Influence of particle size and dielectric environment on the dispersion behaviour and surface plasmon in nickel nanoparticles.

Nickel nanoparticles (NPs) are promising candidates for various applications, including biomedical ones, as they have good magnetic properties as well as high thermal conductivity. We used well-characterized Ni NPs of average Scherrer sizes from 1.31 nm to 22.23 nm and investigated the effects of the primary particle size, size distribution and dielectric environments, and of separately adding non-ionic polyvinylpyrrolidone (PVP), cationic cetyltrimethylammonium bromide (CTAB) and anionic ethylenediaminetetraacetic acid (EDTA) in ethanol, on their stability and agglomeration behaviour using atomic force microscopy (AFM), particle size analysis and zeta potential study through dynamic light scattering (DLS) combined with UV-visible spectroscopy data. The dominant influence of surfactants, additives, particles size and shape on the surface plasmon resonance (SPR) was found. SPR is considerably sensitive to the dielectric environment in addition to size and shape. Moreover, increasing the concentration of PVP led to an enhanced SPR intensity and a shift in its position towards higher wavelength. 1.31 nm NPs with EDTA as an additive yielded the best dispersibility and also showed superparamagnetic behaviour at 300 K, indicating their favourable application potentials.

Correction: Influence of particle size and dielectric environment on the dispersion behaviour and surface plasmon in nickel nanoparticles.

Correction for 'Influence of particle size and dielectric environment on the dispersion behaviour and surface plasmon in nickel nanoparticles' by Vikash Sharma et al., Phys. Chem. Chem. Phys., 2017, 19, 14096-14106.

High coercive field and magnetization reversal in core-shell cum nanotwin driven Ni/NiO nanospheres.

We report here nanotwin-core-shell Ni(core)NiO(shell) spheres of average size 25 nm prepared through polyol method. They exhibit high coercive field at 2 K, sharp peak at approximately 20 K in magnetization curve and magnetization reversal. Interestingly, exchange bias due to antiferromagnetic NiO shell is absent. Among other possibilities, anisotropy variations due to particle size distribution and twinning associated with disorder appear to play an important role. Further, magnetic interactions of twinned bigger spheres, which may also act as superferrimagnetic-like Ni multilayer cores, with superparamagnetic Ni of smaller spheres, might be the additional causes. These nanostructures therefore seem to have potential interest in memory effect.

A load-based thermopower measurement setup in the temperature range of 5-330 K.

This is a report on the development of an automated precision load-based measurement setup for thermoelectric power (S) of different types of samples in the temperature range of 5-330 K. The problems in the old spring-based setup have been solved in this load-based setup. This setup takes nearly 4 h for each run, and the typical error is within 5%. High quality calibration has been demonstrated using high purity platinum wires and cylinders.

Trioctylphosphine as self-assembly inducer.

Nickel nanoparticles (NPs) of different shapes and sizes in polydispersed as well as monodispersed forms were synthesized using trioctylphosphine (TOP), triphenylphosphine (TPP), oleylamine (OA) and their combinations as surfactants to study their self-assembly inducing capabilities. Randomly agglomerated polydispersed NPs were found for TPP and OA, and TPP or OA separately. However, in consolidation with the earlier report of Singh et al., J. Mater. Chem. C, 2014, 2, 8918, NPs formed using TOP only and a combination of TOP with OA naturally exhibited monodispersed NPs associated with natural nanolattice formation without any other external force or surfactants, demonstrating clearly the self-inducing capacity of TOP into monodispersed NPs and their self-assembled nanolattices. Fourier-transformed infra-red (FTIR) data clearly indicated the capping of these surfactants along with acetylacetonate ligands from nickel acetylacetonate precursor on the surface of the NPs. Remarkably, the narrowest zeta potential (ζ) base-widths were observed for samples possessing a self-assembled nanolattice, compared to the broader ones for randomly agglomerated particles.