Ni 0 /NiO (nickel/nickel oxide) core-shell nanostructures were synthesized through a facile combustible redox reaction. Remarkably, the hetero-phase boundary with different crystalline orientations offered dual properties, which helped in bifunctional catalysis. Presence of a metallic Ni phase changed physicochemical properties and some emerging applications (magnetic properties, optical conductivity, electrochemical sensitivity, catalytic behaviour) could be foreseen. Moreover, formation of a NiO layer on metal surface prevented magnetism-induced aggregation, arrested further oxidation by hindering oxygen diffusion, and acted as a good sorbent to enhance the surface adsorption of the analyte.Hexagonal Ni/NiO nanostructures manifested well-defined ferromagnetic behavior and the catalyst could be collected easily at the end of the catalytic reduction. Ni/NiO core-shell catalysts at the nanoscale had outstanding catalytic performance (reduction of 4-nitrophenol to 4-aminophenol) compared with pure NiO catalysts beyond a reaction time of $9 min. The estimated sensitivity, limit of detection and limit of quantification towards the electrochemical sensing of serotonin were 0.185, 0.43 and 1.47 mM mA À1 , respectively. These results suggest that a bifunctional Ni/NiO nanostructure could be a suitable catalyst for electrochemical detection of serotonin and reduction of 4-nitrophenol.

In this paper, Co-Al layered double hydroxides (LDHs), Co-Al LDHs/poly(o-phenylenediamine) (PoPD) and Ag nanoparticles decorated Co-Al LDHs/PoPD (Ag@Co-Al LDH/PoPD) samples were prepared. The as-prepared samples were characterized by XRD, Raman, XPS, FT-IR, DRS-UV-Vis, PL and TGA techniques. The salient features of morphology and size of the samples were determined using FESEM, and HR-TEM. Then, the samples were coated on glassy carbon electrode (GCE) and employed for sensing of 4-nitrophenol (4-NP), 2,4-dinitrophenol (2,4-DNP)) and uric acid (UA). It was found that Ag@Co-Al LDH/PoPD/GCE showed superior electrochemical sensing behaviour than other modified electrodes. It exhibits the detection limit (DL) of 63 nM, 50 nM and 0.28 µM for 4-NP, 2,4-DNP and UA respectively.

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Gd 2 (SO 4 ) 3 ·8H 2 O , Gd 2 O 2 SO 4 , and Gd 2 O 2 SO 4 :Eu 3+ nanoparticles have been synthesized in the presence of Gd 3+ ion and sodium dodecyl sulphate (SDS) by the simple complexationthermal decomposition (CTD) method. The structural analysis, growth mechanism and optical properties of the Gd 2 (SO 4 ) 3 ·8H 2 O, and Gd 2 O 2 SO 4 is described by diffraction pattern, functional group analysis, Raman, morphology, elemental analysis, and absorbance spectra. The most intriguing future was that the Gd 2 O 2 SO 4 nanoplates are in the range of 42-50 nm without adding any external stabilizer. The study results revealed that the Gd 2 O 2 SO 4 nanoparticles with orthorhombic structure are having a band gap of 3.12 eV. Furthermore, Gd 2 O 2 SO 4 shows an intense red photoluminescence associated with the 5 D 0 → 7 F 2 transition in the presence of Eu 3+ .The results suggest that the Gd 2 O 2 SO 4 :Eu 3+ nanophosphors, may have a beneficial approach in the field of biomedical application as luminescent probe/labels.