Two-dimensional (2D) materials have recently drawn tremendous attention because of their novel properties and potential applications in high-speed transistors, solar cells, and catalysts. Few-layer SnSe is a new member of the 2D family with excellent performance in optoelectronic and thermoelectric devices. It is necessary to synthesize few-layer SnSe nanosheets in large scale for various applications. In this work, we develop a scalable liquid-phase exfoliation method to synthesize high-quality crystalline SnSe nanosheets. The morphology and microstructure of SnSe nanosheets are systematically investigated with high-resolution transmission electron microscopy, atomic force microscopy, and Raman spectroscopy. The thinnest nanosheets are bilayered. The optical absorption properties of SnSe nanosheets from near-infrared to ultraviolet light are studied. It is worth noting that the band gap of the nanosheets monotonically increases with the reduction of the nanosheet thickness. The electronic structure of SnSe nanosheets with various thicknesses is calculated by first-principles calculations, the evolution of the band gap as a function of the nanosheet thickness is confirmed, and the mechanism of the band gap evolution is discussed. Our work paves the way for the scalable synthesis of 2D SnSe with tunable optical absorption and band gap, which has potential for use in photoelectronic and photocatalytic applications.

Photocatalysis is attracting huge interest for addressing current energy and environmental issues by converting solar light into chemical energy. For this purpose, we investigated the effect of La3+ and Se4+ co-doping on the photocatalytic activity of BiFeO3. BiFeO3 and Bi0.92La0.08FeO3 nanoparticles containing different Se4+ doping content (BiFe(1−x)SexO3, x = 0.0, 0.02, 0.05, and Bi0.92La0.08Fe(1−x)SexO3, x = 0.0, 0.02, 0.05, 0.075, 0.1) were synthesized by a double solvent sol–gel route. The co-doped nanoparticles were characterized by X-ray diffractometry (XRD), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), and UV-vis diffuse reflectance spectroscopy (DRS), and their photocatalytic activity was studied by the photocatalytic degradation of Congo Red (CR) in aqueous solution under different wavelengths of light illumination. The band-gap of the pure BiFeO3 was significantly decreased from 2.06 eV to 1.94 eV. It was found that La3+ and Se4+ co-doping significantly affected the photocatalytic performance of pure BiFeO3. Moreover, with the increment of Se4+ doping into Bi0.92La0.08FeO3 up to an optimal value, the photocatalytic activity was maximized. In order to study the photosensitization process, photo-degradation of a colourless organic compound (acetophenone) was also observed. On the basis of these experimental results, the enhanced photocatalytic activities with La3+ and Se4+ co-doping could be attributed to the increased optical absorption, and efficient separation and migration of photo-generated charge carriers with the decreased recombination of electrons–holes resulting from co-doping effects. The possible photocatalytic mechanism of La3+ and Se4+ co-doped BiFeO3 was critically discussed.

•All-solid-state lithium batteries were assembled by a simple approach.•Composite cathodes possessed highly conducting network for ions and electrons.•A high surface capacity of 15 mAh/cm2 was obtained.•Excellent cyclic and rate performance were achieved.A simple way to assemble an all-solid-state lithium-ion battery with ultrahigh surface capacity and energy density was established. Polyethylene oxide-based solid-state electrolyte was prepared via solution method and nano-SiO2 was added into the electrolyte to increase the conductivity. Thick compact LiFePO4 pellet infused with dry polymer electrolyte was used as the composite cathode in the all-solid-state lithium battery. The compact composite cathode not only showed large ionic and electronic conductivity, but also provided sufficient “free space” to compensate the volumetric change of the active materials during cycling. The all-solid-state lithium battery (composite cathode/dry polymer electrolyte/Li) was cycled at a constant current density of 200 μA/cm2 at 60 °C. A maximum discharge specific capacity of 157 mAh/g was achieved and the surface capacity reached 15 mAh/cm2, which was of critical significance for all-solid-state lithium batteries. Good capacity retention was achieved after 10 cycles and great rate performance was obtained. Even at a current density of 1000 μA/cm2, the battery delivered a specific discharge capacity of 71 mAh/g, corresponding to a surface capacity of 6 mAh/cm2. The experimental data demonstrated that the composite cathode was a promising design in high-performance bulk-type all-solid-state lithium batteries.

•SnOP2O5 glass frits were synthesized by melt-quenching.•Pb-free Ag pastes with SnOP2O5 glass frits were developed.•C-Si solar cells with SnO-based Ag pastes were fabricated and tested.•A cell efficiency of 7.2% was achieved with the optimal SnO-based Ag paste.•Unique interfacial morphology was observed for sintered SnO-based Ag pastes.We developed a new Pb-free Ag paste with a SnOP2O5 glass frit for front contact electrodes of crystalline silicon solar cells. First, we synthesized SnOP2O5 glass frits with various compositions, whose glass transition temperatures were 225–245 °C, by using a melt-quenching method. It was experimentally verified that the glass component SnO etched through the silicon nitride anti-reflection coating on the Si emitter. Then, four kinds of Ag pastes with various SnOP2O5 glass frits were prepared, screen-printed on a Si emitter, and fired to fabricate solar cells. The composition of the SnOP2O5 glass frit affected the surface and interfacial morphology and microstructure of sintered Ag grids, which played an important role in the series resistance and photovoltaic properties of the solar cells. It was worth noting that the cells fabricated with SnO-based Ag pastes revealed no glass layer at the interface between the Ag grids and Si emitter. This differed from cells fabricated with Ag pastes containing Pb- or Bi-based glass frits. The highest efficiency of 7.2% was achieved for cells fabricated with the Ag paste containing 67SnO33P2O5 (mol%) glass frit at a firing temperature of 950 °C and a time of 5 min. This was because this Ag paste possessed the densest structure and lowest interfacial contact resistance.

•Ab initio electronic structures of La or Ce-doped Bi2Te3 were calculated.•Thermoelectric Transport properties of La or Ce-doped Bi2Te3 were obtained.•La or Ce doping increased the Seebeck coefficient of p-type Bi2Te3.•La or Ce doping decreased the electrical conductivity of Bi2Te3.Thermoelectric properties of La or Ce-doped Bi2Te3 alloys were systematically investigated by ab initio calculations of electronic structures and Boltzmann transport equations. The Seebeck coefficient of p-type LaBi7Te12 and La2Bi6Te12 was larger than that of Bi2Te3, because La doping increased the effective mass of carriers. On the other hand, the electrical conductivity of LaBi7Te12 and La2Bi6Te12 decreased, which caused a reduction of power factor of these La-doped Bi2Te3 alloys in comparison with Bi2Te3. The influence of Ce doping on the band structure and thermoelectric properties of Bi2Te3 was similar to that of La doping. The theoretical calculation provided an insight into the transport properties of La or Ce-doped Bi2Te3-based thermoelectric materials.

•Interfacial IMCs in Sn–Pb/Co–P joints were studied with high-resolution TEM.•CoSn3 with or without stacking fault in crystal grains was found.•Morphology of CoSn3 depended on its growth rate.A systematical microscopic analysis on structure, morphology, and growth of CoSn3 intermetallic compound (IMC) that formed at the interface between Sn–Pb alloy and Co–P films was carried out using scanning electron microscopy with back-scattered electron imaging and high-resolution transmission electron microscopy with energy dispersive spectrometry. CoSn3 IMC with two kinds of morphology was found out after Sn–Pb alloy reacted with Co–P films with different microstructures. One kind of CoSn3 with stacking fault was distributed densely on nanocrystalline and amorphous Co–P films, and the other kind of CoSn3 without stacking fault existed sparsely on the Co–P film with nanocrystalline/amorphous mixed structure. The stacking fault was caused by the fast growth of CoSn3 for the cases of Co-7 at.% P and Co-23 at.% P. Co-12 at.% P film with a nanocrystalline/amorphous mixed microstructure had the best diffusion-barrier property among Co–P films with different compositions, because the diffusion of Sn into Co–P was the least. Our study shed light on diffusion-barrier performance of Co-based metallization.

•Ag nanoparticles promote the firing of silver paste on c-Si solar cells.•A continuous layer of Ag precipitates at the interface between glass frit and Si.•Ag nanoparticles reduced the contact resistance of silver paste on c-Si solar cells.•Firing mechanism of Ag nanoparticle-aided silver paste is proposed.We synthesized silver nanoparticles (AgNPs) with a diameter ranging from 300 to 800 nm by chemical reduction, added them into commercial silver paste used for the front-contact metallization of crystalline Si (c-Si) solar cells, and investigated the effects of AgNPs on the firing behavior of the silver paste on c-Si solar cells by differential scanning calorimetry, electron scanning microscopy, and contact resistance measurement. It was observed that surface sintering of AgNPs occurred at a lower temperature compared with that of micrometer-sized Ag particles in commercial silver paste. With the assistance of AgNPs, more Ag+ ions were dissolved in fluidized glass frit during the firing process of the paste, and a continuous layer of Ag was reduced and deposited between glass frit and Si substrate. The Ag layer enhanced electrical conduction and decreased the specific contact resistivity of the paste on c-Si solar cells. Thus, a firing mechanism of AgNP-aided silver paste was proposed. The experimental data demonstrate that AgNPs can be used to improve the properties of the fired paste on c-Si solar cells and AgNP-aided silver paste is a promising material used for the front-contact grids on c-Si solar cells.

We investigated the plasmon absorption of Au-in-CoAl2O4 linear nanopeapod chains experimentally and theoretically. The Au-in-CoAl2O4 nanopeapods with uniform Au nanospheres (25–40 nm in radius) were synthesized by pulsed electrodeposition, followed by heat treatment, and the plasmon absorption peaks of the Au nanospheres (AuNS) embedded in CoAl2O4 red-shifted due to the size effect of the AuNS and the effect of the cladding dielectric medium. As a result of localized surface plasmon resonance, the plasmon absorption of the peapods can be modulated by tuning the size of the AuNS in CoAl2O4, and the experimental data are in good agreement with the calculated results based on Mie theory. In addition, we carried out the first-principles calculation based on the density functional theory with the LDA+U scheme to study the electronic structure and dielectric properties of CoAl2O4, and the theoretical results are consistent with the experimental data, which proves that LDA+U is a good approximation for CoAl2O4 or other spinels containing transition elements.

•Vertically-layered Fe triangle prism nanoarrays were synthesized by GLAD.•Growth mechanism of Fe nanoprisms was explained with zone model theory of GLAD.•Deposition rate significantly affected the morphology of Fe nanoprisms.•Deposition angle affected the areal density of Fe nanoprisms.Fe triangular nanoprisms consisting of vertically-layered nanoplates were synthesized on Si substrate by glancing angle deposition (GLAD) with an electron beam evaporation system. It was found that Fe nanoplates with a crystallographic plane index of BCC (110) were stacked vertically to form triangular nanoprisms and the axial direction of the nanoprisms, BCC 〈001〉, was normal to the substrate. The effects of experimental parameters of GLAD on the growth and morphology of Fe nanoprisms were systematically studied. The deposition rate played an important role in the morphology of Fe nanoprisms at the same length, the deposition angle just affected the areal density of nanoprisms, and the rotation speed of substrate had little influence within the parameter range we investigated. In addition, the crystal growth mechanism of Fe nanoprisms was explained with kinetically-controlled growth mechanism and zone model theory. The driving force of crystal growth was critical to the morphology and microstructure of Fe nanoprisms deposited by GLAD. Our work introduced an oriented crystal structure into the nanomaterials deposited by GLAD, which provided a new approach to manipulate the properties and functions of nanomaterials.

Photocatalysis is attracting huge interest for addressing current energy and environmental issues by converting solar light into chemical energy. For this purpose, we investigated the effect of La3+ and Se4+ co-doping on the photocatalytic activity of BiFeO3. BiFeO3 and Bi0.92La0.08FeO3 nanoparticles containing different Se4+ doping content (BiFe(1−x)SexO3, x = 0.0, 0.02, 0.05, and Bi0.92La0.08Fe(1−x)SexO3, x = 0.0, 0.02, 0.05, 0.075, 0.1) were synthesized by a double solvent sol–gel route. The co-doped nanoparticles were characterized by X-ray diffractometry (XRD), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), and UV-vis diffuse reflectance spectroscopy (DRS), and their photocatalytic activity was studied by the photocatalytic degradation of Congo Red (CR) in aqueous solution under different wavelengths of light illumination. The band-gap of the pure BiFeO3 was significantly decreased from 2.06 eV to 1.94 eV. It was found that La3+ and Se4+ co-doping significantly affected the photocatalytic performance of pure BiFeO3. Moreover, with the increment of Se4+ doping into Bi0.92La0.08FeO3 up to an optimal value, the photocatalytic activity was maximized. In order to study the photosensitization process, photo-degradation of a colourless organic compound (acetophenone) was also observed. On the basis of these experimental results, the enhanced photocatalytic activities with La3+ and Se4+ co-doping could be attributed to the increased optical absorption, and efficient separation and migration of photo-generated charge carriers with the decreased recombination of electrons–holes resulting from co-doping effects. The possible photocatalytic mechanism of La3+ and Se4+ co-doped BiFeO3 was critically discussed.