Recent Advances in Zinc Hydroxystannate-Based Flame Retardant Polymer Blends

During the combustion of polymeric materials, plenty of heat, smoke, and toxic gases are produced that may cause serious harm to human health. Although the flame retardants such as halogen- and phosphorus-containing compounds can inhibit combustion, they cannot effectively reduce the release of toxic fumes. Zinc hydroxystannate (ZHS, ZnSn(OH)6) is an environmentally friendly flame retardant that has attracted extensive interest because of its high efficiency, safety, and smoke suppression properties. However, using ZHS itself may not contribute to the optimal flame retardant effect, which is commonly combined with other flame retardants to achieve more significant efficiency. Few articles systematically review the recent development of ZHS in the fire safety field. This review aims to deliver an insight towards further direction and advancement of ZHS in flame retardant and smoke suppression for multiple polymer blends. In addition, the fire retarded and smoke suppression mechanism of ZHS will be demonstrated and discussed in depth.

Facile synthesis of ZnO/SnO2 hybrids for highly selective and sensitive detection of formaldehyde

The ZnO–SnO2 hybrids show high gas responses and good selectivity to formaldehyde.

An overview on non-spherical semiconductors for heterogeneous photocatalytic degradation of organic water contaminants

Because of their carcinogenicity and mutagenicity, the elimination of organic contaminants from surface and subsurface water is a subject of environmental significance. Conventional water decontamination approaches such as membrane separation, ultrafiltration, adsorption, reverse osmosis, coagulation, etc., have relatively higher operating costs and can generate highly toxic secondary contaminants. On the other hand, heterogeneous photocatalysis, an advanced oxidation process (AOP), is considered a clean and cost-effective process for organic pollutants degradation. Owing to their distinctive structure and physicochemical properties non-spherical semiconductors have gained considerable limelight in the photocatalytic degradation of organic contaminants. The current review briefly introduces a wide range of organic water contaminants. Recent advances in non-spherical semiconductor assembly and their photocatalytic degradation applications are highlighted. The underlying mechanism, fundamentals of photocatalytic reactions, and the factors affecting the degradation performance are also alluded including the current challenges and future research perspectives.

Construction of PdO-decorated double-shell ZnSnO3 hollow microspheres for n-propanol detection at low temperature

The sensor based on 4 wt% PdO-loaded double-shell ZnSnO3 hollow microspheres shows rapid response/recovery speed to n-propanol at low working temperature.

Steering Hollow Multishelled Structures in Photocatalysis: Optimizing Surface and Mass Transport

Hollow multishelled structures (HoMSs) provide a promising platform for fabricating photocatalysts, because the unique structure optimizes the effective surface and mass transport, showing enhanced light absorption, optimized mass transport and highly effective active sites exposed. Subsequently, the rational design on HoMS photocatalytsts is elaborated to boost the photocatalytic activity with efforts in all dimensions, from nanoscale to microscale. Breakthroughs in synthetic methodology of HoMSs have greatly evoked the prosperous photocatalytic researches for HoMSs since the developing of sequential templating approach in 2009. The dawn of HoMS photocatalyst is coming after revealing the temporal-spatial ordering property, which is also discussed in this paper with pioneer works demonstrating the greatly enhanced energy/mass transfer processes. Some insights into the key challenges and perspectives of HoMSs photocatalysts are also discussed. With the reviewed fate and future of HoMSs photocatalysts, hopefully new concepts and innovative works can be inspired to flourish this sun-rise field.

The hydrothermal synthesis of ZnSn(OH)6 and Zn2SnO4 and their photocatalytic performances

The pH value and hydrothermal temperature played an important part in the transition between ZnSn(OH)₆ and Zn₂SnO₄.

Perovskite-related ReO3-type structures

Materials with the perovskite ABX3 structure play a major role across materials chemistry and physics as a consequence of their ubiquity and wide range of useful properties. ReO3-type structures can be described as ABX3 perovskites in which the A-cation site is unoccupied, giving rise to the general composition BX3, where B is typically a cation and X is a bridging anion. The chemical diversity of such structures is extensive, ranging from simple oxides and fluorides, such as WO3 and AlF3, to complex structures in which the bridging anion is polyatomic, such as in the Prussian blue-related cyanides Fe(CN)3 and CoPt(CN)6. The same ReO3-type structure is found in metal-organic frameworks, for example, ln (im)3(im = imidazolate) and the well-known MOF-5 structure, where the B-site cation is polyatomic. The extended 3D connectivity and openness of this structure type leads to compounds with interesting and often unusual properties. Notable among these properties are negative thermal expansion (for example, ScF3), photocatalysis (for example, CoSn(OH)6), thermoelectricity (for example, CoAs3) and superconductivity in a phase that is controversially described as SH3 with a doubly interpenetrating ReO3 structure. We present an account of this exciting family of materials and discuss future opportunities in the area.

Design of Hollow Nanostructures for Energy Storage, Conversion and Production

Hollow nanostructures have shown great promise for energy storage, conversion, and production technologies. Significant efforts have been devoted to the design and synthesis of hollow nanostructures with diverse compositional and geometric characteristics in the past decade. However, the correlation between their structure and energy-related performance has not been reviewed thoroughly in the literature. Here, some representative examples of designing hollow nanostructure to effectively solve the problems of energy-related technologies are highlighted, such as lithium-ion batteries, lithium-metal anodes, lithium-sulfur batteries, supercapacitors, dye-sensitized solar cells, electrocatalysis, and photoelectrochemical cells. The great effect of structure engineering on the performance is discussed in depth, which will benefit the better design of hollow nanostructures to fulfill the requirements of specific applications and simultaneously enrich the diversity of the hollow nanostructure family. Finally, future directions of hollow nanostructure design to solve emerging challenges and further improve the performance of energy-related technologies are also provided.

Multishelled Transition Metal-Based Microspheres: Synthesis and Applications for Batteries and Supercapacitors

With the rapid growth of material innovations, multishelled hollow nanostructures are of tremendous interest due to their unique structural features and attractive physicochemical properties. Continued effort has been made in the geometric manipulation, composition complexity, and construction diversity of this material, expanding its applications. Energy storage technology has benefited from the large surface area, short transport path, and excellent buffering ability of the nanostructures. In this work, the general synthesis of multishelled hollow structures, especially with architecture versatility, is summarized. A wealth of attractive properties is also discussed for a wide area of potential applications based on energy storage systems, including Li-ion/Na-ion batteries, supercapacitors, and Li-S batteries. Finally, the emerging challenges and outlook for multishelled hollow structures are mentioned.

Enhancing the photocatalytic activity of ZnSn(OH)6 achieved by gradual sulfur doping tactics

To solve the intrinsic deficiency inherited from the large band gap of ZnSn(OH)6 (ZSH), a gradual sulfur doping strategy is first proposed here to expand the optical absorption range, improve the separation efficiency of photogenerated electron-hole pairs, and thus enhance the photocatalytic activity. It is demonstrated that the distribution of sulfur in the flower-like ZSH (the sulfur doped sample is denoted as S-ZSH) tends to be largest on the outer most surface and becomes smaller towards the interior. The S-ZSH therefore has a gradual bandgap structure that is beneficial for transferring photogenerated charge carriers from the interior to the surface, which will greatly enhance the utilization of photoelectrons. As a result, the visible light photocurrent density of S-ZSH and the photocatalytic degradation rate of rhodamine (RhB) are about 5 and 10 times higher than with pristine ZSH, respectively.

Functionalized nitrogen-doped carbon dot-modified yolk-shell ZnFe2O4 nanospheres with highly efficient light harvesting and superior catalytic activity

Volatile organic compounds (VOCs), as hazardous gaseous pollutants, have attracted much attention due to their potential threat to both human health and the environment. Accordingly, photocatalysis technology is seen as a promising technology to control low concentration VOCs due to its mild operation conditions, low energy consumption, and mineralization ability. However, there are some issues with photocatalysts, such as low light utility and fast photogenerated carrier recombination, which need to be addressed for practical applications. In this work, novel nitrogen-doped carbon dot (NCD)-modified ZnFe2O4 yolk-shell nanostructure photocatalysts were fabricated for the first time. The yolk-shell structure of ZnFe2O4 efficiently shortened the photogenerated carrier migration path and enhanced light scattering in its void, while the decorated NCDs accelerated the charge transfer from the bulk to the surface. A series of characterizations was conducted to investigate the crystal structure, elemental status, optical properties, and photocatalytic performance of the obtained composite photocatalysts. The NCD-modified ZnFe2O4 yolk-shell photocatalysts exhibited both a wide spectral absorbance and low carrier recombination, resulting in high photocatalytic activity and degradation ability towards gaseous o-dichlorobenzene. Density functional theory (DFT) calculations further revealed that the NCDs effectively promoted charge transfer and weakened the recombination of photo-generated electron-hole pairs. Additionally, in situ Fourier transform infrared (FTIR) spectroscopy was performed to investigate the degradation path in the photocatalytic process, and an electron paramagnetic resonance (EPR) radical trapping experiment was conducted to unveil the reactive oxygen species involved in the system. Combining the results obtained, the synergistic effect in the enhancement of photocatalysis between NCDs and yolk-shell ZnFe2O4 was schematically proposed.

3D Graphene Encapsulated Hollow CoSnO3 Nanoboxes as a High Initial Coulombic Efficiency and Lithium Storage Capacity Anode

3D Graphene sheets encapsulated amorphous hollow CoSnO₃ nanoboxes (H-CoSnO₃ @reduced graphene oxide [RGO]) are successfully fabricated by first preparing 3D graphene oxides encapsulated solid CoSn(OH)₆ nanocubes, followed by an alkaline etching process and subsequent heating treatment in Ar. The hollow CoSnO₃ nanoboxes with average particle size of 230 nm are uniformly and tightly encapsulated by RGO sheets. As an anode material for Li-ion batteries, H-CoSnO₃ @RGO displays high initial Coulombic efficiency of 87.1% and large reversible capacity of 1919 mA h g^-1 after 500 cycles at the current density of 500 mA g^-1 . Moreover, excellent rate capability (1250, 1188, 1141, 1115, 1086, 952, 736, and 528 mA h g^-1 at 100, 200, 300, 400, 500, 1000, 2000, and 5000 mA g^-1 , respectively) is acquired. The reasons for excellent lithium storage properties of H-CoSnO₃ @RGO are discussed in detail.

Intricate Hollow Structures: Controlled Synthesis and Applications in Energy Storage and Conversion

Intricate hollow structures garner tremendous interest due to their aesthetic beauty, unique structural features, fascinating physicochemical properties, and widespread applications. Here, the recent advances in the controlled synthesis are discussed, as well as applications of intricate hollow structures with regard to energy storage and conversion. The synthetic strategies toward complex multishelled hollow structures are classified into six categories, including well-established hard- and soft-templating methods, as well as newly emerging approaches based on selective etching of "soft@hard" particles, Ostwald ripening, ion exchange, and thermally induced mass relocation. Strategies for constructing structures beyond multishelled hollow structures, such as bubble-within-bubble, tube-in-tube, and wire-in-tube structures, are also covered. Niche applications of intricate hollow structures in lithium-ion batteries, Li-S batteries, supercapacitors, Li-O₂ batteries, dye-sensitized solar cells, photocatalysis, and fuel cells are discussed in detail. Some perspectives on the future research and development of intricate hollow structures are also provided.

Hollow ZnSnO3 Cubes with Controllable Shells Enabling Highly Efficient Chemical Sensing Detection of Formaldehyde Vapors

In structural hierarchy, inherently hollow nanostructured materials preferentially possessing high surface area demand attention due to their alluring sensing performances. However, the activity of hollow and structural hierarchy nanomaterials generally remains suboptimal due to their hollow space structure and large lateral size, which greatly hamper and limit the availability of inner space active sites. Here, hollow ZnSnO₃ cubes with a controllable interior structure were successfully prepared through a simple and low-cost coprecipitation approach followed with a calcination process. The solid-, single-, double-, and multishelled ZnSnO₃ hollow cubes could be selectively tailored by repeated addition of alkaline solution. The multishelled architecture displayed outstanding sensing properties for formaldehyde vapors due to large specific surface area, less agglomerations, abundant interfaces, thin shells, and high proportion porous structure, which act synergistically to facilitate charge transfer and promote target gas adsorption.

A family of microscale 2 × 2 × 2 Pocket Cubes

A family of Pocket Cubes with different chemical compositions but with the same overall mesoscale microstructures was prepared for potential applications in energy storage and water treatment.

Synthesis of double-shelled SnO2 nano-polyhedra and their improved gas sensing properties

A new type of non-spherical SnO2 hollow structure with double-shelled and mesoporous shells was prepared via a sacrifice template strategy in the case of SnO2, which shows high response and good selectivity to toluene.

Zinc hydroxide/oxide and zinc hydroxy stannate photocatalysts as potential scaffolds for environmental remediation

ZnSn(OH)₆ cubes as potential material for the efficient photodegradation of organic dyes with high chemical stability.

The surface plasmon resonance effect on the enhancement of photodegradation activity by Au/ZnSn(OH)6 nanocubes

This is the first report on the photocatalytic activity with a combination of the surface plasmon resonance effect through Au/ZnSn(OH)₆ nanocubes. The nanocubes have been used for preparing hybrid coating screens, which exhibited excellent mechanical desirable durability and extended their feasible application in our daily lives.

Mesoporous single-crystal CoSn(OH)6 hollow structures with multilevel interiors

Hollow nanostructures represent a unique class of functional nanomaterials with many applications. In this work, a one-pot and unusual "pumpkin-carving" protocol is demonstrated for engineering mesoporous single-crystal hollow structures with multilevel interiors. Single-crystal CoSn(OH)6 nanoboxes with uniform size and porous shell are synthesized by fast growth of CoSn(OH)6 nanocubes and kinetically-controlled etching in alkaline medium. Detailed investigation on reaction course suggests that the formation of a passivation layer of Co(III) species around the liquid-solid interface is critical for the unusual hollowing process. With reasonable understanding on the mechanism involved, this approach shows high versatility for the synthesis of CoSn(OH)6 hollow architectures with a higher order of interior complexity, such as yolk-shell particles and multishelled nanoboxes. The obtained CoSn(OH)6 hollow nanostructures can be easily converted to hollow nanostructures of tin-based ternary metal oxides with excellent photocatalytic and electrochemical properties.

Room temperature synthesis and highly enhanced visible light photocatalytic activity of porous BiOI/BiOCl composites nanoplates microflowers

This research represents a highly enhanced visible light photocatalytic removal of 450 ppb level of nitric oxide (NO) in air by utilizing flower-like hierarchical porous BiOI/BiOCl composites synthesized by a room temperature template free method for the first time. The facile synthesis method avoids high temperature treatment, use of organic precursors and production of undesirable organic byproducts during synthesis process. The result indicated that the as-prepared BiOI/BiOCl composites samples were solid solution and were self-assembled hierarchically with single-crystal nanoplates. The aggregation of the self-assembled nanoplates resulted in the formation of 3D hierarchical porous architecture containing tri-model mesopores. The coupling to BiOI with BiOCl led to down-lowered valence band (VB) and up-lifted conduction band (CB) in contrast to BiOI, making the composites suitable for visible light excitation. The BiOI/BiOCl composites samples exhibited highly enhanced visible light photocatalytic activity for removal of NO in air due to the large surface areas and pore volume, hierarchical structure and modified band structure, exceeding that of P25, BiOI, C-doped TiO(2) and Bi(2)WO(6). This research results could provide a cost-effective approach for the synthesis of porous hierarchical materials and enhancement of photocatalyst performance for environmental and energetic applications owing to its low cost and easy scaling up.