Sulfide gels and films: Products of non-oxide gelation

The preparation of concentrated sols and transparent stiff gels of II-VI se miconductors nanocrystals is reported. A two-step process for the productio n of cadmium sulfide is reported. Sol stabilization and gelation control ar e achieved through successive passivation and depassivation of the surface of the nanocrystals which are complexed with thiols. The mechanisms driving the aggregation and the gelation are explained on the basis of NMR and SAX S experiments. Thin films as well as monoliths can be produced. The general principles of the method presented are not restricted to chalcogenide syst ems and thus enlarge the domain of application of the inorganic sol-gel pro cess.