Spectral tuning of colloidal Si nanocrystal luminescence by post-laser irradiation in liquid.

Ze Yuan,Toshihiro Nakamura

doi:10.1039/d0ra05205a

Abstract

We report a simple technique to tune the luminescence spectra of blue-emitting colloidal silicon nanocrystals (Si-ncs) to the ultraviolet region via post-laser irradiation. The post-laser irradiation of the as-prepared colloidal Si-ncs which exhibited a broad photoluminescence (PL) centered at ∼390 nm with a bandwidth of 105 nm caused a spectral peak shift to ∼330 nm and a decrease in the bandwidth to 80 nm. The degree of the spectral tuning can be controlled by changing the irradiated laser power. The spectroscopic and transmittance electron microscopy analysis revealed that this spectral tuning effect is due to the size reduction of Si-ncs by selective absorption of post-irradiated laser light by particular-sized Si-ncs that have bandgap energies resonant with the irradiated photon energy, as well as the resultant ablation of these Si-ncs.

Highlights

Semiconductors with optical response in the ultraviolet (UV) region have evoked immense interest from researchers owing to various potential applications, such as light-emitting diodes, photodetectors, and nanomedicine.[1,2,3,4,5,6,7] Speci cally, UV light emission from semiconductors can be utilized for applications in high-density information storage devices because the focus of UV light is more sharp than the longer wavelength light due to the diffraction limit
We report a simple technique to tune the luminescence spectra of blue-emitting colloidal silicon nanocrystals (Si-ncs) to the ultraviolet region via post-laser irradiation
The spectroscopic and transmittance electron microscopy analysis revealed that this spectral tuning effect is due to the size reduction of Si-ncs by selective absorption of post-irradiated laser light by particularsized Si-ncs that have bandgap energies resonant with the irradiated photon energy, as well as the resultant ablation of these Si-ncs

Summary

Introduction

Semiconductors with optical response in the ultraviolet (UV) region have evoked immense interest from researchers owing to various potential applications, such as light-emitting diodes, photodetectors, and nanomedicine (bioimaging).[1,2,3,4,5,6,7] Speci cally, UV light emission from semiconductors can be utilized for applications in high-density information storage devices (i.e., the shorter wavelength a light-emitting device operates, the more information the device can store) because the focus of UV light is more sharp than the longer wavelength light due to the diffraction limit. The optical and structural properties of the spectraltuned colloidal Si-nc to the UV region are investigated in detail These analyses reveal that the spectral tuning is due to the changes in the size distribution of Si-nc by selective absorption of larger Si-nc and the resultant ablation effects. A er laser irradiation, the supernatant liquid was ltered by centrifugation at 13 000 rpm for 20 min with a membrane lter with a pore size of $200 nm Post-laser irradiation was performed for the as-prepared colloidal Si-nc sample In this process, we employed UV pulsed-laser light at 355 nm from a Q-switched Nd:YAG laser (a pulse duration of 5 ns and repetition rate of 15 Hz). All optical measurements were performed in a quartz cuvette at room temperature

Results and discussion

Findings

Conclusions