Surface-Modified Silicon Nanoparticles with Ultrabright Photoluminescence and Single-Exponential Decay for Nanoscale Fluorescence Lifetime Imaging of Temperature

Abstract

In this Communication, we report fabrication of ultrabright water-dispersible silicon nanoparticles (SiNPs) with quantum yields (QYs) up to 75% through a novelly designed chemical surface modification. A simple one-pot surface modification was developed that improves the photoluminescent QYs of SiNPs from 8% to 75% and meanwhile makes SiNPs water-dispersible. Time-correlated single photon counting and femtosecond time-resolved photoluminescence techniques demonstrate the emergence of a single and uncommonly highly emissive recombination channel across the entire NP ensemble induced by surface modification. The extended relatively long fluorescence lifetime (FLT), with a monoexponential decay, makes such surface-modified SiNPs suitable for applications involving lifetime measurements. Experimental results demonstrate that the surface-modified SiNPs can be utilized as an extraordinary nanothermometer through FLT imaging.

Ultrafast optical spectroscopy of surface-modified silicon quantum dots: unraveling the underlying mechanism of the ultrabright and color-tunable photoluminescence

“…44249 In our previous work, we produced novel Si NCs with unprecedented ultrabright fluorescence and single-exponential decay. 23 According to the time-resolved PL dynamics, we demonstrated that no fast PL decay component was present in the range of *These authors contributed equally to this work sub-picosecond to hundreds of nanoseconds in these ultrabright Si NCs. In addition, their steady-state optical properties, i.e., PL quantum yield (QY), excitation-and temperature-dependent PL behaviors, are closely related to the surface organic agents.…”

“…In a typical synthesis of unmodified Si NCs with surface Si-Cl bands (Cl-Si NCs), 23 0.17 g of sodium and 0.75 g of naphthalene were stirred in 20 mL of glyme for approximately 3 h to produce sodium-naphthalide. Then, 0.20 mL of SiCl 4 was added dropwise.…”

“…20222 For the indirect approach, recently reported surface-modified Si NCs could also provide highly effective emissive channels. 23 Furthermore, although the possible modulation mechanisms of the carrier wave function in Si NCs still remain controversial, some researchers have achieved the effect of surface ligands on the low-energy electron states of Si NCs, which would lead to phononless excitonic recombination. 24,25 Thus, the major drawback of Si NCs could be overcome by these effects solely or synergistically.…”

“…Nevertheless, insight into the PL mechanism of Si NCs remains elusive, 26231 in particular for ultrabright Si NCs. 23,32234 In addition, to further tailor and improve the fluorescent properties of Si NCs, such as their color-tunable fluorescence with high brightness, fundamentally understanding the underlying mechanisms is also required.…”

Optical Biosensing and Bioimaging With Porous Silicon and Silicon Quantum Dots (Invited Review)

“…Remarkably, recent observations suggest that certain electron donating, nitrogen containing species can drastically improve the blue emitting quantum yield of silicon quantum dots significantly. i.e., Li et al showed that performing only surface modification with electron donors containing nitrogen drastically improves the emission quantum yield of SiQDs to 50-75% [122]. (Figure 8) This surprising finding was proven by the Sun group [123], where ultrafast microscopy was used to indicate that this high quantum yield emission is indeed related to the surface trap states.…”