且这种逆转作用受AgNO3浓度的影响。在AgNO3的浓度为4 mg·L^-1时,玻璃化苗的逆转率最高为88%,且逆转的黄芩苗的生长状态最好。在此基础上,对逆转1个月的黄芩玻璃化苗的活性成分含量及生物活性进行研究。逆转的黄芩玻璃化苗体内黄芩苷的含量为68.6 mg·g^-1,明显高于玻璃化苗(38.3 mg·g^-1),但低于正常的组培苗(108.2 mg·g^-1)。此外,提取物的抗氧化、抗菌和抗肿瘤实验结果显示,逆转的黄芩玻璃化组培苗明显好于玻璃化苗,但仍低于正常的组培苗。以上研究结果表明,AgNO3对黄芩组培玻璃化苗具有较好的逆转及恢复作用。     

Study of the interaction of artemisinin with bovine serum albumin

The study on the interaction of artemisinin with bovine serum albumin (BSA) has been undertaken at three temperatures, 289, 296 and 303 K and investigated the effect of common ions and UV C (253.7 nm) irradiation on the binding of artemisinin with BSA. The binding mode, the binding constant and the protein structure changes in the presence of artemisinin in aqueous solution at pH 7.40 have been evaluated using fluorescence, UV–vis and Fourier transform infrared (FT-IR) spectroscopy. The quenching constant K_q, K_sv and the association constant K were calculated according to Stern–Volmer equation based on the quenching of the fluorescence of BSA. The thermodynamic parameters, the enthalpy (ΔH) and the entropy change (ΔS) were estimated to be −3.625 kJ mol⁻¹ and 107.419 J mol⁻¹ K⁻¹ using the van’t Hoff equation. The displacement experiment shows that artemisinin can bind to the subdomain IIA. The distance between the tryptophan residues in BSA and artemisinin bound to site I was estimated to be 2.22 nm using Föster's equation on the basis of fluorescence energy transfer. The decreased binding constant in the presence of enough common ions and UV C exposure, indicates that common ions and UV C irradiation have effect on artemisinin binding to BSA.     

Electrospinning of Cross-Linked Magnetic Chitosan Nanofibers for Protein Release

A poly(vinylalcohol) (PVA) electrospun/magnetic/chitosan nanocomposite fibrous cross-linked network was fabricated using in situ cross-linking electrospinning technique and used for bovine serum albumin (BSA) loading and release applications. Sodium tripolyphosphate (TPP) and glutaraldehyde (GA) were used as cross-linkers which modified magnetic-Fe₃O₄ chitosan as Fe₃O_4/CS/TPP and Fe₃O_4/CS/GA, respectively. BSA was used as a model protein drugs which was encapsulated to form Fe₃O₄/CS/TPP/BSA and Fe₃O₄/CS/GA/BSA nanoparticles. The composites were electrospun with PVA to form nanofibers. Nanofibers were characterized by field emission scanning electron microscopy (FESEM) and Fourier transform infrared spectroscopy (FTIR). The characterization results suggest that Fe₃O₄ nanoparticles with average size of 45 nm were successfully bound on the surface of chitosan. The cross-linked nanofibers were found to contain uniformly dispersed Fe₃O₄ nanoparticles. The size and morphology of the nanofibers network was controlled by varying the cross-linker type. FTIR data show that these two polymers have intermolecular interactions. The sample with TPP cross-linker showed an enhancement of the controlled release properties of BSA during 30-h experimental investigation.

Graphical Abstract

Open in a separate windowᅟKEY WORDS: cross-linker, electrospun, magnetite, mano-composite, protein loading     

Influence of Plasmonic Silver Nanoparticles on Fluorescence Quenching of 1,4-dihydroxy-3-methylanthracene-9,10-dione

Optical absorption and fluorescence emission techniques were employed to investigate the size effects of silver nanoparticles (Ag NPs) on 1,4-dihydroxy-3-methylanthracene-9,10-dione (DHMAD). Silver nanoparticles of different sizes were prepared by Creighton method under microwave irradiation. The prepared Ag NPs show the surface plasmon band around 400 nm. Fluorescence quenching of DHMAD by Ag NPs was found to increase with an increase in the size of Ag NPs. The fluorescence quenching is explained by resonant energy transfer mechanism between DHMAD and Ag NPs, orientation of DHMAD on silver nanoparticles through chemisorptions. The Stern–Volmer quenching constant and Benesi–Hildebrand association constant for the above system were calculated. DFT calculations were also performed to study the ground and excited state behavior of DHMAD and DHMAD + Ag system.     

Preparation and characterization of YADH-bound magnetic nanoparticles

The covalently binding of yeast alcohol dehydrogenase (YADH) to magnetic nanoparticles via carbodiimide activation was studied. The magnetic nanoparticles Fe₃O₄ with a mean diameter of 10.6 nm were prepared by co-precipitating Fe²⁺ and Fe³⁺ ions in an ammonia solution and treating under hydrothermal conditions. Transmission electron microscopy (TEM) micrographs showed that the magnetic nanoparticles remained discrete and had no significant change in size after binding YADH. X-ray diffraction (XRD) patterns indicated both the magnetic nanoparticles before and after binding YADH were pure Fe₃O₄. Magnetic measurement revealed the resultant magnetic nanoparticles were superparamagnetic characteristics, and their saturation magnetization was reduced only slightly after enzyme binding. The analysis of Fourier transform infrared (FTIR) spectroscopy confirmed the binding of YADH to magnetic nanoparticles and suggested a possible binding mechanism. In addition, the measurement of protein content revealed that the maximum weight ratio of YADH bound to magnetic nanoparticles was 0.125, below which the binding efficiency of YADH was almost 100%. The kinetic measurements indicated the bound YADH retained 62% of its original activity and exhibited a 10-fold improved stability than did the free enzyme. The maximum specific activities and Michaelis constants were also determined.     

Electron donor-dependent radionuclide reduction and nanoparticle formation by Anaeromyxobacter dehalogenans strain 2CP-C

Anaeromyxobacter dehalogenans strain 2CP-C reduces U(VI) and Tc(VII) to U(IV)O_2(s) (uraninite) and Tc(IV)O_2(S) respectively. Kinetic studies with resting cells revealed that U(VI) or Tc(VII) reduction rates using H₂ as electron donor exceeded those observed in acetate-amended incubations. The reduction of U(VI) by A. dehalogenans 2CP-C resulted in extracellular accumulation of ∼5 nm uraninite nanoparticles in association with a lectin-binding extracellular polymeric substance (EPS). The electron donor did not affect UO_2(S) nanoparticle size or association with EPS, but the utilization of acetate as the source of reducing equivalents resulted in distinct UO_2(S) nanoparticle aggregates that were ∼50 nm in diameter. In contrast, reduction of Tc(VII) by A. dehalogenans 2CP-C cell suspensions produced dense clusters of TcO₂ particles, which were localized within the cell periplasm and on the outside of the outer membrane. In addition to direct reduction, A. dehalogenans 2CP-C cell suspensions reduced Tc(VII) indirectly via an Fe(II)-mediated mechanism. Fe(II) produced by strain 2CP-C from either ferrihydrite or Hanford Site sediment rapidly removed ⁹⁹Tc(VII)O₄^– from solution. These findings expand our knowledge of the radionuclide reduction processes catalysed by Anaeromyxobacter spp. that may influence the fate and transport of radionuclide contaminants in the subsurface.