Photocatalytic Activity Of TiO2 Research Articles

Enhanced performance of TiO2 doped with aluminum for the photocatalytic degradation of a mixture of plasticizers

The Al-doped TiO2 catalyst was synthesized by microwave-assisted sol-gel method. The physicochemical properties of the samples were determined by XRD, XPS, SEM, TEM, UV-Vis DRS, Raman spectroscopy, nitrogen physisorption, zetametry, and photoelectrochemical analysis. MP-AES determined the aluminum content in the catalysts. The evaluation of Al-doped TiO2 photocatalytic activity for degradation of a plasticizer mixture (bisphenol A (BPA) and 4-tert butylphenol (4tBP)) was performed under UV and simulated solar light. The catalysts showed anatase crystalline phase, spherical morphology, and the crystallite size decreased as the Al content increased in TiO2. The substitutional doping of Al3+ ions incorporated into the TiO2 crystal lattice improved the photocatalytic performance of TiO2 due to the enhanced surface acidity, and surface area, and reduced e--h+ recombination rate. A central composite design (CCD) with surface methodology was applied to identify the optimal degradation conditions evaluating the effect of Al doping within the content range 0.05–0.5 wt% on TiO2 and solution pH in the photocatalytic reaction (3, 6, and 9). The Al-TiO2 0.05% catalyst showed enhanced photocatalytic performance at pH 4.9, allowing 55% and 61% degradation percentages for 4tBP and BPA in 3 h under UV light irradiation. The photocatalytic oxidation mechanism of 4tBP and BPA with scavengers revealed that h+ and •O2- were the major reactive species. The transformation products of 4tBP and BPA were identified by LC-MS technique. Coexistent substances in the WWTP showed no inhibitory effects against the photocatalytic decomposition of 4tBP and BPA, and the Al-TiO2 catalyst demonstrated stability during the recycling experiments.

Photocatalytic degradation of Perchloroethylene by a lab-scale continuous-flow annular photoreactor packed with glass beads carbon-doped TiO2 nanoparticles

In this study, the amount of photocatalytic degradation of perchloroethylene in the gas phase was investigated by a fixed bed continuous-flow tubular photoreactor. The photoreactor consists of a cylindrical glass tube, was filled with glass beads coated with nanoparticles of TiO2, TiO2 doped carbon (TiO2-C). These nanoparticles were synthesized by the sol-gel method and deposited on glass beads using the sol-gel dip technique. X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transforms infrared spectroscopy (FT-IR), and diffuse reflectance spectroscopy (DRS) were used for the characterization of synthesized materials. The effect of different parameters such as relative humidity, residence time, PCE concentration on the photocatalytic degradation process was investigated by ultraviolet irradiation to achieve the highest possible degradation efficiency. The PCE degradation and byproduct species were monitored and identified with a gas chromatography-mass spectrometer device (GC-MS). Under the optimum experimental conditions, the photocatalytic activities of TiO2, TiO2-C were investigated and compared together. The results showed that photocatalytic activity of TiO2 for degradation of PCE was extremely increased when doped with carbon. For TiO2-C catalyst, under UV irradiation (3000 ppm initial PCE concentration, 30% humidity and 1 min residence time) approximately 96% of the initial PCE was degraded.

Antibiotics Contaminated Irrigation Water: An Overview on Its Impact on Edible Crops and Visible Light Active Titania as Potential Photocatalysts for Irrigation Water Treatment

Sub-therapeutic levels of antibiotics (ABs) are given to animals and poultry to promote growth and reduce disease. In agricultural environments, ABs reach croplands via animal manure used as fertilizer and/or ABs-contaminated water used for irrigation. The continuous discharge of ABs into the ecosystem raises growing concerns on the ABs contamination of edible crops. Tetracyclines (TCs) are among the most widely used ABs around the world. In this review, we discuss the contamination of irrigation water with TCs, its impact on edible crops, and the potential risks of crop contamination with TCs on human health. We propose solar-mediated photocatalytic degradation using Titania (TiO2) photocatalyst as a promising method to remove TCs from irrigation water. The photocatalytic activity of TiO2 can be enhanced by chemical modification to expand its activity under visible light irradiation. Herein, we aim for providing literature-based guidance on developing a visible light–active TiO2-based system to degrade TCs and other ABs in water streams. We include a summary of recent advances on this topic based on three main modification methods of Titania: metal/non-metal/mixed doping, composite formation, and heterojunction construction. Among the investigated photocatalysts, Fe2O3-TiO2/Fe-zeolite and the N-doped TiO2/rGO immobilized composite catalysts were found to be very efficient in the degradation of TCs under visible light irradiation (i.e., 98% degradation within 60 min). Most immobilized TiO2 based composite systems exhibited improved performances and hence we highlight these as efficient, cost effective and ecofriendly photocatalysts for the degradation of TCs in irrigation water.

In-situ synthesis of phthalocyanines on electrospun TiO2 nanofiber by solvothermal process for photocatalytic degradation of methylene blue.

Titanium dioxide/phthalocyanine (TiO2/Pc), TiO2/fluor containing phthalocyanine (TiO2/FPc), and TiO2/fluor containing cobalt phthalocyanine (TiO2/FCoPc) had been successfully fabricated by a simple combination of phthalocyanines obtained by in-situ synthesis on the surface of TiO2 nanofibers prepared by electrospinning. Scanning electron microscopy micrographs and X-ray diffraction analysis indicated that the phthalocyanines uniformly immobilized on the surface of TiO2 nanofibers. Photocatalytic activity of TiO2, TiO2/Pc, TiO2/FPc, TiO2/FCoPc nanofibers for methylene blue in water was comparatively investigated firstly by ultraviolet-visible absorption measurements with time, and kinetic parameters were calculated. Results indicated that the obtained TiO2/Pc, TiO2/ FPc and TiO2/FCoPc exhibited high photocatalytic activity for the degradation of methylene blue and TiO2/FCoPc was found the best. It showed similar or higher activities than related studies and can be suggested as a promising candidate for environmental and energy applications.

Synthesis and Photocatalytic Activity of TiO2 on Phenol Degradation

Photocatalysis is a process of accelerating reactions that are assisted by energy from light irradiation. Titanium dioxide (TiO2) is one of the most widely developed photocatalysis materials, and is used because of its high catalytic activity, stability and very affordable. The most commonly used precursors of TiO2 are titanium butoxide (TBOT) and titanium tetraisopropoxide (TTIP). These variations in precursor can lead to phase difference in the formation of TiO2 crystals, which further improves its nature in the activity of photocatalysis. In this study, the sol-gel method was used to synthesize titanium dioxide nanoparticles from variations of TBOT and TTIP. Furthermore, the structure, crystallite size and band gap of TiO2 were determined by X-ray diffraction (XRD) and UV-vis reflectance spectroscopy (DRS). Subsequently, TiO2 photocatalytic activity was evaluated in phenol photodegradation as a contaminant model with UV irradiation. The results showed the structure synthesized from TBOT had a higher amount of anatase, higher crystallinity, smaller crystallite size, larger band gap, and better photocatalytic activity than those from TTIP. Furthermore, it was shown that TiO2 from TBOT had an efficiency of 147% greater than TiO2 P25 Degussa, while TiO2 from TTIP had 66% efficiency compared to TiO2 P25.

Synthesis, Characterisation, Photocatalytic Activity, and Aquatic Toxicity Evaluation of TiO2 Nanoparticles.

Imidacloprid (IMD) is a toxic pesticide, and is one of the eight most widely used pesticides globally. Heterogeneous photocatalysis has often been investigated in recent years and can be successfully applied to remove imidacloprid from water. However, less investigated is the toxic effect of both the photocatalyst and the pesticide on aquatic life. Titanium dioxide (TiO2) remains the most effective photocatalyst, provided it is not toxic to the aquatic environment. This study investigated the TiO2 synthesis, characterisation, and photocatalytic activity on imidacloprid degradation and the toxicity of TiO2 nanoparticles and imidacloprid on the green algae Chlorella vulgaris. In the photodegradation process of IMD (initial concentration of 20 mg/L), electrons play an essential role; the degradation efficiency of IMD after 6 h increased from 69 to 90% under UV irradiation when holes (h+) scavengers were added, which allowed the electrons to react with the pollutant, resulting in lowering the recombination rate of electron-hole charge carriers. Growth inhibition of Chlorella vulgaris and effective concentration (EC50) were determined to study the toxic effect of TiO2 nanoparticles and imidacloprid. The EC50 increased from 289.338 mg/L in the first 24 h to 1126.75 mg/L after 96 h Chlorella vulgaris algal age, when the toxicant was TiO2. When IMD was the aquatic toxicant, a decrease in EC50 was observed from 22.8 mg/L (24 h) to 0.00777 mg/L (120 h), suggesting a long-term high toxicity level when pesticides in low concentrations are present in an aquatic environment.

Environmental photochemistry with Sn/F simultaneously doped TiO2 nanoparticles: UV and visible light induced degradation of thiazine dye

Environmental route such as degradation of toxic dyes can be improved through photochemical activity such as light driven photocatalytic degradation. Herein, fluorine and tin simultaneously doped TiO2 nanoparticles were synthesized and characterized. The formation of anatase phase in synthesized samples and the reduction in the crystallite size of doped TiO2 was confirmed from XRD results. The existence of O–Ti–O stretching vibration in pure and co-doped TiO2 confirmed from FTIR results. Optical studies reveal that the band gap of co-doped TiO2 is increased and hence it was concluded that the particle size of co-doped TiO2 is reduced compared with as-synthesized TiO2. The morphologies of TiO2 changed significantly with doping of fluorine and tin. It reveals majority of the particles are hexagons, pentagons and ellipse shaped and some of them are spheres with a mean particle size of 31.17 nm. PL studies showed the reduction in intensity for Sn–F/TiO2 accredited to the lesser recombination rate of electron-hole pair under UV light irradiation. Thus tin and fluorine doped TiO2 could be considered as a good candidate for photocatalytic activity. The photocatalytic activity of TiO2 and Sn–F/TiO2 nanoparticles was analyzed separately through the degradation of methylene blue (MB) under visible and UV light irradiation. The use of Sn and F ions in the synthesis of TiO2 are revealed not only create small sized nanoparticles but these water soluble nanoparticles have very good antibacterial and antifungal action by inhibiting the growth of bacteria and fungus.

Photocatalytic activation of peroxydisulfate by magnetic Fe3O4@SiO2@TiO2/rGO core–shell towards degradation and mineralization of metronidazole

In the present work, the degradation of metronidazole (MNZ) antibiotic by photocatalytic activation of peroxydisulfate (PDS) was studied in a batch environment. In this regard, TiO2 nanoparticles (NPs) with magnetic core–shell structure were anchored on the reduced graphene oxide (rGO) to fabricate the Fe3O4/SiO2/TiO2@rGO nanocomposite (FST@rGO) and applied as a recoverable heterogeneous catalyst along with ultraviolet (UV) light for activation of PDS. The nanocomposite was synthesized successfully by the sol–gel method and then characterized by using FESEM, EDS, XRD, Raman, EIS, BET, TEM, VSM, PL, and UV–VIS techniques. The degradation rate of MNZ was evaluated as a function of different concentrations of catalyst, PDS, and MNZ as well as the solution pH to determine the optimum operational conditions. Photocatalytic activity of TiO2 toward the degradation of MNZ was enhanced significantly after its magnetization by core–shell structure. Activated PDS exhibited excellent performance for degradation of MNZ in the wide range of pH. Under optimum conditions (pH:7, PDS:3 mM and FST@rGO:0.1 g L-1), >94% of MNZ and 58% of total organic carbon (TOC) were removed within 60 min. Based on trapping tests, HO•, 1O2, holes, and SO4•− species were identified as major reactive species during the MNZ degradation process. After four cycles of reuse the FST@rGO was able to remove 63.5% of MNZ, revealing relative reusability potential of the nanocomposite. In summary, integration of UV light and FST@rGO toward the activation of PDS could be introduced as a promising technique for application in environmental objectives, due to the good performance in the degradation/mineralization, easily separation, and high reusability potential of catalyst.

Temperature-dependent photoluminescence and decay times of different phases of grown TiO2 nanoparticles: Carrier dynamics and trap states

Three different phases, namely anatase, mixed and rutile phases of TiO2 nanoparticles (NPs) were developed with varying temperatures from 400 to 900 °C and confirmed using various characterization techniques. The XRD analysis of TiO2 NPs in temperature range of 290 to 77 K with no significant changes predict the thermally stable NPs. Photoinduced carrier dynamics of TiO2 NPs were investigated by the temperature dependence (TD) photoluminescence (PL) and TD time-resolved PL (TRPL) decays. With varying temperatures from 290 to 77 K, the anatase phase exhibits an additional and dominant 530 nm PL band. However, the mixed and rutile phases show three well-resolved PL bands, including 420 nm, 530 nm and near-infrared (NIR) bands at 820 nm at a lower temperature. Again, 530 nm band dominated for mixed-phase.In contrast, for the rutile phase, the 820 nm band dominated at <100 K. The PL lifetime of the 420 nm band is nearly a single exponential for all the phases. And is also true for the 530 and 820 nm PL bands, but bi-exponential for ≤100 K. Both the PL and TRPL results predict the presence of trap states in TiO2 NPs for anatase and rutile phases. The PL is originated due to donor-acceptor recombination, whereas oxygen vacancies served as donor and hydroxyl groups serve as accepter sites. The NIR band is attributed to the trapped electrons in rutile TiO2, which recombine with free holes and intrinsic defects. Also, the trapped electrons were generated in one of two ways: direct trapping or trap-to-trap hopping. The carrier dynamic in NPs depends on the trap states as the photoexcited carriers transfer into surface sites which competes with non-radiative and radiative recombinations during the relaxation process. Thus, the findings show that the trap states in TiO2 can significantly influence TiO2 photocatalytic activity when exposed to appropriate light.

Effects of Reaction Temperature on the Photocatalytic Activity of TiO2 with Pd and Cu Cocatalysts

The aim of this study was to investigate the effects of reaction temperature on the photocatalytic activity of TiO2 with Pd and Cu cocatalysts. N2 sorption, transmission electron microscopy and high-resolution transmission electron microscopy were used to characterize the specific surface area, pore volume, pore size, morphology and metal distribution of the catalysts. The photocatalytic destruction of methylene blue under UV light irradiation was used to test its activity. The concentration of methylene blue in water was determined by UV-vis spectrophotometer. Pd/TiO2 catalyst was more active than Cu/TiO2 and TiO2. At 0–50 °C reaction temperature, the activity of TiO2 and Pd/TiO2 increased with an increase of reaction temperature. When the temperature was as high as 70 °C, the reaction rate of TiO2 drop slightly and Pd/TiO2 became less effective. In contrast, Cu/TiO2 was more active at room temperature than the other temperatures. The results indicate that the photocatalytic activity of the catalyst is influenced by the reaction temperature and the type of cocatalyst. When the reaction temperature is higher than 70 °C, the recombination of charge carriers will increase. The temperature range of 50–80 °C is regarded as the ideal temperature for effective photolysis of organic matter. The effects of reaction temperature mainly influence quantum effect, i.e., electron-hole separation and recombination.

Photocatalytic degradation of tetracycline antibiotics using hydrothermally synthesized two-dimensional molybdenum disulfide/titanium dioxide composites

Tetracycline (TC) is a persistent antibiotic used in many countries, including China, India, and the United States of America (USA), because of its low price and effectiveness in enhancing livestock production. However, such antibiotics can have toxic effects on living organisms via complexation with metals, and their accumulation leading to teratogenicity and carcinogenicity. In this study, two-dimensional molybdenum disulfide/titanium dioxide (MoS2/TiO2) composites with different amounts of molybdenum disulfide (MoS2) were prepared via a simple, cost-effective, and pollution-free hydrothermal route. The synthesized MoS2/TiO2 microstructures were thoroughly characterized and their performance for the photocatalytic degradation of antibiotics such as TC was investigated. In the degradation experiments, the photocatalytic activities of TiO2 and the MoS2/TiO2 composites were compared, and the effects of different parameters, such as catalyst dose and electrolyte solution pH, were investigated. Under irradiation, the MoS2/TiO2 composites possessed superior photodegradation activity toward TC because of their excellent adsorption abilities, suitable band positions, and large surface areas as well as the effective charge-transfer ability of MoS2. Kinetics studies revealed that the photocatalytic degradation process followed pseudo-first-order reaction kinetics. In addition, a degradation mechanism for TC was proposed.

Synthesis of Oxygen Deficient TiO2 for Improved Photocatalytic Efficiency in Solar Radiation

The photocatalytic activities of TiO2 have been limited mainly to absorbing in the ultraviolet spectrum which accounts for only 5% of solar radiation. High energy band gap and electron recombination in TiO2 nanoparticles are responsible for its limitations as a photocatalyst. An oxygen deficient surface can be artificially created on the titanium oxide by zero valent nano iron through the donation of its excess electrons. A visible light active TiO2 nanoparticle was synthesized in the current investigation through simple chemical reduction using sodium boro-hydride. The physical and textural properties of the synthesized oxygen deficient TiO2 photocatalyst was measured using scanning/ transmission electron microscopy while FTIR, XRD and nitrogen sorption methods (BET) were employed for its further characterizations. Photochemical decoloration of orange II sodium dye solution in the presence of the synthesized TiO2 was measured using an UV spectrophotometer. The resulting oxygen deficient TiO2 has a lower energy band-gap, smaller pore sizes, and enhanced photo-catalytic properties. The decoloration (88%) of orange (II) sodium salt solution (pH 2) under simulated solar light was possible at 20 min. This study highlights the effect of surface oxygen defects, crystal size and energy band-gap on the photo-catalytical property of TiO2 nanoparticles as impacted by nano zero valent iron. It opens a new window in the exploitation of instability in the dopant ions for creation of a visible light active TiO2 photocatalyst.

Synthesis Design of Electronegativity Dependent WO3 and WO3∙0.33H2O Materials for a Better Understanding of TiO2/WO3 Composites’ Photocatalytic Activity

The design of a semiconductor or a composite semiconductor system—with applications in materials science—is complex because its morphology and structure depend on several parameters. These parameters are the precursor type, solvent, pH of the solution, synthesis approach, or shaping agents. This study gives meaningful insight regarding the synthesis design of such WO3 materials. By systematically alternating the precursor (sodium tungstate dihydrate—NWH, or ammonium tungstate hydrate—AMT), subsequently shaping the agents (halide salts—NaX, KX, or hydrohalic acids—HX; X = F−, Cl−, Br−, I−), we have obtained WO3 semiconductors by hydrothermal treatment, which in composite systems can enhance the commercial TiO2 photocatalytic activity. We investigated three sample series: WO3-NWH-NaX/WO3-NWH-KX and, subsequently, WO3-AMT-HX. The presence of W+5 centers was evidenced by Raman and X-ray photoelectron spectroscopy. W+5 and W+6 species affected the band gap values of the NaX and KX series; a higher percentage of W+5 and, subsequently, W+6 caused a redshift, while, regarding the HX series, it led to a blue shift. Increased electronegativity of the halide anions has an unfavorable effect on the composites’ photoactivity. In contrast, in the case of hydrohalic acids, it had a positive impact.

Preparation of WS2–TiO2–Au using hydrothermal synthesis for photocatalysis under visible light

In this study, the preparation of ternary photocatalyst using a simple hydrothermal method is shown with high performance. A ternary composite consisting of tungsten sulfide (WS[Formula: see text] nanosheets, titanium oxide (TiO[Formula: see text] and gold (Au) nanoparticles is used to the extend the visible-light absorption region of TiO2. The morphological and spectroscopic natures of the prepared sample were analyzed using scanning electron microscopy (SEM), Raman spectroscopy and ultraviolet–visible (UV–vis) photospectroscopy. The photocatalysis measurement for photodegradation of methylene blue dye was performed under the visible light. The photocatalytic studies suggest that in the ternary composite, consisting of three materials with different energy levels, the electrons excited form a cycle to lower the probability for the recombination of electron–hole pairs enhancing the property of photocatalytic activity of TiO2.

Synthesis and Optimization of a Highly Stable and Efficient BN/TiO2 Nanocomposite for Phenol Degradation: A Photocatalytic, Mechanistic and Environmental Impact Study

AbstractDifferent BN/TiO2 nanocomposites were prepared hydrothermally, and their ratio was optimized to get the best photocatalytic performance towards phenol degradation. They were characterized by x‐ray photoelectron spectroscopy, x‐ray diffraction, Fourier transform infrared spectroscopy, thermal gravimetric analysis, scanning and transmission electron microscopies coupled with energy dispersive x‐ray units, BET surface area, and UV‐Vis diffuse reflectance. The bandgap energy was reduced from 3.35 to 2.95 eV due to the formation of the B−O−Ti bond. This allowed the exploitation of the visible light and inhibited the TiO2 e−/h+ recombination, and consequently, the photocatalytic activity of TiO2 was dramatically improved. Almost 90 % mineralization of 20 ppm phenol solution was achieved within 30 min under simulated sunlight. The as‐prepared composite showed excellent stability and reusability. Mechanistic analysis indicated that and h+ played a crucial role in phenol degradation. The nanocomposite′s biocompatibility and environmental impact were evaluated by analyzing its potential toxicity in vivo using the zebrafish embryos. 96‐hpf acute toxicity assays, including the mortality rate assay (to obtain the LC50 values) and teratogenic assays (to obtain the No Observed Effect Concentration, NOEC) was conducted. The LC50 value for BN/TiO2 was 482.5 mg L−1, and the NOEC was 100 mg L−1. Based on LC50 value and according to the Fish and Wildlife Service (FWS) acute toxicity rating scale, the photocatalyst is “practically not toxic.”

Novel Strategy for the Development of Antibacterial TiO2 Thin Film onto Polymer Substrate at Room Temperature.

This work demonstrates a novel method to deposit an antibacterial TiO2 thin film on a polymer substrate at room temperature. A combination of sol–gel and photon assistance was used in the experiment in order to avoid any thermal processes of thin film crystallization. The morphological photograph of samples indicated that the TiO2 thin film was perfectly coated on the PVC substrate without any cracks or pinholes. Chemical analysis by EDS and XPS reported that the thin film consisted of titanium (Ti), oxygen (O), and carbon (C). The Raman spectrum proved that the thin film was the anatase phase of TiO2 and, furthermore, that it was contaminated with carbon remaining from the photon assistance process. In addition, the optical band gap of the thin film was 3.35 eV, suggesting that the photocatalytic activity of TiO2 should occur under UV-A radiation. The bacteria viability assay was examined using E. coli and S. typhimurium as indicator strains under UV-A irradiation (365 nm) at different times. The data from OD and CFU count revealed that >97% of bacteria were killed after 60 min of irradiation, and the bacteria were completely killed at 120 min for E. coli and 180 min for S. typhimurium.

(Invited) Photoelectrochemical Methanol Oxidation Under Visible and UV Excitation of TiO2-Supported TiN and Zrn Plasmonic Nanoparticles

TiN and ZrN nanoparticles (NPs) are an emerging class of plasmonic materials that can be used for harvesting energy of visible light in order to drive chemical reactions on the photocatalyst surface [1-3]. These refractory NPs effectively absorb light over l = 450-1200 nm, covering most of the solar spectrum. Both TiN and ZrN have the optical appearence of gold, but with the advantages of thermal stability, corrosion resistance and low cost. Previous theoretical and experimental research have shown that TiN does not exhibit as strong of a plasmonic resonance as gold (broader response, sample variability due to defect-dependent metallicity) [2, 4]. ZrN is expected to have a sharper blue-shifted local surface plasmon resonance (LSPR) response in comparison to TiN [4, 5]. Indeed, this theoretical prediction was verified by observation of a sharp plasmonic maximum for ZrN NPs decorated by a thin layer of SiN [4]. However, ZrN NPs appear to be less chemically inert owing to zirconium’s strong affinity for oxygen. A layer of dielectric ZrO2 forms on the surface of ZrN NPs even in the presence of trace oxygen. The oxide layer has a detrimental effect on the LSPR, leading to its broadening and red-shifting [5].Herein both experimental and computational approaches are used in order to optimize the performance of TiO2-supported TiN and ZrN NPs towards photoelectrochemical methanol (CH3OH) oxidation under visible excitation. UV excitation is utilized in order to provide complementary information on the interaction between photogenerated carriers at the plasmonic NP/semiconductor interface.The effects of plasmonic catalyst loading and applied potential were examined. Reaction products were determined by gas chromatography-mass spectrometry analysis of ZrN/TiO2 and TiN/TiO2 aqueous suspensions. Optical spectra for both TiN and ZrN NPs were computed using COMSOL including calculations of these NPs in solution and embedded in a TiO2 matrix. To examine the effect of oxide layer, the NPs were decorated with the corresponding oxide layers.ZrN NPs were synthesized by ammonolysis of Zr(NMe2)4. Clean Zr(NMe2)4 was prepared following a protocol from the literature [6]. In-house made ZrN powder and commercial TiN NPs (PlasmaChem) were dispersed into a P25 TiO2 matrix via the sonochemically mediated mixing of the transition metal nitride and TiO2 NPs in 50:50 (v/v) H2O:ethanol mixture overnight. The resulting photocatalysts contained 0.5 - 5 wt. % loadings of TiN and ZrN on TiO2. The ZrN/TiO2, TiN/TiO2 and bare TiO2 films for photoelectrochemical experiments were prepared by drop-casting 60 mL of ink comprising 20 mg of the photocatalyst, 30 ml of 5 wt% Nafion solution (Ion Power), 2.96 ml H2O and 0.74 ml iso-propanol, on FTO slide (coated surface area of 0.385 cm2). Experiments were conducted in a three-electrode photoelectrochemical cell. The photocatalyst films deposited on FTO-coated glass substrates served as working electrodes, while Pt foil and Ag/AgCl in 3 M NaCl (BioLogic, Inc) were used as counter and reference electrodes, respectively. Nine single-color LED lights were employed for illumination. The intensities varied between 10-100 mW/cm2, and 300-480 mW/cm2 in the wavelength range of 490-670 and 730-960 nm, respectively.Our results indicate that optical properties and photocatalytic activity of ZrN/TiO2 are strongly affected by ZrN surface oxidation and agglomeration. We found that under visible illumination, both in-house synthesized 17 nm ZrN and commercial 30 nm TiN NPs promote TiO2 activity for CH3OH oxidation, while under visible + UV excitation, an inhibition effect is observed. The differences between the TiN/TiO2 and ZrN/TiO2 interfaces are discussed and the mechanisms of promotion/inhibition of TiO2 photocatalytic activity by ZrN and TiN NPs are proposed.

Effects of iron ions, doping methods and nanotubular morphology on TiO2 solar photocatalytic performance.

The effects of Fe2+ and Fe3+ as TiO2 cocatalysts were studied, and the experimental results showed that Fe3+ was more efficient than Fe2+, which needed an intermediate reaction to produce hydroxyl radicals. TiO2 was modified with the aim of improving its structural, optical, and adsorption properties, thus improving its photocatalytic performance. The light range of the catalyst activation process was expanded, which increased the catalyst's ability to absorb visible light. Consequently, this study exploits solar energy in photocatalysis by Fe ion doping using different methods, including impregnation, photodeposition, solvothermal doping, and hydrothermal doping, and evaluates the influence of each doping method on TiO2 optical properties and photocatalytic activity. Enhancing the catalyst adsorption capacity by morphologically modifying TiO2 nanoparticles into nanotubes using the hydrothermal method increases the catalyst surface area from 55 to 294 m2/g, as shown in the SEM and BET results. The effect of combining morphological changes and Fe3+ doping on TiO2 activity was evaluated. We observed a reduction in the TiO2 band gap from 3.29 to 3.01 eV, absorption edge widening, and an increase in the specific surface area up to 279 m2/g; thus, the synthesized catalyst eliminated Cefixime in 120 min.

Photocatalytic degradation of MB by TiO2: studies on recycle and reuse of photocatalyst and treated water for seed germination.

Photocatalysis is an effective way for treatment of wastewater and degradation of dyes. It is important to assess the reusability of photocatalyst and treated water after the treatment process. In this study, the photocatalytic activity of TiO2 (titanium dioxide) and TiO2-TMAOH (titanium dioxide-tetramethylammonium hydroxide) was analyzed for degradation of methylene blue dye. Enhanced degradation of methylene blue is observed while treated with TiO2-TMAOH with photodegradation efficiency (PDE) 80% within 20 min. A further study shows the reusability of TiO2 for degradation of dye for six cycles with a decrease in photodegradation efficiency from 90% (cycle-1) to 50% (cycle-2). Fourier transform infrared spectroscopy (FTIR), energy-dispersive X-ray spectroscopy (EDX), and cyclic voltammetry (CV) analysis were carried out to identify the functional groups in treated water, traces of titanium, and TMAOH, respectively. Seed germination of Vigna radiata using TiO2- and TiO2-TMAOH-treated water shows equivalent and consistent growth. Water quality analysis of treated water shows improved biochemical oxygen demand (BOD) level (1.5 mg L-1), which is suitable for reusability of water for many applications. The outcomes suggest treated water can be used for irrigation and plantation purposes.

Effectiveness and Compatibility of Nanoparticle Based Multifunctional Coatings on Natural and Man-Made Stones

The interaction of microorganisms with stone materials leads to biodeterioration processes, which may cause aesthetic damages and the loss of durability and strength of the substrates. Innovative solutions against this process are represented by nanotechnologies. In our previous works, 2-mercaptobenzothiazole was successfully encapsulated within two silica-based nanodevices: nanocapsules and mesoporous nanoparticles. Such loaded nanodevices have been dispersed in TEOS based coatings, characterized as far as their chemical–physical properties and in vitro biocide efficacy. Here, we adopt a multi-technic approach, to assess the coatings efficacy and compatibility with four types of stones of cultural heritage interest, namely, mortar, brick, travertine, and Carrara marble. In particular, we determine the protective function of the coatings, based on water transport properties (reduction up to a factor 10 of the water absorption for brick and mortar, without significantly influencing water vapor transmission rate), morphology of the surface (absence of coating cracks and color changes), and TiO2 photocatalytic activity. Consequently, these coatings can be considered suitable for application on stone artifacts, without interfering with their artistic appearance.