Temperature and Viscosity Effects on the Photoluminescence Properties of Alkyl-Capped Silicon Nanoparticles Dispersed in Nonpolar Liquids

Abstract

Alkyl-capped silicon nanoparticles (Ac-Si NPs) with diameter size ranging from 4 to 10 nm were prepared by an anodic etching method followed by a surface hydrosililation reaction. Thanks to this surface functionalization, these Ac-Si NPs were homogeneously dispersed in nonpolar liquids (NPLs). They exhibit a visible photoluminescence (PL) as a result of the quantum confinement effect. An important red shift of the PL peak position with temperature of almost 1 meV/K was obtained between 303 and 390 K. This dependence is much higher than most of the literature results for Si NPs. The influence of the viscosity of the NPLs on the red shift value is discussed considering energy transfer between the nanoparticles, which is confirmed by the determination of their mean free path as a function of temperature and the viscosity of the liquids. The high PL thermal sensitivity of the Ac-Si NPs allows consideration of their application as nanothermometers.

Photoluminescent Nanomaterials for Thermometry: Silicon and Carbon Nanoparticles

“…Here, from the average distance between two NPs calculation, an average distance as a function of the concentration for Si NPs with different NPs diameters takes the value of about 80 nm. This average distance agrees well with predicted by Hamza H. et al (2015) for Si NPs with average dimensions. Typically, the second effect is resonant energy transfer, which is occurred between two NPs by dipole-dipole interaction without photon emission disclosed within the Forster Resonance Energy Transfer (FRET) mechanism in (Forster T., 1948).…”

“…They obtained a temperature coefficient of -0.4 meV/K at 300 K, and another group of Kusova K. et al (2012) reported a temperature coefficient value of -1 meV/K close to that of Hamza H. et al (2015). In both above-mentioned cases, the Si NPs size was smaller than those obtained by Hamza H., et al (2015). On the other hand, for the temperature sensing with carbon NPs, Song Z. et al (2016) and Kalytchuk S. et al (2017) determine the PL conditions and measuring the fluorescence and fluorescence lifetime changes of the nitrogen (N) and sulfur (S) co-doped carbon dots (CDs) of ~3 nm and ~ 4.5 nm.…”

“…et al (2013) first reported a redshift higher than the value predicted by the Varshni model for free-standing silicon NPs. They obtained a temperature coefficient of -0.4 meV/K at 300 K, and another group of Kusova K. et al (2012) reported a temperature coefficient value of -1 meV/K close to that of Hamza H. et al (2015). In both above-mentioned cases, the Si NPs size was smaller than those obtained by Hamza H., et al (2015).…”

“…The PL measurements showed that, in the colloidal suspension of luminescent NPs, the PL spectra can be dependent on the interaction between the Si NPs. According to Hamza H. et al (2015) and Van Sickle A.R. et al (2013), the inner filtering effect can be realized because of the reabsorption of the PL emitted by the smaller NPs.…”

Quantitative Viscosity Mapping Using Fluorescence Lifetime Measurements

“…However, as the viscosity of the fluid is not measured directly, the technique is incapable of detecting shear thinning. Phosphorescent nanoparticles have been shown to be sensitive to viscosity; however, information on their sensitivity and applicable range is not available [14]. The sensitivity of the nanoparticles photoluminescence to temperature also adds complexity to the measurements.…”