An Emerging Trend in the Synthesis of Iron Titanate Photocatalyst Toward Water Splitting.

Hydrogen gas is a prominent focus in pursuing renewable and clean alternative energy sources. The quest for maximizing hydrogen production yield involves the exploration of an ideal photocatalyst and the development of a simple, cost-effective technique for its generation. Iron titanate has garnered attention in this context due to its photocatalytic properties, affordability, and non-toxic nature. Over the years, different synthesis routes, different morphologies, and some modifications of iron titanate have been carried out to improve its photocatalytic performance by enhancing light absorption in the visible region, boosting charge carrier transfer, and decreasing recombination of electrons and holes. The use of iron titanate photocatalyst for hydrogen evolution reaction has seen an upward trend in recent times, and based on available findings, more can be done to improve the performance. This review paper provides a comprehensive overview of the fundamental principles of photocatalysis for hydrogen generation, encompassing the synthesis, morphology, and application of iron titanate-based photocatalysts. The discussion delves into the limitations of current methodologies and present and future perspectives for advancing iron titanate photocatalysts. By addressing these limitations and contemplating future directions, the aim is to enhance the properties of materials fabricated for photocatalytic water splitting.

Decoration of Ag nanoparticles on CoMoO4 rods for efficient electrochemical reduction of CO2.

Hydrothermal and photoreduction/deposition methods were used to fabricate Ag nanoparticles (NPs) decorated CoMoO4 rods. Improvement of charge transfer and transportation of ions by making heterostructure was proved by cyclic voltammetry and electrochemical impedance spectroscopy measurements. Linear sweep voltammetry results revealed a fivefold enhancement of current density by fabricating heterostructure. The lowest Tafel slope (112 mV/dec) for heterostructure compared with CoMoO4 (273 mV/dec) suggested the improvement of electrocatalytic performance. The electrochemical CO2 reduction reaction was performed on an H-type cell. The CoMoO4 electrocatalyst possessed the Faraday efficiencies (FEs) of CO and CH4 up to 56.80% and 19.80%, respectively at - 1.3 V versus RHE. In addition, Ag NPs decorated CoMoO4 electrocatalyst showed FEs for CO, CH4, and C2H6 were 35.30%, 11.40%, and 44.20%, respectively, at the same potential. It is found that CO2 reduction products shifted from CO/CH4 to C2H6 when the Ag NPs deposited on the CoMoO4 electrocatalyst. In addition, it demonstrated excellent electrocatalytic stability after a prolonged 25 h amperometric test at - 1.3 V versus RHE. It can be attributed to a synergistic effect between the Ag NPs and CoMoO4 rods. This study highlights the cooperation between Ag NPs on CoMoO4 components and provides new insight into the design of heterostructure as an efficient, stable catalyst towards electrocatalytic reduction of CO2 to CO, CH4, and C2H6 products.

Hydrothermal synthesis of hierarchical microstructure tungsten oxide/carbon nanocomposite for supercapacitor application.

A hierarchical nanocomposite of carbon microspheres decorated with tungsten oxide (WO3) nanocrystals resulted from the hydrothermal treatment of a precursor solution containing glucose and tungstic acid. The dehydration of glucose molecules formed oligosaccharides, which consequently carbonized, turning into carbon microspheres. The carbon microspheres then acted as a spherical nucleus onto which WO3 nanocrystals grew via heterogeneous nucleation. The reaction product showed a phase junction of orthorhombic and monoclinic WO3, which transitioned to mix-phase of tetragonal and monoclinic WO3 after a subsequent heat treatment at 600 °C in an inert condition. The electrochemical tests showed that incorporating WO3 onto the carbon (WO3/C) resulted in a three-fold increase in the specific capacitance compared to WO3 alone and a high coulombic and energy efficiencies of 98.2% and 92.8%, respectively. The nanocomposite exhibited supercapacitance with both Faradaic and non-Faradaic charge storage mechanisms. Electrochemical impedance spectroscopy showed a lower charge transfer resistance for the composite at Rct = 11.7Ω.

Single-Micelle-Templated Synthesis of Hollow Barium Carbonate Nanoparticle for Drug Delivery.

A laboratory-synthesized triblock copolymer poly(ethylene oxide-b-acrylic acid-b-styrene) (PEG-PAA-PS) was used as a template to synthesize hollow BaCO3 nanoparticles (BC-NPs). The triblock copolymer was synthesized using reversible addition-fragmentation chain transfer radical polymerization. The triblock copolymer has a molecular weight of 1.88 × 104 g/mol. Transmission electron microscopy measurements confirm the formation of spherical micelles with a PEG corona, PAA shell, and PS core in an aqueous solution. Furthermore, the dynamic light scattering experiment revealed the electrostatic interaction of Ba2+ ions with an anionic poly(acrylic acid) block of the micelles. The controlled precipitation of BaCO3 around spherical polymeric micelles followed by calcination allows for the synthesis of hollow BC-NPs with cavity diameters of 15 nm and a shell thickness of 5 nm. The encapsulation and release of methotrexate from hollow BC-NPs at pH 7.4 was studied. The cell viability experiments indicate the possibility of BC-NPs maintaining biocompatibility for a prolonged time.

Hollow Structured Transition Metal Phosphates and Their Applications.

Hollow nanostructures of transition metal phosphate are of immense interest in the existing and evolving areas of technology, due to their high surface area, presence of hollow void, and easy tuning of compositions and dimensions. Emerging synthesis methods such as template-free methods, hard-templating, and soft-templating are discussed in this review. Applications of these hollow metal phosphates dominate in energy storage and conversions, with specific advantages as supercapacitor materials. Other applications, including drug delivery, water splitting, catalysis, and adsorption, are reviewed. Finally, additional perspectives on the progress of these nanostructures, and their existing challenges related to the current synthesis routes are covered. Therefore, with the strategic modifications of the unique properties of these hollow metal phosphates, broader application requirements are fulfilled.

Porous Tungsten Oxide: Recent Advances in Design, Synthesis, and Applications.

Tungsten oxide (WO3 ) has received ever more attention and has been highly researched over the last decade due to its being a low-cost transition metal semiconductor with tunable, yet widely stable, band gaps. This minireview briefly highlights the challenges in the design and synthesis of porous WO3 including methods, precursors, solvent effects, crystal phases, and surface activities of the porous WO3 base material. These topics are explored while also drawing a connection of how the morphology and crystal phase affect the band gap. The shifts in band gap not only impact the optical properties of tungsten but also allow tuning to operate on different energy levels, which makes WO3 highly desirable in many applications such as supercapacitors, batteries, solar cells, catalysts, sensors, smart windows, and bioapplications.

Metal-incorporated mesoporous oxides: Synthesis and applications.

Mesoporous oxides are outstanding metal nanoparticle catalyst supports owing to their well-defined porous structures. Such mesoporous architectures not only prevent the aggregation of metal nanoparticles but also enhance their catalytic performance. Metal/metal oxide heterojunctions exhibit unique chemical and physical properties because of the surface reconstruction around the junction and electron transfer/interaction across the interface. This article reviews the methods used for synthesizing metal-supported hybrid nanostructures and their applications as catalysts for environmental remediation and sensors for detecting hazardous materials.

Direct Synthesis of Polymer Vesicles on the Hundred-Nanometer-and-Beyond Scale Using Chemical Oscillations.

The direct synthesis of block copolymer vesicles on the scale of tens to hundreds of nanometers using reversible addition-fragmentation chain transfer (RAFT) dispersion polymerization as an effect of chemical oscillations is reported. RAFT polymerization is successfully accomplished between polyethylene glycol containing a RAFT agent (PEG-CTA) and ethyl acrylate monomer in the presence of the Belousov-Zhabotinsky (B-Z) reaction in oscillatory mode. The self-assembly of poly(ethylene glycol)-b-poly(ethyl acrylate) unimers gives rise to spherical micelles. The self-assembled micelles reorganize and transform to vesicles. All the chemistry of polymerization, self-assembly and self-organization, of macromolecules takes place in a single pot using only a few simple raw materials in aqueous solution.

Autonomous Ex Novo Chemical Assembly with Blebbing and Division of Functional Polymer Vesicles from a "Homogeneous Mixture".

The chemical energy and radicals from an oscillating chemical reaction are used to synthesize a polymer vesicle from a homogeneous solution of monomeric units. Periodically formed radicals from the Belousov-Zhabotinsky (B-Z) reaction initiate radical polymerization between a polyethylene glycol based chain transfer agent (PEG-CTA) and hydrophilic acrylonitrile monomers in water. The growth of a hydrophobic chain on the hydrophilic PEG chain induces self-assembly of polymeric amphiphiles to form micrometer-sized vesicles entrapping an active oscillating B-Z reaction. In our experimental conditions, the different chemical environments inside and outside the vesicles contribute to enlarge the area and diameter of the resulting self-assembled vesicles and, in some cases, promote blebbing and division.

Tailored Design of Bicontinuous Gyroid Mesoporous Carbon and Nitrogen-Doped Carbon from Poly(ethylene oxide-b-caprolactone) Diblock Copolymers.

Highly ordered mesoporous resol-type phenolic resin and the corresponding mesoporous carbon materials were synthesized by using poly(ethylene oxide-b-caprolactone) (PEO-b-PCL) diblock copolymer as a soft template. The self-assembled mesoporous phenolic resin was found to form only in a specific resol concentration range of 40-70 wt % due to an intriguing balance of hydrogen-bonding interactions in the resol/PEO-b-PCL mixtures. Furthermore, morphological transitions of the mesostructures from disordered to gyroid to cylindrical and finally to disordered micelle structure were observed with increasing resol concentration. By calcination under nitrogen atmosphere at 800 °C, the bicontinuous mesostructured gyroid phenolic resin could be converted to mesoporous carbon with large pore size without collapse of the original mesostructure. Furthermore, post-treatment of the mesoporous gyroid phenolic resin with melamine gave rise to N-doped mesoporous carbon with unique electronic properties for realizing high CO2 adsorption capacity (6.72 mmol g-1 at 0 °C).

Facile One-Pot Synthesis of Functional Giant Polymeric Vesicles Controlled by Oscillatory Chemistry.

We introduce a novel application of an oscillatory chemical reaction to the synthesis of block copolymers. The Belousov-Zhabotinsky (B-Z) reaction is coupled with the polymerization of an amphiphilic block copolymer. Radicals generated in the B-Z reaction initiate the polymerization between a polyethylene glycol (PEG) macroreversible addition-fragmentation chain-transfer agent and butyl acrylate monomers. The attachment of a hydrophobic block on PEG leads to self-assembly and formation of spherical micelles. The nanoscale micelles transform into submicrometer vesicles and grow to giant vesicles as a consequence of the oscillatory behavior of the B-Z reaction. The one-pot synthesis of an amphiphilic di-block copolymer and retention of oscillatory behavior for the B-Z reaction with the formation of giant vesicles bring a new insight into possible pathways for the synthesis of active functional microreactors in the range from hundreds of nanometers to tens of micrometers.

Hollow carbon nanospheres using an asymmetric triblock copolymer structure directing agent.

We introduce a simple method to prepare hollow carbon nanospheres (HCNs) by using triblock copolymer poly(styrene-b-2-vinylpyridine-b-ethylene oxide) (PS-b-P2VP-b-PEO) micelles as a new class of soft-templates. Simply by changing the solvent we can prepare ultra-small sized micelles of the triblock copolymer PS-b-P2VP-b-PEO soft template to obtain HCNs with ultra-small diameters (43 nm) and hollow cores (19 nm). Furthermore, we use these HCNs to make electric double-layer capacitors (EDLCs) that exhibit superior performance.

Synthesis of Mesoporous Transition-Metal Phosphates by Polymeric Micelle Assembly.

Mesoporous iron phosphate (FePO4 ) was synthesized through assembly of polymeric micelles made of asymmetric triblock co-polymer (polystyrene-b-poly-2-vinylpyridine-b-ethylene oxide; PS-PVP-PEO). The phosphoric acid solution stimulates the formation of micelles with core-shell-corona architecture. The negatively charged PO4 (3-) ions dissolved in the solution strongly interact with the positively charged PVP(+) units through an electrostatic attraction. Also, the presence of PO4 (3-) ions realizes a bridge between the micelle surface and the metal ions. The removal of polymeric template forms the robust framework of iron phosphate with 30 nm pore diameter and 15 nm wall thickness. Our method is applicable to other mesoporous metal phosphates by changing metal sources. The obtained materials were fully characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), N2 adsorption-desorption, Raman spectroscope, and other techniques.

Direct Assembly of Mesoporous Silica Functionalized with Polypeptides for Efficient Dye Adsorption.

Herein, we introduce a new polypeptide-functionalized mesoporous silica template fabricated from a biodegradable poly(ethylene oxide-b-ɛ-caprolactone) (PEO-b-PCL) diblock copolymer and a poly(tyrosine) (PTyr) biopolymer. The crystallization behavior of the PEO-b-PCL diblock copolymer changes after blending, but the secondary structure of PTry remains stable. After selective solvent extraction in THF, the PEO-b-PCL is removed, but PTyr remains within the silica matrix due to its different solubility. Fourier-transform IR spectroscopic analysis (FTIR), thermal gravitometry analysis (TGA), small-angle X-ray scattering (SAXS), and X-ray diffraction (XRD) studies confirm the retention of PTyr to form a polypeptide-functionalized mesoporous material. The adsorption of methylene blue hydrate (MB) from aqueous solution into the polypeptide-functionalized mesoporous silica is investigated, thus revealing that the nanocomposite exhibits a high adsorption capacity relative to pure silica due to hydrogen-bonding interactions between the hydroxy phenolic group of PTyr and the N-containing aromatic ring from MB.

Polymeric micelle assembly for the smart synthesis of mesoporous platinum nanospheres with tunable pore sizes.

A facile method for the fabrication of well-dispersed mesoporous Pt nanospheres involves the use of a polymeric micelle assembly. A core-shell-corona type triblock copolymer [poly(styrene-b-2-vinylpyridine-b-ethylene oxide), PS-b-P2VP-b-PEO] is employed as the pore-directing agent. Negatively charged PtCl4 (2-) ions preferably interact with the protonated P2VP(+) blocks while the free PEO chains prevent the aggregation of the Pt nanospheres. The size of the mesopores can be finely tuned by varying the length of the PS chain. Furthermore, it is demonstrated that the metallic mesoporous nanospheres thus obtained are promising candidates for applications in electrochemistry.

Easy and General Synthesis of Large-Sized Mesoporous Rare-Earth Oxide Thin Films by 'Micelle Assembly'.

Large-sized (ca. 40 nm) mesoporous Er2O3 thin films are synthesized by using a triblock copolymer poly(styrene-b-2-vinyl pyridine-b-ethylene oxide) (PS-b-P2VP-b-PEO) as a pore directing agent. Each block makes different contributions and the molar ratio of PVP/Er(3+) is crucial to guide the resultant mesoporous structure. An easy and general method is proposed and used to prepare a series of mesoporous rare-earth oxide (Sm2O3, Dy2O3, Tb2O3, Ho2O3, Yb2O3, and Lu2O3) thin films with potential uses in electronics and optical devices.

Synthesis of Highly Photocatalytic TiO2 Microflowers Based on Solvothermal Approach Using N,N-Dimethylformamide.

Crystallized anatase TiO2 microflowers with high surface area are synthesized by a simple template-free solvothermal method using N,N-dimethylformamide (DMF). Titanium sources undergo well-organized assembly in DMF to form flower-shaped TiO2 particles. After the calcination, the anatase frameworks are highly crystallized, and the surface area is increased up to 256 m2 x g(-1). The calcined TiO2 microflowers show superior photocatalytic performance over the commercially available TiO2 product (P25) in the degradation of methylene blue.

Mesoporous TiO2/Zn2Ti3O8 hybrid films synthesized by polymeric micelle assembly.

A hybrid mesoporous TiO2/Zn2Ti3O8 film with a pore size of around 40 nm is successfully synthesized by the polymeric micelle assembly approach. The chemically distinct units of polymeric micelles of the poly(styrene-2-vinylpyridine-ethylene oxide) triblock copolymer simultaneously contribute to the formation of mesoporous TiO2/Zn2Ti3O8 films with enhanced photocatalytic activity during H2 evolution reaction.

Multi-Stimuli-Responsive Polymeric Materials.

Stimuli-responsive materials are of immense importance because of their ability to undergo alteration of their properties in response to their environment. The properties of such materials can be tuned by subtle adjustments in temperature, pH, light, and so forth. Among such smart materials, multi-stimuli-responsive polymeric materials are of pronounced significance as they offer a wide range of applications and their properties can be tuned through several mechanisms. Here, we aim to highlight some recent studies showcasing the multi-stimuli-responsive character of these polymers, which are still relatively little known compared to their single-stimuli-responsive counterpart.

Functionalized magnetic iron oxide/alginate core-shell nanoparticles for targeting hyperthermia.

Hyperthermia is one of the promising treatments for cancer therapy. However, the development of a magnetic fluid agent that can selectively target a tumor and efficiently elevate temperature while exhibiting excellent biocompatibility still remains challenging. Here a new core-shell nanostructure consisting of inorganic iron oxide (Fe3O4) nanoparticles as the core, organic alginate as the shell, and cell-targeting ligands (ie, D-galactosamine) decorated on the outer surface (denoted as Fe3O4@Alg-GA nanoparticles) was prepared using a combination of a pre-gel method and coprecipitation in aqueous solution. After treatment with an AC magnetic field, the results indicate that Fe3O4@Alg-GA nanoparticles had excellent hyperthermic efficacy in a human hepatocellular carcinoma cell line (HepG2) owing to enhanced cellular uptake, and show great potential as therapeutic agents for future in vivo drug delivery systems.