Magnetoplasmonics Lab

Archives February 2024

Our Group Meeting

Our Group Meeting _ Sunday 19 Feb 2024

……………………………………………………………………………………

Ms. Bahrami presented a seminar titled as “Alzheimer’s disease”

News on 1D photonic crystals
In these days, the journal of Faraday Discussions published a paper entitled as “Integration of bio-responsive silver in 1D photonic crystals: towards the colorimetric detection of bacteria"

———————————————————————————————

Abstract

The colour purity and versatility of fabrication of one-dimensional photonic crystals (1D PhCs) make them ideal candidates for colorimetric sensing of a variety of analytes. For instance, the detection of bacterial contaminants in food via colorimetric sensors can be highly appealing, as most of the existing detection techniques are in general time-consuming and the read-out requires specialised personnel. Here, we present a colorimetric sensor based on hybrid plasmonic/photonic 1D crystals. We demonstrate that the modification of the silver plasmon resonance brought about by the effective silver/bacterium interaction can be translated into the visible spectral region, producing a change in the structural colour. In addition, we observe a superior colorimetric sensitivity against the Gram negative Escherichia coli compared to the Gram positive Micrococcus luteus, a result that we attribute to the more efficient electrostatic interaction and cellular adhesion between the silver surface and the Gram-negative bacteria outer membrane. This approach demonstrates that in principle an easy colorimetric detection of bacterial contaminants can be achieved through the use of bio-responsive plasmonic materials, such as silver, whose selective electrostatic interaction with bacterial cell wall is well-known and occurs without the need of chemical functionalisation.

Graphical abstract: Integration of bio-responsive silver in 1D photonic crystals: towards the colorimetric detection of bacteria
Our new paper in Journal of optik

Magneto-Plasmonic-Induced Random Laser in Two-dimensional FeB Square Array

Majid F. Haddawi, J. M. Jassim, S. M. Hamidi

This work aims to enhance the lasing parameters of a random laser using magneto-plasmonic FeB@Au as scattering points. Two-dimensional FeB square arrays are covered by thin films of Rhodamine 6G from the bottom and top, respectively. For this purpose, two-dimensional structures were fabricated using the soft lithography method onto the polydimethylsiloxane (PDMS) substrate and deposited with a 35 nm thick gold layer using a sputtering machine, followed by a FeB (iron boride) thin layer using the radio frequency (RF) sputtering machine method. Finally, the samples were coated by rhodamine 6G dye. The samples were pumped via the second harmonic generation of the Nd:YAG laser under an external magnetic field set to 50 mT, and the random lasing action was measured using a spectrometer. Our results indicated a better ability to achieve random lasing under the external magnetic field. The output emission spectra increased with a decreased laser threshold from 0.66 mJ to 0.35 mJ, and the full width at half maximum (FWHM) decreased from 7.8 nm to 4 nm.

Relative Emission spectrum of samples at different pumping energies from 0.17 to 1.07 mJ and (b) Schematic diagram of the main two-dimensional substances before dye coating.