Magnetically recoverable core–shell nanocomposites γ-Fe2O3@SiO2@TiO2–Ag with enhanced photocatalytic activity and antibacterial activity

Advances in the application of functional nanomaterial and cold plasma for the fresh-keeping active packaging of meat

The most recent advancements in food science and technology include cold sterilization of food and fresh-keeping packaging. Active packaging technology has received much interest due to the photocatalytic activity (PCA) of functional nanoparticles, including titanium dioxide (TiO2) and ferric oxide (Fe2O3). However, there are still significant concerns about the toxicity and safety of these functional nanoparticles. This review emphasizes the bacteriostatic and fresh-keeping properties of functional nanoparticles as well as their packaging strategies using the ultraviolet photo-catalysis effect. High-voltage electric field cold plasma (HVEF-CP) is the most innovative method of cold-sterilizing food. HVEF-CP sterilizes by producing photoelectrons, ions, and active free radicals on food media, which come into contact with the bacteria's surface and destroy their cells. Next, this review also assesses the photocatalytic activity and bacteriostasis kinetics of nanosized TiO2 and Fe2O3 in poultry, beef, and lamb. In addition, this review also emphasizes the importance of exploiting the complex interaction processes between TiO2 and Fe2O3, along with dietary components and their utilization in the fresh meat industry.

Hydrothermal synthesis of spindle structure copper ferrite-graphene oxide nanocomposites for enhanced photocatalytic dye degradation and in-vitro antibacterial activity

In this study, a one-step hydrothermal approach was used to make pure magnetic copper ferrite (CuFe2O4) and copper ferrite-graphene oxide (CuFe2O4-rGO) nanocomposites (NCs) and spinel structure CuFe2O4 with a single phase of tetragonal CuFe2O4-rGO-NCs was confirmed by the XRD. Then, characterization of CuFe2O4-rGO-NCs was done using ng Raman spectroscopy, FT-IR, TGA-DTA, EDS, SEM, and TEM. The synthesized NCs was exposed to UV light to evaluate its photocatalytic activity for the degradation of methylene blue (MB) and rhodamine B (RhB) with CuFe2O4 and CuFe2O4-rGO-NCs, respectively. The catalyst CuFe2O4-rGO-NCs provided higher degradation of MB (94%) than for RhB (86%) under UV light irradiation compared to CuFe2O4. Further, the antibacterial activities of CuFe2O4-NPs and CuFe2O4-rGO-NCs were tested against Gram-negative and -positive bacterial pathogens such as Vibrio cholera (V. cholera); Escherichia coli (E. coli); Pseudomonas aeruginosa (P. aeruginosa); Bacillus subtilis (B. subtilis); Staphylococcus aureus (S. aureus); and Staphylococcus epidermidis (S. epidermidis) by well diffusion method. At 100 μg/mL concentrations of CuFe2O4-rGO-NCs, maximal growth inhibition was shown against E. coli (18 mm) and minimum growth inhibition against S. epidermidis (12 mm). This study suggests that CuFe2O4-rGO-NCs as a high-efficacy antibacterial material and plays an important role in exhibiting higher sensitivity depending on concentrations. The results encourage that the synthesized CuFe2O4-rGO-NCs can be used as a promising material for the antibacterial activity and also for dye degradation in the water/wastewater treatment plants.

Synthesis of mesoporous Ag/α-Fe2O3/TiO2 heterostructures with enhanced and accelerated photo/-catalytic reduction of 4-nitrophenol

4-Nitrophenol (4-NP) is reported to originate disadvantageous effects on the human body collected from industrial pollutants; therefore, the detoxification of 4-NP in aqueous contamination is strongly recommended. In this study, the heterojunction mesoporous α-Fe₂O₃/TiO₂ modulated with diverse Ag percentages has been constructed via a sol-gel route in the occurrence of a soft template P123. The formation of biphasic crystalline TiO₂ anatase and brookite phases has been successfully achieved with the average 10 nm particle sizes. The photo/-catalytic reduction of 4-NP has been performed utilizing NaBH₄ as a reducing agent with and without visible illumination. All Ag/Fe₂O₃/TiO₂ nanocomposites exhibited significantly higher photo/-catalytic reduction efficiency than pure Fe₂O₃, TiO₂ NPs, and Fe₂O₃/TiO₂ nanocomposite. 2.5% Ag/Fe₂O₃/TiO₂ nanocomposite was considered the highest and superior photocatalytic reduction efficiency, and it almost achieved 98% after 9 min. Interestingly, the photocatalytic reduction of 4-NP was accelerated 9 times higher than the catalytic reduction over 2.5% Ag/Fe₂O₃/TiO₂; its rate constant value was 709 and 706 times larger than pure TiO₂ and Fe₂O₃ NPs, respectively. The enhanced photocatalytic reduction ability of Ag/Fe₂O₃/TiO₂ nanocomposite might be referred to as significantly providing visible light absorption and a large surface area, and it can upgrade the effective separation and mobility of electron holes. The stability of the synthesized catalysts exhibited that the obtained catalysts can undergo a slight decrease in reduction efficiency after five successive cycles. This approach highlights a novel route for constructing ternary nanocomposite systems with high photo/-catalytic ability.

Fabrication of Copper(II)-Coated Magnetic Core-Shell Nanoparticles Fe3O4@SiO2: An Effective and Recoverable Catalyst for Reduction/Degradation of Environmental Pollutants

In this work, we report the synthesis of a magnetically recoverable catalyst through immobilizing copper (II) over the Fe3O4@SiO2 nanoparticles (NPs) surface [Fe3O4@SiO2-L–Cu(II)] (L = pyridine-4-carbaldehyde thiosemicarbazide). Accordingly, synthesized catalysts were determined and characterized by energy dispersive X-ray spectrometry (EDS), X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FT-IR), vibrating sample magnetometer (VSM), field emission scanning electron microscopy (FESEM), and thermogravimetric-differential thermal analysis (TG-DTA) procedures. The [Fe3O4@SiO2-L–Cu(II)] was used for the reduction of Cr(VI), 4-nitrophenol (4-NP) and organic dyes such as Congo Red (CR) and methylene blue (MB) in aqueous media. Catalytic performance studies showed that the [Fe3O4@SiO2–L–Cu(II)] has excellent activity toward reduction reactions under mild conditions. Remarkable attributes of this method are high efficiency, removal of a homogeneous catalyst, easy recovery from the reaction mixture, and uncomplicated route. The amount of activity in this catalytic system was almost constant after several stages of recovery and reuse. The results show that the catalyst was easily separated and retained 83% of its efficiency after five cycles without considerable loss of activity and stability.

Immobilization of GOx Enzyme on SiO2-Coated Ni-Co Ferrite Nanocomposites as Magnetic Support and Their Antimicrobial and Photocatalytic Activities

The present study used a sol-gel auto-combustion approach to make silica (SiO2)-coated Ni-Co ferrite nanocomposites that would be used as a platform for enzyme immobilization. Using glutaraldehyde as a coupling agent, glucose oxidase (GOx) was covalently immobilized on this magnetic substrate. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), high-resolution transmission electron microscopy (HRTEM), and fourier transform infrared spectroscopy (FTIR) was used to determine the structural analysis and morphology of Ni-Co ferrite/SiO2 nanocomposites. FTIR spectra confirmed the binding of GOx to Ni-Co ferrite/SiO2 nanocomposites, with a loading efficiency of around 85%. At alkaline pH and higher temperature, the immobilized GOx enzyme exhibited increased catalytic activity. After 10 times of reuses, it still had 69% catalytic activity. Overall, the immobilized GOx displayed higher operational stability than the free enzyme under severe circumstances and was easily recovered by magnetic separation. With increased doping concentration of the nanocomposites, the photocatalytic activity was assessed using a degradation process in the presence of methylene blue dye under UV light irradiation, which revealed that the surface area of the nanocomposites with increased doping concentration played a significant role in improving photocatalytic activity. The antibacterial activity of Ni-Co ferrite/SiO2 nanocomposites was assessed using the agar well diffusion method against Escherichia coli, a gram-negative bacteria (ATCC 25922). Consequently, it was revealed that doping of Ni2+ and Co2+ in Fe2O4/SiO2 nanocomposites at varied concentrations improved their antibacterial properties.

Fabrication and Application of Photocatalytic Composites and Water Treatment Facility Based on 3D Printing Technology

Currently, the degradation of organic pollutants in wastewater by photocatalytic technology has attracted great attention. In this study, a new type of 3D printing material with photocatalytic activity was first prepared to print a water treatment equipment, and then a layer of silver-loaded TiO2 was coated on the equipment to further improve the catalytic degradation performance. The composite filaments with a diameter of 1.75 ± 0.05 mm were prepared by a melt blending method, which contained 10 wt% of modified TiO2 and 90 wt% of PLA. The silver-loaded TiO2 was uniformly coated on the equipment through a UV-curing method. The final results showed that those modified particles were uniformly dispersed in the PLA matrix. The stable printing composite filaments could be produced when 10 wt% TiO2 was added to the PLA matrix. Moreover, the photocatalytic degradation performance could be effectively improved after 5 wt% of silver loading was added. This novel facility showed good degradability of organic compounds in wastewater and bactericidal effect, which had potential applications for the drinking water treatment in the future.

Utilization of induction furnace steel slag based iron oxide nanocomposites for antibacterial studies

Metals and metal oxide-based nanocomposites play a significant role over the control of microbes. In this study, antibacterial activity of iron oxide (Fe2O3) nanocomposites based on induction furnace (IF) steel slag has been carried out. IF steel slag is an industrial by-product generated from secondary steel manufacturing process and has various metal oxides which includes Al2O3 (7.89%), MnO (5.06), CaO (1.49%) and specifically Fe2O3 (14.30%) in higher content along with metalloid SiO2 (66.42). Antibacterial activity of iron oxide nanocomposites has been revealed on bacterial species such as Micrococcus luteus, Bacillus subtilis and Staphylococcus aureus. Micrococcus luteus has undergone maximum zone of inhibition (ZOI) of 12 mm for 10 mg/mL concentration of steel slag iron oxide nanocomposite. Growth inhibitory kinetics of bacterial species has been studied using ELISA microplate reader at 660 nm by varying the concentration of steel slag iron oxide nanocomposites. The results illustrate that IF steel slag is a potential material and can be utilized in building materials to increase the resistance against biodeterioration.

Graphic abstract

Ag-doped magnetic metal organic framework as a novel nanostructured material for highly efficient antibacterial activity

In the last decades, numerous attempts have been made to prevent microbial pollution spreading, using antibacterial agents. Zeolitic imidazolate framework-8 (ZIF-8) belongs to a subgroup of metal organic frameworks (MOFs) merits of attention due to the zinc ion clusters and its effective antibacterial activity. In this work, Ag-doped magnetic microporous γ-Fe₂O₃@SiO₂@ZIF-8-Ag (FSZ-Ag) was successfully synthesized by a facile methodology in room temperature and used as an antibacterial agent against the growth of the Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus bacteria. Several characterization methods were applied to analyze the properties of the materials, and the results confirmed the accuracy of the synthesis procedure. Silver ions have employed to enhance the efficiency of antibacterial activity. As the results illustrated, FSZ-Ag nanostructured material had superior performance to inactive E. coli and S. aureus in growth inhibition test in liquid media. The best antibacterial activity as minimum inhibitory concentration (MIC) was 100 mg/L of FSZ-Ag against both bacteria. Leaching rates of silver ions showed that 80% of Ag released in the solutions, which was responsible for inhibiting the growth of bacteria. Also, fluorescence microscopy was used to investigate bacterial viability after 20 h contacting FSZ-Ag to distinguish live and dead bacteria by staining with DAPI and PI fluorescence stains. This novel magnetic nanostructured material is an excellent promising candidate to use in biological applications as high potential bactericidal materials.

Fabrication and Characterization of Polysorbate/Ironmolybdophosphate Nanocomposite: Ion Exchange Properties and pH-responsive Drug Carrier System for Methylcobalamin

Background:

Nanocomposites are of great interest due to their competency to show multifunctional properties. They have been recently given much attention due to their credibility to offer the synergistic feature of organic material with those of inorganic constituents. Different types of nanocomposites have been prepared to date and are being used for different applications. The delivery of drugs in the human body at a particular site was one of the major problems in the medicinal field. The nanocomposite formulations can be used to provide controlled release and they can be combined with ligands for targeted drug delivery. Applications of the nanocomposites as ion exchangers are also increasing at a faster rate. Due to this, they help in the softening of the water. They can also be easily recharged by washing them with a solution containing a high concentration of sodium ions. In the present paper, we have worked on the synthesis and applications of the polysorbate/ironmolybdophosphate (PS/FMP) nanocomposite.

Methods:

Polysorbate/ironmolybdophosphate (PS/FMPS) was synthesized by co-precipitation method in the presence of polysorbate. The material was well characterized using X-ray diffraction (XRD) analysis, Fourier transform infrared spectroscopy, (FTIR) scanning transmission microscopy (SEM), and transmission electron microscopy (TEM). Physicochemical properties of material were studied in detail. Drug delivery behavior of polysorbate/ironmolybdophosphate was investigated by using methylcobalamin as a test drug.

Results:

The polysorbate/ironmolybdophosphate nanocomposite show enhanced Na+ ion exchange capacity of 2.1 meq/g. It has been revealed that PS/FMP nanocomposite was thermally stable as it retained the ion exchange capacity of 40.4 % at 400°C. An optimum concentration of sodium nitrate (eluent) was found to be 1.0 M for the complete removal of H+ ions from the PS/FMP column. The optimum volume of sodium nitrate (eluent) was found to be 230 mL. The FTIR spectra showed the changes in intensities of characteristic peaks in PS/FMP and in drug loaded on PS/FMP nanocomposite. The characteristic peak at 1043-1061 cm-1 was observed for ionic phosphate stretching, 560-567 cm-1 for iron group and 959 cm-1 due to molybdate present in the material. The additional peak at 3390 cm-1 and 1711 cm-1 were due to -OH and C=O stretching due to the presence of these groups in the structure of polysorbate. The peak present at 430 cm-1 might be due to the presence of Co-O stretching of methylcobalamin. The XRD results confirmed the semicrystalline structure of FMP and PS/FMP. Scanning electron micrographs results revealed the beaded surface of FMP changes to fibrous surface in case of PS/FMP nanocomposite. The TEM images indicate the appearance of smooth surfactant layer on the surface of FMP. The size of the nanocomposite is between 10- 70 nm. The drug loading efficiency and encapsulation efficiency were found to be 35.2%. and 60.4%, respectively. The cumulative drug release of methylcobalamin was studied for the PS/FMP nanocomposite. The order of drug release was found to be pH 9.4 (54.6%) > pH 7.4 (46.4%) > saline (pH 5.7) (36.2%) > pH 2.2 (33.9%). The release at pH 9.4 was higher. As the pH of medium changes from acidic to basic i.e. 2.2 - 9.4, there is an appreciable increase in drug release from the PS/FMP nanocomposite due to the presence of more OH- ions resulting in neutralization of cationic nanocomposite and thus increasing the rate of drug release by ion exchange process and matrix deterioration.

:

The novel nanocomposite PS/FMP has been synthesized by a simple co-precipitation method. The increase in Na+ ion exchange capacity for nanocomposite is due to the binding of organic part (Polysorbate) with inorganic ironmolybdophosphate. The physiochemical properties of PS/FMP were found to be superior. Fourier transform infrared spectra of PS/FMP and drug loaded PS/FMP confirmed the formation of materials. The SEM results indicated the surface of synthesized FMP is bead-like appearance whereas the beaded surface of FMP changes to fibrous surface on the addition of polysorbate thus indicated the fabrication of nanocomposite. The cumulative drug release of methylcobalamin was studied and the order of drug release was found to be pH 9.4 > pH 7.4 > saline (pH 5.7) > pH 2.2. Thus PS/FMP is a promising multifunctional nanocomposite.

A simple and effective synthesis of magnetic γ-Fe2O3@SiO2@TiO2-Ag microspheres as a recyclable photocatalyst: dye degradation and antibacterial potential

PURPOSE AND METHODS

In this study, an effective technique for synthesizing γ-Fe₂O₃@SiO₂@TiO₂-Ag magnetically separable photocatalyst was introduced by combining co-precipitation, sol-gel, and photo-deposition methods. A series of analyses including FTIR, SEM, EDS, XRD, and VSM were applied to characterize the prepared materials and the investigations on photocatalytic activity of the prepared composites were accomplished.

RESULTS

Compared to bare γ-Fe₂O₃@SiO₂@TiO₂, the Ag-doped composite was more active in terms of photocatalytic characteristics. By applying γ-Fe₂O₃@SiO₂@TiO₂-Ag, the decomposition rate of the Basic blue 41 reached to about 94% after 3 h of UV irradiation; this rate was 63% for pure γ-Fe₂O₃@SiO₂@TiO₂. The results indicated that the dye degradation kinetics followed first-order kinetic model. During the five cycles of separation, it was observed that the Ag-doped composite was greatly effective and stable in terms of recycling. Moreover, the results indicated that antibacterial activity of γ-Fe₂O₃@SiO₂@TiO₂-Ag was remarkably stronger than that of pure Fe₂O₃@SiO₂@TiO₂ particles.

CONCLUSION

It was concluded that by modifying magnetic TiO₂ by silver nanoparticles, charge separation was eased by catching photo-generated electrons, resulted in an enhanced photo- and biological activity. Graphical abstract.

One-step synthesis of magnetic-TiO2-nanocomposites with high iron oxide-composing ratio for photocatalysis of rhodamine 6G

In the study, a facile one-step method for synthesizing magnetic-TiO2-nanophotocatalysts was developed. With the same composing ratio of 0.5 and 0.35 (Fe:Ti, mole:mole), we prepared two types of magnetic-TiO2-nanocomposites as one-step synthesized FexOy-composed TiO2 (FexOy/TiO2-0.5 and FexOy/TiO2-0.35) and two-step synthesized core-shell FexOy@TiO2 (FexOy@TiO2-0.5 and FexOy@TiO2-0.35), and tested their performance in rhodamine 6G (R6G) photodegradation. X-ray diffraction (XRD) analysis showed that FexOy@TiO2-0.5 has the smallest crystallite size (16.8 nm), followed by FexOy@TiO2-0.5 (18.4 nm), FexOy/TiO2-0.35 (21.0 nm) and FexOy/TiO2-0.5 (19.0 nm), and X-ray photoelectron spectroscopy (XPS) suggested the decreasing percentage of Fe3O4 from 52.1% to 36.7%-47.2% after Ti-deposition treatment. The saturated magnetisms followed the order: FexOy@TiO2-0.5 > FexOy@TiO2-0.35 > FexOy/TiO2-0.5 > FexOy/TiO2-0.35. R6G photodegradation followed the first order kinetics and was slightly influenced by pH but significantly affected by initial photocatalyst concentration. FexOy/TiO2-0.35 achieved the highest removal efficiency for R6G (92.5%), followed by FexOy@TiO2-0.35 (88.97%), FexOy@TiO2-0.5 (60.49%) and FexOy/TiO2-0.5 (48.06%). Additionally, all these magnetic-TiO2-nanocomposites had satisfied magnetic recoverability and exhibited laudable reusability after 5-times reuse, even achieving higher R6G removal efficiencies from 97.30% to 98.47%. Our one-step method took only 75 min for nanocomposite synthesis, 90 min less than conventional two-step method, showing its feasibility as a practical method for magnetic-TiO2-nanocomposite synthesis in industrial application.

TiO2 nanotubes/Ti plates modified by silver–benzene with enhanced photocatalytic antibacterial properties

A novel Ag/Benzene-Mod/TiO₂ nanotubes/Ti plate was fabricated via photo-modification by benzene, followed by electrodeposition of Ag on the TiO₂ nanotubes/Ti plate.

Tunable Ag@SiO2 core–shell nanocomposites for broad spectrum antibacterial applications

Silica encapsulated silver nanoparticle core–shell nanocomposites of tunable dimensions were synthesised via a one-pot reverse microemulsion route to achieve controlled release of Ag⁺ ions for broad spectrum antibacterial application.

Advanced removal of C. famata in bioaerosols by simultaneous adsorption and photocatalytic oxidation of Cu-doped TiO2/PU under visible irradiation

Polyurethane (PU), a honeycomb structure material, was used as a substrate onto which TiO₂ and Cu-TiO₂ were deposited in order to integrate the adsorption property to the photocatalysts. TiO₂ deposited on PU (TiO₂/PU) and Cu-doped TiO₂ deposited on PU (Cu-TiO₂/PU) were synthesized and applied to the removal of Candida famata (C. famata), a frequently encountered airborne yeast. The removal capacities of C. famata by PU, TiO₂/PU and Cu-TiO₂/PU were 1.5 × 10⁵, 3.2 × 10⁵ and 6.9 × 10⁵ (CFU/cm³) under dark condition and 1.5 × 10⁵, 3.3 × 10⁵ and 1.8 × 10⁶ (CFU/cm³) under visible light irradiation, respectively. PU and TiO₂/PU seemed to exhibit only an adsorption ability for removing C. famata in aerosols under both dark and visible light. The C. famata removal capacity of Cu-TiO₂/PU under visible light was increased 2.6-fold compared to that under dark condition. This significant increase was attributed to the Cu dopant, which enhanced the electron-hole separation efficiency and capacity of TiO₂, resulting in the high photocatalytic activity of Cu-TiO₂/PU under visible light.

Synthesis of urchin-like Fe3O4@SiO2@ZnO/CdS core–shell microspheres for the repeated photocatalytic degradation of rhodamine B under visible light

Magnetically retrievable Fe₃O₄@SiO₂@ZnO/CdS microspheres with a well-designed core–shell structure and excellent visible-irradiation photocatalytic performance were successfully synthesized.

Novel electrospun bilayered composite fibrous membrane endowed with tunable and simultaneous quadrifunctionality of electricity–magnetism at one layer and upconversion luminescence–photocatalysis at the other layer

A novel [PANI/Fe₃O₄/PAN]/[Bi₂WO₆:Yb³⁺,Er³⁺/PAN] bilayered composite, fibrous membrane with tunable quadrifunctionality of electricity, magnetism, upconversion luminescence and photocatalysis has been successfully synthesized.

Recent progress in magnetic iron oxide-semiconductor composite nanomaterials as promising photocatalysts

Photocatalytic degradation of toxic organic pollutants is a challenging tasks in ecological and environmental protection. Recent research shows that the magnetic iron oxide-semiconductor composite photocatalytic system can effectively break through the bottleneck of single-component semiconductor oxides with low activity under visible light and the challenging recycling of the photocatalyst from the final products. With high reactivity in visible light, magnetic iron oxide-semiconductors can be exploited as an important magnetic recovery photocatalyst (MRP) with a bright future. On this regard, various composite structures, the charge-transfer mechanism and outstanding properties of magnetic iron oxide-semiconductor composite nanomaterials are sketched. The latest synthesis methods and recent progress in the photocatalytic applications of magnetic iron oxide-semiconductor composite nanomaterials are reviewed. The problems and challenges still need to be resolved and development strategies are discussed.

Synthesis, characterization and photocatalytic activity of magnetically separable γ-Fe2O3/N,Fe codoped TiO2 heterojunction for degradation of Reactive Blue 4 dye

Nanocrystalline undoped, N-doped and N,Fe codoped TiO₂ have been synthesized using a sol–gel method for the photocatalytic degradation of Reactive Blue 4 dye under visible light, with N,Fe codoped TiO₂ exhibiting the best activity.

Highly reactive {001} facets of TiO2-based composites: synthesis, formation mechanism and characterization

Titanium dioxide (TiO2) is one of the most widely investigated metal oxides due to its extraordinary surface, electronic and catalytic properties. However, the large band gap of TiO2 and massive recombination of photogenerated electron-hole pairs limit its photocatalytic and photovoltaic efficiency. Therefore, increasing research attention is now being directed towards engineering the surface structure of TiO2 at the most fundamental and atomic level namely morphological control of {001} facets in the range of microscale and nanoscale to fine-tune its physicochemical properties, which could ultimately lead to the optimization of its selectivity and reactivity. The synthesis of {001}-faceted TiO2 is currently one of the most active interdisciplinary research areas and demonstrations of catalytic enhancement are abundant. Modifications such as metal and non-metal doping have also been extensively studied to extend its band gap to the visible light region. This steady progress has demonstrated that TiO2-based composites with {001} facets are playing and will continue to play an indispensable role in the environmental remediation and in the search for clean and renewable energy technologies. This review encompasses the state-of-the-art research activities and latest advancements in the design of highly reactive {001} facet-dominated TiO2via various strategies, including hydrothermal/solvothermal, high temperature gas phase reactions and non-hydrolytic alcoholysis methods. The stabilization of {001} facets using fluorine-containing species and fluorine-free capping agents is also critically discussed in this review. To overcome the large band gap of TiO2 and rapid recombination of photogenerated charge carriers, modifications are carried out to manipulate its electronic band structure, including transition metal doping, noble metal doping, non-metal doping and incorporating graphene as a two-dimensional (2D) catalyst support. The advancements made in these aspects are thoroughly examined, with additional insights related to the charge transfer events for each strategy of the modified-TiO2 composites. Finally, we offer a summary and some invigorating perspectives on the major challenges and new research directions for future exploitation in this emerging frontier, which we hope will advance us to rationally harness the outstanding structural and electronic properties of {001} facets for various environmental and energy-related applications.

Template and silica interlayer tailorable synthesis of spindle-like multilayer α-Fe2O3/Ag/SnO2 ternary hybrid architectures and their enhanced photocatalytic activity

Our study reports a novel iron oxide/noble metal/semiconductor ternary multilayer hybrid structure that was synthesized through template synthesis and layer-by-layer deposition. Three different morphologies of α-Fe2O3/Ag/SiO2/SnO2 hybrid architectures were obtained with different thicknesses of the SiO2 interlayer which was introduced for tailoring and controlling the coupling of noble metal Ag nanoparticles (NPs) with the SnO2 semiconductor. The resulting samples were characterized in terms of morphology, composition, and optical property by various analytical techniques. The as-obtained α-Fe2O3/Ag/SiO2/SnO2 nanocomposites exhibit enhanced visible light or UV photocatalytic abilities, remarkably superior to commercial pure SnO2 products, bare α-Fe2O3 seeds, and α-Fe2O3/SnO2 nanocomposites. Moreover, the sample of α-Fe2O3/Ag/SiO2/SnO2 also exhibits good chemical stability and recyclability because it has higher photocatalytic activity even after eight cycles. The origin of enhanced photocatalytic activity on the multilayer core-shell α-Fe2O3/Ag/SiO2/SnO2 nanocomposites was primarily ascribed to the coupling between noble metal Ag and the two semiconductors Fe2O3 and SnO2, which are proven to be applied in recyclable photocatalysis.

Branch-like hierarchical heterostructure (α-Fe2O3/TiO2): a novel sensing material for trimethylamine gas sensor

A novel hierarchical heterostructure of α-Fe2O3 nanorods/TiO2 nanofibers with branch-like nanostructures was fabricated using a simple two-step process called the electrospinning technique and hydrothermal process. A high density of α-Fe2O3 nanorods (about 200 nm in diameter) was uniformly deposited on a TiO2 nanofibers backbone. The phase purity, morphology, and structure of hierarchical heterostructures are investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and energy-dispersive X-ray (EDX) analysis. The highly branched α-Fe2O3/TiO2 heterostructures provided an extremely porous matrix and high specific surface area required for high-performance gas sensors. Different nanostructured α-Fe2O3/TiO2 heterostructures are also investigated by controlling the volume ratio of the reactants. The α-Fe2O3/TiO2 heterostructures with a proper mixture ratio of the reactants sensor exhibit obviously enhanced sensing characteristics, including higher sensing response, lower operating temperature, faster response speed, and better selectivity in comparison with other ones. Moreover, the α-Fe2O3/TiO2 heterostructures sensor also exhibits excellent sensing performances compared with α-Fe2O3 nanorods and TiO2 nanofibers sensors. Thus, the combination of TiO2 nanofibers backbone and α-Fe2O3 nanorods uniformly decorated endows a fascinating sensing performance as a novel sensing material with high response and rapid responding and recovering speed.

Enhanced visible light photocatalytic activity of interlayer-isolated triplex Ag@SiO2@TiO2 core-shell nanoparticles

Herein, we demonstrate the design and fabrication of a well dispersed triplex Ag@SiO2@TiO2 core-shell photocatalyst, which shows enhanced visible light photocatalytic activity due to the plasmonic field of the inner Ag core. The SiO2 interlayer is coated on the Ag core by a sol-gel process to prevent oxidation of Ag and adjusting the plasmonic field. The Ag@SiO2@TiO2 nanoparticles with systematic variation of the SiO2 interlayer thickness of 2, 4, 8, 20 nm and TiO2 shell thickness of 2, 10, 20, 40 nm are prepared. The enhancement of the photocatalytic efficiency increases with decreased SiO2 thickness. Nanoparticles with a 2 nm SiO2 interlayer and a 20 nm TiO2 shell exhibited the best photocatalytic performance, ca. 31 times larger in photocatalytic activity and ca. 38 times larger in photocurrent density than P25 under visible light. A brief mechanism relating the plasmon resonance energy transfer from Ag to TiO2 and scattering is proposed. Such an intriguing photocatalyst may find significant applications in various fields.