Yttrium substituted Co–Cu–Zn nanoferrite: A synergetic impact of Y3+ on enhanced physical properties and photocatalysis

Co_0.5Cu_0.25Zn_0.25Y_xFe_2-xO₄; (0≤x≤0.1; step 0.02) (CCZY) spinel ferrites were prepared by citrate technique. The prepared CCZY samples have crystallite sizes ranging from 21 to 34 nm. The nanoscale nature of the samples was, also, established by HRTEM micrographs. Even though the substitution route here involves the replacement of magnetic ions Fe³⁺ by a non-magnetic one Y³, the magnetization of CCZY nanoparticles did not show a continual decrease as expected. The nanoferrite Co_0.5Cu_0.25Zn_0.25Y_0.06Fe_1.94O₄, has a moderate value of saturation magnetization 63.45 emu/g (decreased with 11.55% than the pristine sample) and higher coercivity 416.44 Oe (increased with 21.83% than the pristine sample), which may be a suitable candidate for data storage applications. All CCZY nanoferrite have direct optical band gap within the range 1.57 eV–1.50 eV; which doesn't introduce a regular behavior with Y/Fe substitution process. Distinctively, the MB dye removal shows an optimum value with the nanoferrite CCZY (0.1), which gives a degradation efficiency of 95% after 60 min only. The outstanding increase in catalytic performance of the nanoferrite CCZY (0.1) was correlated with the size factor and saturation magnetization. The desirability function approach enabled to distinguish the optimal material (CCZY (0.1)) with the superior catalytic performance; the smallest size and convenient magnetic properties. Hence, the nanoferrite Co_0.5Cu_0.25Zn_0.25Y_0.1Fe_1.9O₄ can be utilized efficaciously for water treatment, via the safe photocatalytic process; without sabotaging the environment.     

Developing the properties of new blue phosphors: TiO2-doped Zn2SiO4

2ZnO + SiO₂ + X mol% TiO₂ (Zn₂SiO₄-X-TiO₂, 1 ≤ X ≤ 3) and 2ZnO + SiO₂ + 3 mol% MnO₂ (Zn₂SiO₄-3-TiO₂) compositions were prepared using nanoscale ZnO, SiO₂, TiO₂, and MnO₂ particles. The mixing powders were calcined between 1000 °C and 1300 °C in a N₂ atmosphere. Zn₂SiO₄ was the only phase in the calcined Zn₂SiO₄-X-TiO₂ phosphors. We found that the photoluminescence (PL) properties of synthesized Zn₂SiO₄-X-TiO₂ phosphors revealed these to be blue rather than green. The effects of TiO₂ content and calcining temperature on the PL properties of Zn₂SiO₄-X-TiO₂ phosphors were rigorously investigated.     

Highly visible light active Ag@ZnO nanocomposites synthesized by gel-combustion route

Highly visible light active 1% and 3% Ag@ZnO nanocomposites were synthesized via a gel combustion route using citric acid as a fuel. The formation of the nanocomposites with enhanced properties was confirmed using a range of characterization techniques, photocatalysis and photoelectrochemical studies. Compared to the pristine ZnO nanoparticles, the Ag@ZnO nanocomposites exhibited enhanced visible light photocatalytic activity for the degradation of methylene blue and photoelectrochemical response. A mechanism was proposed to account for the photocatalytic activities of the Ag@ZnO nanocomposite that showed the surface plasmon resonance (SPR) of Ag is an effective way of enhancing the visible light photocatalytic activities.     

Controllable synthesis, optical and photocatalytic properties of CuS nanomaterials with hierarchical structures

The controlled synthesis of CuS nanomaterials with hierarchical structures has been realized by chemical synthesis between copper nitrate trihydrate and thiourea via a solvothermal route. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy were used to characterize the products. It was shown that CuS nanomaterials with hierarchical structures were composed of numerous nanoplates or nanorods. Experiments demonstrated that the morphologies of CuS nanomaterials were significantly influenced by reaction temperature, growth time and sulfur sources. A growth model was proposed for the selective formation of CuS hierarchical structures. The optical properties of the CuS hierarchical structures were investigated by ultraviolet-visible spectroscopy and photoluminescence spectroscopy. The ultraviolet-visible spectrum had a broad absorption in the visible range and the photoluminescence spectrum showed a strong green emission. Photocatalytic performance of the CuS hierarchical structures was evaluated by measuring the decomposition rate of methylene blue solution under natural light. The CuS hierarchical structures showed good photocatalytic activity.     

Solvothermal Synthesis, Structure and Optical Property of Nanosized CoSb(3) Skutterudite

Binary skutterudite CoSb₃ nanoparticles were synthesized by solvothermal method. The nanostructuring of CoSb₃ material was achieved by the inclusion of various kinds of additives. X-ray diffraction examination indicated the formation of the cubic phase of CoSb₃. Structural analysis by transmission electron microscopy analysis further confirmed the formation of crystalline CoSb₃ nanoparticles with high purity. With the assistance of additives, CoSb₃ nanoparticles with size as small as 10 nm were obtained. The effect of the nanostructure of CoSb₃ on the UV–visible absorption and luminescence was studied. The nanosized CoSb₃ skutterudite may find application in developing thermoelectric devices with better efficiency.     

OPAA template-directed synthesis and optical properties of metal nanocrystals

Ag and Cu nanocrystals (NCs) were assembled into ordered porous anodic alumina (OPAA) by a single-potential-step chronoamperometry technique. The composition, morphology, microstructure, and optical property were analyzed by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, and optical absorption spectroscopy. The results indicate that metallic NCs/OPAA composite possesses a significant surface plasmon resonance absorption. For continuous electrodeposition, metallic nanowires are smooth and uniform with face-centered cubic (fcc) single-crystalline structure; however, for interval electrodeposition, the nanowires are bamboo-like or pearl-chain-like with fcc polycrystalline structure. The length of the nanoparticle nanowires or the single-crystalline nanowires can be controlled well by adjusting the experimental cycle times or the continuous depositing time. The transverse dipole resonance of metallic NCs enhances and displays a blue shift with increasing electrodeposition time or experimental cycle times, which is consistent with Zong''s results but contradictory to Duan''s results. The formation mechanisms of the nanoparticle nanowires and the single-crystalline nanowires were discussed in detail.     

Surface plasmon resonance of Au-Cu bimetallic nanoparticles predicted by a quasi-chemical model

Au-Cu alloys are functional materials with nonlinear optical applications. However, the optical properties of such alloys are difficult to predict due to the random mixing of materials. In this paper, we present a quasi-chemical model to simulate the optical properties of Au-Cu alloy systems based on the mixing of Gibbs free energy. This model is also able to predict the position of the surface plasmon resonance peaks for Au-Cu alloy nanoparticles. The model can be applied to predict the optical properties of alloy systems in the fields of plasmonics and nanophotonics.     

A facile and reliable route to prepare of flower shaped lead sulfide nanostructures from a new sulfur source

Flower shaped PbS nanostructures were prepared by the solvothermal method using propylene glycol and a new sulfuring agent. Novelty of this work is application of a new thio Schiff-base as complexing and sulfuring agent for synthesizing of PbS nanostructures. SEM and TEM was used to examine the surface morphology of the grown samples; also the products were characterized by XRD, SEAD, UV–vis and FT-IR spectra. The results of this paper indicate that the shape and size of lead sulfide nanocrystals can be controlled systematically by setting certain reaction parameters.     

Solvothermal Synthesis of Ternary Sulfides of Sb2 − x Bi x S3 (x = 0.4, 1) with 3D Flower-Like Architectures

Flower-like nanostructures of Sb_{2 − x}Bi_xS₃(x = 0.4, 1.0) were successfully prepared using both antimony diethyldithiocarbamate [Sb(DDTC)₃] and bismuth diethyldithiocarbamate [Bi(DDTC)₃] as precursors under solvothermal conditions at 180 °C. The prepared Sb_{2 − x}Bi_xS₃ with flower-like 3D architectures were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), high-resolution transmission electron microscopy (HRTEM), and selected area electron diffraction (SAED). The flower-like architectures, with an average diameter of ~4 μm, were composed of single-crystalline nanorods with orthorhombic structures. The optical absorption properties of the Sb_{2 − x}Bi_xS₃ nanostructures were investigated by UV–Visible spectroscopy, and the results indicate that the Sb_{2 − x}Bi_xS₃ compounds are semiconducting with direct band gaps of 1.32 and 1.30 eV for x = 0.4 and 1.0, respectively. On the basis of the experimental results, a possible growth mechanism for the flower-like Sb_{2 − x}Bi_xS₃ nanostructures is suggested.     

Synthesis of high efficiency Zn2SiO4:Mn green phosphors using nano-particles

In this study, Zn₂SiO₄:Mn²⁺ luminescent phosphors were prepared by mixing nano-scale ZnO, SiO₂, and MnO₂ particles at the compositions corresponding to 2ZnO + SiO₂ + X mol% MnO₂ (Zn₂SiO₄–X-MnO₂, 0.02 ≤ X ≤ 0.05). The mixing powders were calcined from 900 °C to 1300 °C in air and in N₂ atmosphere. No matter calcined in air or in N₂ atmosphere, Zn₂SiO₄ was the mainly crystalline phase in particles calcined at 900 °C and was the only phase in particles calcined at 1000 °C and higher. The influences of MnO₂ concentration and calcining atmosphere and temperature on wavelength of luminescence peak and the emission intensity were further intensively investigated. We would show that the calcining atmosphere had no apparent influences on the physical and photoluminescence (PL) characteristics of Zn₂SiO₄:Mn²⁺ phosphors. The MnO₂ content and the calcining temperature were the main reasons to influence the physical and PL characteristics of Zn₂SiO₄:Mn²⁺ phosphors.     

Simple fabrication and photocatalytic activity of S-doped TiO2 under low power LED visible light irradiation

A series of S-doped TiO₂ with visible-light photocatalytic activity were prepared by a simple hydrolysis method using titanium tetrachloride (TiCl₄) and sodium sulfate (Na₂SO₄) as precursors. The photocatalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), UV–vis diffuse reflectance spectrophotometer (UV–Vis DRS), and X-ray photoelectron spectroscopy (XPS). With the doping of S, photocatalysts with small crystal size, high content of anatase phase were obtained. The result showed that S-doped TiO₂ demonstrate considerably high photoactivity under low power visible LED light irradiation, while undoped TiO₂ and the Degussa P25 have nearly no activity at all. The possible mechanism of S-doped for the visible-light activity was discussed.