The well-known surface-functionalized method has been employed to synthesize TiO 2 @CdS core-shell nanorods using citric acid as a surface-functionalized agent. By varying the concentration of the citric acid, core-shell nanorods of core diameter 36 nm with different shell thickness (19-34 nm) were formed. The UV-visible absorption spectra of the core-shell nanorods show a red shift of the band edge of uncoated TiO 2 , and the broadening of the absorption spectra is also observed with shell growth. Steady-state photoluminescence (PL) spectra of the core-shell nanorods give a new emission in the visible region and also red shift with the increasing shell thickness. Decay kinetics indicate that the average lifetime 〈τ〉 of the core-shell nanorods is larger than that of the uncoated TiO 2 , and it varies from nanoseconds to picoseconds. The current-voltage (I-V) curves of the core-shell nanorods give a photocurrent density that is 212 times greater than the dark current density.

One dimensional (1D) anatase Co doped TiO2 nanostructures such as nanorods, nanowires, and nanotubes were synthesized by a simple solvothermal method using CoCl2·6H2O as the cobalt source. The effect of the different solvents on the crystal structures, morphologies, and sizes of the Co doped 1D nanostructures was investigated. The doping concentration of the samples primarily depends on the solvents. The X-ray photoelectron spectroscopy studies clearly showed that the Co was incorporated into the TiO2 lattice as Co2+ and oxygen vacancies were created due to the substitution of the Ti4+ ions by Co2+ ions. Optical absorption measurements showed additional absorption bands that are due to the ligand field transitions, 4T1g(4F) → 4T1g(4P) of Co2+ and also due to the transitions from different trap states related to the oxygen vacancies. The effects of the doping concentration on the defect structures and oxygen vacancies of the 1D nanostructures were mainly investigated using steady state photoluminescence (PL) and PL decay.

The ground state properties of the ferromagnetic shape memory alloy of nominal composition Ni2Mn1.36Sn0.64 have been studied by dc magnetization and ac susceptibility measurements. Like few other Ni-Mn based alloys, this sample exhibits exchange bias phenomenon. The observed exchange bias pinning was found to originate right from the temperature where a step-like anomaly is present in the zero-field-cooled magnetization data. The ac susceptibility study indicates the onset of spin glass freezing near this step-like anomaly with clear frequency shift. The sample can be identified as a reentrant spin glass with both ferromagnetic and glassy phases coexisting together at low temperature at least in the field-cooled state. The result provides us an comprehensive view to identify the magnetic character of various Ni-Mn-based shape memory alloys with competing magnetic interactions.PACS numbers: 75.50. Lk, 75.60.Nt,75.47.Np Recently Ni 2 Mn 1+x Z 1−x (Z = In, Sn, and Sb) based ferromagnetic shape memory alloys (FSMAs) have attracted considerable attention due to their multifunctional properties, which include magnetic sueprelasticity, giant magnetoresistance, large inverse magnetocaloric effect and magnetic memory effect [1,2,3,4,5]. The observed phenomena are primarily related to the magnetic field (H) induced reverse transition across the martensitic transformation (MT) [6]. The stoichiometric Heusler compositions (Ni 2 MnZ) are all ferromagnetic with the Curie point (T C ) lying just above room temperature. The excess Mn doping at the expense of Z atoms induces structural instability in the system leading to the ferromagnetic shape memory effect. Short range antiferromagnetic (AFM) interaction between the excess Mn (at the Z site) and the original Mn atoms has been predicted for the doped alloys [7,8]. Although, predominantly ferromagnetic (FM) character is present in the Mn doped alloys with T C around 300 K, the AFM correlation is evident from the gradual decrease of saturation moment with increasing amount of excess Mn [7,9]. Diffuse peaks observed in the powder neutron diffraction data of Ni-Mn-Sn alloys also indicate the existence of incipient AFM coupling [10].Evidently, the magnetic nature of the ground state of the alloys may not be very simple. A fascinating evidence for the complex ground state of the alloys is the recently observed exchange bias (EB) phenomenon in bulk samples [9,11,12]. EB is referred to the shift of the center of the magnetic hysteresis loop from the origin when the sample has been cooled from high temperature in presence of magnetic field [13]. The origin of EB is gener- * Electronic address: sspsm2@iacs.res.in ally ascribed to the presence of FM and AFM interfacial coupling in a heterogeneous sample. EB has also been observed in materials having FM/spin-glass (SG) and FM/Ferrimagnet interfaces [14,15] other than FM/AFM systems. However in all the cases, it is required that the ordering temperature (T N F ) for the non-ferromagnetic phase (may be AFM, SG or ferrimagnet) should be l...

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We report a new synthesis process of colloidal indium (In) doped zinc oxide (ZIO) nanocrystals by a hot injection technique. By fine tuning the synthesis we reached the same nucleation temperature for indium oxide and zinc oxide which helped us to study a dopant precursor dependent In incorporation into the ZnO matrix by using different In sources. The dopant induced shape evolution changes the hexagonal pyramid structured ZnO to a platelet like structure upon 8% In doping. The introduction of trivalent In(3+) into the ZnO lattice and consequent substitution of divalent Zn(2+) generates free electrons in the conduction band which produces a plasmonic resonance in the infrared region. The electron concentration controls plasmon frequency as well as the band gap of host ZnO. The variation of the band gap and the modification of the conduction band have been explained by the Burstein-Moss effect and Mie's theory respectively. The In dopant changes the defect chemistry of pure ZnO nanocrystals which has been studied by photoluminescence and other spectroscopic measurements. The nanocrystals are highly stable in the organic medium and can be deposited as a crack free thin film on different substrates. Careful ligand exchange and thermal annealing of the spin cast film lead to a good conductive film (720 Ω per square to 120 Ω per square) with stable inherent plasmonic absorption in the infrared and 90% transmittance in the visible region. A temperature induced metal-semiconductor transition was found for doped ZnO nanocrystals. The transition temperature shifts to a lower temperature with increase of the doping concentration.