As-prepared TiO2 Research Articles

Highly efficient photocatalytic degradation of tetracycline antibiotic enabled by TiO2 nanodispersion

The growing pollution of antibiotics poses a significant threat to the ecological environment and human health. Photocatalysis is a promising solution for eliminating tetracycline (TC), but developing efficient photocatalysts remains a critical and challenging task. Herein, TiO2 nanodispersion is first used for the removal of TC in water. The as-prepared TiO2 nanodispersion has a uniform size of 10 nm and a large specific surface area of 198.9 m2/g, exhibiting notable adsorption capacity, exceptional photocatalytic performance, and considerable stability. Under UV light, TiO2 nanodispersion achieved 100 % degradation of TC within 60 min, using less than 1/5 of the catalyst dosage typically applied in most studies, and exhibited the highest catalytic activity, reaching 500 mgTC∙gcatalyst-1h-1. Additionally, the photocatalytic rate constant of TiO2 nanodispersion was 2.74 times higher than commercial P25. After five photocatalytic cycles, the catalyst maintained a high degradation efficiency of 94 %. Even under visible light, the degradation efficiency of TC by TiO2 nanodispersion was approximately 90 % within 20 min, which was notably higher than that of P25 (63 %). Moreover, the as-prepared TiO2 nanodispersion demonstrated outstanding photocatalytic degradation ability for other typical antibiotics (chlortetracycline, oxytetracycline, and ciprofloxacin), demonstrating its potential as an efficient photocatalyst for the treatment of antibiotic wastewater.

Synthesis, characterization, electrochemical impedance spectroscopy performance and photodegradation of methylene blue: Mesoporous PEG/TiO2 by sol-gel electrospinning

Sol-gel and electrospinning methods successfully prepared porous TiO2 fibers. The samples were calcined at temperatures of 450 °C and 550 °C and characterized using different techniques. XRD analysis also revealed crystalline anatase and rutile phases of mp-TiO2 observed at calcining temperatures of 450 °C and 550 °C, whereas as-prepared showed an amorphous-like structure. Relatively higher surface area and photocatalytic efficiency were increased with a decrease in crystallite size. All samples absorb UV region. The Rs value of TiO2 calcined at 550 °C was 16.6 Ω, which is much lower than those of the 450 °C calcined TiO2 powder electrode (52.7 Ω) and as-prepared TiO2 electrode (95.3 Ω). In addition, the Rp resistance of TiO2 calcined at 550 °C electrode (5.85 kΩ) was also lower than those of 450 °C calcined TiO2 powder (39.0 kΩ) and as-prepared TiO2 electrode (68.9 kΩ), revealing better electronic and ionic conduction of TiO2 calcined at 550 °C electrode.

From mixed brookite/anatase TiO2 nanopowder to sodium titanates: Insight into morphology, structure, and photocatalytic performance

A method to obtain sodium titanate nanoribbons starting from a mixture of brookite and anatase TiO₂ nanopowder is described. As-prepared TiO2 nanopowder with a major brookite phase was used as a precursor in an alkaline hydrothermal approach, where the temperature was kept at 200 °C. The influence of hydrothermal treatment and consequent annealing temperature (T = 500 °C) on the crystal structure, phase composition, and morphology of samples were investigated by X-ray powder diffraction (XRPD), Raman and FTIR spectroscopy, and electron microscopy techniques (FESEM, HRTEM). All these methods point out that the hydrothermally treated sample, containing the NaTi3O6(OH)(H2O)2, Na2Ti3O7, and Na2Ti9O19, is dominated by layer-structured sodium hydroxititanate dihydrate. The annealing leads to the formation of rare sodium titanates, Na3Ti6O13 and Na2Ti9O19, with tunnel structures where the hexatitanate with increased sodium content prevails. The photocatalytic activity of synthesized nanostructures was tested in the degradation process of Reactive Orange (RO16) azo-dye upon UV excitation. It appears that photocatalytic activity is lower after hydrothermal treatment, but subsequent annealing makes sodium titanate nanoribbons faster in the degradation of RO16. The research implies that these sodium titanate nanostructures are promising photocatalytic materials and should be considered in the future for removing different pollutants from water.

Enhancing electrical and optical properties of anatase TiO2 nanotubes through electrochemical lithiation

In presented paper, anatase TiO2 nanotubes (NTs) were obtained by anodic oxidation of Ti-foil followed by subsequent annealing in air at 400 °C. After thermal treatment, TiO2 nanotubes (NTs) were electrochemically lithiated by means of galvanostatic (GS) discharge, as a part of GS cycling, at 25°C and 55 °C. Microstructural properties of the as-prepared material were observed by scanning and transmission electron microscopy (SEM, TEM), while changes in chemical bonding with lithiation were examined by X-ray photoelectron spectroscopy (XPS). Specific electrical conductivity, obtained by 4-point probe method, showed multifold increase after Li-ion insertion in TiO2 NTs, at both temperatures. By using diffuse reflectance spectroscopy (DRS), the decrease in energy gap, from 3.04 eV for the as-prepared TiO2 NTs to 2.81 eV for lithiated TiO2 NTs, was observed. The photoluminescence (PL) measurements suggest that Li-ion intercalation led to suppression of deep-level trap states within the bandgap, of TiO2 NTs, and promoted shallow defects associated to F-centers. Open-circuit photovoltage decay (OCVD) measurements confirm the promotion of shallow defect states. Furthermore, HER measurements indicate that the electrochemical lithiation is a promising strategy for enhancing the catalytic performance of TiO2.

Bioengineered sustainable phytofabrication of anatase TiO2 -adorned g-C3N4 nanocomposites and unveiling their photocatalytic potential towards advanced environmental remediation

The ecologically friendly properties, low-cost, and readily available titanium dioxide (TiO2) materials have made them a subject of considerable interest for numerous promising applications. Anatase TiO2 nanoparticles were synthesized in the current study through the utilization of a hibiscus leaf extract and the advent of TiO2-doped g-C3N4(TiCN) nanocomposites (varying 0.5 mM, 1.0 mM, 1.5 mM, and 2.0 mM) by thermal polymerization. Here, the proposed study utilized multiple analytical techniques, including UV–Vis spectroscopy, a diffraction pattern (XRD), SEM coupled with EDX analysis, TGA, and EPR, to characterize the as-prepared TiO2 nanoparticles and TiCN nanocomposites. BET analysis the adsorption-desorption isotherms of the TiCN(1.5 mM) nanocomposite, the surface area of the prepared nanocomposite is 112.287 m2/g, and the pore size is 7.056 nm. The XPS spectra support the development of the TiCN(1.5 mM) nanocomposite by demonstrating the presence of C and N elements in the nanocomposite in addition to TiO2. HRTEM images where the formation of stacked that indicates a planar, wrinkled graphitic-like structure is clearly visible. The TiCN (1.5 mM) specimen exhibited enhanced morphology, enhanced surface area, greater capacity to take in visible light, and lowered band gap when compared to g-C3N4 following z-scheme heterojunction. The sample denoted as TiCN (1.5 mM) exhibited superior performance in terms of adsorption and photocatalytic activity using rhodamine B and Bisphenol A. Furthermore, the TiCN (1.5 mM) composite exhibited satisfactory stability over four cyclic runs, indicating its potential application in minimizing the impact of organic wastewater contaminants when compared to g-C3N4.

Doping of photoactive TiO2 films by DC plasma electrolytic oxidation: Effect of transition metals

Several beneficial features maintain TiO2 in the top list of viable materials for photocatalytic purposes. However, its relatively large band-gap (3.0–3.2 eV) still hampers practical applications under sunlight. This work explores Direct Current (DC) Plasma Electrolytic Oxidation (PEO) of titanium as a fast, easily-scalable and single-step tool to synthesise doped TiO2 photoanodes with controlled morphology, crystalline structure and thickness. Zn-, Cu- and Fe-doped crystalline TiO2 films were obtained in H2SO4 aqueous solutions containing ZnSO4, CuSO4 and FeSO4 precursors, respectively. As-prepared TiO2 films showed a porous and homogeneous sponge-like surface morphology, typical of PEO-produced oxides, and a crystalline phase structure consisting of a mixture of anatase and rutile phases. The anatase content varied in the 54–100 % range and correspondingly the band-gap energy was in the 2.85–3.07 eV range. Doped oxides prepared with a low concentration of the metal precursors showed monochromatic incident-photon-to-current-efficiency (IPCE) values exceeding those obtained with pristine TiO2 by up to 24 %, best performing in the order Zn- > Cu- > Fe-doped TiO2. Photocurrent under polychromatic UV-Vis irradiation showed an analogous trend and the estimated efficiency of solar-light harvesting was in the 0.3–4 % range, with Zn- ≈ Cu- > Fe-doped TiO2. Although the superior performance of the PEO-prepared metal-doped TiO2 could not be fully confirmed by photoelectrocatalytic oxidation tests of organics, the present investigation showed the viability of DC PEO for the synthesis of metal-doped TiO2 photoanodes.

Hydrothermal synthesis of Ti3+-self-doped TiO2 photocatalysts using wool fibers as a biotemplate

A biotemplate method was used for the synthesis of self-doped TiO2 photocatalysts via the impregnation of sheep wool fibers with a solution containing titanium hydroxocomplexes under mild hydrothermal conditions (115 °C, 170 kPa), followed by the removal of the wool template during calcination in air at 600 °C. An intermediate wool-TiO2 composite, formed as a product of hydrothermal impregnation of a wool biotemplate, was comprehensively studied using IR spectroscopy, XRD, SEM, TG analysis, and DSC with mass spectrometric analysis of evaporation products to evaluate the mechanism of TiO2 crystallization. The phase composition, morphology, texture, and optical properties of the synthesized TiO2 photocatalysts were studied using XRD, SEM, nitrogen adsorption/desorption, and UV–Vis diffuse reflectance spectroscopy. High-temperature treatment after hydrothermal impregnation led to the formation of anatase and rutile TiO2 nanocrystallites with a characteristic size of 15–20 nm. The as-prepared TiO2 photocatalysts had an optical band gap of ∼3.0 eV due to the high content of the rutile phase but also absorbed visible light due to impurity atoms and defects. The samples exhibited very high photocatalytic activity in the degradation of Rhodamine B dye, which was used as a probe molecule, under both UV and visible light. Based on the XPS and EPR results, the enhanced photocatalytic activity of the prepared photocatalysts was attributed to the self-doping effect due to the many defects (Ti3+ sites and oxygen vacancies) formed during TiO2 crystallization, probably via the reduction of Ti4+ to Ti3+ in disproportionation reactions of disulfide bonds involving titanium hydroxocomplexes.

XAS study of sol–gel synthesized amorphous and anatase TiO2 nanoparticles

Amorphous titanium dioxide (TiO2) nanoparticles were obtained by the sol–gel method with subsequent crystallization to anatase by annealing at 350 °C for 4 h. Based on the research results using XANES and EXAFS X-ray absorption spectroscopy, it was determined that the as-prepared amorphous TiO2 contains vacancies in the oxygen and titanium sublattices.

Photocatalytic hydrogen peroxide production from seawater over graphitic carbon nitride supported titanium dioxide quantum dots

Photosynthesis of hydrogen peroxide (H2O2) from seawater, as a promising technique, is in infancy, and faces challenges of deactivation of photocatalyst and disturbance in H2O2 formation due to the coexisting salts in seawater. Herein, graphitic carbon nitride (g-C3N4) nanosheets supported titanium dioxide (TiO2) quantum dots (QDs) are exploited as novel and efficient photocatalysts for H2O2 photoproduction from seawater. An appropriate content of as-prepared TiO2 QDs are highly and uniformly dispersed on the surface of g-C3N4 nanosheets after a neutralization treatment. TiO2 QDs emerge the synergistic effect and the band gaps regulation effect on g-C3N4 to enhance the H2O2 production. The salt ions in the actual seawater also play the positive role. In actual seawater, the photocatalyst obtains 8.38 mM·h−1·g cat−1 of H2O2 productivity, 11.2% of apparent quantum yields (AQY), and good reusability·H2O2 productivity can be further increased into 30.15 and 23.44 mM·h−1·g cat−1, respectively in alkaline environment and with the addition of electron and proton donor ethanol in seawater. Active species and mechanism of the present photocatalytic system in seawater are also clearly clarified. TiO2 QDs supported on g-C3N4 photocatalyst achieved a major channel of two-electron reduction of O2, and an auxiliary channel of single electron reduction of O2 to produce H2O2 in seawater.

Effects of Ru particle size over TiO2 on the catalytic performance of CO2 hydrogenation

The influence of metal particle size over heterogeneous catalysts on the catalytic performance has always been an interesting subject due to its significance from both fundamental and practical perspectives. In this work, we regulated the synthesis of TiO2 by the hydrolysis of different titanium precursors, and as-prepared TiO2 supports were employed to load Ru with impregnation method. Interestingly, we synthesized three Ru-TiO2 catalysts with different Ru particle sizes of 1.1, 2.9 and 5.2 nm. The Ru-TiO2 catalysts were next tested for CO2 hydrogenation reaction, the results show that the medium Ru particles on TiO2 exhibited the best CO2 methanation activity. Based on the characterizations, we observed that the medium Ru particles exhibited the best redox properties compared with small and large Ru particles, which was beneficial to the H2 dissociation; in addition, the medium Ru particles exhibited a moderate ability to activate CO2, resulting in the most favorable formation and decomposition of bidentate bicarbonate. Consequently, the Ru-TiO2 catalyst with medium Ru particles showed the highest activity for CO2 methanation. This study provides a new method to prepare Ru-TiO2 catalysts with different Ru sizes and also presents an understanding of Ru particle size effects on CO2 hydrogenation.

NH2-MIL-125-Derived N-Doped TiO2@C Visible Light Catalyst for Wastewater Treatment.

The utilization of titanium dioxide (TiO2) as a photocatalyst for the treatment of wastewater has attracted significant attention in the environmental field. Herein, we prepared an NH2-MIL-125-derived N-doped TiO2@C Visible Light Catalyst through an in situ calcination method. The nitrogen element in the organic connector was released through calcination, simultaneously doping into the sample, thereby enhancing its spectral response to cover the visible region. The as-prepared N-doped TiO2@C catalyst exhibited a preserved cage structure even after calcination, thereby alleviating the optical shielding effect and further augmenting its photocatalytic performance by increasing the reaction sites between the catalyst and pollutants. The calcination time of the N-doped TiO2@C-450 °C catalyst was optimized to achieve a balance between the TiO2 content and nitrogen doping level, ensuring efficient degradation rates for basic fuchsin (99.7%), Rhodamine B (89.9%) and tetracycline hydrochloride (93%) within 90 min. Thus, this study presents a feasible strategy for the efficient degradation of pollutants under visible light.

Structural Diversity Design, Four Nucleation Methods Growth and Mechanism of 3D Hollow Box TiO2 Nanocrystals with a Temperature-Controlled High (001) Crystal Facets Exposure Ratio.

Three-dimensional (3D) hollow box TiO2 nanocrystals with structural diversity have been designed and grown by four nucleation methods, including the acid dissolution denucleation method with Fe2O3 as heterogeneous nucleation, the topological phase transition method, the sonic solvothermal method, and the air atmosphere sintering method with TiOF2 as homogeneous nucleation. Through full morphology analysis and structural characterization, reasonable growth mechanisms of 3D hollow box TiO2 nanocrystals were proposed, including nucleation dissolution, Oswald ripening, and hydrolysis reactions. It was found that the high energy (001) crystal facets exposure ratio was closely correlated with reaction temperature of four nucleation-methods, which even reached 92% for the first time. Under simulated sunlight irradiation, their hydrogen production performance and photocatalytic degradation efficiency on model dye molecules rhodamine B (RhB) and methylene blue (MB) were evaluated, and as-prepared hollow box TiO2 nanocrystals prepared by the sonic solvothermal method exhibited the best photocatalytic performance, with a hydrogen production rate of 93.88 μmol/g/h. Within 70 min, the photocatalytic degradation rates of RhB and MB reached 96.59 and 75.25%, respectively, which were 5.74 and 5.54 times that of P25. Their properties are closely connected with the orderly cubic and hierarchy configuration structure of hollow box TiO2 nanocrystals, which have a high exposure ratio of (001) facet controlled by reaction temperatures, thereby greatly improving the photocatalytic activity. This study provides a classic reference for improving the properties of hollow box TiO2 nanocrystals through structural diversity design and various methods of nanocrystal growth.

Surface oxygen vacancies of TiO2–x enabled water transfer photocatalytic hydrogenation of nitrobenzene to aniline without use of co-catalyst

Water transfer photocatalytic hydrogenation of nitrobenzene to aniline is an attractive and environmentally friendly process in chemical manufacturing. Herein, through an in-situ CO reduction pathway, the TiO2-based photocatalysts with surface and subsurface VOs are prepared for water transfer hydrogenation of nitrobenzene to aniline. The CO originated from incomplete combustion of residual organic compounds of the TiO2 precursor (tetrabutyl titanate), can react with the lattice oxygen of TiO2 and obtain rich surface and subsurface VOs TiO2-based photocatalysts without additional reduction reagent. The as-prepared TiO2 catalyst exhibits a desired band structure and rapid separation of photogenerated carriers. Besides, the TiO2 catalyst with surface and subsurface VOs can stabilize intermediates for water transfer hydrogenation. Thus, compared with heteroatom doping and poor-VOs TiO2, the TiO2 catalyst exhibits highly selectivity and conversion for photocatalytic hydrogenation of nitrobenzene substrates without the use of any cocatalyst and reductant H2.

EXAMINING THE PHASE COMPOSITION OF TiO2 NANOPARTICLES DERIVED FROM SOL-GEL: IMPACT OF REACTION AND PROCESSING CONDITIONS

TiO2 nanoparticles with crystallite size less than 15 nm were prepared from TiCl4 precursor by a modified sol-gel route. As-prepared TiO2 nanoparticles were extensively characterized using X-ray diffractometry, and their crystallite size was calculated using Debye-Scherrer formula. The phase composition and crystallite size of TiO2 nanoparticles were dependent on reaction parameters including TiCl4 concentration, reaction temperature, annealing temperature, and surfactant. The crystallite size increases with increasing annealing temperature. Amorphous-anatase phase transition occurs at 400-450oC and anatase-rutile phase transition occurs at ca. 700oC.

Carbon Dots Modification Surface of Titanium Dioxide and Their Photocatalytic Activity

This work, we develop the efficient visible-light-responsive titanium dioxide photocatalyst using carbon dots as a sensitizer (C-dots/TiO2). C-dots was synthesized via a simple one-pot reaction by microwave-assisted pyrolysis method using orange juice as carbon precursors. C-dots/TiO2 samples were prepared by a facile route. Moreover, the micro-structure and optical properties of as-prepared C-dots/TiO2 have been evaluated using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and ultraviolet–visible diffuse reflection spectroscopy (DRS). The modification surface of TiO2 with carbon dots enhanced the light absorption in visible region. The photocatalytic properties of as-prepared pure TiO2 and C-dots/TiO2 were also explored indigo carmine decolorization under visible light. The photocatalytic results revealed that the C-dots/TiO2 exhibited higher catalytic performance than the pure TiO2 under visible light.

Selectivity of Sol-Gel and Hydrothermal TiO2 Nanoparticles towards Photocatalytic Degradation of Cationic and Anionic Dyes.

Titanium dioxide (TiO2) nanoparticles have been extensively studied for catalyzing the photo-degradation of organic pollutants, the photocatalyst being nonselective to the substrate. We, however, found that TiO2 nanoparticles prepared via the sol-gel and hydrothermal synthetic routes each possess a definite specificity to the charge of the substrate for photodegradation. The nanoparticles were characterized by SEM, FTIR, XRD, TGA, and UV-visible spectra, and the photocatalytic degradation under UV-B (285 nm) irradiation of two model compounds, anionic methyl Orange (MO) and cationic methylene blue (MB) was monitored by a UV-visible spectrophotometer. Untreated sol-gel TiO2 nanoparticles (Tsg) preferentially degraded MO over MB (90% versus 40% in two hours), while after calcination at 400 °C for two hours (Tsgc) they showed reversed specificity (50% MO versus 90% MB in one hour). The as-prepared hydrothermal TiO2 nanoparticles (Tht) behaved in the opposite sense of Tsg (41% MO versus 91% MB degraded in one and a half hours); calcination at 400 °C (Thtc) did not reverse the trend but enhanced the efficiency of degradation. The study indicates that TiO2 nanoparticles can be made to degrade a specific class of organic pollutants from an effluent facilitating the recycling of a specific class of pollutants for cost-effective effluent management.

Enhancement of visible light organic dyes photodegradation using TiO2 (001)/Graphene oxide nanocomposite

Photodegradation has been considered one of the most promising ways to treat wastewater. In this work, TiO2 (001)/Graphene Oxide (GO) nanocomposite has been successfully synthesized using hydrogen fluoride as a crystal-directing agent towards (001) facets. The nanocomposite was characterized by FTIR, XRD, Raman, HR-TEM, and diffuse reflectance spectra (DRS). Based on the result, the TiO2 (001) was decorated on the surface of the GO sheet with high absorption of visible light. In addition, as-prepared TiO2 (001)/GO nanocomposite provides a synergistic effect by increasing dye degradation activity with 95% and 99% removal rates for the photodegradation of methylene blue and crystal violet dyes, respectively, under LED irradiation for 10 min. The photodegradation kinetics of TiO2 (001)/GO was also successfully modeled and was found to follow the pseudo-first order kinetic. The enhanced photodegradation of the TiO2 (001)/GO nanocomposite attributed to the excellent synergy between TiO2 (001) nanoparticles and GO, which results in the highly efficient photocatalyst for removing organic pollutants in water.

Bifunctional linker-assisted assembly of core-shell TiO2 @In2S3 with enhanced photocatalytic activity for reduction of Cr(VI)

Monodispersed anatase TiO2 microspheres were prepared by a modified sol-gel method. In2S3 nanoparticles (NPs) were loaded on the as-prepared TiO2 to form non-core-shell TiO2/In2S3 and core-shell TiO2 @In2S3 composites through a direct deposition method and a linker-assisted assembly strategy, respectively. The catalytic activity of TiO2/In2S3 and TiO2 @In2S3 for HCOONH4-mediated photoreduction of Cr(VI) was comparatively studied. Based on soft and hard acid-base theory and experimental results, the mechanisms for forming the core-shell TiO2 @In2S3 and enhancing photocatalytic activity were elucidated. Results indicate: i) When TiO2 surface is functionalized by dimercaptosuccinic acid (DMSA), a bifunctional linker, In2S3 NPs can be uniformly and tightly attached onto the TiO2 to form core-shell TiO2 @In2S3 composite via the strong binding force between In3+ ions and thiol groups (–SH), whereas In2S3 NPs can't be evenly and firmly anchored to bare TiO2 due to the weaker affinity of In2S3 NPs for TiO2 and thereby non-core-shell TiO2/In2S3 composite is obtained. ii) TiO2 @In2S3 exhibits superior photocatalytic activity to TiO2/In2S3, which can be attributed to more efficient interfacial electron transfer between In2S3 and TiO2 in TiO2 @In2S3 than that in TiO2/In2S3.

In Vitro Safety Assessment of In-House Synthesized Titanium Dioxide Nanoparticles: Impact of Washing and Temperature Conditions.

Titanium dioxide nanoparticles (TiO2 NPs) have been widely used in food, cosmetics, and biomedical research. However, human safety following exposure to TiO2 NPs remains to be fully understood. The aim of this study was to evaluate the in vitro safety and toxicity of TiO2 NPs synthesized via the Stöber method under different washing and temperature conditions. TiO2 NPs were characterized by their size, shape, surface charge, surface area, crystalline pattern, and band gap. Biological studies were conducted on phagocytic (RAW 264.7) and non-phagocytic (HEK-239) cells. Results showed that washing amorphous as-prepared TiO2 NPs (T1) with ethanol while applying heat at 550 °C (T2) resulted in a reduction in the surface area and charge compared to washing with water (T3) or a higher temperature (800 °C) (T4) and influenced the formation of crystalline structures with the anatase phase in T2 and T3 and rutile/anatase mixture in T4. Biological and toxicological responses varied among TiO2 NPs. T1 was associated with significant cellular internalization and toxicity in both cell types compared to other TiO2 NPs. Furthermore, the formation of the crystalline structure induced toxicity independent of other physicochemical properties. Compared with anatase, the rutile phase (T4) reduced cellular internalization and toxicity. However, comparable levels of reactive oxygen species were generated following exposure to the different types of TiO2, indicating that toxicity is partially driven via non-oxidative pathways. TiO2 NPs were able to trigger an inflammatory response, with varying trends among the two tested cell types. Together, the findings emphasize the importance of standardizing engineered nanomaterial synthesis conditions and evaluating the associated biological and toxicological consequences arising from changes in synthesis conditions.

The ultrathin PEALD-GaN surface/interface layer-modulated charge dynamics in quantum dot-sensitized solar cells

In this work, gallium nitride (GaN) is employed for the first time to modulate the charge dynamics of quantum dot-sensitized solar cells (QDSCs). An ultrathin GaN layer has been coated on the surface of both mesoporous TiO2 photoanode and quantum dots (QDs) at 240 °C by plasma-enhanced atomic layer deposition (PEALD) approach. It is revealed that there exists a stepped energy level alignment among the as-prepared TiO2 film, GaN layer and QDs, which accelerates the extraction and collection of photogenerated electrons. Meanwhile, a type-II core-shell QD/GaN structure is formed benefiting from the self-limiting reactions of PEALD, resulting in an enhanced light absorption and a redshift of absorption edge. In addition, the dense GaN layer can also effectively inhibit the reverse transfer of photogenerated electrons from TiO2 to QDs or electrolyte while improving the connection between TiO2 and QDs. Ultimately, the QDSCs with a 0.68 nm-thick GaN layer achieve a 29% increase of short-circuit current density and enhanced device efficiency, even with reduced fill factor. This work has shown the multi-functions of GaN in regulating the charge dynamics of QDSCs as well as the potential advantages in replacing TiO2 as photoanode for electronic extraction and transport.