10 research outputs found
Zeta potential and Raman studies of PVP capped Bi2S3 nanoparticles synthesized by polyol method
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Assessment of Patterns of Lower Limb Injuries at a Medical College Hospital of Central India
No full textAssessment of Prevalence of Hypertension amongst Workers of Silk Industry in Kanchipuram District
No full textInvestigation on structural, electrical, magnetic and thermoelectric properties of low bandwidth Sm 1-x Sr x MnO 3 (0.2≤ x ≤0.5) manganites
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Unique properties of nickel nanoparticles
No full textIntroduction: Magnetic nanoparticles (MNPs) are very attractive for applications in magnetic resonance imaging, MRI, magnetic fluids, catalysts, magnetic recording media, rechargeable batteries, optoelectronics, conducting paints, magnetic hyperthermia and other biomedical applications (1). MNPs dispersed in a liquid medium tend to agglomerate due to van der Waals or other attractive forces prevailing on surface. This necessitates them to coat with an appropriate capping agent. The ligand molecules bound to nanoparticle (NP) surface not only control the growth of the particles during synthesis, but also prevent them from aggregation and decides the future of how the NPs form, agglomerate and respond to a given situation. To understand some of these characteristics, we prepared nickel NPs and demonstrate formation of nanolattice, quantum size effect (QSE) and surface plasmon resonance (SPR).
Methods: We prepared the monodispersed Ni NPs by thermal decomposition methods using trioctylphosphine (TOP) or combinations with triphenylphosphine (TPP) and or oleylamine (OA) (1,2); polyol method produces polydispersed NPs (3). They were characterized comprehensively using varieties of experimental techniques such as XRD, XPS, TEM, EDX, SAXS, Raman, FTIR, UV-Visible, dynamic light scattering (Zeta potential and hydrodynamic particle size), and EXAFS. Physical properties studies include electrical resistivity, thermopower, and heat capacity.
Results & Discussions: TEM images prove monodispersed NP formation, and HCP nanolattice that was confirmed from SAXS pattern analysis (1,2). Ni atoms form FCC and HCP lattices inside the nanolattices up to ~6 nm, above which only FCC phase exist (4). Heat capacity data show rare QSE effect (5). Particle size and dielectric environment influence dispersion behavior and SPR (6). The thermopower gradually turns positive at 25 nm below 75 K (7). Electrical resistivity is anomalous at nanoscale (3).
Conclusions: Ni NPs exhibit anomalous electrical resistivity. They switch sign of thermopower from negative to positive as particle size drops. There exists FCC phase only in the atomic structure above ~6 nm but mixed FCC and HCP phases below ~6 nm. Particles size and dielectric environment influence dispersion behavior and SPR. QSE was observed in the heat capacity. Monodispersed Ni NPs form natural nanolattice.
Keywords: nanolattice, quantum size effect, surface plasmon resonance, thermoelectricity
Acknowledgment: The author gratefully acknowledges all the coauthors listed in the references cited herein below.
References
G. S. Okram, et al. Trioctylphosphine as self-assembly inducer. Faraday Discussions. 2015; 181: 211 – 223.
J. Singh, N. Kaurav, N. P. Lalla and G. S. Okram. Naturally self-assembled nickel nanolattice. J. Mater. Chem. C 2014; 2: 8918-8924.
G. S. Okram, A. Soni, R. Rawat. Anomalous electrical transport behavior in nanocrystalline nickel. Nanotechnology 2008; 19, 185711.
Tarachand, et al., G. S. Okram. Size-induced structural phase transition at ~6.0 nm from mixed fcc-hcp to purely fcc structure in monodispersed nickel nanoparticles. J. Phys. Chemistry C 2016; 120: 28354–28362.
J. Singh, Tarachand, S. S. Samatham, D. Venkateshwarlu, N. Kaurav, V. Ganesan and G. S. Okram. Quantum size effect on the heat capacity of nickel nanolattice Appl. Phys. Lett. 2017; 111: 201904-1-4.
V. Sharma, et al. Influence of Particle Size and Dielectric Environment on Dispersion Behavior and Surface Plasmon in Nickel Nanoparticles. Phys. Chem. Chem. Phys. 2017; 19: 14096-14106.
A. Soni and G. S. Okram. Size Dependent Thermopower in Nanocrystalline Nickel. Appl. Phys. Lett. 2009; 95, 013101
