A method of poling an organic polymeric electro-optic material. The method includes doping the organic polymeric electro-optic material with nanoparticles. The method also includes heating the organic polymeric electro-optic material to a poling temperature. The method also includes poling the organic polymeric electro-optic material by applying an electric field across the organic polymeric electro-optic material.

A method for synthesizing carbon nanocages, including N-doped carbon nanocages, includes a first step of forming a solution including a metal salt and an organic carbon source; a second step of drying the solution to obtain a precursor powder; and a third step of annealing the precursor powder to obtain a nanocage including a metal nanoparticle surrounded by a carbon shell. The metal nanoparticle is then removed from the carbon shell by applying an acid solution.

An electrochemical device includes a cathode containing graphene-wrapped Li.sub.2S nanoparticles. The graphene-wrapped Li.sub.2S nanoparticles are prepared by a method including heating lithium metal, and a carbon-sulfur source or a carbon source and a sulfur source in a sealed container at a temperature to produce lithium vapors, and vapors of the carbon-sulfur source or vapors of the carbon source and vapors of the sulfur source; and cooling the sealed container to produce the graphene-wrapped Li.sub.2S nanoparticles.

A method for synthesizing carbon nanocages, including N-doped carbon nanocages, includes a first step of forming a solution including a metal salt and an organic carbon source; a second step of drying the solution to obtain a precursor powder; and a third step of annealing the precursor powder to obtain a nanocage including a metal nanoparticle surrounded by a carbon shell. The metal nanoparticle is then removed from the carbon shell by applying an acid solution.

A method of poling an organic polymeric electro-optic material. The method includes doping the organic polymeric electro-optic material with nanoparticles. The method also includes heating the organic polymeric electro-optic material to a poling temperature. The method also includes poling the organic polymeric electro-optic material by applying an electric field across the organic polymeric electro-optic material.

An electrochemical device includes a cathode containing graphene-wrapped Li.sub.2S nanoparticles. The graphene-wrapped Li.sub.2S nanoparticles are prepared by a method including heating lithium metal, and a carbon-sulfur source or a carbon source and a sulfur source in a sealed container at a temperature to produce lithium vapors, and vapors of the carbon-sulfur source or vapors of the carbon source and vapors of the sulfur source; and cooling the sealed container to produce the graphene-wrapped Li.sub.2S nanoparticles.

An organic solar cell includes a first sub-cell including a first active layer and a second sub-cell including a second active layer, wherein at least one of the first active layer and the second active layer includes at least two types of electron acceptors having different light absorbance from each other.

An optical pre-amplifier is described. The optical pre-amplifier has an optical amplifier region that has a semiconductor active region having a direct electronic band gap with a conduction band edge. The semiconductor active region is embedded within a photonic crystal having an electromagnetic band gap having photon energies overlapping the energy of the conduction band edge of the electronic band gap such that spontaneous emission of photons in the semiconductor active region is suppressed.