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Core level X-ray Photoelectron Spectroscopy (XPS) studies have been carried out on polycrystalline MgB 2 pellets over the whole binding energy range with a view to having an idea of the charge state of Magnesium (Mg). We observe 3 distinct peaks in Mg 2p spectra at 49.3 eV (trace), 51.3 eV (major) and 54.0 eV (trace), corresponding to metallic Mg, MgB 2 and MgCO 3 or, divalent Mg species respectively. Similar trend has been noticed in Mg 2s spectra. The binding energy of Mg in MgB 2 is lower than that corresponding to Mg(2+), indicative of the fact that the charge state of Mg in MgB 2 is less than (2+). Lowering of the formal charge of Mg promotes the σ→π electron transfer in Boron (B) giving rise to holes on the top of the σ-band which are involved in coupling with B E 2g phonons for superconductivity. Through this charge transfer, Mg plays a positive role in hole superconductivity. B 1s spectra consist of 3 peaks corresponding to MgB 2 , boron and B 2 O 3 . There is also evidence of MgO due to surface oxidation as seen from O 1s spectra. PACS No. 74.70.Ad

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Herein, we have reported one-pot synthesis of a fluorescent polymer-like material (pCDs) by exploiting ruthenium doped carbon dot (CDs) as building blocks. The unusual spectral profiles of pCDs with double humped periodic excitation dependent photoluminescence (EDPL) and the regular changes in their corresponding average lifetime indicate the formation of high energy donor states and low energy aggregated states due to the overlap of molecular orbitals throughout the chemically switchable π-network of CDs on polymerization. To probe the electronic distribution of pCDs, we have investigated the occurrence of photoinduced electron transfer with a model electron acceptor, menadione using transient absorption technique, corroborated with low magnetic field, followed by identification of the transient radical ions generated through electron transfer. The experimentally obtained B 1/2 value, a measure of the hyperfine interactions present in the system, indicates the presence of highly conjugated π-electron cloud in pCDs. The mechanism of formation of pCDs and the entire experimental findings have further been investigated through molecular modeling and computational model. The DFT calculations demonstrated the probable electronic transitions from surface moieties of pCDs to the tethered ligands. ASSOCIATED CONTENT Supporting Information Detailed synthetic protocol, additional spectroscopic data, TEM, details of MD-simulations and theoretical calculations are available in supporting information.