bluuebunny/crossref_metadata_2025 huggingface dataset:
Solid-State Lead-Selective Electrodes- a New Insight into Measurements of Ions at Low Analyte Concentrations
Authors: Lisak Grzegorz , Ciepiela Filip , Sokalski Tomasz , Harju Leo , Bobacka Johan , Lewenstam Andrzej
Published: February 2020

In environmental analysis of ions, ion-selective electrodes (ISEs) are frequently investigated as candidates to improve already existing techniques. Potentiometric sensors have several advantages over other analytical techniques, e.g. portability, low energy consumption, and small size. This creates an opportunity to perform analysis at overall lower cost [1, 2]. Despite obvious advantages, ISEs due to the need of re-calibration and fouling are not yet implemented in environmental analysis of ions on an industrial scale [3, 4]. Vast majority or scientific reports dealing with measurements of ions in diluted samples are devoted to solid-contact and conventional (with inner filling solution) ISEs, however, the concept of lowering the detection limit was firstly introduced and studied with solid-state ISEs [5-8].

In this study solid-state membrane electrodes were re-vitalized in measurements of ions at low analyte concentration in environmental samples. We used lead(II)-selective electrodes with PbS/Ag2S membranes to develop two methods lowering of the detection limit based on the concentration time-dependent adsorption of the primary ion on the surface of the membrane [9] and tuned galvanostatic polarization (chronopotentiometry) [10]. Furthermore, solid-state electrodes were used to determine lead concentration in environmental sample. Tuned galvanostatic polarization method was found suitable in measurement of lead(II) in environmental samples collected nearby industrially exposed terrain [11]. The chronopotentiometric determination was compared to the analysis done with inductively coupled plasma mass spectrometry (ICP-MS) and differential pulse anodic stripping voltammetry (DPASV). The tuned galvanostatic polarization method for the determination of lead in environmental sample was employed in our study for the very first time. By this application we open a new important direction for electrochemical measurement of ions at low analyte concentrations.

References:

J. Bobacka, A. Ivaska, A. Lewenstam, Chem. Rev. 108 (2008) 329.

E. Bakker, Anal. Chem. 76 (2004) 3285.

R. Byrne and D. Diamond, Nat. Mater. 5 (2006) 421.

D. Diamond, S. Coyle, S. Scarmagnani and J. Hayes, Chem. Rev. 108 (2008) 652.

R. P. Buck, Anal. Chem. 40 (1968) 1432.

W. E. Morf, G. Kahr, W. Simon, Anal. Chem. 46 (1974) 1538.

A. Hulanicki, A. Lewenstam, Talanta 23 (1976) 661.

A. Hulanicki, A. Lewenstam, M. Maj-Zurawska, Anal. Chim. Acta 107 (1979) 107.

G. Lisak, T. Sokalski, J. Bobacka, L. Harju, A. Lewenstam, Talanta 83 (2010) 436.

G. Lisak, T. Sokalski, J. Bobacka, L. Harju, K. Mikhelson, A. Lewenstam, Anal. Chim. Acta 707 (2011) 1.

G. Lisak, F. Ciepiela, J. Bobacka, T. Sokalski, L. Harju, A. Lewenstam, Electroanalysis 25 (2013) 123.
Impedance Studies of Symmetrical Solid Oxide Cells with LSM Electrodes and YSZ Electrolyte
Authors: Finklea Harry O. , De Silva Kaushalya
Published: February 2020

Our research focuses on understanding and improving the LSM cathode of a solid oxide fuel cell through impedance studies of symmetrical LSM/YSZ/LSM electrodes (LSM = lanthanum strontium manganite, YSZ = yttrium-stabilized zirconia). Because this system has been studied for decades, the literature is filled with impedance spectra with multiple arcs in similar symmetrical cells. The existence of multiple arcs is emphasized through deconvolution analysis (aka distribution of relaxation times) of the impedance spectra combined with equivalent circuit fitting to the impedance data. There is much speculation about the processes associated with the various arcs. Recently, we have found a solution preparation method for LSM on YSZ that yields a single arc in the impedance spectrum over a range of temperatures (600-800ºC). This behavior contrasts strongly with the multiple arcs obtained in the impedance spectra of LSM electrodes prepared in a traditional method using commercial LSM powder in a paste mixture. The impedance spectra of the two types of LSM electrodes are so distinctive that it is possible to track the impedance behavior of each electrode in a hybrid cell with a paste-based LSM electrode on one side and a solution-based LSM electrode on the other side. Two implications will be discussed: (a) the identification of the rate-determining step in the mechanism for oxygen reduction on a LSM electrode, and (b) the development of a composite LSM/YSZ cathode with an unprecedented low polarization resistance.
Synthesis of High Quality Few Layer Graphene from the Exfoliation of Graphite
Authors: Bai Jincheng , Soden Daniel R. , Dong Lifeng
Published: February 2020

The emergence of graphene in the scientific community has been the cause of much excitement among material scientists and physicists due to its potential applications in many aspects. Despite its unusual physical and chemical properties, the much sought after monolayer graphene has proven to be difficult to produce in sufficient quantities, with most processes outputting high layer or even defect ridden graphene instead. This experiment aims to correct this problem, concerning itself with the synthesis of high quality graphene through continuous sonication with surfactant added throughout, as well as the issue of graphene quality as a function of sonication time. This was accomplished through the creation and addition of a Triton X-100 surfactant solution to a graphite suspension during sonication lasting for 50 minutes, 80 minutes, 110 minutes, 140 minutes, 170 minutes, and 200 minutes respectively. The resulting suspension was then filtrated to separate out the graphene, before being tested for quality through Raman spectroscopy, scanning electron microscopy, and X-ray diffraction. It was revealed that graphite had been exfoliated into few layer graphene after a short sonication time (less than 50 minutes). And the quality of graphene was improved with the sonication time increased, indicated by the reduced number of graphene layers. This completely physical method of graphene synthesis provides a simple way to achieve the highly desired few layer graphene, and will hopefully allow for greater use of graphene in industry and its implementation into new technology.
C-MEMS Based Microsupercapacitors and Microsensors
Authors: Song Yin , Agrawal Richa , Hao Yong , Chen Chunhui , Wang Chunlei
Published: February 2020

Micro-supercapacitors with high pulse power and long cycle lifetime have attracted a great deal of attention for various emerging micropower applications. Recently, there have been several efforts to improve device architecture for the next generation high power and energy density micro-supercapacitors. These devices are usually fabricated by depositing the active materials on interdigitally arranged current collectors of micron-size. We have explored various techniques, materials and structural designs for micro-supercapacitors. In this talk, Carbon-Microelectromechanical systems (C-MEMS) based various supercapacitor systems will be briefly introduced. Both two and three dimensional micro-electrodes where fabricated and various electroactive materials where integrated on the microelectrodes. These include carbon nanotubes (CNTs), Polypyrrole and manganese oxide. More recently we have also examined the integration of Graphene sheets into micro-electrodes as promising high power and energy density material.
Effects of Stress and State-of-Charge on Lithium Transport Behavior in Silicon Electrodes
Authors: Pan Jie , Cheng Yang-Tse , Beck Matthew J
Published: February 2020

In recent years, silicon (Si) has been proposed as a promising negative electrode material because of its high specific capacity, low discharge voltage, and abundance. However, the large volume change and high stress during lithiation and de-lithiation of Si1-3, which can lead to cracking and severe degradation, are impeding the commercialization of Si-based electrodes. Furthermore, Li-ion transport behavior, which affects stress generation4 and rate performance of the electrode, must be understood in order to design Si electrodes with improved performance.

In this study, we investigated the transport mechanism of Li in both crystalline and amorphous lithiated Si in the framework of Density Functional Theory as implemented in the Vienna ab initio Simulation Package (VASP)5, 6. The effects of stress/strain and state-of-charge (SOC) on ionic transport were examined. In the study of crystalline phases, we used the Climbing Nudged Elastic Band (CNEB) method to estimate the diffusion barrier for several possible diffusion paths. We prepared amorphous Li-Si systems (Figure 1) by simulated annealing within ab initio Molecular Dynamics (AIMD). We used the Stokes-Einstein relationship7 to obtain diffusion coefficients from AIMD trajectories (Figure 2).

We found that, in crystalline Li-Si alloys, the interstitial diffusion barrier of Li-ion increases monotonically as the system is compressed. However, in amorphous systems, the effect of stress is not monotonic. One possible mechanism of the non-monotonic behavior is the change of local structure, such as the coordination number, in the amorphous Li-Si alloys as a function of stress. From the view of activation volume, this behavior could be explained by the factor that the activation volume due to Li-ion migration is negative in amorphous Li-Si structures. In addition, we investigated the effects of SOC on Li-ion transport using AIMD calculations and Darken’s equation for chemical diffusion. This study provides new insights into the effects of stress and composition on lithium transport in Si.

References:

1. P. Johari, Y. Qi and V. B. Shenoy, Nano Letters 11(12), 5494-5500 (2011).

2. Y. He, X. Yu, G. Li, R. Wang, H. Li, Y. Wang, H. Gao and X. Huang, Journal Of Power Sources 216, 131-138 (2012).

3. J. C. Li, X. C. Xiao, F. Q. Yang, M. W. Verbrugge and Y. T. Cheng, Journal of Physical Chemistry C 116(1), 1472-1478 (2012).

4. R. Deshpande, Y.-T. Cheng, M. W. Verbrugge and A. Timmons, Journal Of The Electrochemical Society 158(6), A718-A724 (2011).

5. G. Kresse and J. Furthmuller, PHYSICAL REVIEW B 54(16), 11169-11186 (1996).

6. G. Kresse and J. Furthmuller, Comp Mater Sci 6(1), 15-50 (1996).

7. J. R. Chelikowsky, J. J. Derby, V. V. Godlevsky, M. Jain and J. Y. Raty, Journal Of Physics-Condensed Matter 13 (41), R817-R854 (2001).
Invited Presentation: Optical Properties of Carbon Nanotube/Chromophores Assemblies
Authors: Vialla Fabien , Delport Géraud , Langlois Benjamin , Filoramo Arianna , Deleporte Emmanuelle , Campidelli Stéphane , Voisin Christophe , Lauret Jean-Sébastien
Published: February 2020

The delocalized π-electronic system of carbon nanotubes allows them to link non-covalently to a lot of different organic molecules. In contrast to covalent functionalization, this weak interaction preserves most of the nanotubes intrinsic properties (photoluminescence or mobility for instance) but still leads to a strong enough coupling so as to give stable compounds and to induce new and efficient functionalities [1, 2]. We focus on nanotubes / chromophores compounds where the latter acts as an optical nano antenna that absorbs light and transfers its energy to the nanotube, allowing a uniform excitation of all the chiral species in the sample [3, 4, 5, 6, 7].

In this presentation, we will focus on the latest developments of our research in this topic.

References:

[1] C. Roquelet, et al, ChemPhysChem 2010, 11, 1667

[2] G. Clave et al, Chem. Mat. 2013, 25, 2700

[3] G. Magadur et al. ChemPhysChem 2008, 9, 1250

[4] C. Roquelet, et al, Appl. Phys. Lett. 2010, 97,141918

[5] D. Garrot et al, J. Phys. Chem C 2011, 115, 23283

[6] C. Roquelet et al, ACS Nano 2012, 6, 8796)

[7] F. Vialla et al, Phys. Rev. Lett. 2013, 111, 137402
Carbon Nanotube Computer: Transforming Scientific Discoveries into Working Systems
Authors: Shulaker Max , Hills Gage , Patil Nishant , Wei Hai , Chen Hong-Yu , Wong H.-S. Philip , Mitra Subhasish
Published: February 2020

The miniaturization of electronic devices has been the principal driving force behind the semiconductor industry, and has brought about major improvements in computational power and energy efficiency. Although advances with silicon-based electronics continue to be made, alternative technologies are being explored. Digital circuits based on transistors fabricated from carbon nanotubes (CNTs) have the potential to outperform silicon by improving the energy– delay product, a metric of energy efficiency, by more than an order of magnitude. Hence, CNTs are an exciting complement to existing semiconductor technologies. However, carbon nanotubes (CNTs) are subject to substantial inherent imperfections that pose major obstacles to the design of robust and very large-scale CNFET digital systems:

• It is nearly impossible to guarantee perfect alignment and positioning of all CNTs. This limitation introduces stray conducting paths, resulting in incorrect circuit functionality.

• CNTs can be metallic or semiconducting depending on chirality. Metallic CNTs cause shorts resulting in excessive leakage and incorrect circuit functionality.

A combination of design and processing technique overcomes these challenges by creating robust CNFET digital circuits that are immune to these inherent imperfections. This imperfection-immune design paradigm enables the first experimental demonstration of the carbon nanotube computer, and, more generally, arbitrary digital systems that can be built using CNFETs. The CNT computer is capable of performing multitasking: as a demonstration, we perform counting and integer-sorting simultaneously. In addition, we emulate 20 different instructions from the commercial MIPS instruction set to demonstrate the generality of our CNT computer. This is the most complex carbon-based electronic system yet demonstrated. It is a considerable advance because CNTs are prominent among a variety of emerging technologies that are being considered for the next generation of highly energy-efficient electronic systems.
Invited Presentation: Covalent Functionalization of Carbon Nanotubes and Graphene: Chemistry, Electronic Structure and Physical Properties
Authors: Haddon Robert C
Published: February 2020

We have demonstrated the covalent functionalization of carbon nanotubes and graphene with a variety of chemistries including the use of nitrophenyl groups, Diels-Alder reactions and organometallic derivatization. The chemical formation of covalent carbon-carbon bonds involving the basal plane carbon atoms modifies the electronic properties of graphene; the transformation of the carbon centers from sp2 to sp3 introduces a barrier to electron flow by saturating the carbon atoms and opening a band gap which potentially allows the generation of insulating and semiconducting regions in graphene wafers. In this talk I will discuss our recent results on the electronic and magnetic properties of chemically modified graphene, the observation of ferromagnetism, and the application of organometallic chemistry to facilitate the interconnection of single-walled carbon nanotubes.
The Macroscopic Preparation of Endohedral Metallofullerene
Authors: Sun Bao yun , Cui Rong li
Published: February 2020

Endohedral metallofullerenes (EMFs) have attracted broad interests because of their unique structures with novel physical and chemical properties. However, thorough investigations on their properties and applications have been hampered and less studied since it is difficult to get enough amounts of metallofullerenes. In 2008, we established a new extraction method so that the content of metallofullerenes in the raw extract could be raised to 80% and gram quantities of Gd@C82, La@C82, Y@C82, Ho@C82 and Er@C82 have been purified in one month. Based on this method, we established a scaling-up pilot plant in 2012, by which tens grams of metallofullerenes with a high purity of 99.5% have been acquired in one month. Gram quantities of metallofullerenes are important toward developing future materials such as biological applications.
Relative Populations of Non-Isomeric Metallofullerenes: La@C76(Td) Vs. La2@C76(Cs,17490)
Authors: Slanina Zdenek , Lee Shyi-Long , Nagase Shigeru , Akasaka Takeshi
Published: February 2020

Very recently, a new member of the lanthanum-containing metallofullerene family has been isolated and its structure determined from X-ray crystallographic analysis, namely [1] La2@C76(Cs,17490), even with two pairs of connected pentagons, hence violating the isolated-pentagon rule (IPR). In order to explain the interesting observation, a computational treatment is suggested for evaluations of the relative populations of non-isomeric metallofullerenes. As a comparative reference structure, the most stable La@C76 isomer is selected - the IPR-C76(Td)-cage based endohedral La@C76(Td). It is found that in the relevant temperature region the La2@C76(Cs,17490) species should be considerably more populated compared to La@C76(Td). The new computational stability treatment is applicable to a wider spectrum of non-isomeric metallofullerenes.

[1] M. Suzuki, N. Mizorogi, T. Yang, F. Uhlik, Z. Slanina, X. Zhao, M. Yamada, Y. Maeda, T. Hasegawa, S. Nagase, X. Lu, T. Akasaka, Chem. Eur. J. 19, doi:10.1002/chem.201302821 (2013).
Synthesis, Characterization, and Unusual Behavior of a Perfluoroarylated Fullerene
Authors: San Long K. , Whitaker James B. , Popov Alexey A. , Strauss Steven H. , Boltalina Olga V.
Published: February 2020

Fullerenes and fullerene derivatives have attracted much attention due to their interesting optical and electronic properties. For example, further chemical elaborations of fullerenes possessing cyclo‐adducts (ie., phenyl‐C61‐butyric acid methyl ester, PCBM,1 and mono‐indene-C60, ICMA2) have shown promising use in photovoltaic energy conversion. Mono‐hydrofullerenes, C60RH, were shown as effective synthons for novel molecules3 with interesting physicochemical properties for various applications. The C‒H bond activation utilizing the acidic fullerenyl C60‒H proton can be realized by the use of strong bases. For instance, the dimerization of two RC60· radicals using NaOH in the presence of C60RH was used to form RC60‒C60R.4

In this work, we use the labile hydrogen atom on C60RH as a synthetic handle for further chemical elaborations, resulting in a novel perfluoroarylfullerene. One such product, a "fullerene-with-a-mohawk," was realized by the use of a base or by an one‐electron reductant. Products were characterized by 19F and 1H NMR spectroscopy, mass spectrometry, cyclic voltammetry, X‐ray crystallography, and DFT calculations.

References

(1) Reyes-Reyes, M.; Kim, K.; Carroll, D. L. Appl. Phys. Lett.
2005, 87, 083506.

(2) Coffey, D. C.; Larson, B. W.; Hains, A. W.; Whitaker, J. B.; Kopidakis, N.; Boltalina, O. V.; Strauss, S. H.; Rumbles, G. J. Phys. Chem. C
2012, 116, 8916.

(3) Allard, E.; Cheng, F.; Chopin, S.; Delaunay, J.; Rondeau, D.; Cousseau, J. New J. Chem.
2003, 27, 188.

(4) Lu, S.; Jin, T.; Bao, M.; Yamamoto, Y. Org. Lett.
2012, 14, 3466.
High Potential Zinc Porphyrin-Fullerene Dyads: Formation and Electron Transfer Studies
Authors: D'Souza Francis , Das Sushanta K. , Song Baiyun , Ito Osamu
Published: February 2020

Supramolecular dyads of photosensitizing halogenated zinc porphyrins (and halogenated zinc phthalocyanines) and redox active fulleropyrolidine derivatives with pyridine or imidazole ligands were constructed based on metal-ligand axial coordination approach. Spectroscopic characterization accompanied by steady-state absorption and fluorescence studies confirmed the high binding affinity of the high potential zinc porphyrin towards fullerene ligands that was also supported by computational studies. Qualitative Benesi-Hildebrand plots allowed us to calculate the association constant, K of the supramolecular dyads. The redox states of the donor and acceptor entities in the dyads were established from electrochemical investigations using cyclic and differential pulse voltammetry techniques. Free energy calculations using Weller’s approach suggested exergonic photoinduced electron transfer process for all of the studied systems. Pump-probe transient absorption studies at the femtosecond and nanosecond time scale confirmed the formation of cation and anion radical ions in the donor-acceptor supramolecular dyads. The kinetics of charge separation and charge recombination evaluated from the transient absorption studies revealed occurrence of ultrafast electron transfer events.
Preparation of Graphene Fibers
Authors: He Yijia
Published: February 2020

Graphene owns intriguing properties in electronic, thermal, and mechanic with unique two-dimension (2D) monolayer structure. The new member of carbon family has not only attracted great attentions in scientific research, but also showed great potential for many applications. Graphene sheets can self-assemble into macroscopic structures, which is conducive to further explore the value of graphene material in application, and also the future major trends.

This dissertation introduces the preparation of graphene fiber by graphene oxide solution as spinning dope. The graphene oxide is selected to solve the poor wettability of graphene hindering its direct wet spinning. The oxygen-containing groups on graphene oxide surface make it hydrophilic. The graphene fibers were prepared in the following steps: Firstly assemble the graphene oxide into graphene oxide fibers by wet spinning; then turning the graphene oxide fibers into graphene fibers by thermal reduction. To observe the graphene oxide immersing in the coagulation bath at different times by SEM and the assembly mechanism of macroscopic graphene oxide fibers could be studied. In this work, the conductivity of the graphene fibers have been measured using the four-point method. Single mast mechanics test system was used for the tensile strength of graphene fibers. So the key process factors in graphene fibers preparation were explored and optimized, including the concentration of wet spinning dope, the composition of the coagulation bath, the change in diameter of the needles, injection rate and collection rate, etc.

In summary, graphene oxide fibers were assembled by wet-spinning of the graphene oxide dope. And by the thermal reduction graphene fibers were prepared successfully. After studying the assembly mechanism of graphene fibers, the better raw materials and the more proper preparation conditions were chosen to make the fibers which have the superior performances.
Hierarchical Construction of ZnO Nanorods on Nanofibers for Hybrid Solar Cells
Authors: Sagawa Takashi
Published: February 2020

Hybrid inorganic/organic photovoltaic devices based on semi-conducting inorganic materials as n-type acceptors in conjunction with p-type conducting polymers have generated much research interest. Zinc oxide (ZnO) is known for its high electron mobility, acceptable refractive index, and the ease in process when tuning its size and shape. Particularly, continuous electron pathways in ZnO are essential for the transport of the generated charge upon exciton separation at the ZnO/polymer interface to the electrode. In this work, the surface area of ZnO nanofibers (NFs) substrates was further increased by the deposition of nanorods (NRs) to form hierarchical-structured ZnO substrates. FE-SEM images of the ZnO NRs on NFs were shown in the Figure. Photovoltaic performance of hybrid ZnO NFs/poly(3-hexylthiophene) (P3HT) solar cell is enhanced through the deposition of ZnO NRs. The deposition of NRs on electrospun NFs led to an increase in short-circuit current density (J
SC) from 0.47 to 0.89 mA cm-2 and open-circuit voltage (V
OC) from 0.08 to 0.27 V. The improvement of V
OC can largely be attributed to the higher J
SC due to the higher surface areas and the suppression of reverse current saturation density (J
0) due to better electrode coverage. These increases led to ten times improvement in power conversion efficiency from 0.01% to 0.10%. The improvements were mainly attributed to the shorter NR lengths decreasing charge injection from the Ag electrode. Further improvements in Vocs can be achieved by improving P3HT coverage or reducing the thickness of the NF mats decreasing the electrospinning time since the decreasing the lengths of the NRs of the hierarchical structure can decrease the minority charge blocking in the FTO/ZnO interface. The hierarchical structure based on NFs anchored on thin-films of ZnO nanoparticles (NPs) with NR deposition can solve the trade-off of surface area and the direct electron pathway of the NRs and NPs morphology.
Nanostructured Films of Conjugated Polyelectrolytes: Fundamental Studies and Application in Hybrid Solar Cells
Authors: Schanze Kirk , Pan Zhenxing , Nepomnyashchii Alex , Zhu Xuzhi , Parkinson Bruce A , Reynolds John
Published: February 2020

Conjugated polyelectrolytes (CPEs) are semiconduciting organic polymers that feature polar/ionic solubilizing groups. We have demonstrated that CPEs can be used as light absorbing sensitizers atop nanocrystalline TiO2 in a dye-sensitized solar cell configuration leading to relatively efficient light-to-electrical power conversion. We have observed interesting corrleations between polymer chain length (degree of polymerization, DP) and solution state (molecularly dissolved vs. aggregated) on the DSSC efficiency. In order to better understand the interaction of CPEs with the metal-oxide interface, we have investigated the interaction of CPEs with single crystal TiO2 interfaces using high resolution atomic force microscopy imaging and photocurrent spectroscopy. Results of this work will be presented, with an emphasis on the fundamental factors that control the interaction and charge injection efficiency of CPEs at TiO2 interfaces.
Photovoltaic Properties of Organic Heterojunctions with Ordered Nanostructures Prepared By Anodic Porous Alumina
Authors: Masuda Hideki , Kondo Toshiaki , Yanagishita Takashi , Nishio Kazuyuki
Published: February 2020

Organic thin film solar cells have attracted much attention as a next generation energy conversion devices due to their unique properties [1-3]. Control of the nanostructures of organic heterojunctions is essential to improve the conversion efficiency of the organic solar cells. In the present report, we describe the fabrication of the organic solar cells with controlled nanostructures and their photovoltaic properties. Fabrication of organic heterojunctions with controlled geometrical nanostructures was carried out by using the substrates with ordered textured patterns of nanometer scale, which were prepared by nanoimprinting using anodic porous alumina molds. Anodic porous alumina, which is formed by anodization of Al in acidic electrolyte, is a typical self-ordered material and is promising candidate for the starting material for making nanostructures [4]. Use of anodic porous alumina as a mold for nanoimprinting allows the high throughput formation of the substrates with ordered nanostructures of polymers [5,6]. The heterojunctions of organic thin layers were formed on the substrates with ITO layer using a vacuum deposition apparatus. The ordered nanostructure of the substrates could be maintained even at the organic layer of heterojunctions. Optical properties of the obtained samples and the photovoltaic properties were examined. In the samples with controlled geometrical structures prepared by the present processes, improvement of conversion efficiencies was confirmed compared to the samples without controlled geometrical structures. This improvement was thought to be caused by the increase of absorption of light at the heterojunctions due to the antireflection effect caused by the periodic nanostructures. The controlled nanostructure of the heterojunction also contributed to the improvement of the conversion efficiency due to the effective charge separation at the junction. The present process, which allows high throughput formation of the organic heterojunctions with controlled geometrical structures, will be used for the formation of organic solar cells with high conversion efficiencies.

1. A. W. Hins, Z. Liang, M. A. Woodhouse, and B. A. Gregg, Chem. Rev., 110, 6689 (2010).

2. C. J. Brabec, S. Gowrisanker, J. J. M. Halls, D. Laird, S. Jia, and S. P. Williams, Adv. Mater., 22, 3839 (2010).

3. T. M. Clark and J. R. Durrant, Chem. Rev., 110, 6736 (2010).

4. H. Masuda and K. Fukuda, Science, 268, 1466 (1995).

5. T. Yanagishita, K. Yasui, T. Kondo, K. Nishio, and H. Masuda, Chem. Lett., 36, 530 (2007).

6. T. Yanagishita, T. Kondo, K. Nishio, and H. Masuda, J. Vac. Sci. Technol. B, 26, 1856 (2008).
Multiple Exciton Generation in Quantum-Confined Semiconductor Nanostructures
Authors: Beard Matthew C
Published: February 2020

Nanomaterials are a flexible material platform that has great promise for providing new ways to approach solar energy conversion. The synthesis, investigation, and utilization of these novel nanostructures lie at the interface between chemistry, physics, materials science and engineering. Semiconductor nanostructures, where at least one dimension is small enough to produce quantum confinement effects, provide new pathways for controlling energy flow and therefore have the potential to increase the efficiency of the primary photo conversion step. In this discussion, I will present the current status our research efforts towards utilizing the unique properties of colloidal quantum dots (NCs confined in three dimensions) in prototype solar cells and demonstrate that these unique systems have the potential to bypass the Shockley-Queisser single-junction limit for solar photon conversion. The solar cells are constructed using a low temperature solution based deposition of PbS or PbSe QDs as the absorber layer. A unique aspect of our devices is that the QDs exhibit multiple exciton generation with an efficiency that is ~ 2 to 3 times greater than the parental bulk semiconductor. I will discuss current status of MEG research and efforts toward further improve the MEG efficiency.
in Situ Observation of O-Metal Vibrations at Pt and Au Electrodes By Plasmonic Crystalline-Based SERS
Authors: Yagi Ichizo , Inokuma Kiyoshi
Published: February 2020

For practical applications of polymer electrolyte fuel cell (PEFC), designing a high performance and low cost membrane electrode assembly (MEA) is necessary, and performance and cost of a MEA is closely related to the properties of catalysts. Improvement of cathode catalyst becomes a key, and fundamental understandings of cathode reaction mechanism has been essential.

For the reaction mechanism investigation, in situ, dynamic measurement tools should be required. We have been developing a combination of surface enhanced vibrational spectroscopic techniques, such as surface enhanced Raman scattering (SERS), surface enhanced infrared absorption spectroscopy (SEIRAS) and sum frequency generation (SFG) spectroscopy. Generator-collector regime in the electrochemical microchannel device has been also investigated to realize time-resolved measurement by detecting adsorbed intermediates during electrocatalytic reaction.

The recent development in nanofabrication technology affects in the field of plasmonics and various types of novel SERS-active substrates have been reported. We have already prepared the micrometer-scale inverse pyramid-type plasmonic crystalline SERS-active substrates [1-2] with flat (111)-oriented Au surfaces and strong SERS signals from self-assembled monolayers (SAMs) of thiophenol were detected[3]. Although SERS activity of the plasmonic crystalline substrate covered by Pt was not high, strong SERS signal has been reported at sphere segment void (SSV)-type plasmonic crystalline substrates covered with Pt or Pd.[4-5] By tuning the size and depth of SSVs, SERS signal from atomically thickness-controlled Pt thin film covering only the top most surfaces of Au-SSV has proved to give information about adorbates on Pt surfaces selectively. Furthermore, by remaining PS templates, only the Pt surface becomes electrochemically active and SERS intensity from Pt-rim is enhanced much higher. Electrochemical SERS measurement are also carried out in situ at Au- and Pt/Au-SSV substrates.

Acknowledgement

This work was supported by New Energy, Industrial Technology Development Organization (NEDO), Fuel Cell Promotion Office of the Agency of Natural Resources and Energy, Ministry of Economy, Trade and Industry (METI).

References

[1] N.M.B. Perney et al., Opt. Exp., 14, 847 (2006)

[2] N.M.B. Perney et al., Phys. Rev. B, 76, 035426 (2007)

[3] N.Ohta et al., J. Phys. Chem. C, 112 , 17603 (2008)

[4]M.E. Abdelsalam et al., J. Am. Chem. Soc., 129, 7399 (2007)

[5] L. Cui et al., Phys. Chem. Chem. Phys., 11, 1023 (2009)
Electron Transfer Dynamics of Supramolecular Solar Cells
Authors: Gobeze Haptom B.
Published: February 2020

Habtom B. Gobeze and Francis D’Souza*

Department of Chemistry, University North Texas, 1155, Union Circle, #305070, Denton, TX 76203-5017, USA

Francis.DSouza@unt.edu

The relation between energy positioning and adsorption geometry on the electron transfer dynamics of donor-acceptor photosynthetic model compounds immobilized mesoporous TiO2 surface will be presented. Novel Zn-porphyrin (ZnP) and Zn-phthalocyanine (ZnPc) electron-donor and fullerene (C60) electron-acceptor bearing photosynthetic model compounds are designed to build supramolecular dye-sensitized solar cells (DSSC). It has been found that the solar cell efficiencies normalized for surface coverage (ηrel) are affected by the molecular spacer connecting the porphyrin sensitizer to the TiO2 surface, orientation of the dye molecule, the sensitization conditions (solvent and time) and dye aggregation. Ultrafast transient absorption spectroscopy shows that the forward and reverse electron transfer rates are strongly dependent on the spacer and sensitization conditions. These results also indicate that the electron transfer between sensitizer and TiO2 occurs “through-space” rather than “through-molecular spacer”. Implications of these findings for optimized solar energy/fuel production, and future sensor/biosensor development will be discussed.
Photocatalytic Conversion of CO2 in H2o over Solid Based Materials
Authors: Teramura Kentaro
Published: February 2020

Conversion of the greenhouse gas CO2 into carbon and useful carbon sources such as CO, HCOOH, HCHO, CH3OH, and CH4 is a potential method of solving energy and environmental problems. Photocatalytic conversion of manmade CO2 is attractive from the viewpoint of sustainable energy production and greenhouse gas reduction. Layered double hydroxides (LDH) are synthetic or natural crystalline clays that consist of brucite (Mg(OH)2)-like positively charged two-dimensional sheets in which some divalent cations such as Mg2+ are substituted by trivalent cations; further, water and exchangeable charge-compensating anions are present in the interlayer. In this study, we carried out the photocatalytic conversion of CO2 in H2O using various LDHs. Considerable amount of CO was obtained over various LDHs in the photocatalytic conversion of CO2 and photocatalytic H2 evolution from H2O competitively took place in all cases. Ni-Al LDH exhibited high selectivity to CO because the amount of H2 evolved was relatively low. Ni-Al LDH (Ni/Al = 4) which was aged for 20 h under hydrothermal condition at 383 K after coprecipitation showed the highest activity for the evolution of CO. GC/MS analysis for the photocatalytic conversion of 13C-labeled CO2 clarified that 13CO (m/z = 29) was evolved in priority to 12CO (m/z = 28). Accordingly, CO2 introduced in the gas phase was adsorbed on the surface of LDHs, and then reduced into CO in the photocatalytic conversion of CO2 in water.
Porous Silicon/Carbon Nanocomposites As Anode Materials for Lithium-Ion Batteries
Authors: Fan Li-Zhen , Wang Mingshan
Published: February 2020

A series of porous silicon/carbon composites were successfully synthesized by employing mesoporous silica (SBA-15 and MCM-48) and diatomite as silicon precursor, followed by low temperature magnesiothermic reduction, impregnation and carbonization of phenolic resin. The structure and morphology of the porous composites were characterized by X-ray diffraction, Raman spectroscopy, field emission scanning electron microscope and nitrogen absorption and desorption. Electrochemical performance of the porous composite electrodes were investigated. The obtained Si/C composites present an interweaved porous structure composed of Si, inactive SiOx and conductive carbon. The ordered pore structure is retained after the magnesiothermic reduction of well-ordered mesoporous silica. The resulting porous Si/C composites exhibit high reversible capacity and excellent cycling performance. These improvements could be attributed to the introduction of carbon in the porous Si/C composites, which effectively improve the electrical conductivity. Moreover, the porous structure can accommodate the volume expansion and improve cycling stability of the electrode materials during lithium ion insertion and extraction.
Functionalized Porphycenes
Authors: Jux Norbert , Brenner Wolfgang
Published: February 2020

Functionalized porphycenes

Norbert Jux, Wolfgang Brenner

Department of Chemistry and Pharmacy & Interdisciplinary Center for Molecular Materials, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91054 Erlangen, Germany

Porphycenes were first synthesized by the group of Emanuel Vogel in 1986.[1] Over the years new synthetic routes have been introduced and since then a variety of porphycenes has been generated[2]and used to some extent in the fields of catalysis, protein mimicry and materials science. Due to their intense absorptions in the long-wavelength region, porphycenes are interesting candidates as dyes in photovoltaic applications.

We have started to look into the preparation of functionalized porphycenes with respect to charges, anchor groups, and arylated materials.

Image

Here, we wish to report on the synthesis and some photovoltaic device formation[3,4]of our novel porphycenes.

References

[1] E. Vogel, M. Köcher, H. Schmickler, J. Lex, Angew.
Chem. Int. Ed.
1986, 25, 257-259.

[2] D. Sánchez-García, J.L. Sessler, Chem. Soc. Rev.
2008, 37, 215-232.

[3] W. Brenner, J. Malig, R.D. Costa, D.M. Guldi, N. Jux, Adv. Mater.
2013,
25, 2314–2318.

[4] R.D. Costa, J. Malig, W. Brenner, N. Jux, D.M. Guldi, Adv. Mater.
2013,
25, 2600–2605.
Designing a Precious Metal-Free Catalyst for Purification of Automotive Exhausts: The Dissociation of NO on Cu2O(111) and CuO(110) Surfaces
Authors: Kasai Hideaki , Padama Allan Abraham Bustria , Moreno Joaquin Lorenzo Valmoria
Published: February 2020

Nitrogen oxide (NOx) is a by-product of fossil fuel combustion and forms nitric acid in the air, which is the main reason for acid rain and smog. The interaction of NOxmolecule on catalysts is the rate-limiting step for its reduction process and is the motivation for recent investigations [1, 2]. Three-way catalysts, which are composed of precious metals such as Rh, Pd and Pt, work well for such purpose; however, their efficiency is compensated by their expensive cost. Therefore, a more readily available and inexpensive material with comparable, if not better, catalytic performance is a major concern among automobile companies and researchers.

In our recent work [3-6], we established the promising performance of Cu-based catalysts for the dissociation of NO by employing Computational Materials Design® based on density functional theory. Our results show that NO dissociation on Cu-terminated Cu2O(111) and Cu-terminated CuO(110) surfaces is comparable with Rh(111) [4], which is characterized by a transition state lying below the reference energy (surface and gas phase NO). This phenomenon is attributed to the modified electronic structure of the surface Cu atoms of Cu oxide surfaces in comparison with that of Cu(111). Specifically, the initially low-lying density of states (d orbital) of the surface Cu atoms in Cu(111) are shifted towards the Fermi energy in the Cu oxide systems. In comparison with Rh(111), the calculated NO dissociation barriers are lower on Cu oxide catalysts. Furthermore, the binding energy of co-adsorbed N and O atoms is weaker on Cu oxides, which is favorable for subsequent reactions (Fig. 1). Likewise, our experimental collaborators have verified that Cu oxides can be better catalysts than Rh, Pd and Pt for the purification of exhaust gases.

Indeed, this study has gained recognition as it ranked first in the Technology Trend Survey (Nikkei Shinbun) and was also publicly acknowledged in Japan. The details of our work, as well as the oxidation of CO in the presence of dissociated NO on Cu oxide surface will be discussed in the meeting.

References:

[1] F. Oemry, H. Kasai et al., J. Nanosci. Nanotechnol.11 (2011) 2844.

[2] N.T. Quang, H. Kasai et al., Comput. Mater. Sci. 47 (2009) 111.

[3] H. Kasai, A.A.B. Padama et al., J. Jpn. Petrol. Inst. 56 (2013) 357.

[4] H. Kishi, H. Kasai et al., J. Phys.: Condens. Matter 24 (2012) 262001.

[5] A.A.B. Padama, H. Kasai et al., J. Phys.: Condens. Matter 24 (2012) 175005.

[6] J.L.V. Moreno, A.A.B. Padama, H. Kasai, CrystEngComm (2013) submitted.
Correlating Elastic Properties and Molecular Organization of an Ionic Binary Porphyrin Nanostructure
Authors: Mazur Ursula , Hipps K W , Eskelsen Jeremy R
Published: February 2020

Mechanical and structural properties of a crystalline porphyrin nanostructure composed of meso-tetra(4-sulfonatophenyl)porphyrin (TSPP) and meso-tetra(4-pyridyl)porphyrin (TPyP) will be presented. X-ray photoelectron spectroscopy (XPS), UV-visible spectra, and elemental analysis all support a stoichiometric 1:1 TSPP to TPyP composition. Atomic force microscopy (AFM), revealed that the porphyrin nanostructure is composed of stacked ribbons about 20 nm tall, 70 nm wide, and several microns in length. Selected area electron diffraction (SAED) and powder x-ray diffraction patterns of TSPP:TPyP are consistent with an orthorhombic system and space group Imm2 with lattice parameters a = 26.71, Å b = 20.16 Å, and c = 8.61Å. Crystallographic data is consistent with an arrangement of alternating face-to-face TSPP and TPyP molecules forming ordered columns along the length of the nanorods. The TSPP:TPyP are thermally stable and do not lose their crystallinity when heated to temperatures up to 150 °C. The structural integrity of the solid is attributed to combined noncovalent interactions that include ionic, hydrogen bonding, and π-π interactions. The values of Young's modulus obtained for the crystalline TSPP:TPyP nanorods averaged 6.5 ± 1.3 GPa. This modulus is comparable to those reported for covalently bonded flexible polymeric systems. The robust bonding character of the TSPP:TPyP nanostructures combined with their mechanical properties makes them excellent candidates for flexible optoelectronic devices.
Ferrochelatase, the Cornerstone Sensor Between Porphyrin Synthesis and Iron Metabolism
Authors: Ferreira Gloria C , Gillam Mallory E , Hunter Gregory A
Published: February 2020

The terminal step of heme biosynthesis links the distinct, but synchronized, pathways of porphyrin synthesis and iron transport in nearly all living organisms. Ferrochelatase (or protoporphyrin IX ferrochelatase; Enzyme Commission number 4.9.9.1.1) catalyzes this step, the incorporation of ferrous iron into protoporphyrin IX to yield heme. How ferrochelatase, which, can also catalyze the insertion of other divalent metal ions into protoporphyrin IX, albeit at lower rates, ensures that only ferrous iron is used as the physiological substrate and prevents the potentially damaging oxidative toxicity of ferrous iron remains an unsolved question. Similarly, the ferrochelatase-catalyzed heme synthesis according to the cellular requirements thwarts the accumulation of protoporphyrin IX, a photoreactive and toxic molecule. To define the path the metal ion takes to the catalytic site, we examined the kinetic mechanism of ferrochelatase and ferrochelatase variants, in which the postulated ferrous iron-binding amino acids were replaced with either non-ferrous iron ligands or potential alternative iron-binding amino acids, using pre-steady state kinetics. In addition, the significance of frataxin, a mitochondrial iron chaperone, as the ferrous iron donor of ferrochelatase, was assessed by studying the kinetic mechanism of the ferrochelatase-catalyzed reaction when the metal ion substrate was supplied in the form of “iron-bound frataxin”. Results from this study demonstrate that ferrochelatase is the ultimate cellular sensor of ferrous iron and protoporphyrin IX, which are directly used in heme synthesis and thus bypass their cellular accumulation and consequent toxicities.

Supported by grant 13GRNT16970019 from the American Heart Association, Greater Southeast Affiliate.
Tailoring Porphyrin (Nano)Structures
Authors: Senge Mathias O.
Published: February 2020

Many possibilities exist to modify the structure of porphyrins. These include variation of the central metal, N-substitution or modulation of the macrocyclic π-system. Recent years have seen a surge in π-annulated systems while a more established approach is the synthesis of nonplanar porphyrins via peripheral macrocycle interactions. Any of these strategies results in porphyrin systems with altered structure, conformation and physicochemical properties. What is lacking is true ‘conformational design’ of porphyrins, i.e., the use of the recent advances in organometallic chemistry in conjunction with structural studies to yield functional systems with predesigned conformations. Such an approach would aid development of new optical materials and catalysts.

Similarly, an expanding body of studies on porphyrin nanomaterials on surfaces is beginning to reveal how surface/macrocycle interactions alter the chemical properties of porphyrins. Metallation and metal exchange reactions are possible and specific types of porphyrin nanostructures are now accessible via logical 2D synthesis on metal surfaces. Initial studies of porphyrin-graphene interactions indicate that a combination of tailor made porphyrins with specific macrocycle-surface interactions can yield functional nanomaterials.
New Covalent and Supramolecular Tetraphenyporphyrin Hybrids As Abiotoc Redox-Macromolecules
Authors: Hirsch Andreas
Published: February 2020

We will report on the synthesis of various families of new hybrid-architectures where tetraphenylporphyrines are combined with other redox-active molecules such as fullerenes. In some cases model compound for globular redox proteins have been developed by incorporation of polar and apolar dendritic architectures. Depending on the microenvironment provided by the nature of the dendritic shell the electron-transfer- and coordination properties can be tuned as demonstrated for example by electrochemistry and time-resolved spectroscopic methods. Also nanoparticles such as ZnO have been functionalized with new tetraphenylporphyrin derivates and the use of such materials in dye-sensitized solar cells will be presented.
Artificial Photosynthetic Devices Based on Phthalocyanines
Authors: Torres Tomas , Ballesteros Beatriz , Bottari Giovanni , Setaro Francesca , Ince Mine , Pardo Rodriguez Virtudes , Tejerina Lara , sanchez Carballo Maria , Medel Maria , Aljarilla Ana , Suanzes Pita Juan , Urbani Maxence , Trukhina Olga
Published: February 2020

Phthalocyanines (Pcs) [1-3] are among the few molecules that reveal an intense NIR absorption and therefore, constitute promising dyes in molecular photovoltaics [4]. Pcs have emerged also as excellent light harvesting antennas for incorporation into donor-acceptor systems, mainly in connection with carbon nanostructures as acceptor moieties [3]. During this talk an overview of the results obtained by our group in Madrid will be given.

References

1. G. de la Torre, C. G. Claessens, T. Torres, Chem. Commun.2000 (2007).

2. (a) M.V. Martínez-Díaz, G. de la Torre; T. Torres T. Chem. Commun. 46, 7090 (2010); (b) M. E. Ragoussi, M. Ince, T. Torres, T. Eur. J. Org. Chem. 29, 6475 (2013).

3. G. Bottari, G. de la Torre, D. M. Guldi, T. Torres, Chem. Rev.
110, 6768 (2010).

4. M. E. Ragoussi, J.J. Cid, J.H. Yum, G. de la Torre, D. Di Censo, M. Graetzel, M.K. Nazeeruddin, T. Torres, Angew. Chem. Int. Ed. Eng. 51, 4375 (2012).