Importance of the size of Ag nanospheres in their magnetoplasmonic responses

Significance 

The application of noble metal nanostructures in future electronics, photonics, chemical or biological imaging and sensing, cannot be overlooked. Such nanomaterials have potential to be the baseline game-changers in the near future as their development can open doors for fabrication of intricate designs of elements. Presently, it has been observed that the characteristic spectroscopic properties of such metal nanostructures give an excitation known as a localized surface plasmon resonance (LSPR). Specifically, silver nanostructures have been seen to be some of the most promising objects that can yield high-quality LSPR with intense optical extinction. Magneto-optical activity measurements, such as magnetic circular dichroism (MCD) spectroscopy are efficient technique for optical/electronic characterization in inorganic materials such as metal nanostructures. Unfortunately, these MCD measurements have only been undertaken for nanoparticles over a small size range, therefore, to offset this shortcoming, further exploration of the size-dependent magneto-optical activity for the circular magnetoplasmonic modes in silver nanoparticles is necessary, in order to gain a better insight into their characteristic features.

Taisuke Shiratsu and Professor Hiroshi Yao at Mie University in Japan proposed a study whose main objective was to undertake a magnetic circular dichroism spectroscopic analysis for silver nanoparticles of dimensions between 10 and 60 nm. The purposed to assess the extent of the size-dependence of the magneto-optical activity in silver nanoparticles. Their work is currently published in the research journal, Physical Chemistry Chemical Physics (2018).

The research method employed commenced with the preparation of the silver nanoparticles on the basis of a seeded-growth strategy using sodium citrate and tannic acid as reducing agents in aqueous solution. Next, the two scholars carried out magnetic circular dichroism spectroscopic measurements where 5mm rectangular cuvettes made of quartz were used for the measurements. They then recorded the UV-vis extinction spectra. Lastly, transmission electron microscopy was conducted using an electron microscope operated at 80 kV.

The authors observed that the obtained nanoparticles were roughly spherical, with those larger than 28 nm having a slight diversity of shapes with quasi-spherical polyhedrons. The two researchers also noted that the obtained nanoparticles exhibited a derivative-like magnetic circular dichroism spectroscopy response in the localized surface plasmon resonance region, which was attributable to the two circular modes of surface magnetoplasmons. Moreover, they observed that as the nanoparticle diameter increased, the bisignated magnetic circular dichroism spectroscopy signal became strongly distorted and weakened.

Taisuke Shiratsu-Hiroshi Yao study demonstrated the size-dependent magneto-optical activity in quasi-spherical silver nanoparticles with diameters between 10 to 60 nanometers with magnetic circular dichroism spectroscopy. It was seen that there was an optimal particle size for obtaining the maximum magneto-optical activity in the system. Furthermore, they found out that the shape distribution strongly influenced the reduction of the maximum MCD amplitude normalized to the LSPR peak absorbance. Altogether, the characteristic magneto-optical activity of metal nanoparticles as a function of spectral inhomogeneity will bring about a wide range of impacts to the application designs of active plasmonics

 size of Ag nanospheres magnetoplasmonic responses - Advances in Engineering

About the author

Hiroshi Yao graduated from Osaka University, and obtained Ph.D. degree in chemistry from Hokkaido University, Japan (1997). He has worked in Mitsui Chemicals, Inc., Hokkaido University, and University of Hyogo. Then he is currently a professor at Mie University.

He is a physical chemist working in multidisciplinary areas of nanomaterials research including chemical synthesis and photophysics/photochemistry of metal-based plasmonic nanoarchitectures, chiral clusters, and photofunctional organic nanoparticles.

About the author

Taisuke Shiratsu was a student at University of Hyogo and Mie University under supervision of Prof. Hiroshi Yao, and received his master’s degree in 2018.

Reference

Taisuke Shiratsu, Hiroshi Yao. Size dependence of magneto-optical activity in silver nanoparticles with dimensions between 10 and 60 nm studied by MCD spectroscopy. Physical Chemistry Chemical Physics, 2018, volume 20, page 4269.

Go To Physical Chemistry Chemical Physics

Check Also

A new constraint DFT technique for self-consistent determination of U values - Advances in Engineering

A new constraint DFT technique for self-consistent determination of U values