Porous Semiconducting Gels and Aerogels from Chalcogenide Clusters

Abstract

tors (17). The resulting density matrix has only positive eigenvalues, and hence it represents a physically possible state. Its fidelity with respect to the expected Bell state, |Y -〉 from Eq. 2, is F = 86.0(4)%, with 0.5 < F ≤ 1 proving entanglement (18). From the density matrix, following (16), we derive a concurrence of C = 0.73(7), with 0 < C ≤ 1 also proving entanglement. Because of technical imperfections, e.g., of polarizers in the detection setups, the observed fidelity/concurrence sets a lower bound for both the atom-photon and photon-photon entanglement achieved. The same measurements were done for B = −0.13 G and t S = 2.8 ms for which the atomic superposition state accumulates a p phase shift (compare to Fig. 3). Therefore, a density matrix corresponding to the Bell stateis expected. This is indeed observed (Fig. 4B) with a fidelity of F = 82.9(6)% and a concurrence of C = 0.72(13). The state evolves between the two photon detections as a result of the constant magnetic field.Future experiments could produce a timeindependent |Y + 〉 Bell state by applying a pulsed magnetic field to the atom between entanglement generation and state mapping. Moreover, partial driving of the Raman transition in combination with atomic state manipulation should allow production of highly entangled multiphoton states (12). Our technique applied to a quasi-permanently trapped intracavity atom (3, 19) will push the probability of success even further, making the scheme truly deterministic. Two (or more) such systems operated in parallel are perfectly suited for teleportation and entanglement experiments in a quantum network (20)(21)(22) or quantum gate operations in a distributed and, hence, scalable quantum computer (23, 24). Inorganic porous materials are being developed for use as molecular sieves, ion exchangers, and catalysts, but most are oxides. We show that various sulfide and selenide clusters, when bound to metal ions, yield gels having porous frameworks. These gels are transformed to aerogels after supercritical drying with carbon dioxide. The aerogels have high internal surface area (up to 327 square meters per gram) and broad pore size distribution, depending on the precursors used. The pores of these sulfide and selenide materials preferentially absorb heavy metals. These materials have narrow energy gaps (between 0.2 and 2.0 electron volts) and low densities, and they may be useful in optoelectronics, as photocatalysts, or in the removal of heavy metals from water.

Summary Report for the Development of Materials for Volatile Radionuclides

“…literature, i.e., 252-287 m 2 /g (i.e., 252, 271, and 287 m 2 /g at temperatures of 100, 60, and 25°C, respectively) for our Ge-S-Pt gels versus the literature values of 276-323 m 2 /g (at 25°C) (Bag et al 2007;Kanatzidis and Bag 2008). See Table 1 for more details.…”

“…Some of the property parameters (e.g., durability) that are important waste form properties are not available in the literature for these types of aerogels, because of their relative recent discovery was only in 2007 (Bag et al 2007). Therefore, many of their properties are estimated based on glasses that had similar chemistries.…”

“…Based on limited thermal analysis data in the literature on these types of aerogels (Bag et al 2007), GeCh-Pt chalcogels appear to be stable at T ≤ 550°C where mass loss is observed to be decomposition, i.e., loss of sulfur (Bag et al 2007). At this temperature, the adsorbed iodine (i.e., desorption) is assumed to be lot, although this remains.…”

“…(Mo,W)S 4 2+ . Bag and Kanatzidis also demonstrated a wide variety of uses for these materials, in which they can be used as sorbents with selective affinity for heavy metals (e.g., Hg vs. Zn) (Bag et al 2007) and selective sorbents or catalysts for gas separation, e.g. hydrodesulfurization (Bag et al 2009), to name a few applications.…”

“…Figure 8 shows how iodine is adsorbed into the network of a Ge-S-c chalcogel. Bag and Kanatzidis demonstrated the wide compositional flexibility of these chalcogels in which the properties, i.e., surface area per unit mass (10-528 m 2 /g) (Bag et al 2009;Bag et al 2007), band gap (2.0-0.8 eV) (Bag et al 2007), selective affinity (i.e., liquids, vapors), etc., can be "tuned" by changing the metal and chalcogen precursors.…”