bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Understanding Anion and Cation Migration in Hybrid Perovskite Solar Cells
Authors: Kuno Masaru
Published: May 2020

Hybrid perovskites are popular materials for realizing low cost, third generation solar cells. Certified power conversion efficiencies of laboratory scale devices now exceed 20%. Despite engineering advances, which have led to these advances, hybrid perovskites are still plagued by instabilities. The best known relate to moisture instabilities. Less, however, is understood about intrinsic limitations of these materials, stemming from both anion and cation migration under illumination or under bias. Understanding the microscopic origin of these instabilities as well as suppressing them represents one of the last major open scientific questions, preventing their commercialization. In this talk, I therefore summarize what is known about anion and cation migration and discuss results from microscopic, spatially-resolved optical measurements we have conducted on both thin films and solar cells.
(Invited) Charge Carrier Dynamics and Single-Particle Photoluminescence of the Caesium Lead Halide Perovskite Nanocrystals
Authors: Samanta Anunay
Published: May 2020

Because of their potential in photovoltaic and photonic applications, great attention is being paid to both hybrid and all-inorganic lead halide perovskite nanocrystals.1,2 However, despite growing interests on these substances, our understanding of different pathways of relaxation of the photo-generated charge carriers and their dynamics, which is key to utilization of the full potential of these materials in various applications, is still quite limited. In this talk, we plan to discuss some of our recent works on charge carrier recombination dynamics of caesium lead halide perovskite (CsPbX3) nanocrystals highlighting how femtosecond pump-probe and single-particle fluorescence based techniques can be effectively employed to obtain information on the identity and energy states of the photogenerated species, pathways and dynamics of relaxation of the charge carriers (including their recombination), location and nature of the trap states and their role in fluctuation of the photoluminescence of different CsPbX3 perovskite nanocrystals.3-7

References:

1. Green, M.A.; Ho-Baillie, A.; Snaith, H.J. Nature Photonics
2014, 8, 506.

2. Yakunin, S.; Protesescu, L.; Krieg, F.; Badnarchuk, M.I.; Nedelcu, G.; Humer, M.; Luca, G.D.; Fiebig, M.; Heiss, W.; Kovalenko, M.V. Nature Communications
2015
, 6, 8056.

3. Mondal, N; De, A.; Das, S.; Paul, S.; Samanta, A. Nanoscale
2019, 4, 9796.

4. Mondal, N; De, A.; Samanta, A. ACS Energy Letts.
2019, 4, 32.

5. Seth, S.; Ahmed, T.; Samanta, A. J. Phys. Chem. Lett.
2018, 9, 7007.

6. Mondal, N; De, A.; Samanta, A. J. Phys. Chem. Lett.
2018, 9, 3673.

7. Ahmed, T; Seth, S; Samanta, A. ACS Nano DOI: 10.1021/acsnano.9b07471.
Dewetting-Alloying of Nicu Bilayers on TiO2 Surfaces for Noble Metal-Free Photocatalytic H2 Evolution
Authors: Altomare Marco , Spanu Davide , Recchia Sandro , Minguzzi Alessandro , Ghigna Paolo , Schmuki Patrik
Published: May 2020

We present an approach to fabricate an efficient noble metal-free photocatalytic platform for H2 evolution and provide evidences that the photocatalyst active state forms via a photo-induced redox process in organic-water mixtures.

To fabricate the photocatalytic platform, NiCu bilayers (thickness in the range of a few nm) are deposited by Ar-plasma sputtering on anodic TiO2 nanocavity arrays.[1] A subsequent thermal treatment triggers solid-state dewetting[2,3] of the metal bilayer, i.e. owing to surface diffusion, the Ni and Cu films agglomerate and inter-mix forming NiCu bimetallic nanoparticles at the TiO2 surface.[4] This approach allows for a full control over key features of the NiCu nanoparticles, e.g. size, loading, composition and co-catalytic H2 generation ability. We found that dewetted-alloyed NiCu nanoparticles not only are significantly more reactive than their pure Ni or Cu counterparts, but also lead to H2 generation rates that approach those of noble metal (Pt) modified TiO2 nanocavities.

Characterization results (EDS-TEM, XPS and XRD) of the as-formed photocatalyst suggest the co-catalyst nanoparticles to feature a NiCu bimetallic core and an oxide (or hydroxide) shell – the latter presumably forms by surface oxidation under ambient conditions.

To identify the chemical state of the NiCu nanoparticles during photocatalysis, we carried out XAS operando experiments[5,6] (beam line P65 at DESY – Petra III, Hamburg, Germany) at the Cu K and Ni K edges, in fluorescence mode, under UV light illumination in degassed ethanol-water solutions.

Our results demonstrate that under operando conditions the co-catalyst is subjected to changes of the Ni and Cu chemical state:[7–9] we observe that surface Ni and Cu oxide species are reduced (by TiO2 conduction band electrons) in the early stage of illumination – this converts the co-catalyst nanoparticles into the active metallic NiCu phase.

[1] J. E. Yoo, K. Lee, M. Altomare, E. Selli, P. Schmuki, Angew. Chemie Int. Ed.
2013, 52, 7514–7517.

[2] C. V. Thompson, Annu. Rev. Mater. Res.
2012, 42, 399–434.

[3] M. Altomare, N. T. Nguyen, P. Schmuki, Chem. Sci.
2016, 7, 6865–6886.

[4] D. Spanu, S. Recchia, S. Mohajernia, O. Tomanec, Š. Kment, R. Zboril, P. Schmuki, M. Altomare, ACS Catal.
2018, 8, 5298–5305.

[5] M. Fracchia, P. Ghigna, A. Vertova, S. Rondinini, A. Minguzzi, Surfaces
2018, 1, 138–150.

[6] A. Minguzzi, O. Lugaresi, C. Locatelli, S. Rondinini, F. D’Acapito, E. Achilli, P. Ghigna, Anal. Chem.
2013, 85, 7009–7013.

[7] J. S. Schubert, J. Popovic, G. M. Haselmann, S. P. Nandan, J. Wang, A. Giesriegl, A. S. Cherevan, D. Eder, J. Mater. Chem. A
2019, 7, 18568–18579.

[8] B. Mei, K. Han, G. Mul, ACS Catal.
2018, 8, 9154–9164.

[9] M. J. Muñoz-Batista, D. Motta Meira, G. Colón, A. Kubacka, M. Fernández-García, Angew. Chemie Int. Ed.
2018, 57, 1199–1203.
(Invited) From Chromophores to Photoactive Materials: The SURMOF Approach
Authors: Wöll Christof
Published: May 2020

Realizing molecular “Designer Solids” by programmed assembly of building units taken from libraries is a very appealing objective. Recently, metal-organic frameworks (MOFs) have attracted a huge interest in this context. Here, we will focus on the integration of chromophores into MOFs, as well as on several applications based on these highly versatile crystalline materials. For numerous MOF-based applications, in particular in the area of optics and photonics, the conventional solvothermal synthesis yielding MOF powders is not well suited. In the context of optical applications, a severe drawback is that the powder particles cause strong scattering, which makes a reliable determination of photophysical parameters difficult. To overcome these problems, we have developed a layer-by-layer (lbl) deposition method to produce well-defined, highly oriented and monolithic MOF thin films on a number of different substrates. The resulting films are referred to as SURMOFs [1,2]. The fabrication of hetero-multilayers (see Fig. 1) is rather straightforward with this lbl method. In this talk, we will describe the principles of SURMOF fabrication as well as the results of systematic investigations of electrical and photophysical properties exhibited by empty MOFs/SURMOFs [3] and after loading their pores with functional guests. Subsequently we will focus on employing SURMOFs for anisotropic exciton transport. Finally, we will point out that MOFs and SURMOFs are expected to play an important role in the digitalization of materials research.

References:

[1] J. Liu, Ch. Wöll, Chem. Soc. Rev. 46, 5730-5770 (2017)

[2] L. Heinke, Ch. Wöll, Advanced Materials 31 (26), 1970184 (2019)

[3] R. Haldar, L. Heinke, Ch. Wöll, Advanced Materials (2020), DOI: 10.1002/adma.201905227

Figure 1
(Invited) Exotic Electronic Excitation to Manipulate Electrochemical Potential of Electrons and Holes at Liquid/Solid Interfaces
Authors: Zhang Jinjiang , Zhou Ruifeng , Minamimoto Hiro , Murakoshi Kei
Published: May 2020

Spectroelectrochemistry is powerful tool to investigate electronic sates and geometrical structures of electrified interfaces in-situ under the conditions where photonic and electronic energy conversion functionalities emerge. One can use plasmon-powered processes to expand the ability of the spectroscopy regarding sensitivities in space, time, and energy resolutions. As their characteristics on localization of surface plasmons into molecule scale, huge intensity gradient of electromagnetic field would break the limit of light-matter interactions via the modification of the selection rule of the electronic excitation process. I have discussed about the possibility for the surface-enhanced-Raman scattering (SERS) as the probe to monitor the exotic electronic excitation processes[1-7]. Based on the observation of a small number of molecules at the plasmonic metal nanostructures by SERS, possibilities leading to the future innovative photo-functionalities were demonstrated by showing improved properties at optical manipulation of electrons and molecules, and ions. In this presentation, we will show that the localized surface plasmons of the Au nanodimer structures prepared on defect-free graphene provide highly-confined electromagnetic field to generate holes and electrons of the electrochemical potentials beyond the limit of far field light illumination [8]. Novel non-zero wavevector excitation results in the generation of highly reductive and oxidative powers for electrochemical reactions. The present findings point to a novel approach to breaking the limit of opto-electronic interactions and photochemical reactions using various materials.

References

[1] K. Murakoshi and L. M. Liz-Marzán et al., ACS nano, DOI:10.1021/acsnano.9b04224 (2019)

[2] T. Konishi et al., J. Am. Chem. Soc., 135, 1009-1014 (2013)

[3] M. Takase et al., Nature Photonics, 7, 550-554 (2013)

[4] F. Nagasawa et al., J. Phys. Chem. Lett. 5, 14-19 (2014)

[5] H. Minamimoto et al., Faraday Discuss. 205, 261-269 (2017)

[6] F. Kato et al., ACS Photonics, 5, 788-796 (2018)

[7] X. Li et al., PhyChemChemPhys, 20, 14818-14827 (2018)

[8] J. Zhang et al., Nano Lett., 19, 7887-7894 (2019)
WITHDRAWN: Flexible, Thin-Layer Solid-State Supercapacitor Based on V2O5-Graphene Composite Electrode and Ionic Liquid Gel Polymer Electrolyte for Portable Electronic Systems
Authors: Azadian Farshad , Asif Omar , Rastogi Alok C
Published: May 2020

This abstract has been withdrawn at the request of the authors.
Record Capacitance Density from Three-Dimensional Silicon-Based Capacitor: Toward Effective on-Chip Energy Storage
Authors: Strambini Lucanos , Paghi Alessandro , Mariani Stefano , Sood Anjali , Kalliomaki Jess , Jarvinen Paivi , Toia Fabrizio Fausto Renzo , Scurati Mario , Morelli Marco , Lamperti Alessio , Barillaro Giuseppe
Published: May 2020

The currently growing request for a continuous connectivity between people and things has increased exponentially the demand for portable and/or wearable electronics. Thus, high performance components with more compact size, lower power consumption, and increased energy storage capability are needed. Although electronic active components have downscaled and and their performance optimized over the years, passive elements (e.g., resistors, capacitors, and inductors) have made only little progress.

Supercapacitors (SCs) are electrochemical capacitors that can achieve very high capacitance density, in the order of 0.1–1 mF/mm2. Nonetheless, SC intrinsic low operation voltage (a few Volts) and reduced frequency range (up to a few hundreds of Hertz), together with their poor compatibility with integrated circuit (IC) processes have inhibited their electronic applications to date1. Dielectric capacitors (DCs) make use of solid-state dielectrics sandwiched between conductive electrodes. DCs can achieve high working frequencies, up to a several MHz, and large operating voltages, easily exceeding 5V 2. However, DC capacitance density is orders of magnitude smaller than that of SCs. Nowadays, it is still challenging to simultaneously achieve capacitors with high capacitance density, wide working frequency range, and small footprint for future electronic applications, with a fabrication process that is compatible with ICs technology.

Here, we demonstrate the possibility to integrate, on a silicon chip, 3D microcapacitors with capacitance density up to 1 μF/mm2 by leveraging the atomic layer deposition of conductive (TiN) and dielectric (Al2O3and HfAlOX) nanocoatings (20 and 40 nm) into trenches electrochemically etched in silicon with high aspect-ratio (up to 100). Power and energy densities of the 3D microcapacitors, namely, 566 W/cm2and 1.7 μWh/cm2, respectively, overcome those of most state-of-the-art dielectric capacitors and supercapacitors. Further, the 3D microcapacitors feature operating frequency up to 70kHz and show excellent stability with voltage (up to 16V) and temperature (up to 100°C), over 100 h of continuous operation (>108charge/discharge cycles) . These results pave a road for effective on-chip energy storage for consumer and wearable electronic applications.
(Invited) High Performance Carbon Composite Anodes for Sodium-Ion Batteries
Authors: Paranthaman Mariappan Parans
Published: May 2020

Conductive networks of waste tire derived carbons were used to produce homogeneous composites via ball milling as a promising anode material for sodium-ion batteries. Sodium half-cells delivered reversible discharge capacities of 207 mAh g–1 at a current density of 37 mA g–1. Carbon composite materials showed impressive capacity retention with 88% after 100 cycles. Rate capability studies at 60 °C yielded enhanced capacity of 300 mAh g–1. From these remarkable results, the waste-tire derived carbon composites enabled stable alloying and dealloying processes as promising anodes for SIBs. We will also report our recent results on reducing the first cycle loss with carbon electrodes.

The research was sponsored by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division.
Porphyrins-based Materials as Efficient Donor in Organic Solar Cells
Authors: Harvey Pierre D. , Tanguy Loïc
Published: May 2020

Twenty years after the discovery of bulk heterojunction solar cells (BHJSCs), porphyrins were underrepresented in the field of organic solar cells (OCSs)1 despite their high epsilon of 300 000 M-1cm-1 and their electron rich aromatic core, which make them a good electron donors. In 2012, a power conversion efficiency (PCE) of 8.08% for a BHJSC built with a small molecule containing a porphyrin core was reported.2 Then in 2017, a PCE of 6.44 % was reported for BHJSC constructed with a polymer containing a porphyrin inside the conjugated chain.3 These advances brought porphyrins at the center of attention in the field of OSCs. In 2019, using a planar non-fullerene acceptor and a porphyrin based-polymer, a 9.16% PCE was reported; a record for this type of dye.4 Both a high Voc of 1.01 V and a low Eloss of 0.45 eV, two BHJSC’s characteristics, make the porphyrin dyes competing with the most efficient donors of the field. Mechanistically speaking, like all donors porphyrin-based donors form interfacial charge transfer (CT) species with the acceptors where upon excitation, a charge separated (CS) state is produced efficiently. However, detailed investigations of the CT signature and photophysical traits of these species simply do exit due to the bulk nature of the materials. We designed a supramolecular porphyrin-graphene nanoribbon (GNR) model taking advantage of π-stacking effects between GNRs and anchoring pyrene groups. Upon selective excitation of the GNRs, the GNRs form excitons for which 95% are involved in an energy transfer with the π-stacked porphyrin-GNR CT species very efficiently (35%in 759 fs; 65% < 135 fs), then an electron transfer (charge separation) occurs from these excited CT species to the GNRs in the ps time scale.

1. Bucher, L.; Desbois, N.; Harvey, P.; Sharma, G.; Gros. C.; Porphyrins and BODIPY as Building Blocks for Efficient Donor Materials in Bulk Heterojunction Solar Cells. Solar RRL
2017, 1, 1700127.

2. Huang, Y.; Li, L.; Peng, X.; Peng, J.; Cao, Y.; Solution processed small molecule bulk heterojunction organic photovoltaics based on a conjugated donor–acceptor porphyrin. J. Mater. Chem.
2012, 22, 21841-21844.

3. Bucher, L.; Tanguy, L.; Fortin, D.; Desbois, N.; Harvey, P.; Sharma, G.; Gros, C.; A Very Low Band Gap Diketopyrrolopyrrole–Porphyrin Conjugated Polymer. Chempluschem
2017, 82, 625-630.

4. Tanguy, L.; Malhotra, P.; Singh, S.; Brisard, G.; Sharma, G.; Harvey, P.; A 9.16% Power Conversion Efficiency Organic Solar Cell with a Porphyrin Conjugated Polymer Using a Nonfullerene Acceptor. ACS Appl. Mater. Interfaces
2019, 11, 31, 28078-28087.

Figure 1
Porphyrin-Hexabenzocoronene-Conjugates and Fullerenes
Authors: Jux Norbert , Lungerich Dominik , Hölzel Helen , Ruppel Michael , Martin Max
Published: May 2020

We will present architectures based on porphyrins and hexaarylbenzenes/ hexabenzocoronenes and fullerene C60. Special emphasis lies on crystal packing phenomena.

We report on the synthesis, characterization, and properties of some of these novel systems.[1-4]

References

[1] D. Lungerich, J. F. Hitzenberger, M. Marcia, F. Hampel, T. Drewello, N. Jux, Angew. Chem. Int. Ed..
2014,
53, 12231-12235.

[2] D. Lungerich, J. F. Hitzenberger, W. Donaubauer, T. Drewello, N. Jux, Chem. Eur. J.
2016, 22, 16755-16759.

[3] M. M. Martin, D. Lungerich, P. Haines, F. Hampel, N. Jux, Angew. Chem. Int. Ed.
2019, 59; 8932-8937.

[4] M. M. Martin, D. Lungerich, F. Hampel, J. Langer, T. K. Ronson, N. Jux, Chem. Eur. J.
2019; doi.org/10.1002/chem.201904005

Figure 1
Oxidative C-N Fusion of Pyridinyl-Based Porphyrins
Authors: Berthelot Mathieu , Hoffmann Guillaume , Bousfiha Asmae , Mankou Makaya Amelle , Echaubard Julie , Roger Julien , Cattey Hélène , Romieu Anthony , Lucas Dominique , Fleurat-Lessard Paul , Devillers Charles H.
Published: May 2020

Porphyrins provide an extremely flexible synthetic scaffold for numerous applications such as artificial photosynthesis, photodynamic therapy, molecular recognition, oxidation/reduction catalysts and molecular materials.[1] The fusion of one or several hydrocarbon(s) or aromatic heterocycle(s) onto the porphyrin periphery forces the porphyrin core and the substituent to be coplanar, that enhances the electronic communication between both fragments. This implies important changes in the optical and electrochemical properties of the fused porphyrin compared to the parent porphyrin core such as decrease of the HOMO/LUMO gap, bathochromic shift in it absorption/emission spectra and large absorption and fluorescence in the NIR range. [[2],[3]] For this reason, π-extension of porphyrins has attracted much attention over the last two decades owing to their potential applications in near infrared electroluminescence displays, non-linear optical materials, photodynamic therapy, photovoltaic solar cells and molecular materials. [2,[4]] Nowadays, π-extended C-C linked porphyrins are commonly obtained using toxic and/or expensive chemicals, often under harsh conditions. [3,[5]] Due to the extension of the conjugation path, the oxidation potential decreases which may lead to over-oxidation during the fusion process.

In this work, we present the mild and selective chemical and electrochemical synthesis of new π-extended porphyrins generated via intramolecular oxidative C-N coupling of peripheral pyridinyl fragment(s) with the porphyrin core. [[6]] As compared to their precursors, these fused pyridinium-porphyrins exhibit higher oxidation potential that prevents their over-oxidation.

[1]. Kadish, K. M.; Smith, K. M.; Guillard, R. In The Porphyrin Handbook; Kadish, K. M., Smith, K. M., Guilard, R., Eds.; Academic Press: 2000; Vol. 1-20.

[2]. Zimmerman, J.D.; Diev, V.V.; Hanson, K.; Lunt, R.R.; Yu, E.K.; Thompson, M.E.; Forrest, S.R. Adv. Mater. 2010, 22, 2780-2783.

[3]. Davis, N.K.S.; Thompson, A.L.; Anderson, H.L. J. Am. Chem. Soc.
2011, 133, 30-31.

[4]. Matsuo, Y.; Stao, Y.; Niinomi, T.. Soga, I.; Nakamura, E. J. Am. Chem. Soc.
2009, 131, 16048-16050.

[5]. (a) Brennan, B. J.; Kenney, M. J.; Liddell, P. A.; Cherry, B. R.; Li, J.; Moore, A. L.; Moore, T. A.; Gust, D. Chem. Commun.
2011, 47, 10034-10036. (b) Scigaj, M.; Gryko, D. T. Org. Biomol. Chem.
2011, 9, 8178-8181. (c) Davis, N. K. S.; Thompson, A. L.; Anderson, H. L. J. Am. Chem. Soc.
2011, 133, 30-31. (d) Lewtak, J. P.; Gryko, D. T. Chem.
Commun.
2012, 48, 10069-10086. (e) Mori, H.; Tanaka, T.; Osuka, A. J. Mater.
Chem. C
2013, 1, 2500-2519.

[6]. Berthelot, M.; Hoffmann, G.; Bousfiha, A.; Echaubard, J.; Roger, J.; Cattey, H.; Romieu, A.; Lucas, D.; Fleurat-Lessard, P.; Devillers, C. H. Chem. Commun.
2018, 54, 5414

Figure 1
Cobalt Corroles: From Monomolecular Binding to Porous Organic Polymers (POPs) for the Selective Detection of Carbon Monoxide (CO)
Authors: Gros Claude P. , Brandes Stéphane , Quesneau Valentin , Yang Jian , Desbois Nicolas , Vanotti Meddy , Blondeau-Patissier Virginie , Kadish Karl M.
Published: May 2020

Detection of carbon monoxide (CO) at few ppm levels is a critical point for quality control of domestic and industrial environment. CO is responsible for thousands of intoxications and hundreds of deaths per year in the world. Moreover, CO is a residual gas found in the industrial dihydrogen used for Proton Exchange Membrane fuel cell, and deactivates the fuel cell prematurely. Corroles have beenlargely used in sensing applications.[1] Cobalt corroles display high binding affinity for carbon monoxide even in the presence of nitrogen and dioxygen.[2] The affinity of the Co(III) metallocorroles for CO is directly correlated with the Lewis acid character of the metal center. Therefore, structural modifications on the aromatic ring have a direct influence on the reactivity of the metal complex. We have recently obtained very low CO detection level (ppm) using SAW devices functionalized by cobalt corrole deposited as a film on a guiding layer of silica or a gold surface.[3] Tetra-coordinated cobalt corroles were found to be not so stable over time. A new approach was developed, using labile axial ligands as a protective group of the tetra-coordinated metal complexes. We will present the e-chem and spectro e-chem properties of the cobalt complexes with different axial ligands. As our previous work on the synthesis of porous sol-gel materials functionalized by cobalt corroles gave us also encouraging results for CO sorption and detection[4], we have prepared new porous structured materials functionalized by corrole complexes for gas detection applications. Among all the methods of synthesis of porous architectures, organic materials belonging to the POP (Porous Organic Polymer) family are an appealing and original approach in this research field.[5] We will thus describe the synthesis of new POPs functionalized by cobalt corroles (Fig. 1). Their selective sorption properties for CO over N2, O2and CO2will be also presented.

Authors would like to acknowledge the ANR program (CO3SENS project), the FEDER and the “Région Bourgogne” for financial support, and for the allocation of a PhD grant (JCE Program).

REFERENCES:[1] Paolesse, R.; Nardis,S.; Monti, D.; Stefanelli, M.; Di Natale, C., Chem. Rev.
2017, 117, 2517–2583;[2] J.-M. Barbe, G. Canard, S. Brandès, F. Jerôme, G. Dubois, R. Guilard, Dalton Trans.
2004, 1208-1214; [3] M. Vanotti, C. Theron, S. Poisson, V. Quesneau, M. Naitana, V. Soumann, S. Brandès, N. Desbois, C. Gros, T.-H. Tran-Thi, V. Blondeau-Patissier, Proceedings
2017, 1, 444-447; [4] J. M. Barbe, G. Canard, S. Brandès, R. Guilard, Chem. Eur. J.
2007, 13, 2118-2129; [5] S. Brandès, V. Quesneau, O. Fonquernie, N. Desbois, V. Blondeau-Patissier, C. P. Gros, Dalton Trans.
2019, 48, 11651-11662 (Cover).

Figure 1
Multicomponent Layer-By-Layer Films of Chitosan/Phthalocyanine/AuNPs As Biosensing Platforms
Authors: Rodriguez-Mendez Maria Luz , Salvo-Comino Coral , Garcia-Hernandez Celia , Rodriguez-Valentin Javier , Garcia-Cabezon Cristina , Martin-Pedrosa Fernando
Published: May 2020

The search of new biosensing platforms is crucial to improve the performance of electrochemical biosensors. In this work, Layer by Layer films containing combinations of materials with different functionalities were used to design electrochemical biosensor platforms for phenols detection [1-3]. Catechol and hydroquinone biosensors were obtained by depositing tyrosinase (Tyr) or laccase (Lac) on the surface of LbL films formed by alternating layers of chitosan (CHI), a cationic species which acted as enzyme linker, and layers of two anionic electrocatalytic materials (sulfonated copper phthalocyanine, CuPcS and citrate capped gold nanoparticles, AuNPs). Films with different sequences [(CHI)-(AuNPs)]2, [(CHI)-(CuPc)]2, [(CHI)-(CuPc)-(CHI)-(AuNPs)]2 [(CHI)-(AuNPs)-(CHI)-(CuPc)]2, and [(CHI)-(AuNPs/CuPc)]2 (with CuPcS and AuNP mixed in the same layer) were characterized by UV–visible, FTIR spectroscopy and AFM.

It was demonstrated that the resulting films provided an efficient immobilization surface for phenol oxidases. At the same time, the LbL platform improved the electron transfer between the enzymes and the electrode surface. Although all the biosensors obtained exhibited excellent performances, the sequence of the anionic and cationic layers strongly influenced the electron transfer process. The best results were obtained when CuPcS was present in the last layer which caused a 2-fold increase in the intensity over the response of the biosensor without the LbL platform. The [CHI-AuNP-CHI-CuPcS]2-Tyr bioelectrode showed an LOD of 8.7∙10-4 mM (S/N=3) for catechol and of 7.77∙10-4 mM (S/N=3) for hydroquinone. The LbL platform was not so efficient for laccase and the [CHI-AuNP-CHI-CuPcS]-Lac biosensor showed a LOD of 1.84∙10-2 mM (S/N=3) for catechol and of 1.27∙10-3 mM (S/N=3) for hydroquinone.

References

[1] C. Medina-Plaza, L.N. Furini, C.J.L. Constantino, J.A. De Saja, M.L. Rodriguez-Mendez, Synergistic electrocatalytic effect of nanostructured mixed films formed by functionalised gold nanoparticles and bisphthalocyanines, Anal. Chim. Acta. 851 (2014) 95–102. doi:10.1016/j.aca.2014.08.049.

[2] C. García-Hernández, C. García-Cabezón, F. Martín-Pedrosa, J. A. De Saja, and M. L. Rodríguez-Méndez, Layered composites of PEDOT:PSS/nanoparticles and PEDOT:PSS/phthalocyanines as electron mediators in sensors and biosensors, Belstein J. Nanotech. 7 (2016) 1948-1959

[3] E. G. R. Fernandes, L.C. Brazaca, M.L Rodríguez-Méndez, J.A. de Saja and V. Zucolotto, Immobilization of Lutetium Bisphthalocyanine in Nanostructured Biomimetic Sensors Using the LbL Technique for Phenol Detection, Biosens. Bioelectr. 26 (2011) 4715- 4719.

Acknowledgements

Financial support by MINECO-FEDER (RTI2018-097990-B-I00) and the Junta de Castilla y Leon FEDER (VA275P18) and AFM UVA01is gratefully acknowledged.
Cooperative Dynamics in Nitrogen Based Ligands Binding to Cobalt Porphyrins at the Solution/Solid Interface
Authors: Mazur Ursula , Hipps K W
Published: May 2020

In biology, key molecules for life processes rely on cooperation between metal containing porphyrins to function effectively. In technology, (catalysis and sensing) cooperative interactions between the support and metal porphyrins play a key role in their efficiency. In this study, we present a molecular level study of cooperative surface reactions between nitrogen based ligands and Co(II) porphyrin adsorbates as a function of their spatial proximity at the solution/solid interface. Central metal ion reactivity as a function of surface coverage is measured at varying temperatures and ligand concentrations. Reaction rates and thermodynamic parameters are extracted from measurements made on single molecules.
The Significant Effect of Electronic Coupling on Electron Transfer between Surface-Bound Porphyrins and Co2+/3+ Complex Electrolytes
Authors: Cho Inseong , Mozer Attila Janos , Wagner Pawel , Mori Shogo , Gordon Keith , Innis Peter , Mapley Joseph , Shahshahan Sayedmohsen
Published: May 2020

The coordination of metal ions such as Zn2+ with the π-conjugated porphyrin ring is one of the simplest and the most often used structural modification to alter the electronic nature of a molecule without significantly affecting its size or geometry. The question answered in this work is to what extent electron transfer rates between a surface bound Zn2+porphyrin and a cationic electron donor (Co2+ polypyridyl complexes) is affected by the altered electrostatic interaction between the two molecules at the same electrochemical driving force (DG°). To date, very few studies addressed the effect of electrostatic intermolecular interactions on electron transfers explicitly.

We measured electron transfer rates between 4 porphyrin (2 freebase and 2 Zn porphyrin) molecules attached to TiO2 electrodes and 5 Co2+/3+ complexes dissolved in electrolytes covering a DG° range of close to 1 V. The porphyrin molecules were photo-excited at 532 nm leading to an oxidized porphyrin and an electron injected into the conduction band of the TiO2 electrode. The rate of electron transfer was been determined using transient absorption spectroscopy (TAS) by monitoring the absorption change of the oxidized porphyrin molecules in the presence of the redox mediators in various concentrations. The measured rate constants were fitted to Marcus theory. We have found that even the simplest dimethyl substitution on the bipyridine ligands of the Co2+/3+ complexes resulted in a significant decrease in electron coupling. To account for the variation in electron coupling among the Co2+/3+ complexes, the electron rate constants were normalized by the square of the ratio of the electronic coupling factors. The normalized rate constants showed a 30% increase in electron coupling of the free base porphyrins with Co2+/3+ compared to the electronic coupling between Zn porphyrins and Co2+/3+. Increased coupling suggests shorter donor – acceptor distance or better wavefunction overlap, which could be due to electrostatic interaction of the Co2+ with the lone pairs of the free base porphyrin, which interaction is blocked by Zn2+ coordination. The measurements were also performed in 1,2-dimethoxyethane instead of acetonitrile with a five times lower dielectric constant, resulting in even larger difference in electron transfer rates between free base and Zn porphyrins. This suggests that the origin of the different coupling is indeed electrostatic in nature.

The key finding of this work is that electronic coupling can be as significant contributor to electron transfer rates as the driving force even between similar molecular structures, hence redox active molecules should not be selected based on their free energy difference alone.
Exciton Coherence in Phthalocyanine Crystalline Thin Films
Authors: Hua Kim Ngan , Liang Libin , Furis Madalina
Published: May 2020

Intermolecular interactions in small molecule crystals play an important role in the exciton delocalization process and can lead to robust exciton coherence. The spatial extension of this delocalization, and the exciton coherence length, significantly influence practical applications that rely on excitonic radiative recombination, dissociation or electron transport. The porphyrins and phthalocyanines derivatives family represent the ideal system for a comprehensive study of excitonic coherence because they represent an iconic example of a one-dimensional
J
-like aggregate system.

At the University of Vermont, the Furis group focuses on exploring excitonic states in solution-processed phthalocyanine thin films using a dual Linear Dichroism/Photoluminescence Laser Scanning Microscope developed in -house. These studies are among the first to directly probe the supramolecular structure-property relationships in these electronic materials. The experiments reported here investigate the effect of alkyl substitutions and dynamic disorder (i.e. exciton-phonon coupling) on exciton coherence in solution-processed crystalline thin films of porphyrin and phthalocyanine derivatives.

Specifically, the largest exciton coherence length (approx.15 nm) was measured for an octabutoxy derivative, where the saddle shape of the molecules and the crystalline packing result in weaker coupling to the acoustic phonons (low energy) modes. Enhancing the size of the macrocycle ring to a naphthalocyanine also results in long coherence lengths despite larger intermolecular nearest-neighbor (NN) distances. Most importantly, this study brings evidence that excitonic coherence can engineered in a systematic manner through chemical and physical routes. For example, applying uniaxial strain to the same thin films deposited on Kapton substrates results in continuous bandgap energy tuning, in analogy to inorganic semiconductors.
Metalloporphyrin-Based Catalysts for CO2 Reduction: Effects of Metal Ions and Acidic Sites
Authors: Hung Chen-Hsiung , Chuang chuan-Hung
Published: May 2020

Low product selectivity and poor long-term stability impede the use of metalloporphyrins as practical catalysts in large-scale CO2 reduction reactions. Metalloporphyrin has been a bench mark catalyst to be used in the CO2 reductions. A variety of reaction conditions and a broad range of porphyrinic molecules have been examined with moderate to good efficiencies in comparison with other homogeneous catalysts. Additionally, due to the presence of a large π conjugation system presence in the macrocycle, porphyrins can readily interact with 2D materials through π-π interactions. Therefore, it is also a molecule commonly used to fabricate into hybrid materials. One of long-term goals in our lab is to examine the potential applications of porphyrin isomers or porphyrin analogues. In this report, we will focus on the effects of central metal ions and the presence of acidic protonation/deprotonation sites on the porphyrinic molecules to the product selectivity and the catalytic efficiency upon the CO2 reduction reactions. Both photocatalytic and electrochemical catalytic systems will be compared and contrasted in the presentation.
Engineering Cells, Membranes and Light Harvesting/Photosystem II Super-Complexes in Bio-Photoelectrochemical Cells
Authors: Adir Noam
Published: May 2020

Photosynthetic organisms, membranes and complexes are attractive starting materials for solar energy conversion (SEC). Our overall goal is to develop methods to perform SEC using these materials in simple, inexpensive and a fashion that will be non-polluting and will not compete with the growth of food materials. I will describe here how the remarkable photocatalytic activity of the photosynthetic apparatus can provide overall water splitting with oxygen and hydrogen production in Bio-Photo-Electro-Chemical (BPEC) cells via the simplest and cleanest of processes wither in the absence or presence of added electron transport molecules. With plant thylakoids, electrons are shuttled by FeCN to a transparent FTO electrode, yielding a photocurrent density of 0.5 mA·cm-2. Hydrogen evolution occurs at the cathode at a bias as low as 0.8 V. A tandem cell comprising the BPEC cell with the thylakoid membranes and a Si photovoltaic module achieves overall water splitting with solar to hydrogen conversion efficiency of 0.3% (Pinhassi et al. Nature Communications 2016). With cyanobacterial cells, following a brief treatment that does not induce loss of cell viability, electrons from both the respiratory and photosynthetic systems are transferred directly to a graphite electrode, utilizing endogenous electron carriers (Saper et al. Nature Communications 2018). The current produced can be used for hydrogen production at low additional bias for significantly longer durations than the plant thylakoids.

Another route is to isolate the photosynthetic complexes and chemically connect them to the electrochemical cell. One of the issues with this strategy is the small number of light absorbing chromophores connected to the complex, lowering the photochemical efficiency. Connection of isolated light harvesting complexes can help to overcome this deficiency. Photosystem II (PSII) is the only enzyme that catalyzes light-induced water oxidation being the basis for its application as a biophotoanode in various bio-photovoltaics and photo-bioelectrochemical cells. However, the absorption spectrum of PSII limits the quantum efficiency in the range of visible light, due to a gap in the green absorption region of chlorophylls (500 - 650 nm). To overcome this limitation, we have stabilized the interaction between PSII and Phycobilisomes (PBSs) – the cyanobacterial light harvesting complex, in vitro. The PBS of different cyanobacteria were analyzed for their ability to transfer energy to Thermosynechococcus elongatus (Te) PSII by fluorescence spill-over and photocurrent action spectra. Integration of the PBS-PSII super-complexes within an Os-complex-modified hydrogel on macro-porous indium tin oxide electrodes (MP-ITO) resulted in notably improved, wavelength dependent, incident photon-to-electron conversion efficiencies (IPCE). IPCE values in the green gap were doubled from 3 % to 6 % compared to PSII electrodes without PBS and a maximum IPCE up to 10.9 % at 670 nm was achieved.

Figure 1
Peptide Targeting of Photosensitisers for Photodynamic Therapy and Drug Delivery
Authors: Eggleston Ian M , Yaghini Elnaz , Dondi Ruggero , Tewari Kunal , Edler Karen J , Loizidou Marilena , MacRobert Alexander J
Published: May 2020

The conjugation of tetrapyrroles and related photosensitisers with proteins or targeting peptides is now a well-established approach for enhancing the solubility and tissue selectivity of such molecules in the photodynamic therapy (PDT) of cancer. We are interested in developing chemical strategies for the generation of novel porphyrin-related molecules for targeted PDT, and also porphyrin-based systems whose structures are tailored for use in the light-triggered delivery of therapeutic agents by photochemical internalisation (PCI) [1]. PCI is a light-based approach that exploits the technique of PDT to enhance the delivery of nano-sized biotherapeutics that would normally be prevented from reaching their intended intracellular targets due to sequestration in certain sub-units or organelles within the cell. Effective PCI requires the use of photosensitisers that have the appropriate physical properties to localize in the membranes of the organelles (endosomes or lysosomes) where a therapeutic agent may be trapped. Upon irradiation, reactive oxygen species that are generated may then induce a highly selective damaging effect and cause partial rupture of the organelles, allowing entrapped molecules to escape to their targets within the cell. In this communication, we will describe some of our studies on the synthesis and biological evaluation of porphyrin and chlorin derivatives that are targeted with cationic cell-penetrating peptides (CPPs) via biorthogonal ligation chemistries [1, 2], and the application of these conjugates for PCI of saporin, a nano-sized protein toxin. We will also describe the extension of this principle to the CPP-targeting of liposomal nanocarriers [3] to produce molecular assemblies that allow the codelivery of a porphyrin photosensitizer and a macromolecular therapeutic in order to produce an optimal PCI effect.

[1] R. Dondi, E. Yaghini, K. M. Tewari, L. Wang, F. Giuntini, M. Loizidou, A. J. MacRobert and I. M. Eggleston, Org. Biomol. Chem. 2016, 14, 11488-11501.

[2] E. Yaghini, R. Dondi, K. M. Tewari, M. Loizidou, I. M. Eggleston and A. J. MacRobert, Sci. Rep. 2017, 7, 6059.

[3] E. Yaghini, R. Dondi, K. J. Edler, M. Loizidou, A. J. MacRobert and I. M. Eggleston, Nanoscale 2108, 10, 20366-20376.
Synthetic Heme Selenolate: Spectral and Reactivity Differences from Synthetic Heme Thiolate
Authors: Higuchi Tsunehiko
Published: May 2020

The relationship between the potent catalytic reactivity of cytochrome P450 and the electron-donating character of the axial thiolate ligand has long been investigated. Here, we synthesize the first synthetic iron porphyrin coordinated by selenolate (Se-SR), which is a better electron-donor than thiolate. At ordinary temperature, the spin state of heme selenolate Se-SR is lower (S = 3/2) than that of our previously synthesized SR complex (S = 5/2), which is structurally identical with complex Se-SR except that the axial ligand is thiolate. The N-O stretching mode of the NO- Se-SR complex clearly indicates that the electron-donating trans-effect of selenolate is larger than that of thiolate. A cyclic voltammogram of Se-SR revealed that the FeIII/FeIV redox couple of Se-SR is lower than that of SR, but the two potentials are unexpectedly identical in the case of the FeII/FeIII redox couple. The catalytic activity of complex Se-SR is 13-fold higher than that of SR complex in substituted phenol oxidation with cumene hydroperoxide, which may reflect the O-O bond cleavage rate. On the other hand, the results of alkane-alkene competitive oxidation indicate that the active intermediate derived from SR has a greater preference than that derived from Se-SR for oxidizing alkane, although Se-SR gave a higher total product yield. Thus, the active intermediate derived from heme thiolate is more effective than that derived from heme selenolate for alkane hydroxylation. This is consistent with the emergence in nature of heme thiolate structure, not heme selenolate, in cytochrome P450, based on its function in alkane hydroxylation.
Polypeptides with Pendant Porphyrins: From the Recognition of Bidentate Bases to Inter-Digitated Photo-Active Strands
Authors: Rein Regis , Solladie Nathalie , Aziat Farid
Published: May 2020

In natural photosynthetic systems, the solar energy is collected by pigment molecules attached to the light harvesting complexes. In these units, the chlorophylls are held in a favored spacing and orientation by fairly short a-helical polypeptides. In this way, the energy contained in a single photon is conducted in a very short time and with minimal loss of energy from the point where it is absorbed to where it is needed. The extraordinary efficiency of the energy migration over long distances with minimal loss of energy is ascribed to the favored spacing and orientation of the chlorophylls which are held in an appropriate parallel conformation. Beyond the control of the structure of multi-chromophoric arrays, monitoring the spatial orientation of the chromophores in artificial light harvesting devices is a challenge of growing interest. Indeed, multi-porphyrinic arrays attract more and more attention for the elaboration of photonic and electronic wires.

An octapeptide and a hexadecapeptide derived from the L-lysine and functionalized with porphyrins have been prepared. Beyond a certain degree of oligomerisation, we observed the development of a secondary structure such as a 310 helix which forces the porphyrins to arrange in a defined spatial arrangement. Due to the overlap of the porphyrins in such a conformation, the chromophores undergo a sufficient electronic coupling to favor a good exciton migration.

The ability of these peptides to accomodate guests was investigated through ligand binding studies carried out in dichloromethane with DABCO as bidentate base. The complexation of DABCO by these peptides was monitored by UV-visible spectrophotometric titration in CH2Cl2. We showed that the enhanced stability of the complexe octapeptide/DABCO can be ascribed to a pre-organization of the octapeptide forming cavities, and provides convincing evidence that the bidentate base is inserted into the cavities of the octapeptide via host/guest interactions.

Acknowledgements

This work was supported by the CNRS and the French Ministry of Research.
(Invited) Vanadium Based Phosphate, Phosphite, Oxalate Cathode Materials for Lithium Batteries
Authors: VenkatashamyReddy MogalahalliVenkatesh
Published: May 2020

Commercial lithium ion batteries (LIBs) use layer-type compounds, lithium cobalt oxide (LiCoO2) or LiFePO4 as the cathode (positive electrode) and graphite (C) as the anode (negative electrode) material, and a non-aqueous Li- ion conducting electrolyte. The liquid electrolyte in the form of a solution or immobilized in a gel-polymer. LIBs with an operating voltage of 3.6 V are extensively used in the present-day portable electronic devices like, cell phones and other low power operated devices. For high-power applications like, electric/hybrid electric vehicles and back-up power supplies and, the LIBs need to satisfy several criteria, namely, cost-reduction, improvement in the energy density, safety-in-operation at high current charge/discharge rates and improvement in the low-temperature-operation. To satisfy the above criteria, researches are being carried out worldwide to find alternative cathode materials.

In my presentation, I will discuss our group studies on V-based Flouro phosphates cathode materials. Specifically, I will focus bare and Fe doped-LiVPO4F, αI-LiVOPO4 and V-based metal organic framework materials, MX[(VO)2N2(C2O4)], where M= K, Li, Na , N= HPO4, HPO3. and LiSiV2O6. Materials were prepared variety of chemical methods carbothermal/Graphenothermal reduction, hot plate and hydrothermal methods. Materials were characterized by Rietveld refinement X-ray diffraction, X-ray photoelectron spectroscopy, Raman, XPS, Microscopy (SEM &TEM) and BET surface area methods. Electro analytical studies like cyclic voltammetry, galvanostatic cycling and electrochemical impedance spectroscopy techniques. Interestingly V-based cathodes showed around 4 V redox couple (except LiSiV2O6) which is higher than that of LiFePO4 (3.5V vs. Li) and observed reversible capacity is order 80-140 mAh/g. Discuss in detail long term cycling studies and rate capabilities and reaction mechanisms.

Keywords: Materials synthesis; Batteries; Cathodes; Electrochemical Properties; Energy storage

References

1. M.V. Reddy, M. V.; G.V. Subba Rao, B.V.R. Chowdari, Chem. Rev. 113 (2013) 5364

2. A.S. Hameed, M.V. Reddy*, M. Nagarathinam, T. Runčevski, R.E. Dinnebier, S. Adams, B.V.R. Chowdari, J.J. Vittal, Scientific Reports, 5 (2015) 16270

3. M. Shahul, M. V. Reddy*, N.Sarakar, B. V. R. Chowdari,J. J. Vittal RSC Adv., 5(2015), 60630

4. M. Shahul, M. Nagarathinam, M. V. Reddy*, B. V. R. Chowdari,J. J. Vittal Journal of Materials Chemistry 22(2012)7206-7213.

5. M. Nagarathinam, K. Saravanan, E. J. Han Phua, M. V. Reddy*, B. V. R. Chowdari,J. J. Vittal Angewandte Chemie Intl. 51(24)(2012)5866-5870.

6. M .V. Reddy, G.V. Subba Rao and B. V. R. Chowdari Journal of Power Sources 195(2010)5768-5774.
Optimization of Micro-Scale Organic Energy Storage Devices
Authors: Herrera Jose Ramon
Published: May 2020

In pseudo-capacitors the energy storage process is due to fast, reversible faradic processes. For their higher specific capacitance with respect to conventional electrical double-layer capacitors that make use of high surface area carbons, these devices are among the most promising to provide high energy density and power necessary for modern and future applications. But the era of searching only for the best performance leaving environmental concerns is in the past: and now we have the moral obligation and responsibility of making every new technology evolving into sustainable and eco-friendly alternatives.

Our group has achieved binder-free eco-friendly organic supercapacitors on different substrates such as carbon paper and polyethylene terephthalate (PET), using drop casting and microfabrication techniques, obtaining a specific capacitance of 167 Fg-1 on carbon paper, and 10.8 Fg-1 on flexible PET [1].

In this work we optimize the microfabricated structure of flexible melanin-based electrodes by modifying the geometric architecture, maximizing the electrode/electrolyte interaction. Specifically, we report about the energy storage of flexible melanin-based micro-capacitors in aqueous electrolytes (NH4CH3COO(aq)).

References

[1] Prajwal Kumar, Eduardo Di Mauro, Shiming Zhang, Alessandro Pezzella, Francesca Soavi, Clara Santato, Fabio Cicoira."Melanin-based flexible supercapacitors". J. Mater. Chem. C, 2016, 4, 9516.