Publications by authors named "Jagadesh Kopula Kesavan"
Utilizing High X-ray Energy Photon-In Photon-Out Spectroscopies and X-ray Scattering to Experimentally Assess the Emergence of Electronic and Atomic Structure of ZnS Nanorods.
Lars Klemeyer Tjark L R Gröne Cecilia de Almeida Zito Olga Vasylieva Melike Gumus Akcaalan Jagadesh Kopula Kesavan
J Am Chem Soc
December 2024
Article Synopsis
- Understanding the reaction mechanism and coordination of ligands and solvents is essential for controlling the fabrication of transition metal sulfide nanocrystals.
- The study employs advanced techniques such as HERFD-XAS and vtc-XES alongside DFT calculations to explore the formation of various zinc complexes during the synthesis of ZnS nanorods in oleylamine.
- The transition in the electronic structure of the zinc complexes is observed, revealing insights into the size-dependent electronic band gaps of synthesized nanocrystals.
Article Synopsis
- Exciton-phonon coupling affects the clarity of light emitted from nanocrystals, making it important to study this phenomenon.
- This research involves single-particle spectroscopy experiments on various colloidal nanocrystals at approximately 10 K to analyze exciton-phonon interactions.
- The results reveal that the intensity of phonon replicas is linked to charge-carrier distribution, with quantum mechanical calculations suggesting that surface charges play a significant role.
Article Synopsis
- High energy resolution fluorescence detected X-ray absorption spectroscopy is an effective technique for investigating the electronic properties of functional materials, especially in operando conditions.
- The method allows for real-time studies in environments like electrochemical cells, making it useful for understanding materials in practical applications.
- The study specifically examines a BiVO photoanode, revealing small changes in spectral lines due to applied potential, which are linked to the occupation of electronic states near the material's band edges.
Doping Evolution of the Local Electronic and Structural Properties of the Double Perovskite BaNa Ca OsO.
J Phys Chem C Nanomater Interfaces
July 2020
We present a combined experimental and computational study of the effect of charge doping in the osmium based double perovskite BaNa Ca OsO for 0 ≤ ≤ 1 in order to provide a structural and electronic basis for understanding this complex Dirac-Mott insulator material. Specifically, we investigate the effects of the substitution of monovalent Na with divalent Ca, a form of charge doping or alloying that nominally tunes the system from Os with a 5d configuration to Os with 5d configuration. After an X-ray diffraction characterization, the local atomic and electronic structure has been experimentally probed by X-ray absorption fine structure at all the cation absorption edges at room temperature; the simulations have been performed using ab initio density functional methods.
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- Expanding the use of wide bandgap semiconductors, especially for green solar photocatalysis, has led to the development of a hybrid system using silver nanoparticles in a CeO film.
- The study employs free electron laser time-resolved soft X-ray absorption spectroscopy to observe how excited Ag NPs transfer electrons to the CeO film.
- Findings show that this electron transfer occurs in less than 200 femtoseconds, highlighting the effectiveness of FEL-based techniques in investigating energy transfer in advanced materials.
Better Together: Ilmenite/Hematite Junctions for Photoelectrochemical Water Oxidation.
ACS Appl Mater Interfaces
October 2020
Article Synopsis
- Hematite (α-FeO) is a semiconductor with a band gap of 2.2 eV, making it effective for visible light absorption and photoelectrochemical water oxidation under basic conditions.
- Modifying hematite thin films with Ti(IV) and oxygen-evolving catalysts boosts photocurrent density by six times compared to unmodified versions.
- Research reveals that Ti(IV) ions integrate within ilmenite (FeTiO) in the mesoporous structure, enhancing the semiconductor-electrolyte interface and improving the efficiency of electron-hole separation, leading to better photoelectrochemical performance.
Article Synopsis
- Researchers investigate the structure of AgBiS nanoparticles using X-ray absorption fine structure and X-ray diffraction, along with simulations.
- The study addresses a conflict between the X-ray findings by utilizing simulations to clarify the data.
- It reveals that disorder in the cation sublattice causes significant local distortions, resulting in shorter Ag-S bonds while maintaining a nearly hexagonal lattice symmetry.
Article Synopsis
- WO/BiVO films were created by depositing BiVO on mesoporous WO and were used to break down emerging contaminants like ketoprofen and levofloxacine in water through photoelectrochemical methods.
- These films showed a mesoporous structure with a notable photoconversion efficiency over 40%, primarily producing oxygen as the dominant reaction product.
- While levofloxacine was effectively degraded, ketoprofen produced stable byproducts that persisted in solution, highlighting limitations of WO/BiVO in broader environmental applications compared to other semiconductor options like TiO and WO.