An oil-in-water self-assembly synthesis,characterization and photocatalytic properties of nano Ag@AgBr sensitized K2Ti4O9

Nano-sized plasmonic Ag@AgBr sensitized K₂Ti₄O₉ composite photocatalysts (hereafter designated as Ag@AgBr/K₂Ti₄O₉) was synthesized via a facile oil-in-water self-assembly method. The photocatalytic activity of the prepared materials for methylene blue (MB) degradation was examined under visible light irradiation. The results reveal that the size of Ag@AgBr, which evenly dispersed on the surface of K₂Ti₄O₉, distributes about 20 nm. The UV–vis diffuse reflectance spectra indicate that Ag@AgBr/K₂Ti₄O₉ samples have a significantly enhanced optical absorption in 420–800 nm. The photocatalytic activities of the Ag@AgBr/K₂Ti₄O₉ samples increase first and then decrease with increasing amount of loading Ag@AgBr and the Ag@AgBr(10 wt%)/K₂Ti₄O₉ sample exhibits the best photocatalytic activity and 95.75% MB was degraded after irradiation for 90 min. Additionally, studies performed using radical scavengers indicated that h⁺, ·OH and Br⁰ acted as the main reactive species.     

Nanostructured copper aluminate spinels: Synthesis,structural, optical,magnetic, and catalytic properties

Copper aluminate nanostructured materials were synthesized by a microwave combustion method (MWCM) using the plant extract (aloe vera) as a fuel without using any other template or surfactant. For comparison, it was also prepared by using the conventional combustion method (CCM). The as-synthesized copper aluminate was characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), high resolution scanning electron microscopy (HR-SEM), energy dispersive X-ray analysis (EDX), diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy, nitrogen adsorption/desorption isotherms, and vibrating sample magnetometer (VSM). The results indicated that the copper aluminate nanomaterials obtained by MWCM shows good crystallinity with the uniform size distribution than the ones prepared by CCM. The XRD and FT-IR results confirmed the crystal structure of copper aluminate. The formation of copper aluminate nano- and microstructures were confirmed by HR-SEM. The optical absorption and photoluminescence emissions were determined by DRS and PL spectra, respectively. The effect of the catalyst and the oxidant on the catalytic oxidation of benzyl alcohol was also investigated.     

Electronic structure,optical and dielectric constant of compounds Indium-based: InAlP2, and InGaP2 in its chalcopyrite,CuPt and CuAu-I structures

First principles calculations within the density functional theory framework were carried out to calculate electronic structures and dielectric constant predictions of InGaP₂ and InAlP₂ compounds. We use three arrangements of these compounds: CuAu-I, CuPt and chalcopyrite ones. Different approximations have been dealt with in order to predict valuable bands gaps energy using DFT calculations. Electronics structure results are promising, due to the good agreement with a number of observable physical-chemistry properties. On the other hand, electron localization function and atom in molecule formalisms have been done to give more insight on the bonding properties. Capabilities that exhibit the InAlP₂ in its CuAu-I structure, such as the anisotropy and second harmonic generation, make it promising for an intensive optoelectronic application.     

Synthesis of micro-nano Ag3PO4/ZnFe2O4 with different organic additives and its enhanced photocatalytic activity under visible light irradiation

Several novel micro-nano Ag₃PO₄/ZnFe₂O₄ with excellent magnetic separation property and photocatalytic performance were successfully synthesized using different organic additives for the first time. In the composite, Ag₃PO₄ with flower-like, quadrangular prism and flake structures were obtained when the organic additive is hexadecyl trimethyl ammonium bromide (CTAB), sodium diethyldithiocarbamate (DDTC), or DL-malic acid (DLMA), respectively, while the ZnFe₂O₄ showed uniform spherical structure. From the results of the photocatalytic activity analysis, the Ag₃PO₄/ZnFe₂O₄ gained with the organic additive of DDTC showed the highest photocatalytic capability for 2, 4-dichlorophenol (2, 4-DCP) degradation under visible light irradiation compared with those of CTAB and DLMA as the additives. Moreover, the composition of the composite seriously influences the photocatalytic activity, and when the mass ratio of Ag₃PO₄ and ZnFe₂O₄ in the Ag₃PO₄/ZnFe₂O₄ (DITCH) is 9:1, the apparent photo degradation rate constant of 2, 4-DC is 0.0155 min⁻¹, which is 5.74 times of ZnFe₂O₄ (0.0027 min⁻¹) and 1.89 times of Ag₃PO₄ (0.0082 min⁻¹). Finally, the photocatalytic mechanism of Ag₃PO₄/ZnFe₂O₄ was discussed based on the heterojunction energy-band theory and Z-Scheme theory in detail.     

Synthesis and characterization of g-C3N4/BiFeO3 composites with an enhanced visible light photocatalytic activity

The novel visible light-induced g-C₃N₄/BiFeO₃ composites were successfully synthesized by introducing BiFeO₃ into polymeric g-C₃N₄. The structures and optical properties of composites were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), field-emission transmission electron microscope (TEM), UV–vis diffuse reflection spectroscopy (DRS), respectively. For the degradation of Rhodamine B (RhB), the g-C₃N₄/BiFeO₃ composites exhibited significantly higher visible light photocatalytic activity than that of a single semiconductor. The optimal percentage of doped g-C₃N₄ was 50%. Both photooxidation and photoreduction processes follow first order kinetics. In addition, the stability of the prepared photocatalyst in the photocatalytic process was also investigated. The enhanced photocatalytic performance could be due to the high separation efficiency of the photogenerated electron–holes pairs. The possible photocatalytic mechanism of g-C₃N₄/BiFeO₃ was proposed to guide the further improvement of their photocatalytic activity.     

Effect of nickel substitution on structural,optical, magnetic properties and photocatalytic activity of ZnS nanoparticles

In the present work, we propose a cost effective, less complicated and an effective way of synthesizing Zn_1−xNi_xS nanoparticle using wet chemical precipitation method. And the material is used for removal of dye decolorization process, which overcomes the constraints caused in the conventional techniques namely chlorination, adsorption, ozonization. The structural analysis shows primary phase cubic zinc blende Zn_1−xNi_xS and rhombohedral α-NiS secondary phase with the average grain size of 20 nm. The electron microscopic analysis clearly depicts the nanophase formation. The strong blue shift in the UV–visible absorption region (410 nm) confirms the nano dimensional state of Zn_1−xNi_xS nano particles. FT-IR analysis shows the presence of functional groups adsorbed on the surface of the nanoparticles. Magnetic measurement by VSM shows that the prepared nanoparticles possess super paramagnetic and room temperature weak ferromagnetic properties. Visible light driven photocatalytic decolorization of methylene blue is observed for Zn_0.90Ni_0.10S nanoparticles with a degradation of 94% during 150 min of irradiation at 150 ppm of dye concentration.     

Synthesis of cysteine,cobalt and copper-doped TiO2 nanophotocatalysts with excellent visible-light-induced photocatalytic activity

Charge separation is a vital process in order to achieve high performance TiO₂-based photocatalysts. In the current study, to enhance the charge separation and suppress the charge recombination, novel nanocomposites of metal (Co and Cu) and nonmetal (C, N, S) doped TiO₂ nanophotocatalyst (labeled as Co@C,N,S-doped TiO₂ and Cu@C,N,S-doped TiO₂) were synthesized via photochemical deposition-assisted sol–gel technique. The crystalline structures and characteristic of the prepared catalysts were analyzed by XRD, SEM, TEM, EDAX, PL, and UV–vis DRS spectroscopies. The photocatalytic performance of the samples was tested through decomposition of methyl orange (MO) aqueous solutions under UV and visible light irradiation. It was found that photodeposition of metals onto TiO₂ slowed charge recombination compared to pure TiO₂ in addition to formation of higher concentration of OH radicals on the TiO₂ photocatalyst surface during light irradiation compared to pure TiO₂. Beyond the optimum content of 2 wt% Cu and Co, a decline in photocatalytic performance was observed which was ascribed to metal agglomeration and blockage of the photosensitive TiO₂ surface.     

Cadmium selenide@sulfide nanoparticle composites: Facile precipitation preparation,characterization, and investigation of their photocatalyst activity

We report a two-step synthesis and structural characterization of CdSe/CdS core/shell nanoparticles by the precipitation method. Besides, the effects of preparation parameters such as reaction temperature, the speed of the reaction stirrer, and the rate of adding sulfide source on the size, morphology, and photocatalyst activity of CdSe/CdS core–shell nanoparticles were studied by SEM images and degradation of methyl orange (MO) dye test. The structure and composition of the obtained products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution field-emission transmission electron microscope (HRTEM), photoluminescence spectroscopy (PL), scanning electronic microscopy (SEM), spectra energy dispersive analysis of X-ray (EDS), and ultraviolet–visible (UV–vis) techniques.     

Study of capping agent effect on the structural,optical and photocatalytic properties of zinc sulfide quantum dots

In this work, the effect of capping agent type on the structural, optical and photocatalytic properties of pure zinc sulfide (ZnS) quantum dots (QDs) has been investigated. ZnS QDs were prepared by a simple, fast and water based chemical precipitation method, in the presence of various capping agents including 2-mercaptoethanol, thiourea, and l-cysteine. The obtained QDs have been characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR), and UV–visible absorption spectroscopy. The results revealed that the optical absorption band of ZnS nanostructures varied by capping agents. In the photocatalytic investigations, the prepared ZnS QDs were applied for the photodecolorization of crystal violet (CV) as a model molecule. Influence of affecting parameters on the decolorization efficiency of the capped ZnS QDs was studied and optimized. The results indicated that the prepared QDs can effectively remove different concentrations of CV dye at alkaline pH, in the presence of low concentrations of QDs. According to the photocatalytic results, the presented method can be considered as a green, quick and efficient strategy for photobleaching of organic pollutants based on the high performance photocatalytic behavior of ZnS QDs capped by different capping agents.     

Structural,optical dispersion and dielectric properties of novel chromium nickel organic crystalline semiconductors

A novel organic crystalline semiconductor, [Cr(DPPP)(DPPM)(Ni-ap)(CO)₂] (Cr–Ni OSC) (6a), (DPPP=diphenylphosphino-propanone, DPPM=diphenylphosphino-methane and Ni-ap=nickel apyrazole ring) (6a) was synthesized. Structural characteristics of the Cr–Ni OSC complex have been investigated by IR, ¹HNMR, ³¹P NMR, thermal analysis (TG/DTA), and XRD. Thermal analysis of Cr–Ni OSC implies that, the complex was thermally stable up to 218 °C, and the melting point of it was 193 °C. Two discrete regions of (44.46%, 128–421 °C) and (41.15%, 600–823 °C) by TG analysis of Cr–Ni OSC complex was determined. XRD crystal data of Cr–Ni OSC showed the formation of monoclinic (P2₁/n). Transmittance and reflectance have been used to determine the optical dispersion and dielectric properties of the Cr–Ni OSC complex in the range of 200–800 nm. The transparency of the complex is 75–80% in the visible range. The optical and transport energy gaps were estimated as 1.87 eV and 2.01 eV respectively. Optical dispersion parameters have been calculated by using single term Sellmeier dispersion relation and Wemple–DiDomenico single oscillator model. Several dispersion parameters were determined by analysis of refractive index dispersion. The optical conductivity, surface and volume energy loss functions, and the electric modulus were also estimated from the optical dielectric constant analysis.     

Structure,morphology and photocatalytic activity of Cu2O/Pt/TiO2 three-layered nanocomposite films

Novel Cu₂O/Pt/TiO₂ three-layered nanocomposite films were prepared by deposition on glass substrates using the magnetron sputtering method. Their structure, surface morphology as well as optical and photocatalytic properties were examined by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, UV–visible spectroscopy, and photoluminescence spectroscopy. As a comparison, Cu₂O/TiO₂ double-layer films were also investigated. The results show that Cu₂O/TiO₂ double-layer films have relatively smooth surfaces with agglomerated Cu₂O particle, whereas the surface layer of the Cu₂O/Pt/TiO₂ three-layered nanocomposite films was composed of fine nano-sized columnar Cu₂O and they had a rough surface morphology due to the insertion of the Pt layer. The photocatalytic activity of the three-layered films is significantly higher than that of the Cu₂O/TiO₂ double-layered composite films. Such enhancement is closely related to the presence of the Pt layer and the rough surface, which was composed of fine nano-sized Cu₂O columns; this increases the utilization of visible light as well as promotes the transfer of interfacial charge and the separation of photogenerated electron–holes.     

双掺Cr,Nd∶ZW晶体的光性、热学和激光性能

生长出Ｃｒ３＋，Ｎｄ３＋：ＺｎＷＯ４（Ｃｒ，Ｎｄ：ＺＷ）单晶，尺寸为２５ｍｍ×５０ｍｍ，研究了Ｃｒ，Ｎｄ：ＺＷ晶体的光学性质、热学性质，测定了其吸收和发射截面，激发态寿命和激光性能。结果表明，双掺有效地改善了激光性能，室温下获得０．９５μｍ单脉冲激光能量输出１．６２ｍＪ，斜效率为０．７９％。     

Solid-state solutions of copper indium disulfide and zinc indium tetrasulfide: Growth,crystallography and opto-electronic properties

Copper indium disulfide–zinc indium tetrasulfide solid solutions with different contents of zinc indium tetrasulfide, ranging from 4 to 16 mol% were grown by the horizontal modification of the Bridgman–Stockbarger method. Their structural properties were investigated by the X-ray analysis. Spectral dependences of their photoconductivity were analyzed at T≈30 K. In the single crystals with 8–12 mol% of zinc indium tetrasulfide the induced photoconduction phenomenon was observed. It could be explained by the model of three recombination and trapping centers with different capture cross sections. Indium vacancies V_In or substitutional defects Cu_In are possibly the fast recombination centers; meanwhile copper vacancies V_Cu act as the slow recombination centers. The presence of electrically active shallow defects was confirmed by the measurements of the temperature dependences of electrical conductivity and thermally stimulated currents of these samples with n-type conductivity.     

Synthesis, optical and electroluminescent properties of novel polyfluorene/carbazole-based conjugated polyelectrolytes and their precursors

A series of novel aminoalkyl-substituted fluorene/carbazole-based main chain copolymers with benzothiadiazole (BTDZ) of different contents: poly[3,6-(N-(2-ethylhexyl)carbazole)-(9,9-bis(3'-(N,N-dimethyl-amino)propyl)-2,7-fluorene)-4,7-(2,1,3-benzothiadiazole)] (PCzN-BTDZ) were synthesized by Suzuki coupling reaction. Through a postpolymerization treatment on the precursor polymer, a corresponding quaternized ammonium polyelectrolyte derivatives: poly[3,6-(N-(2-ethylhexyl)carbazole)-(9,9-bis(3'-((N,N-dimethyl)-N-ethylammonium)propyl)-2,7-fluorene)-4,7-(2,l, 3-benzothiadiazole)] dibromide (PCzNBr-BTDZ) were obtained. It was found that devices from such polymers with high work-function metal cathode such as Al showed similar device performance to that by using low work-function cathode such as Ba, indicating the excellent electron injection ability of these polymers. The efficient energy transfer from fluorene-carbazole segment to the narrow band gap BTDZ site for both the neutral and the quaternized copolymers was also observed. The addition of BTDZ into the polymer main chain can also improve polymer LED (PLED) device performance. When poly(3,4-ethylenedioxythiophene) (PEDOT)/poly(vinylcarbazole) (PVK) was used as an anode buffer, the external quantum efficiency of the copolymer PCzN-BTDZ1 was 0.99%, which was much higher than the copolymer PCzN without the incorporation of BTDZ in the same device configuration.     

Visible-light-driven composite La2O3/TiO2 nanotube arrays: Synthesis and improved photocatalytic activity

In this work, using a lanthanum nitrate solution as lanthanum source, a visible-light responsive La₂O₃/TiO₂ nanotube arrays (TNTs) composite was synthesized by a facile impregnation-calcinations technique. The as-synthesized samples were characterized by field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, UV–vis diffuse reflectance spectroscopy and photocurrent tests. The photocatalytic activity of the La₂O₃/TNTs composite under visible-light irradiation (λ>420 nm) was evaluated by the degradation of Rhodamine B (RhB). The results revealed one part of La was doped, and the other part was dispersed on the TNTs surface in the form of La₂O₃. La-doping narrowed the band gap and La₂O₃ modification accelerated the separation of photo-induced electron-hole pairs. Consequently, the as-prepared La₂O₃/TNTs composite exhibited much higher photocatalytic activity than pure TNTs. The photocatalytic activity of the composite was related to impregnation time of lanthanum nitrate solution, and an optimal time was 2 h. The activity of 2-La₂O₃/TNTs displayed 3.7 times as high as that of pure TNTs. A possible mechanism on the La₂O₃/TNTs photocatalytic activities is suggested. The composite, as promising materials, could be used to degrade dye wastewater or other organic pollutants.     

2D Materials Based on Main Group Element Compounds: Phases,Synthesis, Characterization,and Applications

2D materials based on main group element compounds have recently attracted significant attention because of their rich stoichiometric ratios and structure motifs. This review focuses on the phases in various 2D binary materials including III–VI, IV–VI, V–VI, III–V, IV–V, and V–V materials. Reducing 3D materials to 2D introduces confinement and surface effects as well as stabilizes unstable 3D phases in their 2D form. Their crystal structures, stability, preparation, and applications are summarized based on theoretical predictions and experimental explorations. Moreover, various properties of 2D materials, such as ferroelectric effect, anisotropic optical and electrical properties, ultralow thermal conductivity, and topological state are discussed. Finally, a few perspectives and an outlook are given to inspire readers toward exploring 2D materials with new phases and properties.     

Perovskite Single Crystals: Synthesis,Optoelectronic Properties,and Application

Recently, lead halide perovskite (PVSK) polycrystalline films have drawn much attention as photoactive material and scored tremendous achievements in solar cells, photodetectors, light-emitting diodes, and lasers owing to their engrossing optoelectronic properties and facile solution-processed fabrication. However, large amounts of grain boundaries unfavorably induce ion migration, surface defect, and poor stability, impeding PVSK polycrystalline film-based optoelectronic devices from practical application. In comparison with the polycrystalline counterparts, PVSK single crystals (SCs) with lower trap density serve as a better platform for not only fundamental research but also device applications. In light of this, the idea of using PVSK single crystals (SCs) to construct the optoelectronic devices is then proposed. Since then, a series of synthesis methods of PVSK SCs have emerged. In this review, recent progress of synthesis method of PVSK SCs is tried to be summarized and their advantages and limitations are analyzed. And then, the optoelectronic properties including carrier dynamic, defects, ion migration, and instability issues in these 3D and 2D PVSK SCs are overviewed and accordingly the proper device configurations of corresponding solar cells, photodetectors, X-ray, γ-ray detectors, etc., are proposed. It is believed that this review can provide the guidance for the further development of PVSK SCs and their applications.     

Ab initio studies of structural,electronic, optical,elastic and thermal properties of Ag-chalcopyrites (AgAlX2: X=S,Se)

The ab-initio calculations for the structural, electronic, optical, elastic and thermal properties of Ag-chalcopyrites (AgAlX₂: X=S and Se) have been reported using the full potential linearized augmented plane wave (FP-LAPW) method. In this paper, the recently developed Tran–Blaha modified Becke–Johnson potential is used along with the Wu-Cohen generalized gradient approximation (WC-GGA) for the exchange-correlation potential. Results are presented for lattice constants, bulk modulus and its pressure derivative, band structures, dielectric constants and refractive indices. We have also computed the six elastic constants (C₁₁, C₁₂, C₁₃, C₃₃, C₄₄, C₆₆). The thermodynamical properties such as thermal expansion, heat capacity, Debye temperature, entropy, bulk modulus are calculated employing the quasi-harmonic Debye model at different temperatures (0–900 K) and pressures (0–8 GPa) and the silent results are interpreted. Hardness of the materials is calculated for the first time at different temperatures and pressures.     

Zero-valent nanophase iron and nitrogen co-modified titania nanotube arrays: Synthesis,characterization, and enhanced visible-light photocatalytic performance

We prepared nano-zero-valent iron (nZVI) and N co-modified TiO₂ (nZVI/N–TiO₂) nanotube arrays as an enhanced visible-light photocatalyst. The TiO₂ nanotube arrays were synthesized by electrochemical anodization of Ti foil in a two-electrode system. Amorphous TiO₂ nanotube arrays were immersed in ammonia and then annealed to produce crystalline N-doped TiO₂ (N–TiO₂) nanotube arrays. nZVI spheres were directly deposited on the N–TiO₂ nanotube arrays by borohydride reduction. The photocatalysts were characterized by field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), UV–visible diffuse reflectance spectroscopy (UV–vis DRS), and electrochemical impedance spectroscopy (EIS). The environmental applicability and photocatalytic activity of the proposed nZVI/N–TiO₂ nanotube arrays were tested by phenol degradation in an aqueous system under UV and visible light irradiation. The phenol degradation rate constants of each sample under visible light irradiation were in the following order: nZVI/N–TiO₂ (k_obs=0.006 min⁻¹⁾>N–TiO₂ (k_obs=0.002 min⁻¹) ⪢ nZVI/TiO₂ (k_obs=0.0003 min⁻¹)>TiO₂ (k_obs=0.0001 min⁻¹). This result can be attributed to the synergistic effect of the N–TiO₂ nanotubes with lower energy band gap and the electron transfer from the conduction band (CB) of N–TiO₂ to nZVI spheres highly-dispersed on the N–TiO₂ for enhanced separation of photogenerated electrons and holes.