Orbital and skeletal structure of a single molecule on a metal surface unveiled by scanning tunneling microscopy. - In: The journal of physical chemistry letters, ISSN 1948-7185, Bd. 14 (2023), 16, S. 3946-3952
Atomic-scale spatial characteristics of a phthalocyanine orbital and skeleton are obtained on a metal surface with a scanning tunneling microscope and a CO-functionalized tip. Intriguingly, the high spatial resolution of the intramolecular electronic patterns is achieved without resonant tunneling into the orbital and despite the hybridization of the molecule with the reactive Cu substrate. The resolution can be fine-tuned by the tip-molecule distance, which controls the p-wave and s-wave contribution of the molecular probe to the imaging process. The detailed structure is deployed to minutely track the translation of the molecule in a reversible interconversion of rotational variants and to quantify relaxations of the adsorption geometry. Entering into the Pauli repulsion imaging mode, the intramolecular contrast loses its orbital character and reflects the molecular skeleton instead. The assignment of pyrrolic-hydrogen sites becomes possible, which in the orbital patterns remains elusive.
https://doi.org/10.1021/acs.jpclett.3c00460
Enhancement of graphene phonon excitation by a chemically engineered molecular resonance. - In: Physical review letters, ISSN 1079-7114, Bd. 130 (2023), 11, S. 116201-1-116201-6
The abstraction of pyrrolic hydrogen from a single phthalocyanine on graphene turns the molecule into a sensitive probe for graphene phonons. The inelastic electron transport measured with a scanning tunneling microscope across the molecular adsorbate and graphene becomes strongly enhanced for a graphene out-of-plane acoustic phonon mode. Supporting density functional and transport calculations elucidate the underlying physical mechanism. A molecular orbital resonance close to the Fermi energy controls the inelastic current while specific phonon modes of graphene are magnified due to their coupling to symmetry-equivalent vibrational quanta of the molecule.
https://doi.org/10.1103/PhysRevLett.130.116201
Quantitative stray-field T1 relaxometry with the matrix pencil method. - In: Journal of magnetic resonance, ISSN 1096-0856, Bd. 351 (2023), 107435
The matrix pencil method (MPM) is tested as an approach to quantitatively process multiexponential low-field nuclear magnetic resonance T1 relaxometry data. The data is obtained by measuring T1 saturation recovery curves in the highly inhomogeneous magnetic field of a stray-field sensor. 0.9% brine solutions, doped with different concentrations of a Gd3+ containing contrast agent, serve as test liquids. Relaxation-times as a function of contrast-agent concentration along with the T1 relaxation curves for combinations of multiple different test liquids are measured, and the results from processing using MPM as well as inverse Laplace transformation as a benchmark are compared. The relaxation-time resolution limits of both procedures are probed by gradually reducing the difference between the relaxation-times of two liquids measured simultaneously. The sensitivity to quantify the relative contribution of each component to the magnetization build-up curve is explored by changing their volume ratio. Furthermore, the potential to resolve systems with more than two components is tested. For the systems under test, MPM shows superior performance in separating two or three relaxation components, respectively and effectively quantifying the time constants.
https://doi.org/10.1016/j.jmr.2023.107435
Dangling bond defects on Si surfaces and their consequences on energy band diagrams: from a photoelectrochemical perspective. - In: Solar RRL, ISSN 2367-198X, Bd. 7 (2023), 9, 2201063, S. 1-10
Using silicon in multijunction photocells leads to promising device structures for direct photoelectrochemical water splitting. In this regard, photoelectron spectra of silicon surfaces are used to investigate the energetic condition of contact formation. It is shown that the Fermi-level position at the surface differs from the values expected from their bulk doping concentrations, indicating significant surface band bending which may limit the overall device efficiency. In this study, the influence of different surface preparation procedures for p- and n-doped Si wafers on surface band bending is investigated. With the help of photoemission and X-ray absorption spectroscopy, Si dangling bonds are identified as dominating defect centers at Si surfaces. These defects lead to an occupied defect band in the lower half and an unoccupied defect band in the upper half of the Si bandgap. However, partial oxidation of the defect centers causes a shift of defect bands, with only donor states remaining in the Si bandgap. Source-induced photovoltages at cryogenic temperatures indicate that partial surface oxidation also decreases the recombination activity of these defect centers. It is shown that defect distribution, defect concentration, and source-induced photovoltages need to be considered when analyzing Fermi-level pinning at Si surfaces.
https://doi.org/10.1002/solr.202201063
CO2 conversion toward real-world applications: electrocatalysis versus CO2 batteries. - In: Advanced functional materials, ISSN 1616-3028, Bd. 33 (2023), 32, 2300926, S. 1-38
Electrochemical carbon dioxide (CO2) conversion technologies have become new favorites for addressing environmental and energy issues, especially with direct electrocatalytic reduction of CO2 (ECO2RR) and alkali metal-CO2 (M-CO2) batteries as representatives. They are poised to create new economic drivers while also paving the way for a cleaner and more sustainable future for humanity. Although still far from practical application, ECO2RR has been intensively investigated over the last few years, with some achievements. In stark contrast, M-CO2 batteries, especially aqueous and hybrid M-CO2 batteries, offer the potential to combine energy storage and ECO2RR into an integrated system, but their research is still in the early stages. This article gives an insightful review, comparison, and analysis of recent advances in ECO2RR and M-CO2 batteries, illustrating their similarities and differences, aiming to advance their development and innovation. Considering the crucial role of well-designed functional materials in facilitating ECO2RR and M-CO2 batteries, special attention is paid to the development of rational design strategies for functional materials and components, such as electrodes/catalysts, electrolytes, and membranes/separators, at the industrial level and their impact on CO2 conversion. Moreover, future perspectives and research suggestions for ECO2RR and M-CO2 batteries are presented to facilitate practical applications.
https://doi.org/10.1002/adfm.202300926
Facile microwave plasma driven 3D-WSe2 2H-1T phase modulation for improving NO2 gas sensing performance. - In: Sensors and actuators, ISSN 0925-4005, Bd. 387 (2023), 133822
In recent years, transition metal dichalcogenides (TMDs) have been widely used for gas sensors. Here, three-dimensional (3D) WSe2 nanosheet arrays were surface treated by microwave plasma. Based on the original 3D structure, a 1T/2H hybrid phase structure was constructed by phase modulation, and Se vacancies were introduced to effectively improve its gas sensing performance. After only 60 s of treatment, the response (52.24 %), response/recovery time of the sample for 1 ppm NO2 were significantly improved with excellent stability and selectivity at room temperature. The intrinsic mechanism of its performance enhancement was elicited through various characterizations and molecular model construction. It is demonstrated that microwave plasma is a promising treatment method to improve the gas-sensitive performance of TMDs.
https://doi.org/10.1016/j.snb.2023.133822
An in-depth understanding of photophysics in organic photocatalysts. - In: Journal of semiconductors, ISSN 2058-6140, Bd. 44 (2023), 3, 030401, S. 1-4
https://doi.org/10.1088/1674-4926/44/3/030401
Photochemical and electrochemical co-regulation of the BiVO4 photoanode for water splitting. - In: Chemical communications, ISSN 1364-548X, Bd. 59 (2023), 23, S. 3435-3438
A novel pretreatment strategy that can regulate the amount of oxygen vacancies (Ovac) across the wormlike-BiVO4 photoanode by photochemical and electrochemical co-processing. Upon decorating NiFeOx as an oxygen evolution cocatalyst for promoting the surface oxidation kinetics, a record-high photocurrent density of 6.42 mA cm^-2 is obtained at 1.23 vs. RHE (100 mW cm^-2).
https://doi.org/10.1039/D2CC07093F
Optical in situ studies of Ge(100) interfacial exchange reactions in GaAs-rich MOVPE reactors for low-defect III-P growth. - In: ACS applied electronic materials, ISSN 2637-6113, Bd. 5 (2023), 2, S. 1295-1301
For vertical-cavity surface-emitting lasers (VCSELs) or photoelectrochemical devices and high efficient III-V/Ge(100) photovoltaics, preparation of double-atomic steps on Ge(100) substrates is highly recommended in order to avoid anti-phase boundaries in the III-V buffer layers. These Ge(100) surfaces were investigated in detail under As- and GaAs-rich MOVPE reactor conditions. During initial growth of III-P buffer layers, however, on an atomically well-ordered Ge(100):As surface, As-P exchange takes place, during which double-layer steps should be preserved. Here, we apply in situ monitoring to study the interaction of P with vicinal Ge(100):As surfaces under realistic, GaAs-rich CVD reactor conditions at growth temperature. In situ optical spectroscopy in combination with surface science techniques in ultra-high vacuum ambience is used to investigate the Ge(100) surface. We show that different Ge(100):As/P heterointerfaces are formed depending on the applied molar flow of phosphorus precursors. Despite the lattice-matched quality of the probing III-P layer, this critical heterointerface impacts significantly the surface roughness and the formation of crystal defects in the subsequently grown III-P buffer layers.
https://doi.org/10.1021/acsaelm.2c01775
Recycling of graphite anode from spent lithium-ion batteries: advances and perspectives. - In: EcoMat, ISSN 2567-3173, Bd. 5 (2023), 4, e12321, S. 1-27
There is growing production for lithium-ion batteries (LIBs) to satisfy the booming development renewable energy storage systems. Meanwhile, amounts of spent LIBs have been generated and will become more soon. Therefore, the proper disposal of these spent LIBs is of significant importance. Graphite is the dominant anode in most commercial LIBs. This review specifically focuses on the recent advances in the recycling of graphite anode (GA) from spent LIBs. It covers the significance of GA recycling from spent LIBs, the introduction of the GA aging mechanisms in LIBs, the summary of the developed GA recovery strategies, and the highlight of reclaimed GA for potential applications. In addition, the prospect related to the future challenges of GA recycling is given at the end. It is expected that this review will provide practical guidance for researchers engaged in the field of spent LIBs recycling.
https://doi.org/10.1002/eom2.12321