Surface-activation of semiconductor nanostructures for biological applications
Means and methods for producing surface-activated semiconductor nanoparticles suitable for in vitro and in vivo applications that can fluoresce in response to light excitation. Semiconductor nanostructures can be produced by generating a porous layer in semiconductor substrate comprising a network of nanostructures. Prior or subsequent to cleavage from the substrate, the nanostructures can be activated by an activation means such as exposing their surfaces to a plasma, oxidation or ion implantation. In some embodiments, the surface activation renders the nanostructures more hydrophilic, thereby facilitating functionalization of the nanoparticles for either in vitro or in vivo use.
1. A method of producing semiconductor nanostructures comprising:
depositing a release layer on a semiconductor substrate;
forming a heterostructure over the release layer, the heterostructure providing confinement of charge carriers therein;
applying a mask to a surface of the heterostructure such that a portion of the surface of the heterostructures is rendered resistant to etching;
removing a portion of the heterostructure to form a plurality of separate heterostructure elements disposed on a remaining portion of the release layer;
activating at least a portion of a surface of the heterostructure elements by treating said portion with ions so as to deliver a dose of ions in a range of about 10 12 to 10 17 ions/cm 2 ; and
dissolving the release layer whereby semiconductor nanostructures having activated surfaces are formed.
2. The method of claim 1 , wherein the step of activating further comprises exposing said surface portion to a plasma.
3. The method of claim 2 , wherein the step of activating further comprises exposing said surface portion to an ECR plasma.
4. The method of claim 2 , wherein said plasma is generated in a gas selected from the group consisting of: noble gases, diatomic gases, hydrocarbons, and fluorinated hydrocarbons.
5. The method of claim 1 , wherein said nanostructures are formed from any of silicon, arsenic, germanium composition or any Group III-V or Group II-VI semiconductor compound.
6. The method of claim 1 , wherein the step of applying a mask further comprises applying a plurality of masking nanoparticles to the surface of the heterostructure such that the nanoparticles selectively shield portions of the heterostructure from etching.
7. The method of claim 1 , wherein the mask comprises metallic particles.
8. The method of claim 1 , wherein the semiconductor nanostructures have average maximum diameter in a range of about 5 nm to about 100 nm.
9. The method of claim 1 , wherein the semiconductor nanostructures have an emission maximum between about 400 nm and about 1200 nm.
10. The method of claim 1 , wherein the semiconductor nanostructures have an emission maximum between about 500 nm and about 900 nm.
11. The method of claim 1 , wherein the said nanostructures are coated with a biocompatible coating.
12. The method of claim 11 , wherein the coating is an organic coating.
13. The method of claim 1 , wherein the coated nanostructures have an average maximum dimension between about 5 nm and about 200 nm.
14. The method of claim 1 , wherein said ions used for said activating step are selected from the group consisting of nitrogen ions, oxygen ions, argon ions, carbon ions, hydrogen ions, and helium ions.
15. A method of producing semiconductor nanostructures, comprising:
generating a plurality of nanostructures on a substrate;
activating surfaces of said nanostructures to enhance hydrophilicity thereof by exposing surfaces of said nanostructures to a plasma; and
releasing said activated nanostructures from said substrate,
wherein the step of generating a plurality of nanostructures on a substrate comprises:
etching a semiconductor substrate to generate a porous layer therein, said porous layer comprising a network of nanostructures.
16. The method of claim 15 , further comprising selecting said plasma to be an ECR plasma.
17. The method of claim 15 , wherein said plasma is generated in a gas selected from the group consisting of: noble gases, diatomic gases, hydrocarbons, and fluorinated hydrocarbons.