Alkyl Passivation and Amphiphilic Polymer Coating of Silicon Nanocrystals for Diagnostic Imaging

Abstract

We show a method to produce biocompatible polymer-coated silicon (Si) nanocrystals for medical imaging. Silica-embedded Si nanocrystals are formed by HSQ thermolysis. The nanocrystals are then liberated from the oxide and terminated with Si-H bonds by HF etching, followed by alkyl monolayer passivation by thermal hydrosilylation. The Si nanocrystals have an average diameter of 2.1 ± 0.6 nm and photoluminesce (PL) with a peak emission wavelength of 650 nm, which lies Correspondence to: Brian A. Korgel, korgel@che.utexas.edu. NIH Public AccessAuthor Manuscript Small. Author manuscript; available in PMC 2011 September 20.

Size-Dependent Chemical Reactivity of Silicon Nanocrystals with Water and Oxygen

“…22 For allylbenzene, which has a higher ligand cone angle compared to a linear alkyl group, a higher surface curvature will allow more room for ligands to spread out from the nanocrystal surface, allowing more Si-H species to be converted to Si-AB with decreasing particle size. The presence of adventitious surface oxidation has been reported in previous syntheses of organic capped ncSi, 5c, 23 and the results here show the ratio of the peak associated with Si-O-Si or Si-OR to Si-H increasing with decreasing size, indicating that a greater proportion of oxide species exist at the ncSi:AB surface of smaller particles. This size-dependent adventitious surface oxidation trend is also observed in comparing the atomic % of core Si, O and C species determined by XPS for particles of varying size (SI Figure 3A).…”

A Novel Photothermal Nanocrystals of Cu7S4 Hollow Structure for Efficient Ablation of Cancer Cells

“…The assynthesized Cu 7 S 4 NCs were passivated with oleylamine and could not be dispersed into aqueous or physiological solution, which limited these nanocrystals applying directly to biologicalsystem.To obtain hydrophilic Cu 7 S 4 NCs, an amphiphilic polymer was coated on the surface of Cu 7 S 4 NCs by hydrophobic self-assembly [23,28]. The polymer-modified Cu 7 S 4 NCs could be easily dispersed in water or phosphate buffered saline (PBS) at pH 7.4.…”

“…Synthesis of polymer-modified Cu 7 S 4 NCs: The asprepared Cu 7 S 4 NCs were coated with an amphiphilic hydrolyzed poly (maleic anhydride) pre-modified with dodecylamine according to a literature report [23,28]. In a 50 mL round bottom flask, 530 μL of the amphiphilic polymer stock solution (0.8 M monomer units in CHCl 3 ), 5 mL of the above Cu 7 S 4 NCs chloroform solution and 25 mL of anhydrous CHCl 3 were combined and vortexed with magnetically stirring for 45 minutes at room temperature.…”

Cationic Silicon Nanocrystals with Colloidal Stability, pH‐Independent Positive Surface Charge and Size Tunable Photoluminescence in the Near‐Infrared to Red Spectral Range

“…For example, ncSi based on steric stabilization strategies typically have larger hydrodynamic diameters ranging from 20 to 100 nm, and incorporates many ncSi in one nanoparticle, whereas ncSi based on electrostatic strategies typically have diameters below 5 nm and are dispersible as isolated nanocrystals 12, 15, 17, 21. In general, hydrodynamic diameters below about 5 nm are desirable since nanoparticles below this threshold can be cleared through urinary excretion to minimize potential toxicity effects 4…”