bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Magnetism and Electrochemistry of Fullerene-Based Composites
Authors: Feng Yongqiang , Wang Xiao , Dong Peipei
Published: July 2021

Endohedral metallofullerenes (EMFs), a negatively sp
2-hybridized spherical carbon surface containing alternating hexagons and pentagons doped with metal ion(s) or cluster inside, have attracted more and more interests owing to their unique nesting structures and alluring chemical/physical properties. Herein, we will discuss several typical spin-active endohedral metallofullerenes. To steer the electron spin of paramagnetic fullerene molecules, a solid-state spin system was constructed via encapsulating paramagnetic fullerenes into the pores of metal-organic frameworks (MOFs) forming a EMF/MOF compostie, and an axisymmetric paramagnetic property was found. This kind of solid spin system can be used as a probe for nanoscale nuclear magnetic resonance or for motion imaging of a single biomolecule.

Besides, as a representative allotrope of carbon, fullerene-based composite also exhibit fascinating electrochemistry, e.g., serving as electrocatalyst. In this work, a novel hybrid electrocatalyst comprising fullerene carbon dot (FQD)-decorated cobalt nickel layered double hydroxide (CoNi-LDH) nanosheets anchored on porous nickel foam (NF) is elaborately fabricated. The obtained FQD/CoNi-LDH/NF exhibits superior electrocatalytic activity for hydrogen and oxygen evolution as well as urea oxidation under ambient atmosphere. Both experiment and density functional theory (DFT) calculations demonstrate that the charge transfer from FQD to CoNi-LDH could account for the excellent catalytic performance of the newly-synthesized catalyst, and the decorated FQD finely modulates the electronic structure of CoNi-LDH, favoring the adsorption of active hydrogen atom, and thus promote the catalytic process. The present work would provide useful guidance for designing and developing fullerene-based electrocatalysts for hydrogen production.
(Invited) Understanding Endohedral Metallofullerenes from Theoretical Calculations
Authors: Jin Peng
Published: July 2021

Theoretical calculations based on the density functional theory (DFT) are heavily employed in the current research of endohedral metallofullerenes (EMFs), and they have greatly deepened our understandings of this kind of alluring nanomaterial. Herein, we will show a series of new computational results regarding the structural characterization, electronic properties, bonding pattern, and chemical functionalization of EMFs. The studied systems cover conventional mono-EMFs and novel members such as those containing actinide elements (Th, U). In addition, the molecular structures of several representative endohedral clusterfullerenes are discussed to provide new insight into their stability and formation mechanism. Detailed wavefunction analyses further reveal many intriguing undiscovered phenomena. Finally, our very recent works in close collaboration with experimentalists will be briefly introduced.
(Invited) Preparation of Core@Carbon-Shell Nanostructures and Their Applications as Bifunctional Electrocatalysts for Electrochemical Water Splitting
Authors: Feng Lai , Jin Peng
Published: July 2021

A series of core@carbon-shell nanostructures with size of ~5 nm are prepared, in which RuM-based nanoparticle is encapsulated with an ultra-thin carbon shell (see Figure 1). The optimized catalysts (e-Ni0.6Ru0.4@C and Co0.8Ru0.2Ox@NC) display outstanding HER and OER activities in alkaline media,1,2 which are among the best so far reported for various carbon-based electrocatalysts. The electrode pair of either e-Ni0.6Ru0.4@C‖e- Ni0.6Ru0.4@C or Co0.8Ru0.2Ox@NC‖Co0.8Ru0.2Ox@NC requires a low cell voltage for driving OWS to reach 100 or 500 mA cm-2, far outperforming the benchmark electrode pair of Pt/C‖RuO2. These carbon-based catalysts also exhibit superior durability as compared to those of precious catalysts. The experimental evidences combining with density functional theory (DFT) computations reveal the synergistic effect of core and carbon shell. Thus, our results may further shed light on how to design and optimize carbon-based electrocatalysts to achieve enhanced catalytic performance for electrochemical water splitting.

References

Feng, L.; et al., Ultrafine carbon encapsulated NiRu alloys as bifunctional electrocatalysts for boosting overall water splitting: morphological and electronic modulation through minor Ru alloying. Mater. Chem. A,
2020, 8, 9049–9057.

Feng, L.; et al., Nanosheet-Derived Ultrafine CoRuOx@NC Nanoparticles with a Core@Shell Structure as Bifunctional Electrocatalysts for Electrochemical Water Splitting with High Current Density or Low Power Input. ACS Sustainable Chem. Eng.
2020, 8, 12089-12099.

Figure 1. Schematic structure of e-Ni0.6Ru0.4@C.

Figure 1
(Nanocarbons Division Best Poster Award - 3rd Place) Intrinsic Shear Strain in Graphene Heterostructures Detected Via Raman Spectroscopy
Authors: Schmidt Kirby , Li Xinyi , Pourianejad Sajedeh , Trofe Anthony , Rotkin Slava V. , Ignatova Tetyana
Published: July 2021

Graphene’s electronic band structure is extremely sensitive to small perturbations in its crystal lattice. Because of this it is vital to correctly characterize strain, doping and defects in graphene through nondestructive measurements. Characterization through Raman Spectroscopy allows this nondestructive measurement. Graphene on Transition Metal Dichalcogenides (TMDCs) show increased shear strain which is not caused by defects introduced through the transfer method. We prove this using Raman analysis of graphene samples on silicon oxide and TMDC. Graphene shows G peak splitting and shift indicative strain increasing on top of TMDC when compared to nearby graphene on silicon oxide.

Acknowledgement: Authors acknowledge the JSNN, a member of the Southeastern Nanotechnology Infrastructure Corridor (SENIC) and National Nanotechnology Coordinated Infrastructure (NNCI), supported by the NSF (ECCS-1542174), The PSU Two-Dimensional Crystal Consortium – Materials Innovation Platform 2DCC-MIP, supported by NSF cooperative agreement (DMR- 1539916). Authors are grateful to Dr. S. Aravamudhan (JSNN) and Dr. J. Redwing (2DCC MIP).
(Nanocarbons Division Best Poster Award - 3rd Place) Reversible Quenching of Graphene Oxide Photoluminescence Under the External Electric Field
Authors: Lee Bong Han , Valimukhametova Alina , Ryan Conor , Paz Thomas , Grote Fabian , Naumov Anton V.
Published: July 2021

With the advent of graphene, there has been an interest in utilizing this material and its derivative, graphene oxide (GO) for novel applications in nanodevices such as bio and gas sensors, solid-state supercapacitors and solar cells. Although GO exhibits lower conductivity and structural stability, it possesses an energy band gap that enables fluorescence emission in the visible/near infrared leading to a plethora of optoelectronic applications. In order to allow fine-tuning of its optical properties in the device geometry, new physical techniques are required that, unlike existing chemical approaches, yield substantial alteration of GO structure. Such a desired new technique is one that is electronically controlled and leads to reversible changes in GO optoelectronic properties. In this work, we for the first time investigate the methods to controllably alter the optical response of GO with the electric field and provide theoretical modeling of the electric field-induced changes. Field-dependent GO emission is studied in bulk GO/polyvinylpyrrolidone films with up to 6% reversible decrease under 1.6 V m−1 electric fields. On an individual flake level, a more substantial over 50% quenching is achieved for select GO flakes in a polymeric matrix between interdigitated microelectrodes subject to two orders of magnitude higher fields. This effect is modeled on a single exciton level by utilizing Wentzel, Kremer, and Brillouin approximation for electron escape from the exciton potential well. In an aqueous suspension at low fields, GO flakes exhibit electrophoretic migration, indicating a degree of charge separation and a possibility of manipulating GO materials on a single-flake level to assemble electric field-controlled microelectronics. As a result of this work, we suggest the potential of varying the optical and electronic properties of GO via the electric field for the advancement and control over its optoelectronic device applications.
Non-Covalent and Covalent Nanostructured Functionalization of 2D Materials
Authors: De Feyter Steven
Published: July 2021

In this presentation, I will mainly focus on the functionalization of 2D materials using molecules. Nanostructuring is at the heart of all functionalization protocols that we develop, because it opens new possibilities of control and functionality. A first approach is based on molecular self-assembly at the interface between a liquid or air, and the substrate. A second approach is based on covalent functionalization. It will be demonstrated how in addition to bottom-up strategies, also top-down nanolithography can be used to nanostructure surfaces, and both approaches can even be combined. A third approach does not focus on the functionalization of the surface, but uses the surface as a support for the in-plane covalent stitching of molecules, leading to the formation of on-surface 2D polymers. Advanced interface specific methods provide structural, dynamic, and other types of information, at the nanoscopic level.

Figure 1
Preparation of Gr-Reinforced Cu Foil: A Challenge to Ultrathin Thickness
Authors: Song Gongsheng , Pan Chunxu
Published: July 2021

A layered Cu/Gr/Cu ultrathin foil via a one-step electrochemical route

A layered structure has a better effect on improving performance of the graphene (Gr)-reinforced composites due to its unique two-dimensional structure and excellent properties. In this work, a novel “one-step” electrochemical route was proposed for synthesizing the Gr-reinforced ultrathin copper (Cu) foil with high performance. The process includes: 1) A loose graphene oxide (GO) membrane, was prepared by electrophoresis deposition (EPD), that allows Cu ions passing through; 2) According to the difference of Cu deposition potential on different substrates, a potential step was designed for electrodepositing Cu successively on both sides of the GO membrane, i.e., the bottom Cu layer forms under low over-potential, while the top Cu layer forms under high over-potential. The experimental results show that the foil thickness reaches to as thin as 4-5 μm, and the tensile strength is almost twice as large as that of pure Cu foil. This process is simple, controllable and possible mass production, and expected to further practical applications in fields of Cu clad plate, printed circuit board and lithium-ion battery cathode collector system for saving raw material and also the space. In addition, this work proposes a new idea for preparing the layered composites via electrochemical route.

A Cu-(CNTs+Gr) composite ultrathin foil via electrodeposition

The incorporation of nano-reinforcement, such as carbon nanotubes (CNTs) and graphene (Gr), into copper (Cu) matrix via electrodeposition is a promising method to improve its comprehensive property. However, the challenge is to achieve a uniformly suspended electrolyte with these reinforcements or surfactant due to their inferior dispersibility. In this work, we report a process to produce a kind of high performance Cu-(CNTs+Gr) composite foil by using hybrid self-dispersing reinforcement CNTs+Gr via a direct current (DC) electrodeposition, which further results in an ultrathin foil reach to the thickness as low as 4 μm. In this process, firstly, the precursor graphene oxide (GO) with amphipathicity acts as a surfactant-like substance and disperses CNTs uniformly through the π-π bonding in-between GO and CNTs in the copper sulfate electrolyte. Then, GO is reduced into Gr during electrodeposition, and the synergistic effects of CNTs and Gr play a key rule to improve the ultrathin Cu-(CNTs+Gr) composite foil’s properties, including tensile strength up to 436 MPa, inoxidizability and superior electrical conductivity. This work provides a possibility to have mass-production of Cu foil as thin as 4 μm in industry and broad applications in the future.
(Invited) Two-Dimensional Pnictogens: Van Der Waals Growth, Stability, and Phase Transformation
Authors: Moutanabbir Oussama , Fortin-Deschênes Matthieu
Published: July 2021

Pnictogens (P, As, Sb, Bi) emerged as a new class of elemental 2D materials displaying a wide range of electronic and topological properties. With their ns2 np3 valence electronic configuration and sp3 hybridization, group VA elements are the only elemental group which forms vdW and quasi-vdW structures throughout the entire group, thus providing a rich allotropic system. Light group VA elements crystallize in the semiconducting orthorhombic layered phase (A17) and heavier group VA elements prefer the semi-metallic rhombohedral layered phase (A7). At nanoscale thicknesses, group VA materials undergo various electronic phase transitions. For instance, A17 P – black phosphorus – is a high mobility 2D semiconductor with a thickness-dependent direct band gap gradually varying between 0.3-2 eV as its thickness decreases from bulk to single layer. Similarly, A7 Sb is predicted to exhibit topological semimetal, topological insulator, quantum spin Hall and indirect band gap semiconductor phases at thicknesses between 1 and 22 layers.

Despite their highly attractive scientific and technological potential, 2D materials remain scarcely implemented in scalable devices and technologies due to several challenges including among others the lack of large-area and uniform synthesis methods. In fact, many 2D materials exist only in the realm of theoretical predictions and most 2D materials can only be produced by mechanical or chemical exfoliation from bulk crystals, yielding 2D flakes with limited dimensions and poor thickness control. Developing epitaxial growth methods is therefore a crucial step to enable the integration of 2D materials in emerging technologies. With this perspective, this presentation will address the development of the molecular beam epitaxy (MBE) growth of group VA 2D materials on semiconducting and vdW substrates. Furthermore, thermal, ambient and phase stability of these emerging 2D materials is studied using in situ low-energy electron microscopy, transmission electron microscopy, x-ray photoelectron emission microscopy, and ab initio calculations. MBE growth of 2D-Sb and 2D-AsSb is demonstrated on Ge(111) and graphene. Real-time LEEM measurements of the growth dynamics combined with in situ STM allow to determine the nucleation and growth mechanisms on semiconductor and vdW substrates. Subtle behavior during growth or thermal annealing was revealed based on these in situ studies including the metastability and layered-to-layered phase transformation mechanisms of A17 2D-Sb, which was previously considered as an unstable Sb phase. These results provide a deeper understanding of vdW growth of group VA 2D materials and layered-to-layered phase transformation mechanisms.
(Invited) Processing of 2D Materials Using Ultra-Low Energy Ion Implantation
Authors: Pereira Lino M.C.
Published: July 2021

Functionalization of 2D materials generally requires the modification of their physicochemical properties. Several approaches have been explored: the use of different substrates, creation of intrinsic defects (e.g. vacancies), adsorption and intercalation (of atoms, clusters or molecules), substitutional doping, among others. For incorporation of substitutional or intercalated elements, despite the numerous approaches that have been investigated, a major challenge remains: the limited control over the concentration and form of incorporation. An alternative approach is to incorporate the foreign species by ultra-low energy (ULE) ion implantation, precisely tuning the number of implanted ions and their kinetic energy. Here, I review our recent work on ULE ion implantation of 2D materials, with emphasis on substitutional doping and intercalation of graphene. Our approach is based on a wide range of characterization techniques (structural and electronic), including scanning tunneling microscopy and spectroscopy (STM/STS), synchrotron-based X-ray photoelectron spectroscopy (XPS), angle-resolved photoemission spectroscopy (ARPES), X-ray magnetic circular dichroism (XMCD), transport measurements, among others. These experimental studies are complemented by density functional theory (DFT) and molecular dynamics (MD) simulations.
Impedance Characteristics of Biofilms Formed on Graphene Films and Their Substrates
Authors: Kanematsu Hideyuki , Nakagawa Ryoichi , Torisawa Yuki , Miura Hidekazu , Ishihara Masatou , Ban Masahito , Hirai Nobumitsu , Kogo Takeshi , Barry Dana M.
Published: July 2021

Biofilms are inhomogeneous film-like matters formed on materials by bacterial activities. They bring about many detrimental problems in various fields such as cooling pipes, kitchens, toilets, baths, marine structures, food industries, medical applications, hospitals etc., as well as beneficial purposes. Therefore, they should be controlled properly and the sensing is very important therefore. We have confirmed so far that graphene as one of representative 2D materials has high sensitivity to biofilm formation due to their pi electron clouds. The characteristics would lead to the application of biofilm sensors. In this experiment, we formed one layer, two layers and multi-layers graphenes were formed by a thermal CVD process on copper substrates and in some cases, they were moved to the surfaces of polyethylene and biofilms were formed on graphene films with those substrates. Then the impedance characteristics were measured and the relation between the impedance characteristics and biofilms formation/growth behaviors were investigated and discussed. As a result, we obtained the following results.

1. In the case of graphene films on all substrates, the characteristic peaks of impedance were observed at some specific frequencies.

2. The impedance peaks were different between copper substrates and PE ones.

3. The impedance peaks were also different according to the numbers of graphene layers.

4. The impedance peaks became more remarkable for non-freeze hydrated specimens.

5. In the case of polymeric substrates, the impedance characteristics of biofilms showed different patters.

We presume that the impedance peaks were obtained, since external polymeric substances (EPS) in biofilms would have absorbed electromagnetic waves. Therefore, the polymeric substrates could have affected the absorbance behaviors of electromagnetic waves differently. The application possibilities of the experimental results to biofilm sensors were finally discussed.
Immunoaffinity-Based Graphene Field-Effect Transistor Sensor Platform for Fast Detection of S1 Subunit Protein from COVID-19
Authors: Fu Wangyang , Zhang Xiaoyan
Published: July 2021

The epidemic of the novel coronavirus (COVID-19) pneumonia touches the nerve of every person. To prevent and control the epidemic, early diagnosis must be addressed. Nucleic acid polymerase chain reaction (PCR) is currently used worldwide to identify positive carriers of COVID-19 when the virus attacks. However, it requires sophisticated biological design, trained personnel, bulky instruments, and is impossible or inaccurate to detect infected but recovered people or asymptomatic carriers. Here, in an effort towards expanding the screening coverage, we combined the extremely sensitive graphene field-effect transistor (Gr-FET) with highly selective antibody-antigen interaction to develop a COVID-19 immuno-sensor. The Gr-FET immunosensors can fast identify and accurately capture the subunit S1 protein from COVID-19 at a limit of detection down to 0.2 pM. Further results suggest that antigen S1 functionalized Gr-FET can be applied to screen neutralizing-antibodies with high efficiency. Thus, Gr-FET immunosensors provide an appealing opportunity to address the earlier diagnosis as well as the analysis and design of neutralizing-antibody locking methods of this ongoing public health crisis.
Nanoscale Patterning of Graphene Field-Effect Transistors for Single-Molecule Functionalization and Time Series
Authors: Bencherif Amira , Tie Monique , Martel Richard , Bouilly Delphine
Published: July 2021

With the discovery of low-dimensional materials, the extreme miniaturization of field-effect transistors (FETs) has revealed such devices as powerful sensors for experiments at the single-molecule scale. In particular, FET devices functionalized with an individual molecule have been able to record, via fluctuations in the electrical conductance, various types of single-molecule dynamic changes, for example enzymatic activity1 DNA hybridization2,3 or DNA folding4. So far, such studies have mostly been carried out with FETs based on 1D materials such as carbon nanotubes (CNTs) or silicon nanowires (SiNWs). The 1D geometry of these materials facilitates the capture of a 0D molecule and provides enhanced sensitivity of the conductance to the functionalized site. However, FETs based on 1D materials often present scalability issues, due to challenges in controlling their growth and/or assembly.

Here, we propose an approach based on nanoscale patterning of a 2D material to assemble FET arrays compatible for single-molecule capture and detection. First, we report wafer-scale microfabrication of arrays of graphene field-effect transistors (GFETs) with micron-scale channels. Like its 1D counterpart, graphene presents a high and sensitive electrical conductivity as well as carbon-based surface chemistry for single-molecule functionalization. GFET arrays were built from high-quality graphene synthesized by chemical vapor deposition (CVD) and transferred using a custom automated process on patterned electrodes. Then, we describe the nanoscale patterning of graphene channels in nanoconstrictions suitable for single-molecule functionalization and sensitivity. Using electron-beam lithography (EBL) and deep reactive ion etching (DRIE), we were able to produce a combination of high-resolution features in graphene (<100nm) as well as nanofluidics reactions chambers (<50nm), to promote single-molecule chemistry on the graphene. We will present our recent results in functionalizing these nanoconstrictions with single-stranded DNA and in collecting high-resolution electrical time series from these constructs. Finally, we will discuss the performance of such graphene-based devices for single-molecule experiments.

Bibliography

Choi, Y., Weiss, G. A. & Collins, P. G. Single molecule recordings of lysozyme activity. Physical Chemistry Chemical Physics (2013). doi:10.1039/c3cp51356d

Sorgenfrei, S. & Shepard, K. L. Label-free field-effect-based single-molecule detection of DNA hybridization kinetics. Nat. Nanotechnol.
6, 126–132 (2011).

Vernick, S. et al. Electrostatic melting in a single-molecule field-effect transistor with applications in genomic identification. Nat. Commun.
8, 1–9 (2017).

Bouilly, D. et al. Single-molecule reaction chemistry in patterned nanowells. Nano Lett.
16, 4679–4685 (2016).
Effects of Dielectric Screening and Charge Transfer Pathways on Interlayer Excitons in Atomically Thin Hybrid Heterostructures
Authors: Ji Jaehoon , Choi Jong Hyun
Published: July 2021

Interlayer excitons in 2D heterostructures have been studied extensively as a means to realize the future optoelectronics such as the spin-valleytronics and excitonic devices. Despite significant efforts, the understanding of the parameters that influence interlayer excitons still remain limited. In this work, we have investigated the effects of dielectric screening and charge transfer pathways on interlayer excitons in MoS2/WSe2 heterobilayers. We constructed organic-layer-inserted MoS2/organic/WSe2 hybrid structures using various organic chromophores: 1,3-bis(3,5-dipyrid-3-ylphenyl)benzene (B3PyPB), eosin Y (EY), tetracyanoquinodimethane (TCNQ), and cobalt-centered phthalocyanine (CoPc). We found that the embedded organic layers enhance dielectric screening on interlayer excitons, resulting in a blue-shift of interlayer emission. The interlayer charge transfer between the TMDC layers may also be changed from tunneling to band-assisted transfer with an organic layer that forms the staggered band alignment with TMDC layers. The band-assisted transfer creates a greater population of interlayer excitons, which causes a stronger dipolar interaction and consequently leads to a further PL blue-shift. Lastly, we show that interlayer emission can be quenched by inserting electron or hole trapping organic layers. The results shed critical insights into interlayer excitons and form the basis for next-generation optoelectronic devices.
(Invited) Tuning Interlayer Exciton Energetics in Twisted and Stacked Materials
Authors: Graham Matt
Published: July 2021

Using time-space resolved ultrafast microscopy on individual 2D crystal grains, we show how long-range interlayer electronic coupling can be selectively enhanced either by applying an E-field or by twisting the layer stacking orientation. In both cases, transient interlayer exciton states form and drive the optoelectronic material response. Considering first twisted bilayer graphene (tBLG), we discovered how stacking-angle tunable absorption resonances form a strongly-bound exciton state as a consequence of the symmetrized rehybridization of the interlayer 2p orbitals.[1] Using two-photon photoluminescence and intraband-transient absorption microscopies, we have recently imaged the photoemission and exciton dynamics from single-grains of tBLG. After resonant excitation, our results suggest the formation of strongly-bound (up to 690 meV), metastable interlayer exciton states. Our observation of resonant PL emission from twisted bilayer graphene materials in Fig. 1a is best explained by the theoretically predicted coexistence of strongly-bound interlayer excitons and metallic graphene continuum states. We show how stacking angle -tunable interlayer excitons states may permit new photocurrent extraction routes from quasi-stable interlayer excitons.

Unlike stacked graphene, semiconducting 2D transition metal dichalcogenides (TMDCs) have diffuse interlayer d-orbital overlap. To enhance interlayer electronic coupling in TMDCs, we apply an interlayer directed E-field, inducing electron-hole dissociation [2]. Time-resolved photocurrents show that stacked WSe2 devices can have both IQE >50% and fast (<60 ps) picosecond electron escape times. Our ultrafast photocurrent rates kinetics give the same E-field-dependent electronic escape and dissociation rates seen from optical ultrafast microscopy. To confirm the fast electronic escape rates, we show the ratio of the electronic rates accurately matches our overall WSe2 device IQE in the limit of zero Auger recombination. Collectively, we show how optical and photocurrent-based ultrafast microscopies together provide an analytical extraction of the photocurrent-generating ultrafast dynamics in both TMDCs and tBLG van der Waals stacked materials.

References

[1] H. Patel, L. Huang, C.J. Kim, J. Park, M. W. Graham, Stacking Angle-Tunable Photoluminescence from Interlayer Exciton States in Twisted Bilayer Graphene, Nature Comm, 10, 1445 (2019).

[2] K. T. Vogt, S.-F. Shi, F. Wang, M. W. Graham, Ultrafast photocurrent and absorption microscopy of few-layer TMD devices isolate rate-limiting dynamics driving fast and efficient photoresponse, J Phys Chem C, 124, 28, 15195–15204 (2020)

Figure 1
(Invited) Optical Characterization of Nanomaterial By Means of Hyperspectral Global Imaging
Authors: Blais-Ouellette Sébastien , Dion-Bertrand Laura-Isabelle , Martel Richard , Heller Daniel A.
Published: July 2021

Fluorescence and Raman spectroscopy are powerful techniques to probe the intrinsic properties of low dimensional materials such as carbon nanotubes and graphene. In this study, we present how a hyperspectral imaging platform based on Bragg gratings designed for global imaging can help improve the fabrication methods of various nanomaterials. Spectrally and spatially resolved maps were acquired on different samples over a million points. The intrinsic specificity of Raman scattering combined with the analysis performed by the global imaging modality makes it a useful method to assess large maps (hundreds of microns) of the spatial distribution of defects, number of layers and stacking order. On the other hand, hyperspectral photoluminescence provides straightforward information on photostability and allows multiplexing. This presentation will highlight how hyperspectral microscopy can be used to study carbon nanotubes based fluorophores, CVD graphene and MoS2.
(Invited) A Perovskite Solar Farm at Crete Enabled By the Utilization of 2D Layered Materials
Authors: Kymakis Emmanuel
Published: July 2021

The development of perovskite photovoltaics has matured to a point of industry-scale production; however, their operational long-term stability still remains the main obstacle impeding their commercialization. The utilization of solution processable graphene and related two-dimensional materials (GRMs), at different sections of perovskite solar cells represents an effective approach to enhance both the power conversion efficiency and the lifetime stability of such photovoltaic technology. On top of that, their compatibility with large-scale, solution-processable methods such as sheet-to-sheet and roll-to-roll lay the ground for their direct integration in pilot manufacturing lines, significantly improves the capital expenditure of this technology. In this context, a wide range of GRMs have been used as replacements for conventional charge transport layers and interlayers not only to improve the charge dynamics of the devices but also to protect the perovskite layer against diffusion of external agents, such as oxygen and moisture and the metal ion migration.

In this talk, I will give an overview of our recent activities on the realization of highly efficient and stable perovskite solar cells and modules. I will give a holistic insight on how the hierarchical placement of GRMs in all the perovskite device can tune the transport layers work-function, passivate the interface/surface traps and most importantly protect the interfaces, resulting in a simultaneously improvement of the triangle of performance, stability and scalability of the perovskite PVs. Furthermore, I will discuss the implementation of a Solar Farm consisting of GRM enabled perovskite 0.5 sqm panels at the Hellenic Mediterranean University campus at Crete, in which outdoor field tests are currently performed. The latter is a pivotal information on the commercialization potential of this technology. I will also directly correlate the electrical measurements of the solar farm with environmental parameters, while at the same time, benchmark their outdoor performance against commercial PV panels installed at the same site.
Understanding the Electrochemical Performance of Hybrid Na(2-x)LixFeP2O7 (x= 0, 0.6) Cathode Materials
Authors: James Abraham Jeffin , Arro Christian Randell A. , Tariq Hanan Abdurehman , Shakoor Abdul , Kahraman Ramazan , Al-Qaradawi Siham
Published: July 2021

The need for green energy is increasing every year, and renewable energy and efficient storage require large-scale lithium-ion batteries (LIBs). The use of LIBs has resulted in declining lithium (Li) reserves, which effectively increases the cost of current LIBs. Na ion batteries (NIBs) have been proposed as an alternative to the LIBs as it displays similar properties to them. However, Na ions (Na+), possessing higher ionic radii, and lower energy density than Li ion (Li+), the NIBs have limited commercialization potential. One proposed solution is the development of hybrid cathodes, where the cathode has both Li+ and Na+ in the structure and can be active in both Li and Na cells. The current work describes the development of hybrid cathode material in which the substitution of Li+ for Na+ in the configuration of Na(2-x)LixFeP2O7 (x=0,0,6) is considered to form Na1.4Li0.6FeP2O7 cathodes. The solid-state technique was used for the synthesis of Na(2-x)LixFeP2O7 (x=0.6) cathode. Structural analysis indicates the formation of phase pure crystalline materials with non-uniform and sub-micron particles. It is also noticed that the original triclinic structure of Na2FeP2O7 is preserved with the substitution of Li+. It is also revealed that Na1.4Li0.6FeP2O7 shows improved thermal stability up to 550°C when compared to Na2FeP2O7. The electrochemical performance of Na2FeP2O7 and Na1.4Li0.6FeP2O7 is investigated using various electrochemical characterizations. Both Li and Na half cells show electrochemical activity for Na1.4Li0.6FeP2O7 with decent cyclability. However, Na1.4Li0.6FeP2O7, suffers from lower electrochemical efficiency when compared to Na2FeP2O7. This could mainly be due to the lattice distortion upon substituting larger Na+ ions with smaller Li+ ions. Nevertheless, Na1.4Li0.6FeP2O7 hybrid cathode material can be used as a reference to synthesize new cathode materials with improved efficiency.
(Invited) Rational Design of Quantum Dot/Mediator Interfaces for Efficient Triplet- Annihilation-Based Photon Upconversion Systems
Authors: Lian Tianquan
Published: July 2021

Photon upconversion, where two or more low energy photons are converted into one high energy photon, shows great potential in bioimaging, catalysis and solar energy conversion. Photon upconversion has traditionally been realized with lanthanide-doped nanoparticles, or organic dye sensitized triplet-triplet annihilation (TTA) based upconversion platforms. In recent years, QD sensitized triplet-triplet annihilation based upconversion systems have achieved impressive upconversion quantum efficiency and demonstrated many unique advantages, including high photostability, large extinction coefficient, high spectral coverage and tunability, and low singlet-triplet energy gap. In this talk, we discuss our recent work in developing and understanding QD/mediator interface for efficient QD-sensitized photon upconversion. We summarize the main results of time-resolved spectroscopic studies of various factors affecting the rate of triplet energy transfer (TET) from the QD to the surface attached mediator (TET1) and from the mediator to the emitter in solution (TET2). To identify the key design rules, we compare three PbS sensitized upconversion systems using three mediator molecules with the same tetracene triplet acceptor at different distances from the QD. Our results show that the mediator triplet state is mostly formed by direct TET from quantum dot. With increasing distance between the mediator and PbS QD, the efficiency of the TET1 from the QD to the mediator decreases due to a decrease in the rate of this triplet energy transfer step, while the efficiency of the TET2 from the mediator to emitter increases due to a reduction in the QD induced mediator triplet state decay (via the external heavy atom effect). The rate constant of TET2 is three orders of magnitude slower than the diffusion limited value. We show that the effect of QD/mediator on the total unconversion efficiency measured under CW illumination conditions can be well accounted for by the independently determined efficiencies of TET1 and TET2 steps, providing important insight on the design and rational improvement of efficient photon upconversion systems.
(Invited) Inorganic/Organic Hybride Perovskites for Energy-Related Applications
Authors: Yen Hung-Ju , Chiang Pin-Chieh , Baskoro Febri
Published: July 2021

State-of-the-art energy storage devices work by insertion/extraction of the alkali metal ions into a porous electrode material, where the overall capacity is strongly dependent on the accessibility of the host material interior to the ions. On the other hand, the performance stability depends on various factors governed by the specific constitution of the electrode. Here we show that molecularly engineered hybrid perovskites can be utilized in Lithium-ion batteries as anode materials with good performance. More hybrid perovskites can be targets for further optimization considering the structural diversity. We anticipate that these results open a new direction for the use of hybrid perovskites for energy storage applications.
Efficient Ternary Organic Solar Cells (>14%) Enabled By Non-Fullerene Acceptors
Authors: Privado María , Guijarro Fernando G , Sharma Ganesh D , de la Cruz Pilar , Langa Fernando
Published: July 2021

Organic Solar Cells (OSCs) fabricated from a ternary active layer, comprised of a mixture of either two electron donors and one acceptor or one donor and two acceptors, are presently at the vanguard of competitive OSCs affording an increased PCE when compared to binary counterparts.

In this presentation, we´ll show our last work in ternary OSCs using two small molecule donors or two electron acceptors reaching efficiencies as high as 14%.

References

Privado, P. Malhotra, P. de la Cruz, R. Singhal, J. Cerdá, J. Aragó, E. Ortí, G. D. Sharma, F. Langa. Solar RRL
2020, 4, 1900471.

G. Guijarro, P. Malhotra, G. Gupta, R. Caballero, P. de la Cruz, R. Singhal, G. D. Sharma, F. Langa. J. Mater. Chem. C, 2020, 8, 4763.

G. Guijarro, R. Caballero, P. de la Cruz, R. Singhal, F. Langa, G.D. Sharma. Solar RRL
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Privado, P. de la Cruz, G. Gupta, R. Singhal, G. D. Sharma, F. Langa Solar Energy
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Rodríguez-Seco, L. Cabau, M. Privado, P. de la Cruz, F. Langa, G. D. Sharma, E. Palomares. ACS App. Energy. Mater. 2020. DOI: 10.1021/acsaem.0c02469
Basic Concept and Additive Engineering in All-Inorganic Perovskites-Based Light-Emitting Diodes (PeLEDs)
Authors: Ighodalo Kester O
Published: July 2021

All-inorganic perovskite light-emitting diodes (PeLEDs) have outstanding properties, such as good operational stability, bright luminance, high efficiency, excellent color purity, and low cost. Apart from the device structure of the PeLEDs, the addition of different polymers, organic cations with ammonium functionalities, etc., is other significant factors to guarantees better all-around performance of all inorganic PeLEDs. In this chapter, we provide updated knowledge of all inorganic PeLEDs by analyzing the causes of the poor performance of all inorganic PeLEDs and its behavior in different device structure despite the excellent photoelectronic properties. We also discussed strategies to improve the performance, photoluminescence properties, and operational stability of all-inorganic PeLEDs films with the process of additive engineering.

Keywords: All-inorganic PeLEDs, additive engineering, polymer additive, organic cations.
Luminescent Soft Crystals That Exhibit Color Changes in Response to Vapor
Authors: Kato Masako
Published: July 2021

It is well-known that square-planar Pt(II) complexes exhibit characteristic luminescence when the complex units are stacked with Pt···Pt short contacts. Such assembled systems have interesting properties that the luminescence color can change sensitively in response to the surroundings such as temperature, pressure, and vapor. Therefore, the Pt(II) complexes are attractive as flexible and ordered sensing materials called soft crystals. In this presentation, the latest topics of vapochromic Pt(II) complexes are introduced.

1. Wide-range color tuning of luminescence based on the fine control of the Pt···Pt interactions.1) A series of assembled Pt(II) complexes comprising N-heterocyclic carbene and cyanide ligands was constructed using different substituent groups (Figure 1). All the complexes exhibited highly efficient photoluminescence with an emission quantum yield in the solid state at room temperature, originating from the triplet metal-metal-to ligand charge transfer (3MMLCT) state. Their emission colors cover the entire visible region from red to blue by changing the substituents. It is notable that blue 3MMLCT emission was realized firstly in this system. In addition, vapochromic response was observed based on the single-crystal-to-single-crystal transformation.

2. Fast and stable vapochromic response induced through nanocrystal formation of a luminescent platinum(II) complex on periodic mesoporous organosilica.2) A hybrid vapoluminescent system exhibiting fast and repeatable response was constructed using periodic mesoporous organosilica with bipyridine moieties (Bpy-PMO) and a Pt(II) complex bearing a potentially luminescent 2-phenylpyridinato ligand. An intense red luminescence appeared when the Pt(II)-complex immobilized Bpy-PMO was exposed to methanol vapor and disappeared on exposure to pyridine vapor. The ON-OFF vapochromic behavior occurred repeatedly in a methanol/ pyridine/heating cycle. Interestingly, a rapid response was achieved in the second cycle and cycles thereafter. The unique vapoluminescence triggered by the unprecedented protodesilylation on exposure to protic solvent vapor at room temperature is attributable to Bpy-PMO being a giant ligand and an effective vapor condenser. Consequently, this hybrid system presents a new strategy for developing sensors using bulk powdery materials.

1) D. Saito et al., Angew. Chem. Int. Ed. 2020, 59, 18723–18730.

2) H. Matsukawa et al., Sci. Rep.
2019, 9:15151.

Figure 1
(Invited) A Soft-Crystal Chemiluminescence System: Luminescence Property of Adamantylideneadamantane 1,2-Dioxetanes Conjugated with a Fluorophore
Authors: Matsuhashi Chihiro , Uekusa Hidehiro , Ichiyanagi Kouhei , Sato-Tomita Ayana , Ryu Meguya , Morikawa Junko , Maki Shojiro , Hirano Takashi
Published: July 2021

Chemiluminescence (CL) produces photon by a chemical reaction of a CL substrate to give a product in the excited state. Because emitted photons are readily detectable, CL is a powerful tool to monitor a chemical event in an analyte. In the materials science, CL will be useful to analyze an event at the molecular level in a solid material for developing functional devises. For instance, CL has been used to measure mechanical forces applied to polymers.1 In this study, we have investigated CL reactions in molecular crystals, to create the chemistry of “soft crystals”2 as reaction fields. For this purpose, we investigated CL properties of adamantylideneadamantane 1,2-dioxetanes (Adox) conjugated with a fluorophore in the crystalline state. We report here characteristic CL properties of the Adox derivatives and talk about the molecular mechanism of the crystalline-state CL.3

Adox is one of stable 1,2-dioxetanes, and its thermal decomposition partially gives the excited singlet (S1) or triplet (T1) state of 2-adamantanone (AdCO).4 The S1 state of AdCO can fluoresce weakly with the maximum at 420 nm. A designed Adox derivative 1 has a non-π-conjugatively linked phthahlimide as a crystal structure modulator and the emitting moiety by accepting energy from the excited AdCO. We first prepared syn- and anti-isomers of the Adox derivative 1 and investigated their CL properties in crystals. The isomers showed contrastive CL properties by heating their crystal samples at 160 °C. Each crystal structure of the isomers has its own distinctive packing pattern of the Adox and phthalimide moieties, and the clear differences in CL intensities, emission maxima and reaction kinetics of the isomers are well correlated to the packing patterns. Thus, CL emission properties and reaction kinetics in the crystalline-state were precisely manipulated by the crystal structures. To understand the crystalline-state CL reactions in detail, we further investigated CL of modified Adox derivatives along with thermoanalytical studies. The results provide information on the origins of the characteristic CL behaviors and the reaction mechanism in soft crystals.

1) Chen, Y.; Spiering, A. J. H.; Karthikeyan, S.; Peters, G. W. M.; Meijer, E. W.; Sijbesma, R. P., Nat. Chem., 2012, 4, 559.

2) Kato, M.; Ito, H.; Hasegawa, M.; Ishii, K., Chem. Eur. J., 2019, 25, 5105.

3) Matsuhashi, C.; Ueno, T.; Uekusa, H.; Sato-Tomita, A.; Ichiyanagi, K.; Maki, S.; Hirano, T., Chem. Commun., 2020, 56, 3369.

4) Hummelen, J. C.; Luider, T. M.; Wynberg, H., Pure Appl. Chem., 1987, 59, 639.

Figure 1
(Invited) Upconverted Emission in AC-Driven Electrochemiluminescent Device
Authors: Kobayashi Norihisa
Published: July 2021

Electrochemiluminescence (ECL) is a phenomenon in which light is emitted from the excited state of a redox-active material generated by electrochemical reactions. Among light-emitting device, ECL devices have various advantages in terms of structure and simple fabrication, and they are therefore expected as next generation emitting devices.

Concerning to the ECL device, we have reported the improvement of emission response, ECL intensity and stability of the ECL device by employing alternating current (AC)-driven method [1, 2]. AC-ECL showed further improvement in ECL properties when TiO2 nanoparticles [3], suitable solvent [4] and DNA/Ru complex hybrid films were used [5] In this paper, we report that electrochemically triggered upconverted luminescence through triplet–triplet energy transfer (TTET) and subsequent triplet–triplet annihilation upconversion (TTA-UC) is observed for the first time in the electrochemiluminescence properties of a Ru complex/diphenylantracene (DPA) containing electrochemical device [6]. This mechanism will be discussed. Reference [1]. T. Nobeshima, T. Morimoto, K. Nakamura, N. Kobayashi, J. Mater. Chem., 20, 10630 (2010) [2]. T. Nobeshima, M. Nakakomi, K. Nakamura and N. Kobayashi, Adv. Opt. Mater., 1, 144 (2013) [3]. S. Tsuneyasu, K. Ichihara, K. Nakamura and N. Kobayashi, Phys. Chem. Chem. Phys., 18, 16317 (2016) [4]. S. Tsuneyasu, T. Ichikawa, K. Nakamura and N. Kobayashi, ChemElectroChem, 4, 1731 (2017) [5]. S. Tsuneyasu, R. Takahashi, H. Minami, K. Nakamura and N. Kobayashi, Sci. Report, 7, 8525 (2017) [6]. H. Minami, T. Ichikawa, K. Nakamura and N. Kobayashi, Chem. Commun., 55, 12611 (2019)