Electro-spun fibers and applications thereof

Abstract

A supported nanofiber medium useful for segregating chemical species is provided by selecting a polymer, selecting a substrate; and electrospinning the polymer to form a nanofiber medium on the supporting substrate. When the substrate is a planar surface, the nanofiber medium will be a mat suitable for conducting chromatographic separation. When the substrate is a filament, the nanofiber medium is an annular mat suitable for solid phase microextraction. The nanofiber media formed may be selectively cross-linked and at least partially carbonized to carbon nanofibers. The nanofiber medium is supported on the substrate without the use of binder material.

What is claimed is: 
     
         1 . A method for analytically separating at least two chemical species, comprising the steps of:
 providing a separation medium, comprising a mat of nanofibers disposed on a surface of a substrate;   providing at least two chemical species, mixed together in an appropriate solvent; and   separating the at least two chemical species from each other through contact of the mixture with the separation medium.   
     
     
         2 . The method of  claim 1 , wherein:
 the separating step is achieved by ultrathin layer chromatography (UTLC);   the substrate surface is planar and the mat of nanofibers on the planar surface has a thickness in the range of from about 11.5 to about 17.4 microns and has an average fiber diameter in the range of from about 150 to about 400 nm, such that the separation medium is a UTLC stationary phase; and   the mixture of the at least two chemical species in the appropriate solvent is a UTLC mobile phase.   
     
     
         3 . The method of  claim 2 , wherein:
 the ultra-thin chromatography separating step is achieved by the steps of:
 placing the UTLC mobile phase onto the UTLC stationary phase; and 
 drawing the UTLC mobile phase upward by capillary action. 
   
     
     
         4 . The method of  claim 1 , wherein:
 the ultra-thin chromatography separating step is achieved by the steps of:
 placing the UTLC mobile phase onto the UTLC stationary phase; and 
 drawing the UTLC mobile phase upward by capillary action. 
   
     
     
         5 . The method of  claim 1 , wherein:
 the nanofibers are carbon nanofibers.   
     
     
         6 . The method of  claim 1 , wherein:
 the nanofibers are polymeric nanofibers.   
     
     
         7 . The method of  claim 5 , wherein:
 the carbon nanofibers comprise glassy carbon nanofibers.   
     
     
         8 . The method of  claim 6 , wherein:
 the polymeric nanofibers comprise polyacrylonitrile.   
     
     
         9 . The method of  claim 3 , wherein:
 the nanofibers are carbon nanofibers.   
     
     
         10 . The method of  claim 3 , wherein:
 the nanofibers are polymeric nanofibers.   
     
     
         11 . The method of  claim 9 , wherein:
 the carbon nanofibers comprise glassy carbon nanofibers.   
     
     
         12 . The method of  claim 10 , wherein:
 the polymeric nanofibers comprise polyacrylonitrile.   
     
     
         13 . A method for analytically separating a target chemical species from a bulk sample containing the target chemical species, comprising the steps of:
 providing a solid phase microextraction (SPME) medium, comprising a filament substrate with a coating of nanofibers on a surface of the filament, the coating having an average thickness in the range of from about 3.5 to about 21.1 microns and an average fiber diameter of about 300 nm;   providing a bulk sample containing the target chemical species; and   extracting the target chemical species by exposing the SPME medium to the bulk sample, either by direct exposure or by exposure to a surrounding headspace thereof.   
     
     
         14 . The method of  claim 13 , wherein the filament substrate is electrically conductive. 
     
     
         15 . The method of  claim 13 , wherein the nanofibers comprise carbon nanofibers. 
     
     
         16 . The method of  claim 15 , wherein the carbon nanofibers comprise glassy carbon nanofibers. 
     
     
         17 . A method for segregating at least two chemical species, comprising the steps of:
 providing an ultrathin layer chromatography (“UTLC”) stationary phase, comprising:
 a planar surface; 
 a mat of glassy nanofibers supported on the planar surface, the mat having a thickness in the range of from about 11.5 to about 17.4 microns and the average fiber diameter in the range of from about 150 to about 400 nm; 
   providing a UTLC mobile phase, comprising a mixture of the at least two chemical species to be separated, in a solution provided by an appropriate solvent; and   separating the at least two chemical species by placing the UTLC mobile phase onto the UTLC stationary phase and drawing the UTLC mobile phase upward by capillary action.