Abstract
Silicon nanocrystals (SiNCs) are regarded as a green and environmentally friendly material when compared with other semiconductor nanocrystals. Ultra-small SiNCs (with the size 4.6–5.2 nm) demonstrate strong UV absorption and photoluminescence in the near infrared (NIR) range with the high photoluminescence quantum yield (PLQY) up to 60%. In contrast to nanoporous silicon, ultra-small SiNCs do not possess an intrinsic ability to generate singlet oxygen (1O2). However, we demonstrate that SiNC-dye conjugates synthesized via microwave assistant hydrosilylation reaction produce 1O2 with moderate quantum yield (ΦΔ) up to 27% in cyclohexane. These interesting results were obtained via measurements of singlet oxygen phosphorescence at 1,270 nm. SiNCs play an important role in the production of singlet oxygen as SiNCs harvest UV and blue radiation and transfer absorbed energy to a triplet state of the attached dyes. It increases the population of the triplet states and leads to the enhancement of the singlet oxygen generation. Simultaneously, the SiNC-dye conjugates demonstrate NIR luminescence with the PLQY up to 22%. Thus, the luminescence behavior and photosensitizing properties of the SiNC-dye conjugates can attract interest as a new multifunctional platform in the field of bio-applications.
Highlights
Singlet oxygen (1O2) is an extremely reactive species and powerful oxidant for many types of organic materials (Ogilby, 2010)
Synthesis of Hydrogen Terminated silicon nanocrystals (SiNCs) (H-SiNCs) 1.0 g the ground powder was transferred to a PTFE flask, followed by the addition of 10 ml absolute ethanol and stirring for 5 min
We found that the anchored dyes reduce both the photoluminescence quantum yield (PLQY) of the near infrared (NIR) emission of SiNCs as well as the luminescence lifetime
Summary
Singlet oxygen (1O2) is an extremely reactive species and powerful oxidant for many types of organic materials (Ogilby, 2010). The study of 1O2 has attracted increasing attention due to its potential applications in many fields such as chemical synthesis (Manfrin et al, 2019), photocatalysis (Nosaka and Nosaka, 2017), water purification (García-Fresnadillo, 2018), and photodynamic therapy of cancer (Wang et al, 2004; Vlaskin et al, 2009; Ghogare and Greer, 2016). 1O2 has been used to produced oxygenated hydrocarbons such as endoperoxide (Ahuja et al, 2018), deoxetanes (Camussi et al, 2019), as well as hydroperoxide and phosphine oxide for biomimetic organic synthesis of natural products and drugs (You and Nam, 2014). 1O2 has displayed a huge potential to destroy cancer cells (Campillo et al, 2019; Sun et al, in press). When a source of 1O2 is selectively delivered to a tumor affected tissue, 1O2 can react with many biological molecules—amino acid
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