Species diversity of Ganoderma (Ganodermataceae, Polyporales) with three new species and a key to Ganoderma in Yunnan Province, China.

Ganoderma is a globally distributed genus that encompasses species with forestry ecological, medicinal, economic, and cultural importance. Despite the importance of this fungus, the studies on the species diversity of Ganoderma in Yunnan Province, China (YPC) have poorly been carried out. During this study, opportunistic sampling was used to collect 21 specimens of Ganoderma from YPC. Morphology and multigene phylogeny of the internal transcribed spacer (ITS) regions, the large subunit of nuclear ribosomal RNA gene (nrLSU), the translation elongation factor 1-α gene (TEF1-α), and the second largest subunit of RNA polymerase II (RPB2) were used to identify them. Morphological and molecular characterization of the 21 specimens showed that they belong to 18 species of Ganoderma, of which three are novel viz. G. artocarpicola, G. obscuratum and G. yunnanense. Ganoderma artocarpicola is characterized by the sessile and concrescent basidiomata, reddish brown to yellowish brown pileus surface, heterogeneous context, wavy margin, and ovoid basidiospores. Ganoderma obscuratum is distinguished by small pores (6-9 per mm), dorsolaterally sub-stipitate basidiomata which become greyish-brown when dry, and narrow ellipsoid basidiospores. Ganoderma yunnanense is characterized by cream color pore surface and context, centrally to laterally stipitate basidiomata with reddish-brown to violet-brown strongly laccate pileus surface, and broadly ellipsoid basidiospores. With the help of an extensive literature survey and the results of this study, a checklist of 32 Ganoderma species from YPC was established, which accounts for 71.11% of the known species in China. In addition, a key to the Ganoderma in YPC is also provided.

Tailoring Transition-Metal Hydroxides and Oxides by Photon-Induced Reactions.

Controlled synthesis of transition-metal hydroxides and oxides with earth-abundant elements have attracted significant interest because of their wide applications, for example as battery electrode materials or electrocatalysts for fuel generation. Here, we report the tuning of the structure of transition-metal hydroxides and oxides by controlling chemical reactions using an unfocused laser to irradiate the precursor solution. A Nd:YAG laser with wavelengths of 532 nm or 1064 nm was used. The Ni2+ , Mn2+ , and Co2+ ion-containing aqueous solution undergoes photo-induced reactions and produces hollow metal-oxide nanospheres (Ni0.18 Mn0.45 Co0.37 Ox ) or core-shell metal hydroxide nanoflowers ([Ni0.15 Mn0.15 Co0.7 (OH)2 ](NO3 )0.2 ⋅H2 O), depending on the laser wavelengths. We propose two reaction pathways, either by photo-induced redox reaction or hydrolysis reaction, which are responsible for the formation of distinct nanostructures. The study of photon-induced materials growth shines light on the rational design of complex nanostructures with advanced functionalities.

Strain-Mediated Interfacial Dynamics during Au-PbS Core-Shell Nanostructure Formation.

An understanding of the hierarchical nanostructure formation is of significant importance for the design of advanced functional materials. Here, we report the in situ study of lead sulfide (PbS) growth on gold (Au) nanorod seeds using liquid cell transmission electron microscopy (TEM). By tracking the formation dynamics of Au-PbS core-shell nanoparticles, we found the preferential heterogeneous nucleation of PbS on the ends of a Au nanorod prior to the development of a complete PdS shell. During PbS shell growth, drastic sulfidation of Au nanorod was observed, leading to large volume shrinkage (up to 50%) of the initial Au nanorod seed. We also captured intriguing wavy interfacial behavior, which can be explained by our DFT calculation results that the local strain gradient at the core-shell interface facilitates the mass transport and mediates reversible phase transitions of Au ↔ Au2S during the PbS shell growth.

Tuning complex transition metal hydroxide nanostructures as active catalysts for water oxidation by a laser-chemical route.

Diverse transition metal hydroxide nanostructures were synthesized by laser-induced hydrolysis in a liquid precursor solution for alkaline oxygen evolution reaction (OER). Several active OER catalysts with fine control of composition, structure, and valence state were obtained including (Lix)[Ni0.66Mn0.34(OH)2](NO3)(CO3) · mH2O, Lix[Ni0.67Co0.33(OH)2](NO3)0.25(ORO)0.35 · mH2O, etc. An operate overpotential less than 0.34 V at current density of 10 mA cm(-2) was achieved. Such a controllable laser-chemical route for assessing complex nanostructures in liquids opens many opportunities to design novel functional materials for advanced applications.

Visualization of the coalescence of bismuth nanoparticles.

Coalescence is a significant pathway for the growth of nanostructures. Here we studied the coalescence of Bi nanoparticles in situ by liquid cell transmission electron microscopy (TEM). The growth of Bi nanoparticles was initiated from a bismuth neodecanoate precursor solution by electron beam irradiation inside a liquid cell under the TEM. A significant number of coalescence events occurred from the as-grown Bi nanodots. Both symmetric coalescence of two equal-sized nanoparticles and asymmetric coalescence of two or more unequal-sized nanoparticles were analyzed along their growth trajectories. Our observation suggests that two mass transport mechanisms, i.e., surface diffusion and grain boundary diffusion, are responsible for the shape evolution of nanoparticles after a coalescence event.

Revealing bismuth oxide hollow nanoparticle formation by the Kirkendall effect.

We study the formation of bismuth oxide hollow nanoparticles by the Kirkendall effect using liquid cell transmission electron microscopy (TEM). Rich dynamics of bismuth diffusion through the bismuth oxide shell have been captured in situ. The diffusion coefficient of bismuth through bismuth oxide shell is 3-4 orders of magnitude higher than that of bulk. Observation reveals that defects, temperature, sizes of the particles, and so forth can affect the diffusion of reactive species and modify the kinetics of the hollowing process.

Galvanic replacement reactions of active-metal nanoparticles.

We present a systemic investigation of a galvanic replacement technique in which active-metal nanoparticles are used as sacrificial seeds. We found that different nanostructures can be controllably synthesized by varying the type of more noble-metal ions and liquid medium. Specifically, nano-heterostructures of noble metal (Ag, Au) or Cu nanocrystals on active-metal (Mg, Zn) cores were obtained by the reaction of active-metal nanoparticles with more noble-metal ions in ethanol; Ag nanocrystal arrays were produced by the reaction of active-metal nanoparticles with Ag(+) ions in water; spongy Au nanospheres were generated by the reaction of active-metal nanoparticles with AuCl(4)(-) ions in water; and SnO(2) nanoparticles were prepared when Sn(2+) were used as the oxidant ions. The key factors determining the product morphology are shown to be the reactivity of the liquid medium and the nature of the oxidant-reductant couple, whereas Mg and Zn nanoparticles played similar roles in achieving various nanostructures. When microsized Mg and Zn particles were used as seeds in similar reactions, the products were mainly noble-metal dendrites. The new approach proposed in this study expands the capability of the conventional nanoscale galvanic replacement method and provides new avenues to various structures, which are expected to have many potential applications in catalysis, optoelectronics, and biomedicine.

Revealing dynamic processes of materials in liquids using liquid cell transmission electron microscopy.

The recent development for in situ transmission electron microscopy, which allows imaging through liquids with high spatial resolution, has attracted significant interests across the research fields of materials science, physics, chemistry and biology. The key enabling technology is a liquid cell. We fabricate liquid cells with thin viewing windows through a sequential microfabrication process, including silicon nitride membrane deposition, photolithographic patterning, wafer etching, cell bonding, etc. A liquid cell with the dimensions of a regular TEM grid can fit in any standard TEM sample holder. About 100 nanoliters reaction solution is loaded into the reservoirs and about 30 picoliters liquid is drawn into the viewing windows by capillary force. Subsequently, the cell is sealed and loaded into a microscope for in situ imaging. Inside the TEM, the electron beam goes through the thin liquid layer sandwiched between two silicon nitride membranes. Dynamic processes of nanoparticles in liquids, such as nucleation and growth of nanocrystals, diffusion and assembly of nanoparticles, etc., have been imaged in real time with sub-nanometer resolution. We have also applied this method to other research areas, e.g., imaging proteins in water. Liquid cell TEM is poised to play a major role in revealing dynamic processes of materials in their working environments. It may also bring high impact in the study of biological processes in their native environment.

Control of the morphology and optical properties of ZnO nanostructures via hot mixing of reverse micelles.

ZnO nanostructures with controllable morphology were obtained by hot mixing reverse micelles containing Zn(NO(3))(2) or monoethanol amine aqueous solution. The ratio of water to surfactant concentration (omega(0)) was found to play a decisive role in determining the final morphology, namely, nanotetrahedrons formed at a lower omega(0) value and nanorods formed at a higher value. However, the hot mixing technique is propitious for obtaining nanostructures with uniform size. The ZnO nanotetrahedrons obtained gave a strong blue emission arising from interface state, and the ZnO nanorods emitted green light related to donor defects. Our results indicate that the hot mixing of reverse micelles is a unique way to tune the morphology and properties of nanostructures.

One-step synthesis of MgO hollow nanospheres with blue emission.

MgO hollow nanospheres were produced via one-step laser synthesis in both gas and liquid media. The formation mechanism of MgO hollow nanospheres was investigated by adopting high-speed photography and performing control experiments under different oxidization conditions. The results indicated that the in situ Kirkendall effect is responsible for the formation of the hollow nanospheres. Blue emission was observed from the MgO hollow nanospheres produced in a liquid medium, and is ascribed to the surface state arising from the organic modification.