Anatase

Micro-scale TiO₂ (micro-TiO₂) and 5 nm of TiO₂ in the form of anatase were purchased from Sigma-Aldrich (Shanghai, China), and 10, 60, and 90 nm of TiO₂ (anatase) were purchased from Run He Ltd. (Shanghai, China). The formaldehyde, nitric acid, hydrogen peroxide, and heparin sodium were reagent grade and were purchased from Sigma-Aldrich (Shanghai, China). Phosphate buffer (PBS), penicillin, and streptomycin were purchased from Gibco (San Diego, USA). Total RNA extraction kits were purchased from Takara (Dalian, China). Reactive oxygen species assay kits were purchased from Jianchen Ltd. (Nanjing, China). Stock TiO₂ suspension (1%) in Hank’s solution was sterilized at 121 °C for 30 min. The suspension was sonicated and diluted to the desired concentration just before use.

Doped LiNi_0.5Mn_1.5O₄ was prepared by a mixed mechano-chemical-solid state route. Oxides precursor were weighted and mixed by using a Spex 8000 M high energy miller for 5 hours in stainless-steal jars. The obtained powder was then heat-treated at 800 °C for 1 h under air with heating and cooling scan rates of 10 and 5 °C/min respectively.
Monoclinic TiO₂(B) nanotubes were synthesized from anatase (Sigma Aldrich), by adding it to a solution of 15 mol/L NaOH (Sigma Aldrich) followed by hydrothermal treatment at 150 °C for 72 h^{10 (link)}. Then the product of the hydrothermal reaction was washed with 0.05 mol/L of HCl (Sigma Aldrich), dried in air then heated to 400 °C for 5 h under O₂-flow at 40 ml/min. After the annealing the synthesized TiO₂(B) material has been transferred directly to the glove box without exposure in air. Before casting into film electrodes, the TiO₂-B material has been treated with lithium ethoxide following the procedure illustrated by Brutti and co-workers in ref. 22 (link) to mitigate the irreversible capacity loss in the first cycle. The preparation of the TiO₂(B) based electrode films has been carried out in glove box to avoid the possible contamination with moisture.

The TiO₂NPs used in this study were a mixture of rutile and anatase forms purchased from Sigma Chemical Co., (St. Louis, MO, USA) in the form of odorless and white powder in the nanoscale range <100 nm using Brunauer-Emmett-Teller (BET) method and <50 nm using X-ray diffraction method with a purity of 99.5% and CAS number 13463-67-7. As mentioned in our previous study [17 (link)], TiO₂NPs were ultrasonicated in deionized distilled water using the biologics ultrasonic homogenizer (Model 150VT) immediately prior to characterization and administration and the pH value of TiO₂NPs suspensions was 6.8 and characterized using X-ray diffraction (XRD) to identify the crystal phase and the average crystallite size. Indeed, the particle size and morphology of TiO₂NPs suspensions were detected using transmission electron microscopy (TEM) and the dispersion and aggregation status of these nanoparticles in water were determined by the dynamic light scattering (DLS) method using particle size distribution and zeta potential analyzer (Zeta sizer Nano ZS90, Malven Instruments, UK).

Nitric Acid, titanium dioxide (Anatase), titanium dioxide (Degussa P25), titanium isopropoxide, polyethylene graft maleic anhydride and Rhodamin 6G were purchased from Sigma-Aldrich. Sodium chloride, n-hexane, sodium hydroxide, hydrogen peroxide and sodium sulfate were purchased from Merck. All reagents were used as received.

In this study, two different forms of TiO₂ nanoparticles were used:
commercially available anatase (Sigma Aldrich, USA) and self-produced N-doped
TiO₂ (N-TiO₂) crystallized in the anatase structure.
N-TiO₂ nanoparticles were synthesized using the sol-gel method, as
described in a previous study.^{(24 )}Briefly, 37.5mL titanium isopropoxide (Sigma-Aldrich) with 70mL of 2-propanol
(Sigma-Aldrich) and 9mL aqueous solution of NH₃ (15% V/V) were stirred at
room temperature for 4 hours, then washed with deionized water and dried at 105°C
for 12 hours. The xerogel was finally crushed into a fine powder and calcined at
350°C for 1 hour to complete the crystallization process.
Diffuse reflectance spectrophotometry (JASCO V-570 UV-VIS-NIR, Jasco Int. Co. Ltd.,
Japan), Brunauer-Emmett-Teller (BET, ASAP 2000, Micromeritics, US), X-ray powder
diffraction (XRPD, Philips PW 1830 generator, 40 kV, 30 mA) and transmission
electron microscopy (TEM, JEOL JEM 2010, lanthanum boride crystal operated at 200
kV) were used to characterize the nanoparticles. Scanning electron microscopy (SEM)
with energy-dispersive X-ray spectroscopy (EDS) (StereoScan 360 microscope, Leica
Cambridge Instruments, United Kingdom) was used to study the nanoparticles and the
samples. EDS analysis was performed on different areas of a representative sample to
estimate the chemical composition corresponding to each observed morphological
pattern.