Silicon Nanocrystals with pH-Sensitive Tunable Light Emission from Violet to Blue-Green.

Jing Wang,Junhong Guo,Jing Chen

doi:10.3390/s17102396

Jing Wang, Junhong Guo + Show 1 more

Open Access

https://doi.org/10.3390/s17102396

Copy DOI

Abstract

We fabricated a silicon nanocrystal (NC) suspension with visible, continuous, tunable light emission with pH sensitivity from violet to blue-green. Transmission electron microscopy (TEM) images and X-ray diffraction (XRD) pattern analysis exhibit the highly crystalline nanoparticles of silicon. Photoluminescence (PL) spectra and photoluminescence excitation (PLE) spectra at different pH values, such as 1, 3, 5, 7, 9, and 11, reveal the origins of light emission from the silicon NC suspension, which includes both the quantum confinement effect and surface bonding. The quantum confinement effect dominates the PL origins of silicon NCs, especially determining the tunability and the emission range of PL, while the surface bonding regulates the maximum peak center, full width at half maximum (FWHM), and offsets of PL peaks in response to the changing pH value. The peak fitting of PLE curves reveals one of the divided PLE peaks shifts towards a shorter wavelength when the pH value increases, which implies correspondence with the surface bonding between silicon NCs and hydrogen atoms or hydroxyl groups. The consequent detailed analysis of the PL spectra indicates that the surface bonding results in the transforming of the PL curves towards longer wavelengths with the increasing pH values, which is defined as the pH sensitivity of PL. These results suggest that the present silicon NCs with pH-sensitive tunable light emission could find promising potential applications as optical sources, bio-sensors, etc.

Highlights

The research on low-dimensional silicon nanostructures is an active research field, due to the interesting chemical and physical properties [1,2,3,4,5]
The Transmission electron microscopy (TEM) images of silicon NCs are taken at the accelerating voltage of 200 kV, as shown in images seen of silicon
By monodispersed ultra-small silicon NCs with active surfaces, the tunable photoluminescence from violet to blue-green with pH sensitivity is observed due to both the quantum confinement effect and the bonding interaction between silicon atoms on the NCs’

Summary

Introduction

The research on low-dimensional silicon nanostructures is an active research field, due to the interesting chemical and physical properties [1,2,3,4,5]. Of all the low-dimensional silicon nanomaterials, the silicon NCs with a variety of types, such as porous silicon [6,7,8], silicon/SiO2 , or silicon/silicon nitride nuclear shell nanostructure [9,10,11], soluble quantum dots [12,13,14,15,16,17], silicon NC-based photonic crystal slabs [18], silicon NC ultrathin films [19], etc., have drawn increasing attention. It is still a challenge to achieve controllable blue light emission of free silicon NCs without clustering, since the sizes of silicon NCs have to be much smaller than excitation Bohr radius of 4.3 nm [28] based on the quantum confinement effect [15,30,46,47]. Due to the high surface/volume ratio and the size confinement effects, the surface of silicon

Methods

Results

Conclusion