Process for preparation of surface modified silicon nanoparticles

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This invention relates to a process for producing silicon nanoparticles (1-20 nm in diameter) whose surfaces are fully coated with organic molecular groups covalently bonded via silicon-carbon (Si-C) bonds. This surface modification enables stable and homogeneous silicon nanoparticles with custom luminescence properties and improved dispersibility. The process involves etching silicon nanoparticles to remove oxide layers and then attaching organic chromophores or other groups via Si-C bonds.

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• Optoelectronic devices such as LEDs (light-emitting diodes) and displays with tunable luminescence.
• Use as biomarkers or fluorescent labels in medical diagnostics and bioimaging.
• Functional materials in field-effect transistors (FETs) for electronics and sensor technology.
• Vehicles for intracellular drug delivery, especially for water-insoluble drugs in pharmaceutical applications.
• Fluorescence spectroscopy to study transporter proteins in cancer research.
• Multi-color or customizable display technologies through spectral tuning via surface-attached chromophores.

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• Stable, covalent surface modification (Si-C bond) prevents aggregation and oxidation, leading to highly stable nanoparticles.
• Luminescence yield (quantum yield) can be high (30% or more), with color tunability via surface functionalization.
• Greater control over dispersibility in both aqueous and organic media, enabling broader applications in formulations and inks.
• Surface can be tailored with a wide variety of functional groups, including chromophores or groups for biological interactions (e.g., targeting proteins or DNA).
• Potential for monodisperse particles with consistent properties, important for reproducible device performance and bioanalytical results.
• Improved photostability and chemical stability due to removal of native oxide and covalent organic coating.

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Patent Abstract

Surface modified silicon particle with an average particle diameter of 1-20 nm, is claimed, where the surface of the silicon particles are completely coated and comprises one or more molecular parts (Q), which are covalently bonded to the silicon over silicon-carbon-bond. Surface modified silicon particle with an average particle diameter of 1-20 nm, is claimed, where the surface of the silicon particles are completely coated and comprises one or more molecular parts (Q) of formula (-C 1>-HR-C 2>HR-(CR 2) n-X) (I) or (-C 1>H=CH-(CR 2) n-X) (II), which are covalently bonded to the silicon over silicon-carbon-bond. C 1>a carbon atom, which forms the covalent silicon-carbon-bond; C 2>not defined; X : molecular residue with a delocalized pi-electron system, preferably optionally substituted cyclic, aromatic residue containing one or more heteroatoms of N, O, S or P; R : H (preferred), CH 3, C 2H 5, n-C 3H 7, iso-C 3H 7, n-C 4H 9, iso-C 4H 9; and n : 0-6, preferably 0. An independent claim is included for preparing the surface modified silicon particle, comprising treating silicon oxide layer with a partially or completely coated silicon particle with 1-10 wt.% hydrofluoric acid solution, in a non-oxidizing medium for 1-30 minutes and subsequently separating the hydrofluoric acid solution containing silicon particles, which are free of silicon dioxide, and reacting with one or more olefin compounds of formula (CHR=CR(CR 2) n-X) (III) or (CH=C (CR 2) n-X) (IV).