Manganese‐Based Functional Nanoplatforms: Nanosynthetic Construction,Physiochemical Property,and Theranostic Applicability

Transition metal‐based nanoparticles have shown their broad applications in versatile biomedical applications. Although traditional iron‐based nanoparticles have been extensively explored in biomedicine, transition metal manganese (Mn)‐based nanoparticulate systems have emerged as a multifunctional nanoplatform with their intrinsic physiochemical property and biological effect for satisfying the strict biomedical requirements. This comprehensive review focuses on recent progress of Mn‐based functional nanoplatforms in biomedicine with the particular discussion on their elaborate construction, physiochemical property, and theranostic applicability. Several Mn‐based nanosystems are discussed in detail, including solid/hollow MnO_x nanoparticles, 2D MnO_x nanosheets, MnO_x‐silica/mesoporous silica nanoparticles, MnO_x‐Fe₃O₄ nanoparticles, MnO_x‐Au, MnO_x‐fluorescent nanoparticles, Mn‐based organic composite nanosystem, and some specific/unique Mn‐based nanocomposites. Their versatile biomedical applications include pH/reducing‐responsive T₁‐weighted positive magnetic resonance imaging, controlled drug loading/delivery/release, protection of neurological disorder, photothermal hyperthermia, photodynamic therapy, chemodynamic therapy, alleviation of tumor hypoxia, immunotherapy, and some specific synergistic therapies, which are based on their disintegration behavior under the mildly acidic/reducing condition, multiple enzyme‐mimicking activity, catalytic‐triggering Fenton reaction, etc. The biological effects and biocompatibility of these Mn‐based nanosystems are also discussed, accompanied with a discussion on challenges/critical issues and an outlook on the future developments and clinical‐translation potentials of these intriguing Mn‐based functional nanoplatforms.     

Cd1–xMnxS Diluted Magnetic Semiconductors as Nanostructured Guest Species in Mesoporous Thin‐Film Silica Host Media

Recently, we demonstrated the possibility of synthesizing ordered nanowires of diluted magnetic II/VI semiconductors inside the channels of mesoporous silica host structures. Here, we expand this procedure from mesoporous powders to mesoporous thin films. Diluted magnetic semiconductors Cd_1–xMn_xS were synthesized within the pores of mesoporous thin‐film silica host structures by a wet‐impregnation technique using an aqueous solution of the respective metal acetates, followed by drying steps and a conversion to sulfide by thermal H₂S treatment. The presence of Cd_1–xMn_xS nanoparticles inside the pores was proved by powder X‐ray diffraction, infrared and Raman spectroscopy, and transmission electron microscopy. Photoluminescence excitation measurements clearly demonstrate the quantum size effect of the incorporated nanostructured guest species. The quality of the nanoparticles incorporated into the mesoporous films is comparable to that of those inside the mesoporous powders.     

Nanocasting of Mesoporous In‐TM (TM = Co,Fe, Mn) Oxides: Towards 3D Diluted‐Oxide Magnetic Semiconductor Architectures

Transition metal (Co, Fe, Mn)‐doped In₂O_3?y mesoporous oxides are synthesized by nanocasting using mesoporous silica as hard templates. 3D ordered mesoporous replicas are obtained after silica removal in the case of the In‐Co and In‐Fe oxide powders. During the conversion of metal nitrates into the target mixed oxides, Co, Fe, and Mn ions enter the lattice of the In₂O₃ bixbyite phase via isovalent or heterovalent cation substitution, leading to a reduction in the cell parameter. In turn, non‐negligible amounts of oxygen vacancies are also present, as evidenced from Rietveld refinements of the X‐ray diffraction patterns. In addition to (In_1?xTM_x)₂O_3?y, minor amounts of Co₃O₄, α‐Fe₂O₃, and Mn_xO_y phases are also detected, which originate from the remaining TM cations not forming part of the bixbyite lattice. The resulting TM‐doped In₂O_3?y mesoporous materials show a ferromagnetic response at room temperature, superimposed on a paramagnetic background. Conversely, undoped In₂O_3?y exhibits a mixed diamagnetic‐ferromagnetic behavior with much smaller magnetization. The influence of the oxygen vacancies and the doping elements on the magnetic properties of these materials is discussed. Due to their 3D mesostructural geometrical arrangement and their room‐temperature ferromagnetic behavior, mesoporous oxide‐diluted magnetic semiconductors may become smart materials for the implementation of advanced components in spintronic nanodevices.     

Visible and NIR Upconverting Er3+–Yb3+ Luminescent Nanorattles and Other Hybrid PMO‐Inorganic Structures for In Vivo Nanothermometry

Lanthanide‐doped luminescent nanoparticles are an appealing system for nanothermometry with biomedical applications due to their sensitivity, reliability, and minimal invasive thermal sensing properties. Here, four unique hybrid organic–inorganic materials prepared by combining β‐NaGdF₄ and PMOs (periodic mesoporous organosilica) or mSiO₂ (mesoporous silica) are proposed. PMO/mSiO₂ materials are excellent candidates for biological/biomedical applications as they show high biocompatibility with the human body. On the other hand, the β‐NaGdF₄ matrix is an excellent host for doping lanthanide ions, even at very low concentrations with yet very efficient luminescence properties. A new type of Er³⁺–Yb³⁺ upconversion luminescence nanothermometers operating both in the visible and near infrared regime is proposed. Both spectral ranges permit promising thermometry performance even in aqueous environment. It is additionally confirmed that these hybrid materials are non‐toxic to cells, which makes them very promising candidates for real biomedical thermometry applications. In several of these materials, the presence of additional voids leaves space for future theranostic or combined thermometry and drug delivery applications in the hybrid nanostructures.     

Mesoporous Anatase Titania Hollow Nanostructures though Silica‐Protected Calcination

The crystallization of nanometer‐scale materials during high‐temperature calcination can be controlled by a thin layer of surface coating. Here, a novel silica‐protected calcination process for preparing mesoporous hollow TiO₂ nanostructures with a high surface area and a controllable crystallinity is presented. This method involves the preparation of uniform silica colloidal templates, sequential deposition of TiO₂ and then SiO₂ layers through sol–gel processes, calcination to transform amorphous TiO₂ to crystalline anatase, and finally etching of the inner and outer silica to produce mesoporous anatase TiO₂ shells. The silica‐protected calcination step allows crystallization of the amorphous TiO₂ layer into anatase nanocrystals, while simultaneously limiting the growth of anatase grains to within several nanometers, eventually producing mesoporous anatase shells with a high surface area (～311 m² g^?1) and good water dispersibility upon chemical etching of the silica. When used as photocatalysts for the degradation of Rhodamine B under UV irradiation, the as‐synthesized mesoporous anatase shells show significantly enhanced photocatalytic activity with greater enhancement for samples calcined at higher temperatures thanks to their improved crystallinity.     

Yolk-Shell Structured Zinc-Cobalt-Ruthenium Alloy Oxide Assembled with Ultra-Small Nanoparticles: A Superior Cascade Catalyst toward Oxygen Evolution Reaction

Structure engineering has proven to be an effective strategy for improving the catalytic performance and reducing the cost of ruthenium oxide-based catalysts toward oxygen evolution reactions (OER). Herein, a polyhedron-shaped yolk-shell structure composed of zinc-cobalt-ruthenium ternary metal alloy oxide (ZnCo-RuO₂/C) is prepared, by taking advantage of the Kirkendall effect. The yolk-shell frame and the ensembled metal oxide nanoparticles are 116.9 ± 25.9 nm and 3.1 ± 0.7 nm in diameter, respectively. The porous yolk-shell structure of ZnCo-RuO₂/C exposes abundant active sites and facilitates mass transfer for OER. Theoretical calculations indicate that ZnCo-RuO₂ may break the linear scaling relationship for the OER intermediates and dramatically reduces the energy barrier of the potential determining step, which may be one of the factors that are responsible for the enhanced OER performance of ZnCo-RuO₂/C. In 1 m KOH aqueous electrolyte, ZnCo-RuO₂/C delivers an overpotential of only 180 mV at 10 mA cm⁻² and a Tafel slope of 63 mV dec⁻¹, superior to that of single metal-doped, pristine and commercial RuO₂. As an anode catalyst of zinc-air batteries, ZnCo-RuO₂/C exhibits improved power density and durability relative to commercial RuO₂, very promising for practical application.     

General Synthesis of N‐Doped Macroporous Graphene‐Encapsulated Mesoporous Metal Oxides and Their Application as New Anode Materials for Sodium‐Ion Hybrid Supercapacitors

A general method to synthesize mesoporous metal oxide@N‐doped macroporous graphene composite by heat‐treatment of electrostatically co‐assembled amine‐functionalized mesoporous silica/metal oxide composite and graphene oxide, and subsequent silica removal to produce mesoporous metal oxide and N‐doped macroporous graphene simultaneously is reported. Four mesoporous metal oxides (WO_{3? x} , Co₃O₄, Mn₂O₃, and Fe₃O₄) are encapsulated in N‐doped macroporous graphene. Used as an anode material for sodium‐ion hybrid supercapacitors (Na‐HSCs), mesoporous reduced tungsten oxide@N‐doped macroporous graphene (m‐WO_{3? x} @NM‐rGO) gives outstanding rate capability and stable cycle life. Ex situ analyses suggest that the electrochemical reaction mechanism of m‐WO_{3? x} @NM‐rGO is based on Na⁺ intercalation/de‐intercalation. To the best of knowledge, this is the first report on Na⁺ intercalation/de‐intercalation properties of WO_{3? x} and its application to Na‐HSCs.     

Novel Method of Preparation of Gold‐Nanoparticle‐Doped TiO2 and SiO2 Plasmonic Thin Films: Optical Characterization and Comparison with Maxwell–Garnett Modeling

SiO₂ and TiO₂ thin films with gold nanoparticles (NPs) are of particular interest as photovoltaic materials. A novel method for the preparation of spin‐coated SiO₂–Au and TiO₂–Au nanocomposites is presented. This fast and inexpensive method, which includes three separate stages, is based on the in situ synthesis of both the metal‐oxide matrix and the Au NPs during a baking process at relatively low temperature. It allows the formation of nanocomposite thin films with a higher concentration of Au NPs than other methods. High‐resolution transmission electron microscopy studies revealed a homogeneous distribution of NPs over the film volume along with their narrow size distribution. The optical manifestation of localized surface plasmon resonance was studied in more detail for TiO₂‐based Au‐doped nanocomposite films deposited on glass (in absorption and transmittance) and silicon (in specular reflectance). Maxwell–Garnett effective‐medium theory applied to such metal‐doped nanocomposite films describes the peculiarities of the experimental spectra, including modification of the antireflective properties of bare TiO₂ films deposited on silicon by varying the concentration of metal NPs. The antireflective capabilities of the film are increased after a wet etching process.     

A Low‐Toxic Multifunctional Nanoplatform Based on Cu9S5@mSiO2 Core‐Shell Nanocomposites: Combining Photothermal‐ and Chemotherapies with Infrared Thermal Imaging for Cancer Treatment

Copper chalcogenides have been demonstrated to be a promising photothermal agent due to their high photothermal conversion efficiency, synthetic simplicity, and low cost. However, the hydrophobic and less biocompatible characteristics associated with their synthetic processes hamper widely biological applications. An alternative strategy for improving hydrophilicity and biocompatibility is to coat the copper chalcogenide nanomaterials with silica shell. Herein, the rational preparation design results in successful coating mesoporous silica (mSiO₂) on as‐synthesized Cu₉S₅ nanocrystals, forming Cu₉S₅@mSiO₂‐PEG core‐shell nanostructures. As‐prepared Cu₉S₅@mSiO₂‐PEG core‐shell nanostructures show low cytotoxicity and excellent blood compatibility, and are effectively employed for photothermal ablation of cancer cells and infrared thermal imaging. Moreover, anticancer drug of doxorubicin (DOX)‐loaded Cu₉S₅@mSiO₂‐PEG core‐shell nanostructures show pH sensitive release profile and are therefore beneficial to delivery of DOX into cancer cells for chemotherapy. Importantly, the combination of photothermal‐ and chemotherapies demonstrates better effects of therapy on cancer treatment than individual therapy approaches in vitro and in vivo.     

Interfacially Super-Assembled Asymmetric and H2O2 Sensitive Multilayer-Sandwich Magnetic Mesoporous Silica Nanomotors for Detecting and Removing Heavy Metal Ions

Asymmetric hollow and magnetic mesoporous silica nanocomposites have great potential applications due to their unique structural–functional properties. Here, asymmetric multilayer-sandwich magnetic mesoporous silica nanobottles (MMSNBs) are presented through an interfacial super-assembly strategy. Asymmetric hollow silica nanobottles (SNBs) are first prepared, and Fe₃O₄ nanoparticles monolayers and mesoporous silica layers are uniformly super-assembled on the surfaces of SNBs, respectively. The high Fe₃O₄ nanoparticles loading endows MMSNBs with a high magnetization (8.5 emu g⁻¹), while the mesoporous silica layers exhibit high surface area (613.4 m² g⁻¹) and large pore size (3.6 nm). MMSNBs can be employed as a novel type of enzyme-powered nanomotors by integrating catalase (Cat-MMSNBs), which show an average speed of 7.59 µm s⁻¹ (≈25 body lengths s⁻¹) at 1.5 wt% H₂O₂. Accordingly, the water quality can be monitored by evaluating the movement speed of Cat-MMSNBs. Moreover, MMSNBs act as a good adsorbent for removing more than 90% of the heavy metal ions with the advantage of the mesoporous structure. In addition, the good magnetic response enables the MMSNBs with precise directional control and is conducive to recycling for repeated operation. This bottom-up interfacial super-assembly construction strategy allows for a new understanding of the rational design and synthesis of multi-functional nanomotors.     

Synthesis of Self‐Supported Ordered Mesoporous Cobalt and Chromium Nitrides

Herein, we demonstrate an ammonia nitridation approach to synthesize self‐supported ordered mesoporous metal nitrides (CoN and CrN) from mesostructured metal oxide replicas (Co₃O₄ and Cr₂O₃), which were nanocastly prepared by using mesoporous silica SBA‐15 as a hard template. Two synthetic routes are adopted. One route is the direct nitridation of mesoporous metal oxide nanowire replicas templated from SBA‐15 to metal nitrides. By this method, highly ordered mesoporous cobalt nitrides (CoN) can be obtained by the transformation of Co₃O₄ nanowire replica under ammonia atmosphere from 275 to 350 °C, without a distinct lose of the mesostructural regularity. Treating the samples above 375 °C leads to the formation of metallic cobalt and the collapse of the mesostructure due to large volume shrinkage. The other route is to transform mesostructured metal oxides/silica composites to nitrides/silica composites at 750–1000 °C under ammonia. Ordered mesoporous CrN nanowire arrays can be obtained after the silica template removal by NaOH erosion. A slowly temperature‐program‐decrease process can reduce the influence of silica nitridation and improve the purity of final CrN product. Small‐angle XRD patterns and TEM images showed the 2‐D ordered hexagonal structure of the obtained mesoporous CoN and CrN nanowires. Wide‐angle XRD patterns, HRTEM images, and SAED patterns revealed the formation of crystallized metal nitrides. Nitrogen sorption analyses showed that the obtained materials possessed high surface areas (70–90 m² g^?1) and large pore volumes (about 0.2 cm³ g^?1).     

Single Step Preparation of Novel Hydrophobic Composite Films for Low‐k Applications

Composite films with low dielectric constants (k) containing micro‐ and mesopores are synthesized from precursor solutions for the preparation of mesoporous silica and ethanolic suspensions of silicalite‐1 nanoparticles. The material contains silicalite‐1 nanoparticles (include nanocrystals and nanoslabs/intermediates) embedded in a randomly oriented matrix of highly porous mesoporous silica. Micropores result from the incorporated silicalite‐1 nanoparticles, while decomposition of the porogen F127 leads to additional mesopores. The porosity of the composite films increases from 9 to 60% with the increase in porogen loading, while in parallel the elastic modulus and hardness decrease. The elastic moduli of the films are in the range of 13–20 GPa. Hydrophobic surfaces of the composite films are obtained by introducing methyl triethoxysilane during the preparation of both precursor solutions, leading to the incorporation of ? CH₃ groups in the final composite films. These methyl groups are stable up to at least 500 °C. A low k value of approximately 2 is observed for films cured at 400 °C in N₂ flow, which is ideal for removing templates without decomposing methyl groups. Due to the intrinsic hydrophobicity of the material, post‐silylation is not required rendering the composite films attractive candidates for future low k materials.     

Sequential Hydroboration–Alcoholysis and Epoxidation–Ring Opening Reactions of Vinyl Groups in Mesoporous Vinylsilica

We report the sequential transformation of vinyl groups into hydroborate and alcohol as well as vinyl into epoxide and diol functional groups in hexagonal mesoporous vinylsilica materials, denoted meso‐vinyl‐SiO₂. The first transformation proceeds quantitatively through the hydroborylated derivative. After appropriate quenching, the hydroborylated materials are stable at ambient conditions and can undergo transformation into alcohols and various other functional groups. The pore volume and pore size uniformity were found not to be greatly affected by quenching of the hydroboranes with methanol, but they were reduced by quenching with water due to the deposition of boron‐containing species in the channels. Complete conversion of hydroborylated materials to alcohol‐functionalized materials required basic conditions and treatment time of several hours. Although this led to a significant structural shrinkage, decrease in pore volume, and decrease in ordering, there was no evidence of a partial collapse or removal of substantial parts of the pore walls under optimized synthesis conditions. This is the first successful conversion of organic groups of a functionalized ordered mesoporous silica host in alkaline solution, conditions known to be detrimental for silica frameworks. Epoxidation of the vinyl groups and subsequent conversion of the resulting epoxides into diols are also briefly described. The chemical transformation through epoxidation affords ordered mesoporous silica materials functionalized with potentially chiral organic groups, which could find applications in asymmetric catalysis and chiral separations. It was found that the epoxidation was slower than hydroboration and resulted in a lower degree of conversion. These two examples of hydroboration–alcoholysis and epoxidation–ring opening reactions of terminally bonded vinyl groups in meso‐vinyl‐SiO₂ demonstrate the novel concept of sequential organic chemical transformations harbored inside the ordered channels of mesoporous organosilica materials.     

Simultaneously Crafting Single-Atomic Fe Sites and Graphitic Layer-Wrapped Fe3C Nanoparticles Encapsulated within Mesoporous Carbon Tubes for Oxygen Reduction

The rational design and facile synthesis of 1D hollow tubular carbon-based materials with highly efficient oxygen reduction reaction (ORR) performance remains a challenge. Herein, a simple yet robust route is employed to simultaneously craft single-atomic Fe sites and graphitic layer-wrapped Fe₃C nanoparticles (Fe₃C@GL NPs) encapsulated within 1D N-doped hollow mesoporous carbon tubes (denoted Fe-N-HMCTs). The successional compositional and structural crafting of the hydrothermally self-templated polyimide tubes (PITs), enabled by Fe species incorporation and acid leaching treatment, respectively, yields Fe-N-HMCTs that are subsequently exploited as the ORR electrocatalyst. Remarkably, an alkaline electrolyte capitalizing on Fe-N-HMCTs achieves excellent ORR activity (onset potential, 0.992 V; half-wave potential, 0.872 V), favorable long-term stability, and strong methanol tolerance, outperforming the state-of-the-art Pt/C catalyst. Such impressive ORR performances of the Fe-N-HMCTs originate from the favorable configuration of active sites (i.e., atomically dispersed Fe-N_x sites and homogeneously incorporated Fe₃C@GL NPs) in conjunction with the advantageous 1D hollow tubular architecture containing adequate mesoporous surface. This work offers a new view to fabricate earth-abundant 1D Fe-N-C electrocatalysts with well-designed architecture and outstanding performance for electrochemical energy conversion and storage.     

Ordered Mesoporous Silica Derived from Layered Silicates

Here, the development of ordered mesoporous silica prepared by the reaction of layered silicates with organoammonium surfactants is reviewed. The specific features of mesoporous silica are discussed with relation to the probable formation mechanisms. The recent understanding of the unusual structural changes from the 2D structure to periodic 3D mesostructures is presented. The formation of mesophase silicates from layered silicates with single silicate sheets depends on combined factors including the reactivity of layered silicates, the presence of layered intermediates, the variation of the silicate sheets, and the assemblies of surfactant molecules in the interlayer spaces. FSM‐16‐type (p6mm) mesoporous silica is formed via layered intermediates composed of fragmented silicate sheets and alkyltrimethylammonium (C_nTMA) cations. KSW‐2‐type (c2mm) mesoporous silica can be prepared through the bending of the individual silicate sheets with intralayer and interlayer condensation. Although the structure of the silicate sheets changes during the reactions with C_nTMA cations in a complex manner, the structural units caused by kanemite in the frameworks are retained. Recent development of the structural design in the silicate framework is very important for obtaining KSW‐2‐based mesoporous silica with molecularly ordered frameworks. The structural units originating from layered silicates are chemically designed and structurally stabilized by direct silylation of as‐synthesized KSW‐2. Some proposed applications using these mesoporous silica are also summarized with some remarks on the uniqueness of the use of layered silicates by comparison with MCM‐type mesoporous silica.     

Multifunctional Up‐Converting Nanocomposites with Smart Polymer Brushes Gated Mesopores for Cell Imaging and Thermo/pH Dual‐Responsive Drug Controlled Release

Multifunctional nanocarriers based on the up‐conversion luminescent nanoparticles of NaYF₄:Yb³⁺/Er³⁺ core (UCNPs) and thermo/pH‐coupling sensitive polymer poly[(N‐isopropylacrylamide)‐co‐(methacrylic acid)] (P(NIPAm‐co‐MAA)) gated mesoporous silica shell are reported for cancer theranostics, including fluorescence imaging, and for controlled drug release for therapy. The as‐synthesized hybrid nanospheres UCNPs@mSiO₂‐P(NIPAm‐co‐MAA) show bright green up‐conversion fluorescence under 980 nm laser excitation and the thermo/pH‐sensitive polymer is active as a “valve” to moderate the diffusion of the embedded drugs in‐and‐out of the pore channels of the silica container. The anticancer drug doxorubicin hydrochloride (DOX) can be absorbed into UCNPs@mSiO₂‐P(NIPAm‐co‐MAA) nanospheres and the composite drug delivery system (DDS) shows a low level of leakage at low temperature/high pH values but significantly enhanced release at higher temperature/lower pH values, exhibiting an apparent thermo/pH controlled “on‐off” drug release pattern. The as‐prepared UCNPs@mSiO₂‐P(NIPAm‐co‐MAA) hybrid nanospheres can be used as bioimaging agents and biomonitors to track the extent of drug release. The reported multifunctional nanocarriers represent a novel and versatile class of platform for simultaneous imaging and stimuli‐responsive controlled drug delivery.     

Single-Atom Metal Sites Anchored Hydrogen-Bonded Organic Frameworks for Superior “Two-In-One” Photocatalytic Reaction

Photoredox catalysis is a green solution for organics transformation and CO₂ conversion into valuable fuels, meeting the challenges of sustainable energy and environmental concerns. However, the regulation of single-atomic active sites in organic framework not only influences the photoredox performance, but also limits the understanding of the relationship for photocatalytic selective organic conversion with CO₂ valorization into one reaction system. As a prototype, different single-atomic metal (M) sites (M²⁺ = Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, and Zn²⁺) in hydrogen-bonded organic frameworks (M-HOF) backbone with bridging structure of metal-nitrogen are constructed by a typical “two-in-one” strategy for superior photocatalytic C N coupling reactions integrated with CO₂ valorization. Remarkably, Zn-HOF achieves 100% conversion of benzylamine oxidative coupling reactions, 91% selectivity of N-benzylidenebenzylamine and CO₂ conversion in one photoredox cycle. From X-ray absorption fine structure analysis and density functional theory calculations, the superior photocatalytic performance is attributed to synergic effect of atomically dispersed metal sites and HOF host, decreasing the reaction energy barriers, enhancing CO₂ adsorption and forming benzylcarbamic acid intermediate to promote the redox recycle. This work not only affords the rational design strategy of single-atom active sites in functional HOF, but also facilitates the fundamental insights upon the mechanism of versatile photoredox coupling reaction systems.     

Trifunctional TiO2 Nanoparticles with Exposed {001} Facets as Additives in Cobalt‐Based Porphyrin‐Sensitized Solar Cells

In this study, highly mesoporous TiO₂ composite photoanodes composed of functional {001}‐faceted TiO₂ nanoparticles (NPs) and commercially available 20 nm TiO₂ NPs are employed in efficient porphyrin‐sensitized solar cells together with cobalt polypyridyl‐based mediators. Large TiO₂ NPs (approximately 50 nm) with exposed {001} facets are prepared using a fast microwave‐assisted hydrothermal (FMAH) method. These unique composite photoanodes favorably mitigate the aggregation of porphyrin on the surface of TiO₂ NPs and strongly facilitate the mass transport of cobalt‐polypyridyl‐based electrolytes in the mesoporous structure. Linear sweep voltammetry reveals that the transportation of Co(polypyridyl) redox is a diffusion‐controlled process, which is highly dependent on the porosity of TiO₂ films. Electrochemical impedance spectroscopy confirms that the FMAH TiO₂ NPs effectively suppress the interfacial charge recombination toward [Co(bpy)₃]³⁺ because of their oxidative {001} facets. In an optimal condition of 40 wt% addition of FMAH TiO₂ NPs in the final formula, the power conversion efficiency of the dye‐sensitized cells improves from 8.28% to 9.53% under AM1.5 (1 sun) conditions.     

Enhanced Photocatalytic Activity using Layer‐by‐Layer Electrospun Constructs for Water Remediation

Endocrine disruptors such as bisphenol A (BPA) are environmental pollutants that interfere with the body's endocrine system because of their structural similarity to natural and synthetic hormones. Due to their strong oxidizing potential to decompose such organic pollutants, colloidal metal oxide photocatalysts have attracted increasing attention for water detoxification. However, achieving both long‐term physical stability and high efficiency simultaneously with such photocatalytic systems poses many challenges. Here a layer‐by‐layer (LbL) deposition approach is reported for immobilizing TiO₂ nanoparticles (NPs) on a porous support while maintaining a high catalytic efficiency for photochemical decomposition of BPA. Anatase TiO₂ NPs ≈7 nm in diameter self‐assemble in consecutive layers with positively charged polyhedral oligomeric silsesquioxanes on a high surface area, porous electrospun polymer fiber mesh. The TiO₂ LbL nanofibers decompose approximately 2.2 mg BPA per mg of TiO₂ in 40 h of illumination (AM 1.5G illumination), maintaining first‐order kinetics with a rate constant (k) of 0.15 h^?1 for over 40 h. Although the colloidal TiO₂ NPs initially show significantly higher photocatalytic activity (k ≈ 0.84 h^?1), the rate constant drops to k ≈ 0.07 h^?1 after 4 h of operation, seemingly due to particle agglomeration. In the BPA solution treated with the multilayered TiO₂ nanofibers for 40 h, the estrogenic activity, based on human breast cancer cell proliferation, is significantly lower than that in the BPA solution treated with colloidal TiO₂ NPs under the same conditions. This study demonstrates that water‐based, electrostatic LbL deposition effectively immobilizes and stabilizes TiO₂ NPs on electrospun polymer nanofibers for efficient extended photochemical water remediation.     

Superior Rate Mesoporous Carbon Sphere Array Composite via Intercalation and Conversion Coupling Mechanisms for Potassium-Ion Capacitors

Carbonaceous materials have been usually adopted as the anode for high energy density potassium-ion hybrid capacitors (KICs) owing to their low voltage plateau, high conductivity, and excellent electrochemical compatibility. The improvements of their specific capacity and sluggish intercalation mechanism are still challenges to further boost the energy density of KICs while maintaining high power density and long cycle life. Herein, a N-doped mesoporous carbon sphere array composite is developed by a dual-templates method. The N-doped carbon sphere array with interpenetrated macro- and meso-pores facilitates the fast electron transport and rapid K⁺ diffusion. The uniformly introduced Co₃O₄ nanoparticles (NPs) confined in the array enable a kinetically boosted conversion reaction for excess and fast K⁺ storage. The partially oxidized Co NPs can efficiently enhance the conductivity of the entire composite. By introducing this optimized conversion capacity from encapsulated Co₃O₄ NPs, the composite with intercalation and conversion coupling mechanisms displays superior capacity and cycle life. The assembled KICs exhibit high energy/power densities (148 Wh kg⁻¹/124 W kg⁻¹) and great cycling performance (94% after 5000 cycles, 0.5 A g⁻¹). This promising strategy demonstrates an example for carbonaceous composite anode with synergistic K⁺ storage hybrid mechanism toward high performance KICs.