The dissolution of metal sulfides, such as ZnS, is an important biogeochemical process affecting fate and transport of trace metals in the environment. However, current studies of in situ dissolution of metal sulfides and the effects of structural defects on dissolution are lacking. Here we have examined the dissolution behavior of ZnS nanoparticles synthesized via several abiotic and biological pathways. Specifically, we have examined biogenic ZnS nanoparticles produced by an anaerobic, metal-reducing bacterium Thermoanaerobacter sp. X513 in a Zn-amended, thiosulfate-containing growth medium in the presence or absence of silver (Ag), and abiogenic ZnS nanoparticles were produced by mixing an aqueous Zn solution with either HS-rich gas or NaS solution. The size distribution, crystal structure, aggregation behavior, and internal defects of the synthesized ZnS nanoparticles were examined using high-resolution transmission electron microscopy (TEM) coupled with X-ray energy dispersive spectroscopy. The characterization results show that both the biogenic and abiogenic samples were dominantly composed of sphalerite. In the absence of Ag, the biogenic ZnS nanoparticles were significantly larger (i.e., ∼10 nm) than the abiogenic ones (i.e., ∼3-5 nm) and contained structural defects (e.g., twins and stacking faults). The presence of trace Ag showed a restraining effect on the particle size of the biogenic ZnS, resulting in quantum-dot-sized nanoparticles (i.e., ∼3 nm). In situ dissolution experiments for the synthesized ZnS were conducted with a liquid-cell TEM (LCTEM), and the primary factors (i.e., the presence or absence structural defects) were evaluated for their effects on the dissolution behavior using the biogenic and abiogenic ZnS nanoparticle samples with the largest average particle size. Analysis of the dissolution results (i.e., change in particle radius with time) using the Kelvin equation shows that the defect-bearing biogenic ZnS nanoparticles (γ = 0.799 J/m) have a significantly higher surface energy than the abiogenic ZnS nanoparticles (γ = 0.277 J/m). Larger defect-bearing biogenic ZnS nanoparticles were thus more reactive than the smaller quantum-dot-sized ZnS nanoparticles. These findings provide new insight into the factors that affect the dissolution of metal sulfide nanoparticles in relevant natural and engineered scenarios, and have important implications for tracking the fate and transport of sulfide nanoparticles and associated metal ions in the environment. Moreover, our study exemplified the use of an in situ method (i.e., LCTEM) to investigate nanoparticle behavior (e.g., dissolution) in aqueous solutions.

Mechanical and structural properties of ionically self-assembled nanostructures of meso-tetra(4-sulfonatophenyl)porphyrin (TSPP) and meso-tetra(4-pyridyl)porphyrin (TPyP) are presented. This is the first time that elastic modulus of an ionic porphyrin nanostructure has been reported. X-ray photoelectron spectroscopy (XPS), UV-visible spectra, and elemental analysis all support a stoichiometric 1 : 1 TSPP to TPyP composition. Atomic force microscopy (AFM) revealed that the porphyrin nanostructure is composed of stacked ribbons about 20 nm tall, 70 nm wide, and several microns in length. High resolution transmission electron microscopy (HRTEM) images showed clear lattice fringes 1.5 ± 0.2 nm in width aligned along the length of the nanorod. Selected area electron diffraction (SAED) and powder X-ray diffraction patterns of TSPP:TPyP are consistent with an orthorhombic system and space group Imm2 with lattice parameters a = 26.71 Å, b = 20.16 Å, and c = 8.61 Å. Crystallographic data is consistent with an arrangement of alternating face-to-face TSPP and TPyP molecules forming ordered columns along the length of the nanorods. The structural integrity of the solid is attributed to combined noncovalent interactions that include ionic, hydrogen bonding, and π-π interactions. The values of Young's modulus obtained for the crystalline TSPP:TPyP nanorods averaged 6.5 ± 1.3 GPa. This modulus is comparable to those reported for covalently bonded flexible polymeric systems. The robust bonding character of the TSPP:TPyP nanostructures combined with their mechanical properties makes them excellent candidates for flexible optoelectronic devices.

Self-assembled crystalline nanostructures with sheaf-like morphology fabricated from tetra(4-aminophenyl)porphyrin and tetra(4-sulfonatophenyl)porphyrin are reported for the first time. The hierarchical sheaf-like growth of the assemblies exhibits Arrhenius behaviour. The observed morphology results from crystal splitting during initial oriented attachment growth followed by Ostwald ripening.

Graphene prepared on Cu foil by chemical vapor deposition was studied as a function of post growth cooling conditions. CuO islands embedded in the graphene film were discovered and studied by scanning electron microscopy, atomic force microscopy, and X-ray photoemission spectroscopy. It is shown that nanostructured holes can be formed within a graphene film by reduction using hydrogen cooling immediately after film growth. We also observe the formation of symmetrical oxide islands in these holes. This study provides an easy way to fabricate a graphene + CuO composite, and the method may be extended to other graphene based structures.

Understanding the corrosion of nuclear waste glass is critical to predicting its safe disposal within a geological facility. The corrosion mechanisms and kinetics of the International Simple Glass, a simplified version of high-level nuclear waste glass, was shown to be significantly influenced by a high pH cement solution representative of disposal conditions. We provide the first microscopic characterisation of the porous, Zr-rich aluminoalkali-silica gel corrosion layer that was observed. Ca, Na and K from the cement solution were incorporated into the corrosion layer to charge compensate Si, Al and Zr species; the incorporation of Al was postulated to result in precipitation of an aluminosilicate-rich gel with large voids, facilitating rapid transport of species through the gel layer and significantly enhancing the corrosion rate. Precipitation of Al-containing zeolite and phyllosilicate phases was also observed, indicating that cementitious solutions may promote the detrimental 'rate resumption' stage of glass corrosion.