Dynamical theory for the battery's electromotive force

We propose a dynamical theory of how the chemical energy stored in a battery generates the electromotive force (emf). In this picture, the battery's half-cell acts as an engine, cyclically extracting work from its underlying chemical disequilibrium. We show that the double layer at the electrode–electrolyte interface can exhibit a rapid self-oscillation that pumps an electric current, thus accounting for the persistent conversion of chemical energy into electrical work equal to the emf times the separated charge. We suggest a connection between this mechanism and the slow self-oscillations observed in various electrochemical cells, including batteries, as well as the enhancement of the current observed when ultrasound is applied to the half-cell. Finally, we propose more direct experimental tests of the predictions of this dynamical theory.Foundation for Polish Science/[]/FNP/PoloniaGordon and Betty Moore Foundation/[GBMF45130]//Estados UnidosPolish National Agency for Academic Exchange/[PPN/ULM/2019/1/00284]/NAWA/PoloniaDutch Research Council/[OCENW.XS.040]/NWO/Países BajosFreiburg Institute of Advanced Study/[]/FRIAS/AlemaniapreprintUCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Físic

N → B Ladder Polymers Prepared by Postfunctionalization:Tuning of Electron Affinity and Evaluation as Acceptors in All-Polymer Solar Cells

A poly(biphenylene-pyrazinylene) (PPz, E g opt = 3.10 eV) and a head-to-tail regioregular polypyridine (rr-P4Py, E g opt = 3.25 eV) equipped with 1-alkenyl side chains have been prepared and postfunctionalized by hydroboration with different hydroboranes (9H-BBN, (C 6 F 5 ) 2 B-H (BPF-H), Cl 2 B-H) to give the corresponding ladder polymers featuring intramolecular coordinative N → B bonds. Characterization of the optical and electrochemical properties of the postfunctionalized polymers shows that the borylation strongly increases their electron affinity and lowers the optical gaps. Electron affinities between -3.75 eV (PPzBBN, E g opt = 2.16 eV) and -4.35 eV (PPzBPF, E g opt = 2.07 eV) can be reached for hydroborated PPz, while rr-P4Py-derivatives reach LUMO levels of -3.45 eV (P4PyBBN, E g opt = 2.88 eV), -3.85 eV (P4PyBPF, E g opt = 2.95 eV), and -4.15 eV (P4PyBCl 2 , E g opt = 2.95 eV). The potential of this class of compounds as electron acceptors is demonstrated by the investigation of the semiconducting properties of PPzBBN and PPzBPF, which showed ambipolar charge transport with hole and electron mobilities in order of 2 × 10 -5 cm 2 V -1 s -1 . The polymers were tested as acceptors in all-polymer solar cells, which yielded functioning devices, with open-circuit voltages that directly reflect the electron affinity of the employed acceptor

All-conjugated donor-acceptor block copolymers featuring a pentafulvenyl-polyisocyanide-acceptor

We report a fulvenyl-functionalized polyisocyanide (PIC2) with a high electron mobility of μe = 10-2 cm2 V-1 s-1. PIC2 has been incorporated into block-copolymers with either regioregular poly(3-dodecylthiophene) (P3DT → P(3DT-b-IC2)) or regioregular polythiazole (PTzTHX → P(TzTHX-b-IC2)). Block copolymer batches with different block-sizes have been isolated and their properties have been studied. Fluorescence quenching in the solid state and transient absorption spectroscopy indicate energy transfer from the donor-to the acceptor block upon photo-excitation. Fabrication of proof-of-principle organic photovoltaic cells with P(3DT-b-IC2) gave cells with an open circuit voltage (VOC) of ca. 0.89 V. The aggregation behavior of P(3DT-b-IC2) from solution was also studied, which revealed self-assembly into discreet microspheres of 1-8 μm diameter, with a size distribution of 1.72 (±0.37) μm under optimized aggregation conditions

Theory of Stark spectroscopy transients from thin film organic semiconducting devices

Herein, we propose a model to describe picosecond-nanosecond charge separation and nongeminate recombination in organic semiconductors. The model is used to explain time-resolved electroabsorption (EA) measurements performed on diodes made from phenyl-C61-butyric acid methyl ester. We find that the measured shape of the EA transient is due to a combination of microscopic carrier dynamic effects such as carrier trapping, as well as macroscopic effects such as band bending caused by the nonuniform poloron generation profile across the device. We demonstrate that the initial fast phase of the EA transient is due to hot free carriers being able to move freely within the device; over time these hot free carriers cool and become trapped giving rise to the second slower phase of the transient. We further show that the commonly observed dependence of the EA signal on probe wavelength can be explained in terms of the spatial overlap of electrostatic potential within the device and the optical mode of the probe light. Finally, we discuss the implications of these results for pump-probe experiments on thin organic films

How intermolecular geometrical disorder affects the molecular doping of donor-acceptor copolymers

Molecular doping of conjugated polymers represents an important strategy for improving organic electronic devices. However, the widely reported low efficiency of doping remains a crucial limitation to obtain high performance. Here we investigate how charge transfer between dopant and donor\u2013acceptor copolymers is affected by the spatial arrangement of the dopant molecule with respect to the copolymer repeat unit. We p-dope a donor\u2013acceptor copolymer and probe its charge-sensitive molecular vibrations in films by infrared spectroscopy. We find that, compared with a related homopolymer, a four times higher dopant/polymer molar ratio is needed to observe signatures of charges. By DFT methods, we simulate the vibrational spectra, moving the dopant along the copolymer backbone and finding that efficient charge transfer occurs only when the dopant is close to the donor moiety. Our results show that the donor\u2013acceptor structure poses an obstacle to efficient doping, with the acceptor moiety being inactive for p-type doping

Self-Dual Bending Theory for Vesicles

We present a self-dual bending theory that may enable a better understanding of highly nonlinear global behavior observed in biological vesicles. Adopting this topological approach for spherical vesicles of revolution allows us to describe them as frustrated sine-Gordon kinks. Finally, to illustrate an application of our results, we consider a spherical vesicle globally distorted by two polar latex beads.Comment: 10 pages, 3 figures, LaTeX2e+IOPar

Challenges and perspectives in continuous glucose monitoring

Diabetes is a global epidemic that threatens the health and well-being of hundreds of millions of people. The first step in patient treatment is to monitor glucose levels. Currently this is most commonly done using enzymatic strips. This approach suffers from several limitations, namely it requires a blood sample and is therefore invasive, the quality and the stability of the enzymatic strips vary widely, and the patient is burdened by performing the measurement themselves. This results in dangerous fluctuations in glucose levels often going undetected. There is currently intense research towards new approaches in glucose detection that would enable non-invasive continuous glucose monitoring (CGM). In this review, we explore the state-of-the-art in glucose detection technologies. In particular, we focus on the physical mechanisms behind different approaches, and how these influence and determine the accuracy and reliability of glucose detection. We begin by reviewing the basic physical and chemical properties of the glucose molecule. Although these play a central role in detection, especially the anomeric ratio, they are surprisingly often overlooked in the literature. We then review state-of-the art and emerging detection methods. Finally, we survey the current market for glucometers. Recent results show that past challenges in glucose detection are now being overcome, thereby enabling the development of smart wearable devices for non-invasive continuous glucose monitoring. These new directions in glucose detection have enormous potential to improve the quality of life of millions of diabetics, as well as offer insight into the development, treatment and even prevention of the disease

Echinoderms from the Museum of Zoology from the Universidad de Costa Rica

El Museo de Zoología de la Universidad de Costa Rica (MZUCR) se funda en 1966 y alberga la colección de organismos vertebrados e invertebrados más completa de Costa Rica. El MZUCR cuenta actualmente con 24 colec-ciones que contienen más de cinco millones de especíme-nes, y más de 13 000 especies identificadas. Las primeras colecciones datan 1960 e incluyen peces, reptiles, anfibios, poliquetos, crustáceos y equinodermos. Para este último grupo, el MZUCR posee un total de 157 especies, en 1 173 lotes y 4 316 ejemplares. Estas 157 especies representan el 54% del total de especies de equinodermos que posee Costa Rica (293 especies). El resto de especies están repar-tidas en las siguientes instituciones: Academia de la Cien-cias de California (CAS) (4.8%), Instituto Oceanográfico Scripps (SIO) (5.2%), en la Colección Nacional de equino-dermos “Dra. Ma. Elena Caso” de la Universidad Nacional Autónoma de México (ICML-UNAM) (12.7%), Museo de Zoología Comparada de Harvard (MZC) (19.2%), y en el Museo Nacional de Historia Natural del Instituto Smithso-niano (USNM) (35.1%). Es posible que haya material de Costa Rica en el Museo de Historia Natural de Dinamarca (NCD) y en el Museo de Historia Natural de los Ángeles (LACM), sin embargo, no hubo acceso a dichas coleccio-nes. A su vez hay 9.6% de especies que no aparecen en ningún museo, pero están reportadas en la literatura. Con base en esta revisión de colecciones se actualizó el listado taxonómico de equinodermos para Costa Rica que consta de 293 especies, 152 géneros, 75 familias, 30 órdenes y cinco clases. La costa Pacífica de Costa Rica posee 153 especies, seguida por la isla del Coco con 134 y la costa Caribe con 65. Holothuria resultó ser el género más rico con 25 especies.The Museum of Zoology, Universidad de Costa Rica (MZUCR) was founded in 1966 and houses the most complete collection of vertebrates and invertebrates in Costa Rica. The MZUCR currently has 24 collections containing more than five million specimens, and more than 13 000 species. The earliest collections date back to 1960 and include fishes, reptiles, amphibians, polychaetes, crustaceans and echinoderms. For the latter group, the MZUCR has a total of 157 species, in 1 173 lots and 4 316 specimens. These 157 species represent 54% of the total species of echino-derms from Costa Rica. The remaining species are distributed in the following institutions: California Academy of Sciences (CAS) (4.8%), Scripps Oceanographic Institute (SIO) (5.2%), National Echinoderm Collection “Dr. Ma. Elena Caso” from the National Autonomous University of Mexico (ICML-UNAM) (12.7%), the National Museum of Natural History, Smithsonian Institute (USNM) (35.1%), and the Harvard Museum of Comparative Zoology (19.2%). There may be material from Costa Rica in the Natural History Museum of Denmark (NCD) and the Natural History Museum of Los Angeles (LACM), however, there was no access to such collections. There are 9.6% that do not appear in museums, but are reported in the literature. Based on this revision, the taxonomic list of echinoderms for Costa Rica is updated to 293 species, 152 genera, 75 families, 30 orders and 5 classes. The Pacific coast of Costa Rica has 153 species, followed by the Isla del Coco with 134 and the Caribbean coast with 65. Holothuria is the most diverse genus with 25 species.UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de BiologíaUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigación en Ciencias del Mar y Limnología (CIMAR)UCR::Vicerrectoría de Investigación::Unidades de Investigación::Artes y Letras::Museo de la Universidad de Costa Ric

Impedance Spectroscopy for Emerging Photovoltaics

Impedance spectroscopy has been widely applied over the last decades to study electrochemical systems and solid-state devices. However, performing impedance spectroscopy on emerging photovoltaics presents new challenges related to the unusual material properties and complex device architectures. This review provides an introduction to impedance spectroscopy for researchers in photovoltaics and closely related fields. The review begins with a list of practical guidelines for performing measurements and analyzing data. After this, the mathematical basics are reviewed, and an introduction to circuit elements is given. This is followed by tips for collecting reliable data and reducing artifacts in the frequency spectra. The review then surveys common approaches in the field for analyzing data, including performing equivalent circuit modeling, analysis of capacitance-frequency spectra, and carrier mobility measurements. The underlying assumptions of each analysis approach, as well as the advantages, limitations, and potential pitfalls are discussed