Plasma synthesis and liquid-phase surface passivation of brightly luminescent Si nanocrystals

Plasma‐Assisted Synthesis of Silicon Nanocrystal Inks

“…Liquid-phase hydrosilylation of ≈ 4 nm crystals with 1-dodecene typically leads to samples emitting at a peak wavelength around 800 nm and with a quantum yield between 60 % and 70 %. [15][16][17] The liquid-phase hydrosilylated nanocrystals show remarkable stability against oxidation in air, as determined by FTIR and XPS measurement. [16] The plasma-grafted silicon nanocrystals have comparable chemical stability in air, but unfortunately the quantum yield is typically smaller than 10 %.…”

“…[15][16][17] The liquid-phase hydrosilylated nanocrystals show remarkable stability against oxidation in air, as determined by FTIR and XPS measurement. [16] The plasma-grafted silicon nanocrystals have comparable chemical stability in air, but unfortunately the quantum yield is typically smaller than 10 %. This suggests that there are some delicate differences between plasma-grafted and liquid-phase-functionalized crystals.…”

“…Examples include silicon colloids for which nanocrystals were produced in the gas-phase through laser pyrolysis, [13,14] or non-thermal plasma synthesis. [15][16][17] Unfortunately, performing the surface functionalization as the second step in the liquid phase introduces disadvantages such as long reaction times, and the need to transfer materials after the synthesis into different surface treatment reactors. This transfer step often needs to be performed under exclusion of oxygen, increasing the complexcity of the process.…”

“…First experiments used 1-dodecene, which when grafted to silicon crystals using liquid-phase hydrosilylation had enabled us to achieve stable silicon nanocrystal colloids with high photoluminescence quantum yields of > 60 %. [15][16][17] Figure 1a demonstrates the effectiveness of the in-flight plasma grafting in preparing silicon inks. The vial on the left shows a solution prepared from nanocrystals that were subjected to plasma-grafting of 1-dodecene.…”

“…The liquid phase surface functionalization used here was performed by the recipe described in detail in refs. [15][16][17] The main features present in the spectrum of the untreated nanocrystals are silicon hydride peaks at ∼ 2100 cm -1 and around 900 cm -1 . These peaks are typical signatures for silicon nanocrystals produced in a non-thermal plasma using silane as a precursor.…”