3-methyl-3-buten-1-ol: An aggregation pheromone of the four-eyed spruce bark beetle,Polygraphus rufipennis (Kirby) (Coleoptera: Scolytidae)

Porapak Q-captured volatiles of malePolygraphus rufipennis (Kirby) boring in black spruce and white spruce from Newfoundland and British Columbia, respectively, contained 3-methyl-3-buten-1-ol. Volatiles from logs in which the males had been joined by females contained the compound in reduced quantities. Hindgut extracts from male and femaleP. rufipennis disclosed no male-specific volatiles, but 3-methyl-3-buten-1-ol was detected in extracts of male-produced frass. The compound was not present in extracts from fresh phloem tissue.P. rufipennis of both sexes responded strongly in the field to traps baited with 3-methyl-3-buten-1-ol released at 4390 g/day. There was little response to unbaited traps, fresh uninfested black spruce logs, or to 3-methyl-3-buten-1-ol released at lower rates. Combination of 3-methyl-3-buten-1-ol with either one of five terpenes prevalent in black spruce did not enhance beetle catch. Approximately half of 20 black spruce trees baited with 3-methyl-3-buten-1-ol were attacked, compared to 20.0% of 10 unbaited control trees. This new aggregation pheromone could be used to monitor or manageP. rufipennis populations.     

Using categorisations of citations when assessing the outcomes from health research

Summary This paper describes an attempt to explore how far a categorisation of citations could be used as part of an assessment of the outcomes from health research. A large-scale project to assess the outcomes from basic, or early clinical, research is being planned, but before proceeding with such a project it was thought important to test and refine the developing methods in a preliminary study. Here we describe the development, and initial application, of one element of the planned methods: an approach to categorising citations with the aim of tracing the impact made by a body of research through several generations of papers. The results from this study contribute to methodological development for the large-scale project by indicating that: only for a small minority of citing papers is the cited paper of considerable importance; the number of times a paper is cited can not be used to indicate the importance of that paper to the articles that cite it; and self-citations could play an important role in facilitating the eventual outcomes achieved from a body of research.     

An Efficient, “Burn in” Free Organic Solar Cell Employing a Nonfullerene Electron Acceptor

A comparison of the efficiency, stability, and photophysics of organic solar cells employing poly[(5,6‐difluoro‐2,1,3‐benzothiadiazol‐4,7‐diyl)‐alt‐(3,3′″‐di(2‐octyldodecyl)‐2,2′;5′,2″;5″,2′″‐quaterthiophen‐5,5′″‐diyl)] (PffBT4T‐2OD) as a donor polymer blended with either the nonfullerene acceptor EH‐IDTBR or the fullerene derivative, [6,6]‐phenyl C₇₁ butyric acid methyl ester (PC₇₁BM) as electron acceptors is reported. Inverted PffBT4T‐2OD:EH‐IDTBR blend solar cell fabricated without any processing additive achieves power conversion efficiencies (PCEs) of 9.5 ± 0.2%. The devices exhibit a high open circuit voltage of 1.08 ± 0.01 V, attributed to the high lowest unoccupied molecular orbital (LUMO) level of EH‐IDTBR. Photoluminescence quenching and transient absorption data are employed to elucidate the ultrafast kinetics and efficiencies of charge separation in both blends, with PffBT4T‐2OD exciton diffusion kinetics within polymer domains, and geminate recombination losses following exciton separation being identified as key factors determining the efficiency of photocurrent generation. Remarkably, while encapsulated PffBT4T‐2OD:PC₇₁BM solar cells show significant efficiency loss under simulated solar irradiation (“burn in” degradation) due to the trap‐assisted recombination through increased photoinduced trap states, PffBT4T‐2OD:EH‐IDTBR solar cell shows negligible burn in efficiency loss. Furthermore, PffBT4T‐2OD:EH‐IDTBR solar cells are found to be substantially more stable under 85 °C thermal stress than PffBT4T‐2OD:PC₇₁BM devices.     

Performance Improvements in Conjugated Polymer Devices by Removal of Water‐Induced Traps

The exploration of a wide range of molecular structures has led to the development of high‐performance conjugated polymer semiconductors for flexible electronic applications including displays, sensors, and logic circuits. Nevertheless, many conjugated polymer field‐effect transistors (OFETs) exhibit nonideal device characteristics and device instabilities rendering them unfit for industrial applications. These often do not originate in the material's intrinsic molecular structure, but rather in external trap states caused by chemical impurities or environmental species such as water. Here, a highly efficient mechanism is demonstrated for the removal of water‐induced traps that are omnipresent in conjugated polymer devices even when processed in inert environments; the underlying mechanism is shown, by which small‐molecular additives with water‐binding nitrile groups or alternatively water–solvent azeotropes are capable of removing water‐induced traps leading to a significant improvement in OFET performance. It is also shown how certain polymer structures containing strong hydrogen accepting groups will suffer from poor performances due to their high susceptibility to interact with water molecules; this allows the design guidelines for a next generation of stable, high‐performing conjugated polymers to be set forth.     

n-Type Glycolated Imide-Fused Polycyclic Aromatic Hydrocarbons with High Capacity for Liquid/Solid-Electrolyte-based Electrochemical Devices

Currently, n-type small-molecule mixed ionic-electronic conductors remain less explored and their molecular design rules are not mature enough. Herein, two n-type glycolated imide-fused polycyclic aromatic hydrocarbons (IPAHs), d-gdiPDI and t-gdiPDI, are developed to probe the effects of molecular conformation on the electronic, electrochemical, morphological, and coupled ionic-electronic transport properties. It is found that the highly twisted scaffold in d-gdiPDI, compared to the nearly planar one of t-gdiPDI, has a strong positive effect on the charge storage properties and thus the performance of organic electrochemical transistors (OECTs). d-gdiPDI exhibits a volumetric capacitance of 657 F cm⁻³, obviously outperforming that of t-gdiPDI (261 F cm⁻³), which is the highest value reported to date for small-molecule OECT materials. Moreover, a high charge-storage capacity of up to 479 F g⁻¹ is observed for d-gdiPDI. Arising from such high ionic-electronic coupling characteristic, d-gdiPDI-based OECTs present a ≈2 × times higher geometry-normalized transconductance (g_m,norm) of 105.3 mS cm⁻¹ relative to that of t-gdiPDI counterparts. Significantly, further application of d-gdiPDI in solid-electrolyte OECTs delivers a g_m,norm of 142.4 mS cm⁻¹. These findings indicate that IPAHs are very promising candidates for n-type small-molecule OECTs and highlight the superiority of twisting conformation manipulation in materials design toward high-performance electrochemical devices.     

Balancing Ionic and Electronic Conduction for High‐Performance Organic Electrochemical Transistors

Conjugated polymers that support mixed (electronic and ionic) conduction are in demand for applications spanning from bioelectronics to energy harvesting and storage. To design polymer mixed conductors for high‐performance electrochemical devices, relationships between the chemical structure, charge transport, and morphology must be established. A polymer series bearing the same p‐type conjugated backbone with increasing percentage of hydrophilic, ethylene glycol side chains is synthesized, and their performance in aqueous electrolyte gated organic electrochemical transistors (OECTs) is studied. By using device physics principles and electrochemical analyses, a direct relationship is found between the OECT performance and the balanced mixed conduction. While hydrophilic side chains are required to facilitate ion transport—thus enabling OECT operation—swelling of the polymer is not de facto beneficial for balancing mixed conduction. It is shown that heterogeneous water uptake disrupts the electronic conductivity of the film, leading to OECTs with lower transconductance and slower response times. The combination of in situ electrochemical and structural techniques shown here contributes to the establishment of the structure–property relations necessary to improve the performance of polymer mixed conductors and subsequently of OECTs.     

Membrane‐Free Detection of Metal Cations with an Organic Electrochemical Transistor

Alkali‐metal ions, particularly sodium (Na⁺) and potassium (K⁺), are the messengers of living cells, governing a cascade of physiological processes through the action of ion channels. Devices that can monitor, in real time, the concentrations of these cations in aqueous media are in demand not only for the study of cellular machinery, but also to detect conditions in the human body that lead to electrolyte imbalance. In this work, conducting polymers are developed that respond rapidly and selectively to varying concentrations of Na⁺ and K⁺ in aqueous media. These polymer films, bearing crown‐ether‐functionalized thiophene units specific to either Na⁺ or K⁺, generate an electrical output proportional to the cation type and concentration. Using electropolymerization, the ion‐selective polymers are integrated as the gate electrode of an organic electrochemical transistor (OECT). The OECT current changes with respect to the concentration of the ion to which the polymer electrode is selective. Designed as a single, miniaturized chip, the OECT enables the selective detection of the cations within a physiologically relevant range. These electrochemical ion sensors require neither ion‐selective membranes nor a reference electrode to operate and have the potential to surpass existing technologies for the detection of alkali‐metal ions in aqueous media.     

1-Octen-3-ol,attractive semiochemical for foreign grain beetle,Ahasverus advena (Waltl) (Coleoptera: Cucujidae)

Volatiles were captured on Porapak Q from foreign grain beetles,Ahasverus advena (Waltl), feeding on rolled oats at various population densities. At low population density, males, females, and mixed-sex beetles four to six weeks posteclosion and older produced 1-octen-3-ol. Mixed-sex beetles emitted almost pure (R)-(–) enantiomer. Weekly production rates of 1-octen-3-ol by males were at least four times greater than those of females. Production of 1-octen-3-ol was barely detectable in volatiles from mixed-sex adults maintained at the highest population density. Laboratory bioassays in a two-choice, pitfall olfactometer modified to retain responding beetles revealed that 1-octen-3-ol serves as an aggregation pheromone forA. advena. Both racemic and chiral 1-octen-3-ols were good attractants for mixed-sex adults in the pitfall olfactometer.Research supported by the Natural Sciences and Engineering Research Council of Canada, Strategic Grant G0958 and Operating Grants A3881 and A3785.     

Ipsenol: an aggregation pheromone forIps latidens (Leconte) (Coleoptera: Scolytidae)

Ipsenol was identified from the frass of male, but not female,Ips latidens from British Columbia, feeding in phloem tissue of lodgepole pine,Pinus contorta var.latifolia. The responses ofJ. latidens to sources of ips-enol andcis-verbenol were determined with multiple-funnel traps in stands of lodgepole pine in British Columbia. Ipsenol attracted both male and femaleI. latidens, verifying that it is a pheromone for this species. MaleI. latidens showed a slight preference for (S)-(–)-ipsenol.cis-Verbenol was not produced by beetles of either sex and, in contrast to an earlier report, both enantiomers inhibited attraction to ipsenol-baited traps. The predators,Enoclerus sphegeus andThanasimus undatulus (Cleridae), were attracted to traps baited withcis-verbenol and ipsenol.