TiO2 Photocatalysis Research Articles

Al/TiO2 composite as a photocatalyst for the degradation of organic pollutants.

TiO2 is a catalyst that can effectively degrade organic pollutants with the following advantages, low cost, simplicity, and pollution-free nature. In recent years, the non-noble plasmonic metal Al has effectively improved the photocatalytic performance of TiO2. However, the current reports are limited to the photocatalytic performance of Al/TiO2 on the substrate, which requires expensive large-scale vacuum equipment. In this study, monodispersed Al particles were proposed to enhance the photocatalysis of TiO2. The localized surface plasmon resonance (LSPR) effect of Al is proven by finite difference time domain method (FDTF) simulation. Then, Al/TiO2 composites were prepared by combining monodispersed Al and TiO2. The influence of ligand (glutathione (GSH), glutamic acid (GAG), or 3-mercaptopropane acid (MPA)), Al size (40 to 300 nm), and the ratio of Al to TiO2 (0.5:1 to 10:1) on the photocatalytic degradation of methylene blue (MB) by Al/TiO2 were discussed. The obtained results showed that the Al/TiO2 composite which were prepared with 200 nm Al particles, GSH as the ligand bridge, and an Al:TiO2 ratio of 1:1 had the best MB degradation effect. It can degrade 97.7% of 10 mg/L MB in 100 min. The reaction rate of the Al/TiO2 composite with the optimal photocatalytic performance is k=3.36×10-2 min-1, which is 10 times that of P25 TiO2. In addition, Al/TiO2 has a good photocatalytic effect on rhodamine B (RhB) and crystal violet (CV). Therefore, Al/TiO2 composites with the advantage of high efficiency are a type of potential photocatalytic material that can be used for the photocatalytic treatment of organic pollutants in water.

Use of TiO2 in Photocatalysis for Air Purification and Wastewater Treatment: A Review

This study reviews recent research on the synthesis and application of titanium dioxide (TiO2)-based photocatalysts for environmental applications. The principles of non-homogenous photo-catalysis include utilizing a solid semiconductor, such as titanium dioxide Nano or macro, to form a stable suspension (heterogeneous phase) at the impact of irradiation to elevate a reaction at the surface interface of the different phases in the system. Recently, titanium dioxide has been considered the better semiconductor in non-homogenous photoinduced treatment. TiO2-based photocatalysts have broad applications for industrial processes because of their exceptional physicochemical properties. Nevertheless, having a narrow band near the ultraviolet region limits its applications within visible radiation. As a result of this, there have been considerable research efforts to improve the visible light tendency of TiO2 through modifications of its optical and electronic properties. Several strategies, such as coupling TiO2 tightly and incorporating other metallic components during synthesis, have increased the bandgap of TiO2 for visible light applications. Moreover, an overview of nanotechnology that could enhance the properties of TiO2-based catalysts in an environmentally friendly way to decompose pollutants is also presented. The various TiO2-based photocatalysts have wide applications in degrading recalcitrant pollutants in the air, water, and wastewater treatment under visible light.

Photocatalytic Cementitious Material for Eco-Efficient Construction—A Systematic Literature Review

Photoinduced processes governed by light activated TiO2 have been studied in many ways. One of the most active areas is the development of TiO2 photocatalysis technologies on their application for reducing environmental impacts. The immobilization of TiO2 on solid support, such as cementitious materials, greatly enhances its use in practical applications. In this review, a wide range of applications for achieving eco-efficient building using cementitious composite materials containing TiO2 photocatalyst was presented. The basic mechanism of photocatalysis, such as electron excitation, charge transfer process, reactive oxygen species (ROS) generation, and its role to oxidize the pollutant and microorganisms were extensively discussed. Unlike self-cleaning and air purification systems, the study on the antibacterial function of a cement-based surface containing TiO2 is very limited. In photocatalytic cementitious materials, the key element affecting the photocatalytic performance is the accessible active surface area. However, microstructure of cementitious materials changes with age due to hydration and surface carbonation. Hence, surface area reduction and mass transfer limitation become the main drawbacks of incorporating TiO2 in cementitious materials. This review, therefore, provides the state of the art in photocatalytic cement-based composite materials and identifies the areas in which future improvement is needed.

A Composite Fabric with Dual Functions for High-Performance Water Purification.

The dilemma of diminishing freshwater resources caused by water pollution has always impacted human life. Solar-driven interfacial evaporation technology has the potential for freshwater production via solar-driven distillation. However, in solar-driven interfacial evaporation technology, it is difficult to overcome the problem of wastewater containing various contaminants. In this work, we propose a bifunctional fabric created by depositing titanium dioxide@carbon black nanoparticles onto cotton fabric (TiO2@CB/CF). The TiO2@CB/CF has a coupling effect that includes the photothermal effect of CB and photocatalysis of TiO2, and it can not only generate clean water but can also purify contaminated water. The resulting bifunctional fabric can achieve an outstanding water evaporation rate of 1.42 kg m−2 h−1 and a conversion efficiency of 90.4% in methylene blue (MB) solution under one-sun irradiation. Simultaneously, the TiO2@CB/CF demonstrates a high photocatalytic degradation of 57% for MB solution after 2 h with light irradiation. It still shows a good photocatalysis effect, even when reused in an MB solution for eight cycles. Furthermore, the TiO2@CB/CF delivers excellent performance for actual industrial textile dyeing wastewater. This bifunctional fabric has a good application prospect and will provide a novel way to resolve the issue of freshwater scarcity.

Photocatalysis engineered hydrophilic reactors on hydrophobic paper for the visual and colorimetric assay of alkaline phosphatase activity

Taking advantage of the intrinsic photocatalysis of TiO2, hydrophilic reactor arrays were lithographically patterned on a hydrophobic paper via a simple UV irradiation. As a proof-of-concept, alkaline phosphatase (ALP) was used as the model analyte for colorimetric analysis. As ALP can induce hydrolysis of pyrophosphate-Zn(II) framework, the released Zn2+ ions are subsequently coordinated with red-colored zincon to form blue-colored zincon-Zn(II) chelate complex, and these color differences were applied for further colorimetric assay. The sensing platform showed response to ALP ranging from 20 ~ 800 U L-1 with a detection limit of 3 U L-1, and the recoveries of ALP in serum samples were in the range 95.7 ~ 104.5% with relative standard deviations from 2.10 to 3.84%. Additionally, the distinct wettability features of the proposed sensing platform effectively prevent lateral fluid spread out of hydrophilic reactors, thus allowing not only the use ofminimum amount of analyte but it hasalso a high potential for simultaneous quantification of multiple samples.

Revisiting the mechanisms of nitrite ions and ammonia removal from aqueous solutions: photolysis versus photocatalysis.

Nitrite ions and ammonia are widespread forms of inorganic water pollutants. Nevertheless, the mechanisms of their photolytic and photocatalytic reactions under UV-A irradiation are still fully undisclosed, particularly, at different pH values under aerobic and inert atmospheres. Herein, we have studied the photolytic decomposition of nitrite ions under different conditions using 365nm UV-A LED as a light source instead of mercury lamps that emit photons in the UV-B region and generate a lot of heat. The results indicated that the rate of nitrite disproportionation in the dark at pH ≤ 3.0 is remarkably high relative to the rate of the photolytic decomposition. At pH ˃ 3, the photolytic reaction is negligible and nitrite ions showed considerable stability. In contrast, the photocatalytic oxidation of nitrite ions over TiO2 photocatalysts, namely, TiO2P25, TiO2UV100, and TiO2 anatase/brookite mixture proceeds at pH ˃ 3.0. TiO2 P25 exhibited the highest photocatalytic activity at pH 5. Interestingly, the photolytic simultaneous removal of nitrite ions and ammonia was possible at pH 9.0 in the absence of oxygen (Ar atmosphere). A 42.69 ± 0.66%, 27.75 ± 1.7%, and 32.74 ± 0.59% of nitrogen calculated based on nitrite, ammonia, and both of them, respectively, can be removed after 6h of UV-A irradiation. The selectivity of N2 evolution was 77.6%. The nitrogen removal rate was significantly reduced in the presence of TiO2 photocatalyst evincing that TiO2 photocatalysis is applicable for nitrite ions oxidation, whereas the photolytic process is better suited for the simultaneous removal of nitrite ions and ammonia.

Highly synergistic effect for tetracycline degradation by coupling a transient spark gas–liquid discharge with TiO2 photocatalysis

Water pollution driven by the increasing antibiotic abuse leads to serious ecological impacts and risks to human health. Non-thermal plasma, a sustainable advanced oxidation process, is considered as a promising approach for antibiotic degradation. In this study, a transient spark gas–liquid discharge was developed for the degradation of tetracycline in water and coupled with a photocatalyst (TiO2) to further improve the degradation efficiency. Results show that the discharge was accompanied by intense UV light of up to 28 μW/cm2. The tetracycline degradation performance was strongly dependent on the pulse voltage, working gas, initial concentrations of tetracycline and the catalyst addition. The best degradation performance was achieved in the plasma-TiO2 system with a degradation rate of 90.2% after 10 min treatment. The catalyst exhibits a high efficiency at lower pulse voltages, with the synergetic intensity of plasma and TiO2 showing a decreasing trend with increasing pulse voltage. Radical quenching experiments suggest that hydroxyl radical (∙OH) plays a key role in the tetracycline degradation process. A pathway for tetracycline degradation by the plasma-TiO2 process is deduced according to the analysis of the degradation intermediates. Further, seed germination and plant growth tests for the treated water demonstrated the feasibility of discharging the treated water to irrigate agricultural crops.

Metal oxide-doped elastomeric materials for amplifying visible light-based antimicrobial activity

Healthcare-associated infection through transmission of pathogenic bacteria poses a huge threat to public health. One of the main transmission routes is via contaminated surfaces, including those of medical devices, and therefore significant efforts are being invested in developing new surface decontamination strategies. This includes visible light-based approaches, which offer improved compatibility with mammalian cells but lower germicidal efficacy with respect to UV-light. This study investigates the potential to enhance the antimicrobial efficacy of 405 nm light for surface decontamination through use of a photocatalytic TiO2-doped elastomer, elastomers being selected due to their wide use in biomaterials. Poly(dimethylsiloxane) (PDMS) was doped with TiO2 nanoparticles and the surface elastomer etched to expose the embedded nanoparticles. As etching results in increased surface roughness, samples with control nanoparticles (SiO2 and Fe3O4) were also investigated to decouple the effects of roughness and photoinactivation upon bacterial attachment and inactivation. Characterisation by SEM, AFM and contact angle analysis confirmed that etching produced a rougher (39.3 ± 15.3 versus 5.11 ± 1.29 nm RMS roughness; etched versus unetched TiO2-PDMS), more hydrophobic surface (water contact angle of 120 ± 2.5° versus 110 ± 1.0°; etched TiO2-PDMS versus native PDMS). This surface, rich in exposed photocatalytic TiO2 nanoparticles, allows direct contact between contaminating bacteria and nanoparticles, enabling ROS generation in closer proximity to the bacteria and consequent enhancement of visible light treatment. Incorporating TiO2 into PDMS significantly improved the photoinactivation efficacy (mean bacterial count for light-treated samples normalised to untreated samples of 0.043 ± 0.0081) compared to PDMS alone (0.19 ± 0.036), when seeded with Staphylococcus aureus and exposed to 405 nm, 60 J cm−2 light. However, photoinactivation efficacy was significantly (p < 0.001) enhanced by etching the TiO2-PDMS surface (0.015 ± 0.0074), resulting in greater photoinactivation than that obtained for etched (47.0 ± 14.5 nm RMS roughness), non-photocatalytic SiO2-PDMS (0.10 ± 0.093). Results suggest this doping and etching strategy shows significant potential for facilitating decontamination of elastomer-based biomaterials.

Photocatalytic removal of pharmaceutical water pollutants by TiO2 - Carbon dots nanocomposites: A review.

Pharmaceuticals are becoming increasingly more relevant water contaminants, with photocatalysts (such as TiO2) being a promising approach to remove these compounds from water. However, TiO2 has poor sunlight-harvesting capacity, low photonic efficiency, and poor adsorption towards organic pollutants. One of the emerging strategies to enhance the photocatalytic performance of TiO2 is by conjugating it with fluorescent carbon dots. Herein, we performed a critical review of the development of TiO2 - carbon dots nanocomposites for the photocatalytic removal of pharmaceuticals. We found that carbon dots can improve the photocatalytic efficiency of the resulting nanocomposites, mostly due to increasing the adsorption of organic pollutants and enhancing the absorption in the visible range. However, while this approach shows significant promise, we also identified and discussed several aspects that need to be addressed before this strategy could be more widely used. We hope that this review can guide future studies aiming to the development of enhanced photocatalytic TiO2 - carbon dots nanocomposites.

On the Selectivity of Radical Scavengers Used To Probe Hydroxyl Radical Formation in Heterogeneous Systems

Tris and methanol have been used quite extensively as probes for surface-bound hydroxyl radicals in heterogeneous systems, such as TiO2 photocatalysis and catalytic decomposition of H2O2. Recent studies have indicated that the selectivity for surface-bound hydroxyl radicals is questionable and that the yield of the stable detectable product, formaldehyde, may be different for different reactive species. In this work, we have explored the selectivity as well as the formaldehyde yield of these two probes by experimentally studying formaldehyde formation in homogeneous (gamma radiolysis) and heterogeneous (TiO2 photocatalysis) systems, where hydroxyl radicals and Br2·– can be formed. The latter is formed in the reaction between hydroxyl radicals and Br– at relatively high concentrations of Br–. The experiments clearly show that the formaldehyde yield is reduced by 85% when comparing hydroxyl radicals and Br2·– in a homogeneous methanol system and increased by 50% when making the same comparison for the homogeneous Tris system. The increased yield is attributed to a change in the reaction mechanism as Br2·– is mainly expected to produce a nitrogen-centered radical cation, while the hydroxyl radical mainly produces carbon-centered radicals. The radical cation appears to produce formaldehyde with a higher yield. In the photocatalysis system, the trends are similar but even more emphasized. The rationale for this is discussed, as well as the suitability of methanol and Tris as probes for surface-bound hydroxyl radicals in heterogeneous systems.

Multifunctional core-double-shell C@MnO@TiO2 catalysts with enhanced full-light conversion for the highly efficient photothermal oxidation of toluene

In this study, the integrated core-double-shell structures of C@MnO@TiO2 (abbreviation CMT) composites have been rationally designed and fabricated utilizing of carbon spheres as frameworks and reducing agents, which were introduced a TiO2 outer shell on MnO2 @C nanospheres by sol-gel coating and subsequent in-situ calcination reduction process. Owing to the well-defined structures, the as-prepared CMT composites can efficiently convert full-light into heat energy, achieve the rapid adsorption and enrichment of toluene and motivate the synergistic effects of photocatalysis of TiO2 and full-light driven thermalcatalysis of MnOx @C, resulting in the significantly enhanced photothermal catalytic performance of toluene oxidation upon UV-Vis-IR irradiation of Xe lamp. Furthermore, the strategy on changing the molar ratio of Mn/Ti among CMT composites can not only act as important role in the control of the coating thickness of outer layer TiO2, surface morphologies and physicochemical properties within a certain range, but also yield opportunities to adjust photothermal synergistic effects between ternary components among CMT composites. Compared with other CMT composites, CMT-3 samples with a suitable Mn/Ti molar ratio of 0.4 exhibited much higher photothermal catalytic activity including a high toluene removal efficiency and CO2 production rate (99.1 % within 90 min and 102.5 μmol.g−1.min−1, respectively), which were attributed to its optimized coating thickness of outer layer TiO2, and the optimal distribution ratio of surface oxygen species (Oads/Olatt/Owat) and electronic valence of Mn species (Mn2+/Mn3+/Mn4+). The possible mechanism for photothermal catalytic oxidation of toluene over CMT composites was also discussed in terms of the special core-double-shell structure, matching electronic band levels and photothermal synergistic effects.

Tuning the optical property of titania nanotubes array using CdS microemulsion sensitization for enhanced photocatalytic activity

Titania (TiO2) is a well-known photocatalyst in material science. However, it only works in the UV(Ultra violet) range of the spectrum(Eg = 3.2eV). The doping approach allows TiO2 photocatalysis to function in the visible region.Cadmium sulphide(CdS) was utilized as a dopant to maximize the quantity of visible light passing through, as its bandgap was just 2.4eV. Material manipulation at the nanoscale can have many distinct outcomes. Titania nanotubesarray(TiNT)was created by anodization, and CdS quantum dots were made by microemulsion technique and integrated into TiNT. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed to study morphology. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to determine the composition. UV-diffuse reflectance (UV-DRS) spectroscopy was used for photocatalytic studies. Photocatalytic methyl orange (MO) breakdown and photocatalytic hydrogen evolution were also proven under visible light. According to the study, the CdS/TiNT nanotubes array has more photocatalytic power than pure TiNT. Based on the findings, CdS quantum dots could get into the nanotubes, making them perfect heterostructures for all visible photocatalysis.

Challenges and Opportunities of Using Titanium Dioxide Photocatalysis on Cement-Based Materials

Since the early seventies with the work of Akira Fujishima on photocatalytic and superhydrophilic properties of titanium dioxide (TiO2), also known as the Honda–Fujishima effect, photocatalysis has been investigated and progressively implemented in cement-based materials towards the development of self-cleaning, air-purifying and antiseptic materials, buildings and infrastructure. Although important achievements have been obtained at the laboratory scale, their real scale application has had some limitations mainly due to the low efficiencies obtained during adverse environmental conditions. Therefore, this article presents the challenges and opportunities of using of titanium dioxide in cement-based materials towards the development of truly efficient sustainable building materials. First, TiO2 photocatalysis and its incorporation in cementitious materials are presented. Second, self-cleaning, air-purifying and antimicrobial properties are discussed in terms of the lab and pilot project results. Third, conclusions regarding the different multifunctional properties are given towards the real application of TiO2 photocatalysis. Particularly, complementary technologies and strategies are presented in order to increase the above-mentioned multifunctional properties.

Effect of oxidative and non-oxidative conditions on molecular size fractionation of humic acids: TiO2 and Cu-doped TiO2 photocatalysis.

Natural waters contain some carbonaceous materials referred to as dissolved organic matter, which is mainly composed of humic acids (HA). Owing to its polydispersed character related to the presence of diverse molecular size fractions (< 450kDa to even < 1kDa), HA displays curious reactivity in natural waters and during water treatment train. In this study, a system-based stepwise approach was tracked by characterizing HA following photolysis, adsorptive interactions, and solar photocatalysis using bare TiO2, sol-gel prepared TiO2, and their respective Cu-doped specimens complementary to kinetic evaluation on this respect. For this purpose, prior to and following each treatment, HA was monitored by dissolved organic carbon content, UV-vis parameters, and fluorescence features. Attenuated total reflection Fourier transform infrared (FTIR), surface-enhanced Raman scattering spectroscopy (SERS), XRD, SEM, EDAX XPS, and DRS were used to characterize the materials and solutions reported in this study. Most significant quantitative variations were attained in UV-vis spectroscopic parameters along with fluorescence characteristics; however, infrared and Raman profiles displayed slight deviations in qualitative measures. Differentiation between the selected photocatalyst specimens could be visualized through molecular size effects pointing out the significance of HA 10kDa fraction. For the first time, this study reports the degradation of specific fractions of HA as a function of their molecular size fraction. Cu-TiO2 seems to photocatalyze more effectively the degradation of the diverse HA fractions due to their more extended absorption of solar light by this photocatalyst.

Optimization of hydrolysis temperature in liquid phase deposition for TiO2 photocatalysis

TiO2 nanostructure could be produced at below 100 °C by means of liquid phase deposition (LPD), which is a green approach with low cost and low impact on the environment. The improvement of crystallinity is one of the main challenges toward efficient photocatalysis. Herein, we investigated the dependence of synthesis temperature on the crystal structure of TiO2 photocatalysts to provide higher photocatalytic efficiency. Scanning electron microscopy, X-ray diffraction, and Raman spectroscopy analysis confirmed the formation of waxberry-like TiO2 with an anatase phase with a synthetic temperature up to 80 °C. Both reaction temperature and time are found to dictate the crystallinity, structure, and size of the products, which could be attributed to the hydrolysis of a precursor (ammonium hexafluoro titanate), as well as the aggregation and coagulation of primary particles. The product synthesized at 70 °C for 3 h exhibited higher crystallinity, which led to higher photocatalytic efficiency observed based on the decomposition of methylene blue.

Trapping and detecting nanoplastics by MXene-derived oxide microrobots

Nanoplastic pollution, the final product of plastic waste fragmentation in the environment, represents an increasing concern for the scientific community due to the easier diffusion and higher hazard associated with their small sizes. Therefore, there is a pressing demand for effective strategies to quantify and remove nanoplastics in wastewater. This work presents the “on-the-fly” capture of nanoplastics in the three-dimensional (3D) space by multifunctional MXene-derived oxide microrobots and their further detection. A thermal annealing process is used to convert Ti3C2Tx MXene into photocatalytic multi-layered TiO2, followed by the deposition of a Pt layer and the decoration with magnetic γ-Fe2O3 nanoparticles. The MXene-derived γ-Fe2O3/Pt/TiO2 microrobots show negative photogravitaxis, resulting in a powerful fuel-free motion with six degrees of freedom under light irradiation. Owing to the unique combination of self-propulsion and programmable Zeta potential, the microrobots can quickly attract and trap nanoplastics on their surface, including the slits between multi-layer stacks, allowing their magnetic collection. Utilized as self-motile preconcentration platforms, they enable nanoplastics’ electrochemical detection using low-cost and portable electrodes. This proof-of-concept study paves the way toward the “on-site” screening of nanoplastics in water and its successive remediation.

Z-scheme TiO2−x@ZnIn2S4 architectures with oxygen vacancies-mediated electron transfer for enhanced catalytic activity towards degradation of persistent antibiotics

In photocatalysis as a “green chemistry” technology, the development of efficient strategies to fabricate high-performance micro-nano photocatalysts with robust solar light utilization to deal with persistent pharmaceutical products in the wastewater system is crucially important. In order to improve the photoelectric activity, interfacial charge transfer, and reduce the recombination rate of photo-generated electron-hole pair, a Z-scheme TiO2−x @ZnIn2S4 heterojunction was prepared by hydrothermal method. The morphological structure and optical properties of the prepared catalysts were extensively characterized. Experimental results show that the rich of oxygen vacancies in TiO2−x benefits the formation of local defect energy levels at the bottom of the CB, which can be advantageous to broaden the light absorption range. Likewise, the TiO2−x @ZnIn2S4 showed 12.4-fold and 7.70-fold higher photocatalytic performance pristine TiO2−x and ZnIn2S4 towards the degradation of tetracycline hydrochloride (TCH) and nitrofurantoin (NFT) in real water matrix and solution water. Furthermore, the photo-decomposition pathway of NFT was proposed by HPLC-MS, and the Z-scheme electron transfer mechanism in TiO2−x @ZnIn2S4 heterojunction was proposed and discussed in detail. This work emphasizes a facile method for designing high-efficiency oxygen vacancy mediated titanium-based photocatalysts with excellent photoactivity in environmental remediation.

Photocatalytic activity of anatase-brookite TiO2 nanoparticles synthesized by sol gel method at low temperature

TiO2 photocatalysis is widely used in a variety of applications and products in the environmental and energy fields, including self-cleaning surfaces, air and water purification systems, sterilization, hydrogen evolution, and photoelectrochemical conversion. In this paper TiO2 nanoparticle was investigated for the degradation of Rhodamine B (RhB) under UV light. Nanocrystalline Anatase-Brookite TiO2 catalyst was synthesized via sol-gel method using the Titanium tetraisopropoxide (TTIP) at a temperature of 50 °C under mild conditions. XRD, TEM, SEM, FT-IR and BET were applied to characterize the crystal phase. The Crystalline size of TiO2 powder has been obtained with diameter <30 nm at 500 °C using an acid. The photocatalytic activity of TiO2 nanoparticle show that the degradation of Rhodamine B under UV light have removal of 95% dye was degraded in 60min.

A novel Ga(III) coordination complex as an efficient sensitizer for enhancing photocatalytic activity of TiO2/rGO nanocomposite

Narrow solar-light response range and rapid charges recombination are the main technical barriers in TiO2 photocatalysis technology. To overcome these restrictions, in this work we synthesized a novel binuclear gadolinium (III) coordination complex, [Gd2(DPDB)6(DMF)6(H2O)2] (DPDB = [(4-dimethylamino)phenyldiazenyl] benzenesulfonate), which was used as an inorganic sensitizer for boosting the visible light-harvesting and quantum efficiency of TiO2 supported-reduced graphene oxide (rGO) nanocomposite. Crystal structure of [Gd2(DPDB)6(DMF)6(H2O)2] (Gd-CMP) was determined from single-crystal X-ray diffraction data, which indicates three-dimensional (3D) supramolecular architecture through hydrogen bonding and CH··· πph interactions. The prepared nanohybrid (Gd-CMP/TG) reveals significantly enhanced visible-light-induced photocatalytic activity for degradation of acetaminophen (ACT). The complete removal of 10 mg/L ACT is achieved over Gd-CMP/TG, and the corresponding rate constant of ACT degradation of nanohybrid is 40-fold higher than that of bare TiO2. In prepared ternary nanohybrid, metal-coordination sensitizer (Gd-CMP) acts as an electron donor, and at the same time, rGO serves as an electron acceptor, and the synergistic effect between them efficiently enhances charges separation and inhibits e/h pair recombination in the hybridized species. The radical scavenger tests indicate that the photo-induced O2−• radicals dominate ACT degradation. On the basis of the experimental results and calculated energy of electronic levels, a possible mechanism for the improved photocatalytic activity is discussed.

PH Switchable Water Dispersed Photocatalytic Nanoparticles

Photogeneration of Reactive Oxygen Species (ROS) finds applications in fields as different as nanomedicine, art preservation, air and water depollution and surface decontamination. Here we present photocatalytic nanoparticles (NP) that are active only at acidic pH while they do not show relevant ROS photo‐generation at neutral pH. This dual responsivity (to light and pH) is achieved by stabilizing the surface of TiO2 NP with a specific organic shell during the synthesis and it is peculiar of the achieved core shell‐structure, as demonstrated by comparison with commercial photocatalytic TiO2 NP. For the investigation of the photocatalytic activity, we developed two methods that allow real time detection of the process preventing any kind of artifact arising from post‐treatments and delayed analysis. The reversibility of the pH response was also demonstrated as well as the selective photo‐killing of cancer cells at acidic pH.