CdS with Various Novel Hierarchical Nanostructures by Nanobelts/Nanowires Self-Assembly: Controllable Preparation and Their Optical Properties

Many fascinating CdS hierarchical nanostructures, including nanobelt networks, flower/sphere networks by nanobelts/wires self-assembly, and nanowires, have been successfully prepared in high yields and purities by a novel dithizone (DTZ) and tetraethylenepentamine (TEPA)-synergistically directed method. A detailed study of the effect of experimental parameters on the morphology is presented. Results and analyses demonstrated that the Cd(Ac)2/dithizone (DTZ) molar ratio and the volume ratio of H2O and TEPA have an immense function in the subtle morphology control of CdS products. A possible growth process of DTZ and TEPA-synergistic-assisted gradual crystallization and subsequent self-assembling is proposed as a plausible mechanistic interpretation for the formation of those novel nanostructures. More importantly, this is the first time to synthesize wurtzite CdS ultrathin nanobelts in solution. The photoluminescence properties of various CdS hierarchical structures are also investigated

Density Functional Study of 2D Semiconductor CdSe·<i>hda</i>_0.5 (<i>hda</i> = 1,6-hexanediamine) and Its Excitonic Optical Properties

CdSe·hda0.5 (hda = 1, 6-hexanediamine) is a kind of layered ordered-bonding inorganic/organic hybrid compound. Density functional calculation of CdSe·hda0.5 based on general gradient approximation was carried out to optimize its structure, analyze its energy band, and predict its optical and electric properties. The result shows that in CdSe·hda0.5, the distorted [CdSe3N] tetrahedra interlink with adjacent ones by sharing three Se vertices and form [CdSe] monolayers, which were separated by all-trans hda molecules with the space of 1.38 nm. Compared with bulk CdSe, CdSe·hda0.5 has a direct blue-shifted band gap at Brillouin zone center, narrowed highest valence band (HVB), and lowest conducting band (LCB) with doublet line character. The band-edge states show dispersion anisotropy between the in-plane and normal direction of [CdSe] monolayers, which was attributed to the layered structure character. The hda molecules function as an energy barrier to confine the valence electron in [CdSe] monolayer and result in strong quantum confinement effect in c direction, CdSe·hda0.5 can be consequently regarded as a two-dimensional (2D) semiconductor. The Cd- and Se-atom contributions dominate the band-edge density of states and determine the major optical and electrical properties of CdSe·hda0.5. Its electron mobility was estimated to be 16 cm2 V−1 s−1, which is comparable with other hybrid chalcogenides. The optical properties study reveals that, CdSe·hda0.5 possesses absorption anisotropy and sharp band-edge excitonic emission peak. The analysis of temperature dependence of photoemission spectra (7.5−295 K) indicate that, compared with CdSe bulk films, the 2D exciton of CdSe·hda0.5 has a blue-shifted fundamental state level with a 2-fold linear temperature coefficient, higher Debye temperature/average phonon energy, pronounced electron−phonon interaction and a higher excitonic binding energy (21.5 meV)

CdS Hierarchical Nanostructures with Tunable Morphologies: Preparation and Photocatalytic Properties

CdS, an important II−VI semiconductor, has been extensively studied in the areas of structure engineering and photocatalytic properties related to structure and morphology. In this study, by means of a facile l-cysteine and ethanolamine (EA)-synergistically assisted hydrothermal route, CdS with various novel nanostructures has been prepared on a large scale in a water/EA binary solution. With a focus on the regulation of structure, the formation process of nanofans by self-assembly of nanorod bundles was followed by transmission electron microscopy (TEM) and X-ray diffraction (XRD). On the basis of our experimental results, the consecutive processes of l-cysteine and EA-synergistically assisted nucleation growth, oriented assembly, and sphere-cracking were proposed to explain the growth mechanism. More importantly, CdS nanostructures have been confirmed to possess extraordinary photocatalytic activity for the photodegradation of rhodamine B (RhB) compared to that of TiO2 nanoparticles, which could result from their higher surface area, smaller crystal size, and higher crystallinity of the CdS nanostructures. The present work demonstrates the solvothermal route to be facile, inexpensive, and versatile, which favors scaled-up industrial applications and sheds new light on the synthesis and self-assembly of functional materials

Hydrothermal Synthesis and Electrochemical Properties of Urchin-Like Core−Shell Copper Oxide Nanostructures

Urchin-like core−shell CuO assembled by closely packed nanorods with a diameter of 10 nm has been hydrothermally synthesized in assistance of poly(ethylene glycol) (PEG) at 100 °C for 10 h. HRTEM image shows that the diameter of the inner core is ∼1.5 μm and that of the outer shell is ∼2 μm. Control experiments run at different temperature indicate that higher temperature than 100 °C results in the outer shell consisting of particles and blocks of different size and lower temperature gains no products. According to the 2 and 18 h reaction results, PEG plays two important roles in the construction of the core−shell urchin-like structure: the stabilization from the hydrocarbon chain to prolong the lifetime of Cu(OH)2 and the passivation to the lateral surfaces of the nanorods. The as-prepared CuO with a core−shell urchin-like structure exhibits wide biosensor capability toward H2O2 with a linear response in the concentration ranging from 10 μM to 5.55 mM

Hydrothermal Synthesis of Microscaled Cu@C Polyhedral Composites and Their Sensitivity to Convergent Electron Beams

Copper microparticles (2−5 um) encapsulated in carbonaceous shell polyhedral composites were mildly prepared via a one-pot hydrothermal process using copper nitrate, glucose, and sodium citrate at 150 °C, in which the glucose was found to play reducer and graphite source roles during the formation of these core−shell-like composites. Thermal stability results indicated that their weights remain almost unchanged below 240 °C in ambient atmosphere. It is interesting that the copper microparticles could be partially released out and translated into monodisperse Cu nanoparticles around the initial composites under the convergent electron beams in a transmission electron microscope (TEM). This phenomenon is an appealing discovery, which might endow the Cu@C composite with new functions; for example, it might be applied as a sensitive detector for the leakage of electron beams or other substances for the sake of being a safeguard. In addition, the corresponding hollow carbonaceous polyhedra were also obtained after the acid treatment, which might be used as a template to fabricate other kinds of polyhedra

One-Dimensional Yolk–Shell Sb@Ti–O–P Nanostructures as a High-Capacity and High-Rate Anode Material for Sodium Ion Batteries

Development of high energy/power density and long cycle life of anode materials is highly desirable for sodium ion batteries, because graphite anode cannot be used directly. Sb stands out from the potential candidates, due to high capacity, good electronic conductivity, and moderate sodiation voltage. Here, one-dimensional yolk–shell Sb@Ti–O–P nanostructures are synthesized by reducing core–shell Sb2O3@TiO2 nanorods with NaH2PO2. This structure has Sb nanorod as the core to increase the capacity and Ti–O–P as the shell to stabilize the interface between electrolyte and electrode material. The gap between the core and the shell accommodates the volume change during sodiation/desodiation. These features endow the structure outstanding performances. It could deliver a capacity of about 760 mA h g–1 after 200 cycles at 500 mA g–1, with a capacity retention of about 94%. Even at 10 A g–1, the reversible capacity is still at 360 mA h g–1. The full battery of Sb@Ti–O–P//Na3V2(PO4)3–C presents a high output voltage (∼2.7 V) and a capacity of 392 mA h g–1anode after 150 cycles at 1 A g–1anode

Ni₁₁As₈ Single-Crystalline Nanosheets via Hydrothermal Redox Route

Ni11As8 crystallites 23-nm thick and 250−700-nm wide in lateral dimension were prepared in alkaline hydrothermal condition. Transmission electron microscope (TEM) images and selected area electron diffraction (SAED) analyses showed that the as-prepared Ni11As8 was single-crystalline nanosheets of [331] orientation. The Ni11As8 exhibited an optical absorption onset of 3.00 eV in the visible spectral regime. Its magnetic measurement indicated a weak magnetic hysteresis and unsaturation magnetization with a magnetic susceptibility of 1.37 × 10-4 cm3/g (at 15 kOe) at room temperature, the origin of which was discussed and assigned to the effect of surface species containing Ni ions. The extended Hückel tight-binding calculation revealed that bulk Ni11As8 has a 3d-localized narrow band below Fermi level and complicated band structure with small band gap in the first Brillouin zone, which supply clues to explain the observed optical and magnetic properties. The formation mechanism of Ni11As8 was studied and attributed to an alkaline hydrothermal redox route on the basis of the Marsh reaction

PVA-Assisted Synthesis and Characterization of CdSe and CdTe Nanowires

CdSe and CdTe nanowires were prepared through a poly(vinyl alcohol) (PVA) assisted ethylenediamine solvothermal method in 160−180 °C. The PVA used in the process was favorable for the formation of nanowires. X-ray diffraction (XRD) shows that the CdSe nanowires are mostly in zinc blende phase and CdTe ones are in zinc blende form. TEM images show that the nanowires have straight or zigzag shapes. Both HRTEM images and ED patterns reveal the zinc blende nanowires are mostly growing along 〈111〉 zone axis direction

Ni₁₁As₈ Single-Crystalline Nanosheets via Hydrothermal Redox Route

Ni11As8 crystallites 23-nm thick and 250−700-nm wide in lateral dimension were prepared in alkaline hydrothermal condition. Transmission electron microscope (TEM) images and selected area electron diffraction (SAED) analyses showed that the as-prepared Ni11As8 was single-crystalline nanosheets of [331] orientation. The Ni11As8 exhibited an optical absorption onset of 3.00 eV in the visible spectral regime. Its magnetic measurement indicated a weak magnetic hysteresis and unsaturation magnetization with a magnetic susceptibility of 1.37 × 10-4 cm3/g (at 15 kOe) at room temperature, the origin of which was discussed and assigned to the effect of surface species containing Ni ions. The extended Hückel tight-binding calculation revealed that bulk Ni11As8 has a 3d-localized narrow band below Fermi level and complicated band structure with small band gap in the first Brillouin zone, which supply clues to explain the observed optical and magnetic properties. The formation mechanism of Ni11As8 was studied and attributed to an alkaline hydrothermal redox route on the basis of the Marsh reaction

Ni₁₁As₈ Single-Crystalline Nanosheets via Hydrothermal Redox Route

Ni11As8 crystallites 23-nm thick and 250−700-nm wide in lateral dimension were prepared in alkaline hydrothermal condition. Transmission electron microscope (TEM) images and selected area electron diffraction (SAED) analyses showed that the as-prepared Ni11As8 was single-crystalline nanosheets of [331] orientation. The Ni11As8 exhibited an optical absorption onset of 3.00 eV in the visible spectral regime. Its magnetic measurement indicated a weak magnetic hysteresis and unsaturation magnetization with a magnetic susceptibility of 1.37 × 10-4 cm3/g (at 15 kOe) at room temperature, the origin of which was discussed and assigned to the effect of surface species containing Ni ions. The extended Hückel tight-binding calculation revealed that bulk Ni11As8 has a 3d-localized narrow band below Fermi level and complicated band structure with small band gap in the first Brillouin zone, which supply clues to explain the observed optical and magnetic properties. The formation mechanism of Ni11As8 was studied and attributed to an alkaline hydrothermal redox route on the basis of the Marsh reaction