bluuebunny/crossref_metadata_2025_split huggingface dataset:
NBD-Ferrocene: A New Fluorescence Redox Molecular Switch Based on Photoinduced Electron Transfer
Authors: Čížková Martina , Cattiaux Laurent , Mallet Jean-Maurice , Labbé Eric , Buriez Olivier 
Published: February 2020

Fluorimetric redox switches, sensitive to external electrochemical stimuli, belong to a wide family of molecular sensors in which the switching process is achieved by shifting the molecules between two or more stable states. While the area of pH and ligand-based chemosensors has been extensively explored,[1] the topic on luminescent molecular redox switches has remained rather underdeveloped[2] even though redox modulation of fluorescence affords considerable opportunities in optoelectronic and biological applications.[3]In this context, the development of new electrochemically switchable fluorescent probes is of high interest. Based on DFT calculation, an original nitrobenzoxadiazole (NBD) system containing a redox active ferrocene unit was designed (Figure 1) and its optical, electrochemical, and spectroelectrochemical properties were investigated. The system was nonfluorescent in its initial reduced state as a result of photoinduced electron transfer from ferrocene moiety to the photoexcited NBD part and considerable enhancement of emission intensity was observed during oxidation of NBD-ferrocene to NBD-ferrocenium, in which photoinduced electron transfer was disabled electrochemically.

References

[1]
(a) de Silva, A. P.; Gunaratne, H. Q. N. ; Gunnlaugsson, T. ; Huxley, A. J. M. ; McCoy, C. P. ; Rademacher, J. T.; Rice, T. E. Chem.
Rev.
1997, 97, 1515-1566; (b) Gale, P. A.; Caltagirone, C. Chem. Soc. Rev.
2015, 44, 4212-4227.

[2]
(a) Magri, D. C. Analyst
2015, 140, 7487-7495; (b) Audebert, P.; Miomandre, F. Chem. Sci.
2013, 4, 575-584.

[3]
Liu, Z.; Qi, W.; Xu, G. Chem. Soc. Rev. 2015, 44, 3117-3142.

Acknowledgement

The financial support from the EU Research and Innovation programme Horizon 2020 through the Marie Skłodowska-Curie action (H2020-MSCA-IF-2014, ID 656519) is gratefully acknowledged.

Figure 1 a) Electrochemical oxidation of the new NBD-ferrocene system. b) DFT calculations of orbital energy levels. c) Electrochemically mediated fluorescence enhancement.

Figure 1
The Influence of Anions on the Release of Ag(I) Ions from Silver Nanoparticles (AgNPs)
Authors: Nomor Aondoakaa Steve , Horrocks Benjamin Richard 
Published: February 2020

Silver nanoparticles (AgNPs) are widely being incorporated into products such as socks [1, 2], sports wears and wound dressings [3, 4] to serve as antibacterials and to inhibit unwanted odours. As these products are washed, the silver nanoparticles leach out, dispersing in water where they may release silver ions. Although the only contraindication of high levels of silver in humans is argyria [5], it is said to be very toxic to aquatic organisms that make up the base of a series of food chains. In this study, silver nanoparticles were synthesised by the citrate reduction method following the procedure of Lee and Meisel [6]. The nanoparticles were prepared in the presence of various anions and in pure water in order to examine the effect of the medium on the release of Ag(I). AgNPs were characterised by UV-Vis spectrometry, dynamic light scattering (DLS) and atomic force microscopy (AFM). The decrease in surface plasmon resonance (SPR) peak of the nanoparticles after dialysis indicates that quite a number of conduction electrons have gone into reaction, hence lowering of resonant frequency. The diameters of the nanoparticles as measured by DLS ranged from 102 nm in the 10 mM chloride AgNPs before dialysis to 892 nm in the 50 mM sample after dialysis, indicating aggregation over the dialysis period. On the other hand, particle sizes in terms of both height and diameter as measured by AFM decreased after dialysis. This could be explained that in spite of aggregation in solution, the AgNPs deposit as islands about 1 particle in height on the AFM substrate (Si wafer). Release of Ag(I) from the NPs was monitored by anodic stripping voltammetry at glassy carbon electrodes. Two interesting observations were made: (i) there is substantial (90 mM) Ag(I) present in the initial NP preparation and (ii) the concentration of Ag(I) after 73 h of dialysis remained easily detectable at about 4 µM irrespective of the concentration of chloride present.

References

1 T.M. Benn, P.Westerhoff. Environ. Sci. Technol. 2008, 42, 4133-4139.
2 D.E Meyer, M.A. Curran, M.A. Gonzalez. J Nanopart Res. 2011, 13, 147-156.
3 A. Hebeish, M.H. El-Rafie, M.A. El-Sheikh, A.A. Saleem, M.E. El-Naggar. Intnal. Journ. of Macromolecules. 2014, 65, 509-515.
4 T. Maneerung, S. Tokura, R. Rujiavanit. Carbohydrate Polymers. 2008, 72, 43-51.
5 WHO Guidelines for Drinking-water quality. 2003. World Health Organisation, Geneva.
6 P.C. Lee, D. Meisel. J. Phys. Chem. 1982, 86, 3391-3395.

Figure 1
Highly Organized Ferrocene-Functionalized Nanoporous Silica Films with an Extremely Fast Electron-Transfer Rate for an Intrinsically Nonconducting Oxide-Modified Electrode
Authors: Audebert Pierre , Vila Neus , Allain Clémence , Walcarius Alain , Hapiot Philippe 
Published: February 2020

Modified electrodes from functionalized nanoporous xerogel coatings, prepared by using the electrochemically assisted self-assembly (EASA) method, containing ferrocene moieties grafted onto vertically oriented pores perpendicular to an indium-tin oxide (ITO) electrode, have been prepared and studied. The electrochemical behavior of these new materials exhibits the fastest charge transfer ever observed in oxide-modified electrodes. The cyclic voltammetry curves allow us, however, to discriminate two types of ferrocene species inside the coatings and to determine the rate constants for the electron exchange between the ITO electrode and the coatings, with the help of simulations and an advanced software package1.
Fig. 1: Scheme depicting the electrode building.
While it is not clear why the charge transfer is so fast, some hypotheses will be presented along.

1 P. Audebert, N. Vila, C. Allain, F. Maisonneuve, A. Walcarius, and P. Hapiot ChemElectroChem 2015, 2,1695.

Figure 1
(Keynote) Sunlight-Driven Ionic Power Production Using Ion-Conducting Polymers
Authors: White William , Sanborn Christopher D. , Reiter Ronald S. , Cardon Joseph M. , Ardo Shane 
Published: February 2020

Ion-conducting polymers are passive. They respond to electric biases that are applied across them by transporting ions via migration. However, there is no reason these materials cannot be made active, such that upon absorption of light, ions are driven in directions pre-defined by built-in potential distributions in the materials and collected via selective contacts to generate power. This is exactly how traditional solid-state solar cells work and the physics that dictates this behavior only requires that the mobile carriers be charged, like ions, and not that they specifically be electrons and/or holes.
My research group studies solar energy conversion technologies that generate power from sunlight absorption through ion transport. In my presentation I will report on my research group’s recent demonstration of ion transport against concentration gradients that was driven by solar illumination of dye-sensitized ion-conducting materials. Mechanistically, visible light was used to drive endergonic excited-state proton transfer from a covalent photoacid-modified cation-conductive membrane. Photoacid molecules convert the energy in light into a change in the chemical potential of a proton via weakening of a protic functional group on the photoacid, i.e. a decrease in its pK
a. A cation-conductive membrane served as the selective contact for protons such that absorption of light resulted in photovoltaic action, i.e. a photocurrent and a photovoltage. Bipolar membranes are another class of ion-conductive polymers that were used to demonstrate similar photo-activity. They consist of a monopolar cation-conductive polymer that is in intimate contact with a monopolar anion-conductive polymer. The physics that describes the ion-equilibration processes within bipolar membranes resembles that which occurs during equilibration of semiconductor pn-junctions.
As a model system for ion-channels in phase-segregated ion-conducting polymers, dye-sensitized conical nanopores in poly(ethylene terephthalate) (1 – 108 pores/cm2) were investigated. Remarkably, in a region occupied by ~20 zeptoliters (~2 x 10-20 L) of aqueous electrolyte, electrochemistry and fluorescence microscopy were used to determine the photoacidity of the surface-bound dye molecules, which changed from the values found in bulk solution, likely as a result of surface charges in the confined nanopores.
This body of work represents an underappreciated solar energy conversion process that is being pioneered by my research group to operate via a mechanism similar to that of semiconductor pn-junctions. The applicability and practicality of these materials as standalone devices for desalination of salt water will also be presented.
(Invited) Durability of Electrochromic Films: Ageing Kinetics and Rejuvenation
Authors: Niklasson Gunnar A. , Wen Rui-Tao , Qu Huiying , Arvizu Miguel A , Granqvist Claes-Goran 
Published: February 2020

A major challenge for energy-efficient smart window technology is to ensure the durability of electrochromic (EC) devices over a service life of more than 20 years. Hence, their degradation under operating conditions must be better understood and preferably avoided. In this paper we review our recent results from a fundamental study of the ageing kinetics of EC tungsten oxide and nickel oxide thin films, as well as electrochemical rejuvenation mechanisms that are able to restore the films to their initial state. The ageing of tungsten oxide films upon cycling in the range 2-4 V vs. Li/Li+ displays a power-law decrease of the charge capacity as a function of cycle number. In the case of severe ageing at potentials below 2.0 V there is evidence for a superposition of two processes. In the case of nickel oxide the ageing process seems to be more complex and it can be described by either a power-law or a stretched exponential function. The ageing of nickel oxide was also observed to decrease and even stop after a few thousand cycles just prior to final breakdown of the film. The decay of charge capacity can be understood in terms of models built on so-called dispersive chemical kinetics.
The term “rejuvenation” describes electrochemical processes that may restore aged films to full EC functionality. During severe ageing of tungsten oxide coatings, Li ions are trapped in the film, and subsequently these ions can be released by application of a high electrochemical potential for a few hours. The trapping/detrapping of Li has been verified by Elastic Recoil Detection Analysis (ERDA) measurements. Very recently we have found that a similar process can be applied to EC nickel oxide films, although using a lower potential than for the case of tungsten oxide. For nickel oxide, the rejuvenation mechanism is not yet clear, but ERDA measurements are in progress and are expected to give detailed information.
An increased understanding of ageing and rejuvenation will facilitate large-scale practical application of electrochromic materials. Our phenomenological models of ageing may make it possible to predict the service life of EC devices using empirical relationships. An understanding of rejuvenation processes will be of major importance in order to prevent or minimize performance decrease under extended cycling. The next step will be to investigate whether rejuvenation treatments can be applied successfully to full EC devices.
A Miniaturized High-Throughput Flow Injection Analysis System for Electrochemiluminescence Detection
Authors: Fanjul Bolado Pablo , Pereira Silva Neves Marta Maria , González García María Begoña , Hernández Santos David 
Published: February 2020

In this work a miniaturized flow injection analysis (FIA) system coupled with optical detection for carrying out electrochemiluminescence (ECL) based assays is presented.
Screen-printed electrodes integrated in one channel flow-cell (TLFCL, Thin layer flow-cell) were used as the electrodic surface. In these electrodes a transparent slide, that usefully allows the detection of air bubbles inside the cell, is attached over the screen-printed electrodes platform delimiting a flow channel (height 400 μm; volume 100μL). The injection is done through an “in-line luer injection port” where sample volume can be easily controlled by operator through a precise syringe. This configuration brings important advantages since it simplifies operability and effectiveness of working in FIA systems. TLFCL working electrodes were modified with different nanomaterials in order to carry-out innovative ECL based proofs-of-concept. By combining the bipotentiostat/galvanostat and the UV-VIS spectrometer of SPELEC device, the ECL signal was simultaneously (electrochemically) generated and captured (with the aid of a reflection probe connected to the spectrometer).
The ECL behaviour of the developed electro-generated luminescent assays was carefully evaluated assessing aspects as sensitivity, limits of detection and reproducibility and the analytical figures of merit were obtained. Moreover, 3D dynamic ECL plots were registered for the acquisition of real-time luminescent spectrum, relating wavelength emission, potential, and ECL signal in a 3D perspective.

Acknowledgements

MB González-García work was supported by Torres Quevedo grant (PTQ-13-05994) of the National Program for the Promotion of Talent and Its Employability of the Spanish Ministry of Economy and Competitiveness.
High Volume Zero Power Low Cost PPB Level Printed Nano-Sensors for Iot
Authors: Stetter Joseph R , Carter Michael T 
Published: February 2020

The sensing capabilities of Carbon nanotubes [CNTs] are often reported in the literature [1,2] but we describe here a commercial sensor based on an amperometric detection method using CNT electrodes. The commercial availability means that it has been thoroughly vetted not only for sensitivity, but also for practical response time, selectivity, and stability in T, P, RH and time dimensions. The CNT-composite electrodes are robust, and while not as inert as the sp4 diamond, they exhibit chemical stability >sp3 carbons. The significant advantage is the extremely high surface area with virtually every atom a surface atom and therefore high catalytic activity at low loadings. These characteristics are important in high volume sensors so that small size and low cost are enabled along with the inherent low power of electrochemical sensors. This combination of characteristics along with the practical manufacturing by using printed electronics approaches is our key to bridge the cost-performance gap and penetrate into high volume consumer and environmental markets with these sensors. The first two environmental gases that use the nano-catalyst electrodes are NO2 and O3 in air at ppb levels.
In order to address global problems with sensors, we know that we will need millions to billions of sensors. This implies a low cost and a sensor design amenable to high volume production. The solution to the World Health Organization’s recognized air quality crisis is accelerated by a global air quality network and this network will need Ozone and nitrogen dioxide sensors as these are lung irritants produced by anthropogenic activity. Business models for the practicality of trillions of connected devices and sensors are emerging in the IoT. Our manufacturing process for the nano-catalyst electrodes involves screen printing for low cost and high volume and it combines the best practices of the semiconductor microfabrication industry with the speed and low cost of the Printed Electronics revolution. This approach can meet the needs for new high volume low cost sensors and accelerate our fight against climate change. Many more sensor products and applications are expected as crowd-sourced pollution measurements are enabled and IoT connected devices allow instant communication of vital information.
1] J. R. Stetter and G. J, Maclay, “Carbon Nanotubes and Sensors: A Review,” in Advanced Micro and Nano Systems, Volume I, Chapter 10, Baltes et al., eds. Wiley-VCH Verlag-GmbH and Co., Weinheim, Germany, pp357-382, 2004 ISBN 3-527 30746-X, [Invited].
2] A. Star, T-R.Han, V. Joshi, and J.R. Stetter, “Sensing with Coated Carbon Nanotube Field Effect Transistors,” Electroanalysis 2004, 16 (1-2), 108-112.
In Operando Measurement of Lithium Polysulfides in Lithium-Sulfur Batteries Using Attenuated Total Reflection Spectroscopy
Authors: Saqib Najmus , Ohlhausen Gretchen M , Porter Jason Morgan 
Published: February 2020

Li-S cells promise a theoretical capacity much greater than existing Li-ion technology, but the problem of polysulfide shuttling, which leads to self-discharge and loss of active material, remains one of the largest barriers to commercial adoption. We report a spectro-electrochemical cell designed for in operando measurements of the order and concentration of lithium polysulfides (Li2Sn, where n is the order). The design is a major improvement on existing cells, which typically require significant modifications from commercial cell geometries and require low charge/discharge rates during operation. The optically accessible Li-S cell resembles a CR2032 battery, and is constructed on a metallic disc with a diamond crystal at its center.
Attenuated total reflection (ATR) Fourier transform infrared (FTIR) spectroscopy is used for in-operando measurements of soluble polysulfides, which are present in the electrolyte-saturated pores of the sulfur electrode. The diagnostic was calibrated using ATR spectra of lithium polysulfide standards, prepared from direct reaction of lithium sulfide and sulfur. The order and concentration of lithium polysulfides in a sample are determined from the position and area of a characteristic IR absorption band. The diagnostic routine can measure polysulfide order and concentration to within 5% and 0.1 M, respectively. Polysulfides smaller than Li2S4 are insoluble and are not present in ATR spectra.
Li-S cells were discharged at C rates up to 2 with simultaneous measurement of lithium polysulfide order and concentration. The obtained voltage profiles are consistent with those reported in literature. During discharge, polysulfide order steadily decreases while polysulfide concentration initially increases followed by a steady decrease. The initial increase in concentration is attributed to: i) reduction from elemental sulfur to Li2S8, and ii) reduction of Li2S8 to smaller polysulfides. The subsequent decrease in concentration is attributed to formation of insoluble polysulfides, which are not measured by the diagnostic. Charging the cell follows the opposite trend, except that elemental sulfur is not recovered.
Photopotential and Polarization Characteristics of Ruthenizer Complex Sensitized TiO2 Electrode for Marine Microbial Fuel Cell
Authors: Nay Wunn Htoo , Motoda Shinichi , Morita Motoaki 
Published: February 2020

We have been studied the performance of TiO2 electrode which is assembled in Marine Microbial Fuel Cell (MMFC). To increase the performance of TiO2 electrode and to improve conversion efficiency from solar energy, dye sensitizing was introduced to TiO2 electrode. The dye used for this experiment is a Ruthenizer complex, Di-tetrabutylammonium cis- bis (isothiocyanato) bis (2, 2-bipyridyl-4, 4’-dicarboxylato) ruthenium (II), well known as N719 dye, which shows high reproducibility and stability performance in dye-sensitized solar cells (DSSC). We also tried forming of Hydroxyapatite (HAp) layer on TiO2 surface before dye sensitizing for the purpose of anchorage effect of dye on TiO2 surface. The measurement of photopotential and polarization property were carried out in the artificial seawater as an electrolyte which does not include the redox couple as a mediator.
Photopotential and polarization was measured with a standard calomel electrode (SCE) as a reference electrode under the irradiation of a 150 W Xenon Lamp, and a platinum electrode was used as a counter electrode for polarization curve. In the measurement of photopotential, the potential dropped to active direction when the light was turned on. Once it reached to the most active potential value, it went back to noble direction slightly for 5 to 15 minutes after the light was on. The change in photopotential after that duration became small and it tended to be stable for 2 hours. This behaviour of photopotential was similar in all measurement of test electrodes.
The amount of Ruthenizer after 2-hour measurement of photopotential became relatively smaller compared to that before measuring. This is because dye recombination with TiO2 electrons took place with artificial seawater electrolyte in the absence of a redox couple for dye regeneration. But, the photopotential of dye-sensitized TiO2 electrode with HAp layer showed more active than that without HAp. This showed good compatibility of HAp since it did not disturb the performance of photo-catalytic reaction of TiO2 and it may show the ion or electron selectivity between Ruthenizer and TiO2 phases. The polarization measurement showed no distinct effectiveness of Ruthenizer sensitizing on TiO2 surface other than suppressing the TiO2 photo-catalytic reaction.
As the results, Ruthenizer sensitizing on TiO2 electrode showed lower photo-catalytic effect by the recombination of oxidized Ruthenizer electron due to absence of a redox mediator. On the other hand, using HAp on TiO2 electrode for Ruthenizer sensitizing showed improvement in photopotential characteristics of TiO2 electrode.