Soft X‐ray induced oxidation on acrylic acid grafted luminescent silicon quantum dots in ultrahigh vacuum

Abstract

Water soluble acrylic acid grafted luminescent silicon quantum dots (Si-QDs) were prepared by a simplified method. The resulting Si-QDs dissolved in water and showed stable strong luminescence with peaks at 436 and 604 nm. X-ray photoelectron spectroscopy (XPS) was employed to examine the surface electronic states after the synthesis. The co-existence of the Si2p and C1s core levels infers that the acrylic acid has been successfully grafted on the surface of silicon quantum dots. To fit the Si2p spectrum, four components were needed at 99.45, 100.28, 102.21 and 103.24 eV. The first component at 99.45 eV (I) was assigned to Si-Si within the silicon core of the Si-QDs. The second component at 100.28 eV (II) was from Si-C. The third at 102.21 eV (III) was a sub-oxide state and the fourth at 103.24 eV (IV) was from SiO 2 at Si-QDs surface. With an increase in exposure to soft X-ray photons, the intensity ratio of the two peaks within the Si2p region A and B increased from 0.5 to 1.4 while the peak A intensity decreased, and eventually a steady state was reached. This observation is explained in terms of photon-induced oxidation taking place within the surface dangling bonds. As the PL profile for Si-QDs is influenced by the degree of oxidation within the nanocrystal structure, the inducement of oxidation by soft X-rays will play a role in the range of potential applications where such materials could be used -especially within biomedical labelling.

Tailoring the Charge Transport Properties of Printable Si‐NCs By Conjugated Organic Ligands

“…Spectra of functionalized Si‐NCs (Figure C and D) shows the absence of broad Si‐O peak around 1100 cm −1 and hence confirm that the features around 100 and 102.5 eV of XPS (Figure B) spectrum emerged mainly from SiC bond and not from the oxidation of Si‐NCs. This assumption is also strengthened by the fact that moderate levels of oxygen observed in XPS spectrum is typical of X‐ray induced oxidation of Si‐NCs as reported in literature . The presence of weak component at 103.4 eV which is typical of SiO 2 is also in support of above findings.…”

Synthesis of Diagnostic Silicon Nanoparticles for Targeted Delivery of Thiourea to Epidermal Growth Factor Receptor-Expressing Cancer Cells

“…The last component of O1s spectrum is assigned to O-S at 531.10 eV. 44 The N1s spectrum is presented in Fig. 2e and fitted with two components and a Shirley background.…”

“…42 The third component at 100.91 eV is assigned to Si-Si within silicon core of NPs. [43][44] The C1s spectrum is fitted with three components and a Shirley background, see Fig. 2c.…”

Uptake and Toxicity Studies of Poly‐Acrylic Acid Functionalized Silicon Nanoparticles in Cultured Mammalian Cells

“…As a result, research on the biological effects of SiNPs has grown in importance and gained extensive attention. To address these problems we have synthesized poly‐acrylic acid terminated silicon nanoparticles (PAAc‐SiNPs) that are chemically stable and exhibit strong red luminescence 24, 25. The biocompatibility of PAAc‐SiNPs and cytotoxicity are important parameters to evaluate whether these SiNPs can be used safely in biomedical environments.…”