Article
Physics, Applied
Takatoshi Yamada, Tomoaki Masuzawa, Yuki Okigawa
Summary: To enhance the carrier mobility and suppress the intrinsic carrier density of graphene on a silicon dioxide substrate, a potassium-doped nano graphene intermediate layer was introduced. Electrical properties of the fabricated graphene field-effect transistors were measured, and the results showed a shift in the Dirac point and increased carrier density and mobility. The ionized potassium atoms in the intermediate layer shielded the electric force from the negatively charged impurities, resulting in improved field-effect mobilities.
APPLIED PHYSICS LETTERS
(2023)
Article
Multidisciplinary Sciences
Y. Dong, L. Xiong, I. Y. Phinney, Z. Sun, R. Jing, A. S. McLeod, S. Zhang, S. Liu, F. L. Ruta, H. Gao, Z. Dong, R. Pan, J. H. Edgar, P. Jarillo-Herrero, L. S. Levitov, A. J. Millis, M. M. Fogler, D. A. Bandurin, D. N. Basov
Summary: The phenomenon of dragging light by moving media, predicted by Fresnel and verified by Fizeau, plays a key role in Einstein's special relativity theory. While experiments on dragging photons by an electron flow in solids have inconsistencies, the dragging of surface plasmon polaritons by an electron flow in graphene is a unique and complex phenomenon that challenges simple kinematics explanations.
Article
Chemistry, Multidisciplinary
Mei Ge, Leiting Chu, Miaomiao Guo, Yan Su, Junfeng Zhang
Summary: This study investigates the structural stability and magnetic properties of iridium clusters on two-dimensional substrates using density functional theory (DFT). The results show that the presence of the substrate alters the preferred configurations and reduces the magnetic moments of the clusters, while increasing the magnetic anisotropy energy.
Article
Chemistry, Physical
Li-Juan Ma, Jianfeng Wang, Jianfeng Jia, Hai-Shun Wu
Summary: In this study, defects and interstitial B are utilized to enhance the stability and H2 dissociation ability of palladium nanoparticles supported by graphene. The results indicate that defects can effectively avoid the desorption competition between palladium nanoparticles and hydrogen molecules, and the introduction of interstitial B can decrease the energy barrier for hydrogen dissociation on the surface.
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2022)
Article
Nanoscience & Nanotechnology
Shaoen Jin, Hang Zheng, Junyu Zong, Xuedong Xie, Fan Yu, Wang Chen, Libo Gao, Can Wang, Yi Zhang
Summary: The study demonstrates the etching growth mechanism of a h-BN film on graphene, showing the element composition, chemical bonding formation, and the formation of the new R0 degrees graphene through experiments and measurements. It provides a deeper understanding for further research on h-BN/graphene heterojunctions.
Article
Nanoscience & Nanotechnology
Hai Hu, Na Chen, Hanchao Teng, Renwen Yu, Yunpeng Qu, Jianzhe Sun, Mengfei Xue, Debo Hu, Bin Wu, Chi Li, Jianing Chen, Mengkun Liu, Zhipei Sun, Yunqi Liu, Peining Li, Shanhui Fan, F. Javier Garcia de Abajo, Qing Dai
Summary: In this study, we report a topological transition in the isofrequency dispersion contours of hybrid polaritons supported by a two-dimensional heterostructure consisting of graphene and alpha-phase molybdenum trioxide. By chemically changing the doping level of graphene, we observed a transformation of the topology of polariton isofrequency surfaces. Moreover, when the substrate was changed, the dispersion contour became dominated by flat profiles at the topological transition, thus supporting tunable diffractionless polariton propagation.
NATURE NANOTECHNOLOGY
(2022)
Article
Materials Science, Multidisciplinary
Sangkha Borah, Dinesh Yadav, Maxim Trushin, Fabian Pauly
Summary: This study presents a comprehensive ab initio investigation of the hot carrier dynamics at the h-BN/graphene interface. The results show that there is a weak coupling between low-energy optical phonons and electrons at the h-BN/graphene interface, leading to a reduced thermalization bottleneck effect compared to other bilayer and multilayer structures.
Article
Chemistry, Physical
Remy Pawlak, Ernst Meyer, Khalid N. Anindya, Toshiki Shimizu, Jung-Ching Liu, Takumi Sakamaki, Rui Shang, Alain Rochefort, Eiichi Nakamura
Summary: The substitution of heteroatoms and non-benzenoid carbons in nanographene structure allows for atomic engineering of electronic properties. This study demonstrates the bottom-up synthesis of graphene nanoribbons with embedded BN-doped rubicene components using on-surface chemistry. The incorporation of BN heteroatoms results in an increased electronic band gap, providing opportunities for designing semiconducting graphene nanoribbons with optoelectronic properties.
JOURNAL OF PHYSICAL CHEMISTRY C
(2022)
Article
Physics, Multidisciplinary
Bingyao Liu, Yu -Tian Zhang, Ruixi Qiao, Ruochen Shi, Yuehui Li, Quanlin Guo, Jiade Li, Xiaomei Li, Li Wang, Jiajie Qi, Shixuan Du, Xinguo Ren, Kaihui Liu, Peng Gao, Yu -Yang Zhang
Summary: We investigated the twist-angle-dependent coupling effects of h-BN/graphene heterostructures and found that moire potentials alter the band structure of graphene, resulting in a redshift of the intralayer transition at the M point. We also observed tunable vertical transition energies in the range of 5.1-5.6 eV due to the twisting of the Brillouin zone of h-BN relative to the graphene M point. These findings highlight the importance of considering twist-coupling effects in device fabrications and the potential of twist angles to design optoelectrical devices.
PHYSICAL REVIEW LETTERS
(2023)
Article
Chemistry, Physical
Qingzhong Gui, Zhen Wang, Zhaofu Zhang, Liu Xie, Xiaoming Zha, Jun Wang, Yuzheng Guo
Summary: In this study, a category of 2D materials called graphenelike monolayer monoxides, monochlorides, and mononitrides (GLMMs) are systematically studied using density functional theory and density functional perturbation theory. The stability of different native point defects in GLMMs is investigated energetically, showing their outstanding structural stability and high resistance to vacancy formation. The dielectric properties of GLMMs are explored and found to be promising for device applications.
CHEMISTRY OF MATERIALS
(2023)
Article
Materials Science, Multidisciplinary
Gaia Forghieri, Paolo Bordone, Andrea Bertoni
Summary: Graphene nanoribbons serve as an ideal platform for electronic interferometry in the integer quantum Hall regime. By solving the time-dependent Schrodinger equation for single carriers in graphene, the study reveals the effects of carrier localization on their transport characteristics in pn junctions. Two types of Mach-Zender interferometers are simulated, showing expected and unexpected phenomena.
Article
Chemistry, Physical
Stefan Goodwin, Zachary Coldrick, Sebastian Heeg, Bruce Grieve, Aravind Vijayaraghavan, Ernie W. Hill
Summary: This study presents a method for fabricating pristine monolayer graphene ultramicroelectrodes and characterizing their electrochemical properties. The cyclic voltammetry demonstrated expected behavior for ultramicroelectrodes, while reduction of IrCl62- was used to investigate electron transfer characteristics and reproducibility. Raman spectroscopy confirmed reduced charge doping in the graphene ultramicroelectrodes before and after electrochemical measurements.
Article
Optics
Li Wang, Jinlai Liu, Bin Ren, Jie Song, Yongyuan Jiang
Summary: A heterostructured graphene/hBN/graphene nanodisk array was used to create an electrically tunable absorber within and outside the Reststrahlen band of hBN, achieving tuning of resonance absorption through phonon-plasmon-polariton hybridization. The hybrid phonon mode enabled significant shifts in resonant wavelength and sensitivity to electrical control.
Article
Engineering, Environmental
Anshul Yadav, Shreyas S. Dindorkar, Srinivasa B. Ramisetti, Niraj Sinha
Summary: This study investigated the simultaneous adsorption of heavy metal and organic dye by two-dimensional graphene, hexagonal boron nitride, and hexagonal boron carbon nitride. The results showed that graphene had better adsorption efficiency for real wastewater treatment.
JOURNAL OF WATER PROCESS ENGINEERING
(2022)
Article
Nanoscience & Nanotechnology
Mahmut Can Senel, Mevlut Gurbuz
Summary: In this study, hexagonal boron nitride nanoparticulates and graphene nanoplatelets reinforced aluminum matrix composites were produced via powder metallurgy process. The mechanical properties, including density, hardness, and compressive strength, were significantly improved in composites with 1%BN and 0.15%graphene content. However, exceeding these contents resulted in decreased mechanical strength due to the aggregation of graphene nanoplatelets and nano-BN particles.
ADVANCED COMPOSITES AND HYBRID MATERIALS
(2021)
Article
Chemistry, Physical
Natalie Fehn, Ehsan Vahidzadeh, Karthik Shankar, Ueli Heiz, Aras Kartouzian
Summary: This study presents the surface second harmonic generation spectra of supported gold nanoparticles with titania coating, which can provide additional information on the morphology and size distribution of the sample.
APPLIED SURFACE SCIENCE
(2022)
Article
Chemistry, Physical
Moritz Eder, Carla Courtois, Philip Petzoldt, Sonia Mackewicz, Martin Tschurl, Ueli Heiz
Summary: In the past decade, photocatalytic hydrogen evolution from metal-loaded TiO2 has received significant attention. This study compares size-selected Ni and Pt clusters as co-catalysts on a TiO2(110) single crystal and investigates the size- and coverage-dependent effects on the catalyst performance. Larger clusters and higher coverages of Ni enhance the product formation rate, while Pt co-catalysts exhibit a stable and higher activity, but size-specific effects need to be considered.
Article
Chemistry, Physical
Philip Petzoldt, Moritz Eder, Sonia Mackewicz, Monika Blum, Tim Kratky, Sebastian Guenther, Martin Tschurl, Ueli Heiz, Barbara A. J. Lechner
Summary: In this study, the effect of O-2 and H-2 on Pt/TiO2(110) catalysts was investigated using synchrotron-based near-ambient pressure X-ray photoelectron spectroscopy. The results showed that the rate of formation of the encapsulating oxide layer on Pt particles varied with different O-2 pressures, and once encapsulation occurred, Pt particles remained embedded in the support.
JOURNAL OF PHYSICAL CHEMISTRY C
(2022)
Article
Chemistry, Multidisciplinary
Jozef Lengyel, Nikita Levin, Milan Oncak, Konstantin Jakob, Martin Tschurl, Ueli Heiz
Summary: Understanding molecular-scale reaction mechanisms is critical for designing effective catalysts. This study investigates the direct coupling reaction of CH4 and CO2 mediated by Ta-1,4(+) ions. Experimental results show that methane dehydrogenation is a significant initial step in this reaction, and ion catalysts facilitate the formation of more complex products.
CHEMISTRY-A EUROPEAN JOURNAL
(2022)
Article
Computer Science, Software Engineering
Karl D. Briegel, Felix Riccius, Jakob Filser, Alexander Bourgund, Robert Spitzenpfeil, Mirco Panighel, Carlo Dri, Barbara A. J. Lechner, Friedrich Esch
Summary: Researchers have developed an add-on electronics module to enhance the speed of conventional scanning probe microscopes without modification of the instrument. The pyfastspm package in Python is able to convert the recorded data into a rectangular matrix, correct for various artifacts, and enable efficient and automatic conversion of large data batches.
Article
Instruments & Instrumentation
Clara C. Aletsee, Degenhart Hochfilzer, Anika Kwiatkowski, Markus Becherer, Jakob Kibsgaard, Ib Chorkendorff, Martin Tschurl, Ueli Heiz
Summary: Despite challenges in evaluating the catalytic performance of photoactive materials, a gas phase mu-photoreactor has been developed that is re-openable and re-usable, enabling post-characterization and catalyst screening studies. The reactor allows sensitive and time-resolved reaction monitoring at ambient pressure, and its microfabricated lid enhances sensitivity. The successful operation of the reactor is demonstrated through selective ethanol oxidation over Pt-loaded TiO2.
REVIEW OF SCIENTIFIC INSTRUMENTS
(2023)
Article
Chemistry, Physical
Sebastian Kaiser, Johanna Plansky, Matthias Krinninger, Andrey Shavorskiy, Suyun Zhu, Ueli Heiz, Friedrich Esch, Barbara A. J. Lechner
Summary: Encapsulation via strong metal-support interaction (SMSI) can overcome the sintering problem of metal nanoparticles at elevated temperatures. In this study, Pt5, Pt10, and Pt19 clusters deposited on Fe3O4(001) were encapsulated, and the stability was investigated. The encapsulated clusters could still diffuse as a whole below 823 K, suppressing atom detachment and Ostwald ripening, and resulting in square-shaped crystalline Pt particles.
Article
Chemistry, Multidisciplinary
Deborah Perco, Federico Loi, Luca Bignardi, Luca Sbuelz, Paolo Lacovig, Ezequiel Tosi, Silvano Lizzit, Aras Kartouzian, Ueli Heiz, Alessandro Baraldi
Summary: This study investigates the oxidation process of graphene-supported size-selected Fe-n clusters using high-resolution X-ray Photoelectron Spectroscopy. It is found that the core electron Fe 2p(3/2) binding energy and chemical reactivity of the clusters are dependent on their size. Upon oxidation, the iron atoms in the clusters reach the Fe(II) oxidation state, with no presence of other oxidation states, indicating a Fe-to-O ratio close to 1:1, consistent with previous theoretical calculations and gas-phase experiments. These findings provide insights into the behavior of iron oxide nanoclusters as supported catalysts.
COMMUNICATIONS CHEMISTRY
(2023)
Article
Chemistry, Physical
Matthias Krinninger, Nicolas Bock, Sebastian Kaiser, Johanna Reich, Tobias Bruhm, Felix Haag, Francesco Allegretti, Ueli Heiz, Klaus Kohler, Barbara A. J. Lechner, Friedrich Esch
Summary: Carbon nitrides have gained attention for their applications in both photo- and thermal catalysis. In this study, the authors describe an in situ method for synthesizing monolayer 2D carbon nitride films, which can be combined with other 2D materials. They show that a specific precursor can be evaporated, deposited, and activated to form a stable polyheptazine network using three pathways: electrons, photons, and thermal activation.
CHEMISTRY OF MATERIALS
(2023)
Article
Chemistry, Physical
Moritz Eder, Martin Tschurl, Ueli Heiz
Summary: Heterogeneous photocatalytic systems are often described based on electrochemistry, while neglecting the surface chemistry of the photocatalyst. However, studies on alcohol photoreforming reveal that the electrochemical reaction model is not universally applicable. Therefore, the importance of thermal reactions and the need for systematic studies in different environments for a comprehensive understanding of photocatalysis are highlighted.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2023)
Article
Chemistry, Physical
Matthias Krinninger, Nicolas Bock, Sebastian Kaiser, Johanna Reich, Tobias Bruhm, Felix Haag, Francesco Allegretti, Ueli Heiz, Klaus Kohler, Barbara A. J. Lechner, Friedrich Esch
Summary: Carbon nitrides have gained attention as support materials for metal nanoparticles and as photocatalysts themselves. A new method has been developed to synthesize monolayer 2D carbon nitride films on a single crystalline support through in situ on-surface synthesis. The activation of the carbon nitride films can occur through three pathways: electrons, photons, and thermal energy. This work opens up possibilities for coating materials with stable carbon nitride networks under ambient conditions.
CHEMISTRY OF MATERIALS
(2023)
Article
Chemistry, Multidisciplinary
Natalie Fehn, Melanie Strauss, Christian Jandl, Markus Drees, Ueli Heiz, Klaus Koehler, Aras Kartouzian
Summary: In this work, the transfer of chirality between a chiral metal-organic catalyst and a substrate was investigated through induced circular dichroism (ICD) studies on [Pd(Me)(2)(BINAP)]. The catalyst was successfully synthesized and characterized using single-crystal X-ray diffraction and CD spectroscopy, in addition to density functional theory calculations. It was demonstrated that BINAP not only acted as a steric guide during catalysis, but also influenced the electronic properties of the Pd center through ICD.
NEW JOURNAL OF CHEMISTRY
(2023)
Article
Materials Science, Multidisciplinary
Florian Ristow, Kevin Liang, Johannes Pittrich, Jakob Scheffel, Natalie Fehn, Reinhard Kienberger, Ulrich Heiz, Aras Kartouzian, Hristo Iglev
Summary: In this study, second harmonic generation (SHG) spectroscopy was used to investigate the chiroptical properties of BINOL films with different thicknesses, incidence angles, and degrees of crystallization. The study reveals that SHG-CD measured with large beam areas can directly probe the intrinsic chirality of the sample.
JOURNAL OF MATERIALS CHEMISTRY C
(2022)
Article
Chemistry, Physical
Moritz Eder, Carla Courtois, Philip Petzoldt, Sonia Mackewicz, Martin Tschurl, Ueli Heiz
Summary: In the past decade, research on photocatalytic hydrogen evolution from alcohol oxidation on metal-loaded TiO2 has gained attention. This study compares size-selected Ni and Pt clusters as co-catalysts on a TiO2(110) single crystal and explores the size and coverage effects on the catalyst performance during photocatalytic hydrogen evolution.