Atomic Layer Deposited (ALD) TiO2 on Fibrous Nano-Silica (KCC-1) for Photocatalysis: Nanoparticle Formation and Size Quantization Effect

Enhancing enzymatic catalysis efficiency: Immobilizing laccase on HHSS for synergistic bisphenol A adsorption and biodegradation through optimized external surface utilization

Laccase, a prominent enzyme biomacromolecule, exhibits promising catalytic efficiency in degrading phenolic compounds like bisphenol A (BPA). The laccase immobilized on conventional materials frequently demonstrates restricted loading and suboptimal catalytic performance. Hence, there is a pressing need to optimized external surface utilization to enhance catalytic performance. Herein, we synthesized amino-functionalized modified silica particles with a hierarchical hollow silica spherical (HHSS) structure for laccase immobilization via crosslinking, resulting in HHSS-LE biocatalysts. Through Box-Behnken design (BBD) and response surface methodology (RSM), we achieved a remarkably high enzyme loading of up to 213.102 mg/g. The synergistic effect of adsorption by HHSS and degradation by laccase facilitated efficient removal of BPA. The HHSS-LE demonstrated superior BPA removal capabilities, with efficiencies exceeding 100 % in the 50-200 mg/L BPA concentration range. Compared to MCM-41 and solid silica spheres (SSS), HHSS showed the highest enzyme loading capacity and catalytic activity, underscoring its superior external surface utilization rate per unit mass. Remarkably, the HHSS-LE biocatalyst exhibited remarkable recyclability even after 11 successive cycles of reuse. By preparing high immobilization rate with efficient external surface utilization, this study lays the foundation for the design of universally applicable and efficient enzyme immobilization catalysts.

Collaborative adsorption and photocatalytic degradation of high concentration pharmaceutical pollutants in water using a novel dendritic fibrous nano-silica modified with chitosan and UiO-66

This study presents a novel hybrid mesoporous material for degrading drug pollutants in water. The hybrid materials, derived from UiO-66 metal-organic framework and chitosan, coated on nano-silica, showed excellent drug adsorption through hydrogen-bonding interactions and efficient photodegradation of antibiotics. The hybrid material's enhanced conductivity and reduced band gap significantly improved pollution reduction by minimising electron-hole recombination. This allows for more efficient charge transport and better light absorption, boosting the material's ability to break down pollutants. Structural and morphological analyses were conducted using various techniques, including scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, Brunauer-Emmett-Teller analysis, X-ray photoelectron spectroscopy, and thermogravimetric analysis. Optimising the adsorption-photodegradation process involved investigating pH, catalyst dose, and radiation time. Non-linear optimisation revealed an efficiency exceeding 85 % for 400 mg/L tetracycline and doxycycline, the model antibiotics. The optimal parameters for maximal elimination were determined as pH = 4.3, hybrid mesosphere dose = 4.0 mg/mL, and radiation time = 10 min. Kinetic studies favored pseudo-second-order diffusion models over pseudo-first-order models. The hybrid mesosphere showed sustained efficiency after three cycles and performed well in real aqueous samples, removing over 80 % of each antibiotic. This study demonstrates the potential of the hybrid mesoporous material for removing pharmaceutical pollutants in water systems.

Impact of chitosan extracted from shrimp shells on the shrinkage and mechanical properties of cement-based composites using dendritic fibrous nanosilica

Dendritic fibrous nanosilica (DFNS) was functionalized using microcrystalline chitosan, derived from shrimp exoskeletons, to act as a robust anchor, resulting in DFNS@Chitosan. In order to prevent the restacking of chitosan sheets, the supramolecular polymerized chitosan not only served as a spacer but was also incorporated into cement-based composites. The physical-chemical characteristics of DFNS@Chitosan were assessed through various analytical techniques such as TEM, SEM, TGA, FTIR, AFM, XPS, and EDX. The potency and auto-induced contraction of Cement-based composite materials fortified with DFNS@Chitosan were probed. The incorporation of DFNS@Chitosan resulted in an increase in both compressive and interfacial stretching potency of the cement-based composites. Furthermore, the presence of DFNS@Chitosan effectively inhibited the occurrence of auto-induced contraction in the cement-based paste. This research endeavor is anticipated to promote an alternative utilization of DFNS and shrimp waste shells in the development of sustainable building materials.

CuFeS2 supported on dendritic mesoporous silica-titania for persulfate-assisted degradation of sulfamethoxazole under visible light

Sulfamethoxazole (SMX) is a prevalent sulfonamide antibiotic found in the environment, and it has a variety of detrimental effects on environmental sustainability and water safety. Recently, the combination of photocatalysis and sulfate radical-based advanced oxidation processes (SR-AOPs) has attracted a lot of interest as a viable technique for degradation of refractory pollutants. In this study, a visible light active CuFeS2 supported on dendritic mesoporous silica-titania (CuFeS2-DMST) photocatalyst was synthesized to improve the ability of TiO2 to activate persulfate (PS) by introducing CuFeS2 (Fe2+/Fe3+, Cu+/Cu2+ redox cycles). The CuFeS2-DMST/PS/Vis system demonstrated superior SMX degradation efficiency (88.9%, 0.0146 min-1) than TiO2 because of reduced e-/h+ recombination, excellent charge separation and mobility, and a greater surface area than TiO2. Furthermore, after four consecutive photocatalytic cycles, the system demonstrated moderate stability. From chemical quenching tests, O2●-, h+, 1O2, SO4●- and ●OH were found to be the main reactive oxidizing species. The formed intermediates during the degradation process were identified, and degradation mechanisms were proposed. This study proposes a viable technique for activating PS using a low-cost, stable, and high-surface-area TiO2-based photocatalyst, and this concept can be applied to design photocatalysts for water treatment.

Engineering a hierarchically micro-/nanostructured Si@Au-based artificial enzyme with improved accessibility of active sites for enhanced catalysis

The active site accessibility and high loading of gold nanoparticles (AuNPs) are key factors affecting the catalytic activity of supported AuNP-based catalysts. However, the preparation of supported AuNP-based catalysts with highly accessible active sites still remains a challenge. Herein, sphere-on-sphere (SoS) silica microspheres with a hierarchical structure, good dispersion and high surface density of thiol groups (10 SH nm-2) are prepared and used as a platform for the growth of high-density AuNPs. The obtained hierarchical Si@Au micro-/nanostructure consisting of 0.55 μm SoS silica microspheres and 7.3 nm AuNPs (SoS-0.55@Au-7.3) is found to show excellent peroxidase-mimicking activity (Km = 0.033 mM and Vmax = 34.6 × 10-8 M s-1) with merits of high stability and good reusability. Furthermore, the as-obtained SoS-0.55@Au-7.3-based system can sensitively detect hydrogen peroxide (H2O2) with a low detection limit of 1.6 μM and a wide linear range from 2.5 μM to 1.0 mM. The high catalytic activity, excellent stability and good reusability of SoS-0.55@Au-7.3 imply its great prospects in biosensing and biomedical analysis.

Encapsulation of ZnO and Ho:ZnO Nanoparticles in the Core of Wrinkled Mesoporous Silica

Wrinkled mesoporous silica (WMS) has a flower- or dendritic-like morphology, tunable pore size, and highly ordered and accessible three-dimensional (3D) pore structures. In this research, a method to encapsulate semiconductor nanoparticles in the core of the wrinkled mesoporous silica during synthesis is described. Highly uniform zinc oxide and holmium-doped zinc oxide nanoparticles have been synthesized by a sonochemical method. Zinc oxide and holmium-doped zinc oxide nanoparticles have been encapsulated in wrinkled mesoporous silica during synthesis. The ZnO@WMS and Ho:ZnO@WMS particles have been characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), UV-vis spectroscopy, fluorescence, dynamic light scattering (DLS), confocal microscopy, and X-ray diffraction (XRD).

A theoretical study on the surface reaction of tetrakis(dimethylamino)titanium on titanium oxide

Tetrakis(dimethylamino)-titanium (TDMAT, Ti(NMe2)4) has been used for the low-temperature atomic layer deposition (ALD) process of titanium oxide (TiO2) films. In this study, the chemisorption of TDMAT on a titanium oxide surface using a slab model was simulated by density functional theory (DFT) calculation. We calculated the activation energy for the chemisorption and predicted the final chemisorbed species. A TiO2 slab model was constructed with the optimized number of -OH surface groups. Three serial ligand exchange reactions between a TDMAT molecule and the TiO2 slab were exothermic with low activation energies of 0.16-0.46 eV, which can explain the low processing temperatures of the ALD TiO2 processes. Our DFT calculation showed that three NMe2 ligands of TDMAT would be released and the surface species of -TiNMe2 would be formed, which is in good agreement with the experimental observation in the literature.

Rice husk waste into various template-engineered mesoporous silica materials for different applications: A comprehensive review on recent developments

Following the discovery of Stöber silica, the realm of morphology-controlled mesoporous silica nanomaterials like MCM-41, SBA-15, and KCC-1 has been expanded. Due to their high BET surface area, tunable pores, easiness of functionalization, and excellent thermal and chemical stability, these materials take part a vital role in the advancement of techniques and technologies for tackling the world's largest challenges in the area of water and the environment, energy storage, and biotechnology. Synthesizing these materials with excellent physicochemical properties from cost-efficient biomass wastes is a foremost model of sustainability. Particularly, SiO₂ with a purity >98% can be obtained from rice husk (RH), one of the most abundant biomass wastes, and can be template engineered into various forms of mesoporous silica materials in an economic and eco-friendly way. Hence, this review initially gives insight into why to valorize RH into value-added silica materials. Then the thermal, chemical, hydrothermal, and biological methods of high-quality silica extraction from RH and the principles of synthesis of mesoporous and fibrous mesoporous silica materials like SBA-15, MCM-41, MSNs, and KCC-1 are comprehensively discussed. The potential applications of rice husk-derived mesoporous silica materials in catalysis, drug delivery, energy, adsorption, and environmental remediation are explored. Finally, the conclusion and the future outlook are briefly highlighted.

Technological trends in nanosilica synthesis and utilization in advanced treatment of water and wastewater

Water and wastewater treatment applications stand to benefit immensely from the design and development of new materials based on silica nanoparticles and their derivatives. Nanosilica possesses unique properties, including low toxicity, chemical inertness, and excellent biocompatibility, and can be developed from a variety of sustainable precursor materials. Herein, we provide an account of the recent advances in the synthesis and utilization of nanosilica for wastewater treatment. This review covers key physicochemical aspects of several nanosilica materials and a variety of nanotechnology-enabled wastewater treatment techniques such as adsorption, separation membranes, and antimicrobial applications. It also discusses the prospective design and tuning options for nanosilica production, such as size control, morphological tuning, and surface functionalization. Informative discussions on nanosilica production from agricultural wastes have been offered, with a focus on the synthesis methodologies and pretreatment requirements for biomass precursors. The characterization of the different physicochemical features of nanosilica materials using critical surface analysis methods is discussed. Bio-hybrid nanosilica materials have also been highlighted to emphasize the critical relevance of environmental sustainability in wastewater treatment. To guarantee the thoroughness of the review, insights into nanosilica regeneration and reuse are provided. Overall, it is envisaged that this work's insights and views will inspire unique and efficient nanosilica material design and development with robust properties for water and wastewater treatment applications.

Atomic Layer Assembly Based on Sacrificial Templates for 3D Nanofabrication

Three-dimensional (3D) nanostructures have attracted widespread attention in physics, chemistry, engineering sciences, and biology devices due to excellent functionalities which planar nanostructures cannot achieve. However, the fabrication of 3D nanostructures is still challenging at present. Reliable fabrication, improved controllability, and multifunction integration are desired for further applications in commercial devices. In this review, a powerful fabrication method to realize 3D nanostructures is introduced and reviewed thoroughly, which is based on atomic layer deposition assisted 3D assembly through various sacrificial templates. The aim of this review is to provide a comprehensive overview of 3D nanofabrication based on atomic layer assembly (ALA) in multifarious sacrificial templates for 3D nanostructures and to present recent advancements, with the ultimate aim to further unlock more potential of this method for nanodevice applications.

Dendritic Fibrous Nanosilica: Discovery, Synthesis, Formation Mechanism, Catalysis, and CO2 Capture-Conversion

ConspectusSilica-based mesoporous nanomaterials have been widely used for a range of applications. Although mesopore materials (such as MCM-41 and SBA-15) possess high surface area, due to their tubular pore structures, pore accessibility is restricted, which causes limitations in mass transport. A new nanosilica was needed to overcome these challenges, including better accessibility, controllable particle size, and good stability. In 2010, my group invented dendritic fibrous nanosilica (DFNS), which has now become a family of novel nanosilicas. DFNS has several unique properties: (i) Tunable particle sizes (50 to 1200 nm), (ii) high surface area (500 to 1200 m²/g), (iii) tunable pore volume (0.32 to 2.18 cm³/g), (iv) wide pore size distribution (3.7 to 25 nm) characterized by radially oriented pores, (v) controllable fiber density (number of fibers per sphere), (vi) variable pore size and pore volume, (vi) high thermal (∼800 °C) and hydrothermal stability, and (vii) mechanical stability (∼130 MPa). DFNS possesses unique dendritic fibrous morphology, and hence can be reached from all sides and easily accessible. DFNS can now be synthesized using a open refluxing protocol, which allowed the scale-up of the process with a sustainable E-factor. In the last 12 years, the DFNS family of materials has been extensively studied for their formation mechanism and range of applications such as catalysis, solar energy harvesting, CO₂ capture, CO₂ conversion, sensing, biomedicine, energy storage and many more.This Account discusses the invention of DFNS, its synthesis with tunable particle size, textural properties (surface area, pore volume, and pore size), and fiber density. In addition, the DFNS formation mechanism via the complex interplay of self-assembly, the dynamics, and coalescence of bicontinuous microemulsion droplets (BMDs) is discussed. Finally, applications of DFNS in a range of fields, that include catalysis, photocatalysis, synthesis of plasmonic black gold, nanosponges of aluminosilicates, CO₂ capture, and CO₂ conversion to fuel, are presented.

Thermodynamic Picture of Phase Segregation during the Formation of Bicontinuous Concentric Lamellar (bcl) Silica

The thermodynamic picture describing the formation mechanism of bicontinuous concentric lamellar (bcl) nanostructured silica particles, bcl silica, was investigated thoroughly. A series of classical kinetics of bcl silica by varying the synthesis time were employed to observe the morphological evolution of bcl silica. The formation mechanism of bcl silica is proposed as the hydrolysis and condensation reactions in the reverse micelle, followed by the phase segregation process. The images of the whole part and the cross-section of bcl silica reveal that bcl silica can be obtained just 30 min after the synthesis starts. The particle morphology evolves from bicontinuous lamellar (bl) morphology, with the absence of the dense part in the center of the particle, to bicontinuous concentric lamellar (bcl) morphology. The theoretical part of this study is focused on the phase segregation process of the mixture. This process is divided thermodynamically into several reversible processes based on the reduced Helmholtz free energy state function. The type of the lamellar orientation (i.e., parallel or perpendicular orientation) changed as the stacked lamellae changed in thickness and was followed by the decrease in the free energy. It was merely shown that the segregation of the thin slab of the lamellar polysiloxane stack favors the perpendicular orientation. In contrast, the thick slab of the lamellar polysiloxane stack yields a complex lamellar structure consisting of perpendicular and parallel orientations. A lamellar polymer confined between two planar substrates can experience a topological transformation into a sphere due to an unfavorable environment, i.e., high surface tension. After the topological transformation, lamellae with a perpendicular orientation form bicontinuous lamellae, whereas the complex lamellar structure transforms into a bicontinuous concentric lamellar morphology.

Highly Active CuO/KCC−1 Catalysts for Low-Temperature CO Oxidation

Copper catalysts have been extensively studied for CO oxidation at low temperatures. Previous findings on the stability of such catalysts, on the other hand, revealed that they deactivated badly under extreme circumstances. Therefore, in this work, a series of KCC−1-supported copper oxide catalysts were successfully prepared by impregnation method, of which 5% CuO/KCC−1 exhibited the best activity: CO could be completely converted at 120 °C. The 5% CuO/KCC−1 catalyst exhibited better thermal stability, which is mainly attributed to the large specific surface area of KCC−1 that facilitates the high dispersion of CuO species, and because the dendritic layered walls can lengthen the movement distances from particle-to-particle, thus helping to slow down the tendency of active components to sinter. In addition, the 5% CuO/KCC−1 has abundant mesoporous and surface active oxygen species, which are beneficial to the mass transfer and promote the adsorption of CO and the decomposition of Cu+–CO species, thus improving the CO oxidation performance of the catalyst.

Green carbonaceous material‒fibrous silica-titania composite photocatalysts for enhanced degradation of toxic 2-chlorophenol

In this work, fibrous silica-titania (FST) was successfully prepared by the microemulsion method prior to the addition of three types of carbonaceous materials: graphitic-carbon nitride, g-C3N4 (CN), graphene nanoplatelets (GN), and multi-wall carbon nanotubes, MWCNT (CNT), via a solid-state microwave irradiation technique. The catalysts were characterized using XRD, FESEM, TEM, FTIR, UV-Vis DRS, N2 adsorption-desorption, XPS and ESR, while their photoactivity was examined on the degradation of toxic 2-chlorophenol (2-CP). The result demonstrated that the initial reaction rate was in the following order: CNFST (5.1 × 10^-3 mM min^-1) > GNFST (2.5 × 10^-3 mM min^-1) > CNTFST (2.3 × 10^-3 mM min^-1). The best performance was due to the polymeric structure of g-C3N4 with a good dispersion of C and N on the surface FST. This dispersion contributed towards an appropriate quantity of defect sites, as a consequence of the greater interaction between g-C3N4 and the FST support, that led to narrowed of band gap energy (2.98 eV to 2.10 eV). The effect of scavenger and ESR studies confirmed that the photodegradation over CNFST occurred via a Z-scheme mechanism. It is noteworthy that the addition of green carbonaceous materials on the FST markedly enhanced the photodegradation of toxic 2-CP.

Surface modification and functionalization of powder materials by atomic layer deposition: a review

Powder materials are a class of industrial materials with many important applications. In some circumstances, surface modification and functionalization of these materials are essential for achieving or enhancing their expected performances. However, effective and precise surface modification of powder materials remains a challenge due to a series of problems such as high surface area, diffusion limitation, and particle agglomeration. Atomic layer deposition (ALD) is a cutting-edge thin film coating technology traditionally used in the semiconductor industry. ALD enables layer by layer thin film growth by alternating saturated surface reactions between the gaseous precursors and the substrate. The self-limiting nature of ALD surface reaction offers angstrom level thickness control as well as exceptional film conformality on complex structures. With these advantages, ALD has become a powerful tool to effectively fabricate powder materials for applications in many areas other than microelectronics. This review focuses on the unique capability of ALD in surface engineering of powder materials, including recent advances in the design of ALD reactors for powder fabrication, and applications of ALD in areas such as stabilization of particles, catalysts, energetic materials, batteries, wave absorbing materials and medicine. We intend to show the versatility and efficacy of ALD in fabricating various kinds of powder materials, and help the readers gain insights into the principles, methods, and unique effects of powder fabrication by ALD.

Application of Plasmonic Metal Nanoparticles in TiO2-SiO2 Composite as an Efficient Solar-Activated Photocatalyst: A Review Paper

Over the last decade, interest in the utilization of solar energy for photocatalysis treatment processes has taken centre-stage. Researchers had focused on doping TiO₂ with SiO₂ to obtain an efficient degradation rate of various types of target pollutants both under UV and visible-light irradiation. In order to further improve this degradation effect, some researchers resorted to incorporate plasmonic metal nanoparticles such as silver and gold into the combined TiO₂-SiO₂ to fully optimize the TiO₂-SiO₂’s potential in the visible-light region. This article focuses on the challenges in utilizing TiO₂ in the visible-light region, the contribution of SiO₂ in enhancing photocatalytic activities of the TiO₂-SiO₂ photocatalyst, and the ability of plasmonic metal nanoparticles (Ag and Au) to edge the TiO₂-SiO₂ photocatalyst toward an efficient solar photocatalyst.

Activation of Humic Acid in Lignite Using Molybdate-Phosphorus Hierarchical Hollow Nanosphere Catalyst Oxidation: Molecular Characterization and Rice Seed Germination-Promoting Performances

Although solid-phase activation of lignite using a nanocatalyst has great potential in producing low-cost and sustainable humic acid, the large-scale application of this technology still faces challenges because of the high price and toxicity of the nanocatalyst. Additionally, the specific molecular components of humic acid in activated lignite remain unknown. In this work, a multifunctional molybdate-phosphorus hierarchical hollow nanosphere (Mo-P-HH) catalyst was successfully manufactured by a simple way followed by phosphorization. In comparison with a commercial Pd/C catalyst, the multifunctional Mo-P-HH catalyst was more effective in producing water-soluble humic acid with small molecular functional groups from lignite via solid-phase activation. Moreover, Fourier transform ion cyclotron resonance mass spectrometry revealed the molecular compositions of humic acid in activated lignite. Compared with that from raw lignite, the humic acid after Mo-P-HH activation had less aromatic structure but higher content of lipids, proteins, amino sugar, and carbohydrates. In addition, the activated humic acid simulated seed germination and seedling growth. Therefore, this study provided a high-performance hierarchical hollow nanocatalyst for activation of humic acid and also offered the theoretical basis for the application of humic acid in agriculture.

Crystallization of well-defined anatase nanoparticles in SBA-15 for the photocatalytic decomposition of acetic acid

Anatase nanoparticles with a size of ca. 5 nm were prepared in mesoporous silica (SBA-15 with the pore diameter of 6 nm) by impregnation of the precursor derived from titanium tetraisopropoxide and subsequent heat treatment in air. The mesoporous structure of the anatase–silica hybrid and the size of the anatase particles were kept unchanged during the crystallization of anatase at 200–600 °C. The hybrids were applied as a photocatalyst for the decomposition of acetic acid in water under UV irradiation to find the heat treatment over 400 °C led to higher efficiency of the reaction (45–55 μmol h⁻¹ of carbon-dioxide production) over the samples heated at temperatures lower than 300 °C (3–14 μmol h⁻¹ of carbon-dioxide production).

Crystallization of well-defined anatase nanoparticles (5 nm) in the mesopore (6 nm) of SBA-15 over 400 °C, results the high photocatalytic activity for decomposition of acetic acid compared with other commercial titanium dioxides.

Comprehensive understanding of the synthesis and formation mechanism of dendritic mesoporous silica nanospheres

The interest in the design and controlled fabrication of dendritic mesoporous silica nanospheres (DMSNs) emanates from their widespread application in drug-delivery carriers, catalysis and nanodevices owing to their unique open three-dimensional dendritic superstructures with large pore channels and highly accessible internal surface areas. A variety of synthesis strategies have been reported, but there is no basic consensus on the elucidation of the pore structure and the underlying formation mechanism of DMSNs. Although all the DMSNs show a certain degree of similarity in structure, do they follow the same synthesis mechanism? What are the exact pore structures of DMSNs? How did the bimodal pore size distributions kinetically evolve in the self-assembly? Can the relative fractions of small mesopores and dendritic large pores be precisely adjusted? In this review, by carefully analysing the structures and deeply understanding the formation mechanism of each reported DMSN and coupling this with our research results on this topic, we conclude that all the DMSNs indeed have the same mesostructures and follow the same dynamic self-assembly mechanism using microemulsion droplets as super templates in the early reaction stage, even without the oil phase.

Central-radial bi-porous nanocatalysts with accessible high unit loading and robust magnetic recyclability for 4-nitrophenol reduction

Central-radial bi-porous nanocatalysts were synthesized by derivation from dendritic porous supports with hierarchical inorganic functional layers. The nanostructure exhibited a high unit loading capacity, accessible internal catalytic sites and protective mesoporous shell encapsulation. The nanocatalysts were utilized for efficient and stable heterogeneous catalytic reduction of 4-nitrophenol to 4-aminophenol with robust magnetic recyclability.

Nanoharvesting of bioactive materials from living plant cultures using engineered silica nanoparticles

Plant secondary metabolites are valuable therapeutics not readily synthesized by traditional chemistry techniques. Although their enrichment in plant cell cultures is possible following advances in biotechnology, conventional methods of recovery are destructive to the tissues. Nanoharvesting, in which nanoparticles are designed to bind and carry biomolecules out of living cells, offers continuous production of metabolites from plant cultures. Here, nanoharvesting of polyphenolic flavonoids, model plant-derived therapeutics, enriched in Solidago nemoralis hairy root cultures, is performed using engineered mesoporous silica nanoparticles (MSNPs, 165 nm diameter and 950 m2/g surface area) functionalized with both titanium dioxide (TiO2, 425 mg/g particles) for coordination binding sites, and amines (NH2, 145 mg/g particles) to promote cellular internalization. Intracellular uptake and localization of the nanoparticles (in Murashige and Skoog media) in hairy roots were confirmed by tagging the particles with rhodamine B isothiocyanate, incubating the particles with hairy roots, and quenching bulk fluorescence using trypan blue. Nanoharvesting of biologically active flavonoids was demonstrated by observing increased antiradical activity (using 2,2-diphenyl-1-picrylhydrazyl radical scavenging assay) by nanoparticles after exposure to hairy roots (indicating general antioxidant activity), and by the displacement of the radio-ligand [3H]-methyllycaconitine from rat hippocampal nicotinic receptors by solutes recovered from nanoharvested particles (indicating pharmacological activity specific to S. nemoralis flavonoids). Post-nanoharvesting growth suggests that the roots are viable after nanoharvesting, and capable of continued flavonoid synthesis. These observations demonstrate the potential for using engineered nanostructured particles to facilitate continuous isolation of a broad range of biomolecules from living and functioning plant cultures.

Effects of Surface Functional Groups on the Adhesion of SiO2 Nanospheres to Bio-Based Materials

The interactions between nanoparticles and materials must be considered when preparing functional materials. Although researchers have studied the interactions between nanoparticles and inorganic materials, little attention has been paid to those between nanoparticles and bio-based protein materials, like leather. In this study, organically modified silica nanospheres (SiO₂ nanospheres) loaded with rose fragrance were prepared using (3-aminopropyl) triethoxysilane (APTES), (3-mercaptopropyl) triethoxysilane (MPTES), or 3-(2, 3-epoxypropyloxy) propyl triethoxysilane (GPTES) using the sol-gel method. To study the interactions between the modified SiO₂ nanospheres and leather, a non-cross-linking adsorption experiment was conducted. According to the Dubinin–Radushkevich isotherm calculation, we found that the adsorption process of leather fiber and organically modified silica nanospheres is physical. The average adhesion energies of APTES-, MPTES-, and GPTES-modified SiO₂ nanospheres on the leather are 1.34016, 0.97289, and 2.09326 kJ/mol, respectively. The weight gain, adsorption capacity, and average adhesion energy show that the modified SiO₂ nanospheres can be adsorbed on leather in large quantities. The sensory evaluation confirmed that GPTES-modified SiO₂ nanospheres endowed the leather with an obvious rose aroma.

Electron Localization and Transport in SnO2/TiO2 Mesoporous Thin Films: Evidence for a SnO2/SnxTi1-xO2/TiO2 Structure

A study of SnO₂/TiO₂ core/shell films was undertaken to investigate the influences of shell thickness and post deposition sintering on electron localization and transport properties. Electrochemical reduction of the materials resulted in the appearance of a broad visible-near IR absorbance that provided insights into the electronic state(s) within the core/shell structures. As the shell thickness was increased from 0.5 to 5 nm, evidence for the presence of a Sn_xTi_1-xO₂ interfacial state emerged that was physically located between the core and the shell. The lifetime of photoinjected electrons increased with the shell thickness. Electron transport occurred through the SnO₂ core; however, when materials with shell thicknesses ≥2 nm were annealed at 450 °C, a new electron transport pathway through the shell was evident. The data indicate that these materials are best described as SnO₂/Sn_xTi_1-xO₂/TiO₂ where electrons preferentially localize in a Sn_xTi_1-xO₂ interfacial state and transport through SnO₂ and annealed TiO₂ (if present). The implications of these results for applications in solar energy conversion are discussed.

Vapor growth of binary and ternary phosphorus-based semiconductors into TiO2 nanotube arrays and application in visible light driven water splitting

We report successful synthesis of low band gap inorganic polyphosphide and TiO₂ heterostructures with the aid of short-way transport reactions. Binary and ternary polyphosphides (NaP₇, SnIP, and (CuI)₃P₁₂) were successfully reacted and deposited into electrochemically fabricated TiO₂ nanotubes. Employing vapor phase reaction deposition, the cavities of 100 μm long TiO₂ nanotubes were infiltrated; approximately 50% of the nanotube arrays were estimated to be infiltrated in the case of NaP₇. Intensive characterization of the hybrid materials with techniques including SEM, FIB, HR-TEM, Raman spectroscopy, XRD, and XPS proved the successful vapor phase deposition and synthesis of the substances on and inside the nanotubes. The polyphosphide@TiO₂ hybrids exhibited superior water splitting performance compared to pristine materials and were found to be more active at higher wavelengths. SnIP@TiO₂ emerged to be the most active among the polyphosphide@TiO₂ materials. The improved photocatalytic performance might be due to Fermi level re-alignment and a lower charge transfer resistance which facilitated better charge separation from inorganic phosphides to TiO₂.

The mechanistic role of a support-catalyst interface in electrocatalytic water reduction by Co3O4 supported nanocarbon florets

Comprehending the mechanistic involvement of a support-catalyst interface is critical for effective design of industrially relevant electrocatalytic processes such as the alkaline hydrogen evolution reaction (alHER). The understanding of the kinetically sluggish alHER exhibited by both Pt and Pt-group-metal-free catalysts is primarily derived from indirect electrochemical parameters such as the Tafel slope. To address these issues, we establish the critical role of a nanocarbon floret (NCF) based electrochemical support in generating a key cobalt-oxohydroxo (OH-Co[double bond, length as m-dash]O) intermediate during the alHER through operando Raman spectro-electrochemistry. Specifically, interfacial nano-engineering of a newly designed carbon support (NCF) with a spinel Co₃O₄ nanocube catalyst is demonstrated to achieve a facile alHER (-0.46 V@10 mA cm^-2). Such an efficient alHER is mainly attributed to the unique lamellar morphology with a high mesoporous surface area (936 m² g^-1) of the NCF which catalyses the rate-determining water dissociation step and facilitates rapid ion diffusion. The dissociated water drives the formation of the OH-Co[double bond, length as m-dash]O intermediate, spectroscopically captured for the first time through the emergence of a νOH-Co[double bond, length as m-dash]O Raman peak (1074 cm^-1). The subsequent alHER proceeds through the Volmer-Heyrovsky route (119 mV dec^-1) via the T_d Co²⁺↔ Co³⁺↔ Co⁴⁺ oxidative pathway. Concomitant graphitization of the NCF through the disappearance of νsp³C-H (2946 cm^-1) supports the co-operative dynamics at the Co₃O₄-NCF interface. Thus, the NCF positively contributes towards the lowering of the overpotential with a low charge-transfer resistance (R_ct = 35.8 Ω) and high double layer capacitance (C_dl = 410 mF cm^-2).

Facile synthesis to tune size, textural properties and fiber density of dendritic fibrous nanosilica for applications in catalysis and CO2 capture

Morphology-controlled nanomaterials such as silica play a critical role in the development of technologies for use in the fields of energy, environment (water and air pollution) and health. Since the discovery of Stöber's silica, followed by the discovery of mesoporous silica materials (MSNs) such as MCM-41 and SBA-15, a surge in the design and synthesis of nanosilica with various sizes, shapes, morphologies and textural properties (surface area, pore size and pore volume) has occurred. Dendritic fibrous nanosilica (DFNS; also known as KCC-1) is one of the recent discoveries in morphology-controlled nanomaterials. DFNS shows exceptional performance in large numbers of fields, including catalysis, gas capture, solar energy harvest, energy storage, sensors and biomedical applications. This material possesses a unique fibrous morphology, unlike the tubular porous structure of various conventional silica materials. It has a high surface area to volume ratio, with improved accessibility to the internal surface, tunable pore size and pore volume, controllable particle size and, importantly, improved stability. However, synthesis of DFNS with controllable size, textural properties and fiber density is still tricky because of several of the steps involved. This protocol provides a comprehensive step-wise description of DFNS synthesis and advice regarding how to control size, surface area, pore size, pore volume and fiber density. We also provide details of how to apply DFNS in catalysis and CO₂ capture. Detailed characterization protocols for these materials using scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption and thermal gravimetric analysis (TGA) studies are also provided.

Solution-phase synthesis of two-dimensional silica nanosheets using soft templates and their applications in CO2 capture

The solution-phase synthesis of silica nanosheets with tunable thickness and textural properties is still a challenge. We have developed a robust protocol to synthesize silica nanosheets using lamellar micelles as soft templates in a water-cyclohexane solvent mixture. The synthesized silica nanosheets (∼3.7 nm) possess significantly improved textural properties, with as high as 1420 m2 g-1 surface area and 3.47 cm3 g-1 pore volume. When functionalized with tetraethylenepentamine (TEPA) molecules using a physisorption method, the silica nanosheets showed a CO2 working capture capacity of 3.8 mmol g-1 at 75 °C with fast capture kinetics and good sorbent stability.

Improving the size uniformity of dendritic fibrous nano-silica by a facile one-pot rotating hydrothermal approach

This article provides a facile, low-cost, and reproducible one-pot rotating hydrothermal approach to synthesize dendritic fibrous nano-silica with outstanding uniformity.

Dendritic fibrous nano-silica & titania (DFNST) spheres as novel cataluminescence sensing materials for the detection of diethyl ether

Selective and controllable cataluminescence (CTL) sensors for volatile organic compounds (VOCs) are significant for chemical safety, environmental monitoring, health effects on human beings, and so forth. Most of the exploited CTL-based sensors suffer relatively low response and poor selectivity because of their high sensitivities to interferential substances. In this investigation, dendritic fibrous nano-silica & titania (DFNST) spheres have been synthesized as novel sensing materials and the corresponding DFNST-based CTL sensor has been fabricated to detect diethyl ether with high selectivity via a method of utilizing one 440 nm bandpass filter. The as-prepared DFNST hybrids not only keep the excellent dendritic fibrous morphology but also bear ca. 21 wt% catalytic titanium oxide of anatase crystalline structure. The DFNST-based sensor exhibits extremely strong CTL emission at 440 nm toward diethyl ether against other VOCs like acetone, ethyl acetate, butanol, and so forth. The high response can be attributed to the unique architectural texture of DFNST. Under the optimum parameters, ether could be easily detected in a wide range from 2.0 to 40.0 mM with a fine detection limit of 1.55 mM (S/N = 3). Furthermore, the working life of this CTL sensor is satisfactory with outstanding stability and durability, far from damaging the morphology and activity of the DFNST sensing material. In conclusion, it is expected that this novel sensing material, the relevant CTL sensor, and the approach of employing the bandpass filter will be significant for the detection of diethyl ether in actual applications.

Dendritic fibrous nano-silica & titania (DFNST) nanospheres have been successfully prepared as the sensing materials for the detection of diethyl ether via a DFNST-based cataluminescence (CTL) sensor.

Altering fiber density of cockscomb-like fibrous silica-titania catalysts for enhanced photodegradation of ibuprofen

Fibrous silica-titania (FST) catalysts were synthesized by microemulsion followed by silica seed-crystal crystallization methods under various molar ratios of toluene to water (T/W). The catalysts were characterized by XRD, UV-DRS, FESEM, TEM, AFM, N₂ adsorption-desorption, FTIR, and ESR. The results revealed that altering the T/W ratio affected the growth of the silica and titania and led to different size, fiber density, silica-titania structure, and number of hydroxyl groups, as well as oxygen vacancies in the FSTs, which altered their behavior toward subsequent application. Photodegradation of ibuprofen (IBP) are in the following order: FST(6:1) (90%) > FST(5:1) (84%) > FST(7:1) (79%) > commercial TiO₂ (67%). A kinetics study using Langmuir-Hinshelwood model illustrated that the photodegradation followed the pseudo-first-order and adsorption was the rate-limiting step. Optimization by response surface methodology (RSM) showed that the pH, initial concentration, and catalyst dosage were the remarkable parameters in photodegradation of IBP. The FST (6:1) maintained its photocatalytic activities for up to five cycles reaction without serious catalyst deactivation, and was also able to degrade other endocrine-disrupting chemicals, indicating its potential use for the treatment of those chemicals in wastewater.

SiO2 aerogel monolith allows ultralow amounts of TiO2 for the fast and efficient removal of gaseous pollutants

Coupled adsorption and photocatalytic oxidation brings high expectations regarding the fast and efficient removal of gaseous pollutants in air. However, to fabricate an adsorbent-photocatalyst composite, coating of a photocatalyst on adsorbent support inevitably results in loss of adsorption and light blocking on interior surfaces. In this work, we attempt to develop an adsorbent-photocatalyst monolith composite, which not only perfectly retains original high adsorption capacity, but also allows complete penetration of UV light through the whole monolith. We employ a SiO2 aerogel monolith with a diameter of 2.5 cm and thickness of 0.7 cm as adsorbent and support. After atomic layer deposition (ALD) followed by calcination, 0.32-1.25 wt% TiO2 is dispersed on the skeleton of the SiO2 aerogel. In spite of such a low level of loading, the monolith composites exhibit fast and efficient removal of gaseous acetaldehyde and NO. Therein, the best performance is achieved at a loading of 0.6 wt% TiO2. By dark adsorption, the acetaldehyde pollutant with initial concentration of 200 ppm can be adsorbed by 54% within 10 min. Moreover, the light transmittance at 387 nm can be retained as high as 6% after penetrating through the whole monolith, confirming that all loaded TiO2 nanoparticles can participate in the photocatalytic oxidation of acetaldehyde. Under UV irradiation with intensity close to natural sunlight, the preadsorbed acetaldehyde can be completely mineralized into CO2 by photocatalytic oxidation in another 60 min, benefiting from the ultradispersion of TiO2 nanoparticles inside the SiO2 aerogel. The study provides a novel three-dimensional model of an adsorbent-photocatalyst composite for the fast and efficient removal of gaseous pollutants.

Self-Assembled Photonic Crystals of Monodisperse Dendritic Fibrous Nanosilica for Lasing: Role of Fiber Density

Photonic crystals are essentially a periodic ("crystalline") arrangement of dielectric nanoparticles that respond in unison to incident light. They can be used to harvest light in various applications such as photocatalysis, solar cells, and lasing. In this work, we prepared the photonic crystals of dendritic fibrous nanosilica (DFNS) by their self-assembly. Because of the narrow particle size distribution of the as-synthesized DFNS, they readily formed colored photonic crystals. The photonic band gap was found to be tunable by using DFNS of various sizes and fiber densities. Notably, even after having similar particle sizes (but with different fiber densities), they showed different photonic band gaps, indicating that the fiber density plays a role in the band gap of photonic crystals. Such observations have not been reported before. This could have arisen from the difference in their refractive indices because of the difference in their fiber densities and hence the variation in the silica content, leading to a different optical signature.

Construction of Indium and Cerium Codoped Ordered Mesoporous TiO2 Aerogel Composite Material and Its High Photocatalytic Activity

In this study, ordered mesoporous In2O3-CeO2/TiO2 aerogel composite material is fabricated via a sol-gel method. According to the preparation process of the aerogel, different weight percentages Ce(NO3)3 and In(NO3)3 are dissolved in the solvent, which would be completely dispersed in the porous gel when the system completely becomes gel. The prepared materials are used to degrade the Rhodamine B (Rh B) under visible light irradiation. 0.2 wt% In2O3-0.2 wt% CeO2/TiO2 (In0.2-Ce0.2/TiO2) sample has the highest degradation rate which reaches to 96.20%. When degradation time is continuously increased to 110 min, the degradation efficiency of In0.2-Ce0.2/TiO2 sample is basically retained. The prepared In0.2-Ce0.2/TiO2 sample has much better stability and reproducibility under visible light irradiation, the photocatalytic degradation efficiency of In0.2-Ce0.2/TiO2 sample is still stable at more than 90% after the five times cycle.