groups that is r and r u2032 may be any functional groups and are generally hydrocarbons examples include alkyl or aryl groups one example is ethyl groups according to some embodiments the r groups may contain functional groups with the ability to tailor the hydrophilicity of the qds for example to render the qds more soluble in hydrophilic environments an example of such an r group is a c12 hydrocarbon chain with a carboxylic acid functionality on the c12 position once suitably coordinated to the surface of the dots the carboxylic acid can be deprotonated with a base and the dots transferred to hydrophilic media alternatively the r groups may be an amphiphilic group such as a peg polyethyleneglycol a first dithio capping ligand may be exchanged to bind to the electropositive atoms on the surface for example the first dithio capping ligand may bind to zinc on the surface of a zns or znse surface the first dithio capping ligand compounds 1 4 may be provided as a salt of sodium or potassium the dithio ligands may be provided as a powder or in a solvent such as therminol another example of a suitable dithio ligand is represented by structure 5 in structure 5 r is as defined above and r u2032 is typically an alkyl group compounds of structure 5 may exist in both monomeric and dimeric forms when r u2032 is an ethyl group the monomeric form is a major species compounds according to structure 5 have.