Institute of Solid State Physics

Abstract The optical constants of amorphous Ge are determined for the photon energies from 0.08 to 1.6 eV. From 0.08 to 0.5 eV, the absorption is due to k ‐conserving transitions of holes between the valence bands as in p‐type crystals; the spin‐orbit splitting is found to be 0.20 and 0.21 eV in non‐annealed, and annealed samples respectively. The effective masses of the holes in the three bands are 0.49 m (respectively 0.43 m ); 0.04 m , and 0.08 m . An absorption band is observed below the main absorption edge (at 300 °K the maximum of this band is at 0.86 eV); the absorption in this band increases with increasing temperature. This band is considered to be due to excitons bound to neutral acceptors, and these are presumably the same ones that play a decisive role in the transport properties and which are considered to be associated with vacancies. The absorption edge has the form: ω 2 ϵ 2 ∼(hω− E g ) 2 ( E g = 0.88 eV at 300 °K). This suggests that the optical transitions conserve energy but not k vector, and that the densities of states near the band extrema have the same energy‐dependence as in crystalline Ge. A simple theory describing this situation is proposed, and comparison of it with the experimental results leads to an estimate of the localization of the conduction‐band wavefunctions.

Abstract Electroceramics are advanced materials whose properties and applications depend on the close control of structure, composition, ceramic texture, dopants and dopant (or defect) distribution. Impedance spectroscopy is a powerful technique for unravelling the complexities of such materials, which functions by utilizing the different frequency dependences of the constituent components for their separation. Thus, electrical inhomogeneities in ceramic electrolytes, electrode/electrolyte interfaces, surface layers on glasses, ferroelectricity, positive temperature coefficient of resistance behavior and even ferrimagnetism can all be probed, successfully, using this technique.

Abstract High concentrations of defects are introduced into nanoscale ZnO through non‐equilibrium processes and resultant blue emissions are comprehensively analyzed, focusing on defect origins and broad controls. Some ZnO nanoparticles exhibit very strong blue emissions, the intensity of which first increase and then decrease with annealing. These visible emissions exhibit strong and interesting excitation dependences: 1) the optimal excitation energy for blue emissions is near the bandgap energy, but the effective excitation can obviously be lower, even 420 nm (2.95 eV < E g = 3.26 eV); in contrast, green emissions can be excited only by energies larger than the bandgap energy; and, 2) there are several fixed emitting wavelengths at 415, 440, 455 and 488 nm in the blue wave band, which exhibit considerable stability in different excitation and annealing conditions. Mechanisms for blue emissions from ZnO are proposed with interstitial‐zinc‐related defect levels as initial states. EPR spectra reveal the predominance of interstitial zinc in as‐prepared samples, and the evolutions of coexisting interstitial zinc and oxygen vacancies with annealing. Furthermore, good controllability of visible emissions is achieved, including the co‐emission of blue and green emissions and peak adjustment from blue to yellow.

Supercapacitors (also known as ultracapacitors) are considered to be the most promising approach to meet the pressing requirements of energy storage. Supercapacitive electrode materials, which are closely related to the high-efficiency storage of energy, have provoked more interest. Herein, we present a high-capacity supercapacitor material based on the nitrogen-doped porous carbon nanofibers synthesized by carbonization of macroscopic-scale carbonaceous nanofibers (CNFs) coated with polypyrrole (CNFs@polypyrrole) at an appropriate temperature. The composite nanofibers exhibit a reversible specific capacitance of 202.0 F g(-1) at the current density of 1.0 A g(-1) in 6.0 mol L(-1) aqueous KOH electrolyte, meanwhile maintaining a high-class capacitance retention capability and a maximum power density of 89.57 kW kg(-1). This kind of nitrogen-doped carbon nanofiber represents an alternative promising candidate for an efficient electrode material for supercapacitors.

Ordered semiconductor ZnO nanowire arrays embedded in anodic alumina membranes (AAM) were fabricated by generating alumina templates with nanochannels, electrodepositing Zn in them, and then oxidizing the Zn nanowire arrays. The polycrystalline ZnO nanowires with the diameters ranging from 15 to 90 nm were uniformly assembled into the hexagonally ordered nanochannels of the AAM. Photoluminescence (PL) measurements show a blue PL band in the wavelength range of 450–650 nm caused by the singly ionized oxygen vacancy in ZnO nanowires.

Abstract Laser ablation of solid targets in the liquid medium can be realized to fabricate nanostructures with various compositions (metals, alloys, oxides, carbides, hydroxides, etc.) and morphologies (nanoparticles, nanocubes, nanorods, nanocomposites, etc.). At the same time, the post laser irradiation of suspended nanomaterials can be applied to further modify their size, shape, and composition. Such fabrication and modification of nanomaterials in liquid based on laser irradiation has become a rapidly growing field. Compared to other, typically chemical, methods, laser ablation/irradiation in liquid (LAL) is a simple and “green” technique that normally operates in water or organic liquids under ambient conditions. Recently, the LAL has been elaborately developed to prepare a series of nanomaterials with special morphologies, microstructures and phases, and to achieve one‐step formation of various functionalized nanostructures in the pursuit of novel properties and applications in optics, display, detection, and biological fields. The formation mechanisms and synthetic strategies based on LAL are systematically analyzed and the reported nanostructures derived from the unique characteristics of LAL are highlighted along with a review of their applications and future challenges.

The subkingdom Protozoa now inclues over 65,000 named species, of which over half are fossil and approximately 10,000 are parasitic. Among living species, this includes approximately 250 parasitic and 11,300 free-living sarcodines (of which approximately 4,600 are foraminiferids); approximately 1,8000 parasitic and 5,100 free-living flagellates; approximately 5,600 parasitic "Sporozoa" (including Apicomplexa, Microspora, Myxospora, and Ascetospora); and approximately 2,5000 parasitic and 4,700 free-living ciliates. There are undoubtedly thousands more still unnamed. Seven phyla of PROTOZOA are accepted in this classification--SARCOMASTIGOPHORA, LABYRINTHOMORPHA, APICOMPLEXA, MICROSPORA, ASCETOSPORA, MYXOSPORA, and CILIOPHORA. Diagnoses are given for these and for all higher taxa through suborders, and reporesentative genera of each are named. The present scheme is a considerable revision of the Society's 1964 classification, which was prepared at a time when perhaps 48,000 species had been named. It has been necessitated by the acquisition of a great deal of nex taxonomic information, much of it through electron microscopy. It is hoped that the present classification incorporatesmost of the major changes that will be made for some time, and that it will be used for many years by both protozoologist and non-protozoologists.

By combining the freedom of both the structural design and the orientation of split ring resonator antennas, we demonstrate terahertz metasurfaces that are capable of controlling both the phase and amplitude profiles over a very broad bandwidth. As an example, we show that the phase-amplitude metasurfaces can be engineered to control the diffraction orders arbitrarily.

A bulk nanocrystalline (nc) pure copper with high purity and high density was synthesized by electrodeposition. An extreme extensibility (elongation exceeds 5000%) without a strain hardening effect was observed when the nc copper specimen was rolled at room temperature. Microstructure analysis suggests that the superplastic extensibility of the nc copper originates from a deformation mechanism dominated by grain boundary activities rather than lattice dislocation, which is also supported by tensile creep studies at room temperature. This behavior demonstrates new possibilities for scientific and technological advancements with nc materials.

Abstract Perovskite solar cells with the formula FA 1− x Cs x PbI 3 , where FA is formamidinium, provide an attractive option for integrating high efficiency, durable stability and compatibility with scaled-up fabrication. Despite the incorporation of Cs cations, which could potentially enable a perfect perovskite lattice 1,2 , the compositional inhomogeneity caused by A-site cation segregation is likely to be detrimental to the photovoltaic performance of the solar cells 3,4 . Here we visualized the out-of-plane compositional inhomogeneity along the vertical direction across perovskite films and identified the underlying reasons for the inhomogeneity and its potential impact for devices. We devised a strategy using 1-(phenylsulfonyl)pyrrole to homogenize the distribution of cation composition in perovskite films. The resultant p–i–n devices yielded a certified steady-state photon-to-electron conversion efficiency of 25.2% and durable stability.

16th International Symposium on Metal - Hydrogen Systems, Guangzhou / China, 28 Oct - 2 Nov 2018 (oral); MH2018: Abstract ID 300

Keto defect sites play a key role as the source of low-energy emission bands in polyfluorene type materials. The formation of fluorenone defect sites can be regarded as a dominant degradation mechanism in light-emitting devices based on polyfluorenes. The superiority of difunctionalization (see Figure) at the methylene group in –CR2– bridged polyphenylene and polyarylene derivatives is illustrated.

Highly ordered TiO2 nanowire (TN) arrays were prepared in anodic alumina membranes (AAMs) by a sol-gel method. The TNs are single crystalline anatase phase with uniform diameters around 60 nm. At room temperature, photoluminescence (PL) measurements of the TN arrays show a visible broadband with three peaks, which are located at about 425, 465, and 525 nm that are attributed to self-trapped excitons, F, and F+ centers, respectively. A model is also presented to explain the PL intensity drop-down of the TN arrays embedded in AAMs: the blue PL band of AAMs arises from the F+ centers on the pore walls, and the TNs first form in the center area of the pores and then extend to the pore walls.

Abstract A novel ZnO hierarchical micro/nanoarchitecture is fabricated by a facile solvothermal approach in an aqueous solution of ethylenediamine (EDA). This complex architecture is of a core/shell structure, composed of dense nanosheet‐built networks that stand on a hexagonal‐pyramid‐like microcrystal (core part). The ZnO hexagonal micropyramid has external surfaces that consist of a basal plane (000 ${\bar 1}$ ) and lateral planes {0 ${\bar 1}$ 11}. The nanosheets are a uniform thickness of about 10 nm and have a single‐crystal structure with sheet‐planar surfaces as {2 ${\bar 1}\,{\bar 1}$ 0} planes. These nanosheets interlace and overlap each other with an angle of 60° or 120°, and assemble into a discernible net‐ or grid‐like morphology (about 100 nm in grid‐size) on the micropyramid, which shows a high specific surface area (185.6 m 2 g −1 ). Such a ZnO micro/nanoarchitecture is new in the family of ZnO nanostructures. Its formation depends on the concentration of the EDA solution as well as on the type of zinc source. A two‐step sequential growth model is proposed based on observations from a time‐dependent morphology evolution process. Importantly, such structured ZnO has shown a strong structure‐induced enhancement of photocatalytic performance and has exhibited a much better photocatalytic property and durability for the photodegradation of methyl orange than that of other nanostructured ZnO, such as the powders of nanoparticles, nanosheets, and nanoneedles. This is mainly attributed to its higher surface‐to‐volume ratio and stability against aggregation. This work not only gives insight into understanding the hierarchical growth behaviour of complex ZnO micro/nanoarchitectures in a solution‐phase synthetic system, but also provides an efficient route to enhance the photocatalytic performance of ZnO, which could also be extended to other catalysts, such as the inherently excellent TiO 2 , if they are of the same hierarchical micro/nanoarchitecture with an open and porous nanostructured surface layer.

Abstract Surface plasmon polaritons (SPPs) are electromagnetic excitations existing at the interface between a metal and a dielectric material. Remarkable progress has been made in the field of SPPs in recent years. Control and manipulation of light using SPPs on the nanometre scale exhibit significant advantages in nanophotonics devices with very small elements, and SPPs open a promising way in areas involving environment, energy, biology and medicine. This paper presents an overview of current research activities on SPPs, including fundamental physics and applications. We first discuss the excitation of SPPs based on the SPP dispersion relation, coupling to SPPs by momentum matching between photons and SPPs, and propagation behaviour of SPPs. Based on the physical mechanism and the peculiar properties of SPPs, we demonstrate the major applications of SPPs, such as waveguides, sources, near-field optics, surface-enhanced Raman spectroscopy, data storage, solar cells, chemical sensors and biosensors.

Abstract As a metal‐free nitrogen reduction reaction (NRR) photocatalyst, g‐C 3 N 4 is available from a scalable synthesis at low cost. Importantly, it can be readily functionalized to enhance photocatalytic activities. However, the use of g‐C 3 N 4 ‐based photocatalysts for the NRR has been questioned because of the elusive mechanism and the involvement of N defects. This work reports the synthesis of a g‐C 3 N 4 photocatalyst modified with cyano groups and intercalated K + ( m CNN), possessing extended visible‐light harvesting capacity and superior photocatalytic NRR activity (NH 3 yield: 3.42 mmol g −1 h −1 ). Experimental and theoretical studies suggest that the ‐C≡N in m CNN can be regenerated through a pathway analogous to Mars van Krevelen process with the aid of the intercalated K + . The results confirm that the regeneration of the cyano group not only enhances photocatalytic activity and sustains the catalytic cycle, but also stabilizes the photocatalyst.

In this work, we present the coating regulations of Fe3O4 nanoparticles (NPs) by the reverse microemulsion method to obtain the Fe3O4@SiO2 core/shell NPs. The regulation produces the core/shell NPs with a single core and with different shell thicknesses, and it especially can be applied to different sizes Fe3O4 NPs and avoid the formation of core-free silica particles. Our results reveal that the silica coating parameters suitable for Fe3O4 NPs with certain size are not definitely applicable to that with other sizes, and the match of the number of Fe3O4 NPs with aqueous domain is essential. We found that the small aqueous domain is suitable to coat ultrathin silica shell, while the large aqueous domain is indispensable for coating thicker shells. To avoid the formation of core-free silica particles, the thick silica shell can be achieved by increasing the content of either TEOS through the equivalently fractionated drops or ammonia with a decreased one-off TEOS. The ligand exchange between the intermediate processes of the silica coating is evidenced. Our results provide not only a strategy for synthesizing uniform Fe3O4@SiO2 core/shell NPs with controlled shell thickness, but also a regulation that can be applied to preparation other core–shell NPs.

. We begin with a tutorial on the phase diagram of the V-O system. The second part is a detailed review covering the crystal structure, the synthesis protocols, and the applications of each vanadium oxide, especially in batteries, catalysts, smart windows, and supercapacitors. We conclude with a brief perspective on how material and device improvements can address current deficiencies. This comprehensive review could accelerate the development of novel vanadium oxide structures in related applications.

A weak acid selective etching strategy was put forward to fabricate oxide-based hollow nanoparticles (HNPs) using core/shell nanostructures of active metal/oxide nanoparticles as sacrificial templates. ZnO-based HNPs, including pure ZnO, Au/ZnO, Pt/ZnO, and Au/Pt/ZnO HNPs with diameter below 50 nm and shell thickness below 6 nm has been first achieved at low temperature. The diameter, thickness, and even sizes of ZnO and noble metal ultrafine crystals of HNPs can be well adjusted by the etching process. Synchronous with the formation of HNPs, the internal metal-semiconductor interfaces can be controllably eliminated (Zn-ZnO) and reconstructed (noble metal-ZnO). Excitingly, such microstructure manipulation has endued them with giant improvements in related performances, including the very strong blue luminescence with enhancement over 3 orders of magnitude for the pure ZnO HNPs and the greatly improved photocatalytic activity for the noble metal/ZnO HNPs. These give them strong potentials in relevant applications, such as blue light emitting devices, environment remediation, drug delivery and release, energy storage and conversion, and sensors. The designed fabrication procedure is simple, feasible, and universal for a series of oxide and noble metal/oxide HNPs with controlled microstructure and improved performances.

A novel selenium form, nano red elemental selenium (Nano-Se) was prepared by adding bovine serum albumin to the redox system of selenite and glutathione. Nano-Se has a 7-fold lower acute toxicity than sodium selenite in mice (LD(50) 113 and 15 mg Se/kg body weight respectively). In Se-deficient rat, both Nano-Se and selenite can increase tissue selenium and GPx activity. The biological activities of Nano-Se and selenite were compared in terms of cell proliferation, enzyme induction and protection against free racial-mediated damage in human hepatoma HepG2 cells. Nano-Se and selenite are similarly cell growth inhibited and stimulated synthesis of glutathione peroxidase (GPx), phospholipid hydroperoxide glutathione peroxidase (PHGPx) and thioredoxin reductase (TR). When HepG2 cells were co-treated with selenium and glutathione, Nano-Se showed less pro-oxidative effects than selenite, as measured by cell growth. These results demonstrate that Nano-Se has a similar bioavailability in the rat and antioxidant effects on cells.