Colloidal trivalent gallium (Ga) doped zinc oxide (ZnO) hexagonal nanocrystals have been prepared to introduce more carrier concentration into the wide band gap of ZnO. The dopant (Ga) modifies the morphology and size of ZnO nanocrystals. Low content of Ga enhances the optical band gap of ZnO due to excess carrier concentration in the conduction band of ZnO. The interaction among free carriers arising from higher concentration of Ga gives rise to narrowing of the band gap. Surface plasmon resonance absorption appears in the infrared region due to excessive carrier concentration. A broad emission band consists of blue, yellow and green colors associated with different native defects of ZnO. Intrinsic defects and extrinsic dopant Ga control the defect related emission spectrum in the visible region. Replacement of Zn by Ga induces a room temperature metallic state in a degenerate semiconductor. Cationic disorder leads to metal-semiconductor transition at low temperature strongly dependent on the concentration of Ga. Pure semiconducting behavior up to about 80 K is observed for the highest amount of Ga. Temperature dependent metal-semiconductor transition has been interpreted by localization of charge carriers due to disorder arising from random Ga substitution.

Aliovalent ion doped n-type semiconductor nanocrystals (NC) have presently gained high interest in semiconductor research for their potential applications in plasmonics, transparent conducting oxide (TCO), and high speed optical device. For most of the cases the plasmonic absorbance band appears in the near infrared region (NIR) but it is rarely observed in visible wavelength for aliovalent ion doped semiconductor nanocrystals. In this article, we report the synthesis of Sn-doped ZnO monodispersed nanocrystals and their unique plasmonic absorbance property which is tunable from the visible to the NIR region (550 nm to >3000 nm) by varying the Sn dopant concentration and the degree of Cd-alloying. We have studied the surface enhanced Raman spectroscopy (SERS) of the 4-mercaptopyridine (4-MPy) molecule using Sn:ZnO NC thin film as SERS substrate and found a high enhancement factor value. A TCO thin film with a good figure of merit value has been prepared by Sn:Zn–Cd–O alloyed NCs by taking advantage of high electron density and high mobility of electrons of doped alloyed NCs. Application as SERS substrate and TCO are excellent features of Sn-doped Zn1–x Cd x O NCs.

Ag/Ag2O NPs synthesized using K. abolonga exhibited antimicrobial activity along with carbenicillin against MDR P. aeruginosa.

Solid solution of nickel ferrite (NiFe2O4) and barium titanate (BaTiO3), (100-x)BaTiO3–(x) NiFe2O4 has been prepared by solid state reaction. Compressive strain is developed in NiFe2O4 due to mutual structural interaction across the interface of NiFe2O4 and BaTiO3 phases. Quantitative analysis of X-ray diffraction and X-ray photo electron spectrum suggest mixed spinel structure of NiFe2O4. A systematic study of composition dependence of composite indicates BaTiO3 causes a random distribution of Fe and Ni cations among octahedral and tetrahedral sites during non-equilibrium growth of NiFe2O4. The degree of inversion decreases monotonically from 0.97 to 0.75 with increase of BaTiO3 content. Temperature dependence of magnetization has been analyzed by four sublattice model to describe complex magnetic exchange interactions in mixed spinel phase. Curie temperature and saturation magnetization decrease with increase of BaTiO3 concentration. Enhancement of strain and larger occupancy of Ni2+ at tetrahedral site increase coercivity up to 200 Oe. Magnetostructual coupling induced by BaTiO3 improves coercivity in NiFe2O4. An increase in the demagnetization and homogeneity in magnetization process in NiFe2O4 is observed due to the interaction with diamagnetic BaTiO3.