Synthesis of Hollow Mesoporous TiO2 Microspheres with Single and Double Au Nanoparticle Layers for Enhanced Visible‐Light Photocatalysis

A facile method was used to prepare hollow mesoporous TiO₂ and Au@TiO₂ spheres using polystyrene (PS) templates. Au nanoparticles (NPs) were simultaneously synthesized and attached on the surface of PS spheres by reducing AuCl₄^? ions using sodium citrate which resulted in the uniform deposition of Au NPs. The outer coating of titania via sol‐gel produced PS@Au@TiO₂ core–shell spheres. Removing the templates from these core–shell spheres through calcination produced hollow mesoporous and crystalline Au@TiO₂ spheres with Au NPs inside the TiO₂ shell in a single step. Anatase spheres with double Au NPs layers, one inside and another outside of TiO₂ shell, were also prepared. Different characterization techniques indicated the hollow mesoporous and crystalline morphology of the prepared spheres with Au NPs. Hollow anatase spheres with Au NPs indicated enhanced harvesting of visible light and therefore demonstrated efficient catalytic activity toward the degradation of organic dyes under the irradiation of visible light as compared to bare TiO₂ spheres.     

Electrochemical Quantification of Lead Adsorption on TiO2 Nanoparticles

This work describes a rapid easy-to-use electrochemical method for quantifying lead (Pb²⁺) adsorption on metal oxide nanoparticles (NPs), demonstrated here for titanium dioxide (TiO₂). The method was able to quantify Pb²⁺ adsorption for concentrations as low as 0.95 μM, and up to 200 μM in NP dispersions, and to differentiate ion uptake in the presence and absence of a natural organic material, humic acid (HA). The method was selective for Pb²⁺ against Cu²⁺, As³⁺, Zn²⁺, Cd²⁺ and Cr³⁺ ions when measured in the specific potential range from −0.4 to −0.6 V and was successfully demonstrated in water and home-collected dust.     

Enhancing Photoactivity of TiO2(B)/Anatase Core–Shell Nanofibers by Selectively Doping Cerium Ions into the TiO2(B) Core

Cerium ions (Ce³⁺⁾ can be selectively doped into the TiO₂(B) core of TiO₂(B)/anatase core–shell nanofibers by means of a simple one‐pot hydrothermal treatment of a starting material of hydrogen trititanate (H₂Ti₃O₇) nanofibers. These Ce³⁺ ions (≈0.202 nm) are located on the (110) lattice planes of the TiO₂(B) core in tunnels (width≈0.297 nm). The introduction of Ce³⁺ ions reduces the defects of the TiO₂(B) core by inhibiting the faster growth of (110) lattice planes. More importantly, the redox potential of the Ce³⁺/Ce⁴⁺ couple (E°(Ce³⁺/Ce⁴⁺)=1.715 V versus the normal hydrogen electrode) is more negative than the valence band of TiO₂(B). Therefore, once the Ce³⁺‐doped nanofibers are irradiated by UV light, the doped Ce³⁺ ions—in close vicinity to the interface between the TiO₂(B) core and anatase nanoshell—can efficiently trap the photogenerated holes. This facilitates the migration of holes from the anatase shell and leaves more photogenerated electrons in the anatase nanoshell, which results in a highly efficient separation of photogenerated charges in the anatase nanoshell. Hence, this enhanced charge‐separation mechanism accelerates dye degradation and alcohol oxidation processes. The one‐pot treatment doping strategy is also used to selectively dope other metal ions with variable oxidation states such as Co^2+/3+ and Cu^+/2+ ions. The doping substantially improves the photocatalytic activity of the mixed‐phase nanofibers. In contrast, the doping of ions with an invariable oxidation state, such as Zn²⁺, Ca²⁺, or Mg²⁺, does not enhance the photoactivity of the mixed‐phase nanofibers as the ions could not trap the photogenerated holes.     

Simultaneous removal of Cu2+ and Cr3+ ions from aqueous solution based on Complexation with Eriochrome cyanine‐R and derivative spectrophotometric method

TiO₂ nanoparticles deposited on activated carbon (TiO₂–NP–AC) was prepared and characterized by XRD and SEM analysis. Subsequently, simultaneous ultrasound‐assisted adsorption of Cu²⁺ and Cr³⁺ ions onto TiO₂‐NPs‐AC after complexation via eriochrome cyanine R (ECR) has been investigated with UV–Vis and FAA spectrophotometer. Spectra overlapping of the ECR‐Cu and ECR‐Cr complex was resolve by derivative spectrophotometric technique. The effects of various parameters such as initial Cu²⁺ (A) and Cr³⁺ (B) ions concentrations, TiO₂‐NPs‐AC mass (C), sonication time (D) and pH (E) on the removal percentage were investigated and optimized by central composite design (CCD). The optimize conditions were set as: 4.21 min, 0.019 mg, 20.02 and 13.22 mg L^?1 and 6.63 for sonication time, TiO₂–NP–AC mass, initial Cr³⁺ and Cu²⁺ ions concentration and pH, respectively. The experimental equilibrium data fitting to Langmuir, Freundlich, Temkin and Dubinin–Radushkevich models show that the Langmuir model is a good and suitable model for evaluation and the actual behavior of adsorption process and maximum adsorption capacity of 105.26 and 93.46 mg g^?1 were obtained for Cu²⁺ and Cr³⁺ ions, respectively. Kinetic evaluation of experimental data showed that the adsorption processes followed well pseudo second order and intraparticle diffusion models.     

Preparation of Anatase Hollow TiO2 Spheres and Their Photocatalytic Activity in the Photodegradation of Chlorpyrifos

Hollow anatase titania (TiO₂) spheres were synthesized using fructose and tetrabutyl titanate (Ti(OC₄H₉)₄, TBT) as the precursors via the conventional hard template method. The morphological, structural and thermal properties of the products were characterized using scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG‐DTA), Brunauer? Emmett? Teller (BET) surface area analysis and diffuse reflectance ultraviolet visible (DR UV? Vis) spectroscopy. XRD revealed that the hollow TiO₂ prepared was in the anatase phase and the BET surface area measured was about 22 m² g^?1. The photocatalytic activity of the synthesized hollow anatase TiO₂ in the photodecomposition of chlorpyrifos was 18.67 % higher than that obtained using commercial TiO₂.     

Lead‐ and Iodide‐Deficient (CH3NH3)PbI3 (d‐MAPI): The Bridge between 2D and 3D Hybrid Perovskites

3D and 2D hybrid perovskites, which have been known for more than 20 years, have emerged recently as promising materials for optoelectronic applications, particularly the 3D compound (CH₃NH₃)PbI₃ (MAPI). The discovery of a new family of hybrid perovskites called d ‐MAPI is reported: the association of PbI₂ with both methyl ammonium (MA⁺) and hydroxyethyl ammonium (HEA⁺) cations leads to a series of five compounds with general formulation (MA)_1−2.48x(HEA)_3.48x[Pb_1−xI_3−x]. These materials, which are lead‐ and iodide‐deficient compared to MAPI while retaining 3D architecture, can be considered as a bridge between the 2D and 3D materials. Moreover, they can be prepared as crystallized thin films by spin‐coating. These new 3D materials appear very promising for optoelectronic applications, not only because of their reduced lead content, but also in account of the large flexibility of their chemical composition through potential substitutions of MA⁺, HEA⁺, Pb²⁺ and I⁻ ions.     

New Insights into the Band‐Gap Narrowing of (N,P)‐Codoped TiO2 from Hybrid Density Functional Theory Calculations

The electronic properties of anatase‐TiO₂ codoped by N and P at different concentrations have been investigated via generalized Kohn–Sham theory with the Heyd–Scuseria–Ernzerhof (HSE06) hybrid functional for exchange‐correlation in the context of density functional theory. At high doping concentrations, we find that the high photocatalytic activity of (N, P)‐codoped anatase TiO₂ vis‐à‐vis the N‐monodoped case can be rationalized by a double‐hole‐mediated coupling mechanism [Yin et al., Phys. Rev. Lett. 2011, 106, 066801] via the formation of an effective N? P bond. On the other hand, Ti³⁺ and Ti⁴⁺ ions’ spin double‐exchange results in more substantial gap narrowing for larger separations between N and P atoms. At low doping concentrations, double‐hole‐coupling is dominant, regardless of the N? P distance.     

Synthesis and Characterization of Nanostructured Fe3O4 Micron‐Spheres and Their Application in Removing Toxic Cr Ions from Polluted Water

We present a simple and effective method for the synthesis of nanostructured Fe₃O₄ micron‐spheres (NFMSs) by annealing hydrothermally formed FeCO₃ spheres in argon. The phase structure, particle size, and magnetic properties of the product have been characterized by X‐ray diffraction (XRD), Fourier‐transform infrared spectroscopy (FTIR), X‐ray photoelectron spectroscopy (XPS), field‐emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and by means of a superconducting quantum interference device (SQUID). The results have shown that the as‐obtained NFMSs have a diameter of about 5 μm and are composed of nanometer‐sized porous lamellae. The NFMSs have a large specific surface area (135.9 m² g^?1), reductive Fe²⁺ incorporated into their structure, and intense magnetic properties. These properties suggest that NFMSs have potential application in removing toxic Cr⁶⁺ ions from polluted water. At 25 °C, each gram of NFMSs product can remove 43.48 mg of Cr⁶⁺ ions, as compared to just 10.2 mg for nanometer‐sized Fe₃O₄ and 1.89 mg for micron‐sized Fe₃O₄. The enhanced removal performance can be ascribed to the structural features. Moreover, the Cr⁶⁺ ion removal capacity of the NFMSs can reach up to 71.2 mg g^?1 at 50 °C. The influencing parameters in the removal of Cr⁶⁺ ions, such as contact time, pH, and temperature, have been evaluated. The Cr⁶⁺‐removal mechanism has been investigated. We have found that the NFMSs product not only serves as an effective adsorbent to remove toxic Cr⁶⁺ ions from polluted water, but also as an effective reductant in reducing the adsorbed toxic Cr⁶⁺ ions to much less toxic Cr³⁺ through the Fe²⁺ incorporated into its structure.     

General and Facile Syntheses of Metal Silicate Porous Hollow Nanostructures

Porous hollow nanostructures have attracted intensive interest owing to their unique structure and promising applications in various fields. A facile hydrothermal synthesis has been developed to prepare porous hollow nanostructures of silicate materials through a sacrificial‐templating process. The key factors, such as the concentration of the free metal cation and the alkalinity of the solution, are discussed. Porous hollow nanostructures of magnesium silicate, nickel silicate, and iron silicate have been successfully prepared by using SiO₂ spheres as the template, as well as a silicon source. Several yolk–shell structures have also been fabricated by a similar process that uses silica‐coated composite particles as a template. As‐prepared mesoporous magnesium silicate hollow spheres showed an excellent ability to remove Pb²⁺ ions in water treatment owing to their large specific surface and unique structures.     

Two‐Dimensional Hollow TiO2 Nanoplates with Enhanced Photocatalytic Activity

Two‐dimensional anatase TiO₂ hollow nanoplates were firstly synthesized through a facile synthesis route by using α‐Fe₂O₃ nanoplates as removable templates. Two‐dimensional hollow TiO₂ nanoplates with different ratios of anatase and rutile phases were obtained by adjusting the calcining temperature. The average diameters were around 600 nm, and the shell thickness was approximately 30 nm. The photocatalytic performance of TiO₂ was investigated by decomposing rhodamine B under simulated sunlight. Among the TiO₂ samples, the anatase TiO₂ hollow nanoplates manifested a significant enhancement in the photocatalytic performances. The excellent catalytic performance can be attributed to the unique structure of the two‐dimensional anatase TiO₂ hollow nanoplates, including a large surface area and increased dye–photocatalyst contact areas as well as more active sites for photodegradation.     

混晶海胆状TiO2空心球多级结构的制备及其对亚甲基蓝的光催化降解

用简单的无模板水热法可控合成了金红石相锥刺和锐钛矿相空心球的海胆状TiO2多级结构。研究了制备介质pH值和反应时间对形貌的影响。空心球上锥刺的密度可以通过改变反应条件加以调控。对海胆状TiO2多级结构可能的形成机理进行了研究。将不同锥刺密度的TiO2空心球应用于亚甲基蓝降解的光催化研究,结果表明低锥刺密度的TiO2空心球的光催化效果优于P25-TiO2,更优于锥刺多和无锥刺的光滑TiO2空心球。     

Effective,Low‐Cost Recovery of Toxic Arsenate Anions from Water by Using Hollow‐Sphere Geode Traps

Because of the devastating impact of arsenic on terrestrial and aquatic organisms, the recovery, removal, disposal, and management of arsenic‐contaminated water is a considerable challenge and has become an urgent necessity in the field of water treatment. This study reports the controlled fabrication of a low‐cost adsorbent based on microscopic C‐,N‐doped NiO hollow spheres with geode shells composed of poly‐CN nanospherical nodules (100 nm) that were intrinsically stacked and wrapped around the hollow spheres to form a shell with a thickness of 500–700 nm. This C‐,N‐doped NiO hollow‐sphere adsorbent (termed CNN) with multiple diffusion routes through open pores and caves with connected open macro/meso windows over the entire surface and well‐dispersed hollow‐sphere particles that create vesicle traps for the capture, extraction, and separation of arsenate (AsO₄³⁻) species from aqueous solution. The CNN structures are considered to be a potentially attractive adsorbent for AsO₄³⁻ species due to 1) superior removal and trapping capacity from water samples and 2) selective trapping of AsO₄³⁻ from real water samples that mainly contained chloride and nitrate anions and Fe²⁺, and Mn²⁺, Ca²⁺, and Mg²⁺ cations. The structural stability of the hierarchal geodes was evident after 20 cycles without any significant decrease in the recovery efficiency of AsO₄³⁻ species. To achieve low‐cost adsorbents and toxic‐waste management, this superior CNN AsO₄³⁻ dead‐end trapping and recovery system evidently enabled the continuous control of AsO₄³⁻ disposal in water‐scarce environments, presents a low‐cost and eco‐friendly adsorbent for AsO₄³⁻ species, and selectively produced water‐free arsenate species. These CNN geode traps show potential as excellent adsorbent candidates in environment remediation tools and human healthcare.     

Unconventional Route to Oxygen‐Vacancy‐Enabled Highly Efficient Electron Extraction and Transport in Perovskite Solar Cells

The ability to effectively transfer photoexcited electrons and holes is an important endeavor toward achieving high‐efficiency solar energy conversion. Now, a simple yet robust acid‐treatment strategy is used to judiciously create an amorphous TiO₂ buffer layer intimately situated on the anatase TiO₂ surface as an electron‐transport layer (ETL) for efficient electron transport. The facile acid treatment is capable of weakening the bonding of zigzag octahedral chains in anatase TiO₂, thereby shortening staggered octahedron chains to form an amorphous buffer layer on the anatase TiO₂ surface. Such amorphous TiO₂‐coated ETL possesses an increased electron density owing to the presence of oxygen vacancies, leading to efficient electron transfer from perovskite to TiO₂. Compared to pristine TiO₂‐based devices, the perovskite solar cells (PSCs) with acid‐treated TiO₂ ETL exhibit an enhanced short‐circuit current and power conversion efficiency.     

Synthesis and Studies of the Visible‐Light Photocatalytic Properties of Near‐Monodisperse Bi‐Doped TiO2 Nanospheres

Near‐monodisperse Bi‐doped anatase TiO₂ nanospheres with almost uniform diameters in the range of 117 to 87 nm were prepared simply by introducing different amounts of bismuth nitrate pentahydrate into the reaction system and subsequent calcinations. X‐ray diffraction, UV‐visible diffuse reflectance spectra, and X‐ray photoelectron spectroscopy confirm that the doped ions substitute some of the lattice titanium atoms, and furthermore, Bi³⁺ and Bi⁴⁺ ions coexist. All the Bi‐doped TiO₂ samples show much better photocatalytic activity than pure TiO₂ in the degradation of rhodamine B (RhB) under the irradiation of visible light (λ>420 nm), and, interestingly, it was found that the degradation mechanism is different from the conventional one, which has already been reported elsewhere. The detailed mechanism is discussed in this article.     

反应性模板法合成硫化银中空球-银纳米粒子异质结构

以Cu₂S中空球为反应性模板, 通过在水溶液中与银离子的阳离子交换和氧化还原反应制备了大小均匀的Ag₂S中空球-Ag纳米粒子异质结构, 即Ag₂S-Ag异质中空球. 该异质结构中每个Ag₂S中空球的直径约为600 nm, 壁厚约20–30 nm, 其表面均附着一个Ag纳米粒子. 采用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线衍射(XRD)和能量色散X射线谱(EDS)对所得Ag₂S-Ag异质中空球的结构和组成进行了表征. 若以CuS中空球为反应性模板, 在相似转化条件下则主要得到不含Ag粒子的Ag₂S中空球. 该结果表明, Cu₂S中的Cu(I)的还原性在Ag₂S-Ag异质中空球的形成中发挥了重要作用. 通过对所制备的Ag₂S-Ag异质中空球进行二次生长, 还可以得到Ag₂S中空球的半球表面均被Ag膜所包覆的Ag₂S-Ag异质中空球.     

N‐Doped Yellow TiO2 Hollow Sphere‐Mediated Visible‐Light‐Driven Efficient Esterification of Alcohol and N‐Hydroxyimides to Active Esters

Herein we report a simple synthetic protocol for N‐doped yellow TiO₂ (N‐TiO₂) hollow spheres as an efficient visible‐light‐active photocatalyst using aqueous titanium peroxocarbonate complex (TPCC) solution as precursor and NH₄OH. In the developed strategy, the ammonium ion of TPCC and NH₄OH acts as nitrogen source and structure‐directing agent. The synthesized N‐TiO₂ hollow spheres are capable of promoting the synthesis of active esters of N‐hydroxyimide and alcohol through simultaneous selective oxidation of alcohol to aldehyde followed by cross‐dehydrogenative coupling (CDC) under ambient conditions upon irradiation of visible light. It is possible to develop a novel and cost‐effective one‐pot strategy for the synthesis of important esters and amides on gram scale using the developed strategy. The catalytic activity of N‐TiO₂ hollow spheres is much superior to that of other reported N‐TiO₂ samples as well as TiO₂ with varying morphology.     

Sr,Zn co-doped TiO<Subscript>2</Subscript> xerogel film made of uniform spheres for high-performance dye-sensitized solar cells

This study comes up with the facile preparation of Sr,Zn co-doped TiO₂ xerogel film for boosting the short circuit current density of dye-sensitized solar cells (DSCs). The film contains 2.5-μm-diameter spheres assembled from 60 nm nanoparticles. X-ray photoelectron spectroscopy (XPS) shows that Sr²⁺ and Zn²⁺ ions to be well incorporated into the TiO₂ crystal lattice without forming specific strontium and zinc compositions. The crystallite size, phase composition, and band structure of the spheres depend on the dopants concentration. Isolated energy levels near valence band as a result of the foreign ions introduction improve the photocatalytic activity of the prepared TiO₂ spheres, enhancing the short circuit current density of the cells. The DSC co-doped with 0.075 at.% Sr and 0.4 at.% Zn showed the highest power conversion efficiency of 7.87 % and short circuit current density of 18.75 mA cm^?2 thanks to lower charge transfer resistance (2.16 Ω cm²), lower electron transit time (1.19 ms), and higher electron diffusion coefficient (18.1 × 10⁴ cm² S^?1) compared to the other cells, demonstrated by electrochemical impedance spectroscopy (EIS). The concept of the simultaneous introduction of alkaline earth ions and transition ions into TiO₂ xerogel films will open up a new insight into the fabrication of high performance DSCs.     

Microwave‐Hydrothermal Preparation and Visible‐Light Photoactivity of Plasmonic Photocatalyst Ag‐TiO2 Nanocomposite Hollow Spheres

Visible‐light‐driven plasmonic photocatalyst Ag‐TiO₂ nanocomposite hollow spheres are prepared by a template‐free chemically‐induced self‐transformation strategy under microwave‐hydrothermal conditions, followed by a photochemical reduction process under xenon lamp irradiation. The prepared samples are characterized by using scanning electron microscopy, transmission electron microscopy, X‐ray diffraction, N₂ adsorption‐desorption isotherms, X‐ray photoelectron spectroscopy, UV/Vis and Raman spectroscopy. Production of ?OH radicals on the surface of visible‐light illuminated TiO₂ was detected by using a photoluminescence method with terephthalic acid as the probe molecule. The photocatalytic activity of as‐prepared samples was evaluated by photocatalytic decolorization of Rhodamine B (RhB) aqueous solution at ambient temperature under visible‐light irradiation. The results show that the surface plasmon absorption band of the silver nanoparticles supported on the TiO₂ hollow spheres was red shifted, and a strong surface enhanced Raman scattering effect for the Ag‐TiO₂ nanocomposite sample was observed. The prepared nanocomposite hollow spheres exhibits a highly visible‐light photocatalytic activity for photocatalytic degradation of RhB in water, and their photocatalytic activity is higher than that of pure TiO₂ and commercial Degussa P25 (P25) powders. Especially, the as‐prepared Ag‐TiO₂ nanocomposite hollow spheres at the nominal atomic ratio of silver to titanium ( R ) of 2 showed the highest photocatalytic activity, which exceeds that of P25 by a factor of more than 2.     

Dual‐Confined Sulfur Nanoparticles Encapsulated in Hollow TiO2 Spheres Wrapped with Graphene for Lithium–Sulfur Batteries

Lithium–sulfur (Li?S) batteries are attractive owing to their higher energy density and lower cost compared with the universally used lithium‐ion batteries (LIBs), but there are some problems that stop their practical use, such as low utilization and rapid capacity‐fading of the sulfur cathode, which is mainly caused by the shuttle effect, and the uncontrollable deposition of lithium sulfide species. Herein, we report the design and fabrication of dual‐confined sulfur nanoparticles that were encapsulated inside hollow TiO₂ spheres; the encapsulated nanoparticles were prepared by a facile hydrolysis process combined with acid etching, followed by “wrapping” with graphene (G?TiO₂@S). In this unique composite architecture, the hollow TiO₂ spheres acted as effective sulfur carriers by confining the polysulfides and buffering volume changes during the charge‐discharge processes by means of physical force from the hollow spheres and chemical binding between TiO₂ and the polysulfides. Moreover, the graphene‐wrapped skin provided an effective 3D conductive network to improve the electronic conductivity of the sulfur cathode and, at the same time, to further suppress the dissolution of the polysulfides. As results, the G?TiO₂@S hybrids exhibited a high and stable discharge capacity of up to 853.4 mA h g^?1 over 200 cycles at 0.5 C (1 C=1675 mA g^?1) and an excellent rate capability of 675 mA h g^?1 at a current rate of 2 C; thus, G?TiO₂@S holds great promise as a cathode material for Li?S batteries.     

Poly[nickel(II)‐di‐μ‐4,4′‐bipyridyl‐κ4N:N′‐μ‐dichromato‐κ2O:O′] and poly[copper(II)‐di‐μ‐4,4'‐bipyridyl‐κ4N:N′‐μ‐dichromato‐κ2O:O′]

The novel title hybrid isomorphous organic–inorganic mixed‐metal dichromates, [Ni(Cr₂O₇)(C₁₀H₈N₂)₂] and [Cu(Cr₂O₇)(C₁₀H₈N₂)₂], have been synthesized. A non‐centrosymmetric three‐dimensional (4,6)‐net is formed from a linear chain of vertex‐linked [Cr₂O]²⁻ and [MN₄O]²⁺ (M = Ni and Cu) units, which in turn are linked by the planar bidentate 4,4′‐­bipyridine ligand through the four remaining vertices of the [MN₄O]²⁺ octahedra. There are two such three‐dimensional nets that interpenetrate with inversion symmetry.