Highly stable COF supported Pd(0) and Pd(ii) nanoparticles (i.e.Pd(0)@Tppa-1 and Pd(ii)@TpPa-1) have been synthesized. Pd(0)@TpPa-1 serves as a robust and efficient heterogeneous catalyst for copper free Sonogashira and Heck coupling reactions under basic conditions, whereas Pd(ii)@TpPa-1 satisfactorily catalyzes intramolecular oxidative biaryl synthesis under acidic conditions.

Towards increasing the stability of perovskite solar cells, the addition of Cs is found to be a rational approach. Recently triple cation based perovskite solar cells were found to be more effective in terms of stability and efficiency. Heretofore they were unexplored, so we probed the Cs/MA/FA (cesium/methyl ammonium/formamidinium) cation based perovskites by X-ray photoelectron spectroscopy (XPS) and correlated their compositional features with their solar cell performances. The Cs content was found to be optimum at 5%, when incorporated in the (MAFA)Pb(IBr) lattice, because the corresponding device yielded the highest fill factor compared to the perovskite without Cs and with 10% Cs. XPS studies distinctly reveal how Cs aids in maintaining the expected stoichiometric ratios of I : Pb, I : N and Br : Pb in the perovskites, and how the valence band (VB) edge is dependent on the Cs proportion, which in turn governs the open circuit voltage. Even at a low content of 5%, Cs resides deep within the absorber layer, and ensures minimum distortion of the VB level (compared to 0% and 10% Cs perovskites) upon Ar sputtering, thus allowing the formation of a stable robust material that delivers excellent solar cell response. This study which brings out the role of Cs is anticipated to be of paramount significance to further engineer the composition and improve device performances.

The crystal-structure-dependent luminescence properties of cadmium selenide quantum dots (QDs) in their cubic zincblende (Zb-CdSe) and hexagonal wurtzite (Wz-CdSe) phases have been investigated by maintaining their optical band gaps as well as the relative ratios of capping ligands the same. The Zb-CdSe QDs exhibited excellent photostability and high photoluminescence quantum yield (ϕ L = 0.375) compared with Wz-CdSe QDs (ϕ L = 0.046). Detailed X-ray photoelectron spectroscopic (XPS) investigation revealed an important finding that the surface of Zb-CdSe is rich with Cd 2+ ions, which leads to the formation of CdO layer. This was further confirmed by analyzing the (i) Cd-to-Se stoichiometric ratio of zincblende QDs (2:1 on surface and 1:1 after sputtering) and (ii) core-level XPS spectra of oxygen. In contrast, the Cd-to-Se stoichiometric ratio was found to be same (1:1) for Wz-CdSe QDs throughout the crystal. Thus, the high luminescence of Zb-CdSe is attributed to the formation of a thin layer of CdO, leading to a type-I core−shell structure, which passivates the surface defects and confines the charge carriers. On the basis of the present investigation it is clear that the crystal structure plays a decisive role in modulating the surface properties of QDs, which determine the luminescence properties. SECTION: Physical Processes in Nanomaterials and Nanostructures

Activated reactive evaporation has been used to grow copper oxide nanoparticles in the size range of 8–100 nm. X-ray diffraction spectra clearly show the presence of a single Cu2O phase. Detailed x-ray photoelectron spectroscopy studies show an increase in the ionicity of the Cu2O system with decreasing particle size. Depth profiling and finger printing of x-ray photoelectron spectra reveal that the Cu2O nanoparticles are capped with a CuO surface layer of thickness ≈1.6 nm. This study strongly suggests that the stabilization of the cubic Cu2O nanophase is enhanced by the formation of a CuO surface layer.