Anatase TiO2 Research Articles

Porous TiO2 microspheres containing MgO nanoparticles/epoxy composite with superior thermal conductivity, EMI shielding, and electrical insulation

With the continuous advancement of electronic devices, the amounts of heat as well as electromagnetic (EM) waves generated have increased. Materials with high thermal conductivity and excellent EM interference shielding effectiveness (EMI SE) can be utilized to address this issue. In this work, we synthesized hollow anatase TiO2 microspheres. Through a reaction, MgO nanoparticles were incorporated into the interior of TiO2 microspheres. (H-TiO2/MgO). The heterostructure of the fillers contributed to performance enhancement. TiO2 and MgO particles formed a dual thermal-conduction pathway. H-TiO2/MgO effectively weakened the energy of EM waves upon contact. Additionally, TiO2, MgO, and epoxy all exhibited hydrophilicity. Consequently, the interfacial compatibility between H-TiO2/MgO and epoxy was excellent. They formed strong interfacial interactions by hydrogen bonding. Because of the excellent electrical insulation properties of H-TiO2 and MgO, the composites exhibited superior insulation performance (over 1010 Ω·cm). Our H-TiO2/MgO/Epoxy composites exhibited a maximum thermal conductivity of 7.52 W/m·K, an EMI SE of 64.92 dB, and a tensile strength of 79.10 MPa. Our composites are expected to effectively manage heat and EM waves generated by electronic devices

Adsorption Performance and Photocatalytic Activity of La-TiO2@kaolin Composites

Abstract La-TiO2@kaolin(LTK) composites were prepared via sol-gel method with kaolin, lanthanum nitrate and tetrabutyl titanate as raw materials. The samples were characterized by XRD, SEM/EDS, and UV-Vis. The visible light photocatalytic reduction activity and adsorption performance of samples for Cr(VI) were studied. The results showed that La doping can refine TiO2 grains, stabilize phase structure of anatase TiO2, and expand its absorption spectrum, thereby enhancing its photocatalytic reduction activity. Due to the composite of kaolin, the dispersion of TiO2 is improves and it is endowed with a large specific surface area lead to enhance its adsorption ability for Cr(VI). The adsorption equilibrium process of LTK for Cr(VI) conforms to the Langmuir equation model. The coupling effect of doping and composite modification improves the adsorption and visible light catalytic reduction activity of Cr(VI) over composite material samples. The adsorption-photocatalytic removal rate of LTK for Cr(VI) under visible light irradiation for 6 hours reached the highest of 96.5%. The apparent first-order kinetic constant of its photocatalytic reduction reaction was 2.6 times that of pure TiO2.

Fabrication of Electrospun Porous TiO2 Dielectric Film in a Ti–TiO2–Si Heterostructure for Metal–Insulator–Semiconductor Capacitors

The development of metal–insulator–semiconductor (MIS) capacitors requires device miniaturization and excellent electrical properties. Traditional SiO2 gate dielectrics have reached their physical limits. In this context, high-k materials such as TiO2 are emerging as promising alternatives to SiO2. However, the deposition of dielectric layers in MIS capacitors typically requires high-vacuum equipment and challenging processing conditions. Therefore, in this study, we present a new method to effectively fabricate a poly(vinylidene fluoride) (PVDF)-based TiO2 dielectric layer via electrospinning. Nano-microscale layers were formed via electrospinning by applying a high voltage to a polymer solution, and electrical properties were analyzed as a function of the TiO2 crystalline phase and residual amount of PVDF at different annealing temperatures. Improved electrical properties were observed with increasing TiO2 anatase content, and the residual amount of PVDF decreased with increasing annealing temperature. The sample annealed at 600 °C showed a lower leakage current than those annealed at 300 and 450 °C, with a leakage current density of 7.5 × 10−13 A/cm2 when Vg = 0 V. Thus, electrospinning-based coating is a cost-effective method to fabricate dielectric thin films. Further studies will show that it is flexible and dielectric tunable, thus contributing to improve the performance of next-generation electronic devices.

A Comparison Study of Photocatalytic Performance of TiO2 Anatase Phase Prepared from Different Procedures

In this work, three TiO2 anatase phase samples, labeled as S1, S2, and S3, were synthesized using varying titanium precursors, solvents, and conditions to compare their photocatalytic performances. The structural and morphological properties of the synthesized samples were characterized through X-ray diffraction (XRD), Raman scattering, field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). The obtained results indicated that all samples exhibited an anatase crystalline phase. Sample S1 notably featured nanowires with an average diameter of 38.6 nm. Meanwhile, samples S2 and S3 comprised nanoparticles, each exhibiting unique average sizes of 12.76 nm and 10.11 nm, respectively. The diffuse reflectance spectra reveal that the S3 sample possesses the lowest bandgap, suggesting its potential as the most promising photocatalyst. Additionally, photocurrent response and electrochemical impedance spectroscopy (EIS) were characterized to elucidate the charge transfer mechanisms within the materials. The degradation efficiencies of Rhodamine B (RhB) for samples S1, S2, and S3 were determined to be 17.40%, 17.93%, and 33.04%, respectively, under visible light irradiation. This study provides valuable insights into the criteria for choosing efficient TiO2 photocatalysts.

Facile one-step fabrication of Li4Ti5O12 coatings by suspension plasma spraying

Spinel Li4Ti5O12 (LTO) is a promising anode material for solid state thin film batteries (SSTB) due to its almost-zero volume change and promising Li-ion mobility. However, preparing LTO anodes for SSTB demands tedious vacuum-based processing steps that are not cost effective. In this context, the present study embarks on evaluating the versatile suspension plasma spraying (SPS) approach to fabricate LTO coatings without using any binder. The microstructure and stoichiometry of the fabricated LTO coatings developed through the SPS route reveals retention of ∼76 wt.% of the spinel LTO from the starting feedstock, with minor amounts of rutile and anatase TiO2. The SPS experiments yielded varying thickness build up rates of the LTO coatings depending on the processing parameters adopted. The electrochemical data of the produced LTO based electrode tested in a half-cell through galvanostatic cycling show reversible lithiation and delithiation at expected potential, thereby validating the promise of the SPS technique for potential fabrication of SSTB components once fully optimized.

Hydroxylated TiO2-induced high-density Ni clusters for breaking the activity-selectivity trade-off of CO2 hydrogenation

The reverse water gas shift reaction can be considered as a promising route to mitigate global warming by converting CO2 into syngas in a large scale, while it is still challenging for non-Cu-based catalysts to break the trade-off between activity and selectivity. Here, the relatively high loading of Ni species is highly dispersed on hydroxylated TiO2 through the strong Ni and −OH interactions, thereby inducing the formation of rich and stable Ni clusters (~1 nm) on anatase TiO2 during the reverse water gas shift reaction. This Ni cluster/TiO2 catalyst shows a simultaneous high CO2 conversion and high CO selectivity. Comprehensive characterizations and theoretical calculations demonstrate Ni cluster/TiO2 interfacial sites with strong CO2 activation capacity and weak CO adsorption are responsible for its unique catalytic performances. This work disentangles the activity-selectivity trade-off of the reverse water gas shift reaction, and emphasizes the importance of metal−OH interactions on surface.

Anatase TiO2 Surface Hydration: Infrared Vibrational Assignment and Facet-Specific Stability

Anatase TiO₂ Surface Hydration: Infrared Vibrational Assignment and Facet-Specific Stability

Hydrothermal synthesis of bare TiO2 nanowires and polystyrene (PS)-TiO2 nanowires used for selective photocatalytic oxidation of 3-pyridinemethanol in water and PS photodegradation in solid state

In the present work, nanowire (NW) structured TiO2 nanoparticles were prepared using the hydrothermal method and characterized by X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), and BET specific surface area techniques. They were obtained in the anatase phase and presented a high surface area (ca. 300 m2/g). A commercial TiO2 (anatase, Merck) was used for comparison. The TiO2 catalysts were tested for photocatalytic oxidation of 3-pyridinemethanol to 3-pyridinemethanal and vitamin B3 in water under UVA irradiation. The effects of acid treatment and subsequent calcination for TiO2 catalysts after the hydrothermal synthesis were also investigated. The sample, subjected to acid treatment and calcined at 300 °C (NW-HCl-300), showed the highest photocatalytic activity and selectivity towards the products. Consequently, this sample and Merck TiO2 were used to prepare polystyrene (PS)/TiO2 composites using the hydrothermal method. They were characterized by XRD, SEM–EDX, Nuclear Magnetic Resonance (NMR), Fourier Transform Infrared Spectroscopy (FT-IR), Thermogravimetric analysis (TGA), Differential Scanning Calorimetry (DSC), UV–Vis, Gel Permeation Chromatography (GPC), and contact angle measurements and tested for PS (present in the composite) photodegradation. The results indicated that NW-HCl-300 had a high surface area, and was highly hydroxylated, favouring a good distribution of PS in the composite. The composite presented high thermal stability, but under UVA irradiation the polymer underwent solid-state photocatalytic degradation due to the contact with TiO2. The composite photodegradation was investigated using gravimetric, GPC, FT-IR, UV–Vis, and SEM techniques.

Double nonmetal elements modified porous TiO2 homogeneous junction for efficient photocatalytic oxidation of cyclohexane

The nitrogen-doped TiO2 with mesoporous structure, anatase/rutile homogeneous junction and surface carbon species were successfully synthesized by facile hydrolysis of tetrabutyl titanate and preheating under the sealed condition, followed by a urea-aided calcination process. Interestingly, the as-obtained carbon modified TiO2 intermediates prepared by pretreating at different temperatures showed a certain photocatalytic activity for cyclohexane oxidation, and the carbon species were deposited to the surfaces of TiO2 via the Ti-O-C bond. The microstructure and photocatalytic activity of the double nonmetal elements modified porous mixed-phase TiO2 microspheres were found to depend on the preheating conditions, and nitrogen was doped into TiO2 lattice, the co-modification of nitrogen and carbon jointly improved the light absorption capacity and reduced the band gap of TiO2. The construction of a mixed-phase junction further improved the photocatalytic performance of the co-modified TiO2 compared with pure anatase or rutile TiO2. The optimal catalyst (N-TiO2-3 b) displayed efficient and stable photocatalytic performance for three cycles. When the reaction was conducted in real outdoor circumstances, the high ketone yield (206.22 μmol) and selectivity (99.92 %) were achieved. The synthetic method was simple and cheap, thus this work showed great potential for green production of fine chemicals under moderate conditions.

Preparation of Ag@Au core-shell nanoparticles embedded in TiO2 inverse opal for light harvesting and efficiency enhancement in quantum dot sensitized solar cells

In the fabrication of Quantum dot sensitized solar cells (QDSSCs), it is important to fabricate a photoanode with a high ability to trap photons as well as transfer photogenerated electrons. TiO2 inverse opal (TIO) photonic crystals with their organized porous structures, besides their chemical nature, have unique optical features such as the slow-photon effect, photon localization, and photonic bandgap (PBG). Herein, to improve the efficiency of QDSSCs, gold, silver, and silver/gold core-shell (Ag@Au) plasmonic nanoparticles (nps) are loaded on TIO. The plasmonic nanoparticle-decorated inverse opal improves the light scattering process and provides direct charge transfer tunnels, which can effectively prevent the recombination of electron-hole pairs. In this work, fabricated QDSSCs with TIO (double-layer)/ZnS/CdS/CdSe/ZnSe/ZnS photoanode, and a 6 μm total thickness of the TIO multilayer, has an open circuit voltage (Voc) of 0.745 V and short-circuit current density (JSC) of 16.22 mA/cm2. The obtained results are higher than the common anatase TiO2 (TiO2-A)/ rutile TiO2 (TiO2-R)/QD photoanode. Also, the TIO (double-layer)/Ag@Au/QDs photoanode exhibits JSC=20.3283 mA/cm2, Voc= 0.75 V, and a power conversion efficiency (PCE) of ƞ=10.79 %.

Green synthesis of glycolic acid through the electrocatalytic reduction of oxalic acid over black TiO2: An experimental and theoretical study

Herein, we present the electrocatalytic four-electron hydrogenation of oxalic acid into glycolic acid using black TiO2 as an electrocatalyst. Oxalic acid is an abundant compound found in several sources of organic waste. The results showed a high selectivity of black TiO2 toward glycolic acid, with the formation of glyoxylic acid being the rate-limiting step (glyoxylic acid is the two-electron intermediate). The highest Faradaic efficiency (FE) of 69.6% ± 8.3% was achieved at 10.2 mA cm−2 in 4 h of electrolysis using an H-type cell operated at room temperature, with 50.2% ± 3.8% of oxalic acid conversion (degradation kinetic constant k = 0.0042 ± 0.0001 min−1), 58.8% ± 7.0% of reaction yield and 1.2 ± 0.18 g L−1 of glycolic acid production. A theoretical model of black TiO2 coming from anatase TiO2 was implemented by introducing Ti3+ defects, which gave black TiO2 the theoretical capability to easily transform oxalic acid into glycolic acid as experimentally observed. The reaction mechanism was supported and described in detail by density functional theory calculations, which revealed that surface Ti3+ states were the main catalytic sites. This is the first time that a detailed step-by-step mechanism at the atomic level has been proposed for this electrocatalytic reaction, which represents a valuable contribution to the understanding of this process of high energy/environmental interest. This is also the first time that black TiO2 has been used as an electrocatalyst for this sustainable process.

Preparation of in-situ synthesized TiC/AlSi30Cu5 coating by high velocity oxy-fuel (HVOF) spraying: Microstructure evolution, mechanical properties, and tribological behavior

To enhance the wear resistance of AlSi30Cu5 coating even further, TiC-reinforced AlSi30Cu5 (TiC/AlSi30Cu5) coatings were prepared using TiH2-C-AlSi30Cu5 agglomerates by HVOF. The results confirmed that the phases composition of TiC/AlSi30Cu5 coating included α-Al, β-Si, θ-Al2Cu, β-Ti, TiC, rutile TiO2 (R-TiO2), and anatase TiO2 (A-TiO2). The mechanical properties of TiC/AlSi30Cu5 coating, microhardness and fracture toughness, were greatly improved by 37.8 % and 5.5 times. The combination of high hardness, high fracture toughness and residual graphite significantly strengthened the wear resistance of TiC/AlSi30Cu5 coatings by 91.1 % and 54.1 % over the substrate and AlSi30Cu5 coating. Analysis of the worn morphologies and abrasive debris revealed that the wear mechanisms of TiC/AlSi30Cu5 coating were primarily abrasive wear, with contributions from oxidative wear and fatigue wear.

Unveiling the intrinsic activity of TiO2 in HMF valorisation

In the context of 5-hydroxymethylfurfural (HMF) valorisation, TiO2 has emerged as a promising support. However, its intrinsic activity and underlying structural parameters remained undiscovered. This study elucidates the close relationship between structural and surface properties of TiO2 (e.g. crystalline size, surface area, and the number and type of acid sites) and its activity in HMF conversion. Lewis acid sites were found to be the exclusive acid sites present in anatase TiO2 samples, and their abundance correlated strongly with the overall surface area of TiO2. HMF conversion over TiO2 led to the simultaneous formation of 5-methylfurfural (5-MF) and 2,5-diformylfuran (2,5-DFF). Their formation was attributed to an intermolecular hydride transfer occurring over the Lewis acid sites. This opens up the possibility of selectively obtaining 5-MF and 2,5-DFF using solely TiO2 active sites. These findings provide valuable insights for designing TiO2-supported metal catalysts for future energy and environmental applications, aligning with green chemistry principles.

In situ revealing the dehydration and atomic structure evolution of protonated titanate nanotubes via environmental transmission electron microscopy

The precise control of nanomaterial microstructure at the atomic level relies on the comprehensive understanding of atomic structural transition during the fabrication process at the atomic level. The phase transition from protonated titanate to TiO2 is a prevalent route to synthesize low dimensional TiO2-based nanomaterials, which exhibit excellent photocatalytic, lithium-ion battery performances, while the detailed phase transition mechanism remains to be clarified due to lack of atomic-level in situ information. Herein, the atomic structural transitions from one-dimensional H2Ti3O7 (HT) to TiO2(B) and anatase TiO2 (TB and TA) nanocrystals were revealed through in situ environmental transmission electron microscopy, which exhibited a two-step phase transition at 200–600 °C. (I) H2Ti3O7 to TiO2(B) transition began via an indirect pathway at ∼200 °C: The HT (200) interlayer dehydration occurred firstly with lattice shrinkage; Then TB discretely nucleated at the dehydrated H2Ti3O7 nanotube wall with a crystallographic relationship of (200)HT∥(200)TB {[001]HT∥[001]TB}; At higher temperature, the separated nuclei grew up with defects and distorted crystal lattice among them, which then connected and jointed to a single crystalline TB nanotube by atomic rearrangement. (II) The further transition of TiO2(B) to anatase TiO2 occurred via a direct pathway above 400 °C: Scarce nucleation event of TA phase was observed, which generated within TB nanocrystal with a crystallographic relationship of (200)TB∥(002)TA {[001]TB∥[010]TA}. Once a TA nucleus formed, it grew up to a large crystal by consuming the neighbor TB nanocrystals. These findings may contribute to comprehensively understanding phase transition and precisely manipulating the atomic structure of one-dimensional TiO2 nanocrystals.

Heterophase homojunction construction by amorphous TiOx and N–TiO2 photoanode for oxygen evolution reaction kinetics and charge carriers’ transportation enhancement

Photoelectrochemical (PEC) water splitting by TiO2 photoanode for clean hydrogen production is limited by the poor charge separation and inert oxygen evolution reaction (OER) kinetics issues for now. In this work, a band-matched heterophase homojunction (TiOx/N–TiO2) by amorphous TiOx and N-doped TiO2 nanotube arrays is constructed by two-step anodic oxidation and impregnation. The photocurrent density of TiOx/N–TiO2 reaches 0.69 mA/cm2 at 1.23 V vs. RHE, which is 1.86 folds than bare TiO2. The enhanced charge carriers' injection/separation efficiency, smaller Tafel slope (37.79 mF dec−1) and larger electrochemical active surface area (ECSA) (1.98 mF cm−2) of TiOx/N–TiO2 indicate that N doping and heterophase homojunction with amorphous TiOx effectively facilitate the surface OER kinetics and charge carriers' transportation. TiOx/N–TiO2 is annealed with a transformation of the surface amorphous TiOx layer into anatase TiO2 (a-TiOx/N–TiO2) to study the role of amorphous TiO2 in PEC water splitting. The photocurrent density and applied bias photon-to-current efficiency (ABPE) for a-TiOx/N–TiO2 decrease, even lower than the pristine TiO2. This is due to the reduction of surface oxygen vacancies, which causes the slowdown of OER kinetics and the weakening of charge carrier transportation ability. That is favorable for a better understanding of the OER kinetics and charge carriers’ transportation enhancement mechanism by the surficial modification on the semiconductor during the PEC water splitting.

Inkjet‐Printed Flexible and Transparent Ti3C2Tx/TiO2 Composite Films: A Strategy for Photoelectrically Controllable Photocatalytic Degradation

The 2D Ti3C2Tx MXene has a large specific surface area, abundant functional groups, and low work function, which has potential in the field of photocatalytic materials. However, the manufacturing of controllable films with high photocatalytic properties and desirable transmittance is a challenging task. Herein, low‐cost, large‐scale, and rapid preparation of Ti3C2Tx/TiO2 flexible composite films have been successfully prepared by inkjet printing technology, which can be applied in complex and special environments, as well as in photoelectrically controllable places for photocatalytic performance. With the increase of the anatase TiO2, the transmittance of Ti3C2Tx/TiO2 films increases from 55.37% to 73.27% at 780 nm, corresponding to the square resistance of 1.112–206.496 kΩ sq−1 and the figure of merit of 0.48–0.005. When the amount of anatase TiO2 is 15%, the film has the best photocatalytic effect on methylene blue (MB) dye, reaching 68.94%. After five cycles of testing, the degradation efficiency of MB dye decreases by only 5.68%, showing that the film has good cycling stability. This work provides a new research direction for photoelectrically controllable photocatalytic degradation in complex and special environments.

Adsorption of Guanine on Oxygen-Deficient TiO2 Surface: A Combined MD-DFTB/DFT Strategy.

Metal oxides (MOs) are key materials in many fields, including technological, industrial, and biomedical applications. In most of these implementations, surface reactivity and reducibility properties are critical considerations. In their nanosized form, MOs exhibit enhanced reactivity that is connected to toxicity. Besides the fact that the biological molecule and the surface of the corresponding material interact chemically, little is known about the toxicological mechanisms involved on the atomic scale. The goal of this study is to investigate the role of TiO2 surfaces in interaction with one genetic base, namely guanine. Using a combination of the quasi-electronic density functional-tight binding molecular dynamics simulations and density functional theory calculations, we explored the adsorption modes of guanine with a stoichiometric and oxygen-deficient anatase TiO2 (101) surface. With such an approach, we have characterized new adsorption modes not previously found, and we have highlighted the relevance of defective surfaces in the adsorption of genetic basis, as a model for explaining possible toxicology mechanisms induced by the adsorption process.

Investigation of the Ti active site in TS-1 for phenol hydroxylation via seed and dissolution-recrystallization methods

TS-1 (titanium silicalite-1) zeolite has been one of the most popular catalysts for phenol hydroxylation in the industry to produce hydroquinone and catechol for its high catalytic activity. However, ideal Ti active site in TS-1 for phenol hydroxylation is controversial in academia and still remains urgent to be determined for more convincing guidance to prepare TS-1 with higher catalytic activity. Thus, controlled experiments for detailed research were conducted via seed and dissolution-recrystallization methods to explore the Ti active site for phenol hydroxylation. Through comparison of micron TS-1 and hierarchical TS-1, several factors including crystal size, specific surface area, pore volumes and anatase TiO2 were proved to have an influence on catalytic performance for phenol hydroxylation. Furthermore, hierarchical TS-1 using seeds with different molar ratios of Si/Ti were synthesized to regulate the ratio of framework Ti and hexa-coordinated Ti and exclude above variables. With binding analysis of UV–vis, UV-Raman, and XPS, it was found that TS-1 with the most framework Ti showed the best performance with TON of 1461 and dihydroxybenzenes selectivity of 97.3 %, and TS-1 with less framework Ti and more hexa-coordinated Ti showed worse performance. Hence, it was demonstrated that framework Ti was the active site for phenol hydroxylation rather than hexa-coordinated Ti, while hexa-coordinated Ti would cause excessive oxidation of phenol to benzoquinone.

Crystallographic plane-induced selective mineralization of nanohydroxyapatite on fibrous-grained titanium promotes osteointegration and biocorrosion resistance

The (002) crystallographic plane-oriented hydroxyapatite (HA) and anatase TiO2 enable favorable hydrophilicity, osteogenesis, and biocorrosion resistance. Thus, the crystallographic plane control in HA coating and crystalline phase control in TiO2 is vital to affect the surface and interface bioactivity and biocorrosion resistance of titanium (Ti) implants. However, a corresponding facile and efficient fabrication method is absent to realize the HA(002) mineralization and anatase TiO2 formation on Ti. Herein, we utilized the predominant Ti(0002) plane of the fibrous-grained titanium (FG Ti) to naturally form anatase TiO2 and further achieve a (002) basal plane oriented nanoHA (nHA) film through an in situ mild hydrothermal growth strategy. The formed FG Ti-nHA(002) remarkably improved hydrophilicity, mineralization, and biocorrosion resistance. Moreover, the nHA(002) film reserved the microgroove-like topological structure on FG Ti. It could enhance osteogenic differentiation through promoted contact guidance, showing one order of magnitude higher expression of osteogenic-related genes. On the other hand, the nHA(002) film restrained the osteoclast activity by blocking actin ring formation. Based on these capacities, FG Ti-nHA(002) improved new bone growth and binding strength in rabbit femur implantation, achieving satisfactory osseointegration within 2 weeks.

Nonlinear optical studies of Bismuth-doped Titanium di-oxide colloids achieved by femtosecond Z-Scan technique

In this paper, we explored the nonlinear optical (NLO) properties of Bismuth (Bi) doped titanium dioxide (TiO2) nanoparticle (NP) colloids in ethanol, with laser pulses of duration ∼ 150 femtoseconds (fs). The Bi-doped TiO2 NPs were synthesized via the chemical route, sol-gel method. The increased photo response of TiO2 upon doping it with metals has become a burning issue to extend the applications of metal-doped TiO2 NPs as integral parts in solar cells, catalysts, phototherapy, etc. The bandgap of anatase TiO2 NPs was observed to be reduced to 2.89 eV upon doping Bi. The modified band structure of the Bi-doped TiO2 NPs demonstrates novel chemical, mechanical, and optical properties. NLO studies were conducted on Bismuth-doped TiO2 NPs submerged in ethanol employing femtosecond laser input pulses with incoming wavelengths 700, 750, 800, 850, 900, and 950 nm. It has been detected that open aperture (OA) studies performed at an input peak intensity of 100 MW/cm2 on Bi-doped TiO2 NPs in ethanol were exhibiting complex NLO behavior, i.e., reverse saturable absorption (RSA) in saturable absorption (SA) and SA in RSA with mostly effective two-photon absorption (1 + 1) coefficients. Particularly, at ∼800 nm, the behavior observed was so complex, i.e., RSA in SA in RSA in SA, with an effective 3 PA (2 + 1) co-efficient (γ) ∼6.5 × 10−24 m3/W2. The closed aperture (CA) studies at ∼37 MW/cm2 exhibited self-defocusing effects, i.e., an intensity-dependent refractive index (n2) with a negative signature.