Rutile TiO2 Nanorods Research Articles

Enhanced photoelectric properties of TiO2 nanorod arrays through modulation of precursor concentration

This study synthesized titanium dioxide (TiO2) nanorod arrays and investigated their morphology and defect to the photoelectric response by varying the titanium isopropoxide (TTIP) precursor concentration from 0 to 66 mM. The vertically aligned rutile TiO2 nanorods exhibited film thicknesses ranging from 1 to 4.5 μm when the TTIP concentration equaled or exceeded 33 mM. Their rod length and diameter displayed a linear increase with the TTIP concentration. TiO2 arrays synthesized with a TTIP concentration of 33 mM exhibited the highest photoelectric response, measuring 52 μA/cm2 under xenon-lamp irradiation at a bias voltage of 0.8 V (vs. the Ag/AgCl reference). Notably, photoactivity was observed in the visible-light region as well. Photoluminescence spectra indicated a substantial reduction in electron-hole recombination compared to TiO2 arrays prepared from higher TTIP concentrations. X-ray photoelectron spectroscopy and electron paramagnetic resonance analyses confirmed the presence of oxygen vacancies. Time-resolved photoluminescence spectra corroborated an extended electron lifetime, suggesting that surface oxygen vacancies facilitated the separation of photoexcited charge carriers. The presence of oxygen vacancies, combined with the unique array morphology, resulted in enhanced photocurrent density.

Enhancement of electrochromic efficiency of TiO2 nanorods

In this study, the rutile TiO2 nanorods thin films were deposited via hydrothermal method on fluorine-doped tin oxide (FTO) substrate. To form a porous morphology layer, a thin film of amorphous titanium oxide (TiOx) was deposited on the TiO2 nanorods through sputtering at high pressure. The samples were annelid at 450ᵒC to transform the amorphous surface to anatase phase. Structural, optical, morphology and electrochemical properties of the samples were examined via X-ray diffraction (XRD), Raman scattering, UV–Vis NIR and photoluminescence (PL) spectroscopies, field-emission scanning electron microscopy (FE-SEM) and Potentiostat device respectively. The samples exhibited a large optical bandgap of 3.35–3.40 eV and high transparency of over 77 % at a wavelength of 555 nm. Raman analysis confirmed the formation of anatase phase on the rutile nanorods under thermal treatment. PL analysis indicated that the oxygen vacancies reached their maximum after sputtering, while the intensity of PL emission significantly increased after annealing. Investigation of the electrochromic properties revealed an increase in coloration efficiency from 2.6 C−1cm2 for bare nanorods to 10.0 C−1cm2 for nanorods after sputtering deposition, which decreased to 5.4 C−1cm2 after thermal treatment.

Low dose, high function: Visible light photocatalytic performance of in-situ sensitized Ti3+/Ov self-doped rutile TiO2-x nanorods with a small amount of ultrathin g-C3N4 nanosheets

Harnessing solar energy for photocatalytic sewage purification represents a significant strategy for addressing water pollution. This study focused on synthesizing ultrathin g-C3N4 nanosheets through ultrasonic refluxing g-C3N4 aggregates in a mixture of water and triethylamine. Subsequently, Ti3+/oxygen vacancy (Ov) self-doped rutile TiO2 (TiO2-x) nanorods were synthesized via an in-situ mixed solvothermal reaction. By sensitizing a minimal quantity of these ultrathin g-C3N4 nanosheets, a Z-scheme heterojunction with reduced rutile TiO2-x nanorods was achieved. Various analytical techniques were employed, including X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS), and transient photocurrent analysis. These methods determined the phase, structure, morphology, and photoelectrochemical properties of the fabricated materials. The visible light photocatalytic performance was tested using rhodamine B, methyl orange, and Cr2O72- solutions as simulated pollutants and three distinct types of actual wastewater from a pharmaceutical factory as photocatalytic degradation object. The findings revealed that Ti3+/Ov self-doping significantly enhances the visible light responsiveness of rutile TiO2. The integration of minimal amounts of ultrathin g-C3N4 nanosheets with rutile TiO2-x nanorods, formed via an in-situ mixed solvothermal reaction, effectively promoted the separation of photogenerated electrons and holes, thereby increasing the photocatalytic efficiency. Interestingly, increasing the g-C3N4 content in the mixture led to an increase in the number of defects within TiO2-x and a reduction in crystallinity. Wastewater treatments yielded varied results: wastewater containing solely phenols underwent effective photocatalytic degradation, while samples with high salt content or complex compositions proved more challenging. This study demonstrated that the heterojunction formed by sensitizing rutile TiO2-x nanorods with a small amount of ultrathin g-C3N4 nanosheets retained remarkable photocatalytic activity. These findings offer valuable insights for the design of effective photocatalysts and their application in sewage treatment.

Enhanced dual function of Ag nanoparticles decorated one-dimensional polymorphic TiO2 composites for sustainable environmental applications

The hydrothermally synthesized rutile-TiO2 nanorods were spin-coated with anatase-TiO2 film and decorated with Ag nanoparticles via sputtering to construct Ag nanoparticles decorated heterophase TiO2 composites. By extending the sputtering duration to altering the Ag content in the TiO2 composition, we aim to investigate the correlation between the microstructures and the dual function of photoelectrochemical photocatalytic and gas-sensing performances for environmental applications. The Ag nanoparticles on the anatase/rutile-TiO2 composites facilitate photon absorption through surface plasmon resonance. Also, Ag nanoparticles contribute the hot electron to enhance the synergy effect in the anatase-TiO2/rutile-TiO2 to prevent recombination of photoinduced carriers under irradiation, thereby strengthening the photocatalytic characteristics. Furthermore, the gas sensing performance is improved due to the electronic and chemical sensitization effects caused by the Ag nanoparticles on the anatase-TiO2/rutile-TiO2 composite. This study demonstrates that tuning Ag nanoparticle content in the anatase/rutile-TiO2 composites is a promising material design strategy for use in highly efficient photoexcited and gas-sensing devices. The proposed Ag nanoparticles decorated polymorphic TiO2 composite nanorods are suitable for eliminating organic pollutants in water and ethanol pollution monitoring.

Self-powered SnSx/TiO2 photodetectors (PDs) with dual-band binary response and the applications in imaging and light-encrypted logic gates

In this work, we report the design and fabrication of self-powered binary response PDs based on II-type heterostructures consisting of SnSx nanoflakes (NFs) and rutile TiO2 nanorod arrays (NRs). The TiO2 NRs effectively block light with wavelengths below 400 nm from reaching SnSx. Under 385 nm light, the photoelectrons in TiO2 recombine with holes in SnSx at the interface due to the energy band bending, resulting in a positive photocurrent. Under 410 nm light, the photoelectrons in SnSx and the photogenerated holes in TiO2 accumulate at the interface, overcoming the interfacial potential barriers induced by the higher Fermi levels of SnSx and inducing a negative photocurrent. Based on the bipolar response, the dual-band imaging capability without external filters and the light-encrypted OR, AND, and NOT logic gates using a single device are demonstrated. This work provides a blueprint for the development of multifunctional self-powered PDs that can simplify system architecture, reduce the energy consumption, and improve accuracy for applications, such as visual systems, light-controlled logic circuits, and encrypted optical communications.

An Ultrasensitive Room-Temperature H2 Sensor Based on a TiO2 Rutile–Anatase Homojunction

Metal oxide semiconductor hetero- and homojunctions are commonly constructed to improve the performance of hydrogen sensors at room temperature. In this study, a simple two-step hydrothermal method was employed to prepare TiO2 films with homojunctions of rutile and anatase phases (denoted as TiO2-R/A). Then, the microstructure of anatase-phase TiO2 was altered by controlling the amount of hydrochloric acid to realize a more favorable porous structure for charge transport and a larger surface area for contact with H2. The sensor used a Pt interdigital electrode. At an optimal HCl dosage (25 mL), anatase-phase TiO2 uniformly covered rutile-phase TiO2 nanorods, resulting in a greater response to H2 at 2500 ppm compared with that of a rutile TiO2 nanorod sensor by a factor of 1153. The response time was 21 s, mainly because the homojunction formed by the TiO2 rutile and anatase phases increased the synergistic effect of the charge transfer and potential barrier between the two phases, resulting in the formation of more superoxide (O2−) free radicals on the surface. Furthermore, the porous structure increased the surface area for H2 adsorption. The TiO2-R/A-based sensor exhibited high selectivity, long-term stability, and a fast response. This study provides new insights into the design of commercially competitive hydrogen sensors.

Multifunctional engineering on the ultrasensitive driven-dual plasmonic heterogenous dimer system of 1D semiconductor for accurate SERS sensitivity and quantitation

Self-assembled functional nanomaterials with electromagnetic (EM) hot spots and chemical (CM) enhancement have been recognized as a key in surface-enhanced Raman scattering (SERS) analysis. Herein, a dual-hybrid plasmonic coupling SERS sensor composed of rutile TiO2 nanorod arrays (r-TNRs), Au nanospheres (AuNSs), and Ag nanocubes (AgNCs) has been designed to achieve ultrasensitive detection and obtain unique molecular fingerprints. The AgNCs/AuNSs/r-TNRs-based SERS chip shows an extremely promising SERS enhancement factor (EF) of 1.2 ×1011, detectability at sub-picomolar concentrations (down to the single-molecule level, 10-13 M), and excellent signal reproducibility with a relative standard deviation (RSD) of 3.4 %. Furthermore, this system has been applied for fingerprint detection in complex mixtures, demonstrating impressive specificity and accuracy. The photocatalytic decomposition efficiency of the AgNCs/AuNSs/r-TNRs platform reaches approximately ∼99 % within 20 min. Additionally, the Raman intensity of crystal violet only declined by 15 % after 21 days, illustrating the outstanding stability of the as-proposed ternary SERS sensor.

Sequential doping strategy in rutile TiO2 nanorod for high performance photoanode

Clean hydrogen production technologies are in high demand as an alternative to fossil fuels in order to achieve a carbon–neutral society. One promising approach is photoelectrochemical water splitting, which uses sunlight as an energy source to produce hydrogen. In this study, we propose a strategy for achieving highly efficient photoelectrochemical performance in TiO2 nanorods without the need for additional heterojunction or catalyst reactions. We introduce the plasma-assisted sequential doping process using H and F species to demonstrate highly efficient photoanode for water splitting. In the first stage, hydrogenated TiO2 generated oxygen vacancies and interstitial H in the TiO2 lattice structure, and in the second stage, fluorinated TiO2 exhibited a sequentially cured reaction of oxygen vacancy resulting in enhanced photoelectrochemical performance. Furthermore, theoretical simulations revealed that the sequential doping process induced a stabilized reaction in F compared to direct doping without H plasma doping. This sequential doping strategy can be applied to a wide range of materials and applications, not just to enhance photoelectrochemical devices.

Improvement of the performance of carbon based all-inorganic perovskite solar cells by using ammonium acetate modified rutile TiO2 nanorods array as the electron transport layer

Carbon-based all-inorganic perovskite solar cells are currently emerging as a commercial and promising photovoltaic device. Rutile TiO2 has the function of UV shielding and preventing the decomposition of perovskite, furthermore, TiO2 nanorod array provides the direct 1-D electron transmission channel. Herein, vertically oriented rutile TiO2 nanorods array are synthesized on the FTO substrate by a simple one-step hydrothermal process and used as the electron transfer layer. The analysis of characterization illustrates that the prepared TiO2 is a flawless single rutile phase. TiO2 nanorods are employed as an ETL to provide a passage for the rapid and direct charge transfer. The separation of electrons and holes can be enhanced by ammonium acetate treatment of the TiO2 nanorod ETL/perovskite interface, and the carrier recombination can be efficiently lowered. Based on the structure of FTO/TiO2@CH3COONH4/CsPbI2.25Br0.75/C, the best device containing 2.5 mg/mL ammonium acetate modified TiO2 nanorods showed a short-circuit current density of 14.55 mA/cm2, open-circuit voltage of 1.08 V, and fill factor of 69.45 %, yielding a power conversion efficiency of 11.53 %, which show an increase in efficiency of approximately 22.4% when compared with the control cell. The results show that ammonium acetate interface modification is an effective strategy to enhance the photovoltaic performance of PSCs.

Superior white electroluminescent devices using nitrogen-doped carbon dots/TiO2 nanorods heterostructures

Nitrogen-doped carbon dots (NCDs), exhibiting strong yellow emission in aqueous solution and solid matrices, have been utilized for fabricating heterostructure white electroluminescence devices. These devices consist of nitrogen-doped carbon dots as an emissive layer sandwiched between an organic hole transport layer (PEDOT:PSS) and an array of rutile TiO2 nanorods, acting as an electron transport layer. Under an applied forward bias of 5 V, the device exhibits broadband electroluminescence covering the wavelength range of 390–900 nm, resulting in pure white light emission characteristics at room temperature. The result demonstrates the successful fabrication of all solution-processed, low-cost, eco-friendly NCDs-based LEDs with CIE (Commission Internationale d’Éclairage) coordinate of (0.31, 0.34) and color rendering index (CRI) > 90, which are close to ideal white light emission characteristics. The device functionalities are achieved based on defect-related NIR emission from TiO2 nanorods array and visible emission from nitrogen-doped carbon dots. This result paves a new opportunity to develop low-cost, solution-processed nitrogen-doped carbon dots based on warm White light emitting diodes with high CRI for large-area display and lighting applications.

In-situ construction of TiO2 polymorphic junction nanoarrays without cocatalyst for boosting photocatalytic hydrogen generation

There are significant challenges in developing technologies for high-yield photocatalytic hydrogen production reactions. Current photocatalytic materials face three key problems: low utilization of light, rapid recombination of photogenerated electron-hole pairs, and a limited number of active sites during photocatalytic reactions. As a result, these materials only improve one or two of the three steps involved in photocatalytic hydrogen production reactions. Consequently, achieving simultaneous multifunctional synergy to enhance the efficiency of all three processes is difficult. Here, we report an in situ dissolution-recrystallisation approach to design and fabricate a three-dimensional TiO2 rutile/anatase (AE-TiO2) array photocatalytic material for photocatalytic hydrolysis applications. It is shown that the unique 3D nanoarray structure and in situ fabrication of the AE-TiO2 homojunction with synergistic effects among the components lead to an increase in light harvesting efficiency, charge transport separation efficiency and surface active sites, which remarkably improve the photocatalytic hydrolysis performance. The prepared AE-TiO2 homojunction materials realizes a maximal photoactivity of 4 μmol cm−2·h−1, which is 39 times larger than that of pure TiO2 rutile nanorods.

Synthesis of uniformly ordered single-crystalline TiO2 nanorods on flexible Ti substrate

With high conductivity and ionic mobility, one-dimensional (1D) titanium dioxide (TiO2) nanoarrays have attracted great interest in the photoanode of solar cells and the cathode of lithium-ion/sodium-ion batteries. However, the synthesis of TiO2 nanoarrays often requires highly toxic or corrosive solution circumstances. Meanwhile, the case that most TiO2 nanoarrays are grown on rigid conductive substrate can’t satisfy the demand for application in the space of complex shape. In this work, we developed a simple method to prepare highly ordered single crystalline rutile TiO2 nanorod arrays with high density on flexible metal Ti substrate in relatively weak acid solution, and the orientation of the nanorods were more uniform than those by other means ever before. Based on detailed analysis, an ion-assisted and concentration-limited epitaxial growth mechanism by H+ and is proposed for this uniformly ordered rutile TiO2 nanorod array. This work can promote the research and application of flexible solar cells and lithium-ion batteries, especially their integration.

Seed-Assisted Hydrothermal Synthesis of Radial TiO2 Homomesocrystals and the Application as a Support for Plasmonic Photocatalysts

Radial homomesocrystals consisting of rutile TiO2 nanorods (NRs) were hydrothermally synthesized with TiO2 seed nanocrystals (rad-TiO2 HOMCs). The addition of the seeds greatly reduces the synthesis temperature and time. Transmission electron microscopic analyses show that the formation of rad-TiO2 HOMCs proceeds via epitaxial generation of nanoneedle-like nuclei on the seed surface, the growth of TiO2 NRs in the [001] direction, and their radial self-assembling with the transformation of amorphous to rutile TiO2. Au nanoparticles (NPs) with similar sizes and amounts were highly dispersed on rad-TiO2 HOMCs (Au/rad-TiO2 HOMCs) and two kinds of commercially available rutile TiO2 NPs (Au/TiO2 NPs) by the deposition precipitation method. As a test reaction for the evaluation of the plasmonic photocatalytic activity, degradation of 2-naphthol was examined by using it as a model water pollutant under illumination of weak visible light (λex > 430 nm, AM-1.5, 12.5 mW cm–2). In the Au/TiO2 systems, a positive correlation holds between the photocatalytic activity and the faceting probability of Au NPs on TiO2. The photocatalytic activity of Au/rad-TiO2 HOMCs much higher than those of Au/TiO2 NPs can stem from the plasmonic hot spot formation near the corners and edges of the faceted Au NPs and effective charge separation characteristics of the Au/rad-TiO2 HOMC system.

Surface Oxygen Vacancies of Rutile Nanorods Accelerate Biomineralization.

Titanium dioxide (TiO2) materials have been widely used in biomedical applications of bone tissue engineering. However, the mechanism underlying the induced biomineralization onto the TiO2 surface still remains elusive. In this study, we demonstrated that the surface oxygen vacancy defects of rutile nanorods could be gradually eliminated by the regularly used annealing treatment, which restrained the heterogeneous nucleation of hydroxyapatite (HA) onto rutile nanorods in simulated body fluids (SBFs). Moreover, we also observed that the surface oxygen vacancies upregulated the mineralization of human mesenchymal stromal cells (hMSCs) on rutile TiO2 nanorod substrates. This work therefore emphasized the importance of subtle changes of surface oxygen vacancy defective features of oxidic biomaterials during the regularly used annealing treatment on their bioactive performances and provided new insights into the fundamental understanding of interactions of materials with the biological environment.

Efficient CO2 conversion and organic pollutants degradation over Sm3+ doped and rutile TiO2 nanorods decorated-GdFeO3 nanorods

In this research work, the Sm3+ incorporated and rutile TiO2 nanorods coupled-GdFeO3 nanorods based nanocomposites are successfully prepared and gaged their visible-light photocatalytic activities for CO2 conversion and 2,4,6-trichlorophenol degradation. To this end, our investigation proved, that GdFeO3 and TiO2 nanorods have a wide surface area, high surface-to-volume values, and improved photocatalytic activities as compared to GdFeO3 and TiO2 nanoparticles respectively. Furthermore, the rutile TiO2 nanorods have significant performances as compared to anatase TiO2 nanorods. Based on our experimental and Ab initio approach, it is confirmed that the synergistic doping of Sm3+ interestingly elongated the visible light absorption proficiency via molding surface status and amending the band gap positions. Right after the coupling of rutile TiO2 nanorods performed the dual function of upgrading the charge separation by receiving HLEEs and activating the surface for CO2 adsorption via the photoelectron modulation approach. In contrast to pristine GdFeO3 nanorods, the optimal 4Sm-(GFONR) and 6RT/4Sm-(GFONR) samples showed efficient visible light activities for CO2 conversion and 2,4,6-trichlorophenol degradation. Fruitfully, our experiential investigations are consistent with the Ab initio and theoretical studies. Finally, our current novel findings will provide new feasible routes to synthesize morphology-based GdFeO3 photocatalysts for CO2 conversion and environmental remediation.

Photocatalytic activity of solvothermally synthesized rutile TiO2 nanorods for the removal of water contaminants

The TiO2 nanorods are synthesized via a solvothermal route by varying reaction temperatures. The XRD analysis reveals that the synthesized TiO2 nanorods grown with rutile phase with a 14 to 26 nm average crystallite size. The FESEM and HRTEM analysis confirmed the rod-like shape of the synthesized TiO2 nanoparticles, which grew in the same direction. In addition, the EDS analysis revealed the titanium-oxygen elemental ratio is equal to 1:2, confirming the stoichiometry of the grown sample. The UV–vis analysis of TiO2 nanorods shows a red shift in the band gap with a rising temperature. The TiO2 nanorods synthesized at 180 °C (T2) achieves methyl orange and rhodamine B degradation up to 90 and 97% within 50 and 60 min, respectively, under 125 W mercury light irradiation. Since the T2 sample has a high surface area, small crystallite size and a narrow band gap, it significantly affects the photodegradation of methyl orange and rhodamine B dye.

Decoration of rutile TiO2 nanorod film with g-C3N4/SrTiO3 for efficient photoelectrochemical cathodic protection

A highly efficient g-C3N4/SrTiO3 co-decorated rutile TiO2 nanorod composite film photoanode was fabricated on a conductive glass substrate by a three-step synthesis process involving hydrothermal reactions and chemical vapor deposition. The g-C3N4/SrTiO3/TiO2 composite film with an appropriate cascade energy band structure showed greatly improved visible light absorption and exhibited 4.5 times higher photocurrent density than the undecorated TiO2 film, resulting from its higher separation and transfer efficiency of the photogenerated electron-hole pairs. Under the white light irradiation, the composite film photoanode made the potential of the coupled 403 stainless steel in a 0.5 M NaCl solution decrease by 680 mV from its free corrosion potential, showing a significantly enhanced photoelectrochemical cathodic protection effect.

Super hydrophilic-electrons acceptor regulated rutile TiO2 nanorods for promoting photocatalytic H2 evolution

Photocatalytic H2 evolution from water splitting in liquid–solid two-phase requires an efficient photocatalyst with excellent ability of charge separation and reactant molecular diffusion.In this study, the super hydrophilic-electrons acceptor with abundant –C=O and –OH functional groups were evenly grafted onto rutile TiO2 nanorods surface to speed up the charge separation and water molecular diffusion, respectively. The photocatalytic results showed that the TiO2-CA grafted by citric acid (with three –C=O, three carboxy-(–OH) and one alcohol-(–OH)) presented a 1.48° contact angle and a distinct increased H2-production activity (48.5 mmol·h−1·g−1), whereas the TiO2-PA grafted by propane-1,2,3-tricarboxylicacid (Just lack of one alcohol-(–OH) compared with TiO2-CA) showed a 30.95° contact angle and a decreased H2-production activity (19.3 mmol·h−1·g−1) compared to the unmodified TiO2 (25.8 mmol·h−1·g−1), indicating that the super hydrophilic-electrons acceptor is vitally important to the photocatalytic activity of TiO2. Based on the present results, the carbonyl group (–C=O) possess a stronger reducing capability and act as “electrons acceptor”, while the only alcohol-hydroxyl group (–OH) in TiO2-CA can decrease the mass transfer resistance and serve as “super hydrophilic absorber”. Considering its mild preparation, inexpensive cost, and admirable efficiency, the super hydrophilic-electrons acceptor with dual functional groups regulated TiO2 can become a promising way for potential application in photocatalytic field.

Constructing the Vo-TiO2/Ag/TiO2 Heterojunction for Efficient Photoelectrochemical Nitrogen Reduction to Ammonia

Photoelectrochemical (PEC) nitrogen (N2) fixation technology provides the possibility to produce ammonia (NH3) under mild conditions, but the efficiency of N2 reduction in this process is greatly limited due to the high bond energy and ionic potential of N2. Herein, the Vo-TiO2/Ag/TiO2 photoelectrode consisting of rutile TiO2 nanorod arrays, Ag nanoparticles, and anatase TiO2 nanosheets with oxygen vacancies (Vo-TiO2) was constructed for accelerating the PEC reduction of N2 into ammonia. The separation of photogenerated carriers can be promoted by the heterojunction among TiO2 nanorods, Ag nanoparticles, and Vo-TiO2 nanosheets. Furthermore, the photogenerated electrons from the conduction band of TiO2 and the hot electrons from Ag nanoparticles’ local surface plasmon resonance (LSPR) effect were injected into the conduction band of Vo-TiO2, and they were further captured by Vo-TiO2 oxygen vacancy and can reduce N2 that adsorbed on the catalyst to NH3. Without any sacrificial agent, the average NH3 production rate can reach 51.2 μg h–1 cm–2. The catalyst exhibited excellent stability even after multiple uses. The LSPR effect of Ag nanoparticles and heterojunction structure promote the better PEC performance of TiO2 nanorod arrays.

Visible light-responsive radial TiO2 mesocrystal photocatalysts for the oxidation of organics

Radial TiO2 mesocrystals (rad-TiO2 MCs), or “sea urchin-like microspheres”, usually consisting of rutile TiO2 nanorods, are promising photocatalyst materials owing to their efficient light harvesting ability and large surface area.