bluuebunny/crossref_metadata_2025 huggingface dataset:
High Resolution OLED Using Eco-Friendly Quantum-Dots Functional Color-Filter
Authors: Lee Ji-Eun , Lee Seung-Jae , Kim Seo-Yun , Park Joo-Hyeong , Jung Ui-Hyeon , Sim Tae-hun , Park Jea-Gun
Published: February 2020

Recently, the quantum-dots enhancement film (QDEF) has been introduced to improve the color gamut for LCD technology. Although this QDEF has been realized approximately zero cross-talk between the main blue-(B-), green-(G-), and red-(R-) light emissions in LCDs to almost zero, it would have a considerable loss (> 10%) in the intensity of light due to the light absorbed in the resin medium and transparent sheets. To solve this undesirable loss of light, the LCD technology has been adopted the QD-functional CF LCD which is simply adding the B, G, and R-QDs directly to the color filters (CFs) in conventional LCDs using a blue back-light-unit (BLU).

Motivated by this idea, we suggest this QDCF technology for organic light emitting diode (OLED) devices. In our research, B-, G-, and R-QD-functional CFs were fabricated by using eco-friendly ZnSe / ZnS and InP-based core/shell structure, showing a high photoluminescence-quantum yield (PL-QY) and a narrow full-width at half-maximum (FWHM) as well as a good flexibility in tuning the suitable PL peak wavelength between emitted from QDs and transmitted from CFs. To make the QD-functional color filter layer, blue, green, and red emitting quantum dots dissolved in hexane of 20wt%. Then they were mixed with the blue, green, and red color filters at a rate of 1 to 1. In order to disperse the QD-functional color filter well, ultra-sonication was performed for 10 minutes. Then, the QD-functional color filter solution was coated on the cleaned substrate using the drop process. After drying for 60 minutes, we analyzed the QD-functional CF structures through photoluminescence and UV-visible spectroscopy. It was confirmed that the B-, G, and R-QDs functional CF OLED exhibited that the PL peak emit at 432, 530, and 621 nm-wavelength with a PL FWHM of 13.4, 39, and 42 nm and a PL-QY of 71, 85, and 75 %, respectively. As a result, the RGB color gamut of the proposed OLED using the fabricated QDs function CFs presented a higher value of 118 % (NTSC) and 88.5% (Rec. 2020) result from the zero cross-talk among PL spectrums of RGB colors (Figure 1). These findings make our study unique and applicable for ultra-super high-resolution OLED and become the cornerstone for trying different types of QDs in QD-functional CFs through a simple, environment-issue free, and cost-effective fabrication process.

We will present in detail the wide RGB gamut characteristics and optical properties of QDCF structures using environmentally friendly ZnSe / ZnS and InP quantum dots in addition to driving OLED.

Figure 1
(Invited) Modification By an Ag–Cr Core–Shell Cocatalyst for Highly Selective Photocatalytic Conversion of CO2 by H2o
Authors: Teramura Kentaro
Published: February 2020

A core−shell structure Ag−Cr dual cocatalyst loaded Ga2O3 significantly improved the formation rate of CO and selectivity toward CO evolution, compared with bare Ga2O3, Ag/Ga2O3, Cr/Ga2O3, and other Ag−metals/Ga2O3. The backward reaction tests, which produced CO2 from CO and O2 in H2O, indicated that the modification of Cr on the surface of Ag cocatalyst drastically suppressed the backward reaction for the photocatalytic conversion of CO2. This Ag−Cr dual cocatalyst modification strategy offers a facile approach for remarkably enhancing the photocatalytic efficiency for the conversion of CO2 by H2O.
(Invited) Using Surface Photovoltage Spectroscopy to Observe Photovoltage Generation at the Interfaces of Cu2o, BiVO4, and Rh:SrTiO3 Particles
Authors: Osterloh Frank E. , Wu Zongkai , Melo Mauricio A
Published: February 2020

Surface photovoltage spectroscopy (SPS) allows contact-less measurement of the Galvani photopotential at the interfaces of particles under illumination. Here we use SPS to observe the light intensity and wavelength dependent photopotential in a Ru–SrTiO3:Rh/BiVO4 particle tandem overall water splitting photocatalyst and in particle layers made of Cu2O and BiVO4. For the tandem, a photovoltage develops above 2.20 eV, the effective band gap of the tandem, and reaches its maximal value of −2.45 V at 435 nm (2.44 mW cm–2), which corresponds to 96% of the theoretical limit of the photocatalyst film on the fluorine-doped tin-oxide-coated glass (FTO) substrate. Charge separation is 82% reversible with 18% of charge carriers being trapped in defect states. The unusually strong light intensity dependence of the photovoltage (1.16 V per decade) is attributed to depletion layer changes inside of the BiVO4 microcrystals. Isolated Cu2O particle layers on FTO show p-type behavior and BiVO4 particles show n-type behavior. In a FTO/Cu2O/BiVO4 particle stack, both particles act in tandem, producing up to -2.1 V photovoltage under 2.5 eV excitation, which corresponds to 90% of the ideal limit. The photovoltage spectra also reveal the effects of shading at high excitation energy and the effects of low absorber strength at low excitation energy. These results are relevant to the understanding of photochemical charge transfer at irregular particle surfaces and to the construction of devices for artificial photosynthesis and water splitting.

Figure 1
(Invited) Photoionization in Doped and Undoped Semiconductor Quantum Dots
Authors: Robel Istvan
Published: February 2020

Optoelectronic properties of semiconductor quantum dots strongly depend on the propensity of their band carriers to transition to states extrinsic to the nanocrystal. Photoionization events typically reduce the photoluminescence quantum yield and induce emission intermittency and therefore they are often suppressed in light-emitting applications by the use of passivating barriers in the form of protective ligands or core/shell heterostructuring. In other uses of quantum dots, e.g. as photocatalysts, photocathodes, photodetectors, or solar cells, fast and efficient extraction of carriers to extrinsic states is of key importance. Here, we investigate the photoemission of carriers induced by carrier-carrier or carrier-dopant interactions in intrinsic and intentionally doped nanocrystals. Our studies reveal the ultrafast time scale, spectral response, and interaction mechanism of hot-carrier photoemission in these systems. Application-relevant performance parameters such as quantum efficiency and temporal response will be discussed.
Electrochemistry of Three-Dimensional Porphyrin Arrays and Related Compounds
Authors: Hiroto Satoru
Published: February 2020

Three-dimensional π-conjugated molecules have received extensive attention in many chemical research areas due to their interesting structure and unique characteristics. Among these situations, we found that oxidation of aromatic amines was useful for construction of distorted π-conjugated molecules under laboratory conditions. For example, oxidation of beta-amino substituted porphyrins provided three-dimensional porphyrins in excellent yield. In particular, sequential use of amination and oxidation toward 5,10,15,20-tetramesitylporphyrin effectively afforded highly twisted porphyrin oligomers. These oligomers exhibited high solubility in common organic solvent, which is promising for application to solution-processible molecular wire. In addition, we further investigated the substituent effect on the oxidation of beta-aminoporphyrins. We disclosed that dimerization products were varied dependent on meso-aryl substituents. In this presentation, we will show the electrochemical properties of these porphyrin oligomers in order to investigated the effect of distorted conformation on π-electronic network between porphyrin units.

We also found oxidation of N-aryl beta-amino substituted porphyrins produced dehydropyrazine-bridged porphyrin dimers. Recently, we have succeeded in the synthesis of π-extended dihydrophenazine through oxidation of amino-substituted anthracenes. This molecule exhibited conformational change upon electrochemical and chemical redox conditions. Spectral analysis and theoretical calculation revealed that the aromatic and non-aromatic switch of the central dihydropyrazine moiety by two electron oxidation play important role for this electrochemical responsive behaviors. This time, we also prepared π-extended dihydrophenazine based on porphyrins. The structure was clearly elucidated by X-ray diffraction analysis, showing saddle-shape conformation. The electrochemical analysis exhibited irreversible characteristic upon one-electron oxidation and reduction as observed for anthracene derivatives. In this presentation, we will show the synthetic details and electrochemical behaviors of π-extended dihydrophenazines and related porphyrin arrays.
Extension of π Conjugation System By Functionalization of the Beta Position of Porphyrin
Authors: Perera Rajitha , Wang Hong
Published: February 2020

Porphyrin is a macrocyclic light harvesting molecule that absorbs the light in visible region of the electromagnetic spectrum. Extension of π-conjugation causes the red shifting of the absorbance and adding more fused aromatic rings in to the main macrocycle is a common way to achieve that goal. Heck Coupling reaction can be used to introduce fused aromatic rings in to the β position of porphyrin. π-extended porphyrins possess different and interesting photophysical , Optoelectronic and Physicochemical properties . Aromatic ring fused porphyrins open wide range of applications including in Molecular Rods, Bio sensors, near Infra-red dyes, Photodynamic therapy etc.

In here, we are reporting the use of Heck coupling reaction to synthesis β - extended porphyrin and their red shifted light absorbing properties using its UV-Vis absorption spectrum.
Synthesis, Spectral and Electrochemical Redox Properties of EAA-Appended Porphyrins
Authors: Yadav Inderpal , Sankar Muniappan
Published: February 2020

Porphyrins having nitro substituents at β-position can act as excellent synthons for further functionalization of porphyrins having wide range of applications [1]. β-Nitro-meso-tetraarylporphyrins can be further functionalized in presence of Michael donor such as active methylene compounds which result in the formation of porphyrins and chlorins depending on reaction conditions and bulkiness of the Michael donor [2-5]. A wide variety of active methylene compounds such as 1,3-dicarbonyls, diketoesters and malonates can undergo Michael addition reactions under mild basic conditions [6]. In this regard, we report the selective synthesis of 2-EAA-5,10,15,20-tetraphenylporphyrins and their metal complexes (Fig. 1a) [7].

All of the synthesized EAA-appended porphyrins exhibited enol tautomeric form in solution predominantly. However, there is no keto-enol tautomerism in it as there is no peak for -CH in 1H NMR spectrum. EAA-appended porphyrins have shown multiple oxidations and reductions in cyclic voltammograms possibly due presence of EAA group on porphyrin ring (Fig. 1b).MTPP(EAA) where M = 2H, Co(II), Ni(II), Cu(II) and Zn(II) exhibited a remarkable red shift (10-15 nm) in the B and Q bands as compared to the corresponding MTPPs, whereas all these porphyrins have bands which are blue-shifted by ∼10-14 nm as compared to their precursor, i.e., MTPP(NO2). In this presentation, we will present the synthesis, spectral and electrochemical redox properties of EAA-appended porphyrins.

Figure 1. (a) Molecular structures of synthesized porphyrins and (b) Cyclic voltammograms (CVs) of CuTPP, CuTPP(NO2) and CuEAA complexes in CH2Cl2 at 298 K.

References

1. Serra, V. I. V.; Pires, S. M. G.; Alonso, C. M. A.; Neves, M. G. P. M. S.; Tome, A. C.; Cavaleiro J. A. S. Heterocycl. Chem.
2013, 33, 35.

2. Chaudhri, N.; Grover, N.; Sankar, M. Chem. 2017, 56, 424.

3. Chaudhri, N.; Grover, N.; Sankar, M. Chem. 2017, 56, 11532.

4. Chaudhri, N.; Grover, N.; Sankar, M. Chem. 2018, 57, 6658.

5. Chaudhri, N.; Grover, N.; Sankar, M. Chem. 2018, 57, 11349.

6. Shea, K. M.; Jaquinod L.; Smith, K. M. Org. Chem.
1998,
63, 7013.

7. Giuntini, F.; Faustino,M. A. F.; Neves, M. G. P. M. S.; Tome, C.; Silva, A. M. S.; Cavaleiro, J. A. S. Tetrahedron
2005, 61, 10454.

Figure 1
Synthesis and Computational Study of Pentacenequinone-Fused Porphyrins with Triply-Split Soret Bands
Authors: Moss Austen , Washburn Spenser , Wang Hong
Published: February 2020

Porphyrins are one of nature’s most prolific aromatic macrocycles and are one of the most important components of light harvesting in green plants. In pursuit of organic dyes with applications in artificial photosynthesis, porphyrins with broadened and red-shifted UV-Vis spectra are of interest in optimizing the energy obtained from the solar spectrum. Extension of the conjugation of porphyrins through fused rings to the β-positions of the porphyrin induces red-shifted and broadened UV-Visible absorption spectra, but synthesis and characterization of porphyrins with triply-split Soret bands with potential to further enhance the capture of the solar spectrum are unexplored.

Herein there is report of synthesis, crystal structure, and computational study of cross-conjugated β-extended pentacenequinone-fused porphyrins with triply-split Soret bands, which to the best of our knowledge are the first to exhibit such Soret bands. These molecules’ experimental UV-Vis spectrum is compared to computationally derived UV-Vis spectra, and magnetic circular dichroism (MCD) is used to elucidate the electronic transitions that give rise to the triply-split Soret band.

Figure 1
Structural Design of Porphyrins for Binary and Ternary Organic Solar Cells with High Efficiency and Low Energy Loss
Authors: Cuesta Virginia , Vartanian Maida , Sharma Ganesh , de la Cruz Pilar , Langa Fernando
Published: February 2020

Porphyrin-based molecules have been explored for a long time as the active materials in dye-sensitized solar cells achieving efficiencies as high as 13%. Nevertheless, until the last few years, this family of molecules has been scarcely explored as donor materials in bulk heterojunction (BHJ) organic solar cells (OSCs).

Believing that porphyrin-based molecules should play a more important role in BHJ OSCs we started a few years ago a project in this field using a careful structural optimization. Here I´ll present our last results in this field using porphyrin-based molecules in binary and ternary OSCs, reaching efficiencies close to 10% with low energy loss.

References

1. S. Arrechea, A. Aljarilla, P. de la Cruz, E. Palomares, G. Sharma and F. Langa, Nanoscale, 2016, 8, 17953-17962.

2. G. Morán, S. Arrechea, P. de la Cruz, V. Cuesta, S. Biswas, E. Palomares, G. D. Sharma and F. Langa, J. Mater. Chem. A, 2016, 4, 11009-11022.

3. V. Cuesta, M. Vartanian, P. d. l. Cruz, R. Singhal, G. D. Sharma and F. Langa, J. Mater. Chem. A, 2017, 5, 1057-1065.

4. S. Arrechea, A. Aljarilla, P. de la Cruz, M. K. Singh, G. D. Sharma, F. Langa. J. Mater. Chem. C, 2017, 5, 4742.

5. M. Vartanian, R. Singhal, P. de la Cruz, S. Biswas, G. D. Sharma and F. Langa, ACS Appl. Energy Mater. 2018, 1, 1304.

6. M. Vartanian, P. de la Cruz, F. Langa, S. Biswas, G. D. Sharma. Nanoscale, 2018, 10, 12100.

7. M. Vartanian, R. Singhal, P. de la Cruz, G. D. Sharma and F. Langa. Chem. Commun. 2018, 54, 14144.
Charge Transport within Metal-Organic Frameworks: The Role of Topologically Controlled Charge Hopping Process
Authors: Deria Pravas , Maindan Karan , Li Xinlin
Published: February 2020

Metal-organic frameworks (MOFs), assembled from redox active building blocks such as metalloporphyrins, have defined these 3D crystalline porous molecular assemblies as emerging compositions for energy conversion. In this regards, it was established that MOF-modified working electrodes can provide a high surface concentration of electrocatalytic species that do not need to diffuse in/out. Electrocatalytic conversions involving multi-electron redox activation, such as porphyrinatoiron mediated CO2 reduction, require efficient charge transport process within the framework. However, the potentiometric difference between the metalloporphyrin based catalytic linkers and metal-oxo nodes enforces a hopping type charge transport processes. Analysis of the electron transfer processes within the framework of the Marcus theory suggests that besides the unique reorganization energy required in the porous composition, the initial-state/final-state electronic coupling term (i.e. the charge-transfer integral, HDA
) will play a critical role in such redox hopping process as this term exponentially dependent on the modular molecular geometry, particularly the distance (r) between the donor (D) and acceptor (A). This paper will discuss how the charge-hopping process is inherently controlled by the modular geometries defined by the underlined topological network of the MOF compositions.
Dynamic Molecular Invasion into Multiply Interlocked Catenane Composed of Porphyrins and Phthalocyanine
Authors: Tanaka Kentaro , Yamada Yasuyuki , Ito Ryohei , Ogino Sayaka , Kato Tatsuhisa
Published: February 2020

Commonly, in molecular inclusion phenomena or molecular recognition processes, flexibility on the molecular size or shape of a host molecule is incompatible with a high affinity of association and accuracy of selectivity. However, if the host has a narrow access for incorporating the guest, the transition process during the complexation requires a higher activation energy. A molecular elevator, which is a molecular machine composed of two planar molecular components joined with more than two interlock linkages, could solve the dilemma through dynamic molecular invasion of a guest molecule into the cage surrounded by the planar components. The movable component with macrocyclic rings fused with a planar core can migrate between two competitive recognition sites along the linear threads attached on the other planar component. However, although the macrocyclic rings are attracted to one of the recognition sites, the planar core with the rings still has the ability to move along the threads. This is because the affinity between the ring and recognition point does not help to anchor the ring at this position, but only increases the probability of the position. Therefore, this flexibility of the interlock linkage satisfies the requirement of the dynamic invasion of a guest molecule. The molecular system permits the invasion of a large guest molecule by expanding the access and stabilizing the host–guest interaction by induced fit based on the interactions between the ring and recognition point.

A multiply interlocked catenane with a novel molecular topology was synthesized; a phthalocyanine bearing four peripheral crown ethers was quadruply interlocked with a cofacial porphyrin dimer bridged with four alkylammonium chains (Figure). The supramolecular conjugate has two nanospaces surrounded by a porphyrin, a phthalocyanine, and four alkyl chains to accommodate guest molecules. Because the phthalocyanine is movable along the alkyl chains, it acts as an adjustable wall, permitting the invasion of large molecules to the nanospaces without spoiling the affinity of the association. The dynamic molecular invasion allowed the intercalation of dianionic porphyrins into both the nanospaces with a high affinity.

Figure 1
From Ferrous HRP to Compound I and Back: The Role of Protein and the Mediators in Reversible Redox Transitions
Authors: LeVasseur Grant , Stettler Allsion , Chen Dawei , Zhang Zipin , Proshlyakov Denis A.
Published: February 2020

Highly oxidized iron species play key role in the catalysis of many heme and non-heme enzymes due to their ability to activate substrates via electron or hydrogen atom transfer. In Nature, such highly reactivate and unstable states are typically generated by activation and reduction of molecular oxygen by ferrous porphyrin with the ensuing transfer of redox equivalents onto the cofactor and/or protein itself. Oxygen activation is also associated with a variety of side-reactions, including generation of ROS and self-inactivation. This study investigates alternative approaches to sustaining catalytic activity of highly-oxidized heme species via direct oxidation of cofactor-bound solvent ligand under externally applied electric potential. We developed experimental framework that allows to quickly and reversibly traverse a range of oxidation states of heme cofactor between ferrous iron and Compound I while monitoring redox changes spectroscopically in the UV-Vis or IR domains. We investigate the role of redox mediators, their structures and redox potentials on the ability to catalyze electron transfer to and from the active site of horseradish peroxidase. We show that self-catalyzed modification of the protein moiety enhances the rate the electron transfer, eventually enabling sustained redox transitions in the absence of a mediator. Our results also demonstrate the role on intra-protein solvent molecule as an intrinsic reductant, rationalizing spontaneous conversion of Compounds I and II to the ferric state.
Porphyrin-Based Triad with Exceptionally High Magnetic Field Effects (MFE) on Phosphorescence
Authors: Andrianov Dmitry , Vinogradov Sergei
Published: February 2020

Magnetic control over molecular emissivity presents interests for various fields of technology and medicine. Here, we report experiments exploring magnetic field effects (MFE) on phosphorescence in a new triad, consisting of phosphorescent Pt porphyrin (PtP), rosamine B (RosB) and trialkoxybenzene (TAB), covalently linked together by conductive oligophenylene bridges. Upon photoexcitation the system undergoes two sequential reversible electron transfer processes (ET), generating two radical pairs (RP). The first rate-limiting ET originates in the local PtP triplet state, and it is slightly endergonic, competing with, but not entirely quenching the PtP phosphorescence. The second ET is exergonic, resulting in the formation of the final RP with large inter-radial distance. The RPs recombine either to the ground state (singlet channel) or back to the emissive PtP triplet state (triplet channel). The net distribution over the recombination channels, and hence the phosphorescence decay lifetime and intensity, are governed by the spin dynamics in the RP(s) and, therefore, are sensitive to external magnetic fields.

The triad was found to exhibit remarkably strong positive MFE on phosphorescence at ambient temperatures with the magnitude of ~10% in fields as low as 200 mT. The observed features are characteristic of the hyperfine mechanism, although at higher fields a slight negative MFE was also observed, presumably due to the Δg mechanism. The system was characterized by static and time-resolved optical spectroscopies in the fs, ns and μs-to-ms domains as well as by time-resolved EPR. These studies revealed peculiar dynamics of the system, whereby the initial population of the PtP triplet rapidly equilibrates with the RosB triplet, forming a long-lived triplet reservoir, existing in equilibrium with the RP states. A kinetic model has been developed that allowed us to accurately reproduce the observed charge and energy dynamics of the triad. The model makes it possible to predict how the MFE and the performance of the system can be improved. Overall, this work constitutes an important step forward towards the design of magnetically sensitive luminescent materials.
Electronic Structure of Metal-Organic Complexes from an Optimally-Tuned Range-Separated Hybrid Functional
Authors: Kronik Leeor
Published: February 2020

Metal-organic complexes, e.g., metal-porphyrins, -phthalocyanines, and –corroles, pose significant challenges to first principles theory, often due to competition between different electronic configurations and the need to describe localized and delocalized electronic states on the same footing. This is even more so for spin-crossover compounds, where different spin-configurations are very close in energy by definition. Here, I will present our recent progress on these issues, based on the general strategy of an optimally-tuned range-separated hybrid density functional. I will emphasize quantities that can be verified experimentally via spectroscopy. I will present applications to specific systems, including gas-phase molecules, solvated molecules, and molecular crystals, and discuss successes and remaining challenges.
Thiophene-Fused Expanded Porphyrins with π-System Switching
Authors: Higashino Tomohiro , Imahori Hiroshi
Published: February 2020

Expanded porphyrins that consist of more than five pyrrole units have attracted much attention because of their unique properties such as a flexible π-conjugation circuit, absorption in the visible to near infrared region, and a variable redox state. Since their optical and photophysical properties can be greatly altered by their π-systems, π-system switching based on expanded porphyrins have attracted much interest.

Recently, we designed expanded porphyrins with dithieno[3,4-b:3',4'-d]thiophene (β-DTT) unit, which can be regarded as an alternative to a thiophene-fused pyrrole unit. The β-DTT unit could yield two types of π-networks, one is a macrocyclic π-network with incorporation of the lone pair of the central sulfur atom, and the other is a cross-conjugated π-network without incorporation of the lone pair. Thus we expected that the β-DTT unit would provide a new class of core-modified and aromatic-fused expanded porphyrins with π-system switching. We synthesized octaphyrins with the β-DTT unit and demonstrated that oxidation of sulfur atoms on the β-DTT unit was able to switch the π-network of octaphyrin from a macrocyclic 36π-electron network to a cross-conjugated network. In addition, we also synthesized hexaphyrins with the β-DTT unit and revealed a unique, unprecedented π-system switching between a Möbius cross-conjugated π-system and a Hückel antiaromatic π-system. Therefore, the β-DTT unit is a new effective motif to realize π-system switching of expanded porphyrins.
Novel Porphyrinoids from α,α-Linked Oligopyrroles
Authors: Martínez-Edo Gabriel , Casado-Aguilera Carlos , Anguera Gonzalo , Kauffmann Brice , Borrell José I. , Borrós Salvador , Sánchez-García David
Published: February 2020

α,α-linked oligopyrroles play a crucial role in the synthesis of expanded porphyrins. The preparation of macrocycles such as porphycenes, amethyrins or cyclopyrroles is based on the coupling or condensation of the proper functionalized bipyrrole or terpyrrole. Although longer α,α-linked oligopyrroles have been reported, their chemical instability has hampered their use as synthetic building blocks.

Our group have developed a new family of 2,2’-bipyrroles 1 which possesses a remarkable chemical stability ascribed to the presence of two electron withdrawing groups. Bipyrroles 1 can be easily brominated at the α positions allowing their homologation with pyrrole units by means of palladium catalyzed reactions. This strategy has allowed the concise preparation of quaterpyrrole 2 and sexipyrrole 3. In this presentation, the preparation of these oligomers and their use to synthetize new expanded porphyrins will be discussed.

Figure 1
(Invited) All-in-One Graphene Composite-Based Fiberwearable Supercapacitor
Authors: Yu Aiping
Published: February 2020

Graphene fibers (GF) have generated great interest in wearable electronics applications due to their excellent mechanical flexibility and superior electrical conductivity. Herein, an all-in-one graphene and MnO2 composite hybrid supercapacitor fiber device has been designed and tested. The unique coaxial design of this device enables large scale production and avoids the risk of short circuiting. The backbone of the device consists of GF that not only provides a durable scaffold for the entire device, but also ensures fast electron transfer during charge-discharge. The introduction of a MnO2 (200 nm in length) hierarchical nanostructured film, with abundant active sites contacting the interface of the PVA/H3PO4 gel electrolyte, enhanced the pseudocapacitance dramatically compared to the graphene-only device. The entire device displays outstanding mechanical strength as well as good electrocapacitive performance with a volumetric capacitance of 29.6 F cm-3 at 2 mv s-1. The capacitance of the device maintained under bending testing from 0° to 150°, while the capacitance retention was kept 93% after 1000 cycles. These unique features make this device a promising candidate for applications in wearable fabric supercapacitors.
Facile Synthesis of Industrially Scalable and Cost Effective WO3 for Electrochromic Device and Photocatalysis
Authors: Rakibuddin MD , Shinde Mahesh Ashok , Kim Haekyoung
Published: February 2020

Tungsten trioxide (WO3), an important member of the transition metal oxide family, is a potential candidate for photocatalysis and electrochromic device which have large impact for developing a sustainable environment. The most common chemical strategies for the synthesis of WO3 are the sol−gel and hydrothermal methods, where a tungsten precursor generally a metal tungstate is treated in an acidic environment to generate peroxo−polytungstate acid, followed by heating with capping agents for several hours. However, most of the existing methods are labor intensive, require harsh reaction conditions (high temperature and pressure), have low yields, and also need complex apparatus as well as expensive toxic chemicals. Therefore, the exploration of facile new strategies for the synthesis of WO3 nanostructures continues. Considering the above drawbacks, a simple and low−cost method for the synthesis of WO3 micro–nanostructures by thermal annealing of tungsten powder under ambient conditions is reported. Our strategy is facile, cheap, rapid, and highly reproducible for large–scale production, and the use of toxic precursors or additional capping agents is also eliminated. The as–synthesized WO3 samples are thoroughly characterized. The TEM results show that the size of highly crystalline WO3 particles can be tuned from micro to nano level by simply varying the annealing temperatures. The BET results demonstrate that the surface area and pore size of the synthesized WO3 decreases with increasing annealing temperatures. Furthermore, the WO3 synthesized at 550 °C (WO–550) exhibits higher surface area and pore size, and also excellent photocatalytic activity compared to commercially available WO3. However, among the synthesized WO3 particles, only WO–550 exhibits moderate electrochromic properties. We believe that the synthesis of WO3 nanomaterial by our method could have various industrial applications, and yield an excellent alternative to commercial WO3.

Reference:

1. Ceram. Int.
2018, 452, 400

2. J. Mater. Chem. C 2016, 4, 10887

3. New J. Chem.
2017, 41, 15327
(Invited) Stray Light Suppression Using Carbon Nanotube Based Black Coating
Authors: Wang Dan , Hall Timothy D , Radhakrishnan Rajeswaran , Inman Maria , Taylor E. J. , Skinn Brian , Snyder Stephen
Published: February 2020

Space-borne instruments, such as exo-atmospheric optical sensors and seeker telescopes, require low reflectivity surfaces to minimize stray and reflected light across the visible and infrared wavebands. Black surface coating treatments have been demonstrated as effective approaches to obtain low reflective surfaces. The surface features and intrinsic properties of the coating materials play an important role for scattering, absorbing, or trapping light. The excellent optical absorption performance, light weight, and large surface areas of carbon nanotubes (CNTs) make them as ideal coating materials for obtaining low reflectivity surfaces.

Within this context, Faraday Technology Inc. is developing an electrophoretic deposition process to deposit dense, multi-walled carbon nanotubes onto test substrates. Specifically, we are evaluating the effect of bath formulation and pulsed electric field deposition parameters then characterizing the deposited CNT coatings by reflectance spectra. The bath formulation was controlled by modifying the surface charge of the carbon nanotubes by polymer dispersants or bound functional groups, next these functionalized materials were electrophoretically deposited onto the substrates under an applied pulsed electric field. As shown in Figure 1, it is possible to achieve a uniform CNT coating on a stainless steel substrate (Figure 1 Inset) that achieves a diffuse reflectance of 0.8% ~ 1.2% over the visible range. Currently, we are working to optimize the pulsed electric field conditions to achieve lower reflectivity CNT coating formation.

If successful this program will demonstrate a scalable technique for producing CNT black coatings can not only be used for minimizing stray and reflected light for space-borne instruments, but also offer potential applications in other optical related devices which request low reflective surfaces, such as solar cells.

Acknowledgements: The financial support of NASA Contract No. 80NNSC18P2062 is acknowledged.

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(Keynote) Nanomaterials Transitions to Industry: Energy, Medicine and Devices
Authors: Tour James M.
Published: February 2020

Discussed will be several nanotechnologies that have translated to industry. This will include graphene nanoribbons, graphene-nanotube hybrids, laser-induced graphene, bulk graphene synthesis methods, and other high surface area carbons. The materials are being used in electronic devices, batteries, anti-counterfeiting, medicine, oil recovery and other commercial platforms.
Development of a New Copper Corrosion Screening Methodology for Application in Microelectronics
Authors: Alptekin John , Salunke Ashish Shivaji , Asokan Muthappan , Issac Goutham , Caperton Joshua , Chyan Oliver
Published: February 2020

Due to the constant miniaturization of microelectronics, the aim of the semiconductor industry has been to increase the packaging density of devices. Wire bonds form the primary interconnects between the integrated circuit chip and the metal lead frame in semiconductor packaging. Gold (Au) wire has been used for wire bonding in the electronics industry because of its mechanical and electrical properties, high reliability, and ease of assembly. However, due to the increasingly high cost of Au, alternative wire bonding materials have been considered. Copper (Cu) is gradually replacing Au because it exhibits not only a high resistance to electromigration, but also has excellent electrical conductivity and a low resistivity. The benefit of copper’s conductivity is that it reduces heat generated by joule heating, thus reducing RC delay. However, copper also has its drawbacks; tiny amounts of contaminant can corrode Cu interconnects, leading to the failure of entire microelectronic devices. On-chip corrosion within Cu interconnect microstructures can result in increased defectiveness, which causes serious reliability issues and decreases production yield. Copper is susceptible to corrode in acidic and strong alkaline solutions in the presence of oxygen and other oxidants. Effective corrosion monitoring is critical as an early alert before the onset of corrosion-related failure.

In this study, we report a new method for monitoring the corrosion of copper relevant to the microelectronics industry through the combination of electrical resistance measurement changes of Cu wire and microscopic time-lapse imaging. Industry-grade 99.99% Cu bonding wire (diameter = 25μm) was exposed to the harsh, oxidizing conditions of ammonium persulfate, and its change in resistance was monitored. As the corrosion of Cu bonding wire took place, the cross-sectional area of the wire decreased, causing an increase in its resistance (via R= ρ•l/A). During the resistance monitoring, the simultaneous microscope time-lapse imaging enabled Cu corrosion to be observed in real time. Due to the combined quantitative and qualitative nature of this metrology, it provides detail on the corrosion process that might not be obtained by traditional corrosion tests. While ammonium persulfate will almost never be encountered by an IC device during normal use, it provides a rapid screening environment that can quickly distinguish between corrosion inhibition and no protection at all. This metrology was used to test both bare Cu bonding wire and corrosion-inhibitor coated bonding wire, and showed a drastic difference in their corrosion rate and behavior. This work ultimately aids with inhibitor selection and inhibitor coating design that will help ensure long term reliability of electronics used in industrial applications.

Figure 1
Dynamical Measurements of Surface Transformations By Galvanic Replacement Reactions on Metal Electrode Interfaces
Authors: Schichtl Zebulon , Mehrabi Hamed , Coridan Robert
Published: February 2020

There are a number of possible structural and compositional outcomes for galvanic replacement reactions of noble metal ions on transition metal substrates. Some

combinations nucleate separate layers and eventually cover an entire electrode, while others form complex alloy phases. The chemical mechanism of galvanic replacement is well studied but little is known about the resulting solid-state transformations. Here, we use in situ electrochemical methods to monitor the energetics of galvanic replacement reactions at metal electrode interfaces. We show that open circuit potential and cyclic voltammetry measurements can be used to follow the progress of the reactions and rates of cathodic and anodic half reactions. Tracking the dynamics of the open circuit potential over time allows us to observe the effects galvanic replacement has on the electrode/electrolyte interface, and through cyclic voltammetry, we are able to investigate reaction kinetics of template metal dissolution and metal deposition at any point during the replacement process. Finally, we will discuss how these monitoring strategies can be useful for fabricating hierarchically structured surfaces for selective electrocatalytic reactions.
In-Situ Electrochemical Characterization on Pcmp Cleaning Under Brushing Conditions
Authors: Liu Jun , White Michael , Johnson Cody , Roy Dipankar
Published: February 2020

An in-situ electrochemical method was developed to evaluate pCMP cleaner interaction with substrate of interest under brushing conditions. Results indicate that the kinetics of corrosion inhibitor in PlanarClean(R) AG formulations reacting with copper and cobalt are critical for maintaining galvanic corrosion protection. This technique enables a better understanding of inhibitor adsorption on wafer substrate in real CMP tools. In addition, SEM images obtained on patterned wafer coupons under brushing conditions showed good correlation with in-situ electrochemical data.
Bottom-up Gold Filling of High Aspect Ratio Trenches :Toward a Mechanistic Understanding
Authors: Ambrozik Stephen , Moffat Thomas P. , Josell Daniel
Published: February 2020

Cu is the standard choice for the formation of multi-level 3-D interconnects allowing for microelectronic chip-stacking (1). This is predicated on the well-defined additive chemistries that drive the superconformal Cu filling of through silicon vias (TSVs) and trenches (2). To transition to Au filling of complex 3-D Si architectures for optoelectronic applications, analogous chemistries that enable preferential filling within recessed silicon features must be developed. To date the state of the art for void free Au filling has come from the use of a Pb additive in both KAu(CN)2 (3, 4) and Na3Au(SO3)2 (5) electrolytes. Both of these systems yield superconformal filling via a curvature enhanced accelerator coverage (CEAC) mechanism. However, due to the toxicity of CN-
and Pb2+ containing electrolytes, alternatives must be explored. Recently, it has been demonstrated that the addition of Bi to alkaline Na3Au(SO3)2 electrolytes yields preferential bottom-up Au electrodeposition in Si trenches, with limited deposition on the free surface (6). The addition of Bi to the intrinsically suppressed Na3Au(SO3)2 electrolyte clearly accelerates deposition(6, 7). However, growth in this system does not propagate via the typical CEAC mechanism demonstrated in other accelerated systems (3). Instead the growth propagates via a mechanism more closely resembling that of S-shaped negative differential resistance (S-NDR) based on suppression breakdown, typical for suppressor based additive systems(8). This talk will explore the utilization of this Bi, Na3Au(SO3)2 electrolyte system for the bottom-up filling of high aspect ratio silicon trenches. The effect of; potential, additive concentration and electrolyte transport will be explored on the filling of features with aspect ratios ranging from 1.5 to 17. Additionally, the chemical and morphological nature of the accelerated bottoms of features, and of the passive free surface, will be compared via x-ray photoelectron spectroscopy, scanning electron microscopy and anodic stripping voltammetry to gain mechanistic insight into the role of Bi in deposition acceleration and feature localization.

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A Molten Salt Electrochemical Approach for the Synthesis of Graphite
Authors: Bagri Prashant , Luo Huimin , Dai Sheng
Published: February 2020

Graphite is considered by the US Department of Energy to be a critical element. Due to its widespread use as anodes in batteries, the demand for high purity graphite for battery applications is expected to increase for the foreseeable future. Synthetic graphite, due to its high purity is generally the preferred choice for battery applications. The current process for the synthesis of graphite is very energy intensive and requires heat treatment of carbon precursor to temperature up to 3300 K for successful graphitization. In the paper, a new method for the graphitization is reported, once that requires significantly lower temperatures and employs an electrochemical approach. Cathodic electrochemical polarization of amorphous carbon in molten CaCl2 at around 1100 K for under 2 hours, transforms amorphous carbon to a highly graphitic structure. This process has the potential to save significant energy compared to existing process. Further, a preliminary economic analysis of this new process will also be presented in this paper.
Developing a Physics-Based Model of the Electrocoating Process: Experimentation and Simulation
Authors: Marlar Tyler , Padash Fardin , Trainor Andrew , Liu Wanjiao , Okerberg Brian , Zawacky Steve R. , Harb John N.
Published: February 2020

The objective of this work is to advance the mechanistic understanding of cathodic electrocoating by improving process performance and enhancing the accuracy of process simulation. Our efforts to do this are focused on the initial processes responsible for deposition, which are examined through direct experimentation and simulation. The principal component of the coating is an epoxy-amine resin dispersed in solution as micelles and stabilized by protonated amines. Electrocoating (e-coating) is a global industrial process providing a corrosive resistant base paint to automobile bodies. Automobile bodies exhibit complex geometries, leading to an inherently non-uniform current distribution during e-coating. Exposed areas such as exterior parts coat first. As the exterior parts coat, the electrically resistive polymer coating shifts deposition to less accessible areas and, eventually, to occluded areas such as rocker panels. Presently, empirical models are used to model coating thickness; these models tend to overpredict deposition in occluded areas. Therefore, an understanding of the mechanisms that control the e-coating process will improve the predictive capabilities of e-coat models, with the goal of enabling accurate digital design. A number of factors that may influence the initial stages of deposition have been identified including: i) regions of locally high current density caused by defects or nonuniformities (e.g., bubbles or partial deposits) on the deposition surface, ii) a concentrated micelle layer in solution near the deposition surface, and iii) changes in the composition of the aqueous phase at the deposition surface (e.g., pH changes). Combinations of these factors are also possible. In this study, we use bulk solution flow under controlled conditions to probe, measure and understand the factors that influence deposition. Anionic exchange membranes are also used to decouple important factors to determine their relative importance. Results show that deposition is possible without a pH increase. Deposits have been shown to initiate at locations on the surface where the current density is locally high. One example of this is ring-shaped deposits that form around bubbles on galvanized steel substrates. Simulations of the current distribution validate the role of the local current density, as does the deposition behavior observed at artificially formed defects. Experiments involving the influence of flow on the initial stages of deposition have yielded unexpected results that have important mechanistic implications. These results provide an increased understanding of fundamental processes responsible for initial deposition, which is the foundation needed for advanced physics-based models of the electrocoating process.
Fibrous Organosulfur Compounds As Cathode Materials for High-Performance Lithium-Sulfur Batteries
Authors: Weret Misganaw Adigo , Hwang Bing-Joe , Jeffrey Kuo Chung-Feng , Su Wei-Nien
Published: February 2020

Rechargeable lithium-sulfur (Li-S) batteries consist of lithium metal having high theoretical specific capacity (3860 mAh g-1) as an anode [1] and sulfur with a theoretical capacity (1672 mAh g-1) as a cathode [2] are considered as the most promising candidates for next generation energy storage technologies. Organosulfur compound cathode materials deliver high specific capacity, have low cost, suppress the polysulfide dissolution and decipher issues related to shuttling effect. Though, these cathode materials have promising advantages, inherent problems such as low sulfur loading and poor rate capability hinder practical applications.

Here, we prepare a fibrous organosulfur compounds using an electrospinning method followed by the heat treatment. The nanofiber organosulfur compounds prepared have a high surface area, high porosity, and a unique nanonetwork structure which are important for high electrochemical performance Li-S batteries. As a result, the prepared nanofiber organosulfur compounds offer high lithium storage capacity >1000 mAh g-1 with stable cycle life over 100 cycles at 0.1C, high rate capability, and hold high active material contents (52 wt%).