TiO2 Interlayer Research Articles

Regulating the interfacial structure in percolating graphite nanoplate/PVDF composites via TiO2 as an interlayer towards meliorative dielectric performances

Polymer nanocomposites combining large dielectric permittivity (ε′) but low loss along with high breakdown strength (Eb) have garnered significant attention in the fields of electronic devices and power systems. To concurrently accomplish these desirable performances in pristine graphite nanoplates (GNP)/poly(vinylidene fluoride, PVDF) composites, the GNP were initially encased by a layer of anatase-type titanium dioxide (TiO2) shell, and then incorporated into PVDF to investigate the effect of TiO2 interlayer on the dielectric properties of the nanocomposites, specifically in relation to the thickness of the TiO2 shell and the nanofiller concentration. The TiO2 shell acts as a barrier layer prohibiting the electronic percolating, thus significantly reducing the dielectric loss and leakage conductivity of the GNP@TiO2/PVDF. Moreover, it not only alleviates the strong dielectric mismatch between GNP and PVDF, which restrains local electric field distortion, but also introduces charge traps, raising the energy barrier height for captured charge detrapping and preventing the growth of electric trees and subsequently promoting the Eb. For example, the PVDF with 20 wt% of GNP@TiO2 exhibited good comprehensive dielectric performances: ε′ of 50.63, loss factor of 0.071 (100 Hz) and Eb of 7.89 kV/mm. Additionally, tailoring the TiO2’s thickness can simultaneously modulate the overall dielectric parameters in the GNP@TiO2/PVDF. Theoretical fitting of experimental data via Havriliak-Negami equation uncovers the underlying polarization mechanism and the interlayer’s impact on charge migration. This work provides an efficient method for developing and producing polymeric nanodielectrics that simultaneously incorporate increased Eb with high ε′ but low loss for potential use in power devices and microelectronic devices.

Promoting Photon-to-Chemical Conversion through a Dielectric Antenna-Hybrid Bilayered Reactor Configuration.

The application of scattered light via an antenna-reactor configuration is promising for converting thermocatalysts into photocatalysts. However, the efficiency of dielectric antennas in photon-to-chemical conversion remains suboptimal. Herein, we present an effective approach to promote light utilization efficiency by designing dielectric antenna-hybrid bilayered reactors. Experimental studies and finite-difference time-domain simulations demonstrate that the engineered SiO2-carbon/metal dielectric antenna-hybrid bilayered reactors exhibit a synergy of absorption superposition and electric field confinement between carbon and metals, leading to the improved absorption of scattered light, upgraded charge carriers density, and ultimately promoted photoactivity in hydrogenating chlorobenzene with an average benzene formation rate of 18 258 μmol g-1 h-1, outperforming the reported results. Notably, the carbon interlayer proves to be more effective than the commonly explored dielectric TiO2 interlayer in boosting the benzene formation rate by over 3 times. This research paves the way for promoting near-field scattered photon-to-chemical conversion through a dielectric antenna-hybrid reactor configuration.

IrO2 nanoparticles supported on submicrometer-sized TiO2 as an efficient and stable coating for oxygen evolution reaction

The sluggish kinetics of the oxygen evolution reaction (OER) refers to the major contributor to the energy losses in electrowinning of metals. Improving the stability in the long term and activity of the electrocatalyst for OER take on a critical significance in reducing the energy consumption. An efficient and stable OER electrode (named as Ti/SMST/IrO2 electrode) was prepared in this study by supporting IrO2 nanoparticles on the surface of the submicrometer-sized TiO2 (SMST) interlayer. The obtained results indicated that the IrO2 nanoparticles approximately 14 nm in size were supported onto the submicrometer-sized TiO2 particles’ surface and exhibited a cactus-like morphology. The Ti/SMST/IrO2 electrode with the SMST interlayer prepared at 450 °C exhibited the highest electrocatalytic activity in terms of OER for its largest active surface area. This electrode showed an overpotential of 350 mV at a current density of 50 mA cm−2 and displayed a remarkable electrochemical stability of 443 h at a high current density of 2 A cm−2 in H2SO4 solution without significant change in OER activity. The prepared Ti/SMST/IrO2 electrode with high electrocatalytic performance is considered one of the promising electrodes for OER.

Current transport mechanisms of metal/TiO2/β-Ga2O3 diodes

β-Ga2O3 is of great interest for power electronic devices with efficiency beyond current generation Si, 4H-SiC, and GaN devices due to its large breakdown electric field of ∼8 MV/cm. However, taking advantage of this large field strength in power diodes requires device engineering to reduce leakage current that arises at high electric fields. In this work, we elucidate the current transport mechanisms of metal/TiO2/β-Ga2O3 diodes, showing that thermionic emission is an excellent descriptor of current in forward and reverse bias. It is shown that tunneling current is greatly suppressed, and consequently, that the diodes with the TiO2 interlayer can block orders of magnitude more current than Schottky barrier diodes with the same barrier heights. Finally, a 1200 V diode structure is designed based on the derived transport models, and calculated on- and off-state current characteristics closely align with those of state-of-the-art 4H-SiC commercial devices, indicating that this diode structure is ready to enable the realization of β-Ga2O3 power diodes.

Co-fired tri-layered Mg(Nb0.98Ti0.01W0.01)2O6–Mg doped TiO2–Mg(Nb0.98Ti0.01W0.01)2O6 ceramics with high temperature stability and low dielectric loss

In order to tailor the microwave dielectric performances of Mg(Nb0.98Ti0.01W0.01)2O6–TiO2 composite ceramics, Mg(Nb0.98Ti0.01W0.01)2O6–Mg doped TiO2–Mg(Nb0.98Ti0.01W0.01)2O6 and Mg(Nb0.98Ti0.01W0.01)2O6–TiO2–Mg(Nb0.98Ti0.01W0.01)2O6 tri-layer architectural ceramics with different volume fractions and different TiO2 doping were designed and prepared. This work systematically investigates the crystal structure and microwave dielectric performances of composite ceramics. Raman spectroscopy confirmed the formation of a solid solution at the interface. Raman spectroscopy were used to analyze the ion diffusion behavior at the interface. Based on the law of mixing for composites, the Q×f value of the tri-layer structural ceramics with Mg doped TiO2 interlayer can be increased by nearly 33 % compared with that of the pure TiO2 interlayer. The Mg(Nb0.98Ti0.01W0.01)2O6–Mg doped TiO2–Mg(Nb0.98Ti0.01W0.01)2O6 tri-layer ceramics exhibit remarkably outstanding dielectric performances: εr = 27.5, Q×f = 72,148 GHz, and τf = +6.37 ppm/°C with 0.03 wt% Mg doped TiO2 sintered at 1340 °C for 6 h to achieve a comprehensive optimization of microwave dielectric performances.

Reliable synaptic plasticity of InGaZnO transistor with TiO2 interlayer

We demonstrate an InGaZnO (IGZO)-based synaptic transistor with a TiO2 buffer layer. The structure of the synaptic transistor with TiO2 inserted between the Ti metal electrode and an IGZO semiconductor channel O2 trapping layer produces a large hysteresis window, which is crucial for achieving synaptic functionality. The Ti/TiO2/IGZO synaptic transistor exhibits reliable synaptic plasticity features such as excitatory post-synaptic current, paired-pulse facilitation, and potentiation and depression, originating from the reversible charge trapping and detrapping in the TiO2 layer. Finally, the pattern recognition accuracy of Modified National Institute of Standards and Technology handwritten digit images was modeled using CrossSim simulation software. The simulation results present a high image recognition accuracy of ∼89%. Therefore, this simple approach using an oxide buffer layer can aid the implementation of high-performance synaptic devices for neuromorphic computing systems.

Comparison of Al/TiO2/p-Si and Al/ZnO/p-Si photodetectors

The importance of the photodetectors has grown due to their potential in the automation system and optical communications. We fabricated Al/TiO2/p-Si and Al/ZnO/p-Si Schottky-type photodetectors. TiO2 and ZnO interlayers were grown by atomic layer deposition (ALD). The photodetection properties of these devices were studied and compared by I–V and I-t measurements for various light power densities and various wavelengths. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectra were employed to determine morphological and elemental analysis of the TiO2 and ZnO interlayers. While the SEM images showed smooth surfaces, EDX spectra approved successful synthesis of the TiO2 and ZnO interlayers with good stoichiometry. The diode parameters such as ideality factor, series resistance and barrier height values were calculated and compared in detail. The responsivity and detectivity of the fabricated photodetectors were determined as a function of illumination power density and wavelength. The responsivity values of the Al/TiO2/p-Si and Al/ZnO/p-Si photodetectors were determined as 0.02 and 0.76 A/W, respectively. Both photodetectors exhibited good performance for visible light. However, Al/ZnO/p-Si photodetector reached 173.08% external quantum efficiency (EQE) for 550 nm. According to results, Al/ZnO/p-Si photodetector exhibited better detection performance than Al/TiO2/p-Si.

Plasmonic Nanocrystal Assembly-Semiconductor Hybrids for Boosting Visible to Near-Infrared Photocatalysis.

Plasmonic metal-semiconductor hybrid photocatalysts have received much attention because of their wide light harvesting range and efficient charge carrier generation capability originating from plasmon energy transfer. Here, we introduce a plasmonic metal-semiconductor hybrid nanostructure consisting of a Au core-satellite assembly and crystalline TiO2. The formation of Au@TiO2-Au core-satellite assemblies using TiO2 as a spacer and the subsequent growth of outer TiO2 shells on the core-satellite assemblies, followed by calcination, successfully generated Au core-satellite assembly@TiO2 nanostructures. Exquisite control over the growth of the TiO2 interlayer enabled the regulation of the gap distance between the core and satellite Au nanocrystals within the same hybrid morphology. Due to the structural controllability of the present approach, the gap-distance-dependent plasmonic and photocatalytic properties of the hybrid nanostructures could be explored. The nanostructures possessing the most closely arranged Au nanocrystals showed high photocatalytic activity under visible to near-infrared light irradiation, which can be attributed to strong plasmon coupling between the core and satellite Au nanocrystals that can expedite the formation of intense plasmon energy and its transfer to TiO2.

Vertical metal–dielectric–semiconductor diode on (001) β-Ga2O3 with high-κ TiO2 interlayer exhibiting reduced turn-on voltage and leakage current and improved breakdown

We demonstrate vertical Pt/TiO2/β-Ga2O3 metal–dielectric–semiconductor (MDS) diodes and compare performance with co-fabricated Pt/β-Ga2O3 Schottky diodes (SBDs). The MDS diode exhibits a lower turn-on voltage and leakage current. In addition, the breakdown voltage increased from 548 V for an SBD to 1380 V for a MDS diode. The improvement in the off-state characteristics compared to a SBD while simultaneously reducing on-state losses leads to lower power dissipation at all duty cycles, indicating the great promise of this device architecture for advancing low-loss β-Ga2O3 rectifiers toward material limits.

Functionalization of the Implant Surface Made of NiTi Shape Memory Alloy

To functionalize and improve the biocompatibility of the surface of a medical implant made of NiTi shape memory alloy and used in practice, a clamp, multifunctional layers composed of amorphous TiO2 interlayer, and a hydroxyapatite coating were produced. Electrophoresis, as an efficient method of surface modification, resulted in the formation of a uniform coating under a voltage of 60 V and deposition time of 30 s over the entire volume of the implant. The applied heat treatment (800 °C/2 h) let toa dense, crack-free, well-adhered HAp coating with a thickness of ca. 1.5 μm. and a high crack resistance to deformation associated with the induction of the shape memory effect in the in the deformation range similar to the real implant work after implantation. Moreover, the obtained coating featured a hydrophilic (CA = 59.4 ± 0.3°) and high biocompatibility.

Enhanced high dielectric characteristics tri‐layered structural ceramics for 5G/6G communications

AbstractTri‐layered structural Zn0.997Cu0.003ZrNb2O8–TiO2+ZnO/TiO2+CuO/TiO2–Zn0.997Cu0.003ZrNb2O8 ceramics with different mass fractions of TiO2+ZnO/TiO2+CuO/TiO2 were successfully prepared. The advantages of the multilayered design were completely demonstrated, and the microwave dielectric characteristics were modified by the components of each dielectric layer. In comparison to the random distribution‐type, Zn0.997Cu0.003ZrNb2O8@TiO2+ZnO, this tri‐layered construction could increase the Q f value by approximately 100%. Meanwhile, based on the electronic compensation mechanisms, the Q f value of the tri‐layered structural ceramics with TiO2‐doped interlayer can be increased by nearly 20% compared with that of the pure TiO2 interlayer. The Zn0.997Cu0.003ZrNb2O8–TiO2+ZnO–Zn0.997Cu0.003ZrNb2O8 tri‐layered ceramic exhibited excellent dielectric characteristics ( = 33.75, Q × f = 59 000 GHz, and = +2.27 ppm/°C) with 0.05 wt% TiO2+ZnO sintered at 1240°C for 6 h, and the integrated optimization of microwave dielectric characteristics was achieved. This article provides a strategy for the synthesis of high‐performance microwave dielectric components for application in 5G/6G wireless communication technologies.

MoS2 Transistors with Low Schottky Barrier Contact by Optimizing the Interfacial Layer Thickness

Molybdenum disulfide (MoS2) has attracted great attention from researchers because of its large band gap, good mechanical toughness and stable physical properties; it has become the ideal material for the next-generation optoelectronic devices. However, the large Schottky barrier height (ΦB) and contact resistance are obstacles hampering the fabrication of high-power MoS2 transistors. The electronic transport characteristics of MoS2 transistors with two different contact structures are investigated in detail, including a copper (Cu) metal–MoS2 channel and copper (Cu) metal–TiO2-MoS2 channel. Contact optimization is conducted by adjusting the thickness of the TiO2 interlayer between the metal and MoS2. The metal-interlayer-semiconductor (MIS) structure with a 1.5 nm thick TiO2 layer has a smaller Schottky barrier of 22 meV. The results provide insights into the engineering of MIS contacts and interfaces to improve transistor characteristics.

Polyamide composite nanofiltration membrane modified by nanoporous TiO2 interlayer for enhanced water permeability

The traditional polyamide composite nanofiltration membrane has high selectivity. However, low water permeability is an important problem to be solved. Herein, the conventional polyamide composite nanofiltration (TFC) membrane was modified with nanoporous TiO2 (nTiO2) interlayer through vacuum-assisted strategy for enhanced water permeability. By tuning the nTiO2 nanoparticles loading, the nTiO2 modified TFC membrane with crumpled structure was fabricated. Besides, the thickness of polyamide layer was reduced due to the hydrophilicity and porosity of nTiO2. Because of the larger effective filtration area and thinner polyamide layer, the modified membrane had a permeability of 12.8 L m−2 h−1 bar−1 (increased by 20.8% than that of TFC membrane) and a rejection of 98.2% when filtering Na2SO4 aqueous solution. This work provided a solution for enhanced water permeability and extended the application of TiO2 in the modification of polyamide composite nanofiltration membrane.

Steering the Pathway of Plasmon-Enhanced Photoelectrochemical CO2 Reduction by Bridging Si and Au Nanoparticles through a TiO2 Interlayer.

Photoelectrochemical (PEC) conversion of CO2 in an aqueous medium into high-energy fuels is a creative strategy for storing solar energy and closing the anthropogenic carbon cycle. However, the rational design of catalytic architectures to selectively and efficiently produce a target product such as CO has remained a grand challenge. Herein, an efficient and selective Si photocathode for CO production is reported by utilizing a TiO2 interlayer to bridge the Au nanoparticles and n+ p-Si. The TiO2 interlayer can not only effectively protect and passivate Si surface, but can also exhibit outstanding synergies with Au nanoparticles to greatly promote CO2 reduction kinetics for CO production through stabilizing the key reaction intermediates. Specifically, the TiO2 layer and Au nanoparticles work concertedly to enhance the separation of localized surface plasmon resonance generated hot carriers, contributing to the improved activity and selectivity for CO production by utilizing the hot electrons generated in Au nanoparticles during PEC CO2 reduction. The optimized Au/TiO2 /n+ p-Si photocathode exhibits a Faradaic efficiency of 86% and a partial current density of -5.52mA cm-2 at -0.8 VRHE for CO production, which represent state-of-the-art performance in this field. Such a plasmon-enhanced strategy may pave the way for the development of high-performance PEC photocathodes for energy-efficient CO2 utilization.

Enhanced thermoelectric properties of atomic-layer-deposited ZnO-Based superlattice thin films by tuning the composition and structure of interlayers

Superlattice thin films composed of a lightly Hf-doped ZnO matrix and various periodically inserted interlayers—including TiO2, ZrO2, HfO2, and their combinations, with various thicknesses—were prepared by atomic layer deposition (ALD) and characterized in terms of thermoelectric properties. The effects of interlayer type and thickness on the comprehensive thermoelectric properties of the superlattice films were determined, including electron mobility (μe), electron concentration (ne), electrical conductivity (σ), Seebeck coefficient (S), power factor (PF), thermal conductivity (κ), and ZT value. The TiO2, ZrO2, and HfO2 interlayers provided different potential barriers (HfO2 > ZrO2 ≫ TiO2) and atomic-mass mismatches (HfO2 > ZrO2 > TiO2) with the matrix, resulting in differing trade-off’s among energy filtering (raising S), carrier blocking (lowering σ), and phonon scattering (reducing κ) effects. Favorable balances of the effects were obtained by combining the single-content interlayers into composite interlayers, where the ALD preparation method enabled precise tuning of the interlayer composition and structure for optimal thermoelectric properties of the superlattice films. Specifically, superlattice films with a composite interlayer consisting of an alternating 1 cycle TiO2/1 cycle HfO2 structure at 1.5 nm thickness achieved a maximum of approximately 17-fold increase in ZT over that of bulk ZnO films. The results presented a quantitative guide for designing interlayer structures in superlattice films for enhanced thermoelectric properties.

Microstructure, wettability, and mechanical properties of ADC12 alloy reinforced with TiO2-coated carbon nanotubes

Aluminum matrix composites (AMCs) reinforced by CNTs as lightweight structural materials gain extensive attention. However, the crucial issue limited its application breadth is the poor interfacial bonding between the matrix and CNTs. In this paper, novel TiO2 nanoparticles-coated CNTs (TiO2 @CNTs) fabricated by the alcohol-thermal method were used as the reinforcement to prepare AMCs via high-intensity ultrasonic-assisted casting. The microstructure, wettability, interfacial bonding, and mechanical properties of TiO2 @CNTs/ADC12 composites were investigated in detail. By incorporating TiO2 nanoparticles on the surface of CNTs, the contact angle was reduced from 140.5° to 119°, indicating a significant improvement in the wettability of CNTs to aluminum melt. TEM results revealed that TiO2 nanoparticles homogenously dispersed on the surface of CNTs acted as an interlayer structure between CNTs and matrix, locking the CNTs and improving the CNTs-Al interfacial bonding. The semi-coherent interface was formed at the TiO2/α-Al interface, and the mismatch of (001)TiO2//(100)Al is only 6.52%, indicating a good lattice space matching between TiO2 and α-Al matrix. The TiO2 @CNTs/ADC12 composite with 1.2 wt% TiO2 @CNTs displayed high mechanical properties with yield strength and ultimate tensile strength of 196 MPa and 262 MPa, which were 54% and 29% higher than those of the matrix (127 MPa and 203 MPa), respectively. The better mechanical properties may be attributed to good interfacial bonding caused by the semi-coherent interface created by the TiO2 interlayer, leading to an effective load transfer from matrix to CNTs.

PMMA/High-k Self-assembled TiO2/PMMA Multi-layer Gate Dielectric for P3HT Organic Field Effect Transistors

In this work, a multi-layer structure of poly (methyl methacrylate)/ titanium dioxide/poly (methyl methacrylate) (PMMA/TiO₂ /PMMA; PTP) was proposed as a top-gate insulator for P3HT-based organic field-effect transistors (OFETs). Adding a TiO₂ interlayer as a high dielectric constant (high-k) material into PMMA film enables the modification of the dielectric constant of the multi-layers PTP film. The content of TiO₂ in the PTP film, which can be varied by changing the number of soaking cycles in TiO₂ solution, plays a crucial rule in modifying the dielectric constant of the PTP film. The higher the TiO₂ content used in the PTP film, the higher the dielectric constant of PTP film can be obtained. However, using high TiO₂ content led to a reduction in the dielectric constant of the PTP film due to leakage current induced by the agglomeration of TiO₂. The utilization of the top-gate insulator containing TiO₂ significantly enhanced several P3HT-OFETs characteristics, e.g., an increase in the Ion/Ioff ratio, and a decrease in the threshold voltage. However, the use of the PTP top-gate insulator with a high content of TiO₂ resulted in regressions in the OFETs characteristics, such as a decrease in carrier mobility and reduction in the Ion/Ioff ratio. OFETs operating at the optimum conditions of the PTP gate-insulator, with PTP thickness of 225 nm and RMS roughness of 20.0 nm, provided a dielectric constant of 7.13, a threshold voltage of -8.49 V, a saturation mobility of 2.2× 10-4 cm²V-1s-1, Ion/Ioff ratio of 37.9, and a subthreshold slope of 0.39 V/decade.

Environmentally Friendly Fabrication of Ti/RuO2-IrO2-SnO2-Sb2O5 Anode with In Situ Incorporation of Reduced TiO2 Interlayer

The intensive use of chemical reagents in the pretreatment of Ti substrate and shorter electrode life constrict the wider application of the dimensionally stable anode (DSA). In this study, a simple method was developed to thermally pretreat the Ti substrate in the atmosphere of H2 and N2 (molar ratio 1:5) without chemicals consumption and wastewater discharge. It was found that the reduced TiO2 interlayer could be favorably created at temperature of 750 °C. This rendered Ti/reduced TiO2/RuO2-IrO2-SnO2-Sb2O5 anode with better stability and higher electrocatalytic activity. The accelerated lifetime for Ti/reduced TiO2/RuO2-IrO2-SnO2-Sb2O5 electrode was 65 h with the optimum catalyst loading amount (2.6 ± 0.05 mg cm−2), while it was only 50 h for traditional Ti/RuO2-IrO2-SnO2-Sb2O5 electrode. As compared with the counterparts, Ti/reduced TiO2/RuO2-IrO2-SnO2-Sb2O5 with higher oxygen evolution potential (1.42 V/SCE) and lower chlorine evolution potential (1.12 V/SCE), suggesting higher electro-catalytic activity toward reactive oxidative species formation. The deactivation test indicates that the anode deactivation mainly proceeded via the dissolution of the catalyst layer and then formation of insulated TiO2 on the substrate. Generally, an environmentally friendly Ti substrate pretreatment method was developed and demonstrated promising for upgrading DSA fabrication process in industrial application.

Realizing the impact of the intermediate layer structure on the CO2/CH4 separation performance of carbon molecular sieving membranes: Insights from experimental synthesis and molecular simulation

This work is a continuation of our previous study investigating the role of the intermediate layer in carbon molecular sieve membrane (CMSM) formation and its impact on the gas separation performance. Herein, the effect of key preparation variables of CMS/TiO2 membrane prepared from the polyetherimide (PEI) precursor on the membrane’s structure and CO2/CH4 separation quality was studied. A set of CMS/TiO2/Al2O3 membranes produced under different conditions (pH of the sol-gel for the intermediate TiO2 layer preparation, the TiO2 interlayer thickness and the carbon separation layer thickness) was prepared, characterized by the AFM, FE-SEM and EDXS methods and tested for CO2/CH4 separation efficiency. In addition, a molecular simulation was applied to investigate the effect of intermediate TiO2 layer.All prepared membranes had good separation quality (the separation factor between 37 and 65). The best results for membranes with the thickest TiO2 interlayer prepared at pH = 5 were identified; notably, membrane samples with the thin defect free carbon separation layer achieved the best balance of permeance vs. selectivity and exceeded the Robeson upper bound. The molecular simulation results support the finding of the intermediate layer plays a vital role for the synthesis of gas separation membranes.

The synergistic effects of nanoporous fiber TiO2 and nickel foam interlayer for ultra-stable performance in lithium-selenium batteries

Selenium is an attractive choice of cathode material for lithium-ion batteries because of its high electronic conductivity and high theoretical volumetric capacity. In this report, a Se-TiO2 cathode with a nickel foam interlayer has been designed and tested for lithium-selenium batteries. In this particular architecture, selenium is first mixed with TiO2 nanofibers to form a Se-TiO2 composite by a melt-diffusion process. Next, a nickel foam foil (NFF) is introduced as an interlayer between the electrode and separator. The synthesized Se-TiO2/NFF exhibits reversible discharge capacity of 600.4 mAh g−1 at 0.5C (1C = 675 mA g−1) after 200 cycles, and delivers a discharge capacity as high as 321.3 mAh g−1 even at 30C. This superior electrochemical performance can be ascribed to the synergetic adsorption and fixation of TiO2 and NFF.